WorldWideScience

Sample records for binary stellar populations

  1. Binary Populations and Stellar Dynamics in Young Clusters

    Science.gov (United States)

    Vanbeveren, D.; Belkus, H.; Van Bever, J.; Mennekens, N.

    2008-06-01

    We first summarize work that has been done on the effects of binaries on theoretical population synthesis of stars and stellar phenomena. Next, we highlight the influence of stellar dynamics in young clusters by discussing a few candidate UFOs (unconventionally formed objects) like intermediate mass black holes, η Car, ζ Pup, γ2 Velorum and WR 140.

  2. Inferences about binary stellar populations using gravitational wave observations

    Science.gov (United States)

    Wysocki, Daniel; Gerosa, Davide; O'Shaughnessy, Richard; Belczynski, Krzysztof; Gladysz, Wojciech; Berti, Emanuele; Kesden, Michael; Holz, Daniel

    2018-01-01

    With the dawn of gravitational wave astronomy, enabled by the LIGO and Virgo interferometers, we now have a new window into the Universe. In the short time these detectors have been in use, multiple confirmed detections of gravitational waves from compact binary coalescences have been made. Stellar binary systems are one of the likely progenitors of the observed compact binary sources. If this is indeed the case, then we can use measured properties of these binary systems to learn about their progenitors. We will discuss the Bayesian framework in which we make these inferences, and results which include mass and spin distributions.

  3. Numerical Relativity Simulations of Compact Binary Populations in Dense Stellar Environments

    Science.gov (United States)

    Glennon, Derek Ray; Huerta, Eliu; Allen, Gabrielle; Haas, Roland; Seidel, Edward; NCSA Gravity Group

    2018-01-01

    We present a catalog of numerical relativity simulations that describe binary black hole mergers on eccentric orbits. These simulations have been obtained with the open source, Einstein Toolkit numerical relativity software, using the Blue Waters supercomputer. We use this catalog to quantify observables, such as the mass and spin of black holes formed by binary black hole mergers, as a function of eccentricity. This study is the first of its kind in the literature to quantify these astrophysical observables for binary black hole mergers with mass-ratios q<6, and eccentricities e<0.2. This study is an important step in understanding the properties of eccentric binary black hole mergers, and informs the use of gravitational wave observations to confirm or rule out the existence of compact binary populations in dense stellar environments.

  4. Stellar Populations

    NARCIS (Netherlands)

    Peletier, Reynier F.

    2013-01-01

    This is a summary of my lectures during the 2011 Canary Islands Winter School in Puerto de la Cruz. I give an introduction to the field of stellar populations in galaxies, and highlight some new results. Since the title of the Winter School is Secular Evolution in Galaxies I mostly concentrate on

  5. Binary systems, star clusters and the Galactic-field population. Applied stellar dynamics

    Science.gov (United States)

    Kroupa, Pavel

    2002-01-01

    This book contains the results of recent theoretical work on the evolution of primordial binary systems in young star clusters, their effect on the evolution of their host clusters, implications for the distribution of young stars in the Milky Way, and the formation of bound star clusters. This work shows that if the Galactic-field binary population is a dynamically evolved version of the Taurus-Auriga pre-main sequence population, then most stars form in clusters with typically a few hundred binaries within a radius of about 0.5-1 pc. The results also suggest that the population I primordial binary-star orbital-parameter distribution functions may be universal, much like the initial mass function. Most solar-like planetary systems can survive in such clusters. The work presented here also establishes that most observed triple and quadruple systems must be primordial, but that α Cen A/B-Proxima Cen-like systems can form in clusters through dynamical capture. Precise N-body calculations using Aarseth's N-body codes of clusters containing up to 104 stars are used to create an extensive young-cluster library. These data demonstrate that the primordial binary systems are disrupted on a crossing-time scale, and that the truncation of the surviving period distribution measures the maximum concentration the cluster ever experienced. The N-body calculations demonstrate that Galactic star clusters form readily as nuclei of expanding OB associations despite a star-formation efficiency of typically 30 per cent and gas-expulsion over a time-span shorter than the cluster crossing time.

  6. Interactions of Stellar-Mass Black Holes Around Supermassive Black Hole Binaries

    Science.gov (United States)

    Stafford, Jennifer Nicole; Li, Gongjie; Naoz, Smadar; Hoang, Bao-Minh

    2018-01-01

    Supermassive black hole (SMBH) binaries are expected to reside in the center of galaxies due to galaxy mergers. The gravitational interactions between SMBH binaries and stellar BH binaries can lead to interesting dynamical effects, such as the merger of the stellar mass BHs, via gravitational wave emission. Specifically, we consider the systems where the stellar mass BH binary orbits around one of the SMBH binary components, and the other component perturbs the orbit of the stellar mass BH binary. The key effect leading to the merger is the eccentric Kozai-Lidov oscillation. The calculated rate can be compared with the binary black merger rates detected by LIGO, and provide valuable information on the population of stellar-mass BH binaries in galactic nuclei.

  7. Survival of planets around shrinking stellar binaries

    Science.gov (United States)

    Muñoz, Diego J.; Lai, Dong

    2015-01-01

    The discovery of transiting circumbinary planets by the Kepler mission suggests that planets can form efficiently around binary stars. None of the stellar binaries currently known to host planets has a period shorter than 7 d, despite the large number of eclipsing binaries found in the Kepler target list with periods shorter than a few days. These compact binaries are believed to have evolved from wider orbits into their current configurations via the so-called Lidov–Kozai migration mechanism, in which gravitational perturbations from a distant tertiary companion induce large-amplitude eccentricity oscillations in the binary, followed by orbital decay and circularization due to tidal dissipation in the stars. Here we explore the orbital evolution of planets around binaries undergoing orbital decay by this mechanism. We show that planets may survive and become misaligned from their host binary, or may develop erratic behavior in eccentricity, resulting in their consumption by the stars or ejection from the system as the binary decays. Our results suggest that circumbinary planets around compact binaries could still exist, and we offer predictions as to what their orbital configurations should be like. PMID:26159412

  8. Survival of planets around shrinking stellar binaries.

    Science.gov (United States)

    Muñoz, Diego J; Lai, Dong

    2015-07-28

    The discovery of transiting circumbinary planets by the Kepler mission suggests that planets can form efficiently around binary stars. None of the stellar binaries currently known to host planets has a period shorter than 7 d, despite the large number of eclipsing binaries found in the Kepler target list with periods shorter than a few days. These compact binaries are believed to have evolved from wider orbits into their current configurations via the so-called Lidov-Kozai migration mechanism, in which gravitational perturbations from a distant tertiary companion induce large-amplitude eccentricity oscillations in the binary, followed by orbital decay and circularization due to tidal dissipation in the stars. Here we explore the orbital evolution of planets around binaries undergoing orbital decay by this mechanism. We show that planets may survive and become misaligned from their host binary, or may develop erratic behavior in eccentricity, resulting in their consumption by the stars or ejection from the system as the binary decays. Our results suggest that circumbinary planets around compact binaries could still exist, and we offer predictions as to what their orbital configurations should be like.

  9. Do stellar clusters form fewer binaries? Using moderate separation binaries to distinguish between nature and nurture

    Science.gov (United States)

    Reiter, Megan

    2017-08-01

    Fewer wide-separation binaries are found in dense stellar clusters than in looser stellar associations. It is therefore unclear whether feedback in clusters prevents the formation of multiple systems or dynamical interactions destroy them. Measuring the prevalence of close, bound binary systems provide a key test to distinguish between these possibilities. Systems with separations of 10-50 AU will survive interactions in the cluster environment, and therefore are more representative of the natal population of multiple systems. By fitting a double-star PSF, we will identify visual binaries in the Orion Nebula with separations as small as 0.03. At the distance of Orion, this corresponds to a physical separation of 12 AU, effectively closing the observational gap in the binary separation distribution left between known visual and spectroscopic binaries (>65 AU or PhD thesis.

  10. Dynamical equivalence, the origin of the Galactic field stellar and binary population, and the initial radius-mass relation of embedded clusters

    Science.gov (United States)

    Belloni, Diogo; Kroupa, Pavel; Rocha-Pinto, Helio J.; Giersz, Mirek

    2018-03-01

    In order to allow a better understanding of the origin of Galactic field populations, dynamical equivalence of stellar-dynamical systems has been postulated by Kroupa and Belloni et al. to allow mapping of solutions of the initial conditions of embedded clusters such that they yield, after a period of dynamical processing, the Galactic field population. Dynamically equivalent systems are defined to initially and finally have the same distribution functions of periods, mass ratios and eccentricities of binary stars. Here, we search for dynamically equivalent clusters using the MOCCA code. The simulations confirm that dynamically equivalent solutions indeed exist. The result is that the solution space is next to identical to the radius-mass relation of Marks & Kroupa, ( r_h/pc )= 0.1^{+0.07}_{-0.04} ( M_ecl/M_{⊙} )^{0.13± 0.04}. This relation is in good agreement with the oIMF. This is achieved by applying a similar procedurebserved density of molecular cloud clumps. According to the solutions, the time-scale to reach dynamical equivalence is about 0.5 Myr which is, interestingly, consistent with the lifetime of ultra-compact H II regions and the time-scale needed for gas expulsion to be active in observed very young clusters as based on their dynamical modelling.

  11. Confusing Binaries: The Role of Stellar Binaries in Biasing Disk Properties in the Galactic Center

    Science.gov (United States)

    Naoz, Smadar; Ghez, Andrea M.; Hees, Aurelien; Do, Tuan; Witzel, Gunther; Lu, Jessica R.

    2018-02-01

    The population of young stars near the supermassive black hole (SMBH) in the Galactic Center (GC) has presented an unexpected challenge to theories of star formation. Kinematic measurements of these stars have revealed a stellar disk structure (with an apparent 20% disk membership) that has provided important clues regarding the origin of these mysterious young stars. However, many of the apparent disk properties are difficult to explain, including the low disk membership fraction and the high eccentricities given the youth of this population. Thus far, all efforts to derive the properties of this disk have made the simplifying assumption that stars at the GC are single stars. Nevertheless, stellar binaries are prevalent in our Galaxy, and recent investigations suggested that they may also be abundant in the Galactic Center. Here, we show that binaries in the disk can largely alter the apparent orbital properties of the disk. The motion of binary members around each other adds a velocity component, which can be comparable to the magnitude of the velocity around the SMBH in the GC. Thus, neglecting the contribution of binaries can significantly vary the inferred stars’ orbital properties. While the disk orientation is unaffected, the apparent disk’s 2D width will be increased to about 11.°2, similar to the observed width. For a population of stars orbiting the SMBH with zero eccentricity, unaccounted for binaries will create a wide apparent eccentricity distribution with an average of 0.23. This is consistent with the observed average eccentricity of the stars’ in the disk. We suggest that this high eccentricity value, which poses a theoretical challenge, may be an artifact of binary stars. Finally, our results suggest that the actual disk membership might be significantly higher than the one inferred by observations that ignore the contribution of binaries, alleviating another theoretical challenge.

  12. EVOLUTION OF THE BINARY FRACTION IN DENSE STELLAR SYSTEMS

    International Nuclear Information System (INIS)

    Fregeau, John M.; Ivanova, Natalia; Rasio, Frederic A.

    2009-01-01

    Using our recently improved Monte Carlo evolution code, we study the evolution of the binary fraction in globular clusters. In agreement with previous N-body simulations, we find generally that the hard binary fraction in the core tends to increase with time over a range of initial cluster central densities for initial binary fractions ∼<90%. The dominant processes driving the evolution of the core binary fraction are mass segregation of binaries into the cluster core and preferential destruction of binaries there. On a global scale, these effects and the preferential tidal stripping of single stars tend to roughly balance, leading to overall cluster binary fractions that are roughly constant with time. Our findings suggest that the current hard binary fraction near the half-mass radius is a good indicator of the hard primordial binary fraction. However, the relationship between the true binary fraction and the fraction of main-sequence stars in binaries (which is typically what observers measure) is nonlinear and rather complicated. We also consider the importance of soft binaries, which not only modify the evolution of the binary fraction, but can also drastically change the evolution of the cluster as a whole. Finally, we briefly describe the recent addition of single and binary stellar evolution to our cluster evolution code.

  13. Testing stellar evolution models with detached eclipsing binaries

    Science.gov (United States)

    Higl, J.; Weiss, A.

    2017-12-01

    Stellar evolution codes, as all other numerical tools, need to be verified. One of the standard stellar objects that allow stringent tests of stellar evolution theory and models, are detached eclipsing binaries. We have used 19 such objects to test our stellar evolution code, in order to see whether standard methods and assumptions suffice to reproduce the observed global properties. In this paper we concentrate on three effects that contain a specific uncertainty: atomic diffusion as used for standard solar model calculations, overshooting from convective regions, and a simple model for the effect of stellar spots on stellar radius, which is one of the possible solutions for the radius problem of M dwarfs. We find that in general old systems need diffusion to allow for, or at least improve, an acceptable fit, and that systems with convective cores indeed need overshooting. Only one system (AI Phe) requires the absence of it for a successful fit. To match stellar radii for very low-mass stars, the spot model proved to be an effective approach, but depending on model details, requires a high percentage of the surface being covered by spots. We briefly discuss improvements needed to further reduce the freedom in modelling and to allow an even more restrictive test by using these objects.

  14. FSPS: Flexible Stellar Population Synthesis

    Science.gov (United States)

    Conroy, Charlie; Gunn, James E.

    2010-10-01

    FSPS is a flexible SPS package that allows the user to compute simple stellar populations (SSPs) for a range of IMFs and metallicities, and for a variety of assumptions regarding the morphology of the horizontal branch, the blue straggler population, the post-AGB phase, and the location in the HR diagram of the TP-AGB phase. From these SSPs the user may then generate composite stellar populations (CSPs) for a variety of star formation histories (SFHs) and dust attenuation prescriptions. Outputs include the "observed" spectra and magnitudes of the SSPs and CSPs at arbitrary redshift. In addition to these fortran routines, several IDL routines are provided that allow easy manipulation of the output. FSPS was designed with the intention that the user would make full use of the provided fortran routines. However, the full FSPS package is quite large, and requires some time for the user to become familiar with all of the options and syntax. Some users may only need SSPs for a range of metallicities and IMFs. For such users, standard SSP sets for several IMFs, evolutionary tracks, and spectral libraries are available here.

  15. Busting Up Binaries: Stellar Interactions With Galactic Supermassive Black Holes

    Science.gov (United States)

    Addison, Eric; Larson, S.; Laguna, P.

    2012-05-01

    Gravitational wave astronomy is a new observational tool that will enhance our understanding of the Cosmos. Virtually everything we know about the Cosmos has been learned through observations of light; gravitational waves are a fundamentally different spectrum that can be used to learn about distant astrophysical systems. Einstein's theory of General Relativity predicts the existence of gravitational waves, and it is well known that stellar-mass compact object (CO) binaries will be among the most abundant and easily detectable sources. Extreme mass ratio inspirals are expected to provide an interesting potential source for gravitational wave detectors, however these systems are generally studied in the context of a single star orbiting a black hole. In this work, the case of a CO binary on a parabolic trajectory around a super massive black hole (SMBH) is considered. Numerical simulations are used to explore perturbations to the orbital parameters of the binary after interaction with the SMBH, including de-circularization and possible tidal capture. Additionally, the binary will likely experience an accelerated merger time due to gravitational radiation, which could produce an increase in the predicted CO binary merger rate.

  16. Gravitational Waves from Stellar Black Hole Binaries and the Impact on Nearby Sun-like Stars

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Ilídio [Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Silk, Joseph, E-mail: ilidio.lopes@tecnico.ulisboa.pt, E-mail: silk@astro.ox.ac.uk [Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, Paris F-75014 (France)

    2017-07-20

    We investigate the impact of resonant gravitational waves on quadrupole acoustic modes of Sun-like stars located nearby stellar black hole binary systems (such as GW150914 and GW151226). We find that the stimulation of the low-overtone modes by gravitational radiation can lead to sizeable photometric amplitude variations, much larger than the predictions for amplitudes driven by turbulent convection, which in turn are consistent with the photometric amplitudes observed in most Sun-like stars. For accurate stellar evolution models, using up-to-date stellar physics, we predict photometric amplitude variations of 1–10{sup 3} ppm for a solar mass star located at a distance between 1 au and 10 au from the black hole binary and belonging to the same multi-star system. The observation of such a phenomenon will be within the reach of the Plato mission because the telescope will observe several portions of the Milky Way, many of which are regions of high stellar density with a substantial mixed population of Sun-like stars and black hole binaries.

  17. Rapid and Bright Stellar-mass Binary Black Hole Mergers in Active Galactic Nuclei

    Science.gov (United States)

    Bartos, Imre; Kocsis, Bence; Haiman, Zoltán; Márka, Szabolcs

    2017-02-01

    The Laser Interferometer Gravitational-wave Observatory (LIGO) found direct evidence for double black hole binaries emitting gravitational waves. Galactic nuclei are expected to harbor the densest population of stellar-mass black holes. A significant fraction (˜ 30 % ) of these black holes can reside in binaries. We examine the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. We show that binary black holes can migrate into and then rapidly merge within the disk well within a Salpeter time. The binaries may also accrete a significant amount of gas from the disk, well above the Eddington rate. This could lead to detectable X-ray or gamma-ray emission, but would require hyper-Eddington accretion with a few percent radiative efficiency, comparable to thin disks. We discuss implications for gravitational-wave observations and black hole population studies. We estimate that Advanced LIGO may detect ˜20 such gas-induced binary mergers per year.

  18. Close Binaries in the Orion Nebula Cluster: On the Universality of Stellar Multiplicity and the Origin of Field Stars

    Science.gov (United States)

    Duchene, Gaspard; Lacour, Sylvestre; Moraux, Estelle; Bouvier, Jerome; Goodwin, Simon

    2018-01-01

    While stellar multiplicity is an ubiquitous outcome of star formation, there is a clear dichotomy between the multiplicity properties of young (~1 Myr-old) stellar clusters, like the ONC, which host a mostly field-like population of visual binaries, and those of equally young sparse populations, like the Taurus-Auriga region, which host twice as many stellar companions. Two distinct scenarios can account for this observation: one in which different star-forming regions form different number of stars, and one in which multiplicity properties are universal at birth but where internal cluster dynamics destroy many wide binaries. To solve this ambiguity, one must probe binaries that are sufficiently close so as not to be destroyed through interactions with other cluster members. To this end, we have conducted a survey for 10-100 au binaries in the ONC using the aperture masking technique with the VLT adaptive optics system. Among our sample of the 42 ONC members, we discovered 13 companions in this range of projected separations. This is consistent with the companion frequency observed in the Taurus population and twice as high as that observed among field stars. This survey thus strongly supports the idea that stellar multiplicity is characterized by near-universal initial properties that can later be dynamically altered. On the other hand, this exacerbates the question of the origin of field stars, since only clusters much denser than the ONC can effectively destroyed binaries closer than 100 au.

  19. The formation and gravitational-wave detection of massive stellar black hole binaries

    International Nuclear Information System (INIS)

    Belczynski, Krzysztof; Walczak, Marek; Buonanno, Alessandra; Cantiello, Matteo; Fryer, Chris L.; Holz, Daniel E.; Mandel, Ilya; Miller, M. Coleman

    2014-01-01

    If binaries consisting of two ∼100 M ☉ black holes exist, they would serve as extraordinarily powerful gravitational-wave sources, detectable to redshifts of z ∼ 2 with the advanced LIGO/Virgo ground-based detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by the recent discovery of several ≳ 150 M ☉ stars in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting black hole-black hole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitational-wave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binary-single interactions). We identify key physical factors that shape the population of very massive black hole-black hole binaries. Advanced gravitational-wave detectors will provide important constraints on the formation and evolution of very massive stars.

  20. Black holes in binary stellar systems and galactic nuclei

    International Nuclear Information System (INIS)

    Cherepashchuk, A M

    2014-01-01

    In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M BH =(4−20)M ⊙ ) in X-ray binary systems and of several hundred supermassive black holes (M BH =(10 6 −10 10 )M ⊙ ) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a ∗ have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a ∗ =0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths λ≲1 mm (the international program, Event Horizon Telescope). (100

  1. Ubiquitous time variability of integrated stellar populations

    Science.gov (United States)

    Conroy, Charlie; van Dokkum, Pieter G.; Choi, Jieun

    2015-11-01

    Long-period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to about 1,000 days and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode, which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population. The overall number of long-period variables in a population is directly related to their lifetimes, which is difficult to predict from first principles because of uncertainties associated with stellar mass-loss and convective mixing. The time variability of these stars has not previously been taken into account when modelling the spectral energy distributions of galaxies. Here we construct time-dependent stellar population models that include the effects of long-period variable stars, and report the ubiquitous detection of this expected ‘pixel shimmer’ in the massive metal-rich galaxy M87. The pixel light curves display a variety of behaviours. The observed variation of 0.1 to 1 per cent is very well matched to the predictions of our models. The data provide a strong constraint on the properties of variable stars in an old and metal-rich stellar population, and we infer that the lifetime of long-period variables in M87 is shorter by approximately 30 per cent compared to predictions from the latest stellar evolution models.

  2. Constraining the Statistics of Population III Binaries

    Science.gov (United States)

    Stacy, Athena; Bromm, Volker

    2012-01-01

    We perform a cosmological simulation in order to model the growth and evolution of Population III (Pop III) stellar systems in a range of host minihalo environments. A Pop III multiple system forms in each of the ten minihaloes, and the overall mass function is top-heavy compared to the currently observed initial mass function in the Milky Way. Using a sink particle to represent each growing protostar, we examine the binary characteristics of the multiple systems, resolving orbits on scales as small as 20 AU. We find a binary fraction of approx. 36, with semi-major axes as large as 3000 AU. The distribution of orbital periods is slightly peaked at approx. < 900 yr, while the distribution of mass ratios is relatively flat. Of all sink particles formed within the ten minihaloes, approx. 50 are lost to mergers with larger sinks, and 50 of the remaining sinks are ejected from their star-forming disks. The large binary fraction may have important implications for Pop III evolution and nucleosynthesis, as well as the final fate of the first stars.

  3. Ionization effects in the radiative driving of stellar winds in massive X ray binary systems

    Science.gov (United States)

    Stevens, Ian R.

    1989-01-01

    Massive X ray binaries consist of an early type primary lossing mass via a strong stellar wind driven by the stars radiation field, and an accreting neutron star companion. The X rays from the neutron star affect the wind dynamics by changing the temperature and ionization structure. The effect of the accretion powered X rays on the radiative line force that drives the stellar wind is calculated. The consequences of these calculations for the wind dynamics in massive X ray binaries is discussed.

  4. The formation of eccentric compact binary inspirals and the role of gravitational wave emission in binary-single stellar encounters

    International Nuclear Information System (INIS)

    Samsing, Johan; MacLeod, Morgan; Ramirez-Ruiz, Enrico

    2014-01-01

    The inspiral and merger of eccentric binaries leads to gravitational waveforms distinct from those generated by circularly merging binaries. Dynamical environments can assemble binaries with high eccentricity and peak frequencies within the LIGO band. In this paper, we study binary-single stellar scatterings occurring in dense stellar systems as a source of eccentrically inspiraling binaries. Many interactions between compact binaries and single objects are characterized by chaotic resonances in which the binary-single system undergoes many exchanges before reaching a final state. During these chaotic resonances, a pair of objects has a non-negligible probability of experiencing a very close passage. Significant orbital energy and angular momentum are carried away from the system by gravitational wave (GW) radiation in these close passages, and in some cases this implies an inspiral time shorter than the orbital period of the bound third body. We derive the cross section for such dynamical inspiral outcomes through analytical arguments and through numerical scattering experiments including GW losses. We show that the cross section for dynamical inspirals grows with increasing target binary semi-major axis a and that for equal-mass binaries it scales as a 2/7 . Thus, we expect wide target binaries to predominantly contribute to the production of these relativistic outcomes. We estimate that eccentric inspirals account for approximately 1% of dynamically assembled non-eccentric merging binaries. While these events are rare, we show that binary-single scatterings are a more effective formation channel than single-single captures for the production of eccentrically inspiraling binaries, even given modest binary fractions.

  5. The Ancient stellar population of Leo A.

    NARCIS (Netherlands)

    Saha, Abhijit; Fiorentino, Giuliana; Tolstoy, Eline; Cole, Andrew

    The primary goal of our proposal is the characterisation of the oldest stellar populations in Leo A using the properties of ancient RR Lyrae variable stars as tracers. Well known and long established correlations exist between the periods and luminosities of RR Lyrae variable stars and their ages

  6. The resolved stellar population of Leo A

    NARCIS (Netherlands)

    Tolstoy, E

    1996-01-01

    New observations of the resolved stellar population of the extremely metal-poor Magellanic dwarf irregular galaxy Leo A in Thuan-Gunn r, g, i, and narrowband Ha filters are presented. Using the recent Cepheid variable star distance determination to Leo A by Hoessel et al., we are able to create an

  7. The Resolved Stellar Population of Leo A

    Science.gov (United States)

    Tolstoy, Eline

    1996-05-01

    New observations of the resolved stellar population of the extremely metal-poor Magellanic dwarf irregular galaxy Leo A in Thuan-Gunn r, g, i, and narrowband Hα filters are presented. Using the recent Cepheid variable star distance determination to Leo A by Hoessel et al., we are able to create an accurate color-magnitude diagram (CMD). We have used the Bavesian inference method described by Tolstoy & Saha to calculate the likelihood of a Monte Carlo simulation of the stellar population of Leo A being a good match to the data within the well understood errors in the data. The magnitude limits on our data are sensitive enough to look back at ~1 Gyr of star formation history at the distance of Leo A. To explain the observed ratio of red to blue stars in the observed CMD, it is necessary to invoke either a steadily decreasing star formation rate toward the present time or gaps in the star formation history. We also compare the properties of the observed stellar population with the known spatial distribution of the H I gas and H II regions to support the conclusions from CMD modeling. We consider the possibility that currently there is a period of diminished star formation in Leo A, as evidenced by the lack of very young stars in the CMD and the faint H II regions. How the chaotic H I distribution, with no observable rotation, fits into our picture of the evolution of Leo A is as yet unclear.

  8. Cas A and the Crab were not stellar binaries at death

    Science.gov (United States)

    Kochanek, C. S.

    2018-01-01

    The majority of massive stars are in binaries, which implies that many core collapse supernovae should be binaries at the time of the explosion. Here we show that the three most recent, local (visual) SNe (the Crab, Cas A and SN 1987A) were not stellar binaries at death, with limits on the initial mass ratios of q = M2/M1 ≲ 0.1. No quantitative limits have previously been set for Cas A and the Crab, while for SN 1987A we merely updated existing limits in view of new estimates of the dust content. The lack of stellar companions to these three ccSNe implies a 90 per cent confidence upper limit on the q ≳ 0.1 binary fraction at death of fb Gaia proper motion and parallax catalogues providing a powerful probe of the statistics of such binaries and their role in massive star evolution, neutron star velocity distributions and runaway stars.

  9. Steeper Stellar Cusps in Galactic Centers from Binary Disruption

    Science.gov (United States)

    Fragione, Giacomo; Sari, Re’em

    2018-01-01

    The relaxed distribution of stars around a massive black hole is known to follow a cusp profile, ρ (r)\\propto {r}-α , with a characteristic slope α =7/4. This follows from energy conservation and a scattering rate given by two-body encounters. However, we show that the injection of stars close to the black hole, i.e., a source term in the standard cusp picture, modifies this profile. In the steady-state configuration, the cusp develops a central region with a typical slope α =9/4 in which stars diffuse outward. Binary disruption by the intense tidal field of the massive black hole is among the phenomena that take place in the Galactic Center (GC). In such a disruption, one of the binary members remains bound to the black hole, thus providing a source term of stars close to the black hole. Assuming a binary fraction of 0.1 and an orbital circularization efficiency of 0.35, we show that this source is strong enough to modify the cusp profile within ≈ 0.07 pc of the GC. If the binary fraction at the influence radius is of order unity and the orbits of all captured stars are efficiently circularized, the steeper cusp extends almost as far as the radius of influence of the black hole.

  10. THERMAL X-RAY EMISSION FROM THE SHOCKED STELLAR WIND OF PULSAR GAMMA-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Zabalza, V.; Paredes, J. M. [Departament d' Astronomia i Meteorologia, Institut de Ciencies del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Marti i Franques 1, E08028 Barcelona (Spain); Bosch-Ramon, V., E-mail: vzabalza@am.ub.es [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

    2011-12-10

    Gamma-ray-loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is expected from the shocked stellar wind, but until now it has neither been detected nor studied in the context of gamma-ray binaries. We present a semi-analytic model of the thermal X-ray emission from the shocked stellar wind in pulsar gamma-ray binaries, and find that the thermal X-ray emission increases monotonically with the pulsar spin-down luminosity, reaching luminosities of the order of 10{sup 33} erg s{sup -1}. The lack of thermal features in the X-ray spectrum of gamma-ray binaries can then be used to constrain the properties of the pulsar and stellar winds. By fitting the observed X-ray spectra of gamma-ray binaries with a source model composed of an absorbed non-thermal power law and the computed thermal X-ray emission, we are able to derive upper limits on the spin-down luminosity of the putative pulsar. We applied this method to LS 5039, the only gamma-ray binary with a radial, powerful wind, and obtain an upper limit on the pulsar spin-down luminosity of {approx}6 Multiplication-Sign 10{sup 36} erg s{sup -1}. Given the energetic constraints from its high-energy gamma-ray emission, a non-thermal to spin-down luminosity ratio very close to unity may be required.

  11. The X-ray luminosity functions of field low-mass X-ray binaries in early-type galaxies: Evidence for a stellar age dependence

    Energy Technology Data Exchange (ETDEWEB)

    Lehmer, B. D.; Tzanavaris, P.; Yukita, M. [The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Berkeley, M.; Basu-Zych, A.; Hornschemeier, A. E.; Ptak, A. [NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Zezas, A. [Physics Department, University of Crete, Heraklion (Greece); Alexander, D. M. [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Bauer, F. E. [Pontificia Universidad Catolica de Chile, Departamento de Astronomia y Astrofisica, Casilla 306, Santiago 22 (Chile); Brandt, W. N. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Fragos, T. [IESL, Foundation for Research and Technology, 71110 Heraklion, Crete (Greece); Kalogera, V. [Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Sivakoff, G. R. [Department of Physics, University of Alberta, CCIS 4-183 Edmonton, AB T6G 2E1 (Canada)

    2014-07-01

    We present direct constraints on how the formation of low-mass X-ray binary (LMXB) populations in galactic fields depends on stellar age. In this pilot study, we utilize Chandra and Hubble Space Telescope (HST) data to detect and characterize the X-ray point source populations of three nearby early-type galaxies: NGC 3115, 3379, and 3384. The luminosity-weighted stellar ages of our sample span ≈3-10 Gyr. X-ray binary population synthesis models predict that the field LMXBs associated with younger stellar populations should be more numerous and luminous per unit stellar mass than older populations due to the evolution of LMXB donor star masses. Crucially, the combination of deep Chandra and HST observations allows us to test directly this prediction by identifying and removing counterparts to X-ray point sources that are unrelated to the field LMXB populations, including LMXBs that are formed dynamically in globular clusters, Galactic stars, and background active galactic nuclei/galaxies. We find that the 'young' early-type galaxy NGC 3384 (≈2-5 Gyr) has an excess of luminous field LMXBs (L {sub X} ≳ (5-10) × 10{sup 37} erg s{sup –1}) per unit K-band luminosity (L{sub K} ; a proxy for stellar mass) than the 'old' early-type galaxies NGC 3115 and 3379 (≈8-10 Gyr), which results in a factor of ≈2-3 excess of L {sub X}/L{sub K} for NGC 3384. This result is consistent with the X-ray binary population synthesis model predictions; however, our small galaxy sample size does not allow us to draw definitive conclusions on the evolution field LMXBs in general. We discuss how future surveys of larger galaxy samples that combine deep Chandra and HST data could provide a powerful new benchmark for calibrating X-ray binary population synthesis models.

  12. The X-Ray Luminosity Functions of Field Low-Mass X-Ray Binaries in Early-Type Galaxies: Evidence for a Stellar Age Dependence

    Science.gov (United States)

    Lehmer, B. D.; Berkeley, M.; Zezas, A.; Alexander, D. M.; Basu-Zych, A.; Bauer, F. E.; Brandt, W. N.; Fragos, T.; Hornschemeier, A. E.; Kalogera, V.; hide

    2014-01-01

    We present direct constraints on how the formation of low-mass X-ray binary (LMXB) populations in galactic fields depends on stellar age. In this pilot study, we utilize Chandra and Hubble Space Telescope (HST) data to detect and characterize the X-ray point source populations of three nearby early-type galaxies: NGC 3115, 3379, and 3384. The luminosity-weighted stellar ages of our sample span approximately equal to 3-10 Gyr. X-ray binary population synthesis models predict that the field LMXBs associated with younger stellar populations should be more numerous and luminous per unit stellar mass than older populations due to the evolution of LMXB donor star masses. Crucially, the combination of deep Chandra and HST observations allows us to test directly this prediction by identifying and removing counterparts to X-ray point sources that are unrelated to the field LMXB populations, including LMXBs that are formed dynamically in globular clusters, Galactic stars, and background AGN/galaxies. We find that the "young" early-type galaxy NGC 3384 (approximately equals 2-5 Gyr) has an excess of luminous field LMXBs (L(sub x) approximately greater than (5-10) × 10(exp 37) erg s(exp -1)) per unit K-band luminosity (L(sub K); a proxy for stellar mass) than the "old" early-type galaxies NGC 3115 and 3379 (approximately equals 8-10 Gyr), which results in a factor of 2-3 excess of L(sub X)/L(sub K) for NGC 3384. This result is consistent with the X-ray binary population synthesis model predictions; however, our small galaxy sample size does not allow us to draw definitive conclusions on the evolution field LMXBs in general. We discuss how future surveys of larger galaxy samples that combine deep Chandra and HST data could provide a powerful new benchmark for calibrating X-ray binary population synthesis models.

  13. Orbital Elements and Stellar Parameters of the Active Binary UX Arietis

    Science.gov (United States)

    Hummel, C. A.; Monnier, J. D.; Roettenbacher, R. M.; Torres, G.; Henry, G. W.; Korhonen, H.; Beasley, A.; Schaefer, G. H.; Turner, N. H.; Ten Brummelaar, T.; Farrington, C. D.; Sturmann, J.; Sturmann, L.; Baron, F.; Kraus, S.

    2017-08-01

    Stellar activity observed as large surface spots, radio flares, or emission lines is often found in binary systems. UX Arietis exhibits these signs of activity, originating on the K0 subgiant primary component. Our aim is to resolve the binary, measure the orbital motion, and provide accurate stellar parameters such as masses and luminosities to aid in the interpretation of the observed phenomena. Using the CHARA six-telescope optical long-baseline array on Mount Wilson, California, we obtained amplitudes and phases of the interferometric visibility on baselines up to 330 m in length, resolving the two components of the binary. We reanalyzed archival Center for Astrophysics spectra to disentangle the binary component spectra and the spectrum of the third component, which was resolved by speckle interferometry. We also obtained new spectra with the Nordic Optical Telescope, and we present new photometric data that we use to model stellar surface spot locations. Both interferometric visibilities and spectroscopic radial velocities are modeled with a spotted primary stellar surface using the Wilson-Devinney code. We fit the orbital elements to the apparent orbit and radial velocity data to derive the distance (52.1 ± 0.8 pc) and stellar masses ({M}{{P}}=1.30+/- 0.06 {M}⊙ , {M}{{S}}=1.14+/- 0.06 {M}⊙ ). The radius of the primary can be determined to be {R}{{P}}=5.6+/- 0.1 {R}⊙ and that of the secondary to be {R}{{S}}=1.6+/- 0.2 {R}⊙ . The equivalent spot coverage of the primary component was found to be 62% with an effective temperature 20% below that of the unspotted surface.

  14. STELLAR POPULATION MODELS AND INDIVIDUAL ELEMENT ABUNDANCES. II. STELLAR SPECTRA AND INTEGRATED LIGHT MODELS

    NARCIS (Netherlands)

    Lee, Hyun-Chul; Worthey, Guy; Dotter, Aaron; Chaboyer, Brian; Jevremovic, Darko; Baron, E.; Briley, Michael M.; Ferguson, Jason W.; Coelho, Paula; Trager, Scott C.

    2009-01-01

    The first paper in this series explored the effects of altering the chemical mixture of the stellar population on an element-by-element basis on stellar evolutionary tracks and isochrones to the end of the red giant branch. This paper extends the discussion by incorporating the fully consistent

  15. Comparing the birth rate of stellar black holes in binary black hole mergers and long gamma-ray bursts

    Science.gov (United States)

    Atteia, J.-L.; Dezalay, J.-P.; Godet, O.; Klotz, A.; Turpin, D.; Bernardini, M. G.

    2018-02-01

    Context. Gravitational wave interferometers have proven the existence of a new class of binary black hole (BBH) weighing tens of solar masses, and have provided the first reliable measurement of the rate of coalescing black holes (BHs) in the local Universe. Furthermore, long gamma-ray bursts (GRBs) detected with gamma-ray satellites are believed to be associated with the birth of stellar-mass BHs, providing a measure of the rate of these events across the history of the Universe, thanks to the measure of their cosmological redshift. These two types of sources, which are subject to different detection biases and involve BHs born in different environments with potentially different characteristics, provide complementary information on the birth rate of stellar BHs. Aim. We compare the birth rates of BHs found in BBH mergers and in long GRBs. Methods: We construct a simple model that makes reasonable assumptions on the history of GRB formation, and takes into account some major uncertainties, like the beaming angle of GRBs or the delay between the formation of BBHs and their coalescence. We use this model to evaluate the ratio of the number of stellar mass BHs formed in BBH mergers to those formed in GRBs. Results: We find that in our reference model the birth rate of stellar BHs in BBH mergers represents a significant fraction of the rate of long GRBs and that comparable birth rates are favored by models with moderate beaming angles. These numbers, however, do not consider subluminous GRBs, which may represent another population of sources associated with the birth of stellar mass BHs. We briefly discuss this result in view of our understanding of the progenitors of GRBs and BBH mergers, and we emphasize that this ratio, which will be better constrained in the coming years, can be directly compared with the prediction of stellar evolution models if a single model is used to produce GRBs and BBH mergers with the same assumptions.

  16. Probing the low-stellar-mass domain with Kepler and APOGEE observations of eclipsing binaries

    Science.gov (United States)

    Prsa, Andrej; Hambleton, Kelly

    2018-01-01

    Observations of low-mass stars (M noise, shot noise, nuisance astrophysical signals (such as spots) and the full set of eclipsing binary parameters. The results are obtained within a probabilistic framework, with robust mass and radius uncertainties ~1-4%. We overplot the derived masses, radii and temperatures over evolutionary models and note stellar size bloating w.r.t. model predictions for both systems. This work has been funded by the NSF grant #1517460.

  17. Not-so-simple stellar populations in nearby, resolved massive star clusters

    Science.gov (United States)

    de Grijs, Richard; Li, Chengyuan

    2018-02-01

    Around the turn of the last century, star clusters of all kinds were considered ‘simple’ stellar populations. Over the past decade, this situation has changed dramatically. At the same time, star clusters are among the brightest stellar population components and, as such, they are visible out to much greater distances than individual stars, even the brightest, so that understanding the intricacies of star cluster composition and their evolution is imperative for understanding stellar populations and the evolution of galaxies as a whole. In this review of where the field has moved to in recent years, we place particular emphasis on the properties and importance of binary systems, the effects of rapid stellar rotation, and the presence of multiple populations in Magellanic Cloud star clusters across the full age range. Our most recent results imply a reverse paradigm shift, back to the old simple stellar population picture for at least some intermediate-age (∼1–3 Gyr old) star clusters, opening up exciting avenues for future research efforts.

  18. Emission-line diagnostics of nearby H II regions including interacting binary populations

    Science.gov (United States)

    Xiao, Lin; Stanway, Elizabeth R.; Eldridge, J. J.

    2018-03-01

    We present numerical models of the nebular emission from H II regions around young stellar populations over a range of compositions and ages. The synthetic stellar populations include both single stars and interacting binary stars. We compare these models to the observed emission lines of 254 H II regions of 13 nearby spiral galaxies and 21 dwarf galaxies drawn from archival data. The models are created using the combination of the Binary Population and Spectral Synthesis (BPASS) code with the photoionization code CLOUDY to study the differences caused by the inclusion of interacting binary stars in the stellar population. We obtain agreement with the observed emission line ratios from the nearby star-forming regions and discuss the effect of binary star evolution pathways on the nebular ionization of H II regions. We find that at population ages above 10 Myr, single-star models rapidly decrease in flux and ionization strength, while binary-star models still produce strong flux and high [O III]/Hβ ratios. Our models can reproduce the metallicity of H II regions from spiral galaxies but we find higher metallicities than previously estimated for the H II regions from dwarf galaxies. Comparing the equivalent width of Hβ emission between models and observations, we find that accounting for ionizing photon leakage can affect age estimates for H II regions. When it is included, the typical age derived for H II regions is 5 Myr from single-star models, and up to 10 Myr with binary-star models. This is due to the existence of binary-star evolution pathways which produce more hot WR and helium stars at older ages. For future reference, we calculate new BPASS binary maximal starburst lines as a function of metallicity, and for the total model population, and present these in Appendix A.

  19. Counting black holes: The cosmic stellar remnant population and implications for LIGO

    Science.gov (United States)

    Elbert, Oliver D.; Bullock, James S.; Kaplinghat, Manoj

    2018-01-01

    We present an empirical approach for interpreting gravitational wave signals of binary black hole mergers under the assumption that the underlying black hole population is sourced by remnants of stellar evolution. Using the observed relationship between galaxy mass and stellar metallicity, we predict the black hole count as a function of galaxy stellar mass. We show, for example, that a galaxy like the Milky Way should host millions of ∼30 M⊙ black holes and dwarf satellite galaxies like Draco should host ∼100 such remnants, with weak dependence on the assumed initial mass function and stellar evolution model. Most low-mass black holes (∼10 M⊙) typically reside within massive galaxies (M⋆ ≃ 1011 M⊙) while massive black holes (∼50 M⊙) typically reside within dwarf galaxies (M⋆ ≃ 109 M⊙) today. If roughly 1 per cent of black holes are involved in a binary black hole merger, then the reported merger rate densities from advanced Laser Interferometer Gravitational-Wave Observatory can be accommodated for a range of merger time-scales, and the detection of mergers with >50 M⊙ black holes should be expected within the next decade. Identifying the host galaxy population of the mergers provides a way to constrain both the binary neutron star or black hole formation efficiencies and the merger time-scale distributions; these events would be primarily localized in dwarf galaxies if the merger time-scale is short compared to the age of the Universe and in massive galaxies otherwise. As more mergers are detected, the prospect of identifying the host galaxy population, either directly through the detection of electromagnetic counterparts of binary neutron star mergers or indirectly through the anisotropy of the events, will become a realistic possibility.

  20. Population statistics of faint stellar and non-stellar objects

    Science.gov (United States)

    Vandenbergh, S.

    1979-01-01

    A disc and halo population model is constructed to fit star counts and color data down to V approximately 23 at absolute value of b = 90 deg. This model is used to predict star counts and colors down to V approximately 30. Deviations from these extrapolated relationships provide constraints on the number of faint quasars and black dwarf stars. It is shown that extra-galactic globular clusters start contributing significantly to star counts at V approximately 25 and are more numerous than stars for V 31. Morphological studies of galaxies with approximately 0.5, were made with the space telescope. Significant constraints on theoretical models that describe the evolution of clusters of galaxies are provided.

  1. Stellar population gradients in isolated, local group dwarf galaxies

    Directory of Open Access Journals (Sweden)

    Hidalgo S.L.

    2012-02-01

    Full Text Available We discuss the detailed star formation as a function of radius that we have derived for the LCID galaxies, with particular emphasis on the stellar populations gradient and the effect of the UV-background.

  2. Mapping young stellar populations toward Orion with Gaia DR1

    Science.gov (United States)

    Zari, E.; Brown, A. G. A.; de Bruijne, J.; Manara, C. F.; de Zeeuw, P. T.

    2017-12-01

    In this work we use the first data release of the Gaia mission to explore the three-dimensional arrangement and age ordering of the many stellar groups toward the Orion OB association, aiming at a new classification and characterization of the stellar population not embedded in the Orion A and B molecular clouds. We make use of the parallaxes and proper motions provided in the Tycho Gaia Astrometric Solution (TGAS) subset of the Gaia Data Release 1 (DR1) catalog and of the combination of Gaia DR1 and 2MASS photometry. In TGAS, we find evidence for the presence of a young population at a parallax ϖ 2.65 mas, which is loosely distributed around the following known clusters: 25 Ori, ɛ Ori, and σ Ori, and NGC 1980 (ι Ori) and the Orion Nebula Cluster (ONC). The low mass counterpart of this population is visible in the color magnitude diagrams constructed by combining Gaia DR1 G-band photometry and 2MASS. We study the density distribution of the young sources in the sky using a kernel density estimation (KDE). We find the same groups as in TGAS and also some other density enhancements that might be related to the recently discovered Orion X group, Orion dust ring, and λ Ori complex. The maps also suggest that the 25 Ori group presents a northern elongation. We estimated the ages of this population using a Bayesian isochronal fitting procedure assuming a unique parallax value for all the sources, and we inferred the presence of an age gradient going from 25 Ori (13-15 Myr) to the ONC (1-2 Myr). We confirmed this age ordering by repeating the Bayesian fit using the Pan-STARRS1 data. Intriguingly, the estimated ages toward the NGC 1980 cluster span a broad range of values. This can either be due to the presence of two populations coming from two different episodes of star formation or to a large spread along the line of sight of the same population. Some confusion might arise from the presence of unresolved binaries, which are not modeled in the fit, and usually mimic

  3. Binary Black Hole Mergers from Field Triples: Properties, Rates, and the Impact of Stellar Evolution

    Energy Technology Data Exchange (ETDEWEB)

    Antonini, Fabio [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astrophysics, Northwestern University, Evanston, IL 60208 (United States); Toonen, Silvia [Astronomical Institute Anton Pannekoek, University of Amsterdam, P.O. Box 94249, 1090 GE, Amsterdam (Netherlands); Hamers, Adrian S. [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States)

    2017-06-01

    We consider the formation of binary black hole (BH) mergers through the evolution of field massive triple stars. In this scenario, favorable conditions for the inspiral of a BH binary are initiated by its gravitational interaction with a distant companion, rather than by a common-envelope phase invoked in standard binary evolution models. We use a code that follows self-consistently the evolution of massive triple stars, combining the secular triple dynamics (Lidov–Kozai cycles) with stellar evolution. After a BH triple is formed, its dynamical evolution is computed using either the orbit-averaged equations of motion, or a high-precision direct integrator for triples with weaker hierarchies for which the secular perturbation theory breaks down. Most BH mergers in our models are produced in the latter non-secular dynamical regime. We derive the properties of the merging binaries and compute a BH merger rate in the range (0.3–1.3) Gpc{sup −3} yr{sup −1}, or up to ≈2.5 Gpc{sup −3} yr{sup −1} if the BH orbital planes have initially random orientation. Finally, we show that BH mergers from the triple channel have significantly higher eccentricities than those formed through the evolution of massive binaries or in dense star clusters. Measured eccentricities could therefore be used to uniquely identify binary mergers formed through the evolution of triple stars. While our results suggest up to ≈10 detections per year with Advanced-LIGO, the high eccentricities could render the merging binaries harder to detect with planned space based interferometers such as LISA.

  4. Binary Black Hole Mergers from Field Triples: Properties, Rates, and the Impact of Stellar Evolution

    International Nuclear Information System (INIS)

    Antonini, Fabio; Toonen, Silvia; Hamers, Adrian S.

    2017-01-01

    We consider the formation of binary black hole (BH) mergers through the evolution of field massive triple stars. In this scenario, favorable conditions for the inspiral of a BH binary are initiated by its gravitational interaction with a distant companion, rather than by a common-envelope phase invoked in standard binary evolution models. We use a code that follows self-consistently the evolution of massive triple stars, combining the secular triple dynamics (Lidov–Kozai cycles) with stellar evolution. After a BH triple is formed, its dynamical evolution is computed using either the orbit-averaged equations of motion, or a high-precision direct integrator for triples with weaker hierarchies for which the secular perturbation theory breaks down. Most BH mergers in our models are produced in the latter non-secular dynamical regime. We derive the properties of the merging binaries and compute a BH merger rate in the range (0.3–1.3) Gpc −3 yr −1 , or up to ≈2.5 Gpc −3 yr −1 if the BH orbital planes have initially random orientation. Finally, we show that BH mergers from the triple channel have significantly higher eccentricities than those formed through the evolution of massive binaries or in dense star clusters. Measured eccentricities could therefore be used to uniquely identify binary mergers formed through the evolution of triple stars. While our results suggest up to ≈10 detections per year with Advanced-LIGO, the high eccentricities could render the merging binaries harder to detect with planned space based interferometers such as LISA.

  5. Solving the relativistic inverse stellar problem through gravitational waves observation of binary neutron stars

    Science.gov (United States)

    Abdelsalhin, Tiziano; Maselli, Andrea; Ferrari, Valeria

    2018-04-01

    The LIGO/Virgo Collaboration has recently announced the direct detection of gravitational waves emitted in the coalescence of a neutron star binary. This discovery allows, for the first time, to set new constraints on the behavior of matter at supranuclear density, complementary with those coming from astrophysical observations in the electromagnetic band. In this paper we demonstrate the feasibility of using gravitational signals to solve the relativistic inverse stellar problem, i.e., to reconstruct the parameters of the equation of state (EoS) from measurements of the stellar mass and tidal Love number. We perform Bayesian inference of mock data, based on different models of the star internal composition, modeled through piecewise polytropes. Our analysis shows that the detection of a small number of sources by a network of advanced interferometers would allow to put accurate bounds on the EoS parameters, and to perform a model selection among the realistic equations of state proposed in the literature.

  6. Dynamics in dense stellar clusters: binary black holes in galactic centres

    Science.gov (United States)

    Hemsendorf, M.

    2001-06-01

    The dynamics of a massive binary system in a galactic nucleus are presented. These are the first results from simulations applying a hybrid "self consistent field" (SCF) and direct Aarseth N-body integrator (NBODY6), which synthesises the advantages of the direct force calculation with the efficiency of the field method. The code is aimed for use on parallel architectures and is therefore applicable for collisional N-body integrations with extraordinarily large particle numbers (>105). It opens the perspective to simulate the dynamics of globular clusters with realistic collisional relaxation, as well as stellar systems surrounding a supermassive black hole in galactic nuclei.

  7. Dynamics of Dense Stellar Clusters: Binary Black Holes in Galactic Centres

    Science.gov (United States)

    Hemsendorf, M.

    The dynamics of a massive binary system in a galactic nucleus are presented. These are the first results from simulations applying a hybrid "self consistent field" (SCF) and direct Aarseth N-body integrator (NBODY6), which synthesises the advantages of the direct force calculation with the efficiency of the field method. The code is aimed for use on parallel architectures and is therefore applicable for collisional N-body integrations with extraordinarily large particle numbers (> 105). It opens the perspective to simulate the dynamics of globular clusters with realistic collisional relaxation, as well as stellar systems surrounding a supermassive black hole in galactic nuclei.

  8. The Dark Energy Survey: Prospects for resolved stellar populations

    Energy Technology Data Exchange (ETDEWEB)

    Rossetto, Bruno M. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Santiago, Basílio X. [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Instituto de Fisica, Porto Alegre (Brazil); Girardi, Léo [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Osservatorio Astronomica di Padova-INAF, Padova (Italy); Camargo, Julio I. B. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Balbinot, Eduardo [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Instituto de Fisica, Porto Alegre (Brazil); da Costa, Luiz N. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Yanny, Brian [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Maia, Marcio A. G. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Makler, Martin [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Ogando, Ricardo L. C. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Pellegrini, Paulo S. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Ramos, Beatriz [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); de Simoni, Fernando [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Armstrong, R. [Univ. of Illinois, Urbana, IL (United States); Bertin, E. [Univ. Pierre et Marie Curie, Paris (France); Desai, S. [Univ. of Illinois, Urbana, IL (United States); Kuropatkin, N. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lin, H. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Mohr, J. J. [Max-Planck-Institut fur extraterrestrische Physik, Garching (Germany); Tucker, D. L. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2011-05-06

    Wide angle and deep surveys, regardless of their primary purpose, always sample a large number of stars in the Galaxy and in its satellite system. We here make a forecast of the expected stellar sample resulting from the Dark Energy Survey and the perspectives that it will open for studies of Galactic structure and resolved stellar populations in general. An estimated 1.2 x 108 stars will be sampled in DES grizY filters in the southern equatorial hemisphere. This roughly corresponds to 20% of all DES sources. Most of these stars belong to the stellar thick disk and halo of the Galaxy.

  9. Optical observations of close binaries with the Mark III Stellar Interferometer

    International Nuclear Information System (INIS)

    Pan, X.P.; Shao, M.; Colavita, M.M.; Armstrong, T.; Mozurkewich, D.

    1990-01-01

    For the first time, four spectroscopic binaries have been directly resolved with the Mark III Stellar Interferometer. Observations in 1988 and 1989 were analyzed, and visual orbits for four binaries have been determined. The semimajor axes for Beta Tri, Alpha Equ, Alpha And and Beta Ari are approximately 0.008 arcsec, 0.012 arcsec, 0.024 arcsec and 0.037 arcsec, respectively. The magnitude differences between two components are 0.5, 0.7, 1.8 and 2.6 mag, respectively. All of the orbital elements for Alpha And and Beta Ari were determined from interferometric data only, and agree well with spectroscopic observations. Predictions of relative position between the two components for these binaries are consistent with the measurements to less than 0.001 arcsec. Combined with data from spectroscopy, masses and distance for the double-lined spectroscopic binary Beta Ari are derived, and the results indicate that both components of Beta Ari agree well with the empirical mass-luminosity relation. 12 refs

  10. An updated MILES stellar library and stellar population models (Research Note)

    NARCIS (Netherlands)

    Falcon-Barroso, J.; Sanchez-Blazquez, P.; Vazdekis, A.; Ricciardelli, E.; Cardiel, N.; Cenarro, A. J.; Gorgas, J.; Peletier, R. F.

    Aims: We present a number of improvements to the MILES library and stellar population models. We correct some small errors in the radial velocities of the stars, measure the spectral resolution of the library and models more accurately, and give a better absolute flux calibration of the models.

  11. Single stellar populations in the near-infrared. I. Preparation of the IRTF spectral stellar library

    NARCIS (Netherlands)

    Meneses-Goytia, S.; Peletier, R. F.; Trager, S. C.; Falcón-Barroso, J.; Koleva, M.; Vazdekis, A.

    2015-01-01

    We present a detailed study of the stars of the NASA InfraRed Telescope Facility (IRTF) spectral library to understand its full extent and reliability for use with stellar population (SP) modeling. The library consist of 210 stars, with a total of 292 spectra, covering the wavelength range of 0.94

  12. Accreting Binary Populations in the Earlier Universe

    Science.gov (United States)

    Hornschemeier, Ann

    2010-01-01

    It is now understood that X-ray binaries dominate the hard X-ray emission from normal star-forming galaxies. Thanks to the deepest (2-4 Ms) Chandra surveys, such galaxies are now being studied in X-rays out to z approximates 4. Interesting X-ray stacking results (based on 30+ galaxies per redshift bin) suggest that the mean rest-frame 2-10 keV luminosity from z=3-4 Lyman break galaxies (LBGs), is comparable to the most powerful starburst galaxies in the local Universe. This result possibly indicates a similar production mechanism for accreting binaries over large cosmological timescales. To understand and constrain better the production of X-ray binaries in high-redshift LBGs, we have utilized XMM-Newton observations of a small sample of z approximates 0.1 GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs); local analogs to high-redshift LBGs. Our observations enable us to study the X-ray emission from LBG-like galaxies on an individual basis, thus allowing us to constrain object-to-object variances in this population. We supplement these results with X-ray stacking constraints using the new 3.2 Ms Chandra Deep Field-South (completed spring 2010) and LBG candidates selected from HST, Swift UVOT, and ground-based data. These measurements provide new X-ray constraints that sample well the entire z=0-4 baseline

  13. A COMPLETE SPECTROSCOPIC SURVEY OF THE MILKY WAY SATELLITE SEGUE 1: DARK MATTER CONTENT, STELLAR MEMBERSHIP, AND BINARY PROPERTIES FROM A BAYESIAN ANALYSIS

    International Nuclear Information System (INIS)

    Martinez, Gregory D.; Minor, Quinn E.; Bullock, James; Kaplinghat, Manoj; Simon, Joshua D.; Geha, Marla

    2011-01-01

    We introduce a comprehensive analysis of multi-epoch stellar line-of-sight velocities to determine the intrinsic velocity dispersion of the ultrafaint satellites of the Milky Way. Our method includes a simultaneous Bayesian analysis of both membership probabilities and the contribution of binary orbital motion to the observed velocity dispersion within a 14-parameter likelihood. We apply our method to the Segue 1 dwarf galaxy and conclude that Segue 1 is a dark-matter-dominated galaxy at high probability with an intrinsic velocity dispersion of 3.7 +1.4 -1.1 km s -1 . The dark matter halo required to produce this dispersion must have an average density of ρ-bar 1/2 = 2.5 -1.9 +4.1 , M sun , pc -3 within a sphere that encloses half the galaxy's stellar luminosity. This is the highest measured density of dark matter in the Local Group. Our results show that a significant fraction of the stars in Segue 1 may be binaries with the most probable mean period close to 10 years, but also consistent with the 180 year mean period seen in the solar vicinity at about 1σ. Despite this binary population, the possibility that Segue 1 is a bound star cluster with the observed velocity dispersion arising from the orbital motion of binary stars is disfavored by the multi-epoch stellar velocity data at greater than 99% C.L. Finally, our treatment yields a projected (two-dimensional) half-light radius for the stellar profile of Segue 1 of R 1/2 = 28 +5 -4 pc, in excellent agreement with photometric measurements.

  14. A panchromatic study of the stellar populations in NGC 4303

    Science.gov (United States)

    Dametto, N. Z.; Riffel, R.; Colina, L. R.; Riffel, R. A.; Piqueras López, J.

    2017-07-01

    We present some preliminary results on a panchromatic study of the stellar populations (SPs) in NGC 4303, using HST/STIS long-slit spectroscopy for the ultra-violet (UV) and optical spectral range, while VLT/SINFONI IFU data were used for the near-infrared (NIR) part of the spectra.

  15. Stellar populations a guide from low to high redshift

    CERN Document Server

    Renzini, Alvio

    2011-01-01

    This up-to-date reference on stellar populations and development models includes coverage of distant galaxies, chemical evolution and supernovae. Written by highly acclaimed authorities in the field, the book makes use of specific problems to reveal the ""kitchen secrets.""

  16. The Resolved Stellar Populations Early Release Science Program

    Science.gov (United States)

    Weisz, Daniel; Anderson, J.; Boyer, M.; Cole, A.; Dolphin, A.; Geha, M.; Kalirai, J.; Kallivayalil, N.; McQuinn, K.; Sandstrom, K.; Williams, B.

    2017-11-01

    We propose to obtain deep multi-band NIRCam and NIRISS imaging of three resolved stellar systems within 1 Mpc (NOI 104). We will use this broad science program to optimize observational setups and to develop data reduction techniques that will be common to JWST studies of resolved stellar populations. We will combine our expertise in HST resolved star studies with these observations to design, test, and release point spread function (PSF) fitting software specific to JWST. PSF photometry is at the heart of resolved stellar populations studies, but is not part of the standard JWST reduction pipeline. Our program will establish JWST-optimized methodologies in six scientific areas: star formation histories, measurement of the sub-Solar mass stellar IMF, extinction maps, evolved stars, proper motions, and globular clusters, all of which will be common pursuits for JWST in the local Universe. Our observations of globular cluster M92, ultra-faint dwarf Draco II, and star-forming dwarf WLM, will be of high archival value for other science such as calibrating stellar evolution models, measuring properties of variable stars, and searching for metal-poor stars. We will release the results of our program, including PSF fitting software, matched HST and JWST catalogs, clear documentation, and step-by-step tutorials (e.g., Jupyter notebooks) for data reduction and science application, to the community prior to the Cycle 2 Call for Proposals. We will host a workshop to help community members plan their Cycle 2 observations of resolved stars. Our program will provide blueprints for the community to efficiently reduce and analyze JWST observations of resolved stellar populations.

  17. X-ray illuminated stellar winds - Ionization effects in the radiative driving of stellar winds in massive X-ray binary systems

    Science.gov (United States)

    Stevens, Ian R.; Kallman, Timothy R.

    1990-01-01

    This paper presents calculations of the effect of changing X-ray ionization conditions on the radiative force experienced by the stellar wind material in a massive X-ray binary system. The radiative line force from the radiation field of the primary is parameterized in terms of the Castor et al. (1975) force multiplier. The results show that the line force decreases sharply, but in a nonlinear way, with increasing X-ray ionization. The dynamic consequences of this effect are discussed.

  18. Characterizing the Stellar Population of NGC 1980

    Energy Technology Data Exchange (ETDEWEB)

    Kounkel, Marina; Hartmann, Lee; Calvet, Nuria [Department of Astronomy, University of Michigan, 1085 S. University Street, Ann Arbor, MI 48109 (United States); Megeath, Tom, E-mail: mkounkel@umich.edu [Ritter Astrophsical Research Center, Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States)

    2017-07-01

    NGC 1980 is a young cluster that is located about 0.°5 south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC 1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40 pc. In this work, we present low-resolution spectra toward 148 young stars found toward the NGC 1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction toward them. We determine that based on these observations, the age of the population of NGC 1980 is indistinguishable from L1641, estimated to be ∼3 Myr, comparable with the study by Fang et al.

  19. Characterizing the Stellar Population of NGC 1980

    Science.gov (United States)

    Kounkel, Marina; Hartmann, Lee; Calvet, Nuria; Megeath, Tom

    2017-07-01

    NGC 1980 is a young cluster that is located about 0.°5 south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC 1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40 pc. In this work, we present low-resolution spectra toward 148 young stars found toward the NGC 1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction toward them. We determine that based on these observations, the age of the population of NGC 1980 is indistinguishable from L1641, estimated to be ˜3 Myr, comparable with the study by Fang et al.

  20. Nebular Continuum and Line Emission in Stellar Population Synthesis Models

    Science.gov (United States)

    Byler, Nell; Dalcanton, Julianne J.; Conroy, Charlie; Johnson, Benjamin D.

    2017-05-01

    Accounting for nebular emission when modeling galaxy spectral energy distributions (SEDs) is important, as both line and continuum emissions can contribute significantly to the total observed flux. In this work, we present a new nebular emission model integrated within the Flexible Stellar Population Synthesis code that computes the line and continuum emission for complex stellar populations using the photoionization code Cloudy. The self-consistent coupling of the nebular emission to the matched ionizing spectrum produces emission line intensities that correctly scale with the stellar population as a function of age and metallicity. This more complete model of galaxy SEDs will improve estimates of global gas properties derived with diagnostic diagrams, star formation rates based on Hα, and physical properties derived from broadband photometry. Our models agree well with results from other photoionization models and are able to reproduce observed emission from H II regions and star-forming galaxies. Our models show improved agreement with the observed H II regions in the Ne III/O II plane and show satisfactory agreement with He II emission from z = 2 galaxies, when including rotating stellar models. Models including post-asymptotic giant branch stars are able to reproduce line ratios consistent with low-ionization emission regions. The models are integrated into current versions of FSPS and include self-consistent nebular emission predictions for MIST and Padova+Geneva evolutionary tracks.

  1. Revealing the Formation of Stellar-mass Black Hole Binaries: The Need for Deci-Hertz Gravitational-wave Observatories

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xian [Astronomy Department, School of Physics, Peking University, 100871 Beijing (China); Amaro-Seoane, Pau, E-mail: xian.chen@pku.edu.cn, E-mail: pau@ice.cat [Institut de Ciències de l’Espai (CSIC-IEEC) at Campus UAB, Carrer de Can Magrans s/n, E-08193 Barcelona (Spain)

    2017-06-10

    The formation of compact stellar-mass binaries is a difficult, but interesting problem in astrophysics. There are two main formation channels: in the field via binary star evolution, or in dense stellar systems via dynamical interactions. The Laser Interferometer Gravitational-wave Observatory (LIGO) has detected black hole binaries (BHBs) via their gravitational radiation. These detections provide us with information about the physical parameters of the system. It has been claimed that when the Laser Interferometer Space Antenna (LISA) is operating, the joint observation of these binaries with LIGO will allow us to derive the channels that lead to their formation. However, we show that for BHBs in dense stellar systems dynamical interactions could lead to high eccentricities such that a fraction of the relativistic mergers are not audible to LISA. A non-detection by LISA puts a lower limit of about 0.005 on the eccentricity of a BHB entering the LIGO band. On the other hand, a deci-Hertz observatory, like DECIGO or Tian Qin, would significantly enhance the chances of a joint detection and shed light on the formation channels of these binaries.

  2. Revealing the Formation of Stellar-mass Black Hole Binaries: The Need for Deci-Hertz Gravitational-wave Observatories

    Science.gov (United States)

    Chen, Xian; Amaro-Seoane, Pau

    2017-06-01

    The formation of compact stellar-mass binaries is a difficult, but interesting problem in astrophysics. There are two main formation channels: in the field via binary star evolution, or in dense stellar systems via dynamical interactions. The Laser Interferometer Gravitational-wave Observatory (LIGO) has detected black hole binaries (BHBs) via their gravitational radiation. These detections provide us with information about the physical parameters of the system. It has been claimed that when the Laser Interferometer Space Antenna (LISA) is operating, the joint observation of these binaries with LIGO will allow us to derive the channels that lead to their formation. However, we show that for BHBs in dense stellar systems dynamical interactions could lead to high eccentricities such that a fraction of the relativistic mergers are not audible to LISA. A non-detection by LISA puts a lower limit of about 0.005 on the eccentricity of a BHB entering the LIGO band. On the other hand, a deci-Hertz observatory, like DECIGO or Tian Qin, would significantly enhance the chances of a joint detection and shed light on the formation channels of these binaries.

  3. THE PALOMAR TRANSIENT FACTORY ORION PROJECT: ECLIPSING BINARIES AND YOUNG STELLAR OBJECTS

    International Nuclear Information System (INIS)

    Van Eyken, Julian C.; Ciardi, David R.; Akeson, Rachel L.; Beichman, Charles A.; Von Braun, Kaspar; Gelino, Dawn M.; Kane, Stephen R.; Plavchan, Peter; RamIrez, Solange V.; Rebull, Luisa M.; Stauffer, John R.; Hoard, D. W.; Boden, Andrew F.; Howell, Steve B.; Bloom, Joshua S.; Cenko, S. Bradley; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Law, Nicholas M.; Nugent, Peter E.

    2011-01-01

    The Palomar Transient Factory (PTF) Orion project is one of the experiments within the broader PTF survey, a systematic automated exploration of the sky for optical transients. Taking advantage of the wide (3. 0 5 x 2. 0 3) field of view available using the PTF camera installed at the Palomar 48 inch telescope, 40 nights were dedicated in 2009 December to 2010 January to perform continuous high-cadence differential photometry on a single field containing the young (7-10 Myr) 25 Ori association. Little is known empirically about the formation of planets at these young ages, and the primary motivation for the project is to search for planets around young stars in this region. The unique data set also provides for much ancillary science. In this first paper, we describe the survey and the data reduction pipeline, and present some initial results from an inspection of the most clearly varying stars relating to two of the ancillary science objectives: detection of eclipsing binaries and young stellar objects. We find 82 new eclipsing binary systems, 9 of which are good candidate 25 Ori or Orion OB1a association members. Of these, two are potential young W UMa type systems. We report on the possible low-mass (M-dwarf primary) eclipsing systems in the sample, which include six of the candidate young systems. Forty-five of the binary systems are close (mainly contact) systems, and one of these shows an orbital period among the shortest known for W UMa binaries, at 0.2156509 ± 0.0000071 days, with flat-bottomed primary eclipses, and a derived distance that appears consistent with membership in the general Orion association. One of the candidate young systems presents an unusual light curve, perhaps representing a semi-detached binary system with an inflated low-mass primary or a star with a warped disk, and may represent an additional young Orion member. Finally, we identify 14 probable new classical T-Tauri stars in our data, along with one previously known (CVSO 35) and

  4. Towards a Unified View of Inhomogeneous Stellar Winds in Isolated Supergiant Stars and Supergiant High Mass X-Ray Binaries

    Science.gov (United States)

    Martínez-Núñez, Silvia; Kretschmar, Peter; Bozzo, Enrico; Oskinova, Lidia M.; Puls, Joachim; Sidoli, Lara; Sundqvist, Jon Olof; Blay, Pere; Falanga, Maurizio; Fürst, Felix; Gímenez-García, Angel; Kreykenbohm, Ingo; Kühnel, Matthias; Sander, Andreas; Torrejón, José Miguel; Wilms, Jörn

    2017-10-01

    Massive stars, at least ˜10 times more massive than the Sun, have two key properties that make them the main drivers of evolution of star clusters, galaxies, and the Universe as a whole. On the one hand, the outer layers of massive stars are so hot that they produce most of the ionizing ultraviolet radiation of galaxies; in fact, the first massive stars helped to re-ionize the Universe after its Dark Ages. Another important property of massive stars are the strong stellar winds and outflows they produce. This mass loss, and finally the explosion of a massive star as a supernova or a gamma-ray burst, provide a significant input of mechanical and radiative energy into the interstellar space. These two properties together make massive stars one of the most important cosmic engines: they trigger the star formation and enrich the interstellar medium with heavy elements, that ultimately leads to formation of Earth-like rocky planets and the development of complex life. The study of massive star winds is thus a truly multidisciplinary field and has a wide impact on different areas of astronomy. In recent years observational and theoretical evidences have been growing that these winds are not smooth and homogeneous as previously assumed, but rather populated by dense "clumps". The presence of these structures dramatically affects the mass loss rates derived from the study of stellar winds. Clump properties in isolated stars are nowadays inferred mostly through indirect methods (i.e., spectroscopic observations of line profiles in various wavelength regimes, and their analysis based on tailored, inhomogeneous wind models). The limited characterization of the clump physical properties (mass, size) obtained so far have led to large uncertainties in the mass loss rates from massive stars. Such uncertainties limit our understanding of the role of massive star winds in galactic and cosmic evolution. Supergiant high mass X-ray binaries (SgXBs) are among the brightest X

  5. 10 distinct stellar populations in omega Centauri.

    Science.gov (United States)

    Bellini, Andrea; Anderson, Jay; Bedin, Luigi R.; Cool, Adrienne; King, Ivan R.; van der marel, roeland p.

    2015-08-01

    We are constructing the most comprehensive catalog of photometry and proper motions ever assembled for a globular cluster. The core of omega Centauri has been imaged over 600 times through WFC3’s UVIS and IR channels for the purposes of detector calibration. There exist ~30 exposures each for 26 filters, stretching uniformly from F225W in the UV to F160W in the infrared. Furthermore, the 12-year baseline between this data and a 2002 ACS survey will more than triple both the accuracy and the number of well-measured stars compared to previous studies.This totally unprecedented complete spectral coverage for over 400,000 stars, from the red-giant branch down to the white dwarfs, provides the best chance yet to understand the multiple-population phenomenon in any globular cluster. A preliminary analysis of the color-magnitude diagrams in different bands already allows us to identify 10 distinct sequences.

  6. Inferring the Astrophysical Population of Black Hole Binaries from their Mass Distribution

    Science.gov (United States)

    Omoruyi, Osase; Weinstein, Alan; LIGO Laboratory at Caltech

    2018-01-01

    LIGO’s gravitational wave detections have not only proved the existence of black hole binaries but also confirmed the presence of stellar mass black holes larger than 20 solar masses. Our project aims to develop a system that will allow us to study the mass distribution of these binaries throughout space. Currently, LIGO has made 4 detections of binary black hole (BBH) mergers. However, within the next 10 years, LIGO expects this number of detections to rise significantly. With these future detections in mind, our project utilizes simulated data to generate a large population of BBH systems. From our general astrophysical knowledge about black holes and nature, we expect the underlying population to fall like a power-law in the total mass of the binary black hole system, M-α, in which α is the power-law index. Using the large sample of events our simulations provide, we seek to constrain the value of the power-law index more precisely and accurately. Successfully recovering the simulated value of α, in turn, will allow us to recover the actual value of α when LIGO detects enough events to form a significant population of BBH systems. Understanding the mass distribution of binary black holes will allow us to make inferences about how black hole binaries have formed and evolved over time.

  7. Constraints on stellar populations in elliptical galaxies

    International Nuclear Information System (INIS)

    Rose, J.A.

    1985-01-01

    Photographic image-tube spectra in the wavelength interval 3400--4500 A have been obtained for 12 elliptical galaxy nuclei and for a number of Galactic globular and open clusters in integrated light. The spectra have a wavelength resolution of 2.5 A and a high signal-to-noise ratio. A new quantitative three-dimensional spectral-classification system that has been calibrated on a sample of approx.200 individual stars (Rose 1984) is used to analyze the integrated spectra of the ellipical galaxy nuclei and to compare them with those of the globular clusters. This system is based on spectral indices that are formed by comparing neighborhood spectral features and is unaffected by reddening. The following results have been found: (1) Hot stars (i.e., spectral types A and B) contribute only 2% to the integrated spectra of elliptical galaxies at approx.4000 A, except in the nucleus of NGC 205, where the hot component dominates. This finding is based on a spectral index formed from the relative central intensities in the Ca II H+Hepsilon and Ca II K lines, which is shown to be constant for late-type (i.e., F, G, and K) stars, but changes drastically at earlier types. The observed Ca II H+Hepsilon/Ca II K indices in ellipticals can be reproduced by the inclusion of a small metal-poor population (as in the globular cluster M5) that contributes approx.8% of the light at 4000 A. Such a contribution is qualitatively consistent with the amount of

  8. Stellar mass and population diagnostics of cluster galaxies

    Science.gov (United States)

    Roediger, Joel C.

    2013-12-01

    We conduct a broad investigation about stellar mass and population diagnostics in order to formulate novel constraints related to the formation and evolution of galaxies from a nearby cluster environment. Our work is powered by the use of stellar population models which transform galaxy colours and/or absorption line strengths into estimates of its stellar properties. As input to such models, we assemble an extensive compilation of age and chemical abundance information for Galactic globular clusters. This compilation allows a confident expansion of these models into new regions of parameter space that promise to refine our knowledge of galactic chemical evolution. We then draw upon a state-of-the-art spectroscopic and photometric survey of the Virgo galaxy cluster in order to constrain spatial variations of the stellar ages, metallicities, and masses within its member galaxies, and their dynamical masses. We interpret these data in the context of the histories of star formation, chemical enrichment, and stellar mass assembly to formulate a broad picture of the build-up of this cluster's content over time. In it, the giant early-type galaxies formed through highly dissipational processes at early times that built up most of their stellar mass and drew significant amounts of dark matter within their optical radii. Conversely, dwarf early-types experienced environmental processes that quenched their star formation during either the early stages of cluster assembly or upon infall at later times. Somewhat perplexing is our finding that the internal dynamics of these galaxies are largely explained by their stellar masses. Lastly, Virgo spirals also suffer from their dense environment, through ram pressure stripping and/or tidal harrassment. In addition to quenching, these effects leave an imprint on their internal dynamical evolution too. Late-type spirals exhibit evidence of having ejected significant amounts of baryons from their inner regions, likely via energetic

  9. The evolution of C and O abundances in stellar populations

    DEFF Research Database (Denmark)

    Nissen, Poul E.; Schuster, William J.

    2014-01-01

    Carbon and oxygen abundances in F and G main-sequence stars ranging in metallicity from [Fe/H] = -1.6 to +0.5 are determined from a non-LTE analysis of C i and O i atomic lines in high-resolution spectra. Both C and O are good tracers of stellar populations; distinct trends of [C/Fe] and [O/Fe] a...

  10. Metal-rich, Metal-poor: Updated Stellar Population Models for Old Stellar Systems

    Science.gov (United States)

    Conroy, Charlie; Villaume, Alexa; van Dokkum, Pieter G.; Lind, Karin

    2018-02-01

    We present updated stellar population models appropriate for old ages (>1 Gyr) and covering a wide range in metallicities (‑1.5 ≲ [Fe/H] ≲ 0.3). These models predict the full spectral variation associated with individual element abundance variation as a function of metallicity and age. The models span the optical–NIR wavelength range (0.37–2.4 μm), include a range of initial mass functions, and contain the flexibility to vary 18 individual elements including C, N, O, Mg, Si, Ca, Ti, and Fe. To test the fidelity of the models, we fit them to integrated light optical spectra of 41 Galactic globular clusters (GCs). The value of testing models against GCs is that their ages, metallicities, and detailed abundance patterns have been derived from the Hertzsprung–Russell diagram in combination with high-resolution spectroscopy of individual stars. We determine stellar population parameters from fits to all wavelengths simultaneously (“full spectrum fitting”), and demonstrate explicitly with mock tests that this approach produces smaller uncertainties at fixed signal-to-noise ratio than fitting a standard set of 14 line indices. Comparison of our integrated-light results to literature values reveals good agreement in metallicity, [Fe/H]. When restricting to GCs without prominent blue horizontal branch populations, we also find good agreement with literature values for ages, [Mg/Fe], [Si/Fe], and [Ti/Fe].

  11. First light - II. Emission line extinction, population III stars, and X-ray binaries

    Science.gov (United States)

    Barrow, Kirk S. S.; Wise, John H.; Aykutalp, Aycin; O'Shea, Brian W.; Norman, Michael L.; Xu, Hao

    2018-02-01

    We produce synthetic spectra and observations for metal-free stellar populations and high-mass X-ray binaries in the Renaissance Simulations at a redshift of 15. We extend our methodology from the first paper in the series by modelling the production and extinction of emission lines throughout a dusty and metal-enriched interstellar and circum-galactic media extracted from the simulation, using a Monte Carlo calculation. To capture the impact of high-energy photons, we include all frequencies from hard X-ray to far-infrared with enough frequency resolution to discern line emission and absorption profiles. The most common lines in our sample in order of their rate of occurrence are Ly α, the C IV λλ1548, 1551 doublet, H α, and the Ca II λλλ8498, 8542, 8662 triplet. The best scenario for a direct observation of a metal-free stellar population is a merger between two Population III Galaxies. In mergers between metal-enriched and metal-free stellar populations, some characteristics may be inferred indirectly. Single Population III galaxies are too dim to be observed photometrically at z = 15. Ly α emission is discernible by JWST as an increase in J200w - J277w colour off the intrinsic stellar tracks. Observations of metal-free stars will be difficult, though not impossible, with the next generation of space telescopes.

  12. Empirical tests of pre-main-sequence stellar evolution models with eclipsing binaries

    Science.gov (United States)

    Stassun, Keivan G.; Feiden, Gregory A.; Torres, Guillermo

    2014-06-01

    We examine the performance of standard pre-main-sequence (PMS) stellar evolution models against the accurately measured properties of a benchmark sample of 26 PMS stars in 13 eclipsing binary (EB) systems having masses 0.04-4.0 M⊙ and nominal ages ≈1-20 Myr. We provide a definitive compilation of all fundamental properties for the EBs, with a careful and consistent reassessment of observational uncertainties. We also provide a definitive compilation of the various PMS model sets, including physical ingredients and limits of applicability. No set of model isochrones is able to successfully reproduce all of the measured properties of all of the EBs. In the H-R diagram, the masses inferred for the individual stars by the models are accurate to better than 10% at ≳1 M⊙, but below 1 M⊙ they are discrepant by 50-100%. Adjusting the observed radii and temperatures using empirical relations for the effects of magnetic activity helps to resolve the discrepancies in a few cases, but fails as a general solution. We find evidence that the failure of the models to match the data is linked to the triples in the EB sample; at least half of the EBs possess tertiary companions. Excluding the triples, the models reproduce the stellar masses to better than ∼10% in the H-R diagram, down to 0.5 M⊙, below which the current sample is fully contaminated by tertiaries. We consider several mechanisms by which a tertiary might cause changes in the EB properties and thus corrupt the agreement with stellar model predictions. We show that the energies of the tertiary orbits are comparable to that needed to potentially explain the scatter in the EB properties through injection of heat, perhaps involving tidal interaction. It seems from the evidence at hand that this mechanism, however it operates in detail, has more influence on the surface properties of the stars than on their internal structure, as the lithium abundances are broadly in good agreement with model predictions. The

  13. Stellar binary black holes in the LISA band: a new class of standard sirens

    Science.gov (United States)

    Del Pozzo, Walter; Sesana, Alberto; Klein, Antoine

    2018-04-01

    The recent Advanced LIGO detections of coalescing black hole binaries (BHBs) imply a large population of such systems emitting at milli-Hz frequencies, accessible to the Laser Interferometer Space Antenna (LISA). We show that these systems provide a new class of cosmological standard sirens. Direct LISA luminosity distance - Dl - measurements, combined with the inhomogeneous redshift - z - distribution of possible host galaxies provide an effective way to populate the Dl-z diagram at z level (68 per cent confidence), assuming two and five million kilometre arm-length, respectively.

  14. DYNAMICAL EVIDENCE FOR A MAGNETOCENTRIFUGAL WIND FROM A 20 M☉ BINARY YOUNG STELLAR OBJECT

    International Nuclear Information System (INIS)

    Greenhill, L. J.; Goddi, C.; Humphreys, E. M. L.; Chandler, C. J.; Matthews, L. D.

    2013-01-01

    In Orion BN/KL, proper motions of λ7 mm vibrationally excited SiO masers trace the rotation of a nearly edge-on disk and a bipolar wide-angle outflow 10-100 AU from radio source I, a binary young stellar object of ∼20 M ☉ . Here we map ground-state λ7 mm SiO emission with the Very Large Array and track proper motions over 9 yr. The innermost and strongest emission lies in two extended arcs bracketing Source I. The proper motions trace a northeast-southwest bipolar outflow 100-1000 AU from Source I with a median three-dimensional motion of ∼18 km s –1 . An overlying distribution of λ1.3 cm H 2 O masers betrays similar flow characteristics. Gas dynamics and emission morphology traced by the masers suggest the presence of a magnetocentrifugal disk wind. Reinforcing evidence lies in the colinearity of the flow, apparent rotation across the flow parallel to the disk rotation, and recollimation that narrows the flow opening angle ∼120 AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shocked super-Alfvénic outflow.

  15. Asteroseismology of Stellar Populations in the Milky Way

    CERN Document Server

    Eggenberger, Patrick; Girardi, Léo; Montalbán, Josefina

    2015-01-01

    The detection of radial and non-radial solar-like oscillations in thousands of G-K giants with CoRoT and Kepler is paving the road for detailed studies of stellar populations in the Galaxy. The available average seismic constraints allow largely model-independent determination of stellar radii and masses, and can be used to determine the position and age of thousands of stars in different regions of the Milky Way, and of giants belonging to open clusters. Such a close connection between stellar evolution, Galactic evolution, and asteroseismology opens a new very promising gate in our understanding of stars and galaxies.  This book represents a natural progression from the collection of review papers presented in the book 'Red Giants as Probes of the Structure and Evolution of the Milky Way', which appeared in the  Astrophysics and Space Science Proceedings series in 2012. This sequel volume contains review papers on spectroscopy, seismology of red giants, open questions in Galactic astrophysics, and discu...

  16. THE YOUNG STELLAR POPULATION OF LYNDS 1340. AN INFRARED VIEW

    Energy Technology Data Exchange (ETDEWEB)

    Kun, M.; Moór, A. [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, H-1121 Budapest, Konkoly Thege út 15-17 (Hungary); Wolf-Chase, G. [Astronomy Department, Adler Planetarium, 1300 South Lake Shore Drive, Chicago, IL 60605 (United States); Apai, D. [Steward Observatory, 933 N. Cherry Avenue, Tucson, AZ 85719 (United States); Balog, Z. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); O’Linger-Luscusk, J. [On leave from California Institute of Technology, 1200 E. California Avenue, Pasadena, CA 91125 (United States); Moriarty-Schieven, G. H., E-mail: kun@konkoly.hu [National Research Council—Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)

    2016-06-01

    We present results of an infrared study of the molecular cloud Lynds 1340, forming three groups of low- and intermediate-mass stars. Our goals are to identify and characterize the young stellar population of the cloud, study the relationships between the properties of the cloud and the emergent stellar groups, and integrate L1340 into the picture of the star-forming activity of our Galactic environment. We selected candidate young stellar objects (YSOs) from the Spitzer and WISE databases using various published color criteria and classified them based on the slope of the spectral energy distribution (SED). We identified 170 Class II, 27 flat SED, and 45 Class 0/I sources. High angular resolution near-infrared observations of the RNO 7 cluster, embedded in L1340, revealed eight new young stars of near-infrared excess. The surface density distribution of YSOs shows three groups, associated with the three major molecular clumps of L1340, each consisting of ≲100 members, including both pre-main-sequence stars and embedded protostars. New Herbig–Haro objects were identified in the Spitzer images. Our results demonstrate that L1340 is a prolific star-forming region of our Galactic environment in which several specific properties of the intermediate-mass mode of star formation can be studied in detail.

  17. Yonsei Evolutionary Population Synthesis (YEPS). II. Spectro-photometric Evolution of Helium-enhanced Stellar Populations

    Science.gov (United States)

    Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook

    2017-06-01

    The discovery of multiple stellar populations in Milky Way globular clusters (GCs) has stimulated various follow-up studies on helium-enhanced stellar populations. Here we present the evolutionary population synthesis models for the spectro-photometric evolution of simple stellar populations (SSPs) with varying initial helium abundance (Y ini). We show that Y ini brings about dramatic changes in spectro-photometric properties of SSPs. Like the normal-helium SSPs, the integrated spectro-photometric evolution of helium-enhanced SSPs is also dependent on metallicity and age for a given Y ini. We discuss the implications and prospects for the helium-enhanced populations in relation to the second-generation populations found in the Milky Way GCs. All of the models are available at http://web.yonsei.ac.kr/cosmic/data/YEPS.htm.

  18. Yonsei Evolutionary Population Synthesis (YEPS). II. Spectro-photometric Evolution of Helium-enhanced Stellar Populations

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Chul; Yoon, Suk-Jin; Lee, Young-Wook, E-mail: chulchung@yonsei.ac.kr, E-mail: sjyoon0691@yonsei.ac.kr [Center for Galaxy Evolution Research, Yonsei University, Seoul 03722 (Korea, Republic of)

    2017-06-20

    The discovery of multiple stellar populations in Milky Way globular clusters (GCs) has stimulated various follow-up studies on helium-enhanced stellar populations. Here we present the evolutionary population synthesis models for the spectro-photometric evolution of simple stellar populations (SSPs) with varying initial helium abundance ( Y {sub ini}). We show that Y {sub ini} brings about dramatic changes in spectro-photometric properties of SSPs. Like the normal-helium SSPs, the integrated spectro-photometric evolution of helium-enhanced SSPs is also dependent on metallicity and age for a given Y {sub ini}. We discuss the implications and prospects for the helium-enhanced populations in relation to the second-generation populations found in the Milky Way GCs. All of the models are available at http://web.yonsei.ac.kr/cosmic/data/YEPS.htm.

  19. The Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) Survey: Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Peter, Annika; Price, Paul A.; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay

    2017-01-01

    We discuss the first results of our observational program to comprehensively map nearly the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. These will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. We will detail our discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.

  20. Infalling young clusters in the Galactic Centre: implications for IMBHs and young stellar populations

    Science.gov (United States)

    Petts, J. A.; Gualandris, A.

    2017-06-01

    The central parsec of the Milky Way hosts two puzzlingly young stellar populations, a tight isotropic distribution of B stars around SgrA* (the S-stars) and a disc of OB stars extending to ˜0.5 pc. Using a modified version of Sverre Aarseth's direct summation code nbody6, we explore the scenario in which a young star cluster migrates to the Galactic Centre within the lifetime of the OB disc population via dynamical friction. We find that star clusters massive and dense enough to reach the central parsec form a very massive star via physical collisions on a mass segregation time-scale. We follow the evolution of the merger product using the most up to date, yet conservative, mass-loss recipes for very massive stars. Over a large range of initial conditions, we find that the very massive star expels most of its mass via a strong stellar wind, eventually collapsing to form a black hole of mass ˜ 20-400 M⊙, incapable of bringing massive stars to the Galactic Centre. No massive intermediate mass black hole can form in this scenario. The presence of a star cluster in the central ˜10 pc within the last 15 Myr would also leave an ˜2 pc ring of massive stars, which is not currently observed. Thus, we conclude that the star cluster migration model is highly unlikely to be the origin of either young population, and in situ formation models or binary disruptions are favoured.

  1. Stellar population of NGC 1850 in the LMC

    Science.gov (United States)

    Gilmozzi, Roberto; Panagia, Nino

    1992-01-01

    Observations of the globular cluster NGC 1850 taken with the HST Wide Field Camera are used to constrain the stellar population of this member of the Large Magellanic Cloud. Three exposures were obtained for each band at exposure times of 10, 100, and 1100 seconds, and the longest exposure was halved to minimize the effects of cosmic noise and the saturation of bright objects. A total of about 12,000 stars with magnitudes of 14-24 and masses of 0.8-13 solar mass are measured, and the age of NGC 1850 is given at approximately 25 million years.

  2. Tidal Disruptions Due to Stellar Mass Black Hole Binaries: Modifying the Spin Magnitudes and Directions of LIGO Sources

    Science.gov (United States)

    Lopez, Martin; Batta, Aldo; Ramírez-Ruiz, Enrico

    2018-01-01

    Globular clusters have about a thousand times denser stellar environments than our Milky Way. This crowded setting leads to many interactions between inhabitants of the cluster and the formation of a whole myriad of exotic objects. One such object is a binary system that forms which is composed of two stellar mass black holes (BHs). Due to the recent detection of gravitational waves (GWs), we know that some of these BH binaries (BHBs) are able to merge. Upon coalescence, BHBs produce GW signals that can be measured by the Laser Interferometer Gravitational-Wave Observatory (LIGO) group on Earth. Spin is one such parameter that LIGO can estimate from the type of signals they observe and as such can be used to constrain their production site. After these BHBs are assembled in dense stellar systems they can continue to interact with other members, either through tidal interactions or physical collisions. When a BHB tidally disrupts a star, a significant fraction of the debris can be accreted by the binary, effectively altering the spin of the BH members. Therefore, although a dynamically formed BHB will initially have low randomly aligned spins, through these types of interactions their birth spins can be significantly altered both in direction and magnitude. We have used a Lagrangian 3D Smoothed Particle Hydrodynamics (SPH) code GADGET-3 to simulate these interactions. Our results allow us to understand whether accretion from a tidal disruption event can significantly alter the birth properties of dynamically assembled BHBs such as spin, mass, and orbital attributes. The implications of these results will help us constrain the properties of BHBs in dense stellar systems in anticipation of an exciting decade ahead of us.

  3. A New Method for Deriving the Stellar Birth Function of Resolved Stellar Populations.

    Science.gov (United States)

    Gennaro, M.; Tchernyshyov, K.; Brown, T. M.; Gordon, K. D.

    2015-07-01

    We present a new method for deriving the stellar birth function (SBF) of resolved stellar populations. The SBF (stars born per unit mass, time, and metallicity) is the combination of the initial mass function (IMF), the star formation history (SFH), and the metallicity distribution function (MDF). The framework of our analysis is that of Poisson Point Processes (PPPs), a class of statistical models suitable when dealing with points (stars) in a multidimensional space (the measurement space of multiple photometric bands). The theory of PPPs easily accommodates the modeling of measurement errors as well as that of incompleteness. Our method avoids binning stars in the color-magnitude diagram and uses the whole likelihood function for each data point; combining the individual likelihoods allows the computation of the posterior probability for the population's SBF. Within the proposed framework it is possible to include nuisance parameters, such as distance and extinction, by specifying their prior distributions and marginalizing over them. The aim of this paper is to assess the validity of this new approach under a range of assumptions, using only simulated data. Forthcoming work will show applications to real data. Although it has a broad scope of possible applications, we have developed this method to study multi-band Hubble Space Telescope observations of the Milky Way Bulge. Therefore we will focus on simulations with characteristics similar to those of the Galactic Bulge. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at STScI, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  4. Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions

    Science.gov (United States)

    Paxton, Bill; Marchant, Pablo; Schwab, Josiah; Bauer, Evan B.; Bildsten, Lars; Cantiello, Matteo; Dessart, Luc; Farmer, R.; Hu, H.; Langer, N.; Townsend, R. H. D.; Townsley, Dean M.; Timmes, F. X.

    2015-09-01

    We substantially update the capabilities of the open-source software instrument Modules for Experiments in Stellar Astrophysics (MESA). MESA can now simultaneously evolve an interacting pair of differentially rotating stars undergoing transfer and loss of mass and angular momentum, greatly enhancing the prior ability to model binary evolution. New MESA capabilities in fully coupled calculation of nuclear networks with hundreds of isotopes now allow MESA to accurately simulate the advanced burning stages needed to construct supernova progenitor models. Implicit hydrodynamics with shocks can now be treated with MESA, enabling modeling of the entire massive star lifecycle, from pre-main-sequence evolution to the onset of core collapse and nucleosynthesis from the resulting explosion. Coupling of the GYRE non-adiabatic pulsation instrument with MESA allows for new explorations of the instability strips for massive stars while also accelerating the astrophysical use of asteroseismology data. We improve the treatment of mass accretion, giving more accurate and robust near-surface profiles. A new MESA capability to calculate weak reaction rates “on-the-fly” from input nuclear data allows better simulation of accretion induced collapse of massive white dwarfs and the fate of some massive stars. We discuss the ongoing challenge of chemical diffusion in the strongly coupled plasma regime, and exhibit improvements in MESA that now allow for the simulation of radiative levitation of heavy elements in hot stars. We close by noting that the MESA software infrastructure provides bit-for-bit consistency for all results across all the supported platforms, a profound enabling capability for accelerating MESA's development.

  5. Interaction of Massive Black Hole Binaries with Their Stellar Environment. II. Loss Cone Depletion and Binary Orbital Decay

    Science.gov (United States)

    Sesana, Alberto; Haardt, Francesco; Madau, Piero

    2007-05-01

    We study the long-term evolution of massive black hole binaries (MBHBs) at the centers of galaxies using detailed scattering experiments to solve the full three-body problem. Ambient stars drawn from an isotropic Maxwellian distribution unbound to the binary are ejected by the gravitational slingshot. We construct a minimal, hybrid model for the depletion of the loss cone and the orbital decay of the binary and show that secondary slingshots-stars returning on small-impact parameter orbits to have a second superelastic scattering with the MBHB-may considerably help the shrinking of the pair in the case of large binary mass ratios. In the absence of loss cone refilling by two-body relaxation or other processes, the mass ejected before the stalling of a MBHB is half the binary reduced mass. About 50% of the ejected stars are expelled in a ``burst'' lasting ~104 yr M1/46, where M6 is the binary mass in units of 106 Msolar. The loss cone is completely emptied in a few bulge crossing timescales, ~107 yr M1/46. Even in the absence of two-body relaxation or gas dynamical processes, unequal mass and/or eccentric binaries with M6>~0.1 can shrink to the gravitational wave emission regime in less than a Hubble time and are therefore ``safe'' targets for the planned Laser Interferometer Space Antenna.

  6. The Two Components of the Evolved Massive Binary LZ Cephei: Testing the Effects of Binarity on Stellar Evolution

    Science.gov (United States)

    Mahy, L.; Martins, F.; Donati, J.-F.; Bouret, J.-C.

    2011-01-01

    We present an in-dep(h study of the two components of the binary system LZ Cep to constrain the effects of binarity on the evolution of massive stars. Methods. We analyzed a set of high-resolution, high signal-to-noise ratio optical spectra obtained over the orbital period of the system to perform a spectroscopic disentangling and derive an orbital solution. We subsequently determine the stellar properties of each component by means of an analysis with the CMFGEN atmosphere code. Finally, with the derived stellar parameters, we model the Hipparcos photometric light curve using the program NIGHTFALL to obtain the orbit inclination and the stellar masses. Results.LZ Cep is a O9III+ON9.7V binary. It is as a semi-detailed system in which either the primary or the secondary star almost fills up its Roche lobe. The dynamical masses are about 16.0 Stellar Mass (primary) and 6.5 Stellar Mass (secondary). The latter is lower than the typical mass of late-type O stars. The secondary component is chemically more evolved than the primary (which barely shows any sign of CNO processing), with strong helium and nitrogen enhancements as well as carbon and oxygen depletions. These properties (surface abundances and mass) are typical of Wolf-Rayet stars, although the spectral type is ON9.7V. The luminosity of the secondary is consistent with that of core He-burning objects. The preferred, tentative evolutionary scenario to explain abe observed properties involves mass transfer from the secondary - which was initially more massive- towards the primary. The secondary is now almost a core He-burning object, probably with only a thin envelope of H-rich and CNO processed material. A very inefficient mass transfer is necessary to explain the chemical appearance of the primary. Alternative scenarios are discussed but they are affected by greater uncertainties.

  7. Stellar Populations of Quasar Host Galaxies Using WIYN

    Science.gov (United States)

    Mosby, Gregory; Moravec, E.; Kotulla, R. C.

    2013-06-01

    We now know that most galaxies have supermassive black holes (SMBH) in their centers, and somewhat unexpectedly, there are relationships—such as the M-sigma relation—between the mass of the central black hole and the velocity dispersion of the host galaxy's stellar spheroid (bulge), even though they lie outside the black hole's influence. Galaxy merger models show reasonable evidence for coevolution of the bulge and black hole since the merging process initiates simultaneous growth of the black hole and galaxy by supplying gas to the nucleus for accretion onto the black hole and triggering bursts of star formation. The merging process truncates the growth of both by removing the gas reservoir via feedback from these processes. But recently, it’s been shown that this relation could arise from central limit-like arguments alone. To really judge connections between SMBH and their host, it’s crucial to study these galaxies at the peak of black hole growth—during the quasar phase. Using 3-d spectroscopy methods, namely Sparsepak, an integral field units (IFU) on WIYN, it is possible to successfully recover information about the host galaxy's integrated star formation history that can be used to check merger-induced galaxy evolution predicted by the models. However, it is critical to have a robust and careful analysis of the stellar population modeling. The research presented in this poster focuses on new results from Sparsepak and preliminary WHIRC H-band light profiles of select quasar host galaxies. The stellar populations are derived using a new statistical method called diffusion k-means, and the WHIRC data are analyzed using a Python code written by Ralf Kotulla.

  8. A DYNAMICAL SIGNATURE OF MULTIPLE STELLAR POPULATIONS IN 47 TUCANAE

    International Nuclear Information System (INIS)

    Richer, Harvey B.; Heyl, Jeremy; Anderson, Jay; Kalirai, Jason S.; Shara, Michael M.; Dotter, Aaron; Fahlman, Gregory G.; Rich, R. Michael

    2013-01-01

    Based on the width of its main sequence, and an actual observed split when viewed through particular filters, it is widely accepted that 47 Tucanae contains multiple stellar populations. In this contribution, we divide the main sequence of 47 Tuc into four color groups, which presumably represent stars of various chemical compositions. The kinematic properties of each of these groups are explored via proper motions, and a strong signal emerges of differing proper-motion anisotropies with differing main-sequence color; the bluest main-sequence stars exhibit the largest proper-motion anisotropy which becomes undetectable for the reddest stars. In addition, the bluest stars are also the most centrally concentrated. A similar analysis for Small Magellanic Cloud stars, which are located in the background of 47 Tuc on our frames, yields none of the anisotropy exhibited by the 47 Tuc stars. We discuss implications of these results for possible formation scenarios of the various populations.

  9. Studying stellar binary systems with the Laser Interferometer Space Antenna using delayed rejection Markov chain Monte Carlo methods

    Energy Technology Data Exchange (ETDEWEB)

    Trias, Miquel [Departament de Fisica, Universitat de les Illes Balears, Cra. Valldemossa Km. 7.5, E-07122 Palma de Mallorca (Spain); Vecchio, Alberto; Veitch, John, E-mail: miquel.trias@uib.e, E-mail: av@star.sr.bham.ac.u, E-mail: jveitch@star.sr.bham.ac.u [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom)

    2009-10-21

    Bayesian analysis of Laser Interferometer Space Antenna (LISA) data sets based on Markov chain Monte Carlo methods has been shown to be a challenging problem, in part due to the complicated structure of the likelihood function consisting of several isolated local maxima that dramatically reduces the efficiency of the sampling techniques. Here we introduce a new fully Markovian algorithm, a delayed rejection Metropolis-Hastings Markov chain Monte Carlo method, to efficiently explore these kind of structures and we demonstrate its performance on selected LISA data sets containing a known number of stellar-mass binary signals embedded in Gaussian stationary noise.

  10. Evolution of close binaries under the assumption that they lose angular momentum by a magnetic stellar wind

    International Nuclear Information System (INIS)

    Kraicheva, Z.T.; Tutukov, A.V.; Yungel'son, L.R.

    1986-01-01

    A simple method is proposed for describing the evolution of semidetached close binaries whose secondary components have degenerated helium cores and lose orbital angular momentum by a magnetic stellar wind. The results of calculations are used to estimate the initial parameters of a series of low-mass (M 1 + M 2 ≤ 5M.) systems of Algol type under the two assumptions of conservative and nonconservative evolution with respect to the orbital angular momentum. Only the assumption that the systems with secondary components possessing convective shells lose angular momentum makes it possible to reproduce their initial parameters without contradiction

  11. BINARY ASTROMETRIC MICROLENSING WITH GAIA

    Energy Technology Data Exchange (ETDEWEB)

    Sajadian, Sedighe, E-mail: sajadian@ipm.ir [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of)

    2015-04-15

    We investigate whether or not Gaia can specify the binary fractions of massive stellar populations in the Galactic disk through astrometric microlensing. Furthermore, we study whether or not some information about their mass distributions can be inferred via this method. In this regard, we simulate the binary astrometric microlensing events due to massive stellar populations according to the Gaia observing strategy by considering (i) stellar-mass black holes, (ii) neutron stars, (iii) white dwarfs, and (iv) main-sequence stars as microlenses. The Gaia efficiency for detecting the binary signatures in binary astrometric microlensing events is ∼10%–20%. By calculating the optical depth due to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However, the binary fraction of black holes measured with this method has a large uncertainty owing to a low number of the estimated events. Knowing the binary fractions in massive stellar populations helps with studying the gravitational waves. Moreover, we investigate the number of massive microlenses for which Gaia specifies masses through astrometric microlensing of single lenses toward the Galactic bulge. The resulting efficiencies of measuring the mass of mentioned populations are 9.8%, 2.9%, 1.2%, and 0.8%, respectively. The numbers of their astrometric microlensing events being observed in the Gaia era in which the lens mass can be inferred with the relative error less than 0.5 toward the Galactic bulge are estimated as 45, 34, 76, and 786, respectively. Hence, Gaia potentially gives us some information about the mass distribution of these massive stellar populations.

  12. Population of Nuclei Via 7Li-Induced Binary Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Clark, Rodney M.; Phair, Larry W.; Descovich, M.; Cromaz, Mario; Deleplanque, M.A.; Fall on, Paul; Lee, I-Yang; Macchiavelli, A.O.; McMahan, Margaret A.; Moretto, Luciano G.; Rodriguez-Vieitez, E.; Sinha,Shrabani; Stephens, Frank S.; Ward, David; Wiedeking, Mathis

    2005-08-08

    The authors have investigated the population of nuclei formed in binary reactions involving {sup 7}Li beams on targets of {sup 160}Gd and {sup 184}W. The {sup 7}Li + {sup 184}W data were taken in the first experiment using the LIBERACE Ge-array in combination with the STARS Si {Delta}E-E telescope system at the 88-Inch Cyclotron of the Lawrence Berkeley National Laboratory. By using the Wilczynski binary transfer model, in combination with a standard evaporation model, they are able to reproduce the experimental results. This is a useful method for predicting the population of neutron-rich heavy nuclei formed in binary reactions involving beams of weakly bound nuclei formed in binary reactions involving beams of weakly bound nuclei and will be of use in future spectroscopic studies.

  13. LUT Reveals an Algol-type Eclipsing Binary With Three Additional Stellar Companions in a Multiple System

    Science.gov (United States)

    Zhu, L.-Y.; Zhou, X.; Hu, J.-Y.; Qian, S.-B.; Li, L.-J.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H.

    2016-04-01

    A complete light curve of the neglected eclipsing binary Algol V548 Cygni in the UV band was obtained with the Lunar-based Ultraviolet Telescope in 2014 May. Photometric solutions are obtained using the Wilson-Devinney method. It is found that solutions with and without third light are quite different. The mass ratio without third light is determined to be q = 0.307, while that derived with third light is q = 0.606. It is shown that V548 Cygni is a semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available eclipse times suggests that there are three cyclic variations in the O-C diagram that are interpreted by the light travel-time effect via the presence of three additional stellar companions. This is in agreement with the presence of a large quantity of third light in the system. The masses of these companions are estimated as m sin I‧ ˜ 1.09, 0.20, and 0.52 M⊙. They are orbiting the central binary with orbital periods of about 5.5, 23.3, and 69.9 years, I.e., in 1:4:12 resonance orbit. Their orbital separations are about 4.5, 13.2, and 26.4 au, respectively. Our photometric solutions suggest that they contribute about 32.4% to the total light of the multiple system. No obvious long-term changes in the orbital period were found, indicating that the contributions of the mass transfer and the mass loss due to magnetic braking to the period variations are comparable. The detection of three possible additional stellar components orbiting a typical Algol in a multiple system make V548 Cygni a very interesting binary to study in the future.

  14. Chromospheric activity of periodic variable stars (including eclipsing binaries) observed in DR2 LAMOST stellar spectral survey

    Science.gov (United States)

    Zhang, Liyun; Lu, Hongpeng; Han, Xianming L.; Jiang, Linyan; Li, Zhongmu; Zhang, Yong; Hou, Yonghui; Wang, Yuefei; Cao, Zihuang

    2018-05-01

    The LAMOST spectral survey provides a rich databases for studying stellar spectroscopic properties and chromospheric activity. We cross-matched a total of 105,287 periodic variable stars from several photometric surveys and databases (CSS, LINEAR, Kepler, a recently updated eclipsing star catalogue, ASAS, NSVS, some part of SuperWASP survey, variable stars from the Tsinghua University-NAOC Transient Survey, and other objects from some new references) with four million stellar spectra published in the LAMOST data release 2 (DR2). We found 15,955 spectra for 11,469 stars (including 5398 eclipsing binaries). We calculated their equivalent widths (EWs) of their Hα, Hβ, Hγ, Hδ and Caii H lines. Using the Hα line EW, we found 447 spectra with emission above continuum for a total of 316 stars (178 eclipsing binaries). We identified 86 active stars (including 44 eclipsing binaries) with repeated LAMOST spectra. A total of 68 stars (including 34 eclipsing binaries) show chromospheric activity variability. We also found LAMOST spectra of 12 cataclysmic variables, five of which show chromospheric activity variability. We also made photometric follow-up studies of three short period targets (DY CVn, HAT-192-0001481, and LAMOST J164933.24+141255.0) using the Xinglong 60-cm telescope and the SARA 90-cm and 1-m telescopes, and obtained new BVRI CCD light curves. We analyzed these light curves and obtained orbital and starspot parameters. We detected the first flare event with a huge brightness increase of more than about 1.5 magnitudes in R filter in LAMOST J164933.24+141255.0.

  15. The cosmic merger rate of stellar black hole binaries from the Illustris simulation

    Science.gov (United States)

    Mapelli, Michela; Giacobbo, Nicola; Ripamonti, Emanuele; Spera, Mario

    2017-12-01

    The cosmic merger rate density of black hole binaries (BHBs) can give us an essential clue to constraining the formation channels of BHBs, in light of current and forthcoming gravitational wave detections. Following a Monte Carlo approach, we couple new population-synthesis models of BHBs with the Illustris cosmological simulation, to study the cosmic history of BHB mergers. We explore six population-synthesis models, varying the prescriptions for supernovae, common envelope and natal kicks. In most considered models, the cosmic BHB merger rate follows the same trend as the cosmic star formation rate. The normalization of the cosmic BHB merger rate strongly depends on the treatment of common envelope and on the distribution of natal kicks. We find that most BHBs merging within LIGO's instrumental horizon come from relatively metal-poor progenitors (history, from progenitors with a broad range of metallicities. Future detections will be crucial to put constraints on common envelope, on natal kicks, and on the BHB mass function.

  16. STELLAR POPULATION AND GAS KINEMATICS OF POST-STARBURST QUASARS

    Science.gov (United States)

    Sanmartim, David; Storchi-Bergmann, Thaisa

    2018-01-01

    Post-Starburst Quasars (PSQs) are an intriguing set of galaxies that simultaneously host AGNs and post-starburst stellar populations, making them one of the most suitable objects to investigate the nature of the connection between these two components. The simultaneous presence of a post-starburst population and nuclear activity may be explained by two possible scenarios. In the secular evolutionary scenario star formation may cease due to exhaustion of the gas, while in the quenching one it may cease abruptly when the nuclear activity is triggered. In order to test these scenarios we have mapped the star formation history, manifestations of nuclear activity and excitation mechanisms in the central kpc of two nearby PSQs by using GMOS-IFU observations. In these two first exploratory studies, we have found that the young and intermediate age populations are located in a ring at ≈300-500 kpc, with some contribution of the intermediate age component also in the central region. In both of them, the gas outflow does not coincide with the young stellar population ring, which suggests that the ring is not being affected by the AGN feedback, but only the innermost regions. The individual study one of the PSQs of the sample has supported the evolutionary scenario, since the post-starburst population is not located close enough to the nucleus, where the outflow is observed. As a general behaviour, we found that outflows velocity are on the order of ~600-800 km/s and the mass outflow rates of ≈0.03-0.1 M⊙/yr, one order of magnitude greater than the AGN accretion rate, which suggests a scenario where the AGN-driven wind has entrained material from the circumnuclear region. In order to increase the statistical significance of our previous results and to distinguish between the proposed scenarios, we are conducting the same analysis to a wider sample of PSQs, which we hope will indicate more conclusively which is the favored scenario. During the meeting, we will present

  17. A New Stellar Outburst Associated with the Magnetic Activities of the K-type Dwarf in a White Dwarf Binary

    Energy Technology Data Exchange (ETDEWEB)

    Qian, S.-B.; Han, Z.-T.; Zhang, B.; Zhu, L.-Y.; Zhao, E.-G.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H. [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China); Zejda, M. [Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlářská 2, CZ-611 37 Brno (Czech Republic); Michel, R., E-mail: qsb@ynao.ac.cn [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ensenada, Baja California, México (Mexico)

    2017-10-20

    1SWASP J162117.36+441254.2 was originally classified as an EW-type binary with a period of 0.20785 days. However, it was detected to have undergone a stellar outburst on 2016 June 3. Although the system was later classified as a cataclysmic variable (CV) and the event was attributed as a dwarf nova outburst, the physical reason is still unknown. This binary has been monitored photometrically since 2016 April 19, and many light curves were obtained before, during, and after the outburst. Those light and color curves observed before the outburst indicate that the system is a special CV. The white dwarf is not accreting material from the secondary and there are no accretion disks surrounding the white dwarf. By comparing the light curves obtained from 2016 April 19 to those from September 14, it was found that magnetic activity of the secondary is associated with the outburst. We show strong evidence that the L {sub 1} region on the secondary was heavily spotted before and after the outburst and thus quench the mass transfer, while the outburst is produced by a sudden mass accretion of the white dwarf. These results suggest that J162117 is a good astrophysical laboratory to study stellar magnetic activity and its influences on CV mass transfer and mass accretion.

  18. Dynamical effects on binary X-ray sources in dense stellar clusters

    International Nuclear Information System (INIS)

    Shull, J.M.

    1979-01-01

    We examine the model in which the globular-cluster X-ray sources are binaries. Collisions of field stars in cores of dense clusters may shrink the orbits of tightly bound (''hard'') binaries, with important consequences for the evolution of X-ray sources if one component is a collapsed star. Exchange capture of field stars enables the binary to recycle its mass supplier and to undergo a number of intermittent stages of X-ray activity. ''Hard'' binaries may be formed by three-body encounters or by two-body tidal capture in clusters with large core densities and low velocity dispersions. Alternatively, as suggested by Hills, such objects may form by neutron-star or black-hole capture in exchange collisions with primordial binaries

  19. Resolving the age bimodality of galaxy stellar populations on kpc scales

    NARCIS (Netherlands)

    Zibetti, Stefano; Gallazzi, Anna R.; Ascasibar, Y.; Charlot, S.; Galbany, L.; García Benito, R.; Kehrig, C.; de Lorenzo-Cáceres, A.; Lyubenova, M.; Marino, R. A.; Márquez, I.; Sánchez, S. F.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.

    2017-01-01

    Galaxies in the local Universe are known to follow bimodal distributions in the global stellar population properties. We analyse the distribution of the local average stellar population ages of 654 053 sub-galactic regions resolved on ˜1 kpc scales in a volume-corrected sample of 394 galaxies, drawn

  20. The galaxy population of Abell 1367: the stellar mass-metallicity relation

    Science.gov (United States)

    Mouhcine, M.; Kriwattanawong, W.; James, P. A.

    2011-04-01

    Using wide baseline broad-band photometry, we analyse the stellar population properties of a sample of 72 galaxies, spanning a wide range of stellar masses and morphological types, in the nearby spiral-rich and dynamically young galaxy cluster Abell 1367. The sample galaxies are distributed from the cluster centre out to approximately half the cluster Abell radius. The optical/near-infrared colours are compared with simple stellar population synthesis models from which the luminosity-weighted stellar population ages and metallicities are determined. The locus of the colours of elliptical galaxies traces a sequence of varying metallicity at a narrow range of luminosity-weighted stellar ages. Lenticular galaxies in the red sequence, however, exhibit a substantial spread of luminosity-weighted stellar metallicities and ages. For red-sequence lenticular galaxies and blue cloud galaxies, low-mass galaxies tend to be on average dominated by stellar populations of younger luminosity-weighted ages. Sample galaxies exhibit a strong correlation between integrated stellar mass and luminosity-weighted stellar metallicity. Galaxies with signs of morphological disturbance and ongoing star formation activity, tend to be underabundant with respect to passive galaxies in the red sequence of comparable stellar masses. We argue that this could be due to tidally driven gas flows towards the star-forming regions, carrying less enriched gas and diluting the pre-existing gas to produce younger stellar populations with lower metallicities than would be obtained prior to the interaction. Finally, we find no statistically significant evidence for changes in the luminosity-weighted ages and metallicities for either red-sequence or blue-cloud galaxies, at fixed stellar mass, with location within the cluster. We dedicate this work to the memory of our friend and colleague C. Moss who died suddenly recently.

  1. Modeling tracers of young stellar population age in star-forming galaxies

    International Nuclear Information System (INIS)

    Levesque, Emily M.; Leitherer, Claus

    2013-01-01

    The young stellar population of a star-forming galaxy is the primary engine driving its radiative properties. As a result, the age of a galaxy's youngest generation of stars is critical for a detailed understanding of its star formation history, stellar content, and evolutionary state. Here we present predicted equivalent widths for the Hβ, Hα, and Brγ recombination lines as a function of stellar population age. The equivalent widths are produced by the latest generations of stellar evolutionary tracks and the Starburst99 stellar population synthesis code, and are the first to fully account for the combined effects of both nebular emission and continuum absorption produced by the synthetic stellar population. Our grid of model stellar populations spans six metallicities (0.001 < Z < 0.04), two treatments of star formation history (a 10 6 M ☉ instantaneous burst and a continuous star formation rate of 1 M ☉ yr –1 ), and two different treatments of initial rotation rate (v rot = 0.0v crit and 0.4v crit ). We also investigate the effects of varying the initial mass function. Given constraints on galaxy metallicity, our predicted equivalent widths can be applied to observations of star-forming galaxies to approximate the age of their young stellar populations.

  2. A SEARCH FOR X-RAY EMISSION FROM COLLIDING MAGNETOSPHERES IN YOUNG ECCENTRIC STELLAR BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Getman, Konstantin V.; Broos, Patrick S. [Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States); Kóspál, Ágnes [Konkoly Observatory, Research Center for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, 1525 Budapest (Hungary); Salter, Demerese M. [Department of Astronomy and Laboratory for Millimeter-Wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Garmire, Gordon P. [Huntingdon Institute for X-ray Astronomy, LLC, 10677 Franks Road, Huntingdon, PA 16652 (United States)

    2016-12-01

    Among young binary stars whose magnetospheres are expected to collide, only two systems have been observed near periastron in the X-ray band: the low-mass DQ Tau and the older and more massive HD 152404. Both exhibit elevated levels of X-ray emission at periastron. Our goal is to determine whether colliding magnetospheres in young high-eccentricity binaries commonly produce elevated average levels of X-ray activity. This work is based on Chandra snapshots of multiple periastron and non-periastron passages in four nearby young eccentric binaries (Parenago 523, RX J1622.7-2325 Nw, UZ Tau E, and HD 152404). We find that for the merged sample of all four binaries the current X-ray data show an increasing average X-ray flux near periastron (at a ∼2.5-sigma level). Further comparison of these data with the X-ray properties of hundreds of young stars in the Orion Nebula Cluster, produced by the Chandra Orion Ultradeep Project (COUP), indicates that the X-ray emission from the merged sample of our binaries cannot be explained within the framework of the COUP-like X-ray activity. However, due to the inhomogeneities of the merged binary sample and the relatively low statistical significance of the detected flux increase, these findings are regarded as tentative only. More data are needed to prove that the flux increase is real and is related to the processes of colliding magnetospheres.

  3. Dynamical evolution of a fictitious population of binary Neptune Trojans

    Science.gov (United States)

    Brunini, Adrián

    2018-03-01

    We present numerical simulations of the evolution of a synthetic population of Binary Neptune Trojans, under the influence of the solar perturbations and tidal friction (the so-called Kozai cycles and tidal friction evolution). Our model includes the dynamical influence of the four giant planets on the heliocentric orbit of the binary centre of mass. In this paper, we explore the evolution of initially tight binaries around the Neptune L4 Lagrange point. We found that the variation of the heliocentric orbital elements due to the libration around the Lagrange point introduces significant changes in the orbital evolution of the binaries. Collisional processes would not play a significant role in the dynamical evolution of Neptune Trojans. After 4.5 × 109 yr of evolution, ˜50 per cent of the synthetic systems end up separated as single objects, most of them with slow diurnal rotation rate. The final orbital distribution of the surviving binary systems is statistically similar to the one found for Kuiper Belt Binaries when collisional evolution is not included in the model. Systems composed by a primary and a small satellite are more fragile than the ones composed by components of similar sizes.

  4. International Conference “Ultraviolet Properties of Evolved Stellar Populations

    CERN Document Server

    Chavez Dagostino, Miguel

    2009-01-01

    This book presents an up-to-date collection of reviews and contributed articles in the field of ultraviolet astronomy. Its content has been mainly motivated by the recent access to the rest frame UV light of distant red galaxies, gained through large optical facilities. This driveway has derived in a renewed interest on the stars that presumably dominate or have important effects on the integrated UV properties of evolved systems of the nearby and faraway Universe. The topics included in this volume extend from the fresh spectroscopic analyses of high redshift early-type galaxies observed with the 8-10m class telescopes to the fundamental outcomes from various satellites, from the long-lived International Ultraviolet Explorer to current facilities, such as the Galaxy Evolution Explorer. This is one of the few volumes published in recent years devoted to UV astronomical research and the only one dedicated to the properties of evolved stellar populations at these wavelengths. This contemporary panorama will be ...

  5. Old stellar populations how to study the fossil record of galaxy formation

    CERN Document Server

    Cassisi, Santi

    2013-01-01

    The book discusses the theoretical path to decoding the information gathered from observations of old stellar systems. It focuses on old stellar systems because these are the fossil record of galaxy formation and provide invaluable information ont he evolution of cosmic structures and the universe as a whole. The aim is to present results obtained in the past few years for theoretical developments in low mass star research and in advances in our knowledge of the evolution of old stellar systems. A particularly representative case is the recent discovery of multiple stellar populations in galac

  6. Connection between Dynamically Derived Initial Mass Function Normalization and Stellar Population Parameters

    NARCIS (Netherlands)

    McDermid, Richard M.; Cappellari, Michele; Alatalo, Katherine; Bayet, Estelle; Blitz, Leo; Bois, Maxime; Bournaud, Frédéric; Bureau, Martin; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS3D project. We study trends between our dynamically derived IMF normalization αdyn ≡

  7. Host galaxy properties of mergers of stellar binary black holes and their implications for advanced LIGO gravitational wave sources

    Science.gov (United States)

    Cao, Liang; Lu, Youjun; Zhao, Yuetong

    2018-03-01

    Understanding the host galaxy properties of stellar binary black hole (SBBH) mergers is important for revealing the origin of the SBBH gravitational wave sources detected by advanced LIGO and helpful for identifying their electromagnetic counterparts. Here, we present a comprehensive analysis of the host galaxy properties of SBBHs by implementing semi-analytical recipes for SBBH formation and merger into cosmological galaxy formation model. If the time delay between SBBH formation and merger ranges from ≲ Gyr to the Hubble time, SBBH mergers at redshift z ≲ 0.3 occur preferentially in big galaxies with stellar mass M* ≳ 2 × 1010 M⊙ and metallicities Z peaking at ˜0.6 Z⊙. However, the host galaxy stellar mass distribution of heavy SBBH mergers (M•• ≳ 50 M⊙) is bimodal with one peak at ˜109 M⊙ and the other peak at ˜2 × 1010 M⊙. The contribution fraction from host galaxies with Z ≲ 0.2 Z⊙ to heavy mergers is much larger than that to less heavy mergers. If SBBHs were formed in the early Universe (e.g. z > 6), their mergers detected at z ≲ 0.3 occur preferentially in even more massive galaxies with M* > 3 × 1010 M⊙ and in galaxies with metallicities mostly ≳ 0.2 Z⊙ and peaking at Z ˜ 0.6 Z⊙, due to later cosmic assembly and enrichment of their host galaxies. SBBH mergers at z ≲ 0.3 mainly occur in spiral galaxies, but the fraction of SBBH mergers that occur in elliptical galaxies can be significant if those SBBHs were formed in the early Universe; and about two-thirds of those mergers occur in the central galaxies of dark matter haloes. We also present results on the host galaxy properties of SBBH mergers at higher redshift.

  8. Stellar Obliquity and Magnetic Activity of Planet-hosting Stars and Eclipsing Binaries Based on Transit Chord Correlation

    Science.gov (United States)

    Dai, Fei; Winn, Joshua N.; Berta-Thompson, Zachory; Sanchis-Ojeda, Roberto; Albrecht, Simon

    2018-04-01

    The light curve of an eclipsing system shows anomalies whenever the eclipsing body passes in front of active regions on the eclipsed star. In some cases, the pattern of anomalies can be used to determine the obliquity Ψ of the eclipsed star. Here we present a method for detecting and analyzing these patterns, based on a statistical test for correlations between the anomalies observed in a sequence of eclipses. Compared to previous methods, ours makes fewer assumptions and is easier to automate. We apply it to a sample of 64 stars with transiting planets and 24 eclipsing binaries for which precise space-based data are available, and for which there was either some indication of flux anomalies or a previously reported obliquity measurement. We were able to determine obliquities for 10 stars with hot Jupiters. In particular we found Ψ ≲ 10° for Kepler-45, which is only the second M dwarf with a measured obliquity. The other eight cases are G and K stars with low obliquities. Among the eclipsing binaries, we were able to determine obliquities in eight cases, all of which are consistent with zero. Our results also reveal some common patterns of stellar activity for magnetically active G and K stars, including persistently active longitudes.

  9. Accurate Masses, Radii, and Temperatures for the Eclipsing Binary V2154 Cyg, and Tests of Stellar Evolution Models

    Science.gov (United States)

    Bright, Jane; Torres, Guillermo

    2018-01-01

    We report new spectroscopic observations of the F-type triple system V2154 Cyg, in which two of the stars form an eclipsing binary with a period of 2.6306303 ± 0.0000038 days. We combine the results from our spectroscopic analysis with published light curves in the uvby Strömgren passbands to derive the first reported absolute dimensions of the stars in the eclipsing binary. The masses and radii are measured with high accuracy to better than 1.5% precision. For the primary and secondary respectively, we find that the masses are 1.269 ± 0.017 M⊙ and 0.7542 ± 0.0059 M⊙, the radii are 1.477 ± 0.012 R⊙ and 0.7232 ± 0.0091R⊙, and the temperatures are 6770 ± 150 K and 5020 ± 150 K. Current models of stellar evolution agree with the measured properties of the primary, but the secondary is larger than predicted. This may be due to activity in the secondary, as has been shown for other systems with a star of similar mass with this same discrepancy.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution. GT acknowledges partial support for this work from NSF grant AST-1509375.

  10. Dynamical evolution of spherical stellar systems

    International Nuclear Information System (INIS)

    Lee, H.M.

    1986-01-01

    The dynamical effect of heavy mass stars formed out of successive mergers among tidally captured binaries of evolution of spherical stellar systems is investigated. To maximize such effect assumed all tidally captured systems become mergers. Stellar evolution is simulated by computing mean age of mass group and applying death rate as function of mean age. For stellar systems with N = 10 5-6 , combined effect of three body binary heating among heavy mass stars and stellar evolution provides energy to drive post collapse expansion; long-term evolution is dominated by stellar evolution. Long-term behavior of clusters is similar to tidally captured binaries assuming no merger. Observed chemical inhomogeneities among stars in globular clusters may also be explained by stellar mergers. Three-body heating is important in small-N systems, while stellar evolution dominates evolution of large N systems. The effect of primordial degenerate stars is investigated in the second study. Very hard binaries composed of degenerate-normal pair form via tidal capture process and moderately hard degenerate-degenerate binaries form via three-body process. If initial degenerate population is large, initial core-collapse phase may be approximated as collapse of degenerate star. Three-body binaries among degenerate stars eventually provide enough energy to stop collapse and cause reexpansion

  11. Cosmic reionization by stellar sources: Population II stars

    Science.gov (United States)

    Sokasian, Aaron; Abel, Tom; Hernquist, Lars; Springel, Volker

    2003-09-01

    comparisons with observational constraints on the neutral fraction of hydrogen at z~ 6 derived from the z= 6.28 Sloan Digital Sky Survey (SDSS) quasar of Becker and coworkers. We find that, given the amplitude and form of the underlying star formation predictions, an escape fraction near fesc= 0.10-0.20 is most consistent with the observational results. In these models, reionization is expected to have occurred between z~ 7-8, although the IGM remains fairly opaque until z~= 6. Our method is also capable of handling the simultaneous reionization of the helium component in the IGM, allowing us to explore the plausibility of the scenario where sources with harder spectra are primarily responsible for reionization. In this case, we find that if the sources responsible for reionizing hydrogen by z~ 8 had spectra similar to active galactic nuclei, then the helium component of the IGM should have been reionized by z~ 6. We find that such an early reionization epoch for helium does not necessarily conflict with observational constraints obtained at z~= 3, but may be challenged by future observations at higher redshifts. The recent WMAP measurements of the electron scattering optical depth (τe= 0.17 +/- 0.04 according to the `model independent' analysis of Kogut et al.) appear to be inconsistent with the relatively late onset of reionization by the normal Population II type stars that we consider. In order to simultaneously match the observations from the z= 6.28 SDSS quasar and the optical depth measurement from WMAP with the sources modelled here, we require a boosting factor for the number of ionizing photons released in the fesc= 0.20 model which evolves from unity at z= 6 to >~50 by z~ 18. Such a steep enhancement in the stellar production rate of ionizing photons would be consistent with an IMF that becomes more and more top heavy with increasing redshift.

  12. A POSSIBLE BINARY SYSTEM OF A STELLAR REMNANT IN THE HIGH-MAGNIFICATION GRAVITATIONAL MICROLENSING EVENT OGLE-2007-BLG-514

    Energy Technology Data Exchange (ETDEWEB)

    Miyake, N.; Abe, F.; Furusawa, K.; Itow, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Udalski, A.; Kubiak, M.; Szymanski, M. K.; Pietrzynski, G.; Soszynski, I.; Ulaczyk, K.; Wyrzykowski, L. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Dong, S.; Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Street, R. A. [Las Cumbres Observatory, 6740B Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Greenhill, J. [School of Maths and Physics, University of Tasmania, Private bag 37, GPO Hobart, Tasmania 7001 (Australia); Bond, I. A. [Institute for Information and Mathematical Sciences, Massey University, Private Bag 102-904, Auckland 1330 (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Okayama 719-0232 (Japan); Holderness, S., E-mail: nmiyake@stelab.nagoya-u.ac.jp [Computer Science Department, University of Auckland, Auckland (New Zealand); Collaboration: OGLE Collaboration; MOA Collaboration; muFUN Collaboration; RoboNet Collaboration; PLANET Collaboration; and others

    2012-06-20

    We report the extremely high-magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 {+-} 0.007 and a projected separation of s = 0.072 {+-} 0.001 in units of the Einstein radius. The parallax parameters allow us to determine the lens distance D{sub L} = 3.11 {+-} 0.39 kpc and total mass M{sub L} = 1.40 {+-} 0.18 M{sub Sun }; this leads to the primary and secondary components having masses of M{sub 1} = 1.06 {+-} 0.13 M{sub Sun} and M{sub 2} = 0.34 {+-} 0.04 M{sub Sun }, respectively. The parallax model indicates that the binary lens system is likely constructed by the main-sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 {+-} 0.005, s = 0.083 {+-} 0.001). The primary component of the binary lens is relatively massive, with M{sub 1} = 0.9{sup +4.6}{sub -0.3} M{sub Sun} and it is at a distance of D{sub L} = 2.6{sup +3.8}{sub -0.9} kpc. Given the secure mass ratio measurement, the companion mass is therefore M{sub 2} = 0.2{sup +1.2}{sub -0.1} M{sub Sun }. The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star, or a black hole.

  13. Integrated Spectral Energy Distributions and Absorption Feature Indices of Single Stellar Populations

    OpenAIRE

    Zhang, Fenghui; Han, Zhanwen; Li, Lifang; Hurley, Jarrod R.

    2004-01-01

    Using evolutionary population synthesis, we present integrated spectral energy distributions and absorption-line indices defined by the Lick Observatory image dissector scanner (referred to as Lick/IDS) system, for an extensive set of instantaneous burst single stellar populations (SSPs). The ages of the SSPs are in the range 1-19 Gyr and the metallicities [Fe/H] are in the range -2.3 - 0.2. Our models use the rapid single stellar evolution algorithm of Hurley, Pols and Tout for the stellar e...

  14. Report on the Workshop Resolved and Unresolved Stellar PopUlaTIoNs (RASPUTIN)

    Science.gov (United States)

    Bono, G.; Valenti, E.

    2014-12-01

    The workshop aimed at sharing and discussing observations and diagnostics, together with models and simulations, of the resolved and unresolved stellar populations in galaxies from the Milky Way to the distant Universe. Special attention was paid to recent results concerning galaxy formation and evolution, fostering the exchange of ideas and techniques in dealing with nearby stellar populations. There will be no published proceedings, but presentations are available for download from the workshop web page (www.eso.org/sci/meetings/2014/rasputin2014).

  15. Studying the Stellar Populations of the Local Group with VLT

    Science.gov (United States)

    Tolstoy, Eline

    The best chance we have to understand star formation and how it proceeds in the Universe is going to come from detailed studies of the numerous different environments found within the Local Group (LG). Present day star formation in our Galaxy occurs exclusively in metal rich environments (Z ˜ Z_⊙), so if we want to study how low metallicity stars form (and thus understand observations of galaxies at high-redshift) we have to look beyond our Galaxy, to the smallest star forming dwarf galaxies, which can have extremely low metallicities (Z ˜ 0.02-0.05Z_⊙). Of course in its entirety a stellar population always contains the complete details of the star formation history of a galaxy, however this information is often hard to disentangle retroactively. We also have much to learn from the Magellanic Clouds (Z ˜ 0.1- 0.3Z_⊙), although because they are undergoing interactions with our Galaxy and each other their evolutionary picture and its general applicability less obvious. In our LG there are also a number of "remnants", or galaxies which which currently do not form stars (e.g. the dSph, such as Carina, Leo I, Ursa Minor, etc..). It is not straight forward to draw parallels between galaxies which are forming stars and those which aren't. This is of course because star formation has such a dramatic impact upon a galaxy, and alternative methods have to be used to make the most basic of comparisons of properties (e.g. metallicity, mass, luminosity evolution). It is necessary to put all the dwarf galaxies into a global picture if we are to draw meaningful conclusions about their star formation properties (e.g. Ferrara & Tolstoy 1999). Many of the small LG galaxies contain direct evidence of complicated star formation histories (e.g. Smecker-Hane et al. 1994; Tolstoy et al. 1998; Gallart et al. 1999), which suggests that star formation patterns can change dramatically over long time scales. This kind of evolutionary behaviour can have a dramatic impact upon the

  16. Age gradients in the stellar populations of massive star forming regions based on a new stellar chronometer

    Energy Technology Data Exchange (ETDEWEB)

    Getman, Konstantin V.; Feigelson, Eric D.; Kuhn, Michael A.; Broos, Patrick S.; Townsley, Leisa K.; Luhman, Kevin L. [Department of Astronomy and Astrophysics, 525 Davey Laboratory, Pennsylvania State University, University Park, PA 16802 (United States); Naylor, Tim [School of Physics and Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL (United Kingdom); Povich, Matthew S. [Department of Physics and Astronomy, California State Polytechnic University, 3801 West Temple Avenue, Pomona, CA 91768 (United States); Garmire, Gordon P. [Huntingdon Institute for X-ray Astronomy, LLC, 10677 Franks Road, Huntingdon, PA 16652 (United States)

    2014-06-01

    A major impediment to understanding star formation in massive star-forming regions (MSFRs) is the absence of a reliable stellar chronometer to unravel their complex star formation histories. We present a new estimation of stellar ages using a new method that employs near-infrared (NIR) and X-ray photometry, Age {sub JX} . Stellar masses are derived from X-ray luminosities using the L{sub X} -M relation from the Taurus cloud. J-band luminosities are compared to mass-dependent pre-main-sequence (PMS) evolutionary models to estimate ages. Age {sub JX} is sensitive to a wide range of evolutionary stages, from disk-bearing stars embedded in a cloud to widely dispersed older PMS stars. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) project characterizes 20 OB-dominated MSFRs using X-ray, mid-infrared, and NIR catalogs. The Age {sub JX} method has been applied to 5525 out of 31,784 MYStIX Probable Complex Members. We provide a homogeneous set of median ages for over 100 subclusters in 15 MSFRs; median subcluster ages range between 0.5 Myr and 5 Myr. The important science result is the discovery of age gradients across MYStIX regions. The wide MSFR age distribution appears as spatially segregated structures with different ages. The Age {sub JX} ages are youngest in obscured locations in molecular clouds, intermediate in revealed stellar clusters, and oldest in distributed populations. The NIR color index J – H, a surrogate measure of extinction, can serve as an approximate age predictor for young embedded clusters.

  17. Constraining the origin of multiple stellar populations in globular clusters with N-body simulations

    Science.gov (United States)

    Mastrobuono-Battisti, A.; Perets, H. B.

    2017-12-01

    Globular Clusters (GCs) are composed by multiple stellar populations whose origin is still unknown. Second population (SP) stars are currently thought to arise from gas ejected by first population (FP) stars, which is then accreted into the primordial GC core. Such gas forms a stellar disk whose long-term evolution and effects on the embedding cluster can be followed by means of N-body simulations. Here, we find that as the SP disk relaxes, the old, first stellar population flattens and develops a significant radial anisotropy, making the GC structure become more elliptical. The second stellar population is characterized by a lower velocity dispersion, and a higher rotational velocity, compared with the primordial population. The strength of these signatures increases with the relaxation time of the cluster and with the mass ratio between the SP and FP mass stars. We conclude that GC ellipticities and rotation constitute fossil records that can be used as observational proxies to unveil the origin of multiple stellar populations.

  18. A CAUTIONARY TALE: MARVELS BROWN DWARF CANDIDATE REVEALS ITSELF TO BE A VERY LONG PERIOD, HIGHLY ECCENTRIC SPECTROSCOPIC STELLAR BINARY

    International Nuclear Information System (INIS)

    Mack, Claude E. III; Stassun, Keivan G.; De Lee, Nathan; Ge, Jian; Fleming, Scott W.; Deshpande, Rohit; Mahadevan, Suvrath; Wisniewski, John P.; Gaudi, B. Scott; Eastman, Jason; Beatty, Thomas G.; Ghezzi, Luan; González Hernández, Jonay I.; Femenía, Bruno; Mata Sánchez, Daniel; Ferreira, Letícia; Porto de Mello, Gustavo; Crepp, Justin R.; Agol, Eric; Bizyaev, Dmitry

    2013-01-01

    We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R ∼ Jup ) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e ∼ 0.8), its relatively long period (P ∼ 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (ω ∼ 189°). As a result of these properties, for ∼95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e ∼ 0.3). Only during the ∼5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of ∼15 km s –1 reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.

  19. THE LOW-MASS STELLAR POPULATION IN L1641: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF THE STELLAR INITIAL MASS FUNCTION

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Wen-Hsin; Hartmann, Lee [Department of Astronomy, University of Michigan, 500 Church St., Ann Arbor, MI 48109 (United States); Allen, Lori [National Optical Astronomy Observatory, 950 North Cherry Ave., Tucson, AZ 85719 (United States); Hernandez, Jesus [Centro de Investigaciones de Astronomia, Apdo. Postal 264, Merida 5101-A (Venezuela, Bolivarian Republic of); Megeath, S. T. [Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Mosby, Gregory [Department of Astronomy, University of Wisconsin-Madison, 475 N. Charter Street, Madison, WI 53706 (United States); Tobin, John J. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Espaillat, Catherine [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States)

    2012-06-10

    We present results from an optical photometric and spectroscopic survey of the young stellar population in L1641, the low-density star-forming region of the Orion A cloud south of the Orion Nebula Cluster (ONC). Our goal is to determine whether L1641 has a large enough low-mass population to make the known lack of high-mass stars a statistically significant demonstration of environmental dependence of the upper mass stellar initial mass function (IMF). Our spectroscopic sample consists of IR-excess objects selected from the Spitzer/IRAC survey and non-excess objects selected from optical photometry. We have spectral confirmation of 864 members, with another 98 probable members; of the confirmed members, 406 have infrared excesses and 458 do not. Assuming the same ratio of stars with and without IR excesses in the highly extincted regions, L1641 may contain as many as {approx}1600 stars down to {approx}0.1 M{sub Sun }, comparable within a factor of two to the ONC. Compared to the standard models of the IMF, L1641 is deficient in O and early B stars to a 3{sigma}-4{sigma} significance level, assuming that we know of all the massive stars in L1641. With a forthcoming survey of the intermediate-mass stars, we will be in a better position to make a direct comparison with the neighboring, dense ONC, which should yield a stronger test of the dependence of the high-mass end of the stellar IMF on environment.

  20. CENTRAL DARK MATTER TRENDS IN EARLY-TYPE GALAXIES FROM STRONG LENSING, DYNAMICS, AND STELLAR POPULATIONS

    International Nuclear Information System (INIS)

    Tortora, C.; Jetzer, P.; Napolitano, N. R.; Romanowsky, A. J.

    2010-01-01

    We analyze the correlations between central dark matter (DM) content of early-type galaxies and their sizes and ages, using a sample of intermediate-redshift (z ∼ 0.2) gravitational lenses from the SLACS survey, and by comparing them to a larger sample of z ∼ 0 galaxies. We decompose the deprojected galaxy masses into DM and stellar components using combinations of strong lensing, stellar dynamics, and stellar populations modeling. For a given stellar mass, we find that for galaxies with larger sizes, the DM fraction increases and the mean DM density decreases, consistently with the cuspy halos expected in cosmological formation scenarios. The DM fraction also decreases with stellar age, which can be partially explained by the inverse correlation between size and age. The residual trend may point to systematic dependencies on formation epoch of halo contraction or stellar initial mass functions. These results are in agreement with recent findings based on local galaxies by Napolitano et al. and suggest negligible evidence of galaxy evolution over the last ∼2.5 Gyr other than passive stellar aging.

  1. DYNAMICAL EVIDENCE FOR A MAGNETOCENTRIFUGAL WIND FROM A 20 M{sub Sun} BINARY YOUNG STELLAR OBJECT

    Energy Technology Data Exchange (ETDEWEB)

    Greenhill, L. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Goddi, C.; Humphreys, E. M. L. [Joint Institute for VLBI in Europe, Postbus 2 7990 AA, Dwingeloo (Netherlands); Chandler, C. J. [NRAO, P.O. Box O, Socorro, NM 87801 (United States); Matthews, L. D., E-mail: greenhill@cfa.harvard.edu [MIT Haystack Observatory, Off Route 40, Westford, MA 01886 (United States)

    2013-06-20

    In Orion BN/KL, proper motions of {lambda}7 mm vibrationally excited SiO masers trace the rotation of a nearly edge-on disk and a bipolar wide-angle outflow 10-100 AU from radio source I, a binary young stellar object of {approx}20 M{sub Sun }. Here we map ground-state {lambda}7 mm SiO emission with the Very Large Array and track proper motions over 9 yr. The innermost and strongest emission lies in two extended arcs bracketing Source I. The proper motions trace a northeast-southwest bipolar outflow 100-1000 AU from Source I with a median three-dimensional motion of {approx}18 km s{sup -1}. An overlying distribution of {lambda}1.3 cm H{sub 2}O masers betrays similar flow characteristics. Gas dynamics and emission morphology traced by the masers suggest the presence of a magnetocentrifugal disk wind. Reinforcing evidence lies in the colinearity of the flow, apparent rotation across the flow parallel to the disk rotation, and recollimation that narrows the flow opening angle {approx}120 AU downstream. The arcs of ground-state SiO emission may mark the transition point to a shocked super-Alfvenic outflow.

  2. Virgo cluster and field dwarf ellipticals in 3D - III. Spatially and temporally resolved stellar populations

    NARCIS (Netherlands)

    Ryś, Agnieszka; Koleva, Mina; Falcón-Barroso, Jesús; Vazdekis, Alexandre; Lisker, Thorsten; Peletier, Reynier; van de Ven, Glenn

    2015-01-01

    We present the stellar population analysis of a sample of 12 dwarf elliptical galaxies, observed with the SAURON integral field unit, using the full-spectrum fitting method. We show that star formation histories (SFHs) resolved into two populations can be recovered even within a limited wavelength

  3. CONNECTION BETWEEN DYNAMICALLY DERIVED INITIAL MASS FUNCTION NORMALIZATION AND STELLAR POPULATION PARAMETERS

    Energy Technology Data Exchange (ETDEWEB)

    McDermid, Richard M. [Department of Physics and Astronomy, Macquarie University, Sydney NSW 2109 (Australia); Cappellari, Michele; Bayet, Estelle; Bureau, Martin; Davies, Roger L. [Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Alatalo, Katherine [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Blitz, Leo [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Bois, Maxime [Observatoire de Paris, LERMA and CNRS, 61 Av. de l' Observatoire, F-75014 Paris (France); Bournaud, Frédéric; Duc, Pierre-Alain [Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp- CNRS-Université Paris Diderot, F-91191 Gif-sur-Yvette Cedex (France); Crocker, Alison F. [Ritter Astrophysical Observatory, University of Toledo, Toledo, OH 43606 (United States); Davis, Timothy A.; De Zeeuw, P. T.; Emsellem, Eric; Kuntschner, Harald [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany); Khochfar, Sadegh [Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Krajnović, Davor [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Morganti, Raffaella; Oosterloo, Tom [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Naab, Thorsten, E-mail: richard.mcdermid@mq.edu.au [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); and others

    2014-09-10

    We report on empirical trends between the dynamically determined stellar initial mass function (IMF) and stellar population properties for a complete, volume-limited sample of 260 early-type galaxies from the ATLAS{sup 3D} project. We study trends between our dynamically derived IMF normalization α{sub dyn} ≡ (M/L){sub stars}/(M/L){sub Salp} and absorption line strengths, and interpret these via single stellar population-equivalent ages, abundance ratios (measured as [α/Fe]), and total metallicity, [Z/H]. We find that old and alpha-enhanced galaxies tend to have on average heavier (Salpeter-like) mass normalization of the IMF, but stellar population does not appear to be a good predictor of the IMF, with a large range of α{sub dyn} at a given population parameter. As a result, we find weak α{sub dyn}-[α/Fe] and α{sub dyn} –Age correlations and no significant α{sub dyn} –[Z/H] correlation. The observed trends appear significantly weaker than those reported in studies that measure the IMF normalization via the low-mass star demographics inferred through stellar spectral analysis.

  4. The BANANA Project. IV. Two Aligned Stellar Rotation Axes in the Young Eccentric Binary System EP Crucis: Primordial Orientation and Tidal Alignment

    Science.gov (United States)

    Albrecht, Simon; Setiawan, Johny; Torres, Guillermo; Fabrycky, Daniel C.; Winn, Joshua N.

    2013-04-01

    With observations of the EP Cru system, we continue our series of measurements of spin-orbit angles in eclipsing binary star systems, the BANANA project (Binaries Are Not Always Neatly Aligned). We find a close alignment between the sky projections of the rotational and orbital angular momentum vectors for both stars (βp = -1.°8 ± 1.°6 and |βs| < 17°). We also derive precise absolute dimensions and stellar ages for this system. The EP Cru and DI Her systems provide an interesting comparison: they have similar stellar types and orbital properties, but DI Her is younger and has major spin-orbit misalignments, raising the question of whether EP Cru also had a large misalignment at an earlier phase of evolution. We show that tidal dissipation is an unlikely explanation for the good alignment observed today, because realignment happens on the same timescale as spin-orbit synchronization, and the stars in EP Cru are far from synchronization (they are spinning nine times too quickly). Therefore it seems that some binaries form with aligned axes, while other superficially similar binaries are formed with misaligned axes. Based on observations made with ESOs 2.2 m Telescopes at the La Silla Paranal Observatory under program ID 084.C-1008 (12.5%) and under MPIA guaranteed time (87.5%).

  5. THE STELLAR POPULATION AND STAR FORMATION PROPERTIES OF BLUE COMPACT DWARF GALAXIES

    International Nuclear Information System (INIS)

    Zhao Yinghe; Gao Yu; Gu Qiusheng

    2011-01-01

    We study stellar populations, star formation histories (SFHs), and star formation properties for a sample of blue compact dwarf galaxies (BCDs) selected by cross-correlating the Gil de Paz et al. sample with the Sloan Digital Sky Survey Data Release 6. The sample includes 31 BCDs, which span a large range of galactic parameters. Using a stellar population synthesis method, we derive stellar populations and reconstruct SFHs for these BCDs. Our studies confirm that BCDs are not young systems experiencing their first star formation, but old systems undergoing a starburst activity. The stellar mass-weighted ages can be up to 10 Gyr, while the luminosity-weighted ages might be up to approximately three orders of magnitude younger (∼10 Myr) for most galaxies. Based on multiwavelength data, we also study the integrated star formation properties. The star formation rate (SFR) for our sample galaxies spans nearly three orders of magnitude, from a few 10 -3 to ∼1 M sun yr -1 , with a median value of ∼0.1 M sun yr -1 . We find that about 90% of BCDs in our sample have their birthrate parameter (the ratio of the current SFR to the averaged past SFR) b>2-3. We further discuss correlations of the current SFR with the integrated galactic stellar mass and explore the connection between SFR and metallicity.

  6. Hierarchical Bayesian inference of the initial mass function in composite stellar populations

    Science.gov (United States)

    Dries, M.; Trager, S. C.; Koopmans, L. V. E.; Popping, G.; Somerville, R. S.

    2018-03-01

    The initial mass function (IMF) is a key ingredient in many studies of galaxy formation and evolution. Although the IMF is often assumed to be universal, there is continuing evidence that it is not universal. Spectroscopic studies that derive the IMF of the unresolved stellar populations of a galaxy often assume that this spectrum can be described by a single stellar population (SSP). To alleviate these limitations, in this paper we have developed a unique hierarchical Bayesian framework for modelling composite stellar populations (CSPs). Within this framework, we use a parametrized IMF prior to regulate a direct inference of the IMF. We use this new framework to determine the number of SSPs that is required to fit a set of realistic CSP mock spectra. The CSP mock spectra that we use are based on semi-analytic models and have an IMF that varies as a function of stellar velocity dispersion of the galaxy. Our results suggest that using a single SSP biases the determination of the IMF slope to a higher value than the true slope, although the trend with stellar velocity dispersion is overall recovered. If we include more SSPs in the fit, the Bayesian evidence increases significantly and the inferred IMF slopes of our mock spectra converge, within the errors, to their true values. Most of the bias is already removed by using two SSPs instead of one. We show that we can reconstruct the variable IMF of our mock spectra for signal-to-noise ratios exceeding ˜75.

  7. PROBING THE X-RAY BINARY POPULATIONS OF THE RING GALAXY NGC 1291

    International Nuclear Information System (INIS)

    Luo, B.; Fabbiano, G.; Fragos, T.; Kim, D.-W.; Wang Junfeng; Belczynski, K.; Brassington, N. J.; Pellegrini, S.; Tzanavaris, P.; Zezas, A.

    2012-01-01

    We present Chandra studies of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. We detect 169 X-ray point sources in the galaxy, 75 in the bulge and 71 in the ring, utilizing the four available Chandra observations totaling an effective exposure of 179 ks. We report photometric properties of these sources in a point-source catalog. There are ≈40% of the bulge sources and ≈25% of the ring sources showing >3σ long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (≈75%) and ring (≈65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity active galactic nucleus (AGN) with moderate obscuration; spectral variability is observed between individual observations. We construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. We reach 90% completeness limits of ≈1.5 × 10 37 and ≈2.2 × 10 37 erg s –1 for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. We perform detailed population synthesis modeling of the XRB populations in NGC 1291, which suggests that the observed combined XLF is dominated by an old LMXB population. We compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative overdensity of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

  8. THE BIRTH OF A GALAXY: PRIMORDIAL METAL ENRICHMENT AND STELLAR POPULATIONS

    International Nuclear Information System (INIS)

    Wise, John H.; Turk, Matthew J.; Norman, Michael L.; Abel, Tom

    2012-01-01

    By definition, Population III stars are metal-free, and their protostellar collapse is driven by molecular hydrogen cooling in the gas phase, leading to large characteristic masses. Population II stars with lower characteristic masses form when the star-forming gas reaches a critical metallicity of 10 –6 -10 –3.5 Z ☉ . We present an adaptive mesh refinement radiation hydrodynamics simulation that follows the transition from Population III to Population II star formation. The maximum spatial resolution of 1 comoving parsec allows for individual molecular clouds to be well resolved and their stellar associations to be studied in detail. We model stellar radiative feedback with adaptive ray tracing. A top-heavy initial mass function for the Population III stars is considered, resulting in a plausible distribution of pair-instability supernovae and associated metal enrichment. We find that the gas fraction recovers from 5% to nearly the cosmic fraction in halos with merger histories rich in halos above 10 7 M ☉ . A single pair-instability supernova is sufficient to enrich the host halo to a metallicity floor of 10 –3 Z ☉ and to transition to Population II star formation. This provides a natural explanation for the observed floor on damped Lyα systems metallicities reported in the literature, which is of this order. We find that stellar metallicities do not necessarily trace stellar ages, as mergers of halos with established stellar populations can create superpositions of t–Z evolutionary tracks. A bimodal metallicity distribution is created after a starburst occurs when the halo can cool efficiently through atomic line cooling.

  9. The Resolved Stellar Populations in the LEGUS Galaxies1

    Science.gov (United States)

    Sabbi, E.; Calzetti, D.; Ubeda, L.; Adamo, A.; Cignoni, M.; Thilker, D.; Aloisi, A.; Elmegreen, B. G.; Elmegreen, D. M.; Gouliermis, D. A.; Grebel, E. K.; Messa, M.; Smith, L. J.; Tosi, M.; Dolphin, A.; Andrews, J. E.; Ashworth, G.; Bright, S. N.; Brown, T. M.; Chandar, R.; Christian, C.; Clayton, G. C.; Cook, D. O.; Dale, D. A.; de Mink, S. E.; Dobbs, C.; Evans, A. S.; Fumagalli, M.; Gallagher, J. S., III; Grasha, K.; Herrero, A.; Hunter, D. A.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Kim, H.; Krumholz, M. R.; Lee, J. C.; Lennon, D.; Martin, C.; Nair, P.; Nota, A.; Östlin, G.; Pellerin, A.; Prieto, J.; Regan, M. W.; Ryon, J. E.; Sacchi, E.; Schaerer, D.; Schiminovich, D.; Shabani, F.; Van Dyk, S. D.; Walterbos, R.; Whitmore, B. C.; Wofford, A.

    2018-03-01

    The Legacy ExtraGalactic UV Survey (LEGUS) is a multiwavelength Cycle 21 Treasury program on the Hubble Space Telescope. It studied 50 nearby star-forming galaxies in 5 bands from the near-UV to the I-band, combining new Wide Field Camera 3 observations with archival Advanced Camera for Surveys data. LEGUS was designed to investigate how star formation occurs and develops on both small and large scales, and how it relates to the galactic environments. In this paper we present the photometric catalogs for all the apparently single stars identified in the 50 LEGUS galaxies. Photometric catalogs and mosaicked images for all filters are available for download. We present optical and near-UV color–magnitude diagrams for all the galaxies. For each galaxy we derived the distance from the tip of the red giant branch. We then used the NUV color–magnitude diagrams to identify stars more massive than 14 M ⊙, and compared their number with the number of massive stars expected from the GALEX FUV luminosity. Our analysis shows that the fraction of massive stars forming in star clusters and stellar associations is about constant with the star formation rate. This lack of a relation suggests that the timescale for evaporation of unbound structures is comparable or longer than 10 Myr. At low star formation rates this translates to an excess of mass in clustered environments as compared to model predictions of cluster evolution, suggesting that a significant fraction of stars form in unbound systems. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555.

  10. Morphologies and stellar populations of galaxies in the core of Abell 2218

    NARCIS (Netherlands)

    Sánchez, S. F.; Cardiel, N.; Verheijen, M. A. W.; Pedraz, S.; Covone, G.

    2007-01-01

    We present a study of the stellar populations and morphologies of galaxies in the core of the galaxy cluster Abell 2218. Integral field spectroscopy (IFS) observations were performed using PMAS in the PPAK mode covering a field of view of similar to 74 x 64 arcsec(2) centred on the core of the

  11. Measuring the accreting stellar and intermediate mass black hole populations in the Galaxy and Local Group

    NARCIS (Netherlands)

    Grindlay, J.; Barret, D.; Belloni, T.; Corbel, S.; Kaaret, P.; Allen, B.; Bazzano, A.; Berger, E.; Bignami, G.; Caraveo, P.; De Luca, A.; Fabbiano, P.; Finger, M.; Feroci, M.; Hong, J.; Jernigan, G.; van der Klis, M.; Kouveliotou, C.; Kutyrev, A.; Loeb, A.; Paizis, A.; Pareschi, G.; Skinner, G.; Di Stefano, R.; Ubertini, P.; Wilson-Hodge, C.A.

    2010-01-01

    The population of stellar black holes (SBHs) in the Galaxy and galaxies generally is poorly known in both number and distribution. SBHs are the fossil record of the massive stars in galaxy evolution and may have produced some (if not all) of the intermediate mass (≳100M⊙) black holes (IMBHs) and, in

  12. Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST /MIRI

    Energy Technology Data Exchange (ETDEWEB)

    Jones, Olivia C.; Meixner, Margaret [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218 (United States); Justtanont, Kay [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92 Onsala (Sweden); Glasse, Alistair [UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

    2017-05-20

    The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope ( JWST ) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer -IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)–Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the JWST /MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.

  13. Hot stars in old stellar populations : a continuing need for intermediate ages

    NARCIS (Netherlands)

    Trager, SC; Worthey, G; Faber, SM; Dressler, A

    2005-01-01

    We investigate the effect of a low-level contamination of hot, old, metal-poor starlight on the inferred stellar populations of early-type galaxies in the core of the Coma Cluster. We find that the required correction to the Balmer and metal absorption-line strengths for old, metal-poor stars does

  14. Galaxy and Mass Assembly (GAMA): probing the merger histories of massive galaxies via stellar populations

    NARCIS (Netherlands)

    Ferreras, I.; Hopkins, A. M.; Gunawardhana, M. L. P.; Sansom, A. E.; Owers, M. S.; Driver, S.; Davies, L.; Robotham, A.; Taylor, E. N.; Konstantopoulos, I.; Brough, S.; Norberg, P.; Croom, S.; Loveday, J.; Wang, L.; Bremer, M.

    2017-01-01

    The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand

  15. Stellar Populations of Highly Magnified Lensed Galaxies Young Starburst at Z to Approximately 2

    Science.gov (United States)

    Wuyts, Eva; Rigby, Jane R.; Gladders, Michael D.; Gilbank, David G.; Sharon, Keren; Gralla, Megan B.; Bayliss, Matthew B.

    2011-01-01

    We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature: RCSGA 032727-132609 at z = 170, MS1512-cB58 at z = 2.73, SGAS J152745.1+065219 at z = 2.76 and SGAS J12265L3+215220 at z = 2.92. This includes new Spitzer imaging for RCSGA0327 as well as new spectra, near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226. Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions. We compare star formation rates as measured from the SED fit, the Ha and [O II] .(lambda)3727 emission lines, and the UV+IR bolometric luminosity where 24micron photometry is available. The SFR estimate from the SED fit is consistently higher than the other indicators, which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z approx. 2. Our analysis finds similar stellar population parameters for all four lensed galaxies: stellar masses 3 - 7 x 10(exp 9) Stellar mass, young ages approx. 100 Myr, little dust content E(B - V)=0.10-0.25, and star formation rates around 20- 100 Stellar mass/y. Compared to typical values for the galaxy population at z approx. 2, this suggests we are looking at newly formed, starbursting systems that have only recently started the build-up of stellar mass. These results constitute the first detailed, uniform analysis of a sample of the growing number of strongly lensed galaxies known at z approx. 2. Subject headings: galaxies: high-redshift, strong gravitational lensing, infrared: galaxies

  16. The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

    NARCIS (Netherlands)

    McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive

  17. PHAT+MaNGA: Using resolved stellar populations to improve the recovery of star formation histories from galaxy spectra

    Science.gov (United States)

    Byler, Nell

    2017-08-01

    Stellar Population Synthesis (SPS) models are routinely used to interpret extragalactic observations at all redshifts. Currently, the dominant source of uncertainty in SPS modeling lies in the degeneracies associated with synthesizing and fitting complex stellar populations to observed galaxy spectra. To remedy this, we propose an empirical calibration of SPS models using resolved stellar population observations from Hubble Space Telescope (HST) to constrain the stellar masses, ages, and star formation histories (SFHs) in regions matched to 2D spectroscopic observations from MaNGA. We will take advantage of the state of the art observations from the Panchromatic Hubble Andromeda Treasury (PHAT), which maps the dust content, history of chemical enrichment, and history of star formation across the disk of M31 in exquisite detail. Recently, we have coupled these observations with an unprecedented, spatially-resolved suite of IFU observations from MaNGA. With these two comprehensive data sets we can use the true underlying stellar properties from PHAT to properly interpret the aperture-matched integrated spectra from MaNGA. Our MaNGA observations target 20 regions within the PHAT footprint that fully sample the available range in metallicity, SFR, dust content, and stellar density. This transformative dataset will establish a comprehensive link between resolved stellar populations and the inferred properties of unresolved stellar populations across astrophysically important environments. The net data product will be a library of galaxy spectra matched to the true underlying stellar properties, a comparison set that has lasting legacy value for the extragalactic community.

  18. BINARY CANDIDATES IN THE JOVIAN TROJAN AND HILDA POPULATIONS FROM NEOWISE LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Sonnett, S.; Mainzer, A.; Masiero, J.; Bauer, J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Grav, T., E-mail: Sarah.Sonnett@jpl.nasa.gov [Planetary Science Institute, Tucson, AZ (United States)

    2015-02-01

    Determining the binary fraction for a population of asteroids, particularly as a function of separation between the two components, helps describe the dynamical environment at the time the binaries formed, which in turn offers constraints on the dynamical evolution of the solar system. We searched the NEOWISE archival data set for close and contact binary Trojans and Hildas via their diagnostically large light curve amplitudes. We present 48 out of 554 Hilda and 34 out of 953 Trojan binary candidates in need of follow-up to confirm their large light curve amplitudes and subsequently constrain the binary orbit and component sizes. From these candidates, we calculate a preliminary estimate of the binary fraction without confirmation or debiasing of 14%-23% for Trojans larger than ∼12 km and 30%-51% for Hildas larger than ∼4 km. Once the binary candidates have been confirmed, it should be possible to infer the underlying, debiased binary fraction through estimation of survey biases.

  19. ON THE INCORPORATION OF METALLICITY DATA INTO MEASUREMENTS OF STAR FORMATION HISTORY FROM RESOLVED STELLAR POPULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Dolphin, Andrew E., E-mail: adolphin@raytheon.com [Raytheon Company, Tucson, AZ 85734 (United States)

    2016-07-10

    The combination of spectroscopic stellar metallicities and resolved star color–magnitude diagrams (CMDs) has the potential to constrain the entire star formation history (SFH) of a galaxy better than fitting CMDs alone (as is most common in SFH studies using resolved stellar populations). In this paper, two approaches to incorporating external metallicity information into CMD-fitting techniques are presented. Overall, the joint fitting of metallicity and CMD information can increase the precision of measured age–metallicity relationships (AMRs) and star formation rates by 10% over CMD fitting alone. However, systematics in stellar isochrones and mismatches between spectroscopic and photometric determinations of metallicity can reduce the accuracy of the recovered SFHs. I present a simple mitigation of these systematics that can reduce their amplitude to the level obtained from CMD fitting alone, while ensuring that the AMR is consistent with spectroscopic metallicities. As is the case in CMD-fitting analysis, improved stellar models and calibrations between spectroscopic and photometric metallicities are currently the primary impediment to gains in SFH precision from jointly fitting stellar metallicities and CMDs.

  20. ON THE INCORPORATION OF METALLICITY DATA INTO MEASUREMENTS OF STAR FORMATION HISTORY FROM RESOLVED STELLAR POPULATIONS

    International Nuclear Information System (INIS)

    Dolphin, Andrew E.

    2016-01-01

    The combination of spectroscopic stellar metallicities and resolved star color–magnitude diagrams (CMDs) has the potential to constrain the entire star formation history (SFH) of a galaxy better than fitting CMDs alone (as is most common in SFH studies using resolved stellar populations). In this paper, two approaches to incorporating external metallicity information into CMD-fitting techniques are presented. Overall, the joint fitting of metallicity and CMD information can increase the precision of measured age–metallicity relationships (AMRs) and star formation rates by 10% over CMD fitting alone. However, systematics in stellar isochrones and mismatches between spectroscopic and photometric determinations of metallicity can reduce the accuracy of the recovered SFHs. I present a simple mitigation of these systematics that can reduce their amplitude to the level obtained from CMD fitting alone, while ensuring that the AMR is consistent with spectroscopic metallicities. As is the case in CMD-fitting analysis, improved stellar models and calibrations between spectroscopic and photometric metallicities are currently the primary impediment to gains in SFH precision from jointly fitting stellar metallicities and CMDs.

  1. Comparison of stellar population model predictions using optical and infrared spectroscopy

    Science.gov (United States)

    Baldwin, C.; McDermid, R. M.; Kuntschner, H.; Maraston, C.; Conroy, C.

    2018-02-01

    We present Gemini/GNIRS cross-dispersed near-infrared spectra of 12 nearby early-type galaxies, with the aim of testing commonly used stellar population synthesis models. We select a subset of galaxies from the ATLAS3D sample which span a wide range of ages (single stellar population equivalent ages of 1-15 Gyr) at approximately solar metallicity. We derive star formation histories using four different stellar population synthesis models, namely those of Bruzual & Charlot, Conroy, Gunn & White, Maraston & Strömbäck and Vazdekis et al. We compare star formation histories derived from near-infrared spectra with those derived from optical spectra using the same models. We find that while all models agree in the optical, the derived star formation histories vary dramatically from model to model in the near-infrared. We find that this variation is largely driven by the choice of stellar spectral library, such that models including high-quality spectral libraries provide the best fits to the data, and are the most self-consistent when comparing optically derived properties with near-infrared ones. We also find the impact of age variation in the near-infrared to be subtle, and largely encoded in the shape of the continuum, meaning that the common approach of removing continuum information with a high-order polynomial greatly reduces our ability to constrain ages in the near-infrared.

  2. Galaxy and Mass Assembly (GAMA): probing the merger histories of massive galaxies via stellar populations

    Science.gov (United States)

    Ferreras, I.; Hopkins, A. M.; Gunawardhana, M. L. P.; Sansom, A. E.; Owers, M. S.; Driver, S.; Davies, L.; Robotham, A.; Taylor, E. N.; Konstantopoulos, I.; Brough, S.; Norberg, P.; Croom, S.; Loveday, J.; Wang, L.; Bremer, M.

    2017-06-01

    The merging history of galaxies can be traced with studies of dynamically close pairs. These consist of a massive primary galaxy and a less massive secondary (or satellite) galaxy. The study of the stellar populations of secondary (lower mass) galaxies in close pairs provides a way to understand galaxy growth by mergers. Here we focus on systems involving at least one massive galaxy - with stellar mass above 1011M⊙ in the highly complete Galaxy and Mass Assembly (GAMA) survey. Our working sample comprises 2692 satellite galaxy spectra (0.1 ≤ z ≤ 0.3). These spectra are combined into high S/N stacks, and binned according to both an 'internal' parameter, the stellar mass of the satellite galaxy (I.e. the secondary), and an 'external' parameter, selecting either the mass of the primary in the pair, or the mass of the corresponding dark matter halo. We find significant variations in the age of the populations with respect to environment. At fixed mass, satellites around the most massive galaxies are older and possibly more metal-rich, with age differences ˜1-2 Gyr within the subset of lower mass satellites (˜1010 M⊙). These variations are similar when stacking with respect to the halo mass of the group where the pair is embedded. The population trends in the lower mass satellites are consistent with the old stellar ages found in the outer regions of massive galaxies.

  3. Resolving stellar populations with crowded field 3D spectroscopy

    Science.gov (United States)

    Kamann, S.; Wisotzki, L.; Roth, M. M.

    2013-01-01

    We describe a new method of extracting the spectra of stars from observations of crowded stellar fields with integral field spectroscopy (IFS). Our approach extends the well-established concept of crowded field photometry in images into the domain of 3-dimensional spectroscopic datacubes. The main features of our algorithm follow. (1) We assume that a high-fidelity input source catalogue already exists, e.g. from HST data, and that it is not needed to perform sophisticated source detection in the IFS data. (2) Source positions and properties of the point spread function (PSF) vary smoothly between spectral layers of the datacube, and these variations can be described by simple fitting functions. (3) The shape of the PSF can be adequately described by an analytical function. Even without isolated PSF calibrator stars we can therefore estimate the PSF by a model fit to the full ensemble of stars visible within the field of view. (4) By using sparse matrices to describe the sources, the problem of extracting the spectra of many stars simultaneously becomes computationally tractable. We present extensive performance and validation tests of our algorithm using realistic simulated datacubes that closely reproduce actual IFS observations of the central regions of Galactic globular clusters. We investigate the quality of the extracted spectra under the effects of crowding with respect to the resulting signal-to-noise ratios (S/N) and any possible changes in the continuum level, as well as with respect to absorption line spectral parameters, radial velocities, and equivalent widths. The main effect of blending between two nearby stars is a decrease in the S/N in their spectra. The effect increases with the crowding in the field in a way that the maximum number of stars with useful spectra is always ~0.2 per spatial resolution element. This balance breaks down when exceeding a total source density of one significantly detected star per resolution element. We also explore the

  4. Chemical abundances in LMC stellar populations. II. The bar sample

    Science.gov (United States)

    Van der Swaelmen, M.; Hill, V.; Primas, F.; Cole, A. A.

    2013-12-01

    Aims: This paper compares the chemical evolution of the Large Magellanic Cloud (LMC) to that of the Milky Way (MW) and investigates the relation between the bar and the inner disc of the LMC in the context of the formation of the bar. Methods: We obtained high-resolution and mid signal-to-noise ratio spectra with FLAMES/GIRAFFE at ESO/VLT and performed a detailed chemical analysis of 106 and 58 LMC field red giant stars (mostly older than 1 Gyr), located in the bar and the disc of the LMC respectively. To validate our stellar parameter determinations and abundance measurement procedures, we performed thorough tests using the well-known mildly metal-poor Milky-Way thick disc giant Arcturus (HD 124897, α Boo). We measured elemental abundances for O, Mg, Si, Ca, Ti (α-elements), Na (light odd element), Sc, V, Cr, Co, Ni, Cu (iron-peak elements), Y, Zr, Ba, La, and Eu (s- and r-elements). Results: We find that the α-element ratios [Mg/Fe] and [O/Fe] are lower in the LMC than in the MW while the LMC has similar [Si/Fe], [Ca/Fe], and [Ti/Fe] to the MW. As for the heavy elements, [Ba,La/Eu] exhibit a strong increase with increasing metallicity starting from [Fe/H] ≈ -0.8 dex, and the LMC has lower [Y + Zr/Ba + La] ratios than the MW. Cu is almost constant over all metallicities and about 0.5 dex lower in the LMC than in the MW. The LMC bar and inner disc exhibit differences in their [α/ Fe] (slightly larger scatter for the bar in the metallicity range [-1, -0.5]), their Eu (the bar trend is above the disc trend for [Fe/H] ≥ -0.5 dex), their Y and Zr, their Na and their V (offset between the bar and the disc distributions). Conclusions: Our results show that the chemical history of the LMC experienced a strong contribution from type Ia supernovae as well as a strong s-process enrichment from metal-poor AGB winds. Massive stars made a smaller contribution to the chemical enrichment compared to the MW. The observed differences between the bar and the disc speak in

  5. Old Stellar Populations of The VGS Void Galaxies

    NARCIS (Netherlands)

    Beygu, Burcu; Jarrett, Thomas; Jarrett, Tom; van de Weygaert, Rien; Kreckel, Kathryn; van der Hulst, Thijs; van Gorkom, Jacqueline

    Cosmic voids form an essential ingredient of the Cosmic Web and may harbour a systematically different population of galaxies. Largely unaffected by the complex processes modifying galaxies in high-density environments, the pristine and isolated void regions must hold important clues to the

  6. The Brightest Binaries

    Science.gov (United States)

    Vanbeveren, D., Van Rensbergen, W., De Loore, C.

    Massive stars are distributed all over the upper part of the Hertzsprung-Russell diagram according to their subsequent phases of stellar evolution from main sequence to supernova. Massive stars may either be single or they may be a component of a close binary. The observed single star/binary frequency is known only in a small part of the Galaxy. Whether this holds for the whole galaxy or for the whole cosmos is questionable and needs many more high quality observations. Massive star evolution depends critically on mass loss by stellar wind and this stellar wind mass loss may change dramatically when stars evolve from one phase to another. We start the book with a critical discussion of observations of the different types of massive stars, observations that are of fundamental importance in relation to stellar evolution, with special emphasis on mass loss by stellar wind. We update our knowledge of the physics that models the structure and evolution of massive single stars and we present new calculations. The conclusions resulting from a comparison between these calculations and observations are then used to study the evolution of massive binaries. This book provides our current knowledge of a great variety of massive binaries, and hence of a great variety of evolutionary phases. A large number of case studies illustrates the existence of these phases. Finally, we present the results of massive star population number synthesis, including the effect of binaries. The results indicate that neglecting them leads to a conclusion which may be far from reality. This book is written for researchers in massive star evolution. We hope that, after reading this book, university-level astrophysics students will become fascinated by the exciting world of the `Brightest Binaries'.

  7. Resolving the age bimodality of galaxy stellar populations on kpc scales

    Science.gov (United States)

    Zibetti, Stefano; Gallazzi, Anna R.; Ascasibar, Y.; Charlot, S.; Galbany, L.; García Benito, R.; Kehrig, C.; de Lorenzo-Cáceres, A.; Lyubenova, M.; Marino, R. A.; Márquez, I.; Sánchez, S. F.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.

    2017-06-01

    Galaxies in the local Universe are known to follow bimodal distributions in the global stellar population properties. We analyse the distribution of the local average stellar population ages of 654 053 sub-galactic regions resolved on ˜1 kpc scales in a volume-corrected sample of 394 galaxies, drawn from the Calar Alto Legacy Integral Field Area (CALIFA) DR3 integral-field-spectroscopy survey and complemented by Sloan Digital Sky Survey (SDSS) imaging. We find a bimodal local-age distribution, with an old and a young peak primarily due to regions in early-type galaxies and star-forming regions of spirals, respectively. Within spiral galaxies, the older ages of bulges and interarm regions relative to spiral arms support an internal age bimodality. Although regions of higher stellar mass surface density, μ*, are typically older, μ* alone does not determine the stellar population age and a bimodal distribution is found at any fixed μ*. We identify an 'old ridge' of regions of age ˜9 Gyr, independent of μ*, and a 'young sequence' of regions with age increasing with μ* from 1-1.5 to 4-5 Gyr. We interpret the former as regions containing only old stars, and the latter as regions where the relative contamination of old stellar populations by young stars decreases as μ* increases. The reason why this bimodal age distribution is not inconsistent with the unimodal shape of the cosmic-averaged star formation history is that (I) the dominating contribution by young stars biases the age low with respect to the average epoch of star formation, and (II) the use of a single average age per region is unable to represent the full time extent of the star formation history of 'young sequence' regions.

  8. Evolution of Mass Functions of Coeval Stars through Wind Mass Loss and Binary Interactions

    NARCIS (Netherlands)

    Schneider, F.R.N.; Izzard, R.G.; Langer, N.; de Mink, S.E.

    2015-01-01

    Accurate determinations of stellar mass functions and ages of stellar populations are crucial to much of astrophysics. We analyze the evolution of stellar mass functions of coeval main-sequence stars, including all relevant aspects of single and binary star evolution. We show that the slope of the

  9. Computer simulations of close encounters between binary and single stars: the effect of the impact velocity and the stellar masses

    International Nuclear Information System (INIS)

    Fullerton, L.W.; Hills, J.G.

    1982-01-01

    A total of 45 760 simulated encounters between binary and single stars were run to study the effect of impact velocity and the masses of the three stars on the outcome of the collisions. Letting α be the kinetic energy of impact in units of the minimum kinetic energy required to break up the binary, we find that the crossover point between hard binaries (tightly bound binaries which increase their binding energies in the collisions) and soft binaries (more loosely bound binaries which decrease their binding energies in collisions) occurs at αapprox. =0.5 if the impacting single star is equal to or less massive than the binary components and occurs at αapprox. =10 if its mass is three or more times that of the binary components. This bimodal behavior of the crossover point is even more clearly defined when we find its location in terms of the impact velocity V/sub f/ , expressed in units of the original mean orbital speed V/sub o/ of the binary. We find that the crossover point occurs at V/sub f//V/sub o/ approx. =0.6 when the mass of the impacting star is equal to or less than that of the more massive binary component, and it occurs at V/sub f//V/sub o/ approx. =1.9 when its mass is three or more times greater than that of this binary component. The probability that the binary will be broken up in the encounter depends greatly on the mass of the impacting single star relative to that of the binary components, as well as on the impact velocity. If the single-star mass equals or exceeds that of the individual binary components, there is an interval of impact velocity over which all the binaries are broken up in encounters at the zero-impact parameter. This interval grows as the mass of the impacting single star increases. If the impacting star is less massive than the binary components, then the maximum probability of dissociation drops dramatically

  10. Radio observations confirm young stellar populations in local analogues to z ˜ 5 Lyman break galaxies

    Science.gov (United States)

    Greis, Stephanie M. L.; Stanway, Elizabeth R.; Levan, Andrew J.; Davies, Luke J. M.; Eldridge, J. J.

    2017-09-01

    We present radio observations at 1.5 GHz of 32 local objects selected to reproduce the physical properties of z ˜ 5 star-forming galaxies. We also report non-detections of five such sources in the sub-millimetre. We find a radio-derived star formation rate that is typically half than that derived from H α emission for the same objects. These observations support previous indications that we are observing galaxies with a young dominant stellar population, which has not yet established a strong supernova-driven synchrotron continuum. We stress caution when applying star formation rate calibrations to stellar populations younger than 100 Myr. We calibrate the conversions for younger galaxies, which are dominated by a thermal radio emission component. We improve the size constraints for these sources, compared to previous unresolved ground-based optical observations. Their physical size limits indicate very high star formation rate surface densities, several orders of magnitude higher than the local galaxy population. In typical nearby galaxies, this would imply the presence of galaxy-wide winds. Given the young stellar populations, it is unclear whether a mechanism exists in our sources that can deposit sufficient kinetic energy into the interstellar medium to drive such outflows.

  11. Inflow, Outflow, Yields, and Stellar Population Mixing in Chemical Evolution Models

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Brett H. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Weinberg, David H.; Schönrich, Ralph; Johnson, Jennifer A., E-mail: andrewsb@pitt.edu [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

    2017-02-01

    Chemical evolution models are powerful tools for interpreting stellar abundance surveys and understanding galaxy evolution. However, their predictions depend heavily on the treatment of inflow, outflow, star formation efficiency (SFE), the stellar initial mass function, the SN Ia delay time distribution, stellar yields, and stellar population mixing. Using flexCE, a flexible one-zone chemical evolution code, we investigate the effects of and trade-offs between parameters. Two critical parameters are SFE and the outflow mass-loading parameter, which shift the knee in [O/Fe]–[Fe/H] and the equilibrium abundances that the simulations asymptotically approach, respectively. One-zone models with simple star formation histories follow narrow tracks in [O/Fe]–[Fe/H] unlike the observed bimodality (separate high- α and low- α sequences) in this plane. A mix of one-zone models with inflow timescale and outflow mass-loading parameter variations, motivated by the inside-out galaxy formation scenario with radial mixing, reproduces the two sequences better than a one-zone model with two infall epochs. We present [X/Fe]–[Fe/H] tracks for 20 elements assuming three different supernova yield models and find some significant discrepancies with solar neighborhood observations, especially for elements with strongly metallicity-dependent yields. We apply principal component abundance analysis to the simulations and existing data to reveal the main correlations among abundances and quantify their contributions to variation in abundance space. For the stellar population mixing scenario, the abundances of α -elements and elements with metallicity-dependent yields dominate the first and second principal components, respectively, and collectively explain 99% of the variance in the model. flexCE is a python package available at https://github.com/bretthandrews/flexCE.

  12. The imprints of bars on the vertical stellar population gradients of galactic bulges

    Science.gov (United States)

    Molaeinezhad, A.; Falcón-Barroso, J.; Martínez-Valpuesta, I.; Khosroshahi, H. G.; Vazdekis, A.; La Barbera, F.; Peletier, R. F.; Balcells, M.

    2017-05-01

    This is the second paper of a series aimed to study the stellar kinematics and population properties of bulges in highly inclined barred galaxies. In this work, we carry out a detailed analysis of the stellar age, metallicity and [Mg/Fe] of 28 highly inclined (I > 65°) disc galaxies, from S0 to S(B)c, observed with the SAURON integral-field spectrograph. The sample is divided into two clean samples of barred and unbarred galaxies, on the basis of the correlation between the stellar velocity and h3 profiles, as well as the level of cylindrical rotation within the bulge region. We find that while the mean stellar age, metallicity and [Mg/Fe] in the bulges of barred and unbarred galaxies are not statistically distinct, the [Mg/Fe] gradients along the minor axis (away from the disc) of barred galaxies are significantly different than those without bars. For barred galaxies, stars that are vertically further away from the mid-plane are in general more [Mg/Fe]-enhanced and thus the vertical gradients in [Mg/Fe] for barred galaxies are mostly positive, while for unbarred bulges the [Mg/Fe] profiles are typically negative or flat. This result, together with the old populations observed in the barred sample, indicates that bars are long-lasting structures, and therefore are not easily destroyed. The marked [Mg/Fe] differences with the bulges of unbarred galaxies indicate that different formation/evolution scenarios are required to explain their build-up, and emphasizes the role of bars in redistributing stellar material in the bulge-dominated regions.

  13. SDSS-IV MaNGA: stellar population gradients as a function of galaxy environment

    Science.gov (United States)

    Goddard, D.; Thomas, D.; Maraston, C.; Westfall, K.; Etherington, J.; Riffel, R.; Mallmann, N. D.; Zheng, Z.; Argudo-Fernández, M.; Bershady, M.; Bundy, K.; Drory, N.; Law, D.; Yan, R.; Wake, D.; Weijmans, A.; Bizyaev, D.; Brownstein, J.; Lane, R. R.; Maiolino, R.; Masters, K.; Merrifield, M.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Storchi-Bergmann, T.

    2017-02-01

    We study the internal radial gradients of stellar population properties within 1.5 Re and analyse the impact of galaxy environment. We use a representative sample of 721 galaxies with masses ranging between 109 M⊙ and 1011.5 M⊙ from the SDSS-IV survey MaNGA. We split this sample by morphology into early-type and late-type galaxies. Using the full spectral fitting code FIREFLY, we derive the light and mass-weighted stellar population properties, age and metallicity, and calculate the gradients of these properties. We use three independent methods to quantify galaxy environment, namely the Nth nearest neighbour, the tidal strength parameter Q and distinguish between central and satellite galaxies. In our analysis, we find that early-type galaxies generally exhibit shallow light-weighted age gradients in agreement with the literature and mass-weighted median age gradients tend to be slightly positive. Late-type galaxies, instead, have negative light-weighted age gradients. We detect negative metallicity gradients in both early- and late-type galaxies that correlate with galaxy mass, with the gradients being steeper and the correlation with mass being stronger in late-types. We find, however, that stellar population gradients, for both morphological classifications, have no significant correlation with galaxy environment for all three characterizations of environment. Our results suggest that galaxy mass is the main driver of stellar population gradients in both early and late-type galaxies, and any environmental dependence, if present at all, must be very subtle.

  14. OGLE-ing the Magellanic system: stellar populations in the Magellanic Bridge

    Energy Technology Data Exchange (ETDEWEB)

    Skowron, D. M.; Jacyszyn, A. M.; Udalski, A.; Szymański, M. K.; Skowron, J.; Poleski, R.; Kozłowski, S.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Mróz, P.; Pietrukowicz, P.; Ulaczyk, K.; Wyrzykowski, Ł., E-mail: dszczyg@astrouw.edu.pl [Warsaw University Astronomical Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa (Poland)

    2014-11-10

    We report the discovery of a young stellar bridge that forms a continuous connection between the Magellanic Clouds. This finding is based on number density maps for stellar populations found in data gathered by OGLE-IV that fully cover over 270 deg{sup 2} of the sky in the Magellanic Bridge area. This is the most extensive optical survey of this region to date. We find that the young population is present mainly in the western half of the MBR, which, together with the newly discovered young population in the eastern Bridge, form a continuous stream of stars connecting both galaxies along δ ∼ –73.5 deg. The young population distribution is clumped, with one of the major densities close to the SMC and the other fairly isolated and located approximately mid-way between the Clouds, which we call the OGLE island. These overdensities are well matched by H I surface density contours, although the newly found young population in the eastern Bridge is offset by ∼2 deg north from the highest H I density contour. We observe a continuity of red clump stars between the Magellanic Clouds which represent an intermediate-age population. Red clump stars are present mainly in the southern and central parts of the Magellanic Bridge, below its gaseous part, and their presence is reflected by a strong deviation from the radial density profiles of the two galaxies. This may indicate either a tidal stream of stars, or that the stellar halos of the two galaxies overlap. On the other hand, we do not observe such an overlap within an intermediate-age population represented by the top of the red giant branch and the asymptotic giant branch stars. We also see only minor mixing of the old populations of the Clouds in the southern part of the Bridge, represented by the lowest part of the red giant branch.

  15. On the likelihood of detecting gravitational waves from Population III compact object binaries

    Science.gov (United States)

    Belczynski, Krzysztof; Ryu, Taeho; Perna, Rosalba; Berti, Emanuele; Tanaka, Takamitsu L.; Bulik, Tomasz

    2017-11-01

    We study the contribution of binary black hole (BH-BH) mergers from the first, metal-free stars in the Universe (Pop III) to gravitational wave detection rates. Our study combines initial conditions for the formation of Pop III stars based on N-body simulations of binary formation (including rates, binary fraction, initial mass function, orbital separation and eccentricity distributions) with an updated model of stellar evolution specific for Pop III stars. We find that the merger rate of these Pop III BH-BH systems is relatively small (≲ 0.1 Gpc-3 yr-1) at low redshifts (z 1 per cent) contribution of these stars to low-redshift BH-BH mergers. However, it remains to be tested whether (and at what level) rapidly spinning Pop III stars in the homogeneous evolution scenario can contribute to BH-BH mergers in the local Universe.

  16. The anatomy of the NGC5044 group - II. Stellar populations and star formation histories

    Science.gov (United States)

    Mendel, J. Trevor; Proctor, Robert N.; Rasmussen, Jesper; Brough, Sarah; Forbes, Duncan A.

    2009-07-01

    The distribution of galaxy properties in groups and clusters holds important information on galaxy evolution and growth of structure in the Universe. While clusters have received appreciable attention in this regard, the role of groups as fundamental to formation of the present-day galaxy population has remained relatively unaddressed. Here, we present stellar ages, metallicities and α-element abundances derived using Lick indices for 67 spectroscopically confirmed members of the NGC5044 galaxy group with the aim of shedding light on galaxy evolution in the context of the group environment. We find that galaxies in the NGC5044 group show evidence for a strong relationship between stellar mass and metallicity, consistent with their counterparts in both higher and lower mass groups and clusters. Galaxies show no clear trend of age or α-element abundance with mass, but these data form a tight sequence when fitted simultaneously in age, metallicity and stellar mass. In the context of the group environment, our data support the tidal disruption of low-mass galaxies at small group-centric radii, as evident from an apparent lack of galaxies below ~109Msolar within ~100kpc of the brightest group galaxy. Using a joint analysis of absorption- and emission-line metallicities, we are able to show that the star-forming galaxy population in the NGC5044 group appears to require gas removal to explain the ~1.5dex offset between absorption- and emission-line metallicities observed in some cases. A comparison with other stellar population properties suggests that this gas removal is dominated by galaxy interactions with the hot intragroup medium.

  17. Simple Stellar Population Modeling of Quasar Host Galaxies with Diffusion K-Means Test Results

    Science.gov (United States)

    Mosby, Gregory; Moravec, E. A.; Tremonti, C. A.; Wolf, M. J.

    2013-01-01

    In the last decade, the correlation of the masses of supermassive black holes (SMBHs) and their host galaxy stellar spheroid velocity dispersions (the M-sigma relation) was greeted as clear evidence for the co-evolution of host galaxies and their SMBHs. However, studies in the last five years have posited that this relation could arise from central-limit properties of hierarchical formation alone. To address the question of whether and how often the SMBHs evolve with their host galaxies, it is necessary to look at galaxies whose SMBHs are actively growing—quasars—and determine the host galaxy properties. The central nuclei of quasar host galaxies complicate this type of study because their high luminosity tends to wash out their host galaxies. But, by using 3-D spectroscopy with the integral field unit (IFU) Sparsepak on the WIYN telescope, we have shown that the quasar light can be mostly isolated to one fiber in order to obtain the spectra of the quasar and the host galaxy concurrently. We can then model simultaneously the scattered quasar light and the stellar populations in the host galaxy fiber using a new simple stellar population (SSP) modeling method called diffusion k-means (DFK). The objectives of the research presented in this poster are to model synthetic quasar host galaxies using a DFK basis and a more traditional basis, compare the accuracy of both modeling methods, and test the affects of various prescriptions for masking the quasar lines in the host galaxy fiber. We present results from our SSP modeling and Markov Chain Monte Carlo (MCMC) results for DFK and traditional modeling schemes using synthetic data. By determining and then using the more robust stellar population modeling method, we can more confidently study quasar host galaxies to answer remaining questions in galaxy evolution. This work was partially supported by a National Science Foundation Graduate Fellowship (NSF Grant DGE-0718123) and through the NSF's REU program (NSF Award

  18. Evolution of the stellar mass function in multiple-population globular clusters

    Science.gov (United States)

    Vesperini, Enrico; Hong, Jongsuk; Webb, Jeremy J.; D'Antona, Franca; D'Ercole, Annibale

    2018-05-01

    We present the results of a survey of N-body simulations aimed at studying the effects of the long-term dynamical evolution on the stellar mass function (MF) of multiple stellar populations in globular clusters. Our simulations show that if first-(1G) and second-generation (2G) stars have the same initial MF (IMF), the global MFs of the two populations are affected similarly by dynamical evolution and no significant differences between the 1G and 2G MFs arise during the cluster's evolution. If the two populations have different IMFs, dynamical effects do not completely erase memory of the initial differences. Should observations find differences between the global 1G and 2G MFs, these would reveal the fingerprints of differences in their IMFs. Irrespective of whether the 1G and 2G populations have the same global IMF or not, dynamical effects can produce differences between the local (measured at various distances from the cluster centre) 1G and 2G MFs; these differences are a manifestation of the process of mass segregation in populations with different initial structural properties. In dynamically old and spatially mixed clusters, however, differences between the local 1G and 2G MFs can reveal differences between the 1G and 2G global MFs. In general, for clusters with any dynamical age, large differences between the local 1G and 2G MFs are more likely to be associated with differences in the global MF. Our study also reveals a dependence of the spatial mixing rate on the stellar mass, another dynamical consequence of the multiscale nature of multiple-population clusters.

  19. Evolution of the Stellar Mass Function in Multiple-Population Globular Clusters

    Science.gov (United States)

    Vesperini, Enrico; Hong, Jongsuk; Webb, Jeremy J.; D'Antona, Franca; D'Ercole, Annibale

    2018-02-01

    We present the results of a survey of N-body simulations aimed at studying the effects of the long-term dynamical evolution on the stellar mass function (MF) of multiple stellar populations in globular clusters. Our simulations show that if first-(1G) and second-generation (2G) stars have the same initial MF (IMF), the global MFs of the two populations are affected similarly by dynamical evolution and no significant differences between the 1G and the 2G MFs arise during the cluster's evolution. If the two populations have different IMFs, dynamical effects do not completely erase memory of the initial differences. Should observations find differences between the global 1G and 2G MF, these would reveal the fingerprints of differences in their IMFs. Irrespective of whether the 1G and 2G populations have the same global IMF or not, dynamical effects can produce differences between the local (measured at various distances from the cluster centre) 1G and 2G MFs; these differences are a manifestation of the process of mass segregation in populations with different initial structural properties. In dynamically old and spatially mixed clusters, however, differences between the local 1G and 2G MFs can reveal differences between the 1G and 2G global MFs. In general, for clusters with any dynamical age, large differences between the local 1G and 2G MFs are more likely to be associated with differences in the global MF. Our study also reveals a dependence of the spatial mixing rate on the stellar mass, another dynamical consequence of the multiscale nature of multiple-population clusters.

  20. THE EVOLUTION OF STELLAR POPULATIONS IN THE OUTER DISKS OF SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Alberts, Stacey; Calzetti, Daniela; Dong Hui; Johnson, L. C.; Dale, Daniel A.; Bianchi, Luciana; Thilker, David; Chandar, Rupali; Kennicutt, Robert C.; Meurer, Gerhardt R.; Regan, Michael

    2011-01-01

    We investigate recent star formation in the extended ultraviolet (XUV) disks of five nearby galaxies (NGC 0628, NGC 2090, NGC 2841, NGC 3621, and NGC 5055) using a long wavelength baseline comprised of ultraviolet and mid-infrared imaging from the Galaxy Evolution Explorer and the Spitzer Infrared Array Camera. We identify 229 unresolved stellar complexes across targeted portions of their XUV disks and utilize spectral energy distribution fitting to measure their stellar ages and masses through comparison with Starburst99 population synthesis models of instantaneous burst populations. We find that the median age of outer-disk associations in our sample is ∼100 Myr with a large dispersion that spans the entire range of our models (1 Myr to 1 Gyr). This relatively evolved state for most associations addresses the observed dearth of Hα emission in some outer disks, as Hα can only be observed in star-forming regions younger than ∼10 Myr. The large age dispersion is robust against variations in extinction (in the range E(B - V) = 0-0.3 mag) and variations in the upper end of the stellar initial mass function (IMF). In particular, we demonstrate that the age dispersion is insensitive to steepening of the IMF, up to extreme slopes.

  1. Interacting binaries

    CERN Document Server

    Shore, S N; van den Heuvel, EPJ

    1994-01-01

    This volume contains lecture notes presented at the 22nd Advanced Course of the Swiss Society for Astrophysics and Astronomy. The contributors deal with symbiotic stars, cataclysmic variables, massive binaries and X-ray binaries, in an attempt to provide a better understanding of stellar evolution.

  2. A new stellar spectrum interpolation algorithm and its application to Yunnan-III evolutionary population synthesis models

    Science.gov (United States)

    Cheng, Liantao; Zhang, Fenghui; Kang, Xiaoyu; Wang, Lang

    2018-05-01

    In evolutionary population synthesis (EPS) models, we need to convert stellar evolutionary parameters into spectra via interpolation in a stellar spectral library. For theoretical stellar spectral libraries, the spectrum grid is homogeneous on the effective-temperature and gravity plane for a given metallicity. It is relatively easy to derive stellar spectra. For empirical stellar spectral libraries, stellar parameters are irregularly distributed and the interpolation algorithm is relatively complicated. In those EPS models that use empirical stellar spectral libraries, different algorithms are used and the codes are often not released. Moreover, these algorithms are often complicated. In this work, based on a radial basis function (RBF) network, we present a new spectrum interpolation algorithm and its code. Compared with the other interpolation algorithms that are used in EPS models, it can be easily understood and is highly efficient in terms of computation. The code is written in MATLAB scripts and can be used on any computer system. Using it, we can obtain the interpolated spectra from a library or a combination of libraries. We apply this algorithm to several stellar spectral libraries (such as MILES, ELODIE-3.1 and STELIB-3.2) and give the integrated spectral energy distributions (ISEDs) of stellar populations (with ages from 1 Myr to 14 Gyr) by combining them with Yunnan-III isochrones. Our results show that the differences caused by the adoption of different EPS model components are less than 0.2 dex. All data about the stellar population ISEDs in this work and the RBF spectrum interpolation code can be obtained by request from the first author or downloaded from http://www1.ynao.ac.cn/˜zhangfh.

  3. No Evidence for Multiple Stellar Populations in the Low-mass Galactic Globular Cluster E 3

    Science.gov (United States)

    Salinas, Ricardo; Strader, Jay

    2015-08-01

    Multiple stellar populations are a widespread phenomenon among Galactic globular clusters. Even though the origin of the enriched material from which new generations of stars are produced remains unclear, it is likely that self-enrichment will be feasible only in clusters massive enough to retain this enriched material. We searched for multiple populations in the low mass (M˜ 1.4× {10}4 {M}⊙ ) globular cluster E3, analyzing SOAR/Goodman multi-object spectroscopy centered on the blue cyanogen (CN) absorption features of 23 red giant branch stars. We find that the CN abundance does not present the typical bimodal behavior seen in clusters hosting multistellar populations, but rather a unimodal distribution that indicates the presence of a genuine single stellar population, or a level of enrichment much lower than in clusters that show evidence for two populations from high-resolution spectroscopy. E3 would be the first bona fide Galactic old globular cluster where no sign of self-enrichment is found. Based on observations obtained at the Southern Astrophysical Research (SOAR) Telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  4. WIYN Open Cluster Study: Tidal Interactions in Solar type Binaries

    OpenAIRE

    Meibom, S.; Mathieu, R. D.

    2003-01-01

    We present an ongoing study on tidal interactions in late-type close binary stars. New results on tidal circularization are combined with existing data to test and constrain theoretical predictions of tidal circularization in the pre-main-sequence (PMS) phase and throughout the main-sequence phase of stellar evolution. Current data suggest that tidal circularization during the PMS phase sets the tidal cutoff period for binary populations younger than ~1 Gyr. Binary populations older than ~1 G...

  5. The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations

    Energy Technology Data Exchange (ETDEWEB)

    Calamida, A.; Saha, A. [National Optical Astronomy Observatory—AURA, 950 N Cherry Avenue, Tucson, AZ, 85719 (United States); Strampelli, G.; Rest, A. [Space Telescope Science Institute—AURA, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bono, G.; Ferraro, I.; Iannicola, G. [INAF—Osservatorio Astronomico di Roma—Via Frascati 33, I-00040, Monteporzio Catone, Rome (Italy); Scolnic, D. [The University of Chicago, The Kavli Institute for Cosmological Physics, William Eckhardt Research Center—Suite 499, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); James, D.; Smith, C.; Zenteno, A., E-mail: calamida@noao.edu [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

    2017-04-01

    We present a multi-band photometric catalog of ≈1.7 million cluster members for a field of view of ≈2° × 2° across ω Cen. Photometry is based on images collected with the Dark Energy Camera on the 4 m Blanco telescope and the Advanced Camera for Surveys on the Hubble Space Telescope . The unprecedented photometric accuracy and field coverage allowed us, for the first time, to investigate the spatial distribution of ω Cen multiple populations from the core to the tidal radius, confirming its very complex structure. We found that the frequency of blue main-sequence stars is increasing compared to red main-sequence stars starting from a distance of ≈25′ from the cluster center. Blue main-sequence stars also show a clumpy spatial distribution, with an excess in the northeast quadrant of the cluster pointing toward the direction of the Galactic center. Stars belonging to the reddest and faintest red-giant branch also show a more extended spatial distribution in the outskirts of ω Cen, a region never explored before. Both these stellar sub-populations, according to spectroscopic measurements, are more metal-rich compared to the cluster main stellar population. These findings, once confirmed, make ω Cen the only stellar system currently known where metal-rich stars have a more extended spatial distribution compared to metal-poor stars. Kinematic and chemical abundance measurements are now needed for stars in the external regions of ω Cen to better characterize the properties of these sub-populations.

  6. Timing the formation and assembly of early-type galaxies via spatially resolved stellar populations analysis

    Science.gov (United States)

    Martín-Navarro, Ignacio; Vazdekis, Alexandre; Falcón-Barroso, Jesús; La Barbera, Francesco; Yıldırım, Akın; van de Ven, Glenn

    2018-04-01

    To investigate star formation and assembly processes of massive galaxies, we present here a spatially resolved stellar population analysis of a sample of 45 elliptical galaxies (Es) selected from the Calar Alto Legacy Integral Field Area survey. We find rather flat age and [Mg/Fe] radial gradients, weakly dependent on the effective velocity dispersion of the galaxy within half-light radius. However, our analysis shows that metallicity gradients become steeper with increasing galaxy velocity dispersion. In addition, we have homogeneously compared the stellar population gradients of our sample of Es to a sample of nearby relic galaxies, i.e. local remnants of the high-z population of red nuggets. This comparison indicates that, first, the cores of present-day massive galaxies were likely formed in gas-rich, rapid star formation events at high redshift (z ≳ 2). This led to radial metallicity variations steeper than observed in the local Universe, and positive [Mg/Fe] gradients. Secondly, our analysis also suggests that a later sequence of minor dry mergers, populating the outskirts of early-type galaxies (ETGs), flattened the pristine [Mg/Fe] and metallicity gradients. Finally, we find a tight age-[Mg/Fe] relation, supporting that the duration of the star formation is the main driver of the [Mg/Fe] enhancement in massive ETGs. However, the star formation time-scale alone is not able to fully explain our [Mg/Fe] measurements. Interestingly, our results match the expected effect that a variable stellar initial mass function would have on the [Mg/Fe] ratio.

  7. Gradients of Stellar Population Properties and Evolution Clues in a Nearby Galaxy M101

    Science.gov (United States)

    Lin, Lin; Zou, Hu; Kong, Xu; Lin, Xuanbin; Mao, Yewei; Cheng, Fuzhen; Jiang, Zhaoji; Zhou, Xu

    2013-06-01

    Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of the Sandage star formation history are obtained. When fitting with the models, we use the IRX-A FUV relation, found to depend on a second parameter of birth rate b (ratio of present- and past-averaged star formation rates), to constrain the dust attenuation. There are obvious parameter gradients in the disk of M101, which supports the theory of an "inside-out" disk growth scenario. Two distinct disk regions with different gradients of age and color are discovered, similar to another late-type galaxy, NGC 628. The metallicity gradient of the stellar content is flatter than that of H II regions. The stellar disk is optically thicker inside than outside and the global dust attenuation of this galaxy is lower compared with galaxies of similar and earlier morphological type. We note that a variational star formation timescale describes the real star formation history of a galaxy. The timescale increases steadily from the center to the outskirt. We also confirm that the bulge in this galaxy is a disk-like pseudobulge, whose evolution is likely to be induced by some secular processes of the small bar which is relatively young, metal-rich, and contains much dust.

  8. Auto-consistent test of Galaxy star formation histories derived from resolved stellar population and integral spectroscopy

    Science.gov (United States)

    Rodrigues, M.; Patricio, V.; Rothberg, B.; Sanchez-Janssen, R.; Vale Asari, N.

    We present the first results of our observational project 'Starfish' (STellar Population From Integrated Spectrum). The goal of this project is to calibrate, for the first time, the properties of stellar populations derived from integrated spectra with the same properties derived from direct imaging of stellar populations in the same set of galaxies. These properties include the star-formation history (SFH), stellar mass, age, and metallicity. To date, such calibrations have been demonstrated only in star clusters, globular clusters with single stellar populations, not in complex and composite objects such as galaxies. We are currently constructing a library of integrated spectra obtained from a sample of 38 nearby dwarf galaxies obtained with GEMINI/GMOS-N&S (25h) and VLT/VIMOS-IFU (43h). These are to be compared with color magnitude diagrams (CMDs) of the same galaxies constructed from archival HST imaging sensitive to at least 1.5 magnitudes below the tip of the red giant branch. From this comparison we will assess the systematics and uncertainties from integrated spectral techniques. The spectra library will be made publicly available to the community via a dedicated web-page and Vizier database. This dataset will provide a unique benchmark for testing fitting procedures and stellar population models for both nearby and distant galaxies. http://www.sc.eso.org/˜marodrig/Starfish/

  9. Stellar winds and coronae of low-mass Population II/III stars

    Science.gov (United States)

    Suzuki, Takeru K.

    2018-04-01

    We investigated stellar winds from zero-/low-metallicity low-mass stars by magnetohydrodynamical simulations for stellar winds driven by Alfvén waves from stars with mass M = (0.6-0.8) M⊙ and metallicity Z = (0-1) Z⊙, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Alfvénic waves, which are excited by the surface convection, travel upward from the photosphere and heat up the corona by their dissipation. For lower Z, denser gas can be heated up to the coronal temperature because of the inefficient radiation cooling. The coronal density of Population II/III stars with Z ≤ 0.01 Z⊙ is one to two orders of magnitude larger than that of a solar-metallicity star with the same mass, and as a result, the mass loss rate, \\dot{M}, is 4.5-20 times larger. This indicates that metal accretion on low-mass Pop. III stars is negligible. The soft X-ray flux of the Pop. II/III stars is also expected to be ˜1-30 times larger than that of a solar-metallicity counterpart owing to the larger coronal density, even though the radiation cooling efficiency is smaller. A larger fraction of the input Alfvénic wave energy is transmitted to the corona in low-Z stars because they avoid severe reflection owing to the smaller density difference between the photosphere and the corona. Therefore, a larger fraction is converted to the thermal energy of the corona and the kinetic energy of the stellar wind. From this energetics argument, we finally derived a scaling of \\dot{M} as \\dot{M}∝ L R_{\\star }^{11/9} M_{\\star }^{-10/9} T_eff^{11/2}[\\max (Z/Z_{⊙},0.01)]^{-1/5}, where L, R⋆, and Teff are the stellar luminosity, radius, and effective temperature, respectively.

  10. Walter Baade: Father of the Two Stellar Populations and Pioneer Supernova Researcher

    Science.gov (United States)

    Osterbrock, D. E.

    2001-05-01

    Walter Baade was the great observational astronomer of the middle part of the past century. He lived and worked in Pasadena, where he ``discovered" the two stellar populations and did outstanding pioneer research on supernovae at Mount Wilson and Palomar Observatories from 1931 until 1959, when he returned to his native Germany, and died the following year. Baade was born in a little town in northwest Germany, and educated at Goettingen University, where he received his Ph.D. in 1919, just after the end of World War I. He got a research position at Hamburg Observatory, and quickly jumped into globular cluster and galactic structure work with its 40-in reflector, then the largest telescope in Europe. Baade recognized very early the great importance of the extremely rare ``highly luminous novae" which Heber D. Curtis and Knut Lundmark isolated in 1919-21. In 1929 Baade called these ``Hauptnovae" the key to measuring distances of faint galaxies. We call them supernovae today, a term he and Fritz Zwicky began using in 1932. Similarly Baade's first inkling that there was a spherically symmetric distribution of stars in our Galaxy, which he named Population II in his two great 1944 papers, came when he began picking up field RR Lyrae variables in 1926. Baade's research on the two stellar populations and supernovae was extremely important in opening up the whole fields of stellar and galactic evolution. His invited lectures at meetings and symposia, and his courses as a visiting professor inspired a whole generation of research astrophysicists. Baade's attractive personality made it possible for him to make his great discoveries in a land in which he was officially an enemy alien during World War II.

  11. The spatially resolved stellar population and ionized gas properties in the merger LIRG NGC 2623

    Science.gov (United States)

    Cortijo-Ferrero, C.; González Delgado, R. M.; Pérez, E.; Sánchez, S. F.; Cid Fernandes, R.; de Amorim, A. L.; Di Matteo, P.; García-Benito, R.; Lacerda, E. A. D.; López Fernández, R.; Tadhunter, C.; Villar-Martín, M.; Roth, M. M.

    2017-10-01

    We report on a detailed study of the stellar populations and ionized gas properties in the merger LIRG NGC 2623, analyzing optical integral field spectroscopy from the CALIFA survey and PMAS LArr, multiwavelength HST imaging, and OSIRIS narrow band Hα and [NII]λ6584 imaging. The spectra were processed with the starlight full spectral fitting code, and the results are compared with those for two early-stage merger LIRGs (IC 1623 W and NGC 6090), together with CALIFA Sbc/Sc galaxies. We find that NGC 2623 went through two periods of increased star formation (SF), a first and widespread episode, traced by intermediate-age stellar populations ISP (140 Myr-1.4 Gyr), and a second one, traced by young stellar populations YSP (<140 Myr), which is concentrated in the central regions (<1.4 kpc). Our results are in agreement with the epochs of the first peri-center passage ( 200 Myr ago) and coalescence (<100 Myr ago) predicted by dynamical models, and with high-resolution merger simulations in the literature, consistent with NGC 2623 representing an evolved version of the early-stage mergers. Most ionized gas is concentrated within <2.8 kpc, where LINER-like ionization and high-velocity dispersion ( 220 km s-1) are found, consistent with the previously reported outflow. As revealed by the highest-resolution OSIRIS and HST data, a collection of HII regions is also present in the plane of the galaxy, which explains the mixture of ionization mechanisms in this system. It is unlikely that the outflow in NGC 2623 will escape from the galaxy, given the low SFR intensity ( 0.5 M⊙ yr-1 kpc-2), the fact that the outflow rate is three times lower than the current SFR, and the escape velocity in the central areas is higher than the outflow velocity.

  12. Magnetic Inflation and Stellar Mass. I. Revised Parameters for the Component Stars of the Kepler Low-mass Eclipsing Binary T-Cyg1-12664

    Energy Technology Data Exchange (ETDEWEB)

    Han, Eunkyu; Muirhead, Philip S. [Department of Astronomy and Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Swift, Jonathan J. [The Thacher School, 5025 Thacher Road Ojai, CA 93023 (United States); Baranec, Christoph; Atkinson, Dani [Institute for Astronomy, University of Hawaiì at Mānoa, Hilo, HI 96720-2700 (United States); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States); Riddle, Reed [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Mace, Gregory N. [McDonald Observatory and The University of Texas, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States); DeFelippis, Daniel, E-mail: eunkyuh@bu.edu [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

    2017-09-01

    Several low-mass eclipsing binary stars show larger than expected radii for their measured mass, metallicity, and age. One proposed mechanism for this radius inflation involves inhibited internal convection and starspots caused by strong magnetic fields. One particular eclipsing binary, T-Cyg1-12664, has proven confounding to this scenario. Çakırlı et al. measured a radius for the secondary component that is twice as large as model predictions for stars with the same mass and age, but a primary mass that is consistent with predictions. Iglesias-Marzoa et al. independently measured the radii and masses of the component stars and found that the radius of the secondary is not in fact inflated with respect to models, but that the primary is, which is consistent with the inhibited convection scenario. However, in their mass determinations, Iglesias-Marzoa et al. lacked independent radial velocity measurements for the secondary component due to the star’s faintness at optical wavelengths. The secondary component is especially interesting, as its purported mass is near the transition from partially convective to a fully convective interior. In this article, we independently determined the masses and radii of the component stars of T-Cyg1-12664 using archival Kepler data and radial velocity measurements of both component stars obtained with IGRINS on the Discovery Channel Telescope and NIRSPEC and HIRES on the Keck Telescopes. We show that neither of the component stars is inflated with respect to models. Our results are broadly consistent with modern stellar evolutionary models for main-sequence M dwarf stars and do not require inhibited convection by magnetic fields to account for the stellar radii.

  13. Images in the rocket ultraviolet: The stellar population in the central bulge of M31

    International Nuclear Information System (INIS)

    Bohlin, R.C.; Cornett, R.H.; Hill, J.K.; Hill, R.S.; O'Connell, R.W.; Stecher, T.P.

    1985-01-01

    We discuss imagery of bulge of the M31 obtained with a rocket-borne telescope in two broad bands centered at 1460 A and 2380 A. The UV spatial profiles over a region approx.200'' wide are identical with those at visible wavelengths. The absence of detectable point sources indicates that main-sequence stars hotter than BO V are not present in the bulge. We suggest that the far-UV flux in old stellar populations originates in post-AGB stars. The UV flux from such stars is extremely sensitive to age and the physics of their previous mass loss

  14. VELOCITY DISPERSIONS AND STELLAR POPULATIONS OF THE MOST COMPACT AND MASSIVE EARLY-TYPE GALAXIES AT REDSHIFT ∼1

    International Nuclear Information System (INIS)

    Martinez-Manso, Jesus; Guzman, Rafael; Barro, Guillermo; Cardiel, Nicolas; Gallego, Jesus; Cenarro, Javier; Perez-Gonzalez, Pablo; Sanchez-Blazquez, Patricia; Trujillo, Ignacio; Balcells, Marc; Hempel, Angela; Prieto, Mercedes

    2011-01-01

    We present Gran-Telescopio-Canarias/OSIRIS optical spectra of four of the most compact and massive early-type galaxies (ETGs) in the Groth Strip Survey at redshift z ∼ 1, with effective radii R e = 0.5-2.4 kpc and photometric stellar masses M * = (1.2-4) x 10 11 M sun . We find that these galaxies have velocity dispersions σ = 156-236 km s -1 . The spectra are well fitted by single stellar population models with approximately 1 Gyr of age and solar metallicity. We find that (1) the dynamical masses of these galaxies are systematically smaller by a factor of ∼6 than the published stellar masses using BRIJK photometry, and (2) when estimating stellar masses as 0.7x M dyn , a combination of passive luminosity fading with mass/size growth due to minor mergers can plausibly evolve our objects to match the properties of the local population of ETGs.

  15. Stellar Populations and Ionization States of Lyman Alpha Emitters During the Epoch of Peak Star Formation

    Science.gov (United States)

    Reddy, Naveen

    2014-10-01

    Low luminosity galaxies contribute significantly to the mass and star-formation density of the early Universe. Ly-alpha emitting galaxies (LAEs) are powerful probes of the faint-end of the luminosity function and early mass assembly. LAE studies at z>2 have typically used stacked optical and/or Spitzer data to discern their median properties, but the actual distribution of stellar masses and ionization states of LAEs remain largely unconstrained. To advance our understanding of this important population, we have successfully identified large samples of LAEs (~900 in four 0.33 deg^2 fields) at z~1.9, and have spectroscopically confirmed our selection using Keck. Here we propose to leverage our existing deep HST near-IR and Spitzer/IRAC imaging with the WFC3 G141 grism to measure [OIII]+H-beta for 76 LAE candidates from our sample, 13 of which are already spectroscopically confirmed at z=1.9+/-0.1. Combined with [OII] measurements from the ground, we will: (1) correct the emission line contribution to the HST broadband photometry and thus more accurately measure stellar masses and ages of LAEs; (2) measure ionization states with [OIII]/[OII] to discern the physical conditions in the ISM of these faint, low-mass galaxies; and (3) use systemic velocities derived from [OIII]+Hb, combined with our rest-UV spectra of the Ly-alpha and interstellar absorption lines, to deduce the kinematics of the ISM and the prevalence of galaxy-scale outflows. An economical investment of 16 orbits will enable robust stellar population, ionization, and ISM structure measurements for LAEs, thus illuminating their significance at a time when galaxies were forming most of their stars.

  16. UNDERSTANDING THE UNUSUAL X-RAY EMISSION PROPERTIES OF THE MASSIVE, CLOSE BINARY WR 20a: A HIGH ENERGY WINDOW INTO THE STELLAR WIND INITIATION REGION

    Energy Technology Data Exchange (ETDEWEB)

    Montes, Gabriela; Ramirez-Ruiz, Enrico; De Colle, Fabio; Strickler, Rachel, E-mail: gmontes@ucsc.edu [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-11-10

    The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra observations were taken during the secondary optical eclipse, the X-ray light curve shows no signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous and softer during the optical eclipse, opposite to what has been observed in other binary systems. To aid in our interpretation of the data, we compare with the results of hydrodynamical simulations using the adaptive mesh refinement code Mezcal which includes radiative cooling and a radiative acceleration force term. It is shown that the X-ray emission can be successfully explained in models where the wind-wind collision interface in this system occurs while the outflowing material is still being accelerated. Consequently, WR 20a serves as a critical test-case for how radiatively driven stellar winds are initiated and how they interact. Our models not only procure a robust description of current Chandra data, which cover the orbital phases between 0.3 and 0.6, but also provide detailed predictions over the entire orbit.

  17. Understanding the Unusual X-Ray Emission Properties of the Massive, Close Binary WR 20a: A High Energy Window into the Stellar Wind Initiation Region

    Science.gov (United States)

    Montes, Gabriela; Ramirez-Ruiz, Enrico; De Colle, Fabio; Strickler, Rachel

    2013-11-01

    The problem of explaining the X-ray emission properties of the massive, close binary WR 20a is discussed. Located near the cluster core of Westerlund 2, WR 20a is composed of two nearly identical Wolf-Rayet stars of 82 and 83 solar masses orbiting with a period of only 3.7 days. Although Chandra observations were taken during the secondary optical eclipse, the X-ray light curve shows no signs of a flux decrement. In fact, WR 20a appears slightly more X-ray luminous and softer during the optical eclipse, opposite to what has been observed in other binary systems. To aid in our interpretation of the data, we compare with the results of hydrodynamical simulations using the adaptive mesh refinement code Mezcal which includes radiative cooling and a radiative acceleration force term. It is shown that the X-ray emission can be successfully explained in models where the wind-wind collision interface in this system occurs while the outflowing material is still being accelerated. Consequently, WR 20a serves as a critical test-case for how radiatively driven stellar winds are initiated and how they interact. Our models not only procure a robust description of current Chandra data, which cover the orbital phases between 0.3 and 0.6, but also provide detailed predictions over the entire orbit.

  18. Young LMC clusters: the role of red supergiants and multiple stellar populations in their integrated light and CMDs

    Science.gov (United States)

    Asa'd, Randa S.; Vazdekis, Alexandre; Cerviño, Miguel; Noël, Noelia E. D.; Beasley, Michael A.; Kassab, Mahmoud

    2017-11-01

    The optical integrated spectra of three Large Magellanic Cloud young stellar clusters (NGC 1984, NGC 1994 and NGC 2011) exhibit concave continua and prominent molecular bands which deviate significantly from the predictions of single stellar population (SSP) models. In order to understand the appearance of these spectra, we create a set of young stellar population (MILES) models, which we make available to the community. We use archival International Ultraviolet Explorer integrated UV spectra to independently constrain the cluster masses and extinction, and rule out strong stochastic effects in the optical spectra. In addition, we also analyse deep colour-magnitude diagrams of the clusters to provide independent age determinations based on isochrone fitting. We explore hypotheses, including age spreads in the clusters, a top-heavy initial mass function, different SSP models and the role of red supergiant stars (RSG). We find that the strong molecular features in the optical spectra can be only reproduced by modelling an increased fraction of about ˜20 per cent by luminosity of RSG above what is predicted by canonical stellar evolution models. Given the uncertainties in stellar evolution at Myr ages, we cannot presently rule out the presence of Myr age spreads in these clusters. Our work combines different wavelengths as well as different approaches (resolved data as well as integrated spectra for the same sample) in order to reveal the complete picture. We show that each approach provides important information but in combination we can better understand the cluster stellar populations.

  19. Toward a dust penetrated classification of the evolved stellar Population II disks of galaxies

    Science.gov (United States)

    Block, David L.; Puerari, Ivânio

    1999-02-01

    To derive a coherent physical framework for the excitation of spiral structure in galaxies, one must consider the co-existence of two different dynamical components: a gas-dominated Population I disk (OB associations, HII regions, cold interstellar HI gas) and an evolved stellar Population II component. The Hubble classification scheme has as its focus, the morphology of the Population I component only. In the near-infrared, the morphology of evolved stellar disks indicates a simple classification scheme: the dominant Fourier m-mode in the dust penetrated regime, and the associated pitch angle. On the basis of deprojected K' (2.1microns ) images, we propose that the evolved stellar disks may be grouped into three principal dust penetrated archetypes: those with tightly wound stellar arms characterised by pitch angles at K' of ~ 10(deg) (the alpha class), an intermediate group with pitch angles of ~ 25(deg) (the beta class) and thirdly, those with open spirals demarcated by pitch angles at K' of ~ 40(deg) (the gamma bin). There is no correlation between our dust penetrated classes and optical Hubble binning; the Hubble tuning fork does not constrain the morphology of the old stellar Population II disks. Any specific dust penetrated archetype may be the resident disk of both an early or late type galaxy. The number of arms and the pitch angle of the arms at K' of the early-type `a' spiral NGC 718 are almost identical to those for the late-type `c' spiral NGC 309. We demonstrate that galaxies on opposite ends of the tuning fork can display remarkably similar evolved disk morphologies and belong to the same dust penetrated class. Furthermore, a prototypically flocculent galaxy such as NGC 5055 (Elmegreen arm class 3) can have an evolved disk morphology almost identical to that of NGC 5861, characterised in the optical as having one of the most regular spiral patterns known and of Elmegreen class 12. Both optically flocculent or grand design galaxies can reside within

  20. Tracing the evolution of NGC 6397 through the chemical composition of its stellar populations

    Science.gov (United States)

    Lind, K.; Charbonnel, C.; Decressin, T.; Primas, F.; Grundahl, F.; Asplund, M.

    2011-03-01

    Context. The chemical compositions of globular clusters provide important information on the star formation that occurred at very early times in the Galaxy. In particular the abundance patterns of elements with atomic number z ≤ 13 may shed light on the properties of stars that early on enriched parts of the star-forming gas with the rest-products of hydrogen-burning at high temperatures. Aims: We analyse and discuss the chemical compositions of a large number of elements in 21 red giant branch stars in the metal-poor globular cluster NGC 6397. We compare the derived abundance patterns with theoretical predictions in the framework of the "wind of fast rotating massive star"-scenario. Methods: High-resolution spectra were obtained with the FLAMES/UVES spectrograph on the VLT. We determined non-LTE abundances of Na, and LTE abundances for the remaining 21 elements, including O (from the [OI] line at 630 nm), Mg, Al, α, iron-peak, and neutron-capture elements, many of which had not been previously analysed for this cluster. We also considered the influence of possible He enrichment in the analysis of stellar spectra. Results: We find that the Na abundances of evolved, as well as unevolved, stars in NGC 6397 show a distinct bimodality, which is indicative of two stellar populations: one primordial stellar generation of composition similar to field stars, and a second generation that is polluted with material processed during hydrogen-burning, i.e., enriched in Na and Al and depleted in O and Mg. The red giant branch exhibits a similar bimodal distribution in the Strömgren colour index cy = c1 - (b - y), implying that there are also large differences in the N abundance. The two populations have the same composition for all analysed elements heavier than Al, within the measurement uncertainty of the analysis, with the possible exception of [Y/Fe]. Using two stars with almost identical stellar parameters, one from each generation, we estimate the difference in He

  1. Impact of Stellar Convection Criteria on the Nucleosynthetic Yields of Population III Supernovae.

    Science.gov (United States)

    Teffs, Jacob; Young, Tim; Lawlor, Tim

    2018-01-01

    A grid of 15-80 solar mass Z=0 stellar models are evolved to pre-core collapse using the stellar evolution code BRAHAMA. Each initial zero-age main sequence mass model star is evolved with two different convection criteria, Ledoux and Schwarzchild. The choice of convection produces significant changes in the evolutionary model tracks on the HR diagram, mass loss, and interior core and envelope structures. At onset of core collapse, a SNe explosion is initiated using a one-dimensional radiation-hydrodynamics code and followed for 400 days. The explosion energy is varied between 1-10 foes depending on the model as there are no observationally determined energies for population III supernovae. Due to structure differences, the Schwarzchild models resemble Type II-P SNe in their lightcurve while the Ledoux models resemble SN1987a, a Type IIpec. The nucleosynthesis is calculated using TORCH, a 3,208 isotope network, in a post process method using the hydrodynamic history. The Ledoux models have, on average, higher yields for elements above Fe compared to the Schwarzchild. Using a Salpeter IMF and other recently published population III IMF’s, the net integrated yields per solar mass are calculated and compared to published theoretical results and to published observations of extremely metal poor halo stars of [Fe/H] < -3. Preliminary results show the lower mass models of both criteria show similar trends to the extremely metal poor halo stars but more work and analysis is required.

  2. The VMC survey. XI. Radial stellar population gradients in the galactic globular cluster 47 Tucanae

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengyuan; De Grijs, Richard [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Deng, Licai [Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Rubele, Stefano; Girardi, Leo; Gullieuszik, Marco [INAF-Osservatorio Astronomico di Padova, vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Wang, Chuchu [Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Bekki, Kenji; For, Bi-Qing [ICRAR M468, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); Cioni, Maria-Rosa L. [Department of Physics, Astronomy, and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Clementini, Gisella [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Emerson, Jim [Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Groenewegen, Martin A. T. [Royal Observatory of Belgium, Ringlaan 3, 1180 Ukkel (Belgium); Guandalini, Roald [Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D 2401, 3001 Leuven (Belgium); Marconi, Marcella; Ripepi, Vincenzo [INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Naples (Italy); Piatti, Andrés E. [Observatorio Astrońomico, Universidad Nacional de Córdoba, Laprida 854, 5000 Córdoba (Argentina); Van Loon, Jacco Th., E-mail: joshuali@pku.edu.cn, E-mail: grijs@pku.edu.cn [Astrophysics Group, Lennard-Jones Laboratories, Keele University, Staffordshire ST5 5BG (United Kingdom)

    2014-07-20

    We present a deep near-infrared color-magnitude diagram of the Galactic globular cluster 47 Tucanae, obtained with the Visible and Infrared Survey Telescope for Astronomy (VISTA) as part of the VISTA near-infrared Y, J, K{sub s} survey of the Magellanic System (VMC). The cluster stars comprising both the subgiant and red giant branches exhibit apparent, continuous variations in color-magnitude space as a function of radius. Subgiant branch stars at larger radii are systematically brighter than their counterparts closer to the cluster core; similarly, red-giant-branch stars in the cluster's periphery are bluer than their more centrally located cousins. The observations can very well be described by adopting an age spread of ∼0.5 Gyr as well as radial gradients in both the cluster's helium abundance (Y) and metallicity (Z), which change gradually from (Y = 0.28, Z = 0.005) in the cluster core to (Y = 0.25, Z = 0.003) in its periphery. We conclude that the cluster's inner regions host a significant fraction of second-generation stars, which decreases with increasing radius; the stellar population in the 47 Tuc periphery is well approximated by a simple stellar population.

  3. The LMC geometry and outer stellar populations from early DES data

    Energy Technology Data Exchange (ETDEWEB)

    Balbinot, E.; Santiago, B. X.; Girardi, L.; Pieres, A.; da Costa, L. N.; Maia, M. A. G.; Gruendl, R. A.; Walker, A. R.; Yanny, B.; Drlica-Wagner, A.; Benoit-Levy, A.; Abbott, T. M. C.; Allam, S. S.; Annis, J.; Bernstein, J. P.; Bernstein, R. A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Rosell, A. C.; Cunha, C. E.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Estrada, J.; Evrard, A. E.; Neto, A. F.; Finley, D. A.; Flaugher, B.; Frieman, J. A.; Gruen, D.; Honscheid, K.; James, D.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; March, M.; Marshall, J. L.; Miller, C.; Miquel, R.; Ogando, R.; Peoples, J.; Plazas, A.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Tucker, D. L.; Wechsler, R.; Zuntz, J.

    2015-03-14

    The Dark Energy Camera has captured a large set of images as part of Science Verification (SV) for the Dark Energy Survey (DES). The SV footprint covers a large portion of the outer Large Magellanic Cloud (LMC), providing photometry 1.5 mag fainter than the main sequence turn-off of the oldest LMC stellar population. We derive geometrical and structural parameters for various stellar populations in the LMC disc. For the distribution of all LMC stars, we find an inclination of i = -38 degrees.14 +/- 0 degrees.08 (near side in the north) and a position angle for the line of nodes of theta(0) = 129 degrees.51 +/- 0 degrees.17. We find that stars younger than similar to 4 Gyr are more centrally concentrated than older stars. Fitting a projected exponential disc shows that the scale radius of the old populations is R->4Gyr = 1.41 +/- 0.01 kpc, while the younger population has R-<4Gyr = 0.72 +/- 0.01 kpc. However, the spatial distribution of the younger population deviates significantly from the projected exponential disc model. The distribution of old stars suggests a large truncation radius of R-t = 13.5 +/- 0.8 kpc. If this truncation is dominated by the tidal field of the Galaxy, we find that the LMC is similar or equal to 24(-6)(+9) times less massive than the encircled Galactic mass. By measuring the Red Clump peak magnitude and comparing with the best-fitting LMC disc model, we find that the LMC disc is warped and thicker in the outer regions north of the LMC centre. Our findings may either be interpreted as a warped and flared disc in the LMC outskirts, or as evidence of a spheroidal halo component.

  4. Study of the structure and formation of the thick disc from stellar population modelling

    Science.gov (United States)

    Nasello, G.; Robin, A. C.; Reylé, C.; Lagarde, N.

    2017-12-01

    The thick disc is a major component of the Milky Way but, its characteristics and history are still not yet well constrained. The use of a population synthesis model, based on a scenario of formation and evolution of the Galaxy, a star formation history, and a set of stellar evolution models, is a way to improve the constraints on this population. For this reason, we use the Besançon Galaxy Model (BGM, te{Robin3}). This model in constant evolution has been, thanks to te{Lagarde7}, implemented with new evolutionary tracks (STAREVOL, te{Lagarde}) to provide global asteroseismic and surface chemical properties along the evolutionary stages. Thanks to this updated Galaxy model and the Markov Chain Monte Carlo fitting method (MCMC) we will be able to constrain the thick disc structure and history. We show preliminary results applying this MCMC method to analyse the 2MASS photometric survey.

  5. Survey for {\\delta} Sct components in eclipsing binaries and new correlations between pulsation frequency and fundamental stellar characteristics

    OpenAIRE

    Liakos, Alexios; Niarchos, Panagiotis; Soydugan, Esin; Zasche, Petr

    2014-01-01

    CCD observations of 68 eclipsing binary systems, candidates for containing {\\delta} Scuti components, were obtained. Their light curves are analysed using the PERIOD04 software for possible pulsational behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to det...

  6. Stellar populations, stellar masses and the formation of galaxy bulges and discs at z < 3 in CANDELS

    Science.gov (United States)

    Margalef-Bentabol, Berta; Conselice, Christopher J.; Mortlock, Alice; Hartley, Will; Duncan, Kenneth; Kennedy, Rebecca; Kocevski, Dale D.; Hasinger, Guenther

    2018-02-01

    We present a multicomponent structural analysis of the internal structure of 1074 high-redshift massive galaxies at 1 components, and thus likely forming discs and bulges. We examine the stellar mass, star formation rates (SFRs) and colours of both the inner 'bulge' and outer 'disc' components for these systems using Spectral Energy Distribution (SED) information from the resolved ACS+WFC3 HST imaging. We find that the majority of both inner and outer components lie in the star-forming region of UVJ space (68 and 90 per cent, respectively). However, the inner portions, or the likely forming bulges, are dominated by dusty star formation. Furthermore, we show that the outer components of these systems have a higher SFR than their inner regions, and the ratio of SFR between 'disc' and 'bulge' increases at lower redshifts. Despite the higher SFR of the outer component, the stellar mass ratio of inner to outer component remains constant through this epoch. This suggests that there is mass transfer from the outer to inner components for typical two-component-forming systems, thus building bulges from discs. Finally, using Chandra data we find that the presence of an active galactic nucleus is more common in both one-component spheroid-like galaxies and two-component systems (13 ± 3 and 11 ± 2 per cent) than in one-component disc-like galaxies (3 ± 1 per cent), demonstrating that the formation of a central inner component likely triggers the formation of central massive black holes in these galaxies.

  7. Triple microlens OGLE-2008-BLG-092L: binary stellar system with a circumprimary uranus-type planet

    Energy Technology Data Exchange (ETDEWEB)

    Poleski, Radosław; Gould, Andrew [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Skowron, Jan; Udalski, Andrzej; Kozłowski, Szymon; Wyrzykowski, Łukasz; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Han, Cheongho [Department of Physics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Dong, Subo, E-mail: poleski@astronomy.ohio-state.edu [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871 (China)

    2014-11-01

    We present the gravitational microlensing discovery of a 4 M {sub Uranus} planet that orbits a 0.7 M {sub ☉} star at ≈18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main-sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only about three times smaller than that of the companion star, suggesting significant dynamical interactions.

  8. Triple Microlens OGLE-2008-BLG-092L: Binary Stellar System with a Circumprimary Uranus-type Planet

    Science.gov (United States)

    Poleski, Radosław; Skowron, Jan; Udalski, Andrzej; Han, Cheongho; Kozłowski, Szymon; Wyrzykowski, Łukasz; Dong, Subo; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł; Gould, Andrew

    2014-11-01

    We present the gravitational microlensing discovery of a 4 M Uranus planet that orbits a 0.7 M ⊙ star at ≈18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main-sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only about three times smaller than that of the companion star, suggesting significant dynamical interactions.

  9. A CHANDRA PERSPECTIVE ON GALAXY-WIDE X-RAY BINARY EMISSION AND ITS CORRELATION WITH STAR FORMATION RATE AND STELLAR MASS: NEW RESULTS FROM LUMINOUS INFRARED GALAXIES

    International Nuclear Information System (INIS)

    Lehmer, B. D.; Jenkins, L. P.; Alexander, D. M.; Goulding, A. D.; Roberts, T. P.; Bauer, F. E.; Brandt, W. N.; Ptak, A.

    2010-01-01

    We present new Chandra observations that complete a sample of seventeen (17) luminous infrared galaxies (LIRGs) with D H ∼ 20 cm -2 . The LIRGs in our sample have total infrared (8-1000 μm) luminosities in the range of L IR ∼ (1-8) x 10 11 L sun . The high-resolution imaging and X-ray spectral information from our Chandra observations allow us to measure separately X-ray contributions from active galactic nuclei and normal galaxy processes (e.g., X-ray binaries and hot gas). We utilized total infrared plus UV luminosities to estimate star formation rates (SFRs) and K-band luminosities and optical colors to estimate stellar masses (M * ) for the sample. Under the assumption that the galaxy-wide 2-10 keV luminosity (L gal HX ) traces the combined emission from high-mass X-ray binaries (HMXBs) and low-mass X-ray binaries, and that the power output from these components is linearly correlated with SFR and M * , respectively, we constrain the relation L gal HX = αM * + βSFR. To achieve this, we construct a Chandra-based data set composed of our new LIRG sample combined with additional samples of less actively star-forming normal galaxies and more powerful LIRGs and ultraluminous infrared galaxies (ULIRGs) from the literature. Using these data, we measure best-fit values of α = (9.05 ± 0.37) x 10 28 erg s -1 M -1 sun and β = (1.62 ± 0.22) x 10 39 erg s -1 (M sun yr -1 ) -1 . This scaling provides a more physically meaningful estimate of L gal HX , with ∼0.1-0.2 dex less scatter, than a direct linear scaling with SFR. Our results suggest that HMXBs dominate the galaxy-wide X-ray emission for galaxies with SFR/M * ∼>5.9 x 10 -11 yr -1 , a factor of ∼2.9 times lower than previous estimates. We find that several of the most powerful LIRGs and ULIRGs, with SFR/M * ∼> 10 -9 yr -1 , appear to be X-ray underluminous with respect to our best-fit relation. We argue that these galaxies are likely to contain X-ray binaries residing in compact star-forming regions

  10. Survey for δ Sct components in eclipsing binaries and new correlations between pulsation frequency and fundamental stellar characteristics

    Science.gov (United States)

    Liakos, A.; Niarchos, P.; Soydugan, E.; Zasche, P.

    2012-05-01

    CCD observations of 68 eclipsing binary systems, candidates for containing δ Scuti components, were obtained. Their light curves are analysed using the PERIOD04 software for possible pulsational behaviour. For the systems QY Aql, CZ Aqr, TY Cap, WY Cet, UW Cyg, HL Dra, HZ Dra, AU Lac, CL Lyn and IO UMa, complete light curves were observed due to the detection of a pulsating component. All of them, except QY Aql and IO UMa, are analysed with modern astronomical softwares in order to determine their geometrical and pulsational characteristics. Spectroscopic observations of WY Cet and UW Cyg were used to estimate the spectral class of their primary components, while for HZ Dra radial velocities of its primary were measured. O - C diagram analysis was performed for the cases showing peculiar orbital period variations, namely CZ Aqr, TY Cap, WY Cet and UW Cyg, with the aim of obtaining a comprehensive picture of these systems. An updated catalogue of 74 close binaries including a δ Scuti companion is presented. Moreover, a connection between orbital and pulsation periods, as well as a correlation between evolutionary status and dominant pulsation frequency for these systems, is discussed.

  11. Measuring the Stellar Populations of Individual Lyman Alpha Emitters During the Epoch of Peak Star Formation

    Science.gov (United States)

    Reddy, Naveen

    2010-09-01

    Selecting galaxies by their strong Lyman-alpha emission provides a powerful means of probing the reionization epoch and the faint/low-mass galaxies that dominate star formation at high redshift. Yet, our understanding of high-redshift Lyman-alpha emitters {LAEs} has lagged behind that of other well-studied populations {e.g., Lyman break galaxies} due to their continuum faintness and the shifting of age/mass-sensitive features into the near-IR where the high terrestrial background inhibits deep observations. All existing studies of LAEs at z>2 have used stacked optical and/or Spitzer infrared data to discern their median properties, but the actual distributions of ages, reddenings, and stellar masses for these populations are poorly characterized. To fill this glaring gap in the observations and advance our understanding of this important population, we propose WFC3/IR+F160W imaging of fields where we have conducted a survey of low redshift {z 1.9} Lyman-alpha emitters {LAEs}, in order to measure their ages and stellar masses at an epoch where such observations directly probe the age-sensitive Balmer/4000 AA breaks. The targeted sample will include 45-50 spectroscopically confirmed LAEs at z=1.7-2.1 and roughly twice as many candidates, making it the largest sample of homogeneously selected LAEs with individual measurements of the ages, masses, and dust extinction. With these data we will {1} carefully take into account the age-dependence of the extinction curve to make robust comparisons between LAEs and continuum-selected galaxies at the same redshifts; {2} combine clustering and stellar mass measurements to infer the duty cycles of LAEs and determine if they are triggered in the presence of large-scale structures; and {3} quantify the importance of the LAE phase at different galaxy luminosity and mass scales, over a large dynamic range in these properties. An economical investment of just 12 orbits will allow us to accomplish these goals, and remains the only

  12. Inferring Binary Pulsar Population Statistics Using the NANOGrav 11 YearData Set

    Science.gov (United States)

    Stetzler, Steven; Stovall, Kevin; Demorest, Paul

    2018-01-01

    The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) monitors a set of millisecond pulsars to search for the effects of gravitational waves on pulsar signals. The NANOGrav 11 Year Data Set offers a unique opportunity to explore the statistics of binary pulsar populations. Containing the timing solutions for 31 millisecond pulsars in binary orbits with white dwarf companions, this data set provides us with access to a large number of binary pulsars which have been observed with a unique level of consistency over multi-year time scales. We have used this data set to examine the binary pulsar orbital inclination angle distribution to see if the results are consistent with the standard assumption that the angles are uniformly distributed over the cosine of the inclination. This assumption could be violated if, for example, coupling between a pulsar's spin and its binary orbit causes preferential beaming in certain directions relative to the orbital plane. We will present multiple approaches and statistical tests that we have used to check this assumption. We will discuss our results for each when applied to the binary pulsars in the NANOGrav 11 Year Data Set. While only applied to orbital inclinations, the statistical analysis tools we develop are quite powerful and can be used to infer and test the population statistics of any of the parameters present in a pulsar's timing solution.

  13. Stellar black holes in globular clusters

    Science.gov (United States)

    Kulkarni, S. R.; Hut, Piet; Mcmillan, Steve

    1993-01-01

    The recent discovery of large populations of millisec pulsars associated with neutron stars in globular clusters indicates that several hundred stellar black holes of about 10 solar masses each can form within a typical cluster. While, in clusters of high central density, the rapid dynamical evolution of the black-hole population leads to an ejection of nearly all holes on a short timescale, systems of intermediate density may involve a normal star's capture by one of the surviving holes to form a low-mass X-ray binary. One or more such binaries may be found in the globular clusters surrounding our galaxy.

  14. STELLAR POPULATIONS ACROSS THE BLACK HOLE MASS–VELOCITY DISPERSION RELATION

    Energy Technology Data Exchange (ETDEWEB)

    Martín-Navarro, Ignacio; Brodie, Jean P.; Romanowsky, Aaron J. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Van den Bosch, Remco C. E. [Max-Planck Institut für Astronomie, Konigstuhl 17, D-69117 Heidelberg (Germany); Forbes, Duncan A., E-mail: imartinn@ucsc.edu [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia)

    2016-11-20

    Coevolution between supermassive black holes (BH) and their host galaxies is universally adopted in models for galaxy formation. In the absence of feedback from active galactic nuclei (AGNs), simulated massive galaxies keep forming stars in the local universe. From an observational point of view, however, such coevolution remains unclear. We present a stellar population analysis of galaxies with direct BH mass measurements and the BH mass– σ relation as a working framework. We find that over-massive BH galaxies, i.e., galaxies lying above the best-fitting BH mass– σ line, tend to be older and more α -element-enhanced than under-massive BH galaxies. The scatter in the BH mass– σ –[ α /Fe] plane is significantly lower than that in the standard BH mass– σ relation. We interpret this trend as an imprint of AGN feedback on the star formation histories of massive galaxies.

  15. The Stellar Populations Inside Expanding HI Shells in the Spiral Galaxy M33

    Science.gov (United States)

    Walterbos, Rene

    1997-07-01

    Because of its vigorous star formation activity, favorable inclination, and relative proximity, M33 is an ideal laboratory for the study of expanding HI shells in spiral galaxies. Theoretical models show that the energy deposited into the ISM by high mass stars in OB associations is capable of creating HI superbubbles. However, sparse observational evidence exists to test these models in detail. One essential ingredient of such a test is an improved census of stellar populations inside expanding HI shells. Using multi-color archival HST images of M33, we will {1} verify that association ages are consistent with dynamical ages of related shells and with ages from model predictions for bubbles of matching size and kinematics; {2} Constrain the IMF for each association by combining integrated ground-based HAlpha fluxes with the population age, present day mass function, and luminosity function derived from WFPC2 data; {3} Use this information to infer which fraction of the integrated stellar mechanical luminosity is transferred to a shell over its lifetime. Ground-based observations of associations inside expanding shells lack the UV-sensitivity and spatial resolution to adequately address these issues. Our sample of expanding neutral shells in M33 was selected using a new automated method for analysis of HI datacubes. From this robust catalog we have identified more than 30 HI supershells in M33 already imaged with WFPC2 in suitable broadband filters {F160BW, F170W, F336W, F439W, F555W, and F814W}.

  16. Simple stellar population modelling of low S/N galaxy spectra and quasar host galaxy applications

    Science.gov (United States)

    Mosby, G.; Tremonti, C. A.; Hooper, E. J.; Wolf, M. J.; Sheinis, A. I.; Richards, J. W.

    2015-02-01

    To study the effect of supermassive black holes (SMBHs) on their host galaxies it is important to study the hosts when the SMBH is near its peak activity. A method to investigate the host galaxies of high luminosity quasars is to obtain optical spectra at positions offset from the nucleus where the relative contribution of the quasar and host is comparable. However, at these extended radii the galaxy surface brightness is often low (20-22 mag arcsec-2) and the resulting spectrum might have such low signal-to-noise ratio (S/N) that it hinders analysis with standard stellar population modelling techniques. To address this problem, we have developed a method that can recover galaxy star formation histories (SFHs) from rest-frame optical spectra with S/N ˜ 5 Å-1. This method uses the statistical technique diffusion k-means to tailor the stellar population modelling basis set. Our diffusion k-means minimal basis set, composed of four broad age bins, is successful in recovering a range of galaxy SFHs. Additionally, using an analytic prescription for seeing conditions, we are able to simultaneously model scattered quasar light and the SFH of quasar host galaxies (QHGs). We use synthetic data to compare results of our novel method with previous techniques. We also present the modelling results on a previously published QHG and show that galaxy properties recovered from a diffusion k-means basis set are less sensitive to noise added to this QHG spectrum. Our new method has a clear advantage in recovering information from QHGs and could also be applied to the analysis of other low S/N galaxy spectra such as those typically obtained for high redshift objects or integral field spectroscopic surveys.

  17. The ATLAS3D Project - XXX. Star formation histories and stellar population scaling relations of early-type galaxies

    Science.gov (United States)

    McDermid, Richard M.; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; Morganti, Raffaella; Naab, Thorsten; Oosterloo, Tom; Sarzi, Marc; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie; Young, Lisa M.

    2015-04-01

    We present the stellar population content of early-type galaxies from the ATLAS3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star formation histories, mass-weighted average values of age, metallicity, and half-mass formation time-scales. Using homogeneously derived effective radii and dynamically determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (MJAM, σe, R^maj_e), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50 per cent of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>1010.5 M⊙), which themselves formed 90 per cent of their stars by z ˜ 2. The lower mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced, and have shorter star formation histories with respect to lower density regions.

  18. Lithium in a short-period tidally locked binary of M67: Implications for stellar evolution, Galactic Lithium evolution, and cosmology

    Science.gov (United States)

    Deliyannis, Constantine P.; King, Jeremy R.; Boesgaard, Ann M.; Ryan, Sean G.

    1994-01-01

    In open clusters, late-F stars exhibit a Li maximum (the Li 'peak' region) at lower abundance with age, which could be due either to stellar depletion or Galactic Li enrichment (or some other cause). We have observed a short-period tidally locked binary (SPTLB) on the Li peak region in the old cluster M67 to distinguish between alternatives. SPTLBs which synchronized in the early pre-main sequence would avoid the rotational mixing which, according to Yale models, may be responsible for depleting Li with age in open cluster dwarfs. We find that both components of the M67 SPTLB have a Li abundance lying about a factor of 2 or more above any other M67 single star and about a factor of 3 or more above the mean Li peak region abundance in M67. Our results suggest that the initial Li abundance in M67 is at least as high as approximately 3.0 = 12 + log (N(sub Li)/N(sub H)). Our high M67 SPTLB Li abundance and those in other clusters support the combination of Zahn's tidal circularization and the Yale rotational mixing theories and may indicate that the halo Li plateau (analogous to the cluster Li peak region) abundance has been depleted from a higher primordial value. Implications are discussed.

  19. M13 multiple stellar populations seen with the eyes of Strömgren photometry

    Science.gov (United States)

    Savino, A.; Massari, D.; Bragaglia, A.; Dalessandro, E.; Tolstoy, E.

    2018-03-01

    We present a photometric study of M13 multiple stellar populations over a wide field of view, covering approximately 6.5 half-light radii, using archival Isaac Newton Telescope observations to build an accurate multiband Strömgren catalogue. The use of the Strömgren index cy permits us to separate the multiple populations of M13 on the basis of their position on the red giant branch. The comparison with medium and high resolution spectroscopic analysis confirms the robustness of our selection criterion. To determine the radial distribution of stars in M13, we complemented our data set with Hubble Space Telescope observations of the cluster core, to compensate for the effect of incompleteness affecting the most crowded regions. From the analysis of the radial distributions, we do not find any significant evidence of spatial segregation. Some residuals may be present in the external regions where we observe only a small number of stars. This finding is compatible with the short dynamical time-scale of M13 and represents, to date, one of the few examples of fully spatially mixed multiple populations in a massive globular cluster.

  20. BPASS predictions for binary black hole mergers

    Science.gov (United States)

    Eldridge, J. J.; Stanway, E. R.

    2016-11-01

    Using the Binary Population and Spectral Synthesis code, BPASS, we have calculated the rates, time-scales and mass distributions for binary black hole (BH) mergers as a function of metallicity. We consider these in the context of the recently reported first Laser Interferometer Gravitational-Wave Observatory (LIGO) event detection. We find that the event has a very low probability of arising from a stellar population with initial metallicity mass fraction above Z = 0.010 (Z ≳ 0.5 Z⊙). Binary BH merger events with the reported masses are most likely in populations below 0.008 (Z ≲ 0.4 Z⊙). Events of this kind can occur at all stellar population ages from 3 Myr up to the age of the Universe, but constitute only 0.1-0.4 per cent of binary BH mergers between metallicities of Z = 0.001 and 0.008. However at metallicity Z = 10-4, 26 per cent of binary BH mergers would be expected to have the reported masses. At this metallicity, the progenitor merger times can be close to ≈10 Gyr and rotationally mixed stars evolving through quasi-homogeneous evolution, due to mass transfer in a binary, dominate the rate. The masses inferred for the BHs in the binary progenitor of GW 150914 are amongst the most massive expected at anything but the lowest metallicities in our models. We discuss the implications of our analysis for the electromagnetic follow-up of future LIGO event detections.

  1. The SAURON project : XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

    NARCIS (Netherlands)

    Kuntschner, Harald; Emsellem, Eric; Bacon, Roland; Cappellari, Michele; Davies, Roger L.; de Zeeuw, P. Tim; Falcon-Barroso, Jesus; Krajnovic, Davor; McDermid, Richard M.; Peletier, Reynier F.; Sarzi, Marc; Shapiro, Kristen L.; van den Bosch, Remco C. E.; van de Ven, Glenn; Krajnović, Davor

    2010-01-01

    We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of H beta, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise ratio, together with

  2. The SAURON project - XVII. Stellar population analysis of the absorption line strength maps of 48 early-type galaxies

    NARCIS (Netherlands)

    Kuntschner, Harald; Emsellem, Eric; Bacon, Roland; Cappellari, Michele; Davies, Roger L.; de Zeeuw, P. Tim; Falcón-Barroso, Jesús; Krajnović, Davor; McDermid, Richard M.; Peletier, Reynier F.; Sarzi, Marc; Shapiro, Kristen L.; van den Bosch, Remco C. E.; van de Ven, Glenn

    2010-01-01

    We present a stellar population analysis of the absorption line strength maps for 48 early-type galaxies from the SAURON sample. Using the line strength index maps of Hβ, Fe5015 and Mgb, measured in the Lick/IDS system and spatially binned to a constant signal-to-noise ratio, together with

  3. EVIDENCE FOR INTERMEDIATE-AGE STELLAR POPULATIONS IN EARLY-TYPE GALAXIES FROM K-BAND SPECTROSCOPY

    NARCIS (Netherlands)

    Marmol-Queralto, E.; Cardiel, N.; Sanchez-Blazquez, P.; Trager, S. C.; Peletier, R. F.; Kuntschner, H.; Silva, D. R.; Cenarro, A. J.; Vazdekis, A.; Gorgas, J.

    2009-01-01

    The study of stellar populations in early-type galaxies in different environments is a powerful tool for constraining their star formation histories. This study has been traditionally restricted to the optical range, where dwarfs around the turn-off and stars at the base of the red giant branch

  4. Calibrating Stellar Population Models in the Near-IR: Implications Due to the Presence of Carbon–Rich AGB Stars

    NARCIS (Netherlands)

    Lyubenova, M.; Kuntschner, H.; Rejbuka, M.; Silva, D. R.; Kissler-Patig, M.; Tacconi-Garman, L. E.; Larsen, S.S.|info:eu-repo/dai/nl/304833347

    2011-01-01

    We present our near-IR integrated spectral library of six globular clusters in the LMC and compare the data with existing stellar populations models. We find good agreement between models and data in the case of old, metal-poor clusters, while for intermediate-age and more metal-rich clusters we

  5. Constraining Roche-Lobe Overflow Models Using the Hot-Subdwarf Wide Binary Population

    Science.gov (United States)

    Vos, Joris; Vučković, Maja

    2017-12-01

    One of the important issues regarding the final evolution of stars is the impact of binarity. A rich zoo of peculiar, evolved objects are born from the interaction between the loosely bound envelope of a giant, and the gravitational pull of a companion. However, binary interactions are not understood from first principles, and the theoretical models are subject to many assumptions. It is currently agreed upon that hot subdwarf stars can only be formed through binary interaction, either through common envelope ejection or stable Roche-lobe overflow (RLOF) near the tip of the red giant branch (RGB). These systems are therefore an ideal testing ground for binary interaction models. With our long term study of wide hot subdwarf (sdB) binaries we aim to improve our current understanding of stable RLOF on the RGB by comparing the results of binary population synthesis studies with the observed population. In this article we describe the current model and possible improvements, and which observables can be used to test different parts of the interaction model.

  6. The Age of the Young Bulge-like Population in the Stellar System Terzan 5: Linking the Galactic Bulge to the High-z Universe

    NARCIS (Netherlands)

    Ferraro, F. R.; Massari, D.; Dalessandro, E.; Lanzoni, B.; Origlia, L.; Rich, R. M.; Mucciarelli, A.

    2016-01-01

    The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations

  7. A spectroscopic survey of dwarf galaxies in the Coma cluster: stellar populations, environment and downsizing

    Science.gov (United States)

    Smith, Russell J.; Lucey, John R.; Hudson, Michael J.; Allanson, Steven P.; Bridges, Terry J.; Hornschemeier, Ann E.; Marzke, Ronald O.; Miller, Neal A.

    2009-02-01

    We investigate the stellar populations in a sample of 89 faint red galaxies in the Coma cluster, using high signal-to-noise ratio (S/N) spectroscopy from the 6.5-m MMT. Our sample is drawn from two 1° fields, one centred on the cluster core and the other located 1° to the south-west of the cluster centre. The target galaxies are mostly 2-4mag fainter than M* galaxies with these luminosities have been previously studied only using small samples, or at low S/N. For a comparison sample we use published high-S/N data for red-sequence galaxies in the Shapley supercluster. We use state-of-the-art stellar population models (by R. Schiavon) to interpret the absorption-line indices and infer the single-burst-equivalent age and metallicity (Fe/H) for each galaxy, as well as the abundances of the light elements Mg, Ca, C and N. The ages of the Coma dwarfs span a wide range from 10Gyr, with a strong environmental dependence. The oldest galaxies are found only in the core, while most of the galaxies in the outer south-west field have ages ~3Gyr. The galaxies have a metallicity range -1.0 histories perform no better than single-burst models in reproducing the observed line indices. Assuming a star formation history dominated by a single burst, the number of dwarf galaxies on the red sequence in the Coma core has doubled since z ~ 0.7. Assuming instead an abruptly truncated constant star formation rate, the equivalent redshift is z ~ 0.4. These estimates bracket the red-sequence growth time-scales found by direct studies of distant clusters. In the south-west field, the red sequence was established only at z ~ 0.2 for a burst-dominated star formation history (z ~ 0.1 for the truncated case). Our observations confirm previous indications of very recently quenched star formation in this part of the cluster. Our results strongly support the scenario in which much of the cluster passive dwarf population (in this luminosity range) was generated by environment-driven transformation

  8. The Spatial and Age Distribution of Stellar Populations in DDO 190

    Science.gov (United States)

    Aparicio, A.; Tikhonov, N.

    2000-05-01

    The spatial distribution of stellar populations, the star formation history, and other properties of the dwarf irregular (dIrr) galaxy DDO 190 have been analyzed using color-magnitude diagrams of about 3900 resolved stars and the Hα fluxes of H II regions. From the mean color index of the red giant branch (RGB), a mean metallicity [Fe/H]=-2.0 is obtained. The I magnitude of the tip of the RGB has been used to estimate the distance. DDO 190 is 2.9+/-0.2 Mpc from the Milky Way, 2.1 Mpc from the M94 group (Cn 5-1), 2.4 Mpc from the M81 group, and 2.9 Mpc from the barycenter of the Local Group, all indicating that it is an isolated field galaxy. The surface brightness distribution of the galaxy is well fitted by ellipses of ellipticity e=1-a/b=0.1 and position angle of 82°. The radial star density distribution follows an exponential law of scale length α=43.4", corresponding to 611 pc. The Holmberg semimajor axis to μB=26.5 is estimated to be rB26.5=3.0‧. Stellar populations of different ages in DDO 190 show strong spatial decoupling, the oldest population appearing much more extended than the youngest. Stars younger than 0.1 Gyr occupy only the central 40" (0.55 kpc) stars younger than a few (~4) Gyr extend out to ~80" (125 kpc), and for larger galactocentric distances, only older stars seem to be present. This behavior is found in all the dIrr galaxies for which spatially extended studies have been performed and could be related to the kinematic history of the galaxy. Based on observations made with the 2.5 m Nordic Optical Telescope operated on the island of La Palma by the Nordic Optical Telescope Scientific Association in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  9. Interdependent binary choices under social influence: Phase diagram for homogeneous unbiased populations

    Science.gov (United States)

    Fernández del Río, Ana; Korutcheva, Elka; de la Rubia, Javier

    2012-07-01

    Coupled Ising models are studied in a discrete choice theory framework, where they can be understood to represent interdependent choice making processes for homogeneous populations under social influence. Two different coupling schemes are considered. The nonlocal or group interdependence model is used to study two interrelated groups making the same binary choice. The local or individual interdependence model represents a single group where agents make two binary choices which depend on each other. For both models, phase diagrams, and their implications in socioeconomic contexts, are described and compared in the absence of private deterministic utilities (zero opinion fields).

  10. The vertical metallicity gradients of mono-age stellar populations in the Milky Way with the RAVE and Gaia data

    Science.gov (United States)

    Ciucǎ, Ioana; Kawata, Daisuke; Lin, Jane; Casagrande, Luca; Seabroke, George; Cropper, Mark

    2018-03-01

    We investigate the vertical metallicity gradients of five mono-age stellar populations between 0 and 11 Gyr for a sample of 18 435 dwarf stars selected from the cross-matched Tycho-Gaia Astrometric Solution and Radial Velocity Experiment (RAVE) Data Release 5. We find a correlation between the vertical metallicity gradients and age, with no vertical metallicity gradient in the youngest population and an increasingly steeper negative vertical metallicity gradient for the older stellar populations. The metallicity at disc plane remains almost constant between 2 and 8 Gyr, and it becomes significantly lower for the 8 population. The current analysis also reveals that the intrinsic dispersion in metallicity increases steadily with age. We discuss that our results are consistent with a scenario that (thin) disc stars formed from a flaring (thin) star-forming disc.

  11. BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    El-Badry, Kareem; Geha, Marla [Department of Astronomy, Yale University, New Haven, CT (United States); Wetzel, Andrew; Hopkins, Philip F. [TAPIR, California Institute of Technology, Pasadena, CA USA (United States); Kereš, Dusan; Chan, T. K. [Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, La Jolla (United States); Faucher-Giguère, Claude-André, E-mail: kareem.el-badry@yale.edu [Department of Physics and Astronomy and CIERA, Northwestern University, Evanston, IL (United States)

    2016-04-01

    We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (M{sub star} = 2 × 10{sup 6} − 5 × 10{sup 10} M{sub ⊙}) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the impact on the stellar component: kinematics, radial migration, size evolution, and population gradients. Feedback-driven outflows/inflows drive significant radial stellar migration over both short and long timescales via two processes: (1) outflowing/infalling gas can remain star-forming, producing young stars that migrate ∼1 kpc within their first 100 Myr, and (2) gas outflows/inflows drive strong fluctuations in the global potential, transferring energy to all stars. These processes produce several dramatic effects. First, galaxies’ effective radii can fluctuate by factors of >2 over ∼200 Myr, and these rapid size fluctuations can account for much of the observed scatter in the radius at fixed M{sub star}. Second, the cumulative effects of many outflow/infall episodes steadily heat stellar orbits, causing old stars to migrate outward most strongly. This age-dependent radial migration mixes—and even inverts—intrinsic age and metallicity gradients. Thus, the galactic-archaeology approach of calculating radial star formation histories from stellar populations at z = 0 can be severely biased. These effects are strongest at M{sub star} ≈ 10{sup 7–9.6} M{sub ⊙}, the same regime where feedback most efficiently cores galaxies. Thus, detailed measurements of stellar kinematics in low-mass galaxies can strongly constrain feedback models and test baryonic solutions to small-scale problems in ΛCDM.

  12. The X-Ray Binary Population of the Nearby Dwarf Starburst Galaxy IC 10: Variable and Transient X-Ray Sources

    Energy Technology Data Exchange (ETDEWEB)

    Laycock, Silas; Cappallo, Rigel [Department of Physics and Applied Physics, University of Massachusetts Lowell, MA, 01854 (United States); Williams, Benjamin F.; Binder, Breanna [University of Washington, Department of Astronomy, Box 351580, Seattle, WA 98195 (United States); Prestwich, Andrea [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138 (United States); Christodoulou, Dimitris M. [Department of Mathematical Sciences, University of Massachusetts Lowell, MA, 01854 (United States)

    2017-02-10

    We have monitored the Cassiopeia dwarf galaxy (IC 10) in a series of 10 Chandra ACIS-S observations to capture its variable and transient X-ray source population, which is expected to be dominated by High Mass X-ray Binaries (HMXBs). We present a sample of 21 X-ray sources that are variable between observations at the 3 σ level, from a catalog of 110 unique point sources. We find four transients (flux variability ratio greater than 10) and a further eight objects with ratios >5. The observations span the years 2003–2010 and reach a limiting luminosity of >10{sup 35} erg s{sup −1}, providing sensitivity to X-ray binaries in IC 10 as well as flare stars in the foreground Milky Way. The nature of the variable sources is investigated from light curves, X-ray spectra, energy quantiles, and optical counterparts. The purpose of this study is to discover the composition of the X-ray binary population in a young starburst environment. IC 10 provides a sharp contrast in stellar population age (<10 My) when compared to the Magellanic Clouds (40–200 My) where most of the known HMXBs reside. We find 10 strong HMXB candidates, 2 probable background Active Galactic Nuclei, 4 foreground flare-stars or active binaries, and 5 not yet classifiable sources. Complete classification of the sample requires optical spectroscopy for radial velocity analysis and deeper X-ray observations to obtain higher S/N spectra and search for pulsations. A catalog and supporting data set are provided.

  13. The population of single and binary white dwarfs of the Galactic bulge

    Science.gov (United States)

    Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

    2018-02-01

    Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-disk bulge stars is negligible.

  14. The population of single and binary white dwarfs of the Galactic bulge

    Science.gov (United States)

    Torres, S.; García-Berro, E.; Cojocaru, R.; Calamida, A.

    2018-05-01

    Recent Hubble Space Telescope observations have unveiled the white dwarf cooling sequence of the Galactic bulge. Although the degenerate sequence can be well fitted employing the most up-to-date theoretical cooling sequences, observations show a systematic excess of red objects that cannot be explained by the theoretical models of single carbon-oxygen white dwarfs of the appropriate masses. Here, we present a population synthesis study of the white dwarf cooling sequence of the Galactic bulge that takes into account the populations of both single white dwarfs and binary systems containing at least one white dwarf. These calculations incorporate state-of-the-art cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres, for both white dwarfs with carbon-oxygen and helium cores, and also take into account detailed prescriptions of the evolutionary history of binary systems. Our Monte Carlo simulator also incorporates all the known observational biases. This allows us to model with a high degree of realism the white dwarf population of the Galactic bulge. We find that the observed excess of red stars can be partially attributed to white dwarf plus main sequence binaries, and to cataclysmic variables or dwarf novae. Our best fit is obtained with a higher binary fraction and an initial mass function slope steeper than standard values, as well as with the inclusion of differential reddening and blending. Our results also show that the possible contribution of double degenerate systems or young and thick-discbulge stars is negligible.

  15. The Magellan PFS Planet Search Program: Radial Velocity and Stellar Abundance Analyses of the 360 au, Metal-poor Binary “Twins” HD 133131A & B

    Science.gov (United States)

    Teske, Johanna K.; Shectman, Stephen A.; Vogt, Steve S.; Díaz, Matías; Butler, R. Paul; Crane, Jeffrey D.; Thompson, Ian B.; Arriagada, Pamela

    2016-12-01

    We present a new precision radial velocity (RV) data set that reveals multiple planets orbiting the stars in the ˜360 au, G2+G2 “twin” binary HD 133131AB. Our six years of high-resolution echelle observations from MIKE and five years from the Planet Finder Spectrograph (PFS) on the Magellan telescopes indicate the presence of two eccentric planets around HD 133131A with minimum masses of 1.43 ± 0.03 and 0.63 ± 0.15 {{ M }}{{J}} at 1.44 ± 0.005 and 4.79 ± 0.92 au, respectively. Additional PFS observations of HD 133131B spanning five years indicate the presence of one eccentric planet of minimum mass 2.50 ± 0.05 {{ M }}{{J}} at 6.40 ± 0.59 au, making it one of the longest-period planets detected with RV to date. These planets are the first to be reported primarily based on data taken with the PFS on Magellan, demonstrating the instrument’s precision and the advantage of long-baseline RV observations. We perform a differential analysis between the Sun and each star, and between the stars themselves, to derive stellar parameters and measure a suite of 21 abundances across a wide range of condensation temperatures. The host stars are old (likely ˜9.5 Gyr) and metal-poor ([Fe/H] ˜ -0.30), and we detect a ˜0.03 dex depletion in refractory elements in HD 133131A versus B (with standard errors ˜0.017). This detection and analysis adds to a small but growing sample of binary “twin” exoplanet host stars with precise abundances measured, and represents the most metal-poor and likely oldest in that sample. Overall, the planets around HD 133131A and B fall in an unexpected regime in planet mass-host star metallicity space and will serve as an important benchmark for the study of long-period giant planets. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  16. Exploring Cosmic Voids with GALEX: Stellar Populations and Primordial Jeans Mass Objects

    Science.gov (United States)

    Gregg, Michael

    . Such primordial Jeans mass objects are predicted by theory to exist in voids. Finding them would shed light on the earliest epoch of structure formation in the Universe, while a null result would test theories of cold dark matter and structure formation in critical ways. Most of this research relies on archival data and is enabled particularly by GALEX near and far ultraviolet photometry. Sloan Digital Sky Survey data also play a key role. We will employ stellar population modeling to derive ages and star formation rates for void galaxies, gaining insight into their evolutionary history, past, present, and future. We will obtain follow-up ground-based longslit and multifiber spectroscopy to support the results of the GALEX-SDSS studies, particularly the searches for additional early type galaxies and primordial Jeans mass objects. By sheer weight of numbers, this program will dwarf previous photometric studies of void galaxies, and applying GALEX in a systematic way opens new windows on void galaxy evolution and stellar populations. The search for Jeans mass objects in voids, whether positive or null, will have profound implications for galaxy and large scale structure formation and evolution, testing critical tenets of cold dark matter hierarchical galaxy formation, directly probing the origin of structure in the Universe on galactic and super-galactic scales.

  17. The SLUGGS survey: globular cluster stellar population trends from weak absorption lines in stacked spectra

    Science.gov (United States)

    Usher, Christopher; Forbes, Duncan A.; Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Conroy, Charlie; Foster, Caroline; Pastorello, Nicola; Pota, Vincenzo; Arnold, Jacob A.

    2015-01-01

    As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ˜90 Å-1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.

  18. STELLAR POPULATION GRADIENTS IN ULTRALUMINOUS INFRARED GALAXIES: IMPLICATIONS FOR GAS INFLOW TIMESCALES

    International Nuclear Information System (INIS)

    Soto, Kurt T.; Martin, Crystal L.

    2010-01-01

    Using longslit, optical spectra of ultraluminous infrared galaxies, we measure the evolution in the star formation intensity during galactic mergers. In individual galaxies, we resolve kiloparsec scales allowing comparison of the nucleus, inner disk, and outer disk. We find that the strength of the Hβ absorption line increases with the projected distance from the center of the merger, typically reaching about 9 A around 10 kpc. At these radii, the star formation intensity must have rapidly decreased about 300-400 Myr ago; only stellar populations deficient in stars more massive than Type A produce such strong Balmer absorption. In contrast, we find the star formation history in the central kiloparsec consistent with continuous star formation. Our measurements indicate that gas depletion occurs from the outer disk inward during major mergers. This result is consistent with merger-induced gas inflow and empirically constrains the gas inflow timescale. Numerical simulations accurately calculate the total amount of infalling gas but often assume the timescale for infall. These new measurements are therefore central to modeling merger-induced star formation and active galactic nucleus activity.

  19. YOUNG STELLAR POPULATIONS IN MYStIX STAR-FORMING REGIONS: CANDIDATE PROTOSTARS

    Energy Technology Data Exchange (ETDEWEB)

    Romine, Gregory; Feigelson, Eric D.; Getman, Konstantin V. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Kuhn, Michael A. [Millennium Institute of Astrophysics, Camino El Observatorio 1515, Las Condes, Santiago (Chile); Povich, Matthew S., E-mail: edf@astro.psu.edu [Department of Physics and Astronomy, California State Polytechnic University, 3801 West Temple Ave., Pomona, CA 91768 (United States)

    2016-12-20

    The Massive Young Star-Forming Complex in Infrared and X-ray (MYStIX) project provides a new census on stellar members of massive star-forming regions within 4 kpc. Here the MYStIX Infrared Excess catalog and Chandra -based X-ray photometric catalogs are mined to obtain high-quality samples of Class I protostars using criteria designed to reduce extragalactic and Galactic field star contamination. A total of 1109 MYStIX Candidate Protostars (MCPs) are found in 14 star-forming regions. Most are selected from protoplanetary disk infrared excess emission, but 20% are found from their ultrahard X-ray spectra from heavily absorbed magnetospheric flare emission. Two-thirds of the MCP sample is newly reported here. The resulting samples are strongly spatially associated with molecular cores and filaments on Herschel far-infrared maps. This spatial agreement and other evidence indicate that the MCP sample has high reliability with relatively few “false positives” from contaminating populations. But the limited sensitivity and sparse overlap among the infrared and X-ray subsamples indicate that the sample is very incomplete with many “false negatives.” Maps, tables, and source descriptions are provided to guide further study of star formation in these regions. In particular, the nature of ultrahard X-ray protostellar candidates without known infrared counterparts needs to be elucidated.

  20. Being WISE. I. Validating stellar population models and M {sub *}/L ratios at 3.4 and 4.6 μm

    Energy Technology Data Exchange (ETDEWEB)

    Norris, Mark A.; Meidt, Sharon; Van de Ven, Glenn; Schinnerer, Eva; Groves, Brent; Querejeta, Miguel, E-mail: norris@mpia.de [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)

    2014-12-10

    Using data from the Wide-field Infrared Survey Explorer mission, we have measured near infra-red (NIR) photometry of a diverse sample of dust-free stellar systems (globular clusters, dwarf and giant early-type galaxies) which have metallicities that span the range -2.2 < [Fe/H] (dex) < 0.3. This dramatically increases the sample size and broadens the metallicity regime over which the 3.4 (W1) and 4.6 μm (W2) photometry of stellar populations have been examined. We find that the W1 – W2 colors of intermediate and old (>2 Gyr) stellar populations are insensitive to the age of the stellar population, but that the W1 – W2 colors become bluer with increasing metallicity, a trend not well reproduced by most stellar population synthesis (SPS) models. In common with previous studies, we attribute this behavior to the increasing strength of the CO absorption feature located in the 4.6 μm bandpass with metallicity. Having used our sample to validate the efficacy of some of the SPS models, we use these models to derive stellar mass-to-light ratios in the W1 and W2 bands. Utilizing observational data from the SAURON and ATLAS3D surveys, we demonstrate that these bands provide extremely simple, yet robust stellar mass tracers for dust free older stellar populations that are freed from many of the uncertainties common among optical estimators.

  1. Coupling hydrodynamics with comoving frame radiative transfer. II. Stellar wind stratification in the high-mass X-ray binary Vela X-1

    Science.gov (United States)

    Sander, A. A. C.; Fürst, F.; Kretschmar, P.; Oskinova, L. M.; Todt, H.; Hainich, R.; Shenar, T.; Hamann, W.-R.

    2018-02-01

    Context. Vela X-1, a prototypical high-mass X-ray binary (HMXB), hosts a neutron star (NS) in a close orbit around an early-B supergiant donor star. Accretion of the donor star's wind onto the NS powers its strong X-ray luminosity. To understand the physics of HMXBs, detailed knowledge about the donor star winds is required. Aims: To gain a realistic picture of the donor star in Vela X-1, we constructed a hydrodynamically consistent atmosphere model describing the wind stratification while properly reproducing the observed donor spectrum. To investigate how X-ray illumination affects the stellar wind, we calculated additional models for different X-ray luminosity regimes. Methods: We used the recently updated version of the Potsdam Wolf-Rayet code to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer. Results: The wind flow in Vela X-1 is driven by ions from various elements, with Fe III and S III leading in the outer wind. The model-predicted mass-loss rate is in line with earlier empirical studies. The mass-loss rate is almost unaffected by the presence of the accreting NS in the wind. The terminal wind velocity is confirmed at v∞≈ 600 km s-1. On the other hand, the wind velocity in the inner region where the NS is located is only ≈100 km s-1, which is not expected on the basis of a standard β-velocity law. In models with an enhanced level of X-rays, the velocity field in the outer wind can be altered. If the X-ray flux is too high, the acceleration breaks down because the ionization increases. Conclusions: Accounting for radiation hydrodynamics, our Vela X-1 donor atmosphere model reveals a low wind speed at the NS location, and it provides quantitative information on wind driving in this important HMXB.

  2. THE PROPAGATION OF UNCERTAINTIES IN STELLAR POPULATION SYNTHESIS MODELING. I. THE RELEVANCE OF UNCERTAIN ASPECTS OF STELLAR EVOLUTION AND THE INITIAL MASS FUNCTION TO THE DERIVED PHYSICAL PROPERTIES OF GALAXIES

    International Nuclear Information System (INIS)

    Conroy, Charlie; Gunn, James E.; White, Martin

    2009-01-01

    The stellar masses, mean ages, metallicities, and star formation histories of galaxies are now commonly estimated via stellar population synthesis (SPS) techniques. SPS relies on stellar evolution calculations from the main sequence to stellar death, stellar spectral libraries, phenomenological dust models, and stellar initial mass functions (IMFs) to translate the evolution of a multimetallicity, multi-age set of stars into a prediction for the time-evolution of the integrated light from that set of stars. Each of these necessary inputs carries significant uncertainties that have until now received little systematic attention. The present work is the first in a series that explores the impact of uncertainties in key phases of stellar evolution and the IMF on the derived physical properties of galaxies and the expected luminosity evolution for a passively evolving set of stars. A Monte Carlo Markov Chain approach is taken to fit near-UV through near-IR photometry of a representative sample of low- and high-redshift galaxies with this new SPS model. Significant results include the following. (1) Including uncertainties in stellar evolution, stellar masses at z ∼ 0 carry errors of ∼0.3 dex at 95% CL with little dependence on luminosity or color, while at z ∼ 2, the masses of bright red galaxies are uncertain at the ∼0.6 dex level. (2) Either current stellar evolution models, current observational stellar libraries, or both, do not adequately characterize the metallicity-dependence of the thermally pulsating AGB phase. (3) Conservative estimates on the uncertainty of the slope of the IMF in the solar neighborhood imply that luminosity evolution per unit redshift is uncertain at the ∼0.4 mag level in the K band, which is a substantial source of uncertainty for interpreting the evolution of galaxy populations across time. Any possible evolution in the IMF, as suggested by several independent lines of evidence, will only exacerbate this problem. (4) Assuming a

  3. The Effects of Stellar Dynamics on the Evolution of Young, Dense Stellar Systems

    Science.gov (United States)

    Belkus, H.; van Bever, J.; Vanbeveren, D.

    In this paper, we report on first results of a project in Brussels in which we study the effects of stellar dynamics on the evolution of young dense stellar systems using 3 decades of expertise in massive-star evolution and our population (number and spectral) synthesis code. We highlight an unconventionally formed object scenario (UFO-scenario) for Wolf Rayet binaries and study the effects of a luminous blue variable-type instability wind mass-loss formalism on the formation of intermediate-mass black holes.

  4. Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

    Science.gov (United States)

    Bragaglia, A.; Gratton, R. G.; Carretta, E.; D'Orazi, V.; Sneden, C.; Lucatello, S.

    2012-12-01

    The most massive star clusters include several generations of stars with a different chemical composition (mainly revealed by an Na-O anti-correlation) while low-mass star clusters appear to be chemically homogeneous. We are investigating the chemical composition of several clusters with masses of a few 104 M⊙ to establish the lower mass limit for the multiple stellar population phenomenon. Using VLT/FLAMES spectra we determine abundances of Fe, O, Na, and several other elements (α, Fe-peak, and neutron-capture elements) in the old open cluster Berkeley 39. This is a massive open cluster: M ~ 104 M⊙, approximately at the border between small globular clusters and large open clusters. Our sample size of about 30 stars is one of the largest studied for abundances in any open cluster to date, and will be useful to determine improved cluster parameters, such as age, distance, and reddening when coupled with precise, well-calibrated photometry. We find that Berkeley 39 is slightly metal-poor, ⟨[Fe/H]⟩ = -0.20, in agreement with previous studies of this cluster. More importantly, we do not detect any star-to-star variation in the abundances of Fe, O, and Na within quite stringent upper limits. The rms scatter is 0.04, 0.10, and 0.05 dex for Fe, O, and Na, respectively. This small spread can be entirely explained by the noise in the spectra and by uncertainties in the atmospheric parameters. We conclude that Berkeley 39 is a single-population cluster. Based on observations collected at ESO telescopes under programme 386.B-0009.Tables 2 and 3 are available in electronic form at http://www.aanda.org

  5. A YOUNG MASSIVE STELLAR POPULATION AROUND THE INTERMEDIATE-MASS BLACK HOLE ESO 243-49 HLX-1

    International Nuclear Information System (INIS)

    Farrell, S. A.; Servillat, M.; Pforr, J.; Maraston, C.; Maccarone, T. J.; Knigge, C.; Godet, O.; Webb, N. A.; Barret, D.; Belmont, R.; Gosling, A. J.; Wiersema, K.

    2012-01-01

    We present Hubble Space Telescope and simultaneous Swift X-ray Telescope observations of the strongest candidate intermediate-mass black hole (IMBH) ESO 243-49 HLX-1. Fitting the spectral energy distribution from X-ray to near-infrared wavelengths showed that the broadband spectrum is not consistent with simple and irradiated disk models, but is well described by a model comprised of an irradiated accretion disk plus a ∼10 6 M ☉ stellar population. The age of the population cannot be uniquely constrained, with both young and old stellar populations allowed. However, the old solution requires excessive disk reprocessing and an extremely small disk, so we favor the young solution (∼13 Myr). In addition, the presence of dust lanes and the lack of any nuclear activity from X-ray observations of the host galaxy suggest that a gas-rich minor merger may have taken place less than ∼200 Myr ago. Such a merger event would explain the presence of the IMBH and the young stellar population.

  6. ARGOS - III. Stellar populations in the Galactic bulge of the Milky Way

    Science.gov (United States)

    Ness, M.; Freeman, K.; Athanassoula, E.; Wylie-de-Boer, E.; Bland-Hawthorn, J.; Asplund, M.; Lewis, G. F.; Yong, D.; Lane, R. R.; Kiss, L. L.

    2013-04-01

    We present the metallicity results from the ARGOS spectroscopic survey of the Galactic bulge. Our aim is to understand the formation of the Galactic bulge: did it form via mergers, as expected from Λ cold dark matter theory, or from disc instabilities, as suggested by its boxy/peanut shape, or both? Our stars are mostly red clump giants, which have a well-defined absolute magnitude from which distances can be determined. We have obtained spectra for 28 000 stars at a spectral resolution of R = 11 000. From these spectra, we have determined stellar parameters and distances to an accuracy of -0.5 are part of the boxy/peanut bar/bulge. We associate the lower metallicity stars ([Fe/H] -0.5, we find two discrete populations: (i) stars with [Fe/H] ≈ -0.25 which provide a roughly constant fraction of the stars in the latitude interval b = -5° to -10°, and (ii) a kinematically colder, more metal-rich population with mean [Fe/H] ≈ +0.15 which is more prominent closer to the plane. The changing ratio of these components with latitude appears as a vertical abundance gradient of the bulge. We attribute both of these bulge components to instability-driven bar/bulge formation from the thin disc. We associate the thicker component with the stars of the early less metal-rich thin disc, and associate the more metal-rich population concentrated to the plane with the colder more metal-rich stars of the early thin disc, similar to the colder and younger more metal-rich stars seen in the thin disc in the solar neighbourhood today. We do not exclude a weak underlying classical merger-generated bulge component, but see no obvious kinematic association of any of our bulge stars with such a classical bulge component. The clear spatial and kinematic separation of the two bulge populations (i) and (ii) makes it unlikely that any significant merger event could have affected the inner regions of the Galaxy since the time when the bulge-forming instabilities occurred.

  7. Variable Stars and Stellar Populations in Andromeda XXVII. IV. An Off-centered, Disrupted Galaxy

    Science.gov (United States)

    Cusano, Felice; Garofalo, Alessia; Clementini, Gisella; Cignoni, Michele; Muraveva, Tatiana; Tessicini, Gianni; Testa, Vincenzo; Paris, Diego; Federici, Luciana; Marconi, Marcella; Ripepi, Vincenzo; Musella, Ilaria

    2017-12-01

    We present B and V time-series photometry of the M31 satellite galaxy Andromeda XXVII (And XXVII) that we observed with the Large Binocular Cameras of the Large Binocular Telescope. In the field of And XXVII we have discovered a total of 90 variables: 89 RR Lyrae stars and 1 Anomalous Cepheid. The average period of the fundamental mode RR Lyrae stars (RRab) =0.59 {days} (σ = 0.05 day) and the period-amplitude diagram place And XXVII in the class of Oosterhoff I/Intermediate objects. Combining information from the color-magnitude diagram (CMD) and the variable stars, we find evidence for a single old and metal-poor stellar population with [Fe/H] ˜ -1.8 dex and t ˜ 13 Gyr in And XXVII. The spatial distributions of RR Lyrae and red giant branch (RGB) stars give clear indication that And XXVII is a completely disrupted system. This is also supported by the spread observed along the line of sight in the distance to the RR Lyrae stars. The highest concentration of RGB and RR Lyrae stars is found in a circular area of 4 arcmin in radius, centered about 0.°2 in the southeast direction from Richardson et al.’s center coordinates of And XXVII. The CMD of this region is well-defined, with a prominent RGB and 15 RR Lyrae stars (out of the 18 found in the region) tracing a very tight horizontal branch at =25.24 {mag} σ = 0.06 mag (average over 15 stars). We show that And XXVII is a strong candidate building block of the M31 halo. Based on data collected with the Large Binocular Cameras at the Large Binocular Telescope, PI: G. Clementini.

  8. Galactic globular cluster NGC 6752 and its stellar population as inferred from multicolor photometry

    Energy Technology Data Exchange (ETDEWEB)

    Kravtsov, Valery [Instituto de Astronomía, Universidad Católica del Norte, Avenida Angamos 0610, Casilla 1280, Antofagasta (Chile); Alcaíno, Gonzalo [Isaac Newton Institute of Chile, Ministerio de Educación de Chile, Casilla 8-9, Correo 9, Santiago (Chile); Marconi, Gianni; Alvarado, Franklin, E-mail: vkravtsov@ucn.cl, E-mail: inewton@terra.cl, E-mail: falvarad@eso.org, E-mail: gmarconi@eso.org [ESO-European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)

    2014-03-01

    This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ∼300 Å relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U – B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of ΔU ≈ 0.2 mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U – B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U – B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U – B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter ΔV{sub ZAHB}{sup clump} = 0.98 ± 0.12.

  9. Kinematics and stellar populations of low-luminosity early-type galaxies in the Abell 496 cluster

    Science.gov (United States)

    Chilingarian, I. V.; Cayatte, V.; Durret, F.; Adami, C.; Balkowski, C.; Chemin, L.; Laganá, T. F.; Prugniel, P.

    2008-07-01

    Context: The morphology and stellar populations of low-luminosity early-type galaxies in clusters have until now been limited to a few relatively nearby clusters such as Virgo or Fornax. Scenarii for the formation and evolution of dwarf galaxies in clusters are therefore not well constrained. Aims: We investigate here the morphology and stellar populations of low-luminosity galaxies in the relaxed richness class 1 cluster Abell 496 (z = 0.0330). Methods: Deep multiband imaging obtained with the CFHT Megacam allowed us to select a sample of faint galaxies, defined here as objects with magnitudes 18 Giraffe spectrograph with a resolving power R = 6300. We present structural analysis and colour maps for the 48 galaxies belonging to the cluster. We fit the spectra of 46 objects with PEGASE.HR synthetic spectra to estimate the ages, metallicities, and velocity dispersions. We estimated possible biases by similarly analysing spectra of ~1200 early-type galaxies from the Sloan Digital Sky Survey Data Release 6 (SDSS DR6). We computed values of α/Fe abundance ratios from the measurements of Lick indices. We briefly discuss effects of the fixed aperture size on the measurements. Results: For the first time, high-precision estimates of stellar population properties have been obtained for a large sample of faint galaxies in a cluster, allowing for the extension of relations between stellar populations and internal kinematics to the low-velocity dispersion regime. We have revealed a peculiar population of elliptical galaxies in the core of the cluster, resembling massive early-type galaxies by their stellar population properties and velocity dispersions, but having luminosities of about 2 mag fainter. Conclusions: External mechanisms of gas removal (ram pressure stripping and gravitational harassment) are more likely to have occurred than internal mechanisms such as supernova-driven winds. The violent tidal stripping of intermediate-luminosity, early-type galaxies in the

  10. Binary interaction dominates the evolution of massive stars.

    Science.gov (United States)

    Sana, H; de Mink, S E; de Koter, A; Langer, N; Evans, C J; Gieles, M; Gosset, E; Izzard, R G; Le Bouquin, J-B; Schneider, F R N

    2012-07-27

    The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously measured all relevant binary characteristics in a sample of Galactic massive O stars and quantified the frequency and nature of binary interactions. More than 70% of all massive stars will exchange mass with a companion, leading to a binary merger in one-third of the cases. These numbers greatly exceed previous estimates and imply that binary interaction dominates the evolution of massive stars, with implications for populations of massive stars and their supernovae.

  11. A 'Rosetta Stone' to Interpret the UV-HST Photometry of Multiple Stellar Populations in Globular Clusters

    Science.gov (United States)

    Renzini, Alvio

    2011-10-01

    In this proposal we intend to firmly identify the chemical species responsible for the UV and UV-optical color differences exhibited by the multiple stellar populations harboured by two Galactic globular clusters: omega Centauri and 47 Tucanae, one with highly helium enriched sub-populations {omega Centauri}, the other not.We plan to collect ultraviolet STIS spectra for stars in the crowded cores of the clusters, where HST photometry is already available for thousands of stars in more than 10 filters, from F225W to F850LP. This WFC3+ACS photometric database has allowed us to show that UV colors are remarkably effective in separating the different cluster sub-populations, and with the proposed STIS spectroscopy we can quantify the chemical abundance differences among such sub-populations, most notably in Nitrogen and Oxygen. The resulting calibration of the UV colors in terms of CNO abundances will provide a new effective tool for the chemical characterization of large numbers of globular cluster stars belonging to the various sub-populations in each cluster, and to better isolate the specific role of the helium abundance.The plan is to observe at least one star for each of the main principal stellar sub-populations in each of the two clusters. These objects are selected on the basis of their accurate photometry and astrometry already in hand, based on existing UV-HST images.

  12. INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Bird, Jonathan C.; Kazantzidis, Stelios; Weinberg, David H. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Guedes, Javiera [Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Callegari, Simone [Anthropology Institute and Museum, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Mayer, Lucio [Institute for Theoretical Physics, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Madau, Piero [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-08-10

    We analyze the present day structure and assembly history of a high-resolution hydrodynamic simulation of the formation of a Milky-Way-(MW)-like disk galaxy, from the ''Eris'' simulation suite, dissecting it into cohorts of stars formed at different epochs of cosmic history. At z = 0, stars with t{sub form} < 2 Gyr mainly occupy the stellar spheroid, with the oldest (earliest forming) stars having more centrally concentrated profiles. The younger age cohorts populate disks of progressively longer radial scale lengths and shorter vertical scale heights. At a given radius, the vertical density profiles and velocity dispersions of stars vary smoothly as a function of age, and the superposition of old, vertically extended and young, vertically compact cohorts gives rise to a double-exponential profile like that observed in the MW. Turning to formation history, we find that the trends of spatial structure and kinematics with stellar age are largely imprinted at birth, or immediately thereafter. Stars that form during the active merger phase at z > 3 are quickly scattered into rounded, kinematically hot configurations. The oldest disk cohorts form in structures that are radially compact and relatively thick, while subsequent cohorts form in progressively larger, thinner, colder configurations from gas with increasing levels of rotational support. The disk thus forms ''inside out'' in a radial sense and ''upside down'' in a vertical sense. Secular heating and radial migration influence the final state of each age cohort, but the changes they produce are small compared to the trends established at formation. The predicted correlations of stellar age with spatial and kinematic structure are in good qualitative agreement with the correlations observed for mono-abundance stellar populations in the MW.

  13. Classifying the embedded young stellar population in Perseus and Taurus and the LOMASS database

    NARCIS (Netherlands)

    Carney, M.T.; Yıldız, U.; Mottram, J.C.; Dishoeck, van E.F.; Ramchandani, J.; Jørgensen, J.K.

    2016-01-01

    Context. The classification of young stellar objects (YSOs) is typically done using the infrared spectral slope or bolometric temperature, but either can result in contamination of samples. More accurate methods to determine the evolutionary stage of YSOs will improve the reliability of statistics

  14. Stellar-mass black holes and ultraluminous x-ray sources.

    Science.gov (United States)

    Fender, Rob; Belloni, Tomaso

    2012-08-03

    We review the likely population, observational properties, and broad implications of stellar-mass black holes and ultraluminous x-ray sources. We focus on the clear empirical rules connecting accretion and outflow that have been established for stellar-mass black holes in binary systems in the past decade and a half. These patterns of behavior are probably the keys that will allow us to understand black hole feedback on the largest scales over cosmological time scales.

  15. Stellar-Mass Black Holes and Ultraluminous X-ray Sources

    Science.gov (United States)

    Fender, Rob; Belloni, Tomaso

    2012-08-01

    We review the likely population, observational properties, and broad implications of stellar-mass black holes and ultraluminous x-ray sources. We focus on the clear empirical rules connecting accretion and outflow that have been established for stellar-mass black holes in binary systems in the past decade and a half. These patterns of behavior are probably the keys that will allow us to understand black hole feedback on the largest scales over cosmological time scales.

  16. Carbon and nitrogen abundances of stellar populations in the globular cluster M 2

    Science.gov (United States)

    Lardo, C.; Pancino, E.; Mucciarelli, A.; Milone, A. P.

    2012-12-01

    We present CH and CN index analysis and C and N abundance calculations based on the low-resolution blue spectra of red giant branch (RGB) stars in the Galactic globular cluster NGC 7089 (M 2). Our main goal is to investigate the C-N anticorrelation for this intermediate metallicity cluster. The data were collected with DOLORES, the multiobject, low-resolution facility at the Telescopio Nazionale Galileo. We first looked for CH and CN band strength variations and bimodalities in a sample of RGB stars with 17.5 ≤ V ≤ 14.5. Thus we derived C and N abundances under LTE assumption by comparing observed spectra with synthetic models from the spectral features at 4300 Å (G-band) and at ~3883 Å (CN). Spectroscopic data were coupled with UV photometry obtained during the spectroscopic run. We found a considerable star-to-star variation in both A(C) and A(N) at all luminosities for our sample of 35 targets. These abundances appear to be anticorrelated, with a hint of bimodality in the C content for stars with luminosities below the RBG bump (V ~ 15.7), while the range of variations in N abundances is very large and spans almost ~2 dex. We find additional C depletion as the stars evolve off the RGB bump, in fairly good agreement with theoretical predictions for metal-poor stars in the course of normal stellar evolution. We isolated two groups with N-rich and N-poor stars and found that N abundance variations correlate with the (U - V) color in the DOLORES color-magnitude diagram (CMD). The V, (U - V) CMD for this cluster shows an additional RGB sequence, located at the red of the main RGB and amounting to a small fraction of the total giant population. We identified two CH stars detected in previous studies in our U,V images. These stars, which are both cluster members, fall on this redder sequence, suggesting that the anomalous RGB should have a peculiar chemical pattern. Unfortunately, no additional spectra were obtained for stars in this previously unknown RGB branch

  17. FORMATION OF LATE-TYPE SPIRAL GALAXIES: GAS RETURN FROM STELLAR POPULATIONS REGULATES DISK DESTRUCTION AND BULGE GROWTH

    International Nuclear Information System (INIS)

    Martig, Marie; Bournaud, Frederic

    2010-01-01

    Spiral galaxies have most of their stellar mass in a large rotating disk, and only a modest fraction in a central spheroidal bulge. This challenges present models of galaxy formation: galaxies form at the center of dark matter halos through a combination of hierarchical merging and gas accretion along cold streams. Cosmological simulations thus predict that galaxies rapidly grow their bulge through mergers and instabilities and end up with most of their mass in the bulge and an angular momentum much below the observed level, except in dwarf galaxies. We propose that the continuous return of gas by stellar populations over cosmic times could help to solve this issue. A population of stars formed at a given instant typically returns half of its initial mass in the form of gas over 10 billion years, and the process is not dominated by supernovae explosions but by the long-term mass-loss from low- and intermediate-mass stars. Using simulations of galaxy formation, we show that this gas recycling can strongly affect the structural evolution of massive galaxies, potentially solving the bulge fraction issue, as the bulge-to-disk ratio of a massive galaxy can be divided by a factor of 3. The continuous recycling of baryons through star formation and stellar mass loss helps the growth of disks and their survival to interactions and mergers. Instead of forming only early-type, spheroid-dominated galaxies (S0 and ellipticals), the standard cosmological model can successfully account for massive late-type, disk-dominated spiral galaxies (Sb-Sc).

  18. Cluster galaxy population evolution from the Subaru Hyper Suprime-Cam survey: brightest cluster galaxies, stellar mass distribution, and active galaxies

    Science.gov (United States)

    Lin, Yen-Ting; Hsieh, Bau-Ching; Lin, Sheng-Chieh; Oguri, Masamune; Chen, Kai-Feng; Tanaka, Masayuki; Chiu, I.-non; Huang, Song; Kodama, Tadayuki; Leauthaud, Alexie; More, Surhud; Nishizawa, Atsushi J.; Bundy, Kevin; Lin, Lihwai; Miyazaki, Satoshi; HSC Collaboration

    2018-01-01

    The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z~1 to date. In this exploratory study of cluster galaxy evolution from z=1 to z=0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), and evolution of stellar mass and luminosity distributions, stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Our stellar mass is derived from a machine-learning algorithm, which we show to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs, and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile. The clusters are found to contain more red galaxies compared to the expectations from the field, even after the differences in density between the two environments have been taken into account. We also present the first measurement of the radio luminosity distribution in clusters out to z~1.

  19. THE MAGELLANIC INTER-CLOUD PROJECT (MAGIC). I. EVIDENCE FOR INTERMEDIATE-AGE STELLAR POPULATIONS IN BETWEEN THE MAGELLANIC CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Noeel, N. E. D.; Read, J. I. [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Conn, B. C.; Rix, H.-W. [Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117, Heidelberg (Germany); Carrera, R. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200, La Laguna, Tenerife (Spain); Dolphin, A., E-mail: noelia@phys.ethz.ch [Raytheon Company, P.O. Box 11337, Tucson, AZ 85734-1337 (United States)

    2013-05-10

    The origin of the gas in between the Magellanic Clouds (MCs)-known as the ''Magellanic Bridge'' (MB)-is puzzling. Numerical simulations suggest that the MB formed from tidally stripped gas and stars in a recent interaction between the MCs. However, the apparent lack of stripped intermediate- or old-age stars associated with the MB is at odds with this picture. In this paper, we present the first results from the MAGellanic Inter-Cloud program (MAGIC) aimed at probing the stellar populations in the inter-Cloud region. We present observations of the stellar populations in two large fields located in between the Large and Small Magellanic Clouds (LMC/SMC), secured using the WFI camera on the 2.2 m telescope in La Silla. Using a synthetic color-magnitude diagram technique, we present the first quantitative evidence for the presence of intermediate-age and old stars in the inter-Cloud region. The intermediate-age stars-which make up {approx}28% of all stars in the region-are not present in fields at a similar distance from the SMC in a direction pointing away from the LMC. This provides potential evidence that these intermediate-age stars could have been tidally stripped from the SMC. However, spectroscopic studies will be needed to confirm or rule out the tidal origin for the inter-Cloud gas and stars.

  20. The progenitors of local ultra-massive galaxies across cosmic time: from dusty star-bursting to quiescent stellar populations

    Energy Technology Data Exchange (ETDEWEB)

    Marchesini, Danilo; Marsan, Cemile Z. [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Muzzin, Adam; Franx, Marijn [Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden (Netherlands); Stefanon, Mauro [Physics and Astronomy Department, University of Missouri, Columbia, MO 65211 (United States); Brammer, Gabriel G. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Vulcani, Benedetta [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8582 (Japan); Fynbo, J. P. U.; Milvang-Jensen, Bo [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Dunlop, James S.; Buitrago, Fernando [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)

    2014-10-10

    Using the UltraVISTA catalogs, we investigate the evolution in the 11.4 Gyr since z = 3 of the progenitors of local ultra-massive galaxies (log (M {sub star}/M {sub ☉}) ≈ 11.8; UMGs), providing a complete and consistent picture of how the most massive galaxies at z = 0 have assembled. By selecting the progenitors with a semi-empirical approach using abundance matching, we infer a growth in stellar mass of 0.56{sub −0.25}{sup +0.35} dex, 0.45{sub −0.20}{sup +0.16} dex, and 0.27{sub −0.12}{sup +0.08} dex from z = 3, z = 2, and z = 1, respectively, to z = 0. At z < 1, the progenitors of UMGs constitute a homogeneous population of only quiescent galaxies with old stellar populations. At z > 1, the contribution from star-forming galaxies progressively increases, with the progenitors at 2 < z < 3 being dominated by massive (M {sub star} ≈ 2 × 10{sup 11} M {sub ☉}), dusty (A {sub V} ∼ 1-2.2 mag), star-forming (SFR ∼ 100-400 M {sub ☉} yr{sup –1}) galaxies with a large range in stellar ages. At z = 2.75, ∼15% of the progenitors are quiescent, with properties typical of post-starburst galaxies with little dust extinction and strong Balmer break, and showing a large scatter in color. Our findings indicate that at least half of the stellar content of local UMGs was assembled at z > 1, whereas the remaining was assembled via merging from z ∼ 1 to the present. Most of the quenching of the star-forming progenitors happened between z = 2.75 and z = 1.25, in good agreement with the typical formation redshift and scatter in age of z = 0 UMGs as derived from their fossil records. The progenitors of local UMGs, including the star-forming ones, never lived on the blue cloud since z = 3. We propose an alternative path for the formation of local UMGs that refines previously proposed pictures and that is fully consistent with our findings.

  1. Levels of disability in the older population of England: Comparing binary and ordinal classifications.

    Science.gov (United States)

    Pongiglione, Benedetta; Ploubidis, George B; De Stavola, Bianca L

    2017-10-01

    Recent studies suggest the importance of distinguishing severity levels of disability. Nevertheless, there is not yet a consensus with regards to an optimal classification. Our study seeks to advance the existing binary definitions towards categorical/ordinal manifestations of disability. We define disability according to the WHO's International Classification of Functioning, Disability and Health (ICF) using data collected at the baseline wave of the English Longitudinal Study of Aging, a longitudinal study of the non-institutionalized population, living in England. First, we identify cut-off points in the continuous disability score derived from ICF to distinguish disabled from no-disabled participants. Then, we fit latent class models to the same data to find the optimal number of disability classes according to: (i) model fit indicators; (ii) estimated probabilities of each disability item; (iii) association of the predicted disability classes with observed health and mortality. According to the binary classification criteria, about 32% of both men and women are classified disabled. No optimal number of classes emerged from the latent class models according to model fit indicators. However, the other two criteria suggest that the best-fitting model of disability severity has four classes. Our findings contribute to the debate on the usefulness and relevance of adopting a finer categorization of disability, by showing that binary indicators of disability averaged the burden of disability and masked the very strong effect experienced by individuals having severe disability, and were not informative for low levels of disability. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  2. THE ESTIMATION OF STAR FORMATION RATES AND STELLAR POPULATION AGES OF HIGH-REDSHIFT GALAXIES FROM BROADBAND PHOTOMETRY

    International Nuclear Information System (INIS)

    Lee, Seong-Kook; Ferguson, Henry C.; Somerville, Rachel S.; Wiklind, Tommy; Giavalisco, Mauro

    2010-01-01

    We explore methods to improve the estimates of star formation rates and mean stellar population ages from broadband photometry of high-redshift star-forming galaxies. We use synthetic spectral templates with a variety of simple parametric star formation histories to fit broadband spectral energy distributions. These parametric models are used to infer ages, star formation rates, and stellar masses for a mock data set drawn from a hierarchical semi-analytic model of galaxy evolution. Traditional parametric models generally assume an exponentially declining rate of star formation after an initial instantaneous rise. Our results show that star formation histories with a much more gradual rise in the star formation rate are likely to be better templates, and are likely to give better overall estimates of the age distribution and star formation rate distribution of Lyman break galaxies (LBGs). For B- and V-dropouts, we find the best simple parametric model to be one where the star formation rate increases linearly with time. The exponentially declining model overpredicts the age by 100% and 120% for B- and V-dropouts, on average, while for a linearly increasing model, the age is overpredicted by 9% and 16%, respectively. Similarly, the exponential model underpredicts star formation rates by 56% and 60%, while the linearly increasing model underpredicts by 15% and 22%, respectively. For U-dropouts, the models where the star formation rate has a peak (near z ∼ 3) provide the best match for age-overprediction is reduced from 110% to 26%-and star formation rate-underprediction is reduced from 58% to 22%. We classify different types of star formation histories in the semi-analytic models and show how the biases behave for the different classes. We also provide two-band calibration formulae for stellar mass and star formation rate estimations.

  3. The SAMI Galaxy Survey: Gravitational Potential and Surface Density Drive Stellar Populations. I. Early-type Galaxies

    Science.gov (United States)

    Barone, Tania M.; D’Eugenio, Francesco; Colless, Matthew; Scott, Nicholas; van de Sande, Jesse; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Cortese, Luca; Croom, Scott M.; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; Lorente, Nuria P. F.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.

    2018-03-01

    The well-established correlations between the mass of a galaxy and the properties of its stars are considered to be evidence for mass driving the evolution of the stellar population (SP). However, for early-type galaxies (ETGs), we find that g ‑ i color and stellar metallicity [Z/H] correlate more strongly with gravitational potential Φ than with mass M, whereas SP age correlates best with surface density Σ. Specifically, for our sample of 625 ETGs with integral-field spectroscopy from the Sydney-AAO Multi-object Integral-field Galaxy Survey, compared to correlations with mass, the color–Φ, [Z/H]–Φ, and age–Σ relations show both a smaller scatter and a lower residual trend with galaxy size. For the star formation duration proxy [α/Fe], we find comparable results for trends with Φ and Σ, with both being significantly stronger than the [α/Fe]–M relation. In determining the strength of a trend, we analyze both the overall scatter, and the observational uncertainty on the parameters, in order to compare the intrinsic scatter in each correlation. These results lead us to the following inferences and interpretations: (1) the color–Φ diagram is a more precise tool for determining the developmental stage of the SP than the conventional color–mass diagram; and (2) gravitational potential is the primary regulator of global stellar metallicity, via its relation to the gas escape velocity. Furthermore, we propose the following two mechanisms for the age and [α/Fe] relations with Σ: (a) the age–Σ and [α/Fe]–Σ correlations arise as results of compactness-driven quenching mechanisms; and/or (b) as fossil records of the {{{Σ }}}SFR}\\propto {{{Σ }}}gas} relation in their disk-dominated progenitors.

  4. Environmental effects on stellar populations of star clusters and dwarf galaxies

    Science.gov (United States)

    Pasetto, Stefano; Cropper, Mark; Fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

    2017-03-01

    We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation of gravitationally bound systems in an external environment. Ram pressure, Kelvin-Helmholtz and Rayleigh-Taylor instabilities, and tidal forces are accounted for separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment. We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance. The developed theoretical framework has direct applications to the cases of massive star clusters, dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.

  5. Stellar Populations and the Star Formation Histories of LSB Galaxies—Part I: Optical and Hα Imaging

    Directory of Open Access Journals (Sweden)

    James Schombert

    2011-01-01

    Full Text Available This paper presents optical and Hα imaging for a large sample of LSB galaxies selected from the PSS-II catalogs (Schombert et al., 1992. As noted in previous work, LSB galaxies span a range of luminosities (−10>>−20 and sizes (0.3kpc<25<10kpc, although they are consistent in their irregular morphology. Their Hα luminosities (L(Hα range from 1036 to 1041 ergs s−1 (corresponding to a range in star formation, using canonical prescriptions, from 10−5 to 1 ⨀ yr−1. Although their optical colors are at the extreme blue edge for galaxies, they are similar to the colors of dwarf galaxies (Van Zee, 2001 and gas-rich irregulars (Hunter and Elmegreen, 2006. However, their star formation rates per unit stellar mass are a factor of ten less than other galaxies of the same baryonic mass, indicating that they are not simply quiescent versions of more active star-forming galaxies. This paper presents the data, reduction techniques, and new philosophy of data storage and presentation. Later papers in this series will explore the stellar population and star formation history of LSB galaxies using this dataset.

  6. MONTE CARLO POPULATION SYNTHESIS OF POST-COMMON-ENVELOPE WHITE DWARF BINARIES AND TYPE Ia SUPERNOVA RATE

    Energy Technology Data Exchange (ETDEWEB)

    Ablimit, Iminhaji [Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Maeda, Keiichi [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Li, Xiang-Dong [Department of Astronomy, Nanjing University, Nanjing 210046 (China)

    2016-07-20

    Binary population synthesis (BPS) studies provide a comprehensive way to understand the evolution of binaries and their end products. Close white dwarf (WD) binaries have crucial characteristics for examining the influence of unresolved physical parameters on binary evolution. In this paper, we perform Monte Carlo BPS simulations, investigating the population of WD/main-sequence (WD/MS) binaries and double WD binaries using a publicly available binary star evolution code under 37 different assumptions for key physical processes and binary initial conditions. We considered different combinations of the binding energy parameter ( λ {sub g}: considering gravitational energy only; λ {sub b}: considering both gravitational energy and internal energy; and λ {sub e}: considering gravitational energy, internal energy, and entropy of the envelope, with values derived from the MESA code), CE efficiency, critical mass ratio, initial primary mass function, and metallicity. We find that a larger number of post-CE WD/MS binaries in tight orbits are formed when the binding energy parameters are set by λ {sub e} than in those cases where other prescriptions are adopted. We also determine the effects of the other input parameters on the orbital periods and mass distributions of post-CE WD/MS binaries. As they contain at least one CO WD, double WD systems that evolved from WD/MS binaries may explode as type Ia supernovae (SNe Ia) via merging. In this work, we also investigate the frequency of two WD mergers and compare it to the SNe Ia rate. The calculated Galactic SNe Ia rate with λ = λ {sub e} is comparable to the observed SNe Ia rate, ∼8.2 × 10{sup 5} yr{sup 1} – ∼4 × 10{sup 3} yr{sup 1} depending on the other BPS parameters, if a DD system does not require a mass ratio higher than ∼0.8 to become an SNe Ia. On the other hand, a violent merger scenario, which requires the combined mass of two CO WDs ≥ 1.6 M {sub ⊙} and a mass ratio >0.8, results in a much lower

  7. Using diffusion k-means for simple stellar population modeling of low S/N quasar host galaxy spectra

    Science.gov (United States)

    Mosby, Gregory; Tremonti, Christina A.; Hooper, Eric; Wolf, Marsha J.; Sheinis, Andrew; Richards, Joseph

    2016-01-01

    Quasar host galaxies (QHGs) represent a unique stage in galaxy evolution that can provide a glimpse into the relationship between an active supermassive black hole (SMBH) and its host galaxy. However, observing the hosts of high luminosity, unobscured quasars in the optical is complicated by the large ratio of quasar to host galaxy light. One strategy in optical spectroscopy is to use offset longslit observations of the host galaxy. This method allows the centers of QHGs to be analyzed apart from other regions of their host galaxies. But light from the accreting black hole's point spread function still enters the host galaxy observations, and where the contrast between the host and intervening quasar light is favorable, the host galaxy is faint, producing low signal-to-noise (S/N) data. This stymies traditional stellar population methods that might rely on high S/N features in galaxy spectra to recover key galaxy properties like its star formation history (SFH). In response to this challenge, we have developed a method of stellar population modeling using diffusion k-means (DFK) that can recover SFHs from rest frame optical data with S/N ~ 5 Å^-1. Specifically, we use DFK to cultivate a reduced stellar population basis set. This DFK basis set of four broad age bins is able to recover a range of SFHs. With an analytic description of the seeing, we can use this DFK basis set to simultaneously model the SFHs and the intervening quasar light of QHGs as well. We compare the results of this method with previous techniques using synthetic data and find that our new method has a clear advantage in recovering SFHs from QHGs. On average, the DFK basis set is just as accurate and decisively more precise. This new technique could be used to analyze other low S/N galaxy spectra like those from higher redshift or integral field spectroscopy surveys.This material is based upon work supported by the National Science Foundation under grant no. DGE -0718123 and the Advanced

  8. SDSS-IV MaNGA: global stellar population and gradients for about 2000 early-type and spiral galaxies on the mass-size plane

    Science.gov (United States)

    Li, Hongyu; Mao, Shude; Cappellari, Michele; Ge, Junqiang; Long, R. J.; Li, Ran; Mo, H. J.; Li, Cheng; Zheng, Zheng; Bundy, Kevin; Thomas, Daniel; Brownstein, Joel R.; Roman Lopes, Alexandre; Law, David R.; Drory, Niv

    2018-05-01

    We perform full spectrum fitting stellar population analysis and Jeans Anisotropic modelling of the stellar kinematics for about 2000 early-type galaxies (ETGs) and spiral galaxies from the MaNGA DR14 sample. Galaxies with different morphologies are found to be located on a remarkably tight mass plane which is close to the prediction of the virial theorem, extending previous results for ETGs. By examining an inclined projection (`the mass-size' plane), we find that spiral and early-type galaxies occupy different regions on the plane, and their stellar population properties (i.e. age, metallicity, and stellar mass-to-light ratio) vary systematically along roughly the direction of velocity dispersion, which is a proxy for the bulge fraction. Galaxies with higher velocity dispersions have typically older ages, larger stellar mass-to-light ratios and are more metal rich, which indicates that galaxies increase their bulge fractions as their stellar populations age and become enriched chemically. The age and stellar mass-to-light ratio gradients for low-mass galaxies in our sample tend to be positive (centre < outer), while the gradients for most massive galaxies are negative. The metallicity gradients show a clear peak around velocity dispersion log10 σe ≈ 2.0, which corresponds to the critical mass ˜3 × 1010 M⊙ of the break in the mass-size relation. Spiral galaxies with large mass and size have the steepest gradients, while the most massive ETGs, especially above the critical mass Mcrit ≳ 2 × 1011 M⊙, where slow rotator ETGs start dominating, have much flatter gradients. This may be due to differences in their evolution histories, e.g. mergers.

  9. SDSS-IV MaNGA: Global stellar population and gradients for about 2000 early-type and spiral galaxies on the mass-size plane

    Science.gov (United States)

    Li, Hongyu; Mao, Shude; Cappellari, Michele; Ge, Junqiang; Long, R. J.; Li, Ran; Mo, HJ; Li, Cheng; Zheng, Zheng; Bundy, Kevin; Thomas, Daniel; Brownstein, Joel R.; Lopes, Alexandre Roman; Law, David R.; Drory, Niv

    2018-02-01

    We perform full spectrum fitting stellar population analysis and Jeans Anisotropic modelling (JAM) of the stellar kinematics for about 2000 early-type galaxies (ETGs) and spiral galaxies from the MaNGA DR14 sample. Galaxies with different morphologies are found to be located on a remarkably tight mass plane which is close to the prediction of the virial theorem, extending previous results for ETGs. By examining an inclined projection (`the mass-size' plane), we find that spiral and early-type galaxies occupy different regions on the plane, and their stellar population properties (i.e. age, metallicity and stellar mass-to-light ratio) vary systematically along roughly the direction of velocity dispersion, which is a proxy for the bulge fraction. Galaxies with higher velocity dispersions have typically older ages, larger stellar mass-to-light ratios and are more metal rich, which indicates that galaxies increase their bulge fractions as their stellar populations age and become enriched chemically. The age and stellar mass-to-light ratio gradients for low-mass galaxies in our sample tend to be positive (centregalaxies are negative. The metallicity gradients show a clear peak around velocity dispersion log10σe ≈ 2.0, which corresponds to the critical mass ˜3 × 1010M⊙ of the break in the mass-size relation. Spiral galaxies with large mass and size have the steepest gradients, while the most massive ETGs, especially above the critical mass M_crit≳ 2× 10^{11} M_{\\odot}, where slow rotator ETGs start dominating, have much flatter gradients. This may be due to differences in their evolution histories, e.g. mergers.

  10. Measuring the Evolution of Stellar Populations And Gas Metallicity in Galaxies with Far-Infrared Space Spectroscopy

    Science.gov (United States)

    Stacey, Gordon

    We propose a study of the evolution of stellar populations and gas metallicities in about 80 nearby star forming galaxies based on mining the NASA data archives for observations of the [NIII] 57 µm, [OIII] 52 µm and/or 88 µm, [NII] 122 and [CII] 158 µm far-infrared (FIR) fine- structure lines and other archives for thermal radio continuum. These lines are powerful probes of both stellar populations and gas properties and our primary science derives from these tracers. For sources that show both signs of active galactic nuclei (AGN) and star formation, we will take advantage of the readily available NASA Spitzer IRS data base that includes mid-IR [NeII] 12.8 µm, [NeIII] 15.6 µm and [NeV] 14.3 µm, [OIV] 25.9 µm and PAH observations. These complementary data reveal the relative fractions of the FIR line emission that might arise from star formation and the narrow line regions (NLR) associated with an AGN, thereby providing a robust set of observations to compare with star formation models. Subsets of the FIR lines have been detected from hundreds of nearby galaxies. From both theoretical studies and the results of these pioneering observations we know that these lines can be powerful probes of stellar populations and star formation in galaxies. Here we plan to use various combinations of the lines to constrain (1) the age of the stellar populations (through lines that trace the hardness of the stellar radiation fields, hence stellar spectral type), (2) the degree of processing of the interstellar medium (through lines that trace growth of secondary to primary element abundances for example, the N/O ratio), (3) the efficiency of star formation (through growth in absolute abundances of N and O, the N/H and O/H ratios), and (4) the current day mass function of upper main sequence stars. Surprisingly, there has been no systematic study of the large sample of these line detections made with PACS on Herschel in order to truly assess and calibrate their diagnostic

  11. SPHERE/ZIMPOL observations of the symbiotic system R Aquarii : I. Imaging of the stellar binary and the innermost jet clouds

    NARCIS (Netherlands)

    Schmid, H.M.; Bazzon, A.; Milli, J.; Roelfsema, R.; Engler, N.; Mouillet, D.; Lagadec, E.; Sissa, E.; Sauvage, J.-F.; Ginski, C.; Baruffolo, A.; Beuzit, J.L.; Boccaletti, A.; Bohn, A.J.; Claudi, R.; Costille, A.; Desidera, S.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Gisler, D.; Girard, J.H.; Gratton, R.; Henning, T.; Hubin, N.; Joos, F.; Kasper, M.; Langlois, M.; Pavlov, A.; Pragt, J.; Puget, P.; Quanz, S.P.; Salasnich, B.; Siebenmorgen, R.; Stute, M.; Suarez, M.; Szulágyi, J.; Thalmann, C.; Turatto, M.; Udry, S.; Vigan, A.; Wildi, F.

    Context. R Aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. Because of its proximity to the Sun, this object has been studied in much detail with many types of high resolution imaging and

  12. A PUBLIC Ks -SELECTED CATALOG IN THE COSMOS/ULTRAVISTA FIELD: PHOTOMETRY, PHOTOMETRIC REDSHIFTS, AND STELLAR POPULATION PARAMETERS ,

    International Nuclear Information System (INIS)

    Muzzin, Adam; Franx, Marijn; Labbé, Ivo; Marchesini, Danilo; Stefanon, Mauro; Milvang-Jensen, Bo; Fynbo, J. P. U.; Dunlop, James S.; Brammer, Gabriel; Van Dokkum, Pieter

    2013-01-01

    We present a catalog covering 1.62 deg 2 of the COSMOS/UltraVISTA field with point-spread function (PSF) matched photometry in 30 photometric bands. The catalog covers the wavelength range 0.15-24 μm including the available GALEX, Subaru, Canada-France-Hawaii Telescope, VISTA, and Spitzer data. Catalog sources have been selected from the DR1 UltraVISTA K s band imaging that reaches a depth of K s,tot = 23.4 AB (90% completeness). The PSF-matched catalog is generated using position-dependent PSFs ensuring accurate colors across the entire field. Also included is a catalog of photometric redshifts (z phot ) for all galaxies computed with the EAZY code. Comparison with spectroscopy from the zCOSMOS 10k bright sample shows that up to z ∼ 1.5 the z phot are accurate to Δz/(1 + z) = 0.013, with a catastrophic outlier fraction of only 1.6%. The z phot also show good agreement with the z phot from the NEWFIRM Medium Band Survey out to z ∼ 3. A catalog of stellar masses and stellar population parameters for galaxies determined using the FAST spectral energy distribution fitting code is provided for all galaxies. Also included are rest-frame U – V and V – J colors, L 2800 and L IR . The UVJ color-color diagram confirms that the galaxy bi-modality is well-established out to z ∼ 2. Star-forming galaxies also obey a star-forming 'main sequence' out to z ∼ 2.5, and this sequence evolves in a manner consistent with previous measurements. The COSMOS/UltraVISTA K s -selected catalog covers a unique parameter space in both depth, area, and multi-wavelength coverage and promises to be a useful tool for studying the growth of the galaxy population out to z ∼ 3-4.

  13. The Resolved Stellar Population in 50 Regions of M83 from HST/WFC3 Early Release Science Observations

    Science.gov (United States)

    Kim, Hwihyun; Whitmore, Bradley C.; Chandar, Rupali; Saha, Abhijit; Kaleida, Catherine C.; Mutchler, Max; Cohen, Seth H.; Calzetti, Daniela; O’Connell, Robert W.; Windhorst, Rogier A.; hide

    2012-01-01

    We present a multi-wavelength photometric study of approximately 15,000 resolved stars in the nearby spiral galaxy M83 (NGC 5236, D = 4.61 Mpc) based on Hubble Space Telescope Wide Field Camera 3 observations using four filters: F336W, F438W, F555W, and F814W. We select 50 regions (an average size of 260 pc by 280 pc) in the spiral arm and inter-arm areas of M83 and determine the age distribution of the luminous stellar populations in each region. This is accomplished by correcting for extinction toward each individual star by comparing its colors with predictions from stellar isochrones.We compare the resulting luminosity-weighted mean ages of the luminous stars in the 50 regions with those determined from several independent methods, including the number ratio of red-to-blue supergiants, morphological appearance of the regions, surface brightness fluctuations, and the ages of clusters in the regions. We find reasonably good agreement between these methods. We also find that young stars are much more likely to be found in concentrated aggregates along spiral arms, while older stars are more dispersed. These results are consistent with the scenario that star formation is associated with the spiral arms, and stars form primarily in star clusters and then disperse on short timescales to form the field population. The locations ofWolf-Rayet stars are found to correlate with the positions of many of the youngest regions, providing additional support for our ability to accurately estimate ages. We address the effects of spatial resolution on the measured colors, magnitudes, and age estimates. While individual stars can occasionally show measurable differences in the colors and magnitudes, the age estimates for entire regions are only slightly affected.

  14. The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XII. The RGB bumps of multiple stellar populations

    Science.gov (United States)

    Lagioia, E. P.; Milone, A. P.; Marino, A. F.; Cassisi, S.; Aparicio, A. J.; Piotto, G.; Anderson, J.; Barbuy, B.; Bedin, L. R.; Bellini, A.; Brown, T.; D'Antona, F.; Nardiello, D.; Ortolani, S.; Pietrinferni, A.; Renzini, A.; Salaris, M.; Sarajedini, A.; van der Marel, R.; Vesperini, E.

    2018-04-01

    The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters is providing a major breakthrough in our knowledge of globular clusters (GCs) and their stellar populations. Among the main results, we discovered that all the studied GCs host two main discrete groups consisting of first generation (1G) and second generation (2G) stars. We exploit the multiwavelength photometry from this project to investigate, for the first time, the Red Giant Branch Bump (RGBB) of the two generations in a large sample of GCs. We identified, with high statistical significance, the RGBB of 1G and 2G stars in 26 GCs and found that their magnitude separation as a function of the filter wavelength follows comparable trends. The comparison of observations to synthetic spectra reveals that the RGBB luminosity depends on the stellar chemical composition and that the 2G RGBB is consistent with stars enhanced in He and N and depleted in C and O with respect to 1G stars. For metal-poor GCs the 1G and 2G RGBB relative luminosity in optical bands mostly depends on helium content, Y. We used the RGBB observations in F606W and F814W bands to infer the relative helium abundance of 1G and 2G stars in 18 GCs, finding an average helium enhancement ΔY = 0.011 ± 0.002 of 2G stars with respect to 1G stars. This is the first determination of the average difference in helium abundance of multiple populations in a large number of clusters and provides a lower limit to the maximum internal variation of helium in GCs.

  15. THE RESOLVED STELLAR POPULATION IN 50 REGIONS OF M83 FROM HST/WFC3 EARLY RELEASE SCIENCE OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hwihyun; Cohen, Seth H.; Windhorst, Rogier A. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States); Whitmore, Bradley C.; Mutchler, Max; Bond, Howard E. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Chandar, Rupali [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Saha, Abhijit [National Optical Astronomy Observatories, Tucson, AZ 85726-6732 (United States); Kaleida, Catherine C. [Cerro Tololo Inter-American Observatory, La Serena (Chile); Calzetti, Daniela [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); O' Connell, Robert W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Balick, Bruce [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Carollo, Marcella [Department of Physics, ETH-Zurich, Zurich 8093 (Switzerland); Disney, Michael J. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Dopita, Michael A. [Mount Stromlo and Siding Spring Observatories, Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Frogel, Jay A. [Galaxies Unlimited, 1 Tremblant Court, Lutherville, MD 21093 (United States); Hall, Donald N. B. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Holtzman, Jon A. [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); Kimble, Randy A. [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States); McCarthy, Patrick J., E-mail: hwihyun.kim@asu.edu [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101-1292 (United States); and others

    2012-07-01

    We present a multi-wavelength photometric study of {approx}15,000 resolved stars in the nearby spiral galaxy M83 (NGC 5236, D = 4.61 Mpc) based on Hubble Space Telescope Wide Field Camera 3 observations using four filters: F336W, F438W, F555W, and F814W. We select 50 regions (an average size of 260 pc by 280 pc) in the spiral arm and inter-arm areas of M83 and determine the age distribution of the luminous stellar populations in each region. This is accomplished by correcting for extinction toward each individual star by comparing its colors with predictions from stellar isochrones. We compare the resulting luminosity-weighted mean ages of the luminous stars in the 50 regions with those determined from several independent methods, including the number ratio of red-to-blue supergiants, morphological appearance of the regions, surface brightness fluctuations, and the ages of clusters in the regions. We find reasonably good agreement between these methods. We also find that young stars are much more likely to be found in concentrated aggregates along spiral arms, while older stars are more dispersed. These results are consistent with the scenario that star formation is associated with the spiral arms, and stars form primarily in star clusters and then disperse on short timescales to form the field population. The locations of Wolf-Rayet stars are found to correlate with the positions of many of the youngest regions, providing additional support for our ability to accurately estimate ages. We address the effects of spatial resolution on the measured colors, magnitudes, and age estimates. While individual stars can occasionally show measurable differences in the colors and magnitudes, the age estimates for entire regions are only slightly affected.

  16. THE RESOLVED STELLAR POPULATION IN 50 REGIONS OF M83 FROM HST/WFC3 EARLY RELEASE SCIENCE OBSERVATIONS

    International Nuclear Information System (INIS)

    Kim, Hwihyun; Cohen, Seth H.; Windhorst, Rogier A.; Whitmore, Bradley C.; Mutchler, Max; Bond, Howard E.; Chandar, Rupali; Saha, Abhijit; Kaleida, Catherine C.; Calzetti, Daniela; O'Connell, Robert W.; Balick, Bruce; Carollo, Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.

    2012-01-01

    We present a multi-wavelength photometric study of ∼15,000 resolved stars in the nearby spiral galaxy M83 (NGC 5236, D = 4.61 Mpc) based on Hubble Space Telescope Wide Field Camera 3 observations using four filters: F336W, F438W, F555W, and F814W. We select 50 regions (an average size of 260 pc by 280 pc) in the spiral arm and inter-arm areas of M83 and determine the age distribution of the luminous stellar populations in each region. This is accomplished by correcting for extinction toward each individual star by comparing its colors with predictions from stellar isochrones. We compare the resulting luminosity-weighted mean ages of the luminous stars in the 50 regions with those determined from several independent methods, including the number ratio of red-to-blue supergiants, morphological appearance of the regions, surface brightness fluctuations, and the ages of clusters in the regions. We find reasonably good agreement between these methods. We also find that young stars are much more likely to be found in concentrated aggregates along spiral arms, while older stars are more dispersed. These results are consistent with the scenario that star formation is associated with the spiral arms, and stars form primarily in star clusters and then disperse on short timescales to form the field population. The locations of Wolf-Rayet stars are found to correlate with the positions of many of the youngest regions, providing additional support for our ability to accurately estimate ages. We address the effects of spatial resolution on the measured colors, magnitudes, and age estimates. While individual stars can occasionally show measurable differences in the colors and magnitudes, the age estimates for entire regions are only slightly affected.

  17. The role of the Milky Way hot coronal gas on its dwarf galaxies stellar population

    Science.gov (United States)

    Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

    2015-08-01

    A large amount (˜5 ×1010 Msun) of hot gas is thought to exist in an extended (˜200 kpc) hot diffuse halo around the Milky Way (MW). We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in this external environment. Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in observational applications as well as theoretical interpretations of numerical results.We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of our MW system as well as dwarf galaxies in galaxy clusters or any primordial gas-rich cluster of stars orbiting within its host galaxy.

  18. Environmental effects on stellar populations of dwarf galaxies and star clusters

    Science.gov (United States)

    Pasetto, Stefano; Cropper, Mark; fujita, Yutaka; Chiosi, Cesare; Grebel, Eva K.

    2015-08-01

    We investigate the competitive role of the different dissipative phenomena acting on the onset of star formation history of gravitationally bound system in an external environment. Ram pressure, Kelvin-Helmholtz instability, Rayleigh-Taylor, and tidal forces are accounted separately in an analytical framework and compared in their role in influencing the star forming regions. We present an analytical criterion to elucidate the dependence of star formation in a spherical stellar system on its surrounding environment useful in observational applications as well as theoretical interpretations of numerical results.We consider the different signatures of these phenomena in synthetically realized colour-magnitude diagrams (CMDs) of the orbiting system thus investigating the detectability limits of these different effects for future observational projects and their relevance.The theoretical framework developed has direct applications to the cases of dwarf galaxies in galaxy clusters and dwarf galaxies orbiting our Milky Way system, as well as any primordial gas-rich cluster of stars orbiting within its host galaxy.

  19. Constraining the Stellar Populations and Star Formation Histories of Blue Compact Dwarf Galaxies with SED Fits

    Energy Technology Data Exchange (ETDEWEB)

    Janowiecki, Steven [International Center for Radio Astronomy Research, M468, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009 (Australia); Salzer, John J.; Zee, Liese van [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); Rosenberg, Jessica L. [Department of Physics and Astronomy, George Mason University, Fairfax, VA 22030 (United States); Skillman, Evan, E-mail: steven.janowiecki@uwa.edu.au [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street, SE Minneapolis, MN, 55455 (United States)

    2017-02-10

    We discuss and test possible evolutionary connections between blue compact dwarf galaxies (BCDs) and other types of dwarf galaxies. BCDs provide ideal laboratories to study intense star formation episodes in low-mass dwarf galaxies, and have sometimes been considered a short-lived evolutionary stage between types of dwarf galaxies. To test these connections, we consider a sample of BCDs as well as a comparison sample of nearby galaxies from the Local Volume Legacy (LVL) survey for context. We fit the multi-wavelength spectral energy distributions (SED, far-ultra-violet to far-infrared) of each galaxy with a grid of theoretical models to determine their stellar masses and star formation properties. We compare our results for BCDs with the LVL galaxies to put BCDs in the context of normal galaxy evolution. The SED fits demonstrate that the star formation events currently underway in BCDs are at the extreme of the continuum of normal dwarf galaxies, both in terms of the relative mass involved and in the relative increase over previous star formation rates. Today’s BCDs are distinctive objects in a state of extreme star formation that is rapidly transforming them. This study also suggests ways to identify former BCDs whose star formation episodes have since faded.

  20. A PAndAS view of the resolved stellar populations in M31 dwarf elliptical satellites

    Science.gov (United States)

    Crnojević, D.; PAndAS Collaboration

    We present the first truly global view of the closest elliptical galaxies, the dwarf elliptical (dE) companions of M31 NGC147 and NGC185. We exploit the deep PAndAS photometric dataset in order to investigate the resolved stellar content and structure of these dEs out to larger distances than ever previously probed. From the analysis of their old red giant branch stars, we derive density maps, full surface brightness profiles and metallicity distribution functions. We find that NGC147 shows pronounced tidal tails likely due to its interaction with M31, while NGC185 retains a regular elliptical shape over its entire extent. The two dEs follow a Sersic profile out to ˜5 kpc, and the effective radii derived in this study are a factor of two larger than previous literature values. While NGC185 shows a significant gradient in metallicity (˜-0.05 dex/kpc), this is almost absent in NGC147. The detailed understanding of nearby dEs is crucial for the studies of more distant objects, and we discuss how internal and environmental processes could have influenced the evolution of NGC147 and NGC185 in light of our results.

  1. First Results on the Cluster Galaxy Population from the Subaru Hyper Suprime-Cam Survey. III. Brightest Cluster Galaxies, Stellar Mass Distribution, and Active Galaxies

    Science.gov (United States)

    Lin, Yen-Ting; Hsieh, Bau-Ching; Lin, Sheng-Chieh; Oguri, Masamune; Chen, Kai-Feng; Tanaka, Masayuki; Chiu, I.-Non; Huang, Song; Kodama, Tadayuki; Leauthaud, Alexie; More, Surhud; Nishizawa, Atsushi J.; Bundy, Kevin; Lin, Lihwai; Miyazaki, Satoshi

    2017-12-01

    The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z∼ 1 to date. In this exploratory study of cluster galaxy evolution from z = 1 to z = 0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), the evolution of stellar mass and luminosity distributions, the stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high-redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Over the 230 deg2 area of the current HSC-SSP footprint, selecting the top 100 clusters in each of the four redshift bins allows us to observe the buildup of galaxy population in descendants of clusters whose z≈ 1 mass is about 2× {10}14 {M}ȯ . Our stellar mass is derived from a machine-learning algorithm, which is found to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs (about 35% between z = 1 and 0.3), and no evidence for evolution in both the total stellar mass–cluster mass correlation and the shape of the stellar mass surface density profile. We also present the first measurement of the radio luminosity distribution in clusters out to z∼ 1, and show hints of changes in the dominant accretion mode powering the cluster radio galaxies at z∼ 0.8.

  2. Spectroscopic Binaries in the Orion Nebula Cluster and NGC 2264

    Science.gov (United States)

    Kounkel, Marina; Hartmann, Lee; Tobin, John J.; Mateo, Mario; Bailey, John I., III; Spencer, Meghin

    2016-04-01

    We examine the spectroscopic binary population for two massive nearby regions of clustered star formation, the Orion Nebula Cluster (ONC) and NGC 2264, supplementing the data presented by Tobin et al. with more recent observations and more extensive analysis. The inferred multiplicity fraction up to 10 au based on these observations is 5.3 ± 1.2% for NGC 2264 and 5.8 ± 1.1% for the ONC; these values are consistent with the distribution of binaries in the field in the relevant parameter range. Eight of the multiple systems in the sample have enough epochs to perform an initial fit for the orbital parameters. Two of these sources are double-lined spectroscopic binaries; for them, we determine the mass ratio. Our reanalysis of the distribution of stellar radial velocities toward these clusters presents a significantly better agreement between stellar and gas kinematics than was previously thought.

  3. Globular cluster formation with multiple stellar populations: self-enrichment in fractal massive molecular clouds

    Science.gov (United States)

    Bekki, Kenji

    2017-08-01

    Internal chemical abundance spreads are one of fundamental properties of globular clusters (GCs) in the Galaxy. In order to understand the origin of such abundance spreads, we numerically investigate GC formation from massive molecular clouds (MCs) with fractal structures using our new hydrodynamical simulations with star formation and feedback effects of core-collapse supernovae (SNe) and asymptotic giant branch (AGB) stars. We particularly investigate star formation from gas chemically contaminated by SNe and AGB stars ('self-enrichment') in forming GCs within MCs with different initial conditions and environments. The principal results are as follows. GCs with multiple generations of stars can be formed from merging of hierarchical star cluster complexes that are developed from high-density regions of fractal MCs. Feedback effects of SNe and AGB stars can control the formation efficiencies of stars formed from original gas of MCs and from gas ejected from AGB stars. The simulated GCs have strong radial gradients of helium abundances within the central 3 pc. The original MC masses need to be as large as 107 M⊙ for a canonical initial stellar mass function (IMF) so that the final masses of stars formed from AGB ejecta can be ˜105 M⊙. Since star formation from AGB ejecta is rather prolonged (˜108 yr), their formation can be strongly suppressed by SNe of the stars themselves. This result implies that the so-called mass budget problem is much more severe than ever thought in the self-enrichment scenario of GC formation and thus that IMF for the second generation of stars should be 'top-light'.

  4. Runaway stars from young star clusters containing initial binaries. I. Equal-mass, equal-energy binaries

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, P.J.T.; Duncan, M.J.

    1988-07-01

    The production of runaway stars by the dynamical-ejection mechanism in an open star cluster containing 50 percent binaries of equal mass and energy is investigated theoretically by means of numerical simulations using the NBODY5 code of Aarseth (1985). The construction of the models is outlined, and the results are presented graphically and characterized in detail. It is shown that binary-binary collisions capable of producing runaways can occur (via formation and disruption, with some stellar collisions, of hierarchical double binaries) in clusters of relatively low density (e.g., pc-sized clusters of O or B stars). The frequency of binaries in the runaway population is found to vary between 0 and 50 percent, with the majority of runaways being unevolved early-type stars. 38 references.

  5. Normal and outlying populations of the Milky Way stellar halo at [Fe/H] <–2

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Judith G. [Palomar Observatory, Mail Stop 249-17, California Institute of Technology, Pasadena, CA 91125 (United States); Christlieb, Norbert [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117, Heidelberg (Germany); Thompson, Ian; McWilliam, Andrew; Shectman, Stephen [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Reimers, Dieter [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Wisotzki, Lutz [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Kirby, Evan, E-mail: jlc@astro.caltech.edu, E-mail: N.Christlieb@lsw.uni-heidelberg.de, E-mail: ian@obs.carnegiescience.edu, E-mail: shec@obs.carnegiescience.edu, E-mail: andy@obs.carnegiescience.edu, E-mail: dreimers@hs.uni-hamburg.de, E-mail: lutz@aip.de, E-mail: ekirby@uci.edu [University of California, Department of Physics and Astronomy, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States)

    2013-11-20

    From detailed abundance analysis of >100 Hamburg/ESO candidate extremely metal-poor (EMP) stars we find 45 with [Fe/H] < –3.0 dex. We identify a heretofore unidentified group: Ca-deficient stars with sub-solar [Ca/Fe] ratios and the lowest neutron-capture abundances; the Ca-deficient group comprises ∼10% of the sample, excluding Carbon stars. Our radial velocity distribution shows that the carbon-enhanced stars with no s-process enhancements, CEMP-no, and which do not show C{sub 2} bands are not preferentially binary systems. Ignoring Carbon stars, approximately 15% of our sample are strong (≥5σ) outliers in one or more elements between Mg and Ni; this rises to ∼19% if very strong (≥10σ) outliers for Sr and Ba are included. Examples include: HE0305–0554 with the lowest [Ba/H] known; HE1012–1540 and HE2323–0256, two (non-velocity variable) C-rich stars with very strong [Mg,Al/Fe] enhancements; and HE1226–1149, an extremely r-process rich star.

  6. Stellar magnetic activity

    International Nuclear Information System (INIS)

    Schrijver, C.J.

    1986-01-01

    The stellar emission in the chromospheric Ca II H+K lines is compared with the coronal soft X-ray emission, measuring the effects of non-radiative heating in the outer atmosphere at temperatures differing two orders of magnitude. The comparison of stellar flux densities in Ca II H+K and X-rays is extended to fluxes from the transition-region and the high-temperature chromosphere. The stellar magnetic field is probably generated in the differentially rotating convective envelope. The relation between rotation rate and the stellar level of activity measured in chromospheric, transition-region, and coronal radiative diagnostics is discovered. X-ray observations of the binary λ Andromedae are discussed. The departure of M-type dwarfs from the main relations, and the implications for the structure of the chromospheres of these stars are discussed. Variations of the average surface flux densities of the Sun during the 11-year activity cycle agree with flux-flux relations derived for other cool stars, suggesting that the interpretation of the stellar relations may be furthered by studying the solar analogue in more detail. (Auth.)

  7. Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267

    Science.gov (United States)

    Tucker, Evan; Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W.; Bailey, John I., III; Crane, Jeffrey D.; Shectman, Stephen A.

    2017-09-01

    We report the results of a pilot program to use the Magellan/M2FS spectrograph to survey the galactic populations and internal kinematics of galaxy clusters. For this initial study, we present spectroscopic measurements for 223 quiescent galaxies observed along the line of sight of the galaxy cluster Abell 267 (z˜ 0.23). We develop a Bayesian method for modeling the integrated light from each galaxy as a simple stellar population, with free parameters that specify the redshift ({v}{los}/c) and characteristic age, metallicity ([{Fe}/{{H}}]), alpha-abundance ([α /{Fe}]), and internal velocity dispersion ({σ }{int}) for individual galaxies. Parameter estimates derived from our 1.5 hr observation of A267 have median random errors of {σ }{v{los}}=20 {km} {{{s}}}-1, {σ }{Age}=1.2 {Gyr}, {σ }[{Fe/{{H}}]}=0.11 {dex}, {σ }[α /{Fe]}=0.07 {dex}, and {σ }{σ {int}}=20 {km} {{{s}}}-1. In a companion paper, we use these results to model the structure and internal kinematics of A267.

  8. Optical and Radio Observations of the T Tauri Binary KH 15D (V582 Mon): Stellar Properties, Disk Mass Limit, and Discovery of a CO Outflow

    Science.gov (United States)

    Aronow, Rachel A.; Herbst, William; Hughes, A. Meredith; Wilner, David J.; Winn, Joshua N.

    2018-01-01

    We present VRIJHK photometry of the KH 15D T Tauri binary system for the 2015/2016 and 2016/2017 observing seasons. For the first time in the modern (CCD) era, we are seeing Star B fully emerge from behind the trailing edge of the precessing circumbinary ring during each apastron passage. We are, therefore, able to measure its luminosity and color. Decades of photometry on the system now allow us to infer the effective temperature, radius, mass, and age of each binary component. We find our values to be in good agreement with previous studies, including archival photographic photometry from the era when both stars were fully visible, and they set the stage for a full model of the system that can be constructed once radial velocity measurements are available. We also present the first high-sensitivity radio observations of the system, taken with the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array. The respective 2.0 and 0.88 mm observations provide an upper limit on the circumbinary (gas and dust) disk mass of 1.7 M Jup and reveal an extended CO outflow, which overlaps with the position, systemic velocity, and orientation of the KH 15D system and is certainly associated with it. The low velocity, tight collimation, and extended nature of the emission suggest that the outflow is inclined nearly orthogonal to the line of sight, implying it is also orthogonal to the circumbinary ring. The position angle of the radio outflow also agrees precisely with the direction of polarization of the optical emission during the faint phase. A small offset between the optical image of the binary and the central line of the CO outflow remains a puzzle and possible clue to the jet launching mechanism.

  9. Population synthesis to constrain Galactic and stellar physics. I. Determining age and mass of thin-disc red-giant stars

    Science.gov (United States)

    Lagarde, N.; Robin, A. C.; Reylé, C.; Nasello, G.

    2017-05-01

    Context. The cornerstone mission of the European Space Agency, Gaia, together with forthcoming complementary surveys (CoRoT, Kepler, K2, APOGEE, and Gaia-ESO), will revolutionize our understanding of the formation and history of our Galaxy, providing accurate stellar masses, radii, ages, distances, as well as chemical properties for a very large sample of stars across different Galactic stellar populations. Aims: Using an improved population synthesis approach and new stellar evolution models we attempt to evaluate the possibility of deriving ages and masses of clump stars from their chemical properties. Methods: A new version of the Besançon Galaxy models (BGM) is used in which new stellar evolutionary tracks are computed from the stellar evolution code STAREVOL. These provide global, chemical, and seismic properties of stars from the pre-main sequence to the early-AGB. For the first time, the BGM can explore the effects of an extra-mixing occurring in red-giant stars. In particular we focus on the effects of thermohaline instability on chemical properties as well as on the determination of stellar ages and masses using the surface [C/N] abundance ratio. Results: The impact of extra-mixing on 3He, 12C/13C, nitrogen, and [C/N] abundances along the giant branch is quantified. We underline the crucial contribution of asteroseismology to discriminate between evolutionary states of field giants belonging to the Galactic disc. The inclusion of thermohaline instability has a significant impact on 12C/13C, 3He as well as on the [C/N] values. We clearly show the efficiency of thermohaline mixing at different metallicities and its influence on the determined stellar mass and age from the observed [C/N] ratio. We then propose simple relations to determine ages and masses from chemical abundances according to these models. Conclusions: We emphasize the usefulness of population synthesis tools to test stellar models and transport processes inside stars. We show that transport

  10. THE STELLAR POPULATION OF h AND χ PERSEI: CLUSTER PROPERTIES, MEMBERSHIP, AND THE INTRINSIC COLORS AND TEMPERATURES OF STARS

    International Nuclear Information System (INIS)

    Currie, Thayne; Irwin, Jonathan; Kenyon, Scott J.; Tokarz, Susan; Hernandez, Jesus; Balog, Zoltan; Bragg, Ann; Berlind, Perry; Calkins, Mike

    2010-01-01

    From photometric observations of ∼ 47,000 stars and spectroscopy of ∼ 11,000 stars, we describe the first extensive study of the stellar population of the famous Double Cluster, h and χ Persei, down to subsolar masses. By analyzing optical spectra and optical/infrared photometry, we constrain the distance moduli (dM), reddening (E(B - V)), and ages for h Persei, χ Persei, and the low-density halo population surrounding both cluster cores. With the exception of mass and spatial distribution, the clusters are nearly identical in every measurable way. Both clusters have E(B - V) ∼ 0.52-0.55 and dM = 11.8-11.85; the halo population, while more poorly constrained, likely has identical properties. As determined from the main-sequence turnoff, the luminosity of M supergiants, and pre-main-sequence isochrones, ages for h Persei, χ Persei, and the halo population all converge on ∼14 Myr, thus showing a stunning agreement between estimates based on entirely different physics. From these data, we establish the first spectroscopic and photometric membership lists of cluster stars down to early/mid M dwarfs. At minimum, there are ∼ 5000 members within 10' of the cluster centers, while the entire h and χ Persei region has at least ∼ 13,000 and as many as 20,000 members. The Double Cluster contains ∼ 8400 M sun of stars within 10' of the cluster centers. We estimate a total mass of at least 20,000 M sun . We conclude our study by outlining outstanding questions regarding the past and present properties of h and χ Persei. From comparing recent work, we compile a list of intrinsic colors and derive a new effective temperature scale for O-M dwarfs, giants, and supergiants.

  11. A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy

    Science.gov (United States)

    Hailey, Charles J.; Mori, Kaya; Bauer, Franz E.; Berkowitz, Michael E.; Hong, Jaesub; Hord, Benjamin J.

    2018-04-01

    The existence of a ‘density cusp’—a localized increase in number—of stellar-mass black holes near a supermassive black hole is a fundamental prediction of galactic stellar dynamics. The best place to detect such a cusp is in the Galactic Centre, where the nearest supermassive black hole, Sagittarius A*, resides. As many as 20,000 black holes are predicted to settle into the central parsec of the Galaxy as a result of dynamical friction; however, so far no density cusp of black holes has been detected. Low-mass X-ray binary systems that contain a stellar-mass black hole are natural tracers of isolated black holes. Here we report observations of a dozen quiescent X-ray binaries in a density cusp within one parsec of Sagittarius A*. The lower-energy emission spectra that we observed in these binaries is distinct from the higher-energy spectra associated with the population of accreting white dwarfs that dominates the central eight parsecs of the Galaxy. The properties of these X-ray binaries, in particular their spatial distribution and luminosity function, suggest the existence of hundreds of binary systems in the central parsec of the Galaxy and many more isolated black holes. We cannot rule out a contribution to the observed emission from a population (of up to about one-half the number of X-ray binaries) of rotationally powered, millisecond pulsars. The spatial distribution of the binary systems is a relic of their formation history, either in the stellar disk around Sagittarius A* (ref. 7) or through in-fall from globular clusters, and constrains the number density of sources in the modelling of gravitational waves from massive stellar remnants, such as neutron stars and black holes.

  12. Multiple stellar populations in Magellanic Cloud clusters. VI. A survey of multiple sequences and Be stars in young clusters

    Science.gov (United States)

    Milone, A. P.; Marino, A. F.; Di Criscienzo, M.; D'Antona, F.; Bedin, L. R.; Da Costa, G.; Piotto, G.; Tailo, M.; Dotter, A.; Angeloni, R.; Anderson, J.; Jerjen, H.; Li, C.; Dupree, A.; Granata, V.; Lagioia, E. P.; Mackey, A. D.; Nardiello, D.; Vesperini, E.

    2018-03-01

    The split main sequences (MSs) and extended MS turnoffs (eMSTOs) detected in a few young clusters have demonstrated that these stellar systems host multiple populations differing in a number of properties such as rotation and, possibly, age. We analyze Hubble Space Telescope photometry for thirteen clusters with ages between ˜40 and ˜1000 Myrs and of different masses. Our goal is to investigate for the first time the occurrence of multiple populations in a large sample of young clusters. We find that all the clusters exhibit the eMSTO phenomenon and that MS stars more massive than ˜1.6 M_⊙ define a blue and red MS, with the latter hosting the majority of MS stars. The comparison between the observations and isochrones suggests that the blue MSs are made of slow-rotating stars, while the red MSs host stars with rotational velocities close to the breakup value. About half of the bright MS stars in the youngest clusters are H-alpha emitters. These Be stars populate the red MS and the reddest part of the eMSTO thus supporting the idea that the red MS is made of fast rotators. We conclude that the split MS and the eMSTO are a common feature of young clusters in both Magellanic Clouds. The phenomena of a split MS and an eMSTO occur for stars that are more massive than a specific threshold which is independent of the host-cluster mass. As a by-product, we report the serendipitous discovery of a young SMC cluster, GALFOR1.

  13. The hELENa project - I. Stellar populations of early-type galaxies linked with local environment and galaxy mass

    Science.gov (United States)

    Sybilska, A.; Lisker, T.; Kuntschner, H.; Vazdekis, A.; van de Ven, G.; Peletier, R.; Falcón-Barroso, J.; Vijayaraghavan, R.; Janz, J.

    2017-09-01

    We present the first in a series of papers in The role of Environment in shaping Low-mass Early-type Nearby galaxies (hELENa) project. In this paper, we combine our sample of 20 low-mass early types (dEs) with 258 massive early types (ETGs) from the ATLAS3D survey - all observed with the SAURON integral field unit - to investigate early-type galaxies' stellar population scaling relations and the dependence of the population properties on local environment, extended to the low-σ regime of dEs. The ages in our sample show more scatter at lower σ values, indicative of less massive galaxies being affected by the environment to a higher degree. The shape of the age-σ relations for cluster versus non-cluster galaxies suggests that cluster environment speeds up the placing of galaxies on the red sequence. While the scaling relations are tighter for cluster than for the field/group objects, we find no evidence for a difference in average population characteristics of the two samples. We investigate the properties of our sample in the Virgo cluster as a function of number density (rather than simple clustrocentric distance) and find that dE ages correlate with the local density such that galaxies in regions of lower density are younger, likely because they are later arrivals to the cluster or have experienced less pre-processing in groups, and consequently used up their gas reservoir more recently. Overall, dE properties correlate more strongly with density than those of massive ETGs, which was expected as less massive galaxies are more susceptible to external influences.

  14. Estimate of stellar masses from their QPO frequencies

    Indian Academy of Sciences (India)

    Abstract. Kilohertz quasiperiodic oscillations (kHz QPOs) are observed in binary stellar systems. For such a system, the stellar radius is very close to the marginally stable orbit Rms as predicted by. Einstein's general relativity. Many models have been proposed to explain the origin of the kHz QPO features in the binaries.

  15. STAR CLUSTER PROPERTIES IN TWO LEGUS GALAXIES COMPUTED WITH STOCHASTIC STELLAR POPULATION SYNTHESIS MODELS

    International Nuclear Information System (INIS)

    Krumholz, Mark R.; Adamo, Angela; Fumagalli, Michele; Wofford, Aida; Calzetti, Daniela; Grasha, Kathryn; Lee, Janice C.; Whitmore, Bradley C.; Bright, Stacey N.; Ubeda, Leonardo; Gouliermis, Dimitrios A.; Kim, Hwihyun; Nair, Preethi; Ryon, Jenna E.; Smith, Linda J.; Thilker, David; Zackrisson, Erik

    2015-01-01

    We investigate a novel Bayesian analysis method, based on the Stochastically Lighting Up Galaxies (slug) code, to derive the masses, ages, and extinctions of star clusters from integrated light photometry. Unlike many analysis methods, slug correctly accounts for incomplete initial mass function (IMF) sampling, and returns full posterior probability distributions rather than simply probability maxima. We apply our technique to 621 visually confirmed clusters in two nearby galaxies, NGC 628 and NGC 7793, that are part of the Legacy Extragalactic UV Survey (LEGUS). LEGUS provides Hubble Space Telescope photometry in the NUV, U, B, V, and I bands. We analyze the sensitivity of the derived cluster properties to choices of prior probability distribution, evolutionary tracks, IMF, metallicity, treatment of nebular emission, and extinction curve. We find that slug's results for individual clusters are insensitive to most of these choices, but that the posterior probability distributions we derive are often quite broad, and sometimes multi-peaked and quite sensitive to the choice of priors. In contrast, the properties of the cluster population as a whole are relatively robust against all of these choices. We also compare our results from slug to those derived with a conventional non-stochastic fitting code, Yggdrasil. We show that slug's stochastic models are generally a better fit to the observations than the deterministic ones used by Yggdrasil. However, the overall properties of the cluster populations recovered by both codes are qualitatively similar

  16. SPHERE/ZIMPOL observations of the symbiotic system R Aquarii. I. Imaging of the stellar binary and the innermost jet clouds

    Science.gov (United States)

    Schmid, H. M.; Bazzon, A.; Milli, J.; Roelfsema, R.; Engler, N.; Mouillet, D.; Lagadec, E.; Sissa, E.; Sauvage, J.-F.; Ginski, C.; Baruffolo, A.; Beuzit, J. L.; Boccaletti, A.; Bohn, A. J.; Claudi, R.; Costille, A.; Desidera, S.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Gisler, D.; Girard, J. H.; Gratton, R.; Henning, T.; Hubin, N.; Joos, F.; Kasper, M.; Langlois, M.; Pavlov, A.; Pragt, J.; Puget, P.; Quanz, S. P.; Salasnich, B.; Siebenmorgen, R.; Stute, M.; Suarez, M.; Szulágyi, J.; Thalmann, C.; Turatto, M.; Udry, S.; Vigan, A.; Wildi, F.

    2017-06-01

    Context. R Aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. Because of its proximity to the Sun, this object has been studied in much detail with many types of high resolution imaging and interferometric techniques. We have used R Aqr as test target for the visual camera subsystem ZIMPOL, which is part of the new extreme adaptive optics (AO) instrument SPHERE at the Very Large Telescope (VLT). Aims: We describe SPHERE/ZIMPOL test observations of the R Aqr system taken in Hα and other filters in order to demonstrate the exceptional performance of this high resolution instrument. We compare our observations with data from the Hubble Space Telescope (HST) and illustrate the complementarity of the two instruments. We use our data for a detailed characterization of the inner jet region of R Aqr. Methods: We analyze the high resolution ≈ 25 mas images from SPHERE/ZIMPOL and determine from the Hα emission the position, size, geometric structure, and line fluxes of the jet source and the clouds in the innermost region <2'' (<400 AU) of R Aqr. The data are compared to simultaneous HST line filter observations. The Hα fluxes and the measured sizes of the clouds yield Hα emissivities for many clouds from which one can derive the mean density, mass, recombination time scale, and other cloud parameters. Results: Our Hα data resolve for the first time the R Aqr binary and we measure for the jet source a relative position 45 mas West (position angle -89.5°) of the mira. The central jet source is the strongest Hα component with a flux of about 2.5 × 10-12 erg cm-2 s-1. North east and south west from the central source there are many clouds with very diverse structures. Within 0.5'' (100 AU) we see in the SW a string of bright clouds arranged in a zig-zag pattern and, further out, at 1''-2'', fainter and more extended bubbles. In the N and NE we see a bright, very

  17. Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

    Science.gov (United States)

    Marks, M.; Martín, E. L.; Béjar, V. J. S.; Lodieu, N.; Kroupa, P.; Manjavacas, E.; Thies, I.; Rebolo López, R.; Velasco, S.

    2017-08-01

    Context. One of the key questions of the star formation problem is whether brown dwarfs (BDs) form in the manner of stars directly from the gravitational collapse of a molecular cloud core (star-like) or whether BDs and some very low-mass stars (VLMSs) constitute a separate population that forms alongside stars comparable to the population of planets, for example through circumstellar disk (peripheral) fragmentation. Aims: For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2 M⊙, while for BDs the binary fraction is population synthesis model in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), their own orbital parameter distributions for binaries, and small binary fractions, according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component was accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results: The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the mass limits for star-like and peripheral formation. Such a trend might be unique to low density regions, such as Taurus, which host binary populations that are largely unprocessed dynamically in which the binary fraction is large for stars down to M-dwarfs and small for BDs. Conclusions: The existence of a strong decline in the binary fraction - primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star-forming region. The binary fraction - primary mass diagram is a diagnostic of the (non-)continuity of star formation along the mass

  18. Classifying the embedded young stellar population in Perseus and Taurus and the LOMASS database

    DEFF Research Database (Denmark)

    Carney, M. T.; Ylldlz, U. A.; Mottram, J. C.

    2016-01-01

    and Taurus in order to characterize the presence and morphology of emission from high density (ncrit > 106 cm-3) and high column density gas, respectively. These are supplemented with archival dust continuum maps observed with SCUBA on the JCMT and Herschel PACS to compare the morphology of the gas and dust...... in the protostellar envelopes. The spatial concentration of HCO+J = 4-3 and 850 μm dust emission are used to classify the embedded nature of YSOs. Results. Approximately 30% of Class 0+I sources in Perseus and Taurus are not Stage I, but are likely to be more evolved Stage II pre-main sequence (PMS) stars with disks...... in the Perseus star forming region are truly embedded Stage I sources (71%), while the Taurus cloud hosts a majority of evolved PMS stars with disks (68%). The concentration factor method is useful to correct misidentified embedded YSOs, yielding higher accuracy for YSO population statistics and Stage timescales...

  19. Tidal effects on stellar activity

    Science.gov (United States)

    Poppenhaeger, K.

    2017-10-01

    The architecture of many exoplanetary systems is different from the solar system, with exoplanets being in close orbits around their host stars and having orbital periods of only a few days. We can expect interactions between the star and the exoplanet for such systems that are similar to the tidal interactions observed in close stellar binary systems. For the exoplanet, tidal interaction can lead to circularization of its orbit and the synchronization of its rotational and orbital period. For the host star, it has long been speculated if significant angular momentum transfer can take place between the planetary orbit and the stellar rotation. In the case of the Earth-Moon system, such tidal interaction has led to an increasing distance between Earth and Moon. For stars with Hot Jupiters, where the orbital period of the exoplanet is typically shorter than the stellar rotation period, one expects a decreasing semimajor axis for the planet and enhanced stellar rotation, leading to increased stellar activity. Also excess turbulence in the stellar convective zone due to rising and subsiding tidal bulges may change the magnetic activity we observe for the host star. I will review recent observational results on stellar activity and tidal interaction in the presence of close-in exoplanets, and discuss the effects of enhanced stellar activity on the exoplanets in such systems.

  20. The search for multiple populations in Magellanic Cloud Clusters IV: Coeval multiple stellar populations in the young star cluster NGC 1978

    Science.gov (United States)

    Martocchia, S.; Niederhofer, F.; Dalessandro, E.; Bastian, N.; Kacharov, N.; Usher, C.; Cabrera-Ziri, I.; Lardo, C.; Cassisi, S.; Geisler, D.; Hilker, M.; Hollyhead, K.; Kozhurina-Platais, V.; Larsen, S.; Mackey, D.; Mucciarelli, A.; Platais, I.; Salaris, M.

    2018-04-01

    We have recently shown that the ˜2 Gyr old Large Magellanic Cloud star cluster NGC 1978 hosts multiple populations in terms of star-to-star abundance variations in [N/Fe]. These can be seen as a splitting or spread in the sub-giant and red giant branches (SGB and RGB) when certain photometric filter combinations are used. Due to its relative youth, NGC 1978 can be used to place stringent limits on whether multiple bursts of star-formation have taken place within the cluster, as predicted by some models for the origin of multiple populations. We carry out two distinct analyses to test whether multiple star-formation epochs have occurred within NGC 1978. First, we use UV CMDs to select stars from the first and second population along the SGB, and then compare their positions in optical CMDs, where the morphology is dominantly controlled by age as opposed to multiple population effects. We find that the two populations are indistinguishable, with age differences of 1 ± 20 Myr between them. This is in tension with predictions from the AGB scenario for the origin of multiple populations. Second, we estimate the broadness of the main sequence turnoff (MSTO) of NGC 1978 and we report that it is consistent with the observational errors. We find an upper limit of ˜65 Myr on the age spread in the MSTO of NGC 1978. This finding is in conflict with the age spread scenario as origin of the extendend MSTO in intermediate age clusters, while it fully supports predictions from the stellar rotation model.

  1. Age as a major factor in the onset of multiple populations in stellar clusters

    Science.gov (United States)

    Martocchia, S.; Cabrera-Ziri, I.; Lardo, C.; Dalessandro, E.; Bastian, N.; Kozhurina-Platais, V.; Usher, C.; Niederhofer, F.; Cordero, M.; Geisler, D.; Hollyhead, K.; Kacharov, N.; Larsen, S.; Li, C.; Mackey, D.; Hilker, M.; Mucciarelli, A.; Platais, I.; Salaris, M.

    2018-01-01

    It is now well established that globular clusters (GCs) exhibit star-to-star light-element abundance variations (known as multiple populations, MPs). Such chemical anomalies have been found in (nearly) all the ancient GCs (more than 10 Gyr old) of our Galaxy and its close companions, but so far no model for the origin of MPs is able to reproduce all the relevant observations. To gain new insights into this phenomenon, we have undertaken a photometric Hubble Space Telescope survey to study clusters with masses comparable to that of old GCs, where MPs have been identified, but with significantly younger ages. Nine clusters in the Magellanic Clouds with ages between ∼1.5 and 11 Gyr have been targeted in this survey. We confirm the presence of MPs in all clusters older than 6 Gyr and we add NGC 1978 to the group of clusters for which MPs have been identified. With an age of ∼2 Gyr, NGC 1978 is the youngest cluster known to host chemical abundance spreads found to date. We do not detect evident star-to-star variations for slightly younger massive clusters (∼1.7 Gyr), thus pointing towards an unexpected age dependence for the onset of MPs. This discovery suggests that the formation of MPs is not restricted to the early Universe and that GCs and young massive clusters share common formation and evolutionary processes.

  2. Two distinct halo populations in the solar neighborhood. Evidence from stellar abundance ratios and kinematics

    Science.gov (United States)

    Nissen, P. E.; Schuster, W. J.

    2010-02-01

    Aims: Precise abundance ratios are determined for 94 dwarf stars with Teff K, -1.6 FIES spectra with resolutions R≃ 55 000 and R ≃ 40 000, respectively. An LTE abundance analysis based on MARCS models is applied to derive precise differential abundance ratios of Na, Mg, Si, Ca, Ti, Cr, and Ni with respect to Fe. Results: The halo stars fall into two populations, clearly separated in [α/Fe], where α refers to the average abundance of Mg, Si, Ca, and Ti. Differences in [Na/Fe] and [Ni/Fe] are also present with a remarkably clear correlation between these two abundance ratios. Conclusions: The “high-α” stars may be ancient disk or bulge stars “heated” to halo kinematics by merging satellite galaxies or they could have formed as the first stars during the collapse of a proto-Galactic gas cloud. The kinematics of the “low-α” stars suggest that they have been accreted from dwarf galaxies, and that some of them may originate from the ω Cen progenitor galaxy. Based on observations made with the Nordic Optical Telescope on La Palma, and on data from the European Southern Observatory ESO/ST-ECF Science Archive Facility.Tables 3 and 4 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/511/L10Figures 5-8 and Tables 1-4 are only available in electronic form at http://www.aanda.org

  3. A clumpy stellar wind and luminosity-dependent cyclotron line revealed by the first Suzaku observation of the high-mass X-ray binary 4U 1538–522

    Energy Technology Data Exchange (ETDEWEB)

    Hemphill, Paul B.; Rothschild, Richard E.; Markowitz, Alex [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 920093-0424 (United States); Fürst, Felix [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MC 290-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Pottschmidt, Katja [Center for Space Science and Technology, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 (United States); Wilms, Jörn, E-mail: pbhemphill@physics.ucsd.edu [Dr. Karl Remeis-Sternwarte and Erlangen Center for Astroparticle Physics, Sternwartstr. 7, D-96049 Bamberg (Germany)

    2014-09-01

    We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538–522. The broadband spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at 23.0 ± 0.4 keV and the iron Kα line at 6.426 ± 0.008 keV, as well as placing limits on the strengths of the iron Kβ line and the iron K edge. We track the evolution of the spectral parameters both in time and in luminosity, notably finding a significant positive correlation between cyclotron line energy and luminosity. A dip and spike in the light curve is shown to be associated with an order-of-magnitude increase in column density along the line of sight, as well as significant variation in the underlying continuum, implying the accretion of a overdense region of a clumpy stellar wind. We also present a phase-resolved analysis, with most spectral parameters of interest showing significant variation with phase. Notably, both the cyclotron line energy and the iron Kα line intensity vary significantly with phase, with the iron line intensity significantly out of phase with the pulse profile. We discuss the implications of these findings in the context of recent work in the areas of accretion column physics and cyclotron resonance scattering feature formation.

  4. Understanding the formation and evolution of early-type galaxies based on newly developed single-burst stellar population synthesis models in the infrared

    Science.gov (United States)

    Roeck, Benjamin

    2015-12-01

    The detailed study of the different stellar populations which can be observed in galaxies is one of the most promising methods to shed light on the evolutionary histories of galaxies. So far, stellar population analysis has been carried out mainly in the optical wavelength range. The infrared spectral range, on the other hand, has been poorly studied so far, although it provides very important insights, particularly into the cooler stellar populations which are present in galaxies. However, in the last years, space telescopes like the Spitzer Space Telescope or the Wide-field Infrared Survey Explorer and instruments like the spectrograph X-Shooter on the Very Large Telescope have collected more and more photometric and spectroscopic data in this wavelength range. In order to analyze these observations, it is necessary to dispose of reliable and accurate stellar population models in the infrared. Only a small number of stellar population models in the infrared exist in the literature. They are mostly based on theoretical stellar libraries and very often cover only the near-infrared wavelength range at a rather low resolution. Hence, we developed new single-burst stellar population models between 8150 and 50000Å which are exclusively based on 180 spectra from the empirical Infrared Telescope Facility stellar library. We computed our single stellar population models for two different sets of isochrones and various types of initial mass functions of different slopes. Since the stars of the Infrared Telescope Facility library present only a limited coverage of the stellar atmospheric parameter space, our models are of sufficient quality only for ages larger than 1 Gyr and metallicities between [Fe/H] = 0.40 and 0.26. By combining our single stellar population models in the infrared with the extended medium-resolution Isaac Newton Telescope library of empirical spectra in the optical spectral range, we created the first single stellar population models covering the

  5. A GALEX-BASED SEARCH FOR THE SPARSE YOUNG STELLAR POPULATION IN THE TAURUS-AURIGAE STAR FORMING REGION

    International Nuclear Information System (INIS)

    Gómez de Castro, Ana I.; Lopez-Santiago, Javier; López-Martínez, Fatima; Sánchez, Néstor; Sestito, Paola; Gestoso, Javier Yañez; De Castro, Elisa; Cornide, Manuel

    2015-01-01

    In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), optical (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J–K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J–K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions

  6. A GALEX-BASED SEARCH FOR THE SPARSE YOUNG STELLAR POPULATION IN THE TAURUS-AURIGAE STAR FORMING REGION

    Energy Technology Data Exchange (ETDEWEB)

    Gómez de Castro, Ana I.; Lopez-Santiago, Javier; López-Martínez, Fatima; Sánchez, Néstor; Sestito, Paola; Gestoso, Javier Yañez [AEGORA Research Group, Universidad Complutense de Madrid, Plaza de Ciencias 3, E-28040 Madrid (Spain); De Castro, Elisa; Cornide, Manuel [Fac. de CC. Físicas, Universidad Complutense de Madrid, Plaza de Ciencias 1, E-28040 Madrid (Spain)

    2015-02-01

    In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), optical (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J–K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J–K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions.

  7. Binary Stars and Globular Cluster Dynamics

    Science.gov (United States)

    Fregeau, John M.

    2008-05-01

    In this brief proceedings article I summarize the review talk I gave at the IAU 246 meeting in Capri, Italy, glossing over the well-known results from the literature, but paying particular attention to new, previously unpublished material. This new material includes a careful comparison of the apparently contradictory results of two independent methods used to simulate the evolution of binary populations in dense stellar systems (the direct N-body method of Hurley, Aarseth, & Shara (2007) and the approximate Monte Carlo method of Ivanova et al. (2005)), that shows that the two methods may not actually yield contradictory results, and suggests future work to more directly compare the two methods.

  8. SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION

    International Nuclear Information System (INIS)

    Daemgen, Sebastian; Bonavita, Mariangela; Jayawardhana, Ray; Lafrenière, David; Janson, Markus

    2015-01-01

    We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ∼3 M ☉ and low-mass stars at ∼0.2 M ☉ . We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ∼2 M Jup . The inferred multiplicity frequency within our sensitivity limits between ∼10-1500 AU is 26.3 −4.9 +6.6 %. Applying a completeness correction, 62% ± 14% of all Taurus stars between 0.7 and 1.4 M ☉ appear to be multiple. Higher order multiples were found in 1.8 −1.5 +4.2 % of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ∼3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ∼2 Myr and ∼20 Myr, respectively

  9. SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION

    Energy Technology Data Exchange (ETDEWEB)

    Daemgen, Sebastian [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5H 3H4 (Canada); Bonavita, Mariangela [The University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Jayawardhana, Ray [Physics and Astronomy, York University, Toronto, Ontario L3T 3R1 (Canada); Lafrenière, David [Department of Physics, University of Montréal, Montréal, QC (Canada); Janson, Markus, E-mail: daemgen@astro.utoronto.ca [Department of Astronomy, Stockholm University, Stockholm (Sweden)

    2015-02-01

    We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ∼3 M {sub ☉} and low-mass stars at ∼0.2 M {sub ☉}. We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ∼2 M {sub Jup}. The inferred multiplicity frequency within our sensitivity limits between ∼10-1500 AU is 26.3{sub −4.9}{sup +6.6}%. Applying a completeness correction, 62% ± 14% of all Taurus stars between 0.7 and 1.4 M {sub ☉} appear to be multiple. Higher order multiples were found in 1.8{sub −1.5}{sup +4.2}% of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ∼3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ∼2 Myr and ∼20 Myr, respectively.

  10. Looking for Galaxies in All the Right Places: A Search for Stellar Populations in ALFALFA’s Ultra-compact High Velocity Clouds

    Science.gov (United States)

    Janesh, William; Rhode, Katherine L.; Salzer, John J.; Janowiecki, Steven; Adams, Elizabeth; Haynes, Martha P.; Giovanelli, Riccardo; Cannon, John M.

    2018-01-01

    Nearby gas-rich dwarf galaxies are excellent laboratories for investigating the baryonic feedback processes that govern star formation and galaxy evolution in galaxies at the extreme end of the mass function. Detecting and studying such objects may help resolve the well-known tension between cosmological model predictions for low-mass dark matter halos and observations. The ALFALFA neutral hydrogen (Hi) survey has detected a sample of isolated ultra-compact high-velocity Hi clouds (UCHVCs) with kinematic properties that make them likely members of the Local Volume, but that have no optical counterparts in existing optical surveys. This UCHVC sample possesses Hi properties (at 1 Mpc, Hi masses of ~105-106 M⊙, Hi diameters of ~2-3 kpc, and dynamical masses of ~107-108 M⊙) similar to other known ultra-faint dwarf galaxies like Leo T. Following the discovery of Leo P, an extremely metal-poor, gas-rich star-forming dwarf galaxy associated with an ALFALFA UCHVC, we have initiated a campaign to obtain deep optical imaging of 56 UCHVCs using the wide field-of-view, high-resolution ODI camera on the WIYN 3.5-m telescope. Here we present a brief overview of our campaign to search for resolved stellar populations associated with the UCHVCs in our optical images, and initial results from our survey.After creating a stellar catalog from the pipeline-reduced and stacked ODI g- and i-band images, we apply a color-magnitude filter tuned for old, metal-poor stellar populations to select red giant branch stars at distances between 250 kpc and 2 Mpc. The spatial distribution of the stars selected by the filter is then smoothed, and overdensities in the fields are identified. Of the 22 targets analyzed to date, seven have associated stellar populations detected at a high confidence (92% to 99.9% significance). The detected objects have a range of distances (from 350 kpc to 1.6 Mpc) and have optical properties similar to those of ultra-faint dwarf galaxies. These objects have

  11. Stellar-mass black holes in young massive and open stellar clusters and their role in gravitational-wave generation - II

    Science.gov (United States)

    Banerjee, Sambaran

    2018-01-01

    The study of stellar-remnant black holes (BH) in dense stellar clusters is now in the spotlight, especially due to their intrinsic ability to form binary black holes (BBH) through dynamical encounters, which potentially coalesce via gravitational-wave (GW) radiation. In this work, which is a continuation from a recent study (Paper I), additional models of compact stellar clusters with initial masses ≲ 105 M⊙ and also those with small fractions of primordial binaries (≲ 10 per cent) are evolved for long term, applying the direct N-body approach, assuming state-of-the-art stellar-wind and remnant-formation prescriptions. That way, a substantially broader range of computed models than that in Paper I is achieved. As in Paper I, the general-relativistic BBH mergers continue to be mostly mediated by triples that are bound to the clusters rather than happen among the ejected BBHs. In fact, the number of such in situ BBH mergers, per cluster, tends to increase significantly with the introduction of a small population of primordial binaries. Despite the presence of massive primordial binaries, the merging BBHs, especially the in situ ones, are found to be exclusively dynamically assembled and hence would be spin-orbit misaligned. The BBHs typically traverse through both the LISA's and the LIGO's detection bands, being audible to both instruments. The 'dynamical heating' of the BHs keeps the electron-capture-supernova (ECS) neutron stars (NS) from effectively mass segregating and participating in exchange interactions; the dynamically active BHs would also exchange into any NS binary within ≲1 Gyr. Such young massive and open clusters have the potential to contribute to the dynamical BBH merger detection rate to a similar extent as their more massive globular-cluster counterparts.

  12. New binaries among UV-selected, hot subdwarf stars and population properties

    Czech Academy of Sciences Publication Activity Database

    Kawka, Adela; Vennes, Stephane; O' Toole, S.; Nemeth, P.; Burton, D.; Kotze, E.; Buckley, D.A.H.

    2015-01-01

    Roč. 450, č. 4 (2015), s. 3514-3548 ISSN 0035-8711 R&D Projects: GA ČR GAP209/12/0217; GA ČR GA13-14581S; GA MŠk LG14013 Institutional support: RVO:67985815 Keywords : close binaries * spectroscopic * subdwarfs Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.952, year: 2015

  13. On the Observability of Individual Population III Stars and Their Stellar-mass Black Hole Accretion Disks through Cluster Caustic Transits

    Science.gov (United States)

    Windhorst, Rogier A.; Timmes, F. X.; Wyithe, J. Stuart B.; Alpaslan, Mehmet; Andrews, Stephen K.; Coe, Daniel; Diego, Jose M.; Dijkstra, Mark; Driver, Simon P.; Kelly, Patrick L.; Kim, Duho

    2018-02-01

    We summarize panchromatic Extragalactic Background Light data to place upper limits on the integrated near-infrared surface brightness (SB) that may come from Population III stars and possible accretion disks around their stellar-mass black holes (BHs) in the epoch of First Light, broadly taken from z ≃ 7–17. Theoretical predictions and recent near-infrared power spectra provide tighter constraints on their sky signal. We outline the physical properties of zero-metallicity Population III stars from MESA stellar evolution models through helium depletion and of BH accretion disks at z≳ 7. We assume that second-generation non-zero-metallicity stars can form at higher multiplicity, so that BH accretion disks may be fed by Roche-lobe overflow from lower-mass companions. We use these near-infrared SB constraints to calculate the number of caustic transits behind lensing clusters that the James Webb Space Telescope and the next-generation ground-based telescopes may observe for both Population III stars and their BH accretion disks. Typical caustic magnifications can be μ ≃ {10}4{--}{10}5, with rise times of hours and decline times of ≲ 1 year for cluster transverse velocities of {v}T≲ 1000 km s‑1. Microlensing by intracluster-medium objects can modify transit magnifications but lengthen visibility times. Depending on BH masses, accretion-disk radii, and feeding efficiencies, stellar-mass BH accretion-disk caustic transits could outnumber those from Population III stars. To observe Population III caustic transits directly may require monitoring 3–30 lensing clusters to {AB}≲ 29 mag over a decade.

  14. Neutron-Star Radius from a Population of Binary Neutron Star Mergers.

    Science.gov (United States)

    Bose, Sukanta; Chakravarti, Kabir; Rezzolla, Luciano; Sathyaprakash, B S; Takami, Kentaro

    2018-01-19

    We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies, we utilize analytical fits to postmerger numerical relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass. We further exploit quasiuniversal relations to derive errors in compactness from those frequencies. Measuring the average radius to well within 10% is possible for a sample of 100 binaries distributed uniformly in volume between 100 and 300 Mpc, so long as the equation of state is not too soft or the binaries are not too heavy. We also give error estimates for the Einstein Telescope.

  15. Neutron-Star Radius from a Population of Binary Neutron Star Mergers

    Science.gov (United States)

    Bose, Sukanta; Chakravarti, Kabir; Rezzolla, Luciano; Sathyaprakash, B. S.; Takami, Kentaro

    2018-01-01

    We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies, we utilize analytical fits to postmerger numerical relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass. We further exploit quasiuniversal relations to derive errors in compactness from those frequencies. Measuring the average radius to well within 10% is possible for a sample of 100 binaries distributed uniformly in volume between 100 and 300 Mpc, so long as the equation of state is not too soft or the binaries are not too heavy. We also give error estimates for the Einstein Telescope.

  16. Circumstellar disks around binary stars in Taurus

    International Nuclear Information System (INIS)

    Akeson, R. L.; Jensen, E. L. N.

    2014-01-01

    We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10 –4 M ☉ . We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F mm ∝M ∗ 1.5--2.0 to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.

  17. Circumstellar disks around binary stars in Taurus

    Energy Technology Data Exchange (ETDEWEB)

    Akeson, R. L. [NASA Exoplanet Science Institute, IPAC/Caltech, Pasadena, CA 91125 (United States); Jensen, E. L. N. [Swarthmore College, Department of Physics and Astronomy, Swarthmore, PA 19081 (United States)

    2014-03-20

    We have conducted a survey of 17 wide (>100 AU) young binary systems in Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The observations were designed to measure the masses of circumstellar disks in these systems as an aid to understanding the role of multiplicity in star and planet formation. The ALMA observations had sufficient resolution to localize emission within the binary system. Disk emission was detected around all primaries and 10 secondaries, with disk masses as low as 10{sup –4} M {sub ☉}. We compare the properties of our sample to the population of known disks in Taurus and find that the disks from this binary sample match the scaling between stellar mass and millimeter flux of F{sub mm}∝M{sub ∗}{sup 1.5--2.0} to within the scatter found in previous studies. We also compare the properties of the primaries to those of the secondaries and find that the secondary/primary stellar and disk mass ratios are not correlated; in three systems, the circumsecondary disk is more massive than the circumprimary disk, counter to some theoretical predictions.

  18. Binary interactions on the calibrations of star formation rate

    Science.gov (United States)

    Zhang, Fenghui; Li, Lifang; Zhang, Yu; Kang, Xiaoyu; Han, Zhanwen

    2012-03-01

    Using the Yunnan evolutionary population synthesis (EPS) models with and without binary interactions, we present the luminosity of Hα recombination line (LHα), the luminosity of [O II] λ3727 forbidden line doublet (?), the ultraviolet (UV) fluxes at 1500 and 2800 Å (Li, UV) and far-infrared flux (LFIR) for burst, S0, Sa-Sd and Irr galaxies, and present the calibrations of star formation rate (SFR) in terms of these diagnostics. By comparison, we find that binary interactions lower the SFR versus LHα and SFR versus ? conversion factors by ˜0.2 dex. The main reason is that binary interactions raise the UV flux (shortwards of the Lyman limit) of the stellar population (SP) in the age range 6.7 Aarseth-Hurley, Kroupa-Tout-Gilmore and Miller-Scalo IMFs, partly caused by the difference in the IMF), respectively. At last, we give the conversion coefficients between SFR and these diagnostics for all models.

  19. Stellar formation

    CERN Document Server

    Reddish, V C

    1978-01-01

    Stellar Formation brings together knowledge about the formation of stars. In seeking to determine the conditions necessary for star formation, this book examines questions such as how, where, and why stars form, and at what rate and with what properties. This text also considers whether the formation of a star is an accident or an integral part of the physical properties of matter. This book consists of 13 chapters divided into two sections and begins with an overview of theories that explain star formation as well as the state of knowledge of star formation in comparison to stellar structure

  20. Stellar remnants

    CERN Document Server

    Kawaler, S D; Srinivasan, G

    1997-01-01

    This volume examines the internal structure, origin and evolution of white dwarfs, neutron stars and black holes, all objects at the final stage of stellar evolution. It covers topics such as: pulsation of white dwarfs; millisecond pulsars; and the dynamics around black holes.

  1. The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters - XIV. Multiple stellar populations within M 15 and their radial distribution.

    Science.gov (United States)

    Nardiello, D.; Milone, A. P.; Piotto, G.; Anderson, J.; Bedin, L. R.; Bellini, A.; Cassisi, S.; Libralato, M.; Marino, A. F.

    2018-03-01

    In the context of the Hubble Space Telescope UV Survey of Galactic Globular Clusters (GCs), we derived high-precision, multi-band photometry to investigate the multiple stellar populations in the massive and metal-poor GC M 15. By creating for red-giant branch (RGB) stars of the cluster a `chromosome map', which is a pseudo two-colour diagram made with appropriate combination of F275W, F336W, F438W, and F814W magnitudes, we revealed colour spreads around two of the three already known stellar populations. These spreads cannot be produced by photometric errors alone and could hide the existence of (two) additional populations. This discovery increases the complexity of the multiple-population phenomenon in M 15. Our analysis shows that M 15 exhibits a faint sub-giant branch (SGB), which is also detected in colour-magnitude diagrams (CMDs) made with optical magnitudes only. This poorly-populated SGB includes about 5% of the total number of SGB stars and evolves into a red RGB in the mF336W vs. mF336W - mF814W CMD, suggesting that M 15 belongs to the class of Type II GCs. We measured the relative number of stars in each population at various radial distances from the cluster centre, showing that all of these populations share the same radial distribution within statistic uncertainties. These new findings are discussed in the context of the formation and evolution scenarios of the multiple populations.

  2. Astrophysics of white dwarf binaries

    NARCIS (Netherlands)

    Nelemans, G.A.

    2006-01-01

    White dwarf binaries are the most common compact binaries in the Universe and are especially important for low-frequency gravitational wave detectors such as LISA. There are a number of open questions about binary evolution and the Galactic population of white dwarf binaries that can be solved using

  3. Stellar Population Synthesis of Star-forming Clumps in Galaxy Pairs and Non-interacting Spiral Galaxies

    Science.gov (United States)

    Zaragoza-Cardiel, Javier; Smith, Beverly J.; Rosado, Margarita; Beckman, John E.; Bitsakis, Theodoros; Camps-Fariña, Artemi; Font, Joan; Cox, Isaiah S.

    2018-02-01

    We have identified 1027 star-forming complexes in a sample of 46 galaxies from the Spirals, Bridges, and Tails (SB&T) sample of interacting galaxies, and 693 star-forming complexes in a sample of 38 non-interacting spiral (NIS) galaxies in 8 μm observations from the Spitzer Infrared Array Camera. We have used archival multi-wavelength UV-to IR observations to fit the observed spectral energy distribution of our clumps with the Code Investigating GALaxy Emission using a double exponentially declined star formation history. We derive the star formation rates (SFRs), stellar masses, ages and fractions of the most recent burst, dust attenuation, and fractional emission due to an active galactic nucleus for these clumps. The resolved star formation main sequence holds on 2.5 kpc scales, although it does not hold on 1 kpc scales. We analyzed the relation between SFR, stellar mass, and age of the recent burst in the SB&T and NIS samples, and we found that the SFR per stellar mass is higher in the SB&T galaxies, and the clumps are younger in the galaxy pairs. We analyzed the SFR radial profile and found that the SFR is enhanced through the disk and in the tidal features relative to normal spirals.

  4. Infalling clouds on to supermassive black hole binaries - II. Binary evolution and the final parsec problem

    Science.gov (United States)

    Goicovic, Felipe G.; Sesana, Alberto; Cuadra, Jorge; Stasyszyn, Federico

    2017-11-01

    The formation of massive black hole binaries (MBHBs) is an unavoidable outcome of galaxy evolution via successive mergers. However, the mechanism that drives their orbital evolution from parsec separations down to the gravitational wave dominated regime is poorly understood, and their final fate is still unclear. If such binaries are embedded in gas-rich and turbulent environments, as observed in remnants of galaxy mergers, the interaction with gas clumps (such as molecular clouds) may efficiently drive their orbital evolution. Using numerical simulations, we test this hypothesis by studying the dynamical evolution of an equal mass, circular MBHB accreting infalling molecular clouds. We investigate different orbital configurations, modelling a total of 13 systems to explore different possible impact parameters and relative inclinations of the cloud-binary encounter. We focus our study on the prompt, transient phase during the first few orbits when the dynamical evolution of the binary is fastest, finding that this evolution is dominated by the exchange of angular momentum through gas capture by the individual black holes and accretion. Building on these results, we construct a simple model for evolving an MBHB interacting with a sequence of clouds, which are randomly drawn from reasonable populations with different levels of anisotropy in their angular momenta distributions. We show that the binary efficiently evolves down to the gravitational wave emission regime within a few hundred million years, overcoming the 'final parsec' problem regardless of the stellar distribution.

  5. Thin shell morphology in the circumstellar medium of massive binaries

    NARCIS (Netherlands)

    van Marle, A. J.; Keppens, R.; Meliani, Z.

    2011-01-01

    Context. In massive binaries, the powerful stellar winds of the two stars collide, leading to the formation of shock-dominated environments that can be modeled only in 3D. Aims. We investigate the morphology of the collision-front shell between the stellar winds of binary components in two

  6. Constraining the Main Belt Binary Asteroid Population Using Doublet Craters on Ceres

    Science.gov (United States)

    Wren, P.; Fevig, R. A.

    2017-12-01

    Doublet craters are two impact craters created by the same primary impact event [Oberbeck and Aoyagi, 1972, JGR 77], and are believed to be caused by well-separated binary asteroids [Bottke and Melosh, 1996, Icarus 124]. We report on our efforts to estimate the percentage of impact craters on the dwarf planet Ceres that are doublet craters, and to assess their implications for bounding the percentage of Main Belt asteroids that are binaries. Using an approach inspired by Melosh, Ingram, and Bottke [1996, LPS XXVII Abstract #1432], we identified all craters 3km or larger in our initial study region on Ceres using Framing Camera images from the Dawn spacecraft. All pairs of craters with separations less than 20km were evaluated as potential doublets, using criteria such as similar age, and the presence of a septum and/or ejecta lobes. Out of 172 unique pairs, four were initially identified as "possible" or "likely" doublets. Comparing the distribution of observed crater pair separations impact locations generated by a Monte Carlo simulation showed non-random excesses at separation distances consistent with our four possible doublets. Further analysis of crater rims using form and circularity ratios [Selkirk 1982, Pattern and Place, Cambridge] eliminated three of the candidate pairs since they are likely secondary impact craters. If the one remaining possible doublet pair is treated as a true doublet, it would indicate a lower bound of 1.3% for impact events that are doublets in the initial study region. This is lower than the 2-3% seen for Earth and Mars [Miljković et al., 2013, Earth Planet Sc Lett, 363]. The present work is applying the same approach to another roughly 28,000 square kilometer region to increase our sample size, and to consider any constrasts in the nature of impact features on a different part of Ceres.

  7. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  8. Stellarator physics

    International Nuclear Information System (INIS)

    1990-07-01

    This document consists of the proceedings of the Seventh International Workshop on Stellarators, held in Oak Ridge, Tennessee, USA, 10-14 April, 1989. The document consists of a summary of presentations, an overview of experimental results, and papers presented at the workshop on transport, impurities and divertors, diagnostics, ECH confinement experiments, equilibrium and stability studies, RF heating, confinement, magnetic configurations, and new experiments. Refs, figs and tabs

  9. The origin of the young stellar population in the solar neighborhood -- A link to the formation of the Local Bubble?

    Science.gov (United States)

    Berghöfer, T. W.; Breitschwerdt, D.

    2002-07-01

    We have analyzed the trajectories of moving stellar groups in the solar neighborhood in an attempt to estimate the number of supernova explosions in our local environment during the past 20 million years. Using Hipparcos stellar distances and the results of kinematical analyses by Asiain et al. (\\cite{Asiain1999a}a) on the Pleiades moving groups, we are able to show that subgroup B1, consisting of early type B stars up to 10 Msun, but lacking more massive objects, has passed through the local interstellar medium within less than 100 pc. Comparing the stellar content of B1 with the initial mass function derived from the analysis of galactic OB associations, we estimate the number of supernova explosions and find that about 20 supernovae must have occurred during the past ~ 10 - 20 million years, which is suggested to be the age of the Local Bubble; the age of the star cluster is about ~ 20 - 30 million years. For the first time, this provides strong evidence that the Local Bubble must have been created and shaped by multi-supernova explosions and presumably been reheated more than 1 million years ago, consistent with recent findings of an excess of 60Fe in a deep ocean ferromanganese crust. Calculating similarity solutions of an expanding superbubble for time-dependent energy input, we show that the number of explosions is sufficient to explain the size of the Local Bubble. The present energy input rate is about dot ESN ~ 5 x 1036 erg/s, in good agreement with the estimated local soft X-ray photon output rate. It seems plausible that the origin of the Local Bubble is also linked to the formation of the Gould Belt, which originated about 30-60 Myrs ago.

  10. Gravitational-wave localization alone can probe origin of stellar-mass black hole mergers.

    Science.gov (United States)

    Bartos, I; Haiman, Z; Marka, Z; Metzger, B D; Stone, N C; Marka, S

    2017-10-10

    The recent discovery of gravitational waves from stellar-mass binary black hole mergers by the Laser Interferometer Gravitational-wave Observatory opened the door to alternative probes of stellar and galactic evolution, cosmology and fundamental physics. Probing the origin of binary black hole mergers will be difficult due to the expected lack of electromagnetic emission and limited localization accuracy. Associations with rare host galaxy types-such as active galactic nuclei-can nevertheless be identified statistically through spatial correlation. Here we establish the feasibility of statistically proving the connection between binary black hole mergers and active galactic nuclei as hosts, even if only a sub-population of mergers originate from active galactic nuclei. Our results are the demonstration that the limited localization of gravitational waves, previously written off as not useful to distinguish progenitor channels, can in fact contribute key information, broadening the range of astrophysical questions probed by binary black hole observations.Binary black hole mergers have recently been observed through the detection of gravitational wave signatures. The authors demonstrate that their association with active galactic nuclei can be made through a statistical spatial correlation.

  11. Stellar evolution

    CERN Document Server

    Meadows, A J

    2013-01-01

    Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

  12. A simple model for binary star evolution

    International Nuclear Information System (INIS)

    Whyte, C.A.; Eggleton, P.P.

    1985-01-01

    A simple model for calculating the evolution of binary stars is presented. Detailed stellar evolution calculations of stars undergoing mass and energy transfer at various rates are reported and used to identify the dominant physical processes which determine the type of evolution. These detailed calculations are used to calibrate the simple model and a comparison of calculations using the detailed stellar evolution equations and the simple model is made. Results of the evolution of a few binary systems are reported and compared with previously published calculations using normal stellar evolution programs. (author)

  13. STELLAR POPULATIONS FROM SPECTROSCOPY OF A LARGE SAMPLE OF QUIESCENT GALAXIES AT Z > 1: MEASURING THE CONTRIBUTION OF PROGENITOR BIAS TO EARLY SIZE GROWTH

    Energy Technology Data Exchange (ETDEWEB)

    Belli, Sirio; Ellis, Richard S. [Department of Astronomy, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Newman, Andrew B. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States)

    2015-02-01

    We analyze the stellar populations of a sample of 62 massive (log M {sub *}/M {sub ☉} > 10.7) galaxies in the redshift range 1 < z < 1.6, with the main goal of investigating the role of recent quenching in the size growth of quiescent galaxies. We demonstrate that our sample is not biased toward bright, compact, or young galaxies, and thus is representative of the overall quiescent population. Our high signal-to-noise ratio Keck/LRIS spectra probe the rest-frame Balmer break region that contains important absorption line diagnostics of recent star formation activity. We obtain improved measures of the various stellar population parameters, including the star formation timescale τ, age, and dust extinction, by fitting templates jointly to both our spectroscopic and broadband photometric data. We identify which quiescent galaxies were recently quenched and backtrack their individual evolving trajectories on the UVJ color-color plane finding evidence for two distinct quenching routes. By using sizes measured in the previous paper of this series, we confirm that the largest galaxies are indeed among the youngest at a given redshift. This is consistent with some contribution to the apparent growth from recent arrivals, an effect often called progenitor bias. However, we calculate that recently quenched objects can only be responsible for about half the increase in average size of quiescent galaxies over a 1.5 Gyr period, corresponding to the redshift interval 1.25 < z < 2. The remainder of the observed size evolution arises from a genuine growth of long-standing quiescent galaxies.

  14. BHMcalc: Binary Habitability Mechanism Calculator

    Science.gov (United States)

    Zuluaga, Jorge I.; Mason, Paul; Cuartas-Restrepo, Pablo A.; Clark, Joni

    2018-02-01

    BHMcalc provides renditions of the instantaneous circumbinary habital zone (CHZ) and also calculates BHM properties of the system including those related to the rotational evolution of the stellar components and the combined XUV and SW fluxes as measured at different distances from the binary. Moreover, it provides numerical results that can be further manipulated and used to calculate other properties.

  15. Microlensing Signature of Binary Black Holes

    Science.gov (United States)

    Schnittman, Jeremy; Sahu, Kailash; Littenberg, Tyson

    2012-01-01

    We calculate the light curves of galactic bulge stars magnified via microlensing by stellar-mass binary black holes along the line-of-sight. We show the sensitivity to measuring various lens parameters for a range of survey cadences and photometric precision. Using public data from the OGLE collaboration, we identify two candidates for massive binary systems, and discuss implications for theories of star formation and binary evolution.

  16. Stellar Populations from Spectroscopy of a Large Sample of Quiescent Galaxies at Z > 1: Measuring the Contribution of Progenitor Bias to Early Size Growth

    Science.gov (United States)

    Belli, Sirio; Newman, Andrew B.; Ellis, Richard S.

    2015-02-01

    We analyze the stellar populations of a sample of 62 massive (log M */M ⊙ > 10.7) galaxies in the redshift range 1 backtrack their individual evolving trajectories on the UVJ color-color plane finding evidence for two distinct quenching routes. By using sizes measured in the previous paper of this series, we confirm that the largest galaxies are indeed among the youngest at a given redshift. This is consistent with some contribution to the apparent growth from recent arrivals, an effect often called progenitor bias. However, we calculate that recently quenched objects can only be responsible for about half the increase in average size of quiescent galaxies over a 1.5 Gyr period, corresponding to the redshift interval 1.25 < z < 2. The remainder of the observed size evolution arises from a genuine growth of long-standing quiescent galaxies.

  17. Measuring the Binary Black Hole Mass Spectrum with an Astrophysically Motivated Parameterization

    Science.gov (United States)

    Talbot, Colm; Thrane, Eric

    2018-04-01

    Gravitational-wave detections have revealed a previously unknown population of stellar mass black holes with masses above 20 M ⊙. These observations provide a new way to test models of stellar evolution for massive stars. By considering the astrophysical processes likely to determine the shape of the binary black hole mass spectrum, we construct a parameterized model to capture key spectral features that relate gravitational-wave data to theoretical stellar astrophysics. In particular, we model the signature of pulsational pair-instability supernovae, which are expected to cause all stars with initial mass 100 M ⊙ ≲ M ≲ 150 M ⊙ to form ∼40 M ⊙ black holes. This would cause a cutoff in the black hole mass spectrum along with an excess of black holes near 40 M ⊙. We carry out a simulated data study to illustrate some of the stellar physics that can be inferred using gravitational-wave measurements of binary black holes and demonstrate several such inferences that might be made in the near future. First, we measure the minimum and maximum stellar black hole mass. Second, we infer the presence of a peak due to pair-instability supernovae. Third, we measure the distribution of black hole mass ratios. Finally, we show how inadequate models of the black hole mass spectrum lead to biased estimates of the merger rate and the amplitude of the stochastic gravitational-wave background.

  18. Investigation of the role of electron cyclotron resonance heating and magnetic configuration on the suprathermal ion population in the stellarator TJ-II using a luminescent probe

    Science.gov (United States)

    Martínez, M.; Zurro, B.; Baciero, A.; Jiménez-Rey, D.; Tribaldos, V.

    2018-02-01

    Numerous observation exist of a population of high energetic ions with energies well above the corresponding thermal values in plasmas generated by electron cyclotron resonance (ECR) heating in TJ-II stellarator and in other magnetically confined plasmas devices. In this work we study the impact of ECR heating different conditions (positions and powers) on fast ions escaping from plasmas in the TJ-II stellarator. For this study, an ion luminescent probe operated in counting mode is used to measure the energy distribution of suprathermal ions, in the range from 1 to 30 keV. It is observed that some suprathermal ions characteristics (such as temperature, particle and energy fluxes) are related directly with the gyrotron power and focus position of the heating beam in the plasma. Moreover, it is found that suprathermal ion characteristics vary during a magnetic configuration scan (performed along a single discharge). By investigating the suprathermal ions escaping from plasmas generated using two gyrotrons, one with fixed power and the other modulated (on/off) at low frequency (10 Hz), the de-confinement time of the suprathermal ions can be measured, which is of the order of a few milliseconds (<4 ms). A model that uses a zero-dimensional power balance is used to understand the de-confinement times in terms of the interaction of suprathermal ions and plasma components. This model also can be used to interpret experimental results of energy loss due to suprathermal ions. Finally, observations of increases (peaks) in the population of escaping suprathermal ions, which are well localized at discrete energies, is documented, these peaks being observed in the energy distributions along a discharge.

  19. Binary interaction dominates the evolution of massive stars

    NARCIS (Netherlands)

    Sana, H.; de Mink, S.E.; de Koter, A.; Langer, N.; Evans, C.J.; Gieles, M.; Gosset, E.; Izzard, R.G.; Le Bouquin, J.-B.; Schneider, F.R.N.

    2012-01-01

    The presence of a nearby companion alters the evolution of massive stars in binary systems, leading to phenomena such as stellar mergers, x-ray binaries, and gamma-ray bursts. Unambiguous constraints on the fraction of massive stars affected by binary interaction were lacking. We simultaneously

  20. A study of the stellar population in the Lynds 1641 dark cloud. I. The IRAS catalog sources

    International Nuclear Information System (INIS)

    Strom, K.M.; Newton, G.; Strom, S.E.; Seaman, R.L.; Carrasco, L.

    1989-01-01

    The character of the sources identified in the IRAS Point Source Catalog and located within the boundaries of the nearest giant molecular cloud, Lynds 1641 is discussed. New optical and near-infrared photometry are combined to provide spectral energy distributions (SEDs) for these objects divided into three classes: class I objects with flat or rising spectra, class II objects with spectra intermediate in slope between a flat and blackbody spectrum, and class III objects with spectra similar to those of blackbodies. It is found that L1641 contains a much larger percentage of class I sources than does the nearby Taurus-Auriga star-forming complex. Spectral energy distributions for the IRAS-selected sample are examined and compared with SEDs for young stellar objects (YSOs) located in Taurus-Auriga. The IRAS-selected sources having optical counterparts in the H-R diagram are identified and discussed along with the distribution of masses and ages for these YSOs. 86 refs

  1. The Frequency of Binary Stars in the Globular Cluster M71

    Science.gov (United States)

    Barden, S. C.; Armandroff, T. E.; Pryor, C. P.

    1994-12-01

    The frequency of binary stars is a fundamental property of a stellar population. A comparison of the frequency of binaries in globular clusters with those in the field halo and disk populations tests the similarity of star formation in those environments. Binary stars in globular clusters also act as an energy source which ``heats" the cluster through super-elastic encounters with other stars and binaries. Such encounters can not only profoundly affect the dynamical evolution of the cluster, they can disrupt the widely separated binaries and catalyze the formation of exotic objects such as blue stragglers, x-ray binaries, and milli-second pulsars. We have used the KPNO 4-m and the multi-fiber instruments Nessie and Hydra to measure radial velocities at 4 epochs over two years for a sample of 126 stars in the globular cluster M71. Velocity errors are under 1 km s(-1) for the brighter stars and under 2 km s(-1) for the majority of our data set. These velocities will be valuable for studying the kinematics of M71, but here we focus on searching for binaries. The faintest stars are at V=17, or just above the main sequence turnoff. Our sample is thus deeper than any published globular cluster binary search utilizing spectroscopic techniques. By observing smaller stars, we double the number of decades of binary periods sampled compared to previous studies and come within a factor of 4 of the shortest possible periods for turnoff stars. This wider period window has produced the largest known sample of binaries in a globular cluster. Four stars show velocity ranges larger than 20 km s(-1) , nine have ranges larger than 10 km s(-1) , and others are clearly variable. We will compare the radial distribution of these stars to that predicted by theory and derive the main-sequence binary fraction.

  2. Low-mass X-ray binaries from black-hole retaining globular clusters

    Science.gov (United States)

    Giesler, Matthew; Clausen, Drew; Ott, Christian D.

    2018-03-01

    Recent studies suggest that globular clusters (GCs) may retain a substantial population of stellar-mass black holes (BHs), in contrast to the long-held belief of a few to zero BHs. We model the population of BH low-mass X-ray binaries (BH-LMXBs), an ideal observable proxy for elusive single BHs, produced from a representative group of Milky Way GCs with variable BH populations. We simulate the formation of BH-binaries in GCs through exchange interactions between binary and single stars in the company of tens to hundreds of BHs. Additionally, we consider the impact of the BH population on the rate of compact binaries undergoing gravitational wave driven mergers. The characteristics of the BH-LMXB population and binary properties are sensitive to the GCs structural parameters as well as its unobservable BH population. We find that GCs retaining ˜1000 BHs produce a galactic population of ˜150 ejected BH-LMXBs whereas GCs retaining only ˜20 BHs produce zero ejected BH-LMXBs. Moreover, we explore the possibility that some of the presently known BH-LMXBs might have originated in GCs and identify five candidate systems.

  3. STELLAR ATMOSPHERES, ATMOSPHERIC EXTENSION, AND FUNDAMENTAL PARAMETERS: WEIGHING STARS USING THE STELLAR MASS INDEX

    Energy Technology Data Exchange (ETDEWEB)

    Neilson, Hilding R.; Lester, John B. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON, M5S 3H4 (Canada); Baron, Fabien; Norris, Ryan; Kloppenborg, Brian, E-mail: neilson@astro.utoronto.ca [Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P.O. Box 5060, Atlanta, GA 30302-5060 (United States)

    2016-10-20

    One of the great challenges of understanding stars is measuring their masses. The best methods for measuring stellar masses include binary interaction, asteroseismology, and stellar evolution models, but these methods are not ideal for red giant and supergiant stars. In this work, we propose a novel method for inferring stellar masses of evolved red giant and supergiant stars using interferometric and spectrophotometric observations combined with spherical model stellar atmospheres to measure what we call the stellar mass index, defined as the ratio between the stellar radius and mass. The method is based on the correlation between different measurements of angular diameter, used as a proxy for atmospheric extension, and fundamental stellar parameters. For a given star, spectrophotometry measures the Rosseland angular diameter while interferometric observations generally probe a larger limb-darkened angular diameter. The ratio of these two angular diameters is proportional to the relative extension of the stellar atmosphere, which is strongly correlated to the star’s effective temperature, radius, and mass. We show that these correlations are strong and can lead to precise measurements of stellar masses.

  4. Stellar Atmospheres, Atmospheric Extension, and Fundamental Parameters: Weighing Stars Using the Stellar Mass Index

    Science.gov (United States)

    Neilson, Hilding R.; Baron, Fabien; Norris, Ryan; Kloppenborg, Brian; Lester, John B.

    2016-10-01

    One of the great challenges of understanding stars is measuring their masses. The best methods for measuring stellar masses include binary interaction, asteroseismology, and stellar evolution models, but these methods are not ideal for red giant and supergiant stars. In this work, we propose a novel method for inferring stellar masses of evolved red giant and supergiant stars using interferometric and spectrophotometric observations combined with spherical model stellar atmospheres to measure what we call the stellar mass index, defined as the ratio between the stellar radius and mass. The method is based on the correlation between different measurements of angular diameter, used as a proxy for atmospheric extension, and fundamental stellar parameters. For a given star, spectrophotometry measures the Rosseland angular diameter while interferometric observations generally probe a larger limb-darkened angular diameter. The ratio of these two angular diameters is proportional to the relative extension of the stellar atmosphere, which is strongly correlated to the star’s effective temperature, radius, and mass. We show that these correlations are strong and can lead to precise measurements of stellar masses.

  5. Stellar astrophysics

    International Nuclear Information System (INIS)

    1988-01-01

    Enhanced mass loss occurs at critical stages in the evolution of stars over a wide range of stellar mass. Observationally, these stages are difficult to identify because of their short duration and because the star is often obscured by dust which condenses in the ejecta. A study of a G-type star, of which only the outer envelope was directly visible, was undertaken by the South African Astronomical Observatory (SAAO). The star itself was obscured by dust clouds and its light was only feebly seen by reflection from some of these clouds. Other studies of the galaxy undertaken by the SAAO include observations of the following: the extreme carbon star IRAS 15194-5115; RV Tauri and T Tauri stars; pre-main sequence stars; the properties of circumstellar dust; rotational modulation and flares on RS CVn and BY Dra stars; heavy-element stars; hydrogen-deficient stars; the open cluster NGC6192; stars in Omega Centauri, and lunar occulations of stars. Simultaneous x-ray, radio and optical data of the flare star YZ CMi were also obtained. 1 fig

  6. PREFACE: A Stellar Journey A Stellar Journey

    Science.gov (United States)

    Asplund, M.

    2008-10-01

    astronomical talk, student lecture, musical concert or theatre play. Another attribute of Bengt is his boundless optimism, which not the least has helped many of his students overcome the unavoidable moments of despair (this is only true as long as one is aware of the well-known BG factor: multiply any of Bengt's estimates for the time required to complete a task by at least a factor of three). His personal traits make working with Bengt always very enjoyable as well as highly educating. Bengt's work also extends well beyond the domain of astronomy, including music, literature, theatre, religion, research ethics, science policy and science popularization. Bengt is an excellent role model for a successful scientist with a rich and rewarding life outside of academia. The symposium A Stellar Journey was divided into five sessions covering basically the main research areas Bengt has worked on: Stellar atmospheres, Solar/stellar spectroscopy, Stellar parameters, Stellar evolution and nucleosynthesis and Stellar populations. In addition, one afternoon was devoted to a session entitled Anything but astronomy (see the symposium program), which tried to showcase Bengt's diverse interests outside of astronomy with talks ranging from religion and history of science over science popularization and future studies to literature and music. My task, as chair of the Scientific Organizing Committee, to put together an exciting scientific program of invited reviews and talks was made considerably easier thanks to the excellent suggestions by the other SOC members: Ann Boesgaard, Sofia Feltzing, John Lattanzio, Andre Maeder, Bertrand Plez and Monique Spite. I believe in the end we were successful in achieving our charge, an impression corroborated by the many encouraging comments from various participants during and after the conference. I am particularly grateful to Nils Bergvall, Bengt Edvardsson and Bertrand Plez for their time-consuming efforts in arranging the extraordinary and greatly

  7. Erratum: New binaries among UV-selected, hot subdwarf stars and population properties (vol 450, pg 3514, 2015)

    Czech Academy of Sciences Publication Activity Database

    Kawka, Adela; Vennes, Stephane; O' Toole, S.; Nemeth, P.; Burton, D.; Kotze, E.; Buckley, D.A.H.

    2015-01-01

    Roč. 451, č. 4 (2015), s. 3986-3986 ISSN 0035-8711 Institutional support: RVO:67985815 Keywords : addenda * close binaries * spectroscopic Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.952, year: 2015

  8. STELLAR POPULATIONS IN COMPACT GALAXY GROUPS: A MULTI-WAVELENGTH STUDY OF HCGs 16, 22, AND 42, THEIR STAR CLUSTERS, AND DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Konstantopoulos, I. S. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Maybhate, A. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Charlton, J. C.; Gronwall, C. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Fedotov, K.; Desjardins, T. D.; Gallagher, S. C. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Durrell, P. R. [Department of Physics and Astronomy, Youngstown State University, Youngstown, OH 44555 (United States); Mulchaey, J. S. [Carnegie Observatories, Pasadena, CA 91101 (United States); English, J. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Walker, L. M.; Johnson, K. E. [Department of Astronomy, University of Virginia, P.O. Box 3813, Charlottesville, VA 22904 (United States); Tzanavaris, P., E-mail: iraklis@aao.gov.au [Laboratory for X-ray Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-06-20

    We present a multi-wavelength analysis of three compact galaxy groups, Hickson compact groups (HCGs) 16, 22, and 42, which describe a sequence in terms of gas richness, from space- (Swift, Hubble Space Telescope (HST), and Spitzer) and ground-based (Las Campanas Observatory and Cerro Tololo Inter-American Observatory) imaging and spectroscopy. We study various signs of past interactions including a faint, dusty tidal feature about HCG 16A, which we tentatively age-date at <1 Gyr. This represents the possible detection of a tidal feature at the end of its phase of optical observability. Our HST images also resolve what were thought to be double nuclei in HCG 16C and D into multiple, distinct sources, likely to be star clusters. Beyond our phenomenological treatment, we focus primarily on contrasting the stellar populations across these three groups. The star clusters show a remarkable intermediate-age population in HCG 22, and identify the time at which star formation was quenched in HCG 42. We also search for dwarf galaxies at accordant redshifts. The inclusion of 33 members and 27 ''associates'' (possible members) radically changes group dynamical masses, which in turn may affect previous evolutionary classifications. The extended membership paints a picture of relative isolation in HCGs 16 and 22, but shows HCG 42 to be part of a larger structure, following a dichotomy expected from recent studies. We conclude that (1) star cluster populations provide an excellent metric of evolutionary state, as they can age-date the past epochs of star formation; and (2) the extended dwarf galaxy population must be considered in assessing the dynamical state of a compact group.

  9. STELLAR POPULATIONS IN COMPACT GALAXY GROUPS: A MULTI-WAVELENGTH STUDY OF HCGs 16, 22, AND 42, THEIR STAR CLUSTERS, AND DWARF GALAXIES

    International Nuclear Information System (INIS)

    Konstantopoulos, I. S.; Maybhate, A.; Charlton, J. C.; Gronwall, C.; Fedotov, K.; Desjardins, T. D.; Gallagher, S. C.; Durrell, P. R.; Mulchaey, J. S.; English, J.; Walker, L. M.; Johnson, K. E.; Tzanavaris, P.

    2013-01-01

    We present a multi-wavelength analysis of three compact galaxy groups, Hickson compact groups (HCGs) 16, 22, and 42, which describe a sequence in terms of gas richness, from space- (Swift, Hubble Space Telescope (HST), and Spitzer) and ground-based (Las Campanas Observatory and Cerro Tololo Inter-American Observatory) imaging and spectroscopy. We study various signs of past interactions including a faint, dusty tidal feature about HCG 16A, which we tentatively age-date at <1 Gyr. This represents the possible detection of a tidal feature at the end of its phase of optical observability. Our HST images also resolve what were thought to be double nuclei in HCG 16C and D into multiple, distinct sources, likely to be star clusters. Beyond our phenomenological treatment, we focus primarily on contrasting the stellar populations across these three groups. The star clusters show a remarkable intermediate-age population in HCG 22, and identify the time at which star formation was quenched in HCG 42. We also search for dwarf galaxies at accordant redshifts. The inclusion of 33 members and 27 ''associates'' (possible members) radically changes group dynamical masses, which in turn may affect previous evolutionary classifications. The extended membership paints a picture of relative isolation in HCGs 16 and 22, but shows HCG 42 to be part of a larger structure, following a dichotomy expected from recent studies. We conclude that (1) star cluster populations provide an excellent metric of evolutionary state, as they can age-date the past epochs of star formation; and (2) the extended dwarf galaxy population must be considered in assessing the dynamical state of a compact group.

  10. Orbital synchronization capture of two binaries emitting gravitational waves

    Science.gov (United States)

    Seto, Naoki

    2018-03-01

    We study the possibility of orbital synchronization capture for a hierarchical quadrupole stellar system composed by two binaries emitting gravitational waves. Based on a simple model including the mass transfer for white dwarf binaries, we find that the capture might be realized for inter-binary distances less than their gravitational wavelength. We also discuss related intriguing phenomena such as a parasitic relation between the coupled white dwarf binaries and significant reductions of gravitational and electromagnetic radiations.

  11. Heating the intergalactic medium by X-rays from population III binaries in high-redshift galaxies

    International Nuclear Information System (INIS)

    Xu, Hao; Norman, Michael L.; Ahn, Kyungjin; Wise, John H.; O'Shea, Brian W.

    2014-01-01

    Due to their long mean free path, X-rays are expected to have an important impact on cosmic reionization by heating and ionizing the intergalactic medium (IGM) on large scales, especially after simulations have suggested that Population III (Pop III) stars may form in pairs at redshifts as high as 20-30. We use the Pop III distribution and evolution from a self-consistent cosmological radiation hydrodynamic simulation of the formation of the first galaxies and a simple Pop III X-ray binary model to estimate their X-ray output in a high-density region larger than 100 comoving (Mpc) 3 . We then combine three different methods—ray tracing, a one-zone model, and X-ray background modeling—to investigate the X-ray propagation, intensity distribution, and long-term effects on the IGM thermal and ionization state. The efficiency and morphology of photoheating and photoionization are dependent on the photon energies. The sub-kiloelectronvolt X-rays only impact the IGM near the sources, while the kiloelectronvolt photons contribute significantly to the X-ray background and heat and ionize the IGM smoothly. The X-rays just below 1 keV are most efficient in heating and ionizing the IGM. We find that the IGM might be heated to over 100 K by z = 10 and the high-density source region might reach 10 4 K, limited by atomic hydrogen cooling. This may be important for predicting the 21 cm neutral hydrogen signals. On the other hand, the free electrons from X-ray ionizations are not enough to contribute significantly to the optical depth of the cosmic microwave background to the Thomson scattering.

  12. Stellar Streams in the Dark Energy Survey

    Science.gov (United States)

    Shipp, Nora; Drlica-Wagner, Alex; Balbinot, Eduardo; DES Collaboration

    2018-01-01

    We present a search for Galactic stellar streams in the Dark Energy Survey (DES), using three years of optical data taken across 5000 sq. degrees of the southern sky. The wide-field, uniform DES photometry provides unprecedented sensitivity to the stellar density field in the southern hemisphere, allowing for the detection of faint stellar populations. We follow the “Field of Streams” procedure developed in the Sloan Digital Sky Survey (Belokurov et al., 2006) to identify stellar density features such as dwarf galaxies, globular clusters, and the stellar streams resulting from the tidal disruption of these objects. Improved analysis techniques applied to the DES data enable the discovery of new stellar streams, and provide added insight into the origin and stellar populations of previously identified objects. An increased sample size together with detailed characterization of individual stellar streams and their progenitors can inform our understanding of the formation of the Milky Way stellar halo, as well as the large and small scale distribution of dark matter in the Milky Way.

  13. Stellar Metamorphosis:

    Science.gov (United States)

    2002-01-01

    [TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae

  14. Formation and Evolution of X-ray Binaries

    Science.gov (United States)

    Shao, Y.

    2017-07-01

    use of both binary population synthesis and detailed binary evolution calculations. We find that the birthrate is around 10-4 yr-1 for the incipient X-ray binaries in both cases. We demonstrate the distribution of the ULX population in the donor mass - orbital period plane. Our results suggest that, compared with black hole X-ray binaries, neutron star X-ray binaries may significantly contribute to the ULX population, and high/intermediate-mass X-ray binaries dominate the neutron star ULX population in M82/Milky Way-like galaxies, respectively. In Chapter 6, the population of intermediate- and low-mass X-ray binaries in the Galaxy is explored. We investigate the formation and evolutionary sequences of Galactic intermediate- and low-mass X-ray binaries by combining binary population synthesis (BPS) and detailed stellar evolutionary calculations. Using an updated BPS code we compute the evolution of massive binaries that leads to the formation of incipient I/LMXBs, and present their distribution in the initial donor mass vs. initial orbital period diagram. We then follow the evolution of I/LMXBs until the formation of binary millisecond pulsars (BMSPs). We show that during the evolution of I/LMXBs they are likely to be observed as relatively compact binaries. The resultant BMSPs have orbital periods ranging from about 1 day to a few hundred days. These features are consistent with observations of LMXBs and BMSPs. We also confirm the discrepancies between theoretical predictions and observations mentioned in the literature, that is, the theoretical average mass transfer rates of LMXBs are considerably lower than observed, and the number of BMSPs with orbital periods ˜ 0.1-1 \\unit{d} is severely underestimated. Both imply that something is missing in the modeling of LMXBs, which is likely to be related to the mechanisms of the orbital angular momentum loss. Finally in Chapter 7 we summarize our results and give the prospects for the future work.

  15. STELLAR MASS DEPENDENT DISK DISPERSAL

    International Nuclear Information System (INIS)

    Kennedy, Grant M.; Kenyon, Scott J.

    2009-01-01

    We use published optical spectral and infrared (IR) excess data from nine young clusters and associations to study the stellar mass dependent dispersal of circumstellar disks. All clusters older than ∼3 Myr show a decrease in disk fraction with increasing stellar mass for solar to higher mass stars. This result is significant at about the 1σ level in each cluster. For the complete set of clusters we reject the null hypothesis-that solar and intermediate-mass stars lose their disks at the same rate-with 95%-99.9% confidence. To interpret this behavior, we investigate the impact of grain growth, binary companions, and photoevaporation on the evolution of disk signatures. Changes in grain growth timescales at fixed disk temperature may explain why early-type stars with IR excesses appear to evolve faster than their later-type counterparts. Little evidence that binary companions affect disk evolution suggests that photoevaporation is the more likely mechanism for disk dispersal. A simple photoevaporation model provides a good fit to the observed disk fractions for solar and intermediate-mass stars. Although the current mass-dependent disk dispersal signal is not strong, larger and more complete samples of clusters with ages of 3-5 Myr can improve the significance and provide better tests of theoretical models. In addition, the orbits of extra-solar planets can constrain models of disk dispersal and migration. We suggest that the signature of stellar mass dependent disk dispersal due to photoevaporation may be present in the orbits of observed extra-solar planets. Planets orbiting hosts more massive than ∼1.6 M sun may have larger orbits because the disks in which they formed were dispersed before they could migrate.

  16. Binary and Millisecond Pulsars

    OpenAIRE

    Lorimer, D. R.

    2005-01-01

    We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic b...

  17. The “Building Blocks” of Stellar Halos

    Directory of Open Access Journals (Sweden)

    Kyle A. Oman

    2017-08-01

    Full Text Available The stellar halos of galaxies encode their accretion histories. In particular, the median metallicity of a halo is determined primarily by the mass of the most massive accreted object. We use hydrodynamical cosmological simulations from the apostle project to study the connection between the stellar mass, the metallicity distribution, and the stellar age distribution of a halo and the identity of its most massive progenitor. We find that the stellar populations in an accreted halo typically resemble the old stellar populations in a present-day dwarf galaxy with a stellar mass ∼0.2–0.5 dex greater than that of the stellar halo. This suggests that had they not been accreted, the primary progenitors of stellar halos would have evolved to resemble typical nearby dwarf irregulars.

  18. The Pelican Nebula and its Vicinity: a New Look at Stellar Population in the Cloud and around It

    Science.gov (United States)

    Boyle, Richard P.; Janusz, R.; Vrba, F. J.; Straizys, V.; Laugalys, V.; Kazlauskas, A.; Stott, J.; Philip, A. G. D.

    2011-01-01

    A region of active star formation is located in the complex of dust and molecular clouds known as the Pelican Nebula and the dark cloud L935. In this paper we describe the results of our investigation in the area bounded by the coordinates (2000) RA 20h50m - 20h54m and DEC +44d20m - 44m55d. Our CCD photometry in the Vilnius seven-color system, obtained on the 1.8 m Vatican Advanced Technology Telescope, Mt. Graham, and the 1 m telescope of the USNO Flagstaff Station, is used to classify stars down to V = 17 mag in spectral and luminosity classes. The interstellar extinction values and distances to these stars are determined. Additionally, the data from the 2MASS, MegaCam, IPHAS and Spitzer surveys are analyzed. We present star population maps in the foreground and background of the complex and within it. The known and newly identified YSOs in the area are tabulated.

  19. HST-WFC3 Near-Infrared Spectroscopy of Quenched Galaxies at zeta approx 1.5 from the WISP Survey: Stellar Populations Properties

    Science.gov (United States)

    Bedregal, A. G.; Scarlata, C.; Henry, A. L.; Atek, H.; Rafelski, M.; Teplitz, H. I.; Dominguez, A.; Siana, B.; Colbert, J. W.; Malkan, M.; hide

    2013-01-01

    We combine Hubble Space Telescope (HST) G102 and G141 near-IR (NIR) grism spectroscopy with HST/WFC3- UVIS, HST/WFC3-IR, and Spitzer/IRAC [3.6 microns] photometry to assemble a sample of massive (log(Mstar/M solar mass) at approx 11.0) and quenched (specific star formation rate spectroscopy for quenched sources at these redshifts. In contrast to the local universe, zeta approx 1.5 quenched galaxies in the high-mass range have a wide range of stellar population properties. We find that their spectral energy distributions (SEDs) are well fitted with exponentially decreasing star formation histories and short star formation timescales (tau less than or equal to 100 M/yr). Quenched galaxies also show a wide distribution in ages, between 1 and 4 G/yr. In the (u - r)0-versus-mass space quenched galaxies have a large spread in rest-frame color at a given mass. Most quenched galaxies populate the zeta appro. 1.5 red sequence (RS), but an important fraction of them (32%) have substantially bluer colors. Although with a large spread, we find that the quenched galaxies on the RS have older median ages (3.1 G/yr) than the quenched galaxies off the RS (1.5 G/yr). We also show that a rejuvenated SED cannot reproduce the observed stacked spectra of (the bluer) quenched galaxies off the RS. We derive the upper limit on the fraction of massive galaxies on the RS at zeta approx 1.5 to be 2 and the zeta approx 1.5 RS. According to their estimated ages, the time required for quenched galaxies off the RS to join their counterparts on the z approx. 1.5 RS is of the order of approx. 1G/yr.

  20. Evidence for a constant initial mass function in early-type galaxies based on their X-ray binary populations

    OpenAIRE

    Peacock, Mark B.; Zepf, Stephen E.; Maccarone, Thomas J.; Kundu, Arunav; Gonzalez, Anthony H.; Lehmer, Bret D.; Maraston, Claudia

    2014-01-01

    A number of recent studies have proposed that the stellar initial mass function (IMF) of early type galaxies varies systematically as a function of galaxy mass, with higher mass galaxies having bottom heavy IMFs. These bottom heavy IMFs have more low-mass stars relative to the number of high mass stars, and therefore naturally result in proportionally fewer neutron stars and black holes. In this paper, we specifically predict the variation in the number of black holes and neutron stars based ...

  1. Science with Synthetic Stellar Surveys

    Science.gov (United States)

    Sanderson, Robyn Ellyn

    2018-04-01

    A new generation of observational projects is poised to revolutionize our understanding of the resolved stellar populations of Milky-Way-like galaxies at an unprecedented level of detail, ushering in an era of precision studies of galaxy formation. In the Milky Way itself, astrometric, spectroscopic and photometric surveys will measure three-dimensional positions and velocities and numerous chemical abundances for stars from the disk to the halo, as well as for many satellite dwarf galaxies. In the Local Group and beyond, HST, JWST and eventually WFIRST will deliver pristine views of resolved stars. The groundbreaking scale and dimensionality of this new view of resolved stellar populations in galaxies challenge us to develop new theoretical tools to robustly compare these surveys to simulated galaxies, in order to take full advantage of our new ability to make detailed predictions for stellar populations within a cosmological context. I will describe a framework for generating realistic synthetic star catalogs and mock surveys from state-of-the-art cosmological-hydrodynamical simulations, and present several early scientific results from, and predictions for, resolved stellar surveys of our Galaxy and its neighbors.

  2. Two distinct halo populations in the solar neighborhood. II. Evidence from stellar abundances of Mn, Cu, Zn, Y, and Ba

    Science.gov (United States)

    Nissen, P. E.; Schuster, W. J.

    2011-06-01

    Context. Current models of galaxy formation predict that the Galactic halo was assembled hierarchically. By measuring abundance ratios in stars it may be possible to identify substructures in the halo resulting from this process. Aims: A previous study of 94 dwarf stars with -1.6 FIES spectra and used to derive abundance ratios from an LTE analysis based on MARCS model atmospheres. The analysis is made relative to two thick-disk stars, HD 22879 and HD 76932, such that very precise differential values are obtained. Results: Systematic differences between the "high-α" and "low-α" halo populations are found for [Cu/Fe], [Zn/Fe], and [Ba/Y], whereas there is no significant difference in the case of [Mn/Fe]. At a given metallicity, [Cu/Fe] shows a large scatter that is closely correlated with a corresponding scatter in [Na/Fe] and [Ni/Fe]. Conclusions: The metallicity trends of [Cu/Fe], [Zn/Fe], and [Ba/Y] can be explained from existing nucleosynthesis calculations if the high-α stars formed in regions with such a high star formation rate that only massive stars and type II supernovae contributed to the chemical enrichment. The low-α stars, on the other hand, most likely originate from systems with a slower chemical evolution, characterized by additional enrichment from type Ia supernovae and low-mass AGB stars. Based on observations made with the Nordic Optical Telescope on La Palma, and on data from the European Southern Observatory ESO/ST-ECF Science Archive Facility (programs 65.L-0507, 67.D-0086, 67.D-0439, 68.D-0094, 68.B-0475, 69.D-0679, 70.D-0474, 71.B-0529, 72.B-0585, 76.B-0133 and 77.B-0507).Tables 1, 2, and excerpt of Table 3 are available in electronic form at http://www.aanda.orgTables 1, 2, and full Table 3 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A15

  3. Two stellar-mass black holes in the globular cluster M22.

    Science.gov (United States)

    Strader, Jay; Chomiuk, Laura; Maccarone, Thomas J; Miller-Jones, James C A; Seth, Anil C

    2012-10-04

    Hundreds of stellar-mass black holes probably form in a typical globular star cluster, with all but one predicted to be ejected through dynamical interactions. Some observational support for this idea is provided by the lack of X-ray-emitting binary stars comprising one black hole and one other star ('black-hole/X-ray binaries') in Milky Way globular clusters, even though many neutron-star/X-ray binaries are known. Although a few black holes have been seen in globular clusters around other galaxies, the masses of these cannot be determined, and some may be intermediate-mass black holes that form through exotic mechanisms. Here we report the presence of two flat-spectrum radio sources in the Milky Way globular cluster M22, and we argue that these objects are black holes of stellar mass (each ∼10-20 times more massive than the Sun) that are accreting matter. We find a high ratio of radio-to-X-ray flux for these black holes, consistent with the larger predicted masses of black holes in globular clusters compared to those outside. The identification of two black holes in one cluster shows that ejection of black holes is not as efficient as predicted by most models, and we argue that M22 may contain a total population of ∼5-100 black holes. The large core radius of M22 could arise from heating produced by the black holes.

  4. The ORNL stellarator program

    International Nuclear Information System (INIS)

    Lyon, J.F.

    1986-11-01

    The main focus of magnetic confinement studies at Oak Ridge National Laboratory (ORNL) is stellarator research. The principal elements of the ORNL stellarator program are the Advanced Toroidal Facility (ATF), stellarator theory, and related plasma technology development. These elements are discussed breifly. 2 figs., 1 tab

  5. Stellar X-Ray Polarimetry

    Science.gov (United States)

    Swank, J.

    2011-01-01

    Most of the stellar end-state black holes, pulsars, and white dwarfs that are X-ray sources should have polarized X-ray fluxes. The degree will depend on the relative contributions of the unresolved structures. Fluxes from accretion disks and accretion disk corona may be polarized by scattering. Beams and jets may have contributions of polarized emission in strong magnetic fields. The Gravity and Extreme Magnetism Small Explorer (GEMS) will study the effects on polarization of strong gravity of black holes and strong magnetism of neutron stars. Some part of the flux from compact stars accreting from companion stars has been reflected from the companion, its wind, or accretion streams. Polarization of this component is a potential tool for studying the structure of the gas in these binary systems. Polarization due to scattering can also be present in X-ray emission from white dwarf binaries and binary normal stars such as RS CVn stars and colliding wind sources like Eta Car. Normal late type stars may have polarized flux from coronal flares. But X-ray polarization sensitivity is not at the level needed for single early type stars.

  6. IRAS high resolution studies and modeling of closely interacting galaxies. Galaxy collisions: Infrared observations and analysis of numerical models. UV spectroscopy of massive young stellar populations in interacting galaxies

    Science.gov (United States)

    Lamb, Susan A.

    1993-01-01

    The Final Technical Report covering the period from 15 Aug. 1989 to 14 Aug. 1991 is presented. Areas of research included Infrared Astronomy Satellite (IRAS) high resolution studies and modeling of closely interacting galaxies; galaxy collisions: infrared observations and analysis of numerical models; and UV spectroscopy of massive young stellar populations in interacting galaxies. Both observational studies and theoretical modelling of interacting galaxies are covered. As a consequence the report is divided into two parts, one on each aspect of the overall project.

  7. A discovery of young stellar objects in older clusters of the Large Magellanic Cloud

    Science.gov (United States)

    For, Bi-Qing; Bekki, Kenji

    2017-06-01

    Recent studies have shown that an extended main-sequence turn-off is a common feature among intermediate-age clusters (1-3 Gyr) in the Magellanic Clouds. Multiple-generation star formation and stellar rotation or interacting binaries have been proposed to explain the feature. However, it remains controversial in the field of stellar populations. Here we present the main results of an ongoing star formation among older star clusters in the Large Magellanic Cloud. Cross-matching the positions of star clusters and young stellar objects has yielded 15 matches, with 7 located in the cluster centre. We demonstrate that this is not by chance by estimating local number densities of young stellar objects for each star cluster. This method is not based on isochrone fitting, which leads to some uncertainties in age estimation and methods of background subtraction. We also find no direct correlation between atomic hydrogen and the clusters. This suggests that gas accretion for fueling the star formation must be happening in situ. These findings support for the multiple-generations scenario as a plausible explanation for the extended main-sequence turn-off.

  8. STELLAR POPULATIONS AND EVOLUTION OF EARLY-TYPE CLUSTER GALAXIES: CONSTRAINTS FROM OPTICAL IMAGING AND SPECTROSCOPY OF z = 0.5–0.9 GALAXY CLUSTERS

    International Nuclear Information System (INIS)

    Jørgensen, Inger; Chiboucas, Kristin

    2013-01-01

    We present an analysis of stellar populations and evolutionary history of galaxies in three similarly rich galaxy clusters MS0451.6–0305 (z = 0.54), RXJ0152.7–1357 (z = 0.83), and RXJ1226.9+3332 (z = 0.89). Our analysis is based on high signal-to-noise ground-based optical spectroscopy and Hubble Space Telescope imaging for a total of 17-34 members in each cluster. Using the dynamical masses together with the effective radii and the velocity dispersions, we find no indication of evolution of sizes or velocity dispersions with redshift at a given galaxy mass. We establish the Fundamental Plane (FP) and scaling relations between absorption line indices and velocity dispersions. We confirm that the FP is steeper at z ≈ 0.86 compared to the low-redshift FP, indicating that under the assumption of passive evolution the formation redshift, z form , depends on the galaxy velocity dispersion (or alternatively mass). At a velocity dispersion of σ = 125 km s –1 (Mass = 10 10.55 M ☉ ) we find z form = 1.24 ± 0.05, while at σ = 225 km s –1 (Mass = 10 11.36 M ☉ ) the formation redshift is z form = 1.95 +0.3 –0.2 , for a Salpeter initial mass function. The three clusters follow similar scaling relations between absorption line indices and velocity dispersions as those found for low-redshift galaxies. The zero point offsets for the Balmer lines depend on cluster redshifts. However, the offsets indicate a slower evolution, and therefore higher formation redshift, than the zero point differences found from the FP, if interpreting the data using a passive evolution model. Specifically, the strength of the higher order Balmer lines Hδ and Hγ implies z form > 2.8. The scaling relations for the metal indices in general show small and in some cases insignificant zero point offsets, favoring high formation redshifts for a passive evolution model. Based on the absorption line indices and recent stellar population models from Thomas et al., we find that MS0451.6–0305

  9. The Phase Space and Stellar Populations of Cluster Galaxies at z ~ 1: Simultaneous Constraints on the Location and Timescale of Satellite Quenching

    Science.gov (United States)

    Muzzin, Adam; van der Burg, R. F. J.; McGee, Sean L.; Balogh, Michael; Franx, Marijn; Hoekstra, Henk; Hudson, Michael J.; Noble, Allison; Taranu, Dan S.; Webb, Tracy; Wilson, Gillian; Yee, H. K. C.

    2014-11-01

    We investigate the velocity versus position phase space of z ~ 1 cluster galaxies using a set of 424 spectroscopic redshifts in nine clusters drawn from the GCLASS survey. Dividing the galaxy population into three categories, that is, quiescent, star-forming, and poststarburst, we find that these populations have distinct distributions in phase space. Most striking are the poststarburst galaxies, which are commonly found at small clustercentric radii with high clustercentric velocities, and appear to trace a coherent "ring" in phase space. Using several zoom simulations of clusters, we show that the coherent distribution of the poststarbursts can be reasonably well reproduced using a simple quenching scenario. Specifically, the phase space is best reproduced if these galaxies are quenched with a rapid timescale (0.1 0.5 Gyr) or by quenching galaxies at larger radii (R ~ R 200). We compare this quenching timescale to the timescale implied by the stellar populations of the poststarburst galaxies and find that the poststarburst spectra are well-fit by a rapid quenching (τ Q = 0.4+0.3-0.4 Gyr) of a typical star-forming galaxy. The similarity between the quenching timescales derived from these independent indicators is a strong consistency check of the quenching model. Given that the model implies satellite quenching is rapid and occurs well within R 200, this would suggest that ram-pressure stripping of either the hot or cold gas component of galaxies are the most plausible candidates for the physical mechanism. The high cold gas consumption rates at z ~ 1 make it difficult to determine whether hot or cold gas stripping is dominant; however, measurements of the redshift evolution of the satellite quenching timescale and location may be capable of distinguishing between the two. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on

  10. Accretion Disk Assembly During Common Envelope Evolution: Implications for Feedback and LIGO Binary Black Hole Formation

    Energy Technology Data Exchange (ETDEWEB)

    Murguia-Berthier, Ariadna; Ramirez-Ruiz, Enrico; Antoni, Andrea; Macias, Phillip [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); MacLeod, Morgan, E-mail: armurgui@ucsc.edu [School of Natural Sciences, Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540 (United States)

    2017-08-20

    During a common envelope (CE) episode in a binary system, the engulfed companion spirals to tighter orbital separations under the influence of drag from the surrounding envelope material. As this object sweeps through material with a steep radial gradient of density, net angular momentum is introduced into the flow, potentially leading to the formation of an accretion disk. The presence of a disk would have dramatic consequences for the outcome of the interaction because accretion might be accompanied by strong, polar outflows with enough energy to unbind the entire envelope. Without a detailed understanding of the necessary conditions for disk formation during CE, therefore, it is difficult to accurately predict the population of merging compact binaries. This paper examines the conditions for disk formation around objects embedded within CEs using the “wind tunnel” formalism developed by MacLeod et al. We find that the formation of disks is highly dependent on the compressibility of the envelope material. Disks form only in the most compressible of stellar envelope gas, found in envelopes’ outer layers in zones of partial ionization. These zones are largest in low-mass stellar envelopes, but comprise small portions of the envelope mass and radius in all cases. We conclude that disk formation and associated accretion feedback in CE is rare, and if it occurs, transitory. The implication for LIGO black hole binary assembly is that by avoiding strong accretion feedback, CE interactions should still result in the substantial orbital tightening needed to produce merging binaries.

  11. Astrospheres and Solar-like Stellar Winds

    Directory of Open Access Journals (Sweden)

    Wood Brian E.

    2004-07-01

    Full Text Available Stellar analogs for the solar wind have proven to be frustratingly difficult to detect directly. However, these stellar winds can be studied indirectly by observing the interaction regions carved out by the collisions between these winds and the interstellar medium (ISM. These interaction regions are called "astrospheres", analogous to the "heliosphere" surrounding the Sun. The heliosphere and astrospheres contain a population of hydrogen heated by charge exchange processes that can produce enough H I Ly alpha absorption to be detectable in UV spectra of nearby stars from the Hubble Space Telescope (HST. The amount of astrospheric absorption is a diagnostic for the strength of the stellar wind, so these observations have provided the first measurements of solar-like stellar winds. Results from these stellar wind studies and their implications for our understanding of the solar wind are reviewed here. Of particular interest are results concerning the past history of the solar wind and its impact on planetary atmospheres.

  12. In search of a signature of binary Kuiper Belt Objects in the Pluto-Charon crater population

    Science.gov (United States)

    Zangari, Amanda Marie; Parker, Alex; Singer, Kelsi N.; Stern, S. Alan; Young, Leslie; Olkin, Catherine B.; Ennico, Kimberly; Weaver, Harold A.; New Horizons Geology, Geophysics and Imaging Science Theme Team

    2016-10-01

    In July 2015, New Horizons flew by Pluto and Charon, allowing mapping of the encounter hemisphere at high enough resolution to produce crater counts from the surfaces of the pair. We investigate the distribution of craters in search of a signature of binary impactors. The Kuiper Belt -- especially the cold classical region -- has a large fraction of binary objects, many of which are close-in, equal-mass binaries. We will present results on how the distribution of craters seen on Pluto and Charon compares to a random distribution of single body impactors on the surfaces of each. Examining the surfaces of Pluto and Charon proves challenging due to resurfacing, and the presence of tectonic and other geographic features. For example, the informally-named Cthulhu region is among the oldest on Pluto, yet it abuts a craterless region millions of years young. On Charon, chastmata divide the surface into regions informally named Vulcan Planum and Oz terra. In our statistics, we pay careful attention to the boundaries of where craters may appear, and the dependence of our results on crater size. This work was supported by NASA's New Horizons project.

  13. Detecting unresolved binary stars in Euclid VIS images

    Science.gov (United States)

    Kuntzer, T.; Courbin, F.

    2017-10-01

    Measuring a weak gravitational lensing signal to the level required by the next generation of space-based surveys demands exquisite reconstruction of the point-spread function (PSF). However, unresolved binary stars can significantly distort the PSF shape. In an effort to mitigate this bias, we aim at detecting unresolved binaries in realistic Euclid stellar populations. We tested methods in numerical experiments where (I) the PSF shape is known to Euclid requirements across the field of view; and (II) the PSF shape is unknown. We drew simulated catalogues of PSF shapes for this proof-of-concept paper. Following the Euclid survey plan, the objects were observed four times. We propose three methods to detect unresolved binary stars. The detection is based on the systematic and correlated biases between exposures of the same object. One method is a simple correlation analysis, while the two others use supervised machine-learning algorithms (random forest and artificial neural network). In both experiments, we demonstrate the ability of our methods to detect unresolved binary stars in simulated catalogues. The performance depends on the level of prior knowledge of the PSF shape and the shape measurement errors. Good detection performances are observed in both experiments. Full complexity, in terms of the images and the survey design, is not included, but key aspects of a more mature pipeline are discussed. Finding unresolved binaries in objects used for PSF reconstruction increases the quality of the PSF determination at arbitrary positions. We show, using different approaches, that we are able to detect at least binary stars that are most damaging for the PSF reconstruction process. The code corresponding to the algorithms used in this work and all scripts to reproduce the results are publicly available from a GitHub repository accessible via http://lastro.epfl.ch/software

  14. GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Camp, Jordan B.; hide

    2016-01-01

    We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5(sigma). The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4(+0.7/-0.9) x 10(exp -22). The inferred source-frame initial black hole masses are 14.2(+8.3/-3.7 Stellar Mass and 7.5(+2.3/-2.3) Stellar Mass, and the final black hole mass is 20.8(+6.1/-1.7) Stellar Mass. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440(+180/-190) Mpc corresponding to a redshift of 0.090(+.030/-0.04). All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.

  15. Estimating precise metallicity and stellar mass evolution of galaxies

    Science.gov (United States)

    Mosby, Gregory

    2018-01-01

    The evolution of galaxies can be conveniently broken down into the evolution of their contents. The changing dust, gas, and stellar content in addition to the changing dark matter potential and periodic feedback from a super-massive blackhole are some of the key ingredients. We focus on the stellar content that can be observed, as the stars reflect information about the galaxy when they were formed. We approximate the stellar content and star formation histories of unresolved galaxies using stellar population modeling. Though simplistic, this approach allows us to reconstruct the star formation histories of galaxies that can be used to test models of galaxy formation and evolution. These models, however, suffer from degeneracies at large lookback times (t > 1 Gyr) as red, low luminosity stars begin to dominate a galaxy’s spectrum. Additionally, degeneracies between stellar populations at different ages and metallicities often make stellar population modeling less precise. The machine learning technique diffusion k-means has been shown to increase the precision in stellar population modeling using a mono-metallicity basis set. However, as galaxies evolve, we expect the metallicity of stellar populations to vary. We use diffusion k-means to generate a multi-metallicity basis set to estimate the stellar mass and chemical evolution of unresolved galaxies. Two basis sets are formed from the Bruzual & Charlot 2003 and MILES stellar population models. We then compare the accuracy and precision of these models in recovering complete (stellar mass and metallicity) histories of mock data. Similarities in the groupings of stellar population spectra in the diffusion maps for each metallicity hint at fundamental age transitions common to both basis sets that can be used to identify stellar populations in a given age range.

  16. Binary black hole merger rates inferred from luminosity function of ultra-luminous X-ray sources

    Science.gov (United States)

    Inoue, Yoshiyuki; Tanaka, Yasuyuki T.; Isobe, Naoki

    2016-10-01

    The Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) has detected direct signals of gravitational waves (GWs) from GW150914. The event was a merger of binary black holes whose masses are 36^{+5}_{-4} M_{{⊙}} and 29^{+4}_{-4} M_{{⊙}}. Such binary systems are expected to be directly evolved from stellar binary systems or formed by dynamical interactions of black holes in dense stellar environments. Here we derive the binary black hole merger rate based on the nearby ultra-luminous X-ray source (ULX) luminosity function (LF) under the assumption that binary black holes evolve through X-ray emitting phases. We obtain the binary black hole merger rate as 5.8(tULX/0.1 Myr)- 1λ- 0.6exp ( - 0.30λ) Gpc- 3 yr- 1, where tULX is the typical duration of the ULX phase and λ is the Eddington ratio in luminosity. This is coincident with the event rate inferred from the detection of GW150914 as well as the predictions based on binary population synthesis models. Although we are currently unable to constrain the Eddington ratio of ULXs in luminosity due to the uncertainties of our models and measured binary black hole merger event rates, further X-ray and GW data will allow us to narrow down the range of the Eddington ratios of ULXs. We also find the cumulative merger rate for the mass range of 5 M⊙ ≤ MBH ≤ 100 M⊙ inferred from the ULX LF is consistent with that estimated by the aLIGO collaboration considering various astrophysical conditions such as the mass function of black holes.

  17. The fate of close encounters between binary stars and binary supermassive black holes

    Science.gov (United States)

    Wang, Yi-Han; Leigh, Nathan; Yuan, Ye-Fei; Perna, Rosalba

    2018-04-01

    The evolution of main-sequence binaries that reside in the Galactic Centre can be heavily influenced by the central supermassive black hole (SMBH). Due to these perturbative effects, the stellar binaries in dense environments are likely to experience mergers, collisions, or ejections through secular and/or non-secular interactions. More direct interactions with the central SMBH are thought to produce hypervelocity stars (HVSs) and tidal disruption events (TDEs). In this paper, we use N-body simulations to study the dynamics of stellar binaries orbiting a central SMBH primary with an outer SMBH secondary orbiting this inner triple. The effects of the secondary SMBH on the event rates of HVSs, TDEs, and stellar mergers are investigated, as a function of the SMBH-SMBH binary mass ratio. Our numerical experiments reveal that, relative to the isolated SMBH case, the TDE and HVS rates are enhanced for, respectively, the smallest and largest mass ratio SMBH-SMBH binaries. This suggests that the observed event rates of TDEs and HVSs have the potential to serve as a diagnostic of the mass ratio of a central SMBH-SMBH binary. The presence of a secondary SMBH also allows for the creation of hypervelocity binaries. Observations of these systems could thus constrain the presence of a secondary SMBH in the Galactic Centre.

  18. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Duncan R. Lorimer

    1998-09-01

    Full Text Available Our knowledge of binary and millisecond pulsars has greatly increased in recent years. This is largely due to the success of large-area surveys which have brought the known population of such systems in the Galactic disk to around 50. As well as being interesting as a population of astronomical sources, many pulsars turn out to be superb celestial clocks. In this review we summarise the main properties of binary and millisecond pulsars and highlight some of their applications to relativistic astrophysics.

  19. First Hα and Revised Photometric Studies of Contact Binary ...

    Indian Academy of Sciences (India)

    Common among the variable stars are the contact binaries which form an excellent source in determining the stellar parameters with high degree of accuracy (Southworth. 2012). These binaries which are also referred to as W Ursae Majoris (W UMa) stars occur when both components of the system fill their Roche lobes ...

  20. The Young Visual Binary Survey

    Science.gov (United States)

    Prato, Lisa; Avilez, Ian; Lindstrom, Kyle; Graham, Sean; Sullivan, Kendall; Biddle, Lauren; Skiff, Brian; Nofi, Larissa; Schaefer, Gail; Simon, Michal

    2018-01-01

    Differences in the stellar and circumstellar properties of the components of young binaries provide key information about star and disk formation and evolution processes. Because objects with separations of a few to a few hundred astronomical units share a common environment and composition, multiple systems allow us to control for some of the factors which play into star formation. We are completing analysis of a rich sample of about 100 pre-main sequence binaries and higher order multiples, primarily located in the Taurus and Ophiuchus star forming regions. This poster will highlight some of out recent, exciting results. All reduced spectra and the results of our analysis will be publicly available to the community at http://jumar.lowell.edu/BinaryStars/. Support for this research was provided in part by NSF award AST-1313399 and by NASA Keck KPDA funding.

  1. Asteroseismic modelling of the Binary HD 176465

    Directory of Open Access Journals (Sweden)

    Nsamba B.

    2017-01-01

    Full Text Available The detection and analysis of oscillations in binary star systems is critical in understanding stellar structure and evolution. This is partly because such systems have the same initial chemical composition and age. Solar-like oscillations have been detected by Kepler in both components of the asteroseismic binary HD 176465. We present an independent modelling of each star in this binary system. Stellar models generated using MESA (Modules for Experiments in Stellar Astrophysics were fitted to both the observed individual frequencies and complementary spectroscopic parameters. The individual theoretical oscillation frequencies for the corresponding stellar models were obtained using GYRE as the pulsation code. A Bayesian approach was applied to find the probability distribution functions of the stellar parameters using AIMS (Asteroseismic Inference on a Massive Scale as the optimisation code. The ages of HD 176465 A and HD 176465 B were found to be 2.81 ± 0.48 Gyr and 2.52 ± 0.80 Gyr, respectively. These results are in agreement when compared to previous studies carried out using other asteroseismic modelling techniques and gyrochronology.

  2. The Benchmark Eclipsing Binary V530 Ori

    DEFF Research Database (Denmark)

    Torres, Guillermo; Lacy, Claud H. Sandberg; Pavlovski, Kresimir

    2015-01-01

    We report accurate measurements of the physical properties (mass, radius, temperature) of components of the G+M eclipsing binary V530 On. The M-type secondary shows a larger radius and a cooler temperature than predicted by standard stellar evolution models, as has been found for many other low...

  3. Stellar dynamics and black holes

    Indian Academy of Sciences (India)

    The history of that discovery is fascinating and well known [1]. The first (1942) edition of Principles of ... variables defining the relative orbit of the binary (test star, field star) system. The smoothed- out component was .... It would be interesting to address this question using an N-body code. Why do the two populations – stars ...

  4. Binary Black Hole Mergers from Globular Clusters: Implications for Advanced LIGO.

    Science.gov (United States)

    Rodriguez, Carl L; Morscher, Meagan; Pattabiraman, Bharath; Chatterjee, Sourav; Haster, Carl-Johan; Rasio, Frederic A

    2015-07-31

    The predicted rate of binary black hole mergers from galactic fields can vary over several orders of magnitude and is extremely sensitive to the assumptions of stellar evolution. But in dense stellar environments such as globular clusters, binary black holes form by well-understood gravitational interactions. In this Letter, we study the formation of black hole binaries in an extensive collection of realistic globular cluster models. By comparing these models to observed Milky Way and extragalactic globular clusters, we find that the mergers of dynamically formed binaries could be detected at a rate of ∼100 per year, potentially dominating the binary black hole merger rate. We also find that a majority of cluster-formed binaries are more massive than their field-formed counterparts, suggesting that Advanced LIGO could identify certain binaries as originating from dense stellar environments.

  5. Relativistic Binaries in Globular Clusters

    Directory of Open Access Journals (Sweden)

    Matthew J. Benacquista

    2013-03-01

    Full Text Available Galactic globular clusters are old, dense star systems typically containing 10^4 – 10^6 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of tight binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker–Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.

  6. Stellar structure and evolution

    International Nuclear Information System (INIS)

    Kippernhahn, R.; Weigert, A.

    1990-01-01

    This book introduces the theory of the internal structure of stars and their evolution in time. It presents the basic physics of stellar interiors, methods for solving the underlying equations, and the most important results necessary for understanding the wide variety of stellar types and phenomena. The evolution of stars is discussed from their birth through normal evolution to possibly spectacular final stages. Chapters on stellar oscillations and rotation are included

  7. Stellar Physics 2: Stellar Evolution and Stability

    CERN Document Server

    Bisnovatyi-Kogan, Gennady S

    2011-01-01

    "Stellar Physics" is a an outstanding book in the growing body of literature on star formation and evolution. Not only does the author, a leading expert in the field, very thoroughly present the current state of knowledge on stellar physics, but he handles with equal care the many problems that this field of research still faces. A bibliography with well over 1000 entries makes this book an unparalleled reference source. "Stellar Evolution and Stability" is the second of two volumes and can be read, as can the first volume "Fundamental Concepts and Stellar Equilibrium," as a largely independent work. It traces in great detail the evolution of protostars towards the main sequence and beyond this to the last stage of stellar evolution, with the corresponding vast range from white dwarfs to supernovae explosions, gamma-ray bursts and black hole formation. The book concludes with special chapters on the dynamical, thermal and pulsing stability of stars. This second edition is carefully updated in the areas of pre...

  8. A Search for Exoplanets in Short-Period Binary Star Systems

    Directory of Open Access Journals (Sweden)

    Ronald Kaitchuck

    2012-03-01

    Full Text Available This paper reports the progress of a search for exoplanets with S-type orbits in short-period binary star systems. The selected targets have stellar orbital periods of just a few days. These systems are eclipsing binaries so that exoplanet transits, if planets exist, will be highly likely. We report the results for seven binary star systems.

  9. Detection Rates for Close Binaries via Microlensing

    Science.gov (United States)

    Gaudi, B. Scott; Gould, Andrew

    1997-06-01

    Microlensing is one of the most promising methods of reconstructing the stellar mass function down to masses even below the hydrogen-burning limit. The fundamental limit to this technique is the presence of unresolved binaries, which can, in principle, significantly alter the inferred mass function. Here we quantify the fraction of binaries that can be detected using microlensing, considering specifically the mass ratio and separation of the binary. We find that almost all binary systems with separations greater than b ~ 0.4 of their combined Einstein ring radius are detectable assuming a detection threshold of 3%. For two M dwarfs, this corresponds to a limiting separation of >~1 AU. Since very few observed M dwarfs have companions at separations corrupt the measurements of the mass function. We find that the detectability depends only weakly on the mass ratio. For those events for which individual masses can be determined, we find that binaries can be detected down to b ~ 0.2.

  10. Evolution of Supermassive Black-Hole Binaries

    Science.gov (United States)

    Milosavljevic, M.; Merritt, D.

    2000-10-01

    Binary supermassive black holes are expected to form in galactic nuclei following galaxy mergers. We report large-scale N-body simulations using the Aarseth/Spurzem parallel code NBODY6++ of the formation and evolution of such binaries. Initial conditions are drawn from a tree-code simulation of the merger of two spherical galaxies with ρ ~ r-2 density cusps (Cruz & Merritt, AAS Poster). Once the two black holes form a bound pair at the center of the merged galaxies, the evolution is continued using NBODY6++ at much higher resolution. Its exact force calculations generate faithful binary dynamics until the onset of gravity wave-dominated dissipation. We discuss the binary hardening rate, the amplitude of the binary's wandering, and the evolution of the structure of the galactic stellar nucleus.

  11. No tension between assembly models of super massive black hole binaries and pulsar observations.

    Science.gov (United States)

    Middleton, Hannah; Chen, Siyuan; Del Pozzo, Walter; Sesana, Alberto; Vecchio, Alberto

    2018-02-08

    Pulsar timing arrays are presently the only means to search for the gravitational wave stochastic background from super massive black hole binary populations, considered to be within the grasp of current or near-future observations. The stringent upper limit from the Parkes Pulsar Timing Array has been interpreted as excluding (>90% confidence) the current paradigm of binary assembly through galaxy mergers and hardening via stellar interaction, suggesting evolution is accelerated or stalled. Using Bayesian hierarchical modelling we consider implications of this upper limit for a range of astrophysical scenarios, without invoking stalling, nor more exotic physical processes. All scenarios are fully consistent with the upper limit, but (weak) bounds on population parameters can be inferred. Recent upward revisions of the black hole-galaxy bulge mass relation are disfavoured at 1.6σ against lighter models. Once sensitivity improves by an order of magnitude, a non-detection will disfavour the most optimistic scenarios at 3.9σ.

  12. A Survey for Stellar Variability in the Inner Regions of M3: An application of image subtraction

    Science.gov (United States)

    Uglesich, R.; Mirabal, N.; Sugerman, B.; Crotts, A.

    2000-05-01

    Globular clusters are useful laboratories for the study of extreme stellar dynamical effects in high density environments as well as stellar evolution. Binary stars are dynamically important populations in globulars and even a small change (on the order of a few %) in their relative frequency can dramatically alter the long term evolution of the cluster (Heggie & Aarseth 1992). A census of the short-period binary systems as well as the number of cataclysmic variables in a globular cluster provides important constraints on models of their dynamical evolution. Here we present results from a study for stellar variability in M3 conducted with the MDM 1.3m telescope. The data were processed with the image subtraction technique of Tomaney & Crotts (1996) which allows us to remove the background of non-variable sources, preserving only signals from the relatively few variables. In the inner 1 sq. arcminute, Guhathakurta et al. (1994) discovered 40 variable stars, whereas we have been able to monitor 72 (primarily RR Lyrae) in this same region. We present light curves for our detected variables as well as some upper limits on the detection of cataclysmic variables within the half-mass radius of the cluster. We show that ground-based image subtraction studies can match, if not exceed, the performance of HST and do so in a much more economical manner which suggests the possibility of systematic ground-based surveys of the cores of most Galactic globular clusters.

  13. SECULAR EVOLUTION OF BINARIES NEAR MASSIVE BLACK HOLES: FORMATION OF COMPACT BINARIES, MERGER/COLLISION PRODUCTS AND G2-LIKE OBJECTS

    International Nuclear Information System (INIS)

    Prodan, Snezana; Antonini, Fabio; Perets, Hagai B.

    2015-01-01

    Here we discuss the evolution of binaries around massive black holes (MBHs) in nuclear stellar clusters. We focus on their secular evolution due to the perturbation by the MBHs, while simplistically accounting for their collisional evolution. Binaries with highly inclined orbits with respect to their orbits around MBHs are strongly affected by secular processes, which periodically change their eccentricities and inclinations (e.g., Kozai-Lidov cycles). During periapsis approach, dissipative processes such as tidal friction may become highly efficient, and may lead to shrinkage of a binary orbit and even to its merger. Binaries in this environment can therefore significantly change their orbital evolution due to the MBH third-body perturbative effects. Such orbital evolution may impinge on their later stellar evolution. Here we follow the secular dynamics of such binaries and its coupling to tidal evolution, as well as the stellar evolution of such binaries on longer timescales. We find that stellar binaries in the central parts of nuclear stellar clusters (NSCs) are highly likely to evolve into eccentric and/or short-period binaries, and become strongly interacting binaries either on the main sequence (at which point they may even merge), or through their later binary stellar evolution. The central parts of NSCs therefore catalyze the formation and evolution of strongly interacting binaries, and lead to the enhanced formation of blue stragglers, X-ray binaries, gravitational wave sources, and possible supernova progenitors. Induced mergers/collisions may also lead to the formation of G2-like cloud-like objects such as the one recently observed in the Galactic center

  14. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Lorimer Duncan R.

    2005-11-01

    Full Text Available We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1700. There are now 80 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 103 pulsars in 24 of the Galactic globular clusters. Recent highlights have been the discovery of the first ever double pulsar system and a recent flurry of discoveries in globular clusters, in particular Terzan 5.

  15. Electromagnetic Signals Following Stellar-mass Black Hole Mergers

    NARCIS (Netherlands)

    de Mink, S.E.; King, A.

    2017-01-01

    It is often assumed that gravitational-wave (GW) events resulting from the merger of stellar-mass black holes are unlikely to produce electromagnetic (EM) counterparts. We point out that the progenitor binary has probably shed a mass ≳10 M⊙ during its prior evolution. If even a tiny fraction of this

  16. Spectral properties of binary asteroids

    Science.gov (United States)

    Pajuelo, Myriam; Birlan, Mirel; Carry, Benoît; DeMeo, Francesca E.; Binzel, Richard P.; Berthier, Jérôme

    2018-04-01

    We present the first attempt to characterize the distribution of taxonomic class among the population of binary asteroids (15% of all small asteroids). For that, an analysis of 0.8-2.5{μ m} near-infrared spectra obtained with the SpeX instrument on the NASA/IRTF is presented. Taxonomic class and meteorite analog is determined for each target, increasing the sample of binary asteroids with known taxonomy by 21%. Most binary systems are bound in the S-, X-, and C- classes, followed by Q and V-types. The rate of binary systems in each taxonomic class agrees within uncertainty with the background population of small near-Earth objects and inner main belt asteroids, but for the C-types which are under-represented among binaries.

  17. Stability in straight stellarators

    International Nuclear Information System (INIS)

    Kulsrud, R.M.; Yoshikawa, S.

    1981-07-01

    The stability of the straight stellarator against localized interchange modes is investigated employing the Mercier-Greene-Johnson criterion. Critical values of β are obtained both numerically and analytically. The conclusion is that for classical helical stellarators the average limiting β's are quite low of order three to four percent

  18. Stellar photometry and polarimetry

    International Nuclear Information System (INIS)

    Golay, M.; Serkowski, K.

    1976-01-01

    A critical review of progress made in stellar photometry and polarimetry over the period 1973-1975 is presented. Reports of photometric measurements from various observatories throughout the world are summarized. The summary of work on stellar polarimetry lists the review papers, the catalogues and lists of standard stars, and descriptions of new observing techniques. (B.R.H.)

  19. Clues from stellar catastrophes

    NARCIS (Netherlands)

    Rimoldi, Alexander

    2016-01-01

    This thesis uses catastrophic stellar events (supernovae and stellar collisions) to investigate different aspects of their environment. The first part of the thesis examines what happens to supernova remnants near supermassive black holes like the one in the Milky Way Galaxy. To do so, a technique

  20. Compact stellarators as reactors

    International Nuclear Information System (INIS)

    Lyon, J.F.; Valanju, P.; Zarnstorff, M.C.; Hirshman, S.; Spong, D.A.; Strickler, D.; Williamson, D.E.; Ware, A.

    2001-01-01

    Two types of compact stellarators are examined as reactors: two- and three-field-period (M=2 and 3) quasi-axisymmetric devices with volume-average =4-5% and M=2 and 3 quasi-poloidal devices with =10-15%. These low-aspect-ratio stellarator-tokamak hybrids differ from conventional stellarators in their use of the plasma-generated bootstrap current to supplement the poloidal field from external coils. Using the ARIES-AT model with B max =12T on the coils gives Compact Stellarator reactors with R=7.3-8.2m, a factor of 2-3 smaller R than other stellarator reactors for the same assumptions, and neutron wall loadings up to 3.7MWm -2 . (author)

  1. Constraints on the Dynamical Environments of Supermassive Black-Hole Binaries Using Pulsar-Timing Arrays.

    Science.gov (United States)

    Taylor, Stephen R; Simon, Joseph; Sampson, Laura

    2017-05-05

    We introduce a technique for gravitational-wave analysis, where Gaussian process regression is used to emulate the strain spectrum of a stochastic background by training on population-synthesis simulations. This leads to direct Bayesian inference on astrophysical parameters. For pulsar timing arrays specifically, we interpolate over the parameter space of supermassive black-hole binary environments, including three-body stellar scattering, and evolving orbital eccentricity. We illustrate our approach on mock data, and assess the prospects for inference with data similar to the NANOGrav 9-yr data release.

  2. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Lorimer Duncan R.

    2008-11-01

    Full Text Available We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic binary system PSR J1906+0746, a rejuvination in globular cluster pulsar research including growing numbers of pulsars with masses in excess of 1.5M_⊙, a precise measurement of relativistic spin precession in the double pulsar system and a Galactic millisecond pulsar in an eccentric (e = 0.44 orbit around an unevolved companion.

  3. Dynamical effects of successive mergers on the evolution of spherical stellar systems

    International Nuclear Information System (INIS)

    Lee, H.M.

    1987-01-01

    Numerical investigations are carried out to study the dynamical effects of high-mass stars formed out of successive mergers among tidally captured binaries on the evolution of spherical stellar systems. It is assumed that all tidally captured systems become mergers in order to maximize these effects. Stellar systems with N greater than about 10 to the 7th are susceptible to merger instability which may lead to the formation of a central black hole. It is shown that globular clusters are likely to achieve postcollapse expansion due to three-body binary heating and stellar evolution, while galactic nuclei can easily be overcome by the merger instability in the core. 25 references

  4. A Test of Stellar Cohabitation in Multiple Transiting Planet Systems

    Science.gov (United States)

    Morehead, Robert C.; Ford, E. B.

    2013-01-01

    The Kepler mission has discovered over 2,300 exoplanet candidates, including more than 885 associated with target stars with multiple transiting planet candidates. While these putative multiple planet systems are predicted to have an extremely low false positive rate, it is important to test what fraction are indeed transiting a single star and what fraction are some sort of blend (e.g., one transiting planet and an eclipsing binary, or two planet-hosting stars blended within the photometric aperture). We perform such a test for stellar cohabitation using the observed distribution of ξ, the period-normalized transit duration ratio of pairs of transiting planet candidates. We developed a Bayesian framework to estimate the probability that two candidates orbit the target star based on the observed orbital periods and light curve properties with an emphasis on ξ. For priors distributions, we use empirical planet, binary star, and hierarchical triple star occurrence rates and galactic population synthesis models. Using Monte Carlo simulations, we calculate the implied distributions of ξ for all plausible blend scenarios; i.e., a planet around the target star and a background or physically associated eclipsing binary star, a planet around the the target star and a planet around a background or physically associated secondary star, as well as a single star with two planets and no blend. Finally, we compute the posterior probability that a given pair of transiting planet candidates are indeed a pair of planets in orbit around the target star given the observed values. We present the results of our test for a selection Kepler multiple planet candidates and for systems confirmed through other methods, such as transit timing variations. We demonstrate the utility of this technique for the confirmation and characterization of multiple transiting planet systems.

  5. The COBAIN (COntact Binary Atmospheres with INterpolation) Code for Radiative Transfer

    Science.gov (United States)

    Kochoska, Angela; Prša, Andrej; Horvat, Martin

    2018-01-01

    Standard binary star modeling codes make use of pre-existing solutions of the radiative transfer equation in stellar atmospheres. The various model atmospheres available today are consistently computed for single stars, under different assumptions - plane-parallel or spherical atmosphere approximation, local thermodynamical equilibrium (LTE) or non-LTE (NLTE), etc. However, they are nonetheless being applied to contact binary atmospheres by populating the surface corresponding to each component separately and neglecting any mixing that would typically occur at the contact boundary. In addition, single stellar atmosphere models do not take into account irradiance from a companion star, which can pose a serious problem when modeling close binaries. 1D atmosphere models are also solved under the assumption of an atmosphere in hydrodynamical equilibrium, which is not necessarily the case for contact atmospheres, as the potentially different densities and temperatures can give rise to flows that play a key role in the heat and radiation transfer.To resolve the issue of erroneous modeling of contact binary atmospheres using single star atmosphere tables, we have developed a generalized radiative transfer code for computation of the normal emergent intensity of a stellar surface, given its geometry and internal structure. The code uses a regular mesh of equipotential surfaces in a discrete set of spherical coordinates, which are then used to interpolate the values of the structural quantites (density, temperature, opacity) in any given point inside the mesh. The radiaitive transfer equation is numerically integrated in a set of directions spanning the unit sphere around each point and iterated until the intensity values for all directions and all mesh points converge within a given tolerance. We have found that this approach, albeit computationally expensive, is the only one that can reproduce the intensity distribution of the non-symmetric contact binary atmosphere and

  6. Stellar Streams Discovered in the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Shipp, N.; et al.

    2018-01-09

    We perform a search for stellar streams around the Milky Way using the first three years of multi-band optical imaging data from the Dark Energy Survey (DES). We use DES data covering $\\sim 5000$ sq. deg. to a depth of $g > 23.5$ with a relative photometric calibration uncertainty of $< 1 \\%$. This data set yields unprecedented sensitivity to the stellar density field in the southern celestial hemisphere, enabling the detection of faint stellar streams to a heliocentric distance of $\\sim 50$ kpc. We search for stellar streams using a matched-filter in color-magnitude space derived from a synthetic isochrone of an old, metal-poor stellar population. Our detection technique recovers four previously known thin stellar streams: Phoenix, ATLAS, Tucana III, and a possible extension of Molonglo. In addition, we report the discovery of eleven new stellar streams. In general, the new streams detected by DES are fainter, more distant, and lower surface brightness than streams detected by similar techniques in previous photometric surveys. As a by-product of our stellar stream search, we find evidence for extra-tidal stellar structure associated with four globular clusters: NGC 288, NGC 1261, NGC 1851, and NGC 1904. The ever-growing sample of stellar streams will provide insight into the formation of the Galactic stellar halo, the Milky Way gravitational potential, as well as the large- and small-scale distribution of dark matter around the Milky Way.

  7. Teaching stellar interferometry with polymer optical fibers

    Science.gov (United States)

    Illarramendi, M. A.; Arregui, L.; Zubia, J.; Hueso, R.; Sanchez-Lavega, A.

    2017-08-01

    In this manuscript we show the design of a simple experiment that reproduces the operation of the Michelson stellar interferometer by using step-index polymer optical fibers. The emission of stellar sources, single or binary stars, has been simulated by the laser light emerging from the output surface of the 2 meter-long polymer optical fiber. This light has an emission pattern that is similar to the emission pattern of stellar sources - circular, uniform, spatially incoherent, and quasi-monochromatic. Light coming from the fiber end faces passes through two identical pinholes located on a lid covering the objective of a small telescope, thus producing interference. Interference fringes have been acquired using a camera that is coupled to a telescope. The experiments have been carried out both outdoors in the daytime and indoors. By measuring the fringe visibilities, we have determined the size of our artificial stellar sources and the distance between them, when placing them at distances of 54 m from the telescope in the indoor measurements and of 75 m in the outdoor ones.

  8. Development of a simple binary response questionnaire to identify airflow obstruction in a smoking population in Argentina.

    Science.gov (United States)

    Bergna, Miguel A; García, Gabriel R; Alchapar, Ramon; Altieri, Hector; Casas, Juan C Figueroa; Larrateguy, Luis; Nannini, Luis J; Pascansky, Daniel; Grabre, Pedro; Zabert, Gustavo; Miravitlles, Marc

    2015-06-01

    The CODE questionnaire (COPD detection questionnaire), a simple, binary response scale (yes/no), screening questionnaire, was developed for the identification of patients with chronic obstructive pulmonary disease (COPD). We conducted a survey of 468 subjects with a smoking history in 10 public hospitals in Argentina. Patients with a previous diagnosis of COPD, asthma and other respiratory illness were excluded. Items that measured conceptual domains in terms of characteristics of symptoms, smoking history and demographics data were considered. 96 (20.5%) subjects had a diagnosis of COPD according to the 2010 Global Initiative for Chronic Obstructive Lung Disease strategy document. The variables selected for the final questionnaire were based on univariate and multivariate analyses and clinical criteria. Finally, we selected the presence or absence of six variables (age ≥50 years, smoking history ≥30 pack-years, male sex, chronic cough, chronic phlegm and dyspnoea). Of patients without any of these six variables (0 points), none had COPD. The ability of the CODE questionnaire to discriminate between subjects with and without COPD was good (the area under the receiver operating characteristic curve was 0.75). Higher scores were associated with a greater probability of COPD. The CODE questionnaire is a brief, accurate questionnaire that can identify smoking individuals likely to have COPD. Copyright ©ERS 2015.

  9. Physical properties and catalog of EW-type eclipsing binaries observed by LAMOST

    Science.gov (United States)

    Qian, Sheng-Bang; He, Jia-Jia; Zhang, Jia; Zhu, Li-Ying; Shi, Xiang-Dong; Zhao, Er-Gang; Zhou, Xiao

    2017-08-01

    EW-type eclipsing binaries (hereafter called EWs) are strong interacting systems in which both component stars usually fill their critical Roche lobes and share a common envelope. Numerous EWs were discovered by several deep photometric surveys and there were about 40 785 EW-type binary systems listed in the international variable star index (VSX) by 2017 March 13. 7938 of them were observed with LAMOST by 2016 November 30 and their spectral types were identified. Stellar atmospheric parameters of 5363 EW-type binary stars were determined based on good spectroscopic observations. In the paper, those EWs are cataloged and their properties are analyzed. The distributions of orbital period (P), effective temperature (T), gravitational acceleration (log(g)), metallicity ([Fe/H]) and radial velocity (RV) are presented for these observed EW-type systems. It is shown that about 80.6% of sample stars have metallicity below zero, indicating that EW-type systems are old stellar populations. This is in agreement with the conclusion that EW binaries are formed from moderately close binaries through angular momentum loss via magnetic braking that takes a few hundred million to a few billion years. The unusually high metallicities of a few percent of EWs may be caused by contamination of material from the evolution of unseen neutron stars or black holes in the systems. The correlations between orbital period and effective temperature, gravitational acceleration and metallicity are presented and their scatters are mainly caused by (i) the presence of third bodies and (ii) sometimes wrongly determined periods. It is shown that some EWs contain evolved component stars and the physical properties of EWs mainly depend on their orbital periods. It is found that extremely short-period EWs may be older than their long-period cousins because they have lower metallicities. This reveals that they have a longer timescale of pre-contact evolution and their formation and evolution aremainly

  10. New science catalogs of UV sources from the GALEX sky surveys, matched to optical-IR surveys. Related science tools, models, and first results on the characterization of evolved Galactic stellar populations.

    Science.gov (United States)

    Bianchi, Luciana; Shiao, Bernie; Thilker, David; Barr, Robert; Girardi, Leo

    2018-01-01

    GUVcat is a new, expanded and improved catalog of Ultraviolet (UV) sources from the GALEX surveys (Bianchi et al. 2017, ApJ Suppl, 230, 24; arXiv:1704.05903). It contains 83million unique sources measured in FUV and NUV (duplicate measurements and rim artifacts removed) at AIS depth (about FUV colors to classify sources by astrophysical class, and to characterize classes of stellar sources to which UV data are uniquely sensitive, such as hot white dwarfs (WD), including elusive types of binaries. We compared the content of Galactic sources with Milky Way models, computed with different prescriptions. We also matched GUVcat with the first Gaia source and Gaia TGAS releases, which add precise position and G-band photometry for the bright sources, and direct distance measurements for a few very bright sources. GALEX spectra are also available and included in the analysis. Follow-up observations with HST are ongoing for an exploratory subsample.The source catalogs and related tools are available from the uvsky web site http://dolomiti.pha.jhu.edu/uvsky/#GUVcat . GUVcat_AIS is also available from MAST casjobs and soon from Vizier. A useful tool for calculating the effective area coverage of GUVcat, and of the matched catalogs, in user-chosen regions of the sky, is also available at the above url.Acknowledgements: Partial support for this work was provided by NASA grants: NNX16AF40G, NNX14AF88G, HST-GO-14119.001

  11. The Evolution of Compact Binary Star Systems

    Directory of Open Access Journals (Sweden)

    Yungelson, Lev R.

    2006-12-01

    Full Text Available We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs, neutron stars (NSs, and black holes (BHs. Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA. Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

  12. Principles of Stellar Interferometry

    CERN Document Server

    Glindemann, Andreas

    2011-01-01

    Over the last decade, stellar interferometry has developed from a specialist tool to a mainstream observing technique, attracting scientists whose research benefits from milliarcsecond angular resolution. Stellar interferometry has become part of the astronomer’s toolbox, complementing single-telescope observations by providing unique capabilities that will advance astronomical research. This carefully written book is intended to provide a solid understanding of the principles of stellar interferometry to students starting an astronomical research project in this field or to develop instruments and to astronomers using interferometry but who are not interferometrists per se. Illustrated by excellent drawings and calculated graphs the imaging process in stellar interferometers is explained starting from first principles on light propagation and diffraction wave propagation through turbulence is described in detail using Kolmogorov statistics the impact of turbulence on the imaging process is discussed both f...

  13. Stellar Chromospheric Activity

    Directory of Open Access Journals (Sweden)

    Hall Jeffrey C.

    2008-03-01

    Full Text Available The Sun, stars similar to it, and many rather dissimilar to it, have chromospheres, regions classically viewed as lying above the brilliant photosphere and characterized by a positive temperature gradient and a marked departure from radiative equilibrium. Stellar chromospheres exhibit a wide range of phenomena collectively called activity, stemming largely from the time evolution of their magnetic fields and the mass flux and transfer of radiation through the complex magnetic topology and the increasingly optically thin plasma of the outer stellar atmosphere. In this review, I will (1 outline the development of our understanding of chromospheric structure from 1960 to the present, (2 discuss the major observational programs and theoretical lines of inquiry, (3 review the origin and nature of both solar and stellar chromospheric activity and its relationship to, and effect on, stellar parameters including total energy output, and (4 summarize the outstanding problems today.

  14. Advanced Stellar Compass

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, John Leif; Thuesen, Gøsta

    1997-01-01

    This document describes all interface properties for the Advanced Stellar Compass, developed for the German Research Satellite "CHAMP". Basic operations, modes, software protocol, calibration methods and closed loop test strategies are described.......This document describes all interface properties for the Advanced Stellar Compass, developed for the German Research Satellite "CHAMP". Basic operations, modes, software protocol, calibration methods and closed loop test strategies are described....

  15. Evidence for Strange Stellar Family (Artist Concept)

    Science.gov (United States)

    2007-01-01

    This artist concept depicts a quadruple-star system called HD 98800. The system is approximately 10 million years old, and is located 150 light-years away in the constellation TW Hydrae. HD 98800 contains four stars, which are paired off into doublets, or binaries. The stars in the binary pairs orbit around each other, and the two pairs also circle each other like choreographed ballerinas. One of the stellar pairs, called HD 98800B, has a disk of dust around it, while the other pair does not. Although the four stars are gravitationally bound, the distance separating the two binary pairs is about 50 astronomical units (AU) -- slightly more than the average distance between our sun and Pluto. Using NASA's Spitzer Space Telescope, scientists finally have a detailed view of HD 98800B's potential planet-forming disk. Astronomers used the telescope's infrared spectrometer to detect the presence of two belts in the disk made of large dust grains. One belt sits approximately 5.9 AU away from the central binary, or about the distance from the sun to Jupiter, and is likely made up of asteroids and comets. The other belt sits at 1.5 to 2 AU, comparable to the area where Mars and the asteroid belt sit, and is made up of sand-sized dust grains.

  16. Stellar Companions of Exoplanet Host Stars in K2

    Science.gov (United States)

    Matson, Rachel; Howell, Steve; Horch, Elliott; Everett, Mark

    2018-01-01

    Stellar multiplicity has significant implications for the detection and characterization of exoplanets. A stellar companion can mimic the signal of a transiting planet or distort the true planetary radii, leading to improper density estimates and over-predicting the occurrence rates of Earth-sized planets. Determining the fraction of exoplanet host stars that are also binaries allows us to better determine planetary characteristics as well as establish the relationship between binarity and planet formation. Using high-resolution speckle imaging to obtain diffraction limited images of K2 planet candidate host stars we detect stellar companions within one arcsec and up to six magnitudes fainter than the host star. By comparing our observed companion fraction to TRILEGAL star count simulations, and using the known detection limits of speckle imaging, we find the binary fraction of K2 planet host stars to be similar to that of Kepler host stars and solar-type field stars. Accounting for stellar companions in exoplanet studies is therefore essential for deriving true stellar and planetary properties as well as maximizing the returns for TESS and future exoplanet missions.

  17. Stellar Populations of Lyman Break Galaxies at z approx. to 1-3 in the HST/WFC3 Early Release Science Observations

    Science.gov (United States)

    Hathi, N. P.; Cohen, S. H.; Ryan, R. E., Jr.; Finkelstein, S. L.; McCarthy, P. J.; Windhorst, R. A.; Yan, H.; Koekemoer, A. M.; Rutkowski, M. J.; OConnell, R. W.; hide

    2012-01-01

    We analyze the spectral energy distributions (SEDs) of Lyman break galaxies . (LBGs) at z approx = 1-3 selected using the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) UVIS channel filters. These HST /WFC3 obse,rvations cover about 50 arcmin2 in the GOODS-South field as a part of the WFC3 Early Release Science program. These LBGs at z approx = 1-3 are selected using dropout selection criteria similar to high redshift LBGs. The deep multi-band photometry in this field is used to identify best-fit SED models, from which we infer the following results: (1) the photometric redshift estimate of these dropout selected LBGs is accurate to within few percent; (2) the UV spectral slope f3 is redder than at high redshift (z > 3), where LBGs are less dusty; (3) on average, LBGs at .z approx = 1-3 are massive, dustier and more highly star-forming, compared to LBGs at higher redshifts with similar luminosities, though their median values are similar within 1a uncertainties. This could imply that identical dropout selection technique, at all. redshifts, find physically similar galaxies; and (4) the stellar masses of these LBGs are directly proportional to their UV luminosities with a logarithmic slope of approx 0.46, and star-formation rates are proportional to their stellar masses with a logarithmic slope of approx 0.90. These relations hold true - within luminosities probed in this study - for LBGs from z approx = 1.5 to 5. The star-forming galaxies selected using other color-based techniques show similar correlations at z approx = 2, but to avoid any selection biases, and for direct comparison with LBGs at z > 3, a true Lyman break selection at z approx = 2 is essential. The future HST UV surveys,. both wider and deeper, covering a large luminosity range are important to better understand LBG properties, and their evolution.

  18. An X-ray View of Interacting Binaries Outside the Galaxy

    Science.gov (United States)

    Prestwich, A. H.

    2004-07-01

    Chandra and XMM-Newton are revolutionizing our understanding of compact binaries in external galaxies, allowing us to study sources in detail in Local Group Galaxies and study populations in more distant systems. In M31 the X-ray luminosity function depends on the local stellar population in the sense that areas with active star formation have more high luminosity sources, and a higher overall source density (Kong, Di Stefano, Garcia, & Greiner 2003). This result is also true in galaxies outside the Local Group; starburst galaxies have flatter X-ray luminosity functions than do spiral galaxies which are in turn flatter than elliptical galaxies. These observational results suggest that the high end of the luminosity function in star forming regions is dominated by short-lived high mass X-ray binaries. In Chandra Cycle 2 we started a Large Project to survey a sample of 11 nearby (< 10Mpc) face-on spiral galaxies. We find that sources can be approximately classified on the basis of their X-ray color into low mass X-ray binaries, high mass X-ray binaries and supersoft sources. There is an especially interesting class of source that has X-ray colors softer (``redder'') than a typical low mass X-ray binary source, but not so extreme as supersoft sources. Most of these are probably X-ray bright supernova remnants, but some may be a new type of black hole accretor. Finally, when we construct a luminosity function of sources selecting only sources with low mass X-ray binary colors (removing soft sources) we find that there is a dip or break probably associated with the Eddington luminosity for a neutron star.

  19. RCSED—A Value-added Reference Catalog of Spectral Energy Distributions of 800,299 Galaxies in 11 Ultraviolet, Optical, and Near-infrared Bands: Morphologies, Colors, Ionized Gas, and Stellar Population Properties

    Science.gov (United States)

    Chilingarian, Igor V.; Zolotukhin, Ivan Yu.; Katkov, Ivan Yu.; Melchior, Anne-Laure; Rubtsov, Evgeniy V.; Grishin, Kirill A.

    2017-02-01

    We present RCSED, the value-added Reference Catalog of Spectral Energy Distributions of galaxies, which contains homogenized spectrophotometric data for 800,299 low- and intermediate-redshift galaxies (0.007studies of galaxy formation and evolution over the last 5 Gyr. We provide tabulated color transformations for galaxies of different morphologies and luminosities, and analytic expressions for the red sequence shape in different colors. RCSED comprises integrated k-corrected photometry in up to 11 ultraviolet, optical, and near-infrared bands published by the GALEX, SDSS, and UKIDSS wide-field imaging surveys; results of the stellar population fitting of SDSS spectra including best-fitting templates, velocity dispersions, parameterized star formation histories, and stellar metallicities computed for instantaneous starburst and exponentially declining star formation models; parametric and non-parametric emission line fluxes and profiles; and gas phase metallicities. We link RCSED to the Galaxy Zoo morphological classification and galaxy bulge+disk decomposition results of Simard et al. We construct the color-magnitude, Faber-Jackson, and mass-metallicity relations; compare them with the literature; and discuss systematic errors of the galaxy properties presented in our catalog. RCSED is accessible from the project web site and via VO simple spectrum access and table access services using VO-compliant applications. We describe several examples of SQL queries to the database. Finally, we briefly discuss existing and future scientific applications of RCSED and prospective catalog extensions to higher redshifts and different wavelengths. .

  20. On the Progenitor of Binary Neutron Star Merger GW170817

    Science.gov (United States)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva, A.; Anderson, S. B.; Anderson, W. G.; Angelova, S. V.; Antier, S.; Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Atallah, D. V.; Aufmuth, P.; Aulbert, C.; AultONeal, K.; Austin, C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae, S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barkett, K.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Bawaj, M.; Bayley, J. C.; Bazzan, M.; Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Bero, J. J.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.; Biscoveanu, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.; Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonilla, E.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bossie, K.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, D. D.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.; Calloni, E.; Camp, J. B.; Canepa, M.; Canizares, P.; Cannon, K. C.; Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Carney, M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerdá-Durán, P.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chase, E.; Chassande-Mottin, E.; Chatterjee, D.; Cheeseboro, B. D.; Chen, H. Y.; Chen, X.; Chen, Y.; Cheng, H.-P.; Chia, H.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani, G.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.; Clark, J. A.; Clearwater, P.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P.-F.; Cohen, D.; Colla, A.; Collette, C. G.; Cominsky, L. R.; Constancio, M., Jr.; Conti, L.; Cooper, S. J.; Corban, P.; Corbitt, T. R.; Cordero-Carrión, I.; Corley, K. R.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Dálya, G.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davis, D.; Daw, E. J.; Day, B.; De, S.; DeBra, D.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Demos, N.; Denker, T.; Dent, T.; De Pietri, R.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; De Rossi, C.; DeSalvo, R.; de Varona, O.; Devenson, J.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Dreissigacker, C.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dupej, P.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Estevez, D.; Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fee, C.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finstad, D.; Fiori, I.; Fiorucci, D.; Fishbach, M.; Fisher, R. P.; Fitz-Axen, M.; Flaminio, R.; Fletcher, M.; Fong, H.; Font, J. A.; Forsyth, P. W. F.; Forsyth, S. S.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar, S. G.; Garcia-Quiros, C.; Garufi, F.; Gateley, B.; Gaudio, S.; Gaur, G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.; Goncharov, B.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Gretarsson, E. M.; Groot, P.; Grote, H.; Grunewald, S.; Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Halim, O.; Hall, B. R.; Hall, E. D.; Hamilton, E. Z.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hannuksela, O. A.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C.-J.; Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hinderer, T.; Hoak, D.; Hofman, D.; Holgado, A. M.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough, J.; Houston, E. A.; Howell, E. J.; Hreibi, A.; Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J.-M.; Isi, M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi, C. V.; Kalogera, V.; Kamai, B.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.; Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, K.; Kim, W.; Kim, W. S.; Kim, Y.-M.; Kimball, C.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kinley-Hanlon, M.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Knowles, T. D.; Koch, P.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia, A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Larson, S. L.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.; Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.; Linker, S. D.; Littenberg, T. B.; Liu, J.; Lo, R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace, G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macas, R.; Macfoy, S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña Hernandez, I.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.; Markosyan, A. S.; Markowitz, A.; Maros, E.; Marquina, A.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Mason, K.; Massera, E.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matas, A.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McCuller, L.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McNeill, L.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Mejuto-Villa, E.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, B. B.; Miller, J.; Millhouse, M.; Milovich-Goff, M. C.; Minazzoli, O.; Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moffa, D.; Moggi, A.; Mogushi, K.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muñiz, E. A.; Muratore, M.; Murray, P. G.; Napier, K.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Neilson, J.; Nelemans, G.; Nelson, T. J. N.; Nery, M.; Neunzert, A.; Nevin, L.; Newport, J. M.; Newton, G.; Ng, K. K. Y.; Nguyen, T. T.; Nichols, D.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; North, C.; Nuttall, L. K.; Oberling, J.; O'Dea, G. D.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Okada, M. A.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ormiston, R.; Ortega, L. F.; O'Shaughnessy, R.; Ossokine, S.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pace, A. E.; Page, J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, Howard; Pan, Huang-Wei; Pang, B.; Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Parida, A.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patil, M.; Patricelli, B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pirello, M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell, J.; Prasad, J.; Pratt, J. W. W.; Pratten, G.; Predoi, V.; Prestegard, T.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rajbhandari, B.; Rakhmanov, M.; Ramirez, K. E.; Ramos-Buades, A.; Rapagnani, P.; Raymond, V.; Razzano, M.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Ren, W.; Reyes, S. D.; Ricci, F.; Ricker, P. M.; Rieger, S.; Riles, K.; Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romel, C. L.; Romie, J. H.; Rosińska, D.; Ross, M. P.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Rutins, G.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sanchez, L. E.; Sanchis-Gual, N.; Sandberg, V.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.; Scheel, M.; Scheuer, J.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schulte, B. W.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.; Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shaner, M. B.; Shao, L.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Singer, L. P.; Singh, A.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.; Somala, S.; Son, E. J.; Sonnenberg, J. A.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.; Srivastava, A. K.; Staats, K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stevenson, S. P.; Stone, R.; Stops, D. J.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Strunk, A.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Suresh, J.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Tait, S. C.; Talbot, C.; Talukder, D.; Tanner, D. B.; Tápai, M.; Taracchini, A.; Tasson, J. D.; Taylor, J. A.; Taylor, R.; Tewari, S. V.; Theeg, T.; Thies, F.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.; Torres-Forné, A.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.; Tso, R.; Tsukada, L.; Tsuna, D.; Tuyenbayev, D.; Ueno, K.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano, F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walet, R.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, J. Z.; Wang, W. H.; Wang, Y. F.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wessel, E. K.; Weßels, P.; Westerweck, J.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Wilken, D.; Williams, D.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Wofford, J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.; Wysocki, D. M.; Xiao, S.; Yamamoto, H.; Yancey, C. C.; Yang, L.; Yap, M. J.; Yazback, M.; Yu, Hang; Yu, Haocun; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zelenova, T.; Zendri, J.-P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang, Y.-H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.; Zhu, X. J.; Zucker, M. E.; Zweizig, J.; (LIGO Scientific Collaboration; Virgo Collaboration

    2017-12-01

    On 2017 August 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (GW170817), gamma-ray (GRB 170817A), and optical (SSS17a/AT 2017gfo) observations. The optical source was associated with the early-type galaxy NGC 4993 at a distance of just ˜40 Mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ˜2 kpc away from the galaxy’s center. We use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of GW170817 at the time of the second supernova (SN). We generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (BNS) birth to the merger time, accounting for pre-SN galactic motion, for considerably different input distributions of the progenitor mass, pre-SN semimajor axis, and SN-kick velocity. Though not considerably tight, we find these constraints to be comparable to those for Galactic BNS progenitors. The derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second SN and having the merger occur relatively close to the center of the galaxy. These constraints are insensitive to the galaxy’s star formation history, provided the stellar populations are older than 1 Gyr.

  1. A dearth of short-period massive binaries in the young massive star forming region M 17. Evidence for a large orbital separation at birth?

    Science.gov (United States)

    Sana, H.; Ramírez-Tannus, M. C.; de Koter, A.; Kaper, L.; Tramper, F.; Bik, A.

    2017-03-01

    Aims: The formation of massive stars remains poorly understood and little is known about their birth multiplicity properties. Here, we aim to quantitatively investigate the strikingly low radial-velocity dispersion measured for a sample of 11 massive pre- and near-main-sequence stars (σ1D= 5.6 ± 0.2 km s-1) in the very young massive star forming region M 17, in order to obtain first constraints on the multiplicity properties of young massive stellar objects. Methods: We compute the radial-velocity dispersion of synthetic populations of massive stars for various multiplicity properties and we compare the obtained σ1D distributions to the observed value. We specifically investigate two scenarios: a low binary fraction and a dearth of short-period binary systems. Results: Simulated populations with low binary fractions () or with truncated period distributions (Pcutoff > 9 months) are able to reproduce the low σ1D observed within their 68%-confidence intervals. Furthermore, parent populations with fbin > 0.42 or Pcutoff < 47 d can be rejected at the 5%-significance level. Both constraints are in stark contrast with the high binary fraction and plethora of short-period systems in few Myr-old, well characterized OB-type populations. To explain the difference in the context of the first scenario would require a variation of the outcome of the massive star formation process. In the context of the second scenario, compact binaries must form later on, and the cut-off period may be related to physical length-scales representative of the bloated pre-main-sequence stellar radii or of their accretion disks. Conclusions: If the obtained constraints for the M 17's massive-star population are representative of the multiplicity properties of massive young stellar objects, our results may provide support to a massive star formation process in which binaries are initially formed at larger separations, then harden or migrate to produce the typical (untruncated) power-law period

  2. Survey of the MAgellanic Stellar History -- SMASH

    NARCIS (Netherlands)

    Nidever, David; Olsen, Knut; Besla, Gurtina; Gruendl, Robert; Saha, Abhijit; Gallart, Carme; Olszewski, Edward W.; Munoz, Ricardo; Monelli, Matteo; Kunder, Andrea; Kaleida, Catherine; Walker, Alistair; Stringfellow, Guy; Zaritsky, Dennis; van der Marel, Roeland; Blum, Robert; Vivas, Kathy; Chu, You-Hua; Martin, Nicolas; Conn, Blair; Noel, Noelia; Majewski, Steven; Jin, Shoko; Kim, Hwihyun; Cioni, Maria-Rosa; Bell, Eric; Monachesi, Antonela; de Boer, Thomas

    Over the last several years, various discoveries have drastically altered our view of the iconic Magellanic Clouds (MCs), the nearest interacting galaxy system. The best evidence is now that they are on first infall into the Milky Way, that their stellar populations extend much further than

  3. Introduction to stellar structure

    CERN Document Server

    Maciel, Walter J

    2016-01-01

    In the first part of this book, the author presents the basic properties of the stellar interior and describes them thoroughly, along with deriving the main stellar structure equations of temperature, density, pressure and luminosity, among others. The process and application of solving these equations is explained, as well as linking these results with actual observations.  The second part of the text describes what happens to a star over time, and how to determine this by solving the same equations at different points during a star’s lifetime. The fate of various stars is quite different depending on their masses, and this is described in the final parts of the book. This text can be used for an upper level undergraduate course or an introductory graduate course on stellar physics.

  4. On the Origin of Sub-subgiant Stars. II. Binary Mass Transfer, Envelope Stripping, and Magnetic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Leiner, Emily; Mathieu, Robert D. [Department of Astronomy, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706 (United States); Geller, Aaron M., E-mail: leiner@astro.wisc.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

    2017-05-10

    Sub-subgiant stars (SSGs) lie to the red of the main sequence and fainter than the red giant branch in cluster color–magnitude diagrams (CMDs), a region not easily populated by standard stellar evolution pathways. While there has been speculation on what mechanisms may create these unusual stars, no well-developed theory exists to explain their origins. Here we discuss three hypotheses of SSG formation: (1) mass transfer in a binary system, (2) stripping of a subgiant’s envelope, perhaps during a dynamical encounter, and (3) reduced luminosity due to magnetic fields that lower convective efficiency and produce large starspots. Using the stellar evolution code MESA, we develop evolutionary tracks for each of these hypotheses, and compare the expected stellar and orbital properties of these models with six known SSGs in the two open clusters M67 and NGC 6791. All three of these mechanisms can create stars or binary systems in the SSG CMD domain. We also calculate the frequency with which each of these mechanisms may create SSG systems, and find that the magnetic field hypothesis is expected to create SSGs with the highest frequency in open clusters. Mass transfer and envelope stripping have lower expected formation frequencies, but may nevertheless create occasional SSGs in open clusters. They may also be important mechanisms to create SSGs in higher mass globular clusters.

  5. STELLAR POPULATIONS OF LYMAN BREAK GALAXIES AT z {approx_equal} 1-3 IN THE HST/WFC3 EARLY RELEASE SCIENCE OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Hathi, N. P.; McCarthy, P. J. [Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States); Cohen, S. H.; Windhorst, R. A.; Rutkowski, M. J. [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States); Ryan, R. E. Jr.; Koekemoer, A. M.; Bond, H. E. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Finkelstein, S. L. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Yan, H. [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); O' Connell, R. W. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 (United States); Straughn, A. N.; Kimble, R. A. [NASA-Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Disney, M. J. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Dopita, M. A. [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Frogel, Jay A. [Astronomy Department, King Abdulaziz University, P.O. Box 80203, Jeddah (Saudi Arabia); Hall, D. N. B. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Holtzman, J. A., E-mail: nhathi@obs.carnegiescience.edu [Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 (United States); and others

    2013-03-10

    We analyze the spectral energy distributions (SEDs) of Lyman break galaxies (LBGs) at z {approx_equal} 1-3 selected using the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) UVIS channel filters. These HST/WFC3 observations cover about 50 arcmin{sup 2} in the GOODS-South field as a part of the WFC3 Early Release Science program. These LBGs at z {approx_equal} 1-3 are selected using dropout selection criteria similar to high-redshift LBGs. The deep multi-band photometry in this field is used to identify best-fit SED models, from which we infer the following results: (1) the photometric redshift estimate of these dropout-selected LBGs is accurate to within few percent; (2) the UV spectral slope {beta} is redder than at high redshift (z > 3), where LBGs are less dusty; (3) on average, LBGs at z {approx_equal} 1-3 are massive, dustier, and more highly star forming, compared to LBGs at higher redshifts with similar luminosities (0.1L* {approx}< L {approx}< 2.5L*), though their median values are similar within 1{sigma} uncertainties. This could imply that identical dropout selection technique, at all redshifts, finds physically similar galaxies; and (4) the stellar masses of these LBGs are directly proportional to their UV luminosities with a logarithmic slope of {approx}0.46, and star formation rates are proportional to their stellar masses with a logarithmic slope of {approx}0.90. These relations hold true-within luminosities probed in this study-for LBGs from z {approx_equal} 1.5 to 5. The star-forming galaxies selected using other color-based techniques show similar correlations at z {approx_equal} 2, but to avoid any selection biases, and for direct comparison with LBGs at z > 3, a true Lyman break selection at z {approx_equal} 2 is essential. The future HST UV surveys, both wider and deeper, covering a large luminosity range are important to better understand LBG properties and their evolution.

  6. STELLAR: fast and exact local alignments

    Directory of Open Access Journals (Sweden)

    Weese David

    2011-10-01

    Full Text Available Abstract Background Large-scale comparison of genomic sequences requires reliable tools for the search of local alignments. Practical local aligners are in general fast, but heuristic, and hence sometimes miss significant matches. Results We present here the local pairwise aligner STELLAR that has full sensitivity for ε-alignments, i.e. guarantees to report all local alignments of a given minimal length and maximal error rate. The aligner is composed of two steps, filtering and verification. We apply the SWIFT algorithm for lossless filtering, and have developed a new verification strategy that we prove to be exact. Our results on simulated and real genomic data confirm and quantify the conjecture that heuristic tools like BLAST or BLAT miss a large percentage of significant local alignments. Conclusions STELLAR is very practical and fast on very long sequences which makes it a suitable new tool for finding local alignments between genomic sequences under the edit distance model. Binaries are freely available for Linux, Windows, and Mac OS X at http://www.seqan.de/projects/stellar. The source code is freely distributed with the SeqAn C++ library version 1.3 and later at http://www.seqan.de.

  7. Stellar Absorption Line Analysis of Local Star-forming Galaxies: The Relation between Stellar Mass, Metallicity, Dust Attenuation, and Star Formation Rate

    International Nuclear Information System (INIS)

    Jabran Zahid, H.; Kudritzki, Rolf-Peter; Ho, I-Ting; Conroy, Charlie; Andrews, Brett

    2017-01-01

    We analyze the optical continuum of star-forming galaxies in the Sloan Digital Sky Survey by fitting stacked spectra with stellar population synthesis models to investigate the relation between stellar mass, stellar metallicity, dust attenuation, and star formation rate. We fit models calculated with star formation and chemical evolution histories that are derived empirically from multi-epoch observations of the stellar mass–star formation rate and the stellar mass–gas-phase metallicity relations, respectively. We also fit linear combinations of single-burst models with a range of metallicities and ages. Star formation and chemical evolution histories are unconstrained for these models. The stellar mass–stellar metallicity relations obtained from the two methods agree with the relation measured from individual supergiant stars in nearby galaxies. These relations are also consistent with the relation obtained from emission-line analysis of gas-phase metallicity after accounting for systematic offsets in the gas-phase metallicity. We measure dust attenuation of the stellar continuum and show that its dependence on stellar mass and star formation rate is consistent with previously reported results derived from nebular emission lines. However, stellar continuum attenuation is smaller than nebular emission line attenuation. The continuum-to-nebular attenuation ratio depends on stellar mass and is smaller in more massive galaxies. Our consistent analysis of stellar continuum and nebular emission lines paves the way for a comprehensive investigation of stellar metallicities of star-forming and quiescent galaxies.

  8. The Age of Upper Scorpius from Eclipsing Binaries

    Science.gov (United States)

    David, Trevor; Hillenbrand, Lynne

    2018-01-01

    The Upper Scorpius OB association is the nearest region of recent massive star formation and thus an important benchmark for investigations concerning astrophysical timescales. Classical estimates of the association age based on the kinematics of high-mass members and a Hertzsprung-Russell (H-R) diagram of the full stellar population established an age of 5 Myr. However, recent analyses based on the H-R diagram for intermediate- and high-mass members suggest an older age of 11 Myr. Importantly, the H-R diagram ages of stars in Upper Scorpius (and other clusters of a similar age) are mass-dependent, such that low-mass members appear younger than their high-mass counterparts. Here we report an age that is self-consistent in the mass range of 0.3–5 M⊙, and based on the fundamentally-determined masses and radii of eclipsing binaries (EBs). We present nine EBs in Upper Scorpius, four of which are newly reported here and all of which were discovered from K2 photometry. Joint fitting of the eclipse photometry and radial velocities from newly acquired Keck-I/HIRES spectra yields precise masses and radii for those systems that are spectroscopically double-lined. We identify one of the EB components as a slowly pulsating B-star. We use these EBs to develop an empirical mass-radius relation for pre-main-sequence stars, and to evaluate the predictions of widely-used stellar evolutionary models. Our results are consistent with previous studies that indicate most models underestimate the masses of low-mass stars by tens of percent based on H-R diagram analyses. Models including the effects of magnetic fields produce better agreement between the observed bulk and radiative parameters of these young, low-mass stars. From the orbital elements and photometrically inferred rotation periods, we consider the dynamical states of several binaries and compare with expectations from tidal dissipation theories.

  9. Compact stellarator coils

    International Nuclear Information System (INIS)

    Pomphrey, N.; Berry, L.A.; Boozer, A.H.

    2001-01-01

    Experimental devices to study the physics of high-beta (β>∼4%), low aspect ratio (A<∼4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility, and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, we have made several innovations that may be useful in future stellarator design efforts. These include: the use of Singular Value Decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a Control Matrix Method for identifying which few of the many detailed elements of the stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of Genetic Algorithms for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the tradeoff between physics objective and engineering constraints; the development of a new coil optimization code for designing modular coils, and the identification of a 'natural' basis for describing current sheet distributions. (author)

  10. 8. stellarator workshop

    International Nuclear Information System (INIS)

    1991-07-01

    The technical reports in this collection of papers were presented at the 8th International Workshop on Stellarators, and International Atomic Energy Agency Technical Committee Meeting. They include presentations on transport, magnetic configurations, fluctuations, equilibrium, stability, edge plasma and wall aspects, heating, diagnostics, new concepts and reactor studies. Refs, figs and tabs

  11. Stellar Structure and Evolution

    CERN Document Server

    Kippenhahn, Rudolf; Weiss, Achim

    2013-01-01

    This long-awaited second edition of the classical textbook on Stellar Structure and Evolution by Kippenhahn and Weigert is a thoroughly revised version of the original text. Taking into account modern observational constraints as well as additional physical effects such as mass loss and diffusion, Achim Weiss and Rudolf Kippenhahn have succeeded in bringing the book up to the state-of-the-art with respect to both the presentation of stellar physics and the presentation and interpretation of current sophisticated stellar models. The well-received and proven pedagogical approach of the first edition has been retained. The book provides a comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The models developed to explain the stability, dynamics and evolution of the stars are presented and great care is taken to detail the various stages in a star’s life. Just as the first edition, which remained a standard work for more than 20 years after its...

  12. Really focused stellar winds in X-ray binaries

    Czech Academy of Sciences Publication Activity Database

    Hadrava, Petr; Čechura, Jan

    2012-01-01

    Roč. 542, June (2012), A42/1-A42/11 ISSN 0004-6361 R&D Projects: GA MŠk(CZ) LC06014; GA ČR GA202/09/0772; GA ČR GD205/09/H033 Grant - others:GAUK(CZ) 139810 Institutional research plan: CEZ:AV0Z10030501 Keywords : accretion disk * hydrodynamics * numerical methods Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.084, year: 2012

  13. Parameters for binary TNOs which could be detected by TAOS-II

    Science.gov (United States)

    Castro Chacón, Joel; Reyes-Ruiz, Mauricio; Bosco Hernández-Águila, Joannes; Lehner, Matthew; Hernández, Benjamín; Sanchez, Edilberto; Silva, J. S.; Garcia-Díaz, Teresa; Alcock, Charles; Wang, Shiang-Yu; Chu, You-Hua; Chen, Wen-Ping; Alvarez, Fernando; Figueroa, Liliana; Geary, John C.; Huang, Chung-Kai; Cook, Kem H.; Norton, Timothy; Szentgyorgyi, Andrew; Yen, Wei-Ling; Zhang, Zhi-Wei; TAOS-II

    2017-10-01

    The main goal of the TAOS-II project is to characterize the population of small TNOs by means of detecting serendipitous stellar occultations. The result of an occultation event is a particular feature in the observed light curves resulting from the sampling of the diffraction profile. This diffraction profile contains information about the shape of the occulting object, which can, in principle, also be used to determine if it is a member of a binary system. The combination of physical parameters for binary objects and the capabilities of TAOS-II constrain the properties of the objects that can be detected. In this work we discuss under what conditions and physical parameters, a binary object can be detected by TAOS-II. In order to detect a binary TNO, the following conditions must be met: in first place, the size of the TNO must be big enough to be discriminated in shape and small enough to produce a diffraction pattern that fits into the reading area for just one background star. Secondly, the combination of object size and distance to the Sun have to be such that, diffraction and silhouette contribute to the light curve. The size of a binary object, in terms of detectability, depends on the mass of the system, angular speed and alignment in the moment of detection. Considering these physical parameters and detectability conditions we calculated the corresponding diffraction profiles and compared them with single object profiles. The methodology includes the computation of 2D diffraction patterns by solving the diffraction integral, for possible binary TNOs.

  14. Future prospects for stellar intensity interferometry

    International Nuclear Information System (INIS)

    Lake, R.J.W.

    2002-01-01

    Full text: The technique of Stellar Intensity lnterferometry (SII) was first successfully demonstrated by Hanbury-Brown in 1956 at Jodrell Bank. SII uses the correlation in intensity fluctuations of starlight as a function of observational baseline to determine angular diameters and other gross features of main sequence stars. In 1962 an observatory was established by Hanbury-Brown in Narrabri NSW. Between 1965 and 1972 the angular diameters of 32 stars covering the spectral range O to F were measured. Orbital parameters of several unresolved binary stars were also determined and attempts were made by the author to directly measure the limb darkening of Sirius and the rotational distortion of Altair. Following the success of the Narrabri SII the Australian Federal Government provided a grant to Sydney University to develop a Very Large SII capable of making observational measurements on about a thousand stars. The development of this VLSII was however shelved in preference to the development of a potentially more sensitive long baseline Michelson Stellar Interferometer. This latter instrument known as SUSI (Sydney University Stellar Interferometer) has been in operation at Narrabri since 1995. Encouraged by the early results of SUSI and their own efforts in the use of active optics to reduce the effects of atmospheric scintillation a number of international observatories are now active in the development of long baseline or large aperture Michelson Stellar Interferometers. However SII while sacrificing sensitivity has a number of technical advantages over MSI as SII is far less sensitive to atmospheric effects and can be readily developed to work over very long baselines. This paper through technical review and theoretical modeling examines how a modern VLSII could be constructed and operated and addresses the limitations to its sensitivity. In particular it examines how existing Australian industry could contribute to the development of a VLSII with sufficient

  15. Stellar Pulsations and Stellar Evolution: Conflict, Cohabitation, or Symbiosis?

    Science.gov (United States)

    Weiss, Achim

    While the analysis of stellar pulsations allows the determination of current properties of a star, stellar evolution models connect it with its previous history. In many cases results from both methods do not agree. In this review some classical and current cases of disagreement are presented. In some cases these conflicts led to an improvement of the theory of stellar evolution, while in others they still remain unsolved. Some well-known problems of stellar physics are pointed out as well, for which it is hoped that seismology—or in general the analysis of stellar pulsations—will help to resolve them. The limits of this symbiosis will be discussed as well.

  16. Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. VI. Age and abundance structure of the stellar populations in the central sub-kpc of the Milky Way

    Science.gov (United States)

    Bensby, T.; Feltzing, S.; Gould, A.; Yee, J. C.; Johnson, J. A.; Asplund, M.; Meléndez, J.; Lucatello, S.; Howes, L. M.; McWilliam, A.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Poleski, R.; Wyrzykowski, Ł.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J.; Mróz, P.; Pawlak, M.; Abe, F.; Asakura, Y.; Bhattacharya, A.; Bond, I. A.; Bennett, D. P.; Hirao, Y.; Nagakane, M.; Koshimoto, N.; Sumi, T.; Suzuki, D.; Tristram, P. J.

    2017-09-01

    We present a detailed elemental abundance study of 90 F and G dwarf, turn-off, and subgiant stars in the Galactic bulge. Based on high-resolution spectra acquired during gravitational microlensing events, stellar ages and abundances for 11 elements (Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Zn, Y and Ba) have been determined. Four main findings are presented: (1) a wide metallicity distribution with distinct peaks at [Fe/H] = -1.09, -0.63, -0.20, + 0.12, + 0.41; (2) ahigh fraction of intermediate-age to young stars where at [Fe/H] > 0 more than 35% are younger than 8 Gyr, and for [Fe/H] ≲ -0.5 most stars are 10 Gyr or older; (3) several episodes of significant star formation in the bulge has been identified: 3, 6, 8, and 11 Gyr ago; (4) tentatively the "knee" in the α-element abundance trends of the sub-solar metallicity bulge is located at a slightly higher [Fe/H] than in the local thick disk. These findings show that the Galactic bulge has complex age and abundance properties that appear to be tightly connected to the main Galactic stellar populations. In particular, the peaks in the metallicity distribution, the star formation episodes, and the abundance trends, show similarities with the properties of the Galactic thin and thick disks. At the same time, the star formation rate appears to have been slightly faster in the bulge than in the local thick disk, which most likely is an indication of the denser stellar environment closer to the Galactic centre. There are also additional components not seen outside the bulge region, and that most likely can be associated with the Galactic bar. Our results strengthen the observational evidence that support the idea of a secular origin for the Galactic bulge, formed out of the other main Galactic stellar populations present in the central regions of our Galaxy. Additionally, our analysis of this enlarged sample suggests that the (V-I)0 colour of the bulge red clump should be revised to 1.09. Based on data obtained with the

  17. Mass accretion rate fluctuations in black hole X-ray binaries

    NARCIS (Netherlands)

    Rapisarda, S.

    2017-01-01

    This thesis is about the first systematic and quantitative application of propagating mass accretion rate fluctuations models to black hole X-ray binaries. Black hole X-ray binaries are systems consisting of a solar mass star orbiting around a stellar mass black hole. Eventually, the black hole

  18. An Explanation for Metallicity Effects on X-Ray Binary Properties

    NARCIS (Netherlands)

    Maccarone, T.J.; Kundu, A.; Zepf, S.E.

    2004-01-01

    We show that irradiation-induced stellar winds can explain two important metallicity effects in X-ray binaries: the higher numbers and softer spectra of X-ray binaries in metal-rich globular clusters (GCs) compared to those in metal-poor ones. As has been previously noted by Iben, Tutukov, and

  19. TIDAL NOVAE IN COMPACT BINARY WHITE DWARFS

    International Nuclear Information System (INIS)

    Fuller, Jim; Lai Dong

    2012-01-01

    Compact binary white dwarfs (WDs) undergoing orbital decay due to gravitational radiation can experience significant tidal heating prior to merger. In these WDs, the dominant tidal effect involves the excitation of outgoing gravity waves in the inner stellar envelope and the dissipation of these waves in the outer envelope. As the binary orbit decays, the WDs are synchronized from outside in (with the envelope synchronized first, followed by the core). We examine the deposition of tidal heat in the envelope of a carbon-oxygen WD and study how such tidal heating affects the structure and evolution of the WD. We show that significant tidal heating can occur in the star's degenerate hydrogen layer. This layer heats up faster than it cools, triggering runaway nuclear fusion. Such 'tidal novae' may occur in all WD binaries containing a CO WD, at orbital periods between 5 minutes and 20 minutes, and precede the final merger by 10 5 -10 6 years.

  20. Estimating the Binary Fraction of Central Stars of Planetary Nebulae

    Science.gov (United States)

    Douchin, Dimitri

    2015-01-01

    Planetary nebulae are the end-products of intermediate-mass stars evolution, following a phase of expansion of their atmospheres at the end of their lives. Observationally, it has been estimated that 80% of them have non-spherical shapes. Such a high fraction is puzzling and has occupied the planetary nebula community for more than 30 years. One scenario that would allow to justify the observed shapes is that a comparable fraction of the progenitors of central stars of planetary nebula (CSPN) are not single, but possess a companion. The shape of the nebulae would then be the result of an interaction with this companion. The high fraction of non-spherical planetary nebulae would thus imply a high fraction of binary central stars of planetary nebulae, making binarity a preferred channel for planetary nebula formation. After presenting the current state of knowledge regarding planetary nebula formation and shaping and reviewing the diverse efforts to find binaries in planetary nebulae, I present my work to detect a near-infrared excess that would be the signature of the presence of cool companions. The first part of the project consists in the analysis of data and photometry acquired and conducted by myself. The second part details an attempt to make use of archived datasets: the Sloan Digital Sky Survey Data Release 7 optical survey and the extended database assembled by Frew (2008). I also present results from a radial velocity analysis of VLT/UVES spectra for 14 objects aiming to the detection of spectroscopic companions. Finally I give details of the analysis of optical photometry data from our observations associated to the detection of companions around central stars of planetary nebulae using the photometric variability technique. The main result of this thesis is from the near-infrared excess studies which I combine with previously published data. I conclude that if the detected red and NIR flux excess is indicative of a stellar companion then the binary

  1. Eclipsing Binary B-Star Mass Determinations

    Science.gov (United States)

    Townsend, Amanda; Eikenberry, Stephen S.

    2016-01-01

    B-stars in binary pairs provide a laboratory for key astrophysical measurements of massive stars, including key insights for the formation of compact objects (neutron stars and black holes). In their paper, Martayan et al (2004) find 23 Be binary star pairs in NGC2004 in the Large Magellanic Cloud, five of which are both eclipsing and spectroscopic binaries with archival data from VLT-Giraffe and photometric data from MACHO. By using the Wilson eclipsing binary code (e.g., Wilson, 1971), we can determine preliminary stellar masses of the binary components. We present the first results from this analysis. This study also serves as proof-of-concept for future observations with the Photonic Synthesis Telescope Array (Eikenberry et al., in prep) that we are currently building for low-cost, precision spectroscopic observations. With higher resolution and dedicated time for observations, we can follow-up observations of these Be stars as well as Be/X-ray binaries, for improved mass measurements of neutron stars and black holes and better constraints on their origin/formation.

  2. Comparison of population-averaged and cluster-specific models for the analysis of cluster randomized trials with missing binary outcomes: a simulation study

    Directory of Open Access Journals (Sweden)

    Ma Jinhui

    2013-01-01

    Full Text Available Abstracts Background The objective of this simulation study is to compare the accuracy and efficiency of population-averaged (i.e. generalized estimating equations (GEE and cluster-specific (i.e. random-effects logistic regression (RELR models for analyzing data from cluster randomized trials (CRTs with missing binary responses. Methods In this simulation study, clustered responses were generated from a beta-binomial distribution. The number of clusters per trial arm, the number of subjects per cluster, intra-cluster correlation coefficient, and the percentage of missing data were allowed to vary. Under the assumption of covariate dependent missingness, missing outcomes were handled by complete case analysis, standard multiple imputation (MI and within-cluster MI strategies. Data were analyzed using GEE and RELR. Performance of the methods was assessed using standardized bias, empirical standard error, root mean squared error (RMSE, and coverage probability. Results GEE performs well on all four measures — provided the downward bias of the standard error (when the number of clusters per arm is small is adjusted appropriately — under the following scenarios: complete case analysis for CRTs with a small amount of missing data; standard MI for CRTs with variance inflation factor (VIF 50. RELR performs well only when a small amount of data was missing, and complete case analysis was applied. Conclusion GEE performs well as long as appropriate missing data strategies are adopted based on the design of CRTs and the percentage of missing data. In contrast, RELR does not perform well when either standard or within-cluster MI strategy is applied prior to the analysis.

  3. Finding binaries from phase modulation of pulsating stars with Kepler

    Directory of Open Access Journals (Sweden)

    Shibahashi Hiromoto

    2017-01-01

    Full Text Available Binary orbital motion causes a periodic variation in the path length travelled by light emitted from a star towards us. Hence, if the star is pulsating, the observed phase of the pulsation varies over the orbit. Conversely, once we have observed such phase variation, we can extract information about the binary orbit from photometry alone. Continuous and precise space-based photometry has made it possible to measure these light travel time effects on the pulsating stars in binary systems. This opens up a new way of finding unseen brown dwarfs, planets, or massive compact stellar remnants: neutron stars and black holes.

  4. Neutron Stars in X-ray Binaries and their Environments

    Indian Academy of Sciences (India)

    Biswajit Paul

    2017-09-07

    Sep 7, 2017 ... (GX 301–2: Islam & Paul 2014). Predictably, both of these parameters also show strong variation over the orbital phase, especially in binaries with large eccentricity (GX 301–2). In certain orbital phases of GX 301–2, the neutron star goes through an extremely dense component of the stellar wind, and the.

  5. The G+M eclipsing binary v530 orionis

    DEFF Research Database (Denmark)

    Torres, Guillermo; Lacy, Claud H Sandberg; Pavlovski, Krešimir

    2014-01-01

    We report extensive photometric and spectroscopic observations of the 6.1 day period, G+M-type detached double-lined eclipsing binary V530 Ori, an important new benchmark system for testing stellar evolution models for low-mass stars. We determine accurate masses and radii for the components...

  6. Determining the population properties of spinning black holes

    Science.gov (United States)

    Talbot, Colm; Thrane, Eric

    2017-07-01

    There are at least two formation scenarios consistent with the first gravitational-wave observations of binary black hole mergers. In field models, black hole binaries are formed from stellar binaries that may undergo common envelope evolution. In dynamic models, black hole binaries are formed through capture events in globular clusters. Both classes of models are subject to significant theoretical uncertainties. Nonetheless, the conventional wisdom holds that the distribution of spin orientations of dynamically merging black holes is nearly isotropic while field-model black holes prefer to spin in alignment with the orbital angular momentum. We present a framework in which observations of black hole mergers can be used to measure ensemble properties of black hole spin such as the typical black hole spin misalignment. We show how to obtain constraints on population hyperparameters using minimal assumptions so that the results are not strongly dependent on the uncertain physics of formation models. These data-driven constraints will facilitate tests of theoretical models and help determine the formation history of binary black holes using information encoded in their observed spins. We demonstrate that the ensemble properties of binary detections can be used to search for and characterize the properties of two distinct populations of black hole mergers.

  7. Detection of Gravitational Wave Emission by Supermassive Black Hole Binaries Through Tidal Disruption Flares.

    Science.gov (United States)

    Hayasaki, Kimitake; Loeb, Abraham

    2016-10-21

    Galaxy mergers produce supermassive black hole binaries, which emit gravitational waves prior to their coalescence. We perform three-dimensional hydrodynamic simulations to study the tidal disruption of stars by such a binary in the final centuries of its life. We find that the gas stream of the stellar debris moves chaotically in the binary potential and forms accretion disks around both black holes. The accretion light curve is modulated over the binary orbital period owing to relativistic beaming. This periodic signal allows to detect the decay of the binary orbit due to gravitational wave emission by observing two tidal disruption events that are separated by more than a decade.

  8. ROTATIONAL SYNCHRONIZATION MAY ENHANCE HABITABILITY FOR CIRCUMBINARY PLANETS: KEPLER BINARY CASE STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Mason, Paul A. [Department of Physics, University of Texas at El Paso, El Paso, TX 79968 (United States); Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A. [FACom-Instituto de Fisica-FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellin (Colombia); Clark, Joni M. [Department of Mathematics and Physical Sciences, New Mexico State University-DACC, Las Cruces, NM 88003 (United States)

    2013-09-10

    We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.

  9. Strange Quark Stars in Binaries: Formation Rates, Mergers, and Explosive Phenomena

    Science.gov (United States)

    Wiktorowicz, G.; Drago, A.; Pagliara, G.; Popov, S. B.

    2017-09-01

    Recently, the possible coexistence of a first family composed of “normal” neutron stars (NSs) with a second family of strange quark stars (QSs) has been proposed as a solution of problems related to the maximum mass and to the minimal radius of these compact stellar objects. In this paper, we study the mass distribution of compact objects formed in binary systems and the relative fractions of quark and NSs in different subpopulations. We incorporate the strange QS formation model provided by the two-families scenario, and we perform a large-scale population synthesis study in order to obtain the population characteristics. According to our results, the main channel for strange QS formation in binary systems is accretion from a secondary companion on an NS. Therefore, a rather large number of strange QSs form by accretion in low-mass X-ray binaries and this opens the possibility of having explosive GRB-like phenomena not related to supernovae and not due to the merger of two NSs. The number of double strange QS systems is rather small, with only a tiny fraction that merge within a Hubble time. This drastically limits the flux of strangelets produced by the merger, which turns out to be compatible with all limits stemming from Earth and lunar experiments. Moreover, this value of the flux rules out at least one relevant channel for the transformation of all NSs into strange QSs by strangelets’ absorption.

  10. Stellar Astrophysics with Arcus

    Science.gov (United States)

    Brickhouse, Nancy S.; Huenemoerder, David P.; Wolk, Scott; Schulz, Norbert; Foster, Adam; Brenneman, Laura; Poppenhaeger, Katja; Arcus Team

    2018-01-01

    The Arcus mission is now in Phase A of the NASA Medium-Class Explorer competition. We present here the Arcus science case for stellar astrophysics. With spectral resolving power of at least 2500 and effective area greater than 400 cm^2, Arcus will measure new diagnostic lines, e.g. for H- and He-like ions of oxygen and other elements. Weak dielectronic recombination lines will provide sensitive measurements of temperature to test stellar coronal heating models. Arcus will also resolve the coronal and accretion line components in young accreting stars, allowing detailed studies of accretion shocks and their post-shock behavior. Arcus can resolve line shapes and variability in hot star winds to study inhomogeneities and dynamics of wind structure. Such profiles will provide an independent measure of mass loss rates, for which theoretical and observational discrepancies can reach an order of magnitude. Arcus will also study exoplanet atmospheres through X-ray absorption, determing their extent and composition.

  11. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    energy exchange between convection and pulsations, i.e. the modal part of the surface effect. Studying excitation and damping mechanisms requires a non-adiabatic treatment. A major part of my research has been modelling damping rates of red giant stars observed by {\\Kp}. The basis for the non...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them....... However, the effects are barely prominent enough to be distinguishable with today's observational precision. But it does provide means of determining the mixing-length and enables consistent patching. The previously mentioned investigations are based on adiabatic frequency calculations, which neglect...

  12. Young and Waltzing Binary Stars

    Science.gov (United States)

    2001-10-01

    ADONIS Observes Low-mass Eclipsing System in Orion Summary A series of very detailed images of a binary system of two young stars have been combined into a movie . In merely 3 days, the stars swing around each other. As seen from the earth, they pass in front of each other twice during a full revolution, producing eclipses during which their combined brightness diminishes . A careful analysis of the orbital motions has now made it possible to deduce the masses of the two dancing stars . Both turn out to be about as heavy as our Sun. But while the Sun is about 4500 million years old, these two stars are still in their infancy. They are located some 1500 light-years away in the Orion star-forming region and they probably formed just 10 million years ago . This is the first time such an accurate determination of the stellar masses could be achieved for a young binary system of low-mass stars . The new result provides an important piece of information for our current understanding of how young stars evolve. The observations were obtained by a team of astronomers from Italy and ESO [1] using the ADaptive Optics Near Infrared System (ADONIS) on the 3.6-m telescope at the ESO La Silla Observatory. PR Photo 29a/01 : The RXJ 0529.4+0041 system before primary eclipse PR Photo 29b/01 : The RXJ 0529.4+0041 system at mid-primary eclipse PR Photo 29c/01 : The RXJ 0529.4+0041 system after primary eclipse PR Photo 29d/01 : The RXJ 0529.4+0041 system before secondary eclipse PR Photo 29e/01 : The RXJ 0529.4+0041 system at mid-secondary eclipse PR Photo 29f/01 : The RXJ 0529.4+0041 system after secondary eclipse PR Video Clip 06/01 : Video of the RXJ 0529.4+0041 system Binary stars and stellar masses Since some time, astronomers have noted that most stars seem to form in binary or multiple systems. This is quite fortunate, as the study of binary stars is the only way in which it is possible to measure directly one of the most fundamental quantities of a star, its mass. The mass of a

  13. Merger rates of black hole binaries: prospects for gravitational wave detectors

    OpenAIRE

    Zwart, Simon Portegies; McMillan, Stephen

    1999-01-01

    Mergers of black-hole binaries are expected to release large amounts of energy in the form of gravitational radiation. However, binary evolution models predict merger rates too low to be of observational interest. In this paper we explore the possibility that black holes become members of close binaries via dynamical interactions with other stars in dense stellar systems. In star clusters, black holes become the most massive objects within a few tens of millions of years; dynamical relaxation...

  14. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing...... with well-covered light curves increases with new-generation searches....

  15. Eliciting Subjective Probabilities with Binary Lotteries

    DEFF Research Database (Denmark)

    Harrison, Glenn W.; Martínez-Correa, Jimmy; Swarthout, J. Todd

    objective probabilities. Drawing a sample from the same subject population, we find evidence that the binary lottery procedure induces linear utility in a subjective probability elicitation task using the Quadratic Scoring Rule. We also show that the binary lottery procedure can induce direct revelation...

  16. Eclipsing binary stars with a δ Scuti component

    Science.gov (United States)

    Kahraman Aliçavuş, F.; Soydugan, E.; Smalley, B.; Kubát, J.

    2017-09-01

    Eclipsing binaries with a δ Sct component are powerful tools to derive the fundamental parameters and probe the internal structure of stars. In this study, spectral analysis of six primary δ Sct components in eclipsing binaries has been performed. Values of Teff, v sin I, and metallicity for the stars have been derived from medium-resolution spectroscopy. Additionally, a revised list of δ Sct stars in eclipsing binaries is presented. In this list, we have only given the δ Sct stars in eclipsing binaries to show the effects of the secondary components and tidal-locking on the pulsations of primary δ Sct components. The stellar pulsation, atmospheric and fundamental parameters (e.g. mass, radius) of 92 δ Sct stars in eclipsing binaries have been gathered. Comparison of the properties of single and eclipsing binary member δ Sct stars has been made. We find that single δ Sct stars pulsate in longer periods and with higher amplitudes than the primary δ Sct components in eclipsing binaries. The v sin I of δ Sct components is found to be significantly lower than that of single δ Sct stars. Relationships between the pulsation periods, amplitudes and stellar parameters in our list have been examined. Significant correlations between the pulsation periods and the orbital periods, Teff, log g, radius, mass ratio, v sin I and the filling factor have been found.

  17. THE AGES OF HIGH-MASS X-RAY BINARIES IN NGC 2403 AND NGC 300

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Benjamin F.; Binder, Breanna A.; Dalcanton, Julianne J. [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Eracleous, Michael [Department of Astronomy and Astrophysics and Center for Gravitational Wave Physics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16803 (United States); Dolphin, Andrew, E-mail: ben@astro.washington.edu, E-mail: bbinder@astro.washington.edu, E-mail: jd@astro.washington.edu, E-mail: mce@astro.psu.edu, E-mail: adolphin@raytheon.com [Raytheon Company, Tucson, AZ 85734 (United States)

    2013-07-20

    We have examined resolved stellar photometry from HST imaging surrounding 18 high-mass X-ray binary (HMXB) candidates in NGC 300 and NGC 2403 as determined from combined Chandra/HST analysis. We have fit the color-magnitude distribution of the surrounding stars with stellar evolution models. All but one region in NGC 300 and two in NGC 2403 contain a population with an age between 20 and 70 Myr. One of the candidates is the ultraluminous X-ray source in NGC 2403, which we associate with a 60 {+-} 5 Myr old population. These age distributions provide additional evidence that 16 of these 18 candidates are HMXBs. Furthermore, our results suggest that the most common HMXB age in these galaxies is 40-55 Myr. This preferred age is similar to observations of HMXBs in the Small Magellanic Cloud, providing new evidence of this formation timescale, but in higher metallicity populations. We suggest that this preferred HMXB age is the result of the fortuitous combination of two physical effects. First, this is the age of a population when the greatest rate of core-collapse events should be occurring, maximizing neutron star production. Second, this is the age when B stars are most likely to be actively losing mass. We also discuss our results in the context of HMXB feedback in galaxies, confirming HMXBs as a potentially important source of energy for the interstellar medium in low-mass galaxies.

  18. Accretion-induced Collapse from Helium Star + White Dwarf Binaries

    Science.gov (United States)

    Brooks, Jared; Schwab, Josiah; Bildsten, Lars; Quataert, Eliot; Paxton, Bill

    2017-07-01

    Accretion-induced collapse (AIC) occurs when an O/Ne white dwarf (WD) grows to nearly the Chandrasekhar mass ({M}{Ch}), reaching central densities that trigger electron captures in the core. Using Modules for Experiments in Stellar Astrophysics (MESA), we present the first true binary simulations of He star + O/Ne WD binaries, focusing on a 1.5 {M}⊙ He star in a 3 hr orbital period with 1.1{--}1.3 {M}⊙ O/Ne WDs. The helium star fills its Roche lobe after core helium burning is completed and donates helium on its thermal timescale to the WD, \\dot{M}≈ 3× {10}-6 {M}⊙ {{yr}}-1, which is a rate high enough that the accreting helium burns stably on the WD. The accumulated carbon/oxygen ashes from the helium burning undergo an unstable shell flash that initiates an inwardly moving, carbon burning flame. This flame is only quenched when it runs out of carbon at the surface of the original O/Ne core. Subsequent accumulation of fresh carbon/oxygen layers also undergo thermal instabilities, but no mass loss is triggered, which allows {M}{WD}\\to {M}{Ch}, and then triggers the onset of AIC. We also discuss the scenario of accreting C/O WDs that experience shell carbon ignitions to become O/Ne WDs, and then, under continuing mass transfer, lead to AIC. Studies of the AIC event rate using binary population synthesis should include all of these channels, especially this latter channel, which has been previously neglected but might dominate the rate.

  19. ENHANCED TIDAL DISRUPTION RATES FROM MASSIVE BLACK HOLE BINARIES

    International Nuclear Information System (INIS)

    Chen Xian; Liu, F. K.; Madau, Piero; Sesana, Alberto

    2009-01-01

    'Hard' massive black hole (MBH) binaries embedded in steep stellar cusps can shrink via three-body slingshot interactions. We show that this process will inevitably be accompanied by a burst of stellar tidal disruptions, at a rate that can be several orders of magnitude larger than that appropriate for a single MBH. Our numerical scattering experiments reveal that (1) a significant fraction of stars initially bound to the primary hole are scattered into its tidal disruption loss cone by gravitational interactions with the secondary hole, an enhancement effect that is more pronounced for very unequal mass binaries; (2) about 25% (40%) of all strongly interacting stars are tidally disrupted by an MBH binary of mass ratio q = 1/81 (q = 1/243) and eccentricity 0.1; and (3) two mechanisms dominate the fueling of the tidal disruption loss cone, a Kozai nonresonant interaction that causes the secular evolution of the stellar angular momentum in the field of the binary, and the effect of close encounters with the secondary hole that change the stellar orbital parameters in a chaotic way. For a hard MBH binary of 10 7 M sun and mass ratio 10 -2 , embedded in an isothermal stellar cusp of velocity dispersion σ * = 100 km s -1 , the tidal disruption rate can be as large as N-dot * ∼1 yr -1 . This is 4 orders of magnitude higher than estimated for a single MBH fed by two-body relaxation. When applied to the case of a putative intermediate-mass black hole inspiraling onto Sgr A*, our results predict tidal disruption rates N-dot * ∼0.05-0.1 yr -1 .

  20. Dynamical evolution of stars and gas of young embedded stellar sub-clusters

    Science.gov (United States)

    Sills, Alison; Rieder, Steven; Scora, Jennifer; McCloskey, Jessica; Jaffa, Sarah

    2018-03-01

    We present simulations of the dynamical evolution of young embedded star clusters. Our initial conditions are directly derived from X-ray, infrared, and radio observations of local systems, and our models evolve both gas and stars simultaneously. Our regions begin with both clustered and extended distributions of stars, and a gas distribution which can include a filamentary structure in addition to gas surrounding the stellar subclusters. We find that the regions become spherical, monolithic, and smooth quite quickly, and that the dynamical evolution is dominated by the gravitational interactions between the stars. In the absence of stellar feedback, the gas moves gently out of the centre of our regions but does not have a significant impact on the motions of the stars at the earliest stages of cluster formation. Our models at later times are consistent with observations of similar regions in the local neighbourhood. We conclude that the evolution of young proto-star clusters is relatively insensitive to reasonable choices of initial conditions. Models with more realism, such as an initial population of binary and multiple stars and ongoing star formation, are the next step needed to confirm these findings.

  1. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    Science.gov (United States)

    Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri; hide

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M.) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 Solar Mass, an unusually high value.

  2. An eccentric binary millisecond pulsar in the galactic plane.

    Science.gov (United States)

    Champion, David J; Ransom, Scott M; Lazarus, Patrick; Camilo, Fernando; Bassa, Cees; Kaspi, Victoria M; Nice, David J; Freire, Paulo C C; Stairs, Ingrid H; van Leeuwen, Joeri; Stappers, Ben W; Cordes, James M; Hessels, Jason W T; Lorimer, Duncan R; Arzoumanian, Zaven; Backer, Don C; Bhat, N D Ramesh; Chatterjee, Shami; Cognard, Ismaël; Deneva, Julia S; Faucher-Giguère, Claude-André; Gaensler, Bryan M; Han, Jinlin; Jenet, Fredrick A; Kasian, Laura; Kondratiev, Vlad I; Kramer, Michael; Lazio, Joseph; McLaughlin, Maura A; Venkataraman, Arun; Vlemmings, Wouter

    2008-06-06

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value.

  3. Collisional Dynamics around Binary Black Holes in Galactic Centers

    Science.gov (United States)

    Hemsendorf, Marc; Sigurdsson, Steinn; Spurzem, Rainer

    2002-12-01

    We follow the sinking of two massive black holes in a spherical stellar system where the black holes become bound under the influence of dynamical friction. Once bound, the binary hardens by three-body encounters with surrounding stars. We find that the binary wanders inside the core, providing an enhanced supply of reaction partners for the hardening. The binary evolves into a highly eccentric orbit leading to coalescence well beyond a Hubble time. These are the first results from a hybrid ``self-consistent field'' (SCF) and direct Aarseth N-body integrator (NBODY6), which combines the advantages of the direct force calculation with the efficiency of the field method. The code is designed for use on parallel architectures and is therefore applicable to collisional N-body integrations with extraordinarily large particle numbers (>105). This creates the possibility of simulating the dynamics of both globular clusters with realistic collisional relaxation and stellar systems surrounding supermassive black holes in galactic nuclei.

  4. TRACING EMBEDDED STELLAR POPULATIONS IN CLUSTERS AND GALAXIES USING MOLECULAR EMISSION: METHANOL AS A SIGNATURE OF THE LOW-MASS END OF THE IMF

    International Nuclear Information System (INIS)

    Kristensen, Lars E.; Bergin, Edwin A.

    2015-01-01

    Most low-mass protostars form in clusters, in particular high-mass clusters; however, how low-mass stars form in high-mass clusters and what the mass distribution is are still open questions both in our own Galaxy and elsewhere. To access the population of forming embedded low-mass protostars observationally, we propose using molecular outflows as tracers. Because the outflow emission scales with mass, the effective contrast between low-mass protostars and their high-mass cousins is greatly lowered. In particular, maps of methanol emission at 338.4 GHz (J = 7 0 –6 0 A + ) in low-mass clusters illustrate that this transition is an excellent probe of the low-mass population. We present here a model of a forming cluster where methanol emission is assigned to every embedded low-mass protostar. The resulting model image of methanol emission is compared to recent ALMA observations toward a high-mass cluster and the similarity is striking: the toy model reproduces observations to better than a factor of two and suggests that approximately 50% of the total flux originates in low-mass outflows. Future fine-tuning of the model will eventually make it a tool for interpreting the embedded low-mass population of distant regions within our own Galaxy and ultimately higher-redshift starburst galaxies, not just for methanol emission but also water and high-J CO

  5. TRACING EMBEDDED STELLAR POPULATIONS IN CLUSTERS AND GALAXIES USING MOLECULAR EMISSION: METHANOL AS A SIGNATURE OF THE LOW-MASS END OF THE IMF

    Energy Technology Data Exchange (ETDEWEB)

    Kristensen, Lars E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bergin, Edwin A., E-mail: lkristensen@cfa.harvard.edu [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States)

    2015-07-10

    Most low-mass protostars form in clusters, in particular high-mass clusters; however, how low-mass stars form in high-mass clusters and what the mass distribution is are still open questions both in our own Galaxy and elsewhere. To access the population of forming embedded low-mass protostars observationally, we propose using molecular outflows as tracers. Because the outflow emission scales with mass, the effective contrast between low-mass protostars and their high-mass cousins is greatly lowered. In particular, maps of methanol emission at 338.4 GHz (J = 7{sub 0}–6{sub 0} A{sup +}) in low-mass clusters illustrate that this transition is an excellent probe of the low-mass population. We present here a model of a forming cluster where methanol emission is assigned to every embedded low-mass protostar. The resulting model image of methanol emission is compared to recent ALMA observations toward a high-mass cluster and the similarity is striking: the toy model reproduces observations to better than a factor of two and suggests that approximately 50% of the total flux originates in low-mass outflows. Future fine-tuning of the model will eventually make it a tool for interpreting the embedded low-mass population of distant regions within our own Galaxy and ultimately higher-redshift starburst galaxies, not just for methanol emission but also water and high-J CO.

  6. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10 6 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ∼10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  7. ON THE ORIGIN OF THE METALLICITY DEPENDENCE IN DYNAMICALLY FORMED EXTRAGALACTIC LOW-MASS X-RAY BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Ivanova, N.; Avendano Nandez, J. L.; Sivakoff, G. R. [Department of Physics, University of Alberta, Edmonton, AB T6G 2E1 (Canada); Fragos, T.; Kim, D.-W.; Fabbiano, G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lombardi, J. C. [Department of Physics, Allegheny College, Meadville, PA 16335 (United States); Voss, R. [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Jordan, A., E-mail: nata.ivanova@ualberta.ca [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Macul, Santiago (Chile)

    2012-12-01

    Globular clusters (GCs) effectively produce dynamically formed low-mass X-ray binaries (LMXBs). Observers detect {approx}100 times more LMXBs per stellar mass in GCs compared to stars in the fields of galaxies. Observationally, metal-rich GCs are about three times more likely to contain an X-ray source than their metal-poor counterparts. Recent observations have shown that this ratio holds in extragalactic GCs for all bright X-ray sources with L{sub X} between 2 Multiplication-Sign 10{sup 37} and 5 Multiplication-Sign 10{sup 38} erg s{sup -1}. In this Letter, we propose that the observed metallicity dependence of LMXBs in extragalactic GCs can be explained by the differences in the number densities and average masses of red giants in populations of different metallicities. Red giants serve as seeds for the dynamical production of bright LMXBs via two channels-binary exchanges and physical collisions-and the increase of the number densities and masses of red giants boost LMXB production, leading to the observed difference. We also discuss a possible effect of the age difference in stellar populations of different metallicities.

  8. Star formation history: Modeling of visual binaries

    Science.gov (United States)

    Gebrehiwot, Y. M.; Tessema, S. B.; Malkov, O. Yu.; Kovaleva, D. A.; Sytov, A. Yu.; Tutukov, A. V.

    2018-05-01

    Most stars form in binary or multiple systems. Their evolution is defined by masses of components, orbital separation and eccentricity. In order to understand star formation and evolutionary processes, it is vital to find distributions of physical parameters of binaries. We have carried out Monte Carlo simulations in which we simulate different pairing scenarios: random pairing, primary-constrained pairing, split-core pairing, and total and primary pairing in order to get distributions of binaries over physical parameters at birth. Next, for comparison with observations, we account for stellar evolution and selection effects. Brightness, radius, temperature, and other parameters of components are assigned or calculated according to approximate relations for stars in different evolutionary stages (main-sequence stars, red giants, white dwarfs, relativistic objects). Evolutionary stage is defined as a function of system age and component masses. We compare our results with the observed IMF, binarity rate, and binary mass-ratio distributions for field visual binaries to find initial distributions and pairing scenarios that produce observed distributions.

  9. THE ADVANCED STELLAR COMPASS

    DEFF Research Database (Denmark)

    Jørgensen, John Leif; Liebe, Carl Christian

    1997-01-01

    The science objective of the Danish Geomagnetic Research Satellite "Ørsted" is to map the magnetic field of the Earth, with a vector precision of a fraction of a nanotesla. This necessitates an attitude reference instrument with a precision of a few arcseconds onboard the satellite. To meet...... this demand the Advanced Stellar Compass (ASC), a fully autonomous miniature star tracker, was developed. This ASC is capable of both solving the "lost in space" problem and determine the attitude with arcseconds precision. The development, principles of operation and instrument autonomy of the ASC...

  10. Stellar Populations in Compact Galaxy Groups: a Multi-wavelength Study of HCGs 16, 22, and 42, Their Star Clusters, and Dwarf Galaxies

    Science.gov (United States)

    Konstantopoulos, I. S.; Maybhate, A.; Charlton, J. C.; Fedotov, K.; Durrell, P. R.; Mulchaey, J. S.; English, J.; Desjardins, T. D.; Gallagher, S. C.; Walker, L. M.; hide

    2013-01-01

    We present a multi-wavelength analysis of three compact galaxy groups, Hickson compact groups (HCGs) 16, 22, and 42, which describe a sequence in terms of gas richness, from space- (Swift, Hubble Space Telescope (HST), and Spitzer) and ground-based (Las Campanas Observatory and Cerro Tololo Inter-American Observatory) imaging and spectroscopy.We study various signs of past interactions including a faint, dusty tidal feature about HCG 16A, which we tentatively age-date at dwarf galaxies at accordant redshifts. The inclusion of 33 members and 27 "associates" (possible members) radically changes group dynamical masses, which in turn may affect previous evolutionary classifications. The extended membership paints a picture of relative isolation in HCGs 16 and 22, but shows HCG 42 to be part of a larger structure, following a dichotomy expected from recent studies. We conclude that (1) star cluster populations provide an excellent metric of evolutionary state, as they can age-date the past epochs of star formation; and (2) the extended dwarf galaxy population must be considered in assessing the dynamical state of a compact group.

  11. Using Gaussian Processes to Construct Flexible Models of Stellar Spectra

    Science.gov (United States)

    Czekala, Ian

    2018-01-01

    The use of spectra is fundamental to astrophysical fields ranging from exoplanets to stars to galaxies. In spite of this ubiquity, or perhaps because of it, there are a plethora of use cases that do not yet have physics-based forward models that can fit high signal-to-noise data to within the observational noise. These inadequacies result in subtle but systematic residuals not captured by any model, which complicates and biases parameter inference. Fortunately, the now-prevalent collection and archiving of large spectral datasets also provides an opening for empirical, data-driven approaches. We introduce one example of a time-series dataset of high-resolution stellar spectra, as is commonly delivered by planet-search radial velocity instruments like TRES, HIRES, and HARPS. Measurements of radial velocity variations of stars and their companions are essential for stellar and exoplanetary study; these measurements provide access to the fundamental physical properties that dictate all phases of stellar evolution and facilitate the quantitative study of planetary systems. In observations of a (spatially unresolved) spectroscopic binary star, one only ever records the composite sum of the spectra from the primary and secondary stars, complicating photospheric analysis of each individual star. Our technique “disentangles” the composite spectra by treating each underlying stellar spectrum as a Gaussian process, whose posterior predictive distribution is inferred simultaneously with the orbital parameters. To demonstrate the potential of this technique, we deploy it on red-optical time-series spectra of the mid-M-dwarf eclipsing binary LP661-13, which was recently discovered by the MEarth project. We successfully reconstruct the primary and secondary stellar spectra and report orbital parameters with improved precision compared to traditional radial velocity analysis techniques.

  12. Identification of Stellar Sequences in Various Stellar Systems ...

    Indian Academy of Sciences (India)

    GIREESH C. JOSHI

    2017-11-27

    Nov 27, 2017 ... (CMRD) approach is used to separate the stellar sequences of cluster systems. The age, distance and reddening of each ... gravitational bound systems (Joshi & Tyagi 2015). Gen- erally, these objects are identified ...... identification of stellar clusters within embedded region of the Galactic disk and highly ...

  13. Stellar axion models

    Energy Technology Data Exchange (ETDEWEB)

    Nowakowski, Daniel; Kuster, Markus; Meister, Claudia V.; Fuelbert, Florian; Hoffmann, Dieter H.H. [TU Darmstadt (Germany). Institut fuer Kernphysik; Weiss, Achim [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    2010-07-01

    An axion helioscope is typically operated to observe the sun as an axion source. Additional pointings at celestial sources, e.g. stars in other galaxies, result in possible detections of axions from distant galactic objects. For the observation of supplementary axion sources we therefore calculate the thereotical axion flux from distant stars by extending axionic flux models for the axion Primakoff effect in the sun to other main sequence stars. The main sequence star models used for our calculations are based on full stellar structure calculations. To deduce the effective axion flux of stellar objects incident on the Earth the All-Sky catalogue was used to obtain the spectral class and distance of the stars treated. Our calculations of the axion flux in the galactic plane show that for a zero age main sequence star an maximum axion flux of {phi}{sub a}=303.43 cm{sup -2}s{sup -1} could be expected. Furthermore we present estimates of axion fluxes from time-evolved stars.

  14. The DEMO Quasisymmetric Stellarator

    Directory of Open Access Journals (Sweden)

    Geoffrey B. McFadden

    2010-02-01

    Full Text Available The NSTAB nonlinear stability code solves differential equations in conservation form, and the TRAN Monte Carlo test particle code tracks guiding center orbits in a fixed background, to provide simulations of equilibrium, stability, and transport in tokamaks and stellarators. These codes are well correlated with experimental observations and have been validated by convergence studies. Bifurcated 3D solutions of the 2D tokamak problem have been calculated that model persistent disruptions, neoclassical tearing modes (NTMs and edge localized modes (ELMs occurring in the International Thermonuclear Experimental Reactor (ITER, which does not pass the NSTAB simulation test for nonlinear stability. So we have designed a quasiaxially symmetric (QAS stellarator with similar proportions as a candidate for the demonstration (DEMO fusion reactor that does pass the test [1]. The configuration has two field periods and an exceptionally accurate 2D symmetry that furnishes excellent thermal confinement and good control of the prompt loss of alpha particles. Robust coils are found from a filtered form of the Biot-Savart law based on a distribution of current over a control surface for the coils and the current in the plasma defined by the equilibrium calculation. Computational science has addressed the issues of equilibrium, stability, and transport, so it remains to develop an effective plan to construct the coils and build a diverter.

  15. Physical Properties and Evolutionary States of EA-type Eclipsing Binaries Observed by LAMOST

    Science.gov (United States)

    Qian, S.-B.; Zhang, J.; He, J.-J.; Zhu, L.-Y.; Zhao, E.-G.; Shi, X.-D.; Zhou, X.; Han, Z.-T.

    2018-03-01

    About 3196 EA-type binaries (EAs) were observed by LAMOST by 2017 June 16 and their spectral types were derived. Meanwhile, the stellar atmospheric parameters of 2020 EAs were determined. In this paper, those EAs are cataloged and their physical properties and evolutionary states are investigated. The period distribution of EAs suggests that the period limit of tidal locking for the close binaries is about 6 days. It is found that the metallicity of EAs is higher than that of EW-type binaries (EWs), indicating that EAs are generally younger than EWs and they are the progenitors of EWs. The metallicities of long-period EWs (0.4values of Log (g) are usually smaller than those of EAs. These support the evolutionary process that EAs evolve into long-period EWs through the combination of angular momentum loss (AML) via magnetic braking and case A mass transfer. For short-period EWs, their metallicities are lower than those of EAs, while their gravitational accelerations are higher. These reveal that they may be formed from cool short-period EAs through AML via magnetic braking with little mass transfer. For some EWs with high metallicities, they may be contaminated by material from the evolution of unseen neutron stars and black holes or they have third bodies that may help them to form rapidly through a short timescale of pre-contact evolution. The present investigation suggests that the modern EW populations may have formed through a combination of these mechanisms.

  16. A new method to unveil embedded stellar clusters

    Science.gov (United States)

    Lombardi, Marco; Lada, Charles J.; Alves, João

    2017-11-01

    In this paper we present a novel method to identify and characterize stellar clusters deeply embedded in a dark molecular cloud. The method is based on measuring stellar surface density in wide-field infrared images using star counting techniques. It takes advantage of the differing H-band luminosity functions (HLFs) of field stars and young stellar populations and is able to statistically associate each star in an image as a member of either the background stellar population or a young stellar population projected on or near the cloud. Moreover, the technique corrects for the effects of differential extinction toward each individual star. We have tested this method against simulations as well as observations. In particular, we have applied the method to 2MASS point sources observed in the Orion A and B complexes, and the results obtained compare very well with those obtained from deep Spitzer and Chandra observations where presence of infrared excess or X-ray emission directly determines membership status for every star. Additionally, our method also identifies unobscured clusters and a low resolution version of the Orion stellar surface density map shows clearly the relatively unobscured and diffuse OB 1a and 1b sub-groups and provides useful insights on their spatial distribution.

  17. Discovery of a Red Giant with Solar-like Oscillations in an Eclipsing Binary System from Kepler Space-based Photometry

    DEFF Research Database (Denmark)

    Hekker, S.; Debosscher, J.; Huber, D.

    2010-01-01<