WorldWideScience

Sample records for interstellar matter galaxy

  1. The interstellar medium in galaxies

    CERN Document Server

    1997-01-01

    It has been more than five decades ago that Henk van de Hulst predicted the observability of the 21-cm line of neutral hydrogen (HI ). Since then use of the 21-cm line has greatly improved our knowledge in many fields and has been used for galactic structure studies, studies of the interstellar medium (ISM) in the Milky Way and other galaxies, studies of the mass distribution of the Milky Way and other galaxies, studies of spiral struc­ ture, studies of high velocity gas in the Milky Way and other galaxies, for measuring distances using the Tully-Fisher relation etc. Regarding studies of the ISM, there have been a number of instrumen­ tal developments over the past decade: large CCD's became available on optical telescopes, radio synthesis offered sensitive imaging capabilities, not only in the classical 21-cm HI line but also in the mm-transitions of CO and other molecules, and X-ray imaging capabilities became available to measure the hot component of the ISM. These developments meant that Milky Way was n...

  2. The life cycle of the Interstellar Medium in other galaxies

    Science.gov (United States)

    Knapp, G. R.

    1995-01-01

    Gas in spiral galaxies cycles between the diffuse and dense phases as clouds collapse, form stars and are dispersed back into the ISM. Far infrared observations of continuum emission from interstellar dust and line emission from interstellar gas have revealed a wealth of information on the state of the ISM in galaxies of different morphological types. The analysis of these observations gives us information about the processes of star formation and about the evolution of the ISM. Star formation rates vary widely from galaxy to galaxy, with the rates in starburst galaxies being 10 - 100 times those in quiescent spiral galaxies. Far infrared spectroscopy of star-forming galaxies shows that the interstellar pressure increases with star formation rate. The structure of the interstellar medium in starburst galaxies is quite different from that of quiescent galaxies - much of the mass and volume are in HII regions and photodissociation regions. The size distribution of dust grains seems to depend on environment; small grains are abundant in the diffuse interstellar medium but not in dense molecular star forming regions. Quiescent spiral and elliptical galaxies contain a significant population of small grains, but starburst galaxies do not. Dwarf irregular galaxies also seem to contain few small grains; this may be the result of the higher UV flux in these galaxies. The star forming regions in dwarf irregulars also have a higher ratio of atomic to molecular gas than do those in the Galaxy. These results show that the ISM in galaxies of different morphological types reaches different equilibria, resulting in different modes of star formation and global galaxy evolution.

  3. Mapping the interstellar medium in galaxies with Herschel/SPIRE

    CERN Document Server

    Eales, S A; Wilson, C D; Bendo, G J; Cortese, L; Pohlen, M; Boselli, A; Gomez, H L; Auld, R; Baes, M; Barlow, M J; Bock, J J; Bradford, M; Buat, V; Castro-Rodriguez, N; Chanial, P; Charlot, S; Ciesla, L; Clements, D L; Cooray, A; Cormier, D; Davies, J I; Dwek, E; Elbaz, D; Galametz, M; Galliano, F; Gear, W K; Glenn, J; Griffin, M; Hony, S; Isaak, K G; Levenson, L R; Lu, N; Madden, S; O'Halloran, B; Okumura, K; Oliver, S; Page, M J; Panuzzo, P; Papageorgiou, A; Parkin, T J; Perez-Fournon, I; Rangwala, N; Rigby, E E; Roussel, H; Rykala, A; Sacchi, N; Sauvage, M; Schulz, B; Schirm, M R P; Spinoglio, L; Srinivasan, S; Stevens, J A; Symeonidis, M; Trichas, M; Vaccari, M; Vigroux, L; Wozniak, H; Wright, G S; Zeilinger, W W

    2010-01-01

    The standard method of mapping the interstellar medium in a galaxy, by observing the molecular gas in the CO 1-0 line and the atomic gas in the 21-cm line, is largely limited with current telescopes to galaxies in the nearby universe. In this letter, we use SPIRE observations of the galaxies M99 and M100 to explore the alternative approach of mapping the interstellar medium using the continuum emission from the dust. We have compared the methods by measuring the relationship between the star-formation rate and the surface density of gas in the galaxies. We find the two methods give relationships with a similar dispersion, confirming that observing the continuum emission from the dust is a promising method of mapping the interstellar medium in galaxies.

  4. The Interstellar Medium in External Galaxies: Summaries of contributed papers

    Science.gov (United States)

    Hollenbach, David J. (Editor); Thronson, Harley A., Jr. (Editor)

    1990-01-01

    The Second Wyoming Conference entitled, The Interstellar Medium in External Galaxies, was held on July 3 to 7, 1989, to discuss the current understanding of the interstellar medium in external galaxies and to analyze the basic physical processes underlying interstellar phenomena. The papers covered a broad range of research on the gas and dust in external galaxies and focused on such topics as the distribution and morphology of the atomic, molecular, and dust components; the dynamics of the gas and the role of the magnetic field in the dynamics; elemental abundances and gas depletions in the atomic and ionized components; cooling flows; star formation; the correlation of the nonthermal radio continuum with the cool component of the interstellar medium; the origin and effect of hot galactic halos; the absorption line systems seen in distant quasars; and the effect of galactic collisions.

  5. The crystalline fraction of interstellar silicates in starburst galaxies

    CERN Document Server

    Kemper, F; Woods, Paul M

    2010-01-01

    We present a model using the evolution of the stellar population in a starburst galaxy to predict the crystallinity of the silicates in the interstellar medium of this galaxy. We take into account dust production in stellar ejecta, and amorphisation and destruction in the interstellar medium and find that a detectable amount of crystalline silicates may be formed, particularly at high star formation rates, and in case supernovae are efficient dust producers. We discuss the effect of dust destruction and amorphisation by supernovae, and the effect of a low dust-production efficiency by supernovae, and find that when taking this into account, crystallinity in the interstellar medium becomes hard to detect. Levels of 6.5-13% crystallinity in the interstellar medium of starburst galaxies have been observed and thus we conclude that not all these crystalline silicates can be of stellar origin, and an additional source of crystalline silicates associated with the Active Galactic Nucleus must be present.

  6. Dark matter properties implied by gamma ray interstellar emission models

    Science.gov (United States)

    Balázs, Csaba; Li, Tong

    2017-02-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. To trivially respect flavor constraints, we only couple the mediator to third generation fermions. Using this theoretical hypothesis, and the Fermi residuals, we calculate Bayesian evidences, including Fermi-LAT exclusion limits from 15 dwarf spheroidal galaxies as well. Our evidence ratios single out one of the Fermi scenarios as most compatible with the simplified dark matter model. In this scenario the dark matter (mediator) mass is in the 25-200 (1-1000) GeV range and its annihilation is dominated by bottom quark final state. Our conclusion is that the properties of dark matter extracted from gamma ray data are highly sensitive to the modeling of the interstellar emission.

  7. Detection of organic matter in interstellar grains.

    Science.gov (United States)

    Pendleton, Y J

    1997-06-01

    Star formation and the subsequent evolution of planetary systems occurs in dense molecular clouds, which are comprised, in part, of interstellar dust grains gathered from the diffuse interstellar medium (DISM). Radio observations of the interstellar medium reveal the presence of organic molecules in the gas phase and infrared observational studies provide details concerning the solid-state features in dust grains. In particular, a series of absorption bands have been observed near 3.4 microns (approximately 2940 cm-1) towards bright infrared objects which are seen through large column densities of interstellar dust. Comparisons of organic residues, produced under a variety of laboratory conditions, to the diffuse interstellar medium observations have shown that aliphatic hydrocarbon grains are responsible for the spectral absorption features observed near 3.4 microns (approximately 2940 cm-1). These hydrocarbons appear to carry the -CH2- and -CH3 functional groups in the abundance ratio CH2/CH3 approximately 2.5, and the amount of carbon tied up in this component is greater than 4% of the cosmic carbon available. On a galactic scale, the strength of the 3.4 microns band does not scale linearly with visual extinction, but instead increases more rapidly for objects near the Galactic Center. A similar trend is noted in the strength of the Si-O absorption band near 9.7 microns. The similar behavior of the C-H and Si-O stretching bands suggests that these two components may be coupled, perhaps in the form of grains with silicate cores and refractory organic mantles. The ubiquity of the hydrocarbon features seen in the near infrared near 3.4 microns throughout out Galaxy and in other galaxies demonstrates the widespread availability of such material for incorporation into the many newly forming planetary systems. The similarity of the 3.4 microns features in any organic material with aliphatic hydrocarbons underscores the need for complete astronomical observational

  8. Dark matter properties implied by gamma ray interstellar emission models

    CERN Document Server

    Balázs, Csaba

    2016-01-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion limits from 15 dwarf spheroidal galaxies as well. Our Bayes factors single out four of the Fermi scenarios as compatible with the simplified dark matter model. In the most preferred scenario the dark matter (mediator) mass is in the 100-500 (1-200) GeV range and its annihilation is dominated by top quark final state. Less preferred but still plausible is annihilation into b\\bar{b} and tau^+tau^- final states with an order of magnitude lower dark matter mass. Our conclusion is that the properties of dark matter extracted ...

  9. Water in the interstellar media of galaxies

    CERN Document Server

    van der Tak, Floris

    2015-01-01

    This paper reviews recent observations of water in Galactic interstellar clouds and nearby galactic nuclei. Two results are highlighted: (1) Multi-line H$_2$O mapping of the Orion Bar shows that the water chemistry in PDRs is driven by photodissociation and -desorption, unlike in star-forming regions. (2) High-resolution spectra of H$_2$O and its ions toward 5 starburst / AGN systems reveal low ionization rates, unlike as found from higher-excitation lines. We conclude that the chemistry of water strongly depends on radiation environment, and that the ionization rates of interstellar clouds decrease by at least 10 between galactic nuclei and disks.

  10. The interstellar dust reservoir: SPICA's view on dust production and the interstellar medium in galaxies

    CERN Document Server

    Kemper, F; Jones, O C; Srinivasan, S

    2016-01-01

    Typical galaxies emit about one third of their energy in the infrared. The origin of this emission reprocessed starlight absorbed by interstellar dust grains and reradiated as thermal emission in the infrared. In particularly dusty galaxies, such as starburst galaxies, the fraction of energy emitted in the infrared can be as high as 90%. Dust emission is found to be an excellent tracer of the beginning and end stages of a star's life, where dust is being produced by post-main-sequence stars, subsequently added to the interstellar dust reservoir, and eventually being consumed by star and planet formation. This work reviews the current understanding of the size and properties of this interstellar dust reservoir, by using the Large Magellanic Cloud as an example, and what can be learned about the dust properties and star formation in galaxies from this dust reservoir, using SPICA, building on previous work performed with the Herschel and Spitzer Space Telescopes, as well as the Infrared Space Observatory.

  11. Hydrostatic equilibrium of interstellar gas and magnetic fields in the 6 kpc region of the galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, B.; Spreckels, H.; Thielheim, K.O.

    1980-01-01

    A two-component gas model is applied to the vertical hydrogen distribution in the 6 kpc region of the Galaxy. Galactic gravitational field and interstellar magnetic field determination of the dynamics of interstellar gas is reviewed.

  12. Dark matter in the Galaxy

    OpenAIRE

    Bilic, Neven; Tupper, Gary B.; Viollier, Raoul D.

    2002-01-01

    After a brief introduction to standard cosmology and the dark matter problem in the the Universe, we consider a self-gravitating noninteracting fermion gas at nonzero temperature as a model for the dark matter halo of the Galaxy. This fermion gas model is then shown to imply the existence of a supermassive compact dark object at the Galactic center.

  13. The chemistry of interstellar HnO+ beyond the Galaxy

    CERN Document Server

    van der Tak, Floris

    2010-01-01

    The astrochemistry of the HnO+ (n=1..3) ions is important as the main gas-phase formation route for water, and as tracer of the interstellar ionization rate by cosmic rays and other processes. While interstellar H3O+ has been known since the early 1990's, interstellar OH+ and H2O+ have only recently been detected using the Herschel space observatory and also from the ground. This paper reviews detections of HnO+ toward external galaxies and compares with ground-based work. The similarities and differences of the HnO+ chemistry within the Galaxy and beyond are discussed. Special attention is given to the low H2O/H3O+ ratio in M82 of only 3.3, suggesting rapid H2O photodissociation, and the high apparent OH+ and H2O+ abundances in Mrk 231, suggesting radiative excitation and/or formation pumping. Photodissociation rates for H3O+ and collisional cross-sections for OH+ and H2O+ with H, He and electrons are needed to test these interpretations.

  14. Origins Space Telescope: Interstellar Medium, Milky Way, and Nearby Galaxies

    Science.gov (United States)

    Battersby, Cara; Origins Space Telescope Study Team

    2017-01-01

    The Origins Space Telescope (OST) is the mission concept for the Far-Infrared Surveyor, a study in development by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey. Origins is planned to be a large aperture, actively-cooled telescope covering a wide span of the mid- to far-infrared spectrum. Its imagers and spectrographs will enable a variety of surveys of the sky that will discover and characterize the most distant galaxies, Milky-Way, exoplanets, and the outer reaches of our Solar system. Origins will enable flagship-quality general observing programs led by the astronomical community in the 2030s. The Science and Technology Definition Team (STDT) would like to hear your science needs and ideas for this mission. The team can be contacted at firsurveyor_info@lists.ipac.caltech.edu.This presentation will provide a summary of the science case related to the Interstellar Medium (ISM), the Milky Way, and Nearby Galaxies. Origins will enable a comprehensive view of magnetic fields, turbulence, and the multi-phase ISM; connecting physics at all scales, from galaxies to protostellar cores. With unprecedented sensitivity, Origins will measure and characterize the mechanisms of feedback from star formation and Active Galactic Nuclei (AGN) over cosmic time and trace the trail of water from interstellar clouds, to protoplanetary disks, to Earth itself in order to understand the abundance and availability of water for habitable planets.

  15. On the Energy Required to Eject Processed Matter from Galaxies

    CERN Document Server

    Tenorio-Tagle, G

    2001-01-01

    We evaluate the minimum energy input rate that starbursts require for expelling their newly processed matter from their host galaxies. Special attention is given to the pressure caused by the environment in which a galaxy is situated, as well as to the intrinsic rotation of the gaseous component. We account for these factors and for a massive dark matter distribution, and develop a self-consistent solution for the interstellar matter gas distribution. Our results are in excellent agreement with the results of Mac Low & Ferrara (1999) for galaxies with a flattened disk-like ISM density distribution and a low intergalactic gas pressure ($P_{IGM}/k$ $\\leq $ 1 cm$^{-3}$ K). However, our solution also requires a much larger energy input rate threshold when one takes into consideration both a larger intergalactic pressure and the possible existence of a low-density, non-rotating, extended gaseous halo component.

  16. At the heart of the matter: the origin of bulgeless dwarf galaxies and Dark Matter cores

    CERN Document Server

    Governato, Fabio; Mayer, Lucio; Brooks, Alyson; Rhee, George; Wadsley, James; Jonsson, Patrik; Willman, Beth; Stinson, Greg; Quinn, Thomas; Madau, Piero

    2009-01-01

    For almost two decades the properties of "dwarf" galaxies have challenged the Cold Dark Matter (CDM) paradigm of galaxy formation. Most observed dwarf galaxies consists of a rotating stellar disc embedded in a massive DM halo with a near constant-density core. Yet, models based on the CDM scenario invariably form galaxies with dense spheroidal stellar "bulges" and steep central DM profiles, as low angular momentum baryons and DM sink to the center of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different DM particle candidate. This Letter presents new hydrodynamical simulations in a Lambda$CDM framework where analogues of dwarf galaxies, bulgeless and with a shallow central DM profile, are formed. This is achieved by resolving the inhomogeneous interstellar medium, resultin...

  17. Estimating interstellar extinction toward to elliptical galaxies and star clusters

    Science.gov (United States)

    Amores, E. B.; Lépine, J. R. D.

    2006-08-01

    The ability to estimate interstellar extinction is essential for color corrections and distance calculations of all sorts of astronomical objects being fundamental for galactic structure studies. We performed comparisons of interstellar extinction models by Amores & Lépine ( 2005). These models are based on the hypothesis that gas and dust are homogeneously mixed, and make use of the dust-to gas ratio. The gas density distribution used in the models is obtained from the gas large scale surveys: Berkeley and Parkes HI surveys and from the Columbia University CO survey. In the present work, we compared these models with extinction predictions of elliptical galaxies (gE) and star clusters. We used the similar sample of gE galaxies proposed by Burstein for the comparison between the extinction calculation methods of Burstein & Heiles (1978, 1982) and of Schlegel et al. (1998) extending the comparison to our models. We found rms differences equal to 0.0179 and 0.0189 mag respectively, in the comparison of the predictions of our "model A" with the two methods mentioned. The comparison takes into account the "zero points" introduced by Burstein. The correlation coefficient obtained in the comparison is around 0.85. These results bring to light that our models can be safely used for the estimation of extinction in our Galaxy for extragalactic work, as an alternative method to the BH and SFD predictions. In the comparison with the globular clusters we found rms differences equal to 0.32 and 0.30 for our models A and S, respectively. For the open clusters we made comparisons using different samples and the rms differences were around 0.25.

  18. Estimating interstellar extinction towards elliptical galaxies and star clusters.

    Science.gov (United States)

    de Amôres, E. B.; Lépine, J. R. D.

    The ability to estimate interstellar extinction is essential for color corrections and distance calculations of all sorts of astronomical objects being fundamental for galactic structure studies. We performed comparisons of interstellar extinction models by Amores & Lépine (2005) that are available at: http://www.astro.iag.usp.br/\\symbol{126}amores. These models are based on the hypothesis that gas and dust are homogeneously mixed, and make use of the dust-to gas ratio. The gas density distribution used in the models is obtained from the gas large scale surveys: Berkeley and Parkes HI surveys and from the Columbia University CO survey. In the present work, we compared these models with extinction predictions of elliptical galaxies (gE) and star clusters. We used the similar sample of gE galaxies proposed by Burstein for the comparison between the extinction calculation methods of Burstein & Heiles (1978, 1982) and of Schlegel et al. (1998) extending the comparison to our models. We found rms differences equal to 0.0179 and 0.0189 mag respectively, in the comparison of the predictions of our "model A" with the two methods mentioned. The comparison takes into account the "zero points" introduced by Burstein. The correlation coefficient obtained in the comparison is around 0.85. These results bring to light that our models can be safely used for the estimation of extinction in our Galaxy for extragalactic work, as an alternative method to the BH and SFD predictions. In the comparison with the globular clusters we found rms differences equal to 0.32 and 0.30 for our models A and S, respectively. For the open clusters we made comparisons using different samples and the rms differences were around 0.25.

  19. The interstellar medium in Andromeda's dwarf spheroidal galaxies - I. Content and origin of the interstellar dust

    Science.gov (United States)

    De Looze, Ilse; Baes, Maarten; Bendo, George J.; Fritz, Jacopo; Boquien, Médéric; Cormier, Diane; Gentile, Gianfranco; Kennicutt, Robert C.; Madden, Suzanne C.; Smith, Matthew W. L.; Young, Lisa

    2016-07-01

    Dwarf spheroidal galaxies are among the most numerous galaxy population in the Universe, but their main formation and evolution channels are still not well understood. The three dwarf spheroidal satellites (NGC 147, NGC 185, and NGC 205) of the Andromeda galaxy are characterized by very different interstellar medium properties, which might suggest them being at different galaxy evolutionary stages. While the dust content of NGC 205 has been studied in detail in an earlier work, we present new Herschel dust continuum observations of NGC 147 and NGC 185. The non-detection of NGC 147 in Herschel SPIRE maps puts a strong constraint on its dust mass (≤128^{+124}_{-68} M⊙). For NGC 185, we derive a total dust mass Md = 5.1±1.0 × 103 M⊙, which is a factor of ˜2-3 higher than that derived from ISO and Spitzer observations and confirms the need for longer wavelength observations to trace more massive cold dust reservoirs. We, furthermore, estimate the dust production by asymptotic giant branch (AGB) stars and supernovae (SNe). For NGC 147, the upper limit on the dust mass is consistent with expectations of the material injected by the evolved stellar population. In NGC 185 and NGC 205, the observed dust content is one order of magnitude higher compared to the estimated dust production by AGBs and SNe. Efficient grain growth, and potentially longer dust survival times (3-6 Gyr) are required to account for their current dust content. Our study confirms the importance of grain growth in the gas phase to account for the current dust reservoir in galaxies.

  20. The galactic interstellar medium

    CERN Document Server

    Burton, WB; Genzel, R

    1992-01-01

    This volume contains the papers of three extended lectures addressing advanced topics in astronomy and astrophysics. The topics discussed include the most recent observational data on interstellar matter outside our galaxy and the physics and chemistry of molecular clouds.

  1. Dark matter properties implied by gamma ray interstellar emission models

    OpenAIRE

    Balázs, Csaba; Li, Tong

    2016-01-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion...

  2. Connecting The Interstellar Gas And Dust Properties Of Distant Galaxies

    Science.gov (United States)

    Kulkarni, Varsha

    The properties of interstellar gas and dust in distant galaxies are fundamental parameters in constraining galaxy evolution models. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous background quasars, provide invaluable tools to directly study gas and dust in distant normal galaxies. Recent studies of QASs have found interesting trends in both gas and dust properties, such as correlations in metallicity with redshift and dust depletions. Our Spitzer spectroscopic studies also indicate that silicate dust grains are present in QASs, and in fact, at a level higher than expected for diffuse gas in the Milky Way. Moreover, the silicate dust grains in these distant galaxies may be substantially more crystalline than those in the Milky Way interstellar medium. We now propose a comprehensive study of the gas and dust properties of all QASs with strong Ly-alpha and/or metal absorption lines that have adequate archival IR data to probe the study of dust. Our analysis will include data primarily from the NASA-supported Spitzer, Herschel, HST, and Keck Observatory archives, along with a small amount of VLT/SDSS archival data. Our specific goals are as follows: (1) We will measure a large range of metal absorption lines in high-resolution quasar spectra from Keck, HST, and VLT archives to uniformly determine the metallicity, dust depletions, ionization, and star formation rates in the foreground QASs. In particular, we will study the variations in these quantities with gas velocity, using Voigt profile fitting techniques to determine the velocity structure. This analysis will also allow us to quantify the kinematics of the absorbing gas. (2) We will use archival Spitzer IRS quasar spectra to search for and measure the strengths of the 10 and 18 micron silicate dust absorption features for a much larger sample of QASs than previously studied. (3) We will fit the observed silicate absorption features in the Spitzer archival

  3. Aspects of the interstellar medium in starburst galaxies

    Science.gov (United States)

    Fanelli, Michael N.

    1990-01-01

    Researchers are engaged in a multifaceted program to investigate the stellar content and star formation history of actively star-forming galaxies. A large body of stellar spectra have been examined to identify spectral features characteristic of specific stellar types. These spectral diagnostics are then calibrated in terms of temperature (spectral type), gravity (luminosity class) and metallicity. The spectral data is compiled into a stellar library whose members represent specific locations in the HR diagram. Through the use of population synthesis techniques, both optimizing and evolutionary approaches, the stellar luminosity function in composite populations can be determined by analysis of their integrated light. Researchers have concentrated on the ultraviolet wavelength region (lambda lambda 1200 to 3200), utilizing the International Ultraviolet Explorer (IUE) archives supplemented by additional observations. In the optical, virtually all stars will contribute to the integrated light. In the ultraviolet however, cool stars will produce negligible flux due to their steep ultraviolet-to-visual continua, greatly simplifying the investigation of the hot component in a composite population. The researchers' initial stellar library has been applied to several blue compact galaxies, (BCGs), a class of starburst galaxy which is UV luminous. BCGs possess a complex interstellar medium which affects the emergent stellar continuum in several ways. This presents a challenge to the stellar analysis but affords insight into the properties of the gas and dust from which the massive OB stars have formed. The optimizing synthesis method solves for the stellar luminosity function and extinction simultaneously. This therefore provides an independent measure of the extinction affecting the hot population component. Despite the rise of the reddening law towards the ultraviolet, BCGs are found to be brighter in the ultraviolet than expected.

  4. Measuring dark matter by modeling interacting galaxies

    CERN Document Server

    Petsch, H P; Theis, Ch

    2009-01-01

    The dark matter content of galaxies is usually determined from galaxies in dynamical equilibrium, mainly from rotationally supported galactic components. Such determinations restrict measurements to special regions in galaxies, e.g. the galactic plane(s), whereas other regions are not probed at all. Interacting galaxies offer an alternative, because extended tidal tails often probe outer or off-plane regions of galaxies. However, these systems are neither in dynamical equilibrium nor simple, because they are composed of two or more galaxies, by this increasing the associated parameter space.We present our genetic algorithm based modeling tool which allows to investigate the extended parameter space of interacting galaxies. From these studies, we derive the dynamical history of (well observed) galaxies. Among other parameters we constrain the dark matter content of the involved galaxies. We demonstrate the applicability of this strategy with examples ranging from stellar streams around theMilkyWay to extended ...

  5. Dark Matter and Galaxy Formation

    Science.gov (United States)

    Primack, Joel R.

    2009-12-01

    The four lectures that I gave in the XIII Ciclo de Cursos Especiais at the National Observatory of Brazil in Rio in October 2008 were (1) a brief history of dark matter and structure formation in a ΛCDM universe; (2) challenges to ΛCDM on small scales: satellites, cusps, and disks; (3) data on galaxy evolution and clustering compared with simulations; and (4) semi-analytic models. These lectures, themselves summaries of much work by many people, are summarized here briefly. The slides [1] contain much more information.

  6. Dark Matter and Galaxy Formation

    CERN Document Server

    Primack, Joel R

    2009-01-01

    The four lectures that I gave in the XIII Ciclo de Cursos Especiais at the National Observatory of Brazil in Rio in October 2008 were (1) a brief history of dark matter and structure formation in a LambdaCDM universe; (2) challenges to LambdaCDM on small scales: satellites, cusps, and disks; (3) data on galaxy evolution and clustering compared with simulations; and (4) semi-analytic models. These lectures, themselves summaries of much work by many people, are summarized here briefly.

  7. ASTRO-H White Paper - High Resolution Spectroscopy of Interstellar and Circumgalactic Gas in the Milky Way and Other Galaxies

    CERN Document Server

    Paerels, F; Anabuki, N; Costantini, E; de Vries, C; Fujimoto, R; Hornschemeier, A; Iizuka, R; Kilbourne, C; Konami, S; LaMassa, S; Loewenstein, M; McCammon, D; Matsushita, K; McNamara, B; Mitsuishi, I; Nagino, R; Nakagawa, T; Porter, S; Sakai, K; Smith, R K; Takei, Y; Tsuru, T; Uchiyama, H; Yamaguchi, H; Yamauchi, S

    2014-01-01

    We describe the potential of high resolution imaging spectroscopy with the SXS on ASTRO-H to advance our understanding of the interstellar- and circumgalactic media of our own Galaxy, and other galaxies. Topics to be addressed range from absorption spectroscopy of dust in the Galactic interstellar medium, to observations to constrain the total mass-, metal-, and energy flow out of starburst galaxies.

  8. Missing dark matter in dwarf galaxies?

    CERN Document Server

    Oman, Kyle A; Sales, Laura V; Fattahi, Azadeh; Frenk, Carlos S; Sawala, Till; Schaller, Matthieu; White, Simon D M

    2016-01-01

    We use cosmological hydrodynamical simulations of the APOSTLE project to examine the fraction of baryons in $\\Lambda$CDM haloes that collect into galaxies. This `galaxy formation efficiency' correlates strongly and with little scatter with halo mass, dropping steadily towards dwarf galaxies. The baryonic mass of a galaxy may thus be used to place a lower limit on total halo mass and, consequently, on its asymptotic maximum circular velocity. A number of dwarfs seem to violate this constraint, having baryonic masses up to ten times higher than expected from their rotation speeds, or, alternatively, rotating at only half the speed expected for their mass. Taking the data at face value, either these systems have formed galaxies with extraordinary efficiency - highly unlikely given their shallow potential wells - or they inhabit haloes with extreme deficits in their dark matter content. This `missing dark matter' is reminiscent of the inner mass deficits of galaxies with slowly-rising rotation curves, but extends...

  9. Tiny galaxies help unravel dark matter mystery

    CERN Multimedia

    O'Hanlon, Larry

    2007-01-01

    "The 70-year effort to unravel the mysteries of dark matter just got a big boost from some very puny galaxies. In the pas few years, a score of dwarf galaxies have been discovered hanging about the fringes of the Milky way. Now new measurements of the few stars int hese dwarfs reveal them to be dark mater distilleries, with upwards of 1'000 times more dark than normal matter." (3 pages)

  10. The dark matter of galaxy voids

    Science.gov (United States)

    Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

    2014-03-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

  11. The cold interstellar medium - An HI view of spiral galaxies

    NARCIS (Netherlands)

    Sancisi, R; Bender, R; Davies, RL

    1996-01-01

    An HI view of spiral galaxies is presented. In the first part the standard picture of isolated, normal spiral galaxies is briefly reviewed. In the second part attention is drawn to all those phenomena, such as tidal interactions, accretion and mergers, that depend on the galaxy environment and seem

  12. Interstellar Extinction

    Science.gov (United States)

    Gontcharov, G. A.

    2016-12-01

    This review describes our current understanding of interstellar extinction. This differ substantially from the ideas of the 20th century. With infrared surveys of hundreds of millions of stars over the entire sky, such as 2MASS, SPITZER-IRAC, and WISE, we have looked at the densest and most rarefied regions of the interstellar medium at distances of a few kpc from the Sun. Observations at infrared and microwave wavelengths, where the bulk of the interstellar dust absorbs and radiates, have brought us closer to an understanding of the distribution of the dust particles on scales of the Galaxy and the universe. We are in the midst of a scientific revolution in our understanding of the interstellar medium and dust. Progress in, and the key results of, this revolution are still difficult to predict. Nevertheless, (a) a physically justified model has been developed for the spatial distribution of absorbing material over the nearest few kiloparsecs, including the Gould belt as a dust container, which gives an accurate estimate of the extinction for any object just by its galactic coordinates. It is also clear that (b) the interstellar medium contains roughly half the mass of matter in the galactic vicinity of the solar system (the other half is made up of stars, their remnants, and dark matter) and (c) the interstellar medium and, especially, dust, differ substantially in different regions of space and deep space cannot be understood by only studying near space.

  13. Probing the interstellar dust in galaxies over >10 Gyr of cosmic history

    Science.gov (United States)

    Kulkarni, Varsha P.; Aller, Monique C.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam

    2016-11-01

    Dust has a profound effect on the physics and chemistry of the interstellar gas in galaxies and on the appearance of galaxies. Understanding the cosmic evolution of dust with time is therefore crucial for understanding the evolution of galaxies. Despite the importance of interstellar dust, very little is known about its nature and composition in distant galaxies. We summarize the results of our ongoing programs using observations of distant quasars to obtain better constraints on dust grains in foreground galaxies that happen to lie along the quasar sightlines. These observations consist of a combination of mid-infrared data obtained with the Spitzer Space Telescope and optical/UV data obtained with ground-based telescopes and/or the Hubble Space Telescope. The mid-IR data target the 10 μm and 18 μm silicate absorption features, while the optical/UV data allow determinations of element depletions, extinction curves, 2175 Å bumps, etc. Measurements of such properties in absorption-selected galaxies with redshifts ranging from z 0 to z > 2 provide constraints on the evolution of interstellar dust over the past > 10 Gyr . The optical depth of the 10 μm silicate absorption feature (τ10) in these galaxies is correlated with the amount of reddening along the sightline. But there are indications (e.g., based on the τ10 / E(B - V) ratio and possible grain crystallinity) that the dust in these distant galaxies differs in structure and composition from the dust in the Milky Way and the Magellanic Clouds. We briefly discuss the implications of these results for the evolution of galaxies and their star formation history.

  14. Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust

    Science.gov (United States)

    Messenger, Scott; Nakamura-Messenger, Keiko

    2015-01-01

    Interplanetary dust particles (IDPs) collected in the Earth's stratosphere derive from collisions among asteroids and by the disruption and outgassing of short-period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP-IDPs have been linked to cometary parent bodies by their mineralogy, textures, C-content, and dynamical histories. CP-IDPs are fragile, fine-grained (less than um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP-IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP-IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10-100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub-um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub-um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild-2 samples returned by the Stardust mission.

  15. Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows.

    Science.gov (United States)

    Governato, F; Brook, C; Mayer, L; Brooks, A; Rhee, G; Wadsley, J; Jonsson, P; Willman, B; Stinson, G; Quinn, T; Madau, P

    2010-01-14

    For almost two decades the properties of 'dwarf' galaxies have challenged the cold dark matter (CDM) model of galaxy formation. Most observed dwarf galaxies consist of a rotating stellar disk embedded in a massive dark-matter halo with a near-constant-density core. Models based on the dominance of CDM, however, invariably form galaxies with dense spheroidal stellar bulges and steep central dark-matter profiles, because low-angular-momentum baryons and dark matter sink to the centres of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present-day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different dark-matter particle candidate. Here we report hydrodynamical simulations (in a framework assuming the presence of CDM and a cosmological constant) in which the inhomogeneous interstellar medium is resolved. Strong outflows from supernovae remove low-angular-momentum gas, which inhibits the formation of bulges and decreases the dark-matter density to less than half of what it would otherwise be within the central kiloparsec. The analogues of dwarf galaxies-bulgeless and with shallow central dark-matter profiles-arise naturally in these simulations.

  16. The Interstellar Medium In Galaxies Seen A Billion Years After The Big Bang

    CERN Document Server

    Capak, P L; Jones, G; Casey, C M; Riechers, D; Sheth, K; Carollo, C M; Ilbert, O; Karim, A; LeFevre, O; Lilly, S; Scoville, N; Smolcic, V; Yan, L

    2015-01-01

    Evolution in the measured rest frame ultraviolet spectral slope and ultraviolet to optical flux ratios indicate a rapid evolution in the dust obscuration of galaxies during the first 3 billion years of cosmic time (z>4). This evolution implies a change in the average interstellar medium properties, but the measurements are systematically uncertain due to untested assumptions, and the inability to measure heavily obscured regions of the galaxies. Previous attempts to directly measure the interstellar medium in normal galaxies at these redshifts have failed for a number of reasons with one notable exception. Here we report measurements of the [CII] gas and dust emission in 9 typical (~1-4L*) star-forming galaxies ~1 billon years after the big bang (z~5-6). We find these galaxies have >12x less thermal emission compared with similar systems ~2 billion years later, and enhanced [CII] emission relative to the far-infrared continuum, confirming a strong evolution in the interstellar medium properties in the early u...

  17. Local Analogs for High-redshift Galaxies: Resembling the Physical Conditions of the Interstellar Medium in High-redshift Galaxies

    CERN Document Server

    Bian, Fuyan; Dopita, Michael; Juneau, Stephanie

    2016-01-01

    We present a sample of local analogs for high-redshift galaxies selected in the Sloan Digital Sky Survey (SDSS). The physical conditions of the interstellar medium (ISM) in these local analogs resemble those in high-redshift galaxies. These galaxies are selected based on their positions in the [OIII]/H$\\beta$ versus [NII]/H$\\alpha$ nebular emission-line diagnostic diagram. We show that these local analogs share similar physical properties with high-redshift galaxies, including high specific star formation rates (sSFRs), flat UV continuums and compact galaxy sizes. In particular, the ionization parameters and electron densities in these analogs are comparable to those in $z\\simeq2-3$ galaxies, but higher than those in normal SDSS galaxies by $\\simeq$0.6~dex and $\\simeq$0.9~dex, respectively. The mass-metallicity relation (MZR) in these local analogs shows $-0.2$~dex offset from that in SDSS star-forming galaxies at the low mass end, which is consistent with the MZR of the $z\\sim2-3$ galaxies. We compare the lo...

  18. The dark matter of galaxy voids

    CERN Document Server

    Sutter, P M; Wandelt, Benjamin D; Weinberg, David H; Warren, Michael S

    2013-01-01

    How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter, and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ~20%, they have somewhat shallower density profiles, and they have centers offset by ~0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though ...

  19. The Interstellar Medium and Star Formation of Nearby, Low-Mass Galaxies

    Science.gov (United States)

    Warren, Steven Ray

    This thesis presents four different studies of the interstellar medium (ISM) and stellar content of ˜40 nearby (D ≲ 4 Mpc), low-mass galaxies. We aim to address two fundamental questions: "How do stellar processes effect the ISM in low-mass galaxies?" and "What are the local gas conditions which lead to molecular cloud formation?". Much of the data presented here come from our survey the "Very Large Array - Advanced Camera for Surveys Nearby Galaxy Survey Treasury" (VLA-ANGST). VLA-ANGST is a targeted atomic hydrogen (H I) emission line survey directed towards 35 low-mass galaxies selected from the ANGST Hubble Space Telescope (HST) galaxy sample of the nearby universe. The VLA-ANGST project is the largest survey of its kind, demanding nearly 600 hours of VLA observing time. This unprecedented amount of observing time gives us data which has long lasting legacy value for its wealth of high resolution and high sensitivity information on the H I gas content and dynamics in a large sample of nearby, low-mass galaxies. H I data from the VLA-ANGST project will be used to explore the interactions between the gas and stellar content as well as trace the underlying dark matter distribution. Combining the H I and HST data with other tracers of recent star formation (e.g., emission processes from far ultraviolet star light, dust in the infrared, and carbon monoxide in the submillimeter) provides a comprehensive census of each galaxy, useful for understanding their evolution. We investigate the role of multiple generations of star formation in the formation of large, kiloparsec scale cavities observed in the global H I distributions of five nearby, low mass galaxies. The small gravitational potential wells of some low-mass galaxies allow the outflow of energy from stellar processes (e.g., winds, supernovae, etc.) to help shape their gas distributions. We find that stellar processes produce ample energy (at least an order of magnitude or more) to have been the dominant

  20. Exploring the Interstellar Media of Optically Compact Dwarf Galaxies

    CERN Document Server

    Most, Hans P; Salzer, John J; Rosenberg, Jessica J; Engstrom, Eric; Fliss, Palmer

    2013-01-01

    We present new Very Large Array HI spectral line, archival Sloan Digital Sky Survey, and archival Spitzer Space Telescope imaging of eight star-forming blue compact dwarf galaxies that were selected to be optically compact (optical radii less than 1 kpc). These systems have faint blue absolute magnitudes (M_B >= -17), ongoing star formation (based on emission-line selection by the H alpha or [OIII] lines), and are nearby (mean velocity = 3315 km/s = 45 Mpc). One galaxy in the sample, ADBS 113845+2008, is found to have an HI halo that extends 58 r-band scale lengths from its stellar body. In contrast, the rest of the sample galaxies have HI radii to optical-scale-length ratios ranging from 9.3 to 26. The size of the HI disk in the "giant disk" dwarf galaxy ADBS 113845+2008 appears to be unusual as compared to similarly compact stellar populations.

  1. Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

    Science.gov (United States)

    Aller, Monique C.; Dwek, Eliahu; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim; hide

    2016-01-01

    Gas and dust grains are fundamental components of the interstellar medium and significantly impact many of the physical processes driving galaxy evolution, such as star-formation, and the heating, cooling, and ionization of the interstellar material. Quasar absorption systems (QASs), which trace intervening galaxies along the sightlines to luminous quasars, provide a valuable tool to directly study the properties of the interstellar gas and dust in distant, normal galaxies. We have established the presence of silicate dust grains in at least some gas-rich QASs, and find that they exist at higher optical depths than expected for diffuse gas in the Milky Way. Differences in the absorption feature shapes additionally suggest variations in the silicate dust grain properties, such as in the level of grain crystallinity, from system-to-system. We present results from a study of the gas and dust properties of QASs with adequate archival IR data to probe the silicate dust grain properties. We discuss our measurements of the strengths of the 10 and 18 micron silicate dust absorption features in the QASs, and constraints on the grain properties (e.g., composition, shape, crystallinity) based on fitted silicate profile templates. We investigate correlations between silicate dust abundance, reddening, and gas metallicity, which will yield valuable insights into the history of star formation and chemical enrichment in galaxies.

  2. TANGO I: Interstellar medium in nearby radio galaxies. Molecular gas

    Science.gov (United States)

    Ocaña Flaquer, B.; Leon, S.; Combes, F.; Lim, J.

    2010-07-01

    Context. Powerful radio-AGN are hosted by massive elliptical galaxies that are usually very poor in molecular gas. Nevertheless, gas is needed at their very center to feed the nuclear activity. Aims: We study the molecular gas properties (i.e., mass, kinematics, distribution, origin) of these objects, and compare them with results for other known samples. Methods: At the IRAM-30m telescope, we performed a survey of the CO(1-0) and CO(2-1) emission from the most powerful radio galaxies of the Local Universe, selected only on the basis of their radio continuum fluxes. Results: The main result of our survey is that the molecular gas content of these galaxies is very low compared to spiral or FIR-selected galaxies. The median value of the molecular gas mass, including detections and upper limits, is 2.2 × 108 M⊙. When separated into FR-I and FR-II types, a difference in their H2 masses is found. The median value of FR-I galaxies is about 1.9 × 108 M⊙ and higher for FR-II galaxies, at about 4.5 × 108 M⊙. Which is probably entirely because of a Malmquist bias. Our results contrast with those of previous surveys, whose targets were mainly selected by means of their FIR emission, implying that we measure higher observed masses of molecular gas. Moreover, the shape of CO spectra suggest that a central molecular gas disk exists in 30% of these radio galaxies, a lower rate than in other active galaxy samples. Conclusions: We find a low level of molecular gas in our sample of radio-selected AGNs, indicating that galaxies do not need much molecular gas to host an AGN. The presence of a molecular gas disk in some galaxies and the wide range of molecular gas masses may be indicative of different origins for the gas, which we can not exclude at present (e.g., minor/major mergers, stellar mass loss, or accretion). Appendices and Figure 15 are only available in electronic form at http://www.aanda.org

  3. Is the interstellar gas of starburst galaxies well mixed?

    CERN Document Server

    Lebouteiller, V; Lebouteiller, Vianney; Kunth, Daniel

    2004-01-01

    The extent to which the ISM in galaxies is well mixed is not yet settled. Measured metal abundances in the diffuse neutral gas of star--forming gas--rich dwarf galaxies are deficient with respect to that of the ionized gas. The reasons, if real, are not clear and need to be based on firm grounds. Far-UV spectroscopy of giant HII regions such as NGC604 in the spiral galaxy M33 using FUSE allows us to investigate possible systematic errors in the metallicity derivation. We still find underabundances of nitrogen, oxygen, argon, and iron in the neutral phase by a factor of~6. This could either be explained by the presence of less chemically evolved gas pockets in the sightlines or by dense clouds out of which HIIregions form. Those could be more metallic than the diffuse medium.

  4. Missing dark matter in dwarf galaxies?

    Science.gov (United States)

    Oman, Kyle A.; Navarro, Julio F.; Sales, Laura V.; Fattahi, Azadeh; Frenk, Carlos S.; Sawala, Till; Schaller, Matthieu; White, Simon D. M.

    2016-08-01

    We use cosmological hydrodynamical simulations of the APOSTLE project along with high-quality rotation curve observations to examine the fraction of baryons in ΛCDM haloes that collect into galaxies. This `galaxy formation efficiency' correlates strongly and with little scatter with halo mass, dropping steadily towards dwarf galaxies. The baryonic mass of a galaxy may thus be used to place a lower limit on total halo mass and, consequently, on its asymptotic maximum circular velocity. A number of observed dwarfs seem to violate this constraint, having baryonic masses up to 10 times higher than expected from their rotation speeds, or, alternatively, rotating at only half the speed expected for their mass. Taking the data at face value, either these systems have formed galaxies with extraordinary efficiency - highly unlikely given their shallow potential wells - or their dark matter content is much lower than expected from ΛCDM haloes. This `missing dark matter' is reminiscent of the inner mass deficit of galaxies with slowly rising rotation curves, but cannot be explained away by star formation-induced `cores' in the dark mass profile, since the anomalous deficit applies to regions larger than the luminous galaxies themselves. We argue that explaining the structure of these galaxies would require either substantial modification of the standard ΛCDM paradigm or else significant revision to the uncertainties in their inferred mass profiles, which should be much larger than reported. Systematic errors in inclination may provide a simple resolution to what would otherwise be a rather intractable problem for the current paradigm.

  5. Dark matter in dwarf galaxies

    OpenAIRE

    Roos, Matts

    2017-01-01

    Although the cusp-core controversy for dwarf galaxies is seen as a problem, I argue that the cored central profiles can be explained by flattened cusps because they suffer from conflicting measurements and poor statistics and because there is a large number of conventional processes that could have flattened them since their creation, none of which requires new physics. Other problems, such as "too big to fail", are not discussed.

  6. Observations of the impact of starbursts on the interstellar medium in dwarf galaxies

    Science.gov (United States)

    Marlowe, Amanda T.; Heckman, Timothy M.; Wyse, Rosemary F. G.; Schommer, Robert

    1995-01-01

    Dwarf galaxies play a crucial role in our understanding of the formation and evolution of galaxies, and the concept of supernova-driven mass outflows is a vital ingredient in theories of the structure and evolution of dwarf galaxies. Despite the theoretical importance of these outflows, there is a very limited amount of direct observational evidence for their existence. We have therefore begun a detailed multi-wave-band search for outflows in dwarf (M(sub B) greater than or = -18) galaxies with extensive recent or ongoing centrally concentrated star formation. We report the first results of this search in the present paper. Observations of the ionized gas in dwarf amorphous galaxies with centrally concentrated populations of massive stars provide evidence for the large-scale expansion of their expansion of their ionized interstellar media. Fabry-Perot H alpha images reveal the presence of kiloparsec-scale 'superbubbles' and filaments which tend to be oriented along the galaxy minor axis. These structures are comparable in size to the chracteristic optical sizes of the galaxies, and dominate the morphology of the galaxies at low surface brightness in H alpha. Since expanding structure of this size and velocity are not observed in all low-mass galaxies with recent or ongoing star formation, we suggest that we are witnessing transient events that likely have a relatively low 'duty cycle' in such galaxies. That is, we argue that the particular galaxies in the present paper have had significantly elevated star formation rates over the past 10(exp 7)-10(exp 8) yr (i.e., these are starburst or young poststarburst systems). This interpretation is consistent with the optical colors and emission-line properties of these galaxies.

  7. Physical Conditions of the Interstellar Medium in Star-forming Galaxies at z1.5

    Science.gov (United States)

    Hayashi, Masao; Ly, Chun; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A.; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-01-01

    We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at z approximately equal to 1.5 in the Subaru Deep Field. These galaxies are selected as [O II] lambda 3727 emitters at z approximately equal to 1.47 and 1.62 from narrow-band imaging. We detect H alpha emission line in 115 galaxies, [O III] lambda 5007 emission line in 45 galaxies, and H Beta, [N II] lambda 6584, and [S II]lambda lambda 6716, 6731 in 13, 16, and 6 galaxies, respectively. Including the [O II] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at z approximately equal to 1.5. We find a tight correlation between H alpha and [O II], which suggests that [O II] can be a good star formation rate (SFR) indicator for galaxies at z approximately equal to 1.5. The line ratios of H alpha / [O II] are consistent with those of local galaxies. We also find that [O II] emitters have strong [O III] emission lines. The [O III]/[O II] ratios are larger than normal star-forming galaxies in the local Universe, suggesting a higher ionization parameter. Less massive galaxies have larger [O III]/[O II] ratios. With evidence that the electron density is consistent with local galaxies, the high ionization of galaxies at high redshifts may be attributed to a harder radiation field by a young stellar population and/or an increase in the number of ionizing photons from each massive star.

  8. EXPLORING THE INTERSTELLAR MEDIA OF OPTICALLY COMPACT DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Most, Hans P.; Cannon, John M.; Engstrom, Eric; Fliss, Palmer [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Salzer, John J. [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); Rosenberg, Jessica L., E-mail: hmost@macalester.edu, E-mail: jcannon@macalester.edu, E-mail: slaz@astro.indiana.edu, E-mail: jrosenb4@gmu.edu [School of Physics, Astronomy, and Computational Science, George Mason University, Fairfax, VA 22030 (United States)

    2013-06-15

    We present new Very Large Array H I spectral line, archival Sloan Digital Sky Survey, and archival Spitzer Space Telescope imaging of eight star-forming blue compact dwarf galaxies that were selected to be optically compact (optical radii <1 kpc). These systems have faint blue absolute magnitudes (M{sub B} {approx}> -17), ongoing star formation (based on emission-line selection by the H{alpha} or [O III] lines), and are nearby (mean velocity = 3315 km s{sup -1} {approx_equal} 45 Mpc). One galaxy in the sample, ADBS 113845+2008, is found to have an H I halo that extends 58 r-band scale lengths from its stellar body. In contrast, the rest of the sample galaxies have H I radii to optical-scale-length ratios ranging from 9.3 to 26. The size of the H I disk in the 'giant disk' dwarf galaxy ADBS 113845+2008 appears to be unusual as compared with similarly compact stellar populations.

  9. Probing the Interstellar Dust in Galaxies over > 10 Gyr of Cosmic History

    CERN Document Server

    Kulkarni, Varsha P; York, Donald G; Welty, Daniel E; Vladilo, Giovanni; Som, Debopam

    2016-01-01

    This article is based on an invited talk given by V. P. Kulkarni at the 8th Cosmic Dust meeting. Dust has a profound effect on the physics and chemistry of the interstellar gas in galaxies and on the appearance of galaxies. Understanding the cosmic evolution of dust with time is therefore crucial for understanding the evolution of galaxies. Despite the importance of interstellar dust, very little is known about its nature and composition in distant galaxies. We summarize the results of our ongoing programs using observations of distant quasars to obtain better constraints on dust grains in foreground galaxies that happen to lie along the quasar sightlines. These observations consist of a combination of mid-infrared data obtained with the Spitzer Space Telescope and optical/UV data obtained with ground-based telescopes and/or the Hubble Space Telescope. The mid-IR data target the 10 $\\mu$m and 18 $\\mu$m silicate absorption features, while the optical/UV data allow determinations of element depletions, extincti...

  10. Physical conditions of the interstellar medium in star-forming galaxies at z~1.5

    CERN Document Server

    Hayashi, Masao; Shimasaku, Kazuhiro; Motohara, Kentaro; Malkan, Matthew A; Nagao, Tohru; Kashikawa, Nobunari; Goto, Ryosuke; Naito, Yoshiaki

    2015-01-01

    We present results from Subaru/FMOS near-infrared (NIR) spectroscopy of 118 star-forming galaxies at $z\\sim1.5$ in the Subaru Deep Field. These galaxies are selected as [OII]$\\lambda$3727 emitters at $z\\approx$ 1.47 and 1.62 from narrow-band imaging. We detect H$\\alpha$ emission line in 115 galaxies, [OIII]$\\lambda$5007 emission line in 45 galaxies, and H$\\beta$, [NII]$\\lambda$6584, and [SII]$\\lambda\\lambda$6716,6731 in 13, 16, and 6 galaxies, respectively. Including the [OII] emission line, we use the six strong nebular emission lines in the individual and composite rest-frame optical spectra to investigate physical conditions of the interstellar medium in star-forming galaxies at $z\\sim$1.5. We find a tight correlation between H$\\alpha$ and [OII], which suggests that [OII] can be a good star formation rate (SFR) indicator for galaxies at $z\\sim1.5$. The line ratios of H$\\alpha$/[OII] are consistent with those of local galaxies. We also find that [OII] emitters have strong [OIII] emission lines. The [OIII]/[...

  11. The interstellar medium and feedback in the progenitors of the compact passive galaxies at z~2

    CERN Document Server

    Williams, Christina C; Lee, Bomee; Tundo, Elena; Mobasher, Bahram; Nayyeri, Hooshang; Ferguson, Henry C; Koekemoer, Anton; Trump, Jonathan R; Cassata, Paolo; Dekel, Avishai; Guo, Yicheng; Lee, Kyoung-Soo; Pentericci, Laura; Bell, Eric F; Castellano, Marco; Finkelstein, Steven L; Fontana, Adriano; Grazian, Andrea; Grogin, Norman; Kocevski, Dale; Koo, David C; Lucas, Ray A; Ravindranath, Swara; Santini, Paola; Vanzella, Eros; Weiner, Benjamin J

    2014-01-01

    The first quenched galaxies (z>2) are both the most massive, and most compact, suggesting a physical connection between high stellar density and efficient, rapid cessation of star-formation. We present rest-frame UV spectra of Lyman-break galaxies (LBGs) at z~3 selected to be candidate progenitors of the quenched galaxies at z~2, compared to other LBGs of similar mass and star-formation rate (non-candidates). We find that candidate progenitors have faster outflow velocities and higher equivalent widths of interstellar absorption lines, implying larger velocity spread among absorbing clouds. Candidates deviate from the relationship between equivalent widths of Lyman-alpha and interstellar absorption lines in that their Lyman-alpha emission remains strong despite high interstellar absorption, possibly indicating that the neutral HI fraction is patchy, such that Lyman-alpha photons can escape. We detect stronger CIV P-Cygni features (emission and absorption) and HeII emission in candidates, indicative of larger ...

  12. Modelling galaxy spectra in presence of interstellar dust-III. From nearby galaxies to the distant Universe

    CERN Document Server

    Cassarà, Letizia P; Chiosi, Cesare

    2014-01-01

    Improving upon the standard evolutionary population synthesis (EPS) technique, we present spectrophotometric models of galaxies whose morphology goes from spherical structures to discs, properly accounting for the effect of dust in the interstellar medium (ISM). These models enclose three main physical components: the diffuse ISM composed by gas and dust, the complexes of molecular clouds (MCs) where active star formation occurs and the stars of any age and chemical composition. These models are based on robust evolutionary chemical models that provide the total amount of gas and stars present at any age and that are adjusted in order to match the gross properties of galaxies of different morphological type. We have employed the results for the properties of the ISM presented in Piovan, Tantalo & Chiosi (2006a) and the single stellar populations calculated by Cassar\\`a et al. (2013) to derive the spectral energy distributions (SEDs) of galaxies going from pure bulge to discs passing through a number of co...

  13. The Structure of the Interstellar Medium of Star Forming Galaxies

    CERN Document Server

    Hopkins, Philip F; Murray, Norman

    2011-01-01

    We present numerical methods for including stellar feedback in galaxy-scale simulations. We include heating by SNe (I & II), gas recycling and shock-heating from O-star & AGB winds, HII photoionization, and radiation pressure from stellar photons. The energetics and time-dependence are taken directly from stellar evolution models. We implement these in simulations with pc-scale resolution, modeling galaxies from SMC-like dwarfs and MW analogues to massive z~2 starburst disks. Absent feedback, gas cools and collapses without limit. With feedback, the ISM reaches a multi-phase steady state in which GMCs continuously form, disperse, and re-form. Our primary results include: (1) Star forming galaxies generically self-regulate at Toomre Q~1. Most of the volume is in diffuse hot gas with most of the mass in dense GMC complexes. The phase structure and gas mass at high densities are much more sensitive probes of stellar feedback physics than integrated quantities (Toomre Q or gas velocity dispersion). (2) Di...

  14. Structure and Evolution of Interstellar Gas in Flattened, Rotating Elliptical Galaxies

    Science.gov (United States)

    Brighenti, Fabrizio; Mathews, William G.

    1996-10-01

    We study the time-dependent evolution of interstellar gas in a family of elliptical galaxies having identical masses and central densities but various ellipticities and total angular momenta. Dark halos are assumed to be flattened in the same manner as the stars. Normal mass loss from evolving galactic stars is sufficient to account for the amount of hot interstellar gas observed. Gas ejected from stars shares the random motions of the stars and the bulk stellar velocity relative to the local interstellar medium; the ejected gas thermalizes to a temperature similar to the virial temperature of the stellar system. The random stellar motions and galactic rotation are found by solving Jeans's equations in cylindrical geometry. For a sequence of galaxies differing only in degree of flattening-E0, E2, and E4-we find that the X-ray images and luminosities are not very different. As the hot interstellar gas loses energy by radiation, it cools to the very center of these nonrotating galaxies regardless of flattening. The X-ray surface brightness is generally slightly steeper than the optical surface brightness of starlight. However, when a small but typical galactic rotation is introduced, the evolution of the interstellar medium is radically altered. The average X- ray surface brightness {SIGMA}_X_ is lower in the galactic center compared to nonrotating galaxies. This lower {SIGMA}_X_ can be achieved without invoking an ad hoc mass dropout from the hot gas. As the gas cools in rotating galaxies, it is deposited in a large disk comparable in size to the effective radius. Alter evolving for several gigayears, most of the new gas in the cooling flow is constrained by angular momentum conservation to arrive at the outer edge of the disk, Causing a local enhancement in the X-ray surface brightness. This results in flattened inner X-ray surface brightness contours that have peanut shapes when viewed nearly perpendicular to the axis of galactic rotation. As gas approaches the

  15. The effect of models of the interstellar media on the central mass distribution of galaxies

    Science.gov (United States)

    Christensen, C. R.; Governato, F.; Quinn, T.; Brooks, A. M.; Shen, S.; McCleary, J.; Fisher, D. B.; Wadsley, J.

    2014-05-01

    We compared the central mass distribution of dwarf and spiral galaxies simulated with three different models of the interstellar medium with increasing complexity: primordial (H+He) cooling, additional cooling via metal lines, and molecular hydrogen ( H2) with shielding of atomic and molecular hydrogen, in addition to metal-line cooling. We followed the evolution of four high-resolution, simulated galaxies with Vpeak gas was hotter and the feedback-heated gas cooled relatively slowly so less energy was required to expel it. When H2 was included, the accompanying shielding produced large amounts of clumpy, cold gas, and the supernova feedback was more highly concentrated. In contrast to the spiral galaxies, the dwarfs had similarly realistic concentrations and displayed similar behaviour across all models because their low metallicities resulted in smaller differences is the behaviour of the gas.

  16. The interstellar environment in the outer Galaxy as seen in gamma rays by Fermi

    CERN Document Server

    Tibaldo, Luigi; Mizuno, Tsunefumi

    2010-01-01

    Gamma-ray emission produced by interactions between cosmic rays (CRs) and interstellar gas traces the product of their densities throughout the Milky Way. The outer Galaxy is a privileged target of investigation to separate interstellar structures seen along the line of sight. Recent observations by the Fermi Large Area Telescope (LAT) shed light on open questions of the EGRET era about the distribution of CR densities and the census of the interstellar medium. The gradient of gamma-ray emissivities measured in the outer Galaxy is significantly flatter than predictions from widely used CR propagation models given the rapid decline of putative CR sources beyond the solar circle. Large propagation volumes, with halo heights up to 20 kpc, or a flat CR source distribution are required to match the data. Other viable possibilities include non-uniform CR diffusion properties or more gas than accounted for by the radio/mm-wave data. Gamma-ray data constrain the evolution of the Xco=N(H2)/W(CO) ratio within a few kpc...

  17. Cosmic ray propagation in the Galaxy and associated interstellar emissions

    Science.gov (United States)

    Moskalenko, Igor

    Last several years were highlighted by many breakthroughs and discoveries in astrophysics of cosmic rays (CRs), thanks to superior instruments such as PAMELA, Fermi-LAT, Agile, INTEGRAL, HESS, VERITAS, Milagro, ATIC, CREAM, ACE, Voyager 1, 2 and others. They provide key pieces of information that may lead to the solution of the century-old puzzle of the origin of CRs and may contain signatures of new physics. The long-awaited AMS-02 data will be published by the time of the conference; they may confirm earlier measurements at the new precision level and/or outline significant discrepancies. I will review the CR measurements and relevant observations of the Galactic CR sources and the diffuse emissions and discuss what we can learn about CRs and their propagation in the Galaxy.

  18. The JCMT Nearby Galaxies Legacy Survey IV. Velocity Dispersions in the Molecular Interstellar Medium in Spiral Galaxies

    CERN Document Server

    Wilson, C D; Irwin, J; Knapen, J H; Israel, F P; Serjeant, S; Attewell, D; Bendo, G J; Brinks, E; Butner, H M; Clements, D L; Leech, J; Matthews, H E; Muehle, S; Mortier, A M J; Parkin, T J; Petitpas, G; Tan, B K; Tilanus, R P J; Usero, A; Vaccari, M; van der Werf, P; Wiegert, T; Zhu, M

    2010-01-01

    An analysis of large-area CO J=3-2 maps from the James Clerk Maxwell Telescope for 12 nearby spiral galaxies reveals low velocity dispersions in the molecular component of the interstellar medium. The three lowest luminosity galaxies show a relatively flat velocity dispersion as a function of radius while the remaining nine galaxies show a central peak with a radial fall-off within 0.2-0.4 r(25). Correcting for the average contribution due to the internal velocitydispersions of a population of giant molecular clouds, the average cloud-cloud velocity dispersion across the galactic disks is 6.1 +/- 1.0 km/s (standard deviation 2.9 km/s), in reasonable agreement with previous measurements for the Galaxy andM33. The cloud-cloud velocity dispersion derived from the CO data is on average two times smaller than the HI velocity dispersion measured in the same galaxies. The low cloud-cloudvelocity dispersion implies that the molecular gas is the critical component determining the stability of the galactic disk against...

  19. The effect of models of the interstellar media on the central mass distribution of galaxies

    CERN Document Server

    Christensen, Charlotte; Quinn, Thomas; Brooks, Alyson M; Fisher, David B; Shen, Sijing; McCleary, Jacqueline; Wadsley, James

    2012-01-01

    We compare the central mass distribution of galaxies simulated with three different models of the interstellar medium (ISM) with increasing complexity: primordial (H+He) cooling down to 10^4 K, additional cooling via metal lines and to lower temperatures, and molecular hydrogen (H_2) with shielding of atomic and molecular hydrogen in addition to metal line cooling. In order to analyze the effect of these models, we follow the evolution of four field galaxies with V_peak < 120 km/s to a redshift of zero using high-resolution Smoothed Particle Hydrodynamic simulations in a fully cosmological LCDM context. The spiral galaxies produced in simulations with either primordial cooling or H_2 physics have bulge magnitudes and scale lengths very similar to observed galaxies and realistic, rising rotation curves. In contrast, the metal line cooling simulation produced galaxies with more massive and concentrated bulges and with the peaked rotation curves typical of most previous LCDM simulations of spiral galaxies. Th...

  20. The interstellar medium and star formation in nearby galaxies. Ludwig Biermann Award Lecture 2013

    Science.gov (United States)

    Bigiel, F.; Cormier, D.; Schmidt, T.

    In this overview article we present some of the key projects we pursue in our Emmy Noether group. Our work is focused on nearby galaxies, where we use multi-wavelength, state-of-the-art survey data to probe distribution, abundance and properties of gas and dust in the interstellar medium (ISM) on [Si II] kpc scales. We study the average, radial distributions of atomic (H I) and molecular hydrogen (H2) across the disks of spiral galaxies and assess local (on 1 kpc scales) correlations between H I, H2 and star formation rate (SFR) surface densities across the inner, optical disks of our sample of [Si II] 30 spiral galaxies. The short H2 depletion times ([Si II] 2 Gyr) we find raises the question of if and how star formation is refueled in galactic disks. We look for such signatures of radial gas flows in our H I data and find compelling evidence at least in one case. We extend and compare our gas-SFR studies to the outer disks of galaxies, where conditions change significantly in the ISM, e.g., low metallicity and dust abundance. We focus on star formation at low-metallicity further with detailed ISM studies in dwarf galaxies, where we combine spectroscopic observations in the infrared with detailed modelling to learn about composition and detailed physical properties of the ISM. Of particular interest is the question of what drives large scale star formation in galaxies at low metallicity.

  1. Interstellar Silicate Dust Grain Properties in Distant Galaxies Probed by Quasar Absorption Systems

    Science.gov (United States)

    Aller, Monique C.; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam

    2015-01-01

    Dust grains are a fundamental component of the interstellar medium, and significantly impact many of the physical processes driving galaxy evolution, including star formation, and the heating, cooling and ionization of interstellar material. Using the absorption features produced by dust in the spectra of luminous background quasars, it is possible to study the properties of extragalactic interstellar dust grains. We will present results from an ongoing program utilizing existing Spitzer Space Telescope infrared quasar spectra to probe silicate dust grain properties in z<1.4 quasar absorption systems. In combination with complementary ground-based data on associated gas-phase metal absorption lines, we explore connections between the interstellar dust and gas in the quasar absorption systems. Our project yields clear detections of the 10 micron silicate dust absorption feature in the studied systems, as well as detections of the 18 micron silicate dust absorption feature in sources with adequate spectral coverage. Based on measured variations in the breath, peak wavelength, and substructure of the 10 micron absorption features, there appear to be differences in the silicate dust grain properties from system-to-system. We also show indications of trends between the gas-phase metal properties, such as metallicity and gas velocity spread, with the silicate dust grain absorption properties. Support for this work is provided by NASA through an award issued by JPL/Caltech and through NASA grant NNX14AG74G, and from National Science Foundation grants AST-0908890 and AST-1108830 to the University of South Carolina.

  2. Dark matter response to galaxy formation

    CERN Document Server

    Tissera, Patricia B; Pedrosa, Susana; Scannapieco, Cecilia

    2009-01-01

    We have resimulated the six galaxy-sized haloes of the Aquarius Project including metal-dependent cooling, star formation and supernova feedback. This allows us to study not only how dark matter haloes respond to galaxy formation, but also how this response is affected by details of halo assembly history. In agreement with previous work, we find baryon condensation to lead to increased dark matter concentration. Dark matter density profiles differ substantially in shape from halo to halo when baryons are included, but in all cases the velocity dispersion decreases monotonically with radius. Some haloes show an approximately constant dark matter velocity anisotropy with $ \\beta \\approx 0.1-02$, while others retain the anisotropy structure of their baryon-free versions. Most of our haloes become approximately oblate in their inner regions, although a few retain the shape of their dissipationless counterparts. Pseudo-phase-space densities are described by a power law in radius of altered slope when baryons are i...

  3. CONNECTION BETWEEN THE CIRCUMGALACTIC MEDIUM AND THE INTERSTELLAR MEDIUM OF GALAXIES: RESULTS FROM THE COS-GASS SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Borthakur, Sanchayeeta; Heckman, Timothy [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Tumlinson, Jason; Bordoloi, Rongmon; Thom, Christopher [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Catinella, Barbara [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, VIC 3122 (Australia); Schiminovich, David [Department of Astronomy, Columbia University, New York, NY 10027 (United States); Davé, Romeel [University of the Western Cape, Bellville, Cape Town 7535 (South Africa); Kauffmann, Guinevere [Max-Planck Institut für Astrophysik, D-85741 Garching (Germany); Moran, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Saintonge, Amelie, E-mail: sanch@pha.jhu.edu [Department of Physics and Astronomy, University College London, Gower Place, London WC1E 6BT (United Kingdom)

    2015-11-01

    We present a study exploring the nature and properties of the circumgalactic medium (CGM) and its connection to the atomic gas content in the interstellar medium (ISM) of galaxies as traced by the H i 21 cm line. Our sample includes 45 low-z (0.026–0.049) galaxies from the GALEX Arecibo SDSS Survey (Galaxy Evolution Explorer/Arecibo/Sloan Digital Sky Survey). Their CGM was probed via absorption in the spectra of background quasi-stellar objects at impact parameters of 63–231 kpc. The spectra were obtained with the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. We detected neutral hydrogen (Lyα absorption lines) in the CGM of 92% of the galaxies. We find that the radial profile of the CGM as traced by the Lyα equivalent width can be fit as an exponential with a scale length of roughly the virial radius of the dark matter halo. We found no correlation between the orientation of the sightline relative to the galaxy’s major axis and the Lyα equivalent width. The velocity spread of the circumgalactic gas is consistent with that seen in the atomic gas in the ISM. We find a strong correlation (99.8% confidence) between the gas fraction (M(H i)/M{sub ⋆}) and the impact-parameter-corrected Lyα equivalent width. This is stronger than the analogous correlation between corrected Lyα equivalent width and specific star formation rate (SFR)/M{sub ⋆} (97.5% confidence). These results imply a physical connection between the H i disk and the CGM, which is on scales an order of magnitude larger. This is consistent with the picture in which the H i disk is nourished by accretion of gas from the CGM.

  4. Wave Dark Matter and Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Parry, Alan R.

    We explore a model of dark matter called wave dark matter (also known as scalar field dark matter and boson stars) which has recently been motivated by a new geometric perspective by Bray. Wave dark matter describes dark matter as a scalar field which satisfies the Einstein-Klein-Gordon equations. These equations rely on a fundamental constant Upsilon (also known as the "mass term'' of the Klein-Gordon equation). Specifically, in this dissertation, we study spherically symmetric wave dark matter and compare these results with observations of dwarf spheroidal galaxies as a first attempt to compare the implications of the theory of wave dark matter with actual observations of dark matter. This includes finding a first estimate of the fundamental constant Upsilon. In the introductory Chapter 1, we present some preliminary background material to define and motivate the study of wave dark matter and describe some of the properties of dwarf spheroidal galaxies. In Chapter 2, we present several different ways of describing a spherically symmetric spacetime and the resulting metrics. We then focus our discussion on an especially useful form of the metric of a spherically symmetric spacetime in polar-areal coordinates and its properties. In particular, we show how the metric component functions chosen are extremely compatible with notions in Newtonian mechanics. We also show the monotonicity of the Hawking mass in these coordinates. Finally, we discuss how these coordinates and the metric can be used to solve the spherically symmetric Einstein-Klein-Gordon equations. In Chapter 3, we explore spherically symmetric solutions to the Einstein-Klein-Gordon equations, the defining equations of wave dark matter, where the scalar field is of the form f(t, r) = eiotF(r) for some constant o ∈ R and complex-valued function F(r). We show that the corresponding metric is static if and only if F( r) = h(r)eia for some constant alpha ∈ R and real-valued function h(r). We describe the

  5. Study of the Interstellar Medium and Star Formation of a complete sample of 760 isolated galaxies

    CERN Document Server

    Lisenfeld, U; Espada, D; García, E; Leon, S

    2002-01-01

    A key problem in astronomy involves the role of the environment in the formation and evolution of galaxies. In order to answer this question it is necessary to characterize a reference sample with minimum influence from the environment, so that its evolution is completeley determined by nature. The aim of this project is to provide such reference, quantifying the ISM properties of a well defined and statistically significant sample of 760 isolated galaxies. Based on optical, Halpha and infrared luminosities, radiocontinuum emission, molecular and atomic gas content, compiled from the bibliography or observed by ourselves, together with POSS-II digitized images, we will perform a statistical study of the Interstellar Medium (ISM) properties as a function of isolation, and its relation to star formation, morphology and luminosities, as well as nuclear activity frequency. This sample will be different from previous studies by three essential characteristics: a) strict definition of isolation, b) statistical sign...

  6. A multi wavelength study of the young star clusters and interstellar medium in the antennae galaxies

    CERN Document Server

    Zhang, Q; Whitmore, B C; Zhang, Qing; Whitmore, Bradley C.

    2001-01-01

    We report on a multi-wavelength study of the relationship between young star clusters in the Antennae galaxies (NGC 4038/9) and their interstellar environment, with the goal of understanding the formation and feedback effects of star clusters in merging galaxies. This is possible for the first time because various new observations (from X-rays to radio wavelengths) have become available in the past several years. Quantitative comparisons are made between the positions of the star clusters (broken into three age groups) and the properties of the interstellar medium by calculating the two-point correlation functions. We find that young star clusters are distributed in a clustered fashion. The youngest star clusters are associated with molecular cloud complexes with characteristic radii of about 1 kpc. In addition, there is a weak tendency for them to be found in regions with steeper CO velocity gradients and higher HI velocity dispersions. No dominant triggering mechanism is identified for the majority of the c...

  7. The evolution of the cold interstellar medium in galaxies following a starburst

    CERN Document Server

    Rowlands, K; Nesvadba, N; Sibthorpe, B; Mortier, A; Lehnert, M; da Cunha, E

    2014-01-01

    We present the evolution of dust and molecular gas properties in a sample of 11 $z\\sim0.03$ starburst to post-starburst (PSB) galaxies selected to span an age sequence from ongoing starburst to 1 Gyr after the starburst ended. All PSBs harbour significant molecular gas and dust reservoirs and residual star formation, indicating that complete quenching of the starburst due to exhaustion or expulsion of gas has not occurred during this timespan. As the starburst ages, we observe a clear decrease in the star-formation efficiency, molecular gas and SFR surface density, and effective dust temperature, from levels coincident with starburst galaxies to those of normal star-forming galaxies. These trends are consistent with a natural decrease in the SFR following consumption of molecular gas by the starburst, and corresponding decrease in the interstellar radiation field strength as the starburst ages. The gas and dust contents of the PSBs are coincident with those of star-forming galaxies and molecular gas-rich earl...

  8. Synchrotron spectral index and interstellar medium densities of star-forming galaxies

    CERN Document Server

    Basu, Aritra; Schmidt, Philip; Roy, Subhashis

    2015-01-01

    The spectral index of synchrotron emission is an important parameter in understanding the properties of cosmic ray electrons (CREs) and the interstellar medium (ISM). We determine the synchrotron spectral index ($\\alpha_{\\rm nt}$) of four nearby star-forming galaxies, namely NGC 4736, NGC 5055, NGC 5236 and NGC 6946 at sub-kpc linear scales. The $\\alpha_{\\rm nt}$ was determined between 0.33 and 1.4 GHz for all the galaxies. We find the spectral index to be flatter ($\\gtrsim -0.7$) in regions with total neutral (atomic + molecular) gas surface density, $\\Sigma_{\\rm gas} \\gtrsim \\rm 50~M_\\odot pc^{-2}$, typically in the arms and inner parts of the galaxies. In regions with $\\Sigma_{\\rm gas} \\lesssim \\rm 50~M_\\odot pc^{-2}$, especially in the interarm and outer regions of the galaxies, the spectral index steepens sharply to $<-1.0$. The flattening of $\\alpha_{\\rm nt}$ is unlikely to be caused due to thermal free--free absorption at 0.33 GHz. Our result is consistent with the scenario where the CREs emitting a...

  9. Drivers of Turbulence in the Neutral Interstellar Medium of Dwarf Galaxies

    Science.gov (United States)

    Stilp, Adrienne M.

    The cause of HI velocity dispersions in the interstellar medium (ISM) of galaxies is often attributed to star formation, but recent evidence has shown these two quantities are not connected in regions of low star formation. This lack of connection is most apparent in dwarf galaxies and the outer disks of spiral galaxies. However, unique data sets have recently been collected that can help address this discrepancy. The ACS Nearby Survey Treasury Project (ANGST) has measured time-resolved star formation histories (SFHs) in ˜ 70 nearby galaxies. The followup Very Large Array-ANGST survey (VLA-ANGST) provides complementary HI observations of a subset of ANGST galaxies. In this thesis, I explore the connection between star formation and HI kinematics in a number of nearby dwarf galaxies. I first present the Very Large Array-ACS Nearby Galaxy Survey Treasury Project (ANGST). VLA-ANGST was designed to provide high spatial and velocity resolution observations of the HI component of the interstellar medium (ISM) in ANGST galaxies. I describe the data calibration and imaging procedures, and then present the publicly-available data products. The observations from this survey and from The HI Nearby Galaxy Survey (THINGS) comprise the majority of data in my thesis. Using VLA-ANGST and THINGS data, I present a method to measure the average HI kinematics in a number of nearby dwarf galaxies by co-adding individual line-of-sight profiles. These "superprofiles" are composed of a central narrow peak (˜ 6-10 km s-1) with higher velocity wings to either side. When scaled to the same half-width half-maximum, the shapes of the superprofiles are very similar. I interpret the central peak as representative of the average turbulent motion; the wings are then due to HI moving faster than expected compared to the average kinematics. I then compare the superprofile parameters to physical properties such as mass surface density and star formation intensity. The average velocity dispersion

  10. Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy

    CERN Document Server

    Tavakoli, Maryam; Evoli, Carmelo; Ullio, Piero

    2014-01-01

    Recent advances in gamma-ray cosmic ray, infrared and radio astronomy have allowed us to develop a significantly better understanding of the galactic medium properties in the last few years. In this work using the DRAGON code, that numerically solves the CR propagation equation and calculating gamma-ray emissivities in a 2-dimensional grid enclosing the Galaxy, we study in a self consistent manner models for the galactic diffuse gamma-ray emission. Our models are cross-checked to both the available CR and gamma-ray data. We address the extend to which dark matter annihilations in the Galaxy can contribute to the diffuse gamma-ray flux towards different directions on the sky. Moreover we discuss the impact that astrophysical uncertainties of non DM nature, have on the derived gamma-ray limits. Such uncertainties are related to the diffusion properties on the Galaxy, the interstellar gas and the interstellar radiation field energy densities. Light ~10 GeV dark matter annihilating dominantly to hadrons is more s...

  11. Neutral interstellar medium phases and star formation tracers in dwarf galaxies

    Science.gov (United States)

    Cigan, Phillip Johnathan

    Dwarf galaxies present interesting observational challenges for the studies of various galaxy properties: despite their abundance and proximity to the Milky Way, they typically have very low surface brightnesses and small physical sizes. Until now, only the extreme variety of dwarfs --- those undergoing strong bouts of star formation --- have been observed in the FIR, due to observational difficulties. However, this population does not represent the majority of dwarfs, which have only moderate star formation rates and extremely low metallicity (the fraction of heavy elements to hydrogen). The advent of the Herschel Space Telescope, with its superior resolution and sensitivity over previous generations of telescopes, has made it possible to measure FIR spectral lines and broadband continuum in normal dwarf galaxies, expanding the scope of studies beyond the brighter, but more extreme, varieties. The general goal of my research was to study the conditions in the interstellar media (ISM) of typical dwarf galaxies. The LITTLE THINGS (Local Irregulars That Trace Luminosity Extremes, TheHI Nearby Galaxy Survey) project aims to unravel many mysteries of nearby dwarfs using a suite of multi-wavelength data, and the new additions from Herschel help provide insight into the physics of these systems. I reduced and analyzed FIR fine-structure spectral line data for the LITTLE THINGS sample to study the different phases of the ISM, as well as FIR photometry data to access the dust properties and infrared continuum emission in these systems. The FIR spectral lines are diagnostics for the conditions in the ISM of galaxies, telling us about heating efficiency, the fraction of gas that resides in photodissociation regions (PDRs), abundance of highly ionized gas from massive stars, and other physical descriptions. The photometric continuum observations enable the modeling of interstellar dust properties -- dust plays an important role in shielding and cooling molecular clouds which

  12. Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Tavakoli, Maryam; Evoli, Carmelo [II. Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Cholis, Ilias [Fermi National Accelerator Laboratory, Center for Particle Astrophysics, Batavia, IL 60510 (United States); Ullio, Piero, E-mail: maryam.tavakoli@desy.de, E-mail: cholis@fnal.gov, E-mail: carmelo.evoli@desy.de, E-mail: ullio@sissa.it [SISSA, Via Bonomea 265, 34136 Trieste (Italy)

    2014-01-01

    Recent advances in γ-ray cosmic ray, infrared and radio astronomy have allowed us to develop a significantly better understanding of the galactic medium properties in the last few years. In this work using the DRAGON code, that numerically solves the CR propagation equation and calculating γ-ray emissivities in a 2-dimensional grid enclosing the Galaxy, we study in a self consistent manner models for the galactic diffuse γ-ray emission. Our models are cross-checked to both the available CR and γ-ray data. We address the extend to which dark matter annihilations in the Galaxy can contribute to the diffuse γ-ray flux towards different directions on the sky. Moreover we discuss the impact that astrophysical uncertainties of non DM nature, have on the derived γ-ray limits. Such uncertainties are related to the diffusion properties on the Galaxy, the interstellar gas and the interstellar radiation field energy densities. Light ∼ 10 GeV dark matter annihilating dominantly to hadrons is more strongly constrained by γ-ray observations towards the inner parts of the Galaxy and influenced the most by assumptions of the gas distribution; while TeV scale DM annihilating dominantly to leptons has its tightest constraints from observations towards the galactic center avoiding the galactic disk plane, with the main astrophysical uncertainty being the radiation field energy density. In addition, we present a method of deriving constraints on the dark matter distribution profile from the diffuse γ-ray spectra. These results critically depend on the assumed mass of the dark matter particles and the type of its end annihilation products.

  13. Dust grain growth in the interstellar medium of galaxies at redshifts 4

    CERN Document Server

    Michałowski, Michał J; Hjorth, Jens; Watson, Darach; Gall, Christa; Dunlop, James S

    2011-01-01

    To discriminate between different dust formation processes is a key issue in order to understand its properties. We analysed six submillimeter galaxies at redshifts 4galaxies. SN could be responsible for dust production, but only if dust destruction in the SN shocks is not taken into account. Otherwise even SNe are not efficient enough, which advocates for some other dust production mechanism. We present the hypothesis that grain growth in the interstellar medium is responsible for bulk of the dust mass accumulation in these galaxies.

  14. The distribution of interstellar dust in CALIFA edge-on galaxies via oligochromatic radiative transfer fitting

    CERN Document Server

    De Geyter, Gert; Camps, Peter; Fritz, Jacopo; De Looze, Ilse; Hughes, Thomas M; Viaene, Sebastien; Gentile, Gianfranco

    2014-01-01

    We investigate the amount and spatial distribution of interstellar dust in edge-on spiral galaxies, using detailed radiative transfer modeling of a homogeneous sample of 12 galaxies selected from the CALIFA survey. Our automated fitting routine, FitSKIRT, was first validated against artificial data. This is done by simultaneously reproducing the SDSS $g$-, $r$-, $i$- and $z$-band observations of a toy model in order to combine the information present in the different bands. We show that this combined, oligochromatic fitting, has clear advantages over standard monochromatic fitting especially regarding constraints on the dust properties. We model all galaxies in our sample using a three-component model, consisting of a double exponential disc to describe the stellar and dust discs and using a S\\'ersic profile to describe the central bulge. The full model contains 19 free parameters, and we are able to constrain all these parameters to a satisfactory level of accuracy without human intervention or strong bounda...

  15. The Strikingly Uniform, Highly Turbulent Interstellar Medium of the Most Luminous Galaxy in the Universe

    CERN Document Server

    Diaz-Santos, T; Blain, A W; Tsai, C -W; Aravena, M; Eisenhardt, P; Wu, J; Stern, D; Bridge, C

    2015-01-01

    Observed at z = 4.601 and with L_bol = 3.5 x 10^14 Lsun, W2246-0526 is the most luminous galaxy known in the Universe, and hosts a deeply-buried active galactic nucleus (AGN)/super-massive black hole (SMBH). Discovered using the Wide-field Infrared Survey Explorer (WISE), W2246-0526 is classified as a Hot Dust Obscured Galaxy (Hot DOG), based on its luminosity and dust temperature. Here we present spatially resolved ALMA [CII]157.7um observations of W2246-0526, providing unique insight into the kinematics of its interstellar medium (ISM). The measured [CII]-to-far-infrared ratio is ~2 x 10^-4, implying ISM conditions that compare only with the most obscured, compact starbursts and AGN in the local Universe today. The spatially resolved [CII] line is strikingly uniform and very broad, 500-600 km/s wide, extending throughout the entire galaxy over about 2.5 kpc, with modest shear. Such a large, homogeneous velocity dispersion indicates a highly turbulent medium. W2246-0526 is unstable in terms of the energy and...

  16. Sommerfeld enhancement of invisible dark matter annihilation in galaxies and galaxy clusters

    CERN Document Server

    Chan, Man Ho

    2016-01-01

    Recent observations indicate that core-like dark matter structures exist in many galaxies, while numerical simulations reveal a singular dark matter density profile at the center. In this article, I show that if the annihilation of dark matter particles gives invisible sterile neutrinos, the Sommerfeld enhancement of the annihilation cross-section can give a sufficiently large annihilation rate to solve the core-cusp problem. The resultant core density, core radius, and their scaling relation generally agree with recent empirical fits from observations. Also, this model predicts that the resultant core-like structures in dwarf galaxies can be easily observed, but not for large normal galaxies and galaxy clusters.

  17. Deficient Reasoning for Dark Matter in Galaxies

    CERN Document Server

    Feng, James Q

    2014-01-01

    Astronomers have been using the measured luminosity to estimate the {\\em luminous mass} of stars, based on empirically established mass-to-light ratio which seems to be only applicable to a special class of stars---the main-sequence stars---with still considerable uncertainties. Another basic tool to determine the mass of a system of stars or galaxies comes from the study of their motion, as Newton demonstrated with his law of gravitation, which yields the {\\em gravitational mass}. Because the luminous mass can at best only represent a portion of the gravitational mass, finding the luminous mass to be different or less than the gravitational mass should not be surprising. Using such an apparent discrepancy as a compelling evidence for the so-called dark matter, which has been believed to possess mysterious nonbaryonic properties and present a dominant amount in galaxies and the universe, seems to be too far a stretch when seriously examining the facts and uncertainties in the measurement techniques. In our op...

  18. Interstellar chemistry recorded in organic matter from primitive meteorites.

    Science.gov (United States)

    Busemann, Henner; Young, Andrea F; Alexander, Conel M O'd; Hoppe, Peter; Mukhopadhyay, Sujoy; Nittler, Larry R

    2006-05-05

    Organic matter in extraterrestrial materials has isotopic anomalies in hydrogen and nitrogen that suggest an origin in the presolar molecular cloud or perhaps in the protoplanetary disk. Interplanetary dust particles are generally regarded as the most primitive solar system matter available, in part because until recently they exhibited the most extreme isotope anomalies. However, we show that hydrogen and nitrogen isotopic compositions in carbonaceous chondrite organic matter reach and even exceed those found in interplanetary dust particles. Hence, both meteorites (originating from the asteroid belt) and interplanetary dust particles (possibly from comets) preserve primitive organics that were a component of the original building blocks of the solar system.

  19. Dwarf Galaxies in Voids: Dark Matter Halos and Gas Cooling

    CERN Document Server

    Hoeft, Matthias

    2010-01-01

    Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in Universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed, that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultra-violet background radiation low-mass haloes show generally are reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40 km/s. The suppressed baryon accretion is caused by the...

  20. Condensation and Evaporation of Interstellar Clouds in Chemodynamical Models of Galaxies

    CERN Document Server

    Köppen, J; Hensler, G; Theis, Ch.

    1997-01-01

    The network of interactions between hot gas, cool clouds, massive stars, and stellar remnants used in the chemodynamical modeling of the interstellar medium is investigated for the types of its solutions. In a physically consistent formulation for the energy transfer during condensation, oscillations due to a cyclic switching between condensation and evaporation never occur. A closed-box system evolves in a hierarchy of equilibria: thermal balance in the cloud gas, star-formation self-regulated due to heating of the clouds by massive stars, and the balance of condensation and evaporation. Except for an initial transitory phase, the evolution of the metallicity follows that of the Simple Model quite closely. For galaxies with a high initial density, or if the condensation rate is low, the metals produced by the stars may remain stored in the hot gas phase even in evolved systems with low gas fractions.

  1. The violent interstellar medium in Milky-Way like disk galaxies

    Science.gov (United States)

    Karoline Walch, Stefanie

    2015-08-01

    Molecular clouds are cold, dense, and turbulent filamentary structures that condense out of the multi-phase interstellar medium. They are also the sites of star formation. The minority of new-born stars is massive, but these stars are particularly important for the fate of their parental molecular clouds as their feedback drives turbulence and regulates star formation.I will present results from the SILCC project (SImulating the Life Cycle of molecular Clouds), in which we study the formation and dispersal of molecular clouds within the multi-phase ISM using high-performance, three-dimensional simulations of representative pieces of disk galaxies. Apart from stellar feedback, self-gravity, an external stellar potential, and magnetic fields, we employ an accurate description of gas heating and cooling as well as a small chemical network including molecule formation and (self-)shielding from the interstellar radiation field. We study the impact of the supernova rate and the positioning of the supernova explosions with respect to the molecular gas in a well defined set of simulations. This allows us to draw conclusions on structure of the multi-phase ISM, the amount of molecular gas formed, and the onset of galactic outflows. Furthermore, we show how important stellar wind feedback is for regulating star formation in these disks.

  2. Dissipative dark matter and the rotation curves of dwarf galaxies

    CERN Document Server

    Foot, R

    2015-01-01

    There is ample evidence from rotation curves that dark matter halo's around disk galaxies have nontrivial dynamics. Of particular significance are: a) the cored dark matter profile of disk galaxies, b) correlations of the shape of rotation curves with baryonic properties, and c) the Tully-Fisher relation. Dark matter halo's around disk galaxies may have nontrivial dynamics if dark matter is strongly self interacting and dissipative. Multicomponent hidden sector dark matter featuring a massless `dark photon' (from an unbroken dark $U(1)$ gauge interaction) which kinetically mixes with the ordinary photon provides a concrete example of such dark matter. The kinetic mixing interaction facilitates halo heating by enabling ordinary supernovae to be a source of these `dark photons'. Dark matter halo's can expand and contract in response to the heating and cooling processes, but for a sufficiently isolated halo should have evolved to a steady state or `equilibrium' configuration where heating and cooling rates local...

  3. Kinematics of Interstellar Gas in Nearby UV-selected Galaxies Measured with HST STIS Spectroscopy

    Science.gov (United States)

    Schwartz, C. M.; Martin, C. L.; Chandar, R.; Leitherer, C.; Heckman, T. M.; Oey, M. S.

    2006-08-01

    We measure Doppler shifts of interstellar absorption lines in HST STIS spectra of individual star clusters in nearby UV-selected galaxies. Values for systemic velocities, which are needed to quantify outflow speeds, are taken from the literature and verified with stellar lines. We detect outflowing gas in 8 of 17 galaxies via low-ionization lines (e.g., C II, Si II, Al II), which trace cold and/or warm gas. The starbursts in our sample are intermediate in luminosity (and mass) to dwarf galaxies and luminous infrared galaxies (LIRGs), and we confirm that their outflow speeds (ranging from -100 to nearly -520 km s-1, with an accuracy of ~80 km s-1) are intermediate to those previously measured in dwarf starbursts and LIRGs. We do not detect the outflow in high-ionization lines (such as C IV or Si IV); higher quality data will be needed to empirically establish how velocities vary with the ionization state of the outflow. We do verify that the low-ionization UV lines and optical Na I doublet give roughly consistent outflow velocities, solidifying an important link between studies of galactic winds at low and high redshift. To obtain a higher signal-to-noise ratio (S/N), we create a local average composite spectrum and compare it to the high-z Lyman break composite spectrum. It is surprising that the low-ionization lines show similar outflow velocities in the two samples. We attribute this to a combination of weighting toward higher luminosities in the local composite, as well as both samples being, on average, brighter than the ``turnover'' luminosity in the v-SFR relation. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO-9036.

  4. Dissipative dark matter and the rotation curves of dwarf galaxies

    Science.gov (United States)

    Foot, R.

    2016-07-01

    There is ample evidence from rotation curves that dark matter halos around disk galaxies have nontrivial dynamics. Of particular significance are: a) the cored dark matter profile of disk galaxies, b) correlations of the shape of rotation curves with baryonic properties, and c) Tully-Fisher relations. Dark matter halos around disk galaxies may have nontrivial dynamics if dark matter is strongly self interacting and dissipative. Multicomponent hidden sector dark matter featuring a massless `dark photon' (from an unbroken dark U(1) gauge interaction) which kinetically mixes with the ordinary photon provides a concrete example of such dark matter. The kinetic mixing interaction facilitates halo heating by enabling ordinary supernovae to be a source of these `dark photons'. Dark matter halos can expand and contract in response to the heating and cooling processes, but for a sufficiently isolated halo could have evolved to a steady state or `equilibrium' configuration where heating and cooling rates locally balance. This dynamics allows the dark matter density profile to be related to the distribution of ordinary supernovae in the disk of a given galaxy. In a previous paper a simple and predictive formula was derived encoding this relation. Here we improve on previous work by modelling the supernovae distribution via the measured UV and Hα fluxes, and compare the resulting dark matter halo profiles with the rotation curve data for each dwarf galaxy in the LITTLE THINGS sample. The dissipative dark matter concept is further developed and some conclusions drawn.

  5. Galaxy distribution in a cold dark matter universe

    Energy Technology Data Exchange (ETDEWEB)

    White, S.D.M.; Davis, M.; Efstathiou, G.; Frenk, C.S.

    1987-12-03

    The gravitational growth of structure by hierarchical clustering is shown to lead automatically to a bias in the distribution of galaxies. The strength of this bias is such that if the Universe does indeed conform to the cold dark matter model then its density must approach the closure value. The mechanism predicts a significant dependence of the strength of galaxy clustering on the depth of the potential well of the galaxies considered.

  6. THE INTERSTELLAR MEDIUM AND FEEDBACK IN THE PROGENITORS OF THE COMPACT PASSIVE GALAXIES AT z ∼ 2

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Christina C.; Giavalisco, Mauro; Lee, Bomee [Department of Astronomy, University of Massachusetts, 710 North Pleasant Street, Amherst, MA 01003 (United States); Tundo, Elena [INAF, Osservatorio Astrofisico di Firenze, Largo Enrico Fermi 5, I-50125, Firenze (Italy); Mobasher, Bahram; Nayyeri, Hooshang [Department of Physics and Astronomy, University of California, Riverside, 900 University Avenue, Riverside, CA 92521 (United States); Ferguson, Henry C.; Koekemoer, Anton; Grogin, Norman [Space Telescope Science Institute, 3700 San Martin Boulevard, Baltimore, MD 21218 (United States); Trump, Jonathan R. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Cassata, Paolo [Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Valparaíso (Chile); Dekel, Avishai [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Guo, Yicheng [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Lee, Kyoung-Soo [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States); Pentericci, Laura; Castellano, Marco; Fontana, Adriano; Grazian, Andrea [INAF - Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone (Italy); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Finkelstein, Steven L., E-mail: ccwilliams@email.arizona.edu [Department of Astronomy, University of Texas, Austin (United States); and others

    2015-02-10

    Quenched galaxies at z > 2 are nearly all very compact relative to z ∼ 0, suggesting a physical connection between high stellar density and efficient, rapid cessation of star-formation. We present rest-frame UV spectra of Lyman-break galaxies (LBGs) at z ∼ 3 selected to be candidate progenitors of the quenched galaxies at z ∼ 2 based on their compact rest-frame-optical sizes and high Σ{sub SFR}. We compare their UV properties to those of more extended LBGs of similar mass and star-formation rate (non-candidates). We find that candidate progenitors have faster bulk interstellar medium (ISM) gas velocities and higher equivalent widths of interstellar absorption lines, implying larger velocity spread among absorbing clouds. Candidates deviate from the relationship between equivalent widths of Lyα and interstellar absorption lines in that their Lyα emission remains strong despite high interstellar absorption, possibly indicating that the neutral H I fraction is patchy, such that Lyα photons can escape. We detect stronger C IV P-Cygni features (emission and absorption) and He II emission in candidates, indicative of larger populations of metal-rich Wolf-Rayet stars compared to non-candidates. The faster bulk motions, broader spread of gas velocity, and Lyα properties of candidates are consistent with their ISM being subject to more energetic feedback than non-candidates. Together with their larger metallicity (implying more evolved star-formation activity) this leads us to propose, if speculatively, that they are likely to quench sooner than non-candidates, supporting the validity of selection criteria used to identify them as progenitors of z ∼ 2 passive galaxies. We propose that massive, compact galaxies undergo more rapid growth of their stellar mass content, perhaps because the gas accretion mechanisms are different, and quench sooner than normally sized LBGs at these (early) epochs.

  7. An IceCube Search for Dark Matter Annihilation in nearby Galaxies and Galaxy Clusters

    CERN Document Server

    Aartsen, M G; Abdou, Y; Ackermann, M; Adams, J; Aguilar, J A; Ahlers, M; Altmann, D; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Baum, V; Bay, R; Beatty, J J; Bechet, S; Tjus, J Becker; Becker, K -H; Benabderrahmane, M L; BenZvi, S; Berghaus, P; Berley, D; Bernardini, E; Bernhard, A; Bertrand, D; Besson, D Z; Binder, G; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohaichuk, S; Bohm, C; Bose, D; Böser, S; Botner, O; Brayeur, L; Bretz, H -P; Brown, A M; Bruijn, R; Brunner, J; Carson, M; Casey, J; Casier, M; Chirkin, D; Christov, A; Christy, B; Clark, K; Clevermann, F; Coenders, S; Cohen, S; Cowen, D F; Silva, A H Cruz; Danninger, M; Daughhetee, J; Davis, J C; Day, M; De Clercq, C; De Ridder, S; Desiati, P; de Vries, K D; de With, M; DeYoung, T; D'\\iaz-Vélez, J C; Dunkman, M; Eagan, R; Eberhardt, B; Eisch, J; Ellsworth, R W; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feintzeig, J; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Flis, S; Franckowiak, A; Frantzen, K; Fuchs, T; Gaisser, T K; Gallagher, J; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Golup, G; Gonzalez, J G; Goodman, J A; Góra, D; Grandmont, D T; Grant, D; Groß, A; Ha, C; Ismail, A Haj; Hallen, P; Hallgren, A; Halzen, F; Hanson, K; Heereman, D; Heinen, D; Helbing, K; Hellauer, R; Hickford, S; Hill, G C; Hoffman, K D; Hoffmann, R; Homeier, A; Hoshina, K; Huelsnitz, W; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobi, E; Jacobsen, J; Jagielski, K; Japaridze, G S; Jero, K; Jlelati, O; Kaminsky, B; Kappes, A; Karg, T; Karle, A; Kelley, J L; Kiryluk, J; Kläs, J; Klein, S R; Köhne, J -H; Kohnen, G; Kolanosk, H; Köpke, L; Kopper, C; Kopper, S; Koskinen, D J; Kowalski, M; Krasberg, M; Krings, K; Kroll, G; Kunnen, J; Kurahashi, N; Kuwabara, T; Labare, M; Landsman, H; Larson, M J; Lesiak-Bzdak, M; Leuermann, M; Leute, J; Lünemann, J; Macías, O; Madsen, J; Maggi, G; Maruyama, R; Mase, K; Matis, H S; McNally, F; Meagher, K; Merck, M; Meures, T; Miarecki, S; Middell, E; Milke, N; Miller, J; Mohrmann, L; Montaruli, T; Morse, R; Nahnhauer, R; Naumann, U; Niederhausen, H; Nowicki, S C; Nygren, D R; Obertacke, A; Odrowski, S; Olivas, A; Omairat, A; O'Murchadha, A; Paul, L; Pepper, J A; Heros, C Pérez de los; Pfendner, C; Pieloth, D; Pinat, E; Posselt, J; Price, P B; Przybylski, G T; Rädel, L; Rameez, M; Rawlins, K; Redl, P; Reimann, R; Resconi, E; Rhode, W; Ribordy, M; Richman, M; Riedel, B; Rodrigues, J P; Rott, C; Ruhe, T; Ruzybayev, B; Ryckbosch, D; Saba, S M; Salameh, T; Sander, H -G; Santander, M; Sarkar, S; Schatto, K; Scheriau, F; Schmidt, T; Schmitz, M; Schoenen, S; Schöneberg, S; Schönwald, A; Schukraft, A; Schulte, L; Schulz, O; Seckel, D; Sestayo, Y; Seunarine, S; Shanidze, R; Sheremata, C; Smith, M W E; Soldin, D; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stasik, A; Stezelberger, T; Stokstad, R G; Stößl, A; Strahler, E A; Ström, R; Sullivan, G W; Taavola, H; Taboada, I; Tamburro, A; Tepe, A; Ter-Antonyan, S; Tešić, G; Tilav, S; Toale, P A; Toscano, S; Unger, E; Usner, M; Vallecorsa, S; van Eijndhoven, N; Van Overloop, A; van Santen, J; Vehring, M; Voge1, M; Vraeghe, M; Walck, C; Waldenmaier, T; Wallraff, M; Weaver, Ch; Wellons, M; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wissing, H; Wolf, M; Wood, T R; Woschnagg, K; Xu, D L; Xu, X W; Yanez, J P; Yodh, G; Yoshida, S; Zarzhitsky, P; Ziemann, J; Zierke, S; Zoll, M

    2013-01-01

    We present the results of a first search for self-annihilating dark matter in nearby galaxies and galaxy clusters using a sample of high energy neutrinos acquired in 339.8 days of livetime during 2009/10 with the IceCube neutrino observatory in its 59-string configuration. The targets of interest include the Virgo and Coma galaxy clusters, the Andromeda galaxy and several dwarf galaxies. We obtain upper limits on the cross section as function of the WIMP mass between 300 GeV and 100 TeV for the annihilation into b bbar, W+W-, \\tau+\\tau-, \\mu+\\mu- and \

  8. Dark matter in low surface brightness galaxies

    NARCIS (Netherlands)

    de Blok, WJG; McGaugh, SS; Persic, M; Salucci, P

    1997-01-01

    Low Surface Brightness (LSB) galaxies form a large population of disc galaxies that extend the Hubble sequence towards extreme late-types. They are only slowly evolving, and still in an early evolutionary state. The Tully-Fisher relation and rotation curves of LSB galaxies both show that LSB

  9. The interstellar medium in Andromeda's dwarf spheroidal galaxies - II. Multiphase gas content and ISM conditions

    Science.gov (United States)

    De Looze, Ilse; Baes, Maarten; Cormier, Diane; Kaneko, Hiroyuki; Kuno, Nario; Young, Lisa; Bendo, George J.; Boquien, Médéric; Fritz, Jacopo; Gentile, Gianfranco; Kennicutt, Robert C.; Madden, Suzanne C.; Smith, Matthew W. L.; Wilson, Christine D.

    2017-03-01

    We make an inventory of the interstellar medium material in three low-metallicity dwarf spheroidal galaxies of the Local Group (NGC 147, NGC 185 and NGC 205). Ancillary H I, CO, Spitzer Infrared Spectrograph spectra, Hα and X-ray observations are combined to trace the atomic, cold and warm molecular, ionized and hot gas phases. We present new Nobeyama CO(1-0) observations and Herschel SPIRE FTS [C I] observations of NGC 205 to revise its molecular gas content. We derive total gas masses of Mg = 1.9-5.5 × 105 M⊙ for NGC 185 and Mg = 8.6-25.0 × 105 M⊙ for NGC 205. Non-detections combine to an upper limit on the gas mass of Mg ≤ 0.3-2.2 × 105 M⊙ for NGC 147. The observed gas reservoirs are significantly lower compared to the expected gas masses based on a simple closed-box model that accounts for the gas mass returned by planetary nebulae and supernovae. The gas-to-dust mass ratios GDR ∼ 37-107 and 48-139 are also considerably lower compared to the expected GDR ∼ 370 and 520 for the low metal abundances in NGC 185 (0.36 Z⊙) and NGC 205 (0.25 Z⊙), respectively. To simultaneously account for the gas deficiency and low gas-to-dust ratios, we require an efficient removal of a large gas fraction and a longer dust survival time (∼1.6 Gyr). We believe that efficient galactic winds (combined with heating of gas to sufficiently high temperatures in order for it to escape from the galaxy) and/or environmental interactions with neighbouring galaxies are responsible for the gas removal from NGC 147, NGC 185 and NGC 205.

  10. A new constraint on millicharged dark matter from galaxy clusters

    CERN Document Server

    Kadota, Kenji; Tashiro, Hiroyuki

    2016-01-01

    We propose a new constraint on millicharged dark matter from considerations on galaxy clusters. The charged dark matter moves under the influence of the randomly oriented magnetic fields in galaxy clusters, and the corresponding dark matter density profile can significantly differ from the concordance CDM predictions which are well supported from the galaxy cluster observations. With a typical amplitude of magnetic fields $B=\\mathcal O(1)\\,\\mu$G and dark matter velocity $v=\\mathcal O(100)\\,$km/sec at a cluster radius $R\\simeq 1\\,$Mpc, we claim that the charge $\\epsilon e$ ($e$ is the elementary charge) of dark matter with mass $m$ should be bounded as $\\epsilon \\lesssim 10^{-14}(m/{\\rm GeV})$ which is substantially tighter than the other previous constraints.

  11. X-Ray Spectroscopy of diffuse Galactic Interstellar Matter with Chandra

    Science.gov (United States)

    Schulz, Norbert S.; Paerels, Frits

    One of the expectations with the advent of the High Energy Transmission Grating (HETG) spectrometer onboard the Chandra X-ray Observatory was to measure precise photoelectric edges of major cosmic elements such as O, Ne, Mg, Si, S, Ar, Ca, and Fe. Early studies revealed complex absorption structures around the O K, Fe L, and Ne K edges which were identified with absorption from the various phases of the interstellar medium and which could place limits on ionization fractions in these phases. The dust content in interstellar matter as well as, for example, the fraction of how much oxygen is locked into dust are issues of importance and here resolved X-ray edges can determine significant limits. I will review predictions made by cross-sections and depletion factors and compare with current observations specifically with respect to silicon absorption in the interstellar medium. Dust grain models and in conjunction with laboratory measurements are now used to improve current interstellar X-ray absorption models.

  12. Measuring Dark Matter Halos by Modeling Interacting Galaxies

    Science.gov (United States)

    Theis, C.

    2004-07-01

    The richness of tidal features seen in interacting galaxies allows for the determination of their characteristic parameters, provided one can deal with the extended parameter space. Genetic algorithm based methods -- like our code MINGA -- have proven to be such a tool. Here I discuss the implementation of dark matter halo descriptions in the restricted N-body simulations of MINGA. I show that the final morphology of a galaxy encounter strongly depends on the halo properties. Thus, modeling tidal features of interacting galaxies might allow also for conclusions on the galactic dark matter content.

  13. Dwarf Galaxies in Voids: Dark Matter Halos and Gas Cooling

    Directory of Open Access Journals (Sweden)

    Matthias Hoeft

    2010-01-01

    Full Text Available Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in the universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultraviolet background radiation low-mass haloes show generally a reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40 kms−1. The suppressed baryon accretion is caused by the photo-heating due to the UV background. We set up a spherical halo model and show that the effective equation of the state of the gas in the periphery of dwarf galaxies determines the characteristic mass. This implies that any process which heats the gas around dwarf galaxies increases the characteristic mass and thus reduces the number of observable dwarf galaxies.

  14. Properties of the Interstellar Medium in Star-Forming Galaxies at z ~ 1.4 Revealed with ALMA

    Science.gov (United States)

    Seko, Akifumi; Ohta, Kouji; Yabe, Kiyoto; Hatsukade, Bunyo; Akiyama, Masayuki; Iwamuro, Fumihide; Tamura, Naoyuki; Dalton, Gavin

    2016-03-01

    We conducted observations of 12CO(J = 5-4) and dust thermal continuum emission toward 20 star-forming galaxies on the main sequence at z ˜ 1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass versus star formation rate and stellar mass versus metallicity. We detected CO emission lines from 11 galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Masses of molecular gas and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) × 1010 M⊙ and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. Dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9-38) × 107 M⊙. We derived gas-to-dust ratios and found they are 3-4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4-36) × 108 yr while the results of the stacking analysis show ˜3 × 108 yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.

  15. The Dark-Matter World: are There Dark-Matter Galaxies?

    Science.gov (United States)

    Pauchy Hwang, W.-Y.

    2012-12-01

    We attempt to answer whether neutrinos and antineutrinos, such as those in the cosmic neutrino background, would clusterize among themselves or even with other dark-matter particles, under certain time span, say 1 Gyr. With neutrino masses in place, the similarity with the ordinary matter increases and so is our confidence for neutrino clustering if time is long enough. In particular, the clusterings could happen with some seeds (cf. see the text for definition), the chance in the dark-matter world to form dark-matter galaxies increases. If the dark-matter galaxies would exist in a time span of 1 Gyr, then they might even dictate the formation of the ordinary galaxies (i.e. the dark-matter galaxies get formed first); thus, the implications for the structure of our Universe would be tremendous.

  16. The Herschel exploitation of local galaxy Andromeda (HELGA) VI: Strengthening the case for substantial interstellar grain growth

    CERN Document Server

    Mattsson, L; Andersen, A C; Smith, M W L; De Looze, I; Baes, M; Viaene, S; Gentile, G; Fritz, J; Spinoglio, L

    2014-01-01

    In this paper we consider the implications of the distributions of dust and metals in the disc of M31. We derive mean radial dust distributions using a dust map created from Herschel images of M31 sampling the entire far-infrared (FIR) peak. Modified blackbodies are fit to approximately 4000 pixels with a varying, as well as a fixed, dust emissivity index (beta). An overall metal distribution is also derived using data collected from the literature. We use a simple analytical model of the evolution of the dust in a galaxy with dust contributed by stellar sources and interstellar grain growth, and fit this model to the radial dust-to-metals distribution across the galaxy. Our analysis shows that the dust-to-gas gradient in M31 is steeper than the metallicity gradient, suggesting interstellar dust growth is (or has been) important in M31. We argue that M31 helps build a case for cosmic dust in galaxies being the result of substantial interstellar grain growth, while the net dust production from stars may be lim...

  17. Mapping stellar content to dark matter halos using galaxy clustering and galaxy-galaxy lensing in the SDSS DR7

    CERN Document Server

    Zu, Ying

    2015-01-01

    The mapping between the distributions of the observed galaxy stellar mass and the underlying dark matter halos provides the crucial link from theories of large-scale structure formation to interpreting the complex phenomena of galaxy formation and evolution. We develop a novel statistical method, based on the Halo Occupation Distribution model (HOD), to solve for this mapping by jointly fitting the galaxy clustering and the galaxy-galaxy lensing measured from the Sloan Digital Sky Survey (SDSS). The method, called the iHOD model, extracts maximum information from the survey by including ~80% more galaxies than the traditional HOD methods, and takes into account the incompleteness of the stellar mass samples in a statistically consistent manner. The derived stellar-to-halo mass relation not only explains the clustering and lensing of SDSS galaxies over almost four decades in stellar mass, but also successfully predicts the stellar mass functions observed in SDSS. Due to its capability of modelling significantl...

  18. Physics of antimatter-matter reactions for interstellar propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Morgan, D.L. Jr.

    1986-08-22

    At the stage of the antiproton-nucleon annihilation chain of events relevant to propulsion the annihilation produces energetic charged pions and gamma rays. If annihilation occurs in a complex nucleus, protons, neutrons, and other nuclear fragments are also produced. The charge, number, and energy of the annihilation products are such that annihilation rocket engine concepts involving relatively low specific impulse (I/sub sp/ approx. = 1000 to 2000 s) and very high I/sub sp/ (3 x 10/sup 7/ s) appear feasible and have efficiencies on the order of 50% for annihilation energy to propulsion energy conversion. At I/sub sp/'s of around 15,000 s, however, it may be that only the kinetic energy of the charged nuclear fragments can be utilized for propulsion in engines of ordinary size. An estimate of this kinetic energy was made from known pieces of experimental and theoretical information. Its value is about 10% of the annihilation energy. Control over the mean penetration depth of protons into matter prior to annihilation is necessary so that annihilation occurs in the proper region within the engine. Control is possible by varying the antiproton kinetic energy to obtain a suitable annihilation cross section. The annihilation cross section at low energies is on the order of or larger than atomic areas due to a rearrangement reaction, but it is very low at high energy where its value is closer to nuclear areas.

  19. Dark Matter Deprivation in Field Elliptical Galaxy NGC 7507

    CERN Document Server

    Lane, Richard R; Richtler, Tom

    2014-01-01

    Previous studies have shown that the kinematics of the field elliptical galaxy NGC 7507 do not necessarily require dark matter. This is troubling because, in the context of LCDM cosmologies, all galaxies should have a large dark matter component. We use penalised pixel fitting software to extract velocities and velocity dispersions from GMOS slit mask spectra. Using Jeans and MONDian modelling we produce best fit models to the velocity dispersion. We find that NGC 7507 has a two component stellar halo, with the outer halo and inner haloes counter rotating. The velocity dispersion profile exhibits an increase at ~70" (~7.9 kpc), reminiscent of several other elliptical galaxies. Our best fit models are those under mild anisotropy which include ~100 times less dark matter than predicted by LCDM, although mildly anisotropic models that are completely dark matter free fit almost equally well. Our MONDian models, both isotropic and anisotropic, systematically fail to reproduce the measured velocity dispersions at a...

  20. Laboratory experimental simulations: Chemical evolution of the organic matter from interstellar and cometary ice analogs

    Science.gov (United States)

    Abou Mrad, N.; Vinogradoff, V.; Duverney, F.; Danger, G.; Theulé, P.; Borget, F.; Chiavassa, T.

    2015-01-01

    This contribution addresses the different approaches that are developed in our laboratory to study the chemical evolution of organic matter in stellar or interplanetary environments. In the first approach, starting from interstellar or cometary ice analogs subjected to different energy processes (thermal, photochemical), we aim to explain the mechanism of formation of key molecules (RING project: Reactivity in INterstellar ice Grains) such as HMT, POM or amino acid precursors that are or may be detected in future space missions. In a second approach, we are interested in the detection of volatile molecules sublimating from ice analogs when these latter are heated and/or irradiated (VAHIIA project: Volatile Analysis from the Heating of Interstellar Ice Analogs) through an online experimental device coupling the simulation chamber where ices are formed to a GC-MS instrument. The objective is thus to simulate the effects of the ice material warming when a young star forms or when a comet becomes active. This project provides an inventory of molecules that can be found in hot corinos or in the gaseous phase of comets. In a third approach, we analyze the organic matter contained in the refractory residues that can be considered as cometary analogs (RAHIIA Project: Residue Analysis from the Heating of Interstellar Ice Analogs) using very high resolution mass spectrometry (VHRMS). The results of these analyses show that residues present an important molecular diversity. This technique gives also the possibility to determine the elementary composition of these residues that can be compared to the meteorite composition. These residues can then be a basic material to develop, in a specific planetary environment, a prebiotic chemistry.

  1. Recovering dark-matter clustering from galaxies with Gaussianization

    Science.gov (United States)

    McCullagh, Nuala; Neyrinck, Mark; Norberg, Peder; Cole, Shaun

    2016-04-01

    The Gaussianization transform has been proposed as a method to remove the issues of scale-dependent galaxy bias and non-linearity from galaxy clustering statistics, but these benefits have yet to be thoroughly tested for realistic galaxy samples. In this paper, we test the effectiveness of the Gaussianization transform for different galaxy types by applying it to realistic simulated blue and red galaxy samples. We show that in real space, the shapes of the Gaussianized power spectra of both red and blue galaxies agree with that of the underlying dark matter, with the initial power spectrum, and with each other to smaller scales than do the statistics of the usual (untransformed) density field. However, we find that the agreement in the Gaussianized statistics breaks down in redshift space. We attribute this to the fact that red and blue galaxies exhibit very different fingers of god in redshift space. After applying a finger-of-god compression, the agreement on small scales between the Gaussianized power spectra is restored. We also compare the Gaussianization transform to the clipped galaxy density field and find that while both methods are effective in real space, they have more complicated behaviour in redshift space. Overall, we find that Gaussianization can be useful in recovering the shape of the underlying dark-matter power spectrum to k ˜ 0.5 h Mpc-1 and of the initial power spectrum to k ˜ 0.4 h Mpc-1 in certain cases at z = 0.

  2. Lost and found dark matter in elliptical galaxies.

    Science.gov (United States)

    Dekel, A; Stoehr, F; Mamon, G A; Cox, T J; Novak, G S; Primack, J R

    2005-09-29

    There is strong evidence that the mass of the Universe is dominated by dark matter, which exerts gravitational attraction but whose exact nature is unknown. In particular, all galaxies are believed to be embedded in massive haloes of dark matter. This view has recently been challenged by the observation of surprisingly low random stellar velocities in the outskirts of ordinary elliptical galaxies, which has been interpreted as indicating a lack of dark matter. Here we show that the low velocities are in fact compatible with galaxy formation in dark-matter haloes. Using numerical simulations of disk-galaxy mergers, we find that the stellar orbits in the outer regions of the resulting ellipticals are very elongated. These stars were torn by tidal forces from their original galaxies during the first close passage and put on outgoing trajectories. The elongated orbits, combined with the steeply falling density profile of the observed tracers, explain the observed low velocities even in the presence of large amounts of dark matter. Projection effects when viewing a triaxial elliptical can lead to even lower observed velocities along certain lines of sight.

  3. The Interstellar Medium in High-redshift Submillimeter Galaxies as Probed by Infrared Spectroscopy*

    Science.gov (United States)

    Wardlow, Julie L.; Cooray, Asantha; Osage, Willow; Bourne, Nathan; Clements, David; Dannerbauer, Helmut; Dunne, Loretta; Dye, Simon; Eales, Steve; Farrah, Duncan; Furlanetto, Cristina; Ibar, Edo; Ivison, Rob; Maddox, Steve; Michałowski, Michał M.; Riechers, Dominik; Rigopoulou, Dimitra; Scott, Douglas; Smith, Matthew W. L.; Wang, Lingyu; van der Werf, Paul; Valiante, Elisabetta; Valtchanov, Ivan; Verma, Aprajita

    2017-03-01

    Submillimeter galaxies (SMGs) at z≳ 1 are luminous in the far-infrared, and have star formation rates, SFR, of hundreds to thousands of solar masses per year. However, it is unclear whether they are true analogs of local ULIRGs or whether the mode of their star formation is more similar to that in local disk galaxies. We target these questions by using Herschel-PACS to examine the conditions in the interstellar medium (ISM) in far-infrared luminous SMGs at z∼ 1–4. We present 70–160 μm photometry and spectroscopy of the [O iv]26 μm, [Fe ii]26 μm, [S iii]33 μm, [Si ii]34 μm, [O iii]52 μm, [N iii]57 μm, and [O i]63 μm fine-structure lines and the S(0) and S(1) hydrogen rotational lines in 13 lensed SMGs identified by their brightness in early Herschel data. Most of the 13 targets are not individually spectroscopically detected; we instead focus on stacking these spectra with observations of an additional 32 SMGs from the Herschel archive—representing a complete compilation of PACS spectroscopy of SMGs. We detect [O i]63 μm, [Si ii]34 μm, and [N iii]57 μm at ≥slant 3σ in the stacked spectra, determining that the average strengths of these lines relative to the far-IR continuum are (0.36+/- 0.12)× {10}-3, (0.84+/- 0.17)× {10}-3, and (0.27+/- 0.10)× {10}-3, respectively. Using the [O iii]52 μm/[N iii]57 μm emission line ratio, we show that SMGs have average gas-phase metallicities ≳ {Z}ȯ . By using PDR modeling and combining the new spectral measurements with integrated far-infrared fluxes and existing [C ii]158 μm data, we show that SMGs have average gas densities, n, of ∼ {10}1-3 {{cm}}-3 and FUV field strengths, {G}0∼ {10}2.2-4.5 (in Habing units: 1.6× {10}-3 {erg} {{cm}}-2 {{{s}}}-1), consistent with both local ULIRGs and lower luminosity star-forming galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia, and important participation from NASA.

  4. SHM of Galaxies Embedded within Condensed Neutrino Matter

    CERN Document Server

    Morley, Peter D

    2014-01-01

    We re-examine the question of condensed neutrino objects (de- generate neutrino matter) based on new calculations. The potential show-stopper issue of free-streaming light neutrinos inhibiting galaxy formation is addressed. We compute the period associated with sim- ple harmonic motion (SHM) of galaxies embedded within condensed neutrino objects. For observational consequences, we examine the ro- tational velocities of embedded galaxies using Hickson 88A (N6978) as the prototype. Finally, we point out that degenerate neutrino objects repel each other in overlap and we compute directly the repulsive force between two interesting and relevant con?gurations. An outstanding issue is whether the accompanying tidal forces generated by condensed neutrino matter on embedded galaxies give rise to galactic bulges and halos.

  5. Consequences of dark matter self-annihilation for galaxy formation

    CERN Document Server

    Natarajan, Priyamvada; Bertone, Gianfranco

    2007-01-01

    Galaxy formation requires a process that continually heats gas and quenches star formation in order to reproduce the observed shape of the luminosity function of bright galaxies. To accomplish this, current models invoke heating from supernovae, and energy injection from active galactic nuclei. However, observations of radio-loud active galactic nuclei suggest that their feedback is likely to not be as efficient as required, signaling the need for additional heating processes. We propose the self-annihilation of weakly interacting massive particles that constitute dark matter as a steady source of heating. In this paper, we explore the circumstances under which this process may provide the required energy input. To do so, dark matter annihilations are incorporated into a galaxy formation model within the Millennium cosmological simulation. Energy input from self-annihilation can compensate for all the required gas cooling and reproduce the observed galaxy luminosity function only for what appear to be extreme...

  6. Dwarf spheroidal galaxies and Bose-Einstein condensate dark matter

    CERN Document Server

    Diez-Tejedor, Alberto; Profumo, Stefano

    2014-01-01

    We constrain the parameters of a self-interacting massive dark matter scalar particle in a condensate using the kinematics of the eight brightest dwarf spheroidal satellites of the Milky Way. For the case of an attractive self-interaction the condensate develops a mass density profile with a characteristic scale radius that is closely related to the fundamental parameters of the theory. We find that the velocity dispersion of dwarf spheroidal galaxies suggests a scale radius of the order of 1 kpc, in tension with previous results found using the rotational curve of low-surface-brightness and dwarf galaxies. We discuss the implications of our findings for the particle dark matter model and argue that a single classical coherent state cannot play, in general, a relevant role for the description of dark matter in galaxies.

  7. Properties of Interstellar Medium in Star-Forming Galaxies at z~1.4 revealed with ALMA

    CERN Document Server

    Seko, Akifumi; Yabe, Kiyoto; Hatsukade, Bunyo; Akiyama, Masayuki; Iwamuro, Fumihide; Tamura, Naoyuki; Dalton, Gavin

    2016-01-01

    We conducted observations of 12CO(J=5-4) and dust thermal continuum emission toward twenty star-forming galaxies on the main sequence at z~1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass-star formation rate and stellar mass-metallicity. We detected CO emission lines from eleven galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H2 conversion factor and assuming a CO(5-4)/CO(1-0) luminosity ratio of 0.23. Molecular gas masses and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9-12) x 10^{10} Msun and 0.25-0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and that t...

  8. A filament of dark matter between two clusters of galaxies.

    Science.gov (United States)

    Dietrich, Jörg P; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora

    2012-07-12

    It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this 'cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm–hot intergalactic medium (a sparse plasma with temperatures of 10(5) kelvin to 10(7) kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament.

  9. Hubble tracks down a galaxy cluster's dark matter

    Science.gov (United States)

    2003-07-01

    Unique mass map hi-res Size hi-res: 495 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Unique mass map This is a mass map of galaxy cluster Cl0024+1654 derived from an extensive Hubble Space Telescope campaign. The colour image is made from two images: a dark-matter map (the blue part of the image) and a 'luminous-matter' map determined from the galaxies in the cluster (the red part of the image). They were constructed by feeding Hubble and ground-based observations into advanced mathematical mass-mapping models. The map shows that dark matter is present where the galaxies clump together. The mass of the galaxies is shown in red, the mass of the dark matter in blue. The dark matter behaves like a 'glue', holding the cluster together. The dark-matter distribution in the cluster is not spherical. A secondary concentration of dark-matter mass is shown in blue to the upper right of the main concentration. Sky around galaxy cluster Cl0024+1654 hi-res Size hi-res: 3742 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Sky around galaxy cluster Cl0024+1654 This is a 2.5-degree field around galaxy cluster Cl0024+1654. The cluster galaxies are visible in the centre of the image in yellow. The image is a colour composite constructed from three Digitized Sky Survey 2 images: Blue (shown in blue), Red (shown in green), and Infrared (shown in red). HST observes shapes of more than 7000 faint background galaxies hi-res Size hi-res: 5593 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Hubble observes shapes of more than 7000 faint background galaxies Five days of observations produced the altogether 39 Hubble Wide Field and Planetary Camera 2 (WFPC2) images required to map the mass of the galaxy cluster Cl0024+1654. Each WFPC2 image has a size of about 1/150 the diameter of the full Moon. In

  10. Dark matter deprivation in the field elliptical galaxy NGC 7507

    Science.gov (United States)

    Lane, Richard R.; Salinas, Ricardo; Richtler, Tom

    2015-02-01

    Context. Previous studies have shown that the kinematics of the field elliptical galaxy NGC 7507 do not necessarily require dark matter. This is troubling because, in the context of ΛCDM cosmologies, all galaxies should have a large dark matter component. Aims: Our aims are to determine the rotation and velocity dispersion profile out to larger radii than do previous studies, and, therefore, more accurately estimate of the dark matter content of the galaxy. Methods: We use penalised pixel-fitting software to extract velocities and velocity dispersions from GMOS slit mask spectra. Using Jeans and MONDian modelling, we then produce models with the goal of fitting the velocity dispersion data. Results: NGC 7507 has a two-component stellar halo, with the outer halo counter rotating with respect to the inner halo, with a kinematic boundary at a radius of ~110'' (~12.4 kpc). The velocity dispersion profile exhibits an increase at ~70'' (~7.9 kpc), reminiscent of several other elliptical galaxies. Our best fit models are those under mild anisotropy, which include ~100 times less dark matter than predicted by ΛCDM, although mildly anisotropic models that are completely dark matter free fit the measured dynamics almost equally well. Our MONDian models, both isotropic and anisotropic, systematically fail to reproduce the measured velocity dispersions at almost all radii. Conclusions: The counter-rotating outer halo implies a merger remnant, as does the increase in velocity dispersion at ~70''. From simulations it seems plausible that the merger that caused the increase in velocity dispersion was a spiral-spiral merger. Our Jeans models are completely consistent with a no dark matter scenario, however, some dark matter can be accommodated, although at much lower concentrations than predicted by ΛCDM simulations. This indicates that NGC 7507 may be a dark matter free elliptical galaxy. Regardless of whether NGC 7507 is completely dark matter free or very dark matter poor

  11. Galaxy rotations from quantised inertia and visible matter only

    Science.gov (United States)

    McCulloch, M. E.

    2017-09-01

    It is shown here that a model for inertial mass, called quantised inertia, or MiHsC (Modified inertia by a Hubble-scale Casimir effect) predicts the rotational acceleration of the 153 good quality galaxies in the SPARC dataset (2016 AJ 152 157), with a large range of scales and mass, from just their visible baryonic matter, the speed of light and the co-moving diameter of the observable universe. No dark matter is needed. The performance of quantised inertia is comparable to that of MoND, yet it needs no adjustable parameter. As a further critical test, quantised inertia uniquely predicts a specific increase in the galaxy rotation anomaly at higher redshifts. This test is now becoming possible and new data shows that galaxy rotational accelerations do increase with redshift in the predicted manner, at least up to Z=2.2.

  12. Asymmetric warps in disk galaxies: dependence on dark matter halo

    CERN Document Server

    Jog, K S C J

    2006-01-01

    Recent observations have shown that most of the warps in the disk galaxies are asymmetric. However there exists no generic mechanism to generate these asymmetries in warps. We have shown that a rich variety of possible asymmetries in the z-distribution of the spiral galaxies can naturally arise due to a dynamical wave interference between the first two bending modes i.e. bowl-shaped mode(m=0) and S-shaped warping mode(m=1) in the galactic disk embedded in a dark matter halo. We show that the asymmetric warps are more pronounced when the dark matter content within the optical disk is lower as in early-type galaxies.

  13. Galaxy clustering and the dark-matter problem

    Energy Technology Data Exchange (ETDEWEB)

    Frenk, C.S.

    1986-12-17

    Recent observational and theoretical results on galaxy clustering are reviewed. A major difficulty in relating observations to theory is that the former refer to luminous material whereas the latter is most directly concerned with the gravitationally dominant but invisible dark matter. The simple assumption that the distribution of galaxies generally follows that of the mass appears to conflict with evidence suggesting that galaxies of different kinds are clustered in different ways. If galaxies are indeed biased tracers of the mass, then dynamical estimates of the mean cosmic density, which give ..cap omega.. approx. = 0.2 may underestimate the global value of ..cap omega... There are now several specific models for the behaviour of density fluctuations from very early times to the present epoch. The late phases of this evolution need to be followed by N-body techniques; simulations of scale-free universes and of universes dominated by various types of elementary particles are discussed.

  14. Quintessence-like Dark Matter in Spiral Galaxies

    CERN Document Server

    Matos, T; Núñez, D; Ramírez, E

    2000-01-01

    Through the geodesic analysis of a static and axially symmetric space time,we present conditions over the state equation of an isotropic perfect fluid$p=\\omega d$, when it is considered as dark matter in spiral galaxies. The mainconclusion is that it can be an exotic fluid ($-1<\\omega <-1/3$) as it is foundfor Quintessence at cosmological scale.

  15. On the distribution of dark matter in clusters of galaxies

    Science.gov (United States)

    Sand, David J.

    2006-07-01

    The goal of this thesis is to provide constraints on the dark matter density profile in galaxy clusters by developing and combining different techniques. The work is motivated by the fact that a precise measurement of the logarithmic slope of the dark matter on small scales provides a powerful test of the Cold Dark Matter paradigm for structure formation, where numerical simulations suggest a density profile r DM 0( r -1 or steeper in the innermost regions. We have obtained deep spectroscopy of gravitational arcs and the dominant brightest cluster galaxy in six carefully chosen galaxy clusters. Three of the clusters have both radial and tangential gravitational arcs while the other three display only tangential arcs. We analyze the stellar velocity dispersion for the brightest cluster galaxies in conjunction with axially symmetric lens models to jointly constrain the dark and baryonic mass profiles jointly. For the radial are systems we find the inner dark matter density profile is consistent with r DM 0( r -b , with [left angle bracket]b[right angle bracket] = [Special characters omitted.] (68% CL). Likewise, an upper limit on b for the tangential arc sample is found to be b work, we present a more elaborate two dimensional lens model of the cluster MS2137 using a new ly upgraded gravitational lensing code. (Abstract shortened by UMI.)

  16. Extended Stellar Components of Galaxies & the Nature of Dark Matter

    CERN Document Server

    Power, Chris

    2016-01-01

    Deep observations of galaxies reveal faint extended stellar components (hereafter ESCs) of streams, shells, and halos. These are a natural prediction of hierarchical galaxy formation, as accreted satellite galaxies are tidally disrupted by their host. We investigate whether or not global properties of the ESC could be used to test of dark matter, reasoning that they should be sensitive to the abundance of low-mass satellites, and therefore the underlying dark matter model. Using cosmological simulations of galaxy formation in the favoured Cold Dark Matter (CDM) and Warm Dark Matter (WDM) models ($m_{\\rm WDM}$=0.5,1,2 keV/$c^2$), which suppress the abundance of low-mass satellites, we find that the kinematics and orbital structure of the ESC is consistent across models. However, we find striking differences in its spatial structure, as anticipated -- a factor of $\\sim$10 drop in spherically averaged mass density between $\\sim$10% and $\\sim$75% of the virial radius in the more extreme WDM runs ($m_{\\rm WDM}$=0....

  17. Stellar, Gas, and Dark Matter Content of Barred Galaxies

    Science.gov (United States)

    Cervantes Sodi, Bernardo

    2017-01-01

    We select a sample of galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) where galaxies are classified, through visual inspection, as hosting strong bars, weak bars, or as unbarred galaxies, and make use of H i mass and kinematic information from the Arecibo Legacy Fast ALFA survey catalog, to study the stellar, atomic gas, and dark matter content of barred disk galaxies. We find, in agreement with previous studies, that the bar fraction increases with increasing stellar mass. A similar trend is found with total baryonic mass, although the dependence is not as strong as with stellar mass, due to the contribution of gas. The bar fraction shows a decrease with increasing gas mass fraction. This anticorrelation between the likelihood of a galaxy hosting a bar with the gas richness of the galaxy results from the inhibiting effect the gas has in the formation of bars. We also find that for massive galaxies with stellar masses larger than 1010 M⊙, at fixed stellar mass, the bar fraction decreases with increasing global halo mass (i.e., halo mass measured up to a radius of the order of the H i disk extent).

  18. Stellar, gas and dark matter content of barred galaxies

    CERN Document Server

    Sodi, Bernardo Cervantes

    2016-01-01

    We select a sample of galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) where galaxies are classified, through visual inspection, as hosting strong bars, weak bars or as unbarred galaxies, and make use of HI mass and kinematic information from the Arecibo Legacy Fast ALFA (ALFALFA) survey catalog, to study the stellar, atomic gas and dark matter content of barred disk galaxies. We find, in agreement with previous studies, that the bar fraction increases with increasing stellar mass. A similar trend is found with total baryonic mass, although the dependence is not as strong as with stellar mass, this due to the contribution of gas. The bar fraction shows a decrease with increasing gas mass fraction. This anticorrelation between the likelihood of a galaxy hosting a bar with the gas richness of the galaxy results from the inhibiting effect the gas has in the formation of bars. We also find that for massive galaxies with stellar masses larger than 10$^{10} M_{\\odot}$, at fixed stellar mass, the...

  19. Recovering dark-matter clustering from galaxies with Gaussianization

    CERN Document Server

    McCullagh, Nuala; Norberg, Peder; Cole, Shaun

    2015-01-01

    The Gaussianization transform has been proposed as a method to remove the issues of scale-dependent galaxy bias and nonlinearity from galaxy clustering statistics, but these benefits have yet to be thoroughly tested for realistic galaxy samples. In this paper, we test the effectiveness of the Gaussianization transform for different galaxy types by applying it to realistic simulated blue and red galaxy samples. We show that in real space, the shapes of the Gaussianized power spectra of both red and blue galaxies agree with that of the underlying dark matter, with the initial power spectrum, and with each other to smaller scales than do the statistics of the usual (untransformed) density field. However, we find that the agreement in the Gaussianized statistics breaks down in redshift space. We attribute this to the fact that red and blue galaxies exhibit very different fingers of god in redshift space. After applying a finger-of-god compression, the agreement on small scales between the Gaussianized power spect...

  20. The evolution of the galaxy content of dark matter haloes

    Science.gov (United States)

    Contreras, S.; Zehavi, I.; Baugh, C. M.; Padilla, N.; Norberg, P.

    2017-03-01

    We use the halo occupation distribution (HOD) framework to characterize the predictions from two independent galaxy formation models for the galactic content of dark matter haloes and its evolution with redshift. Our galaxy samples correspond to a range of fixed number densities defined by stellar mass and span 0 ≤ z ≤ 3. We find remarkable similarities between the model predictions. Differences arise at low galaxy number densities which are sensitive to the treatment of heating of the hot halo by active galactic nuclei. The evolution of the form of the HOD can be described in a relatively simple way, and we model each HOD parameter using its value at z = 0 and an additional evolutionary parameter. In particular, we find that the ratio between the characteristic halo masses for hosting central and satellite galaxies can serve as a sensitive diagnostic for galaxy evolution models. Our results can be used to test and develop empirical studies of galaxy evolution, and can facilitate the construction of mock galaxy catalogues for future surveys.

  1. Absorption variability as a probe of the multiphase interstellar media surrounding active galaxies

    CERN Document Server

    Macquart, Jean-Pierre

    2016-01-01

    We examine a model for the variable free-free and neutral hydrogen absorption inferred towards the cores of some compact radio galaxies in which a spatially fluctuating medium drifts in front of the source. We relate the absorption-induced intensity fluctuations to the statistics of the underlying opacity fluctuations. We investigate models in which the absorbing medium consists of either discrete clouds or a power-law spectrum of opacity fluctuations. We examine the variability characteristics of a medium comprised of Gaussian-shaped clouds in which the neutral and ionized matter are co-located, and in which the clouds comprise spherical constant-density neutral cores enveloped by ionized sheaths. The cross-power spectrum indicates the spatial relationship between neutral and ionized matter, and distinguishes the two models, with power in the Gaussian model declining as a featureless power-law, but that in the ionized sheath model oscillating between positive and negative values. We show how comparison of th...

  2. Testing Ultra-Light Dark Matter Axions Using Galaxy Surveys

    Science.gov (United States)

    Trott, Emery; Smith, Tristan L.; Grin, Daniel

    2017-01-01

    The axion is a particle that has been strongly motivated by symmetry arguments in particle physics since the 1970s and has recently become promising in a cosmological context as well. Ultra-light axions are among the candidates for dark matter and would produce a characteristic suppression of the matter power spectrum at high wavenumbers. The strength of this suppression is heavily dependent on both the mass of the axion and on what fraction of the dark matter it constitutes. In this work, we forecast the sensitivity of future galaxy surveys to determine the ultra-light axion abundance at a variety of axion masses, using Fisher-matrix analysis.

  3. Testing Lorentz invariance of dark matter with satellite galaxies

    Science.gov (United States)

    Bettoni, Dario; Nusser, Adi; Blas, Diego; Sibiryakov, Sergey

    2017-05-01

    We develop the framework for testing Lorentz invariance in the dark matter sector using galactic dynamics. We consider a Lorentz violating (LV) vector field acting on the dark matter component of a satellite galaxy orbiting in a host halo. We introduce a numerical model for the dynamics of satellites in a galactic halo and for a galaxy in a rich cluster to explore observational consequences of such an LV field. The orbital motion of a satellite excites a time dependent LV force which greatly affects its internal dynamics. Our analysis points out key observational signatures which serve as probes of LV forces. These include modifications to the line of sight velocity dispersion, mass profiles and shapes of satellites. With future data and a more detailed modeling these signatures can be exploited to constrain a new region of the parameter space describing the LV in the dark matter sector.

  4. Signatures of Dark Matter Halo Expansion in Galaxy Populations

    CERN Document Server

    Brook, Chris B

    2015-01-01

    Dark matter cores within galaxy haloes can be formed by energy feedback from star forming regions: an energy balance suggests that the maximum core formation efficiency arises in galaxies with M$_{\\star}\\sim10^{8.5}$M$_{\\odot}$. We show that a model population of galaxies, in which the density profile has been modified by such baryonic feedback, is able to explain the observed galaxy velocity function and Tully-Fisher relations significantly better than a model in which a universal cuspy density profile is assumed. Alternative models, namely warm or self-interacting dark matter, also provide a better match to these observed relations than a universal profile model does, but make different predictions for how halo density profiles vary with mass compared to the baryonic feedback case. We propose that different core formation mechanisms may be distinguished based on the imprint they leave on galaxy populations over a wide range of mass. Within the current observational data we find evidence of the expected sign...

  5. Dark Matter and the Chemical Evolution of Irregular Galaxies

    Directory of Open Access Journals (Sweden)

    L. Carigi

    2001-01-01

    Full Text Available We present three types of chemical evolution models for irregular galaxies: closed-box with continuous star formation rates (SFRs, closed-box with burstin g SFRs, and O-rich outflow with continuous SFRs. We discuss the chemical evolution of the irregular galaxies NGC 1560 and II Zw 33, and a "typical" irregular galaxy. The fraction of low-mass stars needed by our models is larger than that derived for the solar vicinity, but similar to that found in globular clusters. For our typical irregular galaxy we need a mass fraction of about 40% in the form of substellar objects plus non baryonic dark matter inside the Holmberg radius, in good agreement with the results derived for NGC 1560 and II Zw 33 where we do have an independent estimate of the mass fraction in non baryonic dark matter. Closed-box models are better than O-rich outflow models in explaining the C/O and Z/O observed values for our typical irregular galaxy.

  6. Constraining Dark Matter Through the Study of Merging Galaxy Clusters

    Science.gov (United States)

    Dawson, William Anthony

    2013-03-01

    Context: The majority (~85%) of the matter in the universe is composed of dark matter, a mysterious particle that does not interact via the electromagnetic force yet does interact with all other matter via the gravitational force. Many direct detection experiments have been devoted to finding interactions of dark matter with baryonic matter via the weak force. It is still possible that dark matter interacts with itself via a strong scale force and has a self-scattering cross-section of ~0.5 cm2g -1. In fact such a strong scale scattering force could resolve several outstanding astronomical mysteries: a discrepancy between the cuspy density profiles seen in ΛCDM simulations and the cored density profiles observed in low surface brightness galaxies, dwarf spheroidal galaxies, and galaxy clusters, as well as the discrepancy between the significant number of massive Milky Way dwarf spheroidal halos predicted by ΛCDM and the dearth of observed Milky Way dwarf spheroidal halos. Need: While such observations are in conflict with ΛCDM and suggest that dark matter may self-scatter, each suffers from a baryonic degeneracy, where the observations might be explained by various baryonic processes (e.g., AGN or supernove feedback, stellar winds, etc.) rather than self-interacting dark matter (SIDM). If dark matter lags behind the effectively collisionless galaxies then this is clear evidence that dark matter self-interacts. The expected galaxy-dark matter offset is typically >25 kpc (for cross-sections that would explain the other aforementioned issues with ΛCDM), this is larger than the scales of that are plagued by the baryonic degeneracies. Task: To test whether dark matter self-interacts we have carried out a comprehensive survey of the dissociative merging galaxy cluster DLSCL J0916.2+2951 (also known as the Musket Ball Cluster). This survey includes photometric and spectroscopic observations to quantify the position and velocity of the cluster galaxies, weak

  7. Scalar Field Dark Matter in Clusters of Galaxies

    CERN Document Server

    Bernal, Tula; Matos, Tonatiuh

    2016-01-01

    One alternative to the CDM paradigm is the Scalar Field Dark Matter (SFDM) model, which assumes dark matter is a spin-0 ultra-light scalar field with a typical mass $m\\sim10^{-22}\\mathrm{eV}/c^2$ and positive self-interactions. Due to the ultra-light boson mass, the SFDM could form Bose-Einstein condensates in the very early universe, which are interpreted as the dark matter haloes. Although cosmologically the model behaves as CDM, they differ at small scales: SFDM naturally predicts fewer satellite haloes, cores in dwarf galaxies and the formation of massive galaxies at high redshifts. The ground state (or BEC) solution at zero temperature suffices to describe low-mass galaxies but fails for larger systems. A possible solution is adding finite-temperature corrections to the SF potential which allows combinations of excited states. In this work we test the finite-temperature multistate SFDM solution at galaxy cluster scales and compare our results with the NFW and BEC profiles. We achieve this by fitting the ...

  8. The evolution of the galaxy content of dark matter haloes

    CERN Document Server

    Contreras, S; Baugh, C M; Padilla, N; Norberg, P

    2016-01-01

    We use the halo occupation distribution (HOD) framework to characterise the predictions from two independent galaxy formation models for the galactic content of dark matter haloes and its evolution with redshift. Our galaxy samples correspond to a range of fixed number densities defined by stellar mass and span $0 \\le z \\le 3$. We find remarkable similarities between the model predictions. Differences arise at low galaxy number densities which are sensitive to the treatment of heating of the hot halo by active galactic nuclei. The evolution of the form of the HOD can be described in a relatively simple way, and we model each HOD parameter using its value at $z=0$ and an additional evolutionary parameter. In particular, we find that the ratio between the characteristic halo masses for hosting central and satellite galaxies can serve as a sensitive diagnostic for galaxy evolution models. Our results can be used to test and develop empirical studies of galaxy evolution and can facilitate the construction of mock...

  9. Dark Matter Identification using Gamma Rays from Dwarf Galaxies

    CERN Document Server

    Shakya, Bibhushan

    2010-01-01

    If the positron fraction and combined electron-positron flux excesses recently observed by PAMELA, Fermi and HESS have a dark matter origin, final state radiation (FSR) photons from dark matter annihilation into lepton-rich final states may be detected with observations of satellite dwarf galaxies of the Milky Way by ground-based atmospheric Cherenkov telescopes (ACTs). We find that current and near-future ACTs have excellent potential for such detection, although a discovery cannot be guaranteed due to large uncertainties in the distribution of dark matter within the dwarfs. We find that models predicting dark matter annihilation into two-lepton final states and those favoring four-lepton final states (as in, for example, "axion portal" models) can be reliably distinguished using the FSR photon spectrum once measured, and the dark matter particle mass can also be accurately determined.

  10. Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

    CERN Document Server

    Sanchez-Conde, Miguel A; Zandanel, F; Gomez, Mario E; Prada, F

    2011-01-01

    In the last few years, most of the attention in gamma-ray dark matter (DM) searches has been devoted to neutralino annihilations in nearby dwarf galaxies. However, massive galaxy clusters in the local Universe may constitute very good targets as well. The main aim of this work is to compare both dwarf galaxies and local galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies and galaxy clusters, and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman~1 appears as the best candidate in the sample and, given the morphology of its annihilation signal, it is also one of the objects more readily observable by IACTs. As for galaxy clusters, Virgo represents the one with the hi...

  11. Ellipticity of dark matter halos with galaxy-galaxy weak lensing

    CERN Document Server

    Mandelbaum, R; Broderick, T; Seljak, U; Brinkmann, J; Mandelbaum, Rachel; Hirata, Christopher M.; Broderick, Tamara; Seljak, Uros; Brinkmann, Jonathan

    2005-01-01

    We present the results of attempts to detect the ellipticity of dark matter halos using galaxy-galaxy weak lensing with SDSS data. We use 2,020,256 galaxies brighter than r=19 with photometric redshifts (divided into colour and luminosity subsamples) as lenses and 31,697,869 source galaxies. We search for and identify several signal contaminants, which if not removed lead to a spurious detection. These include systematic shear that leads to a slight spurious alignment of lens and source ellipticities, intrinsic alignments (due to contamination of the source sample by physically-associated lens source pairs), and anisotropic magnification bias. We develop methods that allow us to remove these contaminants to the signal. We split the analysis into blue (spiral) and red (elliptical) galaxies. Assuming Gaussian errors as in previous work and a power-law profile, we find f_h=e_h/e_g=0.1+/-0.06 for red galaxies and -0.8+/-0.4 for blue galaxies using 20-300 kpc/h, averaged over luminosity. Inclusion of the more real...

  12. Dark Matter Inelastic Up-Scattering with the Interstellar Plasma: An Exciting New Source of X-Ray Lines, including at 3.5 keV

    CERN Document Server

    D'Eramo, Francesco; Profumo, Stefano; Stefaniak, Tim

    2016-01-01

    We explore the phenomenology of a class of models where the dark matter particle can inelastically up-scatter to a heavier excited state via off-diagonal dipolar interactions with the interstellar plasma (gas or free electrons). The heavier particle then rapidly decays back to the dark matter particle plus a quasi-monochromatic photon. For the process to occur at appreciable rates, the mass splitting between the heavier state and the dark matter must be comparable to, or smaller than, the kinetic energy of particles in the plasma. As a result, the predicted photon line falls in the soft X-ray range, or, potentially, at arbitrarily lower energies. We explore experimental constraints from cosmology and particle physics, and present accurate calculations of the dark matter thermal relic density and of the flux of monochromatic X-rays from thermal plasma excitation. We find that the model provides a natural explanation for the observed 3.5 keV line from clusters of galaxies and from the Galactic center, and is co...

  13. Central dark matter trends in early-type galaxies .

    Science.gov (United States)

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

    We analyze the correlations between the central dark matter 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. 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.

  14. The dark matter halos of spheroidal galaxies and clusters of galaxies

    CERN Document Server

    Treu, T; Sand, D J; Smith, G P; Ellis, Richard S

    2003-01-01

    We describe the first results from two observational projects aimed at measuring the amount and spatial distribution of dark matter in distant early-type galaxies (E/S0s) and clusters of galaxies. At the galaxy scale, the Lenses Structure and Dynamics (LSD) Survey is gathering kinematic data for distant (up to $z\\sim1$) E/S0s that are gravitational lenses. A joint lensing and dynamical analysis constrains the fraction of dark matter within the Einstein radius, the mass-to-light ratio of the stellar component, and the total slope of the mass density profile. These properties and their evolution with redshift are briefly discussed in terms of the formation and evolution of E/S0 galaxies and measurement of the Hubble Constant from gravitational time delay systems. At the cluster scale -- after careful removal of the stellar component with a joint lensing and dynamical analysis -- systems with giant radial arcs can be used to measure precisely the inner slope of the dark matter halo. An HST search for radial arcs...

  15. Rotation curves of 967 spiral galaxies: implications for dark matter.

    Science.gov (United States)

    Persic, M.; Salucci, P.; Stel, F.

    1996-02-01

    The authors present the rotation curves of 967 spiral galaxies, obtained by deprojecting and folding the raw Hα data published by Mathewson et al. (1992). Of these, 80 meet objective excellence criteria and are suitable for individual detailed mass modelling, while 820 are suitable for statistical studies. A preliminary analysis of their properties confirms that rotation curves are a universal function of luminosity and that the dark matter fraction in spirals increases with decreasing luminosity.

  16. A simple model linking galaxy and dark matter evolution

    Energy Technology Data Exchange (ETDEWEB)

    Birrer, Simon; Lilly, Simon; Amara, Adam; Paranjape, Aseem; Refregier, Alexandre, E-mail: simon.birrer@phys.ethz.ch, E-mail: simon.lilly@phys.ethz.ch [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich (Switzerland)

    2014-09-20

    We construct a simple phenomenological model for the evolving galaxy population by incorporating predefined baryonic prescriptions into a dark matter hierarchical merger tree. The model is based on the simple gas-regulator model introduced by Lilly et al., coupled with the empirical quenching rules of Peng et al. The simplest model already does quite well in reproducing, without re-adjusting the input parameters, many observables, including the main sequence sSFR-mass relation, the faint end slope of the galaxy mass function, and the shape of the star forming and passive mass functions. Similar to observations and/or the recent phenomenological model of Behroozi et al., which was based on epoch-dependent abundance-matching, our model also qualitatively reproduces the evolution of the main sequence sSFR(z) and SFRD(z) star formation rate density relations, the M{sub s} – M{sub h} stellar-to-halo mass relation, and the SFR – M{sub h} relation. Quantitatively the evolution of sSFR(z) and SFRD(z) is not steep enough, the M{sub s} – M{sub h} relation is not quite peaked enough, and, surprisingly, the ratio of quenched to star forming galaxies around M* is not quite high enough. We show that these deficiencies can simultaneously be solved by ad hoc allowing galaxies to re-ingest some of the gas previously expelled in winds, provided that this is done in a mass-dependent and epoch-dependent way. These allow the model galaxies to reduce an inherent tendency to saturate their star formation efficiency, which emphasizes how efficient galaxies around M* are in converting baryons into stars and highlights the fact that quenching occurs at the point when galaxies are rapidly approaching the maximum possible efficiency of converting baryons into stars.

  17. Dark Matter Identification with Gamma Rays from Dwarf Galaxies

    CERN Document Server

    Perelstein, Maxim

    2010-01-01

    If the positron fraction and combined electron-positron flux excesses recently observed by PAMELA, FERMI and HESS are due to dark matter annihilation into lepton-rich final states, the accompanying final state radiation (FSR) photons may be detected by ground-based atmospheric Cherenkov telescopes (ACTs). Satellite dwarf galaxies in the vicinity of the Milky Way are particularly promising targets for this search. We find that current and near-future ACTs have an excellent potential for discovering the FSR photons from dwarfs, although a discovery cannot be guaranteed due to large uncertainties in the fluxes resulting from lack of precise knowledge of dark matter distribution within the dwarfs. We also investigate the possibility of discriminating between different dark matter models based on the measured FSR photon spectrum. For typical parameters, we find that the ACTs can reliably distinguish models predicting dark matter annihilation into two-lepton final states from those favoring four-lepton final states...

  18. Scalar Field Dark Matter and Galaxy Formation

    CERN Document Server

    Alcubierre, M; Matos, T; Núñez, D; Urena-Lopez, L A; Wiederhold, P; Alcubierre, Miguel; Matos, Tonatiuh; Nunez, Dario; Wiederhold, Petra

    2002-01-01

    We present a general description of the scalar field dark matter (SFDM) hypothesis in the cosmological context. The scenario of structure formation under such a hypothesis is based on Jeans instabilities of fluctuations of the scalar field. It is shown that it is possible to form stable long lived objects consisting of a wide range of typical galactic masses around $10^{12}M_{\\odot}$ once the parameters of the effective theory are fixed with the cosmological constraints. The energy density at the origin of such an object is smooth as it should.

  19. Diffuse interstellar bands (DIB): co-planar doubly excited He and metal atoms embedded in Rydberg Matter

    CERN Document Server

    Holmlid, Leif

    2011-01-01

    The interpretation of the more than 300 diffuse interstellar bands (DIBs) is one of the most long-standing problems in interstellar spectra since the two first bands were reported in 1921. We now predict the frequencies of 260 diffuse interstellar bands (DIBs) using the Rydberg Matter model we have developed previously. These transitions involve mainly He atoms, but other two-electron atoms like Ca and other metals can take part in the absorption processes. Approximately 70% of the total intensity of the DIBs is due to absorption in doubly excited states and 30% in singly excited He atoms. The doubly excited states are in inverted states while the He atoms are thermal. The possibilities to observe DIBs in the UV and NIR ranges are discussed and band positions are predicted.

  20. Dying Stars Indicate Lots of Dark Matter in Giant Galaxy

    Science.gov (United States)

    1994-04-01

    Very difficult and time-consuming observations performed with the ESO 3.5-metre New Technology Telescope (NTT) in November 1993 by an international team of astronomers [1], indicate that up to 90 percent of the matter in a distant giant galaxy may be of a kind that cannot be seen by normal telescopes. The astronomers were able to observe the individual motions of 37 extremely faint Planetary Nebulae [2] in the outskirts of the giant elliptical galaxy NGC 1399 that is located at the centre of the southern Fornax cluster of galaxies, at a distance of about 50 million light-years. The mass of the galaxy can be inferred from these motions: the faster they are, the more massive is the galaxy. Surprisingly, the total mass of NGC 1399 found from these new measurements is about ten times as large as the combined mass of the stars and nebulae seen in this galaxy. These new results also have important implications for the current ideas about the formation of giant galaxies. GIANT GALAXIES Galaxies are the basic building blocks of the Universe. Some look like spinning spirals, like our own Milky Way galaxy, with its several hundreds of billions of stars in a flat, rotating disk. Some galaxies lead a comparatively quiet life, others are violent and explosive. But perhaps the most enigmatic of them all are the largest ones, the giant elliptical galaxies. They are huge collections of stars and hot gas, 100 times brighter than the Milky Way and in many of them, the hot gas is a powerful emitter of radio waves and X-rays. The giant galaxies are mostly found at the centres of vast clusters of hundreds or thousands of smaller galaxies, like swarms of bees about the central hive. How did these great galaxies form at the centres of their clusters? Astronomers who make computer simulations of the early Universe believe they know the answer. In their simulations, they see these giant galaxies forming by gradual aggregation of small clumps of matter falling towards the centre, thereby

  1. The Interstellar Line of Sight to the Interacting Galaxy NGC 5195

    CERN Document Server

    Ritchey, Adam M

    2015-01-01

    We present moderately-high resolution echelle observations of the nucleus of NGC 5195, the line of sight to which samples intervening interstellar material associated with the outer spiral arm of M51. Our spectra reveal absorption from interstellar Na I, K I, Ca II, and CH+, and from a number of diffuse interstellar bands (DIBs), at a velocity close to that exhibited by H I 21 cm emission from M51 at the position of NGC 5195. The H I column density implied by the equivalent width of the 5780.5 DIB, based on the relationship between W(5780.5) and N(H I) derived for sight lines in the local Galactic interstellar medium, is consistent with the column density obtained from the integrated H I emission. The H2 column density predicted from the observed column density of K I, using the Galactic relationship between N(K I) and N(H2), is comparable to N(H I), suggesting a high molecular fraction (~0.65) for the M51 gas toward NGC 5195. The DIBs toward NGC 5195 are, on average, ~40% weaker than would be expected based ...

  2. Looking for dark matter trails in colliding galaxy clusters

    Science.gov (United States)

    Harvey, David; Robertson, Andrew; Massey, Richard; Kneib, Jean-Paul

    2017-02-01

    If dark matter interacts, even weakly, via non-gravitational forces, simulations predict that it will be preferentially scattered towards the trailing edge of the halo during collisions between galaxy clusters. This will temporarily create a non-symmetric mass profile, with a trailing overdensity along the direction of motion. To test this hypothesis, we fit (and subtract) symmetric haloes to the weak gravitational data of 72 merging galaxy clusters observed with the Hubble Space Telescope. We convert the shear directly into excess κ and project in to a one-dimensional profile. We generate numerical simulations and find that the one-dimensional profile is well described with simple Gaussian approximations. We detect the weak lensing signal of trailing gas at a 4σ confidence, finding a mean gas fraction of Mgas/Mdm = 0.13 ± 0.035. We find no evidence for scattered dark matter particles with an estimated scattering fraction of f = 0.03 ± 0.05. Finally, we find that if we can reduce the statistical error on the positional estimate of a single dark matter halo to test for other complimentary studies of the self-interaction cross-section of dark matter.

  3. The evolution of the atomic and molecular interstellar medium in star-forming galaxies

    NARCIS (Netherlands)

    Popping, Gergö

    2014-01-01

    In this thesis I developed models to make predictions for the atomic and molecular gas content of galaxies. Main results of my thesis include that the atomic hydrogen content of galaxies remained relatively constant with over the last 10 Billion years, whereas the molecular hydrogen content decrease

  4. VALES - III. The calibration between the dust continuum and interstellar gas content of star-forming galaxies

    Science.gov (United States)

    Hughes, T. M.; Ibar, E.; Villanueva, V.; Aravena, M.; Baes, M.; Bourne, N.; Cooray, A.; Davies, L. J. M.; Driver, S.; Dunne, L.; Dye, S.; Eales, S.; Furlanetto, C.; Herrera-Camus, R.; Ivison, R. J.; van Kampen, E.; Lara-López, M. A.; Maddox, S.; Michałowski, M. J.; Oteo, I.; Smith, D.; Smith, M. W. L.; Valiante, E.; van der Werf, P.; Viaene, S.; Xue, Y. Q.

    2017-06-01

    We present the calibration between the dust continuum luminosity and interstellar gas content obtained from the Valparaíso ALMA Line Emission Survey (VALES) sample of 67 main-sequence star-forming galaxies at 0.02 Assembly survey. Adopting αCO = 6.5 (K km s-1 pc2)-1, the average ratio of L_{ν _{850}}/MH2 = (6.4 ± 1.4)× 1019 erg s-1 Hz-1 M_{⊙}^{-1}, in excellent agreement with literature values. We obtain a linear fit of log _{10} ({M}_{H2}/{M_{⊙}}) = (0.92± 0.02) log _{10} (L_{ν _{850}}/{erg s^{-1} Hz^{-1}})-(17.31± 0.59). We provide relations between L_{ν _{850}}, MH2 and MISM when combining the VALES and literature samples, and adopting a Galactic αCO value.

  5. The Interstellar Medium and Star Formation in Local Galaxies: Variations of the Star Formation Law in Simulations

    CERN Document Server

    Becerra, Fernando

    2014-01-01

    We use the Adaptive Mesh Refinement code Enzo to model the interstellar medium in isolated local disk galaxies. The simulation includes a treatment for star formation and stellar feedback. We get a highly supersonic turbulent disk, which is fragmented at multiple scales and characterized by a multi-phase interstellar medium. We show that a Kennicutt-Schmidt (KS) relation only holds when averaging over large scales. However, values of star formation rates and gas surface densities lie close in the plot for any averaging size. This suggests an intrinsic relation between stars and gas at cell-size scales, which dominates over the global dynamical evolution. To investigate this effect, we develop a method to simulate the creation of stars based on the density field from the snapshots, without running the code again. We also investigate how the star formation law is affected by the characteristic star formation timescale, the density threshold and the efficiency considered in the recipe. We find that the slope of ...

  6. The nongravitational interactions of dark matter in colliding galaxy clusters.

    Science.gov (United States)

    Harvey, David; Massey, Richard; Kitching, Thomas; Taylor, Andy; Tittley, Eric

    2015-03-27

    Collisions between galaxy clusters provide a test of the nongravitational forces acting on dark matter. Dark matter's lack of deceleration in the "bullet cluster" collision constrained its self-interaction cross section σ(DM)/m dark matter) for long-ranged forces. Using the Chandra and Hubble Space Telescopes, we have now observed 72 collisions, including both major and minor mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6σ significance. The position of the dark mass has remained closely aligned within 5.8 ± 8.2 kiloparsecs of associated stars, implying a self-interaction cross section σ(DM)/m < 0.47 cm(2)/g (95% CL) and disfavoring some proposed extensions to the standard model.

  7. Copernicus observations of interstellar matter in the direction of HR 1099

    Science.gov (United States)

    Anderson, R. C.; Weiler, E. J.

    1978-01-01

    Results are reported for high-resolution Copernicus U1 and V2 scans of the bright RS CVn spectroscopic binary HR 1099. The observations reveal strong UV emission lines at L-alpha and Mg II h and k from the stars as well as interstellar H I and D I L-alpha absorption lines and interstellar Mg II h and k absorption in the direction of the binary system. Column densities, bulk velocities, and temperatures are derived for the interstellar features. A comparison of the derived number density of interstellar H I with data for the nearby star Epsilon Eri indicates an inhomogeneous distribution of interstellar hydrogen along the line of sight. The range of values obtained for the D/H ratio is shown to be consistent with results of other studies. A depletion factor of at least 5 with respect to the solar abundance is estimated for the interstellar magnesium.

  8. Galaxy Clusters in the Context of Superfluid Dark Matter

    CERN Document Server

    Hodson, Alistair; Khoury, Justin; Famaey, Benoit

    2016-01-01

    It has recently been proposed, by assuming that dark matter is a superfluid, that MOND-like effects can be achieved on small scales whilst preserving the success of $\\Lambda$CDM on large scales. Here we aim to provide the first set of spherical models of galaxy clusters in the context of superfluid dark matter. We first outline the theoretical structure of the superfluid core and the surrounding "normal phase" dark halo of quasi-particles in thermal equlibrium. The latter should encompass the largest part of galaxy clusters. Here, we set the SfDM transition at the radius where the density and pressure of the superfluid and normal phase coincides, neglecting the effect of phonons in the suprefluid core. We then apply the theory to a sample of galaxy clusters, and directly compare the SfDM predicted mass profiles to data. We find that the superfluid formulation can reproduce the X-ray dynamical mass profile of clusters, with less free parameters than the corresponding CDM fits with NFW profiles. The SfDM fits h...

  9. CONFRONTING COLD DARK MATTER PREDICTIONS WITH OBSERVED GALAXY ROTATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Obreschkow, Danail; Meyer, Martin; Power, Chris; Staveley-Smith, Lister [International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Ma, Xiangcheng [The University of Sciences and Technology of China, Centre for Astrophysics, Hefei, Anhui 230026 (China); Zwaan, Martin [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching b. Muenchen (Germany); Drinkwater, Michael J. [School of Mathematics and Physics, The University of Queensland, Brisbane, QLD 4072 (Australia)

    2013-04-01

    The rich statistics of galaxy rotations as captured by the velocity function (VF) provide invaluable constraints on galactic baryon physics and the nature of dark matter (DM). However, the comparison of observed galaxy rotations against cosmological models is prone to subtle caveats that can easily lead to misinterpretations. Our analysis reveals full statistical consistency between {approx}5000 galaxy rotations, observed in line-of-sight projection, and predictions based on the standard cosmological model ({Lambda}CDM) at the mass-resolution of the Millennium simulation (H I line-based circular velocities above {approx}50 km s{sup -1}). Explicitly, the H I linewidths in the H I Parkes All Sky Survey (HIPASS) are found to be consistent with those in S{sup 3}-SAX, a post-processed semi-analytic model for the Millennium simulation. Previously found anomalies in the VF can be plausibly attributed to (1) the mass-limit of the Millennium simulation, (2) confused sources in HIPASS, (3) inaccurate inclination measurements for optically faint sources, and (4) the non-detectability of gas-poor early-type galaxies. These issues can be bypassed by comparing observations and models using linewidth source counts rather than VFs. We investigate if and how well such source counts can constrain the temperature of DM.

  10. The Fine-Scale Structure of the neutral Interstellar Medium in nearby Galaxies

    CERN Document Server

    Bagetakos, I; Walter, F; de Blok, W J G; Usero, A; Leroy, A K; Rich, J W; Kennicutt, R C

    2010-01-01

    We present an analysis of the properties of HI holes detected in 20 galaxies that are part of "The HI Nearby Galaxy Survey" (THINGS). We detected more than 1000 holes in total in the sampled galaxies. Where they can be measured, their sizes range from about 100 pc (our resolution limit) to about 2 kpc, their expansion velocities range from 4 to 36 km/s, and their ages are estimated to range between 3 and 150 Myr. The holes are found throughout the disks of the galaxies, out to the edge of the HI; 23% of the holes fall outside R25. We find that shear limits the age of holes in spirals (shear is less important in dwarf galaxies) which explains why HI holes in dwarfs are rounder, on average than in spirals. Shear, which is particularly strong in the inner part of spiral galaxies, also explains why we find that holes outside R25 are larger and older. We derive the scale height of the HI disk as a function of galactocentric radius and find that the disk flares up in all galaxies. We proceed to derive the surface a...

  11. Indirect dark matter detection for flattened dwarf galaxies

    Science.gov (United States)

    Sanders, Jason L.; Evans, N. Wyn; Geringer-Sameth, Alex; Dehnen, Walter

    2016-09-01

    Gamma-ray experiments seeking to detect evidence of dark matter annihilation in dwarf spheroidal galaxies require knowledge of the distribution of dark matter within these systems. We analyze the effects of flattening on the annihilation (J) and decay (D) factors of dwarf spheroidal galaxies with both analytic and numerical methods. Flattening has two consequences: first, there is a geometric effect as the squeezing (or stretching) of the dark matter distribution enhances (or diminishes) the J-factor; second, the line of sight velocity dispersion of stars must hold up the flattened baryonic component in the flattened dark matter halo. We provide analytic formulas and a simple numerical approach to estimate the correction to the J- and D-factors required over simple spherical modeling. The formulas are validated with a series of equilibrium models of flattened stellar distributions embedded in flattened dark-matter distributions. We compute corrections to the J- and D-factors for the Milky Way dwarf spheroidal galaxies under the assumption that they are all prolate or all oblate and find that the hierarchy of J-factors for the dwarf spheroidals is slightly altered (typical correction factors for an ellipticity of 0.4 are 0.75 for the oblate case and 1.6 for the prolate case). We demonstrate that spherical estimates of the D-factors are very insensitive to the flattening and introduce uncertainties significantly less than the uncertainties in the D-factors from the other observables for all the dwarf spheroidals (for example, +10 per cent/-3 per cent for a typical ellipticity of 0.4). We conclude by investigating the spread in correction factors produced by triaxial figures and provide uncertainties in the J-factors for the dwarf spheroidals using different physically motivated assumptions for their intrinsic shape and axis alignments. We find that the uncertainty in the J-factors due to triaxiality increases with the observed ellipticity and, in general, introduces

  12. The same with less: The cosmic web of warm versus cold dark matter dwarf galaxies

    CERN Document Server

    Reed, Darren S; Smith, Robert E; Potter, Doug; Stadel, Joachim; Moore, Ben

    2014-01-01

    We explore fundamental properties of the distribution of low mass dark matter halos within the cosmic web using warm dark matter (WDM) and cold dark matter (CDM) cosmological simulations. Using self abundance-matched mock galaxy catalogs, we show that the distribution of dwarf galaxies in a WDM universe, wherein low mass halo formation is heavily suppressed, is nearly indistinguishable to that of a CDM universe whose low mass halos are not seen because galaxy formation is suppressed below some threshold halo mass. However, if the scatter between dwarf galaxy luminosity and halo properties is large enough, low mass CDM halos would sometimes host relatively bright galaxies thereby populating CDM voids with the occasional isolated galaxy and reducing the numbers of completely empty voids. Otherwise, without high mass to light scatter, all mock galaxy clustering statistics that we consider--the auto-correlation function, the numbers and radial profiles of satellites, the numbers of isolated galaxies, and the PDF ...

  13. Studying the Interstellar Medium of H II/BCD Galaxies Using IFU Spectroscopy

    Directory of Open Access Journals (Sweden)

    Patricio Lagos

    2013-01-01

    Full Text Available We review the results from our studies, and previous published work, on the spatially resolved physical properties of a sample of H ii/BCD galaxies, as obtained mainly from integral-field unit spectroscopy with Gemini/GMOS and VLT/VIMOS. We confirm that, within observational uncertainties, our sample galaxies show nearly spatially constant chemical abundances similar to other low-mass starburst galaxies. They also show He ii  λ4686 emission with the properties being suggestive of a mix of excitation sources and with Wolf-Rayet stars being excluded as the primary ones. Finally, in this contribution, we include a list of all H ii/BCD galaxies studied thus far with integral-field unit spectroscopy.

  14. Studying the interstellar medium of HII/BCD galaxies using IFU spectroscopy

    CERN Document Server

    Lagos, Patricio

    2013-01-01

    We review the results from our studies, and previous published work, on the spatially resolved physical properties of a sample of HII/BCD galaxies, as obtained mainly from integral-field unit spectroscopy with Gemini/GMOS and VLT/VIMOS. We confirm that, within observational uncertainties, our sample galaxies show nearly spatially constant chemical abundances, similar to other low-mass starburst galaxies. They also show He II 4686 emission with properties being suggestive of a mix of excitation sources, with Wolf-Rayet stars being excluded as the primary one. Finally, in this contribution we include a list of all HII/BCD galaxies studied thus far with integral-field unit spectroscopy.

  15. Indirect Dark Matter Detection for Flattened Dwarf Galaxies

    CERN Document Server

    Sanders, Jason L; Geringer-Sameth, Alex; Dehnen, Walter

    2016-01-01

    We analyze the effects of flattening on the annihilation (J) and decay (D) factors of dwarf spheroidal galaxies with both analytic and numerical methods. Flattening has two consequences: first, there is a geometric effect as the squeezing (or stretching) of the dark matter distribution enhances (or diminishes) the J-factor; second, the line of sight velocity dispersion of stars must hold up the flattened baryonic component in the flattened dark matter halo. We provide analytic formulae and a simple numerical approach to estimate the correction to the J- and D-factors required over simple spherical modeling. The formulae are validated with a series of equilibrium models of flattened stellar distributions embedded in flattened dark-matter distributions. We compute corrections to the J- and D-factors for the Milky Way dwarf spheroidal galaxies under the assumption that they are prolate or oblate and find that the hierarchy of J-factors for the dwarf spheroidals is slightly altered. We demonstrate that spherical ...

  16. Understanding the Toothbrush Merging Galaxy Cluster to Constrain Dark Matter

    Science.gov (United States)

    Dawson, William; Brüggen, M.; Van Weeren, R. J.; Wittman, D. M.

    2014-01-01

    Merging galaxy clusters have proven to be one of the most important probes of dark matter self-interaction properties. If their full dark matter constraining power is to be realized though, we must accurately quantify the properties of these dissociative mergers. Some properties such as mass and relative line of sight velocity can be directly measured and sufficiently constrained, but there remains considerable uncertainty on indirect properties of the mergers. Indirect properties such as the angle of the merger axis with the plane of the sky and collision velocity are crucial to translating the gravitational lensing measurements of the mass, X-ray measurements of the cluster gas and optical measurements of the galaxies into constraints on the dark matter properties. By utilizing multi-wavelength measurements (X-ray to radio), of the Toothbrush radio relic dissociative merger (1RXS J0603+4212) we show that we can improve the constraints on the indirect parameters of the merger by up to an order of magnitude vs. traditional approaches. By utilizing multi-wavelength measurements (X-ray to radio), of the Toothbrush radio relic dissociative merger we show that we can improve the constraints on the indirect parameters of the merger by up to an order of magnitude vs. traditional approaches.

  17. Jeans Analysis for Dwarf Spheroidal Galaxies in Wave Dark Matter

    CERN Document Server

    Chen, Shu-Rong; Chiueh, Tzihong

    2016-01-01

    Observations suggest that dwarf spheroidal (dSph) galaxies exhibit large constant-density cores in the centers, which can hardly be explained by dissipationless cold dark matter simulations. Wave dark matter (${\\psi {\\rm DM}}$), characterized by a single parameter, the dark matter particle mass $m_{\\psi}$, predicts a central soliton core in every galaxy arising from quantum pressure against gravity. Here we apply Jeans analysis to the kinematic data of eight classical dSphs so as to constrain $m_{\\psi}$, and obtain $m_{\\psi}=1.18_{-0.24}^{+0.28}\\times10^{-22}{\\,\\rm eV}$ and $m_{\\psi}=1.79_{-0.33}^{+0.35}\\times10^{-22}{\\,\\rm eV}~(2\\sigma)$ using the observational data sets of Walker et al. (2007) and Walker et al. (2009b), respectively. We show that the estimate of $m_{\\psi}$ is sensitive to the dSphs kinematic data sets and is robust to various models of stellar density profile. We also consider multiple stellar subpopulations in dSphs and find consistent results. This mass range of $m_{\\psi}$ is in good agre...

  18. The cycle of interstellar dust in galaxies of different morphological types

    Science.gov (United States)

    Calura, F.; Pipino, A.; Matteucci, F.

    2008-03-01

    Aims:We used chemical evolution models for galaxies of different morphological type to perform a detailed study of the evolution of the cosmic dust properties in different environments: the solar neighbourhood, elliptical galaxies and dwarf irregular galaxies. Thanks to the uptodate observations available in the solar vicinity, we intend to study the effects of dust in the chemical evolution of different types of galaxies and, at the same time, to refine investigation of the parameter space to satisfactorily fine-tune the parameters in our study. Methods: We have considered dust production from low and intermediate mass stars, supernovae Ia, supernovae II, and both dust destruction and dust accretion processes in a detailed model of chemical evolution for the solar vicinity. Then, by means of the same dust prescriptions, but adopting different galactic models (different star formation histories and the presence of galactic winds), we extended our study to ellipticals and dwarf irregular galaxies. In all these systems, dust evolution was calculated by means of chemical evolution models that relax the instantaneous recycling approximation and already reproduce the main features of the various galaxies. Results: We have investigated how the assumption of different star formation histories affects the dust production rates, dust depletion, the dust accretion, and destruction rates. We predict dust-to-gas and dust-to-metal ratios in very good agreement with those observed in the solar vicinity. We show how the inclusion of the dust treatment is helpful in solving the so-called Fe discrepancy, as observed in the hot gaseous halos of local ellipticals, and in reproducing the chemical abundances observed in the Lyman Break Galaxies. Finally, our new models can be very useful in future detailed spectro-photometric studies of galaxies.

  19. Interstellar Medium Oxygen Abundances of Dwarf Irregular Galaxies in Centaurus A and Nearby Groups

    CERN Document Server

    Lee, Henry; Grebel, E K; 10.1111/j.1365-2966.2007.11481.x

    2008-01-01

    We present results of optical spectroscopy of 35 H II regions from eight dwarf galaxies in the Centaurus A group. [O III]4363 A is detected in ESO272-G025 and ESO324-G024, and direct oxygen abundances of 12+log(O/H) = 7.76 +/- 0.09 and 7.94 +/- 0.11 are derived, respectively. For the remaining galaxies, abundances are derived using common bright-line methods. To compare the influence of group environments on dwarf galaxies, we have also gathered data for additional dwarf irregular galaxies from the Cen A and the Sculptor groups from the literature. We have examined possible relationships between oxygen abundance, gas fraction, effective chemical yield, and tidal indices. Despite large positive tidal indices for a number of Cen A dwarfs in the present sample, there is no clear separation between galaxies with positive tidal indices and galaxies with negative tidal indices in the luminosity-metallicity, metallicity-gas fraction, and metallicity-tidal index diagrams. The H I surface mass density decreases with i...

  20. The Properties of the Interstellar Medium within a Star-Forming Galaxy at z=2.3

    CERN Document Server

    Danielson, A L R; Smail, Ian; Cox, P; Edge, A C; Weiss, A; Harris, A I; Baker, A J; De Breuck, C; Geach, J E; Ivison, R J; Krips, M; Lungdren, A; Longmore, S; Neri, R; Flacquer, B Ocana

    2010-01-01

    We present an analysis of the molecular and atomic gas emission in the rest-frame far-infrared and sub-millimetre, from the lensed z=2.3 sub-millimetre galaxy SMM J2135-0102. We obtain very high signal-to-noise detections of 11 transitions from 3 species and limits on a further 20 transitions from 9 species. We use the 12CO, [CI] and HCN line strengths to investigate the gas mass, kinematic structure and interstellar medium (ISM) chemistry, and find strong evidence for a two-phase medium comprising a hot, dense, luminous component and an underlying extended cool, low-excitation massive component. Employing photo-dissociation region models we show that on average the molecular gas is exposed to a UV radiation field that is ~1000 x more intense than the Milky Way, with star-forming regions having a characteristic density of n~10^4 /cm^3. These conditions are similar to those found in local ULIRGs and in the central regions of typical starburst galaxies, even though the star formation rate is far higher in this ...

  1. Satellite galaxies in semi-analytic models of galaxy formation with sterile neutrino dark matter

    CERN Document Server

    Lovell, Mark R; Boyarsky, Alexey; Cole, Shaun; Frenk, Carlos S; Gonzalez-Perez, Violeta; Kennedy, Rachel; Ruchayskiy, Oleg; Smith, Alex

    2015-01-01

    The sterile neutrino is a viable dark matter candidate that can be produced in the early Universe via non-equilibrium processes, and would therefore possess a highly non-thermal spectrum of primordial velocities. In this paper we analyse the process of structure formation with this class of dark matter particles. To this end we construct primordial dark matter power spectra as a function of the lepton asymmetry, $L_6$, that is present in the primordial plasma and leads to resonant sterile neutrino production. We compare these power spectra with those of thermally produced dark matter particles and show that resonantly produced sterile neutrinos are much colder than their thermal relic counterparts. We also demonstrate that the shape of these power spectra are not determined by the free-streaming scale alone. We then use the power spectra as an input for semi-analytic models of galaxy formation in order to predict the number of luminous satellite galaxies in a Milky Way-like halo. By assuming that the mass of ...

  2. The dark and visible matter content of low surface brightness disc galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS

    1997-01-01

    We present mass models of a sample of 19 low surface brightness (LSB) galaxies and compare the properties of their constituent mass components with those of a sample of high surface brightness (HSB) galaxies. We find that LSB galaxies are dark matter dominated, Their halo parameters are only slightl

  3. On the apparent coupling of neutral hydrogen and dark matter in spiral galaxies

    NARCIS (Netherlands)

    Hoekstra, H; van Albada, TS; Sancisi, R

    2001-01-01

    We have studied a mass model for spiral galaxies in which the dark matter surface density is a scaled version of the observed H I surface density. Applying this mass model to a sample of 24 spiral galaxies with reliable rotation curves, one obtains good fits for most galaxies. The scaling factors cl

  4. Dark Matter in $\\gamma$ lines: Galactic Center vs dwarf galaxies

    CERN Document Server

    Lefranc, Valentin; Panci, Paolo; Sala, Filippo; Silk, Joseph

    2016-01-01

    We provide CTA sensitivities to Dark Matter (DM) annihilation in $\\gamma$-ray lines, from the observation of the Galactic Center (GC) as well as, for the first time, of dwarf Spheroidal galaxies (dSphs). We compare the GC reach with that of dSphs as a function of a putative core radius of the DM distribution, which is itself poorly known. We find that the currently best dSph candidates constitute a more promising target than the GC, for core radii of one to a few kpc. We use the most recent instrument response functions and background estimations by CTA, on top of which we add the diffuse photon component. Our analysis is of particular interest for TeV-scale electroweak multiplets as DM candidates, such as the supersymmetric Wino and the Minimal Dark Matter fiveplet, whose predictions we compare with our projected sensitivities.

  5. Observing the dark matter density profile of isolated galaxies

    CERN Document Server

    Prada, F; Klypin, A; Holtzman, J A; Schlegel, D J; Grebel, E K; Rix, H W; Brinkmann, J; McKay, T A; Csabai, I; Prada, Francisco; Vitvitska, Mayrita; Klypin, Anatoly; Holtzman, Jon A.; Schlegel, David J.; Grebel, Eva K.

    2003-01-01

    Using the Sloan Digital Sky Survey (SDSS), we probe the halo mass distribution by studying the velocities of satellites orbiting isolated galaxies. In a subsample that covers 2500 sq. degrees on the sky, we detect about 3000 satellites with absolute blue magnitudes going down to M_B = -14; most of the satellites have M_B=-16 to -18, comparable to the magnitudes of M32 and the Magellanic Clouds. After a careful, model-independent removal of interlopers, we find that the line-of-sight velocity dispersion of satellites declines with distance to the primary. For an L* galaxy the r.m.s. line-of-sight velocity changes from ~120 km/s at 20 kpc to ~60 km/s at 350 kpc. This decline agrees remarkably well with theoretical expectations, as all modern cosmological models predict that the density of dark matter in the peripheral parts of galaxies declines as rho_DM propto r^{-3}. Thus, for the first time we find direct observational evidence of the density decline predicted by cosmological models; we also note that this r...

  6. Galaxy interactions: dark matter vs. Modified Newtonian dynamics (MOND)

    CERN Document Server

    Bílek, Michal

    2016-01-01

    (doctoral thesis of Michal Bilek, finished on June 19, 2015) MOND is an observational rule for predicting the acceleration of stars and galaxies from the distribution of the visible matter. It possibly stems from a new law of physics. I list the theoretical aspects of MOND, its achievements and problems. MOND has been tested mainly in disc galaxies so far. Its tests in elliptical galaxies are rare because the MOND effects are small for them in the parts observable by the conventional methods. In the thesis, I explain the methods and ideas I developed for testing MOND in the ellipticals using stellar shells. Moreover, the shells enable us to test MOND for stars in radial orbits for the first time. The shells are results of galactic interactions. I discuss the shell formation mechanisms and summarize the findings from shell observations and simulations. The thesis contains as yet unpublished results mainly in: 1) the introduction of Sect. 3 (the expected differences in the shell morphology in the Newtonian dyna...

  7. On the Fate of Processed Matter in Dwarf Galaxies

    CERN Document Server

    Silich, S A; Silich, Sergey A.; Tenorio-Tagle, Guillermo

    1998-01-01

    Two dimensional calculations of the evolution of remnants generated by the strong mechanical energy deposited by stellar clusters in dwarf galaxies (M \\si $10^9 - 10^{10}$ \\msun) are presented. The evolution is followed for times longer than both the blowout time and the presumed span of energy injection generated by a coeval massive stellar cluster. The remnants are shown to end up wrapping around the central region of the host galaxy, while growing to kpc-scale dimensions. Properties of the remnants such as luminosity, size, swept up mass, and expansion speed are given as a function of time for all calculated cases. The final fate of the swept-up galactic gas and of the matter processed by the central starburst is shown to be highly-dependent on the properties of the low density galactic halo. Superbubbles powered by star clusters, with properties similar to those inferred from the observations, slow down in the presence of an extended halo to expansion speeds smaller than the host galaxy escape velocity. V...

  8. Galaxy Mass Models: MOND versus Dark Matter Halos

    CERN Document Server

    Randriamampandry, Toky

    2014-01-01

    Mass models of 15 nearby dwarf and spiral galaxies are presented. The galaxies are selected to be homogeneous in terms of the method used to determine their distances, the sampling of their rotation curves (RCs) and the mass-to-light ratio (M/L) of their stellar contributions, which will minimize the uncertainties on the mass model results. Those RCs are modeled using the MOdified Newtonian Dynamics (MOND) prescription and the observationally motivated pseudo-isothermal (ISO) dark matter (DM) halo density distribution. For the MOND models with fixed (M/L), better fits are obtained when the constant a$_{0}$ is allowed to vary, giving a mean value of (1.13 $\\pm$ 0.50) $\\times$ 10$^{-8}$ cm s$^{-2}$, compared to the standard value of 1.21 $\\times$ 10$^{-8}$ cm s$^{-2}$. Even with a$_{0}$ as a free parameter, MOND provides acceptable fits (reduced $\\chi^{2}_{r}$ $<$ 2) for only 60% (9/15) of the sample. The data suggest that galaxies with higher central surface brightnesses tend to favor higher values of the c...

  9. The presence of interstellar turbulence could explain the velocity flattening in galaxies

    CERN Document Server

    Vatistas, Georgios H

    2010-01-01

    Expanding our previous work on turbulent whirls [1] we have uncovered a similarity within the similarity shared by intense vortices. Using the new information we compress the tangential velocity profiles of a diverse set of vortices into one and thus identify those that belong to the same genus. Examining the Laser Doppler Anemometer (LDA) results of mechanically produced vortices and radar data of several tropical cyclones, we find that the uplift and flattening effect of tangential velocity is a consequence of turbulence. Reasoning by analogy we conclude that turbulence in the interstellar medium could indeed introduce a flattening effect in the galactic rotation curves.

  10. Statistical Physics of Dark and Normal Matter Distribution in Galaxy Formation : Dark Matter Lumps and Black Holes in Core and Halo of Galaxy

    CERN Document Server

    Patwardhan, Ajay

    2008-01-01

    In unified field theory the cosmological model of the universe has supersymmetric fields. Supersymmetric particles as dark and normal matter in galaxy clusters have a phase separation. Dark matter in halos have a statistical physics equation of state. Neutralino particle gas with gravitation can have a collapse of dark matter lumps. A condensate phase due to boson creation by annhillation and exchange can occur at high densities. The collapse of the boson condensate, including neutralinos, into the Schwarzschild radius creates dark matter black holes. Microscopic dark matter black holes can evaporate with Hawking effect giving gamma ray bursts and create a spectrum of normal particles. The phase separation of normal and dark matter in galaxy clusters and inside galaxies is given by statistical physics.

  11. Young tidal dwarf galaxies cannot be used to probe dark matter in galaxies

    CERN Document Server

    Flores, H; Fouquet, S; Puech, M; Kroupa, P; Yang, Y; Pawlowski, M

    2015-01-01

    The location of dark-matter free, tidal dwarf galaxies (TDGs) in the baryonic Tully Fisher (bTF) diagram has been used to test cosmological scenarios, leading to various and controversial results. Using new high-resolution 3D spectroscopic data, we re-investigate the morpho-kinematics of these galaxies to verify whether or not they can be used for such a purpose. We find that the three observed TDGs are kinematically not virialized and show complex morphologies and kinematics, leading to considerable uncertainties about their intrinsic rotation velocities and their locations on the bTF. Only one TDG can be identify as a (perturbed) rotation disk that it is indeed a sub-component of NGC5291N and that lies at $<$1$\\sigma$ from the local bTF relation. It results that the presently studied TDGs are young, dynamically forming objects, which are not enough virialized to robustly challenge cosmological scenarios.

  12. Reionization and Galaxy Formation in Warm Dark Matter Cosmologies

    Science.gov (United States)

    Dayal, Pratika; Choudhury, Tirthankar Roy; Bromm, Volker; Pacucci, Fabio

    2017-02-01

    We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ≃ 5-20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth (τ es) and the ionizing photon emissivity ({\\dot{n}}{ion}), to shed light on the reionization history and sources in Cold (CDM) and Warm Dark Matter (WDM; particle masses of {m}x = 1.5, 3, and 5 keV) cosmologies. This model includes all of the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass and the effect of the ultra-violet background (UVB), created during reionization, in photo-evaporating the gas content of galaxies in halos with M h ≲ 109 {M}⊙ . We find that the delay in the start of reionization in light (1.5 keV) WDM models can be compensated by a steeper redshift evolution of the ionizing photon escape fraction and a faster mass assembly, resulting in reionization ending at comparable redshifts (z ≃ 5.5) in all the dark matter models considered. We find that the bulk of the reionization photons come from galaxies with a halo mass of M h ≲ 109 {M}⊙ and a UV magnitude of -15 ≲ M UV ≲ -10 in CDM. The progressive suppression of low-mass halos with decreasing {m}x leads to a shift in the “reionization” population to larger halo masses of M h ≳ 109 {M}⊙ and -17 ≲ M UV ≲ -13 for 1.5 keV WDM. We find that current observations of τ es and the ultra violet luminosity function are equally compatible with all the (cold and warm) dark matter models considered in this work. Quantifying the impact of the UVB on galaxy observables (luminosity functions, stellar mass densities, and stellar to halo mass ratios) for different DM models, we propose that global indicators including the redshift evolution of the stellar mass density and the stellar mass-halo mass relation, observable with the James Webb Space Telescope, can be used to distinguish between CDM and WDM (1

  13. On the distribution of dark matter in galaxies: Quantum treatments

    Science.gov (United States)

    Argüelles, Carlos R.; Ruffini, Remo; Siutsou, Ivan; Fraga, Bernardo

    2014-09-01

    The problem of modeling the distribution of dark matter in galaxies in terms of equilibrium configurations of collisionless self-gravitating quantum particles is considered. We first summarize the pioneering model of a Newtonian self-gravitating Fermi gas in thermodynamic equilibrium developed by Ruffini and Stella (1983), which is shown to be a generalization of the King model for fermions. We further review the extension of the former model developed by Gao, Merafina and Ruffini (1990), done for any degree of fermion degeneracy at the center ( θ 0), within general relativity. Finally, we present here for the first time the solutions of the density profiles and rotation curves corresponding to the model of Gao et al. Those solutions have a definite mass M h and a circular velocity v h at the halo radius r h of the configurations, which are typical of spiral galaxies. This treatment allows us to determine a novel core-halo morphology for the dark-matter profiles, as well as a novel bound on the particle mass associated with those profiles.

  14. On the distribution of dark matter in galaxies: quantum treatments

    Energy Technology Data Exchange (ETDEWEB)

    Arguelles, Carlos R.; Ruffini, Remo; Siutsou, Ivan [Sapienza Universita di Roma, Rome (Italy); ICRANet, P.zza della Repubblica, Pescara (Italy); Fraga, Bernardo [Sapienza Universita di Roma, Rome (Italy); Universite de Nice Sophia di Antipolis, Nice (France)

    2014-09-15

    The problem of modeling the distribution of dark matter in galaxies in terms of equilibrium configurations of collisionless self-gravitating quantum particles is considered. We first summarize the pioneering model of a Newtonian self-gravitating Fermi gas in thermodynamic equilibrium developed by Ruffini and Stella (1983), which is shown to be a generalization of the King model for fermions. We further review the extension of the former model developed by Gao, Merafina and Ruffini (1990), done for any degree of fermion degeneracy at the center (θ{sub 0}), within general relativity. Finally, we present here for the first time the solutions of the density profiles and rotation curves corresponding to the model of Gao et al. Those solutions have a definite mass M{sub h} and a circular velocity v{sub h} at the halo radius r{sub h} of the configurations, which are typical of spiral galaxies. This treatment allows us to determine a novel core-halo morphology for the dark-matter profiles, as well as a novel bound on the particle mass associated with those profiles.

  15. On the distribution of dark matter in galaxies: quantum treatments

    CERN Document Server

    Argüelles, Carlos R; Siutsou, Ivan; Fraga, Bernardo

    2014-01-01

    The problem of modeling the distribution of dark matter in galaxies in terms of equilibrium configurations of collisionless self-gravitating quantum particles is considered. We first summarize the pioneering model of a Newtonian self-gravitating Fermi gas in thermodynamic equilibrium developed by Ruffini and Stella (1983), which is shown to be the generalization of the King model for fermions. We further review the extension of the former model developed by Gao, Merafina and Ruffini (1990), done for any degree of fermion degeneracy at the center ($\\theta_0$), within general relativity. Finally, we present here for the first time the solutions of the density profiles and rotation curves corresponding to the Gao et. al. model, which have a definite mass $M_h$ and circular velocity $v_h$, at the halo radius $r_h$ of the configurations, typical of spiral galaxies. This treatment allow us to determine a novel core-halo morphology for the dark matter profiles, as well as a novel particle mass bound associated with ...

  16. Dark Matter Fraction in Lens Galaxies: New Estimates from Microlensing

    CERN Document Server

    Jiménez-Vicente, J; Kochanek, C S; Muñoz, J A

    2014-01-01

    We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars from microlensing measurements of 27 quasar image pairs seen through 19 lens galaxies. The maximum likelihood estimate for the fraction of the surface mass density in the form of stars is $\\alpha=0.2^{+0.1}_{-0.1}$ near the Einstein radius of the lenses ($\\sim 1 - 2$ effective radii). The estimate for the average accretion disk size is $r_s=6.0^{+3.0}_{-1.1}\\sqrt{M/0.3M_\\sun}$ light-days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local dark matter fraction of 80\\ is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.

  17. Looking for dark matter trails in colliding galaxy clusters

    CERN Document Server

    Harvey, David; Massey, Richard; Kneib, Jean-Paul

    2016-01-01

    If dark matter interacts, even weakly, via non-gravitational forces, simulations predict that it will be preferentially scattered towards the trailing edge of the halo during collisions between galaxy clusters. This will temporarily create a non-symmetric mass profile, with a trailing over-density along the direction of motion. To test this hypothesis, we fit (and subtract) symmetric halos to the weak gravitational data of 72 merging galaxy clusters observed with the Hubble Space Telescope. We convert the shear directly into excess {\\kappa} and project in to a one dimensional profile. We generate numerical simulations and find that the one dimensional profile is well described with simple Gaussian approximations. We detect the weak lensing signal of trailing gas at a 4{\\sigma} confidence, finding a mean gas fraction of Mgas/Mdm = 0.13 +/- 0.035. We find no evidence for scattered dark matter particles with a estimated scattering fraction of f = 0.03 +/- 0.05. Finally we find that if we can reduce the statistic...

  18. Cores in dwarf galaxies from dark matter with a Yukawa potential.

    Science.gov (United States)

    Loeb, Abraham; Weiner, Neal

    2011-04-29

    We show that cold dark matter particles interacting through a Yukawa potential could naturally explain the recently observed cores in dwarf galaxies without affecting the dynamics of objects with a much larger velocity dispersion, such as clusters of galaxies. The velocity dependence of the associated cross section as well as the possible exothermic nature of the interaction alleviates earlier concerns about strongly interacting dark matter. Dark matter evaporation in low-mass objects might explain the observed deficit of satellite galaxies in the Milky Way halo and have important implications for the first galaxies and reionization.

  19. Challenges in Cosmology from the Big Bang to Dark Energy, Dark Matter and Galaxy Formation

    CERN Document Server

    Silk, Joseph

    2016-01-01

    I review the current status of Big Bang Cosmology, with emphasis on current issues in dark matter, dark energy, and galaxy formation. These topics motivate many of the current goals of experimental cosmology which range from targeting the nature of dark energy and dark matter to probing the epoch of the first stars and galaxies.

  20. The composition of the interstellar medium in the Galaxy as seen through X-rays

    NARCIS (Netherlands)

    Pinto, C.

    2013-01-01

    The term “Milky Way” usually refers to the hundreds billion stars of our Galaxy, which emit most of its visible light. This name derives from its appearance as a weak ”milky” band which arches across the night sky. It is made of individual stars that cannot be distinguished by the naked eye as it is

  1. Signatures of Interstellar-Intracluster Medium Interactions Spiral Galaxy Rotation Curves in Abell 2029

    CERN Document Server

    Dale, D A; Dale, Daniel A.; Uson, Juan M.

    2000-01-01

    We investigate the rich cluster Abell 2029 (z~0.08) using optical imaging and long-slit spectral observations of 52 disk galaxies distributed throughout the cluster field. No strong emission-line galaxies are present within ~400 kpc of the cluster center, a region largely dominated by the similarly-shaped X-ray and low surface brightness optical envelopes centered on the giant cD galaxy. However, two-thirds of the galaxies observed outside the cluster core exhibit line emission. H-alpha rotation curves of 14 cluster members are used in conjunction with a deep I band image to study the environmental dependence of the Tully-Fisher relation. The Tully-Fisher zero-point of Abell 2029 matches that of clusters at lower redshifts, although we do observe a relatively larger scatter about the Tully-Fisher relation. We do not observe any systematic variation in the data with projected distance to the cluster center: we see no environmental dependence of Tully-Fisher residuals, R-I color, H-alpha equivalent width, and t...

  2. Intragroup dark matter distribution in small galaxy group-like systems in a LCDM cosmology

    CERN Document Server

    Aceves, Hector; Altamirano-Devora, L; Ramon-Fox, F G; Cañas, R

    2013-01-01

    In this paper we study the distribution of dark matter in small galaxy groups, in a LCDM cosmology, identified using a physical criterion. We quantify the amount of intra-group dark matter and characterize its distribution. We find that compact associations of galaxies, as well as those intermediate and loose groups, have a rather flat profiles with a logarithmic slope of gamma =-0.2. Hence, the intra-group dark matter does not follow the same cuspy tendency that haloes of galaxies have. In intermediate and loose galaxy associations the intragroup matter tends to be <50% that of the total mass of the group, and in compact associations is <20% within their group radius. So, in general, common dark matter haloes of small galaxy groups are not cuspy nor massive.

  3. Dark Matter in Galaxy Clusters: Shape, Projection, and Environment

    Science.gov (United States)

    Groener, Austen M.

    We explore the intrinsic distribution of dark matter within galaxy clusters, by combining insights from the largest N-body simulations as well as the largest observational dataset of its kind. Firstly, we study the intrinsic shape and alignment of isodensities of galaxy cluster halos extracted from the MultiDark MDR1 cosmological simulation. We find that the simulated halos are extremely prolate on small scales and increasingly spherical on larger ones. Due to this trend, analytical projection along the line of sight produces an overestimate of the concentration index as a decreasing function of radius, which we quantify by using both the intrinsic distribution of 3D concentrations (c200) and isodensity shape on weak and strong lensing scales. We find this difference to be ˜ 18% (˜ 9%) for low (medium) mass cluster halos with intrinsically low concentrations (c200=1- 3), while we find virtually no difference for halos with intrinsically high concentrations. Isodensities are found to be fairly well-aligned throughout the entirety of the radial scale of each halo population. However, major axes of individual halos have been found to deviate by as much as ˜ 30°. We also present a value-added catalog of our analysis results, which we have made publicly available to download. Following that, we then turn to observational measurements galaxy clusters. Scaling relations of clusters have made them particularly important cosmological probes of structure formation. In this work, we present a comprehensive study of the relation between two profile observables, concentration (cvir ) and mass (Mvir). We have collected the largest known sample of measurements from the literature which make use of one or more of the following reconstruction techniques: Weak gravitational lensing (WL), strong gravitational lensing (SL), Weak+Strong Lensing (WL+SL), the Caustic Method (CM), Line-of-sight Velocity Dispersion (LOSVD), and X-ray. We find that the concentration-mass (c-M) relation

  4. Magnetic fields in ring galaxies

    CERN Document Server

    Moss, D; Silchenko, O; Sokoloff, D; Horellou, C; Beck, R

    2016-01-01

    Many galaxies contain magnetic fields supported by galactic dynamo action. However, nothing definitive is known about magnetic fields in ring galaxies. Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. We use tested methods for modelling $\\alpha-\\Omega$ galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513 where th...

  5. THE CONNECTION BETWEEN GALAXIES AND DARK MATTER STRUCTURES IN THE LOCAL UNIVERSE

    Energy Technology Data Exchange (ETDEWEB)

    Reddick, Rachel M.; Wechsler, Risa H.; Behroozi, Peter S. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, Stanford, CA 94305 (United States); Tinker, Jeremy L., E-mail: rmredd@stanford.edu, E-mail: rwechsler@stanford.edu [Physics Department, New York University, New York, NY 10003 (United States)

    2013-07-01

    We provide new constraints on the connection between galaxies in the local universe, identified by the Sloan Digital Sky Survey, and dark matter halos and their constituent substructures in the {Lambda}-cold dark matter model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with dark matter halos and subhalos using subhalo abundance matching, and perform a comprehensive analysis which investigates the underlying assumptions of this technique including (1) which halo property is most closely associated with galaxy stellar masses and luminosities, (2) how much scatter is in this relationship, and (3) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. We find that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 {+-} 0.03 dex in stellar mass at a given peak velocity is included. This confirms the theoretical expectation that the stellar mass of galaxies is tightly correlated with the potential wells of their dark matter halos before they are impacted by larger structures. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass and on the scatter between halo and galaxy properties, and rule out several alternative abundance matching models that have been considered. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy-halo connection can be modeled with sufficient fidelity for future precision studies of the dark universe.

  6. Constraints on decaying dark matter from Fermi observations of nearby galaxies and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Dugger, Leanna; Profumo, Stefano [Department of Astronomy and Department of Physics, University of California Berkeley, 601 Campbell Hall, Berkeley, CA (United States); Jeltema, Tesla E., E-mail: greentee01@gmail.com, E-mail: tesla@ucolick.org, E-mail: profumo@scipp.ucsc.edu [UCO/Lick Observatories, 1156 High St., Santa Cruz, CA 95064 (United States)

    2010-12-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results put strong constraints on the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as those from galaxy clusters, while still improving on previous constraints in some cases.

  7. Constraints on Decaying Dark Matter from Fermi Observations of Nearby Galaxies and Clusters

    CERN Document Server

    Dugger, Leanna; Profumo, Stefano

    2010-01-01

    We analyze the impact of Fermi gamma-ray observations (primarily non-detections) of selected nearby galaxies, including dwarf spheroidals, and of clusters of galaxies on decaying dark matter models. We show that the fact that galaxy clusters do not shine in gamma rays puts the most stringent limits available to-date on the lifetime of dark matter particles for a wide range of particle masses and decay final states. In particular, our results rule out the possibility of ascribing to decaying dark matter both the increasing positron fraction reported by PAMELA and the high-energy feature in the electron-positron spectrum measured by Fermi. Observations of nearby dwarf galaxies and of the Andromeda Galaxy (M31) do not provide as strong constraints as those from galaxy clusters, while still improving on previous limits in some cases.

  8. Made-to-Measure Dark Matter Haloes, Elliptical Galaxies and Dwarf Galaxies in Action Coordinates

    CERN Document Server

    Williams, A A

    2014-01-01

    We provide a family of action-based distribution functions (DFs) for the double-power law family of densities often used to model galaxies. The DF itself is a double-power law in combinations of the actions, and reduces to the known limits in the case of a pure power-law at small and large radii. Our method enables the velocity anisotropy of the model to be tuned, and so the anisotropy in the inner and outer parts can be specified for the application in hand. We provide self-consistent DFs for the Hernquist and Jaffe models - both with everywhere isotropic velocity dispersions, and with kinematics that gradually becomes more radially anisotropic on moving outwards. We also carry out this exercise for a cored dark-matter model. These are tailored to represent dark haloes and elliptical galaxies respectively with kinematic properties inferred from simulations or observational data. Finally, we relax a cored luminous component within a dark matter halo to provide a self-consistent model of a dwarf spheroidal emb...

  9. The interstellar medium in Andromeda's dwarf spheroidal galaxies: II. Multi-phase gas content and ISM conditions

    CERN Document Server

    De Looze, Ilse; Cormier, Diane; Kaneko, Hiroyuki; Kuno, Nario; Young, Lisa; Bendo, George J; Boquien, Mederic; Fritz, Jacopo; Gentile, Gianfranco; Kennicutt, Robert C; Madden, Suzanne C; Smith, Matthew W L; Wilson, Christine D

    2016-01-01

    We make an inventory of the interstellar medium material in three low-metallicity dwarf spheroidal galaxies of the Local Group (NGC147, NGC185 and NGC205). Ancillary HI, CO, Spitzer IRS spectra, H{\\alpha} and X-ray observations are combined to trace the atomic, cold and warm molecular, ionised and hot gas phases. We present new Nobeyama CO(1-0) observations and Herschel SPIRE FTS [CI] observations of NGC205 to revise its molecular gas content. We derive total gas masses of M_gas = 1.9-5.5x10^5 Msun for NGC185 and M_gas = 8.6-25.0x10^5 Msun for NGC205. Non-detections combine to an upper limit on the gas mass of M_gas =< 0.3-2.2x10^5 Msun for NGC147. The observed gas reservoirs are significantly lower compared to the expected gas masses based on a simple closed-box model that accounts for the gas mass returned by planetary nebulae and supernovae. The gas-to-dust mass ratios GDR~37-107 and GDR~48-139 are also considerably lower compared to the expected GDR~370 and GDR~520 for the low metal abundances in NGC 1...

  10. Strong lensing by fermionic dark matter in galaxies

    CERN Document Server

    Gómez, L Gabriel; Perlick, Volker; Rueda, J A; Ruffini, R

    2016-01-01

    It has been shown that a self-gravitating system of massive keV fermions in thermodynamic equilibrium correctly describes the dark matter (DM) distribution in galactic halos and predicts a denser quantum core towards the center of the configuration. Such a quantum core, for a fermion mass in the range of $50$ keV $\\lesssim m c^2 \\lesssim 345$ keV, can be an alternative interpretation of the central compact object in Sgr A*. We present in this work the gravitational lensing properties of this novel DM model in Milky Way-like spiral galaxies. We describe the lensing effects of the pure DM component both on halo scales, where we compare them to the effects of the Navarro-Frenk-White and the Non-Singular Isothermal Sphere DM models, and near the galaxy center, where we compare them with the effects of a Schwarzschild BH. For the particle mass leading to the most compact DM core, $m c^2\\approx 10^{2}$ keV, we draw the following conclusions. At distances $r\\gtrsim 20$ pc from the center of the lens the effect of th...

  11. Rotation curves of 967 spiral galaxies implications for dark matter

    CERN Document Server

    Persic, M; Stel, F; Persic, Massimo; Salucci, Paolo; Stel, Fulvio

    1995-01-01

    We present the rotation curves of 967 spiral galaxies, obtained by deprojecting and folding the raw data published by Mathewson et al. (1992). Of these, 80 meet objective excellence criteria and are suitable for individual detailed mass modelling, while 820 are suitable for statistical studies. A preliminary analysis of theire properties confirms that rotation curves are a universal function of luminosity and that the dark matter fraction in spirals increase with decreasing luminosity. Quantitative considerations on the virial radius of dark halos allow us to make hypotheses about their structure and nature. The deprojected folded curves, the smoothed curves, and various related quantities are available via anonymous ftp at ftp://galileo.sissa.it/users/ftp/pub/psrot

  12. The Connection between Galaxies and Dark Matter Structures in the Local Universe

    Energy Technology Data Exchange (ETDEWEB)

    Reddick, Rachel M.; Wechsler, Risa H.; Tinker, Jeremy L.; Behroozi, Peter S.

    2012-07-11

    We provide new constraints on the connection between galaxies in the local Universe, identified by the Sloan Digital Sky Survey (SDSS), and dark matter halos and their constituent substructures in the {Lambda}CDM model using WMAP7 cosmological parameters. Predictions for the abundance and clustering properties of dark matter halos, and the relationship between dark matter hosts and substructures, are based on a high-resolution cosmological simulation, the Bolshoi simulation. We associate galaxies with dark matter halos and subhalos using subhalo abundance matching, and perform a comprehensive analysis which investigates the underlying assumptions of this technique including (a) which halo property is most closely associated with galaxy stellar masses and luminosities, (b) how much scatter is in this relationship, and (c) how much subhalos can be stripped before their galaxies are destroyed. The models are jointly constrained by new measurements of the projected two-point galaxy clustering and the observed conditional stellar mass function of galaxies in groups. We find that an abundance matching model that associates galaxies with the peak circular velocity of their halos is in good agreement with the data, when scatter of 0.20 {+-} 0.03 dex in stellar mass at a given peak velocity is included. This confirms the theoretical expectation that the stellar mass of galaxies is tightly correlated with the potential wells of their dark matter halos before they are impacted by larger structures. The data put tight constraints on the satellite fraction of galaxies as a function of galaxy stellar mass and on the scatter between halo and galaxy properties, and rule out several alternative abundance matching models that have been considered. This will yield important constraints for galaxy formation models, and also provides encouraging indications that the galaxy - halo connection can be modeled with sufficient fidelity for future precision studies of the dark Universe.

  13. An algorithm for the direct reconstruction of the dark matter correlation function from weak lensing and galaxy clustering

    CERN Document Server

    Baldauf, Tobias; Seljak, Uros; Mandelbaum, Rachel

    2009-01-01

    The clustering of matter on cosmological scales is an essential probe for studying the physical origin and composition of our Universe. To date, most of the direct studies have focused on shear-shear weak lensing correlations, but it is also possible to extract the dark matter clustering by combining galaxy-clustering and galaxy-galaxy-lensing measurements. In this study we develop a method that can constrain the dark matter correlation function from galaxy clustering and galaxy-galaxy-lensing measurements, by focusing on the correlation coefficient between the galaxy and matter overdensity fields. To generate a mock galaxy catalogue for testing purposes, we use the Halo Occupation Distribution approach applied to a large ensemble of N-body simulations to model pre-existing SDSS Luminous Red Galaxy sample observations. Using this mock catalogue, we show that a direct comparison between the excess surface mass density measured by lensing and its corresponding galaxy clustering quantity is not optimal. We devel...

  14. Dirbe evidence for a wrap in the interstellar dust layer and stellar disk of the galaxy

    Science.gov (United States)

    Freudenreich, H. T.; Berriman, G. B.; Dwek, E.; Hauser, M. G.; Kelsall, T.; Moseley, S. H.; Silverberg, R. F.; Sodroski, T. J.; Toller, G. N.; Weiland, J. L.

    1994-01-01

    The Diffuse Infrared Background Experiment (DIRBE) of the Cosmic Background Explorer (COBE) has mapped the surface brightness distributions of the Galactic plane at wavelengths from 1.25 to 240 micrometers. In these maps the latitude of peak brightness, as a function of longitude, traces a roughly sinusoidal curve of period approximately 360 deg. In the far-infrared, where emission by interstellar dust dominates the surface brightness, this curve agrees well with that derived from maps of the velocity-integrated H 1, suggesting that the layers of dust and neutral atomic hydrogen are similarly displaced from the Galactic plane. In the near-infrared (lambda less than 5 micrometers), where old disk stars dominate the emission, the brightness crest exhibits the same phase but roughly half the amplitude. The reduced amplitude of the warp in stellar light could result from a lesser warping of the stellar disk, or from a more rapid falloff of the density of stars relative to the density of gas, possibly due to a radial truncation of the disk.

  15. UV Interstellar Absorption Lines towards the Starburst Dwarf Galaxy NGC 1705

    CERN Document Server

    Sahu, M S

    1997-01-01

    Archival Goddard High Resolution Spectrograph low-resolution spectra of NGC 1705, with wavelength ranges 1170.3 to 1461.7 A and 1453.5 to 1740.1 A and a velocity resolution of about 100 km\\s, have been used to derive the velocity structure and equivalent widths of the absorption lines of Si II 1190.42, 1260.42, 1304.37 and 1526.71 A, S II 1253 , Al II 1670.79 Aand Fe II 1608.45 A in this sightline. Three relatively narrow absorption components are seen at LSR velocities --20 km/s, 260 km/sand 540 km/s. Arguments are presented to show these absorption features are interstellar rather than stellar in origin based on a comparison with the C III 1175.7 A absorption feature. We identify the --20 km/s component with Milky Way disk/halo gas and the 260 km/s component with an isolated high-velocity cloud HVC 487. This small HVC is located about 10 degrees from the H I gas which envelops the Magellanic Clouds and the Magellanic Stream (MS). The (Si/H) ratio for this HVC is > 0.6 (Si/H)solar which together with velocit...

  16. Star Formation in Galaxy Mergers with Realistic Models of Stellar Feedback & the Interstellar Medium

    CERN Document Server

    Hopkins, Philip F; Hernquist, Lars; Narayanan, Desika; Hayward, Christopher C; Murray, Norman

    2012-01-01

    We use simulations with realistic models for stellar feedback to study galaxy mergers. These high resolution (1 pc) simulations follow formation and destruction of individual GMCs and star clusters. The final starburst is dominated by in situ star formation, fueled by gas which flows inwards due to global torques. The resulting high gas density results in rapid star formation. The gas is self gravitating, and forms massive (~10^10 M_sun) GMCs and subsequent super-starclusters (masses up to 10^8 M_sun). However, in contrast to some recent simulations, the bulk of new stars which eventually form the central bulge are not born in superclusters which then sink to the center of the galaxy, because feedback efficiently disperses GMCs after they turn several percent of their mass into stars. Most of the mass that reaches the nucleus does so in the form of gas. The Kennicutt-Schmidt law emerges naturally as a consequence of feedback balancing gravitational collapse, independent of the small-scale star formation micro...

  17. Dark matter density profiles of the halos embedding early-type galaxies: characterizing halo contraction and dark matter annihilation strength

    CERN Document Server

    Chae, Kyu-Hyun; Frieman, Joshua A; Bernardi, Mariangela

    2012-01-01

    Identifying dark matter and characterizing its distribution in the inner region of halos embedding galaxies are inter-related problems of broad importance. We devise a new procedure of determining dark matter distribution in halos. We first make a self-consistent bivariate statistical match of stellar mass and velocity dispersion with halo mass as demonstrated here for the first time. Then, selecting early-type galaxy-halo systems we perform Jeans dynamical modeling with the aid of observed statistical properties of stellar mass profiles and velocity dispersion profiles. Dark matter density profiles derived specifically using Sloan Digital Sky Survey galaxies and halos from up-to-date cosmological dissipationless simulations deviate significantly from the dissipationless profle of Navarro-Frenk-White or Einasto in terms of inner density slope and/or concentration. From these dark matter profiles we find that dark matter density is enhanced in the inner region of most early-type galactic halos providing an ind...

  18. Strong lensing by fermionic dark matter in galaxies

    Science.gov (United States)

    Gómez, L. Gabriel; Argüelles, C. R.; Perlick, Volker; Rueda, J. A.; Ruffini, R.

    2016-12-01

    It has been shown that a self-gravitating system of massive keV fermions in thermodynamic equilibrium correctly describes the dark matter (DM) distribution in galactic halos (from dwarf to spiral and elliptical galaxies) and that, at the same time, it predicts a denser quantum core towards the center of the configuration. Such a quantum core, for a fermion mass in the range of 50 keV ≲m c2≲345 keV , can be an alternative interpretation of the central compact object in Sgr A*, traditionally assumed to be a black hole (BH). We present in this work the gravitational lensing properties of this novel DM configuration in nearby Milky-Way-like spiral galaxies. We describe the lensing effects of the pure DM component both on halo scales, where we compare them to the effects of the Navarro-Frenk-White and the nonsingular isothermal sphere DM models, and near the galaxy center, where we compare them with the effects of a Schwarzschild BH. For the particle mass leading to the most compact DM core, m c2≈1 02 keV , we draw the following conclusions. At distances r ≳20 pc from the center of the lens the effect of the central object on the lensing properties is negligible. However, we show that measurements of the deflection angle produced by the DM distribution in the outer region at a few kpc, together with rotation curve data, could help to discriminate between different DM models. In the inner regions 1 0-6≲r ≲20 pc , the lensing effects of a DM quantum core alternative to the BH scenario becomes a theme of an analysis of unprecedented precision which is challenging for current technological developments. We show that at distances ˜1 0-4 pc strong lensing effects, such as multiple images and Einstein rings, may occur. Large differences in the deflection angle produced by a DM central core and a central BH appear at distances r ≲1 0-6 pc ; in this regime the weak-field formalism is no longer applicable and the exact general-relativistic formula has to be used

  19. The distribution of the dark matter in galaxies as the imprint of its Nature

    Science.gov (United States)

    Frigerio Martins, Christiane

    2009-03-01

    The standard framework within which cosmological measurements are confronted and interpreted nowadays, called Lambda Cold Dark Matter, presents a Universe dominated by unknown forms of energy and matter. My Thesis is devoted to investigate the distribution of dark matter in galaxies and addresses the fact that the local universe-the small objects that orbit galaxies and the galaxy cores-turns out to be a marvelous laboratory for examining the nature of dark matter and the fundamental physics involved in structure formation and evolution. I develop tests, based on mass modeling of rotation curves, for the validation of dark matter models on galactic scales. These tests have been applied in analyzing the phenomenology of the cusp vs core controversy, and the phenomenon of non-Keplerian rotation curves as modification of the laws of gravity. I further investigate the properties and scaling laws of dark matter halos. My conclusion is that galactic observations provide strong imprints on the nature of dark matter.

  20. The distribution of the dark matter in galaxies as the imprint of its Nature

    CERN Document Server

    Martins, Christiane Frigerio

    2009-01-01

    The standard framework within which cosmological measurements are confronted and interpreted nowadays, called Lambda Cold Dark Matter, presents a Universe dominated by unknown forms of energy and matter. My Thesis is devoted to investigate the distribution of dark matter in galaxies and addresses the fact that the local universe-the small objects that orbit galaxies and the galaxy cores-turns out to be a marvelous laboratory for examining the nature of dark matter and the fundamental physics involved in structure formation and evolution. I develop tests, based on mass modeling of rotation curves, for the validation of dark matter models on galactic scales. These tests have been applied in analyzing the phenomenology of the cusp vs core controversy, and the phenomenon of non-Keplerian rotation curves as modification of the laws of gravity. I further investigate the properties and scaling laws of dark matter halos. My conclusion is that galactic observations provide strong imprints on the nature of dark matter.

  1. The NGC 672 and NGC 784 Galaxy Groups: Evidence for Galaxy Formation and Growth Along a Nearby Dark Matter Filament

    CERN Document Server

    Zitrin, Adi

    2008-01-01

    (Abridged): We present U, B, V, R, I, H-alpha and NUV photometry of 14 galaxies in the very local Universe (within 10 Mpc that are dwarf irregular galaxies (dIrr), are at low redshift (511-10 Gyr) and one "young" population (<30 Myr) with the recent SF bursts occurring a few to a few 10s of Myr ago, arguing for synchronicity in star formation in these objects. We propose that the ~synchronous star formation in all objects is caused by the accretion of cold gas from intergalactic space onto dark matter haloes arranged along a filament threading the void where these dwarf galaxies reside and point out this galaxy sample as an ideal target to study hierarchical clustering and galaxy formation among very nearby objects.

  2. Towards DIB mapping in galaxies beyond 100 Mpc. A radial profile of the $\\lambda$5780.5 diffuse interstellar band in AM 1353-272 B

    CERN Document Server

    Monreal-Ibero, Ana; Wendt, Martin; Selman, Fernando; Lallement, Rosine; Brinchmann, Jarle; Kamann, Sebastian; Sandin, Christer

    2015-01-01

    Diffuse Interstellar Bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of Interstellar Medium (ISM). Research of DIBs outside the Milky Way is currently very limited. Specifically spatially resolved investigations of DIBs outside of the Local Group is, to our knowledge, inexistent. Here, we explore the capability of the high sensitivity Integral Field Spectrograph, MUSE, as a tool to map diffuse interstellar bands at distances larger than 100 Mpc. We use MUSE commissioning data for AM 1353-272 B, the member with highest extinction of the "The Dentist's Chair", an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings. We derived decreasing radial profiles for the equivalent width of the $\\lambda$5780.5 DIB both in the receding and approaching side of the companion galaxy up to distan...

  3. Interstellar processes; Proceedings of the Symposium, Grand Teton National Park, WY, July 1-7, 1986

    Science.gov (United States)

    Hollenbach, David J. (Editor); Thronson, Harley A., Jr. (Editor)

    1987-01-01

    The conference presents papers on the Milky Way as a galaxy; observations of components of the interstellar medium; interstellar magnetic properties; interstellar processes on a galactic scale; dynamical processes in interstellar clouds; interstellar dust grains; interstellar chemical processes; and heating, cooling, and radiative processes. Attention is given to H2 in the Galaxy, hot interstellar gas in the Galactic disk and halo, interstellar magnetic fields, cloud formation and destruction, theoretical approaches to interstellar turbulence, and infrared absorption and emission characteristics of interstellar PAHs. Other topics include gas phase chemical processes in molecular clouds, the chemical evolution of galaxies, and the atomic and molecular physics of interstellar heating and cooling.

  4. Dark Matter in the Universe and in the Galaxy

    Science.gov (United States)

    Kamionkowski, Marc

    1999-01-01

    During the past four years, Prof. Kamionkowski and collaborators have made progress in research on the nature and distribution of dark-matter in the Universe and in the Galaxy, and on related topics in astrophysics and cosmology. We have made progress on research on the cosmic microwave background, large-scale structure, issues related to particle dark matter, and the gamma-ray-burst enigma. A significant fraction of the research supported by this ATP has been on the cosmic microwave background (CMB). Prof. Kamionkowski and collaborators showed how the polarization of the CMB could be used to detect long-wavelength gravitational waves, such as those produced by inflation. With Kosowsky, Prof. Kamionkowski calculated the amplitude of a stochastic gravitational-wave background that could be detected for a satellite experiment of a given sensitivity and angular resolution. They showed that polarization should improve the sensitivity oa MAP to these gravity waves, and that the Planck Surveyor should do even better. Prof. Kamionkowski, Caldwell, and a student calculated and illustrated the CMB temperature/polarization pattern produced by a single plane-wave gravitational wave. They calculated the amplitude of such a wave that would be detectable with MAP and Planck, and compared that with the sensitivity of traditional gravitational-wave detectors like LIGO and LISA. With Lue and Wang, the PI showed how parity violation from new high-energy physics could conceivably give rise to an observable signature in the CMB polarization. With Loeb, Prof. Kamionkowski showed how measurement of the polarization of CMB photons scattered by hot gas in a cluster could be used to determine the quadrupole moment of the CMB incident on that cluster. Prof. Kamionkowski and Jaffe calculated the amplitude of secondary anisotropies produced by scattering of CMB photons from reionized regions. Research has also been carried out on probing the large-scale distribution of mass in the Universe

  5. The Luminous Convolution Model as an alternative to dark matter in spiral galaxies

    CERN Document Server

    Cisneros, S; Formaggio, J A; Ott, R A; Chester, D; Battaglia, D J; Ashley, A; Robinson, R; Rodriguez, A

    2014-01-01

    The Luminous Convolution Model (LCM) demonstrates that it is possible to predict the rotation curves of spiral galaxies directly from estimates of the luminous matter. We consider two frame-dependent effects on the light observed from other galaxies: relative velocity and relative curvature. With one free parameter, we predict the rotation curves of twenty-three (23) galaxies represented in forty-two (42) data sets. Relative curvature effects rely upon knowledge of both the gravitational potential from luminous mass of the emitting galaxy and the receiving galaxy, and so each emitter galaxy is compared to four (4) different Milky Way luminous mass models. On average in this sample, the LCM is more successful than either dark matter or modified gravity models in fitting the observed rotation curve data. Implications of LCM constraints on populations synthesis modeling are discussed in this paper. This paper substantially expands the results in arXiv:1309.7370.

  6. Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

    CERN Document Server

    Napolitano, N R; Coccato, L; Capaccioli, M; Douglas, N G; Noordermeer, E; Merrifield, M R; Kuijken, K; Arnaboldi, M; Gerhard, O; Freeman, K C; De Lorenzi, F; Das, P

    2007-01-01

    We examine the dark matter properties of nearby early-type galaxies using planetary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities with best efficiency. The primary scientific objective of this custom-built instrument is the study of the PN kinematics in 12 ordinary round galaxies. Preliminary results showing a dearth of dark matter in ordinary galaxies (Romanowsky et al. 2003) are now confirmed by the first complete PN.S datasets. On the other hand early-type galaxies with a "regular" dark matter content are starting to be observed among the brighter PN.S target sample, thus confirming a correlation between the global dark-to-luminous mass virial ratio (f_DM=M_DM/M_star) and the galaxy luminosity and mass.

  7. The offsets between galaxies and their dark matter in {\\Lambda}CDM

    CERN Document Server

    Schaller, Matthieu; Massey, Richard; Bower, Richard G; Eke, Vincent R

    2015-01-01

    We use the "Evolution and Assembly of GaLaxies and their Environments" ( EAGLE ) suite of hydrodynamical cosmological simulations to measure offsets between the centres of stellar and dark matter components of galaxies. We find that the vast majority (>95%) of the simulated galaxies display an offset smaller than the gravitational softening length of the simulations ($\\epsilon = 700$ pc), both for field galaxies and satellites in clusters and groups. We also find no systematic trailing or leading of the dark matter along a galaxy's direction of motion. The offsets are consistent with being randomly drawn from a Maxwellian distribution with $\\sigma = 196$ pc. Since astrophysical effects produce no feasible analogues for the $1.62^{+0.47}_{-0.49}$ kpc offset recently observed in Abell 3827, this observational result is in tension with the collisionless cold dark matter model assumed in the simulations.

  8. On Wave Dark Matter, Shells in Elliptical Galaxies, and the Axioms of General Relativity

    CERN Document Server

    Bray, Hubert L

    2012-01-01

    This paper is a sequel to the author's paper entitled "On Dark Matter, Spiral Galaxies, and the Axioms of General Relativity" [arXiv:1004.4016] which explored a geometrically natural axiomatic definition for dark matter modeled by a scalar field satisfying the Einstein-Klein-Gordon wave equations which, after much calculation, was shown to be consistent with the observed spiral and barred spiral patterns in disk galaxies. We give an update on where things stand on this "wave dark matter" model of dark matter (aka scalar field dark matter and boson stars), an interesting alternative to the WIMP model of dark matter, and discuss how it has the potential to help explain the long-observed interleaved shell patterns, also known as ripples, in the images of elliptical galaxies.

  9. The interstellar medium and star formation in local galaxies: Variations of the star formation law in simulations

    Energy Technology Data Exchange (ETDEWEB)

    Becerra, Fernando; Escala, Andrés, E-mail: fbecerra@cfa.harvard.edu [Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile)

    2014-05-01

    We use the adaptive mesh refinement code Enzo to model the interstellar medium (ISM) in isolated local disk galaxies. The simulation includes a treatment for star formation and stellar feedback. We get a highly supersonic turbulent disk, which is fragmented at multiple scales and characterized by a multi-phase ISM. We show that a Kennicutt-Schmidt relation only holds when averaging over large scales. However, values of star formation rates and gas surface densities lie close in the plot for any averaging size. This suggests an intrinsic relation between stars and gas at cell-size scales, which dominates over the global dynamical evolution. To investigate this effect, we develop a method to simulate the creation of stars based on the density field from the snapshots, without running the code again. We also investigate how the star formation law is affected by the characteristic star formation timescale, the density threshold, and the efficiency considered in the recipe. We find that the slope of the law varies from ∼1.4 for a free-fall timescale, to ∼1.0 for a constant depletion timescale. We further demonstrate that a power law is recovered just by assuming that the mass of the new stars is a fraction of the mass of the cell m {sub *} = ερ{sub gas}Δx {sup 3}, with no other physical criteria required. We show that both efficiency and density threshold do not affect the slope, but the right combination of them can adjust the normalization of the relation, which in turn could explain a possible bi-modality in the law.

  10. Gemini GMOS--IFU spectroscopy of the compact HII galaxies Tol 0104-388 and Tol 2146-391: The dependence on the properties of the interstellar medium

    CERN Document Server

    Lagos, P; Nigoche-Netro, A; Carrasco, E R

    2012-01-01

    Using GMOS--IFU spectroscopic observations of the compact HII/BCD galaxies Tol 0104-388 and Tol 2146-391, we study the spatial distribution of emission lines, equivalent width EW(Hb), extinction c(Hb), ionization ratios ([OIII]5007/Hb, [SII]6717,6731/Ha and [NII]6584/Ha), kinematics, and the chemical pattern (O/H, N/H and N/O) of the warm interstellar medium in these galaxies. We also investigate a possible dependence of these properties on the I(HeII4686)/I(Hb) ratio and find no significant correlation between these variables. In fact, the oxygen abundances appear to be uniform in the regions where the HeII4686 emission line was measured. It can be interpreted in the sense that these correlations are related to global properties of the galaxies and not with small patches of the interstellar medium. Although a possible weak N/H gradient is observed in Tol 2146-391, the available data suggest that the metals from previous star-formation events are well mixed and homogeneously distributed through the optical ex...

  11. The SLUGGS survey: globular clusters and the dark matter content of early-type galaxies

    Science.gov (United States)

    Forbes, Duncan A.; Alabi, Adebusola; Romanowsky, Aaron J.; Brodie, Jean P.; Strader, Jay; Usher, Christopher; Pota, Vincenzo

    2016-05-01

    A strong correlation exists between the total mass of a globular cluster (GC) system and the virial halo mass of the host galaxy. However, the total halo mass in this correlation is a statistical measure conducted on spatial scales that are some 10 times that of a typical GC system. Here we investigate the connection between GC systems and galaxy's dark matter on comparable spatial scales, using dynamical masses measured on a galaxy-by-galaxy basis. Our sample consists of 17 well-studied massive (˜1011 M⊙) early-type galaxies from the SLUGGS survey. We find the strongest correlation to be that of the blue (metal-poor) GC subpopulation and the dark matter content. This correlation implies that the dark matter mass of a galaxy can be estimated to within a factor of 2 from careful imaging of its GC system. The ratio of the GC system mass to that of the enclosed dark matter is nearly constant. We also find a strong correlation between the fraction of blue GCs and the fraction of enclosed dark matter, so that a typical galaxy with a blue GC fraction of 60 per cent has a dark matter fraction of 86 per cent over similar spatial scales. Both halo growth and removal (via tidal stripping) may play some role in shaping this trend. In the context of the two-phase model for galaxy formation, we find galaxies with the highest fractions of accreted stars to have higher dark matter fractions for a given fraction of blue GCs.

  12. Searching for neutrinos from dark matter annihilations in (dwarf) galaxies and clusters with IceCube

    Energy Technology Data Exchange (ETDEWEB)

    With, Meike de [Institut fuer Physik, Humboldt-Universitaet zu Berlin, D-12489 Berlin (Germany); Bernardini, Elisa [DESY, D-15735 Zeuthen (Germany); Collaboration: IceCube-Collaboration

    2015-07-01

    In many models, the self-annihilation of dark matter particles will create neutrinos which can be detected on Earth. An excess flux of these neutrinos is expected from regions of increased dark matter density, like (dwarf) galaxies and galaxy clusters. The IceCube neutrino observatory, a cubic-kilometer neutrino detector at the South Pole, is capable of detecting neutrinos down to energies of few 10 GeV and is therefore able to constrain the self-annihilation cross section as a function of the mass of the dark matter particle. In this talk, the current status of the search for neutrinos from dark matter annihilations in (dwarf) galaxies and galaxy clusters with IceCube is discussed.

  13. What can the outskirts of galaxies tell us about dark matter?

    CERN Document Server

    Power, Chris

    2016-01-01

    Deep observations of galaxy outskirts reveal faint extended stellar components (ESCs) of streams, shells, and halos, which are ghostly remnants of the tidal disruption of satellite galaxies. We use cosmological galaxy formation simulations in Cold Dark Matter (CDM) and Warm Dark Matter (WDM) models to explore how the dark matter model influences the spatial, kinematic, and orbital properties of ESCs. These reveal that the spherically averaged stellar mass density at large galacto-centric radius can be depressed by up to a factor of 10 in WDM models relative to the CDM model, reflecting the anticipated suppressed abundance of satellite galaxies in WDM models. However, these differences are much smaller in WDM models that are compatible with observational limits, and are comparable in size to the system-to-system variation we find within the CDM model. This suggests that it will be challenging to place limits on dark matter using only the unresolved ESC.

  14. What can the outskirts of galaxies tell us about dark matter?

    Science.gov (United States)

    Power, Chris

    2017-03-01

    Deep observations of galaxy outskirts reveal faint extended stellar components (ESCs) of streams, shells, and halos, which are ghostly remnants of the tidal disruption of satellite galaxies. We use cosmological galaxy formation simulations in Cold Dark Matter (CDM) and Warm Dark Matter (WDM) models to explore how the dark matter model influences the spatial, kinematic, and orbital properties of ESCs. These reveal that the spherically averaged stellar mass density at large galacto-centric radius can be depressed by up to a factor of ~10 in WDM models relative to the CDM model, reflecting the anticipated suppressed abundance of satellite galaxies in WDM models. However, these differences are much smaller in WDM models that are compatible with observational limits, and are comparable in size to the system-to-system variation we find within the CDM model. This suggests that it will be challenging to place limits on dark matter using only the unresolved ESC.

  15. On the Clustering of Compact Galaxy Pairs in Dark Matter Haloes

    CERN Document Server

    Wang, Yiran

    2014-01-01

    We analyze the clustering of photometrically selected galaxy pairs by using the halo-occupation distribution (HOD) model. We measure the angular two-point auto-correlation function, $\\omega(\\theta)$, for galaxies and galaxy pairs in three volume-limited samples and develop an HOD to model their clustering. Our results are successfully fit by these HOD models, and we see the separation of "1-halo" and "2-halo" clustering terms for both single galaxies and galaxy pairs. Our clustering measurements and HOD model fits for the single galaxy samples are consistent with previous results. We find that the galaxy pairs generally have larger clustering amplitudes than single galaxies, and the quantities computed during the HOD fitting, e.g., effective halo mass, $M_{eff}$, and linear bias, $b_{g}$, are also larger for galaxy pairs. We find that the central fractions for galaxy pairs are significantly higher than single galaxies, which confirms that galaxy pairs are formed at the center of more massive dark matter haloe...

  16. Modeling the distribution of dark matter and its connection to galaxies

    Science.gov (United States)

    Mao, Yao-Yuan

    2016-06-01

    Despite the mysterious nature of dark matter and dark energy, the Lambda-Cold Dark Matter (LCDM) model provides a reasonably accurate description of the evolution of the cosmos and the distribution of galaxies. Today, we are set to tackle more specific and quantitative questions about the galaxy formation physics, the nature of dark matter, and the connection between the dark and the visible components. The answers to these questions are however elusive, because dark matter is not directly observable, and various unknowns lie between what we can observe and what we can calculate. Hence, mathematical models that bridge the observable and the calculable are essential for the study of modern cosmology. The aim of my thesis work is to improve existing models and also to construct new models for various aspects of the dark matter distribution, as dark matter structures the cosmic web and forms the nests of visible galaxies. Utilizing a series of cosmological dark matter simulations which span a wide dynamical range and a statistical sample of zoom-in simulations which focus on individual dark matter halos, we develop models for the spatial and velocity distribution of dark matter particles, the abundance of dark substructures, and the empirical connection between dark matter and galaxies. As more precise observational results become available, more accurate models are then required to test the consistency between these results and the LCDM predictions. For all the models we investigate, we find that the formation history of dark matter halos always plays a crucial role. Neglecting the halo formation history would result in systematic biases when we interpret various observational results, including dark matter direct detection experiments, the detection of dark substructures with strong-lensed systems, the large-scale spatial clustering of galaxies, and the abundance of dwarf galaxies. Rectifying this, our work will enable us to fully utilize the complementary power of

  17. Quark nugget dark matter: Comparison with radio observations of nearby galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, K., E-mail: klawson@phas.ubc.ca; Zhitnitsky, A.R.

    2016-06-10

    It has been recently claimed that radio observations of nearby spiral galaxies essentially rule out a dark matter source for the galactic haze [1]. Here we consider the low energy thermal emission from a quark nugget dark matter model in the context of microwave emission from the galactic centre and radio observations of nearby Milky Way like galaxies. We demonstrate that observed emission levels do not strongly constrain this specific dark matter candidate across a broad range of the allowed parameter space in drastic contrast with conventional dark matter models based on the WIMP paradigm.

  18. Quark Nugget Dark Matter: Comparison with radio observations of nearby galaxies

    CERN Document Server

    Lawson, K

    2015-01-01

    It has been recently claimed that radio observations of nearby spiral galaxies essentially rule out a dark matter source for the galactic haze. Here we consider the low energy thermal emission from a quark nugget dark matter model in the context of microwave emission from the galactic centre and radio observations of nearby Milky Way like galaxies. We demonstrate that observed emission levels do not strongly constrain this specific dark matter candidate across a broad range of the allowed parameter space in drastic contrast with conventional dark matter models based on the WIMP paradigm.

  19. PROPERTIES OF THE INTERSTELLAR MEDIUM IN STAR-FORMING GALAXIES AT z ∼ 1.4 REVEALED WITH ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Seko, Akifumi; Ohta, Kouji; Iwamuro, Fumihide, E-mail: seko@kusastro.kyoto-u.ac.jp [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto, 606-8502 (Japan); and others

    2016-03-01

    We conducted observations of {sup 12}CO(J = 5–4) and dust thermal continuum emission toward 20 star-forming galaxies on the main sequence at z ∼ 1.4 using ALMA to investigate the properties of the interstellar medium. The sample galaxies are chosen to trace the distributions of star-forming galaxies in diagrams of stellar mass versus star formation rate and stellar mass versus metallicity. We detected CO emission lines from 11 galaxies. The molecular gas mass is derived by adopting a metallicity-dependent CO-to-H{sub 2} conversion factor and assuming a CO(5–4)/CO(1–0) luminosity ratio of 0.23. Masses of molecular gas and its fractions (molecular gas mass/(molecular gas mass + stellar mass)) for the detected galaxies are in the ranges of (3.9–12) × 10{sup 10} M{sub ⊙} and 0.25–0.94, respectively; these values are significantly larger than those in local spiral galaxies. The molecular gas mass fraction decreases with increasing stellar mass; the relation holds for four times lower stellar mass than that covered in previous studies, and the molecular gas mass fraction decreases with increasing metallicity. Stacking analyses also show the same trends. Dust thermal emissions were clearly detected from two galaxies and marginally detected from five galaxies. Dust masses of the detected galaxies are (3.9–38) × 10{sup 7} M{sub ⊙}. We derived gas-to-dust ratios and found they are 3–4 times larger than those in local galaxies. The depletion times of molecular gas for the detected galaxies are (1.4–36) × 10{sup 8} yr while the results of the stacking analysis show ∼3 × 10{sup 8} yr. The depletion time tends to decrease with increasing stellar mass and metallicity though the trend is not so significant, which contrasts with the trends in local galaxies.

  20. Effect of dark matter halo on global spiral modes in galaxies

    Science.gov (United States)

    Ghosh, Soumavo; Saini, Tarun Deep; Jog, Chanda J.

    2016-02-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here, we study the role of the dark matter halo on the grand-design, m = 2, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First, a typical superthin, LSB galaxy UGC 7321 is studied by taking only the galactic disc, modelled as a fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, these are not triggered in LSB galaxies. For comparison, we carried out a similar analysis for the Galaxy, for which the dark matter halo does not dominate in the inner regions. We show that here too the dark matter halo has little effect, hence the disc embedded in a halo is also able to support global modes. The derived pattern speed of the global mode agrees fairly well with the observed value for the Galaxy.

  1. Baryons Matter: Why Luminous Satellite Galaxies Have Reduced Central Masses

    CERN Document Server

    Zolotov, Adi; Willman, Beth; Governato, Fabio; Pontzen, Andrew; Christensen, Charlotte; Dekel, Avishai; Quinn, Tom; Shen, Sijing; Wadsley, James

    2012-01-01

    Using high resolution cosmological hydrodynamical simulations of Milky Way-massed disk galaxies, we demonstrate that supernovae feedback and tidal stripping lower the central masses of bright (-14 10^9 Msun, Mstar > 10^7 Msun) compared to DM-only simulations. The progenitors of the lower mass satellites are unable to maintain bursty star formation histories, due to both heating at reionization and gas loss from initial star forming events, preserving the steep inner density profile predicted by DM-only simulations. After infall, tidal stripping acts to further reduce the central densities of the luminous satellites, particularly those that enter with cored dark matter halos, increasing the discrepancy in the central masses predicted by baryon+DM and DM-only simulations. We show that DM-only simulations, which neglect the baryonic effects described in this work, produce denser satellites with larger central velocities. We provide a simple correction to the central DM mass predicted for satellites by DM-only s...

  2. Entropy of gas and dark matter in galaxy clusters

    CERN Document Server

    Faltenbacher, A; Gottlöber, S; Yepes, G

    2006-01-01

    On the basis of a large scale 'adiabatic', namely non-radiative and non-dissipative, cosmological smooth particle hydrodynamic simulation we compare the entropy profiles of the gas and the dark matter (DM) in galaxy clusters. The quantity K_g = T_g \\rho_g^{-2/3} provides a measure for the entropy of the intra-cluster gas. By analogy with the thermodynamic variables of the gas the velocity dispersion of the DM is associated with a formal temperature and thereby K_DM = \\sigma_DM^2 \\rho_DM^{-2/3} is defined. This DM entropy is related to the DM phase space density by K_DM \\propto Q_DM^{-2/3}. In accord with other studies the DM phase space density follows a power law behaviour, Q_DM \\propto r^{-1.82}, which corresponds to K_DM \\propto r^{1.21}. The simulated intra-cluster gas has a flat entropy core within (0.8 \\pm 0.4) R_s, where R_s is the NFW scale radius. The outer profile follows the DM behaviour, K_g \\propto r^{1.21}, in close agreement with X-ray observations. Upon scaling the DM and gas densities by thei...

  3. Supermassive black holes do not correlate with dark matter haloes of galaxies.

    Science.gov (United States)

    Kormendy, John; Bender, Ralf

    2011-01-20

    Supermassive black holes have been detected in all galaxies that contain bulge components when the galaxies observed were close enough that the searches were feasible. Together with the observation that bigger black holes live in bigger bulges, this has led to the belief that black-hole growth and bulge formation regulate each other. That is, black holes and bulges coevolve. Therefore, reports of a similar correlation between black holes and the dark matter haloes in which visible galaxies are embedded have profound implications. Dark matter is likely to be non-baryonic, so these reports suggest that unknown, exotic physics controls black-hole growth. Here we show, in part on the basis of recent measurements of bulgeless galaxies, that there is almost no correlation between dark matter and parameters that measure black holes unless the galaxy also contains a bulge. We conclude that black holes do not correlate directly with dark matter. They do not correlate with galaxy disks, either. Therefore, black holes coevolve only with bulges. This simplifies the puzzle of their coevolution by focusing attention on purely baryonic processes in the galaxy mergers that make bulges.

  4. Ultra faint dwarf galaxies: an arena for testing dark matter versus modified gravity

    Science.gov (United States)

    Lin, Weikang; Ishak, Mustapha

    2016-10-01

    The scenario consistent with a wealth of observations for the missing mass problem is that of weakly interacting dark matter particles. However, arguments or proposals for a Newtonian or relativistic modified gravity scenario continue to be made. A distinguishing characteristic between the two scenarios is that dark matter particles can produce a gravitational effect, in principle, without the need of baryons while this is not the case for the modified gravity scenario where such an effect must be correlated with the amount of baryonic matter. We consider here ultra-faint dwarf (UFD) galaxies as a promising arena to test the two scenarios based on the above assertion. We compare the correlation of the luminosity with the velocity dispersion between samples of UFD and non-UFD galaxies, finding a significant loss of correlation for UFD galaxies. For example, we find for 28 non-UFD galaxies a strong correlation coefficient of -0.688 which drops to -0.077 for the 23 UFD galaxies. Incoming and future data will determine whether the observed stochasticity for UFD galaxies is physical or due to systematics in the data. Such a loss of correlation (if it is to persist) is possible and consistent with the dark matter scenario for UFD galaxies but would constitute a new challenge for the modified gravity scenario.

  5. On the cross-section of Dark Matter using substructure infall into galaxy clusters

    CERN Document Server

    Harvey, David; Massey, Richard; Kitching, Thomas D; Taylor, Andy; Pike, Simon R; Kay, Scott T; Lau, Erwin T; Nagai, Daisuke

    2013-01-01

    We develop a statistical method to measure the interaction cross-section of Dark Matter, exploiting the continuous minor merger events in which small substructures fall into galaxy clusters. We find that by taking the ration of the distances between the galaxies and Dark Matter, and galaxies and gas in accreting sub-halos, we are able to calibrate and measure the Dark Matter self-interaction cross-section, remove any inherent line-of-sight projections. In order to interpret this ratio as a cross-section of Dark Matter we derive an analytical description of sub-halo infall which encompasses; the force of the main cluster potential, the drag on a gas sub-halo, a model for Dark Matter self-interactions and the resulting sub-halo drag, the force on the gas and galaxies due to the Dark Matter sub-halo potential, and finally the buoyancy on the gas and Dark Matter. We create mock observations from cosmological simulations of structure formation and find that collisionless Dark Matter becomes physically separated fr...

  6. VALES: II. The physical conditions of interstellar gas in normal star-forming galaxies up to z=0.2 revealed by ALMA

    CERN Document Server

    Hughes, T M; Villanueva, V; Aravena, M; Baes, M; Bourne, N; Cooray, A; Dunne, L; Dye, S; Eales, S; Furlanetto, C; Herrera-Camus, R; Ivison, R J; van Kampen, E; Lara-López, M A; Maddox, S J; Michałowski, M J; Smith, M W L; Valiante, E; van der Werf, P; Xue, Y Q

    2016-01-01

    We use new Band-3 CO(1-0) observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the physical conditions in the interstellar gas of a sample of 27 dusty main-sequence star-forming galaxies at 0.035$\\sigma$ in 26 sources. We find an average [CII] to CO(1-0) luminosity ratio of 3500$\\pm$1200 for our sample that is consistent with previous studies. Using the [CII], CO and FIR measurements as diagnostics of the physical conditions of the interstellar medium, we compare these observations to the predictions of a photodissociation region (PDR) model to determine the gas density, surface temperature, pressure, and the strength of the incident far-ultraviolet (FUV) radiation field, $G_{0}$, normalised to the Habing Field. The majority of our sample exhibit hydrogen densities of 4 < $\\log n/\\mathrm{cm}^{3}$ < 5.5 and experience an incident FUV radiation field with strengths of 2 < $\\log G_0$ < 3 when adopting standard adjustments. A comparison to galaxy samples at differen...

  7. Medium-resolution spectroscopy of FORJ0332-3557: Probing the interstellar medium and stellar populations of a lensed Lyman-break galaxy at z=3.77

    CERN Document Server

    Cabanac, Remi A; Lidman, Chris

    2008-01-01

    We recently reported the discovery of FORJ0332-3557, a lensed Lyman-break galaxy at z=3.77 in a remarkable example of strong galaxy-galaxy gravitational lensing. We present here a medium-resolution rest-frame UV spectrum of the source, which appears to be similar to the well-known Lyman-break galaxy MS1512-cB58 at z=2.73. The spectral energy distribution is consistent with a stellar population of less than 30 Ma, with an extinction of A(V)=0.5 mag and an extinction-corrected star formation rate SFR(UV) of 200-300 Msun/a. The Lyman-alpha line exhibits a damped profile in absorption produced by a column density of about N(HI) = (2.5+_1.0) 10^21 atoms/cm^2, superimposed on an emission line shifted both spatially (0.5 arcsec with respect to the UV continuum source) and in velocity space (+830 km/s with respect to the low-ionisation absorption lines from its interstellar medium), a clear signature of outflows with an expansion velocity of about 270 km/s. A strong emission line from HeII 164.04nm indicates the pres...

  8. Separating galaxies from the cluster dark matter halo in Abell 611

    Science.gov (United States)

    Monna, A.; Seitz, S.; Geller, M. J.; Zitrin, A.; Mercurio, A.; Suyu, S. H.; Postman, M.; Fabricant, D. G.; Hwang, H. S.; Koekemoer, A.

    2017-03-01

    We investigate the mass content of galaxies in the core of the galaxy cluster Abell 611. We perform a strong lensing analysis of the cluster core and use velocity dispersion measurements for individual cluster members as additional constraints. Despite the small number of multiply-imaged systems and cluster members with central velocity dispersions available in the core of A611, the addition of velocity dispersion measurements leads to tighter constraints on the mass associated with the galaxy component, and as a result, on the mass associated with the dark matter halo. Without the spectroscopic velocity dispersions, we would overestimate the mass of the galaxy component by a factor of ∼1.5, or, equivalently, we would underestimate the mass of the cluster dark halo by ∼5 per cent. We perform an additional lensing analysis using surface brightness (SB) reconstruction of the tangential giant arc. This approach improves the constraints on the mass parameters of the five galaxies close to the arc by a factor up to ∼10. The resulting parameters are in good agreement with the σ-rtr scaling relation derived in the pointlike analysis. The galaxy velocity dispersions resulting from the SB analysis are consistent at the 1σ confidence level with the spectroscopic measurements. In contrast, the truncation radii for 2-3 galaxies depart significantly from the galaxy scaling relation and suggest differences in the stripping history from galaxy to galaxy.

  9. Antiprotons from dark matter annihilation in the Galaxy. Astrophysical uncertainties

    Energy Technology Data Exchange (ETDEWEB)

    Evoli, Carmelo [Chinese Academy of Sciences, Beijing (China). National Astronomical Observatories; Cholis, Ilias; Ullio, Piero [SISSA, Sezione di Trieste (Italy); INFN, Sezione di Trieste (Italy); Grasso, Dario [INFN, Sezione di Pisa (Italy); Maccione, Luca [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

    2011-08-15

    The latest years have seen steady progresses in WIMP dark matter (DM) searches, with hints of possible signals suggested by both direct and indirect detection experiments. Antiprotons can play a key role validating those interpretations since they are copiously produced by WIMP annihilations in the Galactic halo, and the secondary antiproton background produced by Cosmic Ray (CR) interactions is predicted with fair accuracy and matches the observed spectrum very well. Using the publicly available numerical DRAGON code, we reconsider antiprotons as a tool to constrain DM models discussing its power and limitations. We provide updated constraints on a wide class of annihilating DM models by comparing our predictions against the most up-to-date anti p measurements, taking also into account the latest spectral information on the p, He and other CR nuclei fluxes. Doing that, we probe carefully the uncertainties associated to both secondary and DM originated antiprotons, by using a variety of distinctively different assumptions for the propagation of CRs and for the DM distribution in the Galaxy. We find that the impact of the astrophysical uncertainties on constraining the DM properties can be much stronger, up to a factor of {proportional_to}50, than the one due to uncertainties on the DM distribution ({proportional_to}2-6). Remarkably, even reducing the uncertainties on the propagation parameters derived by local observables, non-local effects can still change DM model constraints even by 50%. Nevertheless, current anti p data place tight constraints on DM models, excluding some of those suggested in connection with indirect and direct searches. Finally we discuss the power of upcoming CR spectral data from the AMS-02 observatory to drastically reduce the uncertainties discussed in this paper and estimate the expected sensitivity of this instrument to some sets of DM models. (orig.)

  10. Comparative testing of dark matter models with 9 HSB and 9 LSB galaxies

    CERN Document Server

    Kun, E; Keresztes, Z; Gergely, L Á

    2016-01-01

    We ensemble a database of 9 high-surface brightness (HSB) and 9 low-surface brightness (LSB) galaxies, for which both surface brightness density and spectroscopic rotation curve data are available in the literature, and are representative for the various morphologies. We use this dataset for a comparative testing of the Navarro-Frenk-White, the Einasto, and the pseudo-isothermal sphere dark matter models. We investigate the compatibility of the pure baryonic model and baryonic plus one of the three dark matter models with observations on the assembled galaxy database. When dark matter component is necessary to explain the spectroscopic rotational curves, we rank the models according to the goodness of fitting to the datasets. We construct the spatial luminosity density of the baryonic component based on the surface brightness profile of the galaxies. An axissymetric, baryonic mass model with variable axis ratios and three dark matter models are employed to fit the theoretical rotational velocity curves to the...

  11. A dark matter gravitational accretion scenario for E galaxy activity

    NARCIS (Netherlands)

    Valentijn, E. A.

    1988-01-01

    The application of gravitational accretion into massive galaxies is reviewed. A strong correlation between central radio activity, optical and X-ray luminosity over five decades in both the radio and the X-ray bands and ranging from ordinary elliptical to D and cD type galaxies is reported and the i

  12. Characteristic size and mass of galaxies in the Bose–Einstein condensate dark matter model

    Directory of Open Access Journals (Sweden)

    Jae-Weon Lee

    2016-05-01

    Full Text Available We study the characteristic length scale of galactic halos in the Bose–Einstein condensate (or scalar field dark matter model. Considering the evolution of the density perturbation we show that the average background matter density determines the quantum Jeans mass and hence the spatial size of galaxies at a given epoch. In this model the minimum size of galaxies increases while the minimum mass of the galaxies decreases as the universe expands. The observed values of the mass and the size of the dwarf galaxies are successfully reproduced with the dark matter particle mass m≃5×10−22 eV. The minimum size is about 6×10−3m/Hλc and the typical rotation velocity of the dwarf galaxies is O(H/m c, where H is the Hubble parameter and λc is the Compton wave length of the particle. We also suggest that ultra compact dwarf galaxies are the remnants of the dwarf galaxies formed in the early universe.

  13. Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation

    CERN Document Server

    Kroupa, Pavel

    2014-01-01

    (Abridged) Galaxies are observed to be simple systems but the standard model of cosmology (SMoC) implies a haphazard merger history driven by dynamical friction on dark matter halos. The SMoC is tested here with the results that the dual dwarf galaxy theorem is in contradiction to the data if the SMoC is true, and the action of dynamical friction is not evident in the galaxy population. A consistency test for this conclusion comes from the significantly anisotropic distributions of satellite galaxies which orbit in the same direction around their hosting galaxies in disk-like structures which cannot be derived from dark-matter models. The implication for fundamental physics is that exotic dark matter particles do not exist and that consequently effective gravitational physics on the scales of galaxies and beyond ought to be non-Newtonian/non-Einsteinian. The data imply that scale-invariant dynamics, as discovered by Milgrom, is an excellent description of galaxies in the weak-field regime. Observations of ste...

  14. The impact of baryonic processes on the two-point correlation functions of galaxies, subhaloes and matter

    CERN Document Server

    van Daalen, Marcel P; McCarthy, Ian G; Booth, C M; Vecchia, Claudio Dalla

    2013-01-01

    The observed clustering of galaxies and the cross-correlation of galaxies and mass (a measure of galaxy-galaxy lensing) provide important constraints on both cosmology and models of galaxy formation. Even though the dissipation, and more importantly the feedback processes associated with galaxy formation are thought to affect the distribution of matter, essentially all models used to predict clustering data are based on dark matter only simulations. Here, we use large hydrodynamical simulations to investigate how galaxy formation affects the autocorrelation functions of galaxies, subhaloes, as well as their cross-correlation with matter. We show that the changes due to the inclusion of baryons are not limited to small scales and are even present in samples selected by subhalo mass. Samples selected by subhalo mass cluster ~10% more strongly in a baryonic run on scales r ~ 1Mpc/h or larger, and this difference increases for smaller separations. While the inclusion of baryons boosts the clustering at fixed subh...

  15. Searching for Dark Matter with X-ray Observations of Local Dwarf Galaxies

    CERN Document Server

    Jeltema, Tesla E

    2008-01-01

    A generic feature of weakly interacting massive particle (WIMP) dark matter models is the emission of photons over a broad energy band resulting from the stable yields of dark matter pair annihilation. Inverse Compton scattering off cosmic microwave background photons of energetic electrons and positrons produced in dark matter annihilation is expected to produce significant diffuse X-ray emission. Dwarf galaxies are ideal targets for this type of dark matter search technique, being nearby, dark matter dominated systems free of any astrophysical diffuse X-ray background. In this paper, we present the first systematic study of X-ray observations of local dwarf galaxies aimed at the search for WIMP dark matter. We outline the optimal energy and angular ranges for current telescopes, and analyze the systematic uncertainties connected to electron/positron diffusion. We do not observe any significant X-ray excess, and translate this null result into limits on the mass and pair annihilation cross section for partic...

  16. The SLUGGS Survey: globular clusters and the dark matter content of early-type galaxies

    CERN Document Server

    Forbes, Duncan A; Romanowsky, Aaron J; Brodie, Jean P; Strader, Jay; Usher, Christopher; Pota, Vincenzo

    2016-01-01

    A strong correlation exists between the total mass of a globular cluster (GC) system and the virial halo mass of the host galaxy. However, the total halo mass in this correlation is a statistical measure conducted on spatial scales that are some ten times that of a typical GC system. Here we investigate the connection between GC systems and galaxy's dark matter on comparable spatial scales, using dynamical masses measured on a galaxy-by-galaxy basis. Our sample consists of 17 well-studied massive (stellar mass $\\sim$10$^{11}$ M$_{\\odot}$) early-type galaxies from the SLUGGS survey. We find the strongest correlation to be that of the blue (metal-poor) GC subpopulation and the dark matter content. This correlation implies that the dark matter mass of a galaxy can be estimated to within a factor of two from careful imaging of its GC system. The ratio of the GC system mass to that of the enclosed dark matter is nearly constant. We also find a strong correlation between the fraction of blue GCs and the fraction of...

  17. Study of the nature of dark matter in halos of dwarf galaxies

    Science.gov (United States)

    Karmakar, Pradip; Chattopadhyay, Tanuka; Chattopadhyay, Asis Kumar

    2015-08-01

    The kinematics of dwarf galaxies are strongly influenced by dark matter down to small galactocentric radii. So they are good candidates to investigate the nature of Dark Matter. In the present work we have carried out mass modeling of a number of recently observed dwarf galaxies Swaters et al. in Astron. Astrophys. 493:871, 2009. We have used a Navarro-Frenk-White (NFW) halo, Freeman disc along with a gaseous disc for modeling the observed rotation curves of those dwarf galaxies. For comparison we also used a Burkert halo, Freeman disc and gaseous disc. For both the scenario we have performed Kolmogorov-Smirnov (KS) test between the observed and predicted rotational velocity profiles. The tests are rejected for NFW halo almost in 50 per cent cases but they are accepted almost for all cases for Burkert halo, preferring a Burkert halo model generally for dwarf galaxies. The above results reveal a constant density core of dark matter (DM) in the halos of dwarf galaxies compared to a cuspy nature of NFW halo and a possible challenge to -CDM scenario for the nature of dark matter in most of the dwarf galaxies.

  18. Low-mass disc galaxies and the issue of stability: MOND versus dark matter

    Science.gov (United States)

    Sánchez-Salcedo, F. J.; Martínez-Gómez, E.; Aguirre-Torres, V. M.; Hernández-Toledo, H. M.

    2016-11-01

    We analyse the rotation curves and gravitational stability of a sample of six bulgeless galaxies for which detailed images reveal no evidence for strong bars. We explore two scenarios: Newtonian dark matter models and MOdified Newtonian Dynamics (MOND). By adjusting the stellar mass-to-light ratio, dark matter models can match simultaneously both the rotation curve and bar-stability requirements in these galaxies. To be consistent with stability constraints, in two of these galaxies, the stellar mass-to-light ratio is a factor of ˜1.5-2 lower than the values suggested from galaxy colours. In contrast, MOND fits to the rotation curves are poor in three galaxies, perhaps because the gas tracer contains non-circular motions. The bar stability analysis provides a new observational test to MOND. We find that most of the galaxies under study require abnormally high levels of random stellar motions to be bar stable in MOND. In particular, for the only galaxy in the sample for which the line-of-sight stellar velocity dispersion has been measured (NGC 6503), the observed velocity dispersion is not consistent with MOND predictions because it is far below the required value to guarantee bar stability. Precise measurements of mass-weighted velocity dispersions in (unbarred and bulgeless) spiral galaxies are crucial to test the consistency of MOND.

  19. Dynamical response of dark matter to galaxy evolution affects direct-detection experiments

    Science.gov (United States)

    Petersen, Michael S.; Katz, Neal; Weinberg, Martin D.

    2016-12-01

    Over a handful of rotation periods, dynamical processes in barred galaxies induce nonaxisymmetric structure in dark matter halos. Using n -body simulations of a Milky Way-like barred galaxy, we identify both a trapped dark matter component, a shadow bar, and a strong response wake in the dark matter distribution that affects the predicted dark matter detection rates for current experiments. The presence of a baryonic disk, together with well-known dynamical processes (e.g. spiral structure and bar instabilities), increases the dark matter density in the disk plane. We find that the magnitude of the combined stellar and shadow bar evolution, when isolated from the effect of the axisymmetric gravitational potential of the disk, accounts for >30 % of this overall increase in disk-plane density. This is significantly larger than that of previously claimed deviations from the standard halo model. The dark matter density and kinematic wakes driven by the Milky Way bar increase the detectability of dark matter overall, especially for the experiments with higher vmin . These astrophysical features increase the detection rate by more than a factor of 2 when compared to the standard halo model and by a factor of 10 for experiments with high minimum recoil energy thresholds. These same features increase (decrease) the annual modulation for low (high) minimum recoil energy experiments. We present physical arguments for why these dynamics are generic for barred galaxies such as the Milky Way rather than contingent on a specific galaxy model.

  20. Cuspy no more: how outflows affect the central dark matter and baryon distribution in Λ cold dark matter galaxies

    Science.gov (United States)

    Governato, F.; Zolotov, A.; Pontzen, A.; Christensen, C.; Oh, S. H.; Brooks, A. M.; Quinn, T.; Shen, S.; Wadsley, J.

    2012-05-01

    We examine the evolution of the inner dark matter (DM) and baryonic density profile of a new sample of simulated field galaxies using fully cosmological, Λ cold dark matter (ΛCDM), high-resolution SPH+N-Body simulations. These simulations include explicit H2 and metal cooling, star formation (SF) and supernovae-driven gas outflows. Starting at high redshift, rapid, repeated gas outflows following bursty SF transfer energy to the DM component and significantly flatten the originally 'cuspy' central DM mass profile of galaxies with present-day stellar masses in the 104.5-109.8 M⊙ range. At z= 0, the central slope of the DM density profile of our galaxies (measured between 0.3 and 0.7 kpc from their centre) is well fitted by ρDM ∝ rα with α≃-0.5 + 0.35 log10(M★/108 M⊙), where M★ is the stellar mass of the galaxy and 4 < log M★ < 9.4. These values imply DM profiles flatter than those obtained in DM-only simulations and in close agreement with those inferred in galaxies from the THINGS and LITTLE THINGS surveys. Only in very small haloes, where by z= 0 SF has converted less than ˜0.03 per cent of the original baryon abundance into stars, outflows do not flatten the original cuspy DM profile out to radii resolved by our simulations. The mass (DM and baryonic) measured within the inner 500 pc of each simulated galaxy remains nearly constant over 4 orders of magnitudes in stellar mass for M★ < 109 M⊙. This finding is consistent with estimates for faint Local Group dwarfs and field galaxies. These results address one of the outstanding problems faced by the CDM model, namely the strong discrepancy between the original predictions of cuspy DM profiles and the shallower central DM distribution observed in galaxies.

  1. The Extended Stellar Component of Galaxies the Nature of Dark Matter

    Science.gov (United States)

    Power, C.; Robotham, A. S. G.

    2016-07-01

    Deep observations of galaxies reveal faint extended stellar components (hereafter ESCs) of streams, shells, and halos. These are a natural prediction of hierarchical galaxy formation, as accreted satellite galaxies are tidally disrupted by their host. We investigate whether or not global properties of the ESC could be used to test of dark matter, reasoning that they should be sensitive to the abundance of low-mass satellites, and therefore the underlying dark matter model. Using cosmological simulations of galaxy formation in the favored Cold Dark Matter (CDM) and Warm Dark Matter (WDM) models ({m}{{WDM}}=0.5,1,2 {{keV}}/{c}2), which suppress the abundance of low-mass satellites, we find that the kinematics and orbital structure of the ESC is consistent across models. However, we find striking differences in its spatial structure, as anticipated—a factor of ˜10 drop in spherically averaged mass density between ˜10% and ˜75% of the virial radius in the more extreme WDM runs ({m}{{WDM}} = 0.5, 1 {{keV}}/{c}2) relative to the CDM run. These differences are consistent with the mass assembly histories of the different components, and are present across redshifts. However, even the least discrepant of the WDM models is incompatible with current observational limits on {m}{{WDM}}. Importantly, the differences we observe when varying the underlying dark matter are comparable to the galaxy-to-galaxy variation we expect within a fixed dark matter model. This suggests that it will be challenging to place limits on dark matter using only the unresolved spatial structure of the the ESC.

  2. Galaxy clusters as probes for cosmology and dark matter

    CERN Document Server

    Battistelli, Elia S; de Bernardis, Paolo; Kirillov, Alexander A; Neto, Gastao B Lima; Masi, Silvia; Norgaard-Nielsen, Hans U; Ostermann, Peter; Roman, Matthieu; Rosati, Piero; Rossetti, Mariachiara

    2016-01-01

    In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev--Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR and X-ray facilities, thus opening new avenues to constraint cosmological models using structure growth and geometrical tests. A census of galaxy clusters sets constraints on reionization mechanisms and epochs, which need to be reconciled with recent limits on the reionization optical depth from cosmic microwave background (CMB) experiments. Future advances in SZ effect measurements will include the possibility to (unambiguously) measure directly the kinematic SZ effect, to build an even larger catalogue of galaxy clusters able to study the high redshift universe, and to make (spatially-)resolved galaxy cluster maps with even spectral capability to (spectrally-)resolve the relativistic corrections of the SZ effect.

  3. Prebiotic Organic Matter from the Center of the Galaxy

    Science.gov (United States)

    Halfen, DeWayne; Ziurys, Lucy M.

    2016-06-01

    The origins of life on Earth must have begun with simple organic compounds. A plausible source of such prebiotic molecules was the interstellar medium (ISM). Of the over 160 molecules that have been identified in interstellar gas, about half have been discovered in one source, Sagittarius B2(N), located in the Galactic Center. This giant molecular cloud is also home to many large organic species observed in the ISM. How complex these species can become is unknown. In order to accurately establish an inventory of potentially, prebiotic organic molecules, we completed a continuous spectral-line survey of Sgr B2(N) at the confusion limit using the Arizona Radio Observatory facilities: the Kitt Peak 12 m and the Submillimeter Telescope. The survey covers the 1, 2, and 3 mm atmospheric windows in the range 68 - 280 GHz, and about 15,000 individual spectral lines have been observed. Seventy-four molecules have been identified in the data, including several potential prebiotic species, such as glycolaldehyde, acetamide, and methyl isocyanate. These molecules are relatively abundant in Sgr B2(N), with fractional abundances of f ~ 10-10 - 10-12 relative to H2. Current results of this survey will be presented, along with its implications for interstellar organic chemistry and prebiotic synthesis. A comparison with organics found in comets and meteorites will also be discussed.

  4. Central dark matter trends in early-type galaxies from strong lensing, dynamics and stellar populations

    CERN Document Server

    Tortora, C; Romanowsky, A J; Jetzer, Ph

    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, Romanowsky & Tortora...

  5. Low-mass disc galaxies and the issue of stability: MOND vs dark matter

    CERN Document Server

    Sanchez-Salcedo, F J; Aguirre-Torres, V M; Hernandez-Toledo, H M

    2016-01-01

    We analyse the rotation curves and gravitational stability of a sample of six bulgeless galaxies for which detailed images reveal no evidence for strong bars. We explore two scenarios: Newtonian dark matter models and MOdified Newtonian Dynamics (MOND). By adjusting the stellar mass-to-light ratio, dark matter models can match simultaneously both the rotation curve and bar-stability requirements in these galaxies. To be consistent with stability constraints, in two of these galaxies, the stellar mass-to-light ratio is a factor of ~1.5-2 lower than the values suggested from galaxy colours. In contrast, MOND fits to the rotation curves are poor in three galaxies, perhaps because the gas tracer contains noncircular motions. The bar stability analysis provides a new observational test to MOND. We find that most of the galaxies under study require abnormally-high levels of random stellar motions to be bar stable in MOND. In particular, for the only galaxy in the sample for which the line-of-sight stellar velocity ...

  6. SPT 0538–50: Physical conditions in the interstellar medium of a strongly lensed dusty star-forming galaxy at z = 2.8

    Energy Technology Data Exchange (ETDEWEB)

    Bothwell, M. S. [Cavendish Laboratory, University of Cambridge, JJ Thompson Avenue, Cambridge CB3 0HA (United Kingdom); Aguirre, J. E. [University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States); Chapman, S. C. [Dalhousie University, Halifax, Nova Scotia (Canada); Marrone, D. P. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Vieira, J. D.; Bock, J. J.; Downes, T. P. [California Institute of Technology, 1200 East California Blvd., Pasadena, CA 91125 (United States); Ashby, M. L. N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Aravena, M.; De Breuck, C.; Gullberg, B. [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001 Vitacura Santiago (Chile); Benson, B. A.; Carlstrom, J. E.; Crawford, T. M. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Bradford, C. M. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Fassnacht, C. D. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, A. H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Greve, T. R. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Hezaveh, Y. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); and others

    2013-12-10

    We present observations of SPT-S J053816–5030.8, a gravitationally lensed dusty star-forming galaxy (DSFG) at z = 2.7817 that was first discovered at millimeter wavelengths by the South Pole Telescope. SPT 0538–50 is typical of the brightest sources found by wide-field millimeter-wavelength surveys, being lensed by an intervening galaxy at moderate redshift (in this instance, at z = 0.441). We present a wide array of multi-wavelength spectroscopic and photometric data on SPT 0538–50, including data from ALMA, Herschel PACS and SPIRE, Hubble, Spitzer, the Very Large Telescope, ATCA, APEX, and the Submillimeter Array. We use high-resolution imaging from the Hubble Space Telescope to de-blend SPT 0538–50, separating DSFG emission from that of the foreground lens. Combined with a source model derived from ALMA imaging (which suggests a magnification factor of 21 ± 4), we derive the intrinsic properties of SPT 0538–50, including the stellar mass, far-IR luminosity, star formation rate, molecular gas mass, and—using molecular line fluxes—the excitation conditions within the interstellar medium. The derived physical properties argue that we are witnessing compact, merger-driven star formation in SPT 0538–50 similar to local starburst galaxies and unlike that seen in some other DSFGs at this epoch.

  7. Rest-frame ultraviolet spectrum of the gravitationally lensed galaxy `the 8 o'clock arc': stellar and interstellar medium properties

    CERN Document Server

    Dessauges-Zavadsky, M; Schaerer, D; Modigliani, A; Tapken, C; Vernet, J

    2009-01-01

    We present the first detailed analysis of the rest-frame UV spectrum of the gravitationally lensed Lyman break galaxy (LBG), the `8 o'clock arc'. The spectrum of the 8 o'clock arc is rich in stellar and interstellar medium (ISM) features, and presents several similarities to the well-known MS1512-cB58 LBG. The stellar photospheric absorption lines allowed us to constrain the systemic redshift, z_sys = 2.7350+/-0.0003, of the galaxy, and derive its stellar metallicity, Z=0.82 Z_sol. With a total stellar mass of ~4.2x10^{11} M_sol, the 8 o'clock arc agrees with the mass-metallicity relation found for z>2 star-forming galaxies. The 31 ISM absorption lines detected led to the abundance measurements of 9 elements. The metallicity of the ISM, Z=0.65 Z_sol (Si), is very comparable to the metallicity of stars and ionized gas, and suggests that the ISM of the 8 o'clock arc has been rapidly polluted and enriched by ejecta of OB stars. The ISM lines extend over ~1000 km/s and have their peak optical depth blueshifted re...

  8. Investigating Nearby Star-Forming Galaxies in the Ultraviolet with HST/COS Spectroscopy. I: Spectral Analysis and Interstellar Abundance Determinations

    CERN Document Server

    James, Bethan L; Heckman, Timothy M; Sohn, Sangmo Tony; Wolfe, Michael A

    2014-01-01

    This is the first in a series of three papers describing a project with the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure abundances of the neutral interstellar medium (ISM) in a sample of 9 nearby star-forming galaxies. The goal is to assess the (in)homogeneities of the multiphase ISM in galaxies where the bulk of metals can be hidden in the neutral phase, yet the metallicity is inferred from the ionized gas in the HII regions. The sample, spanning a wide range in physical properties, is to date the best suited to investigate the metallicity behavior of the neutral gas at redshift z=0. ISM absorption lines were detected against the far-ultraviolet spectra of the brightest star-forming region(s) within each galaxy. Here we report on the observations, data reduction, and analysis of these spectra. Column densities were measured by a multi-component line-profile fitting technique, and neutral-gas abundances were obtained for a wide range of elements. Several caveats were considered includ...

  9. Confronting semi-analytic galaxy models with galaxy-matter correlations observed by CFHTLenS

    CERN Document Server

    Saghiha, Hananeh; Schneider, Peter; Hilbert, Stefan

    2016-01-01

    Testing predictions of semi-analytic models of galaxy evolution against observations help to understand the complex processes that shape galaxies. We compare predictions from the Garching and Durham models implemented on the Millennium Run with observations of galaxy-galaxy lensing (GGL) and galaxy-galaxy-galaxy lensing (G3L) for various galaxy samples with stellar masses in the range 0.5 < (M_* / 10^10 M_Sun) < 32 and photometric redshift range 0.2 < z < 0.6 in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We find that the predicted GGL and G3L signals are in qualitative agreement with CFHTLenS data. Quantitatively, the models succeed in reproducing the observed signals in the highest stellar mass bin 16 < ( M_* / 10^10 M_Sun) < 32 but show different degrees of tension for the other stellar mass samples. The Durham model is strongly excluded on a 95% confidence level by the observations as it largely over-predicts the amplitudes of GGL and G3L signals, probably owing to a la...

  10. THE FORMATION OF SHELL GALAXIES SIMILAR TO NGC 7600 IN THE COLD DARK MATTER COSMOGONY

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Andrew P. [Max Planck Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); Martinez-Delgado, David [Max Planck Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Helly, John; Frenk, Carlos; Cole, Shaun [Institute for Computational Cosmology, Department of Physics, University of Durham, South Road, DH1 3LE Durham (United Kingdom); Crawford, Ken [Rancho del Sol Observatory, Camino, CA 95709 (United States); Zibetti, Stefano [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Carballo-Bello, Julio A. [Instituto de Astrofisica de Canarias, Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Jay GaBany, R., E-mail: acooper@mpa-garching.mpg.de, E-mail: delgado@mpia-hd.mpg.de [Black Bird Observatory II, 5660 Brionne Drive, San Jose, CA 95118 (United States)

    2011-12-10

    We present new deep observations of 'shell' structures in the halo of the nearby elliptical galaxy NGC 7600, alongside a movie of galaxy formation in a cold dark matter (CDM) universe. The movie, based on an ab initio cosmological simulation, shows how continuous accretion of clumps of dark matter and stars creates a swath of diffuse circumgalactic structures. The disruption of a massive clump on a near-radial orbit creates a complex system of transient concentric shells which bare a striking resemblance to those of NGC 7600. With the aid of the simulation we interpret NGC 7600 in the context of the CDM model.

  11. On the dark matter haloes inner structure and galaxy morphology

    CERN Document Server

    Del Popolo, A

    2016-01-01

    In the present paper, we extend the study of Del Popolo (2010) to determine the slope of the inner density profile of galaxy haloes with different morphologies. We study how galaxy morphology changes the relation between the inner slope of the galaxy halo density profile, $\\alpha$, and the stellar mass, $M_{*}$, or rotation velocity $V_{\\rm rot}$. For this, we use the model of Del Popolo (2009) in combination with observed data from the Romanowsky \\& Fall (2012) sample of elliptical and spiral galaxies, the Local Group sample compiled by McConnachie (2012), and the simulation results by Cloet-Osselaer et al. (2014). We find that the slope $\\alpha$ flattens monotonically, from $\\alpha \\simeq -1 $ at $V_{\\rm rot} \\simeq 250$ km/s, to $\\alpha \\simeq 0 $. After $V_{\\rm rot}\\simeq 25$ km/s the slope starts to steepen. The steepening happens in the mass range dominated by non-rotationally supported galaxies (e.g., dSphs) and depends on the level of offset in the angular momentum of rotationally and non-rotation...

  12. Inverse Compton Gamma Rays from Dark Matter Annihilation in the Dwarf Galaxies

    Indian Academy of Sciences (India)

    Jayashri Medhi; H. L. Duorah; A. G. Barua; K. Duorah

    2016-09-01

    Dwarf spheroidal (dSph) galaxies are thought to be good candidates for dark matter search due to their high mass-to-light (M/L) ratio. One of the most favored dark matter candidates is the lightest neutralino(neutral $\\chi$ particle) as predicted in the Minimal Supersymmetric Standard Model (MSSM). In this study, we model the gamma ray emission from dark matter annihilation coming from the nearby dSph galaxies Draco, Segue 1, Ursa Minor and Willman 1, taking into account the contribution from prompt photons and photons produced from inverse Compton scattering off starlight and Cosmic Microwave Background (CMB) photons by the energetic electrons and positrons from dark matter annihilation. We also compute the energy spectra of electrons and positrons from the decay of dark matter annihilation products. Gamma ray spectra and fluxes for both prompt and inverse Compton emission have been calculated for neutralino annihilation over a range of masses and found to be in agreement with the observed data. It has been found that the ultra faint dSph galaxy Segue 1 gives the largest gamma ray flux limits while the lowest gamma ray flux limits has been obtained from Ursa Minor. It is seen that for larger M/L ratio of dwarf galaxies the intensity pattern originating from $e^+e^−-$ pairs scattering off CMB photons is separated by larger amount from that off the starlight photons for the same neutralino mass. As the $e^+e^−-$ energy spectra have an exponential cut off at high energies, this may allow to discriminate some dark matter scenarios from other astrophysical sources. Finally, some more detailed study about the effect of inverse Compton scattering may help constrain the dark matter signature in the dSph galaxies.

  13. Inverse Compton Gamma Rays from Dark Matter Annihilation in the Dwarf Galaxies

    Science.gov (United States)

    Medhi, Jayashri; Duorah, H. L.; Barua, A. G.; Duorah, K.

    2016-09-01

    Dwarf spheroidal (dSph) galaxies are thought to be good candidates for dark matter search due to their high mass-to-light (M/L) ratio. One of the most favored dark matter candidates is the lightest neutralino (neutral χ particle) as predicted in the Minimal Supersymmetric Standard Model (MSSM). In this study, we model the gamma ray emission from dark matter annihilation coming from the nearby dSph galaxies Draco, Segue 1, Ursa Minor and Willman 1, taking into account the contribution from prompt photons and photons produced from inverse Compton scattering off starlight and Cosmic Microwave Background (CMB) photons by the energetic electrons and positrons from dark matter annihilation. We also compute the energy spectra of electrons and positrons from the decay of dark matter annihilation products. Gamma ray spectra and fluxes for both prompt and inverse Compton emission have been calculated for neutralino annihilation over a range of masses and found to be in agreement with the observed data. It has been found that the ultra faint dSph galaxy Segue 1 gives the largest gamma ray flux limits while the lowest gamma ray flux limits has been obtained from Ursa Minor. It is seen that for larger M/L ratio of dwarf galaxies the intensity pattern originating from e + e - pairs scattering off CMB photons is separated by larger amount from that off the starlight photons for the same neutralino mass. As the e + e - energy spectra have an exponential cut off at high energies, this may allow to discriminate some dark matter scenarios from other astrophysical sources. Finally, some more detailed study about the effect of inverse Compton scattering may help constrain the dark matter signature in the dSph galaxies.

  14. Elliptical Galaxy Kinematics and Dark Matter Halos with VIRUS-P

    Science.gov (United States)

    Murphy, Jeremy; Gebhardt, K.; Greene, J. E.; Graves, G.

    2012-01-01

    Dark matter is now ubiquitous in galactic astronomy, yet our understanding of both its extent, shape, and influence on the evolution of galaxies remains poorly understood. In the case of giant elliptical galaxies, which typically reside in dense environments and accumulate their mass via a range of processes, yet maintain tight scaling relations between a wide variety of their parameters, our understanding of the dizzying variety of mechanisms involved is a work in progress. To this end I will discuss an ongoing project being carried out at McDonald Observatory using the VIRUS-P integral field spectrograph to characterize the dark matter halos, stellar anisotropy and stellar abundance patterns of the most massive galaxies in the local universe from measurements of integrated stellar light. We have observed 23 giant elliptical galaxies over a range of environments. Seven of the 23 galaxies in our data set our Brightest Cluster Galaxies (BCG). I will present spectra and kinematics for a subsample of the survey. Three-integral axisymmetric dynamical modeling, based on Schwarzschild's method of orbit-superposition, will be presented for 3 BCGs in our sample (NGC 4472, M87 and NGC 2832). For the case of M87 we have data extending to 5 effective radii which allows for a direct comparison between stellar kinematics and other mass tracers typically used at large radial distances where the stellar light has historically been too faint to extract reliable kinematics. The mass distribution of all 3 of these galaxies is dominated by their dark matter halo at large radii. The degree of stellar radial and tangential anisotropy of the stars is returned from the modeling process. I will discuss how the stellar anisotropy, combined with stellar abundance patterns from measurements of the Lick indices, can be used to infer how the most massive galaxies accumulated their mass over time.

  15. Enhancements to velocity-dependent dark matter interactions from tidal streams and shells in the Andromeda galaxy

    NARCIS (Netherlands)

    Sanderson, Robyn E.; Mohayaee, Roya; Silk, Joe

    2012-01-01

    Dark matter substructures around nearby galaxies provide an interesting opportunity for confusion-free indirect detection of dark matter. We calculate the boost over a smooth background distribution of dark matter for gamma-ray emission from dark matter self-annihilations in tidal structures in M31,

  16. Enhancements to velocity-dependent dark matter interactions from tidal streams and shells in the Andromeda galaxy

    NARCIS (Netherlands)

    Sanderson, Robyn E.; Mohayaee, Roya; Silk, Joe

    2012-01-01

    Dark matter substructures around nearby galaxies provide an interesting opportunity for confusion-free indirect detection of dark matter. We calculate the boost over a smooth background distribution of dark matter for gamma-ray emission from dark matter self-annihilations in tidal structures in M31,

  17. Improving the sensitivity of gamma-ray telescopes to dark matter annihilation in dwarf spheroidal galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, Eric [Univ. of California, Santa Cruz, CA (United States). Dept. of Physics; Hooper, Dan [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States). Center for Particle Astrophysics; Univ. of Chicago, IL (United States). Dept. of Astronomy and Astrophysics; Linden, Tim [Univ. of Chicago, IL (United States). Kavli Inst. for Cosmological Physics

    2015-03-01

    The Fermi-LAT Collaboration has studied the gamma-ray emission from a stacked population of dwarf spheroidal galaxies and used this information to set constraints on the dark matter annihilation cross section. Interestingly, their analysis uncovered an excess with a test statistic (TS) of 8.7. If interpreted naively, this constitutes a 2.95σ local excess (p-value=0.003), relative to the expectations of their background model. In order to further test this interpretation, the Fermi-LAT team studied a large number of blank sky locations and found TS>8.7 excesses to be more common than predicted by their background model, decreasing the significance of their dwarf excess to 2.2σ(p-value=0.027). We argue that these TS>8.7 blank sky locations are largely the result of unresolved blazars, radio galaxies, and star-forming galaxies, and show that multiwavelength information can be used to reduce the degree to which such sources contaminate the otherwise blank sky. In particular, we show that masking regions of the sky that lie within 1° of sources contained in the BZCAT or CRATES catalogs reduce the fraction of blank sky locations with TS>8.7 by more than a factor of 2. Taking such multiwavelength information into account can enable experiments such as Fermi to better characterize their backgrounds and increase their sensitivity to dark matter in dwarf galaxies, the most important of which remain largely uncontaminated by unresolved point sources. We also note that for the range of dark matter masses and annihilation cross sections currently being tested by studies of dwarf spheroidal galaxies, simulations predict that Fermi should be able to detect a significant number of dark matter subhalos. These subhalos constitute a population of subthreshold gamma-ray point sources and represent an irreducible background for searches for dark matter annihilation in dwarf galaxies.

  18. Star formation and the interstellar medium in low surface brightness galaxies - II. Deep CO observations of low surface brightness disk galaxies

    NARCIS (Netherlands)

    de Blok, WJG; van der Hulst, JM

    1998-01-01

    We present deep, pointed (CO)-C-12(J = 2 - 1) observations of three late-type LSB galaxies. The beam-size was small enough that we could probe different environments (HI maximum, HI mininum, star forming region) in these galaxies. No CO was found at any of the positions observed. We argue that the i

  19. Modeling dark matter subhalos in a constrained galaxy: Global mass and boosted annihilation profiles

    CERN Document Server

    Stref, Martin

    2016-01-01

    The interaction properties of cold dark matter (CDM) particle candidates, such as those of weakly interacting massive particles (WIMPs), generically lead to the structuring of dark matter on scales much smaller than typical galaxies, potentially down to $\\sim 10^{-10}M_\\odot$. This clustering translates into a very large population of subhalos in galaxies and affects the predictions for direct and indirect dark matter searches (gamma rays and antimatter cosmic rays). In this paper, we elaborate on previous analytic works to model the Galactic subhalo population, while consistently with current observational dynamical constraints on the Milky Way. In particular, we propose a self-consistent method to account for tidal effects induced by both dark matter and baryons. Our model does not strongly rely on cosmological simulations as they can hardly be fully matched to the real Milky Way, but for setting the initial subhalo mass fraction. Still, it allows to recover the main qualitative features of simulated system...

  20. Quark nugget dark matter: no contradiction with 511 keV line emission from dwarf galaxies

    Science.gov (United States)

    Lawson, Kyle; Zhitnitsky, Ariel

    2017-02-01

    The observed galactic 511 keV line has been interpreted in a number of papers as a possible signal of dark matter annihilation within the galactic bulge. If this is the case then it is possible that a similar spectral feature may be observed in association with nearby dwarf galaxies. These objects are believed to be strongly dark matter dominated and present a relatively clean observational target. Recently INTEGRAL observations have provided new constraints on the 511 keV flux from nearby dwarf galaxies [1] motivating further investigation into the mechanism by which this radiation may arise. In the model presented here dark matter in the form of heavy quark nuggets produces the galactic 511 keV emission line through interactions with the visible matter. It is argued that this type of interaction is not strongly constrained by the flux limits reported in [2].

  1. Statistical properties of the dark matter haloes of dwarf galaxies and correlations with the environment

    CERN Document Server

    Del Popolo, A

    2012-01-01

    According to the now strongly supported concordance $\\Lambda$CDM model, galaxies may be grossly described as a luminous component embedded in a dark matter halo. The density profile of these mass dominating haloes may be determined by N - body simulations which mimic the evolution of the tiny initial density perturbations during the process leading to the structures we observe today. Unfortunately, when the effect of baryons is taken into account, the situation gets much more complicated due to the difficulties in simulating their physics. As a consequence, a definitive prediction of how dark matter haloes should presently look like is still missing. We revisit here this issue from an observational point of view devoting our attention to dwarf galaxies. Being likely dark matter dominated, these systems are ideal candidates to investigate the present day halo density profiles and check whether dark matter related quantities correlate with the stellar ones or the environment. By fitting a large sample of well m...

  2. Medium-resolution spectroscopy of FORJ0332-3557: probing the interstellar medium and stellar populations of a lensed Lyman-break galaxy at z = 3.77

    Science.gov (United States)

    Cabanac, Rémi A.; Valls-Gabaud, David; Lidman, Chris

    2008-06-01

    We recently reported the discovery of FORJ0332-3557, a lensed Lyman-break galaxy at z = 3.77 in a remarkable example of strong galaxy-galaxy gravitational lensing. We present here a medium-resolution rest-frame ultraviolet (UV) spectrum of the source, which appears to be similar to the well-known Lyman-break galaxy MS1512-cB58 at z = 2.73. The spectral energy distribution is consistent with a stellar population of less than 30Ma, with an extinction of Av = 0.5 mag and an extinction-corrected star formation rate SFRUV of 200-300h-170Msolara-1. The Lyα line exhibits a damped profile in absorption produced by a column density of about NHI = (2.5 +/- 1.0) × 1021cm-2, superimposed on an emission line shifted both spatially (0.5 arcsec with respect to the UV continuum source) and in velocity space (+830kms-1 with respect to the low-ionization absorption lines from its interstellar medium), a clear signature of outflows with an expansion velocity of about 270kms-1. A strong emission line from HeII λ164.04 nm indicates the presence of Wolf-Rayet stars and reinforces the interpretation of a very young starburst. The metallic lines indicate subsolar abundances of elements Si, Al and C in the ionized gas phase. Based on observations made at the ESO VLT under programmes 74.A-0536 and 78.A-0240. E-mail: remi.cabanac@ast.obs-mip.fr (RAC); david.valls-gabaud@obspm.fr (DV-G); clidman@eso.org (CL)

  3. Evolution of central dark matter of early-type galaxies up to z ~ 0.8

    CERN Document Server

    Tortora, C; Saglia, R P; Romanowsky, A J; Covone, G; Capaccioli, M

    2014-01-01

    We investigate the evolution of dark and luminous matter in the central regions of early-type galaxies (ETGs) up to z ~ 0.8. We use a spectroscopically selected sample of 154 cluster and field galaxies from the EDisCS survey, covering a wide range in redshifts (z ~ 0.4-0.8), stellar masses ($\\log M_{\\star}/ M_{\\odot}$ ~ 10.5-11.5 dex) and velocity dispersions ($\\sigma_{\\star}$ ~ 100-300 \\, km/s). We obtain central dark matter (DM) fractions by determining the dynamical masses from Jeans modelling of galaxy aperture velocity dispersions and the $M_{\\star}$ from galaxy colours, and compare the results with local samples. We discuss how the correlations of central DM with galaxy size (i.e. the effective radius, $R_{\\rm e}$), $M_{\\star}$ and $\\sigma_{\\star}$ evolve as a function of redshift, finding clear indications that local galaxies are, on average, more DM dominated than their counterparts at larger redshift. This DM fraction evolution with $z$ can be only partially interpreted as a consequence of the size-r...

  4. Galaxy clusters as probes for cosmology and dark matter

    DEFF Research Database (Denmark)

    Battistelli, Elia S.; Burigana, Carlo; De Bernardis, Paolo

    2016-01-01

    In recent years, significant progress has been made in building new galaxy clusters samples, at low and high redshifts, from wide-area surveys, particularly exploiting the Sunyaev-Zel'dovich (SZ) effect. A large effort is underway to identify and characterize these new systems with optical/NIR an...

  5. Reionization and Galaxy Formation in Warm Dark Matter Cosmologies

    NARCIS (Netherlands)

    Dayal, Pratika; Choudhury, Tirthankar Roy; Bromm, Volker; Pacucci, F.

    2017-01-01

    We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ' 5 − 20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth (τes) and the ionizing photon emissivity ( ˙nion), to shed light on the reionization his

  6. Reionization and Galaxy Formation in Warm Dark Matter Cosmologies

    NARCIS (Netherlands)

    Dayal, Pratika; Choudhury, Tirthankar Roy; Bromm, Volker; Pacucci, F.

    2017-01-01

    We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ' 5 − 20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth (τes) and the ionizing photon emissivity ( ˙nion), to shed light on the reionization

  7. Ultra faint dwarf galaxies: an arena for testing dark matter versus modified gravity

    CERN Document Server

    Lin, Weikang

    2016-01-01

    The scenario consistent with a wealth of observations for the missing mass problem is that of weakly interacting dark matter particles. However, arguments or proposals for a Newtonian or relativistic modified gravity scenario continue to be made. A distinguishing characteristic between the two scenarios is that dark matter particles can produce a gravitational effect, in principle, without the need of baryons while this is not the case for the modified gravity scenario where such an effect must be correlated with the amount of baryonic matter. We consider here ultra-faint dwarf (UFD) galaxies as a promising arena to test the two scenarios based on the above assertion. We compare the correlation of the luminosity with the velocity dispersion between samples of UFD and non-UFD galaxies, finding a trend of loss of correlation for the UFD galaxies. For example, we find for 28 non-UFD galaxies a strong correlation coefficient of -0.688 which drops to -0.077 for the 23 UFD galaxies. Incoming and future data will de...

  8. Properties of Local Group galaxies in hydrodynamical simulations of sterile neutrino dark matter cosmologies

    CERN Document Server

    Lovell, Mark R; Boyarsky, Alexey; Crain, Robert A; Frenk, Carlos S; Hellwing, Wojciech A; Ludlow, Aaron D; Navarro, Julio F; Ruchayskiy, Oleg; Sawala, Till; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2016-01-01

    We study galaxy formation in sterile neutrino dark matter models that differ significantly from both cold and from `warm thermal relic' models. We use the EAGLE code to carry out hydrodynamic simulations of the evolution of pairs of galaxies chosen to resemble the Local Group, as part of the APOSTLE simulations project. We compare cold dark matter (CDM) with two sterile neutrino models with 7 keV mass: one, the warmest among all models of this mass (LA120) and the other, a relatively cold case (LA10). We show that the lower concentration of sterile neutrino subhalos compared to their CDM counterparts makes the inferred inner dark matter content of galaxies like Fornax (or Magellanic Clouds) less of an outlier in the sterile neutrino cosmologies. In terms of the galaxy number counts the LA10 simulations are \\emph{indistinguishable} from CDM when one takes into account halo-to-halo (or `simulation-to-simulation') scatter. In order for the LA120 model to match the number of Local Group dwarf galaxies, a higher f...

  9. Dark matter dominance at all radii in the superthin galaxy UGC 7321

    CERN Document Server

    Banerjee, Arunima; Jog, Chanda J

    2009-01-01

    We model the shape and density profile of the dark matter halo of the low surface brightness, superthin galaxy UGC 7321, using the observed rotation curve and the HI scale height data as simultaneous constraints. We treat the galaxy as a gravitationally coupled system of stars and gas, responding to the gravitational potential of the dark matter halo. An isothermal halo of spherical shape with a core density in the range of 0.039 - 0.057 M_sun/pc^3 and a core radius between 2.5 - 2.9 kpc, gives the best fit to the observations for a range of realistic gas parameters assumed. We find that the best-fit core radius is only slightly higher than the stellar disc scale length (2.1 kpc), unlike the case of the high surface brightness galaxies where the halo core radius is typically 3-4 times the disc scale length of the stars. Thus our model shows that the dark matter halo dominates the dynamics of the low surface brightness, superthin galaxy UGC 7321 at all radii, including the inner parts of the galaxy.

  10. Understanding the internal dynamics of elliptical galaxies without non-baryonic dark matter

    CERN Document Server

    Dabringhausen, J; Famaey, B; Fellhauer, M

    2016-01-01

    Assuming virial equilibrium and Newtonian dynamics, low-mass early-type galaxies have larger velocity dispersions than expected from the amount of baryons they contain. The conventional interpretation of this finding is that their dynamics is dominated by non-baryonic matter. However, there is also strong evidence that many low-mass early-type galaxies formed as tidal dwarf galaxies, which would contain almost no dark matter. Using an extensive catalogue of early-type galaxies, we therefore discuss how the internal dynamics of early-type galaxies in general can be understood by replacing the assumption of non-baryonic dark matter with two alternative assumptions. The first assumption is that Milgromian dynamics (i.e., MOND) is valid, which changes the effective gravitational force in the weak-field limit. The second assumption is that binary stars affect the observed line-of-sight velocity dispersions. Some moderate discrepancies between observed and predicted velocity dispersions remain also when these effec...

  11. Diffuse interstellar absorption bands

    Institute of Scientific and Technical Information of China (English)

    XIANG FuYuan; LIANG ShunLin; LI AiGen

    2009-01-01

    The diffuse interstellar bands (DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s, the exact nature of DIBs still remains unclear. This article reviews the history of the detec-tions of DIBs in the Milky Way and external galaxies, the major observational characteristics of DIBs, the correlations or anti-correlations among DIBs or between DIBs and other interstellar features (e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise), and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  12. Diffuse interstellar absorption bands

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The diffuse interstellar bands(DIBs) are a large number of absorption bands that are superposed on the interstellar extinction curve and are of interstellar origin. Since the discovery of the first two DIBs in the 1920s,the exact nature of DIBs still remains unclear. This article reviews the history of the detections of DIBs in the Milky Way and external galaxies,the major observational characteristics of DIBs,the correlations or anti-correlations among DIBs or between DIBs and other interstellar features(e.g. the prominent 2175 Angstrom extinction bump and the far-ultraviolet extinction rise),and the proposed candidate carriers. Whether they are also present in circumstellar environments is also discussed.

  13. Physics of the interstellar and intergalactic medium

    CERN Document Server

    Draine, Bruce T

    2010-01-01

    This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium

  14. Dark Matter Cores in the Fornax and Sculptor Dwarf Galaxies

    DEFF Research Database (Denmark)

    C. Amorisco, Nicola; Zavala Franco, Jesus; J. L. de Boer, Thomas

    2014-01-01

    We combine the detailed Star Formation Histories of the Fornax and Sculptor dwarf Spheroidals with the mass assembly history of their dark matter halo progenitors to estimate if the energy deposited by Supernova type II (SNeII) is sufficient to create a substantial dark matter core. Assuming...... the efficiency of energy injection of the SNeII into dark matter particles is \\epsilon=0.05, we find that a single early episode, z...

  15. SCALING LAWS FOR DARK MATTER HALOS IN LATE-TYPE AND DWARF SPHEROIDAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Kormendy, John [Department of Astronomy, University of Texas at Austin, 2515 Speedway, Mail Stop C1400, Austin, TX 78712-1205 (United States); Freeman, K. C., E-mail: kormendy@astro.as.utexas.edu, E-mail: kenneth.freeman@anu.edu.au [Research School of Astronomy and Astrophysics, The Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia)

    2016-02-01

    Dark matter (DM) halos of Sc–Im and dwarf spheroidal (dSph) galaxies satisfy scaling laws: halos in lower-luminosity galaxies have smaller core radii, higher central densities, and smaller velocity dispersions. These results are based on maximum-disk rotation curve decompositions for giant galaxies and Jeans equation analysis for dwarfs. (1) We show that spiral, Im, and Sph galaxies with absolute magnitudes M{sub V} > −18 form a sequence of decreasing baryon-to-DM surface density with decreasing luminosity. We suggest that this is a sequence of decreasing baryon retention versus supernova-driven losses or decreasing baryon capture after cosmological reionization. (2) The structural differences between S+Im and Sph galaxies are small. Both are affected mostly by the physics that controls baryon depletion. (3) There is a linear correlation between the maximum rotation velocities of baryonic disks and the outer circular velocities V{sub circ} of test particles in their DM halos. Baryons become unimportant at V{sub circ} = 42 ± 4 km s{sup −1}. Smaller galaxies are dim or dark. (4) We find that, absent baryon “depletion” and with all baryons converted into stars, dSph galaxies would be brighter by ∼4.6 mag and dIm galaxies would be brighter by ∼3.5 mag. Both have DM halos that are massive enough to help to solve the “too big to fail” problem with DM galaxy formation. (5) We suggest that there exist many galaxies that are too dark to be discovered by current techniques, as required by cold DM theory. (6) Central surface densities of DM halos are constant from M{sub B} ∼ −5 to −22. This implies a Faber–Jackson law with halo mass M ∝ (halo dispersion){sup 4}.

  16. The Preferential Tidal Stripping of Dark Matter versus Stars in Galaxies

    CERN Document Server

    Smith, Rory; Lee, Jaehyun; Rhee, Jinsu; Sanchez-Janssen, Ruben; Yi, Sukyoung K

    2016-01-01

    Using high resolution hydrodynamical cosmological simulations, we conduct a comprehensive study of how tidal stripping removes dark matter and stars from galaxies. We find that dark matter is always stripped far more significantly than the stars -- galaxies that lose $\\sim$80$\\%$ of their dark matter, typically lose only 10$\\%$ of their stars. This is because the dark matter halo is initially much more extended than the stars. As such, we find the stellar-to-halo size-ratio (measured using r$_{\\rm{eff}}$/r$_{\\rm{vir}}$) is a key parameter controlling the relative amounts of dark matter and stellar stripping. We use simple fitting formulae to measure the relation between the fraction of bound dark matter and fraction of bound stars. We measure a negligible dependence on cluster mass or galaxy mass. Therefore these formulae have general applicability in cosmological simulations, and are ideal to improve stellar stripping recipes in semi-analytical models, and/or to estimate the impact that tidal stripping would...

  17. Size Evolution of Early-Type Galaxies and Massive Compact Objects as the Dark Matter

    CERN Document Server

    Totani, Tomonori

    2009-01-01

    The dramatic size evolution of early-type galaxies from z ~ 2 to 0 poses a new challenge in the theory of galaxy formation, which may not be explained by the standard picture. It is shown here that the size evolution can be explained if the non-baryonic cold dark matter is composed of compact objects having a mass scale of ~10^5 M_sun. This form of dark matter is consistent with or only weakly constrained by the currently available observations. The kinetic energy of the dark compact objects is transferred to stars by dynamical friction, and stars around the effective radius are pushed out to larger radii, resulting in a pure size evolution. This scenario has several good properties to explain the observations, including the ubiquitous nature of size evolution and faster disappearance of higher density galaxies.

  18. Low dark matter content of the nearby early-type galaxy NGC 821

    Directory of Open Access Journals (Sweden)

    Samurović S.

    2014-01-01

    Full Text Available In this paper we analyze the kinematics and dynamics of the nearby early-type galaxy NGC 821 based on its globular clusters (GCs and planetary nebulae (PNe. We use PNe and GCs to extract the kinematics of NGC 821 which is then used for the dynamical modelling based on the Jeans equation. We apply the Jeans equation using the Newtonian mass-follows-light approach assuming constant mass-to-light ratio and find that using such an approach we can successfully fit the kinematic data. The inferred constant mass-to-light ratio, 4:2 < M=LB < 12:4 present throughout the whole galaxy, implies the lack of significant amount of dark matter. We also used three different MOND approaches and found that we can fit the kinematic data without the need for additional, dark, component. [Projekat Ministarstva nauke Republike Srbije, br. 176021: Visible and invisible matter in nearby galaxies: theory and observations

  19. Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

    NARCIS (Netherlands)

    Napolitano, N.R.; Romanowsky, A.J.; Coccato, L; Capaccioli, M.; Douglas, N.G.; Noordermeer, E.; Merrifield, M.R.; Kuijken, K.; Arnaboldi, M.; Gerhard, O.; Freeman, K.C.; De Lorenzi, F.; Das, P.

    2007-01-01

    Abstract. We examine the dark matter properties of nearby early-type galaxies using plane- tary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities

  20. The DiskMass Survey. VII. The distribution of luminous and dark matter in spiral galaxies

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass s

  1. RCSLenS: A new estimator for large-scale galaxy-matter correlations

    CERN Document Server

    Buddendiek, A; Hildebrandt, H; Blake, C; Choi, A; Erben, T; Heymans, C; van Waerbeke, L; Viola, M; Harnois-Deraps, J; Koens, L; Nakajima, R

    2015-01-01

    We present measurements of the galaxy bias $b$ and the galaxy-matter cross-correlation coefficient $r$ for the BOSS LOWZ luminous red galaxy sample. Using a new statistical weak lensing analysis of the Red Sequence Cluster Lensing Survey (RCSLenS) we find the bias properties of this sample to be higher than previously reported with $b=2.45^{+0.05}_{-0.05}$ and $r=1.64^{+0.17}_{-0.16}$ on scales between $3'$ and $20'$. We repeat the measurement for angular scales of $20'\\leq \\vartheta \\leq70'$, which yields $b=2.39^{+0.07}_{-0.07}$ and $r=1.24^{+0.26}_{-0.25}$. This is the first application of a data compression analysis using a complete set of discrete estimators for galaxy-galaxy lensing and galaxy clustering. As cosmological data sets grow, our new method of data compression will become increasingly important in order to interpret joint weak lensing and galaxy clustering measurements and to estimate the data covariance. In future studies this formalism can be used as a tool to study the large-scale structur...

  2. A Theoretical Framework for Combining Techniques that Probe the Link Between Galaxies and Dark Matter

    Science.gov (United States)

    Leauthaud, Alexie; Tinker, Jeremy; Behroozi, Peter S.; Busha, Michael T.; Wechsler, Risa H.

    2011-09-01

    We develop a theoretical framework that combines measurements of galaxy-galaxy lensing, galaxy clustering, and the galaxy stellar mass function in a self-consistent manner. While considerable effort has been invested in exploring each of these probes individually, attempts to combine them are still in their infancy. These combinations have the potential to elucidate the galaxy-dark matter connection and the galaxy formation physics responsible for it, as well as to constrain cosmological parameters and to test the nature of gravity. In this paper, we focus on a theoretical model that describes the galaxy-dark matter connection based on standard halo occupation distribution techniques. Several key modifications enable us to extract additional parameters that determine the stellar-to-halo mass relation and to simultaneously fit data from multiple probes while allowing for independent binning schemes for each probe. We construct mock catalogs from numerical simulations to investigate the effects of sample variance and covariance for each probe. Finally, we analyze how trends in each of the three observables impact the derived parameters of the model. In particular, we investigate various features of the observed galaxy stellar mass function (low-mass slope, "plateau," knee, and high-mass cutoff) and show how each feature is related to the underlying relationship between stellar and halo mass. We demonstrate that the observed "plateau" feature in the stellar mass function at M * ~ 2 × 1010 M sun is due to the transition that occurs in the stellar-to-halo mass relation at Mh ~ 1012 M sun from a low-mass power-law regime to a sub-exponential function at higher stellar mass.

  3. Observational probes of the connection between Star Formation Efficiency and Dark Matter halo mass of galaxies

    Science.gov (United States)

    Kalinova, Veselina; Colombo, Dario; Rosolowsky, Erik

    2015-08-01

    Modern simulations predict that the stellar mass and the star formation efficiency of a galaxy are tightly linked to the dark matter (DM) halo mass of that galaxy. This prediction relies on a specific model of galaxy evolution and so testing this prediction directly tests our best models of galaxy formation and evolution. Recent DM numerical studies propose relationships between star formation efficiency and the DM halo mass with two domains based on SF feedback (low-mass) vs. AGN feedback (high-mass), see Moster et al. (2013). The observational probe of such parameters in the relationship imply globally important physics that are fundamental as, e.g., the star formation law (e.g., Kennicutt et al., 1998), the universal depletion time (Leroy et al. 2008), and the origin of the cold gas phase with respect to the stellar disc (Davis et al.2011). Thus, we can directly measure whether this parameterization is correct by estimating the stellar mass, star formation efficiency and dynamical (DM) mass for a set of galaxies at strategically selected points to test if they fall on the predicted relationship.We use CO data from the Extragalactic Database for Galaxy Evolution survey (EDGE) in conjunction with archival 21-cm data and spectroscopic data from Calar Alto Legacy Integral Field spectroscopy Area survey (CALIFA) to measure the stellar vs. halo mass and star-formation-efficiency vs. halo mass relations of the galaxies. We also analyze archival 21-cm spectra to estimate rotation speeds, atomic gas masses and halo masses for a set of EDGE galaxies. Data from CALIFA are used for high quality star formation efficiency and stellar mass measurements. By linking these three parameters - stellar mass, star formation efficiency (SFE) and DM halo mass - we can test the simulation models of how the gas is cooling in the potential wells of the dark matter halos and then forms stars.

  4. Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Conde, Miguel A.; /KIPAC, Menlo Park /SLAC /IAC, La Laguna /Laguna U., Tenerife; Cannoni, Mirco; /Huelva U.; Zandanel, Fabio; /IAA, Granada; Gomez, Mario E.; /Huelva U.; Prada, Francisco; /IAA, Granada

    2012-06-06

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  5. Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Conde, Miguel A. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Cannoni, Mirco; Gómez, Mario E. [Dpto. Física Aplicada, Facultad de Ciencias Experimentales, Universidad de Huelva, 21071 Huelva (Spain); Zandanel, Fabio; Prada, Francisco, E-mail: masc@stanford.edu, E-mail: mirco.cannoni@dfa.uhu.es, E-mail: fabio@iaa.es, E-mail: mario.gomez@dfa.uhu.es, E-mail: fprada@iaa.es [Instituto de Astrofísica de Andalucía (CSIC), E-18008, Granada (Spain)

    2011-12-01

    In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We

  6. A Flash In The Dark: Searching For Decaying Dark Matter Signal In Galaxy Clusters

    Science.gov (United States)

    Bulbul, Esra

    Galaxy clusters contain the largest concentrated reservoirs of dark matter, making them unique laboratories for the search for dark matter signatures. Despite intensive search, there is as yet no definitive detection of WIMP dark matter, viable alternative candidates ought to be considered. Some of these - including the well-motivated keV sterile neutrino dark matter candidate - radiatively decay, emitting X-rays that may be detected in observations of large dark matter aggregations such as clusters of galaxies. The decay of sterile neutrinos produces photons with energy half of the sterile neutrino rest mass, resulting in a monochromatic emission line broadened only by the cluster dark matter velocity dispersion. The stacking analysis of XMM-Newton observations of seventy of the brightest nearby galaxy clusters has recently strongly suggested an unknown and unidentified emission feature with a best fit energy of 3.54+/-0.02 keV, which would match ~7 keV sterile neutrino. The flux of the detected line implies a mixing angle, which is consistent with the previous upper limits on sterile neutrino radiative decay. This profound result must be verified using a variety of data sets, employing a variety of methods of data reduction, background subtraction, and statistical techniques to confirm/reject the validity of the detection. We propose to stack Suzaku archival observations of 47 galaxy clusters to verify/rule out the detection of this unidentified signal. The funding we request will support the data analysis and publication of results from this analysis. This work will directly address NASA's objective 2.4.1 in Astrophysics, as it will improve the understanding of the origin and destiny of the universe, and the nature of black holes, dark energy, dark matter, and gravity.

  7. On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344

    CERN Document Server

    Lagos, P; Gomes, J M; Castelli, A V Smith; Vega, L R; .,

    2014-01-01

    The main goal of this study is to carry out a spatially resolved investigation of the warm interstellar medium (ISM) in the extremely metal-poor Blue Compact Dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on the analysis of the spatial distribution of chemical abundances, emission-line ratios and kinematics of the ISM, and to the recent star-forming activity in this galaxy. This study is based on optical integral field unit spectroscopy data from Gemini Multi-Object Spectrograph at the Gemini North telescope and archival Sloan Digital Sky Survey images. The data were obtained in two different positions across the galaxy, obtaining a total 4 arcsec X 8 arcsec field which encompasses most of its ISM. Emission-line maps and broad-band images obtained in this study indicate that HS 2236+1344 hosts three Giant HII regions. Our data also reveal some faint curved features in the BCD periphery that might be due to tidal perturbations or expanding ionized-gas shells. The ISM velocity field shows systematic ...

  8. Constraints on the Star-Forming Interstellar Medium in Galaxies Back to the First Billion Years of Cosmic Time

    CERN Document Server

    Riechers, Dominik A

    2011-01-01

    Constraints on the molecular gas content of galaxies at high redshift are crucial to further our understanding of star formation and galaxy evolution through cosmic times, as molecular gas is the fuel for star formation. Since its initial detection at large cosmic distances almost two decades ago, studies of molecular gas in the early universe have come a long way. We have detected CO emission from >100 galaxies, covering a range of galaxy populations at z>1, reaching out to z>6, down to sub-kpc scale resolution, and spanning ~2 orders of magnitude in gas mass (aided by gravitational lensing). Recently, it has even become possible to directly identify distant galaxies through their molecular emission lines without prior knowledge of their redshifts. The new generation of powerful long wavelength interferometers such as the Expanded Very Large Array (EVLA) and Atacama Large (sub)Millimeter Array (ALMA) thus hold the promise to liberate studies of molecular gas in high redshift galaxies from their heavy pre-sel...

  9. Search for annihilating Dark Matter towards dwarf galaxies with the Cherenkov Telescope Array

    Science.gov (United States)

    Morselli, Aldo; Rodríguez, Gonzalo

    2017-03-01

    The standard model of cosmology indicates that approximately 27% of the energy density of the Universe is in the form of dark matter. The nature of dark matter is an open question in modern physics. Indirect dark matter searches with imaging atmospheric Cherenkov telescopes are playing a crucial role in constraining the nature of the dark matter particle through the study of their potential annihilation that could produce very high energy gamma rays from different astrophysical structures. The Cherenkov Telescope Array will provide an unprecedented sensitivity over a range of dark matter mass from 100 GeV to 30 TeV. In this contribution we review the status of indirect dark matter searches at dwarf spheroidal galaxies.

  10. Is Sextans dwarf galaxy in a scalar field dark matter halo?

    Energy Technology Data Exchange (ETDEWEB)

    Lora, V. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg (Germany); Magaña, Juan, E-mail: vlora@ari.uni-heidelberg.de, E-mail: juan.magana@uv.cl [Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso (Chile)

    2014-09-01

    The Bose-Einstein condensate/scalar field dark matter model, considers that the dark matter is composed by spinless-ultra-light particles which can be described by a scalar field. This model is an alternative model to the Λ-cold dark matter paradigm, and therefore should be studied at galactic and cosmological scales. Dwarf spheroidal galaxies have been very useful when studying any dark matter theory, because the dark matter dominates their dynamics. In this paper we study the Sextans dwarf spheroidal galaxy, embedded in a scalar field dark matter halo. We explore how the dissolution time-scale of the stellar substructures in Sextans, constrain the mass, and the self-interacting parameter of the scalar field dark matter boson. We find that for masses in the range (0.12< m{sub φ}<8) ×10{sup -22} eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the stellar substructures in Sextans, and small enough mass to be compatible with dynamical limits. If the self-interacting parameter is distinct to zero, then the mass of the boson could be as high as m{sub φ}≈2×10{sup -21} eV, but it would correspond to an unrealistic low mass for the Sextans dark matter halo . Therefore, the Sextans dwarf galaxy could be embedded in a scalar field/BEC dark matter halo with a preferred self-interacting parameter equal to zero.

  11. Static structure of chameleon dark matter as an explanation of dwarf spheroidal galaxy cores

    Science.gov (United States)

    Chanda, Prolay Krishna; Das, Subinoy

    2017-04-01

    We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance r ≥1 kpc from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.

  12. Constraints on MACHO Dark Matter from the Star Cluster in the Dwarf Galaxy Eridanus II

    CERN Document Server

    Brandt, Timothy D

    2016-01-01

    I show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy Eridanus II provides strong constraints on massive compact halo objects (MACHOs) of >~5 M_sun as the main component of dark matter. MACHO dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. The star cluster has a luminosity of just ~2000 L_sun and is relatively puffy, with a half-light radius of 13 pc, making it much more fragile than other known clusters in dwarf galaxies. For a wide range of plausible dark matter halo properties, Eri II's star cluster combines with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of MACHOs from ~10$^{-7}$ M_sun up to arbitrarily high masses. The cluster in Eri II closes the ~20--100 M_sun window of allowed MACHO dark matter and provides much stronger constraints than wide Galactic binaries for MACHOs of up to thousands o...

  13. Evidence for dark matter contraction and a Salpeter IMF in a massive early-type galaxy

    CERN Document Server

    Sonnenfeld, Alessandro; Gavazzi, Raphael; Marshall, Philip J; Auger, Mattew W; Suyu, Sherry H; Koopmans, Leon V E; Bolton, Adam S

    2011-01-01

    Stars and dark matter account for most of the mass of early-type galaxies, but uncertainties in the stellar population and the dark matter profile make it challenging to distinguish between the two components. Nevertheless, precise observations of stellar and dark matter are extremely valuable for testing the many models of structure formation and evolution. We present a measurement of the stellar mass and inner slope of the dark matter halo of a massive early-type galaxy at $z=0.222$. The galaxy is the foreground deflector of the double Einstein ring gravitational lens system SDSSJ0946+1006, also known as the "Jackpot". By combining the tools of lensing and dynamics, we first constrain the mean slope of the total mass density profile ($\\rho_{\\rm{tot}}\\propto r^{-\\gamma'}$) within the radius of the outer ring to be $\\gamma' = 1.98\\pm0.02\\pm0.01$. Then we obtain a bulge-halo decomposition, assuming a power-law form for the dark matter halo. Our analysis yields $\\gamma_{\\rm{DM}} = 1.7\\pm0.2$ for the inner slope...

  14. The stellar and dark matter distributions in elliptical galaxies from the ensemble of strong gravitational lenses

    CERN Document Server

    Oguri, Masamune; Falco, Emilio E

    2013-01-01

    We derive the average mass profile of elliptical galaxies from the ensemble of 161 strong gravitational lens systems selected from several surveys, assuming that the mass profile scales with the stellar mass and effective radius of each lensing galaxy. The total mass profile is well fitted by a power-law \\rho(r) \\propto r^\\gamma with best-fit slope \\gamma = -2.11+/-0.05. The decomposition of the total mass profile into stellar and dark matter distributions is difficult due to a fundamental degeneracy between the stellar initial mass function (IMF) and the dark matter fraction f_DM. We demonstrate that this IMF-f_DM degeneracy can be broken by adding direct stellar mass fraction measurements by quasar microlensing observations. Our best-fit model prefers the Salpeter IMF over the Chabrier IMF, and a smaller central dark matter fraction than that predicted by adiabatic contraction models.

  15. Testing Lorentz invariance of dark matter with satellite galaxies arXiv

    CERN Document Server

    Bettoni, Dario; Blas, Diego; Sibiryakov, Sergey

    We develop the framework for testing Lorentz invariance in the dark matter sector using galactic dynamics. We consider a Lorentz violating (LV) vector field acting on the dark matter component of a satellite galaxy orbiting in a host halo. We introduce a numerical model for the dynamics of satellites in a galactic halo and for a galaxy in a rich cluster to explore observational consequences of such an LV field. The orbital motion of a satellite excites a time dependent LV force which greatly affects its internal dynamics. Our analysis points out key observational signatures which serve as probes of LV forces. These include modifications to the line of sight velocity dispersion, mass profiles and shapes of satellites. With future data and a more detailed modeling these signatures can be exploited to constrain a new region of the parameter space describing the LV in the dark matter sector.

  16. Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

    CERN Document Server

    Stewart, Kyle R; Barton, Elizabeth J; Wechsler, Risa H

    2008-01-01

    We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies--such as close pair counts, starburst counts, and the morphologically disturbed fraction--likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z=0 to z=4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M>0.3 mass ratio events into typical L > f L* galaxies follows the simple relation dN/dt=0.03(1+f)(1+z)^2.1 Gyr^-1. Despite the rapid increase in merger rate with redshift, only a small fraction of >0.4 L* high-redshift galaxies (~3% at z=2) should have experienced a major merger (m/M >0.3) in the very recent past (t0.3) in t...

  17. A tight relation between the age distributions of stellar clusters and the properties of the interstellar medium in the host galaxy

    Science.gov (United States)

    Miholics, Meghan; Kruijssen, J. M. Diederik; Sills, Alison

    2017-09-01

    The age distributions of stellar cluster populations have long been proposed to probe the recent formation history of the host galaxy. However, progress is hampered by the limited understanding of cluster disruption by evaporation and tidal shocks. We study the age distributions of clusters in smoothed particle hydrodynamics simulations of isolated disc galaxies, which include a self-consistent, physical model for the formation and dynamical evolution of the cluster population and account for the variation of cluster disruption in time and space. We show that the downward slope of the cluster age distribution due to disruption cannot be reproduced with a single functional form, because the disruption rate exhibits systematic trends with cluster age (the 'cruel cradle effect'). This problem is resolved by using the median cluster age to trace cluster disruption. Across 120 independent galaxy snapshots and simulated cluster populations, we perform two-dimensional power-law fits of the median cluster age to various macroscopic physical quantities and find that it scales as t_med∝ Σ ^{-0.51± 0.03}σ _1D^{-0.85± 0.10}M_min^γ, for the gas surface density Σ, gas velocity dispersion σ1D, and minimum cluster mass Mmin. This scaling accurately describes observed cluster populations and indicates disruption by impulsive tidal shocks from the interstellar medium. The term M_min^γ provides a model-independent way to measure the mass dependence of the cluster disruption time γ. Finally, the ensemble-average cluster lifetime depends on the gas density less strongly than the instantaneous disruption time of single clusters. These results reflect the variation of cluster disruption in time and space. We provide quantitative ways of accounting for these physics in cluster population studies.

  18. Thermal and non-thermal components of the interstellar medium at sub-kiloparsec scales in galaxies

    CERN Document Server

    Paladino, R; Helfer, T T; Wong, T; Ekers, R; Blitz, L; Gregorini, L; Moscadelli, L

    2006-01-01

    Aims: We present new radio continuum observations of ten BIMA SONG galaxies, taken at 1.4 GHz with the Very Large Array. These observations allow us to extend the study of the relationships between the radio continuum (RC) and CO emission to 22 CO luminous galaxies for which single dish CO images have been added to interferometric data. New Spitzer infrared (IR) images of six of these galaxies have been released. The analysis of these high resolution images allowed us to probe the RC-IR-CO correlations down to linear scales of a few hundred pc. Results: for the 22 galaxies analysed, the RC-CO correlation on scales from $\\sim10$ kpc down to $\\sim100$ pc is nearly linear and has a scatter of a factor of two, i.e. comparable to that of the global correlations. There is no evidence for any severe degradation of the scatter below the kpc scale. This also applies to the six galaxies for which high-resolution mid-IR data are available. In the case of NGC 5194, we find that the non-thermal radio spectral index is cor...

  19. The Effect of Coupled Dark Energy on the Alignment between Dark Matter and Galaxy Distributions in Clusters

    CERN Document Server

    Baldi, Marco; Maccio, Andrea V

    2011-01-01

    We investigate the effects of a coupled Dark Energy (cDE) scalar field on the alignment between satellites and matter distributions in galaxy clusters. Using high-resolution N-body simulations for LCDM and cDE cosmological models, we compute the probability density distribution for the alignment angle between the satellite galaxies and underlying matter distributions, finding a difference between the two scenarios. With respect to LCDM, in cDE cosmologies the satellite galaxies are less preferentially located along the major axis of the matter distribution, possibly reducing the tension with obersevational data. A physical explanation is that the coupling between dark matter and dark energy acts as an additional tidal force on the satellite galaxies diminishing the alignments between their distribution and the matter one. Through a likelihood ratio test based on the generalized chi square statistics, the null hypothesis that the two probability distributions come from the same parent population is rejected at...

  20. The Dynamical Response of Dark Matter to Galaxy Evolution Affects Direct-Detection Experiments

    CERN Document Server

    Petersen, Michael S; Weinberg, Martin D

    2016-01-01

    Over a handful of rotation periods, dynamical processes in barred galaxies induce non-axisymmetric structure in dark matter halos. Using n-body simulations of a Milky Way-like barred galaxy, we identify both a trapped dark-matter component, a shadow bar, and a strong response wake in the dark-matter distribution that affects the predicted dark-matter detection rates for current experiments. The presence of a baryonic disk together with well-known dynamical processes (e.g. spiral structure and bar instabilities) increase the dark matter density in the disk plane. We find that the magnitude of the combined stellar and shadow bar evolution, when isolated from the effect of the axisymmetric gravitational potential of the disk, accounts for >30% of this overall increase in disk-plane density. This is significantly larger that of previously claimed deviations from the standard halo model. The dark-matter density and kinematic wakes driven by the Milky Way bar increase the detectability of dark matter overall, espec...

  1. Suppression of gravitational instabilities by dominant dark matter halo in low surface brightness galaxies

    CERN Document Server

    Ghosh, Soumavo

    2014-01-01

    The low surface brightness galaxies are gas-rich and yet have a low star formation rate, this is a well-known puzzle. The spiral features in these galaxies are weak and difficult to trace, although this aspect has not been studied much. These galaxies are known to be dominated by the dark matter halo from the innermost regions. Here we do a stability analysis for the galactic disc of UGC 7321, a low surface brightness, superthin galaxy, for which the various observational input parameters are available. We show that the disc is stable against local, linear axisymmetric and non-axisymmetric perturbations. The Toomre Q parameter values are found to be large (>> 1) mainly due to the low disc surface density and the high rotation velocity resulting due to the dominant dark matter halo, which could explain the observed low star formation rate. For the stars-alone case, the disc shows finite swing amplification but the addition of dark matter halo suppresses that amplification almost completely. Even the inclusion ...

  2. Uncovering mass segregation with galaxy analogues in dark-matter simulations

    Science.gov (United States)

    Joshi, Gandhali D.; Parker, Laura C.; Wadsley, James

    2016-10-01

    We investigate mass segregation in group and cluster environments by identifying galaxy analogues in high-resolution dark-matter simulations. Subhaloes identified by the Amiga's Halo Finder (AHF) and ROCKSTAR halo finders have similar mass functions, independent of resolution, but different radial distributions due to significantly different subhalo hierarchies. We propose a simple way to classify subhaloes as galaxy analogues. The radial distributions of galaxy analogues agree well at large halocentric radii for both AHF and ROCKSTAR but disagree near parent halo centres where the phase-space information used by ROCKSTAR is essential. We see clear mass segregation at small radii (within 0.5 rvir) with average galaxy analogue mass decreasing with radius. Beyond the virial radius, we find a mild trend where the average galaxy analogue mass increases with radius. These mass segregation trends are strongest in small groups and dominated by the segregation of low-mass analogues. The lack of mass segregation in massive galaxy analogues suggests that the observed trends are driven by the complex accretion histories of the parent haloes rather than dynamical friction.

  3. CFHTLenS: The relation between galaxy dark matter haloes and baryons from weak gravitational lensing

    CERN Document Server

    Velander, Malin; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta

    2013-01-01

    We present a study of the relation between dark matter halo mass and the baryonic content of host galaxies, quantified through luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. We employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction, and our analysis is limited to lenses at redshifts between 0.2 and 0.4. We express the relationship between halo mass and baryonic observable as a power law. For the luminosity-halo mass relation we find a slope of 1.56+0.04-0.06 and a normalisation of 1.26+0.07-0.06x10^13 h70^-1 Msun for red galaxies, while for blue galaxies the best-fit slope is 0.73+0.09-0.08 and the normalisation is 0.16+/-0.03x10^13 h70^-1 Msun. Similarly, we find a best-fit slope of 1.49+0.06-0.04 and a normalisation of 1.30+0.05-0.09x10^13 h70^-1 Msun for the stellar mass-halo mass relation of red galaxies, whil...

  4. An empirical model to form and evolve galaxies in dark matter halos

    Science.gov (United States)

    Li, Shi-Jie; Zhang, You-Cai; Yang, Xiao-Hu; Wang, Hui-Yuan; Tweed, Dylan; Liu, Cheng-Ze; Yang, Lei; Shi, Feng; Lu, Yi; Luo, Wen-Tao; Wei, Jian-Wen

    2016-08-01

    Based on the star formation histories of galaxies in halos with different masses, we develop an empirical model to grow galaxies in dark matter halos. This model has very few ingredients, any of which can be associated with observational data and thus be efficiently assessed. By applying this model to a very high resolution cosmological N-body simulation, we predict a number of galaxy properties that are a very good match to relevant observational data. Namely, for both centrals and satellites, the galaxy stellar mass functions up to redshift z ≃ 4 and the conditional stellar mass functions in the local universe are in good agreement with observations. In addition, the two point correlation function is well predicted in the different stellar mass ranges explored by our model. Furthermore, after applying stellar population synthesis models to our stellar composition as a function of redshift, we find that the luminosity functions in the 0.1 u, 0.1 g, 0.1 r, 0.1 i and 0.1 z bands agree quite well with the SDSS observational results down to an absolute magnitude at about -17.0. The SDSS conditional luminosity function itself is predicted well. Finally, the cold gas is derived from the star formation rate to predict the HI gas mass within each mock galaxy. We find a remarkably good match to observed HI-to-stellar mass ratios. These features ensure that such galaxy/gas catalogs can be used to generate reliable mock redshift surveys.

  5. Phase-space constraints on visible and dark matter distributions in elliptical galaxies

    CERN Document Server

    Ciotti, L

    1999-01-01

    There are observational and theoretical indications that both the visible (stars) and the dark matter density distributions in elliptical galaxies increase significantly up to the galactic center. I present here some analytical results obtained with the aid of self-consistent, spherically symmetric two component galaxy models. These results suggest the possibility that this similar behavior could be a direct consequence of the structural and dynamical constraints imposed by the request of positivity of the phase-space distribution function of each density component.

  6. Mass-to-light ratios in early-type galaxies and the dark matter content

    CERN Document Server

    Capaccioli, M; Arnaboldi, M

    2002-01-01

    The distribution of the radial trends of the mass-to-light ratios (M/L) within an assorted sample of early-type galaxies is discussed. Three classes of galaxies are identified according to their M/L gradients. Two such classes are characterized by the presence or by the absence of a radial gradient of the dark-matter (DM) distribution. A third class contains objects which are likely undergoing interaction; they exhibit steep M/L gradients which are possibly the result of a wrong assumption on their equilibrium conditions. Finally, a possible correlation between DM content and morphological types is briefly discussed.

  7. NUMERICAL SIMULATIONS OF GALAXY FORMATION IN A ¿ COLD DARK MATTER UNIVERSE

    Directory of Open Access Journals (Sweden)

    M. G. Abadi

    2009-01-01

    Full Text Available The success of the A Cold Dark Matter model in reproducing observational results from the large scale structure of the Universe has established it as the new paradigm for galaxy formation and evolution. Cosmological gravitational/hydrodynamical numerical simulations are an invaluable tool to study the origin and evolution of di erent galactic components in this cosmological framework. In the following we review the main ideas presently accepted regarding galaxy formation, and stress the importance of di erent complex astrophysical e ects usually invoked during this process. We emphasise, as well, the fundamental role that satellite accretion events play in shaping the formation of galactic systems.

  8. Evidence for Dark Matter Contraction and a Salpeter Initial Mass Function in a Massive Early-type Galaxy

    NARCIS (Netherlands)

    Sonnenfeld, A.; Treu, T.; Gavazzi, R.; Marshall, P. J.; Auger, M. W.; Suyu, S. H.; Koopmans, L. V. E.; Bolton, A. S.

    2012-01-01

    Stars and dark matter account for most of the mass of early-type galaxies, but uncertainties in the stellar population and the dark matter profile make it challenging to distinguish between the two components. Nevertheless, precise observations of stellar and dark matter are extremely valuable for t

  9. A mass-dependent density profile for dark matter haloes including the influence of galaxy formation

    CERN Document Server

    Di Cintio, Arianna; Dutton, Aaron A; Macciò, Andrea V; Stinson, Greg S; Knebe, Alexander

    2014-01-01

    We introduce a mass dependent density profile to describe the distribution of dark matter within galaxies, which takes into account the stellar-to-halo mass dependence of the response of dark matter to baryonic processes. The study is based on the analysis of hydrodynamically simulated galaxies from dwarf to Milky Way mass, drawn from the MaGICC project, which have been shown to match a wide range of disk scaling relationships. We find that the best fit parameters of a generic double power-law density profile vary in a systematic manner that depends on the stellar-to-halo mass ratio of each galaxy. Thus, the quantity Mstar/Mhalo constrains the inner ($\\gamma$) and outer ($\\beta$) slopes of dark matter density, and the sharpness of transition between the slopes($\\alpha$), reducing the number of free parameters of the model to two. Due to the tight relation between stellar mass and halo mass, either of these quantities is sufficient to describe the dark matter halo profile including the effects of baryons. The ...

  10. Dark matter distribution and its impact on the evolution of galaxy disks

    CERN Document Server

    Combes, F

    2012-01-01

    The role of dark matter halos in galaxy disk evolution is reviewed, in particular the stabilisation of disks through self-gravity reduction, or the bar development through angular momentum exchange. Triaxial dark halos tend to weaken bars. When the dark mass inside the bar region is negligible, the bar develops through angular momentum exchange between inner and outer disk, and between stars and gas. Self-regulating cycles on the bar strength may develop in the presence of external gas accretion. Dynamical friction on dark halos slows down bars, which puts constraints on the dark matter amount inside the inner disk. During galaxy formation, baryons can lose most of their angular momentum if the infall is misaligned with the dark matter axes. Stable disks can form aligned with the minor axis of the dark halo. A sudden change in the infall direction, otherwise steady, can produce the peculiar polar ring galaxies. The dark matter halo can then be aligned along the polar disk. Misaligned infall can also maintain ...

  11. Effect of dark matter halo on global spiral modes in galaxies

    CERN Document Server

    Ghosh, Soumavo; Jog, Chanda J

    2015-01-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here we study the role of dark matter halo on the grand-design, $m=2$, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First a typical superthin LSB galaxy, UGC 7321 is studied by taking only the galactic disc, modelled as fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, ...

  12. The Interstellar Medium and Star Formation in Edge-On Galaxies. II. NGC 4157, 4565, and 5907

    NARCIS (Netherlands)

    Yim, Kijeong; Wong, Tony; Xue, Rui; Rand, Richard J.; Rosolowsky, Erik; van der Hulst, J. M.; Benjamin, Robert; Murphy, Eric J.

    2014-01-01

    We present a study of the vertical structure of the gaseous and stellar disks in a sample of edge-on galaxies (NGC 4157, 4565, and 5907) using BIMA/CARMA 12COJ=1\\to 0, VLA Hi, and Spitzer 3.6 μm data. In order to take into account projection effects when we measure the disk thickness as a function

  13. The Evolving Interstellar Medium of Star Forming Galaxies Since z=2 as Probed by Their Infrared Spectral Energy Distributions

    CERN Document Server

    Magdis, Georgios E; Bethermin, M; Sargent, M; Elbaz, D; Pannella, M; Dickinson, M; Dannerbauer, H; Da Cunha, E; Walter, F; Rigopoulou, D; Charmandaris, V; Hwang, H -S; Kartaltepe, J

    2012-01-01

    Using data from the mid-infrared to millimeter wavelengths for individual galaxies and for stacked ensembles at 0.5, which is proportional to the dust mass weighted luminosity (LIR/Mdust), and the primary parameter defining the shape of the SED, is equivalent to SFE/Z. For MS galaxies we measure this quantity, , showing that it does not depend significantly on either the stellar mass or the sSFR. This is explained as a simple consequence of the existing correlations between SFR-M*, M*-Z and Mgas-SFR. Instead, we show that (or LIR/Mdust) does evolve, with MS galaxies having harder radiation fields and thus warmer temperatures as redshift increases from z=0 to 2, a trend which can also be understood based on the redshift evolution of the M*-Z and SFR-M* relations. These results motivate the construction of a universal set of SED templates for MS galaxies which vary as a function of redshift with only one parameter, .

  14. Star cluster evolution in dark matter dominated galaxies

    NARCIS (Netherlands)

    Praagman, Anneke; Hurley, Jarrod; Power, Chris

    2010-01-01

    We investigate the influence of the external tidal field of a dark matter halo on the dynamical evolution of star clusters using direct N-body simulations, where we assume that the halo is described by a Navarro, Frenk and White mass profile which has an inner density cusp. We assess how varying the

  15. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; et al.

    2014-02-11

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma-ray background modeling, and assumed dark matter density profile.

  16. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    Science.gov (United States)

    Ackermann, M.; Albert, A.; Anderson, B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bouvier, A.; Brandt, T. J.; Hays, E.; Perkins, J. S.

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma ray flux upper limits between 500MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse gamma ray background modeling, and assumed dark matter density profile.

  17. Brightest cluster galaxy formation in the cluster C0037-2522: flattening of the dark matter cusp

    CERN Document Server

    Nipoti, C; Ciotti, L; Treu, T; Rosati, P

    2003-01-01

    The X-ray cluster C0337-2522 at redshift $z=0.59$ hosts in its core a group of five elliptical galaxies. Using N-body simulations we show that a multiple merging event among the five galaxies is expected to take place in the next few Gyrs, forming a central brightest cluster galaxy. We also find indications that dynamical friction heating associated with this event is likely to modify the central slope of the cluster dark matter density profile.

  18. Star formation and the interstellar medium in low surface brightness galaxies; 1, Oxygen abundances and abundance gradients in low surface brightness disk galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; Hulst, J. M. van der

    1998-01-01

    Submitted to: Astron. Astrophys. Abstract: We present measurements of the oxygen abundances in 64 HII regions in 12 LSB galaxies. We find that oxygen abundances are low. No regions with solar abundance have been found, and most have oxygen abundances $sim 0.5$ to 0.1 solar. The oxygen abundance appe

  19. Baryonic Distributions in Galaxy Dark Matter Haloes I: New Observations of Neutral and Ionized Gas Kinematics

    CERN Document Server

    Richards, Emily E; Barnes, K L; Staudaher, S; Dale, D A; Braun, T T; Wavle, D C; Dalcanton, J J; Bullock, J S; Chandar, R

    2016-01-01

    We present a combination of new and archival neutral hydrogen (HI) observations and new ionized gas spectroscopic observations for sixteen galaxies in the statistically representative EDGES kinematic sample. HI rotation curves are derived from new and archival radio synthesis observations from the Very Large Array (VLA) as well as processed data products from the Westerbork Radio Synthesis Telescope (WSRT). The HI rotation curves are supplemented with optical spectroscopic integral field unit (IFU) observations using SparsePak on the WIYN 3.5 m telescope to constrain the central ionized gas kinematics in twelve galaxies. The full rotation curves of each galaxy are decomposed into baryonic and dark matter halo components using 3.6$\\mu$m images from the Spitzer Space Telescope for the stellar content, the neutral hydrogen data for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. Differences in the inferred distribution of mass are illustrated under fixe...

  20. Equation of state, universal profiles, scaling and macroscopic quantum effects in warm dark matter galaxies

    Science.gov (United States)

    de Vega, H. J.; Sanchez, N. G.

    2017-02-01

    The Thomas-Fermi approach to galaxy structure determines self-consistently and non-linearly the gravitational potential of the fermionic warm dark matter (WDM) particles given their quantum distribution function f( E). This semiclassical framework accounts for the quantum nature and high number of DM particles, properly describing gravitational bounded and quantum macroscopic systems as neutron stars, white dwarfs and WDM galaxies. We express the main galaxy magnitudes as the halo radius r_h , mass M_h , velocity dispersion and phase space density in terms of the surface density which is important to confront to observations. From these expressions we derive the general equation of state for galaxies, i.e., the relation between pressure and density, and provide its analytic expression. Two regimes clearly show up: (1) Large diluted galaxies for M_h ≳ 2.3 × 10^6 M_⊙ and effective temperatures T_0 > 0.017 K described by the classical self-gravitating WDM Boltzman gas with a space-dependent perfect gas equation of state, and (2) Compact dwarf galaxies for 1.6 × 10^6 M_⊙ ≳ M_h ≳ M_{h,min} ˜eq 3.10 × 10^4 (2 {keV}/m)^{16/5} M_⊙, T_0 < 0.011 K described by the quantum fermionic WDM regime with a steeper equation of state close to the degenerate state. In particular, the T_0 = 0 degenerate or extreme quantum limit yields the most compact and smallest galaxy. In the diluted regime, the halo radius r_h , the squared velocity v^2(r_h) and the temperature T_0 turn to exhibit square-root of M_h scaling laws. The normalized density profiles ρ (r)/ρ (0) and the normalized velocity profiles v^2(r)/ v^2(0) are universal functions of r/r_h reflecting the WDM perfect gas behavior in this regime. These theoretical results contrasted to robust and independent sets of galaxy data remarkably reproduce the observations. For the small galaxies, 10^6 ≳ M_h ≥ M_{h,min} , the equation of state is galaxy mass dependent and the density and velocity profiles are not

  1. Galaxy Mergers and Dark Matter Halo Mergers in LCDM: Mass, Redshift, and Mass-Ratio Dependence

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; Barton, Elizabeth J.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC

    2009-08-03

    We employ a high-resolution LCDM N-body simulation to present merger rate predictions for dark matter halos and investigate how common merger-related observables for galaxies - such as close pair counts, starburst counts, and the morphologically disturbed fraction - likely scale with luminosity, stellar mass, merger mass ratio, and redshift from z = 0 to z = 4. We provide a simple 'universal' fitting formula that describes our derived merger rates for dark matter halos a function of dark halo mass, merger mass ratio, and redshift, and go on to predict galaxy merger rates using number density-matching to associate halos with galaxies. For example, we find that the instantaneous merger rate of m/M > 0.3 mass ratio events into typical L {approx}> fL{sub *} galaxies follows the simple relation dN/dt {approx_equal} 0.03(1+f)Gyr{sup -1} (1+z){sup 2.1}. Despite the rapid increase in merger rate with redshift, only a small fraction of > 0.4L{sub *} high-redshift galaxies ({approx} 3% at z = 2) should have experienced a major merger (m/M > 0.3) in the very recent past (t < 100 Myr). This suggests that short-lived, merger-induced bursts of star formation should not contribute significantly to the global star formation rate at early times, in agreement with observational indications. In contrast, a fairly high fraction ({approx} 20%) of those z = 2 galaxies should have experienced a morphologically transformative merger within a virial dynamical time. We compare our results to observational merger rate estimates from both morphological indicators and pair-fraction based determinations between z = 0-2 and show that they are consistent with our predictions. However, we emphasize that great care must be made in these comparisons because the predicted observables depend very sensitively on galaxy luminosity, redshift, overall mass ratio, and uncertain relaxation timescales for merger remnants. We show that the majority of bright galaxies at z = 3 should have undergone a

  2. Flat Central Density Profile and Constant DM Surface Density in Galaxies from Scalar Field Dark Matter

    CERN Document Server

    Robles, Victor H

    2012-01-01

    The scalar field dark matter (SFDM) model proposes that galaxies form by condensation of a scalar field (SF) very early in the universe forming Bose-Einstein Condensates (BEC) drops, i.e., in this model haloes of galaxies are gigantic drops of SF. Here big structures form like in the LCDM model, by hierarchy, thus all the predictions of the LCDM model at big scales are reproduced by SFDM. This model predicts that all galaxies must be very similar and exist for bigger redshifts than in the LCDM model. In this work we show that BEC dark matter haloes fit high-resolution rotation curves of a sample of thirteen low surface brightness galaxies. We compare our fits to those obtained using a Navarro-Frenk-White and Pseudo-Isothermal (PI) profiles and found a better agreement with the SFDM and PI profiles. The mean value of the logarithmic inner density slopes is -0.27 +/- 0.18. As a second result we find a natural way to define the core radius with the advantage of being model-independent. Using this new definition ...

  3. A multi-wavelength study of 30 Doradus: The Interstellar Medium in a low-metallicity galaxy

    Science.gov (United States)

    Poglitsch, Albrecht; Genzel, R.; Herrmann, F.; Krabbe, A.; Madden, S. C.; Geis, Norbert; Stacey, G. J.; Townes, C. H.; Johannson, L. E. B.

    1995-01-01

    We report maps of the 158 micron (C II) line, the 63 micron and 146 micron (C I) lines, the 2.2 micron Br gamma line, and the 2.6 mm CO (1-0) line toward the 30 Doradus complex in the Large Magellanic Cloud. The maps of all tracers emphasize the shell-like structure of the 30 Doradus region which is seen edge-on. The fact that the molecular gas as traced by CO (1-0) and the photo dissociated gas as traced by (C II) are co-extensive over tens of parsecs can only be explained by a highly fragmented structure of the interstellar medium which allows UV radiation to penetrate deep into the molecular cloud. Clumpiness is also the key to understanding the extremely high (C II)/CO line intensity ratios.

  4. Observational Constraints of 30–40 GeV Dark Matter Annihilation in Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Man Ho Chan

    2016-01-01

    Full Text Available Recently, it has been shown that the annihilation of 30–40 GeV dark matter particles through bb- channel can satisfactorily explain the excess GeV gamma-ray spectrum near the Galactic Center. In this paper, we apply the above model to galaxy clusters and use the latest upper limits of gamma-ray flux derived from Fermi-LAT data to obtain an upper bound of the annihilation cross section of dark matter. By considering the extended density profiles and the cosmic ray profile models of 49 galaxy clusters, the upper bound of the annihilation cross section can be further tightened to σv≤9×10-26 cm3 s−1. This result is consistent with the one obtained from the data near the Galactic Center.

  5. Progressively more prolate dark matter halo in the outer Galaxy as traced by flaring HI gas

    CERN Document Server

    Banerjee, Arunima

    2011-01-01

    A galactic disk in a spiral galaxy is generally believed to be embedded in an extended dark matter halo, which dominates its dynamics in the outer parts. However, the shape of the halo is not clearly understood. Here we show that the dark matter halo in the Milky Way Galaxy is prolate in shape. Further, it is increasingly more prolate at larger radii, with the vertical-to-planar axis ratio monotonically increasing to 2.0 at 24 kpc. This is obtained by modeling the observed steeply flaring atomic hydrogen gas layer in the outer Galactic disk, where the gas is supported by pressure against the net gravitational field of the disk and the halo. The resulting prolate-shaped halo can explain several long-standing puzzles in galactic dynamics, for example, it permits long-lived warps thus explaining their ubiquitous nature.

  6. Impact of axisymmetric mass models for dwarf spheroidal galaxies on indirect dark matter searches

    CERN Document Server

    Klop, Niki; Hayashi, Kohei; Ando, Shin'ichiro

    2016-01-01

    Dwarf spheroidals are low-luminosity satellite galaxies of the Milky Way highly dominated by dark matter. Therefore, they are prime targets to search for signals from dark matter annihilation using gamma-ray observations. We analyse about 7 years of PASS8 Fermi data for seven classical dwarf galaxies, including Draco, adopting both the widely used Navarro-Frenk-White (NFW) profile and observationally motivated axisymmetric density profiles. For four of the selected dwarfs (Sextans, Carina, Sculptor and Fornax) axisymmetric mass models suggest a cored density profile rather than the commonly adopted cusped profile. We found that upper limits on the annihilation cross section for some of these dwarfs are significantly higher than the ones achieved using an NFW profile. Therefore, upper limits in the literature obtained using cusped profiles like the NFW might have been overestimated. Our results eventually show that it is extremely important to use observationally motivated density profiles going beyond the usu...

  7. Interstellar PAHs

    Science.gov (United States)

    Allamandola, Louis J.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    Tremendous strides have been made in our understanding of interstellar material over the past twenty years thanks to significant, parallel developments in two closely related areas: observational astronomy and laboratory astrophysics. Twenty years ago the composition of interstellar dust was largely guessed at and the notion of abundant, gas phase, polycyclic aromatic hydrocarbons (PAHs) anywhere in the interstellar medium (ISM) considered impossible. Today the dust composition of the diffuse and dense ISM is reasonably well constrained and the spectroscopic case for interstellar PAHs, shockingly large molecules by early interstellar chemistry standards, is very strong.

  8. Modeling dark matter subhalos in a constrained galaxy: Global mass and boosted annihilation profiles

    Science.gov (United States)

    Stref, Martin; Lavalle, Julien

    2017-03-01

    The interaction properties of cold dark matter (CDM) particle candidates, such as those of weakly interacting massive particles (WIMPs), generically lead to the structuring of dark matter on scales much smaller than typical galaxies, potentially down to ˜10-10 M⊙ . This clustering translates into a very large population of subhalos in galaxies and affects the predictions for direct and indirect dark matter searches (gamma rays and antimatter cosmic rays). In this paper, we elaborate on previous analytic works to model the Galactic subhalo population, while keeping consistent with current observational dynamical constraints on the Milky Way. In particular, we propose a self-consistent method to account for tidal effects induced by both dark matter and baryons. Our model does not strongly rely on cosmological simulations, as they can hardly be fully matched to the real Milky Way, apart from setting the initial subhalo mass fraction. Still, it allows us to recover the main qualitative features of simulated systems. It can further be easily adapted to any change in the dynamical constraints, and can be used to make predictions or derive constraints on dark matter candidates from indirect or direct searches. We compute the annihilation boost factor, including the subhalo-halo cross product. We confirm that tidal effects induced by the baryonic components of the Galaxy play a very important role, resulting in a local average subhalo mass density ≲1 % of the total local dark matter mass density, while selecting the most concentrated objects and leading to interesting features in the overall annihilation profile in the case of a sharp subhalo mass function. Values of global annihilation boost factors range from ˜2 to ˜20 , while the local annihilation rate is about boosted half as much.

  9. CFHTLenS: Co-evolution of galaxies and their dark matter haloes

    CERN Document Server

    Hudson, Michael J; Coupon, Jean; Hildebrandt, Hendrik; Erben, Thomas; Heymans, Catherine; Hoekstra, Henk; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Velander, Malin

    2013-01-01

    Galaxy-galaxy weak lensing is a direct probe of the mean matter distribution around galaxies. The depth and sky coverage of the CFHT Legacy Survey yield statistically significant galaxy halo mass measurements over a much wider range of stellar masses ($10^{8.75}$ to $10^{11.3} M_{\\odot}$) and redshifts ($0.2 < z < 0.8$) than previous weak lensing studies. The stellar-to-halo mass ratio (SHMR) reaches a maximum of $3.4\\pm0.2$ percent as a function of halo mass at $\\sim 10^{12.25} M_{\\odot}$ (at redshift $z =0.5$). We find, for the first time from weak lensing alone, evidence for significant evolution in the SHMR: the peak ratio falls as a function of cosmic time from $3.8 \\pm 0.3$ percent at $z \\sim 0.7$ to $3.0 \\pm 0.2$ percent at $z \\sim 0.3$, and shifts to lower stellar mass haloes. These evolutionary trends are dominated by red galaxies, and are consistent with a model in which the stellar mass above which star formation is quenched "downsizes" with cosmic time. In contrast, the SHMR of blue, star-fo...

  10. Size matters: abundance matching, galaxy sizes, and the Tully-Fisher relation in EAGLE

    CERN Document Server

    Ferrero, Ismael; Abadi, Mario G; Sales, Laura V; Bower, Richard G; Crain, Robert A; Frenk, Carlos S; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

    2016-01-01

    The Tully-Fisher relation (TFR) links the stellar mass of a disk galaxy, $M_{\\rm str}$, to its rotation speed: it is well approximated by a power law, shows little scatter, and evolves weakly with redshift. The relation has been interpreted as reflecting the mass-velocity scaling ($M\\propto V^3$) of dark matter halos, but this interpretation has been called into question by abundance-matching (AM) models, which predict the galaxy-halo mass relation to be non-monotonic and rapidy evolving. We study the TFR of luminous spirals and its relation to AM using the EAGLE set of $\\Lambda$CDM cosmological simulations. Matching both relations requires disk sizes to satisfy constraints given by the concentration of halos and their response to galaxy assembly. EAGLE galaxies approximately match these constraints and show a tight mass-velocity scaling that compares favourably with the observed TFR. The TFR is degenerate to changes in galaxy formation efficiency and the mass-size relation; simulations that fail to match the...

  11. Separating Galaxies from the Cluster Dark Matter Halo in Abell 611

    CERN Document Server

    Monna, A; Geller, M J; Zitrin, A; Mercurio, A; Suyu, S H; Postman, M; Fabricant, D G; Hwang, H S; Koekemoer, A

    2016-01-01

    We investigate the mass content of galaxies in the core of the galaxy cluster Abell 611. We perform a strong lensing analysis of the cluster core and use velocity dispersion measurements for individual cluster members as additional constraints. Despite the small number of multiply-imaged systems and cluster members with central velocity dispersions available in the core of A611, the addition of velocity dispersion measurements leads to tighter constraints on the mass associated with the galaxy component, and as a result, on the mass associated with the dark matter halo. Without the spectroscopic velocity dispersions, we would overestimate the mass of the galaxy component by a factor of $\\sim1.5$, or, equivalently, we would underestimate the mass of the cluster dark halo by $\\sim5\\%$. We perform an additional lensing analysis using surface brightness (SB) reconstruction of the tangential giant arc. This approach improves the constraints on the mass parameters of the 5 galaxies close to the arc by up to a facto...

  12. Are Wolf-Rayet Stars Able to Pollute the Interstellar Medium of Galaxies? Results from Integral Field Spectroscopy

    Directory of Open Access Journals (Sweden)

    Enrique Pérez-Montero

    2013-01-01

    Full Text Available We investigate the spatial distribution of chemical abundances in a sample of low metallicity Wolf-Rayet (WR galaxies selected from the SDSS. We used the integral field spectroscopy technique in the optical spectral range (3700 Å–6850 Å with PMAS attached to the CAHA 3.5 m telescope. Our statistical analysis of the spatial distributions of O/H and N/O, as derived using the direct method or strong-line parameters consistent with it, indicates that metallicity is homogeneous in five out of the six analysed objects in scales of the order of several kpc. Only in the object WR404 is a gradient of metallicity found in the direction of the low surface brightness tail. In contrast, we found an overabundance of N/O in spatial scales of the order of hundreds of pc associated with or close to the positions of the WR stars in 4 out of the 6 galaxies. We exclude possible hydrodynamical causes, such as the metal-poor gas inflow, for this local pollution by means of the analysis of the mass-metallicity relation (MZR and mass-nitrogen-to-oxygen relation (MNOR for the WR galaxies catalogued in the SDSS.

  13. Wheels of Fire IV. Star Formation and the Neutral Interstellar Medium in the Ring Galaxy AM0644-741

    CERN Document Server

    Higdon, James L; Rand, Richard J

    2011-01-01

    We combine data from the ATNF and SEST to investigate the neutral ISM in AM0644-741, a large robustly star forming ring galaxy. The galaxy's ISM is concentrated in the 42-kpc diameter ring and appears dominated by HI, with a global molecular fraction of only 6.2%. Outside the starburst peak, the gas ring appears gravitationally stable (Q_gas = 3-11). Including the stellar component lowers Q overall, but not enough to make Q100 Myr confinement time in the starburst ring, which amplifies the effects of embedded massive stars and SNe. The ring's molecular ISM becomes dominated by small clouds, causing H2 to be significantly underestimated by 12CO line fluxes: in effect X_CO >> X_Gal despite the ring's >solar metallicity. The observed HI is primarily a low density photo-dissociation product, i.e., a tracer rather than a precursor of star formation. Such an "over-cooked" ISM may be a general characteristic of evolved ring galaxies.

  14. Interstellar and circumstellar fullerenes

    CERN Document Server

    Bernard-Salas, J; Jones, A P; Peeters, E; Micelotta, E R; Otsuka, M; Sloan, G C; Kemper, F; Groenewegen, M

    2014-01-01

    Fullerenes are a particularly stable class of carbon molecules in the shape of a hollow sphere or ellipsoid that might be formed in the outflows of carbon stars. Once injected into the interstellar medium (ISM), these stable species survive and are thus likely to be widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. In recent years, the fullerene species C60 (and to a lesser extent C70) have been detected in a wide variety of circumstellar and interstellar environments showing that when conditions are favourable, fullerenes are formed efficiently. Fullerenes are the first and only large aromatics firmly identified in space. The detection of fullerenes is thus crucial to provide clues as to the key chemical pathways leading to the formation of large complex organic molecules in space, and offers a great diagnostic tool to describe the environment in which they reside. Since fullerenes share many physical properties with PAHs, understand...

  15. Dark Matter is Baryons

    CERN Document Server

    Soberman, R K; Soberman, Robert K.; Dubin, Maurice

    2001-01-01

    A comet-like, but magnitudes smaller, extremely low albedo interstellar meteoroid population of fragile aggregates with solar type composition, measured in space and terrestrially, is most probably the universal dark matter. Although non-baryonic particles cannot be excluded, only "Big Bang" cosmology predicts an appreciable fraction of such alternate forms. As more counter-physics hypotheses are added to fit observation to the expanding universe assumption, a classical physics alternative proffers dark matter interactive red shifts normally correlated with distance. The cosmic microwave background results from size-independent thermal plateau radiation that emanates from dark matter gravitationally drawn into the Galaxy.

  16. Scalar Field Dark Matter mass model and evolution of rotation curves for Lsb galaxies

    CERN Document Server

    Martinez-Medina, Luis A

    2014-01-01

    We study the evolution of gas rotation curves within the scalar field dark matter (SFDM) model. In this model the galactic haloes are astronomical Bose-Einstein Condensate drops of scalar field. These haloes are characterized by a constant-density core and are consistent with observed rotation curves of dark matter dominated galaxies, a missing feature in CDM haloes resulting from DM-only simulations. We add the baryonic component to the SFDM haloes and simulate the evolution of the dark matter tracer in a set of grid-based hydrodynamic simulations aimed to analyse the evolution of the rotation curves and the gas density distribution in the case of dark matter dominated galaxies. Previous works had found that when considering an exact analytic solution for a static SF configuration, the free parameters of the model allows for good fits to the rotation curves, we confirm that in our simulations but now taking into account the evolution of the baryonic component in a static dark matter and stellar disk potentia...

  17. Cold or Warm? Constraining Dark Matter with Primeval Galaxies and Cosmic Reionization after Planck

    CERN Document Server

    Lapi, A

    2015-01-01

    Dark matter constitutes the great majority of the matter content in the Universe, but its microscopic nature remains an intriguing mystery, with profound implications for particle physics, astrophysics and cosmology. Here we shed light on the longstanding issue of whether the dark matter is warm or cold by combining the measurements of the galaxy luminosity functions out to high redshifts z~10 from the Hubble Space Telescope with the recent cosmological data on the reionization history of the Universe from the Planck mission. We derive robust and tight bounds on the mass of warm dark matter particle, finding that the current data require it to be in the narrow range between 2 and 3 keV. In addition, we show that a mass not exceeding 3 keV is also concurrently indicated by astrophysical constraints related to the local number of satellites in Milky Way-sized galaxies, though it is in marginal tension with analysis of the Lyman-alpha forest. For warm dark matter masses above 3 keV as well as for cold dark matte...

  18. The Shape of Dark Matter Haloes, V. Analysis of observations of edge-on galaxies

    CERN Document Server

    Peters, S P C; Allen, R J; Freeman, K C

    2016-01-01

    In the previous papers in this series, we have measured the stellar and \\hi content in a sample of edge-on galaxies. In the present paper, we perform a simultaneous rotation curve and vertical force field gradient decomposition for five of these edge-on galaxies. The rotation curve decomposition provides a measure of the radial dark matter potential, while the vertical force field gradient provide a measure of the vertical dark matter potential. We fit dark matter halo models to these potentials. Using our \\hi self-absorption results, we find that a typical dark matter halo has a less dense core ($0.094\\pm0.230$\\,M$_\\odot$/pc$^3$) compared to an optically thin \\hi model ($0.150\\pm0.124$\\,M$_\\odot$/pc$^3$). The HI self-absorption dark matter halo has a longer scale length $R_c$ of $1.42\\pm 3.48$\\,kpc, versus $1.10\\pm 1.81$\\,kpc for the optically thin HI model. The median halo shape is spherical, at $q=1.0\\pm0.6$ (self-absorbing \\hi), while it is prolate at $q=1.5\\pm0.6$ for the optically thin. Our best results...

  19. Dark Matter Constraints from Observations of 25 Milky Way Satellite Galaxies with the Fermi Large Area Telescope

    CERN Document Server

    :,; Albert, A; Anderson, B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Bloom, E D; Bonamente, E; Bouvier, A; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caragiulo, M; Caraveo, P A; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; D'Ammando, F; de Angelis, A; Dermer, C D; Digel, S W; Silva, E do Couto e; Drell, P S; Drlica-Wagner, A; Essig, R; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giroletti, M; Godfrey, G; Gomez-Vargas, G A; Grenier, I A; Guiriec,; Gustafsson, M; Hayashida, M; Hays, E; Hewitt, J; Hughes, R E; Jogler, T; Kamae, T; Knödlseder, J; Kocevski, D; Kuss, M; Larsson,; Latronico, L; Garde, M Llena; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Martinez, G; Mayer, M; Mazziotta, M N; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nemmen, R; Nuss, E; Ohsugi, T; Orlando, E; Ormes, J F; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Ritz, S; Sànchez-Conde, M; Sehgal, N; Sgrò, C; Siskind, E J; Spinelli, P; Strigari, L; Suson, D J; Tajima, H; Takahashi, H; Thayer, J B; Tibaldo, L; Tinivella, M; Torres, D F; Uchiyama, Y; Usher, T L; Vandenbroucke, J; Vianello, G; Vitale, V; Werner, M; Winer, B L; Wood, K S; Wood, M; Zaharijas, G; Zimmer, S

    2013-01-01

    The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on gamma-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in gamma rays, and we present gamma-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical Standard Model channels. W...

  20. Marriage \\`a-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle

    CERN Document Server

    Milgrom, Mordehai

    2007-01-01

    I start with a brief introduction to MOND phenomenology and its possible roots in cosmology--a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine: MOND's successes imply that baryons determine everything. For DM this would mean that the puny tail of leftover baryons in galaxies wags the hefty DM dog. This has to occur in many intricate ways, and despite the haphazard construction history of galaxies--a very tall order. I then concentrate on galaxy clusters in light of MOND, which still requires some yet undetected cluster dark matter, presumably in some baryonic form (CBDM). This CBDM might contribute to the heating of the x-ray emitting gas and thus alleviate the cooling-flow puzzle. MOND, qua theory of dynamics, does not directly enter the microphysics of the gas; however, it does force a new outlook on the role of DM in shaping the cluster gasdynamics: MOND tells us that the cluster DM is not cold dark matter, is no...

  1. The response of dark matter haloes to elliptical galaxy formation: a new test for quenching scenarios

    CERN Document Server

    Dutton, Aaron A; Stinson, Gregory S; Gutcke, Thales A; Penzo, Camilla; Buck, Tobias

    2015-01-01

    We use cosmological hydrodynamical zoom-in simulations with the SPH code gasoline of four haloes of mass M_{200} \\sim 10^{13}\\Msun to study the response of the dark matter to elliptical galaxy formation. At z=2 the progenitor galaxies have stellar to halo mass ratios consistent with halo abundance matching, assuming a Salpeter initial mass function. However by z=0 the standard runs suffer from the well known overcooling problem, overpredicting the stellar masses by a factor of > 4. To mimic a suppressive halo quenching scenario, in our forced quenching (FQ) simulations, cooling and star formation are switched off at z=2. The resulting z=0 galaxies have stellar masses, sizes and circular velocities close to what is observed. Relative to the control simulations, the dark matter haloes in the FQ simulations have contracted, with central dark matter density slopes d\\log\\rho/d\\log r \\sim -1.5, showing that dry merging alone is unable to fully reverse the contraction that occurs at z>2. Simulations in the literatur...

  2. Ultra-light dark matter in ultra-faint dwarf galaxies

    Science.gov (United States)

    Calabrese, Erminia; Spergel, David N.

    2016-08-01

    Cold Dark Matter (CDM) models struggle to match the observations at galactic scales. The tension can be reduced either by dramatic baryonic feedback effects or by modifying the particle physics of CDM. Here, we consider an ultra-light scalar field DM particle manifesting a wave nature below a DM particle mass-dependent Jeans scale. For DM mass m ˜ 10-22 eV, this scenario delays galaxy formation and avoids cusps in the centre of the dark matter haloes. We use new measurements of half-light mass in ultra-faint dwarf galaxies Draco II and Triangulum II to estimate the mass of the DM particle in this model. We find that if the stellar populations are within the core of the density profile then the data are in agreement with a Wave Dark Matter model having a DM particle with m ˜ 3.7-5.6 × 10-22 eV. The presence of this extremely light particle will contribute to the formation of a central solitonic core replacing the cusp of a Navarro-Frenk-White profile and bringing predictions closer to observations of cored central density in dwarf galaxies.

  3. Interstellar X-ray Absorption Spectroscopy of Oxygen, Neon, and Iron with the Chandra LETGS Spectrum of X0614+091

    CERN Document Server

    Paerels, F B S; Van der Meer, R L J; Kaastra, J S; Kuulkers, E; Den Boggende, A J F; Predehl, P; Drake, J J; Kahn, S M; Savin, D W; McLaughlin, B M; Paerels, Frits; Drake, Jeremy J.; Kahn, Steven M.; Savin, Daniel W.; Laughlin, Brendan M. Mc

    2000-01-01

    We find resolved interstellar O K, Ne K, and Fe L absorption spectra in the Chandra Low Energy Transmission Grating Spectrometer spectrum of the low mass X-ray binary X0614+091. We measure the column densities in O and Ne, and find direct spectroscopic constraints on the chemical state of the interstellar O. These measurements probably probe a low-density line of sight through the Galaxy and we discuss the results in the context of our knowledge of the properties of interstellar matter in regions between the spiral arms.

  4. Cold Dark Matter Substructures in Early-Type Galaxy Halos

    CERN Document Server

    Fiacconi, Davide; Potter, Doug; Stadel, Joachim

    2016-01-01

    We present initial results from the "Ponos" zoom-in numerical simulations of dark matter substructures in massive ellipticals. Two very highly resolved dark matter halos with $M_{\\rm vir}=1.2\\times 10^{13}$ $M_{\\odot}$ and $M_{\\rm vir}=6.5\\times 10^{12}$ $M_{\\odot}$ and different ("violent" vs. "quiescent") assembly histories have been simulated down to $z=0$ in a $\\Lambda$CDM cosmology with a total of 921,651,914 and 408,377,544 particles, respectively. Within the virial radius, the total mass fraction in self-bound $M_{\\rm sub}>10^6$ $M_{\\odot}$ subhalos at the present epoch is 15% for the violent host and 16.5% for the quiescent one. At $z=0.7$, these fractions increase to 19 and 33%, respectively, as more recently accreted satellites are less prone to tidal destruction. In projection, the average fraction of surface mass density in substructure at a distance of $R/R_{\\rm vir}=0.02$ ($\\sim 5-10$ kpc) from the two halo centers ranges from 0.6% to $\\gtrsim 2$%, significantly higher than measured in simulatio...

  5. CFHTLenS: Weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment

    CERN Document Server

    Schrabback, Tim; Hoekstra, Henk; Simon, Patrick; van Uitert, Edo; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bett, Philip; Coupon, Jean; Fu, Liping; Hudson, Michael J; Joachimi, Benjamin; Kilbinger, Martin; Kuijken, Konrad

    2015-01-01

    We present weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment. Using data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), we measure the weighted-average ratio of the aligned projected ellipticity components of galaxy matter haloes and their embedded galaxies, $f_\\mathrm{h}$, split by galaxy type. We then compare our observations to measurements taken from the Millennium Simulation, assuming different models of galaxy-halo misalignment. Using the Millennium Simulation we verify that the statistical estimator used removes contamination from cosmic shear. We also detect an additional signal in the simulation, which we interpret as the impact of intrinsic shape-shear alignments between the lenses and their large-scale structure environment. These alignments are likely to have caused some of the previous observational constraints on $f_\\mathrm{h}$ to be biased high. From CFHTLenS we find $f_\\mathrm{h}=-0.04 \\pm 0.25$ for early-type galaxie...

  6. The shape of dark matter haloes - V. Analysis of observations of edge-on galaxies

    Science.gov (United States)

    Peters, S. P. C.; van der Kruit, P. C.; Allen, R. J.; Freeman, K. C.

    2017-01-01

    In previous papers in this series, we measured the stellar and H I content in a sample of edge-on galaxies. In the present paper, we perform a simultaneous rotation curve and vertical force field gradient decomposition for five of these edge-on galaxies. The rotation curve decomposition provides a measure of the radial dark matter potential, while the vertical force field gradient provides a measure of the vertical dark matter potential. We fit dark matter halo models to these potentials. Using our H I self-absorption results, we find that a typical dark matter halo has a less dense core (0.094 ± 0.230 M⊙ pc-3) than that for an optically thin H I model (0.150 ± 0.124 M⊙ pc-3). The H I self-absorption dark matter halo has a longer scale-length Rc of 1.42 ± 3.48 kpc, versus 1.10 ± 1.81 kpc for the optically thin H I model. The median halo shape is spherical at q = 1.0 ± 0.6 for self-absorbing H I, while it is prolate at q = 1.5 ± 0.6 for the optically thin case. Our best results were obtained for ESO 274-G001 and UGC 7321, for which we were able to measure the velocity dispersion in Paper III. These two galaxies have very different halo shapes, with one oblate and one strongly prolate. Overall, we find that the many assumptions required make this type of analysis susceptible to errors.

  7. Hot-warm unstable supersymmetric dark matter and galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Asselin, X.; Girardi, G.; Salati, P.; Blanchard, A.

    1988-12-12

    Recent observational results had lead to a revival of interest in neutrino-dominated universe. However, we recall that current constraints make the neutrino an unlikely candidate for the dark matter. In this paper, we show that a supersymmetric particle with a typical mass of a few tens of eV will be a much better candidate. Such a particle is radiatively unstable, and its lifetime is a few times larger than the age of the universe. This can drastically change the thermal history of the universe. We investigate in detail the heating of the intergalactic medium in the period z=100-z=10. In particular, we find that the universe can be fully reionized for lifetime less than or equal to 10/sup 24/. This, in turn, lowers the level of temperature fluctuations of the background radiation. We conclude that this model avoids the major problems of the neutrino picture.

  8. Antiprotons from dark matter annihilation in the Galaxy: astrophysical uncertainties

    CERN Document Server

    Evoli, Carmelo; Grasso, Dario; Maccione, Luca; Ullio, Piero

    2011-01-01

    The latest years have seen steady progresses in WIMP dark matter (DM) searches, with hints of possible signals suggested by both direct and indirect detection experiments. Antiprotons can play a key role validating those interpretations since they are copiously produced by WIMP annihilations in the Galactic halo, and the secondary antiproton background produced by Cosmic Ray (CR) interactions is predicted with fair accuracy and matches the observed spectrum very well. Using the publicly available numerical DRAGON code, we reconsider antiprotons as a tool to constrain DM models discussing its power and limitations. We provide updated constraints on a wide class of annihilating DM models by comparing our predictions against the most up-to-date ap measurements, taking also into account the latest spectral information on the p, He and other CR nuclei fluxes. Doing that, we probe carefully the uncertainties associated to both secondary and DM originated antiprotons, by using a variety of distinctively different as...

  9. Marriage à-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle

    Science.gov (United States)

    Milgrom, Mordehai

    2008-05-01

    I start with a brief introduction to MOND phenomenology and its possible roots in cosmology—a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine: MOND's successes imply that baryons determine everything. For DM this would mean that the puny tail of leftover baryons in galaxies wags the hefty DM dog. This has to occur in many intricate ways, and despite the haphazard construction history of galaxies—a very tall order. I then concentrate on galaxy clusters in light of MOND, which still requires some yet undetected cluster dark matter, presumably in some baryonic form (CBDM). This CBDM might contribute to the heating of the X-ray emitting gas and thus alleviate the cooling flow puzzle. MOND, qua theory of dynamics, does not directly enter the microphysics of the gas; however, it does force a new outlook on the role of DM in shaping the cluster gas dynamics: MOND tells us that the cluster DM is not cold dark matter, is not so abundant, and is not expected in galaxies; it is thus not subject to constraints on baryonic DM in galaxies. The mass in CBDM required in a whole cluster is, typically, similar to that in hot gas, but is rather more centrally concentrated, totally dominating the core. The CBDM contribution to the baryon budget in the universe is thus small. Its properties, deduced for isolated clusters, are consistent with the observations of the "bullet cluster". Its kinetic energy reservoir is much larger than that of the hot gas in the core, and would suffice to keep the gas hot for many cooling times. Heating can be effected in various ways depending on the exact nature of the CBDM, from very massive black holes to cool, compact gas clouds.

  10. Evolution of a Dwarf Satellite Galaxy Embedded in a Scalar Field Dark Matter Halo

    Science.gov (United States)

    Robles, Victor H.; Lora, V.; Matos, T.; Sánchez-Salcedo, F. J.

    2015-09-01

    The cold dark matter (CDM) model has two unsolved issues: simulations overpredict the satellite abundance around the Milky Way (MW) and it disagrees with observations of the central densities of dwarf galaxies which prefer constant density (core) profiles. One alternative explanation known as the scalar field dark matter (SFDM) model, assumes that dark matter is a scalar field of mass (˜10-22 eV/c2); this model can reduce the overabundance issue due to the lack of halo formation below a mass scale of ˜108M⊙ and successfully fits the density distribution in dwarfs. One of the attractive features of the model is predicting core profiles in halos, although the determination of the core sizes is set by fitting the observational data. We perform N-body simulations to explore the influence of tidal forces over a stellar distribution embedded in an SFDM halo orbiting a MW-like SFDM host halo with a disk. Our simulations intend to test the viability of SFDM as an alternative model by comparing the tidal effects that result in this paradigm with those obtained in the CDM for similar mass halos. We found that galaxies in subhalos with core profiles and high central densities survive for 10 Gyr. The same occurs for galaxies in low density subhalos located far from the host disk influence, whereas satellites in low density DM halos and in tight orbits can eventually be stripped of stars. We conclude that SFDM shows consistency with results from the CDM for dwarf galaxies, but naturally offer a possibility to solve the missing satellite problem.

  11. Are Wolf-Rayet stars able to pollute the interstellar medium of galaxies? Results from the integral field spectroscopy

    CERN Document Server

    Perez-Montero, Enrique; Brinchmann, Jarle; Vilchez, Jose M; Kunth, Daniel; Durret, Florence

    2013-01-01

    We investigate the spatial distribution of chemical abundances in a sample of low metallicity Wolf-Rayet (WR) galaxies selected from the SDSS. We used the integral field spectroscopy technique in the optical spectral range (3700-6850 AA) with PMAS attached to the CAHA 3.5 m telescope. Our statistical analysis of the spatial distributions of O/H and N/O, as derived using the direct method or strong-line parameters consistent with it, indicates that metallicity is homogeneous in five out of the six analysed objects in scales of the order of several kpc. Only in the object WR404, a gradient of metallicity is found in the direction of the low surface brightness tail. In contrast,we found an overabundance of N/O in spatial scales of the order of hundreds of pc associated with or close to the positions of the WR stars in 4 out of the 6 galaxies. We exclude possible hydrodynamical causes, such as the metal-poor gas inflow, for this local pollution by means of the analysis of the mass-metallicity relation (MZR) and m...

  12. The interstellar medium and star formation in edge-on galaxies. II. NGC 4157, 4565, and 5907

    Energy Technology Data Exchange (ETDEWEB)

    Yim, Kijeong; Wong, Tony; Xue, Rui [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Rand, Richard J. [Department of Physics and Astronomy, University of New Mexico, 1919 Lomas Boulevard NE, Albuquerque, NM 87131-1156 (United States); Rosolowsky, Erik [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1 (Canada); Hulst, J. M. van der [Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen (Netherlands); Benjamin, Robert [Department of Physics, University of Wisconsin-Whitewater, 800 West Main Street, Whitewater, WI 53190 (United States); Murphy, Eric J., E-mail: k.yim@astro.rug.nl [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2014-12-01

    We present a study of the vertical structure of the gaseous and stellar disks in a sample of edge-on galaxies (NGC 4157, 4565, and 5907) using BIMA/CARMA {sup 12}COJ=1→0, VLA Hi, and Spitzer 3.6 μm data. In order to take into account projection effects when we measure the disk thickness as a function of radius, we first obtain the inclination by modeling the radio data. Using the measurement of the disk thicknesses and the derived radial profiles of gas and stars, we estimate the corresponding volume densities and vertical velocity dispersions. Both stellar and gas disks have smoothly varying scale heights and velocity dispersions, contrary to assumptions of previous studies. Using the velocity dispersions, we find that the gravitational instability parameter Q follows a fairly uniform profile with radius and is ⩾1 across the star-forming disk. The star formation law has a slope that is significantly different from those found in more face-on galaxy studies, both in deprojected and pixel-by-pixel plots. Midplane gas pressure based on the varying scale heights and velocity dispersions appears to roughly hold a power-law correlation with the midplane volume density ratio.

  13. Light versus dark in strong-lens galaxies: dark matter haloes that are rounder than their stars

    Science.gov (United States)

    Bruderer, Claudio; Read, Justin I.; Coles, Jonathan P.; Leier, Dominik; Falco, Emilio E.; Ferreras, Ignacio; Saha, Prasenjit

    2016-02-01

    We measure the projected density profile, shape and alignment of the stellar and dark matter mass distribution in 11 strong-lens galaxies. We find that the projected dark matter density profile - under the assumption of a Chabrier stellar initial mass function - shows significant variation from galaxy to galaxy. Those with an outermost image beyond ˜10 kpc are very well fit by a projected Navarro-Frenk-White (NFW) profile; those with images within 10 kpc appear to be more concentrated than NFW, as expected if their dark haloes contract due to baryonic cooling. We find that over several half-light radii, the dark matter haloes of these lenses are rounder than their stellar mass distributions. While the haloes are never more elliptical than edm = 0.2, their stars can extend to e* > 0.2. Galaxies with high dark matter ellipticity and weak external shear show strong alignment between light and dark; those with strong shear (γ ≳ 0.1) can be highly misaligned. This is reassuring since isolated misaligned galaxies are expected to be unstable. Our results provide a new constraint on galaxy formation models. For a given cosmology, these must explain the origin of both very round dark matter haloes and misaligned strong-lens systems.

  14. Dark matter inside early-type galaxies as function of mass and redshift

    Science.gov (United States)

    Nigoche-Netro, A.; Ramos-Larios, G.; Lagos, P.; Ruelas-Mayorga, A.; de la Fuente, E.; Kemp, S. N.; Navarro, S. G.; Corral, L. J.; Hidalgo-Gámez, A. M.

    2016-10-01

    We study the behaviour of the dynamical and stellar mass inside the effective radius (re) of early-type galaxies (ETGs). We use several samples of ETGs - ranging from 19 000 to 98 000 objects - from the ninth data release of the Sloan Digital Sky Survey. We consider Newtonian dynamics, different light profiles and different initial mass functions (IMF) to calculate the dynamical and stellar mass. We assume that any difference between these two masses is due to dark matter and/or a non-universal IMF. The main results for galaxies in the redshift range 0.0024 dark matter or a non-universal IMF or a combination of both; (v) the amount of dark matter inside ETGs would be equal to or less than the difference between dynamical and stellar mass depending on the impact of the IMF on the stellar mass estimation; (vi) the previous results go in the same direction of some results of the Fundamental Plane (FP) found in the literature in the sense that they could be interpreted as an increase of dark matter along the FP and a dependence of the FP on redshift.

  15. Dark matter annihilation and decay profiles for the Reticulum II dwarf spheroidal galaxy

    CERN Document Server

    Bonnivard, V; Maurin, D; Geringer-Sameth, A; Koushiappas, S M; Walker, M G; Mateo, M; Olszewski, E; Bailey, J I

    2015-01-01

    The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter. In this work, we reconstruct the dark matter annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum~II. This is done using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System (M2FS). We find Reticulum~II to have one of the highest J-factor when compared to the other Milky Way dSphs. We have also checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum~II may provide a unique window on dark matter particle properties.

  16. Dark Matter and IMF normalization in Virgo dwarf early-type galaxies

    CERN Document Server

    Tortora, C; Napolitano, N R

    2015-01-01

    In this work we analyze the dark matter (DM) fraction, \\fdm, and mass-to-light ratio mismatch parameter, \\dimf\\ (computed with respect to a Milky-Way-like IMF), for a sample of 39 dwarf early-type galaxies (dEs) in the Virgo cluster. Both \\fdm\\ and \\dimf\\ are estimated within the central (one effective radius) galaxy regions, with a Jeans dynamical analysis that relies on galaxy velocity dispersions, structural parameters, and stellar mass-to-light ratios from the SMAKCED survey. In this first attempt to constrain, simultaneously, the IMF normalization and the dark matter content, we explore the impact of different assumptions on the DM model profile. On average, for a NFW profile, the \\dimf\\ is consistent with a Chabrier-like normalization ($\\dimf \\sim 1$), with $\\fdm \\sim 0.35$. One of the main results of the present work is that for at least a few systems the \\dimf\\ is heavier than the Milky-Way-like value (i.e. either top- or bottom-heavy). When introducing tangential anisotropy, larger \\dimf\\ and smaller...

  17. A Census of Baryons and Dark Matter in an Isolated, Milky Way-sized Elliptical Galaxy

    CERN Document Server

    Humphrey, Philip J; Canizares, Claude R; Fabian, Andrew C; Miller, Jon M

    2010-01-01

    We present a study of the dark and luminous matter in the isolated elliptical galaxy NGC720, based on deep X-ray data taken with Chandra and Suzaku. The gas is reliably measured to ~R2500, allowing us to place good constraints on the enclosed mass and baryon fraction (fb) within this radius (M2500=1.6e12+/-0.2e12 Msun, fb(2500)=0.10+/-0.01; systematic errors are <~20%). The data indicate that the hot gas is close to hydrostatic, which is supported by good agreement with a kinematical analysis of the dwarf satellite galaxies. We confirm a dark matter (DM) halo at ~20-sigma. Assuming an NFW DM profile, our physical model for the gas distribution enables us to obtain meaningful constraints at scales larger than R2500, revealing that most of the baryons are in the hot gas. We find that fb within Rvir is consistent with the Cosmological value, confirming theoretical predictions that a ~Milky Way-mass (Mvir=3.1e12+/-0.4e12 Msun) galaxy can sustain a massive, quasi-hydrostatic gas halo. While fb is higher than th...

  18. Dark matter inner slope and concentration in galaxies: from the Fornax dwarf to M87

    CERN Document Server

    Mamon, G A; Romanowsky, A J; Wojtak, R

    2014-01-01

    We apply two new state-of-the-art methods that model the distribution of observed tracers in projected phase space to lift the mass / velocity anisotropy (VA) degeneracy and deduce constraints on the mass profiles of galaxies, as well as their VA. We first show how a distribution function based method applied to the satellite kinematics of otherwise isolated SDSS galaxies shows convincing observational evidence of age matching: red galaxies have more concentrated dark matter (DM) halos than blue galaxies of the same stellar or halo mass. Then, applying the MAMPOSSt technique to M87 (traced by its red and blue globular clusters) we find that very cuspy DM is favored, unless we release priors on DM concentration or stellar mass (leading to unconstrained slope). For the Fornax dwarf spheroidal (traced by its metal-rich and metal-poor stars), the inner DM slope is unconstrained, with weak evidence for a core if the stellar mass is fixed. This highlights how priors are crucial for DM modeling. Finally, we find tha...

  19. Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics

    CERN Document Server

    Adams, Joshua J; Fabricius, Maximilian H; Bosch, Remco C E van den; Barentine, John C; Bender, Ralf; Gebhardt, Karl; Hill, Gary J; Murphy, Jeremy D; Swaters, R A; Thomas, Jens; van de Ven, Glenn

    2014-01-01

    We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high resolution integral field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although 2/7 galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, gamma, are generally robust. The mean and standard deviation of the logarithmic slope for the population are gamma=0.67+/-0.10 when measured in the stars and gamma=0.58+/-0.24 when measured in the gas. We als...

  20. Hints against the cold and collisionless nature of dark matter from the galaxy velocity function

    CERN Document Server

    Schneider, Aurel; Papastergis, Emmanouil; Reed, Darren S; Lake, George

    2016-01-01

    The observed number of dwarf galaxies as a function of rotation velocity is significantly smaller than predicted by the $\\Lambda$CDM model. This discrepancy cannot be simply solved by assuming strong baryonic processes, since they would violate the observed relation between maximum circular velocity ($v_{\\rm max}$) and baryon mass of galaxies. A speculative but tantalising possibility is that the mismatch between observation and theory points towards the existence of non-cold or non-collisionless dark matter (DM). In this paper, we investigate the effects of warm, mixed (i.e warm plus cold), and self-interacting DM scenarios on the abundance of dwarf galaxies and the relation between observed HI line-width and maximum circular velocity. Both effects have the potential to alleviate the apparent mismatch between the observed and theoretical abundance of galaxies as a function of $v_{\\rm max}$. For the case of warm and mixed DM, we show that the discrepancy disappears, even for luke-warm models that evade string...

  1. Molecular anions in circumstellar envelopes, interstellar clouds and planetary atmospheres: quantum dynamics of formation and evolution

    OpenAIRE

    Carelli, Fabio

    2011-01-01

    Nowadays, it is a well known fact that most of the matter in our Solar System, in our Galaxy and, probably, within the whole Universe, exists in the form of ionized particles. For decades astronomers and astrophysicists believed that only positively charged ions were worthy of relevance in drawing the networks for possible chemical reactions in the interstellar medium, as well as in modeling the physical conditions in most of astrophysical environments. Thus, negative ions (and especially mol...

  2. Constraints on dark matter annihilation in clusters of galaxies with the Fermi large area telescope

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Blandford, R.D.; Bloom, E.D.; Borgland, A.W.; Bouvier, A.; Buehler, R. [W.W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L.; Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T.J. [Centre d' Étude Spatiale des Rayonnements, CNRS/UPS, BP 44346, F-30128 Toulouse Cedex 4 (France); Brigida, M. [Dipartimento di Fisica ' ' M. Merlin' ' dell' Università e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: tesla@ucolick.org, E-mail: profumo@scipp.ucsc.edu [Laboratoire Leprince-Ringuet, École polytechnique, CNRS/IN2P3, Palaiseau (France); and others

    2010-05-01

    Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from clusters in the first 11 months of observations with the Fermi Large Area Telescope. We interpret this non-detection in terms of constraints on dark matter particle properties. In particular for leptonic annihilation final states and particle masses greater than ∼ 200 GeV, gamma-ray emission from inverse Compton scattering of CMB photons is expected to dominate the dark matter annihilation signal from clusters, and our gamma-ray limits exclude large regions of the parameter space that would give a good fit to the recent anomalous Pamela and Fermi-LAT electron-positron measurements. We also present constraints on the annihilation of more standard dark matter candidates, such as the lightest neutralino of supersymmetric models. The constraints are particularly strong when including the fact that clusters are known to contain substructure at least on galaxy scales, increasing the expected gamma-ray flux by a factor of ∼ 5 over a smooth-halo assumption. We also explore the effect of uncertainties in cluster dark matter density profiles, finding a systematic uncertainty in the constraints of roughly a factor of two, but similar overall conclusions. In this work, we focus on deriving limits on dark matter models; a more general consideration of the Fermi-LAT data on clusters and clusters as gamma-ray sources is forthcoming.

  3. Probing dark matter decay and annihilation with Fermi LAT observations of nearby galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaoyuan [Chinese Academy of Sciences, Beijing (China). National Astronomical Observatories; Max-Planck-Institut fuer Physik, Muenchen (Germany); Vertongen, Gilles [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institut d' Astrophysique de Paris, 75 - Paris (France); Weniger, Christoph [Max-Planck-Institut fuer Physik, Muenchen (Germany)

    2011-09-15

    Galaxy clusters are promising targets for indirect dark matter searches. Gamma-ray signatures from the decay or annihilation of dark matter particles inside these clusters could be observable with the Fermi Large Area Telescope (LAT). Based on three years of Fermi LAT gamma-ray data, we analyze the flux coming from eight nearby clusters individually as well as in a combined likelihood analysis. Concentrating mostly on signals from dark matter decay, we take into account uncertainties of the cluster masses as determined by X-ray observations and model the cluster emission with extended sources. We do not find significant emission from any of the considered clusters and present limits on the dark matter lifetime and annihilation cross-section. We compare our lifetime limits derived from cluster observations with the limits that can be obtained from the extragalactic gamma-ray background, and find that in case of hadronic decay the cluster limits become competitive at dark matter masses below a few hundred GeV. Finally, we show that in presence of dark matter substructures down to 10{sup -6} solar masses the limits on the dark matter annihilation cross-section could improve by a factor of a few hundred, possibly going down to the thermal cross-section of 3 x 10{sup -26} cm{sup 3}s{sup -1} for dark matter masses matter in scenarios with R-parity violation. Implications of these limits for the possible observation of long-lived superparticles at the LHC are discussed. (orig.)

  4. Probing dark matter decay and annihilation with Fermi LAT observations of nearby galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Xiaoyuan [Chinese Academy of Sciences, Beijing (China). National Astronomical Observatories; Max-Planck-Institut fuer Physik, Muenchen (Germany); Vertongen, Gilles [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Institut d' Astrophysique de Paris, 75 - Paris (France); Weniger, Christoph [Max-Planck-Institut fuer Physik, Muenchen (Germany)

    2011-09-15

    Galaxy clusters are promising targets for indirect dark matter searches. Gamma-ray signatures from the decay or annihilation of dark matter particles inside these clusters could be observable with the Fermi Large Area Telescope (LAT). Based on three years of Fermi LAT gamma-ray data, we analyze the flux coming from eight nearby clusters individually as well as in a combined likelihood analysis. Concentrating mostly on signals from dark matter decay, we take into account uncertainties of the cluster masses as determined by X-ray observations and model the cluster emission with extended sources. We do not find significant emission from any of the considered clusters and present limits on the dark matter lifetime and annihilation cross-section. We compare our lifetime limits derived from cluster observations with the limits that can be obtained from the extragalactic gamma-ray background, and find that in case of hadronic decay the cluster limits become competitive at dark matter masses below a few hundred GeV. Finally, we show that in presence of dark matter substructures down to 10{sup -6} solar masses the limits on the dark matter annihilation cross-section could improve by a factor of a few hundred, possibly going down to the thermal cross-section of 3 x 10{sup -26} cm{sup 3}s{sup -1} for dark matter masses matter in scenarios with R-parity violation. Implications of these limits for the possible observation of long-lived superparticles at the LHC are discussed. (orig.)

  5. Is Cold Dark Matter Still a Strong Buy? The Lesson from Galaxy Clusters

    CERN Document Server

    Governato, F; Moore, B; Governato, Fabio; Ghigna, Sebastiano; Moore, Ben

    2001-01-01

    For the last few years the Cold Dark Matter model (ticker: CDM), has been the dominant theory of structure formation. We briefly review the recent advancements and predictions of the model in the field of galaxy clusters. A new set of very high resolution simulations of galaxy clusters show that they have (1) density profiles with central slopes very close to -1.6 and (2) abundance of subhalos similar to the ones observed in real clusters. These results show a remarkably small cluster to cluster variation and a weak dependence from the particular CDM cosmology chosen (LCDM having ~40% less substructure than SCDM). While still a speculative theory with a high prediction/evidence ratio, subject to strong challenges from observational data and competition from other hierarchical theories, we give CDM a rating of ``market outperform'' and of ``long term BUY''.

  6. Copernicus observations of interstellar matter toward the Orion OB1 association. I - Epsilon and Pi-5 Orionis

    Science.gov (United States)

    Shull, J. M.

    1979-01-01

    Copernicus UV data on interstellar lines toward Epsilon Ori and Pi-5 Ori are analyzed to study abundances and physical conditions in both low- and intermediate-velocity components. Clouds at -8 and +5 km/s (LSR) toward Epsilon Ori show typical depletions of Fe, Ti, Mg, and Si in dense (H number density about 100 per cu cm) gas. Low-column-density intermediate-velocity clouds toward both stars, with low densities (hydrogen number density less than 1 per cu cm) and near-cosmic Si abundances, are consistent with a widespread pattern of high-velocity gas over a 15-deg area surrounding the Orion region. Such activity may be attributed to the repeated action of supernovae in a patchy low-density region of interstellar gas.

  7. Disentangling cosmic-ray and dark matter induced gamma-rays in galaxy clusters?

    CERN Document Server

    Maurin, D; Nezri, E; Pointecouteau, E

    2012-01-01

    Galaxy clusters are among the best targets for indirect dark matter detection in gamma-rays, despite the large astrophysical background expected from these objects. Detection is now within reach of current observatories (Fermi-LAT or Cerenkov telescopes), however, assessing the origin of this signal might be difficult. We investigate whether the `number of stacked objects - flux' dependence (log N-log F) could be a signature of the dominant process at stake. We use the CLUMPY code to integrate the signal from decaying/annihilating DM and cosmic rays along the line of sight. We assume the standard NFW profile for the dark matter density and rely on a parametrised emissivity for the cosmic-ray component. In this context, the consequences of stacking are explored using the MCXC meta-catalog of galaxy clusters. The log N-log F power-law behaviour may be a clear signature to disentangle decaying dark matter from cosmic-ray induced gamma-rays (and DM annihilation), contrarily to DM annihilation that has the same sl...

  8. Ultra-Light Dark Matter in Ultra-Faint Dwarf Galaxies

    CERN Document Server

    Calabrese, Erminia

    2016-01-01

    Cold Dark Matter (CDM) models struggle to match the observations at galactic scales. The tension can be reduced either by dramatic baryonic feedback effects or by modifying the particle physics of CDM. Here, we consider an ultra-light scalar field DM particle manifesting a wave nature below a DM particle mass-dependent Jeans scale. For DM mass $m\\sim10^{-22}{\\rm eV}$, this scenario delays galaxy formation and avoids cusps in the center of the dark matter haloes. We use new measurements of half-light mass in ultra-faint dwarf galaxies Draco II and Triangulum II to estimate the mass of the DM particle in this model. We find that if the stellar populations are within the core of the density profile then the data are in agreement with a wave dark matter model having a DM particle with $m\\sim 3.7-5.6\\times 10^{-22}{\\rm eV}$. The presence of this extremely light particle will contribute to the formation of a central solitonic core replacing the cusp of a Navarro-Frenk-White profile and bringing predictions closer t...

  9. THE AVERAGE STAR FORMATION HISTORIES OF GALAXIES IN DARK MATTER HALOS FROM z = 0-8

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, Peter S.; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford, CA 94305 (United States); Conroy, Charlie [Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States)

    2013-06-10

    We present a robust method to constrain average galaxy star formation rates (SFRs), star formation histories (SFHs), and the intracluster light (ICL) as a function of halo mass. Our results are consistent with observed galaxy stellar mass functions, specific star formation rates (SSFRs), and cosmic star formation rates (CSFRs) from z = 0 to z = 8. We consider the effects of a wide range of uncertainties on our results, including those affecting stellar masses, SFRs, and the halo mass function at the heart of our analysis. As they are relevant to our method, we also present new calibrations of the dark matter halo mass function, halo mass accretion histories, and halo-subhalo merger rates out to z = 8. We also provide new compilations of CSFRs and SSFRs; more recent measurements are now consistent with the buildup of the cosmic stellar mass density at all redshifts. Implications of our work include: halos near 10{sup 12} M{sub Sun} are the most efficient at forming stars at all redshifts, the baryon conversion efficiency of massive halos drops markedly after z {approx} 2.5 (consistent with theories of cold-mode accretion), the ICL for massive galaxies is expected to be significant out to at least z {approx} 1-1.5, and dwarf galaxies at low redshifts have higher stellar mass to halo mass ratios than previous expectations and form later than in most theoretical models. Finally, we provide new fitting formulae for SFHs that are more accurate than the standard declining tau model. Our approach places a wide variety of observations relating to the SFH of galaxies into a self-consistent framework based on the modern understanding of structure formation in {Lambda}CDM. Constraints on the stellar mass-halo mass relationship and SFRs are available for download online.

  10. Interplay between Dark Matter and Galactic Structure in Disk and Oblate Elliptical Galaxies

    Indian Academy of Sciences (India)

    Euaggelos E. Zotos; Nicolaos D. Caranicolas

    2014-12-01

    Understanding the regular or chaotic nature of orbits in galaxies is undoubtedly an issue of great importance. We determine the character of orbits of stars moving in the meridional plane (, ) of an axially symmetric time-independent galactic model with a spherical central nucleus, and a flat biaxial oblate dark matter halo component. In particular, we try to reveal the influence of the fractional portion of dark matter on the structure and also on the different families of orbits of the galaxy, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when the ratio of dark matter to luminous mass varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish between ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. The investigation is carried out both in the physical (, ) and the phase (, $\\dot{R}$) space for a better understanding of the orbital properties of the system. The numerical computations reveal that in both cases, the fractional portion of dark matter influences more or less, the overall orbital structure of the system. It was observed however, that the evolution of the percentages of all types of orbits as a function of the fractional portion of dark matter strongly depends on the particular type of space (physical or phase) in which the initial conditions of orbits are launched. The results are compared with the similar earlier work.

  11. The dark matter distribution of merging galaxy cluster PLCKG287.0+32.9 by weak lensing

    Science.gov (United States)

    Finner, Kyle; Jee, James; Dawson, William; Golovich, Nathan; Gruen, Daniel; Lemaux, Brian; Wittman, David M.

    2017-01-01

    The merging galaxy cluster, PLCKG287.0+32.9, is the second most significant detection of the Planck SZ survey. As part of a sample of galaxy clusters being investigated by the Merging Cluster Collaboration ($MC^2$), PLCKG287.0+32.9 is studied to further constrain dark matter properties and improve our understanding of galaxy cluster physics. The galaxy cluster hosts two megaparsec sized radio relics and a radio halo, evidence of its merger nature. The radio relics are located approximately one and three megaparsecs from the X-ray peak, requiring a somewhat complex merging scenario. A detailed study of the dark matter distribution will provide key information to constrain the merger scenario. With Subaru g- and r-band data, we perform a weak-lensing analysis and determine the dark matter distribution of the merging galaxy cluster. We fit a 2-parameter NFW profile to the tangential shear to quantify the mass. We find that the dark matter peak is aligned with the luminosity peak. Using the dark matter mass distribution, we discuss the significance of the merging constituents and their relation to the luminous emissions.

  12. Equation of state, universal profiles, scaling and macroscopic quantum effects in warm dark matter galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Vega, H.J. de [Sorbonne Universites, Universite Pierre et Marie Curie UPMC Paris VI, LPTHE CNRS UMR 7589, Paris Cedex 05 (France); Sanchez, N.G. [Observatoire de Paris PSL Research University, Sorbonne Universites UPMC Paris VI, Observatoire de Paris, LERMA CNRS UMR 8112, Paris (France)

    2017-02-15

    The Thomas-Fermi approach to galaxy structure determines self-consistently and non-linearly the gravitational potential of the fermionic warm dark matter (WDM) particles given their quantum distribution function f(E). This semiclassical framework accounts for the quantum nature and high number of DM particles, properly describing gravitational bounded and quantum macroscopic systems as neutron stars, white dwarfs and WDM galaxies. We express the main galaxy magnitudes as the halo radius r{sub h}, mass M{sub h}, velocity dispersion and phase space density in terms of the surface density which is important to confront to observations. From these expressions we derive the general equation of state for galaxies, i.e., the relation between pressure and density, and provide its analytic expression. Two regimes clearly show up: (1) Large diluted galaxies for M{sub h} >or similar 2.3 x 10{sup 6} M {sub CircleDot} and effective temperatures T{sub 0} > 0.017 K described by the classical self-gravitating WDM Boltzman gas with a space-dependent perfect gas equation of state, and (2) Compact dwarf galaxies for 1.6 x 10{sup 6} M {sub CircleDot} >or similar M{sub h} >or similar M{sub h,min} ≅ 3.10 x 10{sup 4} (2 keV/m){sup (16)/(5)} M {sub CircleDot}, T{sub 0} < 0.011 K described by the quantum fermionic WDM regime with a steeper equation of state close to the degenerate state. In particular, the T{sub 0} = 0 degenerate or extreme quantum limit yields the most compact and smallest galaxy. In the diluted regime, the halo radius r{sub h}, the squared velocity v{sup 2}(r{sub h}) and the temperature T{sub 0} turn to exhibit square-root of M{sub h} scaling laws. The normalized density profiles ρ(r)/ρ(0) and the normalized velocity profiles v{sup 2}(r)/v{sup 2}(0) are universal functions of r/r{sub h} reflecting the WDM perfect gas behavior in this regime. These theoretical results contrasted to robust and independent sets of galaxy data remarkably reproduce the observations. For

  13. Probabilistic Inference of Dark Matter Properties in Galaxy Clusters and the Cosmic Web

    Science.gov (United States)

    Ng, Yin-Yee

    "Mass tells spacetime how to curve, spacetime tells mass how to move". This famous quote by physicist John Archibald Wheeler succinctly summarizes General Relativity, the most successful theory that describes our universe at large scale. However, most of the mass that General Relativity describes, namely dark matter (DM), remains a mystery. We have solid evidence of the existence of DM from various observations, but we know little or nothing about the particle nature of DM and how DM particles interact with different particles. Completing this knowledge gap would improve or revolutionize our established cosmological model, the Lambda Cold-Dark Matter (CDM) model, and give directions to theories beyond the standard particle physics model. This work attempts to study DM by examining and extending existing modeling approaches of DM and its visible tracers in a probabilistic way. The single verified form of DM interaction is gravitational. Currently, the only way to infer the properties of DM is through visible tracers. Most of these indirect detections either have low signal-to-noise, sparse coverage, or missing variables. These limitations introduce additional modeling choices and uncertainties. A probabilistic approach allows us to propagate the uncertainties appropriately and marginalize any missing variables. There are two recurring types of visible tracers that my work uses. The first type of tracers are galaxies and observables in the overdense regions of DM. These tracers allow us to infer the macroscopic dynamical properties of DM distribution that we want to study. The second type of tracers, on the hand, are in the background, i.e. further away than the foreground dark matter, from us observers. The gravity of DM can bend spacetime such that the path of light traveling in the vicinity would also curve, leaving distortions in the galaxy images. In the introduction (first chapter) of this thesis, I will lay out the technical history, terminology and the

  14. Interstellar shock studies: the SOFIA/GREAT contribution

    CERN Document Server

    Gusdorf, Antoine

    2015-01-01

    Shocks are ubiquitous in the interstellar medium of galaxies, where they contribute to the energetic balance and to the cycle of matter, and where they are thought to be the primary sites for cosmic rays acceleration. Most of the time: in jets and outflows, supernova remnants, or colliding flows, they are linked with star formation. The study of shocks is hence a powerful tool to probe the evolution of the interstellar medium and to better understand star formation. To these aims, the most precise observations must be compared with the most precise models of shocks. The SOFIA/GREAT instrument represents a powerful observational tool to support our progresses, as it allows to observe numerous shock tracers in the far-infrared range.

  15. THE SL2S GALAXY-SCALE LENS SAMPLE. V. DARK MATTER HALOS AND STELLAR IMF OF MASSIVE EARLY-TYPE GALAXIES OUT TO REDSHIFT 0.8

    Energy Technology Data Exchange (ETDEWEB)

    Sonnenfeld, Alessandro; Treu, Tommaso [Physics Department, University of California, Santa Barbara, CA 93106 (United States); Marshall, Philip J. [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Suyu, Sherry H. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Gavazzi, Raphaël [Institut d' Astrophysique de Paris, UMR7095 CNRS-Université Pierre et Marie Curie, 98bis bd Arago, F-75014 Paris (France); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Nipoti, Carlo, E-mail: sonnen@physics.ucsb.edu [Department of Physics and Astronomy, Bologna University, viale Berti-Pichat 6/2, I-40127 Bologna (Italy)

    2015-02-20

    We investigate the cosmic evolution of the internal structure of massive early-type galaxies over half of the age of the universe. We perform a joint lensing and stellar dynamics analysis of a sample of 81 strong lenses from the Strong Lensing Legacy Survey and Sloan ACS Lens Survey and combine the results with a hierarchical Bayesian inference method to measure the distribution of dark matter mass and stellar initial mass function (IMF) across the population of massive early-type galaxies. Lensing selection effects are taken into account. We find that the dark matter mass projected within the inner 5 kpc increases for increasing redshift, decreases for increasing stellar mass density, but is roughly constant along the evolutionary tracks of early-type galaxies. The average dark matter slope is consistent with that of a Navarro-Frenk-White profile, but is not well constrained. The stellar IMF normalization is close to a Salpeter IMF at log M {sub *} = 11.5 and scales strongly with increasing stellar mass. No dependence of the IMF on redshift or stellar mass density is detected. The anti-correlation between dark matter mass and stellar mass density supports the idea of mergers being more frequent in more massive dark matter halos.

  16. Improved Constraints on Dark Matter Annihilation to a Line using Fermi-LAT observations of Galaxy Clusters

    CERN Document Server

    Adams, Douglas Quincy; Spolyar, Douglas

    2016-01-01

    Galaxy clusters are dominated by dark matter, and may have a larger proportion of surviving substructure than, e.g, field galaxies. Due to the presence of galaxy clusters in relative proximity and their high dark matter content, they are promising targets for the indirect detection of dark matter via Gamma-rays. Indeed, dedicated studies of sets of up to 100 clusters have been made previously, so far with no clear indication of a dark matter signal. Here we report on Gamma-ray observations of some 26,000 galaxy clusters based on Pass-7 Fermi Large Area Telescope (LAT) data, with clusters selected from the Tully 2MASS Groups catalog. None of these clusters is significantly detected in Gamma-rays, and we present Gamma-ray flux upper limits between 20 GeV and 500 GeV. We estimate the dark matter content of each of the clusters in these catalogs, and constrain the dark matter annihilation cross section, by analyzing Fermi-LAT data from the directions of the clusters. We set some of the tightest cluster-based cons...

  17. The effects of galaxy formation on the matter power spectrum: A challenge for precision cosmology

    CERN Document Server

    van Daalen, Marcel P; Booth, C M; Vecchia, Claudio Dalla

    2011-01-01

    Upcoming weak lensing surveys, such as LSST, EUCLID, and WFIRST, aim to measure the matter power spectrum with unprecedented accuracy. In order to fully exploit these observations, models are needed that, given a set of cosmological parameters, can predict the non-linear matter power spectrum at the level of 1% or better for scales corresponding to comoving wave numbers 0.170 h/Mpc. Therefore, baryons, and particularly AGN feedback, cannot be ignored in theoretical power spectra for k>0.3 h/Mpc. It will thus be necessary to improve our understanding of feedback processes in galaxy formation, or at least to constrain them through auxiliary observations, before we can fulfil the goals of upcoming weak lensing surveys.

  18. The non-gravitational interactions of dark matter in colliding galaxy clusters

    CERN Document Server

    Harvey, David; Kitching, Thomas; Taylor, Andy; Tittley, Eric

    2015-01-01

    Collisions between galaxy clusters provide a test of the non-gravitational forces acting on dark matter. Dark matter's lack of deceleration in the `bullet cluster collision' constrained its self-interaction cross-section \\sigma_DM/m < 1.25cm2/g (68% confidence limit) for long-ranged forces. Using the Chandra and Hubble Space Telescopes we have now observed 72 collisions, including both `major' and `minor' mergers. Combining these measurements statistically, we detect the existence of dark mass at 7.6\\sigma significance. The position of the dark mass has remained closely aligned within 5.8+/-8.2 kpc of associated stars: implying a self-interaction cross-section \\sigma_DM/m < 0.47 cm2/g (95% CL) and disfavoring some proposed extensions to the standard model.

  19. Herschel observations of interstellar chloronium

    NARCIS (Netherlands)

    Neufeld, David A.; Roueff, Evelyne; Snell, Ronald L.; Lis, Dariusz; Benz, Arnold O.; Bruderer, Simon; Black, John H.; De Luca, Massimo; Gerin, Maryvonne; Goldsmith, Paul F.; Gupta, Harshal; Indriolo, Nick; Le Bourlot, Jacques; Le Petit, Franck; Larsson, Bengt; Melnick, Gary J.; Menten, Karl M.; Monje, Raquel; Nagy, Zsofia; Phillips, Thomas G.; Sandqvist, Aage; Sonnentrucker, Paule; van der Tak, Floris; Wolfire, Mark G.

    2012-01-01

    Using the Herschel Space Observatory's Heterodyne Instrument for the Far-Infrared, we have observed parachloronium (H2Cl+) toward six sources in the Galaxy. We detected interstellar chloronium absorption in foreground molecular clouds along the sight lines to the bright submillimeter continuum sourc

  20. The Dark Matter Content of the Triangulum II Ultra-Faint Dwarf Galaxy

    Science.gov (United States)

    Kirby, Evan N.; Cohen, Judith G.; Simon, Joshua D.

    2017-01-01

    Triangulum II is an ultra-faint galaxy with a luminosity of 450 L⊙ discovered through Pan-STARRS imaging in 2015. Since then, two independent studies—including one of our own—based on Keck/DEIMOS spectroscopy found that the galaxy has a stellar velocity dispersion of about 5 km/s, indicating a very high concentration of dark matter. Here, we present additional DEIMOS observations over six epochs. We show that a combination of radial velocity variability (likely due to binarity) and inaccuracies in the previous measurements led to a spurious detection of a velocity dispersion in excess of what would be expected from the stellar population alone. Instead, we place an upper limits of 3.4 km/s (90% C.L.) and 4.3 km/s (95% C.L.) on the velocity dispersion. While these limits are compatible with very high mass-to-light ratios (1700 at 90% C.L. or 2600 at 95% C.L.), Triangulum II no longer seems extreme compared to dwarf galaxies of similar luminosity. Because the stars still span a large range of metallicity (-2.8 < [Fe/H] < -1.5), the galactic nature of Triangulum II is not in dispute.

  1. Baryon oscillations in galaxy and matter power-spectrum covariance matrices

    CERN Document Server

    Neyrinck, Mark C

    2007-01-01

    We investigate large-amplitude baryon acoustic oscillations (BAO's) in off-diagonal entries of cosmological power-spectrum covariance matrices. These covariance-matrix BAO's describe the increased attenuation of power-spectrum BAO's caused by upward fluctuations in large-scale power. We derive an analytic approximation to covariance-matrix entries in the BAO regime, and check the analytical predictions using N-body simulations. These BAO's look much stronger than the BAO's in the power spectrum, but seem detectable only at about a one-sigma level in gigaparsec-scale galaxy surveys. In estimating cosmological parameters using matter or galaxy power spectra, including the covariance-matrix BAO's can have a several-percent effect on error-bar widths for some parameters directly related to the BAO's, such as the baryon fraction. Also, we find that including the numerous galaxies in small haloes in a survey can reduce error bars in these cosmological parameters more than the simple reduction in shot noise might su...

  2. CMB-galaxy correlation in Unified Dark Matter scalar field cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Bertacca, Daniele; Bartolo, Nicola; Matarrese, Sabino [Dipartimento di Fisica Galileo Galilei Università di Padova, via F. Marzolo 8, I-35131 Padova (Italy); Raccanelli, Alvise [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Piattella, Oliver F. [Departamento de Física, Universidade Federal do Espírito Santo, avenida Ferrari 514, 29075-910 Vitória, ES (Brazil); Pietrobon, Davide [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, 91109 Pasadena CA U.S.A. (United States); Giannantonio, Tommaso, E-mail: daniele.bertacca@pd.infn.it, E-mail: alvise.raccanelli@port.ac.uk, E-mail: oliver.piattella@gmail.com, E-mail: davide.pietrobon@jpl.nasa.gov, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it, E-mail: tommaso.giannantonio@Universe-cluster.de [Excellence Cluster Universe, Technical University Munich, Boltzmannstraße 2, D-85748 Garching bei München (Germany)

    2011-03-01

    We present an analysis of the cross-correlation between the CMB and the large-scale structure (LSS) of the Universe in Unified Dark Matter (UDM) scalar field cosmologies. We work out the predicted cross-correlation function in UDM models, which depends on the speed of sound of the unified component, and compare it with observations from six galaxy catalogues (NVSS, HEAO, 2MASS, and SDSS main galaxies, luminous red galaxies, and quasars). We sample the value of the speed of sound and perform a likelihood analysis, finding that the UDM model is as likely as the ΛCDM, and is compatible with observations for a range of values of c{sub ∞} (the value of the sound speed at late times) on which structure formation depends. In particular, we obtain an upper bound of c{sub ∞}{sup 2} ≤ 0.009 at 95% confidence level, meaning that the ΛCDM model, for which c{sub ∞}{sup 2} = 0, is a good fit to the data, while the posterior probability distribution peaks at the value c{sub ∞}{sup 2} = 10{sup −4} . Finally, we study the time dependence of the deviation from ΛCDM via a tomographic analysis using a mock redshift distribution and we find that the largest deviation is for low-redshift sources, suggesting that future low-z surveys will be best suited to constrain UDM models.

  3. Dynamics of the NGC 4636 globular cluster system. An extremely dark matter dominated galaxy?

    Science.gov (United States)

    Schuberth, Y.; Richtler, T.; Dirsch, B.; Hilker, M.; Larsen, S. S.; Kissler-Patig, M.; Mebold, U.

    2006-11-01

    Context: .We present the first dynamical study of the globular cluster system of NGC 4636. It is the southernmost giant elliptical galaxy of the Virgo cluster and is claimed to be extremely dark matter dominated, according to X-ray observations. Aims: .Globular clusters are used as dynamical tracers to investigate, by stellar dynamical means, the dark matter content of this galaxy. Methods: .Several hundred medium resolution spectra were acquired at the VLT with FORS 2/MXU. We obtained velocities for 174 globular clusters in the radial range 0.90 arcmin Jeans-models. Results: .We find some indication of a rotation of the red (metal-rich) clusters about the minor axis. Out to a radius of 30 kpc, we find a roughly constant projected velocity dispersion for the blue clusters of σ ≈ 200~km s-1. The red clusters are found to have a distinctly different behavior: at a radius of about 3', the velocity dispersion drops by ~50~km s-1 to about 170~km s-1, which then remains constant out to a radius of 7'. The cause might be the steepening of the number density profile at ~3' observed for the red clusters. Using only the blue clusters as dynamical tracers, we perform Jeans-analyses for different assumptions of the orbital anisotropy. Enforcing the model dark halos to be of the NFW type, we determine their structural parameters. Depending on the anisotropy and the adopted M/L-values, we find that the dark matter fraction within one effective radius can vary between 20% and 50%, with most a probable range between 20% and 30%. The ambiguity of the velocity dispersion in the outermost bin is a main source of uncertainty. A comparison with cosmological N-body simulations reveals no striking disagreement. Conclusions: .Although the dark halo mass still cannot be strongly constrained, NGC 4636 does not seem to be extremely dark matter dominated. The derived circular velocities are also consistent with Modified Newtonian Dynamics.

  4. DARK MATTER MASS FRACTION IN LENS GALAXIES: NEW ESTIMATES FROM MICROLENSING

    Energy Technology Data Exchange (ETDEWEB)

    Jiménez-Vicente, J. [Departamento de Física Teórica y del Cosmos, Universidad de Granada, Campus de Fuentenueva, E-18071 Granada (Spain); Mediavilla, E. [Instituto de Astrofísica de Canarias, Vía Láctea S/N, La Laguna E-38200, Tenerife (Spain); Kochanek, C. S. [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, The Ohio State University, 4055 McPherson Lab, 140 West 18th Avenue, Columbus, OH 43221 (United States); Muñoz, J. A. [Departamento de Astronomía y Astrofísica, Universidad de Valencia, E-46100 Burjassot, Valencia (Spain)

    2015-02-01

    We present a joint estimate of the stellar/dark matter mass fraction in lens galaxies and the average size of the accretion disk of lensed quasars based on microlensing measurements of 27 quasar image pairs seen through 19 lens galaxies. The Bayesian estimate for the fraction of the surface mass density in the form of stars is α = 0.21 ± 0.14 near the Einstein radius of the lenses (∼1-2 effective radii). The estimate for the average accretion disk size is R{sub 1/2}=7.9{sub −2.6}{sup +3.8}√(M/0.3 M{sub ⊙}) light days. The fraction of mass in stars at these radii is significantly larger than previous estimates from microlensing studies assuming quasars were point-like. The corresponding local dark matter fraction of 79% is in good agreement with other estimates based on strong lensing or kinematics. The size of the accretion disk inferred in the present study is slightly larger than previous estimates.

  5. Galaxy and cluster formation in a universe dominated by cold dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Primack, J.R.

    1984-07-01

    The dark matter (DM) that appears to be gravitationally dominant on all astronomical scales larger than the cores of galaxies can be classified, on the basis of its characteristic free-streaming damping mass M/sub D/, as hot (M/sub D/ approx. 10/sup 15/ M/sub mass/), warm (M/sub D/ approx. 10/sup 11/ M/sub mass/), or cold (M/sub D < 10/sup 8/ M/sub mass/). For the case of cold DM, the shape of the DM fluctuation spectrum is determined by (a) the primordial spectrum (on scales larger than the horizon), and (b) stagspansion, the stagnation of the growth of DM fluctuations that enter the horizon while the universe is still radiation-dominated. An attractive feature of the cold dark matter hypothesis is its considerable predictive power: the post-recombination fluctuation spectrum is calculable, and it in turn governs the formation of galaxies and clusters. Good agreement with the data is obtained for a Zeldovich spectrum of primordial fluctuations.

  6. Cusp-core transformations in dwarf galaxies: observational predictions

    CERN Document Server

    Teyssier, Romain; Dubois, Yohan; Read, Justin

    2012-01-01

    The presence of a dark matter core in the central kiloparsec of many dwarf galaxies has been a long standing problem in galaxy formation theories based on the standard cold dark matter paradigm. Recent cosmological simulations, based on Smooth Particle Hydrodynamics and rather strong feedback recipes have shown that it was indeed possible to form extended dark matter cores using baryonic processes related to a more realistic treatment of the interstellar medium. Using adaptive mesh refinement, together with a new, stronger supernovae feedback scheme that we have recently implemented in the RAMSES code, we show that it is also possible to form a prominent dark matter core within the well-controlled framework of an isolated, initially cuspy, 10 billion solar masses dark matter halo. Although our numerical experiment is idealized, it allows a clean and unambiguous identification of the dark matter core formation process. Our dark matter inner profile is well fitted by a pseudo-isothermal profile with a core radi...

  7. Black Holes Make Stars which explains the Mystery of the Newly Discovered PHOENIX GALAXY, while Dark Matter is described in the explanation

    Science.gov (United States)

    Cimorelli, S. A.

    2013-12-01

    A prevailing theory is some Stars change their energy field and are reduced to Black Holes (BHs). Consider an expanded modified Black Hole from the original Big Bang which might have been a massive Black Hole can become a Galaxy and or a Star. We theorize something is not made of nothing; and the universe was created by a massive Black Hole which had enough mass to produce what is contained in our universe today. We categorized BH by their mass. Our concept could explain the Mystery of the Newly Discovered PHOENIX GALAXY. We define and categorize black holes and the space they inhabit. We describe mechanisms for their formation and mechanisms of black hole collisions and bursts, inside of the universe. These are linked to the formation of galaxies, stars, planets and planetary processes. Insight is gained regarding the formation and evolution of galaxies and the matter contained therein. Space itself is categorized as to its purpose and properties as it relates to the categories of black holes and processes ongoing within the space in which the processes occur. We suggest a category-1 (c-1) black hole burst by collision or on it's own and formed the universe by generating great numbers of c-2 BHs inside the universe, in c-2 space, which become galaxies and which is the start of the universe, 10% of which formed galaxies and 90% remain as dark matter as c-2 and c-3 BHs which are still evolving. C-2 BHs can burst to form a galaxy, containing c-3 space, filled with c-3 and c-4 BHs. C-3 BHs are significantly more modified and expanded than c-2 BHs and are formed from burst c-2 BHs to form gas and dust clouds peppered with the c-3 BHs Remnants from the burst c-2 BH include sizes from minute particles which contribute to the formation of massive gas and dust clouds; to 10 to 20 solar masses that form large stars; and others, tiny stars which eventually become planets and moons. These gas and dust clouds are peppered with c-4 BHs which eventually are seen as new stars

  8. Physical processes in the interstellar medium

    CERN Document Server

    Spitzer, Lyman

    2008-01-01

    Physical Processes in the Interstellar Medium discusses the nature of interstellar matter, with a strong emphasis on basic physical principles, and summarizes the present state of knowledge about the interstellar medium by providing the latest observational data. Physics and chemistry of the interstellar medium are treated, with frequent references to observational results. The overall equilibrium and dynamical state of the interstellar gas are described, with discussions of explosions produced by star birth and star death and the initial phases of cloud collapse leading to star formation.

  9. Constraints on dark matter scenarios from measurements of the galaxy luminosity function at high redshifts

    CERN Document Server

    Corasaniti, P S; Marsh, D J E; Das, S

    2016-01-01

    We use state-of-art measurements of the galaxy luminosity function (LF) at z=6, 7 and 8 to derive constraints on warm dark matter (WDM), late-forming dark matter (LFDM) and ultra-light axion dark matter (ULADM) models alternative to the cold dark matter (CDM) paradigm. To this purpose we have run a suite of high-resolution N-body simulations to accurately characterise the low mass-end of the halo mass function and derive DM model predictions of the high-z luminosity function. In order to convert halo masses into UV-magnitudes we introduce an empirical approach based on halo abundance matching which allows us to model the LF in terms of the amplitude and scatter of the ensemble average star formation rate halo mass relation of each DM model, $\\langle {\\rm SFR}({\\rm M_{ h}},z)\\rangle$. We find that independent of the DM scenario the average SFR at fixed halo mass increases from z=6 to 8, while the scatter remains constant. At halo mass ${\\rm M_{h}}\\gtrsim 10^{12}\\,{\\rm M}_\\odot$ h$^{-1}$ the average SFR as func...

  10. Constraints on Dark Matter Annihilation in Clusters of Galaxies from Diffuse Radio Emission

    CERN Document Server

    Storm, Emma; Profumo, Stefano; Rudnick, Lawrence

    2012-01-01

    Annihilation of dark matter can result in the production of stable Standard Model particles including electrons and positrons that, in the presence of magnetic fields, lose energy via synchrotron radiation, observable as radio emission. Galaxy clusters are excellent targets to search for or to constrain the rate of dark matter annihilation, as they are both massive and dark matter dominated. In this study, we place limits on dark matter annihilation in a sample of nearby clusters using upper limits on the diffuse radio emission, low levels of observed diffuse emission, or detections of radio mini-haloes. We find that the strongest limits on the annihilation cross section are better than limits derived from the non-detection of clusters in the gamma-ray band by a factor of approximately 3 or more when the same annihilation channel and subtructure model, but different best-case clusters, are compared. The limits on the cross section depend on the assumed amount of substructure, varying by as much as 2 orders of...

  11. ISOTOPIC ANOMALIES IN PRIMITIVE SOLAR SYSTEM MATTER: SPIN-STATE-DEPENDENT FRACTIONATION OF NITROGEN AND DEUTERIUM IN INTERSTELLAR CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Wirstroem, Eva S.; Cordiner, Martin A.; Charnley, Steven B.; Milam, Stefanie N., E-mail: ewirstrom@gmail.com [Astrochemistry Laboratory and Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Greenbelt, MD 20770 (United States)

    2012-09-20

    Organic material found in meteorites and interplanetary dust particles is enriched in D and {sup 15}N. This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar nebula. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and {sup 15}N and can account for the largest isotopic enrichments measured in carbonaceous meteorites. However, more recent measurements have shown that, in some primitive samples, a large {sup 15}N enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, {sup 15}N enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H{sub 2}, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both {sup 15}N and D in dense cloud cores. We also show that while the nitriles, HCN and HNC, contain the greatest {sup 15}N enrichment, this is not expected to correlate with extreme D enrichment. These calculations therefore support the view that solar system {sup 15}N and D isotopic anomalies have an interstellar heritage. We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

  12. Isotopic Anomalies in Primitive Solar System Matter: Spin-State Dependent Fractionation of Nitrogen and Deuterium in Interstellar Clouds

    Science.gov (United States)

    Wirstrom, Eva S.; Charnley, Steven B.; Cordiner, Martin A.; Milan, Stefanie N.

    2012-01-01

    Organic material found in meteorites and interplanetary dust particles is enriched in D and N-15, This is consistent with the idea that the functional groups carrying these isotopic anomalies, nitriles and amines, were formed by ion-molecule chemistry in the protosolar core. Theoretical models of interstellar fractionation at low temperatures predict large enrichments in both D and N-15 and can account for the largest isotop c enrichments measured in carbonaceous meteorites, However, more recent measurements have shown that, in some primitive samples, a large N-15 enrichment does not correlate with one in D, and that some D-enriched primitive material displays little, if any, N-15 enrichment. By considering the spin-state dependence in ion-molecule reactions involving the ortho and para forms of H2, we show that ammonia and related molecules can exhibit such a wide range of fractionation for both N-15 and D in dense cloud cores, We also show that while the nitriles, HCN and HNC, contain the greatest N-15 enrichment, this is not expected to correlate with extreme D emichment. These calculations therefore support the view that Solar System N-15 and D isotopic anomalies have an interstellar heritage, We also compare our results to existing astronomical observations and briefly discuss future tests of this model.

  13. Boundary conditions for the paleoenvironment: Chemical and physical processes in the pre-solar nebula. [molecular clouds, interstellar matter, and abundance

    Science.gov (United States)

    Irvine, W. M.; Schloerb, F. P.

    1985-01-01

    Two additional hyperfine components of the interstellar radical C3H were detected. In addition, methanol was discovered in interstellar clouds. The abundance of HCCN and various chemical isomers in molecular clouds was investigated.

  14. Bubbles and holes in the interstellar medium

    NARCIS (Netherlands)

    vanderHulst, JM; Skillman, ED

    1996-01-01

    Studies of the HI in nearby galaxies now clearly begin to show the effects of star formation on the interstellar medium. Holes, filaments, expanding motions and other anomalous velocity signatures are clearly apparent in sensitive observations of the HI in nearby galaxies. A global relation with the

  15. Structure and Dynamics of the Interstellar Medium

    Science.gov (United States)

    Tenorio-Tagle, Guillermo; Moles, Mariano; Melnick, Jorge

    Here for the first time is a book that treats practically all aspects of modern research in interstellar matter astrophysics. 20 review articles and 40 carefully selected and refereed papers give a thorough overview of the field and convey the flavor of enthusiastic colloquium discussions to the reader. The book includes sections on: - Molecular clouds, star formation and HII regions - Mechanical energy sources - Discs, outflows, jets and HH objects - The Orion Nebula - The extragalactic interstellar medium - Interstellar matter at high galactic latitudes - The structure of the interstellar medium

  16. Synchrotron Emission from Dark Matter Annihilation: Predictions for Constraints from Non-detections of Galaxy Clusters with New Radio Surveys

    CERN Document Server

    Storm, Emma; Splettstoesser, Megan; Profumo, Stefano

    2016-01-01

    The annihilation of dark matter particles is expected to yield a broad radiation spectrum via the production of Standard Model particles in astrophysical environments. In particular, electrons and positrons from dark matter annihilation produce synchrotron radiation in the presence of magnetic fields. Galaxy clusters are the most massive collapsed structures in the universe, and are known to host microGauss-scale magnetic fields. They are therefore ideal targets to search for, or to constrain the synchrotron signal from dark matter annihilation. In this work we use the expected sensitivities of several planned surveys from the next generation of radio telescopes to predict the constraints on dark matter annihilation models which will be achieved in the case of non-detections of diffuse radio emission from galaxy clusters. Specifically, we consider the Tier 1 and 2 surveys planned for the Low Frequency Array (LOFAR) at 120 MHz, the EMU survey planned for the Australian Square Kilometre Array Pathfinder (ASKAP)...

  17. Contrasting Galaxy Formation from Quantum Wave Dark Matter, $\\psi$DM, with $\\Lambda$CDM, using Planck and Hubble Data

    CERN Document Server

    Schive, Hsi-Yu; Broadhurst, Tom; Huang, Kuan-Wei

    2015-01-01

    The newly established luminosity functions of high-z galaxies at $4 \\lesssim z \\lesssim 10$ can provide a stringent check on dark matter models that aim to explain the core properties of dwarf galaxies. The cores of dwarf spheroidal galaxies are understood to be too large to be accounted for by free streaming of warm dark matter without overly suppressing the formation of such galaxies. Here we demonstrate with cosmological simulations that wave dark matter, $\\psi$DM, appropriate for light bosons such as axions, does not suffer this problem, given a boson mass of $m_{\\psi} \\ge 1.2 \\times 10^{-22}{\\,\\rm eV}$ ($2\\sigma$). In this case, the halo mass function is suppressed below $\\sim 10^{10}{\\,M_\\odot}$ at a level that is consistent with the high-z luminosity functions, while simultaneously generating the kpc-scale cores in dwarf galaxies arising from the solitonic ground state in $\\psi$DM. We demonstrate that the reionization history in this scenario is consistent with the Thomson optical depth recently report...

  18. Probing the Truncation of Galaxy Dark Matter Halos in High-Density Environments from Hydrodynamical N-Body Simulations

    Science.gov (United States)

    Limousin, Marceau; Sommer-Larsen, Jesper; Natarajan, Priyamvada; Milvang-Jensen, Bo

    2009-05-01

    We analyze high-resolution, N-body hydrodynamical simulations of fiducial galaxy clusters to probe tidal stripping of the dark matter subhalos. These simulations include a prescription for star formation allowing us to track the fate of the stellar component as well. We investigate the effect of tidal stripping on cluster galaxies hosted in these dark matter subhalos as a function of projected cluster-centric radius. To quantify the extent of the dark matter halos of cluster galaxies, we introduce the half-mass radius r 1/2 as a diagnostic, and study its evolution with projected cluster-centric distance R as a function of redshift. We find a well-defined trend for (r 1/2, R): the closer the galaxies are to the center of the cluster, the smaller the half-mass radius. Interestingly, this trend is inferred in all redshift frames examined in this work ranging from z = 0 to z = 0.7. At z = 0, galaxy halos in the central regions of clusters are found to be highly truncated, with the most compact half-mass radius of 10 kpc. We also find that r 1/2 depends on luminosity and we present scaling relations of r 1/2 with galaxy luminosity. The corresponding total mass of the cluster galaxies is also found to increase with projected cluster-centric distance and luminosity, but with more scatter than the (r 1/2, R) trend. Comparing the distribution of stellar mass to total mass for cluster galaxies, we find that the dark matter component is preferentially stripped, whereas the stellar component is much less affected by tidal forces. We compare these results with galaxy-galaxy lensing probes of r 1/2 and find qualitative agreement. Future surveys with space-based telescopes such as DUNE and SNAP, that combine wide-field and high-resolution imaging, will be able to probe the predicted (r 1/2, R) relation observationally.

  19. Mapping stellar content to dark matter haloes - II. Halo mass is the main driver of galaxy quenching

    Science.gov (United States)

    Zu, Ying; Mandelbaum, Rachel

    2016-04-01

    We develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and galaxy-galaxy lensing of red and blue galaxies in Sloan Digital Sky Survey. Building on the iHOD framework developed by Zu & Mandelbaum, we consider two quenching scenarios: (1) a `halo' quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellites; and (2) a `hybrid' quenching model in which the quenched fraction of galaxies depends on their stellar mass, while the satellite quenching has an extra dependence on halo mass. The two best-fitting models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above 1011 h-2 M⊙. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct weak lensing measurements of locally brightest galaxies. Models in which quenching is not tied to halo mass, including an age-matching model in which galaxy colour depends on halo age at fixed M*, fail to reproduce the observed halo mass for massive blue centrals. We find similar critical halo masses responsible for the quenching of centrals and satellites (˜1.5 × 1012 h-1 M⊙), hinting at a uniform quenching mechanism for both, e.g. the virial shock heating of infalling gas. The success of the iHOD halo quenching model provides strong evidence that the physical mechanism that quenches star formation in galaxies is tied principally to the masses of their dark matter haloes rather than the properties of their stellar components.

  20. CONSTRAINTS ON DARK MATTER ANNIHILATION IN CLUSTERS OF GALAXIES FROM DIFFUSE RADIO EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Storm, Emma; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High St., Santa Cruz, CA 95064 (United States); Rudnick, Lawrence [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

    2013-05-10

    Annihilation of dark matter can result in the production of stable Standard Model particles including electrons and positrons that, in the presence of magnetic fields, lose energy via synchrotron radiation, observable as radio emission. Galaxy clusters are excellent targets to search for or to constrain the rate of dark matter annihilation, as they are both massive and dark matter dominated. In this study, we place limits on dark matter annihilation in a sample of nearby clusters using upper limits on the diffuse radio emission, low levels of observed diffuse emission, or detections of radio mini-halos. We find that the strongest limits on the annihilation cross section are better than limits derived from the non-detection of clusters in the gamma-ray band by a factor of {approx}3 or more when the same annihilation channel and substructure model, but different best-case clusters, are compared. The limits on the cross section depend on the assumed amount of substructure, varying by as much as two orders of magnitude for increasingly optimistic substructure models as compared to a smooth Navarro-Frenk-White profile. In our most optimistic case, using the results of the Phoenix Project, we find that the derived limits reach below the thermal relic cross section of 3 Multiplication-Sign 10{sup -26} cm{sup 3} s{sup -1} for dark matter masses as large as 400 GeV, for the b b-bar annihilation channel. We discuss uncertainties due to the limited available data on the magnetic field structure of individual clusters. We also report the discovery of diffuse radio emission from the central 30-40 kpc regions of the groups M49 and NGC 4636.

  1. Dark matter distribution in X-ray luminous galaxy clusters with Emergent Gravity

    Science.gov (United States)

    Ettori, S.; Ghirardini, V.; Eckert, D.; Dubath, F.; Pointecouteau, E.

    2017-09-01

    We present the radial distribution of the dark matter in two massive, X-ray luminous galaxy clusters, Abell 2142 and Abell 2319, and compare it with the quantity predicted as apparent manifestation of the baryonic mass in the context of the 'Emergent Gravity' scenario, recently suggested from Verlinde. Thanks to the observational strategy of the XMM-Newton Cluster Outskirt Programme (X-COP), using the X-ray emission mapped with XMM-Newton and the Sunyaev-Zel'dovich signal in the Planck survey, we recover the gas density, temperature and thermal pressure profiles up to ∼R200, allowing us to constrain at an unprecedented level the total mass through the hydrostatic equilibrium equation. We show that, also including systematic uncertainties related to the X-ray-based mass modelling, the apparent 'dark' matter shows a radial profile that has a shape different from the traditional dark matter distribution, with larger discrepancies (by a factor of 2-3) in the inner (r < 200 kpc) cluster's regions and a remarkable agreement only across R500.

  2. Massive primordial black holes from hybrid inflation as dark matter and the seeds of galaxies

    Science.gov (United States)

    Clesse, Sébastien; García-Bellido, Juan

    2015-07-01

    In this paper we present a new scenario where massive primordial black holes (PBHs) are produced from the collapse of large curvature perturbations generated during a mild-waterfall phase of hybrid inflation. We determine the values of the inflaton potential parameters leading to a PBH mass spectrum peaking on planetarylike masses at matter-radiation equality and producing abundances comparable to those of dark matter today, while the matter power spectrum on scales probed by cosmic microwave background (CMB) anisotropies agrees with Planck data. These PBHs could have acquired large stellar masses today, via merging, and the model passes both the constraints from CMB distortions and microlensing. This scenario is supported by Chandra observations of numerous BH candidates in the central region of Andromeda. Moreover, the tail of the PBH mass distribution could be responsible for the seeds of supermassive black holes at the center of galaxies, as well as for ultraluminous x-ray sources. We find that our effective hybrid potential can originate e.g. from D-term inflation with a Fayet-Iliopoulos term of the order of the Planck scale but sub-Planckian values of the inflaton field. Finally, we discuss the implications of quantum diffusion at the instability point of the potential, able to generate a Swiss-cheese-like structure of the Universe, eventually leading to apparent accelerated cosmic expansion.

  3. On the coherent rotation of diffuse matter in numerical simulations of clusters of galaxies

    Science.gov (United States)

    Baldi, Anna Silvia; De Petris, Marco; Sembolini, Federico; Yepes, Gustavo; Lamagna, Luca; Rasia, Elena

    2017-03-01

    We present a study on the coherent rotation of the intracluster medium and dark matter components of simulated galaxy clusters extracted from a volume-limited sample of the MUSIC project. The set is re-simulated with three different recipes for the gas physics: (i) non-radiative, (ii) radiative without active galactic nuclei (AGN) feedback and (iii) radiative with AGN feedback. Our analysis is based on the 146 most massive clusters identified as relaxed, 57 per cent of the total sample. We classify these objects as rotating and non-rotating according to the gas spin parameter, a quantity that can be related to cluster observations. We find that 4 per cent of the relaxed sample is rotating according to our criterion. By looking at the radial profiles of their specific angular momentum vector, we find that the solid body model is not a suitable description of rotational motions. The radial profiles of the velocity of the dark matter show a prevalence of the random velocity dispersion. Instead, the intracluster medium profiles are characterized by a comparable contribution from the tangential velocity and the dispersion. In general, the dark matter component dominates the dynamics of the clusters, as suggested by the correlation between its angular momentum and the gas one, and by the lack of relevant differences among the three sets of simulations.

  4. The potential of the dwarf galaxy Triangulum II for dark matter indirect detection

    Science.gov (United States)

    Genina, Anna; Fairbairn, Malcolm

    2016-12-01

    The recently discovered object Triangulum II appears to be an ultrafaint dwarf spheroidal galaxy which may be one of the most dark-matter-dominated objects yet known. In this work we try to estimate the potential of this object for studies of the indirect detection of self-annihilating dark matter by obtaining its astrophysical J-factor. We perform a basic estimate of the velocity gradient to look for signs of the halo being tidally disrupted but show that the observed value is statistically compatible with zero velocity gradient. We solve the spherical Jeans equation using Markov chain Monte Carlo engine GreAT and the Jeans analysis part of the CLUMPY package. We find the results point towards a very large J-factor, appearing to make Triangulum II one of the best targets in the search for dark matter. However we stress that the very small number of line of sight velocities currently available for this object make follow-up studies essential.

  5. Baryonic and dark matter distribution in cosmological simulations of spiral galaxies

    CERN Document Server

    Mollitor, Pol; Teyssier, Romain

    2014-01-01

    We study three high resolution cosmological hydrodynamical simulations of Milky Way-sized halos including a comparison with the corresponding DM-only counterparts performed with the adaptive mesh refinement code RAMSES. We analyse the stellar and the gas distribution and find one of our simulated galaxies with interesting Milky Way-like features with regard to several observational tests. Thanks to consistently tuned star formation rate and supernovae feedback, we manage to obtain an extended disk and a flat rotation curve with a circular velocity and a dark matter density in the solar neighbourhood in agreement with observations. With a careful look at the derivation of the stellar-to-halo mass ratio, we also obtain competitive values for this criterion. Concerning the dark matter distribution, we explicitly show the interaction with the baryons and show how the dark matter is first contracted by star formation and then cored by feedback processes. Analysing the clump spectrum, we find a shift in mass with r...

  6. Galaxy UV-luminosity Function and Reionisation Constraints on Axion Dark Matter

    CERN Document Server

    Bozek, Brandon; Silk, Joseph; Wyse, Rosemary F G

    2014-01-01

    If the dark matter (DM) were composed of axions, then structure formation in the Universe would be suppressed below the axion Jeans scale. Using an analytic model for the halo mass function of a mixed dark matter model with axions and CDM, combined with the abundance-matching technique, we construct the UV luminosity function. Axions suppress high-$z$ galaxy formation and the UV-luminosity function is truncated at a faintest limiting magnitude. From the UV-luminosity function, we predict the reionisation history of the universe and find that axion dark matter causes reionisation to occur at lower redshift. We search for evidence of axions using the Hubble ultra-deep field UV-luminosity function in the redshift range $z=6$ to $10$, and the optical depth to reionisation, $\\tau$, as measured from CMB polarisation. All probes we consider consistently exclude $m_a\\lesssim 10^{-23}\\text{ eV}$ from contributing more than half of the DM, with our strongest constraint ruling this model out at more than $8\\sigma$ signi...

  7. NIHAO project II: Halo shape, phase-space density and velocity distribution of dark matter in galaxy formation simulations

    CERN Document Server

    Butsky, Iryna; Dutton, Aaron A; Wang, Liang; Stinson, Greg S; Penzo, Camilla; Kang, Xi; Keller, Ben W; Wadsley, James

    2015-01-01

    We show the effect of galaxy formation on the dark matter (DM) distribution across a wide range of halo masses. We focus on how baryon physics changes the dark matter halo shape, the so called "pseudo phase-space density distribution" and the velocity distribution within the virial radius, Rvir and in the solar neighborhood. This study is based on the NIHAO galaxy formation simulations, a large suite of cosmological zoom-in simulations. The galaxies reproduce key properties of observed galaxies, and hence offer unique insight into how baryons change the dark matter morphology and kinematics. When compared to dark matter only simulations, the NIHAO haloes have similar shapes at Rvir, but are substantially rounder inside ~0.1 Rvir. In DM-only simulations the inner halo has a minor-to-major axis ratio of c/a~0.5. In hydro simulations c/a increases with halo mass and integrated star formation efficiency, reaching ~0.8 at the Milky Way mass, reconciling a long-standing conflict between observations and DM only sim...

  8. The XLENS Project : Do More Massive Early-Type Galaxies Have More Dark Matter or Different Stellar IMFs?

    NARCIS (Netherlands)

    Spiniello, Chiara; Thomas, Daniel; Pasquali, Anna; Ferreras, Ignacio

    The X-shooter Lens Survey (XLENS) aims to study the interplay of dark matter (DM) and stellar content in the inner regions of massive early-type galaxies (ETGs) by combining strong gravitational lensing, dynamical models, and spectroscopic stellar population analysis. XLENS targets a sample of ETGs

  9. Determination of the abundance of cosmic matter via the cell count moments of the galaxy distribution (1)

    CERN Document Server

    Bel, Julien

    2013-01-01

    We demonstrate that accurate and precise information about the matter content of the universe can be retrieved via a simple cell count analysis of the 3D spatial distribution of galaxies. A new clustering statistic, the {\\it galaxy clustering ratio} $\\eta$, is the key in this process. This is defined as the ratio between one- and two-point second-order moments of the smoothed galaxy density distribution. The distinguishing feature of this statistic is its universality: on large cosmic scales both galaxies (in redshift space) and mass (in real space) display the same $\\eta$ amplitude. This quantity, in addition, does not evolve as a function of redshift. As a consequence, the $\\eta$ statistic provides insight into characteristic parameters of the real-space power spectrum of mass density fluctuations without the need to specify the galaxy biasing function, a model for galaxy redshift distortions nor the growing mode of density ripples. We demonstrate the method with the luminous red galaxy (LRG) sample extract...

  10. Gamma Rays from Clusters and Groups of Galaxies: Cosmic Rays versus Dark Matter

    CERN Document Server

    Jeltema, Tesla E; Profumo, Stefano

    2008-01-01

    Clusters of galaxies have not yet been detected at gamma-ray frequencies; however, the recently launched Fermi Gamma-ray Space Telescope, formerly known as GLAST, could provide the first detections in the near future. Clusters are expected to emit gamma rays as a result of (1) a population of high-energy primary and re-accelerated secondary cosmic rays (CR) fueled by structure formation and merger shocks, active galactic nuclei and supernovae, and (2) particle dark matter (DM) annihilation. In this paper, we ask the question of whether the Fermi telescope will be able to discriminate between the two emission processes. We present data-driven predictions for a large X-ray flux limited sample of galaxy clusters and groups. We point out that the gamma ray signals from CR and DM can be comparable. In particular, we find that poor clusters and groups are the systems predicted to have the highest DM to CR emission at gamma-ray energies. Based on detailed Fermi simulations, we study observational handles that might ...

  11. White dwarfs with hydrogen-deficient atmospheres and the dark matter content of the Galaxy

    CERN Document Server

    Torres, S; Isern, J; Garcia-Berro, E

    2010-01-01

    The nature of the several microlensing events observed by the MACHO team towards the Large Magellanic Cloud (LMC) is still a subject of debate. Low-mass substellar objects and stars with masses larger than ~M_{sun} have been ruled out as major components of a Massive Astrophysical Compact Halo Object (MACHO) Galactic halo, while stars of half a solar mass seem to be viable candidates. Main sequence stars have been already discarded, and there are tight restrictions on the role played by white dwarfs with hydrogen-dominated atmospheres. In this paper we evaluate the contribution to the dark matter content of the Galaxy of white dwarfs with hydrogen-deficient atmospheres. For this purpose we use a Monte Carlo simulator which incorporates up-to-date evolutionary sequences of white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres. We also take into account detailed descriptions of the thick disk and the halo of our Galaxy as well as of a reliable model of the LMC. We find that the contribution of whit...

  12. The Warped Science of Interstellar

    CERN Document Server

    Luminet, Jean-Pierre

    2015-01-01

    The science fiction film, Interstellar, tells the story of a team of astronauts searching a distant galaxy for habitable planets to colonize. Interstellar's story draws heavily from contemporary science. The film makes reference to a range of topics, from established concepts such as fast-spinning black holes, accretion disks, tidal effects, and time dilation, to far more speculative ideas such as wormholes, time travel, additional space dimensions, and the theory of everything. The aim of this article is to decipher some of the scientific notions which support the framework of the movie.

  13. No need for dark matter in galaxy clusters within Galileon theory

    CERN Document Server

    Salzano, Vincenzo; Dabrowski, Mariusz P; Capozziello, Salvatore

    2016-01-01

    Modified gravity theories with a screening mechanism have acquired much interest recently in the quest for a viable alternative to General Relativity on cosmological scales, given their intrinsic property of being able to pass Solar System scale tests and, at the same time, to possibly drive universe acceleration on much larger scales. Here, we explore the possibility that the same screening mechanism, or its partial breaking at a certain astrophysical scale, might be responsible of those gravitational effects which, in the context of general relativity, are generally attributed to Dark Matter. We consider a recently proposed extension of covariant Galileon models in the so-called "beyond Horndeski" scenario, where a breaking of the Vainshtein mechanism is possible and, thus, some peculiar observational signatures should be detectable and make it distinguishable from general relativity. We apply this model to a sample of clusters of galaxies observed under the CLASH survey, using both new data from gravitatio...

  14. On the core-halo distribution of dark matter in galaxies

    CERN Document Server

    Ruffini, Remo; Rueda, Jorge Armando

    2014-01-01

    We investigate the distribution of dark matter in galaxies by solving the equations of equilibrium of a self-gravitating system of massive fermions (`inos') at selected temperatures and degeneracy parameters within general relativity. The most general solutions present, as a function of the radius, a segregation of three physical regimes: 1) an inner core of almost constant density governed by degenerate quantum statistics; 2) an intermediate region with a sharply decreasing density distribution followed by an extended plateau, implying quantum corrections; 3) a decreasing density distribution $\\rho\\propto r^{-2}$ leading to flat rotation curves fulfilling the classical Boltzmann statistics. The mass of the inos is determined as an eigenfunction of the mass of the inner quantum cores. We compare and contrast this mass value with the lower limit on the particle mass by Tremaine and Gunn (1979), and show that the latter is approached for the less degenerate quantum cores in agreement with the fixed halo observa...

  15. Secondary infall model and dark matter scaling relations in intermediate redshift early - type galaxies

    CERN Document Server

    Cardone, V F; Tortora, C; Napolitano, N R

    2011-01-01

    Scaling relations among dark matter (DM) and stellar quantities are a valuable tool to constrain formation scenarios and the evolution of galactic structures. However, most of the DM properties are actually not directly measured, but derived through model dependent mass mapping procedures. It is therefore crucial to adopt theoretically and observationally well founded models. We use here an updated version of the secondary infall model (SIM) to predict the halo density profile, taking into account the effects of angular momentum, dissipative friction and baryons collapse. The resulting family of halo profiles depends on one parameter only, the virial mass, and nicely fits the projected mass and aperture velocity dispersion of a sample of intermediate redshift lens galaxies. We derive DM related quantities (namely the column density and the Newtonian acceleration) and investigate their correlations with stellar mass, luminosity, effective radius and virial mass.

  16. Prospects of detecting gamma-ray emission from galaxy clusters: cosmic rays and dark matter annihilations

    CERN Document Server

    Pinzke, Anders; Bergstrom, Lars

    2011-01-01

    We study the possibility for detecting gamma-ray emission in galaxy clusters. We consider 1) cosmic ray (CR) induced pion decay which is thought to dominate the astrophysical signal from clusters, 2) different representative benchmark models of supersymmetric dark matter (DM), and 3) leptophilic models of DM annihilation that include a Sommerfeld enhancement (SFE). To model DM annihilation, we consider hadronization of annihilating neutralinos, internal bremsstrahlung, and inverse Compton emission from the cosmic microwave background as well as from a realistic spatial and spectral distribution of dust and stellar light. We predict the Virgo and Fornax clusters to be the brightest DM sources and find a particularly low CR induced background for Fornax. For a minimum substructure mass given by the DM free-streaming scale, we find a substructure boost factor of more than 1000. Since the annihilation flux of substructures is mostly contributed by the regions around the virial radius, the resulting surface bright...

  17. Dark Matter Annihilation and Decay Profiles for the Reticulum II Dwarf Spheroidal Galaxy

    Science.gov (United States)

    Bonnivard, Vincent; Combet, Céline; Maurin, David; Geringer-Sameth, Alex; Koushiappas, Savvas M.; Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W.; Bailey, John I., III

    2015-08-01

    The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter (DM). In this work, we reconstruct the DM annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum II. Using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System, we find Reticulum II’s J-factor to be among the largest of any Milky Way dSph. We have checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum II may provide a unique window on DM particle properties.

  18. Host galaxies and environment of active galactic nuclei : a study of the XMM large scale structure survey

    NARCIS (Netherlands)

    Tasse, Cyril

    2008-01-01

    Active galactic nuclei (AGN) result from the infall of matter onto the super-massive black holes that are situated at the centres of galaxies. This process releases an enormous amount of energy into the inter-stellar and inter-galactic medium. Hence, the study of AGN becomes essential in the context

  19. Evolution of the stellar-to-dark matter relation: Separating star-forming and passive galaxies from z = 1 to 0

    Energy Technology Data Exchange (ETDEWEB)

    Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Leauthaud, Alexie; Bundy, Kevin [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, and Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Behroozi, Peter; Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, Stanford University, and SLAC National Accelerator Laboratory, Stanford, CA 94305 (United States); Massey, Richard [Institute for Computational Cosmology, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Rhodes, Jason, E-mail: jeremy.tinker@nyu.edu [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

    2013-12-01

    We use measurements of the stellar mass function, galaxy clustering, and galaxy-galaxy lensing within the COSMOS survey to constrain the stellar-to-halo mass relation (SHMR) of star forming and quiescent galaxies over the redshift range z = [0.2, 1.0]. For massive galaxies, M {sub *} ≳ 10{sup 10.6} M {sub ☉}, our results indicate that star-forming galaxies grow proportionately as fast as their dark matter halos while quiescent galaxies are outpaced by dark matter growth. At lower masses, there is minimal difference in the SHMRs, implying that the majority low-mass quiescent galaxies have only recently been quenched of their star formation. Our analysis also affords a breakdown of all COSMOS galaxies into the relative numbers of central and satellite galaxies for both populations. At z = 1, satellite galaxies dominate the red sequence below the knee in the stellar mass function. But the number of quiescent satellites exhibits minimal redshift evolution; all evolution in the red sequence is due to low-mass central galaxies being quenched of their star formation. At M {sub *} ∼ 10{sup 10} M {sub ☉}, the fraction of central galaxies on the red sequence increases by a factor of 10 over our redshift baseline, while the fraction of quenched satellite galaxies at that mass is constant with redshift. We define a 'migration rate' to the red sequence as the time derivative of the passive galaxy abundances. We find that the migration rate of central galaxies to the red sequence increases by nearly an order of magnitude from z = 1 to z = 0. These results imply that the efficiency of quenching star formation for centrals is increasing with cosmic time, while the mechanisms that quench the star formation of satellite galaxies in groups and clusters is losing efficiency.

  20. Dark matter distribution in the Coma cluster from galaxy kinematics: breaking the mass-anisotropy degeneracy

    Science.gov (United States)

    Łokas, Ewa L.; Mamon, Gary A.

    2003-08-01

    We study velocity moments of elliptical galaxies in the Coma cluster using Jeans equations. The dark matter distribution in the cluster is modelled by a generalized formula based upon the results of cosmological N-body simulations. Its inner slope (cuspy or flat), concentration and mass within the virial radius are kept as free parameters, as well as the velocity anisotropy, assumed independent of position. We show that the study of line-of-sight velocity dispersion alone does not allow us to constrain the parameters. By a joint analysis of the observed profiles of velocity dispersion and kurtosis, we are able to break the degeneracy between the mass distribution and velocity anisotropy. We determine the dark matter distribution at radial distances larger than 3 per cent of the virial radius and we find that the galaxy orbits are close to isotropic. Due to limited resolution, different inner slopes are found to be consistent with the data and we observe a strong degeneracy between the inner slope α and concentration c; the best-fitting profiles have the two parameters related with c= 19-9.6α. Our best-fitting Navarro-Frenk-White profile has concentration c= 9, which is 50 per cent higher than standard values found in cosmological simulations for objects of similar mass. The total mass within the virial radius of 2.9h-170 Mpc is 1.4 × 1015h-170 Msolar (with 30 per cent accuracy), 85 per cent of which is dark. At this distance from the cluster centre, the mass-to-light ratio in the blue band is 351h70 solar units. The total mass within the virial radius leads to estimates of the density parameter of the Universe, assuming that clusters trace the mass-to-light ratio and baryonic fraction of the Universe, with Ω0= 0.29 +/- 0.1.

  1. Substructure and galaxy formation in the Copernicus Complexio warm dark matter simulations

    Science.gov (United States)

    Bose, Sownak; Hellwing, Wojciech A.; Frenk, Carlos S.; Jenkins, Adrian; Lovell, Mark R.; Helly, John C.; Li, Baojiu; Gonzalez-Perez, Violeta; Gao, Liang

    2017-02-01

    We use the Copernicus Complexio (COCO) high-resolution N-body simulations to investigate differences in the properties of small-scale structures in the standard cold dark matter (CDM) model and in a model with a cutoff in the initial power spectrum of density fluctuations consistent with both a thermally produced warm dark matter (WDM) particle with a rest mass of 3.3 keV and a sterile neutrino with mass 7 keV and leptogenesis parameter L6 = 8.7. The latter corresponds to the `coldest' model with this sterile neutrino mass compatible with the identification of the recently detected 3.5 keV X-ray line as resulting from particle decay. CDM and WDM predict very different number densities of subhaloes with mass ≲ 109 h-1 M⊙ although they predict similar, nearly universal, normalized subhalo radial density distributions. Haloes and subhaloes in both models have cuspy Navarro-Frenk-White profiles, but WDM subhaloes below the cut-off scale in the power spectrum (corresponding to maximum circular velocities Vmaxz = 0 ≤ 50 kms- 1) are less concentrated than their CDM counterparts. We make predictions for observable properties using the GALFORM semi-analytic model of Galaxy formation. Both models predict Milky Way satellite luminosity functions consistent with observations, although the WDM model predicts fewer very faint satellites. This model, however, predicts slightly more UV bright galaxies at redshift z > 7 than CDM, but both are consistent with observations. Gravitational lensing offers the best prospect of distinguishing between the models.

  2. Evolution of the Stellar-to-Dark Matter Relation: Separating Star-Forming and Passive Galaxies from z=1 to 0

    CERN Document Server

    Tinker, Jeremy L; Bundy, Kevin; George, Matthew R; Behroozi, Peter; Massey, Richard; Rhodes, Jason; Wechsler, Risa

    2013-01-01

    We use measurements of the stellar mass function, galaxy clustering, and galaxy-galaxy lensing within the COSMOS survey to constrain the stellar-to-halo mass relation (SHMR) of star forming and quiescent galaxies over the redshift range z=[0.2,1.0]. For massive galaxies, M*>~10^10.6 Msol, our results indicate that star-forming galaxies grow proportionately as fast as their dark matter halos while quiescent galaxies are outpaced by dark matter growth. At lower masses, there is minimal difference in the SHMRs, implying that the majority low-mass quiescent galaxies have only recently been quenched of their star formation. Our analysis also affords a breakdown of all COSMOS galaxies into the relative numbers of central and satellite galaxies for both populations. At z=1, satellite galaxies dominate the red sequence below the knee in the stellar mass function. But the number of quiescent satellites exhibits minimal redshift evolution; all evolution in the red sequence is due to low-mass central galaxies being quen...

  3. H.E.S.S. constraints on dark matter annihilations towards the sculptor and carina dwarf galaxies

    Science.gov (United States)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Barnacka, A.; Barres de Almeida, U.; Bazer-Bachi, A. R.; Becherini, Y.; Becker, J.; Behera, B.; Bernlöhr, K.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Borrel, V.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L.-M.; Clapson, A. C.; Coignet, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O. C.; Dubois, F.; Dubus, G.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gallant, Y. A.; Gast, H.; Gérard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Göring, D.; Hague, J. D.; Hampf, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Hofverberg, P.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Kerschhaggl, M.; Khangulyan, D.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Laffon, H.; Lamanna, G.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, D.; Maxted, N.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; Olive, J.-F.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Panter, M.; Paz Arribas, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de Los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Ryde, F.; Sahakian, V.; Santangelo, A.; Schlickeiser, R.; Schöck, F. M.; Schönwald, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Sikora, M.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tibolla, O.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Viana, A.; Vincent, P.; Vivier, M.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; Wierzcholska, A.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; H.E.S.S. Collaboration

    2011-03-01

    The Sculptor and Carina dwarf spheroidal galaxies were observed with the H.E.S.S. Cherenkov telescope array between January 2008 and December 2009. The data sets consist of a total of 11.8 h and 14.8 h of high quality data, respectively. No gamma-ray signal was detected at the nominal positions of these galaxies above 220 GeV and 320 GeV, respectively. Upper limits on the gamma-ray fluxes at 95% CL assuming two forms for the spectral energy distribution (a power law shape and one derived from dark matter annihilation) are obtained at the level of 10-13-10-12 cm-2 s-1 in the TeV range. Constraints on the velocity weighted dark matter particle annihilation cross section for both Sculptor and Carina dwarf galaxies range from ˜ 10-21 cm3 s-1 down to ˜ 10-22 cm3 s-1 depending on the dark matter halo model used. Possible enhancements of the gamma-ray flux are studied: the Sommerfeld effect, which is found to exclude some dark matter particle masses, the internal Bremsstrahlung and clumps in the dark-matter halo distributions.

  4. Galaxy growth from redshift 5 to 0 at fixed comoving number density

    CERN Document Server

    van de Voort, Freeke

    2016-01-01

    Studying the average properties of galaxies at a fixed comoving number density over a wide redshift range has become a popular observational method, because it may trace the evolution of galaxies statistically. We test this method by comparing the evolution of galaxies at fixed number density and by following individual galaxies through cosmic time (z=0-5) in cosmological, hydrodynamical simulations from OWLS. Comparing progenitors, descendants, and galaxies selected at fixed number density at each redshift, we find differences of up to a factor of three for galaxy and interstellar medium (ISM) masses. The difference is somewhat larger for black hole masses. The scatter in ISM mass increases significantly towards low redshift with all selection techniques. We use the fixed number density technique to study the assembly of dark matter, gas, stars, and black holes and the evolution in accretion and star formation rates. We find three different regimes for massive galaxies, consistent with observations: at high ...

  5. Contribution from normal and starburst galaxies to the extragalactic gamma-ray background (EGRB)

    Institute of Scientific and Technical Information of China (English)

    Debbijoy Bhattacharya; Parameswaran Sreekumar

    2009-01-01

    The extragalactic diffuse emission at γ-ray energies has interesting cosmo-logical implications since these photons suffer little or no attenuation during their prop-agation from the site of origin. The emission could originate from either truly diffuse processes or from unresolved point sources such as AGNs, normal galaxies and starburst galaxies. Here, we examine the unresolved point source origin of the extragalactic γ-ray background emission from normal galaxies and starburst galaxies. γ-ray emission from normal galaxies is primarily coming from cosmic-ray interactions with interstellar mat-ter and radiation (~90%) along with a small contribution from discrete point sources (~10%). Starburst galaxies are expected to have enhanced supernovae activity which leads to higher cosmic-ray densities, making starburst galaxies sufficiently luminous at γ-ray energies to be detected by the current γ-ray mission (Fermi Gamma-ray Space Telescope).

  6. Dark matter and IMF normalization in Virgo dwarf early-type galaxies

    Science.gov (United States)

    Tortora, C.; La Barbera, F.; Napolitano, N. R.

    2016-01-01

    In this work, we analyse the dark matter (DM) fraction, fDM, and mass-to-light ratio mismatch parameter, δIMF (computed with respect to a Milky Way-like initial mass function), for a sample of 39 dwarf early-type galaxies in the Virgo cluster. Both fDM and δIMF are estimated within the central (one effective radius) galaxy regions, with a Jeans dynamical analysis that relies on galaxy velocity dispersions, structural parameters, and stellar mass-to-light ratios from the SMAKCED survey. In this first attempt to constrain, simultaneously, the initial mass function (IMF) normalization and the DM content, we explore the impact of different assumptions on the DM model profile. On average, for an Navarro, Frenk & White (NFW) profile, the δIMF is consistent with a Chabrier-like normalization ({δ _IMF}˜ 1), with {f_DM}˜ 0.35. One of the main results of this work is that for at least a few systems the δIMF are heavier than the Milky Way-like value (i.e. either top- or bottom-heavy). When introducing tangential anisotropy, larger δIMF and smaller fDM are derived. Adopting a steeper concentration-mass relation than that from simulations, we find lower δIMF ( ≲ 1) and larger fDM. A constant M/L profile with null fDM gives the heaviest δIMF (˜2). In the MONDian framework, we find consistent results to those for our reference NFW model. If confirmed, the large scatter of δIMF for dEs would provide (further) evidence for a non-universal IMF in early-type systems. On average, our reference fDM estimates are consistent with those found for low-σe (˜ 100 km s^{-1}) early-type galaxies (ETGs). Furthermore, we find fDM consistent with values from the SMAKCED survey, and find a double-value behaviour of fDM with stellar mass, which mirrors the trend of dynamical M/L and global star formation efficiency (from abundance matching estimates) with mass.

  7. Dominant dark matter and a counter rotating disc: MUSE view of the low luminosity S0 galaxy NGC 5102

    CERN Document Server

    Mitzkus, Martin; Walcher, C Jakob

    2016-01-01

    The kinematics and stellar populations of the low-mass nearby S0 galaxy NGC 5102 are studied from integral field spectra taken with the Multi-Unit Spectroscopic Explorer (MUSE). The kinematic maps reveal for the first time that NGC 5102 has the characteristic 2 sigma peaks indicative of galaxies with counter-rotating discs. This interpretation is quantitatively confirmed by fitting two kinematic components to the observed spectra. Through stellar population analysis we confirm the known young stellar population in the centre and find steep age and metallicity gradients. We construct axisymmetric Jeans anisotropic models of the stellar dynamics to investigate the initial mass function (IMF) and the dark matter halo of the galaxy. The models show that this galaxy is quite different from all galaxies previously studied with a similar approach: even within the half-light radius, it cannot be approximated with the self-consistent mass-follows-light assumption. Including an NFW dark matter halo, we need a heavy IMF...

  8. Interstellar molecular clouds

    Science.gov (United States)

    Bally, J.

    1986-04-01

    The physical properties of the molecular phase of the interstellar medium are studied with regard to star formation and the structure of the Galaxy. Most observations of molecular clouds are made with single-dish, high-surface precision radio telescopes, with the best resolution attainable at 0.2 to 1 arcmin; the smallest structures that can be resolved are of order 10 to the 17th cm in diameter. It is now believed that: (1) most of the mass of the Galaxy is in the form of giant molecular clouds; (2) the largest clouds and those responsible for most massive star formation are concentrated in spiral arms; (3) the molecular clouds are the sites of perpetual star formation, and are significant in the chemical evolution of the Galaxy; (4) giant molecular clouds determine the evolution of the kinematic properties of galactic disk stars; (5) the total gas content is diminishing with time; and (6) most clouds have supersonic internal motions and do not form stars on a free-fall time scale. It is concluded that though progress has been made, more advanced instruments are needed to inspect the processes operating within stellar nurseries and to study the distribution of the molecular clouds in more distant galaxies. Instruments presently under construction which are designed to meet these ends are presented.

  9. The behaviour of dark matter associated with 4 bright cluster galaxies in the 10kpc core of Abell 3827

    CERN Document Server

    Massey, Richard; Smit, Renske; Swinbank, Mark; Kitching, Thomas; Harvey, David; Jauzac, Mathilde; Israel, Holger; Clowe, Douglas; Edge, Alastair; Hilton, Matt; Jullo, Eric; Leonard, Adrienne; Liesenborgs, Jori; Merten, Julian; Mohammed, Irshad; Nagai, Daisuke; Richard, Johan; Robertson, Andrew; Saha, Prasenjit; Santana, Rebecca; Stott, John; Tittley, Eric

    2015-01-01

    Galaxy cluster Abell 3827 hosts the stellar remnants of four almost equally bright elliptical galaxies within a core of radius 10kpc. Such corrugation of the stellar distribution is very rare, and suggests recent formation by several simultaneous mergers. We map the distribution of associated dark matter, using new Hubble Space Telescope imaging and VLT/MUSE integral field spectroscopy of a gravitationally lensed system threaded through the cluster core. We find that each of the central galaxies retains a dark matter halo, but that (at least) one of these is spatially offset from its stars. The best-constrained offset is 1.62+/-0.48kpc, where the 68% confidence limit includes both statistical error and systematic biases in mass modelling. Such offsets are not seen in field galaxies, but are predicted during the long infall to a cluster, if dark matter self-interactions generate an extra drag force. With such a small physical separation, it is difficult to definitively rule out astrophysical effects operating ...

  10. The SWELLS survey. IV. Precision measurements of the stellar and dark matter distributions in a spiral lens galaxy

    CERN Document Server

    Barnabè, Matteo; Marshall, Philip J; Auger, Matthew W; Brewer, Brendon J; Treu, Tommaso; Bolton, Adam S; Koo, David C; Koopmans, Léon V E

    2012-01-01

    We construct a fully self-consistent mass model for the lens galaxy J2141 at z=0.14, and use it to improve on previous studies by modelling its gravitational lensing effect, gas rotation curve and stellar kinematics simultaneously. We adopt a very flexible axisymmetric mass model constituted by a generalized NFW dark matter halo and a stellar mass distribution obtained by deprojecting the MGE fit to the high-resolution K'-band LGSAO imaging data of the galaxy, with the (spatially constant) M/L ratio as a free parameter. We model the stellar kinematics by solving the anisotropic Jeans equations. We find that the inner logarithmic slope of the dark halo is weakly constrained (gamma = 0.82^{+0.65}_{-0.54}), and consistent with an unmodified NFW profile. We infer the galaxy to have (i) a dark matter fraction within 2.2 disk radii of 0.28^{+0.15}_{-0.10}, independent of the galaxy stellar population, implying a maximal disk for J2141; (ii) an apparently uncontracted dark matter halo, with concentration c_{-2} = 7....

  11. Interstellar holography

    NARCIS (Netherlands)

    Walker, M. A.; Koopmans, L. V. E.; Stinebring, D. R.; van Straten, W.

    2008-01-01

    The dynamic spectrum of a radio pulsar is an in-line digital hologram of the ionized interstellar medium. It has previously been demonstrated that such holograms permit image reconstruction, in the sense that one can determine an approximation to the complex electric field values as a function of Do

  12. Evolution of central dark matter of early-type galaxies up to z ˜ 0.8

    Science.gov (United States)

    Tortora, C.; Napolitano, N. R.; Saglia, R. P.; Romanowsky, A. J.; Covone, G.; Capaccioli, M.

    2014-11-01

    We investigate the evolution of dark and luminous matter in the central regions of early-type galaxies up to z ˜ 0.8. We use a spectroscopically selected sample of 154 cluster and field galaxies from the ESO Distant Clusters Survey (EDisCS), covering a wide range in redshifts (z ˜ 0.4-0.8), stellar masses (log M⋆/M⊙ ˜ 10.5-11.5 dex) and velocity dispersions (σ⋆ ˜ 100-300 km s-1). We obtain central dark matter (DM) fractions by determining the dynamical masses from Jeans modelling of galaxy aperture velocity dispersions and the M⋆ from galaxy colours, and compare the results with local samples. We discuss how the correlations of central DM with galaxy size (i.e. the effective radius, Re), M⋆ and σ⋆ evolve as a function of redshift, finding clear indications that local galaxies are, on average, more DM dominated than their counterparts at larger redshift. This DM fraction evolution with z can be only partially interpreted as a consequence of the size-redshift evolution. We discuss our results within galaxy formation scenarios, and conclude that the growth in size and DM content which we measure within the last 7 Gyr is incompatible with passive evolution, while it is well reproduced in the multiple minor merger scenario. We also discuss the impact of the initial mass function (IMF) on our DM inferences and argue that this can be non-universal with the look-back time. In particular, we find that the Salpeter IMF can be better accommodated by low-redshift systems, while producing stellar masses at high z which are unphysically larger than the estimated dynamical masses (particularly for lower σ⋆ systems).

  13. Systematic or Signal? How dark matter misalignments can bias strong lensing models of galaxy clusters

    CERN Document Server

    Harvey, David; Jauzac, Mathilde

    2016-01-01

    We explore how assuming that mass traces light in strong gravitational lensing models can lead to systematic errors in the predicted position of multiple images. Using a model based on the galaxy cluster MACSJ0416 (z = 0.397) from the Hubble Frontier Fields, we split each galactic halo into a baryonic and dark matter component. We then shift the dark matter halo such that it no longer aligns with the baryonic halo and investigate how this affects the resulting position of multiple images. We find for physically motivated misalignments in dark halo position, ellipticity, position angle and density profile, that multiple images can move on average by more than 0.2" with individual images moving greater than 1". We finally estimate the full error induced by assuming that light traces mass and find that this assumption leads to an expected RMS error of 0.5", almost the entire error budget observed in the Frontier Fields. Given the large potential contribution from the assumption that light traces mass to the erro...

  14. Simulations of galaxies formed in warm dark matter halos of masses at the filtering scale

    CERN Document Server

    Colin, Pedro; Gonzalez-Samaniego, Alejandro; Velazquez, Hector

    2014-01-01

    We present zoom-in N-body + Hydrodynamic simulations of dwarf central galaxies formed in Warm Dark Matter (WDM) halos with masses at present-day of $2-4\\times 10^{10}$ \\msun. Two different cases are considered, the first one when halo masses are close to the corresponding half-mode filtering scale \\Mhm\\ (\\mwdm =1.2 keV), and the second when they are 20 to 30 times the corresponding \\Mhm\\ (\\mwdm = 3.0 keV). The WDM simulations are compared with the respective Cold Dark Matter (CDM) simulations. The dwarfs formed in halos of masses (20-30)\\Mhm have roughly similar properties and evolution than their CDM counterparts; on the contrary, those formed in halos of masses around \\Mhm, are systematically different from their CDM counterparts. As compared to the CDM dwarfs, they assemble the dark and stellar masses later, having mass-weighted stellar ages 1.4--4.8 Gyr younger; their circular velocity profiles are shallower, with maximal velocities 20--60% lower; their stellar distributions are much less centrally concen...

  15. NIHAO X: Reconciling the local galaxy velocity function with Cold Dark Matter via mock HI observations

    CERN Document Server

    Macciò, Andrea V; Dutton, Aaron A; Obreja, Aura; Wang, Liang; Stinson, Greg R; Kang, Xi

    2016-01-01

    We used 87 high resolution hydrodynamical cosmological simulations from the NIHAO suite to investigate the relation between the maximum circular velocity (Vmax) of a dark matter halo in a collisionless simulation and the velocity width of the HI gas in the same halo in the hydrodynamical simulation. These two quantities are normally used to compare theoretical and observational velocity functions and have led to a possible discrepancy between observations and predictions based on the Cold Dark Matter (CDM) model. We show that below 100 km/s, there is clear bias between HI based velocities and Vmax, that leads to an underestimation of the actual circular velocity of the halo. When this bias is taken into account the CDM model has no trouble in reproducing the observed velocity function and no lack of low velocity galaxies is actually present. Our simulations also reproduce the linewidth - stellar mass (Tully-Fisher) relation and HI sizes, indicating that the HI gas in our simulations is as extended as observed...

  16. Neutrino Portal Dark Matter: From Dwarf Galaxies to IceCube

    CERN Document Server

    Cherry, John F; Shoemaker, Ian M

    2014-01-01

    It has been suggested that the baseline scenario of collisionless cold dark matter over-predicts the numbers of satellite galaxies, as well as the dark matter (DM) densities in galactic centers. This apparent lack of structure at small scales can be accounted for if one postulates neutrino-DM and DM-DM interactions mediated by light O(MeV) force carriers. In this letter, we consider a simple, consistent model of neutrinophilic DM with these features where DM and a "secluded" SM-singlet neutrino species are charged under a new $U(1)$ gauge symmetry. An important ingredient of this model is that the secluded sector couples to the Standard Model fields only through neutrino mixing. We observe that the secluded and active neutrinos recouple, leading to a large relic secluded neutrino population. This relic population can prevent small-scale halos from collapsing, while at same time significantly modifying the optical depth of ultra-high-energy neutrinos recently observed at Icecube. We find that the bulk of the p...

  17. gamma-rays from annihilating dark matter in galaxy clusters: stacking vs single source analysis

    CERN Document Server

    Nezri, E; Combet, C; Maurin, D; Pointecouteau, E; Hinton, J A

    2012-01-01

    Clusters of galaxies are potentially important targets for indirect searches for dark matter annihilation. Here, we reassess the detection prospects for annihilation in massive halos, based on a statistical investigation of 1743 clusters from the recent MCXC meta-catalogue. We derive a new data-driven limit for the extra-galactic DM annihilation background Jextra-gal>JGal/5 and consider a source-stacking approach. The number of clusters scales with their brightness (boosted by DM substructures) to the power of -2 for an integration angle 0.1deg. It suggests that stacking may provide a significant improvement over a single target analysis for gamma-ray observations at high-energies where the angular resolution achievable is comparable to this angle. In our study the mean angle containing 80% of the dark-matter signal for the entire sample (assuming an NFW DM profile) is 0.15deg. It indicates that instruments with this angular resolution or better would be optimal for a cluster annihilation search based on stac...

  18. The central dark matter content of early-type galaxies: scaling relations and connections with star formation histories

    CERN Document Server

    Napolitano, Nicola R; Tortora, Crescenzo

    2010-01-01

    We examine correlations between the masses, sizes, and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar populations models. We confirm an anti-correlation between size and stellar age, and survey for trends with the central content of dark matter (DM). An average relation between central DM density and galaxy size of ~ Reff^-2 provides the first clear indication of cuspy DM haloes in these galaxies -- akin to standard LCDM haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as expected, deviating from suggestions of a universal halo profile for dwarf and late-type galaxies. We introduce a new fundamental constraint on galaxy formation by finding that the central DM fraction decreases with stellar age. This result is only partially explained by the size-age dependencies, and the residual trend is in the opposite direction to basic DM halo expectations. Therefore we suggest that there may be a con...

  19. Fermi LAT Observation of Diffuse Gamma-Rays Produced through Interactions Between Local Interstellar Matter and High Energy Cosmic Rays

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, A.A.; /Naval Research Lab, Wash., D.C. /Federal City Coll.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Ajello, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U. /Stockholm U., OKC; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, G.; /INFN, Trieste /Trieste U.; Bastieri, D.; /INFN, Padua /Padua U.; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, E.D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, T.H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /Milan Polytechnic /Royal Inst. Tech., Stockholm /Stockholm U., OKC /DAPNIA, Saclay /INFN, Perugia /Perugia U. /NASA, Goddard /Naval Research Lab, Wash., D.C. /George Mason U. /NASA, Goddard /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Montpellier U. /Stockholm U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Bari U. /INFN, Bari /INFN, Bari; /more authors..

    2012-03-30

    Observations by the Large Area Telescope (LAT) on the Fermi mission of diffuse {gamma}-rays in a mid-latitude region in the third quadrant (Galactic longitude l from 200{sup o} to 260{sup o} and latitude |b| from 22{sup o} to 60{sup o}) are reported. The region contains no known large molecular cloud and most of the atomic hydrogen is within 1 kpc of the solar system. The contributions of {gamma}-ray point sources and inverse Compton scattering are estimated and subtracted. The residual {gamma}-ray intensity exhibits a linear correlation with the atomic gas column density in energy from 100 MeV to 10 GeV. The measured integrated {gamma}-ray emissivity is (1.63 {+-} 0.05) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} and (0.66 {+-} 0.02) x 10{sup -26} photons s{sup -1}sr{sup -1} H-atom{sup -1} above 100 MeV and above 300 MeV, respectively, with an additional systematic error of {approx}10%. The differential emissivity from 100 MeV to 10 GeV agrees with calculations based on cosmic ray spectra consistent with those directly measured, at the 10% level. The results obtained indicate that cosmic ray nuclei spectra within 1 kpc from the solar system in regions studied are close to the local interstellar spectra inferred from direct measurements at the Earth within {approx}10%.

  20. No need for dark matter in galaxy clusters within Galileon theory

    Science.gov (United States)

    Salzano, Vincenzo; Mota, David F.; Dabrowski, Mariusz P.; Capozziello, Salvatore

    2016-10-01

    Modified gravity theories with a screening mechanism have acquired much interest recently in the quest for a viable alternative to General Relativity on cosmological scales, given their intrinsic property of being able to pass Solar System scale tests and, at the same time, to possibly drive universe acceleration on much larger scales. Here, we explore the possibility that the same screening mechanism, or its breaking at a certain astrophysical scale, might be responsible of those gravitational effects which, in the context of general relativity, are generally attributed to Dark Matter. We consider a recently proposed extension of covariant Galileon models in the so-called ``beyond Horndeski'' scenario, where a breaking of the Vainshtein mechanism is possible and, thus, some peculiar observational signatures should be detectable and make it distinguishable from general relativity. We apply this model to a sample of clusters of galaxies observed under the CLASH survey, using both new data from gravitational lensing events and archival data from X-ray intra-cluster hot gas observations. In particular, we use the latter to model the gas density, and then use it as the only ingredient in the matter clusters' budget to calculate the expected lensing convergence map. Results show that, in the context of this extended Galileon, the assumption of having only gas and no Dark Matter at all in the clusters is able to match observations. We also obtain narrow and very interesting bounds on the parameters which characterize this model. In particular, we find that, at least for one of them, the general relativity limit is excluded at 2σ confidence level, thus making this model clearly statistically different and competitive with respect to general relativity.

  1. H.E.S.S. constraints on Dark Matter annihilations towards the Sculptor and Carina Dwarf Galaxies

    CERN Document Server

    Abramowski, A; Aharonian, F; Akhperjanian, A G; Anton, G; Barnacka, A; de Almeida, U Barres; Bazer-Bachi, A R; Becherini, Y; Becker, J; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Bordas, P; Borrel, V; Brucker, J; Brun, F; Brun, P; Bulik, T; Büsching, I; Carrigan, S; Casanova, S; Cerruti, M; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L -M; Clapson, A C; Coignet, G; Conrad, J; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Eger, P; Espigat, P; Fallon, L; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fiasson, A; Frster, A; Fontaine, G; Füßling, M; Gallant, Y A; Gast, H; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Hague, J D; Hampf, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jamrozy, M; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Keogh, D; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Laffon, H; Lamanna, G; Lennarz, D; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Masbou, J; Maurin, D; Maxted, N; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann, C L; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nguyen, N; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; Wilhelmi, E de Oña; Opitz, B; Ostrowski, M; Panter, M; Arribas, M Paz; Pedaletti1, G; Pelletier, G; Petrucci, P -O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raue, M; Rayner, S M; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Ryde, F; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schönwald, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Spengler, G; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Sushch, I; Szostek, A; Tavernet, J -P; Terrier, R; Tibolla, O; Tluczykont, M; Valerius, K; van Eldik, C; Vasileiadis, G; Venter, C; Vialle, J P; Viana, A; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Vorobiov, S; Vorster, M; Wagner, S J; Ward, M; Wierzcholska, A; Zajczyk, A; Zdziarski, A A; Zech, A; Zechlin, H -S; 10.1016/j.astropartphys.2010.12.006

    2010-01-01

    The Sculptor and Carina Dwarf spheroidal galaxies were observed with the H.E.S.S. Cherenkov telescope array between January 2008 and December 2009. The data sets consist of a total of 11.8 and 14.8 hours of high quality data, respectively. No gamma-ray signal was detected at the nominal positions of these galaxies above 220 GeV and 320 GeV, respectively. Upper limits on the gamma-ray fluxes at 95% C.L. assuming two forms for the spectral energy distribution (a power law shape and one derived from dark matter annihilation) are obtained at the level of 10^-13 to 10^-12 cm^-2s^-1 in the TeV range. Constraints on the velocity weighted dark matter particle annihilation cross section for both Sculptor and Carina dwarf galaxies range from ~ 10^-21 cm^3s^-1 down to ~ 10^-22 cm^3s^-1 depending on the dark matter halo model used. Possible enhancements of the gamma-ray flux are studied: the Sommerfeld effect, which is found to exclude some dark matter particle masses, the internal Bremsstrahlung and clumps in the dark...

  2. In the Wake of Dark Giants: New Signatures of Dark Matter Self Interactions in Equal Mass Mergers of Galaxy Clusters

    CERN Document Server

    Kim, Stacy Y; Wittman, David

    2016-01-01

    Merging galaxy clusters have been touted as one of the best probes for constraining self-interacting dark matter, but few simulations exist to back up this claim. We simulate equal mass mergers of 10$^{15}$ M$_\\odot$ halos, like the El Gordo and Sausage clusters, with cosmologically-motivated halo and merger parameters, and with velocity-independent dark-matter self-interactions. Although the standard lore for merging clusters is that self-interactions lead to large separations between the galaxy and dark-matter distributions, we find that maximal galaxy-dark matter offsets of $\\lesssim~20$~kpc form for a self-interaction cross section of $\\sigma_\\text{SI}/m_\\chi$ = 1 cm$^2$/g. This is an order of magnitude smaller than those measured in observed equal mass and near equal mass mergers, and is likely to be even smaller for lower-mass systems. While competitive cross-section constraints are thus unlikely to emerge from offsets, we find other signatures of self-interactions which are more promising. Intriguingly...

  3. The mass loss process in dwarf galaxies from 3D hydrodynamical simulations: the role of dark matter and starbursts

    CERN Document Server

    Ruiz, Luciana O; Lanfranchi, Gustavo A; Caproni, Anderson

    2012-01-01

    Theoretical $\\Lambda$CDM cosmological models predict a much larger number of low mass dark matter haloes than has been observed in the Local Group of galaxies. One possible explanation is the increased difficulty of detecting these haloes if most of the visible matter is lost at early evolutionary phases through galactic winds. In this work we study the current models of triggering galactic winds in dwarf spheroidal galaxies (dSph) from supernovae, and study, based on 3D hydrodynamic numerical simulations, the correlation of the mass loss rates and important physical parameters as the dark matter halo mass and its radial profile, and the star formation rate. We find that the existence of winds is ubiquitous, independent on the gravitational potential. Our simulations revealed that the Rayleigh-Taylor Instability (RTI) may play a major role on pushing matter out of these systems, even for very massive haloes. The instability is responsible for 5 - 40% of the mass loss during the early evolution of the galaxy, ...

  4. Physical Processes in the Interstellar Medium

    OpenAIRE

    2014-01-01

    Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understanding its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolution, the formation of stars, cosmic nucleosynthesis, the origin of large complex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental buil...

  5. Searching for dwarf spheroidal galaxies and other galactic dark matter substructures with the Fermi large area telescope

    Energy Technology Data Exchange (ETDEWEB)

    Drlica-Wagner, Alex [Stanford Univ., CA (United States). Dept. of Physics

    2013-08-01

    Over the past century, it has become clear that about a quarter of the known universe is composed of an invisible, massive component termed ''dark matter''. Some of the most popular theories of physics beyond the Standard Model suggest that dark matter may be a new fundamental particle that could self-annihilate to produce γ rays. Nearby over-densities in the dark matter halo of our Milky Way present some of the most promising targets for detecting the annihilation of dark matter. We used the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope to search for γ rays produced by dark matter annihilation in Galactic dark matter substructures. We searched for γ-ray emission coincident with Milky Way dwarf spheroidal satellite galaxies, which trace the most massive Galactic dark matter substructures. We also sought to identify nearby dark matter substructures that lack all astrophysical tracers and would be detectable only through γ-ray emission from dark matter annihilation. We found no conclusive evidence for γ-ray emission from dark matter annihilation, and we set stringent and robust constraints on the dark matter annihilation cross section. While γ-ray searches for dark matter substructure are currently the most sensitive and robust probes of dark matter annihilation, they are just beginning to intersect the theoretically preferred region of dark matter parameter space. Thus, we consider future prospects for increasing the sensitivity of γ-ray searches through improvements to the LAT instrument performance and through upcoming wide- field optical surveys.

  6. The Co-Evolution of Galaxies, their ISM, and the ICM: The Hydrodynamics of Galaxy Transformation

    Science.gov (United States)

    Vijayaraghavan, Rukmani; Sarazin, Craig L.; Ricker, Paul M.

    2017-01-01

    Cluster of galaxies are hostile environments. Infalling cluster galaxies are stripped of their dark matter, stars, and hot and cold interstellar medium gas. The ISM, in addition to tidal and ram pressure stripping, can evaporate due to thermal conduction. Gas loss and the subsequent suppression of star formation is not straightforward: magnetic fields in the ISM and ICM shield galaxies and their stripped tails from shear instabilities and conduction, radiative cooling can inhibit gas loss, and feedback from stars and AGN can replenish the ISM. While there is observational evidence that these processes operate, a theoretical understanding of the physics controlling the energy cycle in cluster galaxies remains elusive. Additionally, galaxies have a significant impact on ICM evolution: orbiting galaxies stir up and stretch ICM magnetic field lines, inject turbulence into the ICM via their wakes and g-waves, and infuse metals into the ICM. Quantifying the balance between processes that remove, retain, and replenish the ISM, and the impact of galaxies on the ICM require specialized hydrodynamic simulations of the cluster environment and its galaxies. I will present results from some of these simulations that include ram pressure stripping of galaxies' hot ISM, the effect of magnetic fields on this process, and the effectiveness of isotropic and anisotropic thermal conduction in removing and retaining the ISM.

  7. Transonic galactic outflows in a dark matter halo with a central black hole and its application to the Sombrero galaxy

    CERN Document Server

    Igarashi, Asuka; Nitta, Shin-ya

    2014-01-01

    We have classified possible transonic solutions of galactic outflows in the gravitational potential of the dark matter halo (DMH) and super massive black hole (SMBH) under the assumptions of isothermal, spherically symmetric and steady state. It is clarified that the gravity of SMBH adds a new branch of transonic solutions with the transonic point in very close proximity to the centre in addition to the outer transonic point generated by the gravity of DMH. Because these two transonic solutions have substantially different mass fluxes and starting points, these solutions may have different influences on the evolution of galaxies and the release of metals into intergalactic space. We have applied our model to the Sombrero galaxy and obtained a new type of galactic outflow: a slowly accelerated transonic outflow through the transonic point at very distant region ($\\simeq 126$\\ kpc). In this galaxy, previous works reported a discrepancy that although the trace of the galactic outflow is observed by X-ray, the ga...

  8. On the Nature of Interstellar Grains

    Science.gov (United States)

    Hoyle, F.; Wickramasinghe, C.

    Data on interstellar extinction are interpreted to imply an identification of interstellar grains with naturally freeze-dried bacteria and algae. The total mass of such bacterial and algal cells in the galaxy is enormous, ~1040 g. The identification is based on Mie scattering calculations for an experimentally determined size distribution of bacteria. Agreement between our model calculations and astronomical data is remarkably precise over the wavelength intervals 1 μ-1 pigments. The strongest of the diffuse interstellar bands are provisionally assigned to carotenoid-chlorophyll pigment complexes such as exist in algae and pigmented bacteria. The λ2200 Å interstellar absorption feature could be due to `degraded' cellulose strands which form spherical graphitic particles, but could equally well be due to protein-lipid-nucleic acid complexes in bacteria and viruses. Interstellar extinction at wavelengths λ < 1800 Å could be due to scattering by virus particles.

  9. Realistic Detectability of Close Interstellar Comets

    CERN Document Server

    Cook, Nathaniel V; Granvik, Mikael; Stephens, Denise C

    2016-01-01

    During the planet formation process, billions of comets are created and ejected into interstellar space. The detection and characterization of such interstellar comets (also known as extra-solar planetesimals or extra-solar comets) would give us in situ information about the efficiency and properties of planet formation throughout the galaxy. However, no interstellar comets have ever been detected, despite the fact that their hyperbolic orbits would make them readily identifiable as unrelated to the solar system. Moro-Mart\\'in et al. 2009 have made a detailed and reasonable estimate of the properties of the interstellar comet population. We extend their estimates of detectability with a numerical model that allows us to consider "close" interstellar comets, e.g., those that come within the orbit of Jupiter. We include several constraints on a "detectable" object that allow for realistic estimates of the frequency of detections expected from the Large Synoptic Survey Telescope (LSST) and other surveys. The inf...

  10. The FMOS-COSMOS Survey of Star-forming Galaxies at Z ˜ 1.6. V: Properties of Dark Matter Halos Containing Hα Emitting Galaxies

    Science.gov (United States)

    Kashino, Daichi; More, Surhud; Silverman, John D.; Daddi, Emanuele; Renzini, Alvio; Sanders, David B.; Rodighiero, Giulia; Puglisi, Annagrazia; Kajisawa, Masaru; Valentino, Francesco; Kartaltepe, Jeyhan S.; Le Fèvre, Olivier; Nagao, Tohru; Arimoto, Nobuo; Sugiyama, Naoshi

    2017-07-01

    We study the properties of dark matter halos that contain star-forming galaxies at 1.43 ≤ z ≤ 1.74, using the FMOS-COSMOS survey. The sample consists of 516 objects with a detection of the Hα emission line, which represent the star forming population at this epoch, having a stellar mass range of 109.57 ≤ M */M ⊙ ≲ 1011.4 and a star-formation rate range of 15 ≲ SFR/(M ⊙ yr-1) ≲ 600. We measure the projected two-point correlation function while carefully taking into account observational biases, and find a significant clustering amplitude at scales of 0.04-10 h -1 cMpc, with a correlation length {r}0={5.26}-0.62+0.75 {h}-1 {cMpc} and a bias b={2.44}-0.32+0.38. We interpret our clustering measurement using a halo occupation distribution model. The sample galaxies appear to reside in halos with mass {M}{{h}}={4.71}-1.62+1.19× {10}12 {h}-1 {M}⊙ on average, which will likely become present-day halos of mass M h (z = 0) ˜ 2 × 1013 h -1 M ⊙, equivalent to the typical halo mass scale of galaxy groups. We then confirm the decline of the stellar-to-halo mass ratio at M h generation instrument that will provide strong constraints on the galaxy-formation scenario by obtaining precise measurements of galaxy clustering at z > 1.

  11. The formation of Milky Way-mass disk galaxies in the first 500 million years of a cold dark matter universe

    CERN Document Server

    Feng, Yu; Croft, Rupert; Tenneti, Ananth; Bird, Simeon; Battaglia, Nicholas; Wilkins, Stephen

    2015-01-01

    In current cosmological models, galaxies form from the gravitational collapse of small perturbations in the matter distribution. This process involves both a hierarchy of merging structures and smooth accretion, so that early galaxies are predicted to be morphologically irregular, clumpy, and compact. This is supported by recent observational data on samples of galaxies at redshift $z=8$ and beyond. The volumes accessible to these studies, both computational and observational are however thousands of times smaller than those that will be probed by upcoming telescopes, such as WFIRST. As a result, studies so far have never been able to reach the realm of massive galaxies. Whether among the myriad tiny proto-galaxies there exists a population with similarities to present day galaxies is an open question. Here we show, using BlueTides, the first hydrodynamic simulation large enough to resolve the relevant scales, that the first massive galaxies to form are in fact predicted to have extensive rotationally-support...

  12. Search for dark matter annihilation signatures in H.E.S.S. observations of Dwarf Spheroidal Galaxies

    CERN Document Server

    :,; Aharonian, F; Benkhali, F Ait; Akhperjanian, A G; Angüner, E; Backes, M; Balenderan, S; Balzer, A; Barnacka, A; Becherini, Y; Tjus, J Becker; Berge, D; Bernhard, S; Bernlöhr, K; Birsin, E; Biteau, J; Böttcher, M; Boisson, C; Bolmont, J; Bordas, P; Bregeon, J; Brun, F; Brun, P; Bryan, M; Bulik, T; Carrigan, S; Casanova, S; Chadwick, P M; Chakraborty, N; Chalme-Calvet, R; Chaves, R C G; Chrétien, M; Colafrancesco, S; Cologna, G; Conrad, J; Couturier, C; Cui, Y; Dalton, M; Davids, I D; Degrange, B; Deil, C; deWilt, P; Djannati-Ata\\"ı, A; Domainko, W; Donath, A; Drury, L O'C; Dubus, G; Dutson, K; Dyks, J; Dyrda, M; Edwards, T; Egberts, K; Eger, P; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fernandes, M V; Fernandez, D; Fiasson, A; Fontaine, G; Förster, A; Füßling, M; Gabici, S; Gajdus, M; Gallant, Y A; Garrigoux, T; Giavitto, G; Giebels, B; Glicenstein, J F; Gottschall, D; Goudelis, A; Grondin, M -H; Grudzińska, M; Hadsch, D; Häffner, S; Hahn, J; Harris, J; Heinzelmann, G; Henri, G; Hermann, G; Hervet, O; Hillert, A; Hinton, J A; Hofmann, W; Hofverberg, P; Holler, M; Horns, D; Ivascenko, A; Jacholkowska, A; Jahn, C; Jamrozy, M; Janiak, M; Jankowsky, F; Jung, I; Kastendieck, M A; Katarzyński, K; Katz, U; Kaufmann, S; Khélifi, B; Kieffer, M; Klepser, S; Klochkov, D; Kluźniak, W; Kolitzus, D; Komin, Nu; Kosack, K; Krakau, S; Krayzel, F; Krüger, P P; Laffon, H; Lamanna, G; Lefaucheur, J; Lefranc, V; Lemiére, A; Lemoine-Goumard, M; Lenain, J -P; Lohse, T; Lopatin, A; Lu, C -C; Marandon, V; Marcowith, A; Marx, R; Maurin, G; Maxted, N; Mayer, M; McComb, T J L; Méhault, J; Meintjes, P J; Menzler, U; Meyer, M; Mitchell, A M W; Moderski, R; Mohamed, M; Morå, K; Moulin, E; Murach, T; de Naurois, M; Niemiec, J; Nolan, S J; Oakes, L; Odaka, H; Ohm, S; Opitz, B; Ostrowski, M; Oya, I; Panter, M; Parsons, R D; Arribas, M Paz; Pekeur, N W; Pelletier, G; Perez, J; Petrucci, P -O; Peyaud, B; Pita, S; Poon, H; Pühlhofer, G; Punch, M; Quirrenbach, A; Raab, S; Reichardt, I; Reimer, A; Reimer, O; Renaud, M; Reyes, R de los; Rieger, F; Rob, L; Romoli, C; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Sahakian, V; Salek, D; Sanchez, D A; Santangelo, A; Schlickeiser, R; Schüssler, F; Schulz, A; Schwanke, U; Schwarzburg, S; Schwemmer, S; Serpico, P; Sol, H; Spanier, F; Spengler, G; Spieß, F; Stawarz, L; Steenkamp, R; Stegmann, C; Stinzing, F; Stycz, K; Sushch, I; Tavernet, J -P; Tavernier, T; Taylor, A M; Terrier, R; Tluczykont, M; Trichard, C; Valerius, K; van Eldik, C; van Soelen, B; Vasileiadis, G; Veh, J; Venter, C; Viana, A; Vincent, P; Vink, J; Völk, H J; Volpe, F; Vorster, M; Vuillaume, T; Wagner, S J; Wagner, P; Wagner, R M; Ward, M; Weidinger, M; Weitzel, Q; White, R; Wierzcholska, A; Willmann, P; Wörnlein, A; Wouters, D; Yang, R; Zabalza, V; Zaborov, D; Zacharias, M; Zdziarski, A A; Zech, A; Zechlin, H -S

    2014-01-01

    Dwarf spheroidal galaxies of the Local Group are close satellites of the Milky Way characterized by a large mass-to-light ratio and are not expected to be the site of non-thermal high-energy gamma-ray emission or intense star formation. Therefore they are amongst the most promising candidates for indirect dark matter searches. During the last years the High Energy Stereoscopic System (H.E.S.S.) of imaging atmospheric Cherenkov telescopes observed five of these dwarf galaxies for more than 140 hours in total, searching for TeV gamma-ray emission from annihilation of dark matter particles. The new results of the deep exposure of the Sagittarius dwarf spheroidal galaxy, the first observations of the Coma Berenices and Fornax dwarves and the re-analysis of two more dwarf spheroidal galaxies already published by the H.E.S.S. Collaboration, Carina and Sculptor, are presented. In the absence of a significant signal new constraints on the annihilation cross-section applicable to Weakly Interacting Massive Particles (...

  13. Dark-ages Reionization & Galaxy Formation Simulation VIII. Suppressed growth of dark matter halos during the Epoch of Reionization

    Science.gov (United States)

    Qin, Yuxiang; Duffy, Alan R.; Mutch, Simon J.; Poole, Gregory B.; Geil, Paul M.; Angel, Paul W.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2017-01-01

    We investigate how the hydrostatic suppression of baryonic accretion affects the growth rate of dark matter halos during the Epoch of Reionization. By comparing halo properties in a simplistic hydrodynamic simulation in which gas only cools adiabatically, with its collisionless equivalent, we find that halo growth is slowed as hydrostatic forces prevent gas from collapsing. In our simulations, at the high redshifts relevant for reionization (between ˜6 and ˜11), halos that host dwarf galaxies (≲ 109M⊙) can be reduced by up to a factor of 2 in mass due to the hydrostatic pressure of baryons. Consequently, the inclusion of baryonic effects reduces the amplitude of the low mass tail of the halo mass function by factors of 2 to 4. In addition, we find that the fraction of baryons in dark matter halos hosting dwarf galaxies at high redshift never exceeds ˜90% of the cosmic baryon fraction. When implementing baryonic processes, including cooling, star formation, supernova feedback and reionization, the suppression effects become more significant with further reductions of ˜30% to 60%. Although convergence tests suggest that the suppression may become weaker in higher resolution simulations, this suppressed growth will be important for semi-analytic models of galaxy formation, in which the halo mass inherited from an underlying N-body simulation directly determines galaxy properties. Based on the adiabatic simulation, we provide tables to account for these effects in N-body simulations, and present a modification of the halo mass function along with explanatory analytic calculations.

  14. Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies

    CERN Document Server

    Governato, F; Pontzen, A; Christensen, C; Oh, S H; Brooks, A M; Quinn, T; Shen, S; Wadsley, J

    2012-01-01

    We examine the evolution of the inner dark matter (DM) and baryonic density profile of a new sample of simulated field galaxies using fully cosmological, Lambda CDM, high resolution SPH + N-Body simulations. These simulations include explicit H2 and metal cooling, star formation (SF) and supernovae (SNe) driven gas outflows. Starting at high redshift, rapid, repeated gas outflows following bursty SF transfer energy to the DM component and significantly flatten the originally `cuspy' central DM mass profile of galaxies with present day stellar masses in the 10^4.5 -- 10^9.8 Msolar range. At z=0, the central slope of the DM density profile of our galaxies (measured between 0.3 and 0.7 kpc from their centre) is well fitted by rhoDM propto r^alpha with alpha \\simeq -0.5 + 0.35 log_10(Mstar/10^8Msolar) where Mstar is the stellar mass of the galaxy and 4 < log_10 Mstar < 9.4. These values imply DM profiles flatter than those obtained in DM--only simulations and in close agreement with those inferred in galaxi...

  15. Cosmology with massive neutrinos I: towards a realistic modeling of the relation between matter, haloes and galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Villaescusa-Navarro, Francisco; Viel, Matteo [INAF - Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143, Trieste (Italy); Marulli, Federico [Dipartimento di Fisica e Astronomia - Università di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma (Italy); Castorina, Emanuele [SISSA - International School For Advanced Studies, Via Bonomea, 265 34136 Trieste (Italy); Sefusatti, Emiliano [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151, Trieste (Italy); Saito, Shun, E-mail: villaescusa@oats.inaf.it, E-mail: federico.marulli3@unibo.it, E-mail: viel@oats.inaf.it, E-mail: branchin@fis.uniroma3.it, E-mail: ecastori@sissa.it, E-mail: esefusat@ictp.it, E-mail: shun.saito@ipmu.jp [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, The University of Tokyo, Chiba 277-8582 (Japan)

    2014-03-01

    By using a suite of large box-size N-body simulations that incorporate massive neutrinos as an extra set of particles, with total masses of 0.15, 0.30, and 0.60 eV, we investigate the impact of neutrino masses on the spatial distribution of dark matter haloes and on the distribution of galaxies within the haloes. We compute the bias between the spatial distribution of dark matter haloes and the overall matter and cold dark matter distributions using statistical tools such as the power spectrum and the two-point correlation function. Overall we find a scale-dependent bias on large scales for the cosmologies with massive neutrinos. In particular, we find that the bias decreases with the scale, being this effect more important for higher neutrino masses and at high redshift. However, our results indicate that the scale-dependence in the bias is reduced if the latter is computed with respect to the cold dark matter distribution only. We find that the value of the bias on large scales is reasonably well reproduced by the Tinker fitting formula once the linear cold dark matter power spectrum is used, instead of the total matter power spectrum. We also investigate whether scale-dependent bias really comes from purely neutrino's effect or from nonlinear gravitational collapse of haloes. For this purpose, we address the Ω{sub ν}-σ{sub 8} degeneracy and find that such degeneracy is not perfect, implying that neutrinos imprint a slight scale dependence on the large-scale bias. Finally, by using a simple halo occupation distribution (HOD) model, we investigate the impact of massive neutrinos on the distribution of galaxies within dark matter haloes. We use the main galaxy sample in the Sloan Digital Sky Survey (SDSS) II Data Release 7 to investigate if the small-scale galaxy clustering alone can be used to discriminate among different cosmological models with different neutrino masses. Our results suggest that different choices of the HOD parameters can reproduce the

  16. Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    Viola, M; Brouwer, M; Kuijken, K; Hoekstra, H; Norberg, P; Robotham, A S G; van Uitert, E; Alpaslan, M; Baldry, I K; Choi, A; de Jong, J T A; Driver, S P; Erben, T; Grado, A; Graham, Alister W; Heymans, C; Hildebrandt, H; Hopkins, A M; Irisarri, N; Joachimi, B; Loveday, J; Miller, L; Nakajima, R; Schneider, P; Sifón, C; Kleijn, G Verdoes

    2015-01-01

    The Kilo-Degree Survey (KiDS) is an optical wide-field survey designed to map the matter distribution in the Universe using weak gravitational lensing. In this paper, we use these data to measure the density profiles and masses of a sample of $\\sim \\mathrm{1400}$ spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly (GAMA) survey. We detect a highly significant signal (signal-to-noise-ratio $\\sim$ 120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from $M \\sim 10^{13}-10^{14.5} h^{-1}\\mathrm{M_{\\odot}}$. We interpret the results for various subsamples of groups using a halo model framework which accounts for the mis-centring of the Brightest Cluster Galaxy (used as the tracer of the group centre) with respect to the centre of the group's dark matter halo. We find that the density profiles of the haloes are well described by an NFW profile with concentrations that agree with predictions from numerical simulations. ...

  17. Dynamics of the NGC 4636 Globular Cluster System - An extremely dark matter dominated galaxy?

    CERN Document Server

    Schuberth, Y; Hilker, M; Kissler-Patig, M; Larsen, S S; Mebold, U; Richtler, T

    2006-01-01

    We present the first dynamical study of the globular cluster system of NGC 4636. This giant elliptical galaxy is claimed to be extremely dark matter dominated, according to X-ray observations. Using the VLT with FORS2/MXU, we obtained velocities for 174 globular clusters. The clusters have projected galactocentric distances in the range 4 to 70 kpc, the overwhelming majority lie within 30 kpc. We find some indication for a rotation of the red (metal-rich) clusters about the minor axis. Out to a radius of 30 kpc, we find a roughly constant projected velocity dispersion for the blue clusters of ~200 km/s. The red clusters exhibit a distinctly different behavior: at a radius of about 13 kpc, the velocity dispersion drops by ~50 km/s to about 170 km/s which then remains constant out to a radius of 30 kpc. Using only the blue clusters as dynamical tracers, we perform Jeans-analyses for different assumptions of the orbital anisotropy. Depending on the anisotropy and the adopted M/L-values, we find that the dark mat...

  18. Prospects for annihilating Dark Matter towards Milky Way's dwarf galaxies by the Cherenkov Telescope Array

    Science.gov (United States)

    Lefranc, Valentin; Mamon, Gary A.; Panci, Paolo

    2016-09-01

    We derive the Cherenkov Telescope Array (CTA) sensitivity to dark matter (DM) annihilation in several primary channels, over a broad range of DM masses. These sensitivities are estimated when CTA is pointed towards a large sample of Milky Way's dwarf spheroidal galaxies (dSphs) with promising J-factors and small statistical uncertainties. This analysis neglects systematic uncertainties, which we estimate at the level of at least 1 dex. We also present sensitivities on the annihilation cross section from a combined analysis of 4 dSphs. We assess the CTA sensitivity by: i) using, for each dSph, a recent determination of the J-factor and its statistical error; ii) considering the most up-to-date cosmic ray background; and iii) including both spatial and spectral terms in the likelihood analysis. We find that a joint spectral and spatial analysis improves the CTA sensitivity, in particular for primary channels with sharp features in the γ-ray energy spectrum and for dSphs with steep J-factor profiles, as deduced from the internal kinematics. The greatest sensitivities are obtained for observations of Ursa Minor among the classical dSphs and of Ursa Major II for ultra-faint dSphs.

  19. Gamma rays and neutrinos from dark matter annihilation in galaxy clusters

    CERN Document Server

    Yuan, Qiang; Bi, Xiao-Jun; Zhang, Xin-Min; Zhu, Shou-Hua

    2010-01-01

    The $\\gamma$-ray and neutrino emissions from dark matter (DM) annihilation in galaxy clusters are studied. After about one year operation of Fermi-LAT, several nearby clusters are reported with stringent upper limits of GeV $\\gamma$-ray emission. We use the Fermi-LAT upper limits of these clusters to constrain the DM model parameters. We find that the DM model distributed with substructures predicted in cold DM (CDM) scenario is strongly constrained by Fermi-LAT $\\gamma$-ray data. Especially for the leptonic annihilation scenario which may account for the $e^{\\pm}$ excesses discovered by PAMELA/Fermi-LAT/HESS, the constraint on the minimum mass of substructures is of the level $10^3-10^4$ M$_{\\odot}$, which is much larger than that expected in CDM picture, but is consistent with a warm DM scenario. We further investigate the sensitivity of neutrino detections of the clusters by IceCube. It is found that neutrino detection is much more difficult than $\\gamma$-rays. Only for very heavy DM ($\\sim 10$ TeV) togeth...

  20. Stochastic Star Formation & Feedback: Mapping Low-Mass Galaxies to Dark Matter Haloes

    CERN Document Server

    Power, Chris; Robotham, Aaron S G; Lewis, Geraint F; Wilkinson, Mark I

    2014-01-01

    Comparison of observed satellite galaxies of the Milky Way (hereafter MW) with dark matter subhaloes in cosmological $N$-body simulations of MW-mass haloes suggest that such subhaloes, if they exist, are occupied by satellites in a stochastic fashion. We examine how inefficient massive star formation and associated supernova feedback in high-redshift progenitors of present-day low-mass subhaloes might contribute to this stochasticity. Using a Monte Carlo approach to follow the assembly histories of present-day low-mass haloes with $10^7 \\lesssim M \\leq 10^{10}$ ${\\rm M}_{\\odot}$, we identify when cooling and star formation is likely to proceed, and observe that haloes with present-day masses $\\lesssim 10^9 {\\rm M}_{\\odot}$ never grow sufficiently massive to support atomic hydrogen line cooling. Noting that the star formation timescale decreases sharply with stellar mass as $t_{\\rm PMS} \\propto m_{\\ast}^{-2.5}$, we argue that, should the conditions for high mass star formation arise in low-mass haloes, the ens...

  1. Wide binaries in ultrafaint galaxies: a window on to dark matter on the smallest scales

    Science.gov (United States)

    Peñarrubia, Jorge; Ludlow, Aaron D.; Chanamé, Julio; Walker, Matthew G.

    2016-09-01

    We carry out controlled N-body simulations that follow the dynamical evolution of binary stars in the dark matter (DM) haloes of ultrafaint dwarf spheroidals (dSphs). We find that wide binaries with semimajor axes a ≳ at tend to be quickly disrupted by the tidal field of the halo. In smooth potentials the truncation scale, at, is mainly governed by (i) the mass enclosed within the dwarf half-light radius (Rh) and (ii) the slope of the DM halo profile at R ≈ Rh, and is largely independent of the initial eccentricity distribution of the binary systems and the anisotropy of the stellar orbits about the galactic potential. For the reported velocity dispersion and half-light radius of Segue I, the closest ultrafaint, our models predict at values that are a factor of 2-3 smaller in cuspy haloes than in any of the cored models considered here. Using mock observations of Segue I we show that measuring the projected two-point correlation function of stellar pairs with sub-arcsecond resolution may provide a useful tool to constrain the amount and distribution of DM in the smallest and most DM-dominated galaxies.

  2. nIFTy galaxy cluster simulations - I. Dark matter and non-radiative models

    Science.gov (United States)

    Sembolini, Federico; Yepes, Gustavo; Pearce, Frazer R.; Knebe, Alexander; Kay, Scott T.; Power, Chris; Cui, Weiguang; Beck, Alexander M.; Borgani, Stefano; Dalla Vecchia, Claudio; Davé, Romeel; Elahi, Pascal Jahan; February, Sean; Huang, Shuiyao; Hobbs, Alex; Katz, Neal; Lau, Erwin; McCarthy, Ian G.; Murante, Guiseppe; Nagai, Daisuke; Nelson, Kaylea; Newton, Richard D. A.; Perret, Valentin; Puchwein, Ewald; Read, Justin I.; Saro, Alexandro; Schaye, Joop; Teyssier, Romain; Thacker, Robert J.

    2016-04-01

    We have simulated the formation of a galaxy cluster in a Λ cold dark matter universe using 13 different codes modelling only gravity and non-radiative hydrodynamics (RAMSES, ART, AREPO, HYDRA and nine incarnations of GADGET). This range of codes includes particle-based, moving and fixed mesh codes as well as both Eulerian and Lagrangian fluid schemes. The various GADGET implementations span classic and modern smoothed particle hydrodynamics (SPH) schemes. The goal of this comparison is to assess the reliability of cosmological hydrodynamical simulations of clusters in the simplest astrophysically relevant case, that in which the gas is assumed to be non-radiative. We compare images of the cluster at z = 0, global properties such as mass and radial profiles of various dynamical and thermodynamical quantities. The underlying gravitational framework can be aligned very accurately for all the codes allowing a detailed investigation of the differences that develop due to the various gas physics implementations employed. As expected, the mesh-based codes RAMSES, ART and AREPO form extended entropy cores in the gas with rising central gas temperatures. Those codes employing classic SPH schemes show falling entropy profiles all the way into the very centre with correspondingly rising density profiles and central temperature inversions. We show that methods with modern SPH schemes that allow entropy mixing span the range between these two extremes and the latest SPH variants produce gas entropy profiles that are essentially indistinguishable from those obtained with grid-based methods.

  3. Cosmology and Astrophysics from Relaxed Galaxy Clusters V: Consistency with Cold Dark Matter Structure Formation

    CERN Document Server

    Mantz, Adam B; Morris, R Glenn

    2016-01-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the Cold Dark Matter (CDM) paradigm. We present constraints on the concentration--mass relation for massive clusters, finding a power-law mass dependence with a slope of $\\kappa_m=-0.16\\pm0.07$, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with $1+z$ of $\\kappa_\\zeta=-0.17\\pm0.26$), with an intrinsic scatter of $\\sigma_{\\ln c}=0.16\\pm0.03$. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically $\\sim50$kpc--1Mpc), and test for departures from the simple Navarro, Frenk & White (NFW...

  4. On the coherent rotation of diffuse matter in numerical simulations of galaxy clusters

    CERN Document Server

    Baldi, Anna Silvia; Sembolini, Federico; Yepes, Gustavo; Lamagna, Luca; Rasia, Elena

    2016-01-01

    We analyse the dynamical properties of Intra-Cluster Medium (ICM) and dark matter (DM) in galaxy clusters to highlight the presence of coherent motions, in a volume-limited sample extracted from the gas-dynamical simulations of the MUSIC project. We select the most massive haloes and we use three different models to describe the physics of baryons: a non-radiative model, and two models including radiative physics, with and without the AGN feedback. We aim to get a statistics on the contribution from rotational motions to the dynamics of massive clusters, and to possibly characterize them through a suitable model. Our study is focused on the relaxed clusters (57 per cent of our total sample) that we classify as as rotating or non-rotating according to the gas spin parameter, finding that 4 per cent of the relaxed sample is rotating. We study the radial profiles of their specific angular momentum vector, finding that the solid body model is not suitable to describe a rotation. The radial profiles of the tangent...

  5. Dark matter in satellite galaxies: Will future Iimaging Air Cherenkov Telescopes play a role?

    Energy Technology Data Exchange (ETDEWEB)

    Fornasa, Mattia, E-mail: mfornasa@pd.infn.i [University of Padova and I.N.F.N. sezione di Padova, via Marzolo 8, 35131 Padova (Italy)

    2011-02-21

    Addressing the question about the importance of future Imaging Air Cherenkov Telescopes (IACTs) for indirect detection of Dark Matter (DM), I will review the results of a paper by Bringmann et al. (2008) in which the authors computed the gamma-ray flux from DM annihilation associated to the halos of two reference dwarf Spheroidal galaxies, Draco and Willman 1. The previously neglected contribution of Virtual Internal Bremsstrahlung is also taken into account, which produces, when present, a bump in the higher part of the energy spectrum. The boost factor is the quantity used to describe how far the experiment is from probing interesting DM scenarios and it is computed for the next generation of IACTs, namely MAGIC-II and CTA. Due to the presence of spectral features, the boost factors can vary, becoming dependent to the characteristics of the particular DM candidate, obstacling a clear statement about prospects of detection. However, at least for the case of Willman 1 observed by CTA, boost factors may be below 10, even without considering the effect of substructures or the Sommerfeld enhancement. This, added to the comparison with the prospects of detection by the Fermi satellite, clearly demonstrate that the answer to the question in the title is an affirmative one.

  6. A Suzaku Search for Dark Matter Emission Lines in the X-ray Brightest Galaxy Clusters

    CERN Document Server

    Urban, O; Allen, S W; Simionescu, A; Kaastra, J S; Strigari, L E

    2014-01-01

    We present the results of a search for unidentified emission lines in deep Suzaku X-ray spectra for the central regions of the four X-ray brightest galaxy clusters: Perseus, Coma, Virgo and Ophiuchus. We employ an optimized energy range for our analysis (3.2-5.3 keV) that is relatively free of instrumental features, and a baseline plasma emission model that incorporates the abundances of elements with the strongest expected emission lines at these energies (S, Ar, Ca) as free parameters. For the Perseus Cluster core, employing this baseline model, we find evidence for an additional emission feature at an energy $3.51^{+0.02}_{-0.01}$ keV with a flux of ~$2.87\\times10^{-7}$ ph/s/cm^2/arcmin^2. At slightly larger radii, we detect an emission line at 3.59+/-0.02 keV with a flux of ~$4.8\\times10^{-8}$ ph/s/cm^2/arcmin^2. The energies and fluxes of these features are broadly consistent with previous claims, although the radial variation of the line strength appears in tension with standard dark matter (DM) model p...

  7. Prospects for annihilating Dark Matter towards Milky Way's dwarf galaxies by the Cherenkov Telescope Array

    CERN Document Server

    Lefranc, Valentin; Mamon, Gary A

    2016-01-01

    We derive the large Cherenkov Telescope Array (CTA) sensitivity to dark matter (DM) annihilation in several primary channels, over a broad range of DM masses. These sensitivities are estimated when CTA is pointed towards a large sample of Milky Way's dwarf spheroidal galaxies (dSphs) with promising $J$-factors and small statistical uncertainties. This analysis neglects systematic uncertainties, which we estimate at the level of at least 1 dex. We also present sensitivities on the annihilation cross section from a combined analysis of 4 dSphs. We assess the CTA sensitivity by: $i)$ using, for each dSph, recent determination of the $J$-factor and its statistical error; $ii)$ considering the most up-to-date cosmic ray background; and $iii)$ applying a joint spatial and spectral analysis in the likelihood. We find that a joint spectral and spatial analysis improves the CTA sensitivity, in particular for primary channels with sharp features in the $\\gamma$-ray energy spectrum and for dSphs with steep $J$-factor pr...

  8. Condensed matter astrophysics: A prescription for determining the species-specific composition and quantity of interstellar dust using x-rays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Julia C.; Xiang, Jingen; Ravel, Bruce; Kortright, Jeffrey B; Flanagan, Kathryn

    2009-01-05

    We present a newtechnique for determining the quantity and composition of dust in astrophysical environments using<6 keV X-rays.We argue that high-resolution X-ray spectra as enabled by the Chandra and XMM-Newton gratings should be considered a powerful and viable new resource for delving into a relatively unexplored regime for directlydetermining dust properties: composition, quantity, and distribution.We present initial cross section measurements of astrophysically likely iron-based dust candidates taken at the Lawrence Berkeley National Laboratory Advanced Light Source synchrotron beamline, as an illustrative tool for the formulation of our technique for determining the quantity and composition of interstellar dust with X-rays. (Cross sections for the materials presented here will be made available for astrophysical modeling in the near future.) Focused at the 700 eV Fe LIII and LII photoelectric edges, we discuss a technique for modeling dust properties in the soft X-rays using L-edge data to complement K-edge X-ray absorption fine structure analysis techniques discussed by Lee& Ravel. The paper is intended to be a techniques paper of interest and useful to both condensed matter experimentalists andastrophysicists. For the experimentalists, we offer a new prescription for normalizing relatively low signal-to-noise ratio L-edge cross section measurements. For astrophysics interests, we discuss the use of X-ray absorption spectra for determining dust composition in cold and ionized astrophysical environments and a new method for determining species-specific gas and dust ratios. Possible astrophysical applications of interest, including relevance to Sagittarius A*, are offered. Prospects for improving on this work in future X-ray missions with higher throughput and spectral resolution are also presented in the context of spectral resolution goals for gratings and calorimeters, for proposed and planned missions such as Astro-H and the International X

  9. The formation of interstellar jets

    Science.gov (United States)

    Tenorio-Tagle, G.; Canto, J.; Rozyczka, M.

    1988-01-01

    The formation of interstellar jets by convergence of supersonic conical flows and the further dynamical evolution of these jets are investigated theoretically by means of numerical simulations. The results are presented in extensive graphs and characterized in detail. Strong radiative cooling is shown to result in jets with Mach numbers 2.5-29 propagating to lengths 50-100 times their original widths, with condensation of swept-up interstellar matter at Mach 5 or greater. The characteristics of so-called molecular outflows are well reproduced by the simulations of low-Mach-number and quasi-adiabatic jets.

  10. DARK MATTER SEARCHES IN THE GAMMA-RAY EXTRAGALACTIC BACKGROUND VIA CROSS-CORRELATIONS WITH GALAXY CATALOGS

    Energy Technology Data Exchange (ETDEWEB)

    Cuoco, Alessandro; Regis, Marco; Fornengo, Nicolao [Dipartimento di Fisica, Università di Torino, via P. Giuria 1, I-10125 Torino (Italy); Xia, Jun-Qing [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi “Roma Tre,” via della Vasca Navale 84, I-00146 Roma (Italy); Viel, Matteo, E-mail: cuoco@to.infn.it, E-mail: regis@to.infn.it, E-mail: fornengo@to.infn.it, E-mail: xiajq@bnu.edu.cn, E-mail: branchin@fis.uniroma3.it, E-mail: viel@oats.inaf.it [INAF Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34141, Trieste (Italy)

    2015-12-15

    We compare the measured angular cross-correlation between the Fermi-Large Area Telescope γ-ray sky and catalogs of extragalactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical γ-ray emitters such as blazars, misaligned active galactic nucleus (AGN), and star-forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogs are considered: Sloan Digital Sky Survey (SDSS)-DR6 quasars, Two Micron All Sky Survey galaxies, NRAO VLA Sky Survey radio galaxies, SDSS-DR8 Luminous Red Galaxies, and the SDSS-DR8 main galaxy sample. To model the cross-correlation signal, we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalog in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM γ-ray emission. The use of different catalogs probing objects at different redshifts significantly reduces, though not completely, the degeneracy among the different γ-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% level for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM.

  11. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    CERN Document Server

    Popping, G; Peeples, M S

    2014-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the SFR-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer galaxy H I and H2 masses. We present gas scaling relations, gas fractions, and mass functions from z = 0 to z = 3 and the gas properties of galaxies as a function of their host halo masses. Predictions of our work include: 1) there is a ~ 0.2 dex decrease in the H I mass of galaxies as a function of their stellar mass since z = 1.5, whereas the H2 mass of galaxies decreases by > 1 dex over the same period. 2) galaxy cold gas fractions and H2 fractions decrease with increasing stellar mass and time. Galaxies with M* > 10^10 Msun are dominated by their stellar content at z < 1, whereas less-massive galaxies only reach these gas fractions at z = 0. We find the strongest evolution in relative gas content at z < 1.5. 3) the SFR to gas m...

  12. Fundamental Physics with the Hubble Frontier Fields: Constraining Dark Matter Models with the Abundance of Extremely Faint and Distant Galaxies

    Science.gov (United States)

    Menci, N.; Merle, A.; Totzauer, M.; Schneider, A.; Grazian, A.; Castellano, M.; Sanchez, N. G.

    2017-02-01

    We show that the measured abundance of ultra-faint lensed galaxies at z≈ 6 in the Hubble Frontier Fields (HFF) provides stringent constraints on the parameter space of (i) dark matter models based on keV sterile neutrinos; (ii) “fuzzy” wavelike dark matter models, based on Bose–Einstein condensates of ultra-light particles. For the case of sterile neutrinos, we consider two production mechanisms: resonant production through mixing with active neutrinos and the decay of scalar particles. For the former model, we derive constraints for the combination of sterile neutrino mass {m}ν and mixing parameter {\\sin }2(2θ ) which provide the tightest lower bounds on the mixing angle (and hence on the lepton asymmetry) derived so far by methods independent of baryonic physics. For the latter we compute the allowed combinations of the scalar mass, its coupling to the Higgs field, and the Yukawa coupling of scalar to sterile neutrinos. We compare our results to independent existing astrophysical bounds on sterile neutrinos in the same mass range. For the case of “fuzzy” dark matter, we show that the observed number density ≈ 1/{{Mpc}}3 of high-redshift galaxies in the HFF sets a lower limit {m}\\psi ≥slant 8\\cdot {10}-22 eV (at the 3-σ confidence level) on the particle mass, a result that strongly disfavors wavelike bosonic dark matter as a viable model for structure formation. We discuss the impact on our results of uncertainties due to systematics in the selection of highly magnified, faint galaxies at high redshift.

  13. Cosmology and astrophysics from relaxed galaxy clusters – V. Consistency with cold dark matter structure formation

    Energy Technology Data Exchange (ETDEWEB)

    Mantz, A.B.; /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Allen, S.W.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /SLAC; Morris, R.Glenn; /KIPAC, Menlo Park /SLAC

    2016-07-15

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration–mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ~50 kpc–1 Mpc), and test for departures from the simple Navarro–Frenk–White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.

  14. Cosmology and astrophysics from relaxed galaxy clusters - V. Consistency with cold dark matter structure formation

    Science.gov (United States)

    Mantz, A. B.; Allen, S. W.; Morris, R. G.

    2016-10-01

    This is the fifth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Our sample comprises 40 clusters identified as being dynamically relaxed and hot in Papers I and II of this series. Here we use constraints on cluster mass profiles from X-ray data to test some of the basic predictions of cosmological structure formation in the cold dark matter (CDM) paradigm. We present constraints on the concentration-mass relation for massive clusters, finding a power-law mass dependence with a slope of κm = -0.16 ± 0.07, in agreement with CDM predictions. For this relaxed sample, the relation is consistent with a constant as a function of redshift (power-law slope with 1 + z of κζ = -0.17 ± 0.26), with an intrinsic scatter of σln c = 0.16 ± 0.03. We investigate the shape of cluster mass profiles over the radial range probed by the data (typically ˜50 kpc-1 Mpc), and test for departures from the simple Navarro-Frenk-White (NFW) form, for which the logarithmic slope of the density profile tends to -1 at small radii. Specifically, we consider as alternatives the generalized NFW (GNFW) and Einasto parametrizations. For the GNFW model, we find an average value of (minus) the logarithmic inner slope of β = 1.02 ± 0.08, with an intrinsic scatter of σβ = 0.22 ± 0.07, while in the Einasto case we constrain the average shape parameter to be α = 0.29 ± 0.04 with an intrinsic scatter of σα = 0.12 ± 0.04. Our results are thus consistent with the simple NFW model on average, but we clearly detect the presence of intrinsic, cluster-to-cluster scatter about the average.

  15. The FMOS-COSMOS Survey of Star-forming Galaxies at z ≈ 1.6. IV. Excitation State and Chemical Enrichment of the Interstellar Medium

    Science.gov (United States)

    Kashino, D.; Silverman, J. D.; Sanders, D.; Kartaltepe, J. S.; Daddi, E.; Renzini, A.; Valentino, F.; Rodighiero, G.; Juneau, S.; Kewley, L. J.; Zahid, H. J.; Arimoto, N.; Nagao, T.; Chu, J.; Sugiyama, N.; Civano, F.; Ilbert, O.; Kajisawa, M.; Le Fèvre, O.; Maier, C.; Masters, D.; Miyaji, T.; Onodera, M.; Puglisi, A.; Taniguchi, Y.

    2017-01-01

    We investigate the physical conditions of ionized gas in high-z star-forming galaxies using diagnostic diagrams based on the rest-frame optical emission lines. The sample consists of 701 galaxies with an Hα detection at 1.4≲ z≲ 1.7, from the Fiber Multi-Object Spectrograph (FMOS)-COSMOS survey, that represent the normal star-forming population over the stellar mass range {10}9.6≲ {M}* /{M}ȯ ≲ {10}11.6, with those at {M}* > {10}11 {M}ȯ being well sampled. We confirm an offset of the average location of star-forming galaxies in the Baldwin–Phillips–Terlevich (BPT) diagram ({{[O}} {{III}}]/{{H}}β versus {{[N}} {{II}}]/{{H}}α ), primarily toward higher {{[O}} {{III}}]/{{H}}β , compared with local galaxies. Based on the [S ii] ratio, we measure an electron density ({n}{{e}}={220}-130+170 {{cm}}-3), which is higher than that of local galaxies. Based on comparisons to theoretical models, we argue that changes in emission-line ratios, including the offset in the BPT diagram, are caused by a higher ionization parameter both at fixed stellar mass and at fixed metallicity, with additional contributions from a higher gas density and possibly a hardening of the ionizing radiation field. Ionization due to active galactic nuclei is ruled out as assessed with Chandra. As a consequence, we revisit the mass–metallicity relation using {{[N}}{{II}}]/{{H}}α and a new calibration including {{[N}} {{II}}]/{{[S}} {{II}}] as recently introduced by Dopita et al. Consistent with our previous results, the most massive galaxies ({M}* ≳ {10}11 {M}ȯ ) are fully enriched, while those at lower masses have metallicities lower than local galaxies. Finally, we demonstrate that the stellar masses, metallicities, and star formation rates of the FMOS sample are well fit with a physically motivated model for the chemical evolution of star-forming galaxies.

  16. Interstellar Isotopes: Prospects with ALMA

    Science.gov (United States)

    Charnley Steven B.

    2010-01-01

    Cold molecular clouds are natural environments for the enrichment of interstellar molecules in the heavy isotopes of H, C, N and O. Anomalously fractionated isotopic material is found in many primitive Solar System objects, such as meteorites and comets, that may trace interstellar matter that was incorporated into the Solar Nebula without undergoing significant processing. Models of the fractionation chemistry of H, C, N and O in dense molecular clouds, particularly in cores where substantial freeze-out of molecules on to dust has occurred, make several predictions that can be tested in the near future by molecular line observations. The range of fractionation ratios expected in different interstellar molecules will be discussed and the capabilities of ALMA for testing these models (e.g. in observing doubly-substituted isotopologues) will be outlined.

  17. Star formation triggered by galaxy interactions in modified gravity

    CERN Document Server

    Renaud, Florent; Kroupa, Pavel

    2016-01-01

    Together with interstellar turbulence, gravitation is one key player in star formation. It acts both at galactic scales in the assembly of gas into dense clouds, and inside those structures for their collapse and the formation of pre-stellar cores. To understand to what extent the large scale dynamics govern the star formation activity of galaxies, we present hydrodynamical simulations in which we generalise the behaviour of gravity to make it differ from Newtonian dynamics in the low acceleration regime. We focus on the extreme cases of interacting galaxies, and compare the evolution of galaxy pairs in the dark matter paradigm to that in the Milgromian Dynamics (MOND) framework. Following up on the seminal work by Tiret & Combes, this paper documents the first simulations of galaxy encounters in MOND with a detailed Eulerian hydrodynamical treatment of baryonic physics, including star formation and stellar feedback. We show that similar morphologies of the interacting systems can be produced by both the ...

  18. The dark matter halo shape of edge-on disk galaxies I. HI observations

    NARCIS (Netherlands)

    O'Brien, J. C.; Freeman, K. C.; van der Kruit, P. C.; Bosma, A.

    This is the first paper of a series in which we will attempt to put constraints on the flattening of dark halos in disk galaxies. We observe for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer

  19. The dark matter halo shape of edge-on disk galaxies. IV. UGC 7321

    NARCIS (Netherlands)

    O'Brien, J. C.; Freeman, K. C.; van der Kruit, P. C.

    This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer

  20. Testing the dark matter hypothesis with low surface brightness galaxies and other evidence

    NARCIS (Netherlands)

    McGaugh, SS; de Blok, WJG

    1998-01-01

    The severity of the mass discrepancy in spiral galaxies is strongly correlated with the central surface brightness of their disks. Progressively lower surface brightness galaxies have ever larger mass discrepancies. No other parameter (luminosity, size, velocity, morphology) is so well correlated wi

  1. Are observations of the galaxy cluster A1689 consistent with a neutrino dark matter scenario?

    NARCIS (Netherlands)

    Nieuwenhuizen, T.M.; Morandi, A.

    2013-01-01

    Recent weak and strong lensing data of the galaxy cluster A1689 are modelled by dark fermions that are quantum degenerate within some core. The gas density, deduced from X-ray observations up to 1 Mpc and obeying a cored power law, is taken as input, while the galaxy mass density is modelled. An add

  2. The dark matter halo shape of edge-on disk galaxies. IV. UGC 7321

    NARCIS (Netherlands)

    O'Brien, J. C.; Freeman, K. C.; van der Kruit, P. C.

    2010-01-01

    This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flari

  3. The dark matter halo shape of edge-on disk galaxies : IV. UGC 7321

    NARCIS (Netherlands)

    O'Brien, J. C.; Freeman, K. C.; van der Kruit, P. C.

    2010-01-01

    This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flari

  4. Evolution of the atomic and molecular gas content of galaxies in dark matter haloes

    NARCIS (Netherlands)

    Popping, Gergö; Behroozi, Peter S.; Peeples, Molly S.

    2015-01-01

    We present a semi-empirical model to infer the atomic and molecular hydrogen content of galaxies as a function of halo mass and time. Our model combines the star formation rate (SFR)-halo mass-redshift relation (constrained by galaxy abundances) with inverted SFR-surface density relations to infer g

  5. Interstellar Ices

    CERN Document Server

    Boogert, A C A

    2003-01-01

    Currently ~36 different absorption bands have been detected in the infrared spectra of cold, dense interstellar and circumstellar environments. These are attributed to the vibrational transitions of ~17 different molecules frozen on dust grains. We review identification issues and summarize the techniques required to extract information on the physical and chemical evolution of these ices. Both laboratory simulations and line of sight studies are essential. Examples are given for ice bands observed toward high mass protostars, fields stars and recent work on ices in disks surrounding low mass protostars. A number of clear trends have emerged in recent years. One prominent ice component consists of an intimate mixture between H2O, CH3OH and CO2 molecules. Apparently a stable balance exists between low temperature hydrogenation and oxidation reactions on grain surfaces. In contrast, an equally prominent ice component, consisting almost entirely of CO, must have accreted directly from the gas phase. Thermal proc...

  6. INTERSTELLAR TURBULENCE

    Directory of Open Access Journals (Sweden)

    D. Falceta-Gonçalves

    2011-01-01

    Full Text Available The Interstellar Medium (ISM is a complex, multi-phase system, where the history of the stars occurs. The processes of birth and death of stars are strongly coupled to the dynamics of the ISM. The observed chaotic and diffusive motions of the gas characterize its turbulent nature. Understanding turbulence is crucial for understanding the star-formation process and the energy-mass feedback from evolved stars. Magnetic fields, threading the ISM, are also observed, making this effort even more difficult. In this work, I briefly review the main observations and the characterization of turbulence from these observable quantities. Following on, I provide a review of the physics of magnetized turbulence. Finally, I will show the main results from theoretical and numerical simulations, which can be used to reconstruct observable quantities, and compare these predictions to the observations.

  7. Dust in 3CR radio galaxies: On the FR 1 - FR 2 difference

    Science.gov (United States)

    Müller, S. A. H.; Haas, M.; Siebenmorgen, R.; Klaas, U.; Meisenheimer, K.; Chini, R.; Albrecht, M.

    2004-11-01

    We compare three 3CR samples of 11 FR 1 galaxies, 17 FR 2 galaxies and 18 lobe-dominated quasars contained in the ISO Data Archive. In contrast to the powerful FR 2 galaxies with edge-brightened lobes, the low radio power FR 1 galaxies in our sample do not exhibit any high MIR or FIR dust luminosity, which is typical for a buried, intrinsically more luminous AGN. This consolidates the fact already inferred from optical studies that their AGNs have only a relatively low luminosity. Also the FR 1 galaxies show a high FIR/MIR luminosity ratio, compared to quasars, suggesting that their FIR luminosity is substantially powered by the interstellar radiation field (ISRF) of the giant elliptical hosts. Finally, we discuss the FR 1 - FR 2 morphological dichotomy. FR 1 galaxies do not have more interstellar matter (ISM) than FR 2s as traced - on the large scale - by the cool FIR emitting dust and - in the nuclear region - by the warm MIR emitting dust. Due to the lack of central gas we suggest that the black holes of our FR 1 galaxies are fed at a lower accretion rate than those of the FR 2 galaxies. Based on observations with the Infrared Space Observatory ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the UK) and with the participation of ISAS and NASA.

  8. Relations between the Sizes of Galaxies and Their Dark Matter Halos at Redshifts 0 < z < 3

    Science.gov (United States)

    Huang, Kuang-Han; Fall, S. Michael; Ferguson, Henry C.; van der Wel, Arjen; Grogin, Norman; Koekemoer, Anton; Lee, Seong-Kook; Pérez-González, Pablo G.; Wuyts, Stijn

    2017-03-01

    We derive relations between the effective radii R eff of galaxies and the virial radii R 200c of their dark matter halos over the redshift range 0 purpose, we derive a new SMHM relation based on the same selection criteria and other assumptions as for our sample of galaxies with size measurements. As a check on the robustness of our results, we also derive R eff–R 200c relations for three independent SMHM relations from the literature. We find that galaxy R eff is proportional on average to halo R 200c , confirming and extending to high redshifts the z = 0 results of Kravtsov. Late-type galaxies (with low Sérsic index and high specific star formation rate (sSFR)) follow a linear R eff–R 200c relation, with effective radii at 0.5 < z < 3 close to those predicted by simple models of disk formation; at z < 0.5, the sizes of late-type galaxies appear to be slightly below this prediction. Early-type galaxies (with high Sérsic index and low sSFR) follow a roughly parallel R eff–R 200c relation, ∼0.2–0.3 dex below the one for late-type galaxies. Our observational results, reinforced by recent hydrodynamical simulations, indicate that galaxies grow quasi-homologously with their dark matter halos.

  9. Probing the Interstellar Medium of z~1 Ultra-luminous Infrared Galaxies through Interferometric Observations of CO and Spitzer Mid-infrared Spectroscopy

    CERN Document Server

    Pope, Alexandra; Frayer, David; Armus, Lee; Chary, Ranga-Ram; Daddi, Emanuele; Desai, Vandana; Dickinson, Mark E; Elbaz, David; Gabor, Jared; Kirkpatrick, Allison

    2013-01-01

    We explore the relationship between gas, dust and star formation in a sample of 12 ultra-luminous infrared galaxies (ULIRGs) at high redshift compared to a similar sample of local galaxies. We present new CO observations and/or Spitzer mid-IR spectroscopy for 6 70 micron selected galaxies at z~1 in order to quantify the properties of the molecular gas reservoir, the contribution of an active galactic nuclei (AGN) to the mid-IR luminosity and the star formation efficiency (SFE=LIR/L'CO). The mid-IR spectra show strong polycyclic aromatic hydrocarbon (PAH) emission and our spectral decomposition suggests that the AGN makes a minimal contribution (<25%) to the mid-IR luminosity. The 70 micron selected ULIRGs which we find to be spectroscopic close pairs, are observed to have high SFE, similar to local ULIRGs and high redshift submillimeter galaxies, consistent with enhanced IR luminosity due to an ongoing major merger. Combined with existing observations of local and high redshift ULIRGs, we further compare t...

  10. Dark-ages Reionization and Galaxy Formation Simulation - VIII. Suppressed growth of dark matter haloes during the Epoch of Reionization

    Science.gov (United States)

    Qin, Yuxiang; Duffy, Alan R.; Mutch, Simon J.; Poole, Gregory B.; Geil, Paul M.; Angel, Paul W.; Mesinger, Andrei; Wyithe, J. Stuart B.

    2017-05-01

    We investigate how the hydrostatic suppression of baryonic accretion affects the growth rate of dark matter haloes during the Epoch of Reionization. By comparing halo properties in a simplistic hydrodynamic simulation in which gas only cools adiabatically, with its collisionless equivalent, we find that halo growth is slowed as hydrostatic forces prevent gas from collapsing. In our simulations, at the high redshifts relevant for reionization (between ˜6 and ˜11), haloes that host dwarf galaxies (≲109 M⊙) can be reduced by up to a factor of 2 in mass due to the hydrostatic pressure of baryons. Consequently, the inclusion of baryonic effects reduces the amplitude of the low-mass tail of the halo mass function by factors of 2-4. In addition, we find that the fraction of baryons in dark matter haloes hosting dwarf galaxies at high redshift never exceeds ˜90 per cent of the cosmic baryon fraction. When implementing baryonic processes, including cooling, star formation, supernova feedback and reionization, the suppression effects become more significant with further reductions of 30-60 per cent. Although convergence tests suggest that the suppression may become weaker in higher resolution simulations, this suppressed growth will be important for semi-analytic models of galaxy formation, in which the halo mass inherited from an underlying N-body simulation directly determines galaxy properties. Based on the adiabatic simulation, we provide tables to account for these effects in N-body simulations and present a modification of the halo mass function along with explanatory analytic calculations.

  11. High Resolution Simulations for Hierarchical Formation of Dark Matter Halos Hosting Galaxies and AGNs at High Redshift

    Science.gov (United States)

    Ishiyama, Tomoaki

    2015-08-01

    We present the evolution of dark matter halos in six large cosmological N-body simulations, called the ν2GC (New Numerical Galaxy Catalog) simulations on the basis of the LCDM cosmology consistent with observational results obtained by the Planck satellite. The largest simulation consists of 81923 (550 billion) dark matter particles in a box of 1.12h-1Gpc (a mass resolution of 2.20×108 h-1M⊙). Among simulations utilizing boxes larger than 1h-1Gpc, our simulation yields the highest resolution simulation that has ever been achieved. Compared with the Millennium simulation (Springel et al. 2005), our simulation offers the advantages of a mass resolution that is four times better and a spatial volume that is 11 times larger. A ν2GC simulation with the smallest box consists of eight billions particles in a box of 70h-1Mpc (a mass resolution of 3.44×106 -1M⊙). These simulations can follow the evolution of halos over masses of eight orders of magnitude, from small dwarf galaxies to massive clusters. Using the unprecedentedly high resolution and powerful statistics of the ν2GC simulations, we provide statistical results of the halo mass function, mass accretion rate, formation redshift, and merger statistics, and present accurate fitting functions for the Planck cosmology, from redshift 10 to 0. By combining the ν2GC simulations with our new semi-analytic galaxy formation model, we are able to prepare mock catalogs of galaxies and active galactic nuclei, which will be made publicly available in the near future.

  12. Physical Processes in the Interstellar Medium

    CERN Document Server

    Klessen, Ralf S

    2014-01-01

    Interstellar space is filled with a dilute mixture of charged particles, atoms, molecules and dust grains, called the interstellar medium (ISM). Understanding its physical properties and dynamical behavior is of pivotal importance to many areas of astronomy and astrophysics. Galaxy formation and evolution, the formation of stars, cosmic nucleosynthesis, the origin of large complex, prebiotic molecules and the abundance, structure and growth of dust grains which constitute the fundamental building blocks of planets, all these processes are intimately coupled to the physics of the interstellar medium. However, despite its importance, its structure and evolution is still not fully understood. Observations reveal that the interstellar medium is highly turbulent, consists of different chemical phases, and is characterized by complex structure on all resolvable spatial and temporal scales. Our current numerical and theoretical models describe it as a strongly coupled system that is far from equilibrium and where th...

  13. The Effect of the AGN Feedback on the Interstellar Medium of Early-Type Galaxies:2D Hydrodynamical Simulations of the Low-Rotation Case.

    Science.gov (United States)

    Ciotti, Luca; Pellegrini, Silvia; Negri, Andrea; Ostriker, Jeremiah P.

    2017-01-01

    We present two-dimensional hydrodynamical simulations for the evolution of early-type galaxies containing central massive black holes (MBHs), starting at an age of ≃ 2 {Gyr}. The code contains accurate and physically consistent radiative and mechanical active galactic nucleus (AGN) wind feedback, with parsec-scale central resolution. Mass input comes from stellar evolution; energy input includes Type Ia (SNIa) and II supernovae and stellar heating; star formation (SF) is included. Realistic, axisymmetric dynamical galaxy models are built solving the Jeans’ equations. The lowest mass models ({M}\\star =8 {10}10 {M}ȯ ) develop global outflows sustained by SNIa heating, ending with a lower amount of hot gas and new stars. In more massive models, nuclear outbursts last to the present epoch, with large and frequent fluctuations in nuclear emission and from the gas ({L}{{X}}). Each burst lasts ∼ {10}7.5 years, during which cold, inflowing, and hot, outflowing gas phases coexist. The {L}{{X}}{--}{T}{{X}} relation for the gas matches that of local galaxies. AGN activity causes positive feedback for SF. Roughly half of the total mass loss is recycled into new stars ({{Δ }}{M}\\star ), just ≃3% of it is accreted on the MBH, the remainder being ejected from the galaxy. The ratio between the mass of gas expelled to that in new stars, the load factor, is ≃ 0.6. Rounder galaxy shapes lead to larger final MBH masses, {{Δ }}{M}\\star , and {L}{{X}}. Almost all of the time is spent at very low nuclear luminosities, yet one quarter of the total energy is emitted at an Eddington ratio > 0.1. The duty-cycle of AGN activity is approximately 4%.

  14. Constraining the nature of dark matter with the star formation history of the faintest Local Group dwarf galaxy satellites

    CERN Document Server

    Chau, Alice; Governato, Fabio

    2016-01-01

    $\\Lambda$-Warm Dark Matter (WDM) has been proposed as alternative scenario to $\\Lambda$ cold dark matter (CDM), motivated by discrepancies at the scale of dwarf galaxies, with less small-scale power and realized by collisionless particles with energies in the range $1-3$ keV. We present a new approach to constrain the viability of such WDM models using star formation histories of the dwarf spheroidal galaxies (dSphs) in the Local Group. We compare their high time-resolution star formation histories (SFHs) obtained with HST-based color magnitude diagrams with the range of possible collapse redshifts of their dark matter halos expected in CDM and in different WDM scenarios. The collapse redshift is inferred after determining a plausible infall mass of the subhalo. This is based on the current mass of individual dwarf inferred from stellar kinematics combined with results of cosmological simulations providing information on the subhalo evolution. Since WDM subhalos close to the filtering mass scale form signific...

  15. Testing AGN feedback models in galaxy evolution

    Science.gov (United States)

    Shin, Min-Su

    Galaxy formation and evolution have been one of the most challenging problems in astrophysics. A single galaxy has various components (stars, atomic and molecular gas, a supermassive black hole, and dark matter) and has interacted with its cosmic environment throughout its history. A key issue in understanding galaxy evolution is to find the dominant physical processes in the interactions between the components of a galaxy and between a galaxy and its environment. AGN feedback has been proposed as a key process to suppress late star formation in massive elliptical galaxies and as a general consequence of galaxy mergers and interactions. In this thesis, I investigate feedback effects from active galactic nuclei (AGN) using a new simulation code and data from the Sloan Digital Sky Survey. In the first chapter, I test purely mechanical AGN feedback models via a nuclear wind around the central SMBH in elliptical galaxies by comparing simulation results to four well-defined observational constraints: the mass ratio between the SMBH and its host galaxy, the lifetime of the quasar phase, the X-ray luminosity from the hot interstellar medium, and the mass fraction of young stars. Even though purely mechanical AGN feedback is commonly assumed in cosmological simulations, I find that it is inadequate, and cannot reproduce all four observational constraints simultaneously. This result suggests that both mechanical and radiative feedback modes are important physical processes. In the second chapter, I simulate the coevolution of the SMBH and its host galaxy under different environments, represented by different amounts of gas stripping. Though the connection between environment and galaxy evolution has been well-studied, environmental effects on the growth of the SMBH have not been answered yet. I find that strong gas stripping, which satellite galaxies might experience, highly suppresses SMBH mass accretion and AGN activity. Moreover, the suppression of the SMBH growth is

  16. The dark matter halo shape of edge-on disk galaxies - I. HI observations

    CERN Document Server

    O'Brien, J C; van der Kruit, P C; Bosma, A

    2010-01-01

    This is the first paper of a series in which we will attempt to put constraints on the flattening of dark halos in disk galaxies. We observe for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. In this paper, we define a sample of 8 HI-rich late-type galaxies suitable for this purpose and present the HI observations.

  17. Empirical Constraints on the Evolution of the Relationship between Black Hole and Galaxy Mass: Scatter Matters

    OpenAIRE

    Somerville, Rachel S.

    2009-01-01

    I investigate whether useful constraints on the evolution of the relationship between galaxy mass and black hole (BH) mass can be obtained from recent measurements of galaxy stellar mass functions and QSO bolometric luminosity functions at high redshift. I assume a simple power-law relationship between galaxy mass and BH mass, as implied by BH mass measurements at low redshift, and consider only evolution in the zero-point of the relation. I argue that one can obtain a lower limit on the zero...

  18. Scaling relations for galaxies prior to reionization

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pengfei; Norman, Michael L.; Xu, Hao [CASS, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Wise, John H. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, GA 30332 (United States); O' Shea, Brian W., E-mail: pec008@ucsd.edu, E-mail: mlnorman@ucsd.edu, E-mail: hxu@ucsd.edu, E-mail: jwise@gatech.edu, E-mail: oshea@msu.edu [Lyman Briggs College and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2014-11-10

    The first galaxies in the universe are the building blocks of all observed galaxies. We present scaling relations for galaxies forming at redshifts z ≥ 15 when reionization is just beginning. We utilize the 'Rarepeak' cosmological radiation hydrodynamics simulation that captures the complete star formation history in over 3300 galaxies, starting with massive Population III stars that form in dark matter halos as small as ∼10{sup 6} M {sub ☉}. We make various correlations between the bulk halo quantities, such as virial, gas, and stellar masses and metallicities and their respective accretion rates, quantifying a variety of properties of the first galaxies up to halo masses of 10{sup 9} M {sub ☉}. Galaxy formation is not solely relegated to atomic cooling halos with virial temperatures greater than 10{sup 4} K, where we find a dichotomy in galaxy properties between halos above and below this critical mass scale. Halos below the atomic cooling limit have a stellar mass-halo mass relationship log M {sub *} ≅ 3.5 + 1.3log (M {sub vir}/10{sup 7} M {sub ☉}). We find a non-monotonic relationship between metallicity and halo mass for the smallest galaxies. Their initial star formation events enrich the interstellar medium and subsequent star formation to a median of 10{sup –2} Z {sub ☉} and 10{sup –1.5} Z {sub ☉}, respectively, in halos of total mass 10{sup 7} M {sub ☉}, which is then diluted by metal-poor inflows well beyond Population III pre-enrichment levels of 10{sup –3.5} Z {sub ☉}. The scaling relations presented here can be employed in models of reionization, galaxy formation, and chemical evolution in order to consider these galaxies forming prior to reionization.

  19. Two-Dimensional MHD Numerical Simulations of Magnetic Reconnection Triggered by A Supernova Shock in Interstellar Medium, Generation of X-Ray Gas in Galaxy

    CERN Document Server

    Tanuma, S; Kudoh, T; Shibata, K; Tanuma, Syuniti; Yokoyama, Takaaki; Kudoh, Takahiro; Shibata, Kazunari

    2001-01-01

    We examine the magnetic reconnection triggered by a supernova (or a point explosion) in interstellar medium, by performing two-dimensional resistive magnetohydrodynamic (MHD) numerical simulations with high spatial resolution. We found that the magnetic reconnection starts long after a supernova shock (fast-mode MHD shock) passes a current sheet. The current sheet evolves as follows: (i) Tearing-mode instability is excited by the supernova shock, and the current sheet becomes thin in its nonlinear stage. (ii) The current-sheet thinning is saturated when the current-sheet thickness becomes comparable to that of Sweet-Parker current sheet. After that, Sweet-Parker type reconnection starts, and the current-sheet length increases. (iii) ``Secondary tearing-mode instability'' occurs in the thin Sweet-Parker current sheet. (iv) As a result, further current-sheet thinning occurs and anomalous resistivity sets in, because gas density decreases in the current sheet. Petschek type reconnection starts and heats interste...

  20. The Effect of the AGN Feedback on the Interstellar Medium of Early-Type Galaxies: 2D Hydrodynamical Simulations of the Low-Rotation Case

    CERN Document Server

    Ciotti, L; Negri, A; Ostriker, J P

    2016-01-01

    We present 2D hydrodynamical simulations for the evolution of early-type galaxies containing central massive black holes (MBHs), starting at age 2 Gyr. The code contains accurate and physically consistent radiative and mechanical AGN wind feedback, with parsec-scale central resolution. Mass input comes from stellar evolution; energy input includes Type Ia and II supernova and stellar heating; star-formation is included. Realistic, axisymmetric dynamical models for the galaxies are built solving the Jeans' equations. The lowest mass models (Mstar = 8 10^{10}Msun) develop global outflows sustained by SNIa's heating, ending with a significantly lower amount of hot gas and new stars. In more massive models, nuclear outbursts last to the present epoch, with large and frequent fluctuations in nuclear emission and from the gas (Lx). Each burst last ~ 10^{7.5} yr, during which (for r 0.1. The duty-cycle of AGN activity approximates 4% (Abridged).