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Sample records for young clusters ngc

  1. Young globular clusters in NGC 1316

    Science.gov (United States)

    Sesto, Leandro A.; Faifer, Favio R.; Smith Castelli, Analía V.; Forte, Juan C.; Escudero, Carlos G.

    2018-05-01

    We present multi-object spectroscopy of the inner zone of the globular cluster (GC) system associated with the intermediate-age merger remnant NGC 1316. Using the multi-object mode of the GMOS camera, we obtained spectra for 35 GCs. We find pieces of evidence that the innermost GCs of NGC 1316 rotate almost perpendicular to the stellar component of the galaxy. In a second stage, we determined ages, metallicities and α-element abundances for each GC present in the sample, through the measurement of different Lick/IDS indices and their comparison with simple stellar population models. We confirmed the existence of multiple GC populations associated with NGC 1316, where the presence of a dominant subpopulation of very young GCs, with an average age of 2.1 Gyr, metallicities between -0.5 < [Z/H] < 0.5 dex and α-element abundances in the range -0.2 < [α/Fe] < 0.3 dex, stands out. Several objects in our sample present subsolar values of [α/Fe] and a large spread of [Z/H] and ages. Some of these objects could actually be stripped nuclei, possibly accreted during minor merger events. Finally, the results have been analyzed with the aim of describing the different episodes of star formation and thus provide a more complete picture about the evolutionary history of the galaxy. We conclude that these pieces of evidence could indicate that this galaxy has cannibalized one or more gas-rich galaxies, where the last fusion event occurred about 2 Gyr ago.

  2. THE BRIGHTEST YOUNG STAR CLUSTERS IN NGC 5253

    Energy Technology Data Exchange (ETDEWEB)

    Calzetti, D. [Department of Astronomy, University of Massachusetts—Amherst, Amherst, MA 01003 (United States); Johnson, K. E. [Department of Astronomy, University of Virginia, Charlottesville, VA (United States); Adamo, A. [Department of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Gallagher III, J. S.; Ryon, J. E. [Department of Astronomy, University of Wisconsin–Madison, Madison, WI (United States); Andrews, J. E. [Department of Astronomy, University of Arizona, Tucson, AZ (United States); Smith, L. J. [European Space Agency/Space Telescope Science Institute, Baltimore, MD (United States); Clayton, G. C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA (United States); Lee, J. C.; Sabbi, E.; Ubeda, L.; Bright, S. N.; Whitmore, B. C.; Aloisi, A. [Space Telescope Science Institute, Baltimore, MD (United States); Kim, H. [Department of Astronomy, The University of Texas at Austin, Austin, TX (United States); Thilker, D. [Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States); Zackrisson, E. [Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Mink, S. E. de [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam (Netherlands); Chandar, R., E-mail: calzetti@astro.umass.edu [Department of Physics and Astronomy, University of Toledo, Toledo, OH (United States); and others

    2015-10-01

    The nearby dwarf starburst galaxy NGC 5253 hosts a number of young, massive star clusters, the two youngest of which are centrally concentrated and surrounded by thermal radio emission (the “radio nebula”). To investigate the role of these clusters in the starburst energetics, we combine new and archival Hubble Space Telescope images of NGC 5253 with wavelength coverage from 1500 Å to 1.9 μm in 13 filters. These include Hα, Pβ, and Pα, and the imaging from the Hubble Treasury Program LEGUS (Legacy Extragalactic UV Survey). The extraordinarily well-sampled spectral energy distributions enable modeling with unprecedented accuracy the ages, masses, and extinctions of the nine optically brightest clusters (M{sub V} < −8.8) and the two young radio nebula clusters. The clusters have ages ∼1–15 Myr and masses ∼1 × 10{sup 4}–2.5 × 10{sup 5} M{sub ⊙}. The clusters’ spatial location and ages indicate that star formation has become more concentrated toward the radio nebula over the last ∼15 Myr. The most massive cluster is in the radio nebula; with a mass ∼2.5 × 10{sup 5} M{sub ⊙} and an age ∼1 Myr, it is 2–4 times less massive and younger than previously estimated. It is within a dust cloud with A{sub V} ∼ 50 mag, and shows a clear near-IR excess, likely from hot dust. The second radio nebula cluster is also ∼1 Myr old, confirming the extreme youth of the starburst region. These two clusters account for about half of the ionizing photon rate in the radio nebula, and will eventually supply about 2/3 of the mechanical energy in present-day shocks. Additional sources are required to supply the remaining ionizing radiation, and may include very massive stars.

  3. Young stars in the old galactic cluster NGC 188

    International Nuclear Information System (INIS)

    Veer, F. van 't

    1984-01-01

    We first briefly discuss the age of the oldest known galactic clusters, according to recently published determinations. The now definitely established membership of our W UMa type contact binaries in this cluster is difficult to understand if the age of these stars is that of the cluster. It appears therefore that these binaries are much younger and that the several episodes of star formation took place in NGC 188. This conclusion is reached after a new study of the mean density of the four contact binaries and a critical discussion of the chemical composition and the mixing length parameter. (orig.)

  4. CCD photometry of the distant young open cluster NGC 7510

    International Nuclear Information System (INIS)

    Sagar, R.; Bonn Univ.; Griffiths, W.K.

    1991-01-01

    CCD observations in B, V and I passbands have been used to generate deep V, (B-V) and V,(V-I) colour-magnitude diagrams for the open cluster NGC 7510. The sample consists of 592 stars reaching down to V=21 mag. There appears to be non-uniform extinction over the face of the cluster with the value of colour excess, E(B-V), ranging from 1.0 to 1.3 mag. The law of interstellar extinction in the direction of the cluster is found to be normal. A broad main sequence is clearly visible in both colour-magnitude diagrams. From the bluest part of the colour-magnitude diagrams, the true distance modulus to the cluster has been estimated as 12.5±0.3 mag and an upper limit of 10 Myr has been assigned for the cluster age. (author)

  5. An unexpected detection of bifurcated blue straggler sequences in the young globular cluster NGC 2173

    OpenAIRE

    Li, Chengyuan; Deng, Licai; de Grijs, Richard; Jiang, Dengkai; Xin, Yu

    2018-01-01

    Bifurcated patterns of blue straggler stars in their color--magnitude diagrams have atracted significant attention. This type of special (but rare) pattern of two distinct blue straggler sequences is commonly interpreted as evidence of cluster core-collapse-driven stellar collisions as an efficient formation mechanism. Here, we report the detection of a bifurcated blue straggler distribution in a young Large MagellanicCloud cluster, NGC 2173. Because of the cluster's low central stellar numbe...

  6. The Structure of the Young Star Cluster NGC 6231. II. Structure, Formation, and Fate

    Science.gov (United States)

    Kuhn, Michael A.; Getman, Konstantin V.; Feigelson, Eric D.; Sills, Alison; Gromadzki, Mariusz; Medina, Nicolás; Borissova, Jordanka; Kurtev, Radostin

    2017-12-01

    The young cluster NGC 6231 (stellar ages ˜2-7 Myr) is observed shortly after star formation activity has ceased. Using the catalog of 2148 probable cluster members obtained from Chandra, VVV, and optical surveys (Paper I), we examine the cluster’s spatial structure and dynamical state. The spatial distribution of stars is remarkably well fit by an isothermal sphere with moderate elongation, while other commonly used models like Plummer spheres, multivariate normal distributions, or power-law models are poor fits. The cluster has a core radius of 1.2 ± 0.1 pc and a central density of ˜200 stars pc-3. The distribution of stars is mildly mass segregated. However, there is no radial stratification of the stars by age. Although most of the stars belong to a single cluster, a small subcluster of stars is found superimposed on the main cluster, and there are clumpy non-isotropic distributions of stars outside ˜4 core radii. When the size, mass, and age of NGC 6231 are compared to other young star clusters and subclusters in nearby active star-forming regions, it lies at the high-mass end of the distribution but along the same trend line. This could result from similar formation processes, possibly hierarchical cluster assembly. We argue that NGC 6231 has expanded from its initial size but that it remains gravitationally bound.

  7. A KINEMATIC AND PHOTOMETRIC STUDY OF THE GALACTIC YOUNG STAR CLUSTER NGC 7380

    International Nuclear Information System (INIS)

    Chen, W. P.; Chen, C. W.; Pandey, A. K.; Sharma, Saurabh; Chen Li; Sperauskas, J.; Ogura, K.; Chuang, R. J.; Boyle, R. P.

    2011-01-01

    We present proper motions, radial velocities, and a photometric study of the Galactic open cluster NGC 7380, which is associated with prominent emission nebulosity and dark molecular clouds. On the basis of the sample of highly probable member stars, the star cluster is found to be at a distance of 2.6 ± 0.4 kpc, has an age of around 4 Myr, and a physical size of ∼6 pc across with a tidal structure. The binary O-type star DH Cep is a member of the cluster in its late stage of clearing the surrounding material, and may have triggered the ongoing star formation in neighboring molecular clouds which harbor young stars that are coeval and comoving with, but not gravitationally bound by, the star cluster.

  8. An Unexpected Detection of Bifurcated Blue Straggler Sequences in the Young Globular Cluster NGC 2173

    Science.gov (United States)

    Li, Chengyuan; Deng, Licai; de Grijs, Richard; Jiang, Dengkai; Xin, Yu

    2018-03-01

    The bifurcated patterns in the color–magnitude diagrams of blue straggler stars (BSSs) have attracted significant attention. This type of special (but rare) pattern of two distinct blue straggler sequences is commonly interpreted as evidence that cluster core-collapse-driven stellar collisions are an efficient formation mechanism. Here, we report the detection of a bifurcated blue straggler distribution in a young Large Magellanic Cloud cluster, NGC 2173. Because of the cluster’s low central stellar number density and its young age, dynamical analysis shows that stellar collisions alone cannot explain the observed BSSs. Therefore, binary evolution is instead the most viable explanation of the origin of these BSSs. However, the reason why binary evolution would render the color–magnitude distribution of BSSs bifurcated remains unclear. C. Li, L. Deng, and R. de Grijs jointly designed this project.

  9. Observations of Hα-emission stars in the young cluster NGC 2264

    International Nuclear Information System (INIS)

    Rydgren, A.E.

    1979-01-01

    UBVRI photometry is given for a sample of 25 late-type Hα-emission stars in the young cluster NGC 2264. The stars are in the magnitude range 12< or =V<16. Some but not all appear to be T Tauri stars. The color--color diagrams support the view that the deviations from normal photospheric colors (due to ''spectral veiling'' and line emission) decrease with increasing wavelength between the U and I filters. In the (V, V-R) diagram, the Hα-emission stars lie in a well-defined pre-main-sequence band. Within this sample, there is a trend toward stronger line emission and spectral veiling with later spectral type. All of the likely legitimate T Tauri stars have inferred spectral types later than about K3. The question of cluster membership for stars in the cluster field with very small proper motions is considered

  10. Red giants and yellow stragglers in the young open cluster NGC 2447

    Science.gov (United States)

    da Silveira, M. D.; Pereira, C. B.; Drake, N. A.

    2018-06-01

    In this work we analysed, using high-resolution spectroscopy, a sample of 12 single and 4 spectroscopic binary stars of the open cluster NGC 2447. For the single stars, we obtained atmospheric parameters and chemical abundances of Li, C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, Nd, Eu. Rotational velocities were obtained for all the stars. The abundances of the light elements and Eu and the rotational velocities were derived using spectral synthesis technique. We obtained a mean metallicity of [Fe/H] = -0.17 ± 0.05. We found that the abundances of all elements are similar to field giants and/or giants of open clusters, even for the s-process elements, which are enhanced as in other young open clusters. We show that the spectroscopic binaries NGC 2447-26, 38, and 42 are yellow-straggler stars, of which the primary is a giant star and the secondary a main-sequence A-type star.

  11. Search for OB stars running away from young star clusters. I. NGC 6611

    Science.gov (United States)

    Gvaramadze, V. V.; Bomans, D. J.

    2008-11-01

    N-body simulations have shown that the dynamical decay of the young (~1 Myr) Orion Nebula cluster could be responsible for the loss of at least half of its initial content of OB stars. This result suggests that other young stellar systems could also lose a significant fraction of their massive stars at the very beginning of their evolution. To confirm this expectation, we used the Mid-Infrared Galactic Plane Survey (completed by the Midcourse Space Experiment satellite) to search for bow shocks around a number of young (⪉several Myr) clusters and OB associations. We discovered dozens of bow shocks generated by OB stars running away from these stellar systems, supporting the idea of significant dynamical loss of OB stars. In this paper, we report the discovery of three bow shocks produced by O-type stars ejected from the open cluster NGC 6611 (M16). One of the bow shocks is associated with the O9.5Iab star HD165319, which was suggested to be one of “the best examples for isolated Galactic high-mass star formation” (de Wit et al. 2005, A&A, 437, 247). Possible implications of our results for the origin of field OB stars are discussed.

  12. Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 using Kepler

    DEFF Research Database (Denmark)

    Hekker, S.; Basu, S.; Stello, D.

    2011-01-01

    and metallicity contribute to the observed difference in locations in the H-R diagram of the old metal-rich cluster NGC 6791 and the middle-aged solar-metallicity cluster NGC 6819. For the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar...

  13. NGC 1866: First Spectroscopic Detection of Fast-rotating Stars in a Young LMC Cluster

    Energy Technology Data Exchange (ETDEWEB)

    Dupree, A. K.; Dotter, A.; Johnson, C. I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Marino, A. F.; Milone, A. P. [Australian National University, The Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Weston Creek, ACT 2611 (Australia); Bailey, J. I. III [Leiden Observatory, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Crane, J. D. [The Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Mateo, M. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Olszewski, E. W. [The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)

    2017-09-01

    High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (∼200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/ Magellan Fiber System and MSpec spectrograph on the Magellan -Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit H α emission (indicative of Be-star decretion disks), others have shallow broad H α absorption (consistent with rotation ≳150 km s{sup −1}), or deep H α core absorption signaling lower rotation velocities (≲150 km s{sup −1}). The spectra appear consistent with two populations of stars—one rapidly rotating, and the other, younger and slowly rotating.

  14. A young solar twin in the Rosette cluster NGC 2244 line of sight

    Science.gov (United States)

    Huber, Jeremy M.; Kielkopf, John F.; Mengel, Matthew; Carter, Bradley D.; Ferland, Gary J.; Clark, Frank O.

    2018-05-01

    Based on prior precision photometry and cluster age analysis, the bright star GSC 00154-01819 is a possible young pre-main sequence member of the Rosette cluster, NGC 2244. As part of a comprehensive study of the large-scale structure of the Rosette and its excitation by the cluster stars, we noted this star as a potential backlight for a probe of the interstellar medium and extinction along the sight line towards a distinctive nebular feature projected on to the cluster centre. New high-resolution spectra of the star were taken with the University College London Echelle Spectrograph of the AAT. They reveal that rather than being a reddened spectral type B or A star within the Mon OB2 association, it is a nearby, largely unreddened, solar twin of spectral type G2V less than 180 Myr old. It is about 219 pc from the Sun with a barycentric radial velocity of +14.35 ± 1.99 km s-1. The spectrum of the Rosette behind it and along this line of sight shows a barycentric radial velocity of +26.0 ± 2.4 km s-1 in H α, and a full width at half-maximum velocity dispersion of 61.94 ± 1.38 km s-1.

  15. NGC 6705 a young α-enhanced open cluster from OCCASO data

    Science.gov (United States)

    Casamiquela, L.; Carrera, R.; Balaguer-Núñez, L.; Jordi, C.; Chiappini, C.; Anders, F.; Antoja, T.; Miret-Roig, N.; Romero-Gomez, M.; Blanco-Cuaresma, S.; Pancino, E.; Aguado, D. S.; del Pino, A.; Diaz-Perez, L.; Gallart, C.

    2018-03-01

    Context. The stellar [α/Fe] abundance is sometimes used as a proxy for stellar age, following standard chemical evolution models for the Galaxy, as seen by different observational results. Aim. In this work, we aim to show that the open cluster NGC 6705/M 11 has a significant α-enhancement [α/Fe] > 0.1 dex, despite its young age ( 300 Myr), challenging the current paradigm. Methods: We used high resolution (R > 65 000) high signal-to-noise ( 70) spectra of eight red clump stars, acquired within the OCCASO survey. We determined very accurate chemical abundances of several α elements, using an equivalent width methodology (Si, Ca and Ti), and spectral synthesis fits (Mg and O). Results: We obtain [Si/Fe] = 0.13 ± 0.05, [Mg/Fe] = 0.14 ± 0.07, [O/Fe] = 0.17 ± 0.07, [Ca/Fe] = 0.06 ± 0.05, and [Ti/Fe] = 0.03 ± 0.03. Our results place these clusters within the group of young [α/Fe]-enhanced field stars recently found by several authors in the literature. The ages of our stars have an uncertainty of around 50 Myr, much more precise than for field stars. By integrating the cluster's orbit in several non-axisymmetric Galactic potentials, we establish the M 11's most likely birth radius as lying between 6.8-7.5 kpc from the Galactic centre, not far from its current position. Conclusions: With the robust open cluster age scale, our results prove that a moderate [α/Fe]-enhancement is no guarantee for a star to be old, and that not all α-enhanced stars can be explained with an evolved blue straggler scenario. Based on our orbit calculations, we further argue against a Galactic bar origin of M 11. Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A66

  16. Search for OB stars running away from young star clusters. II. The NGC 6357 star-forming region

    Science.gov (United States)

    Gvaramadze, V. V.; Kniazev, A. Y.; Kroupa, P.; Oh, S.

    2011-11-01

    Dynamical few-body encounters in the dense cores of young massive star clusters are responsible for the loss of a significant fraction of their massive stellar content. Some of the escaping (runaway) stars move through the ambient medium supersonically and can be revealed via detection of their bow shocks (visible in the infrared, optical or radio). In this paper, which is the second of a series of papers devoted to the search for OB stars running away from young ( ≲ several Myr) Galactic clusters and OB associations, we present the results of the search for bow shocks around the star-forming region NGC 6357. Using the archival data of the Midcourse Space Experiment (MSX) satellite and the Spitzer Space Telescope, and the preliminary data release of the Wide-Field Infrared Survey Explorer (WISE), we discovered seven bow shocks, whose geometry is consistent with the possibility that they are generated by stars expelled from the young (~1-2 Myr) star clusters, Pismis 24 and AH03 J1725-34.4, associated with NGC 6357. Two of the seven bow shocks are driven by the already known OB stars, HD 319881 and [N78] 34. Follow-up spectroscopy of three other bow-shock-producing stars showed that they are massive (O-type) stars as well, while the 2MASS photometry of the remaining two stars suggests that they could be B0 V stars, provided that both are located at the same distance as NGC 6357. Detection of numerous massive stars ejected from the very young clusters is consistent with the theoretical expectation that star clusters can effectively lose massive stars at the very beginning of their dynamical evolution (long before the second mechanism for production of runaway stars, based on a supernova explosion in a massive tight binary system, begins to operate) and lends strong support to the idea that probably all field OB stars have been dynamically ejected from their birth clusters. A by-product of our search for bow shocks around NGC 6357 is the detection of three circular

  17. PROGRESSIVE STAR FORMATION IN THE YOUNG GALACTIC SUPER STAR CLUSTER NGC 3603

    International Nuclear Information System (INIS)

    Beccari, Giacomo; Spezzi, Loredana; De Marchi, Guido; Andersen, Morten; Paresce, Francesco; Young, Erick; Panagia, Nino; Bond, Howard; Balick, Bruce; Calzetti, Daniela; Carollo, C. Marcella; Disney, Michael J.; Dopita, Michael A.; Frogel, Jay A.; Hall, Donald N. B.; Holtzman, Jon A.; Kimble, Randy A.; McCarthy, Patrick J.; O'Connell, Robert W.; Saha, Abhijit

    2010-01-01

    Early Release Science observations of the cluster NGC 3603 with the WFC3 on the refurbished Hubble Space Telescope allow us to study its recent star formation history. Our analysis focuses on stars with Hα excess emission, a robust indicator of their pre-main sequence (PMS) accreting status. The comparison with theoretical PMS isochrones shows that 2/3 of the objects with Hα excess emission have ages from 1 to 10 Myr, with a median value of 3 Myr, while a surprising 1/3 of them are older than 10 Myr. The study of the spatial distribution of these PMS stars allows us to confirm their cluster membership and to statistically separate them from field stars. This result establishes unambiguously for the first time that star formation in and around the cluster has been ongoing for at least 10-20 Myr, at an apparently increasing rate.

  18. The Young Massive Stellar Cluster Sandage-96 after the Explosion of SN 2004DJ in NGC 2403

    Science.gov (United States)

    Vinko, J.; Sarneczky, K.; Balog, Z.; Immler, S.; Sugerman, B.; Brown, P. J.; Misselt, K.; Szabo, Gy. M.; Klagyivik, P.; Kun, M.; hide

    2008-01-01

    The bright supernova 2004dj occurred within the young massive stellar cluster Sandage-96 in a spiral arm of NGC 2403, close to other star-forming complexes. New multi-wavelength observations obtained with several ground-based- and space telescopes are combined to study the radiation from Sandage-96 after SN 2004dj faded away. The late-time light curves show that Sandage-96 started to dominate the flux in the optical bands after September, 2006 (+800 days after explosion). The optical fluxes are equal to the pre-explosion ones, suggesting that Sandage-96 has survived the explosion without significant changes in its stellar population. An optical Keck-spectrum obtained at +900 days after explosion shows the dominant blue continuum from the cluster stars shortward of 6000 A as well as strong SN nebular emission lines redward. The integrated SED of the cluster has been extended into the UV-region by archival XMM-Newton and new Swift observations, and compared with theoretical models. The outer parts of the cluster have been resolved by HST allowing the construction of a color-magnitude diagram. The fitting of the cluster SED with theoretical isochrones results in two possible solutions with ages being 9+/-1 Myr and 30+/-10 Myr, depending on the assumed metallicity and the theoretical model family. The isochrone fitting of the color-magnitude diagram indicates that the outer part of the cluster consists of stars having an age dispersion of 16 hypothesis that the outskirt of Sandage-96 is contaminated by stars captured from the field during cluster formation. The young age of Sandage-96 and the comparison of its pre- and post-explosion SEDs suggest a progenitor mass of 15 < or equal to M(sub prog) < 25 Stellar Mass.

  19. NEAR-INFRARED IMAGING AND SPECTROSCOPIC SURVEY OF THE SOUTHERN REGION OF THE YOUNG OPEN CLUSTER NGC 2264

    Energy Technology Data Exchange (ETDEWEB)

    Marinas, Naibi; Lada, Elizabeth A. [Astronomy Department, University of Florida, Gainesville, FL 32611 (United States); Teixiera, Paula S. [Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Vienna (Austria); Lada, Charles J. [Harvard-Smithsonian CFA, Cambridge, MA (United States)

    2013-08-01

    We have obtained JHK near-IR images and JH band low-resolution spectra of candidate members of the southern region of the young open cluster NGC 2264. We have determined spectral types from H-band spectra for 54 sources, 25 of which are classified for the first time. The stars in our sample cover a large range of spectral types (A8-M8). Using a cluster distance of 780 pc, we determined a median age of 1 Myr for this region of NGC 2264, with 90% of the stars being 5 Myr or younger. To improve the statistical significance of our sample, we included 66 additional cluster members within our field of view with optical spectral classification in the literature. We derived infrared excesses using stellar properties to model the photospheric emission for each source and the extinction to correct FLAMINGOS near-IR and Spitzer mid-IR photometry, and obtained a disk fraction of 51% {+-} 5% for the region. Binning the stars by stellar mass, we find a disk fraction of 38% {+-} 9% for the 0.1-0.3 solar mass group, 55% {+-} 6% for 0.3-1 solar masses, and 58% {+-} 10% for the higher than 1 solar mass group. The lower disk fraction for the lower mass stars is similar to the results found in non-cluster regions like Taurus and Chamaeleon, but differs from the older 3 Myr cluster IC 348 in which the disk fraction is lower for the higher mass stars. This mass-dependent disk fraction is accentuated in the sample with isochrone ages younger than 2 Myr. Here, we find that 45% {+-} 11% of the 0.1-0.3 solar mass stars have disks, 60% {+-} 7% of the 0.3-1 solar mass stars have disks, and all 1-3 solar mass stars have disks. Stellar masses might be an important factor in the ability of a system to form or retain a disk early on. However, regardless of the stellar mass, the large infrared excesses expected from optically thick disks disappear within the first 2 Myr for all stars in our study and small excesses from optically thin disks are found mostly in sources younger than 4 Myr.

  20. PRE-MAIN-SEQUENCE TURN-ON AS A CHRONOMETER FOR YOUNG CLUSTERS: NGC 346 AS A BENCHMARK

    International Nuclear Information System (INIS)

    Cignoni, M.; Tosi, M.; Sabbi, E.; Nota, A.; Degl'Innocenti, S.; Moroni, P. G. Prada; Gallagher, J. S.

    2010-01-01

    We present a novel approach to deriving the age of very young star clusters, by using the Turn-On (TOn). The TOn is the point in the color-magnitude diagram (CMD) where the pre-main sequence (PMS) joins the main sequence (MS). In the MS luminosity function (LF) of the cluster, the TOn is identified as a peak followed by a dip. We propose that by combining the CMD analysis with the monitoring of the spatial distribution of MS stars it is possible to reliably identify the TOn in extragalactic star-forming regions. Compared to alternative methods, this technique is complementary to the turnoff dating and avoids the systematic biases affecting the PMS phase. We describe the method and its uncertainties and apply it to the star-forming region NGC 346, which has been extensively imaged with the Hubble Space Telescope (HST). This study extends the LF approach in crowded extragalactic regions and opens the way for future studies with HST/WFC3, the James Webb Space Telescope and from the ground with adaptive optics.

  1. High-resolution Spectroscopic Observations of Single Red Giants in Three Open Clusters: NGC 2360, NGC 3680, and NGC 5822

    Science.gov (United States)

    Peña Suárez, V. J.; Sales Silva, J. V.; Katime Santrich, O. J.; Drake, N. A.; Pereira, C. B.

    2018-02-01

    Single stars in open clusters with known distances are important targets in constraining the nucleosynthesis process since their ages and luminosities are also known. In this work, we analyze a sample of 29 single red giants of the open clusters NGC 2360, NGC 3680, and NGC 5822 using high-resolution spectroscopy. We obtained atmospheric parameters, abundances of the elements C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd, as well as radial and rotational velocities. We employed the local thermodynamic equilibrium atmospheric models of Kurucz and the spectral analysis code MOOG. Rotational velocities and light-element abundances were derived using spectral synthesis. Based on our analysis of the single red giants in these three open clusters, we could compare, for the first time, their abundance pattern with that of the binary stars of the same clusters previously studied. Our results show that the abundances of both single and binary stars of the open clusters NGC 2360, NGC 3680, and NGC 5822 do not have significant differences. For the elements created by the s-process, we observed that the open clusters NGC 2360, NGC 3680, and NGC 5822 also follow the trend already raised in the literature that young clusters have higher s-process element abundances than older clusters. Finally, we observed that the three clusters of our sample exhibit a trend in the [Y/Mg]-age relation, which may indicate the ability of the [Y/Mg] ratio to be used as a clock for the giants. Based on the observations made with the 2.2 m telescope at the European Southern Observatory (La Silla, Chile) under an agreement with Observatório Nacional and under an agreement between Observatório Nacional and Max-Planck Institute für Astronomie.

  2. The Gaia-ESO Survey and CSI 2264: Substructures, disks, and sequential star formation in the young open cluster NGC 2264

    Science.gov (United States)

    Venuti, L.; Prisinzano, L.; Sacco, G. G.; Flaccomio, E.; Bonito, R.; Damiani, F.; Micela, G.; Guarcello, M. G.; Randich, S.; Stauffer, J. R.; Cody, A. M.; Jeffries, R. D.; Alencar, S. H. P.; Alfaro, E. J.; Lanzafame, A. C.; Pancino, E.; Bayo, A.; Carraro, G.; Costado, M. T.; Frasca, A.; Jofré, P.; Morbidelli, L.; Sousa, S. G.; Zaggia, S.

    2018-01-01

    Context. Reconstructing the structure and history of young clusters is pivotal to understanding the mechanisms and timescales of early stellar evolution and planet formation. Recent studies suggest that star clusters often exhibit a hierarchical structure, possibly resulting from several star formation episodes occurring sequentially rather than a monolithic cloud collapse. Aims: We aim to explore the structure of the open cluster and star-forming region NGC 2264 ( 3 Myr), which is one of the youngest, richest and most accessible star clusters in the local spiral arm of our Galaxy; we link the spatial distribution of cluster members to other stellar properties such as age and evolutionary stage to probe the star formation history within the region. Methods: We combined spectroscopic data obtained as part of the Gaia-ESO Survey (GES) with multi-wavelength photometric data from the Coordinated Synoptic Investigation of NGC 2264 (CSI 2264) campaign. We examined a sample of 655 cluster members, with masses between 0.2 and 1.8 M⊙ and including both disk-bearing and disk-free young stars. We used Teff estimates from GES and g,r,i photometry from CSI 2264 to derive individual extinction and stellar parameters. Results: We find a significant age spread of 4-5 Myr among cluster members. Disk-bearing objects are statistically associated with younger isochronal ages than disk-free sources. The cluster has a hierarchical structure, with two main blocks along its latitudinal extension. The northern half develops around the O-type binary star S Mon; the southern half, close to the tip of the Cone Nebula, contains the most embedded regions of NGC 2264, populated mainly by objects with disks and ongoing accretion. The median ages of objects at different locations within the cluster, and the spatial distribution of disked and non-disked sources, suggest that star formation began in the north of the cluster, over 5 Myr ago, and was ignited in its southern region a few Myr later

  3. Photoelectric UBVRI sequences in the Magellanic Cloud clusters Lindsay 1, NGC 339, NGC 361, and NGC 1466

    International Nuclear Information System (INIS)

    Alcaino, G.; Alvarado, F.; Wenderoth, E.; Liller, W.

    1990-01-01

    UBVRI sequences in three Small Magellanic Cloud (SMC) clusters Lindsay 1, NGC 339, NGC 361, and in NGC 1466, which lies between the two Magellanic Clouds, are presented. These sequences are appropriate for charge-coupled device (CCD) coverage. Only BV standards have been published in NGC 339 and UBV in NGC 1466; no sequences exist for the two other clusters. 15 refs

  4. A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264: Lithium Abundance of Pre-main Sequence Stars

    Science.gov (United States)

    Lim, Beomdu; Sung, Hwankyung; Kim, Jinyoung S.; Bessell, Michael S.; Hwang, Narae; Park, Byeong-Gon

    2016-11-01

    The timescale of cluster formation is an essential parameter in order to understand the formation process of star clusters. Pre-main sequence (PMS) stars in nearby young open clusters reveal a large spread in brightness. If the spread were considered to be a result of a real spread in age, the corresponding cluster formation timescale would be about 5-20 Myr. Hence it could be interpreted that star formation in an open cluster is prolonged for up to a few tens of Myr. However, difficulties in reddening correction, observational errors, and systematic uncertainties introduced by imperfect evolutionary models for PMS stars can result in an artificial age spread. Alternatively, we can utilize Li abundance as a relative age indicator of PMS star to determine the cluster formation timescale. The optical spectra of 134 PMS stars in NGC 2264 have been obtained with MMT/Hectochelle. The equivalent widths have been measured for 86 PMS stars with a detectable Li line (3500\\lt {T}{eff}[{{K}}]≤slant 6500). Li abundance under the condition of local thermodynamic equilibrium (LTE) was derived using the conventional curve of growth method. After correction for non-LTE effects, we find that the initial Li abundance of NGC 2264 is A({Li})=3.2+/- 0.2. From the distribution of the Li abundances, the underlying age spread of the visible PMS stars is estimated to be about 3-4 Myr and this, together with the presence of embedded populations in NGC 2264, suggests that the cluster formed on a timescale shorter than 5 Myr.

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

    Science.gov (United States)

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

    2018-04-01

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

  6. TWO BARIUM STARS IN THE OPEN CLUSTER NGC 5822

    Energy Technology Data Exchange (ETDEWEB)

    Katime Santrich, O. J.; Pereira, C. B.; De Castro, D. B., E-mail: osantrich@on.br, E-mail: claudio@on.br, E-mail: denise@on.br [Observatorio Nacional/MCT, Rua Gen. Jose Cristino, 77, 20921-400 Rio de Janeiro (Brazil)

    2013-08-01

    Open clusters are very useful examples to explain the constraint of the nucleosynthesis process with the luminosities of stars because the distances of the clusters are better known than those of field stars. We carried out a detailed spectroscopic analysis to derive the chemical composition of two red giants in the young open cluster NGC 5822, NGC 5822-2, and NGC 5822-201. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employed the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that NGC 5822-2 and -201 have, respectively, a mean overabundance of the elements created by the s-process, ''s'', with the notation [s/Fe] of 0.77 {+-} 0.12 and 0.83 {+-} 0.05. These values are higher than those for field giants of similar metallicity. We also found that NGC 5822-2 and -201 have, respectively, luminosities of 140 L{sub Sun} and 76 L{sub Sun }, which are much lower than the luminosity of an asymptotic giant branch star. We conclude that NGC 5822-2 and NGC 5822-201 are two new barium stars first identified in the open cluster NGC 5822. The mass transfer hypothesis is the best scenario to explain the observed overabundances.

  7. A comprehensive study of the young open star cluster NGC 6611 based on deep VRI CCD images and 2MASS data

    Directory of Open Access Journals (Sweden)

    I.M. Selim

    2016-06-01

    Full Text Available In the present study, we have used Deep CCD images of the extremely young open star cluster NGC 6611, up to a limiting magnitude of V ∼ 22.86 mag in V, R and I passbands. The resulting color-magnitude V; (V–I diagram as well as their radial density profiles has been determined. Using 2MASS data, we confirmed the consistency between the 2MASS photometry, by fitting isochrones, the extinction E(V–I = 0.530 ± 0.04 mag, E(J–H = 0.31 ± 0.02, from the color magnitude diagram the cluster distance =2.2 ± 0.21 kpc and age = 3.6 Myr, based on the fitting of theoretical stellar isochrones of solar metallicity Z = 0.019. The distance modulus of the cluster is estimated at 12.3. The radial stellar density profiles and the cluster center have been determined by two methods. The core and cluster radii are determined from the radial stellar density profiles. Only about 40% of the cluster members are present in the core region. The cluster luminosity function has been calculated. The mass function slope of the entire cluster is ∼−0.67 ± 0.12. The effects of mass segregation, most probably due to dynamical evolution, have been observed in the cluster.

  8. Lithium in old open clusters - NGC 188

    International Nuclear Information System (INIS)

    Hobbs, L.M.; Pilachowski, C.

    1988-01-01

    Echelle spectra which include the Li I line at 6707 A are reported for seven main-sequence stars and one subgiant in NGC 188. The Li I line is detected in five of the six dwarfs which are highly probable cluster members. The derived atmospheric Li/H ratios exceed the solar value by factors ranging approximately from 10 to 40, although these apparently closely solarlike stars are about twice as old as the sun. The variation of the lithium abundance with stellar mass along the main sequences of the Pleiades, the Hyades, NGC 752, and NGC 188 are compared. The resulting evolutionary pattern indicates that the lithium fraction in the Galactic gas has shown no appreciable change from Li/H of roughly 10 to the -9th since the birth of NGC 188 about 10 Gyr ago, except that the abundance could have been higher by an uncertain but possibly appreciable factor at the beginning of that epoch. 51 references

  9. Asteroseismology of the Open Clusters NGC 6791, NGC 6811, and NGC 6819 from 19 Months of Kepler Photometry

    DEFF Research Database (Denmark)

    Corsaro, Enrico; Stello, Dennis; Huber, Daniel

    2012-01-01

    We studied solar-like oscillations in 115 red giants in the three open clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters δν02, δν01, and ϵ, which...

  10. Photoelectric UBVRI sequences in the Galactic globular clusters NGC 6752 and NGC 6864

    International Nuclear Information System (INIS)

    Alvarado, F.; Wenderoth, E.; Alcaino, G.; Liller, W.

    1990-01-01

    UBVRI photoelectric sequences for the Galactic globular clusters NGC 6752 and NGC 6864 are presented. Both of them include fields suitable for CCD exposures. From five UBV sequences in NGC 6572, only five stars are in common with the previous works. 15 refs

  11. Open clusters. II. Fundamental parameters of B stars in Collinder 223, Hogg 16, NGC 2645, NGC 3114, and NGC 6025

    Science.gov (United States)

    Aidelman, Y.; Cidale, L. S.; Zorec, J.; Panei, J. A.

    2015-05-01

    Context. The knowledge of accurate values of effective temperature, surface gravity, and luminosity of stars in open clusters is very important not only to derive cluster distances and ages but also to discuss the stellar structure and evolution. Unfortunately, stellar parameters are still very scarce. Aims: Our goal is to study five open clusters to derive stellar parameters of the B and Be star population and discuss the cluster properties. In a near future, we intend to gather a statistically relevant samples of Be stars to discuss their origin and evolution. Methods: We use the Barbier-Chalonge-Divan spectrophotometric system, based on the study of low-resolution spectra around the Balmer discontinuity, since it is independent of the interstellar and circumstellar extinction and provides accurate Hertzsprung-Russell diagrams and stellar parameters. Results: We determine stellar fundamental parameters, such as effective temperatures, surface gravities, spectral types, luminosity classes, absolute and bolometric magnitudes and colour gradient excesses of the stars in the field of Collinder 223, Hogg 16, NGC 2645, NGC 3114, and NGC 6025. Additional information, mainly masses and ages of cluster stellar populations, is obtained using stellar evolution models. In most cases, stellar fundamental parameters have been derived for the first time. We also discuss the derived cluster properties of reddening, age and distance. Conclusions: Collinder 223 cluster parameters are overline{E(B-V) = 0.25 ± 0.03} mag and overline{(mv - M_v)0 = 11.21 ± 0.25} mag. In Hogg 16, we clearly distinguish two groups of stars (Hogg 16a and Hogg 16b) with very different mean true distance moduli (8.91 ± 0.26 mag and 12.51 ± 0.38 mag), mean colour excesses (0.26 ± 0.03 mag and 0.63 ± 0.08 mag), and spectral types (B early-type and B late-/A-type stars, respectively). The farthest group could be merged with Collinder 272. NGC 2645 is a young cluster (age between 40 Myr and 69 Myr. In

  12. Open clusters. III. Fundamental parameters of B stars in NGC 6087, NGC 6250, NGC 6383, and NGC 6530 B-type stars with circumstellar envelopes

    Science.gov (United States)

    Aidelman, Y.; Cidale, L. S.; Zorec, J.; Panei, J. A.

    2018-02-01

    Context. Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Methods: Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the Hα region to confirm the Be nature of these stars. Results: We provide Teff, log g, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC 6087, NGC 6250, NGC 6383, and NGC 6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (operating under agreement of CONICET and the Universities of La Plata, Córdoba, and San Juan, Argentina.Tables 1, 2, 9-16 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A30

  13. Isolated ellipticals and their globular cluster systems. III. NGC 2271, NGC 2865, NGC 3962, NGC 4240, and IC 4889

    Science.gov (United States)

    Salinas, R.; Alabi, A.; Richtler, T.; Lane, R. R.

    2015-05-01

    As tracers of star formation, galaxy assembly, and mass distribution, globular clusters have provided important clues to our understanding of early-type galaxies. But their study has been mostly constrained to galaxy groups and clusters where early-type galaxies dominate, leaving the properties of the globular cluster systems (GCSs) of isolated ellipticals as a mostly uncharted territory. We present Gemini-South/GMOS g'i' observations of five isolated elliptical galaxies: NGC 3962, NGC 2865, IC 4889, NGC 2271, and NGC 4240. Photometry of their GCSs reveals clear color bimodality in three of them, but remains inconclusive for the other two. All the studied GCSs are rather poor with a mean specific frequency SN ~ 1.5, independently of the parent galaxy luminosity. Considering information from previous work as well, it is clear that bimodality and especially the presence of a significant, even dominant, population of blue clusters occurs at even the most isolated systems, which casts doubts on a possible accreted origin of metal-poor clusters, as suggested by some models. Additionally, we discuss the possible existence of ultra-compact dwarfs around the isolated elliptical NGC 3962. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).Globular cluster photometry is available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A59Appendices are available in

  14. The Luminosity Functions of Old and Intermediate-Age Globular Clusters in NGC 3610

    OpenAIRE

    Whitmore, B. C.; Schweizer, F.; Kundu, A.; Miller, B. W.

    2002-01-01

    The WFPC2 Camera on board HST has been used to obtain high-resolution images of NGC 3610, a dynamically young elliptical galaxy. These observations supersede shorter, undithered HST observations where an intermediate-age population of globular clusters was first discovered. The new observations show the bimodal color distribution of globular clusters more clearly, with peaks at (V-I)o = 0.95 and 1.17. The luminosity function (LF) of the blue, metal-poor population of clusters in NGC 3610 turn...

  15. Fibers in the NGC 1333 proto-cluster

    Science.gov (United States)

    Hacar, A.; Tafalla, M.; Alves, J.

    2017-10-01

    Are the initial conditions for clustered star formation the same as for non-clustered star formation? To investigate the initial gas properties in young proto-clusters we carried out a comprehensive and high-sensitivity study of the internal structure, density, temperature, and kinematics of the dense gas content of the NGC 1333 region in Perseus, one of the nearest and best studied embedded clusters. The analysis of the gas velocities in the position-position-velocity space reveals an intricate underlying gas organization both in space and velocity. We identified a total of 14 velocity-coherent, (tran-)sonic structures within NGC 1333, with similar physical and kinematic properties than those quiescent, star-forming (aka fertile) fibers previously identified in low-mass star-forming clouds. These fibers are arranged in a complex spatial network, build-up the observed total column density, and contain the dense cores and protostars in this cloud. Our results demonstrate that the presence of fibers is not restricted to low-mass clouds but can be extended to regions of increasing mass and complexity. We propose that the observational dichotomy between clustered and non-clustered star-forming regions might be naturally explained by the distinct spatial density of fertile fibers in these environments. Based on observations carried out under project number 169-11 with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Based on observations with the 100-m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg.Molecular line observations (spectral cubes) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/A123

  16. New constraints on the star formation history of the star cluster NGC 1856

    NARCIS (Netherlands)

    Correnti, M.; Goudfrooij, P.; Puzia, T.H.; de Mink, S.E.

    2015-01-01

    We use the Wide Field Camera 3 onboard the Hubble Space Telescope to obtain deep, high-resolution photometry of the young (age ∼ 300 Myr) star cluster NGC 1856 in the Large Magellanic Cloud. We compare the observed colour-magnitude diagram (CMD), after having applied a correction for differential

  17. Chemical abundances of globular clusters in NGC 5128 (Centaurus A)

    Science.gov (United States)

    Hernandez, Svea; Larsen, Søren; Trager, Scott; Kaper, Lex; Groot, Paul

    2018-06-01

    We perform a detailed abundance analysis on integrated-light spectra of 20 globular clusters (GCs) in the early-type galaxy NGC 5128 (Centaurus A). The GCs were observed with X-Shooter on the Very Large Telescope (VLT). The cluster sample spans a metallicity range of -1.92 poor GCs in NGC 5128 is genuine, it could hint at a chemical enrichment history different than that experienced by the MW. We also measure Na abundances in 9 out of 20 GCs. We find evidence for intracluster abundance variations in six of these clusters where we see enhanced [Na/Fe] > +0.25 dex. We obtain the first abundance measurements of Cr, Mn, and Ni for a sample of the GC population in NGC 5128 and find consistency with the overall trends observed in the MW, with a slight enhancement (<0.1 dex) in the Fe-peak abundances measured in the NGC 5128.

  18. SPACE VELOCITIES OF SOUTHERN GLOBULAR CLUSTERS. VII. NGC 6397, NGC 6626 (M28), AND NGC 6656 (M22)

    Energy Technology Data Exchange (ETDEWEB)

    Casetti-Dinescu, Dana I.; Girard, Terrence M.; Van Altena, William F. [Astronomy Department, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States); Jilkova, Lucie [Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlarska 2, CZ-61137 Brno (Czech Republic); Podesta, Federico; Lopez, Carlos E., E-mail: dana.casetti@yale.edu, E-mail: terry.girard@yale.edu, E-mail: william.vanaltena@yale.edu, E-mail: jilkoval@physics.muni.cz [Universidad National de San Juan, Observatorio Astronomico ' ' Felix Aguilar' ' and Yale Southern Observatory, Chimbas, 5413 San Juan (Argentina)

    2013-08-01

    We have measured the absolute proper motions of globular clusters NGC 6397, NGC 6626 (M22), and NGC 6656 (M28) as part of our ongoing Southern Proper-Motion Program. The reference system is the ICRS via Hipparcos stars for these three low-Galactic-latitude clusters. Formal errors range between {approx}0.3 and 0.7 mas yr{sup -1}. Notable is the result for NGC 6397, which differs by 2.5 mas yr{sup -1} from two Hubble Space Telescope determinations while agreeing with previous ground-based ones. We determine orbits for all three clusters in an axisymmetric and barred model of the Galaxy and discuss these in the context of globular-cluster formation. M22 is a well-known cluster with an iron abundance spread; such clusters are now believed to have formed in massive parent systems that can retain ejecta of core-collapsed supernovae. We find that the five currently accepted globular clusters with iron/calcium abundance spread show orbits unrelated to each other, thus suggesting at least five independent, massive progenitors that have contributed to the build-up of the Milky-Way halo.

  19. ASTEROSEISMOLOGY OF THE OPEN CLUSTERS NGC 6791, NGC 6811, AND NGC 6819 FROM 19 MONTHS OF KEPLER PHOTOMETRY

    International Nuclear Information System (INIS)

    Corsaro, Enrico; Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Benomar, Othman; White, Timothy R.; Bonanno, Alfio; Brogaard, Karsten; Kallinger, Thomas; Mosser, Benoit; Basu, Sarbani; Chaplin, William J.; Elsworth, Yvonne P.; Mathur, Savita; Christensen-Dalsgaard, Jørgen; García, Rafael A.; Hekker, Saskia; Kjeldsen, Hans; Meibom, Søren; Hall, Jennifer R.

    2012-01-01

    We studied solar-like oscillations in 115 red giants in the three open clusters, NGC 6791, NGC 6811, and NGC 6819, based on photometric data covering more than 19 months with NASA's Kepler space telescope. We present the asteroseismic diagrams of the asymptotic parameters δν 02 , δν 01 , and ε, which show clear correlation with fundamental stellar parameters such as mass and radius. When the stellar populations from the clusters are compared, we see evidence for a difference in mass of the red giant branch stars and possibly a difference in structure of the red clump stars, from our measurements of the small separations δν 02 and δν 01 . Ensemble échelle diagrams and upper limits to the linewidths of l = 0 modes as a function of Δν of the clusters NGC 6791 and NGC 6819 are also shown, together with the correlation between the l = 0 ridge width and the T eff of the stars. Lastly, we distinguish between red giant branch and red clump stars through the measurement of the period spacing of mixed dipole modes in 53 stars among all the three clusters to verify the stellar classification from the color-magnitude diagram. These seismic results also allow us to identify a number of special cases, including evolved blue stragglers and binaries, as well as stars in late He-core burning phases, which can be potentially interesting targets for detailed theoretical modeling.

  20. The Age of the Inner Halo Globular Cluster NGC 6652

    Science.gov (United States)

    Chaboyer, Brian; Sarajedini, Ata; Armandroff, Taft E.

    2000-01-01

    Hubble Space Telescope (HST) (V,I) photometry has been obtained for the inner halo globular cluster NGC 6652. The photometry reaches approximately 4 mag below the turn-off and includes a well populated horizontal branch (HB). This cluster is located close to the Galactic center at RGC approximately equal to 2.0 kpc with a reddening of E(V-I) = 0.15 +/- 0.02 and has a metallicity of [Fe/H] approximately equal to -0.85. Based upon DELTA V (sup SGB) (sub HB), NGC 6652 is 11.7 plus or minus 1.6 Gyr old. Using A HB precise differential ages for 47 Tuc (a thick disk globular), M107 and NGC 1851 (both halo clusters) were obtained. NGC 6652 appears to be the same age as 47 Tuc and NGC 1851 (within +/- 1.2 Gyr), while there is a slight suggestion that M107 is older than NGC 6652 by 2.3 +/- 1.5 Gyr. As this is a less than 2 sigma result, this issue needs to be investigated further before a definitive statement regarding the relative age of M107 and NGC 6652 may be made.

  1. VizieR Online Data Catalog: NGC3115 & NGC1399 VEGAS-SSS globular clusters (Cantiello+, 2018)

    Science.gov (United States)

    Cantiello, M.; D'Abrusco, R.; Spavone, M.; Paolillo, M.; Capaccioli, M.; Limatola, L.; Grado, A.; Iodice, E.; Raimondo, G.; Napolitano, N.; Blakeslee, J. P.; Brocato, E.; Forbes, D. A.; Hilker, M.; Mieske, S.; Peletier, R.; van de Ven, G.; Schipani, P.

    2017-11-01

    Photometric catalogs for globular cluster (GC) candidates over the the 1 sq. degree area around NGC3115 and NGC1399 (ngc3115.dat and ngc1399.dat). The catalogues are based on u-, g- and i- band images from the VST elliptical galaxies survey (VEGAS). Aperture magnitudes, corrected for aperture correction are reported. We also provide the full catalogs of matched sources, which also include the matched background and foreground sources in the frames (ngc3115_full.dat and ngc1399_full.dat). (4 data files).

  2. EXTENDED STAR CLUSTERS IN THE REMOTE HALO OF THE INTRIGUING DWARF GALAXY NGC 6822

    International Nuclear Information System (INIS)

    Hwang, Narae; Lee, Myung Gyoon; Lee, Jong Chul; Park, Hong Soo; Park, Won-Kee; Kim, Sang Chul; Park, Jang-Hyun

    2011-01-01

    We present a study on four new star clusters discovered in the halo of the intriguing dwarf irregular galaxy NGC 6822 from a wide-field survey covering 3 0 x 3 0 area carried out with MegaCam at the Canada-France-Hawaii Telescope. The star clusters have extended structures with half-light radii R h ∼ 7.5-14.0 pc, larger than typical Galactic globular clusters and other known globular clusters in NGC 6822. The integrated colors and color-magnitude diagrams of resolved stars suggest that the new star clusters are 2-10 Gyr old and relatively metal poor with Z = 0.0001-0.004 based on the comparison with theoretical models. The projected distance of each star cluster from the galaxy center ranges from 10.'7 (∼1.5 kpc) to 77' (∼11 kpc), far beyond the optical body of the galaxy. Interestingly, the new star clusters are aligned along the elongated old stellar halo of NGC 6822, which is almost perpendicular to the H I gas distribution where young stellar populations exist. We also find that the colors and half-light radii of the new clusters are correlated with the galactocentric distance: clusters farther from the galaxy center are larger and bluer than those closer to the galaxy center. We discuss the stellar structure and evolution of NGC 6822 implied by these new extended star clusters in the halo. We also discuss the current status of observational and theoretical understandings regarding the origin of extended star clusters in NGC 6822 and other galaxies.

  3. THE INTRIGUING STELLAR POPULATIONS IN THE GLOBULAR CLUSTERS NGC 6388 AND NGC 6441

    International Nuclear Information System (INIS)

    Bellini, A.; Anderson, J.; Piotto, G.; Nardiello, D.; Milone, A. P.; King, I. R.; Renzini, A.; Bedin, L. R.; Cassisi, S.; Pietrinferni, A.; Sarajedini, A.

    2013-01-01

    NGC 6388 and NGC 6441 are two massive Galactic bulge globular clusters that share many properties, including the presence of an extended horizontal branch (HB), quite unexpected because of their high metal content. In this paper we use Hubble Space Telescope's WFPC2, ACS, and WFC3 images and present a broad multicolor study of their stellar content, covering all main evolutionary branches. The color-magnitude diagrams (CMDs) give compelling evidence that both clusters host at least two stellar populations, which manifest themselves in different ways. NGC 6388 has a broadened main sequence (MS), a split sub-giant branch (SGB), and a split red giant branch (RGB) that becomes evident above the HB in our data set; its red HB is also split into two branches. NGC 6441 has a split MS, but only an indication of two SGB populations, while the RGB clearly splits in two from the SGB level upward, and no red HB structure. The multicolor analysis of the CMDs confirms that the He difference between the two main stellar populations in the two clusters must be similar. This is observationally supported by the HB morphology, but also confirmed by the color distribution of the stars in the MS optical band CMDs. However, a MS split becomes evident in NGC 6441 using UV colors, but not in NGC 6388, indicating that the chemical patterns of the different populations are different in the two clusters, with C, N, and O abundance differences likely playing a major role. We also analyze the radial distribution of the two populations.

  4. Blue straggler stars in the globular cluster NGC 5053

    International Nuclear Information System (INIS)

    Nemec, J.M.; Cohen, J.G.

    1989-01-01

    A study of the low central concentration globular cluster NGC 5053 based on photometry to 23 mag is reported. Deep C-M diagrams are presented, a mean metal abundance for the cluster is derived from the color of the RGB at the level of the horizontal branch, and theoretical isochrones are used to derive a distance modulus of (m - M0) = 16.05 + or - 0.14 mag and an age of 18 + or - 3 Gyr. A luminosity function based on subgiant and upper main-sequence stars is also constructed. A total of 24 blue stragglers in NGC 5053 are identified and their properties are studied. 65 references

  5. Chemical abundances in the globular clusters NGC6229 and NGC6779

    Science.gov (United States)

    Khamidullina, D. A.; Sharina, M. E.; Shimansky, V. V.; Davoust, E.

    2014-10-01

    Long-slit medium-resolution spectra of the Galactic globular clusters (GCs) NGC6229 and NGC6779, obtained with the CARELEC spectrograph at the 1.93-m telescope of the Haute-Provence observatory, have been used to determine the age, helium abundance (Y), and metallicity [Fe/H] as well as the first estimate of the abundances of C, N, O, Mg, Ca, Ti, and Cr for these objects. We solved this task by comparing the observed spectra and the integrated synthetic spectra, calculated with the use of the stellar atmosphere models with the parameters preset for the stars from these clusters. The model mass estimates, T eff, and log g were derived by comparing the observed "color-magnitude" diagrams and the theoretical isochrones. The summing-up of the synthetic blanketed stellar spectra was conducted according to the Chabrier mass function. To test the accuracy of the results, we estimated the chemical abundances, [Fe/H], log t, and Y for the NGC5904 and NGC6254 clusters, which, according to the literature, are considered to be the closest analogues of the two GCs of our study. Using the medium-resolution spectra from the library of Schiavon et al., we obtained for these two clusters a satisfactory agreement with the reported estimates for all the parameters within the errors. We derived the following cluster parameters. NGC6229: [Fe/H] = -1.65 dex, t = 12.6 Gyr, Y = 0.26, [ α/Fe] = 0.28 dex; NGC6779: [Fe/H] = -1.9 dex, t = 12.6 Gyr, Y = 0.23, [ α/Fe] = 0.08 dex; NGC5904: [Fe/H] = -1.6 dex, t = 12.6 Gyr, Y = 0.30, [ α/Fe] = 0.35 dex; NGC6254: [Fe/H] = -1.52 dex, t = 11.2 Gyr, Y = 0.30, [ α/Fe] = 0.025 dex. The value [ α/Fe] denotes the average of the Ca and Mg abundances.

  6. Photometry Using Kepler "Superstamps" of Open Clusters NGC 6791 & NGC 6819

    Science.gov (United States)

    Kuehn, Charles A.; Drury, Jason A.; Bellamy, Beau R.; Stello, Dennis; Bedding, Timothy R.; Reed, Mike; Quick, Breanna

    2015-09-01

    The Kepler space telescope has proven to be a gold mine for the study of variable stars. Usually, Kepler only reads out a handful of pixels around each pre-selected target star, omitting a large number of stars in the Kepler field. Fortunately, for the open clusters NGC 6791 and NGC 6819, Kepler also read out larger "superstamps" which contained complete images of the central region of each cluster. These cluster images can be used to study additional stars in the open clusters that were not originally on Kepler's target list. We discuss our work on using two photometric techniques to analyze these superstamps and present sample results from this project to demonstrate the value of this technique for a wide variety of variable stars.

  7. Photometry Using Kepler “Superstamps” of Open Clusters NGC 6791 & NGC 6819

    Directory of Open Access Journals (Sweden)

    Kuehn Charles A.

    2015-01-01

    Full Text Available The Kepler space telescope has proven to be a gold mine for the study of variable stars. Usually, Kepler only reads out a handful of pixels around each pre-selected target star, omitting a large number of stars in the Kepler field. Fortunately, for the open clusters NGC 6791 and NGC 6819, Kepler also read out larger “superstamps” which contained complete images of the central region of each cluster. These cluster images can be used to study additional stars in the open clusters that were not originally on Kepler’s target list. We discuss our work on using two photometric techniques to analyze these superstamps and present sample results from this project to demonstrate the value of this technique for a wide variety of variable stars.

  8. NGC 346: Looking in the Cradle of a Massive Star Cluster

    Science.gov (United States)

    Gouliermis, Dimitrios A.; Hony, Sacha

    2017-03-01

    How does a star cluster of more than few 10,000 solar masses form? We present the case of the cluster NGC 346 in the Small Magellanic Cloud, still embedded in its natal star-forming region N66, and we propose a scenario for its formation, based on observations of the rich stellar populations in the region. Young massive clusters host a high fraction of early-type stars, indicating an extremely high star formation efficiency. The Milky Way galaxy hosts several young massive clusters that fill the gap between young low-mass open clusters and old massive globular clusters. Only a handful, though, are young enough to study their formation. Moreover, the investigation of their gaseous natal environments suffers from contamination by the Galactic disk. Young massive clusters are very abundant in distant starburst and interacting galaxies, but the distance of their hosting galaxies do not also allow a detailed analysis of their formation. The Magellanic Clouds, on the other hand, host young massive clusters in a wide range of ages with the youngest being still embedded in their giant HII regions. Hubble Space Telescope imaging of such star-forming complexes provide a stellar sampling with a high dynamic range in stellar masses, allowing the detailed study of star formation at scales typical for molecular clouds. Our cluster analysis on the distribution of newly-born stars in N66 shows that star formation in the region proceeds in a clumpy hierarchical fashion, leading to the formation of both a dominant young massive cluster, hosting about half of the observed pre-main-sequence population, and a self-similar dispersed distribution of the remaining stars. We investigate the correlation between stellar surface density (and star formation rate derived from star-counts) and molecular gas surface density (derived from dust column density) in order to unravel the physical conditions that gave birth to NGC 346. A power law fit to the data yields a steep correlation between these

  9. Astrometric and photometric study of the open cluster NGC 2323

    Directory of Open Access Journals (Sweden)

    Amin M.Y.

    2017-01-01

    Full Text Available We present a study of the open cluster NGC 2323 using astrometric and photometric data. In our study we used two methods that are able to separate open cluster’s stars from those that belong to the stellar background. Our results of calculations by these two methods indicate that: 1 according to the membership probability, NGC 2323 should contain 497 stars, 2 the cluster center should be at 07h 02m 48.s02 and -08° 20' 17''74,3 the limiting radius of NGC 2323 is 2.31 ± 0.04 pc, the surface number density at this radius is 98.16 stars pc −2, 4 the magnitude function has a maximum at about mv = 14 mag, 5 the total mass of NGC 2323 is estimated dynamically by using astrometric data to be 890 M_, and statistically by using photometric data to be 900 M_, and 6 the distance and age of the cluster are found to be equal to 900 ± 100 pc, and 140 ± 20 Myr, respectively. Finally the dynamical evolution parameter τ of the cluster is about 436.2.

  10. BVRI CCD photometry of the globular cluster NGC 2808

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

    1990-01-01

    As a part of a continuing program, CCD color-magnitude diagrams are presented for the bright globular cluster NGC 2808 in the four colors comprising BVRI. From a comparison of four different CMDs with theoretical isochrones, an age of 16 + or - 2 Gyr is obtained, assuming a value for Fe/H near -1.3. 28 refs

  11. GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

    International Nuclear Information System (INIS)

    Lee, Myung Gyoon; Jang, In Sung

    2016-01-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 10 5 M ⊙ . The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M I (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H 0  = 77.9 ± 3.6 km s −1 Mpc −1 . We estimate the GC specific frequency of NGC 4921 to be S N  = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s

  12. LMC clusters: young

    International Nuclear Information System (INIS)

    Freeman, K.C.

    1980-01-01

    The young globular clusters of the LMC have ages of 10 7 -10 8 y. Their masses and structure are similar to those of the smaller galactic globular clusters. Their stellar mass functions (in the mass range 6 solar masses to 1.2 solar masses) vary greatly from cluster to cluster, although the clusters are similar in total mass, age, structure and chemical composition. It would be very interesting to know why these clusters are forming now in the LMC and not in the Galaxy. The author considers the 'young globular' or 'blue populous' clusters of the LMC. The ages of these objects are 10 7 to 10 8 y, and their masses are 10 4 to 10 5 solar masses, so they are populous enough to be really useful for studying the evolution of massive stars. The author concentrates on the structure and stellar content of these young clusters. (Auth.)

  13. Tidal origin of NGC 1427A in the Fornax cluster

    Science.gov (United States)

    Lee-Waddell, K.; Serra, P.; Koribalski, B.; Venhola, A.; Iodice, E.; Catinella, B.; Cortese, L.; Peletier, R.; Popping, A.; Keenan, O.; Capaccioli, M.

    2018-02-01

    We present new HI observations from the Australia Telescope Compact Array and deep optical imaging from OmegaCam on the VLT Survey Telescope of NGC 1427A, an arrow-shaped dwarf irregular galaxy located in the Fornax cluster. The data reveal a star-less HI tail that contains ˜10 per cent of the atomic gas of NGC 1427A as well as extended stellar emission that shed new light on the recent history of this galaxy. Rather than being the result of ram pressure induced star formation, as previously suggested in the literature, the disturbed optical appearance of NGC 1427A has tidal origins. The galaxy itself likely consists of two individual objects in an advanced stage of merging. The HI tail may be made of gas expelled to large radii during the same tidal interaction. It is possible that some of this gas is subject to ram pressure, which would be considered a secondary effect and implies a north-west trajectory of NGC 1427A within the Fornax cluster.

  14. Color Gradient in the King Type Globular Cluster NGC 7089

    Directory of Open Access Journals (Sweden)

    Young-Jong Sohn

    1999-12-01

    Full Text Available We use BV CCD images to investigate the reality of the color gradient within a King type globular cluster NGC 7089. Surface photometry shows that there is a strong radial color gradient in the central region of the cluster in the sense of bluer center with the amplitude of -0.39 +/- 0.07 mag/arcsec2 in (B - V. In the outer region of the cluster, however, the radial color gradient shows a reverse case, i.e., redder toward the center. (B - V color profile which was derived from resolved stars in VGC 7089 field also shows a significant color gradient in the central region of the clusters, indicating that lights from the combination of red giant stars and blue horizontal branch stars cause the radial color gradient. Color gradient of the outer region of NGC 7089 may be due to the unresolved background of the cluster. Similar color gradients in the central area of clusters have been previously observed exserved exclusively in highly concentrated systems classified as post core collapse clusters. We caution, however, to confirm the reality of the color gradient from resolved stars, we need more accurate imaging data of the cluster with exceptional seeing condition because the effect of completeness correlates with local density of stars.

  15. Chemical Abundances of Red Giant Branch Stars in the Globular Clusters NGC 6333 and NGC 6366

    Science.gov (United States)

    Johnson, Christian I.; Rich, R. M.; Pilachowski, C. A.; Kunder, A. M.

    2013-01-01

    We present chemical abundances and radial velocities for >20 red giant branch (RGB) stars in the Galactic globular clusters NGC 6333 ([Fe/H]≈-1.8) and NGC 6366 ([Fe/H]≈-0.6). The results are based on moderate resolution (R=18,000), high signal-to-noise ratio (>100) spectra obtained with the Hydra multifiber positioner and bench spectrograph on the WIYN 3.5m telescope at Kitt Peak National Observatory. Both objects are likely associated with the Galactic bulge globular cluster system, and we therefore compare the cluster abundance patterns with those of nearby bulge field stars. Additionally, we investigate differences in the O-Na anticorrelation and neutron-capture element dispersion between the two clusters, and compare their abundance patterns with those of similar metallicity halo globular clusters. This material is based upon work supported by the National Science Foundation under award No. AST-1003201 to C.I.J. C.A.P. gratefully acknowledges support from the Daniel Kirkwood Research Fund at Indiana University. R.M.R. acknowledges support from NSF grant AST-0709479 and AST-121120995.

  16. Elemental abundances of intermediate-age open cluster NGC 3680

    Science.gov (United States)

    Mitschang, A. W.; De Silva, G. M.; Zucker, D. B.

    2012-06-01

    We present a new abundance analysis of the intermediate-age Galactic open cluster NGC 3680, based on high-resolution, high signal-to-noise ratio VLT/UVES spectroscopic data. Several element abundances are presented for this cluster for the first time, but most notably we derive abundances for the light and heavy s-process elements Y, Ba, La and Nd. The serendipitous measurement of the rare-earth r-process element Gd is also reported. This cluster exhibits a significant enhancement of Na in giants as compared to dwarfs, which may be a proxy for an O to Na anticorrelation as observed in Galactic globular clusters but not open clusters. We also observe a step-like enhancement of heavy s-process elements towards higher atomic number, contrary to expectations from asymptotic giant branch nucleosynthesis models, suggesting that the r process played a significant role in the generation of both La and Nd in this cluster.

  17. STAR CLUSTER FORMATION AND DESTRUCTION IN THE MERGING GALAXY NGC 3256

    Energy Technology Data Exchange (ETDEWEB)

    Mulia, A. J.; Chandar, R. [Physics and Astronomy Department, University of Toledo, Toledo, OH 43606-3390 (United States); Whitmore, B. C. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2016-07-20

    We use the Advanced Camera for Surveys on the Hubble Space Telescope to study the rich population of young massive star clusters in the main body of NGC 3256, a merging pair of galaxies with a high star formation rate (SFR) and SFR per unit area (Σ{sub SFR}). These clusters have luminosity and mass functions that follow power laws, dN / dL ∝ L{sup α} with α = 2.23 ± 0.07, and dN / dM ∝ M{sup β} with β = 1.86 ± 0.34 for τ < 10 Myr clusters, similar to those found in more quiescent galaxies. The age distribution can be described by dN / dτ ∝ τ{sup γ}, with γ ≈ 0.67 ± 0.08 for clusters younger than about a few hundred million years, with no obvious dependence on cluster mass. This is consistent with a picture where ∼80% of the clusters are disrupted each decade in time. We investigate the claim that galaxies with high Σ{sub SFR} form clusters more efficiently than quiescent systems by determining the fraction of stars in bound clusters (Γ) and the CMF/SFR statistic (CMF is the cluster mass function) for NGC 3256 and comparing the results with those for other galaxies. We find that the CMF/SFR statistic for NGC 3256 agrees well with that found for galaxies with Σ{sub SFR} and SFRs that are lower by 1–3 orders of magnitude, but that estimates for Γ are only robust when the same sets of assumptions are applied. Currently, Γ values available in the literature have used different sets of assumptions, making it more difficult to compare the results between galaxies.

  18. GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Myung Gyoon; Jang, In Sung, E-mail: mglee@astro.snu.ac.kr, E-mail: isjang@astro.snu.ac.kr [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-742 (Korea, Republic of)

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 10{sup 5} M{sub ⊙}. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M{sub I} (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H{sub 0} = 77.9 ± 3.6 km s{sup −1} Mpc{sup −1}. We estimate the GC specific frequency of NGC 4921 to be S{sub N} = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  19. The Age of the Inner Halo Globular Cluster NGC 6652

    OpenAIRE

    Chaboyer, Brian; Sarajedini, Ata; Armandroff, Taft E.

    2000-01-01

    HST (V,I) photometry has been obtained for the inner halo globular cluster NGC 6652. The photometry reaches approximately 4 mag below the turn-off and includes a well populated horizontal branch. This cluster is located close to the Galactic center at a galactocentric distance of approximately 2.0 kpc with a reddening of E(V-I) = 0.15 +/- 0.02 and has a metallicity of [Fe/H] approximately -0.85. Based upon Delta(V) between the point on the sub-giant branch which is 0.05 mag redder than the tu...

  20. Binarity and Variable Stars in the Open Cluster NGC 2126

    Science.gov (United States)

    Chehlaeh, Nareemas; Mkrtichian, David; Kim, Seung-Lee; Lampens, Patricia; Komonjinda, Siramas; Kusakin, Anatoly; Glazunova, Ljudmila

    2018-04-01

    We present the results of an analysis of photometric time-series observations for NGC 2126 acquired at the Thai National Observatory (TNO) in Thailand and the Mount Lemmon Optical Astronomy Observatory (LOAO) in USA during the years 2004, 2013 and 2015. The main purpose is to search for new variable stars and to study the light curves of binary systems as well as the oscillation spectra of pulsating stars. NGC 2126 is an intermediate-age open cluster which has a population of stars inside the δ Scuti instability strip. Several variable stars are reported including three eclipsing binary stars, one of which is an eclipsing binary star with a pulsating component (V551 Aur). The Wilson-Devinney technique was used to analyze its light curves and to determine a new set of the system’s parameters. A frequency analysis of the eclipse-subtracted light curve was also performed. Eclipsing binaries which are members of open clusters are capable of delivering strong constraints on the cluster’s properties which are in turn useful for a pulsational analysis of their pulsating components. Therefore, high-resolution, high-quality spectra will be needed to derive accurate component radial velocities of the faint eclipsing binaries which are located in the field of NGC 2126. The new Devasthal Optical Telescope, suitably equipped, could in principle do this.

  1. Searching for Be stars in the open cluster NGC 663

    Energy Technology Data Exchange (ETDEWEB)

    Yu, P. C.; Lin, C. C.; Chen, W. P.; Lee, C. D.; Ip, W. H.; Ngeow, C. C. [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Kulkarni, Shrinivas R. [Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-02-01

    We present Be star candidates in the open cluster NGC 663, identified by Hα imaging photometry with the Palomar Transient Factory Survey, as a pilot program to investigate how the Be star phenomena, the emission spectra, extended circumstellar envelopes, and fast rotation, correlate with massive stellar evolution. Stellar membership of the candidates was verified by 2MASS magnitudes and colors and by proper motions (PMs). We discover four new Be stars and exclude one known Be star from being a member due to its inconsistent PMs. The fraction of Be stars to member stars [N(Be)/N(members)] in NGC 663 is 3.5%. The spectral type of the 34 Be stars in NGC 663 shows bimodal peaks at B0–B2 and B5–B7, which is consistent with the statistics in most star clusters. Additionally, we also discover 23 emission-line stars of different types, including non-member Be stars, dwarfs, and giants.

  2. LOW-RESOLUTION SPECTROSCOPY FOR THE GLOBULAR CLUSTERS WITH SIGNS OF SUPERNOVA ENRICHMENT: M22, NGC 1851, AND NGC 288

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dongwook; Han, Sang-Il; Lee, Young-Wook; Roh, Dong-Goo [Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of); Sohn, Young-Jong [Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of); Chun, Sang-Hyun [Yonsei University Observatory, Seoul 120-749 (Korea, Republic of); Lee, Jae-Woo [Department of Astronomy and Space Science, Sejong University, Seoul 143-747 (Korea, Republic of); Johnson, Christian I., E-mail: ywlee2@yonsei.ac.kr [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States)

    2015-01-01

    There is increasing evidence for the presence of multiple red giant branches (RGBs) in the color-magnitude diagrams of massive globular clusters (GCs). In order to investigate the origin of this split on the RGB, we have performed new narrow-band Ca photometry and low-resolution spectroscopy for M22, NGC 1851, and NGC 288. We find significant differences (more than 4σ) in calcium abundance from the spectroscopic HK' index for M22 and NGC 1851. We also find more than 8σ differences in CN-band strength between the Ca-strong and Ca-weak subpopulations for these GCs. For NGC 288, however, a large difference is detected only in the CN strength. The calcium abundances of RGB stars in this GC are identical to within the errors. This is consistent with the conclusion from our new Ca photometry where the RGB splits are confirmed in M22 and NGC 1851, but not in NGC 288. We also find interesting differences in the CN-CH correlations among these GCs. While CN and CH are anti-correlated in NGC 288, they show a positive correlation in M22. NGC 1851, however, shows no difference in CH between the two groups of stars with different CN strengths. We suggest that all of these systematic differences would be best explained by how strongly Type II supernovae enrichment has contributed to the chemical evolution of these GCs.

  3. SEARCH FOR RED DWARF STARS IN GLOBULAR CLUSTER NGC 6397

    Science.gov (United States)

    2002-01-01

    Left A NASA Hubble Space Telescope image of a small region (1.4 light-years across) in the globular star cluster NGC 6397. Simulated stars (diamonds) have been added to this view of the same region of the cluster to illustrate what astronomers would have expected to see if faint red dwarf stars were abundant in the Milky Way Galaxy. The field would then contain 500 stars, according to theoretical calculations. Right The unmodified HST image shows far fewer stars than would be expected, according to popular theories of star formation. HST resolves about 200 stars. The stellar density is so low that HST can literally see right through the cluster and resolve far more distant background galaxies. From this observation, scientists have identified the surprising cutoff point below which nature apparently doesn't make many stars smaller that 1/5 the mass of our Sun. These HST findings provide new insights into star formation in our Galaxy. Technical detail:The globular cluster NGC 6397, one of the nearest and densest agglomerations of stars, is located 7,200 light-years away in the southern constellation Ara. This visible-light picture was taken on March 3, 1994 with the Wide Field Planetary Camera 2, as part the HST parallel observing program. Credit: F. Paresce, ST ScI and ESA and NASA

  4. Variable stars in the field of open cluster NGC 2126

    International Nuclear Information System (INIS)

    Liu Shunfang; Wu Zhenyu; Zhang Xiaobin; Wu Jianghua; Ma Jun; Jiang Zhaoji; Chen Jiansheng; Zhou Xu

    2009-01-01

    We report the results of a time-series CCD photometric survey of variable stars in the field of open cluster NGC 2126. In about a one square degree field covering the cluster, a total of 21 variable candidates are detected during this survey, of which 16 are newly found. The periods, classifications and spectral types of 14 newly discovered variables are discussed, which consist of six eclipsing binary systems, three pulsating variable stars, three long period variables, one RS CVn star, and one W UMa or δ Scuti star. In addition, there are two variable candidates, the properties of which cannot be determined. By a method based on fitting observed spectral energy distributions of stars with theoretical ones, the membership probabilities and the fundamental parameters of this cluster are determined. As a result, five variables are probably members of NGC 2126. The fundamental parameters of this cluster are determined as: metallicity to be 0.008 Z o-dot , age log(t) = 8.95, distance modulus (m - M) 0 = 10.34 and reddening value E (B - V) = 0.55 mag.

  5. Overlapping Open Clusters NGC 1750 and NGC 1758 behind the Taurus Dark Clouds. II. CCD Photometry in the Vilnius System

    Directory of Open Access Journals (Sweden)

    Straižys V.

    2003-09-01

    Full Text Available Seven-color photometry in the Vilnius system has been obtained for 420 stars down to V = 16 mag in the area containing the overlapping open clusters NGC 1750 and NGC 1758 in Taurus. Spectral and luminosity classes, color excesses, interstellar extinctions and distances are given for 287 stars. The classification of stars is based on their reddening-free Q-parameters. 18 stars observed photoelectrically were used as standards. The extinction vs. distance diagram exhibits the presence of one dust cloud at a distance of 175 pc which almost coincides with a distance of other dust clouds in the Taurus complex. The clusters NGC 1750 and NGC 1758 are found to be at the same distance of ~760 pc and may penetrate each other. Their interstellar extinction AV is 1.06 mag which corresponds to EB-V = 0.34 mag.

  6. THE VERY MASSIVE STAR CONTENT OF THE NUCLEAR STAR CLUSTERS IN NGC 5253

    Energy Technology Data Exchange (ETDEWEB)

    Smith, L. J. [Space Telescope Science Institute and European Space Agency, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Crowther, P. A. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Calzetti, D. [Department of Astronomy, University of Massachusetts—Amherst, Amherst, MA 01003 (United States); Sidoli, F., E-mail: lsmith@stsci.edu [London Centre for Nanotechnology, University College London, London WC1E 6BT (United Kingdom)

    2016-05-20

    The blue compact dwarf galaxy NGC 5253 hosts a very young starburst containing twin nuclear star clusters, separated by a projected distance of 5 pc. One cluster (#5) coincides with the peak of the H α emission and the other (#11) with a massive ultracompact H ii region. A recent analysis of these clusters shows that they have a photometric age of 1 ± 1 Myr, in apparent contradiction with the age of 3–5 Myr inferred from the presence of Wolf-Rayet features in the cluster #5 spectrum. We examine Hubble Space Telescope ultraviolet and Very Large Telescope optical spectroscopy of #5 and show that the stellar features arise from very massive stars (VMSs), with masses greater than 100 M {sub ⊙}, at an age of 1–2 Myr. We further show that the very high ionizing flux from the nuclear clusters can only be explained if VMSs are present. We investigate the origin of the observed nitrogen enrichment in the circumcluster ionized gas and find that the excess N can be produced by massive rotating stars within the first 1 Myr. We find similarities between the NGC 5253 cluster spectrum and those of metal-poor, high-redshift galaxies. We discuss the presence of VMSs in young, star-forming galaxies at high redshift; these should be detected in rest-frame UV spectra to be obtained with the James Webb Space Telescope . We emphasize that population synthesis models with upper mass cutoffs greater than 100 M {sub ⊙} are crucial for future studies of young massive star clusters at all redshifts.

  7. Embedded clusters in NGC1808 central starburst - Near-infrared imaging and spectroscopy

    OpenAIRE

    Galliano, E.; Alloin, D.

    2008-01-01

    In the course of a mid-infrared imaging campaign of close-by active galaxies, we discovered the mid-infrared counterparts of bright compact radio sources in the central star-forming region of NGC1808. We aim at confirming that these sources are deeply embedded, young star clusters and at deriving some of their intrinsic properties. To complement the mid-infrared data, we have collected a set of near-infrared data with ISAAC at the VLT: J, Ks, and L' images, as well as low-resolution, long-sli...

  8. Young planetary nebula with OH molecules - NGC 6302

    International Nuclear Information System (INIS)

    Payne, H.E.; Phillips, J.A.; Terzian, Y.

    1988-01-01

    The results of a sensitive survey of planetary nebulae in all four ground-state OH lines are reported. The results confirm that evolved planetary nebulas are not OH sources in general. However, one interesting object was not detected: an OH 1612 MHz maser in the young planetary nebula NGC 6302. This nebula may be in a brief evolutionary stage, similar to the young and compact planetary nebula Vy 2-2, where OH has already been detected. In addition, the results of further observations of NGC 6302 are reported, including VLA observations of the 1612 MHz line and continuum emission and detections of rotationally excited OH lines at 5-cm wavelength in absorption. 28 references

  9. BV CCD photometry of the old open cluster NGC 2243

    International Nuclear Information System (INIS)

    Bergbusch, P.A.; Vandenberg, D.A.; Infante, L.

    1991-01-01

    The photometry of NGC 2243 is presented, which reaches approximately 4 mag below the turnoff point calibrated independently of studies of the cluster. The color-magnitude diagram (CMD) and luminosity function (LF) are calibrated by utilizing stars from the lists of Landolt and Graham. A strong binary sequence is noted in the CMD which contributes approximately 30 percent of the stars, a gap is observed in the turnoff region, and a clump of HB stars is located. The CMD data are compared to those for the cluster 47 Tuc and are found to match well, although a slightly higher metal abundance accounts for the redder giant branch of the NGC 2243. The distance modulus and the cluster age are calculated, and the Fe/H = -0.47, O/Fe = +0.23 isochrones are the only isochrones that reproduce the location of the giant branch. A flat mass spectrum characterizes the LF, and a small gap is found where V is 16.1. Convective overshooting in the cores of moderate mass stars is theorized as the cause of the gap, and other models of the structure are shown to provide inadequate descriptions. 41 refs

  10. Discovery of a ~205 Hz X-ray pulsar in the globular cluster NGC 6440

    NARCIS (Netherlands)

    Altamirano, D.; Strohmayer, T.E.; Heinke, C.O.; Markwardt, C.B.; Swank, J.H.; Pereira, D.; Smith, E.; Wijnands, R.; Linares, M.; Patruno, A.; Casella, P.; van der Klis, M.

    2009-01-01

    Discovery of a 205 Hz X-ray pulsar in the globular cluster NGC 6440 The globular cluster NGC 6440 was observed by the PCA instrument aboard RXTE on August 30, 2009 at 01:42 (UTC). The observation lasted for approximately 3000 seconds and the source was detected with an intensity of ~7 mCrab (2-10

  11. Open clusters. I. Fundamental parameters of B stars in NGC 3766 and NGC 4755

    Science.gov (United States)

    Aidelman, Y.; Cidale, L. S.; Zorec, J.; Arias, M. L.

    2012-08-01

    Context. Spectroscopic investigations of galactic open clusters are scarce and limited to a reduced sample of cluster members. Aims: We intend to perform a complete study of the physical parameters of two galactic clusters as well as of their individual members. Methods: To carry out this study, we used the BCD (Barbier-Chalonge-Divan) spectrophotometric system, which is based on the study of the Balmer discontinuity and is independent of interstellar and circumstellar extinction. Additional physical properties were derived from the line profiles (FWHM) and stellar evolution models. We analyzed low-resolution spectra around the Balmer discontinuity for normal B-type and Be stars in two open clusters: NGC 3766 and NGC 4755. We determined the stellar fundamental parameters, such as effective temperatures, surface gravities, spectral types, luminosity classes, absolute and bolometric magnitudes, and color gradient excesses. The stellar rotation velocity was also determined. Complementary information, mainly stellar mass, age, and radius of the star population were calculated using stellar evolution models. In some cases, the stellar fundamental parameters were derived for the first time. The obtained results allowed us also to determine the reddening, age, and distance to the clusters. Results: The cluster parameters obtained through the BCD method agree very well with those derived from classical methods based on photometric data. The BCD system also provides physical properties of the star members. This study enables us to test the good behavior of Mbol(λ1,D)-calibrations and detect systematic discrepancies between log g estimates from model atmospheres and those derived from stellar evolution models. To improve our knowledge on the formation and evolution of the clusters, more statistical studies on the initial mass luminosity and angular momentum distributions should be addressed. Therefore, the BCD spectrophotometric system could be a powerful tool for studying

  12. THE CLUSTERED NATURE OF STAR FORMATION. PRE-MAIN-SEQUENCE CLUSTERS IN THE STAR-FORMING REGION NGC 602/N90 IN THE SMALL MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Gouliermis, Dimitrios A.; Gennaro, Mario; Schmeja, Stefan; Dolphin, Andrew E.; Tognelli, Emanuele; Prada Moroni, Pier Giorgio

    2012-01-01

    Located at the tip of the wing of the Small Magellanic Cloud (SMC), the star-forming region NGC 602/N90 is characterized by the H II nebular ring N90 and the young cluster of pre-main-sequence (PMS) and early-type main-sequence stars NGC 602, located in the central area of the ring. We present a thorough cluster analysis of the stellar sample identified with Hubble Space Telescope/Advanced Camera for Surveys in the region. We show that apart from the central cluster low-mass PMS stars are congregated in 13 additional small, compact sub-clusters at the periphery of NGC 602, identified in terms of their higher stellar density with respect to the average background density derived from star counts. We find that the spatial distribution of the PMS stars is bimodal, with an unusually large fraction (∼60%) of the total population being clustered, while the remaining is diffusely distributed in the intercluster area, covering the whole central part of the region. From the corresponding color-magnitude diagrams we disentangle an age difference of ∼2.5 Myr between NGC 602 and the compact sub-clusters, which appear younger, on the basis of comparison of the brighter PMS stars with evolutionary models, which we accurately calculated for the metal abundance of the SMC. The diffuse PMS population appears to host stars as old as those in NGC 602. Almost all detected PMS sub-clusters appear to be centrally concentrated. When the complete PMS stellar sample, including both clustered and diffused stars, is considered in our cluster analysis, it appears as a single centrally concentrated stellar agglomeration, covering the whole central area of the region. Considering also the hot massive stars of the system, we find evidence that this agglomeration is hierarchically structured. Based on our findings, we propose a scenario according to which the region NGC 602/N90 experiences an active clustered star formation for the last ∼5 Myr. The central cluster NGC 602 was formed first

  13. WIYN Open Cluster Study. XXXII. Stellar Radial Velocities in the Old Open Cluster NGC 188

    Science.gov (United States)

    Geller, Aaron M.; Mathieu, Robert D.; Harris, Hugh C.; McClure, Robert D.

    2008-06-01

    We present the results of our ongoing radial-velocity (RV) survey of the old (7 Gyr) open cluster NGC 188. Our WIYN 3.5 m data set spans a time baseline of 11 years, a magnitude range of 12 =3 measurements, finding 473 to be likely cluster members. We detect 124 velocity-variable cluster members, all of which are likely to be dynamically hard-binary stars. Using our single member stars, we find an average cluster radial velocity of -42.36 ± 0.04 km s-1. We use our precise RV and proper-motion membership data to greatly reduce field-star contamination in our cleaned color-magnitude diagram, from which we identify six stars of note that lie far from a standard single-star isochrone. We present a detailed study of the spatial distribution of cluster-member populations, and find the binaries to be centrally concentrated, providing evidence for the presence of mass segregation in NGC 188. We observe the BSs to populate a bimodal spatial distribution that is not centrally concentrated, suggesting that we may be observing two populations of BSs in NGC 188, including a centrally concentrated distribution as well as a halo population. Finally, we find NGC 188 to have a global RV dispersion of 0.64 ± 0.04 km s-1, which may be inflated by up to 0.23 km s-1 from unresolved binaries. When corrected for unresolved binaries, the NGC 188 RV dispersion has a nearly isothermal radial distribution. We use this mean-corrected velocity dispersion to derive a virial mass of 2300 ± 460 M sun .

  14. The Magellanic Bridge Cluster NGC 796: Deep Optical AO Imaging Reveals the Stellar Content and Initial Mass Function of a Massive Open Cluster

    Science.gov (United States)

    Kalari, Venu M.; Carraro, Giovanni; Evans, Christopher J.; Rubio, Monica

    2018-04-01

    NGC 796 is a massive young cluster located 59 kpc from us in the diffuse intergalactic medium of the 1/5–1/10 Z⊙ Magellanic Bridge, allowing us to probe variations in star formation and stellar evolution processes as a function of metallicity in a resolved fashion, and providing a link between resolved studies of nearby solar-metallicity and unresolved distant metal-poor clusters located in high-redshift galaxies. In this paper, we present adaptive optics griHα imaging of NGC 796 (at 0.″5, which is ∼0.14 pc at the cluster distance) along with optical spectroscopy of two bright members to quantify the cluster properties. Our aim is to explore whether star formation and stellar evolution vary as a function of metallicity by comparing the properties of NGC 796 to higher-metallicity clusters. We find an age of {20}-5+12 Myr from isochronal fitting of the cluster main sequence in the color–magnitude diagram. Based on the cluster luminosity function, we derive a top-heavy stellar initial mass function (IMF) with a slope α = 1.99 ± 0.2, hinting at a metallicity and/or environmental dependence of the IMF, which may lead to a top-heavy IMF in the early universe. Study of the Hα emission-line stars reveals that classical Be stars constitute a higher fraction of the total B-type stars when compared with similar clusters at greater metallicity, providing some support to the chemically homogeneous theory of stellar evolution. Overall, NGC 796 has a total estimated mass of 990 ± 200 M⊙, and a core radius of 1.4 ± 0.3 pc, which classifies it as a massive young open cluster, unique in the diffuse interstellar medium of the Magellanic Bridge.

  15. The globular cluster system of NGC 1316. IV. Nature of the star cluster complex SH2

    Science.gov (United States)

    Richtler, T.; Husemann, B.; Hilker, M.; Puzia, T. H.; Bresolin, F.; Gómez, M.

    2017-05-01

    Context. The light of the merger remnant NGC 1316 (Fornax A) is dominated by old and intermediate-age stars. The only sign of current star formation in this big galaxy is the Hii region SH2, an isolated star cluster complex with a ring-like morphology and an estimated age of 0.1 Gyr at a galactocentric distance of about 35 kpc. A nearby intermediate-age globular cluster, surrounded by weak line emission and a few more young star clusters, is kinematically associated. The origin of this complex is enigmatic. Aims: We want to investigate the nature of this star cluster complex. The nebular emission lines permit a metallicity determination which can discriminate between a dwarf galaxy or other possible precursors. Methods: We used the Integral Field Unit (IFU) of the VIMOS instrument at the Very Large Telescope of the European Southern Observatory in high dispersion mode to study the morphology, kinematics, and metallicity employing line maps, velocity maps, and line diagnostics of a few characteristic spectra. Results: The line ratios of different spectra vary, indicating highly structured Hii regions, but define a locus of uniform metallicity. The strong-line diagnostic diagrams and empirical calibrations point to a nearly solar or even super-solar oxygen abundance. The velocity dispersion of the gas is highest in the region offset from the bright clusters. Star formation may be active on a low level. There is evidence for a large-scale disk-like structure in the region of SH2, which would make the similar radial velocity of the nearby globular cluster easier to understand. Conclusions: The high metallicity does not fit to a dwarf galaxy as progenitor. We favour the scenario of a free-floating gaseous complex having its origin in the merger 2 Gyr ago. Over a long period the densities increased secularly until finally the threshold for star formation was reached. SH2 illustrates how massive star clusters can form outside starbursts and without a considerable field

  16. Radial velocities and metallicities from infrared Ca ii triplet spectroscopy of open clusters. II. Berkeley 23, King 1, NGC 559, NGC 6603, and NGC 7245

    Science.gov (United States)

    Carrera, R.; Casamiquela, L.; Ospina, N.; Balaguer-Núñez, L.; Jordi, C.; Monteagudo, L.

    2015-06-01

    Context. Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R ~ 8000) in the infrared region Ca ii triplet lines (~8500 Å) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5 m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca ii lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain ⟨Vr⟩ = 48.6 ± 3.4, -58.4 ± 6.8, 26.0 ± 4.3, and -65.3 ± 3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603, and NGC 7245, respectively. We found [ Fe/H ] = -0.25 ± 0.14 and -0.15 ± 0.18 for NGC 559 and NGC 7245, respectively. Berkeley 23 has low metallicity, [ Fe/H ] = -0.42 ± 0.13, which is similar to other open clusters in the outskirts of the Galactic disc. In contrast, we derived high metallicity ([ Fe/H ] = +0.43 ± 0.15) for NGC 6603, which places this system among the most metal-rich known open clusters. To our knowledge, this is the first determination of radial velocities and metallicities from spectroscopy for these clusters, except NGC 6603, for which radial velocities had been previously determined. We have also analysed ten stars in the line of sight to King 1. Because of the large dispersion obtained in both radial velocity and metallicity, we cannot be sure that we have sampled true cluster members. Based on observations made with the 2.5 m Isaac Newton Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the

  17. VARIABLE STARS IN THE GLOBULAR CLUSTER NGC 2808

    International Nuclear Information System (INIS)

    Kunder, Andrea; Walker, Alistair R.; Stetson, Peter B.; Catelan, Márcio; Amigo, Pía

    2013-01-01

    The first calibrated broadband BVI time-series photometry is presented for the variable stars in NGC 2808, with observations spanning a range of 28 years. We have also redetermined the variability types and periods for the variable stars identified previously by Corwin et al., revising the number of probable fundamental-mode RR Lyrae variables (RR0) to 11 and the number of first-overtone variables (RR1) to five. Our observations were insufficient to discern the nature of the previously identified RR1 star, V24, and the tentatively identified RR1 star, V13. These two variables are ∼0.8 mag brighter than the RR Lyrae variables, appear to have somewhat erratic period and/or luminosity changes, and lie inside the RR Lyrae instability strip. Curiously, all but one of the RR Lyrae stars studied in this relatively metal-rich cluster exhibit the Blazhko phenomenon, an effect thought to occur with higher frequency in metal-poor environments. The mean periods of the RR0 and RR1 variables are (P) RR0 = 0.56 ± 0.01 d and RR1 = 0.30 ± 0.02 d, respectively, supporting an Oosterhoff I classification of the cluster. On the other hand, the number ratio of RR1-to-RR0-type variables is high, though not unprecedented, for an Oosterhoff I cluster. The RR Lyrae variables have no period shifts at a given amplitude compared to the M3 variables, making it unlikely that these variables are He enhanced. Using the recent recalibration of the RR Lyrae luminosity scale by Catelan and Cortés, a mean distance modulus of (m – M) V = 15.57 ± 0.13 mag for NGC 2808 is obtained, in good agreement with that determined here from its type II Cepheid and SX Phoenicis population. Our data have also allowed the discovery of two new candidate SX Phoenicis stars and an eclipsing binary in the blue straggler region of the NGC 2808 color-magnitude diagram.

  18. Metallicity Variations in the Type II Globular Cluster NGC 6934

    Science.gov (United States)

    Marino, A. F.; Yong, D.; Milone, A. P.; Piotto, G.; Lundquist, M.; Bedin, L. R.; Chené, A.-N.; Da Costa, G.; Asplund, M.; Jerjen, H.

    2018-06-01

    The Hubble Space Telescope photometric survey of Galactic globular clusters (GCs) has revealed a peculiar “chromosome map” for NGC 6934. In addition to a typical sequence, similar to that observed in Type I GCs, NGC 6934 displays additional stars on the red side, analogous to the anomalous Type II GCs, as defined in our previous work. We present a chemical abundance analysis of four red giants in this GC. Two stars are located on the chromosome map sequence common to all GCs, and another two lie on the additional sequence. We find (i) star-to-star Fe variations, with the two anomalous stars being enriched by ∼0.2 dex. Because of our small-size sample, this difference is at the ∼2.5σ level. (ii) There is no evidence for variations in the slow neutron-capture abundances over Fe, at odds with what is often observed in anomalous Type II GCs, e.g., M 22 and ω Centauri (iii) no large variations in light elements C, O, and Na, compatible with locations of the targets on the lower part of the chromosome map where such variations are not expected. Since the analyzed stars are homogeneous in light elements, the only way to reproduce the photometric splits on the sub-giant (SGB) and the red giant (RGB) branches is to assume that red RGB/faint SGB stars are enhanced in [Fe/H] by ∼0.2. This fact corroborates the spectroscopic evidence of a metallicity variation in NGC 6934. The observed chemical pattern resembles only partially the other Type II GCs, suggesting that NGC 6934 might belong either to a third class of GCs, or be a link between normal Type I and anomalous Type II GCs. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and Gemini Telescope at Canada–France–Hawaii Telescope.

  19. High-resolution spectroscopic observations of binary stars and yellow stragglers in three open clusters: NGC 2360, NGC 3680, and NGC 5822

    Energy Technology Data Exchange (ETDEWEB)

    Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F., E-mail: joaovictor@on.br, E-mail: jearim@on.br, E-mail: osantrich@on.br, E-mail: claudio@on.br, E-mail: drake@on.br, E-mail: froig@on.br [Observatório Nacional/MCT, Rua Gen. José Cristino, 77, 20921-400 Rio de Janeiro (Brazil)

    2014-11-01

    Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a

  20. High-resolution Spectroscopic Observations of Binary Stars and Yellow Stragglers in Three Open Clusters : NGC 2360, NGC 3680, and NGC 5822

    Science.gov (United States)

    Sales Silva, J. V.; Peña Suárez, V. J.; Katime Santrich, O. J.; Pereira, C. B.; Drake, N. A.; Roig, F.

    2014-11-01

    Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so chemical peculiarities can be linked directly to the evolutionary status of a star. In addition, binary stars offer the opportunity to verify a relationship between them and the straggler population in both globular and open clusters. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code MOOG. The abundances of the light elements were derived using the spectral synthesis technique. We found that the stars NGC 2360-92 and 96, NGC 3680-34, and NGC 5822-4 and 312 are yellow straggler stars. We show that the spectra of NGC 5822-4 and 312 present evidence of contamination by an A-type star as a secondary star. For the other yellow stragglers, evidence of contamination is given by the broad wings of the Hα. Detection of yellow straggler stars is important because the observed number can be compared with the number predicted by simulations of binary stellar evolution in open clusters. We also found that the other binary stars are not s-process enriched, which may suggest that in these binaries the secondary star is probably a faint main-sequence object. The lack of any s-process enrichment is very useful in setting constraints for the number of white dwarfs in the open cluster, a subject that is related to the birthrate of these kinds of stars in open clusters and also to the age of a

  1. The Secrets of the Nearest Starburst Cluster. I. Very Large Telescope/ISAAC Photometry of NGC 3603

    Science.gov (United States)

    Stolte, Andrea; Brandner, Wolfgang; Brandl, Bernhard; Zinnecker, Hans; Grebel, Eva K.

    2004-08-01

    VLT/ISAAC JHKL photometry with subarcsecond resolution of the dense, massive starburst cluster NGC 3603 YC forming the core of the NGC 3603 giant molecular cloud is analyzed to reveal characteristics of the stellar population in unprecedented detail. The color-magnitude plane features a strong pre-main-sequence/main-sequence (PMS/MS) transition region, including the PMS/MS transition point, and reveals a secondary sequence for the first time in a nearby young starburst cluster. Arguments for a possible binary nature of this sequence are given. The resolved PMS/MS transition region allows isochrone fitting below the hydrogen-burning turn-on in NGC 3603 YC, yielding an independent estimate of global cluster parameters. A distance modulus of 13.9 mag, equivalent to d=6.0+/-0.3 kpc, is derived, as well as a line-of-sight extinction of AV=4.5+/-0.6 toward PMS stars in the cluster center. The interpretation of a binary candidate sequence suggests a single age of 1 Myr for NGC 3603 YC, providing evidence for a single burst of star formation without the need to employ an age spread in the PMS population, as argued for in earlier studies. Disk fractions are derived from L-band excesses, indicating a radial increase in the disk frequency from 20% to 40% from the core to the cluster outskirts. The low disk fraction in the cluster core, as compared to the 42% L-band excess fraction found for massive stars in the Trapezium cluster of a comparably young age, indicates strong photoevaporation in the cluster center. The estimated binary fraction of 30%, as well as the low disk fraction, suggest strong impacts on low-mass star formation due to stellar interactions in the dense starburst. The significant differences between NGC 3603 YC and less dense and massive young star clusters in the Milky Way reveal the importance of using local starbursts as templates for massive extragalactic star formation. Based on observations obtained at the ESO VLT on Paranal, Chile, under programs 63.I

  2. BVRI CCD photometry of the globular cluster NGC 6362

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.

    1986-01-01

    We have obtained 78 BVRI CCD frames with the 1.54 m Danish telescope at ESO, La Silla, and have constructed V vs B-V, V vs V-R, V vs R-I, V vs V-I, and V vs B-I color-magnitude diagrams in a 4' x 2X5 field of the globular cluster NGC 6362. From these five CMDs we find that the main-sequence turnoffs are all close to the same magnitude, namely V/sub TO/ = 18.75 +- 0.1, and the color turn- offs at B-V = 0.50 +- 0.02, V-R = 0.31 +- 0.02, R-I = 0.35 +- 0.02, V-I = 0.68 +- 0.02, and B-I = 1.18 +- 0.03. The magnitude difference between the turnoff and the horizontal branch for the five diagrams is ΔM/sub V/ = 3.40 +- 0.15 in excellent agreement with the value given by Sandage (1982). Using Y = 0.2, Z = 0.001 ([Fe/H] = -1.27), α = 1.65, a distance modulus of (m-M)/sub V/ = 14.74, and E(B-V) = 0.10, we find that the VandenBerg and Bell isochrones (1985) yield a consistent age for NGC 6362 in all colors indexes of 16 +- 1.5 x 10 9 yr. The solar distance to the cluster is 7.7 kpc and the galactic distance is 5.6 kpc assuming R 0 = 9 kpc

  3. SPB stars in the open SMC cluster NGC 371

    Science.gov (United States)

    Karoff, C.; Arentoft, T.; Glowienka, L.; Coutures, C.; Nielsen, T. B.; Dogan, G.; Grundahl, F.; Kjeldsen, H.

    2008-05-01

    Pulsation in β Cep and slowly pulsating B (SPB) stars are driven by the κ mechanism which depends critically on the metallicity. It has therefore been suggested that β Cep and SPB stars should be rare in the Magellanic Clouds which have lower metallicities than the solar neighbourhood. To test this prediction we have observed the open Small Magellanic Cloud (SMC) cluster NGC 371 for 12 nights in order to search for β Cep and SPB stars. Surprisingly, we find 29 short-period B-type variables in the upper part of the main sequence, many of which are probably SPB stars. This result indicates that pulsation is still driven by the κ mechanism even in low-metallicity environments. All the identified variables have periods longer than the fundamental radial period which means that they cannot be β Cep stars. Within an amplitude detection limit of 5 mmag no stars in the top of the Hertzsprung-Russell diagram show variability with periods shorter than the fundamental radial period. So if β Cep stars are present in the cluster they oscillate with amplitudes below 5 mmag, which is significantly lower than the mean amplitude of β Cep stars in the Galaxy. We see evidence that multimode pulsation is more common in the upper part of the main sequence than in the lower. We have also identified five eclipsing binaries and three periodic pulsating Be stars in the cluster field.

  4. AN ASTEROSEISMIC MEMBERSHIP STUDY OF THE RED GIANTS IN THREE OPEN CLUSTERS OBSERVED BY KEPLER: NGC 6791, NGC 6819, AND NGC 6811

    International Nuclear Information System (INIS)

    Stello, Dennis; Huber, Daniel; Bedding, Timothy R.; Meibom, Soeren; Gilliland, Ronald L.; Grundahl, Frank; Brogaard, Karsten; Christensen-Dalsgaard, Joergen; Hekker, Saskia; Chaplin, William J.; Elsworth, Yvonne P.; Mosser, BenoIt; Kallinger, Thomas; Mathur, Savita; GarcIa, Rafael A.; Basu, Sarbani; Molenda-Zakowicz, Joanna; Szabo, Robert; Still, Martin; Jenkins, Jon M.

    2011-01-01

    Studying star clusters offers significant advances in stellar astrophysics due to the combined power of having many stars with essentially the same distance, age, and initial composition. This makes clusters excellent test benches for verification of stellar evolution theory. To fully exploit this potential, it is vital that the star sample is uncontaminated by stars that are not members of the cluster. Techniques for determining cluster membership therefore play a key role in the investigation of clusters. We present results on three clusters in the Kepler field of view based on a newly established technique that uses asteroseismology to identify fore- or background stars in the field, which demonstrates advantages over classical methods such as kinematic and photometry measurements. Four previously identified seismic non-members in NGC 6819 are confirmed in this study, and three additional non-members are found-two in NGC 6819 and one in NGC 6791. We further highlight which stars are, or might be, affected by blending, which needs to be taken into account when analyzing these Kepler data.

  5. The Globular Cluster NGC 6402 (M14). II. Variable Stars

    Science.gov (United States)

    Contreras Peña, C.; Catelan, M.; Grundahl, F.; Stephens, A. W.; Smith, H. A.

    2018-03-01

    We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ∼137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006–2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d}}{{a}}{{y}}{{s}}. This, together with the position of the RR Lyrae stars of both Bailey types in the period–amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster. Based on observations obtained with the 0.9 m and 1 m telescopes at the Cerro Tololo Inter-American Observatory, Chile, operated by the SMARTS consortium.

  6. Legacy ExtraGalactic UV Survey with The Hubble Space Telescope: Stellar Cluster Catalogs and First Insights Into Cluster Formation and Evolution in NGC 628

    Science.gov (United States)

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

    2017-06-01

    We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify their genuine nature, produce multiband photometry (from NUV to NIR), and derive their physical properties via spectral energy distribution fitting analyses. We use the nearby spiral galaxy NGC 628 as a test case for demonstrating the impact that LEGUS will have on our understanding of the formation and evolution of YSCs and compact stellar associations within their host galaxy. Our analysis of the cluster luminosity function from the UV to the NIR finds a steepening at the bright end and at all wavelengths suggesting a dearth of luminous clusters. The cluster mass function of NGC 628 is consistent with a power-law distribution of slopes ˜ -2 and a truncation of a few times 105 {M}⊙ . After their formation, YSCs and compact associations follow different evolutionary paths. YSCs survive for a longer time frame, confirming their being potentially bound systems. Associations disappear on timescales comparable to hierarchically organized star-forming regions, suggesting that they are expanding systems. We find mass-independent cluster disruption in the inner region of NGC 628, while in the outer part of the galaxy there is little or no disruption. We observe faster disruption rates for low mass (≤104 {M}⊙ ) clusters, suggesting that a mass-dependent component is necessary to fully describe the YSC disruption process in NGC 628. Based on observations obtained with the NASA/ESA Hubble Space Telescope, 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.

  7. Star-formation history of very young clusters

    International Nuclear Information System (INIS)

    Stahler, S.W.

    1985-01-01

    The popular idea that star formation has proceeded sequentially from lowest to highest mass members in open clusters is examined critically. For extremely young clusters, such as NGC 2264 and NGC 6530, this sequential hypothesis is a consequence of the assignment of pre-main-sequence contraction ages to all member stars. However, such ages yield a formation history which is implausible from a physical point of view, since the critical time for the onset of formation at any stellar mass is equal to the pre-main-sequence contraction time for that mass. Moreover, these ages are in conflict with the strong observational evidence that a substantial fraction of cluster members have already reached the main sequence. After reconsideration of the probable main-sequence members, the stellar ages in NGC 2264 and NGC 6530 are consistent with a variety of formation histories, and, in particular, with the view that all stellar masses form in approximately the same interval of time within a given cluster, i.e., that there is no mass-age correlation. A notion closely related to the sequential hypothesis, that the total star-formation rate increases exponentially with time, is subject to the same criticism

  8. Keck Spectroscopy of Globular Clusters in the Elliptical Galaxy NGC 3610

    OpenAIRE

    Strader, Jay; Brodie, Jean P.; Schweizer, Francois; Larsen, Soeren S.; Seitzer, Patrick

    2002-01-01

    We present moderate-resolution Keck spectra of nine candidate globular clusters in the possible merger-remnant elliptical galaxy NGC 3610. Eight of the objects appear to be bona fide globular clusters of NGC 3610. We find that two of the clusters belong to an old metal-poor population, five to an old metal-rich population, and only one to an intermediate-age metal-rich population. The estimated age of the intermediate-age cluster is 1-5 Gyr, which is in agreement with earlier estimates of the...

  9. Red Clump stars in Kepler open cluster NGC 6819

    Directory of Open Access Journals (Sweden)

    Abedigamba O.P.

    2015-01-01

    Full Text Available We measure the large frequency separation, Δν, and the frequency of maximum amplitude, νmax, for 10 Red Clump (RC single member (SM stars in the Kepler open cluster NGC 6819. We derive luminosities and masses for each individual RC star. A comparison of the observations with an isochrone of Age = 2.5 Gyr, Z = 0.017 with no mass loss using a statistical techniques is made. A fractional mass loss of 5 ± 3 percent is obtained if we assume that no correction to Δν between RC and red-giant branch (RGB is necessary. However, models suggest that an effective correction of about 1.9 percent in Δν is required to obtain the correct mass of RC stars owing to the different internal structures of stars in the two evolutionary stages. In this case we find that the mass loss in the red giant branch is not significantly different from zero. This finding confirms that of [6]. It is clear that the mass estimate obtained by asteroseismology is not sufficient to deduce the mass loss on the red giant branch. However, it is clearly only a few percent at most.

  10. The X-ray globular cluster NGC 1851

    CERN Document Server

    Alcaino, G

    1976-01-01

    A BV photometric investigation of the Southern Globular Cluster NGC 1851, was carried out using the 1 m telescope of Cerro La Silla (ESO) for the photoelectric work and the 1 m telescope of Cerro Las Campanas (CARSO) for the photographic work. Nineteen stars were observed photoelectrically, the limiting magnitude being V=16.18. Using this sequence, 156 stars were measured photographically. The derived apparent distance modulus is (m-M)/sub app/=15/sup m/.50. The reddening is E(B-V)=0/sup m/.10. The true distance modulus is (m-M) /sub 0/=15/sup m/.20. The distance is 11 kpc from the sun, 6 kpc from the galactic plane and 17 kpc from the galactic centre. The main features of the colour-magnitude diagram are: a well defined horizontal branch abundant in red stars and deficient in blue stars, a rich subgiant and asymptotic branch and a moderately populated red giant branch of medium steepness rising to Delta V=2/sup m/.5 at (B-V) /sub 0/=1.4. At the distance of 11 kpc the maximum observed luminosity of the X-ray ...

  11. Be STARS IN THE OPEN CLUSTER NGC 6830

    International Nuclear Information System (INIS)

    Yu, Po-Chieh; Lin, Chien-Cheng; Lin, Hsing-Wen; Lee, Chien-De; Ngeow, Chow-Choong; Ip, Wing-Huen; Chen, Wen-Ping; Chang, Chan-Kao; Huang, Li-Ching; Cheng, Yu-Chi; Ritter, Andreas; Konidaris, Nick; Chen, Hui-Chen; Malkan, Matthew A.; Laher, Russ; Surace, Jason; Edelson, Rick; Quimby, Robert; Ben-Ami, Sagi; Ofek, Eran O.

    2016-01-01

    We report the discovery of two new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven H α emitters were discovered using the H α imaging photometry of the Palomar Transient Factory Survey. Stellar membership of the candidates was verified with photometric and kinematic information using 2MASS data and proper motions. The spectroscopic confirmation was carried out by using the Shane 3 m telescope at the Lick observatory. Based on their spectral types, three H α emitters were confirmed as Be stars with H α equivalent widths greater than −10 Å. Two objects were also observed by the new spectrograph spectral energy distribution-machine (SED-machine) on the Palomar 60-inch Telescope. The SED-machine results show strong H α emission lines, which are consistent with the results of the Lick observations. The high efficiency of the SED-machine can provide rapid observations for Be stars in a comprehensive survey in the future.

  12. Be STARS IN THE OPEN CLUSTER NGC 6830

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Po-Chieh; Lin, Chien-Cheng; Lin, Hsing-Wen; Lee, Chien-De; Ngeow, Chow-Choong; Ip, Wing-Huen; Chen, Wen-Ping; Chang, Chan-Kao; Huang, Li-Ching; Cheng, Yu-Chi; Ritter, Andreas [Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Jhongli 32001, Taiwan (China); Konidaris, Nick [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125 (United States); Chen, Hui-Chen [Department of Natural Sciences and Sustainable Development, Ministry of Science and Technology, 106, Sec. 2, Heping E. Road, Taipei 10622, Taiwan (China); Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90024 (United States); Laher, Russ; Surace, Jason [Spitzer Science Center, California Institute of Technology, M/S 314-6, Pasadena, CA 91125 (United States); Edelson, Rick [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Quimby, Robert [Kavli-Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba (Japan); Ben-Ami, Sagi; Ofek, Eran O. [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); and others

    2016-05-01

    We report the discovery of two new Be stars, and re-identify one known Be star in the open cluster NGC 6830. Eleven H α emitters were discovered using the H α imaging photometry of the Palomar Transient Factory Survey. Stellar membership of the candidates was verified with photometric and kinematic information using 2MASS data and proper motions. The spectroscopic confirmation was carried out by using the Shane 3 m telescope at the Lick observatory. Based on their spectral types, three H α emitters were confirmed as Be stars with H α equivalent widths greater than −10 Å. Two objects were also observed by the new spectrograph spectral energy distribution-machine (SED-machine) on the Palomar 60-inch Telescope. The SED-machine results show strong H α emission lines, which are consistent with the results of the Lick observations. The high efficiency of the SED-machine can provide rapid observations for Be stars in a comprehensive survey in the future.

  13. The globular cluster system of NGC 1316. II. The extraordinary object SH2

    Science.gov (United States)

    Richtler, T.; Kumar, B.; Bassino, L. P.; Dirsch, B.; Romanowsky, A. J.

    2012-07-01

    Context. SH2 has been described as an isolated HII-region, located about 6.5' south of the nucleus of NGC 1316 (Fornax A), a merger remnant in the the outskirts of the Fornax cluster of galaxies. Aims: We give a first, preliminary description of the stellar content and environment of this remarkable object. Methods: We used photometric data in the Washington system and HST photometry from the Hubble Legacy Archive for a morphological description and preliminary aperture photometry. Low-resolution spectroscopy provides radial velocities of the brightest star cluster in SH2 and a nearby intermediate-age cluster. Results: SH2 is not a normal HII-region, ionized by very young stars. It contains a multitude of star clusters with ages of approximately 108 yr. A ring-like morphology is striking. SH2 seems to be connected to an intermediate-age massive globular cluster with a similar radial velocity, which itself is the main object of a group of fainter clusters. Metallicity estimates from emission lines remain ambiguous. Conclusions: The present data do not yet allow firm conclusions about the nature or origin of SH2. It might be a dwarf galaxy that has experienced a burst of extremely clustered star formation. We may witness how globular clusters are donated to a parent galaxy. Based on observations taken at the European Southern Observatory, Cerro Paranal, Chile, under the programmes 082.B-0680, on observations taken at the Interamerican Observatory, Cerro Tololo, Chile. Furthermore based on observations made with the NASA/ESA Hubble Space Telescope (HST, PI: A. Sandage, Prop.ID: 7504), and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

  14. THE HELIUM CONTENT OF GLOBULAR CLUSTERS: NGC 6121 (M4)

    International Nuclear Information System (INIS)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-01-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ∼ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ∼ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ∼ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = –1.06 ± 0.02 (internal error), in agreement with other studies

  15. The Helium Content of Globular Clusters: NGC 6121 (M4)

    Science.gov (United States)

    Villanova, S.; Geisler, D.; Piotto, G.; Gratton, R. G.

    2012-03-01

    In the context of the multiple stellar population scenario in globular clusters, helium (He) has been proposed as a key element to interpret the observed multiple main sequences, subgiant branches, and red giant branches, as well as the complex horizontal branch (HB) morphology. In particular, second-generation stars belonging to the bluer part of the HB are thought to be more He-rich (ΔY = 0.03 or more) but also more Na-rich/O-poor than those located in the redder part that should have Y equal to the cosmological value. Up to now this hypothesis was only partially confirmed in NGC 6752, where stars of the redder zero-age HB showed an He content of Y = 0.25 ± 0.01, fully compatible with the primordial He content of the universe, and were all Na-poor/O-rich. Here we study hot blue horizontal branch (BHB) stars in the GC NGC 6121 (M4) to measure their He plus O/Na content. Our goal is to complete the partial results obtained for NGC 6752, focusing our attention on targets located on the bluer part of the HB of M4. We observed six BHB stars using the VLT2/UVES spectroscopic facility. Spectra of signal-to-noise ratio ~ 150 were obtained and the very weak He line at 5875 Å measured for all our targets. We compared this feature with synthetic spectra to obtain He abundances. In addition O, Na, and Fe abundances were estimated. Stars turned out to be all Na-rich and O-poor and to have a homogeneous He content with a mean value of Y = 0.29 ± 0.01(random) ± 0.01(systematic), which is enhanced by ΔY ~ 0.04 with respect to the most recent measurements of the primordial He content of the universe (Y ~ 0.24/0.25). The high He content of blue HB stars in M4 is also confirmed by the fact that they are brighter than red HB stars (RHB). Theoretical models suggest the BHB stars are He-enhanced by Δ(Y) = 0.02/0.03 with respect to the RHB stars. The whole sample of stars has a metallicity of [Fe/H] = -1.06 ± 0.02 (internal error), in agreement with other studies available in

  16. RR Lyrae stars in and around NGC 6441: signatures of dissolving cluster stars

    Science.gov (United States)

    Kunder, Andrea

    2018-06-01

    Detailed elemental abundance patterns of metal-poor ([Fe/H]~ -1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of globular clusters. Here an attempt is made to identify such presumptive destroyed stars originating from the massive, inner Galaxy globular cluster NGC~6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of forty RRLs centered on the globular cluster NGC~6441. All of the 13 RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 +- 5~km/s and a star-to-star scatter of 11~km/s. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC~6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster's orbit. Therefore, either the tidal radius of NGC~6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC~6441 that are building up the old spheroidal bulge. Both the mean velocity of the cluster as well as the underlying field population is consistent with belonging to an old spheroidal bulge with low rotation and high velocity dispersion that formed before the bar.

  17. A Starburst in the Core of a Galaxy Cluster: the Dwarf Irregular NGC 1427A in Fornax

    Science.gov (United States)

    Mora, Marcelo D.; Chanamé, Julio; Puzia, Thomas H.

    2015-09-01

    Gas-rich galaxies in dense environments such as galaxy clusters and massive groups are affected by a number of possible types of interactions with the cluster environment, which make their evolution radically different than that of field galaxies. The dwarf irregular galaxy NGC 1427A, presently infalling toward the core of the Fornax galaxy cluster for the first time, offers a unique opportunity to study those processes at a level of detail not possible to achieve for galaxies at higher redshifts, when galaxy-scale interactions were more common. Using the spatial resolution of the Hubble Space Telescope/Advanced Camera for Surveys and auxiliary Very Large Telescope/FORS1 ground-based observations, we study the properties of the most recent episodes of star formation in this gas-rich galaxy, the only one of its type near the core of the Fornax cluster. We study the structural and photometric properties of young star cluster complexes in NGC 1427A, identifying 12 bright such complexes with exceptionally blue colors. The comparison of our broadband near-UV/optical photometry with simple stellar population models yields ages below ˜ 4× {10}6 years and stellar masses from a few 1000 up to ˜ 3× {10}4{M}⊙ , slightly dependent on the assumption of cluster metallicity and initial mass function. Their grouping is consistent with hierarchical and fractal star cluster formation. We use deep Hα imaging data to determine the current star formation rate in NGC 1427A and estimate the ratio, Γ, of star formation occurring in these star cluster complexes to that in the entire galaxy. We find Γ to be among the largest such values available in the literature, consistent with starburst galaxies. Thus a large fraction of the current star formation in NGC 1427A is occurring in star clusters, with the peculiar spatial arrangement of such complexes strongly hinting at the possibility that the starburst is being triggered by the passage of the galaxy through the cluster environment

  18. Properties and origin of the old, metal rich, star cluster, NGC 6791

    OpenAIRE

    Carraro, Giovanni

    2013-01-01

    In this contribution I summarize the unique properties of the old, metal rich, star cluster NGC 6791, with particular emphasis on its population of extreme blue horizontal branch stars. I then conclude providing my personal view on the origin of this fascinating star cluster.

  19. Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 from the Radio to the Ultraviolet

    Science.gov (United States)

    Reines, Amy E.; Johnson, Kelsey E.; Goss, W. M.

    2008-06-01

    We present a multi-wavelength study of embedded massive clusters in the nearby (3.9 Mpc) starburst galaxy NGC 4449 in an effort to uncover the earliest phases of massive cluster evolution. By combining high-resolution imaging from the radio to the ultraviolet, we reveal these clusters to be in the process of emerging from their gaseous and dusty birth cocoons. We use Very Large Array (VLA) observations at centimeter wavelengths to identify young clusters surrounded by ultra-dense H II regions, detectable via their production of thermal free-free radio continuum. Ultraviolet, optical and infrared observations are obtained from the Hubble and Spitzer Space Telescope archives for comparison. We detect 39 compact radio sources toward NGC 4449 at 3.6 cm using the highest resolution (1farcs3) and sensitivity (~12 μJy) VLA image of the galaxy to date. We reliably identify 13 thermal radio sources and derive their physical properties using both nebular emission from the H II regions and spectral energy distribution fitting to the stellar continuum. These radio-detected clusters have ages lsim5 Myr and stellar masses of order 104 M sun. The measured extinctions are quite low: 12 of the 13 thermal radio sources have A V lsim 1.5, while the most obscured source has A V ≈ 4.3. By combining results from the nebular and stellar emission, we find an I-band excess that is anti-correlated with cluster age and an apparent mass-age correlation. Additionally, we find evidence that local processes such as supernovae and stellar winds likely play an important role in triggering the current bursts of star formation within NGC 4449.

  20. ASSESSMENT OF STELLAR STRATIFICATION IN THREE YOUNG STAR CLUSTERS IN THE LARGE MAGELLANIC CLOUD

    International Nuclear Information System (INIS)

    Gouliermis, Dimitrios A.; Rochau, Boyke; Mackey, Dougal; Xin Yu

    2010-01-01

    We present a comprehensive study of stellar stratification in young star clusters in the Large Magellanic Cloud (LMC). We apply our recently developed effective radius method for the assessment of stellar stratification on imaging data obtained with the Advanced Camera for Surveys of three young LMC clusters to characterize the phenomenon and develop a comparative scheme for its assessment in such clusters. The clusters of our sample, NGC 1983, NGC 2002, and NGC 2010, are selected on the basis of their youthfulness, and their variety in appearance, structure, stellar content, and surrounding stellar ambient. Our photometry is complete for magnitudes down to m 814 ≅ 23 mag, allowing the calculation of the structural parameters of the clusters, the estimation of their ages, and the determination of their stellar content. Our study shows that each cluster in our sample demonstrates stellar stratification in a quite different manner and at different degree from the others. Specifically, NGC 1983 shows partial segregation, with the effective radius increasing with fainter magnitudes only for the faintest stars of the cluster. Our method on NGC 2002 provides evidence of strong stellar stratification for both bright and faint stars; the cluster demonstrates the phenomenon with the highest degree in the sample. Finally, NGC 2010 is not segregated, as its bright stellar content is not centrally concentrated, the relation of effective radius to magnitude for stars of intermediate brightness is rather flat, and we find no evidence of stratification for its faintest stars. For the parameterization of the phenomenon of stellar stratification and its quantitative comparison among these clusters, we propose the slope derived from the change in the effective radius over the corresponding magnitude range as indicative parameter of the degree of stratification in the clusters. A positive value of this slope indicates mass segregation in the cluster, while a negative or zero value

  1. Sulphur in the metal poor globular cluster NGC 6397

    Science.gov (United States)

    Koch, A.; Caffau, E.

    2011-10-01

    Sulphur (S) is a non-refractory α-element that is not locked into dust grains in the interstellar medium. Thus no correction to the measured, interstellar sulphur abundance is needed and it can be readily compared to the S content in stellar photospheres. Here we present the first measurement of sulphur in the metal poor globular cluster (GC) NGC 6397, as detected in a MIKE/Magellan high signal-to-noise, high-resolution spectrum of one red giant star. While abundance ratios of sulphur are available for a larger number of Galactic stars down to an [Fe/H] of ~ -3.5 dex, no measurements in globular clusters more metal poor than -1.5 dex have been reported so far. We find aNLTE, 3-D abundance ratio of [S/Fe] = +0.52 ± 0.20 (stat.) ± 0.08 (sys.), based on theS I, Multiplet 1 line at 9212.8 Å. This value is consistent with a Galactic halo plateau as typical of other α-elements in GCs and field stars, but we cannot rule out its membership with a second branch of increasing [S/Fe] with decreasing [Fe/H], claimed in the literature, which leads to a large scatter at metallicities around - 2 dex. The [S/Mg] and [S/Ca] ratios in this star are compatible with a Solar value to within the (large) uncertainties. Despite the very large scatter in these ratios across Galactic stars between literature samples, this indicates that sulphur traces the chemical imprints of the other α-elements in metal poor GCs. Combined with its moderate sodium abundance ([S/Na]NLTE = 0.48), the [S/Fe] ratio in this GC extends a global, positive S-Na correlation that is not seen in field stars and might indicate that proton-capture reactions contributed to the production of sulphur in the (metal poor) early GC environments. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  2. MOCCA-SURVEY Database I: Is NGC 6535 a dark star cluster harbouring an IMBH?

    Science.gov (United States)

    Askar, Abbas; Bianchini, Paolo; de Vita, Ruggero; Giersz, Mirek; Hypki, Arkadiusz; Kamann, Sebastian

    2017-01-01

    We describe the dynamical evolution of a unique type of dark star cluster model in which the majority of the cluster mass at Hubble time is dominated by an intermediate-mass black hole (IMBH). We analysed results from about 2000 star cluster models (Survey Database I) simulated using the Monte Carlo code MOnte Carlo Cluster simulAtor and identified these dark star cluster models. Taking one of these models, we apply the method of simulating realistic `mock observations' by utilizing the Cluster simulatiOn Comparison with ObservAtions (COCOA) and Simulating Stellar Cluster Observation (SISCO) codes to obtain the photometric and kinematic observational properties of the dark star cluster model at 12 Gyr. We find that the perplexing Galactic globular cluster NGC 6535 closely matches the observational photometric and kinematic properties of the dark star cluster model presented in this paper. Based on our analysis and currently observed properties of NGC 6535, we suggest that this globular cluster could potentially harbour an IMBH. If it exists, the presence of this IMBH can be detected robustly with proposed kinematic observations of NGC 6535.

  3. No Evidence of Chemical Abundance Variations in the Intermediate-age Cluster NGC 1783

    Science.gov (United States)

    Zhang, Hao; de Grijs, Richard; Li, Chengyuan; Wu, Xiaohan

    2018-02-01

    We have analyzed multi-passband photometric observations, obtained with the Hubble Space Telescope, of the massive (1.8 × 105 M ⊙), intermediate-age (1.8 Gyr-old) Large Magellanic Cloud star cluster NGC 1783. The morphology of the cluster’s red giant branch does not exhibit a clear broadening beyond its intrinsic width; the observed width is consistent with that owing to photometric uncertainties alone and independent of the photometric selection boundaries we applied to obtain our sample of red giant stars. The color dispersion of the cluster’s red giant stars around the best-fitting ridgeline is 0.062 ± 0.009 mag, which is equivalent to the width of 0.080 ± 0.001 mag derived from artificial simple stellar population tests, that is, tests based on single-age, single-metallicity stellar populations. NGC 1783 is comparably as massive as other star clusters that show clear evidence of multiple stellar populations. After incorporating mass-loss recipes from its current age of 1.8 Gyr to an age of 6 Gyr, NGC 1783 is expected to remain as massive as some other clusters that host clear multiple populations at these intermediate ages. If we were to assume that mass is an important driver of multiple population formation, then NGC 1783 should have exhibited clear evidence of chemical abundance variations. However, our results support the absence of any chemical abundance variations in NGC 1783.

  4. Molecular clouds toward the super star cluster NGC 3603; possible evidence for a cloud-cloud collision in triggering the cluster formation

    Energy Technology Data Exchange (ETDEWEB)

    Fukui, Y.; Ohama, A.; Hanaoka, N.; Furukawa, N.; Torii, K.; Hasegawa, K.; Fukuda, T.; Soga, S.; Moribe, N.; Kuroda, Y.; Hayakawa, T.; Kuwahara, T.; Yamamoto, H.; Okuda, T. [Department of Astrophysics, Nagoya University, Chikusa-ku, Nagoya 464-8602 (Japan); Dawson, J. R. [School of Mathematics and Physics, University of Tasmania, Sandy Bay Campus, Churchill Avenue, Sandy Bay, TAS 7005 (Australia); Mizuno, N.; Kawamura, A. [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Onishi, T.; Maezawa, H. [Department of Astrophysics, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan); Mizuno, A., E-mail: fukui@a.phys.nagoya-u.ac.jp [Solar-terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya 464-8601 (Japan)

    2014-01-01

    We present new large field observations of molecular clouds with NANTEN2 toward the super star cluster NGC 3603 in the transitions {sup 12}CO(J = 2-1, J = 1-0) and {sup 13}CO(J = 2-1, J = 1-0). We suggest that two molecular clouds at 13 km s{sup –1} and 28 km s{sup –1} are associated with NGC 3603 as evidenced by higher temperatures toward the H II region, as well as morphological correspondence. The mass of the clouds is too small to gravitationally bind them, given their relative motion of ∼20 km s{sup –1}. We suggest that the two clouds collided with each other 1 Myr ago to trigger the formation of the super star cluster. This scenario is able to explain the origin of the highest mass stellar population in the cluster, which is as young as 1 Myr and is segregated within the central sub-pc of the cluster. This is the second super star cluster along with Westerlund 2 where formation may have been triggered by a cloud-cloud collision.

  5. A CENSUS OF YOUNG STARS AND BROWN DWARFS IN IC 348 AND NGC 1333

    Energy Technology Data Exchange (ETDEWEB)

    Luhman, K. L.; Esplin, T. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Loutrel, N. P., E-mail: kluhman@astro.psu.edu [Department of Physics, Montana State University, Bozeman, MT 59715 (United States)

    2016-08-10

    We have obtained optical and near-infrared spectra of candidate members of the star-forming clusters IC 348 and NGC 1333. We classify 100 and 42 candidates as new members of the clusters, respectively, which brings the total numbers of known members to 478 and 203. We also have performed spectroscopy on a large majority of the previously known members of NGC 1333 in order to provide spectral classifications that are measured with the same scheme that has been applied to IC 348 in previous studies. The new census of members is nearly complete for K {sub s}< 16.8 at A {sub J}< 1.5 in IC 348 and for K {sub s}< 16.2 at A {sub J}< 3 in NGC 1333, which correspond to masses of ≳0.01 M {sub ⊙} for ages of 3 Myr according to theoretical evolutionary models. The faintest known members extend below these completeness limits and appear to have masses of ∼0.005 M {sub ⊙}. In extinction-limited samples of cluster members, NGC 1333 exhibits a higher abundance of objects at lower masses than IC 348. It would be surprising if the initial mass functions of these clusters differ significantly given their similar stellar densities and formation environments. Instead, it is possible that average extinctions are lower for less massive members of star-forming clusters, in which case extinction-limited samples could be biased in favor of low-mass objects in the more heavily embedded clusters like NGC 1333. In the Hertzsprung–Russell diagram, the median sequences of IC 348 and NGC 1333 coincide with each other for the adopted distances of 300 and 235 pc, which would suggest that they have similar ages. However, NGC 1333 is widely believed to be younger than IC 348 based on its higher abundance of disks and protostars and its greater obscuration. Errors in the adopted distances may be responsible for this discrepancy.

  6. Low-mass X-ray binaries and globular clusters streamers and arcs in NGC 4278

    Energy Technology Data Exchange (ETDEWEB)

    D' Abrusco, R.; Fabbiano, G. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Brassington, N. J. [Center for Astrophysics Research, University of Hertfordshire, College Lane Campus, Hatfield, Hertordshire, AL10 9AB (United Kingdom)

    2014-03-01

    We report significant inhomogeneities in the projected two-dimensional spatial distributions of low-mass X-ray binaries (LMXBs) and globular clusters (GCs) of the intermediate mass elliptical galaxy NGC 4278. In the inner region of NGC 4278, a significant arc-like excess of LMXBs extending south of the center at ∼50'' in the western side of the galaxy can be associated with a similar overdensity of the spatial distribution of red GCs from Brassington et al. Using a recent catalog of GCs produced by Usher et al. and covering the whole field of the NGC 4278 galaxy, we have discovered two other significant density structures outside the D {sub 25} isophote to the W and E of the center of NGC 4278, associated with an overdensity and an underdensity, respectively. We discuss the nature of these structures in the context of the similar spatial inhomogeneities discovered in the LMXBs and GCs populations of NGC 4649 and NGC 4261, respectively. These features suggest streamers from disrupted and accreted dwarf companions.

  7. An Archival Search For Young Globular Clusters in Galaxies

    Science.gov (United States)

    Whitmore, Brad

    1995-07-01

    One of the most intriguing results from HST has been the discovery of ultraluminous star clusters in interacting and merging galaxies. These clusters have the luminosities, colors, and sizes that would be expected of young globular clusters produced by the interaction. We propose to use the data in the HST Archive to determine how prevalent this phenomena is, and to determine whether similar clusters are produced in other environments. Three samples will be extracted and studied in a systematic and consistent manner: 1} interacting and merging galaxies, 2} starburst galaxies, 3} a control sample of ``normal'' galaxies. A preliminary search of the archives shows that there are at least 20 galaxies in each of these samples, and the number will grow by about 50 observations become available. The data will be used to determine the luminosity function, color histogram , spatial distribution, and structural properties of the clusters using the same techniques employed in our study of NGC 7252 {``Atoms -for-Peace'' galaxy} and NGC 4038/4039 {``The Antennae''}. Our ultimate goals are: 1} to understand how globular clusters form, and 2} to use the clusters as evolutionary tracers to unravel the histories of interacting galaxies.

  8. Tracing the assembly history of NGC 1395 through its Globular Cluster System

    Science.gov (United States)

    Escudero, Carlos G.; Faifer, Favio R.; Smith Castelli, Analía V.; Forte, Juan C.; Sesto, Leandro A.; González, Nélida M.; Scalia, María C.

    2018-03-01

    We used deep Gemini-South/GMOS g΄r΄i΄z΄ images to study the globular cluster (GC) system of the massive elliptical galaxy NGC 1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of `blue' and `red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and SN = 7.4 ± 1.4, respectively. Regarding NGC 1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as Mstellar = 9.32 × 1011 M⊙ and Mh = 6.46 × 1013 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.

  9. CHEMICAL ABUNDANCES IN NGC 5053: A VERY METAL-POOR AND DYNAMICALLY COMPLEX GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2015-05-10

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin–Indiana–Yale–NOAO–Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ∼ 75–90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of −2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na–O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  10. Chemical Abundances in NGC 5053: A Very Metal-poor and Dynamically Complex Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2015-05-01

    NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ˜ 75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.

  11. EXTENDED STAR FORMATION IN THE INTERMEDIATE-AGE LARGE MAGELLANIC CLOUD STAR CLUSTER NGC 2209

    International Nuclear Information System (INIS)

    Keller, Stefan C.; Mackey, A. Dougal; Da Costa, Gary S.

    2012-01-01

    We present observations of the 1 Gyr old star cluster NGC 2209 in the Large Magellanic Cloud made with the GMOS imager on the Gemini South Telescope. These observations show that the cluster exhibits a main-sequence turnoff that spans a broader range in luminosity than can be explained by a single-aged stellar population. This places NGC 2209 amongst a growing list of intermediate-age (1-3 Gyr) clusters that show evidence for extended or multiple epochs of star formation of between 50 and 460 Myr in extent. The extended main-sequence turnoff observed in NGC 2209 is a confirmation of the prediction in Keller et al. made on the basis of the cluster's large core radius. We propose that secondary star formation is a defining feature of the evolution of massive star clusters. Dissolution of lower mass clusters through evaporation results in only clusters that have experienced secondary star formation surviving for a Hubble time, thus providing a natural connection between the extended main-sequence turnoff phenomenon and the ubiquitous light-element abundance ranges seen in the ancient Galactic globular clusters.

  12. A new Be star in an open cluster - NGC 6871-8

    Science.gov (United States)

    Grigsby, James A.; Morrison, Nancy D.

    1988-01-01

    Spectroscopic observations of H-alpha show that star eight in the open cluster NGC 6871 is a previously-undiscovered Be star. The H-alpha profile was observed to vary from clear emission to pure absorption over a period of ten days; later observations over a five-day interval show weak emission along with asymmetries and filling in of the profile.

  13. Two transitional type Ia supernovae located in the Fornax cluster member NGC 1404

    DEFF Research Database (Denmark)

    Gall, C.; Stritzinger, M. D.; Ashall, C.

    2018-01-01

    We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Delta m(15)(B) decline-rate values of...

  14. A NEW CENSUS OF THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 2419

    International Nuclear Information System (INIS)

    Di Criscienzo, M.; Greco, C.; Ripepi, V.; Dall' Ora, M.; Marconi, M.; Musella, I.; Clementini, G.; Federici, L.; Di Fabrizio, L.

    2011-01-01

    We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two δ Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification. The pulsation properties of the RR Lyrae variables are close to those of Oosterhoff type II clusters, consistent with the low metal abundance and the cluster horizontal branch morphology, disfavoring (but not totally ruling out) an extragalactic hypothesis for the origin of NGC 2419. The observed properties of RR Lyrae and SX Phoenicis stars are used to estimate the cluster reddening and distance, using a number of different methods. Our final value is μ 0 (NGC 2419) = 19.71 ± 0.08 mag (D = 87.5 ± 3.3 kpc), with E(B - V) = 0.08 ± 0.01 mag, [Fe/H] = -2.1 dex on the Zinn and West metallicity scale, and a value of M V that sets μ 0 (LMC) = 18.52 mag. This value is in good agreement with the most recent literature estimates of the distance to NGC 2419.

  15. Search for continuous gravitational waves from neutron stars in globular cluster NGC 6544

    NARCIS (Netherlands)

    Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Phythian-Adams, A.T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.T.; Aguiar, O. D.; Aiello, L.; Ain, A.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, R.D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Bejger, M.; Bell, A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, M.J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, A.L.S.; Bock, O.; Boer, M.; Bogaert, J.G.; Bogan, C.; Bohe, A.; Bond, T.C; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.; Brown, A.D.; Brown, D.; Brown, N. M.; Brunett, S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Bustillo, J. Calderon; Callister, T. A.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Diaz, J. Casanueva; Casentini, C.; Caudill, S.; Cavaglia, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Baiardi, L. Cerboni; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, D. S.; Charlton, P.; Chassande-Mottin, E.; Cheeseboro, B. D.; Chen, H. Y.; Chen, Y; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Qian; Chua, S. S. Y.; Chung, E.S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P. -F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, A.C.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.; Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, Laura; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dasgupta, A.; Costa, C. F. Da Silva; Dattilo, V.; Dave, I.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; De, S.; Debra, D.; Debreczeni, G.; Degallaix, J.; De laurentis, M.; Deleglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.A.; Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Devine, R. C.; Dhurandhar, S.; Diaz, M. C.; Di Fiore, L.; Giovanni, M. Di; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, T. M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fan, X.M.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Fenyvesi, E.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M; Fournier, J. -D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Geng, P.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.P.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; Gonzalez, Idelmis G.; Castro, J. M. Gonzalez; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Lee-Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.M.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Buffoni-Hall, R.; Hall, E. D.; Hammond, G.L.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hanson, P.J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C. -J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.A.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J. -M.; Isi, M.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, D.H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jian, L.; Jimenez-Forteza, F.; Johnson, W.; Jones, I.D.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.H.; Kanner, J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kefelian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.E.; Key, J. S.; Khalili, F. Y.; Khan, I.; Khan., S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chi-Woong; Kim, Chunglee; Kim, J.; Kim, K.; Kim, Namjun; Kim, W.; Kim, Y.M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kissel, J. S.; Klein, B.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Krishnan, B.; Krolak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kumar, R.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Laxen, M.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C.H.; Lee, K.H.; Lee, M.H.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Lewis, J. B.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Lombardi, A. L.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lueck, H.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magana-Sandoval, F.; Zertuche, L. Magana; Magee, R. M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Marka, S.; Marka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, A. L.; Miller, B.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B.C.; Moore, J.C.; Moraru, D.; Gutierrez Moreno, M.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, S.D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P.G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nedkova, K.; Nelemans, G.; Nelson, T. J. N.; Gutierrez-Neri, M.; Neunzert, A.; Newton-Howes, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J.; Oh, S. H.; Ohme, F.; Oliver, M. B.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.S; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patel, P.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca, A.; Perri, L. M.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Puerrer, M.; Qi, H.; Qin, J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci, F.; Riles, K.; Rizzo, D.M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.; Romie, J. H.; Rosinska, D.; Rowan, S.; Ruediger, A.; Ruggi, P.; Ryan, K.A.; Sachdev, Perminder S; Sadecki, T.; Sadeghian, L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J; Schmidt, P.; Schnabel, R.B.; Schofield, R. M. S.; Schoebeck, A.; Schreiber, K.E.C.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, M.S.; Sellers, D.; Sengupta, A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Setyawati, Y.; Shaddock, D. A.; Shaffer, T. J.; Shahriar, M. S.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, António Dias da; Singer, A; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, R. J. E.; Smith, N.D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stone, J.R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S. E.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton, P. J.; Swinkels, B. L.; Szczepanczyk, M. J.; Tacca, M.D.; Talukder, D.; Tanner, D. B.; Tapai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, W.R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tomlinson, C.; Tonelli, M.; Tornasi, Z.; Torres, C. V.; Torrie, C. I.; Toyra, D.; Travasso, F.; Traylor, G.; Trifiro, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; Van Beuzekom, Martin; van den Brand, J. F. J.; Van Den Broeck, C.F.F.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasuth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P.J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Vicere, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J. -Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, MT; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L. -W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.M.; Wessels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whiting, B. F.; Williams, D.R.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Worden, J.; Wright, J.L.; Wu, D.S.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yu, H.; Yvert, M.; Zadrozny, A.; Zangrando, L.; Zanolin, M.; Zendri, J. -P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Sigurdsson, S.

    2017-01-01

    We describe a directed search for continuous gravitational waves in data from the sixth initial LIGO science run. The target was the nearby globular cluster NGC 6544 at a distance of approximate to 2.7 kpc. The search covered a broad band of frequencies along with first and second frequency

  16. A single population of red globular clusters around the massive compact galaxy NGC 1277

    Science.gov (United States)

    Beasley, Michael A.; Trujillo, Ignacio; Leaman, Ryan; Montes, Mireia

    2018-03-01

    Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies. Here we report optical observations of the massive relic-galaxy candidate NGC 1277—a nearby, un-evolved example of a high-redshift ‘red nugget’ galaxy. We find that the optical colour distribution of the cluster system of NGC 1277 is unimodal and entirely red. This finding is in strong contrast to other galaxies of similar and larger stellar mass, the cluster systems of which always exhibit (and are generally dominated by) blue clusters. We argue that the colour distribution of the cluster system of NGC 1277 indicates that the galaxy has undergone little (if any) mass accretion after its initial collapse, and use simulations of possible merger histories to show that the stellar mass due to accretion is probably at most ten per cent of the total stellar mass of the galaxy. These results confirm that NGC 1277 is a genuine relic galaxy and demonstrate that blue clusters constitute an accreted population in present-day massive galaxies.

  17. A CCD photometric analysis of the old open cluster NGC 2420

    International Nuclear Information System (INIS)

    Anthony-Twarog, B.J.; Twarog, B.A.; Kaluzny, J.; Shara, M.M.

    1990-01-01

    Precision CCD photometry on the BV system of the core of the old open cluster NGC 2420 is analyzed to explore the value of such an approach for open clusters, particularly in the areas of Galactic and stellar evolution. The unevolved main sequence is shown to be narrow and well defined to the completeness limit of V = 18.5, and the distribution of stars away from the main sequence is shown to be bimodal, with a secondary peak located approximately 0.7 mag above the fiducial main sequence. It is estimated that 50 percent of the cluster systems are binary. Near the turnoff the cluster exhibits some detailed structure. Fiducial relations are given for the cluster extending from the lower main sequence to the red giant branch 1.5 mag above the clump. Comparisons are made between the NGC 2420 cluster and NGC 2506, the isochrones of VandenBerg (1985), and 47 Tuc, in order to estimate cluster parameters, including reddening and metallicity. 68 refs

  18. Detailed abundance analysis of globular clusters in the Local Group. NGC 147, NGC 6822, and Messier 33

    Science.gov (United States)

    Larsen, S. S.; Brodie, J. P.; Wasserman, A.; Strader, J.

    2018-06-01

    Context. Globular clusters (GCs) are emerging as powerful tracers of the chemical composition of extragalactic stellar populations. Aims: We present new abundance measurements for 11 GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and Wolf-Lundmark-Melotte (WLM) galaxies. Methods: The abundances were determined from analyses of integrated-light spectra obtained with the HIRES spectrograph on the Keck I telescope and with UVES on the Very Large Telescope (VLT). We used our analysis technique that was developed for this purpose and tested on Milky Way GCs. Results: We find that the clusters with [Fe/H] -1.5, the GCs in M33 are also α-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to solar-scaled α-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly subsolar [Na/Fe] and [Ni/Fe] ratios. In NGC 147, the GCs with [Fe/H] account for about 6% of the total luminosity of stars in the same metallicity range, a lower fraction than those previously found in the Fornax and WLM galaxies, but substantially higher than in the Milky Way halo. Conclusions: At low metallicities, the abundance patterns suggest that GCs in the Milky Way, dwarf galaxies, and M33 experienced similar enrichment histories and/or processes. At higher metallicities, the lower levels of α-enhancement in the GCs found in dwarf galaxies resemble the abundance patterns observed in field stars in nearby dwarfs. Constraining the presence of multiple populations in these GCs is complicated by lack of information about detailed abundances in field stars of the corresponding metallicities. We suggest that correlations such as [Na/Fe] versus [Ni/Fe] may prove useful for this purpose if an accuracy of 0.1 dex or better can be reached for integrated-light measurements. Tables A.1-A.15

  19. Another non-segregated Blue Straggler population in a globular cluster: the case of NGC 2419.

    Science.gov (United States)

    Dalessandro, E.; Lanzoni, B.; Ferraro, F. R.; Vespe, F.; Bellazzini, M.; Rood, R. T.

    We have used a combination of ACS-HST high-resolution and wide-field SUBARU data in order to study the Blue Straggler Star (BSS) population over the entire extension of the remote Galactic globular cluster NGC 2419. The radial distribution of the selected BSS is the same as that of the other cluster stars. In this sense the BSS radial distribution is like that of omega Centauri and unlike that of all Galactic globular clusters studied to date, which have highly centrally segregated distributions and in most cases a pronounced upturn in the external regions. As in the case of omega Centauri, this evidence indicates that NGC 2419 is not yet relaxed even in the central regions. This observational fact is in agreement with estimated half-mass relaxation time, which is of the order of the cluster age.

  20. BVRI CCD photometry of the metal-poor globular cluster M68 (NGC 4590)

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

    1990-01-01

    BVRI photometry of the low metallicity globular cluster M68 (NGC 4590) was obtained with a CCD camera and the 2.2-m ESO telescope. The resulting BV color-magnitude diagrams are compared with the observations of McClure et al. (1987). The observations are also compared with theoretical isochrones, yielding a cluster age of 13 Gyr with a likely external uncertainty of 2 or 3 Gyr. 25 refs

  1. X-Ray and optical study of low core density globular clusters NGC6144 and E3

    NARCIS (Netherlands)

    Lan, S.-H.; Kong, A.K.H.; Verbunt, F.W.M.; Lewin, W.H.G.; Bassa, C.G.; Anderson, S.F.; Pooley, D.

    2010-01-01

    We report on the Chandra X-ray Observatory and Hubble Space Telescope (HST) observations of two low coredensity globular clusters, NGC6144 and E3. By comparing the number of X-ray sources inside the half-mass radius to those outside, we found six X-ray sources within the half-mass radius of NGC6144,

  2. Chemical abundances of giant stars in NGC 5053 and NGC 5634, two globular clusters associated with the Sagittarius dwarf spheroidal galaxy?

    Science.gov (United States)

    Sbordone, L.; Monaco, L.; Moni Bidin, C.; Bonifacio, P.; Villanova, S.; Bellazzini, M.; Ibata, R.; Chiba, M.; Geisler, D.; Caffau, E.; Duffau, S.

    2015-07-01

    Context. The tidal disruption of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) is producing the most prominent substructure in the Milky Way (MW) halo, the Sagittarius Stream. Aside from field stars, it is suspected that the Sgr dSph has lost a number of globular clusters (GC). Many Galactic GC are thought to have originated in the Sgr dSph. While for some candidates an origin in the Sgr dSph has been confirmed owing to chemical similarities, others exist whose chemical composition has never been investigated. Aims: NGC 5053 and NGC 5634 are two of these scarcely studied Sgr dSph candidate-member clusters. To characterize their composition we analyzed one giant star in NGC 5053, and two in NGC 5634. Methods: We analyze high-resolution and signal-to-noise spectra by means of the MyGIsFOS code, determining atmospheric parameters and abundances for up to 21 species between O and Eu. The abundances are compared with those of MW halo field stars, of unassociated MW halo globulars, and of the metal-poor Sgr dSph main body population. Results: We derive a metallicity of [Fe ii/H] = -2.26 ± 0.10 for NGC 5053, and of [Fe i/H] = -1.99 ± 0.075 and -1.97 ± 0.076 for the two stars in NGC 5634. This makes NGC 5053 one of the most metal-poor globular clusters in the MW. Both clusters display an α enhancement similar to the one of the halo at comparable metallicity. The two stars in NGC 5634 clearly display the Na-O anticorrelation widespread among MW globulars. Most other abundances are in good agreement with standard MW halo trends. Conclusions: The chemistry of the Sgr dSph main body populations is similar to that of the halo at low metallicity. It is thus difficult to discriminate between an origin of NGC 5053 and NGC 5634 in the Sgr dSph, and one in the MW. However, the abundances of these clusters do appear closer to that of Sgr dSph than of the halo, favoring an origin in the Sgr dSph system. Appendix A is available in electronic form at http

  3. Chemical analysis of eight giant stars of the globular cluster NGC 6366

    Science.gov (United States)

    Puls, Arthur A.; Alves-Brito, Alan; Campos, Fabíola; Dias, Bruno; Barbuy, Beatriz

    2018-05-01

    The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high-resolution and high-quality spectra (R > 40 000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of Fe I and Fe II lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 ± 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.

  4. TIME-SERIES SPECTROSCOPY OF TWO CANDIDATE DOUBLE DEGENERATES IN THE OPEN CLUSTER NGC 6633

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Kurtis A.; Chakraborty, Subho [Department of Physics and Astrophysics, Texas A and M University-Commerce, P.O. Box 3011, Commerce, TX, 75429 (United States); Serna-Grey, Donald [Department of Astronomy, University of Washington, Box 351580, Seattle, WA, 98195 (United States); Gianninas, A.; Canton, Paul A., E-mail: Kurtis.Williams@tamuc.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK, 73019 (United States)

    2015-12-15

    SNe Ia are heavily used tools in precision cosmology, yet we still are not certain what the progenitor systems are. General plausibility arguments suggest there is potential for identifying double degenerate SN Ia progenitors in intermediate-age open star clusters. We present time-resolved high-resolution spectroscopy of two white dwarfs (WDs) in the field of the open cluster NGC 6633 that had previously been identified as candidate double degenerates in the cluster. However, three hours of continuous observations of each candidate failed to detect any significant radial velocity variations at the ≳10 km s{sup −1} level, making it highly unlikely that either WD is a double degenerate that will merge within a Hubble Time. The WD LAWDS NGC 6633 4 has a radial velocity inconsistent with cluster membership at the 2.5σ level, while the radial velocity of LAWDS NGC 6633 7 is consistent with cluster membership. We conservatively conclude that LAWDS 7 is a viable massive double degenerate candidate, though unlikely to be a Type Ia progenitor. Astrometric data from GAIA will likely be needed to determine if either WD is truly a cluster member.

  5. THE PECULIAR CHEMICAL INVENTORY OF NGC 2419: AN EXTREME OUTER HALO 'GLOBULAR CLUSTER'

    International Nuclear Information System (INIS)

    Cohen, Judith G.; Kirby, Evan N.; Huang Wenjin

    2011-01-01

    NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs.

  6. A SPECTROSCOPIC ANALYSIS OF THE GALACTIC GLOBULAR CLUSTER NGC 6273 (M19)

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christian I.; Caldwell, Nelson [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Pilachowski, Catherine A. [Astronomy Department, Indiana University Bloomington, Swain West 319, 727 East 3rd Street, Bloomington, IN 47405-7105 (United States); Mateo, Mario; Bailey, John I. III [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Crane, Jeffrey D., E-mail: cjohnson@cfa.harvard.edu, E-mail: ncaldwell@cfa.harvard.edu, E-mail: rmr@astro.ucla.edu, E-mail: catyp@astro.indiana.edu, E-mail: mmateo@umich.edu, E-mail: baileyji@umich.edu, E-mail: crane@obs.carnegiescience.edu [The Observatories of the Carnegie Institution for Science, Pasadena, CA 91101 (United States)

    2015-08-15

    A combined effort utilizing spectroscopy and photometry has revealed the existence of a new globular cluster class. These “anomalous” clusters, which we refer to as “iron-complex” clusters, are differentiated from normal clusters by exhibiting large (≳0.10 dex) intrinsic metallicity dispersions, complex sub-giant branches, and correlated [Fe/H] and s-process enhancements. In order to further investigate this phenomenon, we have measured radial velocities and chemical abundances for red giant branch stars in the massive, but scarcely studied, globular cluster NGC 6273. The velocities and abundances were determined using high resolution (R ∼ 27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph on the Magellan–Clay 6.5 m telescope at Las Campanas Observatory. We find that NGC 6273 has an average heliocentric radial velocity of +144.49 km s{sup −1} (σ = 9.64 km s{sup −1}) and an extended metallicity distribution ([Fe/H] = −1.80 to −1.30) composed of at least two distinct stellar populations. Although the two dominant populations have similar [Na/Fe], [Al/Fe], and [α/Fe] abundance patterns, the more metal-rich stars exhibit significant [La/Fe] enhancements. The [La/Eu] data indicate that the increase in [La/Fe] is due to almost pure s-process enrichment. A third more metal-rich population with low [X/Fe] ratios may also be present. Therefore, NGC 6273 joins clusters such as ω Centauri, M2, M22, and NGC 5286 as a new class of iron-complex clusters exhibiting complicated star formation histories.

  7. CM diagram of the nearby globular cluster NGC 6397

    International Nuclear Information System (INIS)

    Alcaino, G.; Buonanno, R.; Corsi, C. E.; Caloi, V.; Castellani, V.; Osservatorio Astronomico di Monte Mario, Rome, Italy; CNR, Istituto di Astrofisica Spaziale, Frascati, Italy; Roma I Universita, Italy; European Southern Observatory, Garching, Germany, F.R.)

    1987-01-01

    CCD photometry for faint stars in NGC 6397, combined with a digital reinvestigation of the photographic plates originally used by Alcaino and Liller (1980), has been used to obtain statistically significant samples for the various evolutionary phases, down to V about 21 mag, i.e., more than 5 mag below the turnoff. Evidence is reported for a flattening of the luminosity function for MS stars fainter than 6 mag, in agreement with previous indications by other authors. It is found that suspected departures from theoretical expectations in the distributions of red giant-branch stars do not have strong statistical significance. 29 references

  8. Multiple stellar generations in the Large Magellanic Cloud Star Cluster NGC 1846

    Science.gov (United States)

    Milone, Antonino

    2010-09-01

    The recent discovery of multiple stellar populations in massive Galactic globular clusters poses a serious challenge for models of star cluster formation and evolution. The finding of multiple main sequences in the massive clusters NGC 2808 and omega Centauri, and multiple sub-giant-branch in NGC 1851 and many other globulars have demonstrated that star clusters are not as simple as we have imagined for decades. Surprisingly the only way to explain the main sequence splitting appears to be Helium enrichment, up to an astonishingly high Y 0.40.An unique angle on this problem can be provided by intermediate-age clusters in the Magellanic Clouds with peculiar main-sequence turn-off morphologies. Recent discoveries, based on ACS data of unparalleled photometric accuracy, have demonstrated that the CMDs of a large fraction of these clusters { 70 %} are not consistent with the simple, single stellar population hypothesis. Explanations for what conditions could give rise to multiple populations in Galactic Globular Clusters remain controversial; this is even more the case for LMC clustersTo properly constraint the multipopulation phenomenon in Magellanic Cloud star clusters, we propose deep UV/IR imaging of NGC 1846, a star cluster where multiple populations have already been identified. The proposed observation will allow us to accurately measure the age difference between the stellar populations providing fundamental clues on the formation mechanism. Our simulations of WFC3 performance suggest that we will be able to detect even the main sequence splitting caused by small He differences {Delta Y 0.02}.

  9. Chemical Compositions of Stars in the Globular Cluster NGC 3201: Tracers of Multi-Epoch Star Formation

    Science.gov (United States)

    Simmerer, Jennifer A.; Ivans, I. I.; Filler, D.

    2012-01-01

    The retrograde halo globular cluster NGC 3201 contains stars of substantially different iron abundance ([Fe/H]), a property that puts it at odds with the vast majority of the Galactic cluster system. Though its unusual orbit prompted speculation that NGC 3201 was the remnant of a captured object, much like the multi-metallicity globular cluster Omega Centauri, NGC 3201 is much less massive than Omega Centauri and all of the other halo globular clusters that have internal metallicity variations. We present the abundances of 21 elements in 24 red giant branch stars in NGC 3201 based on high-resolution (R 40,000), high signal-to-noise (S/N 70) spectra. We find that the detailed abundance pattern of NGC 3201 is unique amongst multi-metallicity halo clusters. Unlike M22, Omega Centauri, and NGC 1851, neither metal-poor nor metal-rich stars show any evidence of s-process enrichment (a product of the advanced evolution of low- and intermediate-mass stars). We find that while Na, O, and Al vary from star to star as is typical in globular clusters, there is no systematic difference between the abundance pattern in the metal-poor cluster stars and that of the metal-rich cluster stars. Furthermore, we find that the metallicity variations in NGC 3201 are independent of the well-known Na-O anticorrelation, which separates it from every other multi-metallicity cluster. In the context of a multi-episode star formation model, this implies that NGC 3201 began life with the [Fe/H] variations we measure now.

  10. THE 100 Myr STAR FORMATION HISTORY OF NGC 5471 FROM CLUSTER AND RESOLVED STELLAR PHOTOMETRY

    International Nuclear Information System (INIS)

    Garcia-Benito, Ruben; Perez, Enrique; Maiz Apellaniz, Jesus; Cervino, Miguel; Diaz, Angeles I.

    2011-01-01

    We show that star formation in the giant H II region NGC 5471 has been ongoing during the past 100 Myr. Using Hubble Space Telescope/Wide-Field Planetary Camera 2 F547M and F675W, ground-based JHK s , and GALEX FUV and NUV images, we have conducted a photometric study of the star formation history (SFH) in the massive giant extragalactic H II region NGC 5471 in M101. We perform a photometric study of the color-magnitude diagram (CMD) of the resolved stars and an integrated analysis of the main individual star-forming clusters and of NGC 5471 as a whole. The integrated UV-optical-NIR photometry for the whole region provides two different reference ages, 8 Myr and 60 Myr, revealing a complex SFH, clearly confirmed by the CMD-resolved stellar photometry analysis. The spatial distribution of the stars shows that the star formation in NGC 5471 has proceeded along the whole region during, at least, the last 100 Myr. The current ionizing clusters are enclosed within a large bubble, which is likely to have been produced by the stars that formed in a major event ∼20 Myr ago.

  11. The helium abundance in the metal-poor globular clusters M30 and NGC 6397

    Energy Technology Data Exchange (ETDEWEB)

    Mucciarelli, A.; Lovisi, L.; Lanzoni, B.; Ferraro, F. R. [Dipartimento di Fisica and Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy)

    2014-05-01

    We present the helium abundance of the two metal-poor clusters M30 and NGC 6397. Helium estimates have been obtained by using the high-resolution spectrograph FLAMES at the European Southern Observatory Very Large Telescope and by measuring the He I line at 4471 Å in 24 and 35 horizontal branch (HB) stars in M30 and NGC 6397, respectively. This sample represents the largest data set of He abundances collected so far in metal-poor clusters. The He mass fraction turns out to be Y = 0.252 ± 0.003 (σ = 0.021) for M30 and Y = 0.241 ± 0.004 (σ = 0.023) for NGC 6397. These values are fully compatible with the cosmological abundance, thus suggesting that the HB stars are not strongly enriched in He. The small spread of the Y distributions are compatible with those expected from the observed main sequence splitting. Finally, we find a hint of a weak anticorrelation between Y and [O/Fe] in NGC 6397 in agreement with the prediction that O-poor stars are formed by (He-enriched) gas polluted by the products of hot proton-capture reactions.

  12. Gems in the outer galaxy: Near-infrared imaging of three young clusters at large galactic radii

    International Nuclear Information System (INIS)

    Davidge, T. J.

    2014-01-01

    Images recorded with the Gemini South Adaptive Optics Imager (GSAOI) and corrected for atmospheric seeing by the Gemini Multi-conjugate Adaptive Optics System are used to investigate the stellar contents of the young outer Galactic disk clusters Haffner 17, NGC 2401, and NGC 3105. Ages estimated from the faint end of the main sequence (MS) and the ridgeline of the pre-main sequence on the (K, J – K) color-magnitude diagrams are consistent with published values that are based on the MS turnoff, with the GSAOI data favoring the younger end of the age range for NGC 2401 in the literature. The mass function (MF) of NGC 2401 is similar to that in the solar neighborhood, and stars spanning a wide range of masses in this cluster have similar clustering properties on the sky. It is concluded that NGC 2401 is not evolved dynamically. In contrast, the MF of Haffner 17 differs significantly from that in the solar neighborhood over all masses covered by these data, while the MF of NGC 3105 is deficient in objects with sub-solar masses when compared with the solar neighborhood. Low-mass objects in Haffner 17 and NGC 3105 are also more uniformly distributed on the sky than brighter, more massive, MS stars. This is consistent with both clusters having experienced significant dynamical evolution.

  13. Modeling and analysis of the spectrum of the globular cluster NGC 2419

    Science.gov (United States)

    Sharina, M. E.; Shimansky, V. V.; Davoust, E.

    2013-06-01

    The properties of the stellar population of the unusual object NGC 2419 are studied; this is the most distant high-mass globular cluster of the Galaxy's outer halo, and a spectrum taken with the 1.93-m telescope of the Haute Provence Observatory displays elemental abundance anomalies. Since traditional high-resolution spectroscopicmethods are applicable to bright stars only, spectroscopic information for the cluster's stellar population as a whole, integrated along the spectrograph slit placed in various positions, is used. Population synthesis is carried out for the spectrum of NGC 2419 using synthetic spectra calculated from a grid of stellar model atmospheres, based on the theoretical isochrone from the literature that best fits the color-magnitude diagram of the cluster. The derived age (12.6 billion years), metallicity ([Fe/H] = -2.25 dex), and abundances of helium ( Y = 0.26) and other chemical elements (a total of 14) are in a good qualitative agreement with estimates from the literature made from high-resolution spectra of eight red giants in the cluster. The influence on the spectrum of deviations from local thermodynamic equilibrium is considered for several elements. The derived abundance of α-elements ([ α/Fe] = 0.13 dex, as the mean of [O/Fe], [Mg/Fe], and [Ca/Fe]) differs from the mean value in the literature ([ α/Fe] = 0.4 for the eight brightest red giants) and may be explained by recently discovered in NGC2419 large [a/Fe] dispersion. Further studies of the integrated properties of the stellar population in NGC 2419 using higher-resolution spectrographs in various wavelength ranges should help improve our understanding of the cluster's chemical anomalies.

  14. DISCOVERY OF 14 NEW SLOWLY PULSATING B STARS IN THE OPEN CLUSTER NGC 7654

    International Nuclear Information System (INIS)

    Luo, Y. P.; Han, Z. W.; Zhang, X. B.; Deng, L. C.

    2012-01-01

    We carried out time-series BV CCD photometric observations of the open cluster NGC 7654 (Messier 52) to search for variable stars. Eighteen slowly pulsating B (SPB) stars have been detected, among which 14 candidates are newly discovered, three known ones are confirmed, and a previously found δ Scuti star is also identified as an SPB candidate. Twelve SPBs are probable cluster members based on membership analysis. This makes NGC 7654 the richest galactic open cluster in terms of SPB star content. It is also a new discovery that NGC 7654 hosts three γ Dor star candidates. We found that all these stars (18 SPB and 3 γ Dor stars) have periods longer than their corresponding fundamental radial mode. With such a big sample of g-mode pulsators in a single cluster, it is clear that multi-mode pulsation is more common in the upper part of the main sequence than in the lower part. All the stars span a narrow strip on the period-luminosity plane, which also includes the γ Dor stars at the low-luminosity extension. This result implies that there may be a single period-luminosity relation applicable to all g-mode main-sequence pulsators. As a by-product, three EA-type eclipsing binaries and an EW-type eclipsing binary are also discovered.

  15. On the kinematic separation of field and cluster stars across the bulge globular NGC 6528

    Energy Technology Data Exchange (ETDEWEB)

    Lagioia, E. P.; Bono, G.; Buonanno, R. [Dipartimento di Fisica, Università degli Studi di Roma-Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy); Milone, A. P. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Stetson, P. B. [Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Prada Moroni, P. G. [Dipartimento di Fisica, Università di Pisa, I-56127 Pisa (Italy); Dall' Ora, M. [INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli (Italy); Aparicio, A.; Monelli, M. [Instituto de Astrofìsica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands (Spain); Calamida, A.; Ferraro, I.; Iannicola, G. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00044 Monte Porzio Catone (Italy); Gilmozzi, R. [European Southern Observatory, Karl-Schwarzschild-Straße 2, D-85748 Garching (Germany); Matsunaga, N. [Kiso Observatory, Institute of Astronomy, School of Science, The University of Tokyo, 10762-30, Mitake, Kiso-machi, Kiso-gun, 3 Nagano 97-0101 (Japan); Walker, A., E-mail: eplagioia@roma2.infn.it [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, Casilla 603, La Serena (Chile)

    2014-02-10

    We present deep and precise multi-band photometry of the Galactic bulge globular cluster NGC 6528. The current data set includes optical and near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board the Hubble Space Telescope. The images cover a time interval of almost 10 yr, and we have been able to carry out a proper-motion separation between cluster and field stars. We performed a detailed comparison in the m {sub F814W}, m {sub F606W} – m {sub F814W} color-magnitude diagram with two empirical calibrators observed in the same bands. We found that NGC 6528 is coeval with and more metal-rich than 47 Tuc. Moreover, it appears older and more metal-poor than the super-metal-rich open cluster NGC 6791. The current evidence is supported by several diagnostics (red horizontal branch, red giant branch bump, shape of the sub-giant branch, slope of the main sequence) that are minimally affected by uncertainties in reddening and distance. We fit the optical observations with theoretical isochrones based on a scaled-solar chemical mixture and found an age of 11 ± 1 Gyr and an iron abundance slightly above solar ([Fe/H] = +0.20). The iron abundance and the old cluster age further support the recent spectroscopic findings suggesting a rapid chemical enrichment of the Galactic bulge.

  16. Ages of the Bulge Globular Clusters NGC 6522 and NGC 6626 (M28) from HST Proper-motion-cleaned Color–Magnitude Diagrams

    Science.gov (United States)

    Kerber, L. O.; Nardiello, D.; Ortolani, S.; Barbuy, B.; Bica, E.; Cassisi, S.; Libralato, M.; Vieira, R. G.

    2018-01-01

    Bulge globular clusters (GCs) with metallicities [Fe/H] ≲ ‑1.0 and blue horizontal branches are candidates to harbor the oldest populations in the Galaxy. Based on the analysis of HST proper-motion-cleaned color–magnitude diagrams in filters F435W and F625W, we determine physical parameters for the old bulge GCs NGC 6522 and NGC 6626 (M28), both with well-defined blue horizontal branches. We compare these results with similar data for the inner halo cluster NGC 6362. These clusters have similar metallicities (‑1.3 ≤ [Fe/H] ≤ ‑1.0) obtained from high-resolution spectroscopy. We derive ages, distance moduli, and reddening values by means of statistical comparisons between observed and synthetic fiducial lines employing likelihood statistics and the Markov chain Monte Carlo method. The synthetic fiducial lines were generated using α-enhanced BaSTI and Dartmouth stellar evolutionary models, adopting both canonical (Y ∼ 0.25) and enhanced (Y ∼ 0.30–0.33) helium abundances. RR Lyrae stars were employed to determine the HB magnitude level, providing an independent indicator to constrain the apparent distance modulus and the helium enhancement. The shape of the observed fiducial line could be compatible with some helium enhancement for NGC 6522 and NGC 6626, but the average magnitudes of RR Lyrae stars tend to rule out this hypothesis. Assuming canonical helium abundances, BaSTI and Dartmouth models indicate that all three clusters are coeval, with ages between ∼12.5 and 13.0 Gyr. The present study also reveals that NGC 6522 has at least two stellar populations, since its CMD shows a significantly wide subgiant branch compatible with 14% ± 2% and 86% ± 5% for first and second generations, respectively. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute.

  17. THE BIZARRE CHEMICAL INVENTORY OF NGC 2419, AN EXTREME OUTER HALO GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Judith G.; Kirby, Evan N., E-mail: jlc@astro.caltech.edu, E-mail: enk@astro.caltech.edu [Palomar Observatory, Mail Stop 249-17, California Institute of Technology, Pasadena, CA 91125 (United States)

    2012-11-20

    We present new Keck/HIRES observations of six red giants in the globular cluster (GC) NGC 2419. Although the cluster is among the most distant and most luminous in the Milky Way, it was considered chemically ordinary until very recently. Our previous work showed that the near-infrared Ca II triplet line strength varied more than expected for a chemically homogeneous cluster, and that at least one star had unusual abundances of Mg and K. Here, we confirm that NGC 2419 harbors a population of stars, comprising about one-third of its mass, that is depleted in Mg by a factor of eight and enhanced in K by a factor of six with respect to the Mg-normal population. Although the majority, Mg-normal population appears to have a chemical abundance pattern indistinguishable from ordinary, inner-halo GCs, the Mg-poor population exhibits dispersions of several elements. The abundances of K and Sc are strongly anti-correlated with Mg, and some other elements (Si and Ca among others) are weakly anti-correlated with Mg. These abundance patterns suggest that the different populations of NGC 2419 sample the ejecta of diverse supernovae in addition to asymptotic giant branch ejecta. However, the abundances of Fe-peak elements except Sc show no star-to-star variation. We find no nucleosynthetic source that satisfactorily explains all of the abundance variations in this cluster. Because NGC 2419 appears like no other GC, we reiterate our previous suggestion that it is not a GC at all, but rather the core of an accreted dwarf galaxy.

  18. The chemical composition of a regular halo globular cluster: NGC 5897

    Science.gov (United States)

    Koch, Andreas; McWilliam, Andrew

    2014-05-01

    We report for the first time on the chemical composition of the halo cluster NGC 5897 (R⊙ = 12.5 kpc), based on chemical abundance ratios for 27 α-, iron-peak, and neutron-capture elements in seven red giants. From our high-resolution, high signal-to-noise spectra obtained with the Magellan/MIKE spectrograph, we find a mean iron abundance from the neutral species of [Fe/H] = - 2.04 ± 0.01 (stat.) ± 0.15 (sys.), which is more metal-poor than implied by previous photometric and low-resolution spectroscopic studies. The cluster NGC 5897 is α-enhanced (to 0.34 ± 0.01 dex) and shows Fe-peak element ratios typical of other (metal-poor) halo globular clusters (GCs) with no overall, significant abundance spreads in iron or in any other heavy element. Like other GCs, NGC 5897 shows a clear Na-O anti-correlation, where we find a prominent primordial population of stars with enhanced O abundances and approximately solar Na/Fe ratios, while two stars are Na-rich, providing chemical proof of the presence of multiple populations in this cluster. Comparison of the heavy element abundances with the solar-scaled values and the metal-poor GC M15 from the literature confirms that NGC 5897 has experienced little contribution from s-process nucleosynthesis. One star of the first generation stands out in that it shows very low La and Eu abundances. Overall, NGC 5897 is a well behaved GC showing archetypical correlations and element-patterns, with little room for surprises in our data. We suggest that its lower metallicity could explain the unusually long periods of RR Lyr that were found in NGC 5897. This paper includes data gathered with the 6.5-m Magellan Telescopes located at Las Campanas Observatory, Chile.Table 5 is available in electronic form at http://www.aanda.orgFull Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A23

  19. Not-so-simple stellar populations in the intermediate-age Large Magellanic Cloud star clusters NGC 1831 and NGC 1868

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengyuan; De Grijs, Richard [Kavli Institute for Astronomy and Astrophysics and Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Deng, Licai, E-mail: joshuali@pku.edu.cn, E-mail: grijs@pku.edu.cn [Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China)

    2014-04-01

    Using a combination of high-resolution Hubble Space Telescope/Wide-Field and Planetary Camera-2 observations, we explore the physical properties of the stellar populations in two intermediate-age star clusters, NGC 1831 and NGC 1868, in the Large Magellanic Cloud based on their color-magnitude diagrams. We show that both clusters exhibit extended main-sequence turn offs. To explain the observations, we consider variations in helium abundance, binarity, age dispersions, and the fast rotation of the clusters' member stars. The observed narrow main sequence excludes significant variations in helium abundance in both clusters. We first establish the clusters' main-sequence binary fractions using the bulk of the clusters' main-sequence stellar populations ≳ 1 mag below their turn-offs. The extent of the turn-off regions in color-magnitude space, corrected for the effects of binarity, implies that age spreads of order 300 Myr may be inferred for both clusters if the stellar distributions in color-magnitude space were entirely due to the presence of multiple populations characterized by an age range. Invoking rapid rotation of the population of cluster members characterized by a single age also allows us to match the observed data in detail. However, when taking into account the extent of the red clump in color-magnitude space, we encounter an apparent conflict for NGC 1831 between the age dispersion derived from that based on the extent of the main-sequence turn off and that implied by the compact red clump. We therefore conclude that, for this cluster, variations in stellar rotation rate are preferred over an age dispersion. For NGC 1868, both models perform equally well.

  20. Chemical Abundances of Red Giant Branch Stars in the Globular Cluster NGC 288

    Science.gov (United States)

    Hsyu, Tiffany; Johnson, C. I.; Pilachowski, C. A.; Lee, Y.; Rich, R. M.

    2013-01-01

    We present chemical abundances and radial velocities for ~30 red giant branch (RGB) stars in the globular cluster NGC 288. The results are based on moderate resolution (R≈18,000) and moderate signal-to-noise ratio 50-75) obtained with the Hydra multi-object spectrograph on the Blanco 4m telescope. NGC 288 has been shown to exhibit two separate RGBs and we investigate possible differences in metallicity and/or light element abundances between stars on each branch. We present a new filter tracing for the CTIO Calcium HK narrow band filter and explore its effects on previous globular cluster color-magnitude diagrams. We also compare the light element abundance patterns of NGC 288 to those of other similar metallicity halo clusters. This material is based upon work supported by the National Science Foundation under award No.AST-1003201 to C.I.J. C.A.P. gratefully acknowledges support from the Daniel Kirkwood Research Fund at Indiana University. R.M.R. acknowledges support from NSF grants AST-0709479 and AST-121120995.

  1. ULTRA-DEEP GEMINI NEAR-INFRARED OBSERVATIONS OF THE BULGE GLOBULAR CLUSTER NGC 6624

    Energy Technology Data Exchange (ETDEWEB)

    Saracino, S.; Dalessandro, E.; Ferraro, F. R.; Lanzoni, B.; Miocchi, P. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Geisler, D.; Mauro, F.; Cohen, R. E.; Villanova, S. [Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción (Chile); Origlia, L. [INAF—Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bidin, C. Moni, E-mail: sara.saracino@unibo.it [Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile)

    2016-11-20

    We used ultra-deep J and K {sub s} images secured with the near-infrared (NIR) GSAOI camera assisted by the multi-conjugate adaptive optics system GeMS at the GEMINI South Telescope in Chile, to obtain a ( K {sub s} , J - K {sub s} ) color–magnitude diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest and most accurate NIR CMD from the ground for this cluster, by reaching K {sub s} ∼ 21.5, approximately 8 mag below the horizontal branch level. The entire extension of the Main Sequence (MS) is nicely sampled and at K {sub s} ∼ 20 we detected the so-called MS “knee” in a purely NIR CMD. By taking advantage of the exquisite quality of the data, we estimated the absolute age of NGC 6624 ( t {sub age} = 12.0 ± 0.5 Gyr), which turns out to be in good agreement with previous studies in the literature. We also analyzed the luminosity and mass functions of MS stars down to M ∼ 0.45 M{sub ⊙}, finding evidence of a significant increase of low-mass stars at increasing distances from the cluster center. This is a clear signature of mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical evolution.

  2. NGC 6273: Towards Defining A New Class of Galactic Globular Clusters?

    Science.gov (United States)

    Johnson, Christian I.; Rich, Robert Michael; Pilachowski, Catherine A.; Caldwell, Nelson; Mateo, Mario L.; Ira Bailey, John; Crane, Jeffrey D.

    2016-01-01

    A growing number of observations have found that several Galactic globular clusters exhibit abundance dispersions beyond the well-known light element (anti-)correlations. These clusters tend to be very massive, have >0.1 dex intrinsic metallicity dispersions, have complex sub-giant branch morphologies, and have correlated [Fe/H] and s-process element enhancements. Interestingly, nearly all of these clusters discovered so far have [Fe/H]~-1.7. In this context, we have examined the chemical composition of 18 red giant branch (RGB) stars in the massive, metal-poor Galactic bulge globular cluster NGC 6273 using high signal-to-noise, high resolution (R~27,000) spectra obtained with the Michigan/Magellan Fiber System (M2FS) and MSpec spectrograph mounted on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. We find that the cluster exhibits a metallicity range from [Fe/H]=-1.80 to -1.30 and is composed of two dominant populations separated in [Fe/H] and [La/Fe] abundance. The increase in [La/Eu] as a function of [La/H] suggests that the increase in [La/Fe] with [Fe/H] is due to almost pure s-process enrichment. The most metal-rich star in our sample is not strongly La-enhanced, but is α-poor and may belong to a third "anomalous" stellar population. The two dominant populations exhibit the same [Na/Fe]-[Al/Fe] correlation found in other "normal" globular clusters. Therefore, NGC 6273 joins ω Centauri, M 22, M 2, and NGC 5286 as a possible new class of Galactic globular clusters.

  3. Probing Shocks of the Young Planetary Nebula NGC 7027

    Science.gov (United States)

    Montez, Rodolfo

    2013-09-01

    The rapid evolution of the planetary nebula NGC 7027 provides a rare glimpse at the evolution of the shocks. We propose a detailed spatial and spectroscopic study of the shock conditions in NGC 7027 that will enhance and bridge our understanding of the shocks seen in other planetary nebula. Comparison between the Cycle 1 observation and a new Cycle 15 observation will (i) confirm the presence of the two components in the extended X-ray emission, (ii) measure the changes (spatial and spectral) in the components, and, (iii) provide a valuable trove of tests and inputs for shock conditions and hydrodynamical simulations. We rely on the unprecedented spatial resolution and soft-sensitivity of Chandra.

  4. WIYN OPEN CLUSTER STUDY. XXIV. STELLAR RADIAL-VELOCITY MEASUREMENTS IN NGC 6819

    International Nuclear Information System (INIS)

    Tabetha Hole, K.; Geller, Aaron M.; Mathieu, Robert D.; Meibom, Soeren; Platais, Imants; Latham, David W.

    2009-01-01

    We present the current results from our ongoing radial-velocity (RV) survey of the intermediate-age (2.4 Gyr) open cluster NGC 6819. Using both newly observed and other available photometry and astrometry, we define a primary target sample of 1454 stars that includes main-sequence, subgiant, giant, and blue straggler stars, spanning a magnitude range of 11 ≤V≤ 16.5 and an approximate mass range of 1.1-1.6 M sun . Our sample covers a 23 arcminute (13 pc) square field of view centered on the cluster. We have measured 6571 radial velocities for an unbiased sample of 1207 stars in the direction of the open cluster NGC 6819, with a single-measurement precision of 0.4 km s -1 for most narrow-lined stars. We use our RV data to calculate membership probabilities for stars with ≥3 measurements, providing the first comprehensive membership study of the cluster core that includes stars from the giant branch through the upper main sequence. We identify 480 cluster members. Additionally, we identify velocity-variable systems, all of which are likely hard binaries that dynamically power the cluster. Using our single cluster members, we find a cluster average RV of 2.34 ± 0.05 km s -1 . We use our kinematic cluster members to construct a cleaned color-magnitude diagram from which we identify rich giant, subgiant, and blue straggler populations and a well defined red clump. The cluster displays a morphology near the cluster turnoff clearly indicative of core convective overshoot. Finally, we discuss a few stars of note, one of which is a short-period red-clump binary that we suggest may be the product of a dynamical encounter.

  5. Four-color and Hβ photometry for open clusters I: NGC 2516

    International Nuclear Information System (INIS)

    Snowden, M.S.

    1975-01-01

    Extensive uvby and Hβ photometry was obtained for stars in the region of the open cluster NGC 2516. A photometric analysis revealed variable reddening and a mean reddening of E(b - y) = 0.088 m. In addition to determining a new age of 137 x 10 6 years and a new adopted distance modulus of 8.01 m, several possible new variable stars were discovered, one of which may be an eclipsing Ap star. From the photometry of the Si-lambda4200 stars in the cluster it appears the absolute magnitudes and masses for this type of star are not as restricted as previously thought

  6. Isochrone Fittings for the Open Star Clusters NGC 3680 and Melotte 66

    Science.gov (United States)

    Guillemaud, Nikolas; Frinchaboy, P. M.; Thompson, B. A.

    2013-01-01

    I will be displaying the results from isochrone fittings on two open star clusters. The stellar evolution models used to generate the isochrones are from Dartmouth (Dotter et al. 2007) and Padova (Mango et al. 2008). Both of the models were applied to two star clusters: NGC 3680 and Melotte 66. The analysis is performed by utilizing infrared observations from the CPAPIR instrument; which is operated in conjunction with CTIO’s 1.5m telescope. This research was made possible by the NSF’s REU grant; award number 0851558.

  7. Modeling and Analysis of a Spectrum of the Globular Cluster NGC 2419

    OpenAIRE

    Sharina, M. E.; Shimansky, V. V.; Davoust, E.

    2012-01-01

    NGC 2419 is the most distant massive globular cluster in the outer Galactic halo. It is unusual also due to the chemical peculiarities found in its red giant stars in recent years. We study the stellar population of this unusual object using spectra obtained at the 1.93-m telescope of the Haute-Provence Observatory. At variance with commonly used methods of high-resolution spectroscopy applicable only to bright stars, we employ spectroscopic information on the integrated light of the cluster....

  8. Double blue straggler sequences in globular clusters: The case of NGC 362

    International Nuclear Information System (INIS)

    Dalessandro, E.; Ferraro, F. R.; Massari, D.; Lanzoni, B.; Miocchi, P.; Mucciarelli, A.; Lovisi, L.; Beccari, G.; Bellini, A.; Sills, A.; Sigurdsson, S.

    2013-01-01

    We used high-quality images acquired with the Wide Field Camera 3 on board the Hubble Space Telescope to probe the blue straggler star (BSS) population of the galactic globular cluster NGC 362. We have found two distinct sequences of BSSs: this is the second case, after M30, where such a feature has been observed. Indeed, the BSS location, their extension in magnitude and color, and their radial distribution within the cluster nicely resemble those observed in M30, thus suggesting that the same interpretative scenario can be applied: the red BSS sub-population is generated by mass-transfer binaries, the blue one by collisions. The discovery of four new W UMa stars, three of which lie along the red BSS sequence, further supports this scenario. We also found that the inner portion of the density profile deviates from a King model and is well reproduced by either a mild power law (α ∼ –0.2) or a double King profile. This feature supports the hypothesis that the cluster is currently undergoing the core-collapse phase. Moreover, the BSS radial distribution shows a central peak and monotonically decreases outward without any evidence of an external rising branch. This evidence is a further indication of the advanced dynamical age of NGC 362; in fact, together with M30, NGC 362 belongs to the family of dynamically old clusters (Family III) in the 'dynamical clock' classification proposed by Ferraro et al. The observational evidence presented here strengthens the possible connection between the existence of a double BSS sequence and a quite advanced dynamical status of the parent cluster.

  9. High resolution infrared spectra of Bulge Globular Clusters: Liller 1, NGC 6553, and Ter 5

    Science.gov (United States)

    Origlia, L.; Rich, R. M.; Castro, S. M.

    2001-12-01

    Using the NIRSPEC spectrograph at Keck II, we have obtained echelle spectra covering the range 1.5-1.8μ m for 2 of the brightest giants in Liller 1 and NGC 6553, old metal rich globular clusters in the Galactic bulge. We also report a preliminary analysis for two giants in the obscured bulge globular cluster Ter 5. We use spectrum synthesis for the abundance analysis, and find [Fe/H]=-0.3+/-0.2 and [O/H]=+0.3+/- 0.1 (from the OH lines) for the giants in Liller 1 and NGC 6553. We measure strong lines for the alpha elements Mg, Ca, and Si, but the lower sensitivity of these lines to abundance permits us to only state a general [α /Fe]=+0.3+/-0.2 dex. The composition of the clusters is similar to that of field stars in the bulge and is consistent with a scenario in which the clusters formed early, with rapid enrichment. Our iron abundance for NGC 6553 is poorly consistent with either the low or the high values recently reported in the literature, unless unusally large, or no α -element enhancements are adopted, respectively. We will also present an abundance analsyis for 2 giants in the highly reddened bulge cluster Ter 5, which appears to be near the Solar metallicity. R. Michael Rich acknowledges finacial support from grant AST-0098739, from the National Science Foundation. Data presented herein were obtained at the W.M.Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The authors gratefully acknowledge those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented would have been possible.

  10. BVI CCD photometry of the broad main-sequence globular cluster NGC 1851

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.; Alvarado, F.; Wenderoth, E.

    1990-01-01

    Three-color CCD C-M diagrams are presented for the globular cluster NGC 1851, showing an extreme breadth of the main-sequence, similar to that of Omega Centauri. It is found that the main-sequence turnoff points are located at V(TO) = 19.44 + or - 0.10, with colors at B-V = 0.54 + or - 0.02, V-I = 0.61 + or - 0.02, and B-I = 1.15 + or - 0.03. The best fit to the VandenBerg and Bell (1985) isochrones is shown to be all C-M diagrams with Y = 0.20, Fe/H abundance ratio = -1.27, and (m-M)v = 15.45. It is concluded that NGC 1851 has a Delta V(TO - HB) = 3.34 + or - 0.10 and an age of 16 + or - 2 Gyr. 29 refs

  11. REVERSED TREND OF RADIAL DISTRIBUTION OF SUBPOPULATIONS IN THE GLOBULAR CLUSTERS NGC 362 AND NGC 6723

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dongwook; Lee, Young-Wook; Pasquato, Mario [Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 03722 (Korea, Republic of); Han, Sang-Il; Roh, Dong-Goo, E-mail: dwlim@galaxy.yonsei.ac.kr, E-mail: ywlee2@yonsei.ac.kr [Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of)

    2016-12-01

    Most globular clusters (GCs) are now known to host multiple stellar populations with different abundances of light elements. Here we use narrow-band photometry and low-resolution spectroscopy for NGC 362 and NGC 6723 to investigate their chemical properties and radial distributions of subpopulations. We confirm that NGC 362 and NGC 6723 are among the GCs with multiple populations showing bimodal CN distribution and CN–CH anticorrelation without a significant spread in calcium abundance. These two GCs show more centrally concentrated CN-weak, earlier generation stars compared to the CN-strong, later generation stars. These trends are reversed with respect to those found in previous studies for many other GCs. Our findings, therefore, seem contradictory to the current scenario for the formation of multiple stellar populations, but mass segregation acting on the two subpopulations might be a possible solution to explain this reversed radial trend.

  12. CSI 2264: characterizing accretion-burst dominated light curves for young stars in NGC 2264

    International Nuclear Information System (INIS)

    Stauffer, John; Cody, Ann Marie; Rebull, Luisa; Carey, Sean; Baglin, Annie; Alencar, Silvia; Hillenbrand, Lynne A.; Carpenter, John; Findeisen, Krzysztof; Venuti, Laura; Bouvier, Jerome; Turner, Neal J.; Plavchan, Peter; Terebey, Susan; Morales-Calderón, María; Micela, Giusi; Flaccomio, Ettore; Song, Inseok; Gutermuth, Rob; Hartmann, Lee

    2014-01-01

    Based on more than four weeks of continuous high-cadence photometric monitoring of several hundred members of the young cluster NGC 2264 with two space telescopes, NASA's Spitzer and the CNES CoRoT (Convection, Rotation, and planetary Transits), we provide high-quality, multi-wavelength light curves for young stellar objects whose optical variability is dominated by short-duration flux bursts, which we infer are due to enhanced mass accretion rates. These light curves show many brief—several hours to one day—brightenings at optical and near-infrared wavelengths with amplitudes generally in the range of 5%-50% of the quiescent value. Typically, a dozen or more of these bursts occur in a 30 day period. We demonstrate that stars exhibiting this type of variability have large ultraviolet (UV) excesses and dominate the portion of the u – g versus g – r color-color diagram with the largest UV excesses. These stars also have large Hα equivalent widths, and either centrally peaked, lumpy Hα emission profiles or profiles with blueshifted absorption dips associated with disk or stellar winds. Light curves of this type have been predicted for stars whose accretion is dominated by Rayleigh-Taylor instabilities at the boundary between their magnetosphere and inner circumstellar disk, or where magneto-rotational instabilities modulate the accretion rate from the inner disk. Among the stars with the largest UV excesses or largest Hα equivalent widths, light curves with this type of variability greatly outnumber light curves with relatively smooth sinusoidal variations associated with long-lived hot spots. We provide quantitative statistics for the average duration and strength of the accretion bursts and for the fraction of the accretion luminosity associated with these bursts.

  13. The Globular Cluster NGC 6402 (M14). II. Variable Stars

    DEFF Research Database (Denmark)

    Contreras Peña, C.; Catelan, M.; Grundahl, F.

    2018-01-01

    approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive =0.589 {{d...

  14. AGB sodium abundances in the globular cluster 47 Tucanae (NGC 104)

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christian I. [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); McDonald, Iain; Zijlstra, Albert A., E-mail: cjohnson@cfa.harvard.edu, E-mail: iain.mcdonald-2@manchester.ac.uk, E-mail: albert.zijlstra@manchester.ac.uk [Jodrell Bank Centre for Astrophysics, Alan Turing Building, Manchester M13 9PL (United Kingdom); and others

    2015-02-01

    A recent analysis comparing the [Na/Fe] distributions of red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster NGC 6752 found that the ratio of Na-poor to Na-rich stars changes from 30:70 on the RGB to 100:0 on the AGB. The surprising paucity of Na-rich stars on the AGB in NGC 6752 warrants additional investigations to determine if the failure of a significant fraction of stars to ascend the AGB is an attribute common to all globular clusters. Therefore, we present radial velocities, [Fe/H], and [Na/Fe] abundances for 35 AGB stars in the Galactic globular cluster 47 Tucanae (47 Tuc; NGC 104), and compare the AGB [Na/Fe] distribution with a similar RGB sample published previously. The abundances and velocities were derived from high-resolution spectra obtained with the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan–Clay 6.5 m telescope. We find the average heliocentric radial velocity and [Fe/H] values to be 〈RV{sub helio.}〉 = −18.56 km s{sup −1} (σ = 10.21 km s{sup −1}) and 〈[Fe/H]〉 = −0.68 (σ = 0.08), respectively, in agreement with previous literature estimates. The average [Na/Fe] abundance is 0.12 dex lower in the 47 Tuc AGB sample compared to the RGB sample, and the ratio of Na-poor to Na-rich stars is 63:37 on the AGB and 45:55 on the RGB. However, in contrast to NGC 6752, the two 47 Tuc populations have nearly identical [Na/Fe] dispersion and interquartile range values. The data presented here suggest that only a small fraction (≲20%) of Na-rich stars in 47 Tuc may fail to ascend the AGB, which is a similar result to that observed in M13. Regardless of the cause for the lower average [Na/Fe] abundance in AGB stars, we find that Na-poor stars and at least some Na-rich stars in 47 Tuc evolve through the early AGB phase. The contrasting behavior of Na-rich stars in 47 Tuc and NGC 6752 suggests that the RGB [Na/Fe] abundance alone is insufficient for predicting if a star will

  15. CHEMICAL COMPOSITION OF INTERMEDIATE-MASS STAR MEMBERS OF THE M6 (NGC 6405) OPEN CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Kılıçoğlu, T.; Albayrak, B. [Ankara University, Faculty of Science, Department of Astronomy and Space Sciences, 06100, Tandoğan, Ankara (Turkey); Monier, R. [LESIA, UMR 8109, Observatoire de Paris Meudon, Place J. Janssen, Meudon (France); Richer, J. [Département de physique, Université de Montréal, 2900, Boulevard Edouard-Montpetit, Montréal QC, H3C 3J7 (Canada); Fossati, L., E-mail: tkilicoglu@ankara.edu.tr, E-mail: balbayrak@ankara.edu.tr, E-mail: Richard.Monier@obspm.fr, E-mail: Jacques.Richer@umontreal.ca, E-mail: lfossati@astro.uni-bonn.de [Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, D-53121, Bonn (Germany)

    2016-03-15

    We present here the first abundance analysis of 44 late B-, A-, and F-type members of the young open cluster M6 (NGC 6405, age about 75 Myr). Low- and medium-resolution spectra, covering the 4500–5840 Å wavelength range, were obtained using the FLAMES/GIRAFFE spectrograph attached to the ESO Very Large Telescopes. We determined the atmospheric parameters using calibrations of the Geneva photometry and by adjusting the H{sub β} profiles to synthetic ones. The abundances of up to 20 chemical elements, from helium to mercury, were derived for 19 late B, 16 A, and 9 F stars by iteratively adjusting synthetic spectra to the observations. We also derived a mean cluster metallicity of [Fe/H] = 0.07 ± 0.03 dex from the iron abundances of the F-type stars. We find that for most chemical elements, the normal late B- and A-type stars exhibit larger star-to-star abundance variations than the F-type stars probably because of the faster rotation of the B and A stars. The abundances of C, O, Mg, Si, and Sc appear to be anticorrelated with that of Fe, while the opposite holds for the abundances of Ca, Ti, Cr, Mn, Ni, Y, and Ba as expected if radiative diffusion is efficient in the envelopes of these stars. In the course of this analysis, we discovered five new peculiar stars: one mild Am, one Am, and one Fm star (HD 318091, CD-32 13109, GSC 07380-01211, CP1), one HgMn star (HD 318126, CP3), and one He-weak P-rich (HD 318101, CP4) star. We also discovered a new spectroscopic binary, most likely a SB2. We performed a detailed modeling of HD 318101, the new He-weak P-rich CP star, using the Montréal stellar evolution code XEVOL which self-consistently treats all particle transport processes. Although the overall abundance pattern of this star is properly reproduced, we find that detailed abundances (in particular the high P excess) resisted modeling attempts even when a range of turbulence profiles and mass-loss rates were considered. Solutions are proposed which are

  16. The CN–CH Positive Correlation in the Globular Cluster NGC 5286

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Dongwook; Hong, Seungsoo; Lee, Young-Wook, E-mail: dwlim@yonsei.ac.kr, E-mail: ywlee2@yonsei.ac.kr [Center for Galaxy Evolution Research and Department of Astronomy, Yonsei University, Seoul 03722 (Korea, Republic of)

    2017-07-20

    We performed low-resolution spectroscopy of the red giant stars in the Galactic globular cluster (GC) NGC 5286, which is known to show intrinsic heavy element abundance variations. We found that the observed stars in this GC are clearly divided into three subpopulations by CN index (CN-weak, CN-intermediate, and CN-strong). The CN-strong stars are also enhanced in the calcium HK′ (7.4 σ ) and CH (5.1 σ ) indices, while the CN-intermediate stars show no significant difference in the strength of the HK′ index from the CN-weak stars. From the comparison with high-resolution spectroscopic data, we found that the CN- and HK′-strong stars are also enhanced in the abundances of Fe and s -process elements. It appears, therefore, that these stars are later-generation stars affected by some supernova enrichment in addition to the asymptotic giant branch ejecta. In addition, unlike normal GCs, sample stars in NGC 5286 show the CN–CH positive correlation, strengthening our previous suggestion that this positive correlation is only discovered in GCs with heavy element abundance variations, such as M22 and NGC 6273.

  17. The Peculiar Chemical Inventory of NGC 2419: An Extreme Outer Halo "Globular Cluster"

    Science.gov (United States)

    Cohen, Judith G.; Huang, Wenjin; Kirby, Evan N.

    2011-10-01

    NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have somewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419 with Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low [Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match the nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo Galactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show that NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs. Based in part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

  18. A Spectroscopic Study of Young Stellar Objects in the Serpens Cloud Core and NGC 1333

    Science.gov (United States)

    Winston, E.; Megeath, S. T.; Wolk, S. J.; Hernandez, J.; Gutermuth, R.; Muzerolle, J.; Hora, J. L.; Covey, K.; Allen, L. E.; Spitzbart, B.; Peterson, D.; Myers, P.; Fazio, G. G.

    2009-06-01

    We present spectral observations of 130 young stellar objects (YSOs) in the Serpens Cloud Core and NGC 1333 embedded clusters. The observations consist of near-IR spectra in the H and K bands from SpeX on the IRTF and far-red spectra (6000-9000 Å) from Hectospec on the Multi-Mirror Telescope. These YSOs were identified in previous Spitzer and Chandra observations, and the evolutionary classes of the YSOs were determined from the Spitzer mid-IR photometry. With these spectra we search for corroborating evidence for the pre-main-sequence nature of the objects, study the properties of the detected emission lines as a function of evolutionary class, and obtain spectral types for the observed YSOs. The temperatures implied by the spectral types are combined with luminosities determined from the near-IR photometry to construct Hertzsprung-Russell (H-R) diagrams for the clusters. By comparing the positions of the YSOs in the H-R diagrams with the pre-main-sequence tracks of Baraffe (1998), we determine the ages of the embedded sources and study the relative ages of the YSOs with and without optically thick circumstellar disks. The apparent isochronal ages of the YSOs in both clusters range from less than 1 Myr to 10 Myr, with most objects below 3 Myr. The observed distributions of ages for the Class II and Class III objects are statistically indistinguishable. We examine the spatial distribution and extinction of the YSOs as a function of their isochronal ages. We find the sources dispersed and are not deeply embedded. Nonetheless, the sources with isochronal ages >3 Myr show all the characteristics of YSOs in their spectra, their IR spectral energy distributions, and their X-ray emission; we find no evidence that they are contaminating background giants or foreground dwarfs. However, we find no corresponding decrease in the fraction of sources with infrared excess with isochronal age; this suggests that the older isochronal ages may not measure the true age of the >3

  19. Ultra-deep GEMINI Near-infrared Observations of the Bulge Globular Cluster NGC 6624.

    Science.gov (United States)

    Saracino, S.; Dalessandro, E.; Ferraro, F. R.; Geisler, D.; Mauro, F.; Lanzoni, B.; Origlia, L.; Miocchi, P.; Cohen, R. E.; Villanova, S.; Moni Bidin, C.

    2016-11-01

    We used ultra-deep J and K s images secured with the near-infrared (NIR) GSAOI camera assisted by the multi-conjugate adaptive optics system GeMS at the GEMINI South Telescope in Chile, to obtain a (K s , J - K s ) color-magnitude diagram (CMD) for the bulge globular cluster NGC 6624. We obtained the deepest and most accurate NIR CMD from the ground for this cluster, by reaching K s ˜ 21.5, approximately 8 mag below the horizontal branch level. The entire extension of the Main Sequence (MS) is nicely sampled and at K s ˜ 20 we detected the so-called MS “knee” in a purely NIR CMD. By taking advantage of the exquisite quality of the data, we estimated the absolute age of NGC 6624 (t age = 12.0 ± 0.5 Gyr), which turns out to be in good agreement with previous studies in the literature. We also analyzed the luminosity and mass functions of MS stars down to M ˜ 0.45 M⊙, finding evidence of a significant increase of low-mass stars at increasing distances from the cluster center. This is a clear signature of mass segregation, confirming that NGC 6624 is in an advanced stage of dynamical evolution. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina). Based on observations gathered with ESO-VISTA telescope (program ID 179.B-2002).

  20. The Metal-poor non-Sagittarius (?) Globular Cluster NGC 5053: Orbit and Mg, Al, and Si Abundances

    Science.gov (United States)

    Tang, Baitian; Fernández-Trincado, J. G.; Geisler, Doug; Zamora, Olga; Mészáros, Szabolcs; Masseron, Thomas; Cohen, Roger E.; García-Hernández, D. A.; Dell’Agli, Flavia; Beers, Timothy C.; Schiavon, Ricardo P.; Sohn, Sangmo Tony; Hasselquist, Sten; Robin, Annie C.; Shetrone, Matthew; Majewski, Steven R.; Villanova, Sandro; Schiappacasse Ulloa, Jose; Lane, Richard R.; Minnti, Dante; Roman-Lopes, Alexandre; Almeida, Andres; Moreno, E.

    2018-03-01

    Metal-poor globular clusters (GCs) exhibit intriguing Al–Mg anti-correlations and possible Si–Al correlations, which are important clues to decipher the multiple-population phenomenon. NGC 5053 is one of the most metal-poor GCs in the nearby universe and has been suggested to be associated with the Sagittarius (Sgr) dwarf galaxy, due to its similarity in location and radial velocity with one of the Sgr arms. In this work, we simulate the orbit of NGC 5053, and argue against a physical connection between Sgr and NGC 5053. On the other hand, the Mg, Al, and Si spectral lines, which are difficult to detect in the optical spectra of NGC 5053 stars, have been detected in the near-infrared APOGEE spectra. We use three different sets of stellar parameters and codes to derive the Mg, Al, and Si abundances. Regardless of which method is adopted, we see a large Al variation, and a substantial Si spread. Along with NGC 5053, metal-poor GCs exhibit different Mg, Al, and Si variations. Moreover, NGC 5053 has the lowest cluster mass among the GCs that have been identified to exhibit an observable Si spread until now.

  1. THE BOTTOM OF THE WHITE DWARF COOLING SEQUENCE IN THE OLD OPEN CLUSTER NGC 2158

    International Nuclear Information System (INIS)

    Bedin, L. R.; Anderson, J.; Salaris, M.; King, I. R.; Piotto, G.; Cassisi, S.

    2010-01-01

    We use 10 orbits of Advanced Camera for Surveys observations to reach the end of the white dwarf (WD) cooling sequence in the solar-metallicity open cluster NGC 2158. Our photometry and completeness tests show that the end falls at magnitude m F606W = 27.5 ± 0.15, which implies an age between ∼1.8 and ∼2.0 Gyr, consistent with the age of 1.9 ± 0.2 Gyr obtained from fits to the main-sequence turn-off. The faintest WDs show a clear turn toward bluer colors, as predicted by theoretical isochrones.

  2. VARIABLE STARS IN LARGE MAGELLANIC CLOUD GLOBULAR CLUSTERS. II. NGC 1786

    International Nuclear Information System (INIS)

    Kuehn, Charles A.; Smith, Horace A.; De Lee, Nathan; Catelan, Márcio; Pritzl, Barton J.; Borissova, Jura

    2012-01-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B–V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters.

  3. New red giant star in the Kepler open cluster NGC 6819

    Science.gov (United States)

    Komucyeya, E.; Abedigamba, O. P.; Jurua, E.; Anguma, S. K.

    2018-05-01

    A recent study indicated that 39 red giant stars showing solar-like oscillations were discovered in the field of Kepleropen cluster NGC 6819. The study was based on photometric distance estimates of 27 stars out of the 39. Using photometric method alone may not be adequate to confirm the membership of these stars. The stars were not previously known in literature to belong to the open cluster NGC 6819. In this study, Kepler data was used to study the membership of the 27 stars. A plot of apparent magnitude as a function of the large frequency separation, supplemented with the proper motion and radial velocity values from literature revealed KIC 5112840 to lie on the same plane with the well known members of the cluster. Echelle diagram was constructed, and the median gravity-mode period spacings (ΔP) calculated for KIC 5112840. A value of ΔP = 66.3 s was obtained, thus placing the red giant star KIC 5112840 on the Red Giant Branch stage of evolution. Our evolutionary status result using the approach in this paper is in agreement with what is in the available literature.

  4. CONSTRAINTS ON HELIUM ENHANCEMENT IN THE GLOBULAR CLUSTER M3 (NGC 5272): THE HORIZONTAL BRANCH TEST

    International Nuclear Information System (INIS)

    Catelan, M.; Valcarce, A. A. R.; Cortes, C.; Grundahl, F.; Sweigart, A. V.

    2009-01-01

    It has recently been suggested that the presence of multiple populations showing various amounts of helium enhancement is the rule, rather than the exception, among globular star clusters. An important prediction of this helium enhancement scenario is that the helium-enhanced blue horizontal branch (HB) stars should be brighter than the red HB stars which are not helium enhanced. In this Letter, we test this prediction in the case of the Galactic globular cluster M3 (NGC 5272), for which the helium-enhancement scenario predicts helium enhancements of ∼>0.02 in virtually all blue HB stars. Using high-precision Stroemgren photometry and spectroscopic gravities for blue HB stars, we find that any helium enhancement among most of the cluster's blue HB stars is very likely less than 0.01, thus ruling out the much higher helium enhancements that have been proposed in the literature.

  5. The sluggs survey: HST/ACS mosaic imaging of the NGC 3115 globular cluster system

    Energy Technology Data Exchange (ETDEWEB)

    Jennings, Zachary G.; Romanowsky, Aaron J.; Brodie, Jean P.; Arnold, Jacob A. [University of California Observatories, Santa Cruz, CA 95064 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan, MI 48824 (United States); Lin, Dacheng; Irwin, Jimmy A.; Wong, Ka-Wah [Department of Physics and Astronomy, University of Alabama, Box 870324, Tuscaloosa, AL 35487 (United States); Sivakoff, Gregory R., E-mail: zgjennin@ucsc.edu [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)

    2014-08-01

    We present Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) g and z photometry and half-light radii R {sub h} measurements of 360 globular cluster (GC) candidates around the nearby S0 galaxy NGC 3115. We also include Subaru/Suprime-Cam g, r, and i photometry of 421 additional candidates. The well-established color bimodality of the GC system is obvious in the HST/ACS photometry. We find evidence for a 'blue tilt' in the blue GC subpopulation, wherein the GCs in the blue subpopulation get redder as luminosity increases, indicative of a mass-metallicity relationship. We find a color gradient in both the red and blue subpopulations, with each group of clusters becoming bluer at larger distances from NGC 3115. The gradient is of similar strength in both subpopulations, but is monotonic and more significant for the blue clusters. On average, the blue clusters have ∼10% larger R {sub h} than the red clusters. This average difference is less than is typically observed for early-type galaxies but does match that measured in the literature for the Sombrero Galaxy (M104), suggesting that morphology and inclination may affect the measured size difference between the red and blue clusters. However, the scatter on the R {sub h} measurements is large. We also identify 31 clusters more extended than typical GCs, which we term ultra-compact dwarf (UCD) candidates. Many of these objects are actually considerably fainter than typical UCDs. While it is likely that a significant number will be background contaminants, six of these UCD candidates are spectroscopically confirmed as NGC 3115 members. To explore the prevalence of low-mass X-ray binaries in the GC system, we match our ACS and Suprime-Cam detections to corresponding Chandra X-ray sources. We identify 45 X-ray-GC matches: 16 among the blue subpopulation and 29 among the red subpopulation. These X-ray/GC coincidence fractions are larger than is typical for most GC systems, probably due to the increased

  6. Discovery of Extended Main-sequence Turnoffs in Four Young Massive Clusters in the Magellanic Clouds

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chengyuan [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); De Grijs, Richard [Kavli Institute for Astronomy and Astrophysics and Department of Astronomy, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871 (China); Deng, Licai [Key Laboratory for Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012 (China); Milone, Antonino P. [Research School of Astronomy and Astrophysics, Australian National University, Mt. Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia)

    2017-08-01

    An increasing number of young massive clusters (YMCs) in the Magellanic Clouds have been found to exhibit bimodal or extended main sequences (MSs) in their color–magnitude diagrams (CMDs). These features are usually interpreted in terms of a coeval stellar population with different stellar rotational rates, where the blue and red MS stars are populated by non- (or slowly) and rapidly rotating stellar populations, respectively. However, some studies have shown that an age spread of several million years is required to reproduce the observed wide turnoff regions in some YMCs. Here we present the ultraviolet–visual CMDs of four Large and Small Magellanic Cloud YMCs, NGC 330, NGC 1805, NGC 1818, and NGC 2164, based on high-precision Hubble Space Telescope photometry. We show that they all exhibit extended main-sequence turnoffs (MSTOs). The importance of age spreads and stellar rotation in reproducing the observations is investigated. The observed extended MSTOs cannot be explained by stellar rotation alone. Adopting an age spread of 35–50 Myr can alleviate this difficulty. We conclude that stars in these clusters are characterized by ranges in both their ages and rotation properties, but the origin of the age spread in these clusters remains unknown.

  7. Bayesian investigation of isochrone consistency using the old open cluster NGC 188

    Energy Technology Data Exchange (ETDEWEB)

    Hills, Shane; Courteau, Stéphane [Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, ON K7L 3N6 Canada (Canada); Von Hippel, Ted [Department of Physical Sciences, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114 (United States); Geller, Aaron M., E-mail: shane.hills@queensu.ca, E-mail: courteau@astro.queensu.ca, E-mail: ted.vonhippel@erau.edu, E-mail: a-geller@northwestern.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

    2015-03-01

    This paper provides a detailed comparison of the differences in parameters derived for a star cluster from its color–magnitude diagrams (CMDs) depending on the filters and models used. We examine the consistency and reliability of fitting three widely used stellar evolution models to 15 combinations of optical and near-IR photometry for the old open cluster NGC 188. The optical filter response curves match those of theoretical systems and are thus not the source of fit inconsistencies. NGC 188 is ideally suited to this study thanks to a wide variety of high-quality photometry and available proper motions and radial velocities that enable us to remove non-cluster members and many binaries. Our Bayesian fitting technique yields inferred values of age, metallicity, distance modulus, and absorption as a function of the photometric band combinations and stellar models. We show that the historically favored three-band combinations of UBV and VRI can be meaningfully inconsistent with each other and with longer baseline data sets such as UBVRIJHK{sub S}. Differences among model sets can also be substantial. For instance, fitting Yi et al. (2001) and Dotter et al. (2008) models to UBVRIJHK{sub S} photometry for NGC 188 yields the following cluster parameters: age = (5.78 ± 0.03, 6.45 ± 0.04) Gyr, [Fe/H] = (+0.125 ± 0.003, −0.077 ± 0.003) dex, (m−M){sub V} = (11.441 ± 0.007, 11.525 ± 0.005) mag, and A{sub V} = (0.162 ± 0.003, 0.236 ± 0.003) mag, respectively. Within the formal fitting errors, these two fits are substantially and statistically different. Such differences among fits using different filters and models are a cautionary tale regarding our current ability to fit star cluster CMDs. Additional modeling of this kind, with more models and star clusters, and future Gaia parallaxes are critical for isolating and quantifying the most relevant uncertainties in stellar evolutionary models.

  8. A Chemical Composition Survey of the Iron-complex Globular Cluster NGC 6273 (M19)

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Christian I.; Caldwell, Nelson [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Rich, R. Michael [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Mateo, Mario [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Bailey, John I. III [Leiden Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden (Netherlands); Clarkson, William I. [Department of Natural Sciences, University of Michigan–Dearborn, 4901 Evergreen Road, Dearborn, MI 48128 (United States); Olszewski, Edward W. [Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Walker, Matthew G., E-mail: cjohnson@cfa.harvard.edu, E-mail: ncaldwell@cfa.harvard.edu, E-mail: rmr@astro.ucla.edu, E-mail: mmateo@umich.edu, E-mail: baileyji@strw.leidenuniv.nl, E-mail: wiclarks@umich.edu, E-mail: eolszewski@as.arizona.edu, E-mail: mgwalker@andrew.cmu.edu [McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)

    2017-02-20

    Recent observations have shown that a growing number of the most massive Galactic globular clusters contain multiple populations of stars with different [Fe/H] and neutron-capture element abundances. NGC 6273 has only recently been recognized as a member of this “iron-complex” cluster class, and we provide here a chemical and kinematic analysis of >300 red giant branch and asymptotic giant branch member stars using high-resolution spectra obtained with the Magellan –M2FS and VLT–FLAMES instruments. Multiple lines of evidence indicate that NGC 6273 possesses an intrinsic metallicity spread that ranges from about [Fe/H] = −2 to −1 dex, and may include at least three populations with different [Fe/H] values. The three populations identified here contain separate first (Na/Al-poor) and second (Na/Al-rich) generation stars, but a Mg–Al anti-correlation may only be present in stars with [Fe/H] ≳ −1.65. The strong correlation between [La/Eu] and [Fe/H] suggests that the s-process must have dominated the heavy element enrichment at higher metallicities. A small group of stars with low [ α /Fe] is identified and may have been accreted from a former surrounding field star population. The cluster’s large abundance variations are coupled with a complex, extended, and multimodal blue horizontal branch (HB). The HB morphology and chemical abundances suggest that NGC 6273 may have an origin that is similar to ω Cen and M54.

  9. Characterizing the Stellar Population of NGC 1980

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-07-01

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

  10. New insights into the origin and evolution of the old, metal-rich open cluster NGC 6791

    Science.gov (United States)

    Martinez-Medina, Luis A.; Gieles, Mark; Pichardo, Barbara; Peimbert, Antonio

    2018-02-01

    NGC 6791 is one of the most studied open clusters, it is massive (˜5000 M⊙), located at the solar circle, old (˜8 Gyr) and yet the most metal-rich cluster ([Fe/H] ≃ 0.4) known in the Milky Way. By performing an orbital analysis within a Galactic model including spiral arms and a bar, we found that it is plausible that NGC 6791 formed in the inner thin disc or in the bulge, and later displaced by radial migration to its current orbit. We apply different tools to simulate NGC 6791, including direct N-body summation in time-varying potentials, to test its survivability when going through different Galactic environments. In order to survive the 8-Gyr journey moving on a migrating orbit, NGC 6791 must have been more massive, M0 ≥ 5 × 104 M⊙, when formed. We find independent confirmation of this initial mass in the stellar mass function, which is observed to be flat; this can only be explained if the average tidal field strength experienced by the cluster is stronger than what it is at its current orbit. Therefore, the birth place and journeys of NGC 6791 are imprinted in its chemical composition, in its mass-loss and in its flat stellar mass function, supporting its origin in the inner thin disc or in the bulge.

  11. DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER NGC 362

    International Nuclear Information System (INIS)

    Boyer, Martha L.; Gordon, Karl D.; Meixner, Margaret; Sewilo, Marta; Shiao, Bernie; Whitney, Barbara; McDonald, Iain; Van Loon, Jacco Th.; Oliveira, Joana M.; Babler, Brian; Bracker, Steve; Meade, Marilyn; Block, Miwa; Engelbracht, Charles; Misselt, Karl; Hora, Joe; Indebetouw, Remy

    2009-01-01

    We investigate dust production and stellar mass loss in the Galactic globular cluster NGC 362. Due to its close proximity to the Small Magellanic Cloud (SMC), NGC 362 was imaged with the Infrared Array Camera and Multiband Imaging Photometer cameras onboard the Spitzer Space Telescope as part of the Surveying the Agents of Galaxy Evolution (SAGE-SMC) Spitzer Legacy program. We detect several cluster members near the tip of the red giant branch (RGB) that exhibit infrared excesses indicative of circumstellar dust and find that dust is not present in measurable quantities in stars below the tip of the RGB. We modeled the spectral energy distribution (SED) of the stars with the strongest IR excess and find a total cluster dust mass-loss rate of 3.0 +2.0 -1.2 x 10 -9 M sun yr -1 , corresponding to a gas mass-loss rate of 8.6 +5.6 -3.4 x 10 -6 M sun yr -1 , assuming [Fe/H] =-1.16. This mass loss is in addition to any dustless mass loss that is certainly occurring within the cluster. The two most extreme stars, variables V2 and V16, contribute up to 45% of the total cluster dust-traced mass loss. The SEDs of the more moderate stars indicate the presence of silicate dust, as expected for low-mass, low-metallicity stars. Surprisingly, the SED shapes of the stars with the strongest mass-loss rates appear to require the presence of amorphous carbon dust, possibly in combination with silicate dust, despite their oxygen-rich nature. These results corroborate our previous findings in ω Centauri.

  12. DIGGING INTO NGC 6334 I(N): MULTIWAVELENGTH IMAGING OF A MASSIVE PROTOSTELLAR CLUSTER

    International Nuclear Information System (INIS)

    Brogan, C. L.; Hunter, T. R.; Indebetouw, R.; Cyganowski, C. J.; Beuther, H.; Menten, K. M.; Thorwirth, S.

    2009-01-01

    We present a high-resolution, multi-wavelength study of the massive protostellar cluster NGC 6334 I(N) that combines new spectral line data from the Submillimeter Array (SMA) and VLA with a re-analysis of archival VLA continuum data, Two Micron All Sky Survey and Spitzer images. As shown previously, the brightest 1.3 mm source SMA1 contains substructure at subarcsecond resolution, and we report the first detection of SMA1b at 3.6 cm along with a new spatial component at 7 mm (SMA1d). We find SMA1 (aggregate of sources a, b, c, and d) and SMA4 to be comprised of free-free and dust components, while SMA6 shows only dust emission. Our 1.''5 resolution 1.3 mm molecular line images reveal substantial hot-core line emission toward SMA1 and to a lesser degree SMA2. We find CH 3 OH rotation temperatures of 165 ± 9 K and 145 ± 12 K for SMA1 and SMA2, respectively. We estimate a diameter of 1400 AU for the SMA1 hot-core emission, encompassing both SMA1b and SMA1d, and speculate that these sources comprise a ∼>800 AU separation binary that may explain the previously suggested precession of the outflow emanating from the SMA1 region. Compact line emission from SMA4 is weak, and none is seen toward SMA6. The LSR velocities of SMA1, SMA2, and SMA4 all differ by 1-2 km s -1 . Outflow activity from SMA1, SMA2, SMA4, and SMA6 is observed in several molecules including SiO(5-4) and IRAC 4.5 μm emission; 24 μm emission from SMA4 is also detected. Eleven water maser groups are detected, eight of which coincide with SMA1, SMA2, SMA4, and SMA6, while two others are associated with the Sandell source SM2. We also detect a total of 83 Class I CH 3 OH 44 GHz maser spots which likely result from the combined activity of many outflows. Our observations paint the portrait of multiple young hot cores in a protocluster prior to the stage where its members become visible in the near-infrared.

  13. LIGHT-ELEMENT ABUNDANCE VARIATIONS AT LOW METALLICITY: THE GLOBULAR CLUSTER NGC 5466

    International Nuclear Information System (INIS)

    Shetrone, Matthew; Martell, Sarah L.; Wilkerson, Rachel; Adams, Joshua; Siegel, Michael H.; Smith, Graeme H.; Bond, Howard E.

    2010-01-01

    We present low-resolution (R ≅850) spectra for 67 asymptotic giant branch (AGB), horizontal branch, and red giant branch (RGB) stars in the low-metallicity globular cluster NGC 5466, taken with the VIRUS-P integral-field spectrograph at the 2.7 m Harlan J. Smith telescope at McDonald Observatory. Sixty-six stars are confirmed, and one rejected, as cluster members based on radial velocity, which we measure to an accuracy of 16 km s -1 via template-matching techniques. CN and CH band strengths have been measured for 29 RGB and AGB stars in NGC 5466, and the band-strength indices measured from VIRUS-P data show close agreement with those measured from Keck/LRIS spectra previously taken for five of our target stars. We also determine carbon abundances from comparisons with synthetic spectra. The RGB stars in our data set cover a range in absolute V magnitude from +2 to -3, which permits us to study the rate of carbon depletion on the giant branch as well as the point of its onset. The data show a clear decline in carbon abundance with rising luminosity above the luminosity function 'bump' on the giant branch, and also a subdued range in CN band strength, suggesting ongoing internal mixing in individual stars but minor or no primordial star-to-star variation in light-element abundances.

  14. High-resolution abundance analysis of red giants in the globular cluster NGC 6522

    Science.gov (United States)

    Barbuy, B.; Chiappini, C.; Cantelli, E.; Depagne, E.; Pignatari, M.; Hirschi, R.; Cescutti, G.; Ortolani, S.; Hill, V.; Zoccali, M.; Minniti, D.; Trevisan, M.; Bica, E.; Gómez, A.

    2014-10-01

    Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic halo stars that are very metal-poor and in a few individual stars of the oldest known Milky Way globular cluster NGC 6522 have been interpreted as evidence of early enrichment by massive fast-rotating stars (spinstars). Because NGC 6522 is a bulge globular cluster, the suggestion was that not only the very-metal poor halo stars, but also bulge stars at [Fe/H] ~ -1 could be used as probes of the stellar nucleosynthesis signatures from the earlier generations of massive stars, but at much higher metallicity. For the bulge the suggestions were based on early spectra available for stars in NGC 6522, with a medium resolution of R ~ 22 000 and a moderate signal-to-noise ratio. Aims: The main purpose of this study is to re-analyse the NGC 6522 stars reported previously by using new high-resolution (R ~ 45 000) and high signal-to-noise spectra (S/N > 100). We aim at re-deriving their stellar parameters and elemental ratios, in particular the abundances of the neutron-capture s-process-dominated elements such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods: High-resolution spectra of four giants belonging to the bulge globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. The spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe i and Fe ii. Results: Our analysis confirms a metallicity [Fe/H] = -0.95 ± 0.15 for NGC 6522 and the overabundance of the studied stars in Eu (with +0.2 < [Eu/Fe] < + 0.4) and alpha-elements O and Mg. The neutron-capture s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced variations from star to star. Enhancements are in the range 0.0 < [Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0 < [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions: The very high overabundances of [Y/Fe] previously reported for the four studied

  15. A VLT/FLAMES STUDY OF THE PECULIAR INTERMEDIATE-AGE LARGE MAGELLANIC CLOUD STAR CLUSTER NGC 1846. I. KINEMATICS

    International Nuclear Information System (INIS)

    Mackey, A. D.; Da Costa, G. S.; Yong, D.; Ferguson, A. M. N.

    2013-01-01

    In this paper we present high-resolution VLT/FLAMES observations of red giant stars in the massive intermediate-age Large Magellanic Cloud star cluster NGC 1846, which, on the basis of its extended main-sequence turnoff (EMSTO), possesses an internal age spread of ≈300 Myr. We describe in detail our target selection and data reduction procedures, and construct a sample of 21 stars possessing radial velocities indicating their membership of NGC 1846 at high confidence. We consider high-resolution spectra of the planetary nebula Mo-17, and conclude that this object is also a member of the cluster. Our measured radial velocities allow us to conduct a detailed investigation of the internal kinematics of NGC 1846, the first time this has been done for an EMSTO system. The key result of this work is that the cluster exhibits a significant degree of systemic rotation, of a magnitude comparable to the mean velocity dispersion. Using an extensive suite of Monte Carlo models we demonstrate that, despite our relatively small sample size and the substantial fraction of unresolved binary stars in the cluster, the rotation signal we detect is very likely to be genuine. Our observations are in qualitative agreement with the predictions of simulations modeling the formation of multiple populations of stars in globular clusters, where a dynamically cold, rapidly rotating second generation is a common feature. NGC 1846 is less than one relaxation time old, so any dynamical signatures encoded during its formation ought to remain present.

  16. DETECTION OF SOLAR-LIKE OSCILLATIONS FROM KEPLER PHOTOMETRY OF THE OPEN CLUSTER NGC 6819

    International Nuclear Information System (INIS)

    Stello, Dennis; Bedding, Timothy R.; Huber, Daniel; Basu, Sarbani; Bruntt, Hans; Mosser, BenoIt; Barban, Caroline; Goupil, Marie-Jo; Stevens, Ian R.; Chaplin, William J.; Elsworth, Yvonne P.; Hekker, Saskia; Brown, Timothy M.; Christensen-Dalsgaard, Joergen; Kjeldsen, Hans; Arentoft, Torben; Gilliland, Ronald L.; Ballot, Jerome; GarcIa, Rafael A.; Mathur, Savita

    2010-01-01

    Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance, and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819-one of the four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation, Δν, and the frequency of maximum oscillation power, ν max . We find that the asteroseismic parameters allow us to test cluster membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about 2 orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler.

  17. Estimating the parameters of globular cluster M 30 (NGC 7099) from time-series photometry

    DEFF Research Database (Denmark)

    Kains, N.; Bramich, D.M.; Figuera Jaimes, R.

    2013-01-01

    Aims. We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive...... values for the cluster's parameters. Methods. We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate...... stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H]ZW =-2.01 ± 0.04, or [Fe/H]UVES =-2.11 ± 0.06, and a distance of 8.32 ± 0.20 kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35 ± 0.42 kpc (using our SX Phoenicis star detection in M 30...

  18. VEGAS-SSS. II. Comparing the globular cluster systems in NGC 3115 and NGC 1399 using VEGAS and FDS survey data. The quest for a common genetic heritage of globular cluster systems

    Science.gov (United States)

    Cantiello, Michele; D'Abrusco, Raffaele; Spavone, Marilena; Paolillo, Maurizio; Capaccioli, Massimo; Limatola, Luca; Grado, Aniello; Iodice, Enrica; Raimondo, Gabriella; Napolitano, Nicola; Blakeslee, John P.; Brocato, Enzo; Forbes, Duncan A.; Hilker, Michael; Mieske, Steffen; Peletier, Reynier; van de Ven, Glenn; Schipani, Pietro

    2018-04-01

    We analyze the globular cluster (GC) systems in two very different galaxies, NGC 3115 and NGC 1399. With the papers of this series, we aim at highlighting common and different properties in the GC systems in galaxies covering a wide range of parameter space. We compare the GCs in NGC 3115 and NGC 1399 as derived from the analysis of one square degree u-, g-, and i-band images taken with the VST telescope as part of the VST early-type galaxy survey (VEGAS) and Fornax deep survey (FDS). We selected GC candidates using as reference the morpho-photometric and color properties of confirmed GCs. The surface density maps of GCs in NGC 3115 reveal a morphology similar to the light profile of field stars; the same is true when blue and red GCs are taken separately. The GC maps for NGC 1399 are richer in structure and confirm the existence of an intra-cluster GC component. We confirm the presence of a spatial offset in the NGC 1399 GC centroid and find that the centroid of the GCs for NGC 3115 coincides well with the galaxy center. Both GC systems show unambiguous color bimodality in (g - i) and (u - i); the color-color relations of the two GC systems are slightly different with NGC 3115 appearing more linear than NGC 1399. The azimuthal average of the radial density profiles in both galaxies reveals a larger spatial extent for the total GCs population with respect to the galaxy surface brightness profile. For both galaxies, the red GCs have radial density profiles compatible with the galaxy light profile, while the radial profiles for blue GCs are shallower. As for the specific frequency of GCs, SN, we find it is a factor of two higher in NGC 1399 than for NGC 3115; this is mainly the result of extra blue GCs. By inspecting the radial behavior of the specific frequency, SN(

  19. Blue straggler stars beyond the Milky Way: a non-segregated population in the Large Magellanic Cloud cluster NGC 2213

    Science.gov (United States)

    Li, Chengyuan; Hong, Jongsuk

    2018-06-01

    Using the high-resolution observations obtained by the Hubble Space Telescope, we analysed the blue straggler stars (BSSs) in the Large Magellanic Cloud cluster NGC 2213. We found that the radial distribution of BSSs is consistent with that of the normal giant stars in NGC 2213, showing no evidence of mass segregation. However, an analytic calculation carried out for these BSSs shows that they are already dynamically old, because the estimated half-mass relaxation time for these BSSs is significantly shorter than the isochronal age of the cluster. We also performed direct N-body simulations for an NGC 2213-like cluster to understand the dynamical processes that lead to this non-segregated radial distribution of BSSs. Our numerical simulation shows that the presence of black hole subsystems inside the cluster centre can significantly affect the dynamical evolution of BSSs. The combined effects of the delayed segregation, binary disruption, and exchange interactions of BSS progenitor binaries may result in this non-segregated radial distribution of BSSs in NGC 2213.

  20. Discovery of a 205.89 Hz accreting millisecond X-ray pulsar in the globular cluster NGC 6440

    NARCIS (Netherlands)

    Altamirano, D.; Patruno, A.; Heinke, C.O.; Markwardt, C.; Strohmayer, T.E.; Linares, M.; Wijnands, R.; van der Klis, M.; Swank, J.H.

    2010-01-01

    We report on the discovery of the second accreting millisecond X-ray pulsar (AMXP) in the globular cluster NGC 6440. Pulsations with a frequency of 205.89 Hz were detected with RXTE on 2009 August 30, October 1 and October 28, during the decays of less than or similar to 4 day outbursts of a newly

  1. Testing modified gravity with globular clusters: the case of NGC 2419

    Science.gov (United States)

    Llinares, Claudio

    2018-05-01

    The dynamics of globular clusters has been studied in great detail in the context of general relativity as well as with modifications of gravity that strongly depart from the standard paradigm such as Modified Newtonian Dynamics. However, at present there are no studies that aim to test the impact that less extreme modifications of gravity (e.g. models constructed as alternatives to dark energy) have on the behaviour of globular clusters. This Letter presents fits to the velocity dispersion profile of the cluster NGC 2419 under the symmetron-modified gravity model. The data show an increase in the velocity dispersion towards the centre of the cluster which could be difficult to explain within general relativity. By finding the best-fitting solution associated with the symmetron model, we show that this tension does not exist in modified gravity. However, the best-fitting parameters give a model that is inconsistent with the dynamics of the Solar system. Exploration of different screening mechanisms should give us the chance to understand if it is possible to maintain the appealing properties of the symmetron model when it comes to globular clusters and at the same time recover the Solar system dynamics properly.

  2. WIYN Open Cluster Study: Binary Orbits and Tidal Circularization in NGC 6819

    Science.gov (United States)

    Morscher, Meagan B.; Mathieu, R. D.; Kaeppler, S.; Hole, K. T.; Meibom, S.

    2006-12-01

    We are conducting a comprehensive stellar radial-velocity survey in NGC 6819, a rich, intermediate age ( 2.4 Gyr) open cluster with [Fe/H] -0.05. As of October 2006, we have obtained 7065 radial-velocity measurements of 1409 stars using the WIYN Hydra Multi-Object Spectrograph, with typical velocity measurement precisions of 0.4 km/s. Using an E/I criterion of 3, we have identified 282 velocity variables. In the past year we have expanded the number of final orbital solutions by 45 to a total of more than 80 solutions. In coeval stellar populations, circular binaries tend to have the shortest orbital periods, while longer period binaries show a distribution of non-zero eccentricities. The circularization of the shortest period orbits is the result of an exchange of stellar and orbital angular momentum due to tidal interactions. We defined a population’s tidal circularization period as the longest orbital period at which a binary of typical initial eccentricity has become circularized (e.g., has evolved to an eccentricity e = 0.01) over the lifetime of the cluster (Meibom & Mathieu, 2005, ApJ, 620, 970). We are studying the trend of increasing tidal circularization periods with population age. Preliminary results in NGC 6819 indicate a tidal circularization period of 7.5 days, which is consistent with this overall trend. We will recalculate the tidal circularization period in order to include the latest sample of orbital solutions. This comprehensive survey also allows us to investigate the relative spatial distributions of spectroscopic binaries and other constant-velocity cluster members of similar mass. We find the spectroscopic binaries to be more centrally concentrated at a statistically significant level, which we attribute to energy equipartition processes. MM was supported by REU NSF grant AST-0453442. RDM, SK, KTH, and SM were supported by NSF grant AST-0406615.

  3. Variable Stars in Large Magellanic Cloud Globular Clusters. II. NGC 1786

    Science.gov (United States)

    Kuehn, Charles A.; Smith, Horace A.; Catelan, Márcio; Pritzl, Barton J.; De Lee, Nathan; Borissova, Jura

    2012-12-01

    This is the second in a series of papers studying the variable stars in Large Magellanic Cloud globular clusters. The primary goal of this series is to study how RR Lyrae stars in Oosterhoff-intermediate systems compare to their counterparts in Oosterhoff I/II systems. In this paper, we present the results of our new time-series B-V photometric study of the globular cluster NGC 1786. A total of 65 variable stars were identified in our field of view. These variables include 53 RR Lyraes (27 RRab, 18 RRc, and 8 RRd), 3 classical Cepheids, 1 Type II Cepheid, 1 Anomalous Cepheid, 2 eclipsing binaries, 3 Delta Scuti/SX Phoenicis variables, and 2 variables of undetermined type. Photometric parameters for these variables are presented. We present physical properties for some of the RR Lyrae stars, derived from Fourier analysis of their light curves. We discuss several different indicators of Oosterhoff type which indicate that the Oosterhoff classification of NGC 1786 is not as clear cut as what is seen in most globular clusters. Based on observations taken with the SMARTS 1.3 m telescope operated by the SMARTS Consortium and observations taken at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  4. THE BLACK HOLE MASS IN THE BRIGHTEST CLUSTER GALAXY NGC 6086

    International Nuclear Information System (INIS)

    McConnell, Nicholas J.; Ma, Chung-Pei; Graham, James R.; Wright, Shelley A.; Gebhardt, Karl; Lauer, Tod R.; Richstone, Douglas O.

    2011-01-01

    We present the first direct measurement of the central black hole mass, M . , in NGC 6086, the Brightest Cluster Galaxy (BCG) in A2162. Our investigation demonstrates for the first time that stellar-dynamical measurements of M . in BCGs are possible beyond the nearest few galaxy clusters. We observed NGC 6086 with laser guide star adaptive optics and the integral-field spectrograph (IFS) OSIRIS at the W. M. Keck Observatory and with the seeing-limited IFS GMOS-N at Gemini Observatory North. We combined the IFS data sets with existing major-axis kinematics and used axisymmetric stellar orbit models to determine M . and the R-band stellar mass-to-light ratio, M * /L R . We find M . = 3.6 +1.7 -1.1 x 10 9 M sun and M * /L R = 4.6 +0.3 -0.7 M sun L sun -1 (68% confidence) from models using the most massive dark matter halo allowed within the gravitational potential of the host cluster. Models fitting only IFS data confirm M . ∼ 3 x 10 9 M sun and M * /L R ∼ 4 M sun L sun -1 , with weak dependence on the assumed dark matter halo structure. When data out to 19 kpc are included, the unrealistic omission of dark matter causes the best-fit black hole mass to decrease dramatically, to 0.6 x 10 9 M sun , and the best-fit stellar mass-to-light ratio to increase to 6.7 M sun L -1 sun,R . The latter value is at further odds with stellar population studies favoring M * /L R ∼ 2 M sun L -1 sun . Biases from dark matter omission could extend to dynamical models of other galaxies with stellar cores, and revised measurements of M . could steepen the empirical scaling relationships between black holes and their host galaxies.

  5. Investigation of Galactic open cluster remnants: the case of NGC 7193

    Science.gov (United States)

    de Souza Angelo, Mateus; Francisco Coelho dos Santos, João, Jr.; Barbosa Corradi, Wagner José; Ferreira de Souza Maia, Francisco; Piatti, Andrés Eduardo

    2017-01-01

    Galactic open clusters (OCs) that survive the early gas-expulsion phase are gradually destroyed over time by the action of disruptive dynamical processes. Their final evolutionary stages are characterized by a poorly populated concentration of stars called an open cluster remnant (OCR). This study is devoted to assessing the real physical nature of the OCR candidate NGC 7193. GMOS/Gemini spectroscopy of 53 stars in the inner target region were obtained to derive radial velocities and atmospheric parameters. We also employed photometric and proper motion data. The analysis method consists of the following steps: (i) analysis of the statistical resemblance between the cluster and a set of field samples with respect to the sequences defined in color-magnitude diagrams (CMDs); (ii) a 5-dimensional iterative exclusion routine was employed to identify outliers from kinematical and positional data; (iii) isochrone fitting to the Ks×(J-Ks) CMD of the remaining stars and the dispersion of spectral types along empirical sequences in the (J-H)×(H-Ks) diagram were checked. A group of stars was identified for which the mean heliocentric distance is compatible with that obtained via isochrone fitting and whose metallicities are compatible with each other. Fifteen of the member stars observed spectroscopically were identified together with another 19 probable members. Our results indicate that NGC 7193 is a genuine OCR, of a once very populous OC, for which the following parameters were derived: d = 501±46 pc, t=2.5+/-1.2 Gyr, =-0.17+/-0.23 and E(B-V)=0.05+/-0.05. Its luminosity and mass functions show depletion of low mass stars, confirming the OCR is in a dynamically evolved state. Based on observations obtained at the Gemini Observatory, which is operated by the AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership: NSF (United States), STFC (United Kingdom), NRC (Canada), CONICYT (Chile), ARC (Australia), CNPq (Brazil) and CONICET (Argentina).

  6. MASSIVE CLUSTERS IN THE INNER REGIONS OF NGC 1365: CLUSTER FORMATION AND GAS DYNAMICS IN GALACTIC BARS

    International Nuclear Information System (INIS)

    Elmegreen, Bruce G.; Galliano, Emmanuel; Alloin, Danielle

    2009-01-01

    Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10 7 M sun clusters near the inner Lindblad resonance (ILR) of the barred spiral NGC 1365. The morphology, mass, and flow of H I and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of ∼6 M sun yr -1 before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to ∼40 M sun yr -1 near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another ∼0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rarefaction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power-law mass distribution. Gas trapping in the most massive clusters could explain their [Ne II] emission, which is not evident from the lower-mass clusters nearby.

  7. THE SLUGGS SURVEY: NGC 3115, A CRITICAL TEST CASE FOR METALLICITY BIMODALITY IN GLOBULAR CLUSTER SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Brodie, Jean P.; Conroy, Charlie; Arnold, Jacob A.; Romanowsky, Aaron J. [University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Usher, Christopher; Forbes, Duncan A. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Strader, Jay, E-mail: brodie@ucolick.org [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

    2012-11-10

    Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.

  8. Variable stars in metal-rich globular clusters. IV. Long-period variables in NGC 6496

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Mohamad A. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Layden, Andrew C.; Guldenschuh, Katherine A. [Physics and Astronomy Department, Bowling Green State University, Bowling Green, OH 43403 (United States); Reichart, D. E.; Ivarsen, K. M.; Haislip, J. B.; Nysewander, M. C.; LaCluyze, A. P. [Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599 (United States); Welch, Douglas L., E-mail: mabbas@ari.uni-heidelberg.de, E-mail: laydena@bgsu.edu [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8 S 4M1 (Canada)

    2015-02-01

    We present VI-band photometry for stars in the metal-rich globular cluster NGC 6496. Our time-series data were cadenced to search for long-period variables (LPVs) over a span of nearly two years, and our variability search yielded the discovery of 13 new variable stars, of which 6 are LPVs, 2 are suspected LPVs, and 5 are short-period eclipsing binaries. An additional star was found in the ASAS database, and we clarify its type and period. We argue that all of the eclipsing binaries are field stars, while five to six of the LPVs are members of NGC 6496. We compare the period–luminosity distribution of these LPVs with those of LPVs in the Large Magellanic Cloud and 47 Tucanae, and with theoretical pulsation models. We also present a VI color–magnitude diagram, display the evolutionary states of the variables, and match isochrones to determine a reddening of E(B−V)= 0.21±0.02 mag and apparent distance modulus of 15.60±0.15 mag.

  9. THE SLUGGS SURVEY: NGC 3115, A CRITICAL TEST CASE FOR METALLICITY BIMODALITY IN GLOBULAR CLUSTER SYSTEMS

    International Nuclear Information System (INIS)

    Brodie, Jean P.; Conroy, Charlie; Arnold, Jacob A.; Romanowsky, Aaron J.; Usher, Christopher; Forbes, Duncan A.; Strader, Jay

    2012-01-01

    Due to its proximity (9 Mpc) and the strongly bimodal color distribution of its spectroscopically well-sampled globular cluster (GC) system, the early-type galaxy NGC 3115 provides one of the best available tests of whether the color bimodality widely observed in GC systems generally reflects a true metallicity bimodality. Color bimodality has alternatively been attributed to a strongly nonlinear color-metallicity relation reflecting the influence of hot horizontal-branch stars. Here, we couple Subaru Suprime-Cam gi photometry with Keck/DEIMOS spectroscopy to accurately measure GC colors and a CaT index that measures the Ca II triplet. We find the NGC 3115 GC system to be unambiguously bimodal in both color and the CaT index. Using simple stellar population models, we show that the CaT index is essentially unaffected by variations in horizontal-branch morphology over the range of metallicities relevant to GC systems (and is thus a robust indicator of metallicity) and confirm bimodality in the metallicity distribution. We assess the existing evidence for and against multiple metallicity subpopulations in early- and late-type galaxies and conclude that metallicity bi/multimodality is common. We briefly discuss how this fundamental characteristic links directly to the star formation and assembly histories of galaxies.

  10. Globular clusters, old and young

    International Nuclear Information System (INIS)

    Samus', N.N.

    1984-01-01

    The problem of similarity of and difference in the globular and scattered star clusters is considered. Star clusters in astronomy are related either to globular or to scattered ones according to the structure of Hertzsprung-Russell diagram constructed for star clusters, but not according to the appearance. The qlobular clusters in the Galaxy are composed of giants and subgiants, which testifies to the old age of the globular clusters. The Globular clusters in the Magellanic clouds are classified into ''red'' ones - similar to the globular clusters of the Galaxy, and ''blue'' ones - similar to them in appearance but differing extremely by the star composition and so by the age. The old star clusters are suggested to be called globular ones, while another name (''populous'', for example) is suggested to be used for other clusters similar to globular ones only in appearance

  11. STAR-TO-STAR IRON ABUNDANCE VARIATIONS IN RED GIANT BRANCH STARS IN THE GALACTIC GLOBULAR CLUSTER NGC 3201

    International Nuclear Information System (INIS)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-01-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  12. Star-to-star Iron Abundance Variations in Red Giant Branch Stars in the Galactic Globular Cluster NGC 3201

    Science.gov (United States)

    Simmerer, Jennifer; Ivans, Inese I.; Filler, Dan; Francois, Patrick; Charbonnel, Corinne; Monier, Richard; James, Gaël

    2013-02-01

    We present the metallicity as traced by the abundance of iron in the retrograde globular cluster NGC 3201, measured from high-resolution, high signal-to-noise spectra of 24 red giant branch stars. A spectroscopic analysis reveals a spread in [Fe/H] in the cluster stars at least as large as 0.4 dex. Star-to-star metallicity variations are supported both through photometry and through a detailed examination of spectra. We find no correlation between iron abundance and distance from the cluster core, as might be inferred from recent photometric studies. NGC 3201 is the lowest mass halo cluster to date to contain stars with significantly different [Fe/H] values.

  13. An Introverted Starburst: Gas and SSC Formation in NGC 5253

    Science.gov (United States)

    Turner, J. L.; Beck, S. C.

    2004-06-01

    High resolution Brackett line spectroscopy with the Keck Telescope reveals relatively narrow recombination lines toward the embedded young super star cluster nebula in NGC 5253. The gas within this nebula is almost certainly gravitationally bound by the massive and compact young star cluster.

  14. VizieR Online Data Catalog: Young star groups in NGC 300 (Rodriguez+, 2016)

    Science.gov (United States)

    Rodriguez, M. J.; Baume, G.; Feinstein, C.

    2016-08-01

    Fundamental characteristics of 1147 young star groups identified in 6 ACS/WFC fields of the galaxy NGC 300. For each group: field of the ACS/WFC, equatorial coordinates, radius, number of stars (the suffix bri indicates bright stars with F555W<25, the suffix dct indicate stars belonging to the decontaminated region, the suffixes blue and red refer to blue and red stars respectively), the magnitude of the brightest star in the group, PDMF slope with its error, and galactocentric distance. (1 data file).

  15. Deep VLA images of the HH 124 IRS radio cluster and its surroundings, and a new determination of the distance to NGC 2264

    Energy Technology Data Exchange (ETDEWEB)

    Dzib, Sergio A. [Max Planck Institut für Radioastronomie, Auf del Hügel 69, D-53121 Bonn (Germany); Loinard, Laurent; Rodríguez, Luis F. [Centro de Radioastronomía y Astrofísica, Universidad NacionalAutónoma de México Apartado Postal 3-72, 58090 Morelia, Michoacán (Mexico); Galli, Phillip, E-mail: sdzib@mpifr-bonn.mpg.de [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, SP (Brazil)

    2014-06-20

    We present new deep (σ ∼ 6 μJy) radio images of the HH 124 IRS radio cluster at 4.8 and 7.5 GHz. We detect a total of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determine the nature of the sources and of their radio emission. A proper motion study was also performed for several of these radio sources using previously reported radio observations. Our analysis shows that 11 radio sources can be associated with Galactic objects, most of them probably young stars. Interestingly, 8 of these sources are in an area less than 1 arcmin{sup 2} in size. The importance of such compact clusters resides in that all of its members can be observed in a single pointing with most telescopes and are, therefore, ideal for multi-wavelength studies of variability. Another 4 of the detected sources are clearly extragalactic. Finally, we propose from statistical arguments that out of the remaining sources, about 10 are Galactic, but our study does not allow us to identify which of the sources fall in that specific category. The relatively large proper motions observed for the sources in HH 124 IRS suggest that this region is located at about 400 pc from the Sun. This is significantly smaller than the ∼800-900 pc distance usually assigned to the nearby open cluster NGC 2264 with which HH 124 is thought to be associated. However, a reanalysis of the Hipparcos parallaxes for members of NGC 2264, a convergent point approach, and a kinematic analysis all argue in favor of a distance of the order of 400 pc for NGC 2264 as well.

  16. VizieR Online Data Catalog: NGC 6802 dwarf cluster members and non-members (Tang+, 2017)

    Science.gov (United States)

    Tang, B.; Geisler, D.; Friel, E.; Villanova, S.; Smiljanic, R.; Casey, A. R.; Randich, S.; Magrini, L.; San, Roman I.; Munoz, C.; Cohen, R. E.; Mauro, F.; Bragaglia, A.; Donati, P.; Tautvaisiene, G.; Drazdauskas, A.; Zenoviene, R.; Snaith, O.; Sousa, S.; Adibekyan, V.; Costado, M. T.; Blanco-Cuaresma, S.; Jimenez-Esteban, F.; Carraro, G.; Zwitter, T.; Francois, P.; Jofre, P.; Sordo, R.; Gilmore, G.; Flaccomio, E.; Koposov, S.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.; Bayo, A.; Damiani, F.; Franciosini, E.; Hourihane, A.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sacco, G.; Worley, C. C.; Zaggia, S.

    2016-11-01

    The dwarf stars in NGC 6802 observed by GIRAFFE spectrograph are separated into four tables: 1. cluster members in the lower main sequence; 2. cluster members in the upper main sequence; 3. non-member dwarfs in the lower main sequence; 4. non-member dwarfs in the upper main sequence. The star coordinates, V band magnitude, V-I color, and radial velocity are given. (4 data files).

  17. Chemical study of the metal-rich globular cluster NGC 5927

    Science.gov (United States)

    Mura-Guzmán, A.; Villanova, S.; Muñoz, C.; Tang, B.

    2018-03-01

    Globular clusters (GCs) are natural laboratories where stellar and chemical evolution can be studied in detail. In addition, their chemical patterns and kinematics can tell us to which Galactic structure (disc, bulge, halo or extragalactic) the cluster belongs to. NGC 5927 is one of most metal-rich GCs in the Galaxy and its kinematics links it to the thick disc. We present abundance analysis based on high-resolution spectra of seven giant stars. The data were obtained using Fibre Large Array Multi Element Spectrograph/Ultraviolet Echelle Spectrograph (UVES) spectrograph mounted on UT2 telescope of the European Southern Observatory. The principal objective of this work is to perform a wide and detailed chemical abundance analysis of the cluster and look for possible Multiple Populations (MPs). We determined stellar parameters and measured 22 elements corresponding to light (Na, Al), alpha (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and heavy elements (Y, Zr, Ba, Ce, Nd, Eu). We found a mean iron content of [Fe/H] = -0.47 ± 0.02 (error on the mean). We confirm the existence of MPs in this GC with an O-Na anti-correlation, and moderate spread in Al abundances. We estimate a mean [α/Fe] = 0.25 ± 0.08. Iron-peak elements show no significant spread. The [Ba/Eu] ratios indicate a predominant contribution from SNeII for the formation of the cluster.

  18. ALMA Detects CO(3-2) within a Super Star Cluster in NGC 5253

    Science.gov (United States)

    Turner, Jean L.; Consiglio, S. Michelle; Beck, Sara C.; Goss, W. M.; Ho, Paul. T. P.; Meier, David S.; Silich, Sergiy; Zhao, Jun-Hui

    2017-09-01

    We present observations of CO(3-2) and 13CO(3-2) emission near the supernebula in the dwarf galaxy NGC 5253, which contains one of the best examples of a potential globular cluster in formation. The 0.″3 resolution images reveal an unusual molecular cloud, “Cloud D1,” that is coincident with the radio-infrared supernebula. The ˜6 pc diameter cloud has a linewidth, Δ v = 21.7 {km} {{{s}}}-1, that reflects only the gravitational potential of the star cluster residing within it. The corresponding virial mass is 2.5 × 105 {M}⊙ . The cluster appears to have a top-heavy initial mass function, with M * ≳ 1-2 {M}⊙ . Cloud D1 is optically thin in CO(3-2), probably because the gas is hot. Molecular gas mass is very uncertain but constitutes <35% of the dynamical mass within the cloud boundaries. In spite of the presence of an estimated ˜1500-2000 O stars within the small cloud, the CO appears relatively undisturbed. We propose that Cloud D1 consists of molecular clumps or cores, possibly star-forming, orbiting with more evolved stars in the core of the giant cluster.

  19. Main sequence of the metal-poor globular cluster M30 (NGC 7099)

    International Nuclear Information System (INIS)

    Alcaino, G.; Liller, W.

    1980-01-01

    We present photographic photometry for 673 stars in the metal-poor globular cluster M30 (NGC 7099). The Racine wedge was used with the CTIO 1-m Yale telescope (Δm=3/sup m/.60), the CTIO 4-m telescope (Δm=6/sup m/.83), and the ESO 3.6-m telescope (Δm=4/sup m/.12) to extend the photoelectric limit from Vapprox. =16.3 to Vapprox. =20.4. For the main-sequence turn-off, we have determined its position to lie at V=18.4 +- 0.1 (m.e.) and B-V=0.49 +- 0.03 (m.e.). From these values, we calculate the intrinsic values M/sub v/ =3.87 and (B-V) 0 =0.47. For the cluster as a whole, we derive a distance modulus (m-M)/sub V/=14.53 +- 0.15 and reddening E(B-V)=0.02 +- 0.02. Using the models of Iben and Rood [Astrophys. J. 159, 605 (1970)] and the isochrones of Demarque and McClure [(1977), in Evolution of Galaxies and Stellar Populations, edited by B. Tinsley and R. B. Larson (Yale University Observatory, New Haven), p. 199], we deduce the cluster's age to be 14.5( +- 4.0) x 10 9 yr. The large uncertainty in this value emphasizes the dire need for more work on cluster evolution

  20. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    Energy Technology Data Exchange (ETDEWEB)

    Valcarce, A. A. R.; De Medeiros, J. R. [Universidade Federal do Rio Grande do Norte, Departamento de Física, 59072-970 Natal, RN (Brazil); Catelan, M. [Pontificia Universidad Católica de Chile, Centro de Astroingeniería, Av. Vicuña Mackena 4860, 782-0436 Macul, Santiago (Chile); Alonso-García, J. [Pontificia Universidad Católica de Chile, Instituto de Astrofísica, Facultad de Física, Av. Vicuña Mackena 4860, 782-0436 Macul, Santiago (Chile); Cortés, C. [Universidad Metropolitana de Ciencias de la Educación, Facultad de Ciencias Básicas, Departamento de Física, Av. José Pedro Alessandri 774, Santiago (Chile)

    2014-02-20

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ΔY ≲ 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)—a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  1. Constraints on helium enhancement in the globular cluster M4 (NGC 6121): The horizontal branch test

    International Nuclear Information System (INIS)

    Valcarce, A. A. R.; De Medeiros, J. R.; Catelan, M.; Alonso-García, J.; Cortés, C.

    2014-01-01

    Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than the exception. In the case of the metal-intermediate globular cluster M4 (NGC 6121), recent high-resolution spectroscopic observations of blue horizontal branch (HB) stars (i.e., HB stars hotter than the RR Lyrae instability strip) suggest that a large fraction of blue HB stars are second-generation stars formed with high helium abundances. In this paper, we test this scenario by using recent photometric and spectroscopic data together with theoretical evolutionary computations for different Y values. Comparing the photometric data with the theoretically derived color-magnitude diagrams, we find that the bulk of the blue HB stars in M4 have ΔY ≲ 0.01 with respect to the cluster's red HB stars (i.e., HB stars cooler than the RR Lyrae strip)—a result which is corroborated by comparison with spectroscopically derived gravities and temperatures, which also favor little He enhancement. However, the possible existence of a minority population on the blue HB of the cluster with a significant He enhancement level is also discussed.

  2. ON THE SERENDIPITOUS DISCOVERY OF A Li-RICH GIANT IN THE GLOBULAR CLUSTER NGC 362

    Energy Technology Data Exchange (ETDEWEB)

    D’Orazi, Valentina; Gratton, Raffaele G.; Lucatello, Sara; Momany, Yazan [INAF—Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122, Padova (Italy); Angelou, George C. [Max Planck Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Bragaglia, Angela; Carretta, Eugenio; Sollima, Antonio [INAF—Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127, Bologna (Italy); Lattanzio, John C., E-mail: valentina.dorazi@oapd.inaf.it [Monash Centre for Astrophysics (MoCA), Monash University, Melbourne, VIC 3800 (Australia)

    2015-03-10

    We have serendipitously identified the first lithium-rich giant star located close to the red giant branch bump in a globular cluster. Through intermediate-resolution FLAMES spectra we derived a lithium abundance of A(Li) = 2.55 (assuming local thermodynamical equilibrium), which is extremely high considering the star’s evolutionary stage. Kinematic and photometric analysis confirm the object as a member of the globular cluster NGC 362. This is the fourth Li-rich giant discovered in a globular cluster, but is the only one known to exist at a luminosity close to the bump magnitude. The three previous detections are clearly more evolved, located close to, or beyond, the tip of their red giant branch. Our observations are able to discard the accretion of planets/brown dwarfs, as well as an enhanced mass-loss mechanism as a formation channel for this rare object. While the star sits just above the cluster bump luminosity, its temperature places it toward the blue side of the giant branch in the color–magnitude diagram. We require further dedicated observations to unambiguously identify the star as a red giant: we are currently unable to confirm whether Li production has occurred at the bump of the luminosity function or if the star is on the pre-zero-age horizontal branch. The latter scenario provides the opportunity for the star to have synthesized Li rapidly during the core helium flash or gradually during its red giant branch ascent via some extra mixing process.

  3. The Mass Function of Young Star Clusters in the "Antennae" Galaxies.

    Science.gov (United States)

    Zhang; Fall

    1999-12-20

    We determine the mass function of young star clusters in the merging galaxies known as the "Antennae" (NGC 4038/9) from deep images taken with the Wide Field Planetary Camera 2 on the refurbished Hubble Space Telescope. This is accomplished by means of reddening-free parameters and a comparison with stellar population synthesis tracks to estimate the intrinsic luminosity and age, and hence the mass, of each cluster. We find that the mass function of the young star clusters (with ages less, similar160 Myr) is well represented by a power law of the form psi&parl0;M&parr0;~M-2 over the range 104 less, similarM less, similar106 M middle dot in circle. This result may have important implications for our understanding of the origin of globular clusters during the early phases of galactic evolution.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-01

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

  5. The galactic globular cluster NGC 1851: its dynamical and evolutionary properties

    Science.gov (United States)

    Saviane, I.; Piotto, G.; Fagotto, F.; Zaggia, S.; Capaccioli, M.; Aparicio, A.

    1998-05-01

    We have completely mapped the Galactic globular cluster NGC 1851 with large-field, ground-based VI CCD photometry and pre-repair HST/WFPC1 data for the central region. The photometric data set has allowed a V vs. (V-I) colour-magnitude diagram for ~ 20500 stars to be constructed. >From the apparent luminosity of the horizontal branch (HB) we derive a true distance modulus (m-M)_0 = 15.44 +/- 0.20. An accurate inspection of the cluster's bright and blue objects confirms the presence of seven ``supra-HB'' stars, six of which are identified as evolved descendants from HB progenitors. The HB morphology is found to be clearly bimodal, showing both a red clump and a blue tail, which are not compatible with standard evolutionary models. Synthetic Hertzsprung-Russell (HR) diagrams demonstrate that the problem could be solved by assuming a bimodal efficiency of the mass loss along the red giant branch (RGB). With the aid of Kolmogorov-Smirnov statistics we find evidence that the radial distribution of the blue HB stars is different from that of the red HB and sub-giant branch (SGB) stars. We give the first measurement of the mean absolute I magnitude for 22 known RR Lyr variables ( = 0.12 +/- 0.20 mag at a metallicity [Fe/H] = -1.28). The mean absolute V magnitude is = 0.58 +/- 0.20 mag, and we confirm that these stars are brighter than those of the zero-age HB (ZAHB). Moreover, we found seven new RR Lyr candidates (six ab type and one c type). With these additional variables the ratio of the two types is now N_c/Nab = 0.38. >From a sample of 25 globular clusters a new calibration for Delta V_bump() HB as a function of cluster metallicity is derived. NGC 1851 follows this general trend fairly well. From a comparison with the theoretical models, we also find some evidence for an age-metallicity relation among globular clusters. We identify 13 blue straggler stars, which do not show any sign of variability. The blue stragglers are less concentrated than the subgiant branch

  6. The enigma of the open cluster M29 (NGC 6913) solved

    Energy Technology Data Exchange (ETDEWEB)

    Straižys, V.; Milašius, K.; Černis, K.; Kazlauskas, A.; Zdanavičius, K.; Zdanavičius, J.; Laugalys, V. [Institute of Theoretical Physics and Astronomy, Vilnius University, Goštauto 12, Vilnius LT-01108 (Lithuania); Boyle, R. P. [Vatican Observatory Research Group, Steward Observatory, Tucson, AZ 85721 (United States); Vrba, F. J. [U.S. Naval Observatory Flagstaff Station, P.O. Box 1149, Flagstaff, AZ 86002 (United States); Munari, U. [INAF Astronomical Observatory of Padova, I-36012, Asiago (VI) (Italy); Walborn, N. R. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Janusz, R. [University School " Ignatianum," Cracow (Poland)

    2014-11-01

    Determining the distance to the open cluster M29 (NGC 6913) has proven difficult, with distances determined by various authors differing by a factor of two or more. To solve this problem, we have initiated a new photometric investigation of the cluster in the Vilnius seven-color photometric system, supplementing it with available data in the BV and JHK {sub s} photometric systems and spectra of the nine brightest stars of spectral classes O and B. Photometric spectral classes and luminosities of 260 stars in a 15' × 15' area down to V = 19 mag are used to investigate the interstellar extinction run with distance and to estimate the distance of the Great Cygnus Rift, ∼ 800 pc. The interstellar reddening law in the optical and near-infrared regions is found to be close to normal, with the ratio of extinction to color excess R{sub BV} = 2.87. The extinction A{sub V} of cluster members is between 2.5 and 3.8 mag, with a mean value of 2.97 mag, or E {sub B–V} = 1.03. The average distance of eight stars of spectral types O9-B2 is 1.54 ± 0.15 kpc. Two stars from the seven brightest stars are field stars: HDE 229238 is a background B0.5 supergiant and HD 194378 is a foreground F star. In the intrinsic color-magnitude diagram, seven fainter stars of spectral classes B3-B8 are identified as possible members of the cluster. The 15 selected members of the cluster of spectral classes O9-B8 plotted on the log L/L {sub ☉} versus log T {sub eff} diagram, together with the isochrones from the Padova database, give the age of the cluster as 5 ± 1 Myr.

  7. Four W Ursae Majoris contact binaries in the old galactic cluster NGC 188

    International Nuclear Information System (INIS)

    Baliunas, S.L.; Guinan, E.F.

    1984-01-01

    The authors calculated the cross-correlation coefficients between the spectra of the contact binaries and slowly-rotating template stars of approximately the same color in NGC 188 (stars I-32 and I-33). From the cross-correlation coefficients they measured the radial velocities of the W UMa stars near the expected phase of velocity crossing with respect to the two other cluster stars. The velocities of the W UMa systems are consistent with cluster membership. In three of the systems, the spectra were obtained at phases where individual stellar components were resolved. Two Gaussians were fit simultaneously to the most significant portion of the blended cross-correlation peaks. The mass ratios of these three systems were determined by assuming that the velocity of the center of mass is equal to the mean radial velocity of the two cluster reference stars. The mass ratios in these three systems suggest the binaries are similar to other short-period, field W UMa systems designated W-type

  8. CCD BVRI and 2MASS photometry of the poorly studied open cluster NGC 6631

    Directory of Open Access Journals (Sweden)

    A.L. Tadross

    2014-12-01

    Full Text Available Here we have obtained the BVRI CCD photometry down to a limiting magnitude of V∼20 for the southern poorly studied open cluster NGC 6631. It is observed from the 1.88 m Telescope of Kottamia Observatory in Egypt. About 3300 stars have been observed in an area of ∼10′×10′ around the cluster center. The main photometric parameters have been estimated and compared with the results that determined for the cluster using JHKs 2MASS photometric database. The cluster’s diameter is estimated to be 10 arcmin; the reddening E(B-V=0.68 ± 0.10 mag, E(J-H=0.21 ± 0.10 mag, the true modulus (m-Mo=12.16 ± 0.10 mag, which corresponds to a distance of 2700 ± 125 pc and age of 500 ± 50 Myr.

  9. Chemical Abundances of Red Giant Stars in the Globular Cluster M107 (NGC 6171)

    Science.gov (United States)

    O'Connell, Julia E.; Johnson, Christian I.; Pilachowski, Catherine A.; Burks, Geoffrey

    2011-10-01

    We present chemical abundances of Al and several Fe-Peak and neutron-capture elements for 13 red giant branch stars in the Galactic globular cluster NGC 6171 (M107). The abundances were determined using equivalent width and spectrum synthesis analyses of moderate-resolution ( R ˜ 15,000), moderate signal-to-noise ratio ( ˜ 80) spectra obtained with the WIYN telescope and Hydra multifiber spectrograph. A comparison between photometric and spectroscopic effective temperature estimates seems to indicate that a reddening value of E(B - V) = 0.46 may be more appropriate for this cluster than the more commonly used value of E(B - V) = 0.33. Similarly, we found that a distance modulus of (m - M)V ≈ 13.7 provided reasonable surface gravity estimates for the stars in our sample. Our spectroscopic analysis finds M107 to be moderately metal-poor with = -0.93 and also exhibits a small star-to-star metallicity dispersion (σ = 0.04). These results are consistent with previous photometric and spectroscopic studies. Aluminum appears to be moderately enhanced in all program stars ( = +0.39, σ = 0.11). The relatively small star-to-star scatter in [Al/Fe] differs from the trend found in more metal-poor globular clusters, and is more similar to what is found in clusters with [Fe/H] ≳ -1. The cluster also appears to be moderately r-process-enriched with = +0.32 (σ = 0.17).

  10. Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sooyoung; Yoon, Suk-Jin, E-mail: sjyoon0691@yonsei.ac.kr [Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2017-07-01

    Spectroscopy on the globular cluster (GC) system of NGC 5128 revealed bimodality in absorption-line index distributions of its old GCs. GC division is a widely observed and studied phenomenon whose interpretation has depicted host galaxy formation and evolution such that it harbors two distinct metallicity groups. Such a conventional view of GC bimodality has mainly been based on photometry. The recent GC photometric data, however, presented an alternative perspective in which the nonlinear metallicity-to-color transformation is responsible for color bimodality of GC systems. Here we apply the same line of analysis to the spectral indices and examine the absorption-line index versus metallicity relations for the NGC 5128 GC system. NGC 5128 GCs display nonlinearity in the metallicity-index planes, most prominently for the Balmer lines and by a non-negligible degree for the metallicity-sensitive magnesium line. We demonstrate that the observed spectroscopic division of NGC 5128 GCs can be caused by the nonlinear nature of the metallicity-to-index conversions and thus one does not need to resort to two separate GC subgroups. Our analysis incorporating this nonlinearity provides a new perspective on the structure of NGC 5128's GC system, and a further piece to the global picture of the formation of GC systems and their host galaxies.

  11. Short-term X-ray variability of the globular cluster source 4U 1820 - 30 (NGC 6624)

    Science.gov (United States)

    Stella, L.; Kahn, S. M.; Grindlay, J. E.

    1984-01-01

    Analytical techniques for improved identification of the temporal and spectral variability properties of globular cluster and galactic bulge X-ray sources are described in terms of their application to a large set of observations of the source 4U 1820 - 30 in the globular cluster NGC 6624. The autocorrelation function, cross-correlations, time skewness function, erratic periodicities, and pulse trains are examined. The results are discussed in terms of current models with particular emphasis on recent accretion disk models. It is concluded that the analyzed observations provide the first evidence for shot-noise variability in a globular cluster X-ray source.

  12. Migration in the shearing sheet and estimates for young open cluster migration

    Science.gov (United States)

    Quillen, Alice C.; Nolting, Eric; Minchev, Ivan; De Silva, Gayandhi; Chiappini, Cristina

    2018-04-01

    Using tracer particles embedded in self-gravitating shearing sheet N-body simulations, we investigate the distance in guiding centre radius that stars or star clusters can migrate in a few orbital periods. The standard deviations of guiding centre distributions and maximum migration distances depend on the Toomre or critical wavelength and the contrast in mass surface density caused by spiral structure. Comparison between our simulations and estimated guiding radii for a few young supersolar metallicity open clusters, including NGC 6583, suggests that the contrast in mass surface density in the solar neighbourhood has standard deviation (in the surface density distribution) divided by mean of about 1/4 and larger than measured using COBE data by Drimmel and Spergel. Our estimate is consistent with a standard deviation of ˜0.07 dex in the metallicities measured from high-quality spectroscopic data for 38 young open clusters (<1 Gyr) with mean galactocentric radius 7-9 kpc.

  13. ANALYSIS OF DETACHED ECLIPSING BINARIES NEAR THE TURNOFF OF THE OPEN CLUSTER NGC 7142

    Energy Technology Data Exchange (ETDEWEB)

    Sandquist, Eric L.; Serio, Andrew W.; Orosz, Jerome [San Diego State University, Department of Astronomy, San Diego, CA 92182 (United States); Shetrone, Matthew, E-mail: esandquist@mail.sdsu.edu, E-mail: aserio@gemini.edu, E-mail: jorosz@mail.sdsu.edu, E-mail: shetrone@astro.as.utexas.edu [University of Texas, McDonald Observatory, HC75 Box 1337-L Fort Davis, TX 79734 (United States)

    2013-08-01

    We analyze extensive BVR{sub C}I{sub C} photometry and radial velocity measurements for three double-lined deeply eclipsing binary stars in the field of the old open cluster NGC 7142. The short period (P = 1.9096825 days) detached binary V375 Cep is a high probability cluster member, and has a total eclipse of the secondary star. The characteristics of the primary star (M = 1.288 {+-} 0.017 M{sub Sun }) at the cluster turnoff indicate an age of 3.6 Gyr (with a random uncertainty of 0.25 Gyr), consistent with earlier analysis of the color-magnitude diagram. The secondary star (M = 0.871 {+-} 0.008 M{sub Sun }) is not expected to have evolved significantly, but its radius is more than 10% larger than predicted by models. Because this binary system has a known age, it is useful for testing the idea that radius inflation can occur in short period binaries for stars with significant convective envelopes due to the inhibition of energy transport by magnetic fields. The brighter star in the binary also produces a precision estimate of the distance modulus, independent of reddening estimates: (m - M){sub V} = 12.86 {+-} 0.07. The other two eclipsing binary systems are not cluster members, although one of the systems (V2) could only be conclusively ruled out as a present or former member once the stellar characteristics were determined. That binary is within 0. Degree-Sign 5 of edge-on, is in a fairly long-period eccentric binary, and contains two almost indistinguishable stars. The other binary (V1) has a small but nonzero eccentricity (e = 0.038) in spite of having an orbital period under 5 days.

  14. The CNO Bi-cycle in the Open Cluster NGC 752

    Science.gov (United States)

    Hawkins, Keith; Schuler, S.; King, J.; The, L.

    2011-01-01

    The CNO bi-cycle is the primary energy source for main sequence stars more massive than the sun. To test our understanding of stellar evolution models using the CNO bi-cycle, we have undertaken light-element (CNO) abundance analysis of three main sequence dwarf stars and three red giant stars in the open cluster NGC 752 utilizing high resolution (R 50,000) spectroscopy from the Keck Observatory. Preliminary results indicate, as expected, there is a depletion of carbon in the giants relative to the dwarfs. Additional analysis is needed to determine if the amount of depletion is in line with model predictions, as seen in the Hyades open cluster. Oxygen abundances are derived from the high-excitation O I triplet, and there is a 0.19 dex offset in the [O/H] abundances between the giants and dwarfs which may be explained by non-local thermodynamic equilibrium (NLTE), although further analysis is needed to verify this. The standard procedure for spectroscopically determining stellar parameters used here allows for a measurement of the cluster metallicity, [Fe/H] = 0.04 ± 0.02. In addition to the Fe abundances we have determined Na, Mg, and Al abundances to determine the status of other nucleosynthesis processes. The Na, Mg and Al abundances of the giants are enhanced relative to the dwarfs, which is consistent with similar findings in giants of other open clusters. Support for K. Hawkins was provided by the NOAO/KPNO Research Experiences for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program and the Department of Defense ASSURE program through Scientific Program Order No. 13 (AST-0754223) of the Cooperative Agreement No. AST-0132798 between the Association of Universities for Research in Astronomy (AURA) and the NSF.

  15. Relative Age Dating of Young Star Clusters from YSOVAR

    Science.gov (United States)

    Johnson, Chelen H.; Gibbs, John C.; Linahan, Marcella; Rebull, Luisa; Bernstein, Alexandra E.; Child, Sierra; Eakins, Emma; Elert, Julia T.; Frey, Grace; Gong, Nathaniel; Hedlund, Audrey R.; Karos, Alexandra D.; Medeiros, Emma M.; Moradi, Madeline; Myers, Keenan; Packer, Benjamin M.; Reader, Livia K.; Sorenson, Benjamin; Stefo, James S.; Strid, Grace; Sumner, Joy; Sundeen, Kiera A.; Taylor, Meghan; Ujjainwala, Zakir L.

    2018-01-01

    The YSOVAR (Young Stellar Object VARiability; Rebull et al. 2014) Spitzer Space Telescope observing program monitored a dozen star forming cores in the mid-infrared (3.6 and 4.5 microns). Rebull et al. (2014) placed these cores in relative age order based on numbers of YSO candidates in SED class bins (I, flat, II, III), which is based on the slope of the SED between 2 and 25 microns. PanSTARRS data have recently been released (Chambers et al. 2016); deep optical data are now available over all the YSOVAR clusters. We worked with eight of the YSOVAR targets (IC1396-N, AFGL 490, NGC 1333, Mon R2, GGD 12-15, L 1688, IRAS 20050+2720, and Ceph C) and the YSO candidates identified therein as part of YSOVAR (through their infrared colors or X-ray detections plus a star-like SED; see Rebull et al. 2014). We created and examined optical and NIR color-magnitude diagrams and color-color diagrams of these YSO candidates to determine if the addition of optical data contradicted or reinforced the relative age dating of the clusters obtained with SED class ratios.This project is a collaborative effort of high school students and teachers from three states. We analyzed data individually and later collaborated online to compare results. This project is the result of many years of work with the NASA/IPAC Teacher Archive Research Program (NITARP).

  16. Strömgren uvby photometry of the peculiar globular cluster NGC 2419

    Science.gov (United States)

    Frank, Matthias J.; Koch, Andreas; Feltzing, Sofia; Kacharov, Nikolay; Wilkinson, Mark I.; Irwin, Mike

    2015-09-01

    NGC 2419 is a peculiar Galactic globular cluster offset from the others in the size-luminosity diagram, and showing several chemical abundance anomalies. Here, we present Strömgren uvby photometry of the cluster. Using the gravity- and metallicity-sensitive c1 and m1 indices, we identify a sample of likely cluster members extending well beyond the formal tidal radius. The estimated contamination by cluster non-members is only one per cent, making our catalogue ideally suited for spectroscopic follow-up. We derive photometric [Fe/H] of red giants, and depending on which metallicity calibration from the literature we use, we find reasonable to excellent agreement with spectroscopic [Fe/H], both for the cluster mean metallicity and for individual stars. We demonstrate explicitly that the photometric uncertainties are not Gaussian and this must be accounted for in any analysis of the metallicity distribution function. Using a realistic, non-Gaussian model for the photometric uncertainties, we find a formal internal [Fe/H] spread of σ=0.11+0.02-0.01 dex. This is an upper limit to the cluster's true [Fe/H] spread and may partially, and possibly entirely, reflect the limited precision of the photometric metallicity estimation and systematic effects. The lack of correlation between spectroscopic and photometric [Fe/H] of individual stars is further evidence against a [Fe/H] spread on the 0.1 dex level. Finally, the CN-sensitive δ4, among other colour indices, anti-correlates strongly with magnesium abundance, indicating that the second-generation stars are nitrogen enriched. The absence of similar correlations in some other CN-sensitive indices supports the second generation being enriched in He, which in these indices approximately compensates the shift due to CN. Compared to a single continuous distribution with finite dispersion, the observed δ4 distribution of red giants is slightly better fit by two distinct populations with no internal spread, with the nitrogen

  17. A VST and VISTA study of globular clusters in NGC 253

    Science.gov (United States)

    Cantiello, Michele; Grado, Aniello; Rejkuba, Marina; Arnaboldi, Magda; Capaccioli, Massimo; Greggio, Laura; Iodice, Enrica; Limatola, Luca

    2018-03-01

    Context. Globular clusters (GCs) are key to our understanding of the Universe, as laboratories of stellar evolution, fossil tracers of the past formation epoch of the host galaxy, and effective distance indicators from local to cosmological scales. Aim. We analyze the properties of the sources in the NGC 253 with the aim of defining an up to date catalog of GC candidates in the galaxy. Given the distance of the galaxy, GCs in NGC 253 are ideal targets for resolved color-magnitude diagram studies of extragalactic GCs with next-generation diffraction limited ground-based telescopes. Methods: Our analysis is based on the science verification data of two ESO survey telescopes, VST and VISTA. Using ugri photometry from VST and JKs from VISTA, GC candidates were selected using as reference the morpho-photometric and color properties of spectroscopically confirmed GCs available in the literature. The strength of the results was verified against available archival HST/ACS data from the GHOSTS survey: all but two of the selected GC candidates appear as star clusters in HST footprints. Results: The adopted GC selection leads to the definition of a sample of ˜350 GC candidates. At visual inspection, we find that 82 objects match all the requirements for selecting GC candidates and 155 are flagged as uncertain GC candidate; however, 110 are unlikely GCs, which are most likely background galaxies. Furthermore, our analysis shows that four of the previously spectroscopically confirmed GCs, i.e., ˜20% of the total spectroscopic sample, are more likely either background galaxies or high-velocity Milky Way stars. The radial density profile of the selected best candidates shows the typically observed r1/4-law radial profile. The analysis of the color distributions reveals only marginal evidence of the presence of color bimodality, which is normally observed in galaxies of similar luminosity. The GC luminosity function does not show the typical symmetry, mainly because of the lack

  18. DEEP CHANDRA OBSERVATIONS OF NGC 1404: CLUSTER PLASMA PHYSICS REVEALED BY AN INFALLING EARLY-TYPE GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Su, Yuanyuan; Kraft, Ralph P.; Nulsen, Paul; Forman, William R.; Randall, Scott W.; Jones, Christine; Machacek, Marie E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Roediger, Elke [E.A. Milne Centre for Astrophysics, Department of Physics and Mathematics, University of Hull, Hull, HU6 7RX (United Kingdom); Churazov, Eugene, E-mail: yuanyuan.su@cfa.harvard.edu [Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741, Garching (Germany)

    2017-01-01

    The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped as it falls through the ICM of the Fornax Cluster. We use the new Chandra X-ray observations of NGC 1404 to study ICM microphysics. The interstellar medium of NGC 1404 is characterized by a sharp leading edge, 8 kpc from the Galaxy center, and a short downstream gaseous tail. Contact discontinuities are resolved on unprecedented spatial scales (0.″5 = 45 pc) due to the combination of the proximity of NGC 1404, the superb spatial resolution of Chandra , and the very deep (670 ks) exposure. At the leading edge, we observe sub-kiloparsec-scale eddies generated by Kelvin–Helmholtz instability (KHI) and put an upper limit of 5% Spitzer on the isotropic viscosity of the hot cluster plasma. We also observe mixing between the hot cluster gas and the cooler galaxy gas in the downstream stripped tail, which provides further evidence of a low viscosity plasma. The assumed ordered magnetic fields in the ICM ought to be smaller than 5 μ G to allow KHI to develop. The lack of an evident magnetic draping layer just outside the contact edge is consistent with such an upper limit.

  19. Young star clusters in nearby molecular clouds

    Science.gov (United States)

    Getman, K. V.; Kuhn, M. A.; Feigelson, E. D.; Broos, P. S.; Bate, M. R.; Garmire, G. P.

    2018-06-01

    The SFiNCs (Star Formation in Nearby Clouds) project is an X-ray/infrared study of the young stellar populations in 22 star-forming regions with distances ≲ 1 kpc designed to extend our earlier MYStIX (Massive Young Star-Forming Complex Study in Infrared and X-ray) survey of more distant clusters. Our central goal is to give empirical constraints on cluster formation mechanisms. Using parametric mixture models applied homogeneously to the catalogue of SFiNCs young stars, we identify 52 SFiNCs clusters and 19 unclustered stellar structures. The procedure gives cluster properties including location, population, morphology, association with molecular clouds, absorption, age (AgeJX), and infrared spectral energy distribution (SED) slope. Absorption, SED slope, and AgeJX are age indicators. SFiNCs clusters are examined individually, and collectively with MYStIX clusters, to give the following results. (1) SFiNCs is dominated by smaller, younger, and more heavily obscured clusters than MYStIX. (2) SFiNCs cloud-associated clusters have the high ellipticities aligned with their host molecular filaments indicating morphology inherited from their parental clouds. (3) The effect of cluster expansion is evident from the radius-age, radius-absorption, and radius-SED correlations. Core radii increase dramatically from ˜0.08 to ˜0.9 pc over the age range 1-3.5 Myr. Inferred gas removal time-scales are longer than 1 Myr. (4) Rich, spatially distributed stellar populations are present in SFiNCs clouds representing early generations of star formation. An appendix compares the performance of the mixture models and non-parametric minimum spanning tree to identify clusters. This work is a foundation for future SFiNCs/MYStIX studies including disc longevity, age gradients, and dynamical modelling.

  20. THE UNUSUAL X-RAY BINARIES OF THE GLOBULAR CLUSTER NGC 6652

    International Nuclear Information System (INIS)

    Coomber, G.; Heinke, C. O.; Cohn, H. N.; Lugger, P. M.; Grindlay, J. E.

    2011-01-01

    Our 5 ks Chandra ACIS-S observation of the globular cluster NGC 6652 detected seven X-ray sources, three of which were previously unidentified. This cluster hosts a well-known bright low-mass X-ray binary, source A (or XB 1832-330). Source B shows unusual rapid flaring variability, with an average L X (0.5-10 keV) ∼2 x 10 34 erg s -1 , but with minutes-long flares up to L X = 9 x 10 34 erg s -1 . Its spectrum can be fit by an absorbed power law of photon index Γ ∼ 1.24 and hardens as the count rate decreases. This suggests that part or all of the variation might be due to obscuration by the rim of a highly inclined accretion disk. Sources C and D, with L X ∼ 10 33 erg s -1 , have soft and unusual spectra. Source C requires a very soft component, with a spectrum peaking at 0.5 keV, which might be the hot polar cap of a magnetically accreting polar cataclysmic variable. Source D shows a soft spectrum (fit by a power law of photon index ∼2.3) with marginal evidence for an emission line around 1 keV; its nature is unclear. The faint new sources E, F, and G have luminosities of 1-2 x 10 32 erg s -1 , if associated with the cluster (which is likely). E and F have relatively hard spectra (consistent with power laws with photon index ∼1.5). G lacks soft photons, suggesting absorption with N H > 10 22 cm -2 .

  1. Uncovering multiple populations with washington photometry. I. The globular cluster NGC 1851

    Energy Technology Data Exchange (ETDEWEB)

    Cummings, Jeffrey D.; Geisler, D.; Villanova, S. [Departamento de Astronomía, Casilla 160-C, Universidad de Concepción (Chile); Carraro, G. [ESO, Alonso de Cordova 3107, Casilla 19001, Santiago de Chile (Chile)

    2014-08-01

    The analysis of multiple populations (MPs) in globular clusters (GCs) has become a forefront area of research in astronomy. Multiple red giant branches (RGBs), subgiant branches (SGBs), and even main sequences (MSs) have now been observed photometrically in many GCs, while broad abundance distributions of certain elements have been detected spectroscopically in most, if not all, GCs. UV photometry has been crucial in discovering and analyzing these MPs, but the Johnson U and the Stromgren and Sloan u filters that have generally been used are relatively inefficient and very sensitive to reddening and atmospheric extinction. In contrast, the Washington C filter is much broader and redder than these competing UV filters, making it far more efficient at detecting MPs and much less sensitive to reddening and extinction. Here, we investigate the use of the Washington system to uncover MPs using only a 1 m telescope. Our analysis of the well-studied GC NGC 1851 finds that the C filter is both very efficient and effective at detecting its previously discovered MPs in the RGB and SGB. Remarkably, we have also detected an intrinsically broad MS best characterized by two distinct but heavily overlapping populations that cannot be explained by binaries, field stars, or photometric errors. The MS distribution is in very good agreement with that seen on the RGB, with ∼30% of the stars belonging to the second population. There is also evidence for two sequences in the red horizontal branch, but this appears to be unrelated to the MPs in this cluster. Neither of these latter phenomena have been observed previously in this cluster. The redder MS stars are also more centrally concentrated than the blue MS. This is the first time MPs in an MS have been discovered from the ground, and using only a 1 m telescope. The Washington system thus proves to be a very powerful tool for investigating MPs, and holds particular promise for extragalactic objects where photons are limited.

  2. The Globular Cluster NGC 2419: A Crucible for Theories of Gravity

    Science.gov (United States)

    Ibata, R.; Sollima, A.; Nipoti, C.; Bellazzini, M.; Chapman, S. C.; Dalessandro, E.

    2011-09-01

    We present the analysis of a kinematic data set of stars in the globular cluster NGC 2419, taken with the DEep Imaging Multi-Object Spectrograph at the Keck II telescope. Combined with a reanalysis of deep Hubble Space Telescope and Subaru Telescope imaging data, which provide an accurate luminosity profile of the cluster, we investigate the validity of a large set of dynamical models of the system, which are checked for stability via N-body simulations. We find that isotropic models in either Newtonian or Modified Newtonian Dynamics (MOND) are ruled out with extremely high confidence. However, a simple Michie model in Newtonian gravity with anisotropic velocity dispersion provides an excellent representation of the luminosity profile and kinematics of the cluster. The anisotropy profiles of these models ensure an isotropic center to the cluster, which progresses to extreme radial anisotropy toward the outskirts. In contrast, with MOND we find that Michie models that reproduce the luminosity profile either overpredict the velocity dispersion on the outskirts of the cluster if the mass-to-light ratio (M/L) is kept at astrophysically motivated values or else they underpredict the central velocity dispersion if the M/L is taken to be very small. We find that the best Michie model in MOND is a factor of ~104 less likely than the Newtonian model that best fits the system. A likelihood ratio of 350 is found when we investigate more general models by solving the Jeans equation with a Markov Chain Monte Carlo scheme. We verified with N-body simulations that these results are not significantly different when the MOND external field effect is accounted for. If the assumptions that the cluster is in dynamical equilibrium, spherical, not on a peculiar orbit, and possesses a single dynamical tracer population of constant M/L are correct, we conclude that the present observations provide a very severe challenge for MOND. Some of the data presented herein were obtained at the W

  3. NGC6819

    DEFF Research Database (Denmark)

    Handberg, R.; Brogaard, K.; Miglio, A.

    2017-01-01

    We present an extensive peakbagging effort on Kepler data of similar to 50 red giant stars in the open star cluster NGC6819. By employing sophisticated pre-processing of the time series and Markov chain Monte Carlo techniques we extracted individual frequencies, heights and line widths for hundre...

  4. Tidal radii of the globular clusters M 5, M 12, M 13, M 15, M 53, NGC 5053 and NGC 5466 from automated star counts.

    Science.gov (United States)

    Lehmann, I.; Scholz, R.-D.

    1997-04-01

    We present new tidal radii for seven Galactic globular clusters using the method of automated star counts on Schmidt plates of the Tautenburg, Palomar and UK telescopes. The plates were fully scanned with the APM system in Cambridge (UK). Special account was given to a reliable background subtraction and the correction of crowding effects in the central cluster region. For the latter we used a new kind of crowding correction based on a statistical approach to the distribution of stellar images and the luminosity function of the cluster stars in the uncrowded area. The star counts were correlated with surface brightness profiles of different authors to obtain complete projected density profiles of the globular clusters. Fitting an empirical density law (King 1962) we derived the following structural parameters: tidal radius r_t_, core radius r_c_ and concentration parameter c. In the cases of NGC 5466, M 5, M 12, M 13 and M 15 we found an indication for a tidal tail around these objects (cf. Grillmair et al. 1995).

  5. JHK photometric study of the variable interstellar extinction in the direction of open star cluster NGC 654

    International Nuclear Information System (INIS)

    Sagar, Ram; Qianzhong Yu

    1989-01-01

    JHK magnitudes have been determined for 18 stars in the field of NGC 654. Study of the interstellar extinction law in the cluster direction indicates an anomalous distribution of interstellar grains causing more extinction in U and B pass-bands compared to that obtained from the colour excesses E(V-J), E(V-H) and E(V-K) using a normal reddening law. This implies a small shift in the grain-size distribution towards smaller than normal sized particles. Patchy distribution of interstellar matter seems to be responsible for the non-uniform extinction in the cluster region. (author)

  6. Ages and chemical compositions of massive globular clusters in NGC147 and M31

    Science.gov (United States)

    Sharina, Margarita; Shimansky, Vladislav

    2015-08-01

    We present estimates of ages, [Fe/H], helium contents (Y) and abundances of C, N, Mg, Ca, Ti, Cr, Mn, Co and Ni for the following globular clusters (GCs): 7 in NGC147, and Mayall II, Mackey 1 and Mackey 6 in M31. Medium-resolution integrated-light spectra of the GCs were conducted with the 6m telescope. To derive the ages and abundances for the GCs we carried out their population synthesis using model stellar atmospheres, the Padova YZVAR isochrones and the Chabrier mass function. We compare the results with the corresponding data obtained using the same method for several massive Galactic GCs. We show that the differences in the Mg and C abundances between GCs with similar ages and metallicities may reach 0.5-0.6 dex. The corresponding differences for other elements are usually ˜2-3 times smaller. We suggest that at least partially the detected differences may be due to Mg and C abundance variations in the atmospheres of high-luminosity red giant branch stars as a consequence of the transportation of the produced elements to the surface layers.

  7. Ages and chemical compositions of massive clusters in NGC147 and M31

    Science.gov (United States)

    Sharina, Margarita; Shimansky, Vladislav

    2017-03-01

    We present estimates of ages, [Fe/H], helium content (Y) and abundances of C, N, Mg, Ca, and several other elements for the following globular clusters (GCs): GC7 in NGC147, and Mayall II, Mackey 1 and Mackey 6 in M31. Medium-resolution integrated-light spectra of the GCs were conducted with the 6m telescope. To derive the ages and abundances for the GCs we carried out their population synthesis using model stellar atmospheres, the Padova YZVAR isochrones and the Chabrier mass function. We compare the results with the corresponding data obtained using the same method for several massive Galactic GCs. We show that the differences in the light-element abundances between GCs with similar ages and metallicities may reach 0.5-0.6 dex. The corresponding differences for other elements are usually 2-3 times smaller. We suggest that at least partially the detected differences may be due to light-element abundance variations in the atmospheres of high-luminosity red giant branch stars as a consequence of the transportation of the produced elements to the surface layers.

  8. Comparative study of dust and young stars in three small galaxies

    International Nuclear Information System (INIS)

    Price, J.S.

    1984-01-01

    A comparative study is presented of dust and young stars in the central regions of the three small galaxies NGC 205, NGC 185, and NGC 3077 in the U, B, V, and K filters, and at six additional optical wavelengths. All three program galaxies have been successfully modeled with the empirical models of Oemler (1976); NGC 205 and NGC 3077 were also modeled with unsharp mask models. Subtracting model galaxies from the data enabled the authors to isolate clusters of young stars and dust clouds in the central regions of each galaxy. A comparison of the colors of the young clusters in NGC 3077 and those in NGC 205 reveals that the colors of the clusters in these two small galaxies are different. In NGC 185, diffuse emission after subtracting an Oemler model was discovered. NGC 205 also showed this remnant emission, with very similar colors to those of the remnant in NGC 185, but NGC 3077 did not. The colors of this diffuse remnant emission in NGC 205 and NGC 185 are interpreted as being due to previous episodes of star formation in the two dwarf ellipticals. A comparison of the author's data with that of Caldwell (1983) on a sample of 33 dwarf elliptical galaxies in Virgo indicates that star formation in dwarf elliptical galaxies is a common phenomenon. The study of dust in NGC 185 and NGC 205 at optical wavelengths shows that the properties of dust in NGC 205 are very similar to those of galactic dust, while the dust in NGC 185 is distinctly different. The optical and 2.2 micron centers of NGC 3077 are found to be different. From comparison of the three galaxies studied here, the author concludes that it is unlikely that NGC 205 and NGC 185 tidally interacted with M31

  9. A search for extra-solar planetary transits in the field of open cluster NGC 6819

    Science.gov (United States)

    Street, Rachel Amanda

    The technique of searching for extra-solar planetary transits is investigated. This technique, which relies on detecting the brief, shallow eclipses caused by planets passing across the line of sight to the primary star, requires high-precision time-series photometry of large numbers of stars in order to detect these statistically rare events. Observations of 18000 stars in the field including the intermediate-age open cluster NGC 6819 are presented. This target field constrasts with the stellar environment surveyed by the radial velocity technique, which concentrates on the Solar neighbourhood. I present the data-reduction techniques used to obtain high-precision photometry in a semi-automated fashion for tens of thousands of stars at a time, together with an algorithm designed to search the resulting lightcurves for the transit signatures of hot Jupiter type planets. I describe simulations designed to test the detection efficiency of this algorithm and, for comparison, predict the number of transits expected from this data, assuming that hot Jupiter planets similar to HD 209458 are as common in the field of NGC 6819 as they are in the Solar neighbourhood. While no planetary transits have yet been identified, the detection of several very low amplitude eclipses by stellar companions demonstrates the effectiveness of the method. This study also indicates that stellar activity and particularly blending are significant causes of false detections. A useful additional consequence of studying this time-series photometry is the census it provides of some of the variable stars in the field. I report on the discovery of a variety of newly-discovered variables, including Algol-type detached eclipsing binaries which are likely to consist of M-dwarf stars. Further study of these stars is strongly recommended in order to help constrain models of stellar structure at the very low mass end. I conclude with a summary of this work in the context of other efforts being made in this

  10. CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

    International Nuclear Information System (INIS)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2016-01-01

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  11. Chemical Abundances in NGC 5024 (M53): A Mostly First Generation Globular Cluster

    Science.gov (United States)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico

    2016-06-01

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = -2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na-O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  12. CHEMICAL ABUNDANCES IN NGC 5024 (M53): A MOSTLY FIRST GENERATION GLOBULAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Boberg, Owen M.; Friel, Eileen D.; Vesperini, Enrico [Astronomy Department, Indiana University, Bloomington, IN 47405 (United States)

    2016-06-10

    We present the Fe, Ca, Ti, Ni, Ba, Na, and O abundances for a sample of 53 red giant branch stars in the globular cluster (GC) NGC 5024 (M53). The abundances were measured from high signal-to-noise medium resolution spectra collected with the Hydra multi-object spectrograph on the Wisconsin–Indiana–Yale–NOAO 3.5 m telescope. M53 is of interest because previous studies based on the morphology of the cluster’s horizontal branch suggested that it might be composed primarily of first generation (FG) stars and differ from the majority of other GCs with multiple populations, which have been found to be dominated by the second generation (SG) stars. Our sample has an average [Fe/H] = −2.07 with a standard deviation of 0.07 dex. This value is consistent with previously published results. The alpha-element abundances in our sample are also consistent with the trends seen in Milky Way halo stars at similar metallicities, with enhanced [Ca/Fe] and [Ti/Fe] relative to solar. We find that the Na–O anti-correlation in M53 is not as extended as other GCs with similar masses and metallicities. The ratio of SG to the total number of stars in our sample is approximately 0.27 and the SG generation is more centrally concentrated. These findings further support that M53 might be a mostly FG cluster and could give further insight into how GCs formed the light element abundance patterns we observe in them today.

  13. HOW TO FIND YOUNG MASSIVE CLUSTER PROGENITORS

    Energy Technology Data Exchange (ETDEWEB)

    Bressert, E.; Longmore, S.; Testi, L. [European Southern Observatory, Karl Schwarzschild Str. 2, D-85748 Garching bei Muenchen (Germany); Ginsburg, A.; Bally, J.; Battersby, C. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309 (United States)

    2012-10-20

    We propose that bound, young massive stellar clusters form from dense clouds that have escape speeds greater than the sound speed in photo-ionized gas. In these clumps, radiative feedback in the form of gas ionization is bottled up, enabling star formation to proceed to sufficiently high efficiency so that the resulting star cluster remains bound even after gas removal. We estimate the observable properties of the massive proto-clusters (MPCs) for existing Galactic plane surveys and suggest how they may be sought in recent and upcoming extragalactic observations. These surveys will potentially provide a significant sample of MPC candidates that will allow us to better understand extreme star-formation and massive cluster formation in the Local Universe.

  14. A Long-Period Totally Eclipsing Binary Star at the Turnoff of the Open Cluster NGC 6819 Discovered with Kepler

    DEFF Research Database (Denmark)

    Sandquist, Eric L.; Mathieu, Robert D.; Brogaard, Karsten

    2012-01-01

    We present the discovery of the totally eclipsing long-period (P = 771.8 d) binary system WOCS 23009 in the old open cluster NGC 6819 that contains both an evolved star near central hydrogen exhaustion and a low-mass (0.45 Msun) star. This system was previously known to be a single-lined spectros......We present the discovery of the totally eclipsing long-period (P = 771.8 d) binary system WOCS 23009 in the old open cluster NGC 6819 that contains both an evolved star near central hydrogen exhaustion and a low-mass (0.45 Msun) star. This system was previously known to be a single......-lined spectroscopic binary, but the discovery of an eclipse near apastron using data from the Kepler space telescope makes it clear that the system has an inclination that is very close to 90 degrees. Although the secondary star has not been identified in spectra, the mass of the primary star can be constrained using...... other eclipsing binaries in the cluster. The combination of total eclipses and a mass constraint for the primary star allows us to determine a reliable mass for the secondary star and radii for both stars, and to constrain the cluster age. Unlike well-measured stars of similar mass in field binaries...

  15. THE UNIQUE Na:O ABUNDANCE DISTRIBUTION IN NGC 6791: THE FIRST OPEN(?) CLUSTER WITH MULTIPLE POPULATIONS

    International Nuclear Information System (INIS)

    Geisler, D.; Villanova, S.; Cummings, J.; Carraro, G.; Pilachowski, C.; Johnson, C. I.; Bresolin, F.

    2012-01-01

    Almost all globular clusters investigated exhibit a spread in their light element abundances, the most studied being an Na:O anticorrelation. In contrast, open clusters show a homogeneous composition and are still regarded as Simple Stellar Populations. The most probable reason for this difference is that globulars had an initial mass high enough to retain primordial gas and ejecta from the first stellar generation and thus formed a second generation with a distinct composition, an initial mass exceeding that of open clusters. NGC 6791 is a massive open cluster and warrants a detailed search for chemical inhomogeneities. We collected high-resolution, high signal-to-noise spectra of 21 members covering a wide range of evolutionary status and measured their Na, O, and Fe content. We found [Fe/H] = +0.42 ± 0.01, in good agreement with previous values, and no evidence for a spread. However, the Na:O distribution is completely unprecedented. It becomes the first open cluster to show intrinsic abundance variations that cannot be explained by mixing, and thus the first discovered to host multiple populations. It is also the first star cluster to exhibit two subpopulations in the Na:O diagram with one being chemically homogeneous while the second has an intrinsic spread that follows the anticorrelation so far displayed only by globular clusters. NGC 6791 is unique in many aspects, displaying certain characteristics typical of open clusters, others more reminiscent of globulars, and yet others, in particular its Na:O behavior investigated here, that are totally unprecedented. It clearly had a complex and fascinating history.

  16. The Unique Na:O Abundance Distribution in NGC 6791: The First Open(?) Cluster with Multiple Populations

    Science.gov (United States)

    Geisler, D.; Villanova, S.; Carraro, G.; Pilachowski, C.; Cummings, J.; Johnson, C. I.; Bresolin, F.

    2012-09-01

    Almost all globular clusters investigated exhibit a spread in their light element abundances, the most studied being an Na:O anticorrelation. In contrast, open clusters show a homogeneous composition and are still regarded as Simple Stellar Populations. The most probable reason for this difference is that globulars had an initial mass high enough to retain primordial gas and ejecta from the first stellar generation and thus formed a second generation with a distinct composition, an initial mass exceeding that of open clusters. NGC 6791 is a massive open cluster and warrants a detailed search for chemical inhomogeneities. We collected high-resolution, high signal-to-noise spectra of 21 members covering a wide range of evolutionary status and measured their Na, O, and Fe content. We found [Fe/H] = +0.42 ± 0.01, in good agreement with previous values, and no evidence for a spread. However, the Na:O distribution is completely unprecedented. It becomes the first open cluster to show intrinsic abundance variations that cannot be explained by mixing, and thus the first discovered to host multiple populations. It is also the first star cluster to exhibit two subpopulations in the Na:O diagram with one being chemically homogeneous while the second has an intrinsic spread that follows the anticorrelation so far displayed only by globular clusters. NGC 6791 is unique in many aspects, displaying certain characteristics typical of open clusters, others more reminiscent of globulars, and yet others, in particular its Na:O behavior investigated here, that are totally unprecedented. It clearly had a complex and fascinating history.

  17. NGC 2782: A Merger Remnant with Young Stars in its Gaseous Tidal Tail

    Science.gov (United States)

    Torres-Flores, S.; de Oliveira, C. Mendes; de Mello, D. F.; Scarano, S. Jr.; Urrutia-Viscarra, R.

    2012-01-01

    We have searched for young star-forming regions around the merger remnant NGC 2782. By using GALEX FUV and NUV imaging and HI data we found seven UV sources, located at distances greater than 26 kpc from the center of NGG 2782, and coinciding with its western HI tidal tail. These regions were resolved in several smaller systems when Gemini/GMOS r-band images were used. We compared the observed colors to stellar population synthesis models and we found that these objects have ages of l to ll11yr and masses ranging from 10(exp 3.9) to l0(exp 4.6) Solar Mass. By using Gemini/GMOS spectroscopic data we confirm memberships and derive high metallicities for three of the young regions in the tail (12+log(O/H)=8.74+/-0.20, 8.81+/-0.20 and 8.78+/-0.20). These metallicities are similar to the value presented by the nuclear region of NGG 2782 and also similar to the value presented for an object located close to the main body of NGG 2782. The high metallicities measured for the star-forming regions in the gaseous tidal tail of NGG 2782 could be explained if they were formed out of highly enriched gas which was once expelled from the center of the merging galaxies when the system collided. An additional possibility is that the tail has been a nursery of a few generations of young stellar systems which ultimately polluted this medium with metals, further enriching the already pre-enriched gas ejected to the tail when the galaxies collided.

  18. THE YOUNG OPEN CLUSTER BERKELEY 55

    Energy Technology Data Exchange (ETDEWEB)

    Negueruela, Ignacio; Marco, Amparo, E-mail: ignacio.negueruela@ua.es, E-mail: amparo.marco@ua.es [Departamento de Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Apdo. 99, E-03080 Alicante (Spain)

    2012-02-15

    We present UBV photometry of the highly reddened and poorly studied open cluster Berkeley 55, revealing an important population of B-type stars and several evolved stars of high luminosity. Intermediate-resolution far-red spectra of several candidate members confirm the presence of one F-type supergiant and six late supergiants or bright giants. The brightest blue stars are mid-B giants. Spectroscopic and photometric analyses indicate an age 50 {+-} 10 Myr. The cluster is located at a distance d Almost-Equal-To 4 kpc, consistent with other tracers of the Perseus Arm in this direction. Berkeley 55 is thus a moderately young open cluster with a sizable population of candidate red (super)giant members, which can provide valuable information about the evolution of intermediate-mass stars.

  19. Stellar Variability at the Main-sequence Turnoff of the Intermediate-age LMC Cluster NGC 1846

    Science.gov (United States)

    Salinas, R.; Pajkos, M. A.; Vivas, A. K.; Strader, J.; Contreras Ramos, R.

    2018-04-01

    Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of δ Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single δ Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of δ Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its δ Sct population. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  20. New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55

    Science.gov (United States)

    Lohr, M. E.; Negueruela, I.; Tabernero, H. M.; Clark, J. S.; Lewis, F.; Roche, P.

    2018-05-01

    As part of a wider investigation of evolved massive stars in Galactic open clusters, we have spectroscopically identified three candidate classical Cepheids in the little-studied clusters Berkeley 51, Berkeley 55 and NGC 6603. Using new multi-epoch photometry, we confirm that Be 51 #162 and Be 55 #107 are bona fide Cepheids, with pulsation periods of 9.83±0.01 d and 5.850±0.005 d respectively, while NGC 6603 star W2249 does not show significant photometric variability. Using the period-luminosity relationship for Cepheid variables, we determine a distance to Be 51 of 5.3^{+1.0}_{-0.8} kpc and an age of 44^{+9}_{-8} Myr, placing it in a sparsely-attested region of the Perseus arm. For Be 55, we find a distance of 2.2±0.3 kpc and age of 63^{+12}_{-11} Myr, locating the cluster in the Local arm. Taken together with our recent discovery of a long-period Cepheid in the starburst cluster VdBH222, these represent an important increase in the number of young, massive Cepheids known in Galactic open clusters. We also consider new Gaia (data release 2) parallaxes and proper motions for members of Be 51 and Be 55; the uncertainties on the parallaxes do not allow us to refine our distance estimates to these clusters, but the well-constrained proper motion measurements furnish further confirmation of cluster membership. However, future final Gaia parallaxes for such objects should provide valuable independent distance measurements, improving the calibration of the period-luminosity relationship, with implications for the distance ladder out to cosmological scales.

  1. EXPLANATION OF A SPECIAL COLOR–MAGNITUDE DIAGRAM OF STAR CLUSTER NGC 1651 FROM DIFFERENT MODELS

    International Nuclear Information System (INIS)

    Li, Zhongmu; Mao, Caiyan; Chen, Li

    2015-01-01

    The color–magnitude diagram (CMD) of globular cluster NGC 1651 has special structures including a broad main sequence, an extended main sequence turn-off, and an extended red giant clump. The reason for such a special CMD remains unclear. In order to test the difference among the results from various stellar population assumptions, we study a high-quality CMD of NGC 1651 from the Hubble Space Telescope archive using eight kinds of models. Distance modulus, extinction, age ranges, star formation mode, fraction of binaries, and fraction of rotational stars are determined and then compared. The results show that stellar populations both with and without age spread can reproduce the special structure of the observed CMD. A composite population with extended star formation from 1.8 Gyrs ago to 1.4 Gyrs ago, which contains 50% binaries and 70% rotational stars, fits the observed CMD best. Meanwhile, a 1.5 Gyr-old simple population that consists of rotational stars can also fit the observed CMD well. The results of CMD fitting are shown to depend strongly on stellar population type (simple or composite), and fraction of rotators. If the member stars of NGC 1651 formed in a single star burst, the effect of stellar rotation should be very important for explaining the observed CMDs. Otherwise, the effect may be small. It is also possible that the special observed CMD is a result of the combined effects of stellar binarity, rotation, and age spread. Therefore, further work on stellar population type and fraction of rotational stars of intermediate-age clusters are necessary to understand their observed CMDs

  2. Seeing Red in NGC 1978, NGC 55, and NGC 3109

    Science.gov (United States)

    Davidge, T. J.

    2018-04-01

    Spectra of the intermediate-age star cluster NGC 1978 and the dwarf irregular galaxies NGC 55 and NGC 3109 are discussed. The spectra were recorded with the Gemini Multi-object Spectrograph on Gemini South and span the 0.7–1.1 μm wavelength interval. Five slit pointings were observed in NGC 1978, and these are used to examine stochastic effects on the integrated red light from an intermediate-age cluster. The removal of either the brightest M giant or the brightest C star from the co-added spectrum has minor effects on the equivalent withs of the Ca triplet. The most robust signature of C stars in the integrated cluster spectrum at these wavelengths is the CN band head near 7900 Å. The equivalent widths of Ca triplet lines in the NGC 1978 spectrum and in the spectra of individual cluster stars are larger than expected for a scaled-solar abundance system. It is suggested that these stars have a lower than expected surface gravity, which might occur if the stars in NGC 1978 have been subject to extra mixing processes, as suggested by Lederer et al. The near-infrared color profile of NGC 1978 is shown to contain a prominent red cusp in the central 10 arcsec, and the suppression of light from this cusp does not affect the depth of the Ca lines in the integrated spectrum. The NGC 55 spectra run parallel to the major axis, and a gradient is found in the strength of the Ca lines, in the sense that the Ca lines weaken with increasing distance from the disk plane. Comparisons with models suggest that the disk light is dominated by stars with ages 1–2 Gyr, in agreement with star-forming histories (SFHs) obtained from the analysis of color–magnitude diagrams (CMDs). The NGC 55 spectra also sample a large star-forming complex. The age of this complex inferred from comparisons with models is broadly consistent with that estimated from a near-infrared CMD of the same region. The CN band head at 7900 Å in this part of NGC 55 is detected, but this is likely a signature of

  3. Suicide clusters among young Kenyan men.

    Science.gov (United States)

    Goodman, Michael L; Puffer, Eve S; Keiser, Philip H; Gitari, Stanley

    2017-11-01

    Suicide is a leading cause of global mortality. Suicide clusters have recently been identified among peer networks in high-income countries. This study investigates dynamics of suicide clustering within social networks of young Kenya men ( n = 532; 18-34 years). We found a strong, statistically significant association between reported number of friends who previously attempted suicide and present suicide ideation (odds ratio = 1.9; 95% confidence interval (1.42, 2.54); p self-esteem (23% of total effect). Meaning in life further mediated the association between collective self-esteem and suicide ideation. Survivors of peer suicide should be evaluated for suicide risk.

  4. THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS. III. A QUINTUPLE STELLAR POPULATION IN NGC 2808

    International Nuclear Information System (INIS)

    Milone, A. P.; Marino, A. F.; Jerjen, H.; Piotto, G.; Renzini, A.; Bedin, L. R.; Anderson, J.; Bellini, A.; Cassisi, S.; Pietrinferni, A.; D’Antona, F.; Ventura, P.

    2015-01-01

    In this study we present the first results from multi-wavelength Hubble Space Telescope (HST) observations of the Galactic globular cluster (GC) NGC 2808 as an extension of the Hubble Space Telescope UV Legacy Survey of Galactic GCs (GO-13297 and previous proprietary and HST archive data). Our analysis allowed us to disclose a multiple-stellar-population phenomenon in NGC 2808 even more complex than previously thought. We have separated at least five different populations along the main sequence and the red giant branch (RGB), which we name A, B, C, D, and E (though an even finer subdivision may be suggested by the data). We identified the RGB bump in four out of the five RGBs. To explore the origin of this complex color–magnitude diagram, we have combined our multi-wavelength HST photometry with synthetic spectra, generated by assuming different chemical compositions. The comparison of observed colors with synthetic spectra suggests that the five stellar populations have different contents of light elements and helium. Specifically, if we assume that NGC 2808 is homogeneous in [Fe/H] (as suggested by spectroscopy for Populations B, C, D, E, but lacking for Population A) and that population A has a primordial helium abundance, we find that populations B, C, D, E are enhanced in helium by ΔY ∼ 0.03, 0.03, 0.08, 0.13, respectively. We obtain similar results by comparing the magnitude of the RGB bumps with models. Planned spectroscopic observations will test whether Population A also has the same metallicity, or whether its photometric differences with Population B can be ascribed to small [Fe/H] and [O/H] differences rather than to helium

  5. The mond external field effect on the dynamics of the globular clusters: general considerations and application to NGC 2419

    Energy Technology Data Exchange (ETDEWEB)

    Derakhshani, Kamran, E-mail: kderakhshani@iasbs.ac.ir [Institute for Advanced Studies in Basic Sciences, P. O. Box 45195-1159 Zanjan (Iran, Islamic Republic of)

    2014-03-01

    In this paper, we investigate the external field effect in the context of the MOdified Newtonian Dynamics (MOND) on the surface brightness and velocity dispersion profiles of globular clusters (GCs). Using N-MODY, which is an N-body simulation code with a MOND potential solver, we show that the general effect of the external field for diffuse clusters, which obey MOND in most of their parts, is that it pushes the dynamics toward the Newtonian regime. On the other hand, for more compact clusters, which are essentially Newtonian in their inner parts, the external field is effective mainly in the outer parts of compact clusters. As a case study, we then choose the remote Galactic GC NGC 2419. By varying the cluster mass, half-light radius, and mass-to-light ratio, we aim to find a model that will reproduce the observational data most effectively, using N-MODY. We find that even if we take the Galactic external field into account, a Newtonian Plummer sphere represents the observational data better than MOND to an order of magnitude in terms of the total χ{sup 2} of surface brightness and velocity dispersion.

  6. The mond external field effect on the dynamics of the globular clusters: general considerations and application to NGC 2419

    International Nuclear Information System (INIS)

    Derakhshani, Kamran

    2014-01-01

    In this paper, we investigate the external field effect in the context of the MOdified Newtonian Dynamics (MOND) on the surface brightness and velocity dispersion profiles of globular clusters (GCs). Using N-MODY, which is an N-body simulation code with a MOND potential solver, we show that the general effect of the external field for diffuse clusters, which obey MOND in most of their parts, is that it pushes the dynamics toward the Newtonian regime. On the other hand, for more compact clusters, which are essentially Newtonian in their inner parts, the external field is effective mainly in the outer parts of compact clusters. As a case study, we then choose the remote Galactic GC NGC 2419. By varying the cluster mass, half-light radius, and mass-to-light ratio, we aim to find a model that will reproduce the observational data most effectively, using N-MODY. We find that even if we take the Galactic external field into account, a Newtonian Plummer sphere represents the observational data better than MOND to an order of magnitude in terms of the total χ 2 of surface brightness and velocity dispersion.

  7. TIME-SERIES PHOTOMETRY OF GLOBULAR CLUSTERS: M62 (NGC 6266), THE MOST RR LYRAE-RICH GLOBULAR CLUSTER IN THE GALAXY?

    International Nuclear Information System (INIS)

    Contreras, R.; Catelan, M.; Smith, H. A.; Kuehn, C. A.; Pritzl, B. J.; Borissova, J.

    2010-01-01

    We present new time-series CCD photometry, in the B and V bands, for the moderately metal-rich ([Fe/H] ≅ -1.3) Galactic globular cluster M62 (NGC 6266). The present data set is the largest obtained so far for this cluster and consists of 168 images per filter, obtained with the Warsaw 1.3 m telescope at the Las Campanas Observatory and the 1.3 m telescope of the Cerro Tololo Inter-American Observatory, in two separate runs over the time span of 3 months. The procedure adopted to detect the variable stars was the optimal image subtraction method (ISIS v2.2), as implemented by Alard. The photometry was performed using both ISIS and Stetson's DAOPHOT/ALLFRAME package. We have identified 245 variable stars in the cluster fields that have been analyzed so far, of which 179 are new discoveries. Of these variables, 133 are fundamental mode RR Lyrae stars (RRab), 76 are first overtone (RRc) pulsators, 4 are type II Cepheids, 25 are long-period variables (LPVs), 1 is an eclipsing binary, and 6 are not yet well classified. Such a large number of RR Lyrae stars places M62 among the top two most RR Lyrae-rich (in the sense of total number of RR Lyrae stars present) globular clusters known in the Galaxy, second only to M3 (NGC 5272) with a total of 230 known RR Lyrae stars. Since this study covers most but not all of the cluster area, it is not unlikely that M62 is in fact the most RR Lyrae-rich globular cluster in the Galaxy. In like vein, thanks to the time coverage of our data sets, we were also able to detect the largest sample of LPVs known so far in a Galactic globular cluster. We analyze a variety of Oosterhoff type indicators for the cluster, including mean periods, period distribution, Bailey diagrams, and Fourier decomposition parameters (as well as the physical parameters derived therefrom). All of these indicators clearly show that M62 is an Oosterhoff type I system. This is in good agreement with the moderately high metallicity of the cluster, in spite of its

  8. Robo-AO Discovery and Basic Characterization of Wide Multiple Star Systems in the Pleiades, Praesepe, and NGC 2264 Clusters

    Science.gov (United States)

    Hillenbrand, Lynne A.; Zhang, Celia; Riddle, Reed L.; Baranec, Christoph; Ziegler, Carl; Law, Nicholas M.; Stauffer, John

    2018-02-01

    We identify and roughly characterize 66 candidate binary star systems in the Pleiades, Praesepe, and NGC 2264 star clusters, based on robotic adaptive optics imaging data obtained using Robo-AO at the Palomar 60″ telescope. Only ∼10% of our imaged pairs were previously known. We detect companions at red optical wavelengths, with physical separations ranging from a few tens to a few thousands of au. A three-sigma contrast curve generated for each final image provides upper limits to the brightness ratios for any undetected putative companions. The observations are sensitive to companions with a maximum contrast of ∼6m at larger separations. At smaller separations, the mean (best) raw contrast at 2″ is 3.ͫ8 (6m), at 1″ is 3.ͫ0 (4.ͫ5), and at 0.″5 is 1.ͫ9 (3m). Point-spread function subtraction can recover nearly the full contrast in the closer separations. For detected candidate binary pairs, we report separations, position angles, and relative magnitudes. Theoretical isochrones appropriate to the Pleiades and Praesepe clusters are then used to determine the corresponding binary mass ratios, which range from 0.2 to 0.9 in q={m}2/{m}1. For our sample of roughly solar-mass (FGK type) stars in NGC 2264 and sub-solar-mass (K and early M-type) primaries in the Pleiades and Praesepe, the overall binary frequency is measured at ∼15.5% ± 2%. However, this value should be considered a lower limit to the true binary fraction within the specified separation and mass ratio ranges in these clusters, given that complex and uncertain corrections for sensitivity and completeness have not been applied.

  9. VizieR Online Data Catalog: Globular cluster candidates in NGC4258 (Gonzalez-Lopezlira+, 2017)

    Science.gov (United States)

    Gonzalez-Lopezlira, R. A.; Lomeli-Nunez, L.; Alamo-Martinez, K.; Ordenes-Briceno, Y.; Loinard, L.; Georgiev, I. Y.; Munoz, R. P.; Puzia, T. H.; Bruzual, G. A.; Gwyn, S.

    2017-08-01

    All data for the present work were obtained with the Canada-France-Hawaii-Telescope (CFHT). The optical images of NGC 4258 are all archival, and were acquired with MegaCam. Images were originally secured through programs 08BH55, 09AH42, 09AH98, 09BH95 (P.I. E. Magnier, u*-band); 09AC04 (P.I. R. Lasker, u* and i' filters); 10AT01 (P.I. C. Ngeow, g', r', and i' bands), and 11AC08 (P.I. G. Harris, g' and i' data) spanning 2008 Dec to 2011 Mar. The Ks-band images of NGC 4258 were acquired on 2013 March 27 UT, through proposal 13AC98 (P.I. R. Gonzalez-Lopezlira), with the Wide-field InfraRed Camera (WIRCam). (2 data files).

  10. Globular clusters and planetary nebulae kinematics and X-ray emission in the early-type galaxy NGC 5128

    Directory of Open Access Journals (Sweden)

    Samurović S.

    2006-01-01

    Full Text Available The estimates of the mass of the galaxy NGC 5128 based on the different mass tracers, globular clusters (GCs and planetary nebulae (PNe, are presented. These estimates are compared with the estimate based on the X-ray methodology and it is found that the results for the mass (and mass-to-light ratio for all three approaches are in very good agreement interior to 25 arcmin; beyond 25 arcmin the X-rays predict the mass which is too high with respect to the one found using GCs and PNe. Some possible explanations for this discrepancy were discussed. The Jeans equation is also solved and its predictions for the velocity dispersion are then compared with the observed values, which extend to ~8 effective radii in the case of the GCs and ~15 effective radii in the case of the PNe. It is found that interior to ~25 arcmin (~5 effective radii dark matter does not dominate because the total mass-to-light ratio in the B band in solar units is less than 10. Based on the GCs and PNe beyond ~25 arcmin the total mass-to-light ratio increases to ~14 (at ~80 arcmin which indicates the existence of dark matter in the outer regions of NGC 5128.

  11. CHEMODYNAMICS OF COMPACT STELLAR SYSTEMS IN NGC 5128: HOW SIMILAR ARE GLOBULAR CLUSTERS, ULTRA-COMPACT DWARFS, AND DWARF GALAXIES?

    International Nuclear Information System (INIS)

    Taylor, Matthew A.; Puzia, Thomas H.; Harris, Gretchen L.; Harris, William E.; Kissler-Patig, Markus; Hilker, Michael

    2010-01-01

    Velocity dispersion measurements are presented for several of the most luminous globular clusters (GCs) in NGC 5128 (Centaurus A) derived from high-resolution spectra obtained with the UVES echelle spectrograph on the 8.2 m ESO/Very Large Telescope. The measurements are made utilizing a penalized pixel-fitting method that parametrically recovers line-of-sight velocity dispersions. Combining the measured velocity dispersions with surface photometry and structural parameter data from the Hubble Space Telescope enables both dynamical masses and mass-to-light ratios to be derived. The properties of these massive stellar systems are similar to those of both massive GCs contained within the Local Group and nuclear star clusters and ultra-compact dwarf galaxies (UCDs). The fundamental plane relations of these clusters are investigated in order to fill the apparent gap between the relations of Local Group GCs and more massive early-type galaxies. It is found that the properties of these massive stellar systems match those of nuclear clusters in dwarf elliptical galaxies and UCDs better than those of Local Group GCs, and that all objects share similarly old (∼>8 Gyr) ages, suggesting a possible link between the formation and evolution of nuclear star clusters in dwarf elliptical galaxies (dE,Ns), UCDs, and massive GCs. We find a very steep correlation between dynamical mass-to-light ratio and dynamical mass of the form Υ V dyn ∝ M dyn 0.24±0.02 above M dyn ∼ 2x10 6 M sun . Formation scenarios are investigated with a chemical abundance analysis using absorption-line strengths calibrated to the Lick/IDS index system. The results lend support to two scenarios contained within a single general formation scheme. Old, massive, super-solar [α/Fe] systems are formed on short (∼ 13 -10 15 M sun potential wells of massive galaxies and galaxy clusters.

  12. Legacy ExtraGalactic UV Survey with The Hubble Space Telescope: Stellar Cluster Catalogs and First Insights Into Cluster Formation and Evolution in NGC 628

    NARCIS (Netherlands)

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

    2017-01-01

    We report the large effort that is producing comprehensive high-level young star cluster (YSC) catalogs for a significant fraction of galaxies observed with the Legacy ExtraGalactic UV Survey (LEGUS) Hubble treasury program. We present the methodology developed to extract cluster positions, verify

  13. Accretion-induced luminosity spreads in young clusters: evidence from stellar rotation

    Science.gov (United States)

    Littlefair, S. P.; Naylor, Tim; Mayne, N. J.; Saunders, Eric; Jeffries, R. D.

    2011-05-01

    We present an analysis of the rotation of young stars in the associations Cepheus OB3b, NGC 2264, 2362 and the Orion Nebula Cluster (ONC). We discover a correlation between rotation rate and position in a colour-magnitude diagram (CMD) such that stars which lie above an empirically determined median pre-main sequence rotate more rapidly than stars which lie below this sequence. The same correlation is seen, with a high degree of statistical significance, in each association studied here. If position within the CMD is interpreted as being due to genuine age spreads within a cluster, then the stars above the median pre-main sequence would be the youngest stars. This would in turn imply that the most rapidly rotating stars in an association are the youngest, and hence those with the largest moments of inertia and highest likelihood of ongoing accretion. Such a result does not fit naturally into the existing picture of angular momentum evolution in young stars, where the stars are braked effectively by their accretion discs until the disc disperses. Instead, we argue that, for a given association of young stars, position within the CMD is not primarily a function of age, but of accretion history. We show that this hypothesis could explain the correlation we observe between rotation rate and position within the CMD.

  14. A new method for measuring metallicities of young super star clusters

    International Nuclear Information System (INIS)

    Gazak, J. Zachary; Kudritzki, Rolf; Bresolin, Fabio; Davies, Ben; Bastian, Nate; Bergemann, Maria; Plez, Bertrand; Evans, Chris; Patrick, Lee; Schinnerer, Eva

    2014-01-01

    We demonstrate how the metallicities of young super star clusters (SSC) can be measured using novel spectroscopic techniques in the J-band. The near-infrared flux of SSCs older than ∼6 Myr is dominated by tens to hundreds of red supergiant stars. Our technique is designed to harness the integrated light of that population and produces accurate metallicities for new observations in galaxies above (M83) and below (NGC 6946) solar metallicity. In M83 we find [Z] = +0.28 ± 0.14 dex using a moderate resolution (R ∼ 3500) J-band spectrum and in NGC 6496 we report [Z] = -0.32 ± 0.20 dex from a low resolution spectrum of R ∼ 1800. Recently commissioned low resolution multiplexed spectrographs on the Very Large Telescope (KMOS) and Keck (MOSFIRE) will allow accurate measurements of SSC metallicities across the disks of star-forming galaxies up to distances of 70 Mpc with single night observation campaigns using the method presented in this paper.

  15. On the Chemical Abundances of Miras in Clusters: V1 in the Metal-rich Globular NGC 5927

    Science.gov (United States)

    D’Orazi, V.; Magurno, D.; Bono, G.; Matsunaga, N.; Braga, V. F.; Elgueta, S. S.; Fukue, K.; Hamano, S.; Inno, L.; Kobayashi, N.; Kondo, S.; Monelli, M.; Nonino, M.; Przybilla, N.; Sameshima, H.; Saviane, I.; Taniguchi, D.; Thevenin, F.; Urbaneja-Perez, M.; Watase, A.; Arai, A.; Bergemann, M.; Buonanno, R.; Dall’Ora, M.; Da Silva, R.; Fabrizio, M.; Ferraro, I.; Fiorentino, G.; Francois, P.; Gilmozzi, R.; Iannicola, G.; Ikeda, Y.; Jian, M.; Kawakita, H.; Kudritzki, R. P.; Lemasle, B.; Marengo, M.; Marinoni, S.; Martínez-Vázquez, C. E.; Minniti, D.; Neeley, J.; Otsubo, S.; Prieto, J. L.; Proxauf, B.; Romaniello, M.; Sanna, N.; Sneden, C.; Takenaka, K.; Tsujimoto, T.; Valenti, E.; Yasui, C.; Yoshikawa, T.; Zoccali, M.

    2018-03-01

    We present the first spectroscopic abundance determination of iron, α-elements (Si, Ca, and Ti), and sodium for the Mira variable V1 in the metal-rich globular cluster NGC 5927. We use high-resolution (R ∼ 28,000), high signal-to-noise ratio (∼200) spectra collected with WINERED, a near-infrared (NIR) spectrograph covering simultaneously the wavelength range 0.91–1.35 μm. The effective temperature and the surface gravity at the pulsation phase of the spectroscopic observation were estimated using both optical (V) and NIR time-series photometric data. We found that the Mira is metal-rich ([Fe/H] = ‑0.55 ± 0.15) and moderately α-enhanced ([α/Fe] = 0.15 ± 0.01, σ = 0.2). These values agree quite well with the mean cluster abundances based on high-resolution optical spectra of several cluster red giants available in the literature ([Fe/H] = ‑ 0.47 ± 0.06, [α/Fe] = + 0.24 ± 0.05). We also found a Na abundance of +0.35 ± 0.20 that is higher than the mean cluster abundance based on optical spectra (+0.18 ± 0.13). However, the lack of similar spectra for cluster red giants and that of corrections for departures from local thermodynamical equilibrium prevents us from establishing whether the difference is intrinsic or connected with multiple populations. These findings indicate a strong similarity between optical and NIR metallicity scales in spite of the difference in the experimental equipment, data analysis, and in the adopted spectroscopic diagnostics. Based on spectra collected with the WINERED spectrograph available as a visitor instrument at the ESO New Technology Telescope (NTT), La Silla, Chile (ESO Proposal: 098.D-0878(A), PI: G. Bono).

  16. CHEMICAL ABUNDANCE EVIDENCE OF ENDURING HIGH STAR FORMATION RATES IN AN EARLY-TYPE GALAXY: HIGH [Ca/Fe] IN NGC 5128 GLOBULAR CLUSTERS

    International Nuclear Information System (INIS)

    Colucci, Janet E.; Durán, María Fernanda; Bernstein, Rebecca A.; McWilliam, Andrew

    2013-01-01

    We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high-resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high-resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between –1.6 and –0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H] <–0.4 is +0.37 ± 0.07, while the average [Ca/Fe] in our Milky Way (MW) and M31 GC samples is +0.29 ± 0.09 and +0.24 ± 0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the MW or M31. This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the MW. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope

  17. CHEMICAL ABUNDANCE EVIDENCE OF ENDURING HIGH STAR FORMATION RATES IN AN EARLY-TYPE GALAXY: HIGH [Ca/Fe] IN NGC 5128 GLOBULAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Colucci, Janet E.; Duran, Maria Fernanda; Bernstein, Rebecca A. [Department of Astronomy and Astrophysics, 1156 High Street, UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); McWilliam, Andrew, E-mail: jcolucci@ucolick.org [Observatories of the Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States)

    2013-08-20

    We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high-resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high-resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between -1.6 and -0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H] <-0.4 is +0.37 {+-} 0.07, while the average [Ca/Fe] in our Milky Way (MW) and M31 GC samples is +0.29 {+-} 0.09 and +0.24 {+-} 0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the MW or M31. This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the MW. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope.

  18. Chemical Abundance Evidence of Enduring High Star Formation Rates in an Early-type Galaxy: High [Ca/Fe] in NGC 5128 Globular Clusters

    Science.gov (United States)

    Colucci, Janet E.; Fernanda Durán, María; Bernstein, Rebecca A.; McWilliam, Andrew

    2013-08-01

    We present [Fe/H], ages, and Ca abundances for an initial sample of 10 globular clusters in NGC 5128 obtained from high-resolution, high signal-to-noise ratio echelle spectra of their integrated light. All abundances and ages are obtained using our original technique for high-resolution integrated light abundance analysis of globular clusters. The clusters have a range in [Fe/H] between -1.6 and -0.2. In this sample, the average [Ca/Fe] for clusters with [Fe/H] <-0.4 is +0.37 ± 0.07, while the average [Ca/Fe] in our Milky Way (MW) and M31 GC samples is +0.29 ± 0.09 and +0.24 ± 0.10, respectively. This may imply a more rapid chemical enrichment history for NGC 5128 than for either the MW or M31. This sample provides the first quantitative picture of the chemical history of NGC 5128 that is directly comparable to what is available for the MW. Data presented here were obtained with the MIKE echelle spectrograph on the Magellan Clay Telescope. This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  19. THE SNAPSHOT HUBBLE U-BAND CLUSTER SURVEY (SHUCS). I. SURVEY DESCRIPTION AND FIRST APPLICATION TO THE MIXED STAR CLUSTER POPULATION OF NGC 4041

    Energy Technology Data Exchange (ETDEWEB)

    Konstantopoulos, I. S. [Australian Astronomical Observatory, P.O. Box 915, North Ryde NSW 1670 (Australia); Smith, L. J. [Space Telescope Science Institute and European Space Agency, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Adamo, A. [Max-Planck-Institut for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Silva-Villa, E. [Departement de Physique, de Genie Physique et d' Optique, and Centre de Recherche en Astrophysique du Quebec (CRAQ), Universite Laval, Quebec (Canada); Gallagher, J. S.; Ryon, J. E. [Department of Astronomy, University of Wisconsin-Madison, 5534 Sterling, 475 North Charter Street, Madison WI 53706 (United States); Bastian, N. [Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead, CH41 1LD (United Kingdom); Westmoquette, M. S. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); Zackrisson, E. [Department of Astronomy, Stockholm University, Oscar Klein Centre, AlbaNova, Stockholm SE-106 91 (Sweden); Larsen, S. S. [Department of Astrophysics/IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Weisz, D. R. [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Charlton, J. C., E-mail: iraklis@aao.gov.au [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2013-05-15

    We present the Snapshot Hubble U-band Cluster Survey (SHUCS), a project aimed at characterizing the star cluster populations of 10 nearby galaxies (d < 23 Mpc, half within Almost-Equal-To 12 Mpc) through new F336W (U-band equivalent) imaging from Wide Field Camera 3, and archival BVI-equivalent data with the Hubble Space Telescope. Completing the UBVI baseline reduces the age-extinction degeneracy of optical colors, thus enabling the measurement of reliable ages and masses for the thousands of clusters covered by our survey. The sample consists chiefly of face-on spiral galaxies at low inclination, in various degrees of isolation (isolated, in group, merging), and includes two active galactic nucleus hosts. This first paper outlines the survey itself, the observational datasets, the analysis methods, and presents a proof-of-concept study of the large-scale properties and star cluster population of NGC 4041, a massive SAbc galaxy at a distance of Almost-Equal-To 23 Mpc, and part of a small grouping of six giant members. We resolve two structural components with distinct stellar populations, a morphology more akin to merging and interacting systems. We also find strong evidence of a truncated, Schechter-type mass function, and a similarly segmented luminosity function. These results indicate that binning must erase much of the substructure present in the mass and luminosity functions, and might account for the conflicting reports on the intrinsic shape of these functions in the literature. We also note a tidal feature in the outskirts of the galaxy in Galaxy Evolution Explorer UV imaging, and follow it up with a comprehensive multi-wavelength study of NGC 4041 and its parent group. We deduce a minor merger as a likely cause of its segmented structure and the observed pattern of a radially decreasing star formation rate. We propose that combining the study of star cluster populations with broadband metrics is not only advantageous, but often easily achievable thorough

  20. DETERMINING THE AGE OF THE KEPLER OPEN CLUSTER NGC 6819 WITH A NEW TRIPLE SYSTEM AND OTHER ECLIPSING BINARY STARS

    International Nuclear Information System (INIS)

    Brewer, Lauren N.; Sandquist, Eric L.; Jeffries, Mark W. Jr.; Orosz, Jerome A.

    2016-01-01

    As part of our study of the old (∼2.5 Gyr) open cluster NGC 6819 in the Kepler field, we present photometric (Kepler and ground-based BVR C I C ) and spectroscopic observations of the detached eclipsing binary WOCS 24009 (Auner 665; KIC 5023948) with a short orbital period of 3.6 days. WOCS 24009 is a triple-lined system, and we verify that the brightest star is physically orbiting the eclipsing binary using radial velocities and eclipse timing variations. The eclipsing binary components have masses M B  = 1.090 ± 0.010 M ⊙ and M C  = 1.075 ± 0.013 M ⊙ , and radii R B  = 1.099 ± 0.006 ± 0.005 R ⊙ and R C  = 1.069 ± 0.006 ± 0.013 R ⊙ . The bright non-eclipsing star resides at the cluster turnoff, and ultimately its mass will directly constrain the turnoff mass: our preliminary determination is M A  = 1.251 ± 0.057 M ⊙ . A careful examination of the light curves indicates that the fainter star in the eclipsing binary undergoes a very brief period of total eclipse, which enables us to precisely decompose the light of the three stars and place them in the color–magnitude diagram (CMD). We also present improved analysis of two previously discussed detached eclipsing stars in NGC 6819 (WOCS 40007 and WOCS 23009) en route to a combined determination of the cluster’s distance modulus (m − M) V  = 12.38 ± 0.04. Because this paper significantly increases the number of measured stars in the cluster, we can better constrain the age of the CMD to be 2.21 ± 0.10 ± 0.20 Gyr. Additionally, using all measured eclipsing binary star masses and radii, we constrain the age to 2.38 ± 0.05 ± 0.22 Gyr. The quoted uncertainties are estimates of measurement and systematic uncertainties (due to model physics differences and metal content), respectively

  1. Interstellar Extinction in 20 Open Star Clusters

    Science.gov (United States)

    Rangwal, Geeta; Yadav, R. K. S.; Durgapal, Alok K.; Bisht, D.

    2017-12-01

    The interstellar extinction law in 20 open star clusters namely, Berkeley 7, Collinder 69, Hogg 10, NGC 2362, Czernik 43, NGC 6530, NGC 6871, Bochum 10, Haffner 18, IC 4996, NGC 2384, NGC 6193, NGC 6618, NGC 7160, Collinder 232, Haffner 19, NGC 2401, NGC 6231, NGC 6823, and NGC 7380 have been studied in the optical and near-IR wavelength ranges. The difference between maximum and minimum values of E(B - V) indicates the presence of non-uniform extinction in all the clusters except Collinder 69, NGC 2362, and NGC 2384. The colour excess ratios are consistent with a normal extinction law for the clusters NGC 6823, Haffner 18, Haffner 19, NGC 7160, NGC 6193, NGC 2401, NGC 2384, NGC 6871, NGC 7380, Berkeley 7, Collinder 69, and IC 4996. We have found that the differential colour-excess ΔE(B - V), which may be due to the occurrence of dust and gas inside the clusters, decreases with the age of the clusters. A spatial variation of colour excess is found in NGC 6193 in the sense that it decreases from east to west in the cluster region. For the clusters Berkeley 7, NGC 7380, and NGC 6871, a dependence of colour excess E(B - V) with spectral class and luminosity is observed. Eight stars in Collinder 232, four stars in NGC 6530, and one star in NGC 6231 have excess flux in near-IR. This indicates that these stars may have circumstellar material around them.

  2. H.E.S.S. OBSERVATIONS OF THE GLOBULAR CLUSTERS NGC 6388 AND M15 AND SEARCH FOR A DARK MATTER SIGNAL

    International Nuclear Information System (INIS)

    Abramowski, A.; Acero, F.; Aharonian, F.; Bernloehr, K.; Bochow, A.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Brucker, J.; Barnacka, A.; Barres de Almeida, U.; Bazer-Bachi, A. R.; Borrel, V.; Becherini, Y.; Becker, J.; Behera, B.; Boisson, C.; Bolmont, J.; Bordas, P.

    2011-01-01

    Observations of the globular clusters (GCs) NGC 6388 and M15 were carried out by the High Energy Stereoscopic System array of Cherenkov telescopes for a live time of 27.2 and 15.2 hr, respectively. No gamma-ray signal is found at the nominal target position of NGC 6388 and M15. In the primordial formation scenario, GCs are formed in a dark matter (DM) halo and DM could still be present in the baryon-dominated environment of GCs. This opens the possibility of observing a DM self-annihilation signal. The DM content of the GCs NGC 6388 and M15 is modeled taking into account the astrophysical processes that can be expected to influence the DM distribution during the evolution of the GC: the adiabatic contraction of DM by baryons, the adiabatic growth of a black hole in the DM halo, and the kinetic heating of DM by stars. Ninety-five percent confidence level exclusion limits on the DM particle velocity-weighted annihilation cross section are derived for these DM halos. In the TeV range, the limits on the velocity-weighted annihilation cross section are derived at the 10 -25 cm 3 s -1 level and a few 10 -24 cm 3 s -1 for NGC 6388 and M15, respectively.

  3. Intracluster age gradients in numerous young stellar clusters

    Science.gov (United States)

    Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Bate, M. R.; Broos, P. S.; Garmire, G. P.

    2018-05-01

    The pace and pattern of star formation leading to rich young stellar clusters is quite uncertain. In this context, we analyse the spatial distribution of ages within 19 young (median t ≲ 3 Myr on the Siess et al. time-scale), morphologically simple, isolated, and relatively rich stellar clusters. Our analysis is based on young stellar object (YSO) samples from the Massive Young Star-Forming Complex Study in Infrared and X-ray and Star Formation in Nearby Clouds surveys, and a new estimator of pre-main sequence (PMS) stellar ages, AgeJX, derived from X-ray and near-infrared photometric data. Median cluster ages are computed within four annular subregions of the clusters. We confirm and extend the earlier result of Getman et al. (2014): 80 per cent of the clusters show age trends where stars in cluster cores are younger than in outer regions. Our cluster stacking analyses establish the existence of an age gradient to high statistical significance in several ways. Time-scales vary with the choice of PMS evolutionary model; the inferred median age gradient across the studied clusters ranges from 0.75 to 1.5 Myr pc-1. The empirical finding reported in the present study - late or continuing formation of stars in the cores of star clusters with older stars dispersed in the outer regions - has a strong foundation with other observational studies and with the astrophysical models like the global hierarchical collapse model of Vázquez-Semadeni et al.

  4. INFRARED OBSERVATIONAL MANIFESTATIONS OF YOUNG DUSTY SUPER STAR CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-González, Sergio; Tenorio-Tagle, Guillermo; Silich, Sergiy, E-mail: sergiomtz@inaoep.mx [Instituto Nacional de Astrofísica Óptica y Electrónica, AP 51, 72000 Puebla (Mexico)

    2016-01-01

    The growing evidence pointing at core-collapse supernovae as large dust producers makes young massive stellar clusters ideal laboratories to study the evolution of dust immersed in a hot plasma. Here we address the stochastic injection of dust by supernovae, and follow its evolution due to thermal sputtering within the hot and dense plasma generated by young stellar clusters. Under these considerations, dust grains are heated by means of random collisions with gas particles which result in the appearance of  infrared spectral signatures. We present time-dependent infrared spectral energy distributions that are to be expected from young stellar clusters. Our results are based on hydrodynamic calculations that account for the stochastic injection of dust by supernovae. These also consider gas and dust radiative cooling, stochastic dust temperature fluctuations, the exit of dust grains out of the cluster volume due to the cluster wind, and a time-dependent grain size distribution.

  5. INFRARED OBSERVATIONAL MANIFESTATIONS OF YOUNG DUSTY SUPER STAR CLUSTERS

    International Nuclear Information System (INIS)

    Martínez-González, Sergio; Tenorio-Tagle, Guillermo; Silich, Sergiy

    2016-01-01

    The growing evidence pointing at core-collapse supernovae as large dust producers makes young massive stellar clusters ideal laboratories to study the evolution of dust immersed in a hot plasma. Here we address the stochastic injection of dust by supernovae, and follow its evolution due to thermal sputtering within the hot and dense plasma generated by young stellar clusters. Under these considerations, dust grains are heated by means of random collisions with gas particles which result in the appearance of  infrared spectral signatures. We present time-dependent infrared spectral energy distributions that are to be expected from young stellar clusters. Our results are based on hydrodynamic calculations that account for the stochastic injection of dust by supernovae. These also consider gas and dust radiative cooling, stochastic dust temperature fluctuations, the exit of dust grains out of the cluster volume due to the cluster wind, and a time-dependent grain size distribution

  6. PROBING THE LOWER MASS LIMIT FOR SUPERNOVA PROGENITORS AND THE HIGH-MASS END OF THE INITIAL-FINAL MASS RELATION FROM WHITE DWARFS IN THE OPEN CLUSTER M35 (NGC 2168)

    International Nuclear Information System (INIS)

    Williams, Kurtis A.; Bolte, Michael; Koester, Detlev

    2009-01-01

    We present a photometric and spectroscopic study of the white dwarf (WD) population of the populous, intermediate-age open cluster M35 (NGC 2168); this study expands upon our previous study of the WDs in this cluster. We spectroscopically confirm 14 WDs in the field of the cluster: 12 DAs, 1 hot DQ, and 1 DB star. For each DA, we determine the WD mass and cooling age, from which we derive each star's progenitor mass. These data are then added to the empirical initial-final mass relation (IFMR), where the M35 WDs contribute significantly to the high-mass end of the relation. The resulting points are consistent with previously published linear fits to the IFMR, modulo moderate systematics introduced by the uncertainty in the star cluster age. Based on this cluster alone, the observational lower limit on the maximum mass of WD progenitors is found to be ∼5.1 M sun - 5.2 M sun at the 95% confidence level; including data from other young open clusters raises this limit to as high as 7.1 M sun , depending on the cluster membership of three massive WDs and the core composition of the most massive WDs. We find that the apparent distance modulus and extinction derived solely from the cluster WDs ((m - M) V = 10.45 ± 0.08 and E(B-V) = 0.185 ± 0.010, respectively) is fully consistent with that derived from main-sequence fitting techniques. Four M35 WDs may be massive enough to have oxygen-neon cores; the assumed core composition does not significantly affect the empirical IFMR. Finally, the two non-DA WDs in M35 are photometrically consistent with cluster membership; further analysis is required to determine their memberships.

  7. New Portraits of Spiral Galaxies NGC 613, NGC 1792 and NGC 3627

    Science.gov (United States)

    2003-12-01

    Not so long ago, the real nature of the "spiral nebulae", spiral-shaped objects observed in the sky through telescopes, was still unknown. This long-standing issue was finally settled in 1924 when the famous American astronomer Edwin Hubble provided conclusive evidence that they are located outside our own galaxy and are in fact "island universes" of their own. Nowadays, we know that the Milky Way is just one of billions of galaxies in the Universe. They come in vastly different shapes - spiral, elliptical, irregular - and many of them are simply beautiful, especially the spiral ones. Astronomers Mark Neeser from the Universitäts-Sternwarte München (Germany) and Peter Barthel from the Kapteyn Institute in Groningen (The Netherlands) were clearly not insensitive to this when they obtained images of three beautiful spiral galaxies with ESO's Very Large Telescope (VLT). They did this in twilight during the early morning when they had to stop their normal observing programme, searching for very distant and faint quasars. The resulting colour images ( ESO PR Photos 33a-c/03 ) were produced by combining several CCD images in three different wavebands from the FORS multi-mode instruments. The three galaxies are known as NGC 613, NGC 1792 and NGC 3627 . They are characterized by strong far-infrared, as well as radio emission, indicative of substantial ongoing star-formation activity. Indeed, these images all display prominent dust as well as features related to young stars, clear signs of intensive star-formation. NGC 613 ESO PR Photo 33a/03 ESO PR Photo 33a/03 [Preview - JPEG: 470 x 400 pix - 25k] [Normal - JPEG: 939 x 800 pix - 416k] [Full Res - JPEG: 2702 x 2301 pix - 3.4M] PR Photo 33a/03 of the barred spiral galaxy NGC 613 was obtained with the FORS1 and FORS2 multi-mode instruments (at VLT MELIPAL and YEPUN, respectively) on December 16-18, 2001. It is a composite of three exposures in different wavebands, cf. the technical note below. The full-resolution version

  8. Dynamic Young Stars and their Disks: A Temporal View of NGC 2264 with Spitzer and CoRoT*

    Directory of Open Access Journals (Sweden)

    Cody Ann Marie

    2014-01-01

    Full Text Available Variability is a signature feature of young stars. Among the well known light curve phenomena are periodic variations attributed to surface spots and irregular changes associated with accretion or circumstellar disk material. While decades of photometric monitoring have provided a framework for classifying young star variability, we still know surprisingly little about its underlying mechanisms and connections to the surrounding disks. In the past few years, dedicated photometric monitoring campaigns from the ground and space have revolutionized our view of young stars in the time domain. We present a selection of optical and infrared time series from several recent campaigns, highlighting the Coordinated Synoptic Investigation of NGC 2264 (“CSI 2264”– a joint30-day effort with the Spitzer, CoRoT, and MOST telescopes. The extraordinary photometric precision, high cadence, and long time baseline of these observations is now enabling correlation of variability properties at very different wavelengths, corresponding to locations from the stellar surface to the inner 0.1 AU of the disk. We present some results of the CSI 2264 program, including new classes of optical/infrared behavior. Further efforts to tie observed variability features to physical models will provide insights into the inner disk environment at a time when planet formation may be underway.

  9. CCD photometry of NGC 2419

    International Nuclear Information System (INIS)

    Christian, C.A.; Heasley, J.N.

    1988-01-01

    The properties of the globular cluster NGC 2419 are reexamined using CCD photometry deepened to the vicinity of the main-sequence turnoff. A new color-magnitude diagram is derived that extends to V = 24.5 mag. It is concluded that NGC 2419 is an outer-halo analog of the metal-poor globulars closer to the Galactic center. NGC 2419 is probably nearly the same age as M15 and differs only slightly, if at all, in metallicity. NGC 2419 has many similarities with the clusters NGC 5466, M15, and M92. Comparison of the data with the isochrones of VandenBerg and Bell (1985) implies a distance modulus of 20.1 with Delta (B-V) = 0.18 mag. Oxygen-rich models can be fit to the data; such a comparison yields a lower limit to the acceptable distance modulus of the cluster. 26 references

  10. Photometric studies of two W UMa type variables in the field of distant open cluster NGC 6866

    International Nuclear Information System (INIS)

    Joshi, Yogesh Chandra; Joshi, Santosh; Jagirdar, Rukmini

    2016-01-01

    We present photometric analysis of the two W UMa type binaries identified in the field of distant open star cluster NGC 6866. Although these systems, namely ID487 and ID494, were reported by Joshi et al., a detailed study of these stars has not been carried out before. The orbital periods of these stars are found to be 0.415110±0.000001 day and 0.366709±0.000004 day, respectively. Based on the photometric and infrared colors, we find their respective spectral types to be K0 and K3. The photometric light variations of both stars show the O'Connell effect which can be explained by employing a dark spot on the secondary components. The V and I band light curves are analyzed using the Wilson-Devinney (WD) code and relations given by Gazeas which yield radii and masses for the binary components of star ID487 of R 1 = 1.24 ± 0.01 R ⊙ , R 2 = 1.11 ± 0.02 R ⊙ , and M 1 = 1.24 ± 0.02 M ⊙ , M 2 = 0.96 ± 0.05 M ⊙ and for star ID494 of R 1 = 1.22±0.02R ⊙ , R 2 = 0.81±0.01 R ⊙ , and M 1 = 1.20±0.06 M ⊙ , M 2 = 0.47±0.01 M ⊙ . (paper)

  11. C-M diagram and luminosity function of the Galactic globular cluster NGC 7099. I. Photographic photometry

    International Nuclear Information System (INIS)

    Piotto, G.; Rosino, L.; Capaccioli, M.; Ortolani, S.; Alcaino, G.; Osservatorio Astronomico, Padua, Italy; Ministerio de Educacion de Chile, Instituto Isaac Newton, Santiago)

    1987-01-01

    New photographic photometry of about 4400 stars in the field of the Galactic globular cluster NGC 7099 = M30 is presented. A C-M diagram and a luminosity function are obtained from this photometry. The distance modulus is estimated at 14.5 + or - 0.5 assuming V(HB) = 15.11 + or - 0.10 and E(B-V) = 0.03 + or - 0.03. The metallicity is (Fe/H) = 1.9 + or - 0.3 based on the dereddened color index (B-V)0,g = 0.71 + or - 0.03. The theoretical isochrones of VandenBerg and Bell (1985) give a better fit to the observations assuming (Fe/H) = -1.8, (m-M)V = 14.6, and E(B-V) = 0.02. A fair fit is also obtained using isochrones of low iron content with an oxygen enhancement of 0.7. From the fit, an age of 17 + or - 4 Gyr is deduced. 41 references

  12. A Young Star Cluster in the Leo a Galaxy

    Directory of Open Access Journals (Sweden)

    Stonkutė R.

    2015-09-01

    Full Text Available We report a serendipitous discovery of a star cluster in the dwarf irregular galaxy Leo A. Young age (~28 Myr and low mass (~510 M⊙ estimates are based on the isochrone fit assuming a metallicity derived for HII regions (Z = 0.0007. The color-magnitude diagrams of the stars, located in and around the cluster area, and the results of aperture photometry of the cluster itself are presented.

  13. FOREST Unbiased Galactic plane Imaging survey with the Nobeyama 45 m telescope (FUGIN). III. Possible evidence for formation of NGC 6618 cluster in M 17 by cloud-cloud collision

    Science.gov (United States)

    Nishimura, Atsushi; Minamidani, Tetsuhiro; Umemoto, Tomofumi; Fujita, Shinji; Matsuo, Mitsuhiro; Hattori, Yusuke; Kohno, Mikito; Yamagishi, Mitsuyoshi; Tsuda, Yuya; Kuriki, Mika; Kuno, Nario; Torii, Kazufumi; Tsutsumi, Daichi; Okawa, Kazuki; Sano, Hidetoshi; Tachihara, Kengo; Ohama, Akio; Fukui, Yasuo

    2018-05-01

    We present 12CO (J = 1-0), 13CO (J = 1-0), and C18O (J = 1-0) images of the M 17 giant molecular clouds obtained as part of the FUGIN (FOREST Ultra-wide Galactic Plane Survey In Nobeyama) project. The observations cover the entire area of the M 17 SW and M 17 N clouds at the highest angular resolution (˜19″) to date, which corresponds to ˜0.18 pc at the distance of 2.0 kpc. We find that the region consists of four different velocity components: a very low velocity (VLV) clump, a low velocity component (LVC), a main velocity component (MVC), and a high velocity component (HVC). The LVC and the HVC have cavities. Ultraviolet photons radiated from NGC 6618 cluster penetrate into the N cloud up to ˜5 pc through the cavities and interact with molecular gas. This interaction is correlated with the distribution of young stellar objects in the N cloud. The LVC and the HVC are distributed complementarily after the HVC is displaced by 0.8 pc toward the east-southeast direction, suggesting that collision of the LVC and the HVC created the cavities in both clouds. The collision velocity and timescale are estimated to be 9.9 km s-1 and 1.1 × 105 yr, respectively. The high collision velocity can provide a mass accretion rate of up to 10^{-3} M_{⊙}yr-1, and the high column density (4 × 1023 cm-2) might result in massive cluster formation. The scenario of cloud-cloud collision likely explains well the stellar population and the formation history of the NGC 6618 cluster proposed by Hoffmeister et al. (2008, ApJ, 686, 310).

  14. A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

    International Nuclear Information System (INIS)

    Gu Meng; Huang Song; Ho, Luis C.; Peng, Chien Y.

    2013-01-01

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M I ≈ –18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ∼90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies

  15. CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited

    Science.gov (United States)

    Arellano Ferro, A.; Giridhar, Sunetra; Bramich, D. M.

    2010-02-01

    We report the results of CCD V, r and I time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images, and their periods are revised. Their V light curves were Fourier decomposed to estimate their physical parameters. A discussion on the accuracy of the Fourier-based iron abundances, temperatures, masses and radii is given. New periods are found for the five known SX Phe stars, and a critical discussion of their secular period changes is offered. The mean iron abundance for the RR Lyrae stars is found to be [Fe/H] ~ -1.97 +/- 0.16 and lower values are not supported by the present analysis. The absolute magnitude calibrations of the RR Lyrae stars yield an average true distance modulus of 16.12 +/- 0.04 or a distance of 16.7 +/- 0.3 kpc. Comparison of the observational colour magnitude diagram (CMD) with theoretical isochrones indicates an age of 12.5 +/- 2.0 Gyr for the cluster. A careful identification of all reported blue stragglers (BS) and their V, I magnitudes leads to the conclusion that BS12, BS22, BS23 and BS24 are not BS. On the other hand, three new BS are reported. Variability was found in seven BS, very likely of the SX Phe type in five of them, and in one red giant star. The new SX Phe stars follow established Period-Luminosity relationships and indicate a distance in agreement with the distance from the RR Lyrae stars. Based on observations collected at the Indian Astrophysical Observatory, Hanle, India. E-mail: armando@astroscu.unam.mx (AAF); giridhar@iiap.res.in (SG); dan.bramich@hotmail.co.uk (DMB)

  16. The Brazil–Argentina Gemini Group for the Study of Globular Cluster Systems (BAGGs GCs: FLAMINGOS-2 and GMOS Data for NGC 1395

    Directory of Open Access Journals (Sweden)

    Favio Faifer

    2017-08-01

    Full Text Available In this letter, we present preliminary results of the analysis of Flamingos-2 and GMOS-S photometry of the globular cluster (GC system of the elliptical galaxy NGC 1395. This is the first step of a long-term Brazilian–Argentinian collaboration for the study of GC systems in early-type galaxies. In the context of this collaboration, we obtained deep NIR photometric data in two different bands (J and K s, which were later combined with high quality optical Gemini + GMOS photometry previously obtained by the Argentinian team. This allowed us to obtain different color indices, less sensitive to the effect of horizontal branch (HB stars for several hundreds of GC candidates, and to make an initial assessment of the presence or absence of multiple GC populations in colors in NGC 1395.

  17. CSI 2264: CHARACTERIZING YOUNG STARS IN NGC 2264 WITH SHORT-DURATION PERIODIC FLUX DIPS IN THEIR LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Stauffer, John; Cody, Ann Marie; Rebull, Luisa; Plavchan, Peter; Carey, Sean [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States); McGinnis, Pauline; Alencar, Silvia H. P. [Departamento de Física—ICEx—UFMG, Av. Antônio Carlos, 6627, 30270-901, Belo Horizonte, MG (Brazil); Hillenbrand, Lynne A.; Carpenter, John [Astronomy Department, California Institute of Technology, Pasadena, CA 91125 (United States); Turner, Neal J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Terebey, Susan [Department of Physics and Astronomy, 5151 State University Drive, California State University at Los Angeles, Los Angeles, CA 90032 (United States); Morales-Calderón, María [Centro de Astrobiología, Dpto. de Astrofísica, INTA-CSIC, PO BOX 78, E-28691, ESAC Campus, Villanueva de la Cañada, Madrid (Spain); Bouvier, Jerome; Venuti, Laura [Université de Grenoble, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG), F-38000 Grenoble (France); CNRS, IPAG, F-38000 Grenoble (France); Hartmann, Lee; Calvet, Nuria [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105 (United States); Micela, Giusi; Flaccomio, Ettore [INAF—Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134, Palermo (Italy); Song, Inseok [Department of Physics and Astronomy, The University of Georgia, Athens, GA 30602–2451 (United States); Gutermuth, Rob, E-mail: stauffer@ipac.caltech.edu [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); and others

    2015-04-15

    We identify nine young stellar objects (YSOs) in the NGC 2264 star-forming region with optical CoRoT light curves exhibiting short-duration, shallow periodic flux dips. All of these stars have infrared excesses that are consistent with their having inner disk walls near the Keplerian co-rotation radius. The repeating photometric dips have FWHMs generally less than 1 day, depths almost always less than 15%, and periods (3 < P < 11 days) consistent with dust near the Keplerian co-rotation period. The flux dips vary considerably in their depth from epoch to epoch, but usually persist for several weeks and, in two cases, were present in data collected in successive years. For several of these stars, we also measure the photospheric rotation period and find that the rotation and dip periods are the same, as predicted by standard “disk-locking” models. We attribute these flux dips to clumps of material in or near the inner disk wall, passing through our line of sight to the stellar photosphere. In some cases, these dips are also present in simultaneous Spitzer IRAC light curves at 3.6 and 4.5 microns. We characterize the properties of these dips, and compare the stars with light curves exhibiting this behavior to other classes of YSOs in NGC 2264. A number of physical mechanisms could locally increase the dust scale height near the inner disk wall, and we discuss several of those mechanisms; the most plausible mechanisms are either a disk warp due to interaction with the stellar magnetic field or dust entrained in funnel-flow accretion columns arising near the inner disk wall.

  18. CSI 2264: CHARACTERIZING YOUNG STARS IN NGC 2264 WITH SHORT-DURATION PERIODIC FLUX DIPS IN THEIR LIGHT CURVES

    International Nuclear Information System (INIS)

    Stauffer, John; Cody, Ann Marie; Rebull, Luisa; Plavchan, Peter; Carey, Sean; McGinnis, Pauline; Alencar, Silvia H. P.; Hillenbrand, Lynne A.; Carpenter, John; Turner, Neal J.; Terebey, Susan; Morales-Calderón, María; Bouvier, Jerome; Venuti, Laura; Hartmann, Lee; Calvet, Nuria; Micela, Giusi; Flaccomio, Ettore; Song, Inseok; Gutermuth, Rob

    2015-01-01

    We identify nine young stellar objects (YSOs) in the NGC 2264 star-forming region with optical CoRoT light curves exhibiting short-duration, shallow periodic flux dips. All of these stars have infrared excesses that are consistent with their having inner disk walls near the Keplerian co-rotation radius. The repeating photometric dips have FWHMs generally less than 1 day, depths almost always less than 15%, and periods (3 < P < 11 days) consistent with dust near the Keplerian co-rotation period. The flux dips vary considerably in their depth from epoch to epoch, but usually persist for several weeks and, in two cases, were present in data collected in successive years. For several of these stars, we also measure the photospheric rotation period and find that the rotation and dip periods are the same, as predicted by standard “disk-locking” models. We attribute these flux dips to clumps of material in or near the inner disk wall, passing through our line of sight to the stellar photosphere. In some cases, these dips are also present in simultaneous Spitzer IRAC light curves at 3.6 and 4.5 microns. We characterize the properties of these dips, and compare the stars with light curves exhibiting this behavior to other classes of YSOs in NGC 2264. A number of physical mechanisms could locally increase the dust scale height near the inner disk wall, and we discuss several of those mechanisms; the most plausible mechanisms are either a disk warp due to interaction with the stellar magnetic field or dust entrained in funnel-flow accretion columns arising near the inner disk wall

  19. The Open Cluster NGC 6811: An Eclipsing Binary, the Turnoff, and Age

    DEFF Research Database (Denmark)

    Sandquist, Eric L.; Jessen-Hansen, Jens; Shetrone, Matthew D.

    . The cluster's turnoff also falls completely within the instability strip, and the majority of the brightest main sequence stars have now been identified as δ Scuti pulsators. The eclipsing binary KIC 9777062/Sanders 195 is a cluster member slightly fainter than the turnoff, containing one star that falls...... stars to produce an improved age determination.We gratefully acknowledge support from the NSF to E.L.S. under grant AST-0908536 and for M.L. as part of the REU program at San Diego State University under grant AST-0850564, and from NASA under grants NNX12AC88G and NNX13AC19G....

  20. Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II

    DEFF Research Database (Denmark)

    Brogaard, K.; VandenBerg, D. A.; Bruntt, H.

    2012-01-01

    Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar systems, and in turn, to improve estimates of their age. In th...

  1. Age of the Kepler Open Cluster NGC 6811 from an Eclipsing Binary

    DEFF Research Database (Denmark)

    Leitner, Marika; Sandquist, E. L.; Shetrone, M. D.

    2013-01-01

    provide an extremely precise age for the cluster. We present the results of modeling Kepler and ground-based photometry as well as radial velocities obtained at the Hobby-Eberly Telescope, Nordic Optical Telescope, and MMT. We demonstrate that the stars have masses near 1.6 and 1.4 solar masses...

  2. WIYN Open Cluster Study. XXXVI. Spectroscopic Binary Orbits in NGC 188

    Science.gov (United States)

    2009-04-01

    2000; Pleiades , Mermilliod et al. 1992; M67, Mathieu et al. 1990). Today, the advent of multi-object spectrographs permits surveys of larger stellar...open clusters (e.g., M67, Mathieu et al. (1990); Praesepe, Mermilliod et al. (1994); Pleiades , Bouvier et al. (1997); Hyades, Patience et al. (1998

  3. Hypervelocity stars from young stellar clusters in the Galactic Centre

    Science.gov (United States)

    Fragione, G.; Capuzzo-Dolcetta, R.; Kroupa, P.

    2017-05-01

    The enormous velocities of the so-called hypervelocity stars (HVSs) derive, likely, from close interactions with massive black holes, binary stars encounters or supernova explosions. In this paper, we investigate the origin of HVSs as consequence of the close interaction between the Milky Way central massive black hole and a passing-by young stellar cluster. We found that both single and binary HVSs may be generated in a burst-like event, as the cluster passes near the orbital pericentre. High-velocity stars will move close to the initial cluster orbital plane and in the direction of the cluster orbital motion at the pericentre. The binary fraction of these HVS jets depends on the primordial binary fraction in the young cluster. The level of initial mass segregation determines the value of the average mass of the ejected stars. Some binary stars will merge, continuing their travel across and out of the Galaxy as blue stragglers.

  4. THE IMPORTANCE OF NEBULAR CONTINUUM AND LINE EMISSION IN OBSERVATIONS OF YOUNG MASSIVE STAR CLUSTERS

    International Nuclear Information System (INIS)

    Reines, Amy E.; Nidever, David L.; Whelan, David G.; Johnson, Kelsey E.

    2010-01-01

    In this spectroscopic study of infant massive star clusters, we find that continuum emission from ionized gas rivals the stellar luminosity at optical wavelengths. In addition, we find that nebular line emission is significant in many commonly used broadband Hubble Space Telescope (HST) filters including the F814W I-band, the F555W V-band, and the F435W B-band. Two young massive clusters (YMCs) in the nearby starburst galaxy NGC 4449 were targeted for follow-up spectroscopic observations after Reines et al. discovered an F814W I-band excess in their photometric study of radio-detected clusters in the galaxy. The spectra were obtained with the Dual Imaging Spectrograph (DIS) on the 3.5 m Apache Point Observatory (APO) telescope and have a spectral range of ∼3800-9800 A. We supplement these data with HST and Sloan Digital Sky Survey photometry of the clusters. By comparing our data to the Starburst99 and GALEV evolutionary synthesis models, we find that nebular continuum emission competes with the stellar light in our observations and that the relative contribution from the nebular continuum is largest in the U- and I-bands, where the Balmer (3646 A) and Paschen jumps (8207 A) are located. The spectra also exhibit strong line emission including the [S III] λλ9069, 9532 lines in the HST F814W I-band. We find that the combination of nebular continuum and line emission can account for the F814W I-band excess previously found by Reines et al. In an effort to provide a benchmark for estimating the impact of ionized gas emission on photometric observations of young massive stellar populations, we compute the relative contributions of the stellar continuum, nebular continuum, and emission lines to the total observed flux of a 3 Myr old cluster through various HST filter/instrument combinations, including filters in the Wide Field Camera 3. We urge caution when comparing observations of YMCs to evolutionary synthesis models since nebular continuum and line emission can

  5. THE LAST GASP OF GAS GIANT PLANET FORMATION: A SPITZER STUDY OF THE 5 Myr OLD CLUSTER NGC 2362

    International Nuclear Information System (INIS)

    Currie, Thayne; Lada, Charles J.; Robitaille, Thomas P.; Irwin, Jonathan; Kenyon, Scott J.; Plavchan, Peter

    2009-01-01

    Expanding upon the Infrared Array Camera (IRAC) survey from Dahm and Hillenbrand, we describe Spitzer IRAC and Multiband Imaging Photometer for Spitzer observations of the populous, 5 Myr old open cluster NGC 2362. We analyze the mid-IR colors of cluster members and compared their spectral energy distributions (SEDs) to star+circumstellar disk models to constrain the disk morphologies and evolutionary states. Early/intermediate-type confirmed/candidate cluster members either have photospheric mid-IR emission or weak, optically thin IR excess emission at λ ≥ 24 μm consistent with debris disks. Few late-type, solar/subsolar-mass stars have primordial disks. The disk population around late-type stars is dominated by disks with inner holes (canonical 'transition disks') and 'homologously depleted' disks. Both types of disks represent an intermediate stage between primordial disks and debris disks. Thus, in agreement with previous results, we find that multiple paths for the primordial-to-debris disk transition exist. Because these 'evolved primordial disks' greatly outnumber primordial disks, our results undermine standard arguments in favor of a ∼ 5 yr timescale for the transition based on data from Taurus-Auriga. Because the typical transition timescale is far longer than 10 5 yr, these data also appear to rule out standard ultraviolet photoevaporation scenarios as the primary mechanism to explain the transition. Combining our data with other Spitzer surveys, we investigate the evolution of debris disks around high/intermediate-mass stars and investigate timescales for giant planet formation. Consistent with Currie et al., the luminosity of 24 μm emission in debris disks due to planet formation peaks at ∼10-20 Myr. If the gas and dust in disks evolve on similar timescales, the formation timescale for gas giant planets surrounding early-type, high/intermediate-mass (∼>1.4 M sun ) stars is likely 1-5 Myr. Most solar/subsolar-mass stars detected by Spitzer

  6. Asteroseismology of old open clusters with Kepler: direct estimate of the integrated red giant branch mass-loss in NGC 6791 and 6819

    DEFF Research Database (Denmark)

    Miglio, A.; Brogaard, Karsten Frank; Stello, D.

    2012-01-01

    Mass-loss of red giant branch (RGB) stars is still poorly determined, despite its crucial role in the chemical enrichment of galaxies. Thanks to the recent detection of solar-like oscillations in G–K giants in open clusters with Kepler, we can now directly determine stellar masses...... for a statistically significant sample of stars in the old open clusters NGC 6791 and 6819. The aim of this work is to constrain the integrated RGB mass-loss by comparing the average mass of stars in the red clump (RC) with that of stars in the low-luminosity portion of the RGB [i.e. stars with L≲L(RC)]. Stellar...... masses were determined by combining the available seismic parameters νmax and Δν with additional photometric constraints and with independent distance estimates. We measured the masses of 40 stars on the RGB and 19 in the RC of the old metal-rich cluster NGC 6791. We find that the difference between...

  7. Modeling blue stragglers in young clusters

    International Nuclear Information System (INIS)

    Lu Pin; Deng Licai; Zhang Xiaobin

    2011-01-01

    A grid of binary evolution models are calculated for the study of a blue straggler (BS) population in intermediate age (log Age = 7.85–8.95) star clusters. The BS formation via mass transfer and merging is studied systematically using our models. Both Case A and B close binary evolutionary tracks are calculated for a large range of parameters. The results show that BSs formed via Case B are generally bluer and even more luminous than those produced by Case A. Furthermore, the larger range in orbital separations of Case B models provides a probability of producing more BSs than in Case A. Based on the grid of models, several Monte-Carlo simulations of BS populations in the clusters in the age range are carried out. The results show that BSs formed via different channels populate different areas in the color magnitude diagram (CMD). The locations of BSs in CMD for a number of clusters are compared to our simulations as well. In order to investigate the influence of mass transfer efficiency in the models and simulations, a set of models is also calculated by implementing a constant mass transfer efficiency, β = 0.5, during Roche lobe overflow (Case A binary evolution excluded). The result shows BSs can be formed via mass transfer at any given age in both cases. However, the distributions of the BS populations on CMD are different.

  8. A NOVEL APPROACH TO CONSTRAIN THE MASS RATIO OF MINOR MERGERS IN ELLIPTICAL GALAXIES: APPLICATION TO NGC 4889, THE BRIGHTEST CLUSTER GALAXY IN COMA

    Energy Technology Data Exchange (ETDEWEB)

    Gu Meng; Huang Song [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Ho, Luis C. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Peng, Chien Y. [Giant Magellan Telescope Organization, 251 South Lake Avenue, Suite 300, Pasadena, CA 91101 (United States)

    2013-08-10

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (M{sub I} Almost-Equal-To -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of {approx}90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies.

  9. A Novel Approach to Constrain the Mass Ratio of Minor Mergers in Elliptical Galaxies: Application to NGC 4889, the Brightest Cluster Galaxy in Coma

    Science.gov (United States)

    Gu, Meng; Ho, Luis C.; Peng, Chien Y.; Huang, Song

    2013-08-01

    Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (MI ≈ -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ~90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies. 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 (AURA), Inc., under NASA contract NAS5-26555.

  10. Two transitional type Ia supernovae located in the Fornax cluster member NGC 1404: SN 2007on and SN 2011iv

    Science.gov (United States)

    Gall, C.; Stritzinger, M. D.; Ashall, C.; Baron, E.; Burns, C. R.; Hoeflich, P.; Hsiao, E. Y.; Mazzali, P. A.; Phillips, M. M.; Filippenko, A. V.; Anderson, J. P.; Benetti, S.; Brown, P. J.; Campillay, A.; Challis, P.; Contreras, C.; Elias de la Rosa, N.; Folatelli, G.; Foley, R. J.; Fraser, M.; Holmbo, S.; Marion, G. H.; Morrell, N.; Pan, Y.-C.; Pignata, G.; Suntzeff, N. B.; Taddia, F.; Robledo, S. Torres; Valenti, S.

    2018-03-01

    We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Δm15 (B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by 0.60 mag and 0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by 14% and 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B - V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, 56Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the differences in the B - V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on. The photometry tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A58

  11. Probing the water and CO snow lines in the young protostar NGC 1333-IRAS4B

    Science.gov (United States)

    Anderl, Sibylle; Maret, Sébastien; André, Philippe; Maury, Anaëlle; Belloche, Arnaud; Cabrit, Sylvie; Codella, Claudio; Lefloch, Bertrand

    2015-08-01

    Today, we believe that the onset of life requires free energy, water, and complex, probably carbon-based chemistry. In the interstellar medium, complex organic molecules seem to mostly form in reactions happening on the icy surface of dust grains, such that they are released into the gas phase when the dust is heated. The resulting “snow lines”, marking regions where ices start to sublimate, play an important role for planet growth and bulk composition in protoplanetary disks. However, they can already be observed in the envelopes of the much younger, low-mass Class 0 protostars that are still in their early phase of heavy accretion. The information on the sublimation regions of different kinds of ices can be used to understand the chemistry of the envelope, its temperature and density structure, and may even hint at the history of the accretion process. Accordingly, it is a crucial piece of information in order to get the full picture of how organic chemistry evolves already at the earliest stages of the formation of sun-like stars. As part of the CALYPSO Large Program (http://irfu.cea.fr/Projets/Calypso/), we have obtained observations of C18O, N2H+ and CH3OH towards the Class 0 protostar NGC 1333-IRAS4B with the IRAM Plateau de Bure interferometer at sub-arcsecond resolution. Of these we use the methanol observations as a proxy for the water snow line, assuming methanol is trapped in water ice. The observed anti-correlation of C18O and N2H+, with N2H+ forming a ring around the centrally peaked C18O emission, reveals for the first time the CO snow line in this protostellar envelope, with a radius of ~300 AU. The methanol emission is much more compact than that of C18O, and traces the water snow line with a radius of ~40 AU. We have modeled the emission using a chemical model coupled with a radiative transfer module. We find that the CO snow line appears further inwards than expected from the binding energy of pure CO ices. This may hint at CO being frozen out

  12. NGC 1980 Is Not a Foreground Population of Orion: Spectroscopic Survey of Young Stars with Low Extinction in Orion A

    International Nuclear Information System (INIS)

    Fang, Min; Kim, Jinyoung Serena; Apai, Dániel; Pascucci, Ilaria; Zhang, Lan; Sicilia-Aguilar, Aurora; Alonso-Martínez, Miguel; Eiroa, Carlos; Wang, Hongchi

    2017-01-01

    We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass of less than 0.018–0.030 M ⊙ , which harbors a flaring disk. Using the H α emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting TDs is lower than that of optically thick disks (46% ± 7% versus 73% ± 9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age of around 1–2 Myr, which is similar to that of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A.

  13. NGC 1980 Is Not a Foreground Population of Orion: Spectroscopic Survey of Young Stars with Low Extinction in Orion A

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Min; Kim, Jinyoung Serena; Apai, Dániel [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Pascucci, Ilaria [Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Zhang, Lan [Key Lab of Optical Astronomy, National Astronomical Observatories, CAS, 20A Datun Road, Chaoyang District, 100012 Beijing (China); Sicilia-Aguilar, Aurora [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom); Alonso-Martínez, Miguel; Eiroa, Carlos [Departamento de Fisica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, E-28049 Cantoblanco, Madrid (Spain); Wang, Hongchi [Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 2 West Beijing Road, 210008 Nanjing (China)

    2017-04-01

    We perform a spectroscopic survey of the foreground population in Orion A with MMT/Hectospec. We use these data, along with archival spectroscopic data and photometric data, to derive spectral types, extinction values, and masses for 691 stars. Using the Spitzer Space Telescope data, we characterize the disk properties of these sources. We identify 37 new transition disk (TD) objects, 1 globally depleted disk candidate, and 7 probable young debris disks. We discover an object with a mass of less than 0.018–0.030 M {sub ⊙}, which harbors a flaring disk. Using the H α emission line, we characterize the accretion activity of the sources with disks, and confirm that the fraction of accreting TDs is lower than that of optically thick disks (46% ± 7% versus 73% ± 9%, respectively). Using kinematic data from the Sloan Digital Sky Survey and APOGEE INfrared Spectroscopy of the Young Nebulous Clusters program (IN-SYNC), we confirm that the foreground population shows similar kinematics to their local molecular clouds and other young stars in the same regions. Using the isochronal ages, we find that the foreground population has a median age of around 1–2 Myr, which is similar to that of other young stars in Orion A. Therefore, our results argue against the presence of a large and old foreground cluster in front of Orion A.

  14. DIVERSE PROTOSTELLAR EVOLUTIONARY STATES IN THE YOUNG CLUSTER AFGL961

    International Nuclear Information System (INIS)

    Williams, Jonathan P.; Mann, Rita K.; Beaumont, Christopher N.; Swift, Jonathan J.; Adams, Joseph D.; Hora, Joe; Kassis, Marc; Lada, Elizabeth A.; Roman-Zuniga, Carlos G.

    2009-01-01

    We present arcsecond resolution mid-infrared and millimeter observations of the center of the young stellar cluster AFGL961 in the Rosette molecular cloud. Within 0.2 pc of each other, we find an early B star embedded in a dense core, a neighboring star of similar luminosity with no millimeter counterpart, a protostar that has cleared out a cavity in the circumcluster envelope, and two massive, dense cores with no infrared counterparts. An outflow emanates from one of these cores, indicating a deeply embedded protostar, but the other is starless, bound, and appears to be collapsing. The diversity of states implies either that protostellar evolution is faster in clusters than in isolation or that clusters form via quasi-static rather than dynamic collapse. The existence of a pre-stellar core at the cluster center shows that some star formation continues after and in close proximity to massive, ionizing stars.

  15. Young Cluster Berkeley 59: Properties, Evolution, and Star Formation

    Science.gov (United States)

    Panwar, Neelam; Pandey, A. K.; Samal, Manash R.; Battinelli, Paolo; Ogura, K.; Ojha, D. K.; Chen, W. P.; Singh, H. P.

    2018-01-01

    Berkeley 59 is a nearby (∼1 kpc) young cluster associated with the Sh2-171 H II region. We present deep optical observations of the central ∼2.5 × 2.5 pc2 area of the cluster, obtained with the 3.58 m Telescopio Nazionale Galileo. The V/(V–I) color–magnitude diagram manifests a clear pre-main-sequence (PMS) population down to ∼0.2 M ⊙. Using the near-infrared and optical colors of the low-mass PMS members, we derive a global extinction of A V = 4 mag and a mean age of ∼1.8 Myr, respectively, for the cluster. We constructed the initial mass function and found that its global slopes in the mass ranges of 0.2–28 M ⊙ and 0.2–1.5 M ⊙ are ‑1.33 and ‑1.23, respectively, in good agreement with the Salpeter value in the solar neighborhood. We looked for the radial variation of the mass function and found that the slope is flatter in the inner region than in the outer region, indicating mass segregation. The dynamical status of the cluster suggests that the mass segregation is likely primordial. The age distribution of the PMS sources reveals that the younger sources appear to concentrate close to the inner region compared to the outer region of the cluster, a phenomenon possibly linked to the time evolution of star-forming clouds. Within the observed area, we derive a total mass of ∼103 M ⊙ for the cluster. Comparing the properties of Berkeley 59 with other young clusters, we suggest it resembles more closely the Trapezium cluster.

  16. IRAS 20050+2720: ANATOMY OF A YOUNG STELLAR CLUSTER

    International Nuclear Information System (INIS)

    Günther, H. M.; Wolk, S. J.; Spitzbart, B.; Forbrich, J.; Wright, N. J.; Bourke, T. L.; Gutermuth, R. A.; Allen, L.; Megeath, S. T.; Pipher, J. L.

    2012-01-01

    IRAS 20050+2720 is young star-forming region at a distance of 700 pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N H /A K ratio compared with the diffuse interstellar medium.

  17. THE HUBBLE SPACE TELESCOPE UV LEGACY SURVEY OF GALACTIC GLOBULAR CLUSTERS: THE INTERNAL KINEMATICS OF THE MULTIPLE STELLAR POPULATIONS IN NGC 2808

    International Nuclear Information System (INIS)

    Bellini, A.; Anderson, J.; Marel, R. P. van der; Vesperini, E.; Hong, J.; Piotto, G.; Milone, A. P.; Marino, A. F.; Bedin, L. R.; Renzini, A.; Cassisi, S.; D’Antona, F.

    2015-01-01

    Numerous observational studies have revealed the ubiquitous presence of multiple stellar populations in globular clusters and cast many difficult challenges for the study of the formation and dynamical history of these stellar systems. In this Letter we present the results of a study of the kinematic properties of multiple populations in NGC 2808 based on high-precision Hubble Space Telescope proper-motion measurements. In a recent study, Milone et al. identified five distinct populations (A–E) in NGC 2808. Populations D and E coincide with the helium-enhanced populations in the middle and the blue main sequences (mMS and bMS) previously discovered by Piotto et al.; populations A–C correspond to the redder main sequence that, in Piotto et al., was associated with the primordial stellar population. Our analysis shows that, in the outermost regions probed (between about 1.5 and 2 times the cluster half-light radius), the velocity distribution of populations D and E is radially anisotropic (the deviation from an isotropic distribution is significant at the ∼3.5σ level). Stars of populations D and E have a smaller tangential velocity dispersion than those of populations A–C, while no significant differences are found in the radial velocity dispersion. We present the results of a numerical simulation showing that the observed differences between the kinematics of these stellar populations are consistent with the expected kinematic fingerprint of the diffusion toward the cluster outer regions of stellar populations initially more centrally concentrated

  18. Mapping diffuse interstellar bands in the local ISM on small scales via MUSE 3D spectroscopy. A pilot study based on globular cluster NGC 6397

    Science.gov (United States)

    Wendt, Martin; Husser, Tim-Oliver; Kamann, Sebastian; Monreal-Ibero, Ana; Richter, Philipp; Brinchmann, Jarle; Dreizler, Stefan; Weilbacher, Peter M.; Wisotzki, Lutz

    2017-11-01

    Context. We map the interstellar medium (ISM) including the diffuse interstellar bands (DIBs) in absorption toward the globular cluster NGC 6397 using VLT/MUSE. Assuming the absorbers are located at the rim of the Local Bubble we trace structures on the order of mpc (milliparsec, a few thousand AU). Aims: We aimed to demonstrate the feasibility to map variations of DIBs on small scales with MUSE. The sightlines defined by binned stellar spectra are separated by only a few arcseconds and we probe the absorption within a physically connected region. Methods: This analysis utilized the fitting residuals of individual stellar spectra of NGC 6397 member stars and analyzed lines from neutral species and several DIBs in Voronoi-binned composite spectra with high signal-to-noise ratio (S/N). Results: This pilot study demonstrates the power of MUSE for mapping the local ISM on very small scales which provides a new window for ISM observations. We detect small scale variations in Na I and K I as well as in several DIBs within few arcseconds, or mpc with regard to the Local Bubble. We verify the suitability of the MUSE 3D spectrograph for such measurements and gain new insights by probing a single physical absorber with multiple sight lines.

  19. THE OLD, SUPER-METAL-RICH OPEN CLUSTER, NGC 6791—ELEMENTAL ABUNDANCES IN TURN-OFF STARS FROM KECK/HIRES SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Merchant Boesgaard, Ann; Lum, Michael G. [Institute for Astronomy, University of Hawai' i at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Deliyannis, Constantine P., E-mail: boes@ifa.hawaii.edu, E-mail: mikelum@ifa.hawaii.edu, E-mail: cdeliyan@indiana.edu [Department of Astronomy, Indiana University 727 East 3rd Street, Swain Hall West 319, Bloomington, IN 47405-7105 (United States)

    2015-02-01

    The study of star clusters has advanced our understanding of stellar evolution, Galactic chemical evolution, and nucleosynthesis. Here we investigate the composition of turn-off stars in the intriguing open cluster, NGC 6791, which is old, but super-metal-rich with high-resolution (R = 46,000) Keck/HIRES spectra. We find [Fe/H] = +0.30 ± 0.02 from measurements of some 40 unblended, unsaturated lines of both Fe I and Fe II in eight turn-off stars. Our O abundances come from the O I triplet near 7774 Å and we perform a differential analysis relative to the Sun from our Lunar spectrum also obtained with Keck/HIRES. The O results are corrected for small nLTE effects. We find consistent ratios of [O/Fe]{sub n} with a mean of –0.06 ± 0.02. This is low with respect to field stars that are also both old and metal-rich and continue the trend of decreasing [O/Fe] with increasing [Fe/H]. The small range in our oxygen abundances is consistent with a single population of stars. Our results for the alpha elements [Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe] are near solar and compare well with those of the old, metal-rich field stars. The two Fe-peak elements, Cr and Ni, are consistent with Fe. These turn-off-star abundances provide benchmark abundances to investigate whether there are any observable abundance differences with the giants that might arise from nuclear-burning and dredge-up processes. Determinations of upper limits were found for Li by spectrum synthesis and are consistent with the upper limits in similar stars in the relatively old, super-metal-rich cluster NGC 6253. Our results support the prediction from standard theory that higher-metallicity stars deplete more Li. Probably no stars in NGC 6791 have retained their initial Li.

  20. THE FORMATION OF SECONDARY STELLAR GENERATIONS IN MASSIVE YOUNG STAR CLUSTERS FROM RAPIDLY COOLING SHOCKED STELLAR WINDS

    Energy Technology Data Exchange (ETDEWEB)

    Wünsch, R.; Palouš, J.; Ehlerová, S. [Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 31 Prague (Czech Republic); Tenorio-Tagle, G. [Instituto Nacional de Astrofísica Optica y Electrónica, AP 51, 72000 Puebla, México (Mexico)

    2017-01-20

    We study a model of rapidly cooling shocked stellar winds in young massive clusters and estimate the circumstances under which secondary star formation, out of the reinserted winds from a first stellar generation (1G), is possible. We have used two implementations of the model: a highly idealized, computationally inexpensive, spherically symmetric semi-analytic model, and a complex, three-dimensional radiation-hydrodynamic, simulation; they are in a good mutual agreement. The results confirm our previous findings that, in a cluster with 1G mass 10{sup 7} M {sub ⊙} and half-mass–radius 2.38 pc, the shocked stellar winds become thermally unstable, collapse into dense gaseous structures that partially accumulate inside the cluster, self-shield against ionizing stellar radiation, and form the second generation (2G) of stars. We have used the semi-analytic model to explore a subset of the parameter space covering a wide range of the observationally poorly constrained parameters: the heating efficiency, η {sub he}, and the mass loading, η {sub ml}. The results show that the fraction of the 1G stellar winds accumulating inside the cluster can be larger than 50% if η {sub he} ≲ 10%, which is suggested by the observations. Furthermore, for low η {sub he}, the model provides a self-consistent mechanism predicting 2G stars forming only in the central zones of the cluster. Finally, we have calculated the accumulated warm gas emission in the H30 α recombination line, analyzed its velocity profile, and estimated its intensity for super star clusters in interacting galaxies NGC4038/9 (Antennae) showing that the warm gas should be detectable with ALMA.

  1. From Globular Clusters to Tidal Dwarfs: Structure Formation in the Tidal Tails of Merging Pairs

    Science.gov (United States)

    Knierman, K. A.; Gallagher, S. C.; Charlton, J. C.; Hunsberger, S. D.; Whitmore, B. C.; Kundu, A.; Hibbard, J. E.; Zaritsky, D. F.

    2001-05-01

    Using V and I images obtained with the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope, we investigate compact stellar structures within tidal tails. Six regions of tidal debris in the four classic ``Toomre Sequence'' mergers: NGC 4038/9 (``Antennae''), NGC 3256, NGC 3921, and NGC 7252 (``Atoms for Peace'') have been studied in order to explore how the star formation depends upon the local and global physical conditions. These mergers sample a range of stages in the evolutionary sequence, and include HI--rich and HI--poor environments. The six tails are found to contain a variety of stellar structures, with sizes ranging from those of globular clusters up to those of dwarf galaxies. From V and I WFPC2 images, we measure the luminosities and colors of the star clusters. NGC 3256 is found to have a large population of young clusters lying along both tails, similar to those found in the inner region of the merger. In contrast, NGC 4038/9 has no clusters in the observed region of the tail, only less luminous point sources likely to be individual stars. NGC 3921 and NGC 7252 have small populations of clusters that are concentrated in certain regions of the tail, and particularly in the prominent tidal dwarfs in the eastern and western tails of NGC 7252. The two cluster--rich tails of NGC 3256 are not distinguished from the others by their ages or by their total HI masses. We acknowledge support from NASA through STScI, and from NSF for an REU supplement for Karen Knierman.

  2. PANCHROMATIC HUBBLE ANDROMEDA TREASURY. XVI. STAR CLUSTER FORMATION EFFICIENCY AND THE CLUSTERED FRACTION OF YOUNG STARS

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, L. Clifton; Sandstrom, Karin [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Seth, Anil C. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Dalcanton, Julianne J.; Beerman, Lori C.; Lewis, Alexia R.; Weisz, Daniel R.; Williams, Benjamin F. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Fouesneau, Morgan [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Bell, Eric F. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); Dolphin, Andrew E. [Raytheon Company, 1151 East Hermans Road, Tucson, AZ 85756 (United States); Larsen, Søren S. [Department of Astrophysics, IMAPP, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen (Netherlands); Skillman, Evan D., E-mail: lcj@ucsd.edu [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States)

    2016-08-10

    We use the Panchromatic Hubble Andromeda Treasury survey data set to perform spatially resolved measurements of star cluster formation efficiency (Γ), the fraction of stellar mass formed in long-lived star clusters. We use robust star formation history and cluster parameter constraints, obtained through color–magnitude diagram analysis of resolved stellar populations, to study Andromeda’s cluster and field populations over the last ∼300 Myr. We measure Γ of 4%–8% for young, 10–100 Myr-old populations in M31. We find that cluster formation efficiency varies systematically across the M31 disk, consistent with variations in mid-plane pressure. These Γ measurements expand the range of well-studied galactic environments, providing precise constraints in an H i-dominated, low-intensity star formation environment. Spatially resolved results from M31 are broadly consistent with previous trends observed on galaxy-integrated scales, where Γ increases with increasing star formation rate surface density (Σ{sub SFR}). However, we can explain observed scatter in the relation and attain better agreement between observations and theoretical models if we account for environmental variations in gas depletion time ( τ {sub dep}) when modeling Γ, accounting for the qualitative shift in star formation behavior when transitioning from a H{sub 2}-dominated to a H i-dominated interstellar medium. We also demonstrate that Γ measurements in high Σ{sub SFR} starburst systems are well-explained by τ {sub dep}-dependent fiducial Γ models.

  3. HST Observations of NGC 7252

    Science.gov (United States)

    Whitmore, Brad; Schweizer, Francois; Leitherer, Claus; Borne, Kirk; Robert, Carmelle

    1993-05-01

    A population of about 40 blue pointlike objects has been discovered in NGC 7252 using the Planetary Camera on board of the Hubble Space Telescope. NGC 7252 (sometimes referred to as the ``Atoms-for-Peace'' galaxy) is one of the prototypical examples of a merger between two disk galaxies. Schweizer (1982: ApJ, 252, 455) has argued that the remnant will eventually become an elliptical galaxy. The luminosities, V-I colors, spatial distribution, and sizes are all compatible with the hypothesis that these objects formed <= 1 Gyr ago during the original merger, and that they are the progenitors of globular clusters similar to those we see around galaxies today. It therefore appears that the number of globular clusters is not a conserved quantity during the merger of two spiral galaxies, but increases instead. This weakens van den Bergh's objection against ellipticals being formed through disk mergers, based mainly on the fact that disk galaxies have fewer globular clusters per unit luminosity than ellipticals galaxies do. The objects found in NGC 7252 are very similar to the pointlike sources recently discovered in NGC 1275 by Holtzman et al. (1992: AJ, 103, 691). However, NGC 1275 is a peculiar galaxy in the center of the Perseus cluster. While Holtzman et al. argue that the objects in NGC 1275 may be the progenitors of globular clusters, Richer et al. (1993: AJ, 105, 877) suggest that these objects may instead be related to the strong cooling flow in the cluster. Our discovery of a population of bright blue pointlike objects in NGC 7252, a prototypical merger, makes a much stronger connection between the formation of globular clusters and the merger history of a galaxy. Other findings are: (1) NGC 7252 has a single, semi-stellar nucleus; (2) spiral arms are seen within 3.5'' (1.6 kpc) of the center, presumably formed through the continued infall of gas into a disk around the center of the galaxy; (3) dust lanes and very weak spiral structure are seen out to about 9

  4. IRAS 20050+2720: ANATOMY OF A YOUNG STELLAR CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, H. M.; Wolk, S. J.; Spitzbart, B.; Forbrich, J.; Wright, N. J.; Bourke, T. L. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gutermuth, R. A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Allen, L. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Megeath, S. T. [Department of Physics and Astronomy, MS-113, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606 (United States); Pipher, J. L., E-mail: hguenther@cfa.harvard.edu [Department of Physics and Astronomy, University of Rochester, 500 Wilson Boulevard, Rochester, NY 14627 (United States)

    2012-10-01

    IRAS 20050+2720 is young star-forming region at a distance of 700 pc without apparent high-mass stars. We present results of our multi-wavelength study of IRAS 20050+2720 which includes observations by Chandra and Spitzer, and Two Micron All Sky Survey and UBVRI photometry. In total, about 300 young stellar objects (YSOs) in different evolutionary stages are found. We characterize the distribution of YSOs in this region using a minimum spanning tree analysis. We newly identify a second cluster core, which consists mostly of class II objects, about 10' from the center of the cloud. YSOs of earlier evolutionary stages are more clustered than more evolved objects. The X-ray luminosity function (XLF) of IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more massive Orion Nebula complex. IRAS 20050+2720 shows a lower N{sub H}/A{sub K} ratio compared with the diffuse interstellar medium.

  5. Massive Star Clusters in Ongoing Galaxy Interactions: Clues to Cluster Formation

    Science.gov (United States)

    Keel, William C.; Borne, Kirk D.

    2003-09-01

    We present HST WFPC2 observations, supplemented by ground-based Hα data, of the star-cluster populations in two pairs of interacting galaxies selected for being in very different kinds of encounters seen at different stages. Dynamical information and n-body simulations provide the details of encounter geometry, mass ratio, and timing. In NGC 5752/4 we are seeing a weak encounter, well past closest approach, after about 2.5×108 yr. The large spiral NGC 5754 has a normal population of disk clusters, while the fainter companion NGC 5752 exhibits a rich population of luminous clusters with a flatter luminosity function. The strong, ongoing encounter in NGC 6621/2, seen about 1.0×108 yr past closest approach between roughly equal-mass galaxies, has produced an extensive population of luminous clusters, particularly young and luminous in a small region between the two nuclei. This region is dynamically interesting, with such a strong perturbation in the velocity field that the rotation curve reverses sign. From these results, in comparison with other strongly interacting systems discussed in the literature, cluster formation requires a threshold level of perturbation, with stage of the interaction a less important factor. The location of the most active star formation in NGC 6621/2 draws attention to a possible role for the Toomre stability threshold in shaping star formation in interacting galaxies. The rich cluster populations in NGC 5752 and NGC 6621 show that direct contact between gas-rich galaxy disks is not a requirement to form luminous clusters and that they can be triggered by processes happening within a single galaxy disk (albeit triggered by external perturbations). Based on observations with the NASA/ESA Hubble Space Telescope, obtained 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.

  6. CSI 2264: simultaneous optical and infrared light curves of young disk-bearing stars in NGC 2264 with CoRoT and Spitzer—evidence for multiple origins of variability

    International Nuclear Information System (INIS)

    Cody, Ann Marie; Stauffer, John; Rebull, Luisa M.; Carey, Sean; Baglin, Annie; Micela, Giuseppina; Flaccomio, Ettore; Morales-Calderón, María; Aigrain, Suzanne; Bouvier, Jèrôme; Hillenbrand, Lynne A.; Carpenter, John; Findeisen, Krzysztof; Gutermuth, Robert; Song, Inseok; Turner, Neal; Alencar, Silvia H. P.; Zwintz, Konstanze; Plavchan, Peter; Terebey, Susan

    2014-01-01

    We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30 day multi-wavelength photometric monitoring campaign on more than 1000 young cluster members using 16 telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and long-duration data opens a new window into the time domain behavior of young stellar objects. Here we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The highlight of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological variability census and then use metrics of periodicity, stochasticity, and symmetry to statistically separate the light curves into seven distinct classes, which we suggest represent different physical processes and geometric effects. We provide distributions of the characteristic timescales and amplitudes and assess the fractional representation within each class. The largest category (>20%) are optical 'dippers' with discrete fading events lasting ∼1-5 days. The degree of correlation between the optical and infrared light curves is positive but weak; notably, the independently assigned optical and infrared morphology classes tend to be different for the same object. Assessment of flux variation behavior with respect to (circum)stellar properties reveals correlations of variability parameters with Hα emission and with effective temperature. Overall, our results point to multiple origins of young star variability, including circumstellar obscuration events, hot spots on the star and/or disk, accretion bursts, and rapid structural changes in the inner disk.

  7. Roche-lobe overflow systems powered by black holes in young star clusters: the importance of dynamical exchanges

    Energy Technology Data Exchange (ETDEWEB)

    Mapelli, Michela; Zampieri, Luca, E-mail: michela.mapelli@oapd.inaf.it [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122, Padova (Italy)

    2014-10-10

    We have run 600 N-body simulations of intermediate-mass (∼3500 M {sub ☉}) young star clusters (SCs; with three different metallicities (Z = 0.01, 0.1, and 1 Z {sub ☉}). The simulations include the dependence of stellar properties and stellar winds on metallicity. Massive stellar black holes (MSBHs) with mass >25 M {sub ☉} are allowed to form through direct collapse of very massive metal-poor stars (Z < 0.3 Z {sub ☉}). We focus on the demographics of black hole (BH) binaries that undergo mass transfer via Roche lobe overflow (RLO). We find that 44% of all binaries that undergo an RLO phase (RLO binaries) formed through dynamical exchange. RLO binaries that formed via exchange (RLO-EBs) are powered by more massive BHs than RLO primordial binaries (RLO-PBs). Furthermore, the RLO-EBs tend to start the RLO phase later than the RLO-PBs. In metal-poor SCs (0.01-0.1 Z {sub ☉}), >20% of all RLO binaries are powered by MSBHs. The vast majority of RLO binaries powered by MSBHs are RLO-EBs. We have produced optical color-magnitude diagrams of the simulated RLO binaries, accounting for the emission of both the donor star and the irradiated accretion disk. We find that RLO-PBs are generally associated with bluer counterparts than RLO-EBs. We compare the simulated counterparts with the observed counterparts of nine ultraluminous X-ray sources. We discuss the possibility that IC 342 X-1, Ho IX X-1, NGC 1313 X-2, and NGC 5204 X-1 are powered by an MSBH.

  8. X-ray Observations of Eight Young Open Star Clusters: I ...

    Indian Academy of Sciences (India)

    XMM-Newton View of Eight Young Open Star Clusters. 395 ... Multi-wavelength surveys of young open clusters provide an effective way to iden- tify young cluster .... First, the input images were built in two energy ranges, a soft band (0.3–2.0 keV) and ..... 3.2 Color-magnitude diagram of X-ray sources with NIR counterparts.

  9. Estrellas variables reconocidas en el campo del cúmulo abierto NGC 6250

    Science.gov (United States)

    Oviedo, C. G.; Palma, T.; Chavero, C.; Dékány, I.; Clariá, J. J.; Minniti, D.

    2017-10-01

    We present preliminary results obtained from a search of variable stars in the field of the moderately young open cluster NGC6250. The present study is based on the analysis of photometric near-infrared data in the and bands obtained with the 4.1m VISTA telescope of the VVV (Vista Variables in the Vía Láctea) Survey. Based on the obtained light curves, we performed a first classification of the newly detected variable stars. We also present the color-magnitude diagram of NGC6250, which is projected towards the galactic center direction, and we examined the possible physical association of the new variables discovered to NGC6250.

  10. Models of red giants in the CoRoT asteroseismology fields combining asteroseismic and spectroscopic constraints - The open cluster NGC 6633 and field stars-

    Science.gov (United States)

    Lagarde, Nadège; Miglio, Andrea; Eggenberger, Patrick; Morel, Thierry; Montalbàn, Josefina; Mosser, Benoit

    2015-08-01

    The availability of asteroseismic constraints for a large sample of red giant stars from the CoRoT and Kepler missions paves the way for various statistical studies of the seismic properties of stellar populations.We use the first detailed spectroscopic study of CoRoT red-giant stars (Morel et al 2014) to compare theoretical stellar evolution models to observations of the open cluster NGC 6633 and field stars.In order to explore the effects of rotation-induced mixing and thermohaline instability, we compare surface abundances of carbon isotopic ratio and lithium with stellar evolution predictions. These chemicals are sensitive to extra-mixing on the red-giant branch.We estimate mass, radius, and distance for each star using the seismic constraints. We note that the Hipparcos and seismic distances are different. However, the uncertainties are such that this may not be significant. Although the seismic distances for the cluster members are self consistent they are somewhat larger than the Hipparcos distance. This is an issue that should be considered elsewhere. Models including thermohaline instability and rotation-induced mixing, together with the seismically determined masses can explain the chemical properties of red-giants targets. Tighter constraints on the physics of the models would be possible if there were detailed knowledge of the core rotation rate and the asymptotic period spacing.

  11. DETAILED ABUNDANCES OF RED GIANTS IN THE GLOBULAR CLUSTER NGC 1851: C+N+O AND THE ORIGIN OF MULTIPLE POPULATIONS

    International Nuclear Information System (INIS)

    Villanova, S.; Geisler, D.; Piotto, G.

    2010-01-01

    We present chemical abundance analysis of a sample of 15 red giant branch (RGB) stars of the globular cluster NGC 1851 distributed along the two RGBs of the (v, v-y) color-magnitude diagram. We determined abundances for C+N+O, Na, α, iron-peak, and s-elements. We found that the two RGB populations significantly differ in their light (N, O, Na) and s-element content. On the other hand, they do not show any significant difference in their α and iron-peak element content. More importantly, the two RGB populations do not show any significant difference in their total C+N+O content. Our results do not support previous hypotheses suggesting that the origins of the two RGBs and the two subgiant branches of the cluster are related to different content of either α (including Ca) or iron-peak elements, or C+N+O abundance, due to a second generation polluted by Type II supernovae.

  12. Evolution of massive stars in very young clusters and associations

    International Nuclear Information System (INIS)

    Stothers, R.B.

    1985-01-01

    The stellar content of very young galactic clusters and associations with well-determined ages has been analyzed statistically to derive information about stellar evolution at high masses. The adopted approach is semiempirical and uses natural spectroscopic groups of stars on the H-R diagram, together with the stars' apparent magnitudes. Cluster distance moduli are not used. Only the most basic elements of stellar evolution theory are required as input. For stellar aggregates with main-sequence turnups at spectral types between O9 and B2, the following conclusions have emerged: (1) O-type main-sequence stars evolve to a spectral type of B1 during core hydrogen burning; (2) most of the O-type blue stragglers are newly formed massive stars, burning core hydrogen; (3) supergiants lying redward of the turnup, as well as most, or all, of the Wolf-Rayet stars, are burning core helium; (4) Wolf-Rayet stars originally had masses greater than 30--40 M/sub sun/, while known M-type supergiants evolved from star less massive than approx.30 M/sub sun/; (5) phases of evolution following core helium burning are unobservably rapid, presumably on account of copious neutrino emission; and (6) formation of stars of high mass continues vigorously in most young clusters and association for approx.8 x 10 6 yr. The important result concerning the evolutionary status of the supergiants depends only on the total number of these stars and not on how they are distributed between blue and red types; the result, however, may be sensitive to the assumed amount of convective core overshooting. Conclusions in the present work refer chiefly to luminous stars in the mass range 10--40 M/sub sun/, belonging to aggregates in the age range (6--25) x 10 6 yr

  13. YOUNG STELLAR CLUSTERS CONTAINING MASSIVE YOUNG STELLAR OBJECTS IN THE VVV SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Borissova, J.; Alegría, S. Ramírez; Kurtev, R.; Medina, N.; Navarro, C.; Kuhn, M.; Gromadzki, M.; Retamales, G.; Fernandez, M. A.; Agurto-Gangas, C.; Amigo, P. [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030 (Chile); Alonso, J.; Decany, I. [Millennium Institute of Astrophysics (MAS), Santiago (Chile); Lucas, P. W.; Pena, C. Contreras; Thompson, M. A. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Chené, A.-N. [Gemini Observatory, Northern Operations Center, 670 N. A’ohoku Place, Hilo, HI 96720 (United States); Minniti, D. [Departamento de Ciencias Físicas, Universidad Andres Bello, Republica 220, Santiago (Chile); Catelan, M. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Morales, E. F. E., E-mail: jura.borissova@uv.cl [Max-Planck-Institute for Astronomy (Germany)

    2016-09-01

    The purpose of this research is to study the connections of the global properties of eight young stellar clusters projected in the Vista Variables in the Via Lactea (VVV) ESO Large Public Survey disk area and their young stellar object (YSO) populations. The analysis is based on the combination of spectroscopic parallax-based reddening and distance determinations with main-sequence and pre-main-sequence ishochrone fitting to determine the basic parameters (reddening, age, distance) of the sample clusters. The lower mass limit estimations show that all clusters are low or intermediate mass (between 110 and 1800  M {sub ⊙}), the slope Γ of the obtained present-day mass functions of the clusters is close to the Kroupa initial mass function. The YSOs in the cluster’s surrounding fields are classified using low resolution spectra, spectral energy distribution fits with theoretical predictions, and variability, taking advantage of multi-epoch VVV observations. All spectroscopically confirmed YSOs (except one) are found to be massive (more than 8 M {sub ⊙}). Using VVV and GLIMPSE color–color cuts we have selected a large number of new YSO candidates, which are checked for variability and 57% are found to show at least low-amplitude variations. In few cases it was possible to distinguish between YSO and AGB classifications on the basis of light curves.

  14. Insights into the properties of the Orion spiral arm. NGC 2302: first result

    Science.gov (United States)

    Costa, E.; Carraro, G.; Moitinho, A.; Radiszc, M.; Méndez, R. A.

    2018-01-01

    We summarize the first results from a program aimed at determining the properties of the Local (Orion) arm - LOA, based on a large and homogeneous set of kinematic and photometric data. We have made a comprehensive study of the young LOA cluster NGC 2302, which includes a UBVRI photometric analysis and determination of its kinematic properties -proper motion (PM) and radial velocity (RV) - and of its orbital parameters.

  15. Circumstellar Disk Lifetimes In Numerous Galactic Young Stellar Clusters

    Science.gov (United States)

    Richert, A. J. W.; Getman, K. V.; Feigelson, E. D.; Kuhn, M. A.; Broos, P. S.; Povich, M. S.; Bate, M. R.; Garmire, G. P.

    2018-04-01

    Photometric detections of dust circumstellar disks around pre-main sequence (PMS) stars, coupled with estimates of stellar ages, provide constraints on the time available for planet formation. Most previous studies on disk longevity, starting with Haisch, Lada & Lada (2001), use star samples from PMS clusters but do not consider datasets with homogeneous photometric sensitivities and/or ages placed on a uniform timescale. Here we conduct the largest study to date of the longevity of inner dust disks using X-ray and 1-8 {μ m} infrared photometry from the MYStIX and SFiNCs projects for 69 young clusters in 32 nearby star-forming regions with ages t ≤ 5 Myr. Cluster ages are derived by combining the empirical AgeJX method with PMS evolutionary models, which treat dynamo-generated magnetic fields in different ways. Leveraging X-ray data to identify disk-free objects, we impose similar stellar mass sensitivity limits for disk-bearing and disk-free YSOs while extending the analysis to stellar masses as low as M ˜ 0.1 M⊙. We find that the disk longevity estimates are strongly affected by the choice of PMS evolutionary model. Assuming a disk fraction of 100% at zero age, the inferred disk half-life changes significantly, from t1/2 ˜ 1.3 - 2 Myr to t1/2 ˜ 3.5 Myr when switching from non-magnetic to magnetic PMS models. In addition, we find no statistically significant evidence that disk fraction varies with stellar mass within the first few Myr of life for stars with masses <2 M⊙, but our samples may not be complete for more massive stars. The effects of initial disk fraction and star-forming environment are also explored.

  16. On a New Near-Infrared Method to Estimate the Absolute Ages of Star Clusters: NGC 3201 as a First Test Case

    Science.gov (United States)

    Bono, G.; Stetson, P. B.; VandenBerg, D. A.; Calamida, A.; Dall'Ora, M.; Iannicola, G.; Amico, P.; Di Cecco, A.; Marchetti, E.; Monelli, M.; Sanna, N.; Walker, A. R.; Zoccali, M.; Buonanno, R.; Caputo, F.; Corsi, C. E.; Degl'Innocenti, S.; D'Odorico, S.; Ferraro, I.; Gilmozzi, R.; Melnick, J.; Nonino, M.; Ortolani, S.; Piersimoni, A. M.; Prada Moroni, P. G.; Pulone, L.; Romaniello, M.; Storm, J.

    2010-01-01

    We present a new method to estimate the absolute ages of stellar systems. This method is based on the difference in magnitude between the main-sequence turnoff (MSTO) and a well-defined knee located along the lower main sequence (MSK). This feature is caused by the collisionally induced absorption of molecular hydrogen, and it can easily be identified in near-infrared (NIR) and in optical-NIR color-magnitude diagrams of stellar systems. We took advantage of deep and accurate NIR images collected with the Multi-Conjugate Adaptive Optics Demonstrator temporarily available on the Very Large Telescope and of optical images collected with the Advanced Camera for Surveys Wide Field Camera on the Hubble Space Telescope and with ground-based telescopes to estimate the absolute age of the globular NGC 3201 using both the MSTO and the Δ(MSTO-MSK). We have adopted a new set of cluster isochrones, and we found that the absolute ages based on the two methods agree to within 1σ. However, the errors of the ages based on the Δ(MSTO-MSK) method are potentially more than a factor of 2 smaller, since they are not affected by uncertainties in cluster distance or reddening. Current isochrones appear to predict slightly bluer (≈0.05 mag) NIR and optical-NIR colors than observed for magnitudes fainter than the MSK. Based on near infrared observations made with ESO telescopes SOFI at NTT, La Silla; MAD at VLT Paranal, projects: 66.D-0557, 074.D-0655, ID96406, and with the Cerro Tololo Inter-American Observatory (CTIO) telescope ISPI at 4m Blanco, La Serena. Based on optical data collected with ESO telescopes and retrieved from the ESO Science Archive Facility. This research used the facilities of the Canadian Astronomy Data Centre operated by the National Research Council of Canada with the support of the Canadian Space Agency.

  17. THE MASSIVE PROTOSTELLAR CLUSTER NGC 6334I AT 220 au RESOLUTION: DISCOVERY OF FURTHER MULTIPLICITY, DIVERSITY, AND A HOT MULTI-CORE

    Energy Technology Data Exchange (ETDEWEB)

    Brogan, C. L.; Hunter, T. R.; Indebetouw, R. [NRAO, 520 Edgemont Rd, Charlottesville, VA 22903 (United States); Cyganowski, C. J. [SUPA, School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom); Chandler, C. J. [NRAO, P.O. Box 0, Socorro, NM 87801 (United States); Friesen, R., E-mail: cbrogan@nrao.edu [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Toronto, Ontario, M5S 3H4 (Canada)

    2016-12-01

    We present Very Large Array and Atacama Large Millimeter/submillimeter Array imaging of the deeply embedded protostellar cluster NGC 6334I from 5 cm to 1.3 mm at angular resolutions as fine as 0.″17 (220 au). The dominant hot core MM1 is resolved into seven components at 1.3 mm, clustered within a radius of 1000 au. Four of the components have brightness temperatures >200 K, radii ∼300 au, minimum luminosities ∼10{sup 4} L {sub ⊙}, and must be centrally heated. We term this new phenomenon a “hot multi-core.” Two of these objects also exhibit compact free–free emission at longer wavelengths, consistent with a hypercompact H ii region (MM1B) and a jet (MM1D). The spatial kinematics of the water maser emission centered on MM1D are consistent with it being the origin of the high-velocity bipolar molecular outflow seen in CO. The close proximity of MM1B and MM1D (440 au) suggests a proto-binary or a transient bound system. Several components of MM1 exhibit steep millimeter spectral energy distributions indicative of either unusual dust spectral properties or time variability. In addition to resolving MM1 and the other hot core (MM2) into multiple components, we detect five new millimeter and two new centimeter sources. Water masers are detected for the first time toward MM4A, confirming its membership in the protocluster. With a 1.3 mm brightness temperature of 97 K coupled with a lack of thermal molecular line emission, MM4A appears to be a highly optically thick 240  L {sub ⊙} dust core, possibly tracing a transient stage of massive protostellar evolution. The nature of the strongest water maser source CM2 remains unclear due to its combination of non-thermal radio continuum and lack of dust emission.

  18. VARIABLE STARS IN THE LARGE MAGELLANIC CLOUD GLOBULAR CLUSTER NGC 2257. I. RESULTS BASED ON 2007-2008 B, V PHOTOMETRY

    International Nuclear Information System (INIS)

    Nemec, James M.; Walker, Alistair; Jeon, Young-Beom

    2009-01-01

    The variable stars in the Large Magellanic Cloud star cluster NGC 2257 are reinvestigated using photometry (to ∼20th mag) of over 400 new B, V CCD images taken with the CTIO 0.9 m telescope on 14 nights in 2007 December and 2008 January. New period searches have been made using two independent algorithms (CLEAN, Period04); the resultant periods of most of the stars are consistent with the pulsation periods derived previously, and where there are discrepancies these have been resolved. For the B and V light curves, accurate Fourier coefficients and parameters are given. Six new variable stars have been discovered (V45-50), including a bright candidate long-period variable star showing secondary oscillations (V45) and two anomalously bright RRc stars (V48 and V50), which are shown to be brightened and reddened by nearby red giant stars. Also discovered among the previously known variable stars are three double-mode RR Lyrae stars (V8, V16, and V34) and several Blazhko variables. Archival Hubble Space Telescope images and the photometry by Johnson et al. have been used to define better the properties of the most crowded variable stars. The total number of cluster variable stars now stands at forty-seven: 23 RRab stars, four of which show Blazhko amplitude variations; 20 RRc stars, one showing clear Blazhko variations and another showing possible Blazhko variations; the three RRd stars, all having the dominant period ∼0.36 day and period ratios P 1 /P 0 ∼0.7450; and an LPV star located near the tip of the red giant branch. A comparison of the RRd stars with those in other environments shows them to be most similar to those in IC4499.

  19. A Detached Eclipsing Binary near the Turnoff of the Open Cluster NGC 6819 and Determining Age Using Kepler

    DEFF Research Database (Denmark)

    Brewer, Lauren; Sandquist, E. L.; Mathieu, R. D.

    2013-01-01

    from the Kepler spacecraft and from the 1 m telescope at Mount Laguna Observatory in B, V, Rc, and Ic. Radial velocities were measured as part of a long-term study of the cluster (e.g., Hole et al. 2009) using the WIYN 3.5-meter telescope. A665 is a triple-lined system, and we verify that the brightest...... in the mass-radius plane. Our target is to reduce the uncertainty on the cluster age to less than 10% using results from A665 and other known DEBs. The results for this system will also help produce a valuable test of the asteroseismic mass estimates for giant stars in the cluster (Stello et al. 2011). We...

  20. Collaborative Research of Open Star Clusters Alisher S. Hojaev

    Indian Academy of Sciences (India)

    Some spectra of the young star candidates with dispersion 50 and 200 Å/mm were .... Color-magnitude diagram for o band and o band minus i band for stars in the region of NGC ... Statistical analysis for open cluster parameters investigation.

  1. PROPER MOTIONS OF YOUNG STELLAR OUTFLOWS IN THE MID-INFRARED WITH SPITZER (IRAC). I. THE NGC 1333 REGION

    International Nuclear Information System (INIS)

    Raga, A. C.; Noriega-Crespo, A.; Carey, S. J.; Arce, H. G.

    2013-01-01

    We use two 4.5 μm Spitzer (IRAC) maps of the NGC 1333 region taken over a ∼7 yr interval to determine proper motions of its associated outflows. This is a first successful attempt at obtaining proper motions of stellars' outflow from Spitzer observations. For the outflow formed by the Herbig-Haro objects HH7, 8, and 10, we find proper motions of ∼9-13 km s –1 , which are consistent with previously determined optical proper motions of these objects. We determine proper motions for a total of eight outflows, ranging from ∼10 to 100 km s –1 . The derived proper motions show that out of these eight outflows, three have tangential velocities ≤20 km s –1 . This result shows that a large fraction of the observed outflows have low intrinsic velocities and that the low proper motions are not merely a projection effect.

  2. Current star formation in S0 galaxies: NGC 4710

    International Nuclear Information System (INIS)

    Wrobel, J.M.

    1990-01-01

    Elliptical (E) and lenticular (S0) galaxies lack the substantial interstellar medium (ISM) found in the star-forming spiral galaxies. However, significant numbers of E and S0 galaxies are known to contain detectable amounts of interstellar matter (e.g., Jura 1988). Thus, it is worth investigating whether these galaxies are currently able to form stars from their ISM, or whether they should be consigned to the dustbin of inert objects (Thronson and Bally 1987). The results strongly imply that current star formation is responsible for NGC 4710's far infrared and radio continuum properties. If this is indeed the case, then one expects this star formation to be fueled by molecular gas, which is presumably dominated by H2 and can be traced by the CO-12 J=1 to 0 line. Both Kenney and Young (1988) and Sage and Wrobel (1989) have detected such an emission line from NGC 4710, and infer the presence of more than 10(exp 8) solar mass of H2. The origin of the molecular gas in NGC 4710 remains a mystery. The galaxy is very deficient in HI (Kenney and Young, in preparation), suggesting that it originally was a spiral galaxy from which the outer, mainly atomic, gas was stripped by the ram pressure of the Virgo Cluster's intracluster medium, leaving only a central interstellar medium (ISM) rich in molecular gas. Alternatively, the CO may have originated via stellar mass loss with subsequent cooling, cooling flows, or capture from a gas-rich companion. Information on the morphology and kinematics of the CO can be compared with that of the galaxy's other gases and stars to distinguish among these various possible origins for the molecular gas. Major axis CO mapping with single dishes indicate an unresolved source. Thus, a millimeter array is currently being used to image NGC 4710 in CO to provide the needed morphological and kinematical data

  3. Dynamical mass of a star cluster in M 83: a test of fibre-fed multi-object spectroscopy

    NARCIS (Netherlands)

    Moll, S.L.; Grijs, R.; Anders, P.; Crowther, P.A.; Larsen, S.S.; Smith, L.J.; Portegies Zwart, S.F.

    2008-01-01

    Aims. We obtained VLT/FLAMES+UVES high-resolution, fibre-fed spectroscopy of five young massive clusters (YMCs) in M 83 (NGC 5236). This forms the basis of a pilot study testing the feasibility of using fibre-fed spectroscopy to measure the velocity dispersions of several clusters simultaneously, in

  4. Dynamical mass of a star cluster in M 83: A test of fibre-fed multi-object spectroscopy

    NARCIS (Netherlands)

    Moll, S.L.; de Grijs, R.; Anders, P.; Crowther, P.A.; Larsen, S.S.; Smith, L.J.; Portegies Zwart, S.F.

    2008-01-01

    Aims. We obtained VLT/FLAMES+UVES high-resolution, fibre-fed spectroscopy of five young massive clusters (YMCs) in M 83 (NGC 5236). This forms the basis of a pilot study testing the feasibility of using fibre-fed spectroscopy to measure the velocity dispersions of several clusters simultaneously, in

  5. VizieR Online Data Catalog: 24um excesses in clusters & membership of NGC2244 (Meng+, 2017)

    Science.gov (United States)

    Meng, H. Y. A.; Rieke, G. H.; Su, K. Y. L.; Gaspar, A.

    2017-09-01

    We re-measured the Spitzer/MIPS 24um photometry for all the clusters except for a few noted in Appendix A. We obtained the 24um data from the Spitzer Heritage Archive between 2004 Jan 28 and 2008 Oct 23. (3 data files).

  6. The origin and orbit of the old, metal-rich, open cluster NGC 6791. Insights from kinematics

    Czech Academy of Sciences Publication Activity Database

    Jílková, L.; Carraro, G.; Jungwiert, Bruno; Minchev, I.

    2012-01-01

    Roč. 541, April (2012), A64/1-A64/11 ISSN 0004-6361 R&D Projects: GA MŠk(CZ) LC06014; GA ČR GD205/08/H005 Institutional research plan: CEZ:AV0Z10030501 Keywords : galaxy * kinematics and dynamics * open clusters and associations Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.084, year: 2012

  7. Origin of γ-rays from young open clusters

    International Nuclear Information System (INIS)

    Giovannelli, F.; Bednarek, W.; Karakula, S.

    1996-01-01

    The young open cluster Berkeley 87 was predicted to be associated with the COS B γ-ray source 2CG 075+00 on the basis of the experimental evidence of the presence of a shock front around the Wolf - Rayet star ST3 placed in the inner part of the cluster. The CGRO phase-1 data confirm this identification. Protons accelerated at the shock boundary can produce π deg. via p-p interactions and then γ-rays. With the measured flux F γ (E > 100 MeV) ≅ 9x10 -7 ph cm -2 s -1 and the power-law proton spectrum with spectral index γ = 2, the cosmic-ray-energy-density in the inner part (∼ 0.8 pc radius) of Berk 87 is about 100 times greater than that in the vicinity of the Earth. We have calculated γ-ray spectra expected from the decay of π d eg. produced in p-p interactions. The spectra have been normalized to the observed flux of Berk 87 by using different input proton spectra. The comparison of these normalized spectra with the upper limit at 140 TeV, coming from the CASA-MIA experiment, provides constraints on the initial proton spectrum in Berk 87. The calculated γ-ray spectra of Berk 87 are also compared with the sensitivities of some present and future experiments for energies greater than 100 GeV, such as the Whipple and GAMT experiments. We suggest the possibility of measuring cosmic-ray induced lines, such as the 4.44 MeV and 6.13 MeV nuclear de-excitation lines of 12 C* and 16 O*, respectively, from Berk 87 with the COMPTEL instrument on board the CGRO. Also the positrons resulting from energetic particle interactions should produce 0.511 MeV annihilation radiation from Berk 87, which could be measured by the OSSE instrument on board the CGRO. (author)

  8. The low-metallicity starburst NGC346: massive-star population and feedback

    Science.gov (United States)

    Oskinova, Lida

    2017-08-01

    The Small Magellanic Cloud (SMC) is ideal to study young, massive stars at low metallicity. The compact cluster NGC346 contains about half of all O-type stars in the entire SMC. The massive-star population of this cluster powers N66, the brightest and largest HII region in the SMC. We propose to use HST-STIS to slice NGC346 with 20 long-slit exposures, in order to obtain the UV spectra of most of the massive early-type stars of this cluster. Archival data of 13 exposures that cover already a minor part of this cluster will be included in our analyses. Our aim is to quantitatively analyze virtually the whole massive-star population of NGC346. We have already secured the optical spectra of all massive stars in the field with the integral-field spectrograph MUSE at the ESO-VLT. However, for the determination of the stellar-wind parameters, i.e. the mass-loss rates and the wind velocities, ultraviolet spectra are indispensable. Our advanced Potsdam Wolf-Rayet (PoWR) code will be used for modeling the stellar and wind spectra in the course of the analysis. Finally, we will obtain:(a) the fundamental stellar and wind parameters of all stars brighter than spectral type B2V in the field, which, e,g,, will constrain the initial mass function in this young low-metallicity starburst;(b) mass-loss rates of many more OB-type stars at SMC metallicity than hitherto known, allowing to better constrain their metallicity dependence;(c) the integrated feedback by ionizing radiation and stellar winds of the whole massive-star population of NGC346, which will be used as input to model the ecology of the giant HII region N66.These HST UV data will be of high legacy value.

  9. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Grasha, K.; Calzetti, D. [Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States); Adamo, A.; Messa, M. [Dept. of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Kim, H. [Gemini Observatory, La Serena (Chile); Elmegreen, B. G. [IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY (United States); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Dale, D. A. [Dept. of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Fumagalli, M. [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Durham University, Durham (United Kingdom); Grebel, E. K.; Shabani, F. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany); Johnson, K. E. [Dept. of Astronomy, University of Virginia, Charlottesville, VA (United States); Kahre, L. [Dept. of Astronomy, New Mexico State University, Las Cruces, NM (United States); Kennicutt, R. C. [Institute of Astronomy, University of Cambridge, Cambridge (United Kingdom); Pellerin, A. [Dept. of Physics and Astronomy, State University of New York at Geneseo, Geneseo NY (United States); Ryon, J. E.; Ubeda, L. [Space Telescope Science Institute, Baltimore, MD (United States); Smith, L. J. [European Space Agency/Space Telescope Science Institute, Baltimore, MD (United States); Thilker, D., E-mail: kgrasha@astro.umass.edu [Dept. of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD (United States)

    2017-05-10

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  10. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    Science.gov (United States)

    Grasha, K.; Calzetti, D.; Adamo, A.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Dale, D. A.; Fumagalli, M.; Grebel, E. K.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Messa, M.; Pellerin, A.; Ryon, J. E.; Smith, L. J.; Shabani, F.; Thilker, D.; Ubeda, L.

    2017-05-01

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3-15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ˜40-60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  11. The Hierarchical Distribution of the Young Stellar Clusters in Six Local Star-forming Galaxies

    International Nuclear Information System (INIS)

    Grasha, K.; Calzetti, D.; Adamo, A.; Messa, M.; Kim, H.; Elmegreen, B. G.; Gouliermis, D. A.; Dale, D. A.; Fumagalli, M.; Grebel, E. K.; Shabani, F.; Johnson, K. E.; Kahre, L.; Kennicutt, R. C.; Pellerin, A.; Ryon, J. E.; Ubeda, L.; Smith, L. J.; Thilker, D.

    2017-01-01

    We present a study of the hierarchical clustering of the young stellar clusters in six local (3–15 Mpc) star-forming galaxies using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey). We identified 3685 likely clusters and associations, each visually classified by their morphology, and we use the angular two-point correlation function to study the clustering of these stellar systems. We find that the spatial distribution of the young clusters and associations are clustered with respect to each other, forming large, unbound hierarchical star-forming complexes that are in general very young. The strength of the clustering decreases with increasing age of the star clusters and stellar associations, becoming more homogeneously distributed after ∼40–60 Myr and on scales larger than a few hundred parsecs. In all galaxies, the associations exhibit a global behavior that is distinct and more strongly correlated from compact clusters. Thus, populations of clusters are more evolved than associations in terms of their spatial distribution, traveling significantly from their birth site within a few tens of Myr, whereas associations show evidence of disruption occurring very quickly after their formation. The clustering of the stellar systems resembles that of a turbulent interstellar medium that drives the star formation process, correlating the components in unbound star-forming complexes in a hierarchical manner, dispersing shortly after formation, suggestive of a single, continuous mode of star formation across all galaxies.

  12. Photometric metal abundances for twenty clusters

    International Nuclear Information System (INIS)

    Jennens, P.A.; Helfer, H.L.

    1975-01-01

    Metal abundances, colour excesses and distance moduli have been determined for individual giant stars, using UBViyz photometry, in NGC 188, 559, 752, 1245, 1342, 1907, 1912, 2099, 5139 (ω cen), 5316, 5617, 5822, 5823, 6067, IC 4651, 6819, 6940, 7142, 7261 and 7789. All six clusters with ages 3 to 8x10 9 yr have metal abundances agreeing with one another; their average value of [Fe/H]=-0.24+-0.05, agrees with the average found for the bright K-giants near the Sun. All six clusters are at least 140pc from the galactic plane. For the younger clusters less than approximately 10 9 yr old, one-third are metal deficient. The very young cluster, NGC 559, is probably very metal weak. (author)

  13. Spectroscopic Study of NGC 281 West

    Science.gov (United States)

    Hasan, Priya

    2018-04-01

    NGC 281 is a complex region of star formation at 2.8 kpc. This complex is situated 300 pc above the Galactic plane, and appears to be part of a 270 pc diameter ring of atomic and molecular clouds expanding at 22 km/s (Megeath et al. 2003). It appears that two modes of triggered star formation are at work here: an initial supernova to trigger the ring complex and the initial O stars and the subsequent triggering of low mass star formation by photoevaporation driven molecular core compression. To get a complete census of the young stellar population, we use observations from Chandra ACIS 100 ksec coupled with data from 2MASS and Spitzer. The Master X-ray catalog has 446 sources detected in different bandpasses. We present the spatial distribution of Class I, II and III sources to study the progress of star formation. We also determine the gas to dust ratio NH/AK to be 1.93 ± 0.47 ×1022 cm‑2 mag‑1 for this region. In this article, we present NGC 281 as a good target to study with the 3.6-m Devasthal Optical Telescope (DOT) in spectroscopy. With these spectra, we look for evidence for the pre-main-sequence (PMS) nature of the objects, study the properties of the detected emission lines as a function of evolutionary class, and obtain spectral types for the observed young stellar objects (YSOs). The temperatures implied by the spectral types can be combined with luminosities determined from the near-infrared (NIR) photometry to construct Hertzsprung–Russell (HR) diagrams for the clusters. By comparing the positions of the YSOs in the HR diagrams with the PMS tracks, we can determine the ages of the embedded sources and study the relative ages of the YSOs with and without optically thick circumstellar disks.

  14. NGC 2770

    DEFF Research Database (Denmark)

    Thöne, Christina C.; Michalowski, Michal; Leloudas, Giorgos

    2009-01-01

    2770 has a small irregular companion, NGC 2770B, which is highly star-forming, has a very low mass and one of the lowest metallicities detected in the nearby universe as derived from longslit spectroscopy. In the most metal poor part, we even detect Wolf-Rayet (WR) features, which is at odds with most...... and specifically the three SN sites to investigate whether this galaxy is in any way peculiar to cause a high frequency of SNe Ib. We model the global spectral energy distribution of the galaxy from broadband data and derive a star formation and SN rate comparable to the values of the Milky Way. We further study...... the galaxy using longslit spectroscopy covering the major axis and the three SN sites. From the spectroscopic study we find subsolar metallicities for the SN sites, a high extinction and a moderate star formation rate. In a high-resolution spectrum, we also detect diffuse interstellar bands in the line...

  15. TIME-SERIES PHOTOMETRY OF STARS IN AND AROUND THE LAGOON NEBULA. I. ROTATION PERIODS OF 290 LOW-MASS PRE-MAIN-SEQUENCE STARS IN NGC 6530

    International Nuclear Information System (INIS)

    Henderson, Calen B.; Stassun, Keivan G.

    2012-01-01

    We have conducted a long-term, wide-field, high-cadence photometric monitoring survey of ∼50,000 stars in the Lagoon Nebula H II region. This first paper presents rotation periods for 290 low-mass stars in NGC 6530, the young cluster illuminating the nebula, and for which we assemble a catalog of infrared and spectroscopic disk indicators, estimated masses and ages, and X-ray luminosities. The distribution of rotation periods we measure is broadly uniform for 0.5 days X /L bol ≈ –3.3). However, we find a significant positive correlation between L X /L bol and corotation radius, suggesting that the observed X-ray luminosities are regulated by centrifugal stripping of the stellar coronae. The period-mass relationship in NGC 6530 is broadly similar to that of the Orion Nebula Cluster (ONC), but the slope of the relationship among the slowest rotators differs from that in the ONC and other young clusters. We show that the slope of the period-mass relationship for the slowest rotators can be used as a proxy for the age of a young cluster, and we argue that NGC 6530 may be slightly younger than the ONC, making it a particularly important touchstone for models of angular momentum evolution in young, low-mass stars.

  16. Molecular cloud-scale star formation in NGC 300

    Energy Technology Data Exchange (ETDEWEB)

    Faesi, Christopher M.; Lada, Charles J.; Forbrich, Jan [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Menten, Karl M. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Bouy, Hervé [Centro de Astrobiología, (INTA-CSIC), Departamento de Astrofísica, POB 78, ESAC Campus, 28691 Villanueva dela Cañada (Spain)

    2014-07-01

    We present the results of a galaxy-wide study of molecular gas and star formation in a sample of 76 H II regions in the nearby spiral galaxy NGC 300. We have measured the molecular gas at 250 pc scales using pointed CO(J = 2-1) observations with the Atacama Pathfinder Experiment telescope. We detect CO in 42 of our targets, deriving molecular gas masses ranging from our sensitivity limit of ∼10{sup 5} M {sub ☉} to 7 × 10{sup 5} M {sub ☉}. We find a clear decline in the CO detection rate with galactocentric distance, which we attribute primarily to the decreasing radial metallicity gradient in NGC 300. We combine Galaxy Evolution Explorer far-ultraviolet, Spitzer 24 μm, and Hα narrowband imaging to measure the star formation activity in our sample. We have developed a new direct modeling approach for computing star formation rates (SFRs) that utilizes these data and population synthesis models to derive the masses and ages of the young stellar clusters associated with each of our H II region targets. We find a characteristic gas depletion time of 230 Myr at 250 pc scales in NGC 300, more similar to the results obtained for Milky Way giant molecular clouds than the longer (>2 Gyr) global depletion times derived for entire galaxies and kiloparsec-sized regions within them. This difference is partially due to the fact that our study accounts for only the gas and stars within the youngest star-forming regions. We also note a large scatter in the NGC 300 SFR-molecular gas mass scaling relation that is furthermore consistent with the Milky Way cloud results. This scatter likely represents real differences in giant molecular cloud physical properties such as the dense gas fraction.

  17. NGC 5291: Implications for the Formation of Dwarf Galaxies

    Science.gov (United States)

    Malphrus, Benjamin K.; Simpson, Caroline E.; Gottesman, S. T.; Hawarden, Timothy G.

    1997-01-01

    The possible formation and evolution of dwarf irregular galaxies from material derived from perturbed evolved galaxies is addressed via an H I study of a likely example, the peculiar system NGC 5291. This system, located in the western outskirts of the cluster Abell 3574, contains the lenticular galaxy NGC 5291 which is in close proximity to a disturbed companion and is flanked by an extensive complex of numerous knots extending roughly 4 min north and 4 min south of the galaxy. In an initial optical and radio study, Longmore et al. (1979, MNRAS, 188, 285) showed that these knots have the spectra of vigorous star-forming regions, and suggested that some may in fact be young dwarf irregular galaxies. High resolution 21-cm line observations taken with the VLA are presented here and reveal that the H I distribution associated with this system encompasses not only the entire N-S complex of optical knots, but also forms an incomplete ring or tail that extends approximately 3 min to the west. The H I associated with NGC 5291 itself shows a high velocity range; the Seashell is not detected. The formation mechanism for this unusual system is unclear and two models - a large, low-luminosity ram-swept disk, and a ram-swept interaction-are discussed. The H I in the system contains numerous concentrations, mostly along the N-S arc of the star-forming complexes, which generally coincide with one or more optical knots; the larger H I features contain several x 10(exp 9) solar mass of gas. Each of the knots is compared to a set of criteria designed to determine if these objects are bound against their own internal kinetic energy and are tidally stable relative to the host galaxy. An analysis of the properties of the H I concentrations surrounding the optical star-forming complexes indicates that at least the largest of these is a bound system; it also possesses a stellar component. It is suggested that this object is a genuinely young dwarf irregular galaxy that has evolved from

  18. Multi-wavelength study of young and massive galaxy clusters

    International Nuclear Information System (INIS)

    Lemonon, Ludovic

    1999-01-01

    Clusters of galaxies are the most massive objects gravitationally bound observed. They are the consequence of the evolution of most important perturbations in the cosmological microwave background. Their formation depends strongly of the cosmology, so they represent key objects to understand the Universe. The aim of this thesis is to study the processes of formation in clusters of galaxies well far away than previous studies clone, by high-resolution observations obtained by using most powerful telescope in each studied wavelength: X-ray, visible, infrared and radio. After data reductions of 12 clusters located at 0.1; z; 0.3, I was able to classified them in three categories: dynamically perturbed clusters, with substructures in their X-ray/optical image or velocity distribution of galaxies; cooling flows clusters, more relaxed than previous, with huge amount of gas cooling in their center; AGN contaminated, where the central dominant galaxy is an AGN which contaminate considerably the X-ray emission. I have obtained a measurement of the baryonic fraction of the Universe mass, and an estimation of the Universe matter density parameter at the mega-parsec scale, claiming for a low density universe. The ISOCAM data showed the effect of the ICM interactions on the star formation in cluster galaxies, and demonstrated that optical and mid-IR deduced star-formation are not basically compatible. They also showed how IR-emitting galaxies distribute in clusters, most noticeably how 15 um galaxies are located preferably on the edge of clusters. X-ray and radio data showed that clusters at z 0.25 could be find in several dynamical state, similarly with nearby ones, from relaxed to severely perturbed. All clusters present signs of past or present merging, in agreement with hierarchical structure formation scenario. This clusters database is an excellent starting point to study process of merging in clusters since they showed different aspect of this evolution. (author) [fr

  19. The Cosmic Christmas Ghost - Two Stunning Pictures of Young Stellar Clusters

    Science.gov (United States)

    2005-12-01

    Just like Charles Dickens' Christmas Carol takes us on a journey into past, present and future in the time of only one Christmas Eve, two of ESO' s telescopes captured various stages in the life of a star in a single image. ESO PR Photo 42a/05 shows the area surrounding the stellar cluster NGC 2467, located in the southern constellation of Puppis (" The Stern" ). With an age of a few million years at most, it is a very active stellar nursery, where new stars are born continuously from large clouds of dust and gas. The image, looking like a colourful cosmic ghost or a gigantic celestial Mandrill [1] , contains the open clusters Haffner 18 (centre) and Haffner 19 (middle right: it is located inside the smaller pink region - the lower eye of the Mandrill), as well as vast areas of ionised gas. The bright star at the centre of the largest pink region on the bottom of the image is HD 64315, a massive young star that is helping shaping the structure of the whole nebular region. ESO PR Photo 42a/05 was taken with the Wide-Field Imager camera at the 2.2m MPG/ESO telescope located at La Silla, in Chile. Another image of the central part of this area is shown as ESO PR Photo 42b/05. It was obtained with the FORS2 instrument at ESO' s Very Large Telescope on Cerro Paranal, also in Chile. ESO PR Photo 42b/05 zooms in on the open stellar cluster Haffner 18, perfectly illustrating three different stages of this process of star formation: In the centre of the picture, Haffner 18, a group of mature stars that have already dispersed their birth nebulae, represents the completed product or immediate past of the star formation process. Located at the bottom left of this cluster, a very young star, just come into existence and, still surrounded by its birth cocoon of gas, provides insight into the very present of star birth. Finally, the dust clouds towards the right corner of the image are active stellar nurseries that will produce more new stars in the future. Haffner 18 contains

  20. Exploring the Dynamics of Exoplanetary Systems in a Young Stellar Cluster

    Science.gov (United States)

    Thornton, Jonathan Daniel; Glaser, Joseph Paul; Wall, Joshua Edward

    2018-01-01

    I describe a dynamical simulation of planetary systems in a young star cluster. One rather arbitrary aspect of cluster simulations is the choice of initial conditions. These are typically chosen from some standard model, such as Plummer or King, or from a “fractal” distribution to try to model young clumpy systems. Here I adopt the approach of realizing an initial cluster model directly from a detailed magnetohydrodynamical model of cluster formation from a 1000-solar-mass interstellar gas cloud, with magnetic fields and radiative and wind feedback from massive stars included self-consistently. The N-body simulation of the stars and planets starts once star formation is largely over and feedback has cleared much of the gas from the region where the newborn stars reside. It continues until the cluster dissolves in the galactic field. Of particular interest is what would happen to the free-floating planets created in the gas cloud simulation. Are they captured by a star or are they ejected from the cluster? This method of building a dynamical cluster simulation directly from the results of a cluster formation model allows us to better understand the evolution of young star clusters and enriches our understanding of extrasolar planet development in them. These simulations were performed within the AMUSE simulation framework, and combine N-body, multiples and background potential code.

  1. Ruprecht 106 - A young metal-poor Galactic globular cluster

    International Nuclear Information System (INIS)

    Buonanno, R.; Buscema, G.; Fusi Pecci, F.; Richer, H.B.; Fahlman, G.G.

    1990-01-01

    The first CCD photometric survey in the Galactic globular cluster Ruprecht 106 has been performed. The results show that Ruprecht 106 is a metal-poor cluster with (Fe/H) about -2 located at about 25 kpc from the Galactic center. A sizable, high centrally concentrated population of blue stragglers was detected. Significant differences in the positions of the turnoffs in the color-magnitude diagram are found compared to those in metal-poor clusters. The cluster appears younger than other typical metal-poor Galactic globulars by about 4-5 Gyr; if true, this object would represent the first direct proof of the existence of a significant age spread among old, very metal-poor clusters. 51 refs

  2. THE INITIAL MASS FUNCTION AND THE SURFACE DENSITY PROFILE OF NGC 6231

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Hwankyung [Department of Astronomy and Space Science, Sejong University, 98, Kunja-dong, Kwangjin-gu, Seoul 143-747 (Korea, Republic of); Sana, Hugues [Astronomical Institute ' Anton Pannekeok' , Amsterdam University, Science Park 904, 1098-XH Amsterdam (Netherlands); Bessell, Michael S., E-mail: sungh@sejong.ac.kr, E-mail: H.Sana@uva.nl, E-mail: bessell@mso.anu.edu.au [Research School of Astronomy and Astrophysics, Australian National University, MSO, Cotter Road, Weston, ACT 2611 (Australia)

    2013-02-01

    We have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initial mass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical to mid-infrared color excess ratios, and found that the total-to-selective extinction ratio is R{sub V} = 3.2, which is very close to the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived the surface density profiles of four member groups, and found that they reach the surface density of field stars at about 10', regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8-45 M{sub Sun }. The slope of the IMF of NGC 6231 ({Gamma} = -1.1 {+-} 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition, the mass function varies systematically, and is a strong function of radius-it is very shallow at the center, and very steep at the outer ring suggesting the cluster is mass segregated. We confirm the mass segregation for the massive stars (m {approx}> 8 M{sub Sun }) by a minimum spanning tree analysis. Using a Monte Carlo method, we estimate the total mass of NGC 6231 to be about 2.6 ({+-} 0.6) Multiplication-Sign 10{sup 3} M{sub Sun }. We constrain the age of NGC 6231 by comparison with evolutionary isochrones. The age of the low-mass stars ranges from 1 to 7 Myr with a slight peak at 3 Myr. However, the age of the high-mass stars depends on the adopted models and is 3.5 {+-} 0.5 Myr from the non-rotating or moderately rotating models of Brott et al. as well as the non-rotating models of Ekstroem et al. But the age is 4.0-7.0 Myr if the rotating models of Ekstroem et al. are adopted. This latter age is in excellent agreement with the timescale of ejection of the high-mass runaway star HD 153919 from NGC 6231, albeit the younger age cannot be entirely excluded.

  3. AN INITIAL MASS FUNCTION STUDY OF THE DWARF STARBURST GALAXY NGC 4214

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, J. E.; Calzetti, D. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States); Chandar, R. [Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Lee, J. C.; Whitmore, B. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Elmegreen, B. G. [IBM T. J. Watson Research Center, Yorktown Heights, NY (United States); Kennicutt, R. C. [Institute of Astronomy, Cambridge University, Cambridge (United Kingdom); Kissel, J. S. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Da Silva, Robert L.; Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States); O' Connell, R. W. [Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States); Dopita, M. A. [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia); Frogel, Jay A. [Galaxies Unlimited, 1 Tremblant Court, Lutherville, MD (United States); Kim, Hwihyun, E-mail: jandrews@astro.umass.edu, E-mail: callzetti@astro.umass.edu [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States)

    2013-04-10

    The production rate of ionizing photons in young ({<=}8 Myr), unresolved stellar clusters in the nearby irregular galaxy NGC 4214 is probed using multi-wavelength Hubble Space Telescope WFC3 data. We normalize the ionizing photon rate by the cluster mass to investigate the upper end of the stellar initial mass function (IMF). We have found that within the uncertainties the upper end of the stellar IMF appears to be universal in this galaxy, and that deviations from a universal IMF can be attributed to stochastic sampling of stars in clusters with masses {approx}<10{sup 3} M{sub Sun }. Furthermore, we have found that there does not seem to be a dependence of the maximum stellar mass on the cluster mass. We have also found that for massive clusters, feedback may cause an underrepresentation in H{alpha} luminosities, which needs to be taken into account when conducting this type of analysis.

  4. Star clusters and K2

    Science.gov (United States)

    Dotson, Jessie; Barentsen, Geert; Cody, Ann Marie

    2018-01-01

    The K2 survey has expanded the Kepler legacy by using the repurposed spacecraft to observe over 20 star clusters. The sample includes open and globular clusters at all ages, including very young (1-10 Myr, e.g. Taurus, Upper Sco, NGC 6530), moderately young (0.1-1 Gyr, e.g. M35, M44, Pleiades, Hyades), middle-aged (e.g. M67, Ruprecht 147, NGC 2158), and old globular clusters (e.g. M9, M19, Terzan 5). K2 observations of stellar clusters are exploring the rotation period-mass relationship to significantly lower masses than was previously possible, shedding light on the angular momentum budget and its dependence on mass and circumstellar disk properties, and illuminating the role of multiplicity in stellar angular momentum. Exoplanets discovered by K2 in stellar clusters provides planetary systems ripe for modeling given the extensive information available about their ages and environment. I will review the star clusters sampled by K2 across 16 fields so far, highlighting several characteristics, caveats, and unexplored uses of the public data set along the way. With fuel expected to run out in 2018, I will discuss the closing Campaigns, highlight the final target selection opportunities, and explain the data archive and TESS-compatible software tools the K2 mission intends to leave behind for posterity.

  5. Unveiling hidden properties of young star clusters: differential reddening, star-formation spread, and binary fraction

    Science.gov (United States)

    Bonatto, C.; Lima, E. F.; Bica, E.

    2012-04-01

    Context. Usually, important parameters of young, low-mass star clusters are very difficult to obtain by means of photometry, especially when differential reddening and/or binaries occur in large amounts. Aims: We present a semi-analytical approach (ASAmin) that, when applied to the Hess diagram of a young star cluster, is able to retrieve the values of mass, age, star-formation spread, distance modulus, foreground and differential reddening, and binary fraction. Methods: The global optimisation method known as adaptive simulated annealing (ASA) is used to minimise the residuals between the observed and simulated Hess diagrams of a star cluster. The simulations are realistic and take the most relevant parameters of young clusters into account. Important features of the simulations are a normal (Gaussian) differential reddening distribution, a time-decreasing star-formation rate, the unresolved binaries, and the smearing effect produced by photometric uncertainties on Hess diagrams. Free parameters are cluster mass, age, distance modulus, star-formation spread, foreground and differential reddening, and binary fraction. Results: Tests with model clusters built with parameters spanning a broad range of values show that ASAmin retrieves the input values with a high precision for cluster mass, distance modulus, and foreground reddening, but they are somewhat lower for the remaining parameters. Given the statistical nature of the simulations, several runs should be performed to obtain significant convergence patterns. Specifically, we find that the retrieved (absolute minimum) parameters converge to mean values with a low dispersion as the Hess residuals decrease. When applied to actual young clusters, the retrieved parameters follow convergence patterns similar to the models. We show how the stochasticity associated with the early phases may affect the results, especially in low-mass clusters. This effect can be minimised by averaging out several twin clusters in the

  6. Comparisons between observational color-magnitude diagrams and synthetic cluster diagrams for young star clusters in the Magellanic Clouds

    International Nuclear Information System (INIS)

    Recker, S.A.; Brunish, W.M.; Mathews, G.J.

    1984-01-01

    Young star clusters ( 8 yr) in the Magellanic Clouds (MC) can be used to test the current status of the theory of stellar evolution as applied to intermediate and massive stars. The color-magnitude diagram of many young clusters in the MC shows large numbers of stars in both the main sequence and post main sequence evolutionary phases. Using a grid of stellar evolution models, synthetic cluster H-R diagrams are constructed and compared to observed color-magnitude diagrams to determine the age, age spread, and composition for any given cluster. In addition, for those cases where the data is of high quality, detailed comparisons between theory and observation can provide a diagnostic of the accuracy of the stellar evolution models. Initial indications of these comparisons suggest that the theoretical models should be altered to include: a larger value for the mixing length parameter, a larger rate of mass loss during the asymptotic giant branch phase, and possibly convective overshoot during the core burning phases. (Auth.)

  7. Clusters of Adolescent and Young Adult Thyroid Cancer in Florida Counties

    Directory of Open Access Journals (Sweden)

    Raid Amin

    2014-01-01

    Full Text Available Background. Thyroid cancer is a common cancer in adolescents and young adults ranking 4th in frequency. Thyroid cancer has captured the interest of epidemiologists because of its strong association to environmental factors. The goal of this study is to identify thyroid cancer clusters in Florida for the period 2000–2008. This will guide further discovery of potential risk factors within areas of the cluster compared to areas not in cluster. Methods. Thyroid cancer cases for ages 15–39 were obtained from the Florida Cancer Data System. Next, using the purely spatial Poisson analysis function in SaTScan, the geographic distribution of thyroid cancer cases by county was assessed for clusters. The reference population was obtained from the Census Bureau 2010, which enabled controlling for population age, sex, and race. Results. Two statistically significant clusters of thyroid cancer clusters were found in Florida: one in southern Florida (SF (relative risk of 1.26; P value of <0.001 and the other in northwestern Florida (NWF (relative risk of 1.71; P value of 0.012. These clusters persisted after controlling for demographics including sex, age, race. Conclusion. In summary, we found evidence of thyroid cancer clustering in South Florida and North West Florida for adolescents and young adult.

  8. HST IMAGING OF DUST STRUCTURES AND STARS IN THE RAM PRESSURE STRIPPED VIRGO SPIRALS NGC 4402 AND NGC 4522: STRIPPED FROM THE OUTSIDE IN WITH DENSE CLOUD DECOUPLING

    International Nuclear Information System (INIS)

    Abramson, A.; Kenney, J.; Crowl, H.; Tal, T.

    2016-01-01

    We describe and constrain the origins of interstellar medium (ISM) structures likely created by ongoing intracluster medium (ICM) ram pressure stripping in two Virgo Cluster spirals, NGC 4522 and NGC 4402, using Hubble Space Telescope (HST) BVI images of dust extinction and stars, as well as supplementary H i, H α , and radio continuum images. With a spatial resolution of ∼10 pc in the HST images, this is the highest-resolution study to date of the physical processes that occur during an ICM–ISM ram pressure stripping interaction, ram pressure stripping's effects on the multi-phase, multi-density ISM, and the formation and evolution of ram-pressure-stripped tails. In dust extinction, we view the leading side of NGC 4402 and the trailing side of NGC 4522, and so we see distinct types of features in both. In both galaxies, we identify some regions where dense clouds are decoupling or have decoupled and others where it appears that kiloparsec-sized sections of the ISM are moving coherently. NGC 4522 has experienced stronger, more recent pressure and has the “jellyfish” morphology characteristic of some ram-pressure-stripped galaxies. Its stripped tail extends up from the disk plane in continuous upturns of dust and stars curving up to ∼2 kpc above the disk plane. On the other side of the galaxy, there is a kinematically and morphologically distinct extraplanar arm of young, blue stars and ISM above a mostly stripped portion of the disk, and between it and the disk plane are decoupled dust clouds that have not been completely stripped. The leading side of NGC 4402 contains two kiloparsec-scale linear dust filaments with complex substructure that have partially decoupled from the surrounding ISM. NGC 4402 also contains long dust ridges, suggesting that large parts of the ISM are being pushed out at once. Both galaxies contain long ridges of polarized radio continuum emission indicating the presence of large-scale, ordered magnetic fields. We propose that

  9. CLUSTER DYNAMICS LARGELY SHAPES PROTOPLANETARY DISK SIZES

    Energy Technology Data Exchange (ETDEWEB)

    Vincke, Kirsten; Pfalzner, Susanne, E-mail: kvincke@mpifr-bonn.mpg.de [Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2016-09-01

    To what degree the cluster environment influences the sizes of protoplanetary disks surrounding young stars is still an open question. This is particularly true for the short-lived clusters typical for the solar neighborhood, in which the stellar density and therefore the influence of the cluster environment change considerably over the first 10 Myr. In previous studies, the effect of the gas on the cluster dynamics has often been neglected; this is remedied here. Using the code NBody6++, we study the stellar dynamics in different developmental phases—embedded, expulsion, and expansion—including the gas, and quantify the effect of fly-bys on the disk size. We concentrate on massive clusters (M {sub cl} ≥ 10{sup 3}–6 ∗ 10{sup 4} M {sub Sun}), which are representative for clusters like the Orion Nebula Cluster (ONC) or NGC 6611. We find that not only the stellar density but also the duration of the embedded phase matters. The densest clusters react fastest to the gas expulsion and drop quickly in density, here 98% of relevant encounters happen before gas expulsion. By contrast, disks in sparser clusters are initially less affected, but because these clusters expand more slowly, 13% of disks are truncated after gas expulsion. For ONC-like clusters, we find that disks larger than 500 au are usually affected by the environment, which corresponds to the observation that 200 au-sized disks are common. For NGC 6611-like clusters, disk sizes are cut-down on average to roughly 100 au. A testable hypothesis would be that the disks in the center of NGC 6611 should be on average ≈20 au and therefore considerably smaller than those in the ONC.

  10. Dusty supernovae running the thermodynamics of the matter reinserted within young and massive super stellar clusters

    Energy Technology Data Exchange (ETDEWEB)

    Tenorio-Tagle, Guillermo; Silich, Sergiy; Martínez-González, Sergio [Instituto Nacional de Astrofísica Óptica y Electrónica, AP 51, 72000 Puebla (Mexico); Muñoz-Tuñón, Casiana [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Palouš, Jan; Wünsch, Richard, E-mail: gtt@inaoep.mx, E-mail: cmt@ll.iac.es [Astronomical Institute, Academy of Sciences of the Czech Republic, Boční II 1401, 141 31 Prague (Czech Republic)

    2013-12-01

    Following the observational and theoretical evidence that points at core-collapse supernovae (SNe) as major producers of dust, here we calculate the hydrodynamics of the matter reinserted within young and massive super stellar clusters under the assumption of gas and dust radiative cooling. The large SN rate expected in massive clusters allows for a continuous replenishment of dust immersed in the high temperature thermalized reinserted matter and warrants a stationary presence of dust within the cluster volume during the type II SN era. We first show that such a balance determines the range of the dust-to-gas-mass ratio, and thus the dust cooling law. We then search for the critical line that separates stationary cluster winds from the bimodal cases in the cluster mechanical luminosity (or cluster mass) versus cluster size parameter space. In the latter, strong radiative cooling reduces considerably the cluster wind mechanical energy output and affects particularly the cluster central regions, leading to frequent thermal instabilities that diminish the pressure and inhibit the exit of the reinserted matter. Instead, matter accumulates there and is expected to eventually lead to gravitational instabilities and to further stellar formation with the matter reinserted by former massive stars. The main outcome of the calculations is that the critical line is almost two orders of magnitude or more, depending on the assumed value of V {sub A∞}, lower than when only gas radiative cooling is applied. And thus, many massive clusters are predicted to enter the bimodal regime.

  11. Formation of the young compact cluster GM 24 triggered by a cloud-cloud collision

    Science.gov (United States)

    Fukui, Yasuo; Kohno, Mikito; Yokoyama, Keiko; Nishimura, Atsushi; Torii, Kazufumi; Hattori, Yusuke; Sano, Hidetoshi; Ohama, Akio; Yamamoto, Hiroaki; Tachihara, Kengo

    2018-05-01

    High-mass star formation is an important step which controls galactic evolution. GM 24 is a heavily obscured star cluster including a single O9 star with more than ˜100 lower-mass stars within a 0.3 pc radius toward (l, b) ˜ (350.5°, 0.96°), close to the Galactic mini-starburst NGC 6334. We found two velocity components associated with the cluster by new observations of 12CO J =2-1 emission, whereas the cloud was previously considered to be single. We found that the distribution of the two components of 5 {km}s-1 separation shows complementary distribution; the two fit well with each other if a relative displacement of 3 pc is applied along the Galactic plane. A position-velocity diagram of the GM 24 cloud is explained by a model based on numerical simulations of two colliding clouds, where an intermediate velocity component created by the collision is taken into account. We estimate the collision time scale to be ˜Myr in projection of a relative motion tilted to the line of sight by 45°. The results lend further support for cloud-cloud collision as an important mechanism of high-mass star formation in the Carina-Sagittarius Arm.

  12. X-ray Observations of Eight Young Open Star Clusters: I ...

    Indian Academy of Sciences (India)

    X-ray Observations of Eight Young Open Star Clusters: I. Membership and X-ray Luminosity. Himali Bhatt, J. C. Pandey, K. P. Singh, Ram Sagar & Brijesh Kumar. J. Astrophys. Astr. 34(4), December 2013, pp. 393–429, c Indian Academy of Sciences. Supplementary Material. Supplementary Table 3 follows.

  13. The Exoplant Migration Timescale from K2 Young Clusters

    Science.gov (United States)

    Rizzuto, Aaron C.; Mann, Andrew; Kraus, Adam L.; Ireland, Michael

    2017-01-01

    Planetary Migration models for close-in exoplanets(a operate on timescales of ~100’s of Myr to ~1Gyr, a lengthier process than disk migration. It is unclear which of these is the dominating mechanism.The K2 mission has measured planet formation timescales and migration pathways by sampling groups of stars at key pre-main-sequence ages: Over the past 10 campaigns, multiple groups of young stars have been observed by K2, ranging from the 10 Myr Upper Scorpius OB association, through the ˜120 Myr Pleiades, the ˜600-800 Myr Hyades and Praesepe moving groups, to the original Kepler Field. The frequency, orbital and compositional properties of the exoplanet population in these samples of different age, with careful treatment of detection completeness, will be sufficient to address the question of exoplanet migration as their host stars are settling onto the main sequence.We will present the initial results of a program to directly address the question of planet migration with a uniform injection-recovery tests on a new K2 detrending pipeline that is optimized for the particular case of young, rotationally variable stars in K2 to robustly measure the detectability of planets of differing size and orbit. Initial results point towards a migration timescale of 200-700 Myr, which is consistent with the slower planet-planet scattering or Kozai migration models.

  14. The young star cluster population of M51 with LEGUS - II. Testing environmental dependences

    Science.gov (United States)

    Messa, Matteo; Adamo, A.; Calzetti, D.; Reina-Campos, M.; Colombo, D.; Schinnerer, E.; Chandar, R.; Dale, D. A.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Elmegreen, B. G.; Fumagalli, M.; Johnson, K. E.; Kruijssen, J. M. D.; Östlin, G.; Shabani, F.; Smith, L. J.; Whitmore, B. C.

    2018-06-01

    It has recently been established that the properties of young star clusters (YSCs) can vary as a function of the galactic environment in which they are found. We use the cluster catalogue produced by the Legacy Extragalactic UV Survey (LEGUS) collaboration to investigate cluster properties in the spiral galaxy M51. We analyse the cluster population as a function of galactocentric distance and in arm and inter-arm regions. The cluster mass function exhibits a similar shape at all radial bins, described by a power law with a slope close to -2 and an exponential truncation around 105 M⊙. While the mass functions of the YSCs in the spiral arm and inter-arm regions have similar truncation masses, the inter-arm region mass function has a significantly steeper slope than the one in the arm region, a trend that is also observed in the giant molecular cloud mass function and predicted by simulations. The age distribution of clusters is dependent on the region considered, and is consistent with rapid disruption only in dense regions, while little disruption is observed at large galactocentric distances and in the inter-arm region. The fraction of stars forming in clusters does not show radial variations, despite the drop in the H2 surface density measured as a function of galactocentric distance. We suggest that the higher disruption rate observed in the inner part of the galaxy is likely at the origin of the observed flat cluster formation efficiency radial profile.

  15. Variable blue straggler stars in NGC 5466

    International Nuclear Information System (INIS)

    Harris, H.C.; Mateo, M.; Olszewski, E.W.; Nemec, J.M.

    1990-01-01

    Nine variable blue stragglers have been found in the globular cluster NGC 5466. The six dwarf Cepheids in this cluster coexist in the instability strip with other nonvariable stars. The three eclipsing binaries are among the hottest of the blue stragglers. The hypothesis is discussed that all blue stragglers in this cluster have undergone mass transfer in close binaries. Under this hypothesis, rotation and spin-down play important roles in controlling the evolution of blue stragglers in old clusters and in affecting some of their observational properties. 14 refs

  16. A photometric study of NGC 2419

    International Nuclear Information System (INIS)

    Racine, R.; Harris, W.E.

    1975-01-01

    Photometry to V=22.2 and B=23.7 is reported for the outer-halo globular cluster NGC 2419. The color-magnitude diagram of the cluster is similar to that of the classic metal-poor cluster M92, and indicates a very low metallicity Zapprox. =1.5times10/sup -4/. The reddening E (B-V) is 0.03plus-or-minus0.01 mag, and the apparent distance modulus is (m-M)/subv/=19.87plus-or-minus0.09, leading to a galactocentric distance of R/subg/=100plus-or-minus5 kpc. The RR Lyrae nature of the numerous short-period variables discovered by Baade is confirmed; of the five known brighter variables, one appears to be a population II Cepheid, while the others fall near the tip of the red giant branch. Attention is drawn to a significant gap in the giant branch. The cluster's age is estimated as T=11.0plus-or-minus0.5times10 9 yr from its HB morphology, or T=11.9plus-or-minus0.3times10 9 yr from a discussion of its galactic orbit. The galactic orbit of NGC 2419 is determined. The cluster is gravitationally bound to the Galaxy, traveling on an orbit of eccentricity 0.62 with a period of 3.4X10 9 yr, and is presently near its apogalaction. It is argued that the cluster was born close to its perigalacticon distance of 24 kpc. A possible gravitational encounter between NGC 2419 and the Magellanic Clouds is mentioned briefly. Finally it is shown that NGC 2419, like clusters with the largest h are among the metals poorest

  17. Very Broad [O III] λλ4959, 5007 Emission from the NGC 4472 Globular Cluster RZ 2109 and Implications for the Mass of Its Black Hole X-Ray Source

    Science.gov (United States)

    Zepf, Stephen E.; Stern, Daniel; Maccarone, Thomas J.; Kundu, Arunav; Kamionkowski, Marc; Rhode, Katherine L.; Salzer, John J.; Ciardullo, Robin; Gronwall, Caryl

    2008-08-01

    We present Keck LRIS spectroscopy of the black hole-hosting globular cluster RZ 2109 in the Virgo elliptical galaxy NGC 4472. We find that this object has extraordinarily broad [O III] λ5007 and [O III] λ4959 emission lines, with velocity widths of approximately 2000 km s-1. This result has significant implications for the nature of this accreting black hole system and the mass of the globular cluster black hole. We show that the broad [O III] λ5007 emission must arise from material driven at high velocity from the black hole system. This is because the volume available near the black hole is too small by many orders of magnitude to have enough [O III]-emitting atoms to account for the observed L([O III] λ5007) at high velocities, even if this volume is filled with oxygen at the critical density for [O III] λ5007. The Balmer emission is also weak, indicating the observed [O III] is not due to shocks. We therefore conclude that the [O III] λλ4959, 5007 is produced by photoionization of material driven across the cluster. The only known way to drive significant material at high velocity is for a system accreting mass near or above its Eddington limit, which indicates a stellar-mass black hole. Since it is dynamically implausible to form an accreting stellar-mass black hole system in a globular cluster with an intermediate-mass black hole (IMBH), it appears this massive globular cluster does not have an IMBH. We discuss further tests of this conclusion, and its implications for the MBH - Mstellar and MBH - σ relations. Based on observations made at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  18. OPTICAL PHOTOMETRIC AND POLARIMETRIC INVESTIGATION OF NGC 1931

    International Nuclear Information System (INIS)

    Pandey, A. K.; Eswaraiah, C.; Sharma, Saurabh; Yadav, Ram Kesh; Samal, M. R.; Chauhan, N.; Chen, W. P.; Jose, J.; Ojha, D. K.; Chandola, H. C.

    2013-01-01

    We present optical photometric and polarimetric observations of stars toward NGC 1931 with the aim of deriving cluster parameters such as distance, reddening, age, and luminosity/mass function as well as understanding dust properties and star formation in the region. The distance to the cluster is found to be 2.3 ± 0.3 kpc and the reddening E(B – V) in the region is found to be variable. The stellar density contours reveal two clusters in the region. The observations suggest a differing reddening law within the cluster region. Polarization efficiency of the dust grains toward the direction of the cluster is found to be less than that for the general diffuse interstellar medium (ISM). The slope of the mass function (–0.98 ± 0.22) in the southern region in the mass range of 0.8 ☉ < 9.8 is found to be shallower in comparison to that in the northern region (–1.26 ± 0.23), which is comparable to the Salpeter value (–1.35). The K-band luminosity function (KLF) of the region is found to be comparable to the average value of the slope (∼0.4) for young clusters obtained by Lada and Lada; however, the slope of the KLF is steeper in the northern region as compared to the southern region. The region is probably ionized by two B2 main-sequence-type stars. The mean age of the young stellar objects (YSOs) is found to be 2 ± 1 Myr, which suggests that the identified YSOs could be younger than the ionizing sources of the region. The morphology of the region, the distribution and ages of the YSOs, and ionizing sources indicate a triggered star formation in the region.

  19. From Globular Clusters to Tidal Dwarfs: Structure Formation in Tidal Tails

    Science.gov (United States)

    Knierman, K.; Hunsberger, S.; Gallagher, S.; Charlton, J.; Whitmore, B.; Hibbard, J.; Kundu, A.; Zaritsky, D.

    1999-12-01

    Galaxy interactions trigger star formation in tidal debris. How does this star formation depend on the local and global physical conditions? Using WFPC2/HST images, we investigate the range of structure within tidal tails of four classic ``Toomre Sequence'' mergers: NGC 4038/9 (``Antennae''), NGC 7252 (``Atoms for Peace''), NGC 3921, and NGC 3256. These tails contain a variety of stellar associations with sizes from globular clusters up to dwarf Irregulars. We explore whether there is a continuum between the two extremes. Our eight fields sample seven tidal tails at a variety of stages in the evolutionary sequence. Some of these tails are rich in HI while others are HI poor. Large tidal dwarfs are embedded in three of the tails. Using V and I WFPC2 images, we measure luminosities and colors of substructures within the tidal tails. The properties of globular cluster candidates in the tails will be contrasted with those of the hundreds of young clusters in the central regions of these mergers. We address whether globular clusters form and survive in the tidal tails and whether tidal dwarfs are composed of only young stars. By comparing the properties of structures in the tails of the four mergers with different ages, we examine systematic evolution of structure along the evolutionary sequence and as a function of HI content. We acknowledge support from NASA through STScI, and from NSF for an REU supplement for Karen Knierman.

  20. Hierarchical Star Formation in Turbulent Media: Evidence from Young Star Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Grasha, K.; Calzetti, D. [Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States); Elmegreen, B. G. [IBM Research Division, T.J. Watson Research Center, Yorktown Heights, NY (United States); Adamo, A.; Messa, M. [Department of Astronomy, The Oskar Klein Centre, Stockholm University, Stockholm (Sweden); Aloisi, A.; Bright, S. N.; Lee, J. C.; Ryon, J. E.; Ubeda, L. [Space Telescope Science Institute, Baltimore, MD (United States); Cook, D. O. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA (United States); Dale, D. A. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY (United States); Fumagalli, M. [Institute for Computational Cosmology and Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham (United Kingdom); Gallagher III, J. S. [Department of Astronomy, University of Wisconsin–Madison, Madison, WI (United States); Gouliermis, D. A. [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Grebel, E. K. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120, Heidelberg (Germany); Kahre, L. [Department of Astronomy, New Mexico State University, Las Cruces, NM (United States); Kim, H. [Gemini Observatory, La Serena (Chile); Krumholz, M. R., E-mail: kgrasha@astro.umass.edu [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia)

    2017-06-10

    We present an analysis of the positions and ages of young star clusters in eight local galaxies to investigate the connection between the age difference and separation of cluster pairs. We find that star clusters do not form uniformly but instead are distributed so that the age difference increases with the cluster pair separation to the 0.25–0.6 power, and that the maximum size over which star formation is physically correlated ranges from ∼200 pc to ∼1 kpc. The observed trends between age difference and separation suggest that cluster formation is hierarchical both in space and time: clusters that are close to each other are more similar in age than clusters born further apart. The temporal correlations between stellar aggregates have slopes that are consistent with predictions of turbulence acting as the primary driver of star formation. The velocity associated with the maximum size is proportional to the galaxy’s shear, suggesting that the galactic environment influences the maximum size of the star-forming structures.

  1. The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution

    Science.gov (United States)

    Messa, M.; Adamo, A.; Östlin, G.; Calzetti, D.; Grasha, K.; Grebel, E. K.; Shabani, F.; Chandar, R.; Dale, D. A.; Dobbs, C. L.; Elmegreen, B. G.; Fumagalli, M.; Gouliermis, D. A.; Kim, H.; Smith, L. J.; Thilker, D. A.; Tosi, M.; Ubeda, L.; Walterbos, R.; Whitmore, B. C.; Fedorenko, K.; Mahadevan, S.; Andrews, J. E.; Bright, S. N.; Cook, D. O.; Kahre, L.; Nair, P.; Pellerin, A.; Ryon, J. E.; Ahmad, S. D.; Beale, L. P.; Brown, K.; Clarkson, D. A.; Guidarelli, G. C.; Parziale, R.; Turner, J.; Weber, M.

    2018-01-01

    Recently acquired WFC3 UV (F275W and F336W) imaging mosaics under the Legacy Extragalactic UV Survey (LEGUS), combined with archival ACS data of M51, are used to study the young star cluster (YSC) population of this interacting system. Our newly extracted source catalogue contains 2834 cluster candidates, morphologically classified to be compact and uniform in colour, for which ages, masses and extinction are derived. In this first work we study the main properties of the YSC population of the whole galaxy, considering a mass-limited sample. Both luminosity and mass functions follow a power-law shape with slope -2, but at high luminosities and masses a dearth of sources is observed. The analysis of the mass function suggests that it is best fitted by a Schechter function with slope -2 and a truncation mass at 1.00 ± 0.12 × 105 M⊙. Through Monte Carlo simulations, we confirm this result and link the shape of the luminosity function to the presence of a truncation in the mass function. A mass limited age function analysis, between 10 and 200 Myr, suggests that the cluster population is undergoing only moderate disruption. We observe little variation in the shape of the mass function at masses above 1 × 104 M⊙ over this age range. The fraction of star formation happening in the form of bound clusters in M51 is ∼ 20 per cent in the age range 10-100 Myr and little variation is observed over the whole range from 1 to 200 Myr.

  2. Are superluminous supernovae and long GRBs the products of dynamical processes in young dense star clusters?

    Energy Technology Data Exchange (ETDEWEB)

    Van den Heuvel, E. P. J. [Astronomical Institute Anton Pannekoek, University of Amsterdam, P.O. Box 94249, 1090 GE Amsterdam (Netherlands); Portegies Zwart, S. F. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

    2013-12-20

    Superluminous supernovae (SLSNe) occur almost exclusively in small galaxies (Small/Large Magellanic Cloud (SMC/LMC)-like or smaller), and the few SLSNe observed in larger star-forming galaxies always occur close to the nuclei of their hosts. Another type of peculiar and highly energetic supernovae are the broad-line Type Ic SNe (SN Ic-BL) that are associated with long-duration gamma-ray bursts (LGRBs). Also these have a strong preference for occurring in small (SMC/LMC-like or smaller) star-forming galaxies, and in these galaxies LGRBs always occur in the brightest spots. Studies of nearby star-forming galaxies that are similar to the hosts of LGRBs show that these brightest spots are giant H II regions produced by massive dense young star clusters with many hundreds of O- and Wolf-Rayet-type stars. Such dense young clusters are also found in abundance within a few hundred parsecs from the nucleus of larger galaxies like our own. We argue that the SLSNe and the SNe Ic-BL/LGRBs are exclusive products of two types of dynamical interactions in dense young star clusters. In our model the high angular momentum of the collapsing stellar cores required for the engines of an SN Ic-BL results from the post-main-sequence mergers of dynamically produced cluster binaries with almost equal-mass components. The merger produces a critically rotating single helium star with sufficient angular momentum to produce an LGRB; the observed 'metal aversion' of LGRBs is a natural consequence of the model. We argue that, on the other hand, SLSNe could be the products of runaway multiple collisions in dense clusters, and we present (and quantize) plausible scenarios of how the different types of SLSNe can be produced.

  3. Formation of new stellar populations from gas accreted by massive young star clusters.

    Science.gov (United States)

    Li, Chengyuan; de Grijs, Richard; Deng, Licai; Geller, Aaron M; Xin, Yu; Hu, Yi; Faucher-Giguère, Claude-André

    2016-01-28

    Stars in clusters are thought to form in a single burst from a common progenitor cloud of molecular gas. However, massive, old 'globular' clusters--those with ages greater than ten billion years and masses several hundred thousand times that of the Sun--often harbour multiple stellar populations, indicating that more than one star-forming event occurred during their lifetimes. Colliding stellar winds from late-stage, asymptotic-giant-branch stars are often suggested to be triggers of second-generation star formation. For this to occur, the initial cluster masses need to be greater than a few million solar masses. Here we report observations of three massive relatively young star clusters (1-2 billion years old) in the Magellanic Clouds that show clear evidence of burst-like star formation that occurred a few hundred million years after their initial formation era. We show that such clusters could have accreted sufficient gas to form new stars if they had orbited in their host galaxies' gaseous disks throughout the period between their initial formation and the more recent bursts of star formation. This process may eventually give rise to the ubiquitous multiple stellar populations in globular clusters.

  4. The Most Distant Mature Galaxy Cluster - Young, but surprisingly grown-up

    Science.gov (United States)

    2011-03-01

    Astronomers have used an armada of telescopes on the ground and in space, including the Very Large Telescope at ESO's Paranal Observatory in Chile to discover and measure the distance to the most remote mature cluster of galaxies yet found. Although this cluster is seen when the Universe was less than one quarter of its current age it looks surprisingly similar to galaxy clusters in the current Universe. "We have measured the distance to the most distant mature cluster of galaxies ever found", says the lead author of the study in which the observations from ESO's VLT have been used, Raphael Gobat (CEA, Paris). "The surprising thing is that when we look closely at this galaxy cluster it doesn't look young - many of the galaxies have settled down and don't resemble the usual star-forming galaxies seen in the early Universe." Clusters of galaxies are the largest structures in the Universe that are held together by gravity. Astronomers expect these clusters to grow through time and hence that massive clusters would be rare in the early Universe. Although even more distant clusters have been seen, they appear to be young clusters in the process of formation and are not settled mature systems. The international team of astronomers used the powerful VIMOS and FORS2 instruments on ESO's Very Large Telescope (VLT) to measure the distances to some of the blobs in a curious patch of very faint red objects first observed with the Spitzer space telescope. This grouping, named CL J1449+0856 [1], had all the hallmarks of being a very remote cluster of galaxies [2]. The results showed that we are indeed seeing a galaxy cluster as it was when the Universe was about three billion years old - less than one quarter of its current age [3]. Once the team knew the distance to this very rare object they looked carefully at the component galaxies using both the NASA/ESA Hubble Space Telescope and ground-based telescopes, including the VLT. They found evidence suggesting that most of the

  5. Dynamical evolution of stars and gas of young embedded stellar sub-clusters

    Science.gov (United States)

    Sills, Alison; Rieder, Steven; Scora, Jennifer; McCloskey, Jessica; Jaffa, Sarah

    2018-03-01

    We present simulations of the dynamical evolution of young embedded star clusters. Our initial conditions are directly derived from X-ray, infrared, and radio observations of local systems, and our models evolve both gas and stars simultaneously. Our regions begin with both clustered and extended distributions of stars, and a gas distribution which can include a filamentary structure in addition to gas surrounding the stellar subclusters. We find that the regions become spherical, monolithic, and smooth quite quickly, and that the dynamical evolution is dominated by the gravitational interactions between the stars. In the absence of stellar feedback, the gas moves gently out of the centre of our regions but does not have a significant impact on the motions of the stars at the earliest stages of cluster formation. Our models at later times are consistent with observations of similar regions in the local neighbourhood. We conclude that the evolution of young proto-star clusters is relatively insensitive to reasonable choices of initial conditions. Models with more realism, such as an initial population of binary and multiple stars and ongoing star formation, are the next step needed to confirm these findings.

  6. From Stars to Superplanets: The Low-Mass Initial Mass Function in the Young Cluster IC 348

    National Research Council Canada - National Science Library

    Najita, Joan R; Tiede, Glenn P; Carr, John S

    2000-01-01

    We investigate the low-mass population of the young cluster IC 348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative...

  7. Two massive stars possibly ejected from NGC 3603 via a three-body encounter

    Science.gov (United States)

    Gvaramadze, V. V.; Kniazev, A. Y.; Chené, A.-N.; Schnurr, O.

    2013-03-01

    We report the discovery of a bow-shock-producing star in the vicinity of the young massive star cluster NGC 3603 using archival data of the Spitzer Space Telescope. Follow-up optical spectroscopy of this star with Gemini-South led to its classification as O6 V. The orientation of the bow shock and the distance to the star (based on its spectral type) suggest that the star was expelled from the cluster, while the young age of the cluster (˜2 Myr) implies that the ejection was caused by a dynamical few-body encounter in the cluster's core. The relative position on the sky of the O6 V star and a recently discovered O2 If*/WN6 star (located on the opposite side of NGC 3603) allows us to propose that both objects were ejected from the cluster via the same dynamical event - a three-body encounter between a single (O6 V) star and a massive binary (now the O2 If*/WN6 star). If our proposal is correct, then one can `weigh' the O2 If*/WN6 star using the conservation of the linear momentum. Given a mass of the O6 V star of ≈30 M⊙, we found that at the moment of ejection the mass of the O2 If*/WN6 star was ≈175 M⊙. Moreover, the observed X-ray luminosity of the O2 If*/WN6 star (typical of a single star) suggests that the components of this originally binary system have merged (e.g., because of encounter hardening).

  8. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    Craig, Jonathan; Krumholz, Mark R.

    2013-01-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  9. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Craig, Jonathan; Krumholz, Mark R., E-mail: krumholz@ucolick.org [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  10. Close Stellar Encounters in Young, Substructured, Dissolving Star Clusters: Statistics and Effects on Planetary Systems

    Science.gov (United States)

    Craig, Jonathan; Krumholz, Mark R.

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  11. Dynamical models of two lenticular galaxies: NGC 1023 and NGC 4526

    Directory of Open Access Journals (Sweden)

    Samurović S.

    2017-01-01

    Full Text Available We study kinematics and dynamics of two lenticular galaxies that possess globular clusters (GCs which extend beyond approximately seven effective radii. We analyze two nearby lenticular galaxies, NGC 1023 and NGC 4526, based on their GCs. We extract the kinematics of these galaxies and use it for dynamical modeling based on the Jeans equation. The Jeans equation was solved in both the Newtonian mass-follows-light approach assuming constant mass-to-light ratio and assuming a dark halo in the Navarro-Frenk-White form. We find that while the first galaxy, NGC 1023, does not need a significant amount of dark matter, in the other galaxy, NGC 4526, the dark component fully dominates stellar matter in the total dynamical mass. In this paper we also used three different MOND approaches and found that while for both galaxies MOND models can provide successful fits of the observed velocity dispersion, in the case of NGC 4526 we have a hint of an additional dark component even in the MOND framework. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176021: Visible and Invisible Matter in Nearby Galaxies: Theory and Observations

  12. Zodiacal Exoplanets in Time (ZEIT). V. A Uniform Search for Transiting Planets in Young Clusters Observed by K2

    Science.gov (United States)

    Rizzuto, Aaron C.; Mann, Andrew W.; Vanderburg, Andrew; Kraus, Adam L.; Covey, Kevin R.

    2017-12-01

    Detection of transiting exoplanets around young stars is more difficult than for older systems owing to increased stellar variability. Nine young open cluster planets have been found in the K2 data, but no single analysis pipeline identified all planets. We have developed a transit search pipeline for young stars that uses a transit-shaped notch and quadratic continuum in a 12 or 24 hr window to fit both the stellar variability and the presence of a transit. In addition, for the most rapid rotators ({P}{rot}Pleiades, Hyades, Praesepe) and conduct a uniform search of the members. We identify all known transiting exoplanets in the clusters, 17 eclipsing binaries, one transiting planet candidate orbiting a potential Pleiades member, and three orbiting unlikely members of the young clusters. Limited injection recovery testing on the known planet hosts indicates that for the older Praesepe systems we are sensitive to additional exoplanets as small as 1-2 R ⊕, and for the larger Upper Scorpius planet host (K2-33) our pipeline is sensitive to ˜4 R ⊕ transiting planets. The lack of detected multiple systems in the young clusters is consistent with the expected frequency from the original Kepler sample, within our detection limits. With a robust pipeline that detects all known planets in the young clusters, occurrence rate testing at young ages is now possible.

  13. A Cluster Randomized Controlled Trial Testing the Effectiveness of Houvast: A Strengths-Based Intervention for Homeless Young Adults

    Science.gov (United States)

    Krabbenborg, Manon A. M.; Boersma, Sandra N.; van der Veld, William M.; van Hulst, Bente; Vollebergh, Wilma A. M.; Wolf, Judith R. L. M.

    2017-01-01

    Objective: To test the effectiveness of Houvast: a strengths-based intervention for homeless young adults. Method: A cluster randomized controlled trial was conducted with 10 Dutch shelter facilities randomly allocated to an intervention and a control group. Homeless young adults were interviewed when entering the facility and when care ended.…

  14. A cluster randomized controlled trial testing the effectiveness of Houvast: A strengths-based intervention for homeless young adults

    NARCIS (Netherlands)

    Krabbenborg, M.A.M.; Boersma, S.N.; Veld, W.M. van der; Hulst, B. van; Vollebergh, W.A.M.; Wolf, J.R.L.M.

    2017-01-01

    Objective: To test the effectiveness of Houvast: a strengths-based intervention for homeless young adults. Method: A cluster randomized controlled trial was conducted with 10 Dutch shelter facilities randomly allocated to an intervention and a control group. Homeless young adults were interviewed

  15. Colour-magnitude diagram of NGC 5053

    Energy Technology Data Exchange (ETDEWEB)

    Walker, M F; Pike, C D [California Univ., Santa Cruz (USA). Lick Observatory; McGee, J D

    1976-06-01

    The colour-magnitude diagram of NGC 5053 has been derived to V = 21.1 from photographic and electronographic observations. The electronographic observations were obtained with an experimental Spectracon image-converter, having photocathode and exit window dimensions of 20 x 30 mm, mounted at the prime-focus of the 120-in. Lick reflector. The photographic observations were obtained with the 20-in. Carnegie astrograph and the 36-in. Crossley reflector. The colour-magnitude diagram resembles that of M92, with the difference that a red horizontal branch is more pronounced than the asymptotic branch in NGC 5053. The topology of the horizontal branch is that of clusters with an intermediate metal content and is thus at variance with the mean period of the RR Lyr stars and the unreddened colour of the subgiant branch read at the magnitude level of the horizontal branch, both of which would indicate an extremely low metal content. If comparison of the colour-magnitude diagrams of NGC 5053 and M92 is valid, then the reddening of NGC 5053 is Esub(B-V) = 0.02 and the apparent distance modulus is m-M = 16.08 +- 0.08.

  16. Photoelectric UBV and DDO photometry of NGC 5138

    International Nuclear Information System (INIS)

    Claria, J.J.

    1980-01-01

    Results of UBV photoelectric photometry in NGC 5138 are presented for 50 stars brighter than 14.0 mag. In addition, four probable red giants were also observed in the DDO system. Sixteen stars previously considered members by Lindoff (1972), were found not to be physically connected with the cluster. NGC 5138 is located 1.80 kpc from the Sun and the visual interstellar absorption determined from the reddened B stars amounts to Asub(v) = 0.75 mag. There of the four red stars observed in the DDO system were found to be cluster members. The mean cyanogen anomaly is = 0.043 +- 0.018(m.e.), which implies that NGC 5138 is richer in CN than the field K giants in the solar neighbourhodd, but poorer than the Hyades giants. The cluster age is estimated to be approx. 1.5 x 10 8 yr. (orig.)

  17. Diffuse γ-ray emission in the vicinity of young star cluster Westerlund 2

    Science.gov (United States)

    Yang, Rui-zhi; de Oña Wilhelmi, Emma; Aharonian, Felix

    2018-04-01

    We report the results of our analysis of the publicly available data obtained by the Large Area Telescope (LAT) on board the Fermi satellite towards the direction of the young massive star cluster Westerlund 2. We found significant extended γ-ray emission in the vicinity of Westerlund 2 with a hard power-law energy spectrum extending from 1 to 250 GeV with a photon index of 2.0 ± 0.1. We argue that amongst several alternatives, the luminous stars in Westerlund 2 are likely sites of acceleration of particles responsible for the diffuse γ-ray emission of the surrounding interstellar medium. In particular, the young star cluster Westerlund 2 can provide sufficient non-thermal energy to account for the γ-ray emission. In this scenario, since the γ-ray production region is significantly larger than the area occupied by the star cluster, we conclude that the γ-ray production is caused by hadronic interactions of accelerated protons and nuclei with the ambient gas. In that case, the total energy budget in relativistic particles is estimated of the order of 1050 erg.

  18. Young stellar population and star formation history ofW4 HII region/Cluster Complex

    Science.gov (United States)

    Panwar, Neelam

    2018-04-01

    The HII region/cluster complex has been a subject of numerous investigations to study the feedback effect of massive stars on their surroundings. Massive stars not only alter the morphology of the parental molecular clouds, but also influence star formation, circumstellar disks and the mass function of low-mass stars in their vicinity. However, most of the studies of low-mass stellar content of the HII regions are limited only to the nearby regions. We study the star formation in the W4 HII region using deep optical observations obtained with the archival data from Canada - France - Hawaii Telescope, Two-Micron All Sky Survey, Spitzer, Herschel and Chandra. We investigate the spatial distribution of young stellar objects in the region, their association with the remnant molecular clouds, and search for the clustering to establish the sites of recent star formation. Our analysis suggests that the influence of massive stars on circumstellar disks is significant only to thei! r immediate neighborhood. The spatial correlation of the young stars with the distribution of gas and dust of the complex indicate that the clusters would have formed in a large filamentary cloud. The observing facilities at the 3.6-m Devasthal Optical Telescope (DOT), providing high-resolution spectral and imaging capabilities, will fulfill the major objectives in the study of HII regions.

  19. The interstellar extinction in the open clusters Tr 14, Tr 15, Tr 16/Cr 232 and Cr 228 in NGC 3372. New near-infrared photometry

    International Nuclear Information System (INIS)

    Tapia, M.; Roth, M.; Ruiz, M.T.

    1988-01-01

    Near-infrared JHKL photometry of more than 200 stars, members of the open clusters Tr14, Tr15, Tr16, Cr228 and Cr232 in the Carina Nebula are presented. From comparing these results with the available visual photometry and spectroscopy, it is found that, except in Tr15, the intracluster reddening is characterized by a 'normal' extinction law at λ > 0.5μm but is highly anomalous and variable in the U- and B-bands. This behaviour may be explained by the presence of intracluster interstellar grains 'processed' by shock waves presumably associated with the explosive history of η Carinae. All clusters are found to be at the same distance from the Sun at d = 2.4 ± 0.2 kpc or Vsub(o) - Msub(v) 11.9 ± 0.2. The total amount of reddening, though, differs significantly from cluster to cluster. (author)

  20. Optical photometric variable stars towards the Galactic H II region NGC 2282

    Science.gov (United States)

    Dutta, Somnath; Mondal, Soumen; Joshi, Santosh; Jose, Jessy; Das, Ramkrishna; Ghosh, Supriyo

    2018-05-01

    We report here CCD I-band time series photometry of a young (2-5 Myr) cluster NGC 2282, in order to identify and understand the variability of pre-main-sequence (PMS) stars. The I-band photometry, down to ˜20.5 mag, enables us to probe the variability towards the lower mass end (˜0.1 M⊙) of PMS stars. From the light curves of 1627 stars, we identified 62 new photometric variable candidates. Their association with the region was established from H α emission and infrared (IR) excess. Among 62 variables, 30 young variables exhibit H α emission, near-IR (NIR)/mid-IR (MIR) excess or both and are candidate members of the cluster. Out of 62 variables, 41 are periodic variables, with a rotation rate ranging from 0.2-7 d. The period distribution exhibits a median period at ˜1 d, as in many young clusters (e.g. NGC 2264, ONC, etc.), but it follows a unimodal distribution, unlike others that have bimodality, with slow rotators peaking at ˜6-8 d. To investigate the rotation-disc and variability-disc connection, we derived the NIR excess from Δ(I - K) and the MIR excess from Spitzer [3.6]-[4.5] μm data. No conclusive evidence of slow rotation with the presence of discs around stars and fast rotation for discless stars is obtained from our periodic variables. A clear increasing trend of the variability amplitude with IR excess is found for all variables.

  1. Gas expulsion vs gas retention in young stellar clusters II: effects of cooling and mass segregation

    Science.gov (United States)

    Silich, Sergiy; Tenorio-Tagle, Guillermo

    2018-05-01

    Gas expulsion or gas retention is a central issue in most of the models for multiple stellar populations and light element anti-correlations in globular clusters. The success of the residual matter expulsion or its retention within young stellar clusters has also a fundamental importance in order to understand how star formation proceeds in present-day and ancient star-forming galaxies and if proto-globular clusters with multiple stellar populations are formed in the present epoch. It is usually suggested that either the residual gas is rapidly ejected from star-forming clouds by stellar winds and supernova explosions, or that the enrichment of the residual gas and the formation of the second stellar generation occur so rapidly, that the negative stellar feedback is not significant. Here we continue our study of the early development of star clusters in the extreme environments and discuss the restrictions that strong radiative cooling and stellar mass segregation provide on the gas expulsion from dense star-forming clouds. A large range of physical initial conditions in star-forming clouds which include the star-forming cloud mass, compactness, gas metallicity, star formation efficiency and effects of massive stars segregation are discussed. It is shown that in sufficiently massive and compact clusters hot shocked winds around individual massive stars may cool before merging with their neighbors. This dramatically reduces the negative stellar feedback, prevents the development of the global star cluster wind and expulsion of the residual and the processed matter into the ambient interstellar medium. The critical lines which separate the gas expulsion and the gas retention regimes are obtained.

  2. The nature of X-ray sources associated to young clusters around Sh2-296

    Science.gov (United States)

    Gregorio-Hetem, J.; Fernandes, B.; Montmerle, T.

    2014-10-01

    Aiming to unravel the star formation activity in the Canis Major R1 (CMaR1), we have studied the young (Sh2-296. Based on our X-ray data complemented by optical and near-IR data, we discovered, near to GU CMa, a stellar cluster that is older by at least a few Myr than the previously known cluster, around Z CMa, where star formation is still very active. Multi-object optical spectroscopy of our X-ray sources nearby Z CMa was performed with Gemini telescopes to confirm the existence of a mixed population from both older and younger clusters around the edge of Sh2-296. In the present work we show the results for optical counterparts candidates of 45 X-ray sources. Spectral type determination was based on comparison with standard spectra library and fitting the continuum and TiO bands. Typical features of young stars were inspected to confirm the nature of the sample that is mainly classified as T Tauri stars (TTs), since their spectra show the Li I line, one of the indicators of youth. The equivalent width of Hα measured at 10% of the total flux was used to separate Classical TTs (CTTs) from weak-line TTs (WTTs). Among 51 optical counterparts candidates, 38 are young stars: 24% of them are classified as CTTs and 76% are WTTs. However the present results correspond to a small fraction (˜ 15%) of the entire sample of X-ray sources we have detected. Aiming a more representative set of spectra, additional GMOS observations have been performed, as well as another ongoing project (see Santos-Silva et al.) dedicated to studying of the X-ray properties.

  3. Hyperfast pulsars as the remnants of massive stars ejected from young star clusters

    Science.gov (United States)

    Gvaramadze, Vasilii V.; Gualandris, Alessia; Portegies Zwart, Simon

    2008-04-01

    Recent proper motion and parallax measurements for the pulsar PSR B1508+55 indicate a transverse velocity of ~1100kms-1, which exceeds earlier measurements for any neutron star. The spin-down characteristics of PSR B1508+55 are typical for a non-recycled pulsar, which implies that the velocity of the pulsar cannot have originated from the second supernova disruption of a massive binary system. The high velocity of PSR B1508+55 can be accounted for by assuming that it received a kick at birth or that the neutron star was accelerated after its formation in the supernova explosion. We propose an explanation for the origin of hyperfast neutron stars based on the hypothesis that they could be the remnants of a symmetric supernova explosion of a high-velocity massive star which attained its peculiar velocity (similar to that of the pulsar) in the course of a strong dynamical three- or four-body encounter in the core of dense young star cluster. To check this hypothesis, we investigated three dynamical processes involving close encounters between: (i) two hard massive binaries, (ii) a hard binary and an intermediate-mass black hole (IMBH) and (iii) a single stars and a hard binary IMBH. We find that main-sequence O-type stars cannot be ejected from young massive star clusters with peculiar velocities high enough to explain the origin of hyperfast neutron stars, but lower mass main-sequence stars or the stripped helium cores of massive stars could be accelerated to hypervelocities. Our explanation for the origin of hyperfast pulsars requires a very dense stellar environment of the order of 106- 107starspc-3. Although such high densities may exist during the core collapse of young massive star clusters, we caution that they have never been observed.

  4. VizieR Online Data Catalog: NGC 2264, NGC 2547 and NGC 2516 stellar radii (Jackson+, 2016)

    Science.gov (United States)

    Jackson, R. J.; Jeffries, R. D.; Randich, S.; Bragaglia, A.; Carraro, G.; Costado, M. T.; Flaccomio, E.; Lanzafame; Lardo, C.; Monaco, L.; Morbidelli, L.; Smiljanic, R.; Zaggia, S.

    2015-11-01

    File Table1.dat contains Photometric and spectroscopic data of GES Survey targets in clusters in NGC 2547, NGC 2516, NGC 22264 downloaded from the Edinburugh GES archive (http://ges/roe.ac.uk/) . Photometric data comprised the (Cousins) I magnitude and 2MASS J, H and K magnitudes. Spectroscopic data comprises the signal to noise ratio, S/N of the target spectrum, the radial velocity, RV (in km/s), the projected equatorial velocity, vsini (in km/s), the number of separate observations co-added to produce the target spectrum and the log of effective temperature (logTeff) of the template spectrum fitted to measure RV and vsini. The absolute precision in RV, pRV (in km/s) and relative precision vsini (pvsini) were estimated, as a function of the logTeff, vsini and S/N, using the prescription described in Jackson et al. (2015A&A...580A..75J, Cat. J/A+A/580/A75). File Table3.dat contains measured and calculated properties of cluster targets with resolved vsini and a reported rotation period. The cluster name, right ascension, RA (deg) and declination, Dec (deg) are given for targets with measured periods given in the literature. Dynamic properties comprise: the radial velocity, RV (in km/s), the absolute precision in RV, pRV (km/s), the projected equatorial velocity, vsini (in km/s), the relative precision in vsini (pvsini) and the rotational period (in days). Also shown are values of absolute K magnitude, MK log of luminosity, log L (in solar units) and probability of cluster membership estimated using cluster data given in the text. Period shows reported values of cluster taken from the literature Estimated values of the projected radius, Rsini (in Rsolar) and uncertainty in projected radius, e_Rsini (in Rsolar) are given for targets where vsini>5km/s and pvsini>0.2. The final column shows a flag which is set to 1 for targets in cluster NGC 2264 where a (H-K) versus (J-H) colour-colour plot indicates possible infra-red excess. Period shows reported values of cluster

  5. Near-infrared imaging survey of faint companions around young dwarfs in the Pleiades cluster

    International Nuclear Information System (INIS)

    Itoh, Yoichi; Funayama, Hitoshi; Hashiguchi, Toshio; Oasa, Yumiko; Hayashi, Masahiko; Fukagawa, Misato; Currie, Thayne

    2011-01-01

    We conducted a near-infrared imaging survey of 11 young dwarfs in the Pleiades cluster using the Subaru Telescope and the near-infrared coronagraph imager. We found ten faint point sources, with magnitudes as faint as 20 mag in the K-band, with around seven dwarfs. Comparison with the Spitzer archive images revealed that a pair of the faint sources around V 1171 Tau is very red in infrared wavelengths, which indicates very low-mass young stellar objects. However, the results of our follow-up proper motion measurements implied that the central star and the faint sources do not share common proper motions, suggesting that they are not physically associated.

  6. Photometric search for variable stars in the young open cluster Berkeley 59

    Science.gov (United States)

    Lata, Sneh; Pandey, A. K.; Maheswar, G.; Mondal, Soumen; Kumar, Brijesh

    2011-12-01

    We present the time series photometry of stars located in the extremely young open cluster Berkeley 59. Using the 1.04-m telescope at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, we have identified 42 variables in a field of ˜13 × 13 arcmin2 around the cluster. The probable members of the cluster have been identified using a (V, V-I) colour-magnitude diagram and a (J-H, H-K) colour-colour diagram. 31 variables have been found to be pre-main-sequence stars associated with the cluster. The ages and masses of the pre-main-sequence stars have been derived from the colour-magnitude diagram by fitting theoretical models to the observed data points. The ages of the majority of the probable pre-main-sequence variable candidates range from 1 to 5 Myr. The masses of these pre-main-sequence variable stars have been found to be in the range of ˜0.3 to ˜3.5 M⊙, and these could be T Tauri stars. The present statistics reveal that about 90 per cent T Tauri stars have period dispersal of the discs of relatively massive stars.

  7. DOUBLE HORIZONTAL BRANCHES IN NGC 6440 AND NGC 6569 UNVEILED BY THE VVV SURVEY

    International Nuclear Information System (INIS)

    Mauro, Francesco; Bidin, Christian Moni; Cohen, Roger; Geisler, Doug; Chené, André-Nicolas; Villanova, Sandro; Minniti, Dante; Catelan, Marcio

    2012-01-01

    We report the discovery of a peculiar horizontal branch (HB) in NGC 6440 and NGC 6569, two massive and metal-rich Galactic globular clusters (GGCs) located in the Galactic bulge, within 4 kpc from the Galactic center. In both clusters, two distinct clumps are detected at the level of the cluster HB, separated by only ∼0.1 mag in the K s band. They were detected with IR photometric data collected with the 'VISTA Variables in the Vía Láctea' Survey, and confirmed in independent IR catalogs available in the literature and Hubble Space Telescope optical photometry. Our analysis demonstrates that these clumps are real cluster features, not a product of field contamination or interstellar reddening. The observed split HBs could be a signature of two stellar sub-populations with different chemical composition and/or age, as recently found in Terzan 5, but it cannot be excluded that they are caused by evolutionary effects, in particular for NGC 6440. This interpretation, however, requires an anomalously high helium content (Y > 0.30). Our discovery suggests that such a peculiar HB morphology could be a common feature of massive, metal-rich bulge GGCs.

  8. A deep Spitzer survey of circumstellar disks in the young double cluster, h and χ Persei

    Energy Technology Data Exchange (ETDEWEB)

    Cloutier, Ryan; Currie, Thayne; Jayawardhana, Ray [University of Toronto, 50 St. George Street, Toronto, ON, M5S 2J7 (Canada); Rieke, George H. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Kenyon, Scott J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02140 (United States); Balog, Zoltan, E-mail: cloutier@cita.utoronto.ca, E-mail: currie@astro.utoronto.ca, E-mail: grieke@as.arizona.edu, E-mail: skenyon@cfa.harvard.edu [Max Planck Institute for Astrophysics, Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-12-01

    We analyze very deep Infrared Array Camera and Multiband Imaging Photometer for Spitzer (MIPS) photometry of ∼12, 500 members of the 14 Myr old Double Cluster, h and χ Persei, building upon our earlier, shallower Spitzer Cycle 1 studies. Numerous likely members show infrared (IR) excesses at 8 μm and 24 μm, indicative of circumstellar dust. The frequency of stars with 8 μm excess is at least 2% for our entire sample, slightly lower (higher) for B/A stars (later type, lower mass stars). Optical spectroscopy also identifies gas in about 2% of systems, but with no clear trend between the presence of dust and gas. Spectral energy distribution modeling of 18 sources with detections at optical wavelengths through MIPS 24 μm reveals a diverse set of disk evolutionary states, including a high fraction of transitional disks, though similar data for all disk-bearing members would provide constraints. Using Monte Carlo simulations, we combine our results with those for other young clusters to study the global evolution of dust/gas disks. For nominal cluster ages, the e-folding times (τ{sub 0}) for the frequency of warm dust and gas are 2.75 Myr and 1.75 Myr, respectively. Assuming a revised set of ages for some clusters, these timescales increase to 5.75 and 3.75 Myr, respectively, implying a significantly longer typical protoplanetary disk lifetime than previously thought. In both cases, the transitional disk duration, averaged over multiple evolutionary pathways, is ≈1 Myr. Finally, 24 μm excess frequencies for 4-6 M {sub ☉} stars appear lower than for 1-2.5 M {sub ☉} stars in other 10-30 Myr old clusters.

  9. Triggered cluster formation in the RMC

    Science.gov (United States)

    Li, Jin Zeng; Smith, Michael D.

    An investigation based on data from the spatially complete 2MASS Survey reveals that a remarkable burst of clustered star formation is taking place throughout the south-east quadrant of the Rosette Molecular Cloud. Compact clusters are forming in a multi-seeded mode, in parallel and at various places. In addition, sparse aggregates of embedded young stars are extensively distributed. Here we present the primary results and implications for high-mass and clustered star formation in this giant molecular cloud. In particular, we incorporate for the first time the birth of medium to low-mass stars into the scenario of sequential formation of OB clusters. Following the emergence of the young OB cluster NGC 2244, a variety of manifestations of forming clusters of medium to high mass appear in the vicinity of the swept-up layer of the H II region as well as further into the molecular cloud. The embedded clusters appear to form in a structured manner, which suggests they follow tracks laid out by the decay of macroturbulence. We address the possible origins of the turbulence. This leads us to propose a tree model to interpret the neat spatial distribution of clusters within a large section of the Rosette complex. Prominent new generation OB clusters are identified at the root of the tree pattern.

  10. The Extended Baryonic Halo of NGC 3923

    Directory of Open Access Journals (Sweden)

    Bryan W. Miller

    2017-07-01

    Full Text Available Galaxy halos and their globular cluster systems build up over time by the accretion of small satellites. We can learn about this process in detail by observing systems with ongoing accretion events and comparing the data with simulations. Elliptical shell galaxies are systems that are thought to be due to ongoing or recent minor mergers. We present preliminary results of an investigation of the baryonic halo—light profile, globular clusters, and shells/streams—of the shell galaxy NGC 3923 from deep Dark Energy Camera (DECam g and i-band imaging. We present the 2D and radial distributions of the globular cluster candidates out to a projected radius of about 185 kpc, or ∼ 37 R e , making this one of the most extended cluster systems studied. The total number of clusters implies a halo mass of M h ∼ 3 × 10 13 M ⊙ . Previous studies had identified between 22 and 42 shells, making NGC 3923 the system with the largest number of shells. We identify 23 strong shells and 11 that are uncertain. Future work will measure the halo mass and mass profile from the radial distributions of the shell, N-body models, and line-of-sight velocity distribution (LOSVD measurements of the shells using the Multi Unit Spectroscopic Explorer (MUSE.

  11. Hot stars in young massive clusters: Mapping the current Galactic metallicity

    Science.gov (United States)

    de la Fuente, Diego; Najarro, Francisco; Davies, Ben; Trombley, Christine; Figer, Donald F.; Herrero, Artemio

    2013-06-01

    Young Massive Clusters (YMCs) with ages guarantee that these objects present the same chemical composition than the surrounding environment where they are recently born. Finally, the YMCs host very massive stars whose extreme luminosities allow to accomplish detailed spectroscopic analyses even in the most distant regions of the Milky Way. Our group has carried out ISAAC/VLT spectroscopic observations of hot massive stars belonging to several YMCs in different locations around the Galactic disk. As a result, high signal-to-noise, near-infrared spectra of dozens of blue massive stars (including many OB supergiants, Wolf-Rayet stars and a B hypergiant) have been obtained. These data are fully reduced, and NLTE spherical atmosphere modeling is in process. Several line diagnostics will be combined in order to calculate metal abundances accurately for each cluster. The diverse locations of the clusters will allow us to draw a two-dimensional chemical map of the Galactic disk for the first time. The study of the radial and azimuthal variations of elemental abundances will be crucial for understanding the chemical evolution of the Milky Way. Particularly, the ratio between Fe-peak and alpha elements will constitute a powerful tool to investigate the past stellar populations that originated the current Galactic chemistry.

  12. BULGELESS GIANT GALAXIES CHALLENGE OUR PICTURE OF GALAXY FORMATION BY HIERARCHICAL CLUSTERING ,

    International Nuclear Information System (INIS)

    Kormendy, John; Cornell, Mark E.; Drory, Niv; Bender, Ralf

    2010-01-01

    To better understand the prevalence of bulgeless galaxies in the nearby field, we dissect giant Sc-Scd galaxies with Hubble Space Telescope (HST) photometry and Hobby-Eberly Telescope (HET) spectroscopy. We use the HET High Resolution Spectrograph (resolution R ≡ λ/FWHM ≅ 15, 000) to measure stellar velocity dispersions in the nuclear star clusters and (pseudo)bulges of the pure-disk galaxies M 33, M 101, NGC 3338, NGC 3810, NGC 6503, and NGC 6946. The dispersions range from 20 ± 1 km s -1 in the nucleus of M 33 to 78 ± 2 km s -1 in the pseudobulge of NGC 3338. We use HST archive images to measure the brightness profiles of the nuclei and (pseudo)bulges in M 101, NGC 6503, and NGC 6946 and hence to estimate their masses. The results imply small mass-to-light ratios consistent with young stellar populations. These observations lead to two conclusions. (1) Upper limits on the masses of any supermassive black holes are M . ∼ 6 M sun in M 101 and M . ∼ 6 M sun in NGC 6503. (2) We show that the above galaxies contain only tiny pseudobulges that make up ∼ circ > 150 km s -1 , including M 101, NGC 6946, IC 342, and our Galaxy, show no evidence for a classical bulge. Four may contain small classical bulges that contribute 5%-12% of the light of the galaxy. Only four of the 19 giant galaxies are ellipticals or have classical bulges that contribute ∼1/3 of the galaxy light. We conclude that pure-disk galaxies are far from rare. It is hard to understand how bulgeless galaxies could form as the quiescent tail of a distribution of merger histories. Recognition of pseudobulges makes the biggest problem with cold dark matter galaxy formation more acute: How can hierarchical clustering make so many giant, pure-disk galaxies with no evidence for merger-built bulges? Finally, we emphasize that this problem is a strong function of environment: the Virgo cluster is not a puzzle, because more than 2/3 of its stellar mass is in merger remnants.

  13. TWO-DIMENSIONAL MAPPING OF YOUNG STARS IN THE INNER 180 pc OF NGC 1068: CORRELATION WITH MOLECULAR GAS RING AND STELLAR KINEMATICS

    Energy Technology Data Exchange (ETDEWEB)

    Storchi-Bergmann, Thaisa; Riffel, Rogerio; Vale, Tiberio Borges [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, IF, CP 15051, 91501-970 Porto Alegre, RS (Brazil); Riffel, Rogemar A.; Diniz, Marlon R. [Departamento de Fisica, Centro de Ciencias Naturais e Exatas, Universidade Federal de Santa Maria, 97105-900 Santa Maria, RS (Brazil); McGregor, Peter J., E-mail: thaisa@ufrgs.br [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia)

    2012-08-20

    We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structure at Almost-Equal-To 100 pc from the nucleus, where it is coincident with an expanding ring of H{sub 2} emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age {>=} 2 Gyr) dominates the mass, while the flux is dominated by blackbody components with temperatures in the range 700 K {<=} T {<=} 800 K which we attribute to the dusty torus. We also find some contribution from blackbody and power-law components beyond the nucleus which we attribute to dust emission and scattered light.

  14. NONLINEAR COLOR-METALLICITY RELATIONS OF GLOBULAR CLUSTERS. II. A TEST ON THE NONLINEARITY SCENARIO FOR COLOR BIMODALITY USING THE u-BAND COLORS: THE CASE OF M87 (NGC 4486)

    International Nuclear Information System (INIS)

    Yoon, Suk-Jin; Lee, Sang-Yoon; Kim, Hak-Sub; Cho, Jaeil; Chung, Chul; Sohn, Sangmo T.; Blakeslee, John P.

    2011-01-01

    The optical color distributions of globular clusters (GCs) in most large elliptical galaxies are bimodal. Based on the assumed linear relationship between GC colors and their metallicities, the bimodality has been taken as evidence of two GC subsystems with different metallicities in each galaxy and has led to a number of theories in the context of galaxy formation. More recent observations and modeling of GCs, however, suggests that the color-metallicity relations (CMRs) are inflected, and thus colors likely trace metallicities in a nonlinear manner. The nonlinearity could produce bimodal color distributions from a broad underlying metallicity spread, even if it is unimodal. Despite the far-reaching implications, whether CMRs are nonlinear and whether the nonlinearity indeed causes the color bimodality are still open questions. Given that the spectroscopic refinement of CMRs is still very challenging, we here propose a new photometric technique to probe the possible nonlinear nature of CMRs. In essence, a color distribution of GCs is a 'projected' distribution of their metallicities. Since the form of CMRs hinges on which color is used, the shape of color distributions varies depending significantly on the colors. Among other optical colors, the u-band related colors (e.g., u – g and u – z) are theoretically predicted to exhibit significantly less inflected CMRs than other preferred CMRs (e.g., for g – z). As a case study, we performed the Hubble Space Telescope (HST)/WFPC2 archival u-band photometry for the M87 (NGC 4486) GC system with confirmed color bimodality. We show that the u-band color distributions are significantly different from that of g – z and consistent with our model predictions. With more u-band measurements, this method will support or rule out the nonlinear CMR scenario for the origin of GC color bimodality with high confidence. The HST/WFC3 observations in F336W for nearby large elliptical galaxies are highly anticipated in this regard.

  15. CCD imagery of the S0 galaxies NGC 3990 and NGC 3998

    International Nuclear Information System (INIS)

    Welch, G.A.; Welch, D.M.K.; Dupuy, D.L.

    1991-01-01

    The structure and colors of NGC 3990 and NGC 3998 are investigated using BR CCD imagery. Fits of bulge-disk models of the galaxies indicate that both disks are somewhat brighter and more compact than typical S0 galaxies in the Virgo and Fornax clusters. Although the two galaxies are separated by only about 3.5 arcmin, none of the obvious signs of gravitational interaction are seen. The colors of both galaxies are normal; the disk of NGC 3998 is somewhat bluer than its bulge. The search has failed to reveal the interstellar dust predicted from the neutral hydrogen observations of NGC 3998. The dust that is seen appears to be mixed with ionized gas which occupies the center of this galaxy and may be the same material seen at longer wavelengths by the IRAS experiment. Its low abundance relative to the neutral gas is consistent with the idea that the ISM was contributed by a gas-rich dwarf galaxy in a destructive merger. 31 refs

  16. Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN Photometry. II. M5 (NGC 5904) and a New Filter System

    Science.gov (United States)

    Lee, Jae-Woo

    2017-07-01

    Using our ingeniously designed new filter systems, we investigate multiple stellar populations of the red giant branch (RGB) and the asymptotic giant branch (AGB) in the globular cluster (GC) M5. Our results are the following. (1) Our {{cn}}{JWL} index accurately traces nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions in both RGB and AGB sequences, with number ratios between CN-weak (CN-w) and CN-strong (CN-s) of n(CN-w):n(CN-s) = 29:71 (±2) and 21:79 (±7), respectively. (3) We also find a bimodal photometric [N/Fe] distribution for M5 RGB stars. (4) Our {{cn}}{JWL}-[O/Fe] and {{cn}}{JWL}-[Na/Fe] relations show clear discontinuities between the two RGB populations. (5) Although small, the RGB bump of CN-s is slightly brighter, {{Δ }}{V}{bump} = 0.07 ± 0.04 mag. If real, the difference in the helium abundance becomes {{Δ }}Y = 0.028 ± 0.016, in the sense that CN-s is more helium enhanced. (6) Very similar radial but different spatial distributions with comparable center positions are found for the two RGB populations. The CN-s RGB and AGB stars are more elongated along the NW-SE direction. (7) The CN-s population shows a substantial net projected rotation, while that of the CN-w population is nil. (8) Our results confirm the deficiency of CN-w AGB stars previously noted by others. We show that it is most likely due to stochastic truncation in the outer part of the cluster. Finally, we discuss the formation scenario of M5. Based on observations made with the Cerro Tololo Inter-American Observatory (CTIO) 1 m telescope, which is operated by the SMARTS consortium.

  17. Young Star Cluster Found Aglow With Mysterious X-Ray Cloud

    Science.gov (United States)

    2002-12-01

    A mysterious cloud of high-energy electrons enveloping a young cluster of stars has been discovered by astronomers using NASA's Chandra X-ray Observatory. These extremely high-energy particles could cause dramatic changes in the chemistry of the disks that will eventually form planets around stars in the cluster. Known as RCW 38, the star cluster covers a region about 5 light years across. It contains thousands of stars formed less than a million years ago and appears to be forming new stars even today. The crowded environment of a star cluster is thought to be conducive to the production of hot gas, but not high-energy particles. Such particles are typically produced by exploding stars, or in the strong magnetic fields around neutron stars or black holes, none of which is evident in RCW 38. "The RCW 38 observation doesn't agree with the conventional picture," said Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, lead author of an Astrophysical Journal Letters paper describing the Chandra observation. "The data show that somehow extremely high-energy electrons are being produced there, although it is not clear how." RCW 38 RCW 38 X-ray, Radio, Infrared Composite Electrons accelerated to energies of trillions of volts are required to account for the observed X-ray spectrum of the gas cloud surrounding the ensemble of stars, which shows an excess of high-energy X-rays. As these electrons move in the magnetic field that threads the cluster, they produce X-rays. One possible origin for the high-energy electrons is a previously undetected supernova that occurred in the cluster. Although direct evidence for the supernova could have faded away thousands of years ago, a shock wave or a rapidly rotating neutron star produced by the outburst could be acting in concert with stellar winds to produce the high-energy electrons. "Regardless of the origin of the energetic electrons," said Wolk, "their presence would change the chemistry of proto

  18. IRAS 06562-0337, The Ironclad Nebula: A New Young Star Cluster

    International Nuclear Information System (INIS)

    Alves, D.R.; Hoard, D.W.; Rodgers, B.

    1998-01-01

    IRAS 06562-0337 has been the recent subject of a classic debate: is it a proto endash planetary nebula or a young stellar object? We present the first 2 μm image of IRAS 06562-0337, which reveals an extended diffuse nebula containing approximately 70 stars inside a 30 double-prime radius around a bright, possibly resolved, central object. The derived stellar luminosity function is consistent with that expected from a single coeval population, and the brightness of the nebulosity is consistent with the predicted flux of unresolved low-mass stars. The stars and nebulosity are spatially coincident with strong CO line emission. We therefore identify IRAS 06562-0337 as a new young star cluster embedded in its placental molecular cloud. The central object is likely a Herbig Be star, M ∼ 20 M circle-dot , which may be seen in reflection. We present medium-resolution high signal-to-noise ratio 1997 epoch optical spectra of the central object. Comparison with previously published spectra shows new evidence for time-variable permitted and forbidden line emission, including Si ii, Fe ii, [Fe ii], and [O i]. We suggest that the origin is a dynamic stellar wind in the extended stratified atmosphere of the massive central star in IRAS 06562-0337. copyright copyright 1998. The American Astronomical Society

  19. Alma Survey of Circumstellar Disks in the Young Stellar Cluster IC 348

    Science.gov (United States)

    Ruíz-Rodríguez, D.; Cieza, L. A.; Williams, J. P.; Andrews, S. M.; Principe, D. A.; Caceres, C.; Canovas, H.; Casassus, S.; Schreiber, M. R.; Kastner, J. H.

    2018-05-01

    We present a 1.3 mm continuum survey of the young (2-3 Myr) stellar cluster IC 348, which lies at a distance of 310 pc, and is dominated by low-mass stars (M⋆ ˜ 0.1-0.6 M⊙). We observed 136 Class II sources (disks that are optically thick in the infrared) at 0.8″ (200 au) resolution with a 3σ sensitivity of ˜ 0.45 mJy (Mdust ˜ 1.3 M⊕). We detect 40 of the targets and construct a mm-continuum luminosity function. We compare the disk mass distribution in IC 348 to those of younger and older regions, taking into account the dependence on stellar mass. We find a clear evolution in disk masses from 1 to 5-10 Myr. The disk masses in IC 348 are significantly lower than those in Taurus (1-3 Myr) and Lupus (1-3 Myr), similar to those of Chamaleon I, (2-3 Myr) and σ Ori (3-5 Myr) and significantly higher than in Upper Scorpius (5-10 Myr). About 20 disks in our sample (˜5% of the cluster members) have estimated masses (dust + gas) >1 MJup and hence might be the precursors of giant planets in the cluster. Some of the most massive disks include transition objects with inner opacity holes based on their infrared SEDs. From a stacking analysis of the 96 non-detections, we find that these disks have a typical dust mass of just ≲ 0.4 M⊕, even though the vast majority of their infrared SEDs remain optically thick and show little signs of evolution. Such low-mass disks may be the precursors of the small rocky planets found by Kepler around M-type stars.

  20. Stellar population of NGC 1850 in the LMC

    Science.gov (United States)

    Gilmozzi, Roberto; Panagia, Nino

    1992-01-01

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

  1. Extinction of NGC 7027

    International Nuclear Information System (INIS)

    Seaton, M.J.

    1979-01-01

    Emission intensities of recombination lines in hydrogenic spectra are known accurately relative to intensities in the free-free radio continuum. For NGC 7027 intensities have been measured for the radio continuum and for H I and He II lines in the wavelength range from lambda = 2.17 μm to lambda = 1640 A: comparison with the calculated emission intensities gives the extinction. Determinations of the standard interstellar extinction function are critically discussed. The extinction deduced for the total radiation from NGC 7027 has a dependence on wavelength for 6563 A >= lambda >= 1640 A which is in excellent agreement with the adopted standard results, but there are some anomalies for longer wavelengths and for the ratio of total to selective extinction. These can be explained using a model which allows for a local contribution to the extinction which is variable over the surface of the nebula. (author)

  2. Abundances of planetary nebulae NGC 7662 and NGC 6741

    NARCIS (Netherlands)

    Pottasch, [No Value; Beintema, DA; Salas, JB; Feibelman, WA

    2001-01-01

    The ISO and IUE spectra of the elliptical nebulae NGC7662 and NGC6741 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous

  3. Photographic surface photometry of NGC 2855 and NGC 6771 galaxies

    International Nuclear Information System (INIS)

    Schroeder, M. de F.S.

    1984-01-01

    Photographic surface photometry in the BV system was carried out two Southern SO's galaxies, NGC 2855 and NGC 6771. B and V isophote maps were obtained as well as geometric and integrated parameters as position angles, inclination, diameters, magnitudes and integrated colors. Each luminosity profile was decomposed into bulge and disk contributions, each component being fitted to convenient laws. For NGC 2855 de Vaucouleurs law described well the bulge whereas the disk showed an exponential distribution. For NGC 6771 the barred nuclear bulge as well as the disk was best fitted by exponential laws. Additional luminosity components due to an inner fragmented ring were identified in NGC 2855 and due to both a quite prominent lens and well defined ring in NGC 6771. In this galaxy the minor axis, oriented almost edge-on, present clues of another luminosity component besides the bulge and the thin disk. For both galaxies the disk central surface brightness was found to be fainter than the standard value observed by Freeman. The fitting parameters were used to determine the bulge-to-disk luminosity ratios as well as their contribution to total luminosity. The domination by the bulge light over the disk light was clear in both galaxies. From the B and V luminosity profile the color gradients were estimated. For both objects the local color indices decreased from inner to outer regions, this effect being relatively smooth in NGC 2855 and more prominent in NGC 6771 [pt

  4. The variable stars of NGC 1866

    International Nuclear Information System (INIS)

    Welch, D.L.; Cote, P.; Fischer, P.; Mateo, M.; Madore, B.F.

    1991-01-01

    A search has been conducted for new variables in the LMC cluster NGC 1866 using new multiepoch CCD photometry. Eight previously unknown Cepheid variables, most near the cluster core, are found. Of the new variables reported by Storm et al. (188), only six of 10 appear to be Cepheids and one of these is not a member. Periods and mean magnitudes and colors for sufficiently uncrowded variables are reported, as is one red giant variable of long period and one Cepheid which is a single-lined spectroscopic binary with a velocity semiamplitude greater than or equal to 10.5 km/s. The variation of light-curve amplitude with position in the instability strip is reported along with an apparently nonvariable star, which is a radial velocity member, in the strip. A true distance modulus of 18.57 + or - 0.01 mag is obtained for the cluster. 36 refs

  5. THE WHITE DWARF AGE OF NGC 2477

    International Nuclear Information System (INIS)

    Jeffery, Elizabeth J.; Von Hippel, Ted; DeGennaro, Steven; Jefferys, William H.; Van Dyk, David A.; Stein, Nathan

    2011-01-01

    We present deep photometric observations of the open cluster NGC 2477 using HST/WFPC2. By identifying seven cluster white dwarf candidates, we present an analysis of the white dwarf age of this cluster, using both the traditional method of fitting isochrones to the white dwarf cooling sequence, and by employing a new Bayesian statistical technique that has been developed by our group. This new method performs an objective, simultaneous model fit of the cluster and stellar parameters (namely, age, metallicity, distance, reddening, as well as individual stellar masses, mass ratios, and cluster membership) to the photometry. Based on this analysis, we measure a white dwarf age of 1.035 ± 0.054 ± 0.087 Gyr (uncertainties represent the goodness of model fits and discrepancy among models, respectively) in good agreement with the cluster's main-sequence turnoff age. This work is part of our ongoing work to calibrate main-sequence turnoff and white dwarf ages using open clusters, and to improve the precision of cluster ages to the ∼5% level.

  6. A SEARCH FOR HERBIG-HARO OBJECTS IN NGC 7023 AND BARNARD 175

    International Nuclear Information System (INIS)

    Rector, T. A.; Schweiker, H.

    2013-01-01

    Wide-field optical imaging was obtained of the cluster and reflection nebula NGC 7023 and the Bok globule B175. We report the discovery of four new Herbig-Haro (HH) objects in NGC 7023, the first HH objects to be found in this region. They were first detected by their Hα and [S II] emission but are also visible at 3.6 and 4.5 μm in archival Spitzer observations of this field. These HH objects are part of at least two distinct outflows. Both outflows are aligned with embedded 'Class I' young stellar objects in a tight group on the western edge of the nebula. One of the outflows may have a projected distance of 0.75 pc, which is a notable length for an embedded source. No new HH objects were discovered in B175. However, we reclassify the knot HH450X, in B175, as a background galaxy. The discovery that HH 450X is not a shock front weakens the argument that HH 450 and SNR G110.3+11.3 are co-located and interacting.

  7. Color maps of X-ray globular clusters

    International Nuclear Information System (INIS)

    Bailyn, C.D.; Grindlay, J.E.; Cohn, H.; Lugger, P.M.

    1988-01-01

    The results of a search for optical counterparts to X-ray sources in six globular clusters, 47 Tuc, NGC 1851, NGC 6441, NGC 6624, NGC 6712, and M15, are reported. Maps of the U-B color of the central regions of the clusters were prepared. A candidate for the optical counterpart of the source in NGC 6712 was found, along with a blue region near the X-ray source in 47 Tuc. Upper limits on the colors and magnitudes of possible optical counterparts are reported for the other three clusters. The use of color maps to determine color gradients in globular clusters is explored. It is found that, while such gradients do exist and vary from cluster to cluster, they can be explained by crowding effects. Crude limits are placed on the excess populations of blue objects such as CVs, which have been postulated to be concentrated in the centers of dense clusters. 32 references

  8. YSOVAR II: Mapping YSO Inner Disk Structure in NGC 2264 with Simultaneous Spitzer and CoRoT Time Series Photometry

    Science.gov (United States)

    Stauffer, John; Morales-Calderon, Maria; Rebull, Luisa; Affer, Laura; Alencar, Sylvia; Allen, Lori; Barrado, David; Bouvier, Jerome; Calvet, Nuria; Carey, Sean; Carpenter, John; Ciardi, David; Covey, Kevin; D'Alessio, Paola; Espaillat, Catherine; Favata, Fabio; Flaccomio, Ettore; Forbrich, Jan; Furesz, Gabor; Hartman, Lee; Herbst, William; Hillenbrand, Lynne; Holtzman, Jon; Hora, Joe; Marchis, Franck; McCaughrean, Mark; Micela, Giusi; Mundt, Reinhard; Plavchan, Peter; Turner, Neal; Skrutzkie, Mike; Smith, Howard; Song, Inseok; Szentgyorgi, Andy; Terebey, Susan; Vrba, Fred; Wasserman, Lawrence; Watson, Alan; Whitney, Barbara; Winston, Elaine; Wood, Kenny

    2011-05-01

    We propose a simultaneous, continuous 30 day observation of the star forming region NGC2264 with Spitzer and CoRoT. NGC2264 is the only nearby, rich star-forming region which can be observed with CoRoT; it is by definition then the only nearby, rich star-forming region where a simultaneous Spitzer/CoRoT campaign is possible. Fortunately, the visibility windows for the two spacecraft overlap, allowing this program to be done in the Nov. 25, 2011 to Jan. 4, 2012 time period. For 10 days, we propose to map the majority of the cluster (a 35'x35' region) to a depth of 48 seconds per point, with each epoch taking 1.7 hours, allowing of order 12 epochs per day. For the other 20 days, we propose to obtaining staring-mode data for two positions in the cluster having a high density of cluster members. We also plan to propose for a variety of other ground and space-based data, most of which would also be simultaneous with the Spitzer and CoRoT observing. These data will allow us to address many astrophysical questions related to the structure and evolution of the disks of young stars and the interaction of those disks with the forming star. The data may also help inform models of planet formation since planets form and migrate through the pre-main sequence disks during the 0.5-5 Myr age range of stars in NGC2264. The data we collect will also provide an archive of the variability properties of young stars that is unmatched in its accuracy, sensitivity, cadence and duration and which therefore could inspire investigation of phenomena which we cannot now imagine. The CoRoT observations have been approved, contingent on approval of a simultaneous Spitzer observing program (this proposal).

  9. Optical and near-infrared photometric study of NGC 6724

    Science.gov (United States)

    Bendary, Reda; Tadross, Ashraf; Hasan, Priya; Osman, Anas; Essam, Ahmed

    2018-02-01

    BVRI CCD photometry of the poorly studied open cluster NGC 6724 has been carried out down to a limiting magnitude of V∼20 mag. The stars of the cluster have been observed using the Newtonian focus (f/4.84) of the 74-inch telescope at Kottamia Astronomical Observatory in Egypt. Also, the 2MASS - JHK system is used to confirm the results we obtained. The main photometric parameters have been estimated for the present object; the diameter is found to be 6 arcmin, the distance is 1530±60 pc from the Sun and the age is 900±50 Myr. The optical reddening E(B-V)=0.65 {mag}, while the infrared reddening is E(J-H)=0.20 {mag}. The slope of the mass function distribution and the relaxation time estimations indicate that cluster NGC 6724 is dynamically relaxed.

  10. The Low-mass Population in the Young Cluster Stock 8: Stellar Properties and Initial Mass Function

    Energy Technology Data Exchange (ETDEWEB)

    Jose, Jessy; Herczeg, Gregory J.; Fang, Qiliang [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871 (China); Samal, Manash R. [Graduate Institute of Astronomy, National Central University 300, Jhongli City, Taoyuan County 32001, Taiwan (China); Panwar, Neelam, E-mail: jessyvjose1@gmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2017-02-10

    The evolution of H ii regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution, and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6 and 4.5 μ m photometry from UKIDSS and Spitzer -IRAC. We use multicolor criteria to identify the candidate young stellar objects in the region. Using evolutionary models, we obtain a median log(age) of ∼6.5 (∼3.0 Myr) with an observed age spread of ∼0.25 dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ∼0.15 dex. The intrinsic age spread in the cluster is ∼0.2 dex. The fraction of young stellar objects surrounded by disks is ∼35%. The K -band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The initial mass function (IMF) of Stock 8 has a Salpeter-like slope at >0.5 M {sub ⊙} and flattens and peaks at ∼0.4 M {sub ⊙}, below which it declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of the IMF due to the proximity of massive stars around the cluster.

  11. Time monitoring of radio jets and magnetospheres in the nearby young stellar cluster R Coronae Australis

    International Nuclear Information System (INIS)

    Liu, Hauyu Baobab; Takami, Michihiro; Yan, Chi-Hung; Karr, Jennifer; Chou, Mei-Yin; Ho, Paul T.-P.; Galván-Madrid, Roberto; Costigan, Gráinne; Manara, Carlo Felice; Forbrich, Jan; Rodríguez, Luis F.; Zhang, Qizhou

    2014-01-01

    We report Karl G. Jansky Very Large Array 8-10 GHz (λ = 3.0-3.7 cm) monitoring observations toward the young stellar object (YSO) cluster R Coronae Australis (R CrA), taken from 2012 March 15 to 2012 September 12. These observations were planned to measure the radio flux variabilities in timescales from 0.5 hr to several days, to tens of days, and up to ∼200 days. We found that among the YSOs detectable in individual epochs, in general, the most reddened objects in the Spitzer observations show the highest mean 3.5 cm Stokes I emission, and the lowest fractional variabilities on <200 day timescales. The brightest radio flux emitters in our observations are the two reddest sources IRS7W and IRS7E. In addition, by comparing our observations with observations taken from 1996 to 1998 and 2005, we found that the radio fluxes of these two sources have increased by a factor of ∼1.5. The mean 3.5 cm fluxes of the three Class I/II sources, IRSI, IRS2, and IRS6, appear to be correlated with their accretion rates derived by a previous near-infrared line survey. The weakly accreting Class I/II YSOs, or those in later evolutionary stages, present radio flux variability on <0.5 hr timescales. Some YSOs were detected only during occasional flaring events. The source R CrA went below our detection limit during a few fading events.

  12. Insulin sensitivity and clustering of coronary heart disease risk factors in young adults. The Northern Ireland Young Hearts Study

    DEFF Research Database (Denmark)

    Andersen, Lars Bo; Boreham, Colin A.G.; Young, Ian S.

    2006-01-01

    risk factor. Subjects with clustered risk were defined as those displaying four or more risk factors. Blood glucose and insulin were measured in the fasting state and 2 h after ingestion of a 75 g glucose load. Results. Fasting insulin and the homeostasis model assessment insulin resistance score (HOMA......) were strong, graded predictors of clustered risk. The odds ratio (OR) for having clustered risk was 10.8 (95% CI: 3.6-32.4) for the upper quartile of fasting insulin compared to the lowest quartile, and the corresponding OR for HOMA was 23.2 (95% CI: 5.3-101.6). Conclusion. HOMA score predicts...

  13. Chandra High Resolution Imaging of NGC 1365 and NGC 4151

    Science.gov (United States)

    Wang, Junfeng; Fabbiano, G.; Elvis, M.; Risaliti, G.; Karovska, M.; Zezas, A.; Mazzarella, J. M.; Lord, S.; Howell, J. H.; Mundell, C. G.

    2010-07-01

    We present Chandra high resolution imaging of the circumnuclear regions of two nearby active galaxies, namely the starburst/AGN composite Seyfert 1.8 NGC 1365 and the archetypal Seyfert 1 NGC 4151. In NGC 1365, the X-ray morphology shows a biconical soft X-ray-emission region extending ~5 kpc in projection from the nucleus, coincident with the optical high-excitation outflows. Chandra HRC imaging of the NGC 4151 nucleus resolves X-ray emission from the 4 arcsec radio jet and the narrow line region (NLR) clouds. Our results demonstrate the unique power of spatially resolved spectroscopy with Chandra, and support previous claims that frequent jet-ISM interaction may explain why jets in Seyfert galaxies appear small, slow, and thermally dominated.

  14. Cluster analysis of behavioural weight management strategies and associations with weight change in young women: a longitudinal analysis.

    Science.gov (United States)

    Madigan, C D; Daley, A J; Kabir, E; Aveyard, P; Brown, W

    2015-11-01

    Maintaining a healthy weight is important for the prevention of many chronic diseases. Little is known about the strategies used by young women to manage their weight, or the effectiveness of these in preventing weight gain. We aimed to identify clusters of weight control strategies used by women and to determine the average annual weight change among women in each cluster from 2000 to 2009. Latent cluster analysis of weight control strategies reported by 8125 participants in the Australian Longitudinal Study of Women's Health. Analyses were performed in March-November 2014. Weight control strategies were used by 79% of the women, and four unique clusters were found. The largest cluster group (39.7%) was named dieters as 90% had been on a diet in the past year, and half of these women had lost 5 kg on purpose. Women cut down on size of meals, fats and sugars and took part in vigorous physical activity. Additionally 20% had used a commercial programme. The next largest cluster (30.2%) was the healthy living group who followed the public health messages of 'eat less and move more'. The do nothing group (20%) did not actively control their weight whereas the perpetual dieters group (10.7%) used all strategies, including unhealthy behaviours. On average women gained 700 g per year (over 9 years); however, the perpetual dieters group gained significantly more weight (210 g) than the do nothing group (Phealth guidelines on health eating and physical activity.

  15. Molecular clouds in the NGC 6334 and NGC 6357 region: Evidence for a 100 pc-scale cloud-cloud collision triggering the Galactic mini-starbursts

    Science.gov (United States)

    Fukui, Yasuo; Kohno, Mikito; Yokoyama, Keiko; Torii, Kazufumi; Hattori, Yusuke; Sano, Hidetoshi; Nishimura, Atsushi; Ohama, Akio; Yamamoto, Hiroaki; Tachihara, Kengo

    2018-05-01

    We carried out new CO (J = 1-0, 2-1, and 3-2) observations with NANTEN2 and ASTE in the region of the twin Galactic mini-starbursts NGC 6334 and NGC 6357. We detected two velocity molecular components of 12 km s-1 velocity separation, which is continuous over 3° along the plane. In NGC 6334 the two components show similar two-peaked intensity distributions toward the young H II regions and are linked by a bridge feature. In NGC 6357 we found spatially complementary distribution between the two velocity components as well as a bridge feature in velocity. Based on these results we hypothesize that the two clouds in the two regions collided with each other in the past few Myr and triggered the formation of the starbursts over ˜ 100 pc. We suggest that the formation of the starbursts happened toward the collisional region of extent ˜ 10 pc with initial high molecular column densities. For NGC 6334 we present a scenario which includes spatial variation of the colliding epoch due to non-uniform cloud separation. The scenario possibly explains the apparent age differences among the young O stars in NGC 6334, which range from 104 yr to 106 yr; the latest collision happened within 105 yr toward the youngest stars in NGC 6334 I(N) and I which exhibit molecular outflows without H II regions. For NGC 6357 the O stars were formed a few Myr ago, and the cloud dispersal by the O stars is significant. We conclude that cloud-cloud collision offers a possible explanation of the mini-starburst over a 100 pc scale.

  16. The Peculiar Filamentary H i Structure of NGC 6145

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Enci; Kong, Xu; Mou, Guobin [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Jing [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); Guo, Fulai; Lin, Lin; Li, Cheng; Xiao, Ting, E-mail: ecwang16@ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Astronomical Society, 80 Nandan Road, Shanghai 200030 (China)

    2017-08-01

    In this paper, we report the peculiar H i morphology of the cluster spiral galaxy NGC 6145, which has a 150 kpc H i filament on one side that is nearly parallel to its major axis. This filament is made up of several H i clouds and the diffuse H i gas between them, with no optical counterparts. We compare its H i distribution with other one-sided H i distributions in the literature and find that the overall H i distribution is very different from the typical tidal and ram-pressure stripped H i shape, and that its morphology is inconsistent with that of a pure accretion event. Only ∼30% of the total H i gas is anchored on the stellar disk, while most of the H i gas forms the filament in the west. At a projected distance of 122 kpc, we find a massive elliptical companion (NGC 6146) with extended radio emission whose axis points to an H i gap in NGC 6145. The velocity of the H i filament shows an overall line-of-sight motion of 80–180 km s{sup −1} with respect to NGC 6145. Using the long-slit spectra of NGC 6145 along its major stellar axis, we find that some outer regions show enhanced star formation, while in contrast, almost no star formation activities are found in its center (<2 kpc). Pure accretion, tidal, or ram-pressure stripping are not likely to produce the observed H i filament. An alternative explanation is the jet stripping from NGC 6146, although direct evidence for a jet-cold gas interaction has not been found.

  17. clusters

    Indian Academy of Sciences (India)

    2017-09-27

    Sep 27, 2017 ... Author for correspondence (zh4403701@126.com). MS received 15 ... lic clusters using density functional theory (DFT)-GGA of the DMOL3 package. ... In the process of geometric optimization, con- vergence thresholds ..... and Postgraduate Research & Practice Innovation Program of. Jiangsu Province ...

  18. clusters

    Indian Academy of Sciences (India)

    environmental as well as technical problems during fuel gas utilization. ... adsorption on some alloys of Pd, namely PdAu, PdAg ... ried out on small neutral and charged Au24,26,27, Cu,28 ... study of Zanti et al.29 on Pdn (n = 1–9) clusters.

  19. New Insights into the Formation of the Blue Main Sequence in NGC 1850

    Science.gov (United States)

    Yang, Yujiao; Li, Chengyuan; Deng, Licai; de Grijs, Richard; Milone, Antonino P.

    2018-06-01

    Recent discoveries of bimodal main sequences (MSs) associated with young clusters (with ages ≲1 Gyr) in the Magellanic Clouds have drawn a lot of attention. One of the prevailing formation scenarios attributes these split MSs to a bimodal distribution in stellar rotation rates, with most stars belonging to a rapidly rotating population. In this scenario, only a small fraction of stars populating a secondary blue sequence are slowly or non-rotating stars. Here, we focus on the blue MS in the young cluster NGC 1850. We compare the cumulative number fraction of the observed blue-MS stars to that of the high-mass-ratio binary systems at different radii. The cumulative distributions of both populations exhibit a clear anti-correlation, characterized by a highly significant Pearson coefficient of ‑0.97. Our observations are consistent with the possibility that blue-MS stars are low-mass-ratio binaries, and therefore their dynamical disruption is still ongoing. High-mass-ratio binaries, on the other hand, are more centrally concentrated.

  20. Group Music Therapy as a Preventive Intervention for Young People at Risk: Cluster-Randomized Trial.

    Science.gov (United States)

    Gold, Christian; Saarikallio, Suvi; Crooke, Alexander Hew Dale; McFerran, Katrina Skewes

    2017-07-01

    Music forms an important part of the lives and identities of adolescents and may have positive or negative mental health implications. Music therapy can be effective for mental disorders such as depression, but its preventive potential is unknown. The aim of this study was to examine whether group music therapy (GMT) is an effective intervention for young people who may be at risk of developing mental health problems, as indicated via unhealthy music use. The main question was whether GMT can reduce unhealthy uses of music and increase potentials for healthy uses of music, compared to self-directed music listening (SDML). We were also interested in effects of GMT on depressive symptoms, psychosocial well-being, rumination, and reflection. In an exploratory cluster-randomized trial in Australian schools, 100 students with self-reported unhealthy music use were invited to GMT (weekly sessions over 8 weeks) or SDML. Changes in the Healthy-Unhealthy Music Scale (HUMS) and mental health outcomes were measured over 3 months. Both interventions were well accepted. No effects were found between GMT and SDML (all p > 0.05); both groups tended to show small improvements over time. Younger participants benefited more from GMT, and older ones more from SDML (p = 0.018). GMT was associated with similar changes as SDML. Further research is needed to improve the processes of selecting participants for targeted interventions; to determine optimal dosage; and to provide more reliable evidence of effects of music-based interventions for adolescents. © the American Music Therapy Association 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

  1. Near infrared observations of the visual reflection nebulae NGC 7023, NGC 2023, and NGC 2068

    International Nuclear Information System (INIS)

    Sellgren, K.

    1984-01-01

    The emission of the nebulae NGC 7023, 2023, and 2068 at visual wavelengths is due to reflected starlight. Recently the infrared emission of these nebulae has been found to consist not of reflected light, but rather to be due to some other emission process. Spectra of the infrared emission at nebular positions in NGC 7023 and NGC 2023 are shown. The infrared emission consists of a smooth continuum which extends at least from 1.25 to 4.8 μm, and strong emission features at 3.3 and 3.4μm. (author)

  2. Structure and evolution of NGC 5128

    International Nuclear Information System (INIS)

    Graham, J.A.

    1979-01-01

    New photographic and spectroscopic observations have been made of the nearby radio galaxy NGC 5128 with the CTIO 4 m telescope. A deep blue photograph shows some faint streamers in the NW quadrant, several arc minutes from the nucleus. No indication of a concentration of globular clusters associated with the galaxy is seen in this photograph. Velocities are given for the gaseous and stellar components of the galaxy. The main body of NGC 5128 resembles in many respects a normal giant elliptical galaxy. Concentric with it, is an inclined rotating disk which contains both stars and gas. In parts of the galaxy, material in the disk gives rise to prominent sharp interstellar absorption lines. The heliocentric velocity indicated by emission lines originating from gas near the nucleus is 548 +- 5 km s -1 . This is consistent with the mean velocity given by the diffuse absorption lines from unresolved stars in the elliptical component, 536 +- 30 km s -1 . A rotation curve for the disk is derived. If a distance of 5 Mpc is assumed, an approximate value for the mass of the galaxy is 3 x 10 11 M/sub sun/ to a distance of 11 kpc from the nucleus. No rotation is observed in the elliptical component greater than 30 km s -1 at a distance of 1.5 kpc in any direction from the nucleus. The origin and evolution of the galaxy are discussed. One possibility is that the optical and radio characteristics of the galaxy have developed from the merger of a gas cloud or small galaxy with a giant elliptical galaxy about 10 9 years ago. The main radio characteristics and the unusual activity in the nucleus of NGC 5128 appear to be a consequence rather than the cause of the peculiar structural features of the galaxy

  3. Kinematic evidence for feedback-driven star formation in NGC 1893

    Science.gov (United States)

    Lim, Beomdu; Sung, Hwankyung; Bessell, Michael S.; Lee, Sangwoo; Lee, Jae Joon; Oh, Heeyoung; Hwang, Narae; Park, Byeong-Gon; Hur, Hyeonoh; Hong, Kyeongsoo; Park, Sunkyung

    2018-06-01

    OB associations are the prevailing star-forming sites in the Galaxy. Up to now, the process of how OB associations were formed remained a mystery. A possible process is self-regulating star formation driven by feedback from massive stars. However, although a number of observational studies uncovered various signposts of feedback-driven star formation, the effectiveness of such feedback has been questioned. Stellar and gas kinematics is a promising tool to capture the relative motion of newborn stars and gas away from ionizing sources. We present high-resolution spectroscopy of stars and gas in the young open cluster NGC 1893. Our findings show that newborn stars and the tadpole nebula Sim 130 are moving away from the central cluster containing two O-type stars, and that the time-scale of sequential star formation is about 1 Myr within a 9 pc distance. The newborn stars formed by feedback from massive stars account for at least 18 per cent of the total stellar population in the cluster, suggesting that this process can play an important role in the formation of OB associations. These results support the self-regulating star formation model.

  4. ON THE HEATING EFFICIENCY DERIVED FROM OBSERVATIONS OF YOUNG SUPER STAR CLUSTERS IN M82

    International Nuclear Information System (INIS)

    Silich, Sergiy; Tenorio-Tagle, Guillermo; Torres-Campos, Ana; Munoz-Tunon, Casiana; Monreal-Ibero, Ana; Melo, Veronica

    2009-01-01

    Here, we discuss the mechanical feedback that massive stellar clusters provide to the interstellar medium of their host galaxy. We apply an analytic theory developed in a previous study for M82-A1 to a sample of 10 clusters located in the central zone of the starburst galaxy M82, all surrounded by compact and dense H II regions. We claim that the only way that such H II regions can survive around the selected clusters, is if they are embedded into a high-pressure ISM and if the majority of their mechanical energy is lost within the star cluster volume via strong radiative cooling. The latter implies that these clusters have a low heating efficiency, η, and evolve in the bimodal hydrodynamic regime. In this regime, the shock-heated plasma in the central zones of a cluster becomes thermally unstable, loses its pressure and is accumulated there, whereas the matter injected by supernovae and stellar winds outside this volume forms a high-velocity outflow-the star cluster wind. We calculated the heating efficiency for each of the selected clusters and found that in all cases it does not exceed 10%. Such low heating efficiency values imply a low mechanical energy output and the impact that the selected clusters provide to the ISM of M82 is thus much smaller than what one would expect using stellar cluster synthetic models.

  5. Optical and X-ray studies of Compact X-ray Binaries in NGC 5904

    Science.gov (United States)

    Bhalotia, Vanshree; Beck-Winchatz, Bernhard

    2018-06-01

    Due to their high stellar densities, globular cluster systems trigger various dynamical interactions, such as the formation of compact X-ray binaries. Stellar collisional frequencies have been correlated to the number of X-ray sources detected in various clusters and we hope to measure this correlation for NGC 5904. Optical fluxes of sources from archival HST images of NGC 5904 have been measured using a DOLPHOT PSF photometry in the UV, optical and near-infrared. We developed a data analysis pipeline to process the fluxes of tens of thousands of objects using awk, python and DOLPHOT. We plot color magnitude diagrams in different photometric bands in order to identify outliers that could be X-ray binaries, since they do not evolve the same way as singular stars. Aligning previously measured astrometric data for X-ray sources in NGC 5904 from Chandra with archival astrometric data from HST will filter out the outlier objects that are not X-ray producing, and provide a sample of compact binary systems that are responsible for X-ray emission in NGC 5904. Furthermore, previously measured X-ray fluxes of NGC 5904 from Chandra have also been used to measure the X-ray to optical flux ratio and identify the types of compact X-ray binaries responsible for the X-ray emissions in NGC 5904. We gratefully acknowledge the support from the Illinois Space Grant Consortium.

  6. New outburst of the accreting millisecond X-ray pulsar NGC 6440 X-2 and discovery of a strong 1 Hz modulation in the light-curve

    NARCIS (Netherlands)

    Patruno, A.; Yang, Y.; Altamirano, D.; Armas-Padilla, M.; Cavecchi, Y.; Degenaar, N.; Kalamkar, M.; Kaur, R.; Klis, M. Van Der; Watts, A.; Wijnands, R.; Linares, M.; Casella, P.; Rea, N.; Soleri, P.; Markwardt, C.; Strohmayer, T.; Heinke, C.

    On June 11th, 2010, RXTE/PCA galactic bulge scan observations showed an increase in activity from the globular cluster NGC 6440. Two accreting millisecond X-ray pulsars (AMXPs) and 22 other X-ray binaries are known in NGC 6440 (see Pooley et al. 2002, ApJ 573, 184, Altarmirano et al. 2010, ApJL 712,

  7. Spectrophotometrical investigation of the NGC 3359 galaxy

    International Nuclear Information System (INIS)

    Burenkov, A.N.; Khchikyan, Eh.E.; AN Armyanskoj SSR, Byurakan. Astrofizicheskaya Observatoriya)

    1986-01-01

    Results of detailed spectrophotometrical investigations of NGC 3353, carried out with 6 m telescope of SAO Academy of Sciences of the USSR are presented (dispersion approximately 65 A/mm). Four separate condensations, the brightest of which is Mark 35, are studied. In the spectrum of Mark 35 the emission lines for Hsub(α) to H 12 , HeI lambda lambda 7065, 6678, 5876, 4922, 4472, 3820 and forbidden lines [01]lambda lambdas 6300/64, [02] lambda 3727, [03] lambda lambda 5007, 4959, 4363, [Ne3] lambda 3869, [N2] lambda lambda 6584/48, [S2] lambda lambda 6717/31, [S3] lambda 6310, [Ar3] lambda 7136 are detected. In the second central condensation, called ''nucleus'', emission lines are weaker and beginning with Hsub(β) the absorption components appear which become stronger in the late members of Balmer lines. The forbidden lines in the nucleus are strong: [Ne3], [O3], [O2], [S2][N2]. The relative intensities and equivalent widths of emission lines as well as the chemical composition of Mark 35 and ''nucleus'' are estimated. Both condensations according to their physical properties look like superassociations. It has been concluded that the source of excitation are young stars. NGC 3353 is probably the net of superassociations

  8. The colour-magnitude diagram of NGC 5053

    International Nuclear Information System (INIS)

    Walker, M.F.; Pike, C.D.; McGee, J.D.

    1976-01-01

    The colour-magnitude diagram of NGC 5053 has been derived to V = 21.1 from photographic and electronographic observations. The electronographic observations were obtained with an experimental Spectracon image-converter, having photocathode and exit window dimensions of 20 x 30 mm, mounted at the prime-focus of the 120-in. Lick reflector. The photographic observations were obtained with the 20-in. Carnegie astrograph and the 36-in. Crossley reflector. The colour-magnitude diagram resembles that of M92, with the difference that a red horizontal branch is more pronounced than the asymptotic branch in NGC 5053. The topology of the horizontal branch is that of clusters with an intermediate metal content and is thus at variance with the mean period of the RR Lyr stars and the unreddened colour of the subgiant branch read at the magnitude level of the horizontal branch, both of which would indicate an extremely low metal content. If comparison of the colour-magnitude diagrams of NGC 5053 and M92 is valid, then the reddening of NGC 5053 is Esub(B-V) = 0.02 and the apparent distance modulus is m-M = 16.08 +- 0.08. (author)

  9. NEW RADIAL ABUNDANCE GRADIENTS FOR NGC 628 AND NGC 2403

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Danielle A.; Skillman, Evan D. [Department of Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Croxall, Kevin V. [Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Marble, Andrew R. [National Solar Observatory, 950 N Cherry Avenue, Tucson, AZ 85719 (United States); Smith, J. D. [Ritter Astrophysical Observatory, University of Toledo, Toledo, OH 43606 (United States); Gordon, Karl [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Kennicutt, Robert C. Jr. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Garnett, Donald R., E-mail: berg@astro.umn.edu, E-mail: skillman@astro.umn.edu, E-mail: croxall.5@osu.edu, E-mail: amarble@nso.edu, E-mail: jd.smith@utoledo.edu, E-mail: kgordon@stsci.edu, E-mail: robk@ast.cam.ac.uk

    2013-10-01

    Motivated by recent interstellar medium studies, we present high quality MMT and Gemini spectroscopic observations of H II regions in the nearby spiral galaxies NGC 628 and NGC 2403 in order to measure their chemical abundance gradients. Using long-slit and multi-object mask optical spectroscopy, we obtained measurements of the temperature sensitive auroral lines [O III] λ4363 and/or [N II] λ5755 at a strength of 4σ or greater in 11 H II regions in NGC 628 and 7 regions in NGC 2403. These observations allow us, for the first time, to derive an oxygen abundance gradient in NGC 628 based solely on 'direct' oxygen abundances of H II regions: 12 + log(O/H) = (8.43 ± 0.03) + (–0.017 ± 0.002) × R{sub g} (dex kpc{sup –1}), with a dispersion in log(O/H) of σ = 0.10 dex, from 14 regions with a radial coverage of ∼2-19 kpc. This is a significantly shallower slope than found by previous 'strong-line' abundance studies. In NGC 2403, we derive an oxygen abundance gradient of 12 + log(O/H) = (8.48 ± 0.04) + (–0.032 ± 0.007)× R{sub g} (dex kpc{sup –1}), with a dispersion in log(O/H) of σ = 0.07 dex, from seven H II with a radial coverage of ∼1-10 kpc. Additionally, we measure the N, S, Ne, and Ar abundances. We find the N/O ratio decreases with increasing radius for the inner disk, but reaches a plateau past R{sub 25} in NGC 628. NGC 2403 also has a negative N/O gradient with radius, but we do not sample the outer disk of the galaxy past R{sub 25} and so do not see evidence for a plateau. This bi-modal pattern measured for NGC 628 indicates dominant contributions from secondary nitrogen inside of the R{sub 25} transition and dominantly primary nitrogen farther out. As expected for α-process elements, S/O, Ne/O, and Ar/O are consistent with constant values over a range in oxygen abundance.

  10. Mothers of young children cluster into 4 groups based on psychographic food decision influencers.

    Science.gov (United States)

    Byrd-Bredbenner, Carol; Abbot, Jaclyn Maurer; Cussler, Ellen

    2008-08-01

    This study explored how mothers grouped into clusters according to multiple psychographic food decision influencers and how the clusters differed in nutrient intake and nutrient content of their household food supply. Mothers (n = 201) completed a survey assessing basic demographic characteristics, food shopping and meal preparation activities, self and spouse employment, exposure to formal food or nutrition education, education level and occupation, weight status, nutrition and food preparation knowledge and skill, family member health and nutrition status, food decision influencer constructs, and dietary intake. In addition, an in-home inventory of 100 participants' household food supplies was conducted. Four distinct clusters presented when 26 psychographic food choice influencers were evaluated. These clusters appear to be valid and robust classifications of mothers in that they discriminated well on the psychographic variables used to construct the clusters as well as numerous other variables not used in the cluster analysis. In addition, the clusters appear to transcend demographic variables that often segment audiences (eg, race, mother's age, socioeconomic status), thereby adding a new dimension to the way in which this audience can be characterized. Furthermore, psychographically defined clusters predicted dietary quality. This study demonstrates that mothers are not a homogenous group and need to have their unique characteristics taken into consideration when designing strategies to promote health. These results can help health practitioners better understand factors affecting food decisions and tailor interventions to better meet the needs of mothers.

  11. The age calibration of integrated ultraviolet colors and young stellar clusters in the Large Magellanic Cloud

    International Nuclear Information System (INIS)

    Barbero, J.; Brocato, E.; Cassatella, A.; Castellani, V.; Geyer, E.H.

    1990-01-01

    Integrated colors in selected far-UV bands are presented for a large sample of Large Magellanic Cloud (LMC) clusters. Theoretical calculations of these integrated colors are derived and discussed. The location in the two-color diagram C(18-28), C(15-31) is expected to be a sensitive but smooth function of cluster age for ages in the range 5 to 800 million yr. Theoretical results appear in very good agreement with the observed colors of LMC clusters. From this comparison, the gap in the observed colors is suggested to be caused by the lack of LMC clusters in the range of ages between 200 million to one billion yr. The two-color location of old globulars is discussed, also in connection with available data for the M31 clusters. 36 refs

  12. Symptoms and Symptom Clusters Identified by Adolescents and Young Adults With Cancer Using a Symptom Heuristics App.

    Science.gov (United States)

    Ameringer, Suzanne; Erickson, Jeanne M; Macpherson, Catherine Fiona; Stegenga, Kristin; Linder, Lauri A

    2015-12-01

    Adolescents and young adults (AYAs) with cancer experience multiple distressing symptoms during treatment. Because the typical approach to symptom assessment does not easily reflect the symptom experience of individuals, alternative approaches to enhancing communication between the patient and provider are needed. We developed an iPad-based application that uses a heuristic approach to explore AYAs' cancer symptom experiences. In this mixed-methods descriptive study, 72 AYAs (13-29 years old) with cancer receiving myelosuppressive chemotherapy used the Computerized Symptom Capture Tool (C-SCAT) to create images of the symptoms and symptom clusters they experienced from a list of 30 symptoms. They answered open-ended questions within the C-SCAT about the causes of their symptoms and symptom clusters. The images generated through the C-SCAT and accompanying free-text data were analyzed using descriptive, content, and visual analyses. Most participants (n = 70) reported multiple symptoms (M = 8.14). The most frequently reported symptoms were nausea (65.3%), feeling drowsy (55.6%), lack of appetite (55.6%), and lack of energy (55.6%). Forty-six grouped their symptoms into one or more clusters. The most common symptom cluster was nausea/eating problems/appetite problems. Nausea was most frequently named as the priority symptom in a cluster and as a cause of other symptoms. Although common threads were present in the symptoms experienced by AYAs, the graphic images revealed unique perspectives and a range of complexity of symptom relationships, clusters, and causes. Results highlight the need for a tailored approach to symptom management based on how the AYA with cancer perceives his or her symptom experience. © 2015 Wiley Periodicals, Inc.

  13. A YOUNG ECLIPSING BINARY AND ITS LUMINOUS NEIGHBORS IN THE EMBEDDED STAR CLUSTER Sh 2-252E

    Energy Technology Data Exchange (ETDEWEB)

    Lester, Kathryn V.; Gies, Douglas R.; Guo, Zhao, E-mail: lester@chara.gsu.edu, E-mail: gies@chara.gsu.edu, E-mail: guo@chara.gsu.edu [Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, P.O. Box 5060, Atlanta, GA 30302-5060 (United States)

    2016-12-01

    We present a photometric and light curve analysis of an eccentric eclipsing binary in the K2 Campaign 0 field, which resides in Sh 2-252E, a young star cluster embedded in an H ii region. We describe a spectroscopic investigation of the three brightest stars in the crowded aperture to identify which is the binary system. We find that none of these stars are components of the eclipsing binary system, which must be one of the fainter nearby stars. These bright cluster members all have remarkable spectra: Sh 2-252a (EPIC 202062176) is a B0.5 V star with razor sharp absorption lines, Sh 2-252b is a Herbig A0 star with disk-like emission lines, and Sh 2-252c is a pre-main-sequence star with very red color.

  14. An Observational Study of Blended Young Stellar Clusters in the Galactic Plane - Do Massive Stars form First?

    Science.gov (United States)

    Martínez-Galarza, Rafael; Protopapas, Pavlos; Smith, Howard A.; Morales, Esteban

    2018-01-01

    From an observational point of view, the early life of massive stars is difficult to understand partly because star formation occurs in crowded clusters where individual stars often appear blended together in the beams of infrared telescopes. This renders the characterization of the physical properties of young embedded clusters via spectral energy distribution (SED) fitting a challenging task. Of particular relevance for the testing of star formation models is the question of whether the claimed universality of the IMF (references) is reflected in an equally universal integrated galactic initial mass function (IGIMF) of stars. In other words, is the set of all stellar masses in the galaxy sampled from a single universal IMF, or does the distribution of masses depend on the environment, making the IGIMF different from the canonical IMF? If the latter is true, how different are the two? We present a infrared SED analysis of ~70 Spitzer-selected, low mass ($facilities.

  15. Perceptions about parents' relationship and parenting quality, attachment styles, and young adults' intimate expectations: a cluster analytic approach.

    Science.gov (United States)

    Einav, Michal

    2014-01-01

    This study examines the associations between young adults' perceptions of their parents' intimate relationship and the quality of their parenting as predictors of their children's expectations about intimacy in their own future relationships. A sample of 111 young adults completed questionnaires assessing their perceptions regarding their parents' intimate relationship and parenting quality, their own attachment styles, and their own expectations regarding intimate relationships. A correlational analysis revealed a positive link between the parents' relationship and parenting quality, and between parenting quality and expectations about intimacy, which supports the attachment theory. A cluster analysis identified three distinct groups of parental profiles interrelated with attachment styles that had varying effects on their children's expectations about intimacy. These findings emphasize the unique characteristics of parental relations in the family of origin relations, which have an enduring effect on the interpersonal styles of adult children, providing additional support to an integrated, intergenerational approach to family dynamics.

  16. The Evolution of Stellar Dynamos; Survey for Low Mass Members of NGC2232; An X-Ray Survey of the Open Cluster CR140; Towards a Better Understanding of the Rotation-Activity Relation for Solar-Type Members of the Pleiades

    Science.gov (United States)

    Stauffer, John R.; Petre, Robert (Technical Monitor)

    2000-01-01

    This grant was originally awarded to Dr. Charles Prosser, who died tragically in a car accident in Tucson in 1998. We had hoped to finish the work Charles had started, which involved analysis of ROSAT data for three programs (observations of the clusters NGC2232, Crl4O and the Pleiades) and also analysis of optical data for each cluster in order to allow interpretation of the ROSAT observations. The Pleiades portion of the program was completed during the past year, and a paper published. We have obtained optical imaging of the other two clusters, and those data are being analyzed. Dr. Brian Patten intends to complete analysis of the ROSAT observations and to combine those data with the optical photometry, but progress on those efforts has been slow due to the press of other work (Dr. Patten is responsible for the pipeline processing of data from SWAS). We intend to publish those results as soon as we can, but it will now be completed without further support from this grant.

  17. NGC 3628-UCD1:A possible $ω$ Cen Analog Embedded in a Stellar Stream

    OpenAIRE

    Jennings, Zachary G.; Romanowsky, Aaron J.; Brodie, Jean P.; Janz, Joachim; Norris, Mark A.; Forbes, Duncan A.; Martinez-Delgado, David; Fagioli, Martina; Penny, Samantha J.

    2015-01-01

    Using Subaru/Suprime-Cam wide-field imaging and both Keck/ESI and LBT/MODS spectroscopy, we identify and characterize a compact star cluster, which we term NGC 3628-UCD1, embedded in a stellar stream around the spiral galaxy NGC 3628. The size and luminosity of UCD1 are similar to $\\omega$ Cen, the most luminous Milky Way globular cluster, which has long been suspected to be the stripped remnant of an accreted dwarf galaxy. The object has a magnitude of $i=19.3$ mag (${\\rm L}_{\\rm i}=1.4\\time...

  18. X-Ray Bursts from NGC 6652

    Science.gov (United States)

    Morgan, Edward

    The possibly transient X-ray Source in the globular cluster NGC 6652 has been seen by BeppoSax and the ASM on RXTE to undergo X-ray bursts, possibly Type I. Very little is known about this X-ray source, and confirmation of its bursts type-I nature would identify it as a neutron star binary. Type I bursts in 6 other sources have been shown to exhibit intervals of millisecond ocsillation that most likely indicate the neutron star spin period. Radius-expansion bursts can reveal information about the mass and size of the neutron star. We propose to use the ASM to trigger an observation of this source to maximize the probability