DOCSLIB.ORG

Spectroscopic Signatures of Multiple Populations in Globular Clusters

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Spectroscopic Signatures of Multiple Populations in Globular Clusters Spectroscopic Signatures of Multiple Populations in Globular Clusters By James T Banister A thesis submitted in partial fulfilment for the requirements for the degree of MSc (by Research) at the University of Central Lancashire & The Jeremiah Horrocks Institute September 2020 STUDENT DECLARATION FORM Type of Award MSc (By Research) School Natural Sciences Sections marked * delete as appropriate 1. Concurrent registration for two or more academic awards Either *I declare that while registered as a candidate for the research degree, I have not been a registered candidate or enrolled student for another award of the University or other academic or professional institution 2. Material submitted for another award Either *I declare that no material contained in the thesis has been used in any other submission for an academic award and is solely my own work 3. Collaboration Where a candidate’s research programme is part of a collaborative project, the thesis must indicate in addition clearly the candidate’s individual contribution and the extent of the collaboration. Please state below: _________________________________________________________________________ 4. Use of a Proof-reader or *No proof-reading service was used in the compilation of this thesis. Signature of Candidate Print name: James Thomas Banister i Spectroscopic Signatures of Multiple Populations in Globular Clusters James T Banister Abstract This thesis presents a study of the integrated light spectra of local globular clusters, looking for chemical enhancements which could be the signatures of multiple populations. Using data from the WiFeS Atlas of Galactic Globular cluster Spectra: the spectra are fit to SSP models via penalised pixel fitting techniques looking for poor fitting regions which could signify chemical enhancements. Line indices of key regions are measured, and nitrogen enhancements are found in the CN region ∼4100 Å for almost all globular clusters with evidence for elemental abundance variations in other regions. Also, nitrogen enhancement is found in other compact stellar systems (UCDs and some cEs) and the inner light of high mass galaxies, suggesting a possible relation between high stellar density and nitrogen enhancement. September, 2020 Supervisors: Mark Norris, Ph.D. and Joanne Pledger, Ph.D. University of Central Lancashire Jeremiah Horrocks Institute ii Contents Declaration i List of Figures vii List of Tables ix 1 Introduction 1 1.1 Globular Clusters . 1 1.2 Multiple Populations . 2 1.3 Integrated Light Observation . 3 1.4 A Brief Preamble to Available Globular Cluster Data . 4 2 Theory 5 2.1 Globular Clusters . 5 2.1.1 Milky Way Globular Clusters & Halo Enrichment Via Tidal Effects . 7 2.1.2 Magellanic Cloud and Fornax DSG Globular Clusters . 9 2.1.3 Extragalactic Globular Clusters . 12 2.2 Multiple Populations . 13 2.2.1 Chemical Abundance Variations & Correlations . 15 2.2.2 Single Population Globular Clusters . 19 2.3 Formation Theories of Multiple Populations . 20 2.3.1 AGB Stars . 21 2.3.2 Fast Rotating Massive Stars (FRMS) . 22 2.3.3 Binary Interactions . 23 2.3.4 Black Hole Accretion Disk Nucleosynthesis . 24 3 Data & Data Reduction 26 3.1 WAGGS . 26 3.1.1 Globular Cluster Selection . 27 iii 3.1.2 Observations . 28 3.1.3 Equipment & Data . 31 3.2 Reduction . 32 3.2.1 Redshift . 33 3.2.2 Combination . 36 3.2.3 Error Spectra . 38 3.2.4 Omitted Globular Clusters . 39 3.3 Additional Data . 39 3.3.1 Galaxies -Trager . 40 3.3.2 M31 GCs -Schiavon . 40 3.3.3 M87 GCs and UCDs . 40 3.3.4 MODS Objects . 41 3.3.5 SDSS Galaxy Bins . 41 4 Fitting to SSP Models 43 4.1 pPXF . 43 4.2 Single Stellar Population Models . 44 4.2.1 MILES SSPs . 44 4.2.2 Conroy . 46 4.3 Fitting Procedure . 46 4.3.1 Example Fitting Procedure . 48 4.3.2 Regions of interest . 48 4.3.3 Fit Comparison . 50 4.3.4 Error calculations . 50 5 Measuring Indices 52 5.1 Line Index Systems . 52 5.1.1 LICK/IDS & LIS . 52 5.2 Measurements . 54 5.3 Offsets from Literature . 54 5.3.1 Current Published Works . 54 5.3.2 Offset Calculation . 55 5.3.3 Thomas SSP Models . 57 6 Signatures of Multiple Populations 59 6.1 Single Stellar Population Fitting . 59 6.1.1 Other Poor Fitting Regions . 61 iv 6.2 Line Index systems . 64 6.2.1 Alpha Insensitive Metallicity Index . 64 6.2.2 Globular Clusters . 64 6.2.3 Extragalactic Stellar Systems . 67 6.2.4 Uncertainty Calculations . 70 7 Conclusions and Discussion of Future Work 73 7.1 Evidence of Multiple Populations . 73 7.1.1 N enhancement in Dense Stellar Systems . 75 7.2 Age Estimation Problem . 76 7.3 Conclusion . 78 7.4 Future Research . 79 Bibliography 81 8 APPENDIX 86 v Acknowledgements Firstly I would like to thank Dr Mark Norris for continued support and advice on the research, without which I would undoubtedly not be here, and thanks for providing additional stellar system data and for prompt replies to any question regardless of time or day. I would also like to thank Dr Chris Usher for providing extra information on the WAGGS survey and data set. Thanks to Thomas Davison and David Glass for advice on the proper use of pPXF and thanks again to Thomas Davison for providing binned SDSS galaxy spectra. For all of the support from the people who shared an office with me before Covid-19 forced us out, I would like to give my thanks. I would also like to thank Covid-19 for giving me no choice but to stay inside these last few months giving me more time to work on the thesis. vi List of Figures 2.1 The CMD of NGC 2808 . 7 2.2 Position of the Sagittarius Dwarf Galaxy relative to the Milky Way . 8 2.3 Age metallicity plot of globular clusters in the Magellanic Clouds . 10 2.4 The positions of globular clusters in the Fornax dwarf spheroidal galaxy . 11 2.5 The CMD of NGC 5139 showing multiple main sequence turn off points . 14 2.6 The first detection of multiple populations in globular clusters . 15 2.7 The elemental correlations present in globular clusters due to multiple popula- tions, here plotted over photometric data of NGC 6752 . 16 2.8 A plot of the split main sequence, multiple turn off points of NGC 5139 with isochrones plotted over the top . 18 2.9 A plot showing how the split main sequence of a globular cluster is detected . 20 3.1 [Fe/H] against Age for the globular clusters in the WAGGS sample. 26 3.2 Field-of-view of the WAGGS observations for 3 GCs . 30 3.3 The fraction of the V-band luminosity in the WiFeS field-of-view compared tothe full v-band luminosity of the GC . 31 3.4 The grating efficiencies of the WiFeS gratings at the most efficient angle of incidence 32 3.5 The redshift adjusted B7000 grating spectra for the majority of the globular clusters separated according to [Fe/H] into 8 bins. 33 3.6 A diagram of the spectra of NGC 2808 during the redshift adjusting and regrid- ding process . 35 3.7 A diagram of the grating combination process used for the WAGGS spectra . 37 3.8 A full WAGGS spectrum with associated 1σ errors for NGC 5694 . 38 3.9 The Voronoi diagram describing the bins of the SDSS galaxy spectra . 42 4.1 An example of the new linearly combined SSP models . 45 4.2 pPXF fit and mass fraction plot of NGC 104 with no regions omitted . 48 4.3 pPXF fit and mass fraction plot of NGC 104 with omitted regions . 49 vii 4.4 A comparison between the mass fraction plots in literature and those found in this project for NGC 6715 . 51 5.1 Example of Lick indices, CN1 and CN2 over the spectra of NGC 104 . 53 5.2 The Offsets between WAGGS line indices and those of literature . 56 6.1 pPXF fit of NGC 104 with omitted regions . 60 6.2 Conroy models showing where C and N effect a stellar spectrum between 3800 and 4600 Å ...................................... 60 6.3 pPXF fit and mass fraction plot of NGC 104 with omitted regions . 62 6.4 Spectral indices plot of CN1 against metallicity showing WAGGS GCs and SSP models with a colour bar of age for the WAGGS globular clusters . 65 6.5 Spectral indices plot of CN2 against metallicity showing WAGGS and M31 GCs and SSP models with a colour bar of age for the WAGGS globular clusters . 66 6.6 Spectral indices plot of CN1 against metallicity showing WAGGS and M31 GCs and enhanced SSP models with a colour bar of age for the WAGGS globular clusters 67 6.7 Spectral indices plot of CN1 against metallicity showing GCs, UCDs, cEs and enhanced SSP models with a colour bar of age for the globular clusters . 68 6.8 Spectral indices plot of CN1 against metallicity showing GCs, UCDs, enhanced SSP models, SDSS binned galaxies and galactic core spectral indices, with a colour bar of age for the globular clusters . 70 6.9 Spectral indices plot of CN1 against metallicity showing GCs, UCDs, cEs, en- hanced SSP models and SDSS binned galaxies with a colour bar of mass in the galaxies . 72 7.1 Spectral indices plot of CN1 against metallicity showing GCs, UCDs, enhanced SSP models and SDSS binned galaxies with a colour bar of stellar density in the galaxies . 76 viii List of Tables 3.1 Signal to noise ratios of the WAGGS data.
Load more

Recommended publications
  • Arxiv:1802.01597V1 [Astro-Ph.GA] 5 Feb 2018 Born 1991)
    Astronomy & Astrophysics manuscript no. AA_2017_32084 c ESO 2018 February 7, 2018 Mapping the core of the Tarantula Nebula with VLT-MUSE? I. Spectral and nebular content around R136 N. Castro1, P. A. Crowther2, C. J. Evans3, J. Mackey4, N. Castro-Rodriguez5; 6; 7, J. S. Vink8, J. Melnick9 and F. Selman9 1 Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109-1107, USA e-mail: [email protected] 2 Department of Physics & Astronomy, University of Sheffield, Hounsfield Road, Sheffield, S3 7RH, UK 3 UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK 4 Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin, Ireland 5 GRANTECAN S. A., E-38712, Breña Baja, La Palma, Spain 6 Instituto de Astrofísica de Canarias, E-38205 La Laguna, Spain 7 Departamento de Astrofísica, Universidad de La Laguna, E-38205 La Laguna, Spain 8 Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, Northern Ireland, UK 9 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile February 7, 2018 ABSTRACT We introduce VLT-MUSE observations of the central 20 × 20 (30 × 30 pc) of the Tarantula Nebula in the Large Magellanic Cloud. The observations provide an unprecedented spectroscopic census of the massive stars and ionised gas in the vicinity of R136, the young, dense star cluster located in NGC 2070, at the heart of the richest star-forming region in the Local Group. Spectrophotometry and radial-velocity estimates of the nebular gas (superimposed on the stellar spectra) are provided for 2255 point sources extracted from the MUSE datacubes, and we present estimates of stellar radial velocities for 270 early-type stars (finding an average systemic velocity of 271 ± 41 km s−1).
    [Show full text]
  • Ngc Catalogue Ngc Catalogue
    NGC CATALOGUE NGC CATALOGUE 1 NGC CATALOGUE Object # Common Name Type Constellation Magnitude RA Dec NGC 1 - Galaxy Pegasus 12.9 00:07:16 27:42:32 NGC 2 - Galaxy Pegasus 14.2 00:07:17 27:40:43 NGC 3 - Galaxy Pisces 13.3 00:07:17 08:18:05 NGC 4 - Galaxy Pisces 15.8 00:07:24 08:22:26 NGC 5 - Galaxy Andromeda 13.3 00:07:49 35:21:46 NGC 6 NGC 20 Galaxy Andromeda 13.1 00:09:33 33:18:32 NGC 7 - Galaxy Sculptor 13.9 00:08:21 -29:54:59 NGC 8 - Double Star Pegasus - 00:08:45 23:50:19 NGC 9 - Galaxy Pegasus 13.5 00:08:54 23:49:04 NGC 10 - Galaxy Sculptor 12.5 00:08:34 -33:51:28 NGC 11 - Galaxy Andromeda 13.7 00:08:42 37:26:53 NGC 12 - Galaxy Pisces 13.1 00:08:45 04:36:44 NGC 13 - Galaxy Andromeda 13.2 00:08:48 33:25:59 NGC 14 - Galaxy Pegasus 12.1 00:08:46 15:48:57 NGC 15 - Galaxy Pegasus 13.8 00:09:02 21:37:30 NGC 16 - Galaxy Pegasus 12.0 00:09:04 27:43:48 NGC 17 NGC 34 Galaxy Cetus 14.4 00:11:07 -12:06:28 NGC 18 - Double Star Pegasus - 00:09:23 27:43:56 NGC 19 - Galaxy Andromeda 13.3 00:10:41 32:58:58 NGC 20 See NGC 6 Galaxy Andromeda 13.1 00:09:33 33:18:32 NGC 21 NGC 29 Galaxy Andromeda 12.7 00:10:47 33:21:07 NGC 22 - Galaxy Pegasus 13.6 00:09:48 27:49:58 NGC 23 - Galaxy Pegasus 12.0 00:09:53 25:55:26 NGC 24 - Galaxy Sculptor 11.6 00:09:56 -24:57:52 NGC 25 - Galaxy Phoenix 13.0 00:09:59 -57:01:13 NGC 26 - Galaxy Pegasus 12.9 00:10:26 25:49:56 NGC 27 - Galaxy Andromeda 13.5 00:10:33 28:59:49 NGC 28 - Galaxy Phoenix 13.8 00:10:25 -56:59:20 NGC 29 See NGC 21 Galaxy Andromeda 12.7 00:10:47 33:21:07 NGC 30 - Double Star Pegasus - 00:10:51 21:58:39
    [Show full text]
  • Arxiv:1803.10763V1 [Astro-Ph.GA] 28 Mar 2018
    Draft version October 10, 2018 Typeset using LATEX default style in AASTeX61 TRACERS OF STELLAR MASS-LOSS - II. MID-IR COLORS AND SURFACE BRIGHTNESS FLUCTUATIONS Rosa A. Gonzalez-L´ opezlira´ 1 1Instituto de Radioastronomia y Astrofisica, UNAM, Campus Morelia, Michoacan, Mexico, C.P. 58089 (Received 2017 October 20; Revised 2018 February 20; Accepted 2018 February 21) Submitted to ApJ ABSTRACT I present integrated colors and surface brightness fluctuation magnitudes in the mid-IR, derived from stellar popula- tion synthesis models that include the effects of the dusty envelopes around thermally pulsing asymptotic giant branch (TP-AGB) stars. The models are based on the Bruzual & Charlot CB∗ isochrones; they are single-burst, range in age from a few Myr to 14 Gyr, and comprise metallicities between Z = 0.0001 and Z = 0.04. I compare these models to mid-IR data of AGB stars and star clusters in the Magellanic Clouds, and study the effects of varying self-consistently the mass-loss rate, the stellar parameters, and the output spectra of the stars plus their dusty envelopes. I find that models with a higher than fiducial mass-loss rate are needed to fit the mid-IR colors of \extreme" single AGB stars in the Large Magellanic Cloud. Surface brightness fluctuation magnitudes are quite sensitive to metallicity for 4.5 µm and longer wavelengths at all stellar population ages, and powerful diagnostics of mass-loss rate in the TP-AGB for intermediater-age populations, between 100 Myr and 2-3 Gyr. Keywords: stars: AGB and post{AGB | stars: mass-loss | Magellanic Clouds | infrared: stars | stars: evolution | galaxies: stellar content arXiv:1803.10763v1 [astro-ph.GA] 28 Mar 2018 Corresponding author: Rosa A.
    [Show full text]
  • Multiple Stellar Populations in Magellanic Cloud Clusters. VI. A
    Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 1 March 2018 (MN LATEX style file v2.2) Multiple stellar populations in Magellanic Cloud clusters.VI. A survey of multiple sequences and Be stars in young clusters A. P.Milone1,2, A. F. Marino2, M. Di Criscienzo3, F. D’Antona3, L.R.Bedin4, G. Da Costa2, G. Piotto1,4, M. Tailo5, A. Dotter6, R. Angeloni7,8, J.Anderson9, H. Jerjen2, C. Li10, A. Dupree6, V.Granata1,4, E. P.Lagioia1,11,12, A. D. Mackey2, D. Nardiello1,4, E. Vesperini13 1Dipartimento di Fisica e Astronomia “Galileo Galilei”, Univ. di Padova, Vicolo dell’Osservatorio 3, Padova, IT-35122 2Research School of Astronomy & Astrophysics, Australian National University, Canberra, ACT 2611, Australia 3Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone, Roma, Italy 4Istituto Nazionale di Astrofisica - Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, Padova, IT-35122 5 Dipartimento di Fisica, Universita’ degli Studi di Cagliari, SP Monserrato-Sestu km 0.7, 09042 Monserrato, Italy 6 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA 7 Departamento de Fisica y Astronomia, Universidad de La Serena, Av. Juan Cisternas 1200 N, La Serena, Chile 8 Instituto de Investigacion Multidisciplinar en Ciencia y Tecnologia, Universidad de La Serena, Raul Bitran 1305, La Serena, Chile 9Space Telescope Science Institute, 3800 San Martin Drive, Baltimore, MD 21218, USA 10 Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109, Australia 11Instituto de Astrof`ısica de Canarias, E-38200 La Laguna, Tenerife, Canary Islands, Spain 12Department of Astrophysics, University of La Laguna, E-38200 La Laguna, Tenerife, Canary Islands, Spain 13Department of Astronomy, Indiana University, Bloomington, IN 47405, USA Accepted 2018 February 27.
    [Show full text]
  • INFRARED SURFACE BRIGHTNESS FLUCTUATIONS of MAGELLANIC STAR CLUSTERS1 Rosa A
    The Astrophysical Journal, 611:270–293, 2004 August 10 A # 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A. INFRARED SURFACE BRIGHTNESS FLUCTUATIONS OF MAGELLANIC STAR CLUSTERS1 Rosa A. Gonza´lez Centro de Radioastronomı´a y Astrofı´sica, Universidad Nacional Autonoma de Me´xico, Campus Morelia, Michoaca´n CP 58190, Mexico; [email protected] Michael C. Liu Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822; [email protected] and Gustavo Bruzual A. Centro de Investigaciones de Astronomı´a, Apartado Postal 264, Me´rida 5101-A, Venezuela; [email protected] Received 2003 November 27; accepted 2004 April 16 ABSTRACT We present surface brightness fluctuations (SBFs) in the near-IR for 191 Magellanic star clusters available in the Second Incremental and All Sky Data releases of the Two Micron All Sky Survey (2MASS) and compare them with SBFs of Fornax Cluster galaxies and with predictions from stellar population models as well. We also construct color-magnitude diagrams (CMDs) for these clusters using the 2MASS Point Source Catalog (PSC). Our goals are twofold. The first is to provide an empirical calibration of near-IR SBFs, given that existing stellar population synthesis models are particularly discrepant in the near-IR. Second, whereas most previous SBF studies have focused on old, metal-rich populations, this is the first application to a system with such a wide range of ages (106 to more than 1010 yr, i.e., 4 orders of magnitude), at the same time that the clusters have a very narrow range of metallicities (Z 0:0006 0:01, i.e., 1 order of magnitude only).
    [Show full text]
  • Wolf–Rayet Star
    Wolf–Rayet star Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of ionised helium and highly ionised nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. Their surface temperatures range from 30,000 K to around 200,000 K, hotter than almost all other stars. They were previously called W-type stars referring to their spectral classification. Classic (or Population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven Hubble Space Telescope image of nebula M1-67 mass loss. A separate group of stars with WR spectra are the around Wolf–Rayet star WR 124. central stars of planetary nebulae (CSPNe), post asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core. All Wolf–Rayet stars are highly luminous objects due to their high temperatures—thousands of times the bolometric luminosity of the Sun (L☉) for the CSPNe, hundreds of thousands L☉ for the Population I WR stars, to over a million L☉ for the WNh stars —although not exceptionally bright visually since most of their radiation output is in the ultraviolet.
    [Show full text]
  • A Large and Homogeneous Sample of Cmds of LMC Stellar Clusters
    Extragalactic Star Clusters fA U Symposium Series, Vol. 207, 2002 Doug Geisler, Eva K. Grebel, and Dante Minniti, eds. A Large and Homogeneous Sample of CMDs of LMC Stellar Clusters Enzo Brocato Osservatorio Astronomico di Teramo, Via Maggini, 1-64100 Teramo, Italy, (email: [email protected]) Elisa Di Carlo Osservatorio Astronomico di Teramo, Via Maggini, 1-64100 Teramo, Italy, (email: [email protected]) Abstract. We present the photometric results of 21 stellar clusters of the Large Magellanic Cloud. The WFPC2 images were retrieved from the HST archive. Simple stellar populations in a large spread of age are well rep- resented in the sample of color-magnitude diagrams shown here. 1. Introduction and data reduction LMC stellar clusters represent an appealing opportunity of probing our under- standing of stellar populations in a wide range of age. Clearly, one of the most powerful tools for this purpose is to study their CMDs. The HST collected a number of images all along the years and we decided to use the archive facility 'to derive a set of homogeneous CMDs for the LMC clusters. All the images were retrieved from the HST archive as observed with the WFPC2 camera in the filters F450W and F555W. DAOPHOT II (Stetson 1987) was used to obtain the instrumental magnitudes. We followed Dolphin (2000) to derive the calibrated magnitudes and colors. We find good agreement (within ~ 0.1 mag) between our data and the results of Sarajedini (1998) for the common clusters NGC 2155, SL 663, and NGC 2121. We performed an additional check of our photometry by comparing our data of NGC 2257 to the ground based photometry by Walker (1989).
    [Show full text]
  • Mass Segregation in Young LMC Clusters I. 1
    CORE Metadata, citation and similar papers at core.ac.uk Provided by CERN Document Server Mass segregation in young LMC clusters I. 1 2001 Mon. Not. R. Astron. Soc. 000, 000–000 (2001) Mass segregation in young compact star clusters in the Large Magellanic Cloud: I. Data and Luminosity Functions R. de Grijs?, R.A. Johnson , G.F. Gilmore and C.M. Frayn Institute of Astronomy, University of Cambridge,† Madingley Road, Cambridge CB3 0HA Accepted —. Received —; in original form —. ABSTRACT We have undertaken a detailed analysis of HST/WFPC2 and STIS imaging observa- tions, and of supplementary wide-field ground-based observations obtained with the NTT of two young ( 10 25 Myr) compact star clusters in the LMC, NGC 1805 and NGC 1818. The ultimate∼ goal− of our work is to improve our understanding of the degree of primordial mass segregation in star clusters. This is crucial for the interpretation of observational luminosity functions (LFs) in terms of the initial mass function (IMF), and for constraining the universality of the IMF. We present evidence for strong luminosity segregation in both clusters. The LF slopes steepen with cluster radius; in both NGC 1805 and NGC 1818 the LF slopes reach a stable level well beyond the clusters' core or half-light radii. In addition, the brightest cluster stars are strongly concentrated within the inner 4Rhl. The global cluster LF, although strongly nonlinear, is fairly∼ well approximated by the core or half-light LF; the (annular) LFs at these radii are dominated by the segregated high-luminosity stars, however. We present tentative evidence for the presence of an excess number of bright stars surrounding NGC 1818, for which we argue that they are most likely massive stars that have been collisionally ejected from the cluster core.
    [Show full text]
  • Large Magellanic Cloud Stellar Clusters
    A&A 374, 523–539 (2001) Astronomy DOI: 10.1051/0004-6361:20010711 & c ESO 2001 Astrophysics Large Magellanic Cloud stellar clusters I. 21 HST colour magnitude diagrams?;?? E. Brocato1;2,E.DiCarlo1;3, and G. Menna1 1 Osservatorio Astronomico di Collurania, Via M. Maggini, 64100 Teramo, Italy 2 Istituto Nazionale di Fisica Nucleare, LNGS, L'Aquila, Italy 3 Area di ricerca in Astrogeofisica, L'Aquila, Italy e-mail: brocato, [email protected] Received 22 June 2000 / Accepted 9 March 2001 Abstract. We present WFPC2 photometry of 21 stellar clusters of the Large Magellanic Cloud obtained on images retrieved from the Hubble Space Telescope archive. The derived colour magnitude diagrams (CMDs) are presented and discussed. This database provides a sample of CMDs representing, with reliable statistics, simple stellar populations with a large spread of age. The stars in the core of the clusters are all resolved and measured at least down to the completeness limit; the magnitudes of the main sequence terminations and of the red giant clump are also evaluated for each cluster, together with the radius at half maximum of the star density. Key words. Galaxy: globular clusters: general { galaxies: evolution { galaxies: Magellanic Clouds 1. Introduction 1998), iii) to evaluate the age of the oldest clusters in this galaxy (Walker 1989, 1990, 1992, 1993a,b; Testa et al. The Large Magellanic Cloud (LMC) offers a unique oppor- 1995; Brocato et al. 1996; Olsen et al. 1998) and iv) tunity to investigate bright populous stellar systems span- to study the luminosity function of MC clusters (Mateo ning a wide range of age and located at a distance short 1988).
    [Show full text]
  • THE MAGELLANIC CLOUDS NEWSLETTER an Electronic Publication Dedicated to the Magellanic Clouds, and Astrophysical Phenomena Therein
    THE MAGELLANIC CLOUDS NEWSLETTER An electronic publication dedicated to the Magellanic Clouds, and astrophysical phenomena therein No. 127 — 1 February 2014 http://www.astro.keele.ac.uk/MCnews Editor: Jacco van Loon Editorial Dear Colleagues, friends, It is my pleasure to present you the 127th issue of the Magellanic Clouds Newsletter. It’s been a little quieter, blame the holidays, bless you. Other distractions of life, perhaps. No worries: The Clouds will be up there for a while still. Plenty on supernova remnants though, and evolved stars and their remnants in general. Check out a fantastic opportunity to work with an inspiring scientist in an amazing team at the Space Telescope Science Institute! The next issue is planned to be distributed on the 1st of April. Have an intense but safe 2014. Editorially Yours, Jacco van Loon 1 Refereed Journal Papers Optical spectra of 5 new Be/X-ray Binaries in the Small Magellanic Cloud and the link of the supergiant B[e] star LHA 115-S 18 with an X-ray source Grigoris Maravelias1, Andreas Zezas1,2,3, Vallia Antoniou3,4 and Despoina Hatzidimitriou5 1University of Crete, Physics Department & Institute of Theoretical & Computational Physics, Heraklion, Greece 2Foundation for Research and Technology-Hellas, Institute of Electronic Structure & Laser, Heraklion, Greece 3Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA 4Iowa State University, Department of Physics & Astronomy, Ames, IA, USA 5University of Athens, Department of Physics, Section of Astrophysics, Astronomy, and Mechanics, Athens, Greece The Small Magellanic Cloud (SMC) is well known to harbor a large number of High-Mass X-ray Binaries (HMXBs).
    [Show full text]
  • Arxiv:0705.3464V1
    DRAFT VERSION JUNE 22, 2021 Preprint typeset using LATEX style emulateapj v. 08/22/09 SURFACE BRIGHTNESS PROFILES FOR A SAMPLE OF LMC, SMC AND FORNAX GALAXY GLOBULAR CLUSTERS E. NOYOLA Astronomy Department, University of Texas at Austin, TX 78712 and Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraçe 85748, Garching K. GEBHARDT Astronomy Department, University of Texas at Austin, TX 78712 Draft version June 22, 2021 ABSTRACT We use Hubble Space Telescope archival images to measure central surface brightness profiles of globular clusters around satellite galaxies of the Milky Way. We report results for 21 clusters around the LMC, 5 around the SMC, and 4 aroundthe Fornaxdwarf galaxy. The profiles are obtained using a recently developed technique based on measuring integrated light, which is tested on an extensive simulated dataset. Our results show that for 70% of the sample, the central photometric points of our profiles are brighter than previous measurements using star counts with deviations as large as 2 mag/acrsec2. About 40% of the objects have central profiles deviating from a flat central core, with central logarithmic slopes continuously distributed between -0.2 and -1.2. These results are compared with those found for a sample of Galactic clusters using the same method. We confirm the known correlation in which younger clusters tend to have smaller core radii, and we find that they also have brighter central surface brightness values. This seems to indicate that globular clusters might be born relatively concentrated, and that a profile with extended flat cores might not be the ideal choice for initial profiles in theoretical models.
    [Show full text]
  • Spectroscopy of Binaries in Globular Clusters
    Spectroscopy of Binaries in Globular Clusters Dissertation for the award of the degree “Doctor rerum naturalium” (Dr.rer.nat.) of the Georg-August-Universität Göttingen within the doctoral program PROPHYS of the Georg-August University School of Science (GAUSS) submitted by Benjamin David Giesers from Oldenburg Göttingen, 2019 Thesis Commitee Prof. Dr. Stefan Dreizler Sonnenphysik und Stellare Astrophysik, Institut für Astrophysik, Georg-August-Universität Göttingen, Germany Dr. Sebastian Kamann Star formation and stellar populations, Astrophysics Research Institute, Liverpool John Moores University, United Kingdom Dr. Tim-Oliver Husser Stellare Astrophysik, Institut für Astrophysik, Georg-August-Universität Göttingen, Germany Members of the Examination Board Reviewer: Prof. Dr. Stefan Dreizler Sonnenphysik und Stellare Astrophysik, Institut für Astrophysik, Georg-August-Universität Göttingen, Germany Second Reviewer: Prof. Dr. Ulrich Heber Stellare Astrophysik, Dr. Karl Remeis Sternwarte, Friedrich-Alexander-Universität Erlangen- Nürnberg, Germany Further members of the Examination Board: Dr. Saskia Hekker Stellar Ages and Galactic Evolution, Max-Planck-Institut für Sonnensystemforschung, Göttin- gen, Germany Prof. Dr. Wolfram Kollatschny Extragalaktische Astrophysik, Institut für Astrophysik, Georg-August-Universität Göttingen, Germany Prof. Dr. Wolfgang Glatzel Sonnenphysik und Stellare Astrophysik, Institut für Astrophysik, Georg-August-Universität Göttingen, Germany PD Dr. Jörn Große-Knetter Kern- und Atomphysik, II. Physikalisches Institut, Georg-August-Universität Göttingen, Ger- many Date of the oral examination: 13 December 2019 Abstract The natural constants in the universe are adjusted so that dense and massive star forming re- gions can end up in gravitational bound star clusters, called globular clusters. These objects are found in all galaxies and are building blocks of galaxies and the universe. The kinematic properties of globular clusters cannot be explained by that of a population consisting only of single stars.
    [Show full text]