DOCSLIB.ORG

LJMU Research Online

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
LJMU Research Online LJMU Research Online Keller, BW, Kruijssen, JMD, Pfeffer, J, Reina-Campos, M, Bastian, N, Trujillo- Gomez, S, Hughes, ME and Crain, RA Where did the globular clusters of the Milky Way form? Insights from the E- MOSAICS simulations http://researchonline.ljmu.ac.uk/id/eprint/13201/ Article Citation (please note it is advisable to refer to the publisher’s version if you intend to cite from this work) Keller, BW, Kruijssen, JMD, Pfeffer, J, Reina-Campos, M, Bastian, N, Trujillo- Gomez, S, Hughes, ME and Crain, RA (2020) Where did the globular clusters of the Milky Way form? Insights from the E-MOSAICS simulations. Monthly Notices of the Royal Astronomical Society, 495 (4). pp. 4248-4267. ISSN LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LJMU Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain. The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription. For more information please contact [email protected] http://researchonline.ljmu.ac.uk/ MNRAS 495, 4248–4267 (2020) doi:10.1093/mnras/staa1439 Advance Access publication 2020 May 23 Where did the globular clusters of the Milky Way form? Insights from the E-MOSAICS simulations Benjamin W. Keller ,1‹ J. M. Diederik Kruijssen ,1 Joel Pfeffer ,2 Downloaded from https://academic.oup.com/mnras/article-abstract/495/4/4248/5843285 by Liverpool John Moores University user on 29 June 2020 Marta Reina-Campos ,1 Nate Bastian,2 Sebastian Trujillo-Gomez ,1 Meghan E. Hughes 2 and Robert A. Crain 2 1Astronomisches Rechen-Institut, Zentrum fur¨ Astronomie der Universitat¨ Heidelberg, Monchhofstraße¨ 12-14, D-69120 Heidelberg, Germany 2Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK Accepted 2020 May 15. Received 2020 April 2; in original form 2019 December 30 ABSTRACT Globular clusters (GCs) are typically old, with most having formed at z 2. This makes understanding their birth environments difficult, as they are typically too distant to observe with sufficient angular resolution to resolve GC birth sites. Using 25 cosmological zoom- in simulations of Milky Way-like galaxies from the E-MOSAICS project, with physically motivated models for star formation, feedback, and the formation, evolution, and disruption of GCs, we identify the birth environments of present-day GCs. We find roughly half of GCs in these galaxies formed in situ (52.0 ± 1.0 per cent) between z ≈ 2–4, in turbulent, high-pressure discs fed by gas that was accreted without ever being strongly heated through a virial shock or feedback. A minority of GCs form during mergers (12.6 ± 0.6 per cent in major mergers, and 7.2 ± 0.5 per cent in minor mergers), but we find that mergers are important for preserving the GCs seen today by ejecting them from their natal, high density interstellar medium (ISM), where proto-GCs are rapidly destroyed due to tidal shocks from ISM substructure. This chaotic history of hierarchical galaxy assembly acts to mix the spatial and kinematic distribution of GCs formed through different channels, making it difficult to use observable GC properties to distinguish GCs formed in mergers from ones formed by smooth accretion, and similarly GCs formed in situ from those formed ex situ. These results suggest a simple picture of GC formation, in which GCs are a natural outcome of normal star formation in the typical, gas-rich galaxies that are the progenitors of present-day galaxies. Key words: galaxies: evolution – galaxies: formation – galaxies: haloes – galaxies: star clus- ters: general – galaxies: star formation. 2014). Age determinations have yet to reach the level of precision, 1 INTRODUCTION however, where observations alone can tell us the precise time line A ubiquitous feature of galaxies in the nearby Universe are their of GC formation in the Milky Way (MW) or elsewhere. The GC populations of globular clusters (GCs). These old (τ ∼ 10 Gyr), populations we see in galaxies across many decades of halo and 4 6 massive (M ∼ 10 –10 M) stellar clusters (e.g. Brodie & Strader stellar mass show remarkable differences compared to the ‘normal’ 2006; Kruijssen 2014; Forbes et al. 2018) are found distributed field stellar populations of those same galaxies. GCs are typically 9 throughout the haloes of nearly all galaxies with M∗ 10 M older (Mar´ın-Franch et al. 2009; VandenBerg et al. 2013), more (Harris, Blakeslee & Harris 2017b). The ages of these objects tell metal poor (Puzia et al. 2005;Sarajedinietal.2007), and broadly us that many of them formed near cosmic noon, at z ∼ 2 (e.g. Dotter distributed through the halo compared to field stars (Zinn 1985). et al. 2010; Forbes & Bridges 2010; Dotter, Sarajedini & Anderson Both the number (Blakeslee, Tonry & Metzger 1997) and total mass 2011; VandenBerg et al. 2013; Choksi, Gnedin & Li 2018; El-Badry (Spitler & Forbes 2009;Harrisetal.2017b) of GCs appears to be a et al. 2019; Reina-Campos et al. 2019;Kruijssenetal.2019a), when constant ratio of halo mass, unlike the total stellar mass, which both the cosmic star formation rate was at its peak (Madau & Dickinson abundance matching (Behroozi, Wechsler & Conroy 2013;Moster, Naab & White 2013) and weak lensing studies (Hudson et al. 2015) have confirmed to be a non-linear function of halo mass. In different E-mail: [email protected] galaxies, unimodal (e..g Harris et al. 2017a), bimodal (e.g. Peng C 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society Globular cluster formation environments 4249 et al. 2006), and even trimodal distributions (e.g. Blom, Spitler & GCs, and they have also not been subject to Gyrs of evolution. Their Forbes 2012; Usher et al. 2012) of GC metallicities have been locations within their host galaxies are also quite different to that observed. Understanding when, where, and how these objects form of GCs. While YMCs are seen forming in the dense ISM of the can help us understand star formation in some of the most extreme present-day galaxy disc, a significant fraction of the GC population cosmic environments. As the epoch of GC formation may coincide orbits the galaxy at large radii, in a spherical distribution through with cosmic noon (Reina-Campos et al. 2019), understanding GC the stellar halo. In order to build a population of GCs in the stellar formation will help us better understand star formation during a key halo, these GCs must either be flung out of the disc by merger events Downloaded from https://academic.oup.com/mnras/article-abstract/495/4/4248/5843285 by Liverpool John Moores University user on 29 June 2020 phase of the Universe’s evolution. (an in situ mechanism), or tidally stripped from accreted galaxies The differences between the populations of stars we see in GCs (an ex situ mechanism), or simply have been formed at large radii and the rest of the field stars have prompted a critical question: (as in Peebles & Dicke 1968). do they signal that special, early Universe physics (distinct from Regardless of the physics involved in the formation of GCs, a ‘normal’ star formation) is required to form GCs? Over time, a second selection step obscures their birth environment: the evolution number of different formation scenarios have been proposed. The of the cluster and dynamical disruption as it orbits within the earliest proposed mechanisms for forming GCs are wildly different galaxy for ∼10 Gyr. Over this time, it will experience heating and to the mechanisms we currently believe produce the vast majority disruption through the tidal field of the galaxy (Ambartsumian 1938; of field stars. Peebles & Dicke (1968) argued that as the Jeans Spitzer 1940;Henon´ 1961;Lee&Ostriker1987; Baumgardt & mass of the typical post-recombination intergalactic medium was Makino 2003), and tidal shocks when eccentric orbits bring them 5 6 comparable to the mass of observed GCs (10 –10 M), and thus the through the galactic disc and bulge (Aguilar, Hut & Ostriker 1988). collapse of pre-galactic gas clouds produced the GCs we see today. Early in the cluster’s lifespan, it may pass through spiral arms and This model cannot produce metal-rich clusters, and would produce giant molecular clouds (GMCs), subjecting it to further intense tidal a cluster population with a radial distribution identical to the dark shocks (Lamers, Gieles & Portegies Zwart 2005; Gieles et al. 2006; matter halo (rather than the more centrally concentrated distribution Elmegreen 2010; Elmegreen & Hunter 2010; Kruijssen et al. 2011; we observe). Naturally, the GCs produced via this mechanism would Kruijssen 2015). Clusters within the halo may inspiral over time, as contain the oldest stars in existence (since the formation of the they lose angular momentum through dynamical friction (Tremaine remaining non-GC stellar populations would necessarily follow the 1976). All of this means that the population of GCs we see today formation of galaxies). Fall & Rees (1985) proposed a mechanism may have little resemblance to the population of proto-GCs that that begins producing GCs once the formation of galaxies has formed within the galaxy. If these disruption processes act much begun, through a two-phase instability in the hot galactic corona.
Load more

Recommended publications
  • 98763 Conroy 2011 Apj 741 72
    Evidence Against Dark Matter Halos Surrounding the Globular Clusters Mgc1 and Ngc 2419 The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Conroy, Charlie, Abraham Loeb, and David N. Spergel. 2011. “EVIDENCE AGAINST DARK MATTER HALOS SURROUNDING THE GLOBULAR CLUSTERS MGC1 AND NGC 2419.” The Astrophysical Journal 741 (2): 72. https://doi.org/10.1088/0004-637x/741/2/72. Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:41393159 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA The Astrophysical Journal, 741:72 (5pp), 2011 November 10 doi:10.1088/0004-637X/741/2/72 C 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A. EVIDENCE AGAINST DARK MATTER HALOS SURROUNDING THE GLOBULAR CLUSTERS MGC1 AND NGC 2419 Charlie Conroy1, Abraham Loeb1, and David N. Spergel2 1 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA, USA 2 Department of Astrophysical Sciences, Princeton University, Princeton, NJ, USA Received 2011 August 3; accepted 2011 August 3; published 2011 October 18 ABSTRACT The conjecture that the ancient globular clusters (GCs) formed at the center of their own dark matter (DM) halos was first proposed by Peebles in 1984 and has recently been revived to explain the puzzling abundance patterns observed within many GCs. In this paper, we demonstrate that the outer stellar density profile of isolated GCs is very sensitive to the presence of an extended dark halo.
    [Show full text]
  • Globular Clusters in the Local Group As Probes of Galaxy Assembly
    This thesis has been submitted in fulfilment of the requirements for a postgraduate degree (e.g. PhD, MPhil, DClinPsychol) at the University of Edinburgh. Please note the following terms and conditions of use: • This work is protected by copyright and other intellectual property rights, which are retained by the thesis author, unless otherwise stated. • A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. • This thesis cannot be reproduced or quoted extensively from without first obtaining permission in writing from the author. • The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the author. • When referring to this work, full bibliographic details including the author, title, awarding institution and date of the thesis must be given. Globular clusters in the Local Group as probes of galaxy assembly Jovan Veljanoski Doctor of Philosophy The University of Edinburgh 13 June 2014 Lay Summary Understanding the formation and evolution of galaxies is one of the most active areas of research in astrophysics. Gradual build-up of matter by merging pre-galactic fragments is the current preferred model of constructing massive galaxies. A key prediction of this theory is that outskirts nearby galaxies should contain remnants of this assembly process in the form of fragmented stellar streams. Found in all but the smallest of galaxies, globular star clusters (GC) are excellent probes for studying properties of galaxies. Having high luminosities, they are favourable targets in the outer regions of galaxies where the associated stellar surface brightness is low.
    [Show full text]
  • The Outer Halo Globular Cluster System of M31 – II. Kinematics
    Mon. Not. R. Astron. Soc. 000, 1–24 (2014) Printed 24 July 2018 (MN LaTEX style file v2.2) The outer halo globular cluster system of M31 – II. Kinematics J. Veljanoski1, A. D. Mackey2, A. M. N. Ferguson1,⋆, A. P. Huxor3, P. Cˆot´e4,⋆ M. J. Irwin5, N. R. Tanvir6, J. Pe˜narrubia1, E. J. Bernard1, M. Fardal7, N. F. Martin8,9, A. McConnachie4, G. F. Lewis10, S. C. Chapman11, R. A. Ibata8, A. Babul12 1 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK 2 Research School of Astronomy & Astrophysics, Australian National University, Mt. Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia 3 Astronomisches Rechen-Institut, Zentrum f¨ur Astronomie der Universit¨at Heidelberg, M¨onchhofstraße 12-14, 69120 Heidelberg, Germany. 4 NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada 5 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK 6 Department of Physics & Astronomy, University of Leicester, Leicester LE1 7RH, UK 7 University of Massachusetts, Department of Astronomy, LGRT 619-E, 710 N. Pleasant Street, Amherst, Massachusetts, 01003-9305, USA 8 Observatoire de Strasbourg, 11, rue de l’Universit´e, F-67000 Strasbourg, France 9 Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg, Germany 10 Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia 11 Dalhousie University, Dept. of Physics and Atmospheric Science, Coburg Road Halifax, B3H1A6, Canada 12 Department of Physics and Astronomy, University of Victoria, Elliott Building, 3800 Finnerty Road Victoria, BC V8P 5C2 Canada 24 July 2018 ABSTRACT We present a detailed kinematic analysis of the outer halo globular cluster system of the Andromeda galaxy (M31).
    [Show full text]
  • December2009
    December2009 On the cover: Saturn and its moon Director s Message “Wild Youth” of Titan obtained using 4 ’ 27 adaptive optics Doug Simons on the Gemini Massive Galaxies North telescope. Mariska Kriek For more details on this image and the Titan Monitoring & Pieter van Dokkum related discovery of 7 unexpected weather on Henry Roe & Emily Schaller Titan see the article by High-Z Band-Shuffling Henry Roe and Emily 30 Schaller starting on Most Distant Known page 7. 10 with GMOS Object in Universe Adam Muzzin & Howard Yee Edo Berger 34 AO Open-Loop Guiding 13 Z~5 Star-forming with Galactic Centers Galaxy with NIFS/IFU Richard McDermid, Davor Krajnović Mark Swinbank & Michele Cappellari IFU Wiki 17 39 Science Highlights Mark Westmoquette & Millicent Maier Nancy A. Levenson 19 Mid-IR Observations 43 Exoplanet Imaging of Seyfert Galaxies Christian Marois & Michael Liu Cristina Ramos Almeida & Chris Packham 47 Time-Sharing 23 Globulars in M31 Programs Dennis Crabtree & Tom Geballe Dougal Mackey, Annette Ferguson & Avon Huxor 2 GeminiFocus Exploring the Universe, Sharing its Wonders 52 Kyoto Science Meeting 77 Introducing Jean-René Roy, Atsuko Nitta Nancy A. Levenson & Nancy A. Levenson Joy Pollard On-site Observing 55 78 Profile: François Rigaut Dennis Crabtree María Antonieta García Planning for Future 57 82 Profile: Dolores Coulson Instruments Peter Michaud Eric Tollestrup 86 Hawai‘i & Chile 60 MCAO Progress Nature Pictures by Staff François Rigaut & Céline D’orgeville Joy Pollard & Manuel Paredes 62 Greening of Gemini Sarah Blanchard Broadening Participation Managing Editor, Peter Michaud 67 Associate Editor, Carolyn Collins Petersen Neil Barker Proof Reader, Stephen James O’Meara Designer, Kirk Pu‘uohau-Pummill 70 GeminiFocus Reader’s Survey Peter Michaud Any opinions, findings, and conclusions or recommendations expressed in this material are PIO Activities those of the author(s) and do not necessarily reflect 72 the views of the National Science Foundation.
    [Show full text]
  • Gravity: Dark Sector, Post-Newtonian Limit and Schwarzschild Solution
    universe Article d Gravity: Dark Sector, Post-Newtonian Limit and Schwarzschild Solution Jorge Alfaro 1,*,† and Pablo González 2,† 1 Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Macul, Santiago 7810000, Chile 2 Sede Esmeralda, Universidad de Tarapacá, Avda. Luis Emilio Recabarren 2477, Iquique 1130000, Chile; [email protected] * Correspondence: jalfaro@fis.puc.cl † These authors contributed equally to this work. Received: 17 March 2019; Accepted: 20 April 2019; Published: 26 April 2019 Abstract: We present a new kind of model, which we call d Theories, where standard theories are modified including new fields, motivated by an additional symmetry (d symmetry). In previous works, we proved that d Theories just live at one loop, so the model in a quantum level can be interesting. In the gravitational case, we have d Gravity, based on two symmetric tensors, gmn and g˜mn, where quantum corrections can be controlled. In this paper, a review of the classical limit of d Gravity in a Cosmological level will be developed, where we explain the accelerated expansion of the universe without Dark Energy and the rotation velocity of galaxies by the Dark Matter effect. Additionally, we will introduce other phenomenon with d Gravity like the deflection of the light produced by the sun, the perihelion precession, Black Holes and the Cosmological Inflation. Keywords: modified gravity; dark energy; dark matter; general relativity 1. Introduction In the last century, the cosmological observations have revealed that the dynamic of the Universe is dominated by an accelerated expansion, apparently due to a mysterious component called Dark Energy [1–3].
    [Show full text]
  • II. Kinematics
    MNRAS 442, 2929–2950 (2014) doi:10.1093/mnras/stu1055 The outer halo globular cluster system of M31 – II. Kinematics J. Veljanoski,1‹ A. D. Mackey,2 A. M. N. Ferguson,1† A. P. Huxor,3 P. Cotˆ e,´ 4† M. J. Irwin,5 N. R. Tanvir,6 J. Penarrubia,˜ 1 E. J. Bernard,1 M. Fardal,7 N. F. Martin,8,9 A. McConnachie,4 G. F. Lewis,10 S. C. Chapman,11 R. A. Ibata8 and A. Babul12 1Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK 2Research School of Astronomy and Astrophysics, Australian National University, Mt Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611, Australia 3Astronomisches Rechen-Institut, Zentrum fur´ Astronomie der Universitat¨ Heidelberg, Monchhofstraße¨ 12-14, D-69120 Heidelberg, Germany 4NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada 5Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 6Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK Downloaded from 7Department of Astronomy, University of Massachusetts, LGRT 619-E, 710 N. Pleasant Street, Amherst, MA 01003-9305, USA 8Observatoire de Strasbourg, 11, rue de l’Universite,´ F-67000 Strasbourg, France 9Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg, Germany 10Institute of Astronomy, School of Physics, University of Sydney, NSW 2006, Australia 11Department of Physics and Atmospheric Science, Dalhousie University, Coburg Road, Halifax, NS B3H1A6, Canada 12Department of Physics and Astronomy, University of Victoria, Elliott Building, 3800 Finnerty Road Victoria, BC V8P 5C2 Canada http://mnras.oxfordjournals.org/ Accepted 2014 May 27.
    [Show full text]
  • The Outer Halo Globular Cluster System of M31-III. Relationship to The
    MNRAS 000, 1–33 (2019) Preprint 8 January 2019 Compiled using MNRAS LATEX style file v3.0 The outer halo globular cluster system of M31 – III. Relationship to the stellar halo A. D. Mackey1, A. M. N. Ferguson2, A. P. Huxor3, J. Veljanoski4, G. F. Lewis5, A. W. McConnachie6, N. F. Martin7,8, R. A. Ibata7, M. J. Irwin9, P. Cˆot´e6, M. L. M. Collins10, N. R. Tanvir11, N. F. Bate9 1Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia 2Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK 3HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK 4Kapteyn Astronomical Institute, University of Groningen, PO Box 800, NL-9700 AV Groningen, The Netherlands 5Sydney Institute for Astronomy, School of Physics, A28, The University of Sydney, Sydney, NSW 2006, Australia 6NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, B.C., V9E 2E7, Canada 7Universit´ede Strasbourg, CNRS, Observatoire astronomique de Strasbourg, UMR 7550, F-67000 Strasbourg, France 8Max-Planck-Institut fur¨ Astronomie, K¨onigstuhl 17, D-69117 Heidelberg, Germany 9Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK 10Department of Physics, University of Surrey, Guildford, GU2 7XH, UK 11Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK Draft version 8 January 2019. ABSTRACT We utilise the final catalogue from the Pan-Andromeda Archaeological Survey to inves- tigate the links between the globular cluster system and field halo in M31 at projected radii Rproj = 25 − 150 kpc. In this region the cluster radial density profile exhibits a power-law decline with index Γ = −2.37 ± 0.17, matching that for the stellar halo component with [Fe/H] < −1.1.
    [Show full text]
  • THE DETAILED CHEMICAL PROPERTIES of M31 STAR CLUSTERS. I. Fe, ALPHA and LIGHT ELEMENTS∗
    The Astrophysical Journal, 797:116 (31pp), 2014 December 20 doi:10.1088/0004-637X/797/2/116 C 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A. THE DETAILED CHEMICAL PROPERTIES OF M31 STAR CLUSTERS. I. Fe, ALPHA AND LIGHT ELEMENTS∗ Janet E. Colucci1,3, Rebecca A. Bernstein1, and Judith G. Cohen2 1 The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101, USA; [email protected] 2 Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, CA 91125, USA Received 2014 July 18; accepted 2014 October 29; published 2014 December 5 ABSTRACT We present ages, [Fe/H] and abundances of the α elements Ca i,Sii,Tii,Tiii, and light elements Mg i,Nai, and Al i for 31 globular clusters (GCs) in M31, which were obtained from high-resolution, high signal-to-noise ratio > 60 echelle spectra of their integrated light (IL). All abundances and ages are obtained using our original technique for high-resolution IL abundance analysis of GCs. This sample provides a never before seen picture of the chemical history of M31. The GCs are dispersed throughout the inner and outer halo, from 2.5 kpc <RM31 < 117 kpc. We find a range of [Fe/H] within 20 kpc of the center of M31, and a constant [Fe/H] ∼−1.6forthe outer halo clusters. We find evidence for at least one massive GC in M31 with an age between 1 and 5 Gyr. The α-element ratios are generally similar to the Milky Way GC and field star ratios.
    [Show full text]
  • An Updated Survey of Globular Clusters in M 31 II
    A&A 471, 127–136 (2007) Astronomy DOI: 10.1051/0004-6361:20077788 & c ESO 2007 Astrophysics An updated survey of globular clusters in M 31 II. Newly discovered bright and remote clusters, S. Galleti1,2, M. Bellazzini2,L.Federici2, A. Buzzoni2, and F. Fusi Pecci2 1 Università di Bologna, Dipartimento di Astronomia Via Ranzani 1, 40127 Bologna, Italy e-mail: [email protected] 2 INAF – Osservatorio Astronomico di Bologna, Via Ranzani 1, 40127 Bologna, Italy e-mail: [michele.bellazzini;luciana.federici;alberto.buzzoni;flavio.fusipecci]@oabo.inaf.it Received 4 May 2007 / Accepted 22 May 2007 ABSTRACT Aims. We present the first results of a large spectroscopic survey of candidate globular clusters located in the extreme outskirts of the nearby M 31 galaxy. The survey is aimed at ascertaining the nature of the selected candidates to increase the sample of confirmed M 31 clusters lying more that 2◦ away from the center of the galaxy. Methods. We obtained low resolution spectra (λ/∆λ 800–1300) of 48 targets selected from the Extended Source Catalogue of 2MASS, as in Galleti et al. (2005, A&A, 436, 535). The observed candidates have been robustly classified according to their radial velocity and by verifying their extended/point-source nature from ground-based optical images. We have also obtained a spectrum and a radial velocity estimate for the remote M 31 globular discovered by Martin et al. (2006b, MNRAS, 371, 1983). Results. Among the 48 observed candidates clusters we found: 35 background galaxies, 8 foreground Galactic stars, and 5 genuine remote globular clusters.
    [Show full text]
  • Astro-Archaeology in the Triangulum Galaxy ASTRO-ARCHAEOLOGY in the TRIANGULUM GALAXY
    Astro-Archaeology in the Triangulum Galaxy ASTRO-ARCHAEOLOGY IN THE TRIANGULUM GALAXY: STUDYING GALAXY FORMATION AND EVOLUTION WITH THE GLOBULAR CLUSTERS AND STELLAR HALO IN M33 By ROBERT COCKCROFT , M.Sci., M.Sc. A Thesis Submitted to the School of Graduate Studies in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy McMaster University c Robert Cockcroft, September 2012 DOCTOR OF PHILOSOPHY (2012) McMaster University (Physics and Astronomy) Hamilton, Ontario TITLE: Astro-Archaeology in the Triangulum Galaxy: Studying Galaxy For- mation and Evolution with the Globular Clusters and Stellar Halo in M33 AUTHOR: Robert Cockcroft, M.Sci. (University College London), M.Sc. (Mc- Master University) SUPERVISOR: Professor William E. Harris NUMBER OF PAGES: xxi, 231 ii Abstract The currently-favoured cosmological paradigm, ΛCDM, predicts that galaxies are built up from smaller galaxies in a bottom-up process known as hierar- chical merging. ΛCDM is extremely successful for large-scale structures, but is less so for the detailed features of individual galaxies. We can study these features - the galaxies’ foundations and the remnants of the smaller compo- nents that built them - only in the closest galaxies in which we can resolve individual stars. In this thesis, we use data from the Canada-France-Hawaii Telescope (CFHT)/MegaCam as part of the Pan-Andromeda Archaeological Survey (PAndAS) to observe M33 (the Triangulum Galaxy) and the detailed features of its old stellar population. The study of these details is vital for our understanding of galaxy formation and evolution. We search for two types of components within the old stellar population: globular star clusters and the faint, diffuse stellar halo.
    [Show full text]
  • Can Tidal Interactions Produce MGC1?
    Can tidal interactions produce MGC1? Eric Andersson Lund Observatory Lund University 2018-EXA131 Degree project of 60 higher education credits (for a degree of Master) May 2018 Supervisor: Melvyn B. Davies Lund Observatory Box 43 SE-221 00 Lund Sweden Abstract The globular cluster population of large spiral galaxies can be divided into two popula- tions: one population which formed in-situ and one which has been assembled through capture of clusters that have been tidally stripped away from other galaxies during close encounters or mergers. In this work, I focus on the globular cluster MGC1, which is orbiting the M31 galaxy. MGC1 is an extremely isolated cluster, located 200 kpc from the M31 centre. Thus, I propose the idea that this cluster was one of those captured from another galaxy. I investigate encounters between dwarf galaxies 7 10 with masses ranging from 10 M⊙ to 10 M⊙ and the M31 galaxy, using numerical simulations, in which I focus on globular clusters that are tidally stripped away from the dwarf and left on wide orbits in the M31 galaxy. Motivated by the absence of ob- served tidal features around MGC1, I constrain my encounters such that, afterwards, the dwarf should remain intact and no visible damage should be caused to M31. I find this to be a viable scenario for the origin of MGC1 if M31 has had approximately 20 encounters with dwarf galaxies that do not merge with M31, but rather leave the system post-encounter. Although my results provide a means to produce MGC1, the encounters I simulate do not reproduce the entire observed population of clusters in M31, especially lacking in clusters located closer in.
    [Show full text]
  • Deep Gemini/GMOS Imaging of an Extremely Isolated Globular Cluster
    Mon. Not. R. Astron. Soc. 000, 1–18 (2009) Printed 30 October 2018 (MN LATEX style file v2.2) Deep Gemini/GMOS imaging of an extremely isolated globular cluster in the Local Group A. D. Mackey1, A. M. N. Ferguson1, M. J. Irwin2, N. F. Martin3, A. P. Huxor4, N. R. Tanvir5, S. C. Chapman2, R. A. Ibata6, G. F. Lewis7, A. W. McConnachie8 1Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK 2Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK 3Max-Planck-Institut f¨ur Astronomie, K¨onigstuhl 17, D-69117 Heidelberg, Germany 4Department of Physics, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, UK 5Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK 6Observatoire Astronomique, Universit´ede Strasbourg, CNRS, 11, rue de l’Universit´e, F-67000 Strasbourg, France 7Institute of Astronomy, School of Physics, A29, University of Sydney, NSW 2006, Australia 8NRC Herzberg Institute for Astrophysics, 5071 West Saanich Road, Victoria, British Columbia, Canada V9E 2E7 Accepted 2009 September 5. Received 2009 September 1; in original form 2009 June 9. ABSTRACT We report on deep imaging of a remote M31 globular cluster, MGC1, obtained with Gemini/GMOS. Our colour-magnitude diagram for this object extends ∼ 5 magni- tudes below the tip of the red giant branch and exhibits features consistent with an an- cient metal-poor stellar population, including a long, well-populated horizontal branch. The red giant branch locus suggests MGC1 has a metal abundance [M/H] ≈−2.3. We measure the distance to MGC1 and find that it lies ∼ 160 kpc in front of M31 with a distance modulus µ = 23.95 ± 0.06.
    [Show full text]