DOCSLIB.ORG

No Globular Cluster Progenitors in Milky Way Satellite Galaxies

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
No Globular Cluster Progenitors in Milky Way Satellite Galaxies MNRAS 000,1–7 (2021) Preprint 18 June 2021 Compiled using MNRAS LATEX style file v3.0 No globular cluster progenitors in Milky Way satellite galaxies Pierre Boldrini1¢ and Jo Bovy2 1Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd Arago, 75014 Paris, France 2Department of Astronomy and Astrophysics, University of Toronto, 50 St George Street, Toronto, ON M5S 3H4, Canada 18 June 2021 ABSTRACT In order to find the possible progenitors of Milky Way globular clusters, we perform orbit integrations to track the orbits of 151 Galactic globular clusters and the eleven classical Milky Way satellite galaxies backward in time for 11 Gyr in a Milky- Way-plus-satellites potential including the effect of dynamical friction on the satellites. To evaluate possible past associations, we devise a globular-cluster–satellite binding criterion based on the satellite’s tidal radius and escape velocity and we test it on globular clusters and satellites associated with the Sagittarius dwarf and with the Large Magellanic Cloud. For these, we successfully recover the dynamical associations highlighted by previous studies and we derive their time of accretion by the Galaxy. Assuming that Milky Way globular clusters are and have been free of dark matter and thus consist of stars alone, we demonstrate that none of the globular clusters show any clear association with the eleven classical Milky Way satellites even though a large fraction of them are believed to be accreted. This means that accreted globular clusters either came in as part of now-disrupted satellite galaxies or that globular clusters may have had dark matter halos in the past – as suggested by the similar metallicity between globular clusters and dwarf galaxies. Key words: galaxy dynamics - methods: orbital integrations - globular clusters - Milky Way - dwarf galaxies 1 INTRODUCTION possible to assess whether GCs formed in the MW or in a satellite galaxy that was later accreted. The origin of compact stellar clusters, also known as globular clusters (GCs), is one of the open questions in modern astrophysics. Many It was found that 62 of the present-day MW GCs likely formed years now since their first discovery, it is still unclear whether they in the MW, ∼55–65 have an extragalactic origin and the rest likely formed within dark matter minihalos or as gravitationally bound has a more heterogeneous origin (Kruijssen, et al. 2019; Massari et clouds in the early universe (Peebles & Dicke 1968; Kravtsov & al. 2019). It was established that the main contribution to the MW Gnedin 2005; Kruijssen 2015; Peebles 1984; Peñarrubia et al. 2017). came from three major accretion events: Sagittarius (Ibata, Gilmore Despite ongoing debates about their origin (Kruijssen 2015; Forbes & Irwin 1994; Law & Majewski 2010), Gaia-Enceladus (Belokurov, et al. 2018), these gravitationally-bound groupings of mainly old et al. 2018; Helmi, et al. 2018), and Sequoia (Myeong, et al. 2019). stars also have a similarly long history of being used as probes of In fact, numerous pieces of evidence indicate that 35% of the clusters the galaxy formation and assembly process, particularly in the Milky are possibly associated with these merger events and then are formed Way (MW) (Searle & Zinn 1978; Dinescu, Girard & van Altena in accreted dwarf galaxies (Leaman, VandenBerg & Mendel 2013; 1999; Brodie et al. 2006). Massari et al. 2019). It has long been recognized that the accretion of satellite galaxies A particularly intriguing set of GCs is the population of eleven has contributed to the growth of the MW (Searle & Zinn 1978)and the loosely bound GCs or at high energies in the MW as defined by Galaxy has accreted around one hundred satellite galaxies (Bland- arXiv:2106.09419v1 [astro-ph.GA] 17 Jun 2021 Massari et al.(2019). These GCs (AM1, Eridanus, Pyxis, Palomar Hawthorn et al. 2016). As a natural result of such events, GCs may 3, Palomar 4, Crater, NGC 6426, NGC 5694, NGC 6584, NGC 6934 have been accreted by the MW (Peñarrubia, Walker & Gilmore 2009). and Palomar 14) do not seem to have formed in situ in the Galaxy Indeed, several authors have used metallicities and horizontal-branch (Massari et al. 2019). In the E-MOSAICS simulations, high-energy morphologies to distinguish GC origin; those formed in satellite GCs are generally old and metal-poor and then it may not be pos- galaxies and those formed in situ within the Galaxy (Zinn 1999; van sible to unambiguously determine their origin (Pfeffer, et al. 2020). den Bergh 1993; Mackey & Gilmore 2004). Some of the 11 GCs have previously been tentatively associated with Recently, full six-dimensional phase-space information for almost MW satellite galaxies such as Fornax, Sculptor, or the Large Magel- all of the Galactic GCs from the second data release of the Gaia lanic Cloud (Irwin, Demers & Kunkel 1995; Koposov, et al. 2014). mission has offered unique insights into their dynamics (Gaia Col- Intriguingly, Fornax is the only one of the classical dwarfs to have laboration, et al. 2018; Vasiliev 2019). Thanks to these data, it is now six GCs in orbit (Wang, et al. 2019), thus demonstrating that most classical dwarfs can have hosted GCs in the past that now have been stripped. Indeed, as the 11 loosely-bound GCs reach far distances from the MW centre over their history, they could have interacted ¢ Contact e-mail: [email protected] with or belonged to MW satellites. © 2021 The Authors 2 P. Boldrini and J. Bovy In this paper, we examine if the eleven satellite galaxies of the dSph Mmin Mmax tinfall 9 9 MW could be progenitors of some of the 151 GCs. We follow the dy- [10 M ][10 M ] [Gyr] 0 namical history backward in time of these GCs in the MW+satellite LMC 100 198.8 4.0 0 environment by using orbital integration methods. The paper is or- SMC 26 73.9 4.0 Sgr 14 62 7.481 ganized as follows. Section 2 provides a description of our orbital- UMi 0.79 2.8 10.72 integration method. In Section 3, we discuss how we decide whether Draco 3.16 3.5 10.42 or not a GC was associated with a satellite galaxy in the past and Sculptor 1.99 5.7 9.92 present our results on associations between GCs and the Sagittarius Sextans 0.316 2.0 8.42 dwarf, satellites of the Large Magellanic Cloud and the Cloud itself, Leo I 1.99 5.6 2.32 and finally all Milky-Way GCs and the classical satellites. Section 4 Leo II 0.316 1.6 7.82 presents our conclusions. Carina 0.398 0.8 9.92 Fornax 0.79 21.9 10.72 Table 1. MW satellite properties: From left to right, the columns give for 2 METHOD each classical satellites: the current mass "200 (Errani, Peñarrubia & Walker 2018) and the pre-infall mass "pi (Read & Erkal 2019); the infall time from: In order to find the possible progenitors of the 151 Galactic GCs, (a) Rocha, Peter, & Bullock(2012), (b) Dierickx & Loeb(2017) and (c) we take their present-day phase-space position derived from Gaia (Fillingham, et al. 2019). DR2 data (Vasiliev 2019) and integrate them backward in time for 11 Gyr in a model for the Milky Way’s gravitational potential. It was recently demonstrated that interactions with MW satellites can orbits backwards in time for 11 Gyr in MWPotential2014 by ap- cause the orbital properties of Galactic GCs to evolve significantly plying dynamical friction to them with a constant mass of Mmin or over time (Garrow, Webb, & Bovy 2020). Therefore, we include the Mmax, given their current positions and proper motions from Fritz, gravitational potential of the eleven classical satellites in the potential et al.(2018). Dynamical friction is implemented by following the model (see Table1). semi-analytic model of Petts, Gualandris, & Read(2015). The GCs We assume that the main component of the Galactic potential is are then integrated in the combined MWPotential2014 plus the well represented by the MWPotential2014 mass model from Bovy time-dependent potential of each of the 11 classical satellites. (2015). Much of the stellar halo was likely accreted between 9 and 11 A mass of 6 × 106 M corresponds to the upper limit of the Gyr ago (Di Matteo, et al. 2019; Mackereth & Bovy 2020). Moreover, stellar mass of Galactic GCs 12 Gyr ago (Baumgardt, et al. 2019). cosmological simulations of the formation of Milky-Way-like galax- The time to change the GC apocentre substantially due to dynamical ies show that the main halo mass, which grows with time, reaches its friction is ≈ "enclosed/"GC ×Cdyn where "enclosed is the host galaxy asymptotic value 9-10 Gyr ago (Diemand, Kuhlen & Madau 2007; mass enclosed within the orbit and Cdyn is the orbital time (Binney Lux, Read & Lake 2010). As a consequence, we establish that our & Tremaine 2008). As the mass ratio between MW enclosed mass model describes the Galaxy well until 9-10 Gyr ago. and GC masses is large, dynamical friction is inefficient over our For the satellites, we assume a Hernquist(1990) density profile timescale (11 Gyr). We thus neglect the mass loss to the clusters for the DM component. Given the halo mass and redshift, both halo assuming that the GC mass remains constant during integrations. concentrations 2200 can be estimated from cosmological #-body Orbit integrations are performed with a time step of 10 Myr us- simulations (Dutton & Macciò 2014). We neglect the stellar contri- ing the publicly available code galpy1 (Bovy 2015) by applying bution of satellites as their dynamics is largely governed by the dark dynamical friction to the clusters and dwarfs.
Load more

Recommended publications
  • Tidal Disruption of Globular Clusters in Dwarf Galaxies with Triaxial Dark Matter Haloes.” by J
    “Tidal disruption of globular clusters in dwarf galaxies with triaxial dark matter haloes.” by J. Peñarrubia, M.J. Walker, and G. Gilmore University of Cambridge and University of Victoria MNRAS accepted Journal Club 5/15/09 Daniel Grin 1/19 Wednesday, September 2, 2009 1 Punchline 2/19 • Globular clusters (GCs) around dwarf spheroidal (dSph) galaxies may survive tidal encounters • Stellar substructure (morphology and kinematics) in dSph galaxies may be explained by past disruptions of GCs • Simulation techniques grossly over-simplify the problem, but useful first step Wednesday, September 2, 2009 2 Outline 3/19 • Motivation: subtructure in dSphs and existence of GCs near them. • Properties of systems modeled • Simulation techniques/caveats • Results Wednesday, September 2, 2009 3 Motivation: Substructure in dSph galaxies 4/19 • Milky Way (MW) dSph galaxies are DM dominated-- : • Ideal testbed for CDM scenario • Standing dispute about presence of cores (triaxiality? projection effect? see work by J. Simon) • dSph galaxies have substructure, contrary to expectation that it should be erased in a few crossing times (~100 Myr): • Morphology: Kinematically cold core in Sextans, kinematically distinct shell in Fornax, asymmetries across major/minor axes in Fornax (claims of butterfly shapes are sketchy) • Ages: 2 Gyr-old stellar populations in Fornax shell • Can prolong life of stellar substructure with cored density profile, challenge to CDM? • Can save CDM with formation of substructure that is not in situ • Blue stragglers in Sextans are mass segregated, not enough time for this in Sextans, do it elsewhere (like a merging G.C.) and disrupt? Wednesday, September 2, 2009 4 Motivation: Globular clusters in dSph 5/19 • Fornax (5) and Sagitarrius (4) contain GCs near : Name Angular sep.
    [Show full text]
  • Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects
    Juliana Crestani Ribeiro de Souza Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects Porto Alegre 2017 Juliana Crestani Ribeiro de Souza Spatial Distribution of Galactic Globular Clusters: Distance Uncertainties and Dynamical Effects Dissertação elaborada sob orientação do Prof. Dr. Eduardo Luis Damiani Bica, co- orientação do Prof. Dr. Charles José Bon- ato e apresentada ao Instituto de Física da Universidade Federal do Rio Grande do Sul em preenchimento do requisito par- cial para obtenção do título de Mestre em Física. Porto Alegre 2017 Acknowledgements To my parents, who supported me and made this possible, in a time and place where being in a university was just a distant dream. To my dearest friends Elisabeth, Robert, Augusto, and Natália - who so many times helped me go from "I give up" to "I’ll try once more". To my cats Kira, Fen, and Demi - who lazily join me in bed at the end of the day, and make everything worthwhile. "But, first of all, it will be necessary to explain what is our idea of a cluster of stars, and by what means we have obtained it. For an instance, I shall take the phenomenon which presents itself in many clusters: It is that of a number of lucid spots, of equal lustre, scattered over a circular space, in such a manner as to appear gradually more compressed towards the middle; and which compression, in the clusters to which I allude, is generally carried so far, as, by imperceptible degrees, to end in a luminous center, of a resolvable blaze of light." William Herschel, 1789 Abstract We provide a sample of 170 Galactic Globular Clusters (GCs) and analyse its spatial distribution properties.
    [Show full text]
  • Authentic Data in the Classroom with the Sloan Digital Sky Survey
    Proc. of the GHOU 2007 in Tokyo Authentic Data in the Classroom with the Sloan Digital Sky Survey M. Jordan Raddick* 1 Student engagement with the process of science is a proven part of high­quality science education, but authentic science activities can be difficult in astronomy because of the difficulty students have in taking data. This paper describes how the Sloan Digital Sky Survey (SDSS) contributes to solving this problem by making its entire dataset available to students and the public, free of charge. The survey's SkyServer website (http://skyserver.sdss.org) includes simple tools to browse and search the data, as well as projects that use the data to teach science. The dataset is also a great source of independent research projects for students. 1. Introduction for each star or galaxy, including magnitudes and object types. Images are available as FITS files. Movements in science education reform in the The survey also measures follow­up spectra for United States and around the world frequently cite stars, galaxies and quasars. These spectra run from engagement with the process of science as a key 3800 to 9200 Ångstroms, and have a resolution of component of effective science learning, and 1.8 Ångstroms per pixel. They are available as GIF scientific inquiry as an important part of images or FITS files, and detailed line widths and understanding science [1,2]. strengths are available for each spectral line. Laboratory activities in other science subjects frequently make use of student inquiry labs, in which 3. SkyServer students make their own observations, interpret the results, and draw conclusions.
    [Show full text]
  • Direct N-Body Simulations of Globular Clusters--III. Palomar\, 4 on An
    MNRAS 000, 1–11 (2013) Preprint 14 September 2018 Compiled using MNRAS LATEX style file v3.0 Direct N-body simulations of globular clusters – III. Palomar4 on an eccentric orbit Akram Hasani Zonoozi1⋆, Hosein Haghi1, Pavel Kroupa2,3, Andreas H.W. K¨upper4†, Holger Baumgardt5 1Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), PO Box 11365-9161, Zanjan, Iran 2Helmholtz-Institut f¨ur Strahlen-und Kernphysik (HISKP), Universit¨at Bonn, Nussallee 14-16, D-53115 Bonn, Germany 3Charles University in Prague, Faculty of Mathematics and Physics, Astronomical Institute, V Holeˇsoviˇck´ach 2, CZ-180 00 Praha 8, Czech Republic 4Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA 5School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia Accepted .... Received ABSTRACT Palomar 4 is a low-density globular cluster with a current mass ≈ 30000 M⊙in the outer halo of the Milky Way with a two-body relaxation time of the order of a Hubble time. Yet, it is strongly mass segregated and contains a stellar mass function depleted of low-mass stars. Pal 4 was either born this way or it is a result of extraordi- nary dynamical evolution. Since two-body relaxation cannot explain these signatures alone, enhanced mass loss through tidal shocking may have had a strong influence on Pal 4. Here, we compute a grid of direct N-body simulations to model Pal4 on various eccentric orbits within the Milky Way potential to find likely initial conditions that reproduce its observed mass, half-light radius, stellar MF-slope and line-of-sight ve- locity dispersion.
    [Show full text]
  • Science in the Urantia Papers
    Science ¾ Scientific Validation of the UB z By Denver Pearson z By Phil Calabrese ¾ Seraphic Velocities ¾ Astronomy The Scientific Integrity of the Urantia Book by Denver Pearson As scientifically minded readers first peruse the Urantia Book, it soon occurs to them that many of its statements on the natural sciences conflict with currently held data and theories. In the minds of many this gives rise to doubts about the truthfulness of those statements. Wisdom would lead us to realize that nothing short of perfection is perfect, and anything touched by human hands has fingerprints. This should be our guiding thoughts as we contemplate the accuracy of the scientific content of the Urantia Papers. Several years ago, at the first scientific symposium, it was implied by one of the speakers that the revelation contains errors. This implication is alarming. More recently, at the second symposium held in Oklahoma, an interesting publication named "The Science Content of The Urantia Book" was made available (this document is obtainable from the Brotherhood of Man Library). In this publication is an article entitled "Time Bombs" in which the author suggests that the revelators planted certain inaccurate scientific statements in the book in order to prevent it from becoming a fetish. He states "...the revelators incorporated safeguards in the papers that would form The Urantia Book to diminish the tendency to regard it as an object of worship. What safeguards did they use? Suppose they decided to make sure that mortals reading it understood that some cosmological statements in the book would be found to be inaccurate".
    [Show full text]
  • Young Globular Clusters and Dwarf Spheroidals
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server Young Globular Clusters and Dwarf Spheroidals Sidney van den Bergh Dominion Astrophysical Observatory Herzberg Institute of Astrophysics National Research Council of Canada 5071 West Saanich Road Victoria, British Columbia, V8X 4M6 Canada ABSTRACT Most of the globular clusters in the main body of the Galactic halo were formed almost simultaneously. However, globular cluster formation in dwarf spheroidal galaxies appears to have extended over a significant fraction of a Hubble time. This suggests that the factors which suppressed late-time formation of globulars in the main body of the Galactic halo were not operative in dwarf spheroidal galaxies. Possibly the presence of significant numbers of “young” globulars at RGC > 15 kpc can be accounted for by the assumption that many of these objects were formed in Sagittarius-like (but not Fornax-like) dwarf spheroidal galaxies, that were subsequently destroyed by Galactic tidal forces. It would be of interest to search for low-luminosity remnants of parental dwarf spheroidals around the “young” globulars Eridanus, Palomar 1, 3, 14, and Terzan 7. Furthermore multi-color photometry could be used to search for the remnants of the super-associations, within which outer halo globular clusters originally formed. Such envelopes are expected to have been tidally stripped from globulars in the inner halo. Subject headings: Globular clusters - galaxies: dwarf The galaxy is, in fact, nothing but a congeries of innumerable stars grouped together in clusters. Galileo (1610) –2– 1. Introduction The vast majority of Galactic globular clusters appear to have formed at about the same time (e.g.
    [Show full text]
  • Galactic Metal-Poor Halo E NCYCLOPEDIA of a STRONOMY and a STROPHYSICS
    Galactic Metal-Poor Halo E NCYCLOPEDIA OF A STRONOMY AND A STROPHYSICS Galactic Metal-Poor Halo Most of the gas, stars and clusters in our Milky Way Galaxy are distributed in its rotating, metal-rich, gas-rich and flattened disk and in the more slowly rotating, metal- rich and gas-poor bulge. The Galaxy’s halo is roughly spheroidal in shape, and extends, with decreasing density, out to distances comparable with those of the Magellanic Clouds and the dwarf spheroidal galaxies that have been collected around the Galaxy. Aside from its roughly spheroidal distribution, the most salient general properties of the halo are its low metallicity relative to the bulk of the Galaxy’s stars, its lack of a gaseous counterpart, unlike the Galactic disk, and its great age. The kinematics of the stellar halo is closely coupled to the spheroidal distribution. Solar neighborhood disk stars move at a speed of about 220 km s−1 toward a point in the plane ◦ and 90 from the Galactic center. Stars belonging to the spheroidal halo do not share such ordered motion, and thus appear to have ‘high velocities’ relative to the Sun. Their orbital energies are often comparable with those of the disk stars but they are directed differently, often on orbits that have a smaller component of rotation or angular Figure 1. The distribution of [Fe/H] values for globular clusters. momentum. Following the original description by Baade in 1944, the disk stars are often called POPULATION I while still used to measure R . The recognizability of globular the metal-poor halo stars belong to POPULATION II.
    [Show full text]
  • Arxiv:1307.6035V1 [Astro-Ph.GA] 23 Jul 2013 Uaeydtriigterpoete,Ms Ftegalac- the of Most Properties, Their Determining Curately Et Ferraro the 1997; on Heggie 2012)
    Draft version July 24, 2013 A Preprint typeset using LTEX style emulateapj v. 12/16/11 STAR COUNT DENSITY PROFILES AND STRUCTURAL PARAMETERS OF 26 GALACTIC GLOBULAR CLUSTERS P. Miocchi1, B. Lanzoni1, F.R. Ferraro1, E. Dalessandro1, E. Vesperini2, M. Pasquato3 , G. Beccari4, C. Pallanca1, and N. Sanna1 1Dipartimento di Fisica e Astronomia, Universit`adi Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy 2Department of Astronomy, Indiana University, Bloomington, Indiana 47405, USA 3Department of Astronomy & Center for Galaxy Evolution Research, Yonsei University, and Yonsei University Observatory, Seoul 120-749, Republic of Korea 4European Organization for Astronomical Research in the Southern Hemisphere, K. Schwarzschild-Str. 2, 85748 Garching, Germany Draft version July 24, 2013 ABSTRACT We used a proper combination of high-resolution HST observations and wide-field ground based data to derive the radial star density profile of 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded on-line). With respect to surface brightness (SB) profiles (which can be biased by the presence of sparse, bright stars), star counts are considered to be the most robust and reliable tool to derive cluster structural parameters. For each system a detailed comparison with both King and Wilson models has been performed and the most relevant best-fit parameters have been obtained. This is the largest homogeneous catalog collected so far of star count profiles and structural parameters derived therefrom. The analysis of the data
    [Show full text]
  • Kiski Astronomers at Cherry Springs: Perseids - August, 2015
    Kiski Astronomers at Cherry Springs: Perseids - August, 2015 After finishing my trip to the Lehigh Valley Amateur Astronomical Society ’s Pulpit Rock Observatory the weekend of August 7 th – 9th, I headed over to Cherry Springs to take in the annual Perseid Meteor shower with several other members of the Kiski Astronomers. Monday 08/10/2015: Leaving a damp Pulpit Rock behind, I made the 3 hour drive from Eastern PA to the Astronomers Paradise – Cherry Springs State Park. Arrived late afternoon to find Bob K already there, and setup my camp across from him. Assembled the telescope, but wasn’t able to do much more, as clouds rolled in at sunset. Headed inside to read and early to bed. Tuesday 08/11/2015: Spent the day setting up a few more camping items and visiting with Bob N from the Kiski Club and Mike P from Niagara Canada who arrived and setup with us, and planning for the observing that evening. The sky stayed clear for the afternoon, and once the sun went down, we all got to work. Using my StellaCam-3 videocamera and 8” SCT optical tube on a C-Gem mount, I started working thru my constellation survey, chasing faint galaxies in Ursa Major. These included NGC-3065 & 3066, 3259, 3348, and 3516. Would like to have gone after more galaxies in the Great Bear, but he was too low in the tree tops. Have to wait till next year to re -visit that dipper! I then chased down the faint and elusive globular cluster Palomar -12 in Capricornus.
    [Show full text]
  • PALOMAR 12 AS a PART of the SAGITTARIUS STREAM: the EVIDENCE from ABUNDANCE RATIOS1 Judith G
    The Astronomical Journal, 127:1545–1554, 2004 March A # 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A. PALOMAR 12 AS A PART OF THE SAGITTARIUS STREAM: THE EVIDENCE FROM ABUNDANCE RATIOS1 Judith G. Cohen2 Received 2003 November 7; accepted 2003 December 11 ABSTRACT We present a detailed abundance analysis for 21 elements based on high-dispersion, high spectral resolution Keck spectra for four members of the outer halo ‘‘young’’ Galactic globular cluster Palomar 12. All four stars show identical abundance distributions with no credible indication of any star-to-star scatter. However, the abundance ratios of the Pal 12 stars are very peculiar. There is no detected enhancement of the -elements; the mean of [Si/Fe], [Ca/Fe], and [Ti/Fe] is À0:07 Æ 0:05 dex, O/Fe is also solar, while Na is very deficient. The distribution among the heavy elements shows anomalies as well. These are inconsistent with those of almost all Galactic globular clusters or of field stars in the Galaxy. The peculiarities shown by the Pal 12 stars are, however, in good general agreement with the trends established by Smecker-Hane & McWilliam and by Bonifacio et al. for stars in the Sagittarius dwarf spheroidal (dSph) galaxy evaluated at the [Fe/H] of Pal 12. This reinforces earlier suggestions that Pal 12 originally was a cluster in the Sgr dSph galaxy that during the process of accretion of this galaxy by our own was tidally stripped from the Sgr galaxy to become part of the extended Sgr stream. Key words: globular clusters: general — globular clusters: individual (Palomar 12) — galaxies: individual (Sagittarius dSph) — stars: abundances On-line material: machine-readable table 1.
    [Show full text]
  • Celestial Home of Stars Magda Streicher [email protected]
    deep-sky delights Celestial Home of Stars Magda Streicher [email protected] In an�quity the Capricornus constella- �on was seen as a monster with the head and forelegs of a goat and the posterior of a fish. The creature could almost be compared to the so-called Mermaid but Image source: Stellarium.org could also some�mes, in the case of Cap- ricornus, refer to the Fishman. served towards the east it indicates the The name ‘Tropic of Capricornus’ origi- point of the winter sols�ce, this sols�ce nates from the fact that when first ob- at present being 33o to the west in the figure of Sagi�arius. The constella�on is special to the au- thor for two good reasons. Not only does she live right inside the old Tropic of Capricorn Circle, but the image also reflects a par�cular shape: it looks very much like a huge lopsided triangle, and special in the star composi�on. Heaven alone knows how anyone could see a sea goat with horns in that par�cular star pa�ern, but be that as it may … We will carefully unravel the constella�on, which holds a large number of bright stars to pleasure the eye. The constella�on occupies 414 square degrees of sky and is situated just east of Sagi�arius, but sadly it is not rich in Monument marking the tropic of Capricorn deep-sky objects. S�ll, it is an easily outside Polokwane, Limpopo province. recognisable compila�on, with several mnassa vol 72 nos 5 & 6 126 127 june 2013 capricornus: celestial home of stars look-alike double stars and is, famously, The lovely double star, alpha Capri- a close neighbour to the centre of the corni, also the star closest to the Sagit- Milky Way.
    [Show full text]
  • Multiwavelength, Machine Learning, and Parallax Studies of X-Ray Binaries in Three Local Group Galaxies
    Western University Scholarship@Western Electronic Thesis and Dissertation Repository 12-7-2018 1:30 PM Multiwavelength, Machine Learning, and Parallax Studies of X-ray Binaries in Three Local Group Galaxies Robin Arnason The University of Western Ontario Supervisor Barmby, Pauline The University of Western Ontario Graduate Program in Astronomy A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Robin Arnason 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the External Galaxies Commons Recommended Citation Arnason, Robin, "Multiwavelength, Machine Learning, and Parallax Studies of X-ray Binaries in Three Local Group Galaxies" (2018). Electronic Thesis and Dissertation Repository. 5931. https://ir.lib.uwo.ca/etd/5931 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract X-ray binary stars are rare systems consisting of a black hole or neutron star and a main- sequence companion star. They are useful probes of galaxy properties and interesting labora- tories for extreme physical conditions. In this thesis, I investigated the X-ray binary population of three galaxies in the Local Group. The Sculptor Dwarf Spheroidal Galaxy offers the chance to study a primordial low-mass X-ray binary (LMXB) population in an isolated, low-metallicity environment. Combining X- ray, optical, and infrared observations, I have studied nine previously identified and discovered four additional LMXB candidates in this galaxy.
    [Show full text]