Elemental Abundances in the Local Group: Tracing the Formation History of the Great Andromeda Galaxy
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The Faint Globular Cluster in the Dwarf Galaxy Andromeda I
Publications of the Astronomical Society of Australia (PASA), Vol. 34, e039, 4 pages (2017). © Astronomical Society of Australia 2017; published by Cambridge University Press. doi:10.1017/pasa.2017.35 The Faint Globular Cluster in the Dwarf Galaxy Andromeda I Nelson Caldwell1, Jay Strader2,7, David J. Sand3,4, Beth Willman5 and Anil C. Seth6 1Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 2Center for Data Intensive and Time Domain Astronomy, Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA 3Department of Physics and Astronomy, Texas Tech University, PO Box 41051, Lubbock, TX 79409, USA 4Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ, 85721, USA 5LSST and Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721, USA 6Department of Physics and Astronomy, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112, USA 7Email: [email protected] (RECEIVED July 7, 2017; ACCEPTED August 10, 2017) Abstract Observations of globular clusters in dwarf galaxies can be used to study a variety of topics, including the structure of dark matter halos and the history of vigorous star formation in low-mass galaxies. We report on the properties of the faint globular cluster (MV ∼−3.4) in the M31 dwarf galaxy Andromeda I. This object adds to the growing population of low-luminosity Local Group galaxies that host single globular clusters. Keywords: galaxies: individual: Andromeda I – globular clusters: general 1 INTRODUCTION a standard cuspy halo were present, the GC would have been very unlikely to have survived to the present day. -
The Tilt of the Velocity Ellipsoid in the Milky Way with Gaia DR2 Jorrit H
Astronomy & Astrophysics manuscript no. aa c ESO 2019 November 10, 2019 The tilt of the velocity ellipsoid in the Milky Way with Gaia DR2 Jorrit H. J. Hagen1, Amina Helmi1, P. Tim de Zeeuw2; 3, and Lorenzo Posti1 1 Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands e-mail: [email protected] 2 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands 3 Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany Received 13 February 2019 / Accepted XX Month 2019 ABSTRACT The velocity distribution of stars is a sensitive probe of the gravitational potential of the Galaxy, and hence of its dark matter dis- tribution. In particular, the shape of the dark halo (e.g. spherical, oblate, prolate) determines velocity correlations, and different halo geometries are expected to result in measurable differences. We here explore and interpret the correlations in the (vR; vz)-velocity distribution as a function of position in the Milky Way. We select a high quality sample of stars from the Gaia DR2 catalog, and char- acterise the orientation of the velocity distribution or tilt angle, over a radial distance range of [3 − 13] kpc and up to 4 kpc away from the Galactic plane while taking into account the effects of the measurement errors. The velocity ellipsoid is consistent with spherical alignment at R ∼ 4 kpc, while it progressively becomes shallower at larger Galactocentric distances and is cylindrically aligned at R = 12 kpc for all heights probed. Although the systematic parallax errors present in Gaia DR2 likely impact our estimates of the tilt angle at large Galactocentric radii, possibly making it less spherically aligned, their amplitude is not enough to explain the deviations from spherical alignment. -
Near-Field Cosmology with Extremely Metal-Poor Stars
AA53CH16-Frebel ARI 29 July 2015 12:54 Near-Field Cosmology with Extremely Metal-Poor Stars Anna Frebel1 and John E. Norris2 1Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; email: [email protected] 2Research School of Astronomy & Astrophysics, The Australian National University, Mount Stromlo Observatory, Weston, Australian Capital Territory 2611, Australia; email: [email protected] Annu. Rev. Astron. Astrophys. 2015. 53:631–88 Keywords The Annual Review of Astronomy and Astrophysics is stellar abundances, stellar evolution, stellar populations, Population II, online at astro.annualreviews.org Galactic halo, metal-poor stars, carbon-enhanced metal-poor stars, dwarf This article’s doi: galaxies, Population III, first stars, galaxy formation, early Universe, 10.1146/annurev-astro-082214-122423 cosmology Copyright c 2015 by Annual Reviews. All rights reserved Abstract The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical condi- tions of the earliest star-forming environments in the Universe. We review Access provided by California Institute of Technology on 01/11/17. For personal use only. the fields of stellar archaeology and dwarf galaxy archaeology by examin- Annu. Rev. Astron. Astrophys. 2015.53:631-688. Downloaded from www.annualreviews.org ing the chemical abundance measurements of various elements in extremely metal-poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal enrichment events. We extend the discussion to near-field cosmology, which is concerned with the forma- tion of the first stars and galaxies, and how metal-poor stars can be used to constrain these processes. -
Near-Field Cosmology with Metal-Poor Stars
NEAR-FIELD COSMOLOGY WITH EXTREMELY METAL-POOR STARS 1 NEAR-FIELD COSMOLOGY WITH EXTREMELY METAL-POOR STARS Anna Frebel Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA; email: [email protected] John E. Norris Research School of Astronomy & Astrophysics, The Australian National University, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611, Australia; email: [email protected] Key Words stars: abundances, carbon, evolution; stellar populations: Popu- arXiv:1501.06921v1 [astro-ph.SR] 27 Jan 2015 lation II, Population III; Galaxy: formation, halo; galaxies: dwarf; cosmology: early Universe, first stars Abstract The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environ- ments in the Universe. We review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal- 2 FREBEL & NORRIS poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal en- richment events. We extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies and how metal-poor stars can be used to constrain these processes. Complementary abundance measurements in high-redshift gas clouds further help to establish the early chemical evolution of the Universe. The data appear consistent with the existence of two distinct channels of star formation at the earliest times. -
Arxiv:1912.02186V1 [Astro-Ph.GA] 4 Dec 2019 Early in the Formation of an L∗ Galaxy
Draft version December 6, 2019 Typeset using LATEX twocolumn style in AASTeX63 Elemental Abundances in M31: The Kinematics and Chemical Evolution of Dwarf Spheroidal Satellite Galaxies∗ Evan N. Kirby,1 Karoline M. Gilbert,2, 3 Ivanna Escala,1, 4 Jennifer Wojno,3 Puragra Guhathakurta,5 Steven R. Majewski,6 and Rachael L. Beaton4, 7, y 1California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125, USA 2Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA 3Department of Physics & Astronomy, Bloomberg Center for Physics and Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218 4Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 5Department of Astronomy & Astrophysics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA 6Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325, USA 7The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (Accepted 3 December 2019) Submitted to AJ ABSTRACT We present deep spectroscopy from Keck/DEIMOS of Andromeda I, III, V, VII, and X, all of which are dwarf spheroidal satellites of M31. The sample includes 256 spectroscopic members across all five dSphs. We confirm previous measurements of the velocity dispersions and dynamical masses, and we provide upper limits on bulk rotation. Our measurements confirm that M31 satellites obey the same relation between stellar mass and stellar metallicity as Milky Way (MW) satellites and other dwarf galaxies in the Local Group. The metallicity distributions show similar trends with stellar mass as MW satellites, including evidence in massive satellites for external influence, like pre-enrichment or gas accretion. -
Observational Aspects of Globular Cluster and Halo Stars in the GALAH Survey
THE UNIVERSITY OF NEW SOUTH WALES DOCTORAL THESIS Observational aspects of globular cluster and halo stars in the GALAH survey Student: Supervisor: Mohd Hafiz MOHD SAADON Associate Professor Sarah MARTELL A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy in the School of Physics Faculty of Science The University of New South Wales 12 March 2021 i ii iii iv Declaration of Authorship I, Mohd Hafiz MOHD SAADON, declare that this thesis titled, “Observational aspects of globular cluster and halo stars in the GALAH survey” and the work presented in it are my own. I confirm that: • This work was done wholly or mainly while in candidature for a research degree at this University. • Where any part of this thesis has previously been submitted for a degree or any other qualification at this University or any other institution, this has been clearly stated. • Where I have consulted the published work of others, this is always clearly at- tributed. • Where I have quoted from the work of others, the source is always given. With the exception of such quotations, this thesis is entirely my own work. • I have acknowledged all main sources of help. Signed: Date: v “In loving memory of my grandmothers, Ramlah and Halijah, who wished to see me this far but could not be here anymore.” – your grandson. “To Amani, my sweet little angel, this thesis is your sibling.” – your father. vi THE UNIVERSITY OF NEW SOUTH WALES Abstract Doctor of Philosophy Observational aspects of globular cluster and halo stars in the GALAH survey by Mohd Hafiz MOHD SAADON This thesis is a study of the observational aspects of globular cluster and halo stars in the Galactic Archaeology with HERMES (GALAH) survey. -
PDF Presentatie Van Frank
13” Frank Hol / Skyheerlen Elfje en Vixen R150S Newton in de jaren ’80 en begin ’90 vooral zon, maan, planeten en Messiers. H.T.S. – vriendin – baan – huis kopen & verbouwen trouwen – kinderen waarneemstop. Vanaf 2006 weer actief waarnemen. Focus op objecten uit de Local Group of Galaxies • 2008: Celestron C14. • 2015: 13” aluminium reisdobson. • 2017-2018-2019: 13” aluminium bino-dobson. Rocherath – SQM 21.2-21.7 13” M31 NGC206 Globulars Stofbanden Stervormings- gebieden … 13” M31 M32 NGC206 Globulars Stofbanden Stervormings- gebieden … NGC206 13” NGC205 M32 M32 is de kern van een NGC 221 galaxy die grotendeels Andromeda opgelokt is door M31. M32 is dan ook net zo X helder als de kern van M31 (met 100 miljoen sterren). Telescoop: ≈ 5.0° x 4.0° verrekijker Locatie: (bijna) overal. De helderste dwerg (vanuit onze breedte) aan de hemel: magnitude 8.1. M110 “Een elliptisch stelsel is NGC 205 dood-saai.” Andromeda Neen, kijk eens hoe mooi het stelsel aan de rand in de X donkere achtergrond verdwijnt. Een watje in de lucht! Telescoop: ≈ 5.0° x 4.0° verrekijker Locatie: (bijna) overal. Een grotere telescoop laat de randen mooi verdwijnen in de omgeving. 30’ x 25’ Burnham’s NGC185 and NGC147 “These two miniature elliptical galaxies appear to be distant Celestial companians of the Great Andromeda Galaxy M31. They are Handbook some 7 degrees north of it in the sky, and are approximately the same distance from us, about 2.2 milion light years.” Start van een lange zoektocht (die nog niet voorbij is). 13” NGC147 Twee elliptische stelsels. & NGC147 is een stuk moeilijker dan NGC185. -
Neutral Hydrogen in Local Group Dwarf Galaxies
Neutral Hydrogen in Local Group Dwarf Galaxies Jana Grcevich Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate School of Arts and Sciences COLUMBIA UNIVERSITY 2013 c 2013 Jana Grcevich All rights reserved ABSTRACT Neutral Hydrogen in Local Group Dwarfs Jana Grcevich The gas content of the faintest and lowest mass dwarf galaxies provide means to study the evolution of these unique objects. The evolutionary histories of low mass dwarf galaxies are interesting in their own right, but may also provide insight into fundamental cosmological problems. These include the nature of dark matter, the disagreement be- tween the number of observed Local Group dwarf galaxies and that predicted by ΛCDM, and the discrepancy between the observed census of baryonic matter in the Milky Way’s environment and theoretical predictions. This thesis explores these questions by studying the neutral hydrogen (HI) component of dwarf galaxies. First, limits on the HI mass of the ultra-faint dwarfs are presented, and the HI content of all Local Group dwarf galaxies is examined from an environmental standpoint. We find that those Local Group dwarfs within 270 kpc of a massive host galaxy are deficient in HI as compared to those at larger galactocentric distances. Ram- 4 3 pressure arguments are invoked, which suggest halo densities greater than 2-3 10− cm− × out to distances of at least 70 kpc, values which are consistent with theoretical models and suggest the halo may harbor a large fraction of the host galaxy’s baryons. We also find that accounting for the incompleteness of the dwarf galaxy count, known dwarf galaxies whose gas has been removed could have provided at most 2.1 108 M of HI gas to the Milky Way. -
Draft181 182Chapter 10
Chapter 10 Formation and evolution of the Local Group 480 Myr <t< 13.7 Gyr; 10 >z> 0; 30 K > T > 2.725 K The fact that the [G]alactic system is a member of a group is a very fortunate accident. Edwin Hubble, The Realm of the Nebulae Summary: The Local Group (LG) is the group of galaxies gravitationally associ- ated with the Galaxy and M 31. Galaxies within the LG have overcome the general expansion of the universe. There are approximately 75 galaxies in the LG within a 12 diameter of ∼3 Mpc having a total mass of 2-5 × 10 M⊙. A strong morphology- density relation exists in which gas-poor dwarf spheroidals (dSphs) are preferentially found closer to the Galaxy/M 31 than gas-rich dwarf irregulars (dIrrs). This is often promoted as evidence of environmental processes due to the massive Galaxy and M 31 driving the evolutionary change between dwarf galaxy types. High Veloc- ity Clouds (HVCs) are likely to be either remnant gas left over from the formation of the Galaxy, or associated with other galaxies that have been tidally disturbed by the Galaxy. Our Galaxy halo is about 12 Gyr old. A thin disk with ongoing star formation and older thick disk built by z ≥ 2 minor mergers exist. The Galaxy and M 31 will merge in 5.9 Gyr and ultimately resemble an elliptical galaxy. The LG has −1 vLG = 627 ± 22 km s with respect to the CMB. About 44% of the LG motion is due to the infall into the region of the Great Attractor, and the remaining amount of motion is due to more distant overdensities between 130 and 180 h−1 Mpc, primarily the Shapley supercluster. -
New Perspectives in Understanding the Galactic Halo
New perspectives in understanding the Galactic halo Amina Helmi New perspectives in understanding the Galactic halo In collaboration with Facundo Gomez, Andrew Cooper, Simon White, Anthony Brown, Yang-Shyang Li Why care about stellar halos? • Most metal-poor and ancient stars in the MW • window into the early Universe • Orbiting outskirts of galaxies: good mass probes • Can form from the superposition of disrupted satellites • stars retain memory of their origin -> merger history Helmi, Cooper et al. (2010) Outer Stellar halo - Substructure common in the halo (SDSS, 2MASS…) -> mergers Broad, diffuse streams (large progenitors? …but beware of biases) -> overdensities -> nature not always clear Belokurov et al 2007 Belokurov Some questions • What are the properties of stellar halos and satellites in ΛCDM? How do they compare to the Milky Way or M31? • What are models predictions for future surveys? • What do we learn about the history of a galaxy from its stellar halo? Stellar halo and Substructure in ΛCDM – Aquarius project: very high-resolution simulations of formation of 6 different dark matter halos ressembling the Milky Way (by mass) - Cooper et al. (2009) combined with phenomenological galaxy formation model -> predict properties of (accreted) stellar halos in CDM See also Bullock & Johnston 2005; De Lucia & Helmi 2008 Springel et al. 2008 Aquarius stellar halos - 1% most bound particles represent stars/stellar pops in these objects - Follow the history, their present-day location and dynamics Stellar halo formation in the Aquarius simulations Cooper et al. 2010 Helmi, Cooper et al. 2010 Aquarius “accreted” stellar halos Large variation from halo to halo -> reflects different histories Large amount of substructure -> history may be recovered Cooper et al. -
View Article [19]
ABSTRACT ON THE NATURE OF RADIAL DISPERSION PROFILES FOR DWARF SPHEROIDAL GALAXIES IN THE LOCAL GROUP ACCORDING TO MOND by Matthew James Walentosky Modified Newtonian Dynamics (MOND) has long been the only proposed plausible alternative to dark matter to explain mass discrepancies observed in a wide array of systems. In this thesis, the ability of MOND to ac- curately predict the radial velocity dispersion profile of Milky Way and Andromeda dwarf spheroidal galaxies (dSphs) is investigated. Using a Hermite Individual Timestep Scheme based algorithm, the motion of 10,000 stars is tracked in a Hernquist potential with a MONDian correction applied to the acceleration of each star. The observable properties are compared to present day observations and used to generate radial velocity dis- persion profiles for 5 Milky Way dSphs which can be compared to present day observations to demonstrate the accuracy of the procedure. Our calculations are in good agreement with observations. In addition, predictions are made for the radial velocity dispersion profiles for 17 Andromeda dSphs. The results of this study will show agreement between simulated, observed and calculated bulk dispersion and radial dispersion profiles. These predictions will serve as a test on the validity of MOND to either be verified or discredited by future observations. ON THE NATURE OF RADIAL DISPERSION PROFILES FOR DWARF SPHEROIDAL GALAXIES IN THE LOCAL GROUP ACCORDING TO MOND A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the -
Cumulative Bio-Bibliography University of California, Santa Cruz June 2020
Cumulative Bio-Bibliography University of California, Santa Cruz June 2020 Puragra Guhathakurta Astronomer/Professor University of California Observatories/University of California, Santa Cruz ACADEMIC HISTORY 1980–1983 B.Sc. in Physics (Honours), Chemistry, and Mathematics, St. Xavier’s College, University of Calcutta 1984–1985 M.Sc. in Physics, University of Calcutta Science College; transferred to Princeton University after first year of two-year program 1985–1987 M.A. in Astrophysical Sciences, Princeton University 1987–1989 Ph.D. in Astrophysical Sciences, Princeton University POSITIONS HELD 1989–1992 Member, Institute for Advanced Study, School of Natural Sciences 1992–1994 Hubble Fellow, Astrophysical Sciences, Princeton University 1994 Assistant Astronomer, Space Telescope Science Institute (UPD) 1994–1998 Assistant Astronomer/Assistant Professor, UCO/Lick Observatory, University of California, Santa Cruz 1998–2002 Associate Astronomer/Associate Professor, UCO/Lick Observatory, University of California, Santa Cruz 2002–2003 Herzberg Fellow, Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria, BC, Canada 2002– Astronomer/Professor, UCO/Lick Observatory, University of California, Santa Cruz 2009– Faculty Director, Science Internship Program, University of California, Santa Cruz 2012–2018 Adjunct Faculty, Science Department, Castilleja School, Palo Alto, CA 2015 Visiting Faculty, Google Headquarters, Mountain View, CA 2015– Co-founder, Global SPHERE (STEM Programs for High-schoolers Engaging in Research