2020 Symposium – the Local Group
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The Chemodynamics of Prograde and Retrograde Milky Way Stars Georges Kordopatis (Γιωργ´ Oς Koρδoπατη´ Σ), Alejandra Recio-Blanco, Mathias Schultheis, and Vanessa Hill
A&A 643, A69 (2020) Astronomy https://doi.org/10.1051/0004-6361/202038686 & c G. Kordopatis et al. 2020 Astrophysics The chemodynamics of prograde and retrograde Milky Way stars Georges Kordopatis (Γιωργ´ o& Koρδoπατη´ &), Alejandra Recio-Blanco, Mathias Schultheis, and Vanessa Hill Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France e-mail: [email protected] Received 18 June 2020 / Accepted 11 September 2020 ABSTRACT Context. The accretion history of the Milky Way is still unknown, despite the recent discovery of stellar systems that stand out in terms of their energy-angular momentum space, such as Gaia-Enceladus-Sausage. In particular, it is still unclear how these groups are linked and to what extent they are well-mixed. Aims. We investigate the similarities and differences in the properties between the prograde and retrograde (counter-rotating) stars and set those results in context by using the properties of Gaia-Enceladus-Sausage, Thamnos/Sequoia, and other suggested accreted populations. Methods. We used the stellar metallicities of the major large spectroscopic surveys (APOGEE, Gaia-ESO, GALAH, LAMOST, RAVE, SEGUE) in combination with astrometric and photometric data from Gaia’s second data-release. We investigated the presence of radial and vertical metallicity gradients as well as the possible correlations between the azimuthal velocity, vφ, and metallicity, [M=H], as qualitative indicators of the presence of mixed populations. Results. We find that a handful of super metal-rich stars exist on retrograde orbits at various distances from the Galactic center and the Galactic plane. We also find that the counter-rotating stars appear to be a well-mixed population, exhibiting radial and vertical metallicity gradients on the order of ∼ − 0:04 dex kpc−1 and −0:06 dex kpc−1, respectively, with little (if any) variation when different regions of the Galaxy are probed. -
A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies J.S. Gallagher, G. J. Madsen, R. J. Reynolds Department of Astronomy, University of Wisconsin–Madison, 475 North Charter Street, Madison, WI 53706-1582; [email protected], [email protected], [email protected] E. K. Grebel Max-Planck Institute for Astronomy, K¨onigstuhl 17, D-69117 Heidelberg, Germany; [email protected] T. A. Smecker-Hane Department of Physics & Astronomy, 4129 Frederick Reines Hall, University of California, Irvine, CA 92697-4575; [email protected] ABSTRACT The Wisconsin Hα Mapper has been used to set the first deep upper limits on the intensity of diffuse Hα emission from warm ionized gas in the Draco and Ursa Minor dwarf spheroidal 1 galaxies. Assuming a velocity dispersion of 15 km s− for the ionized gas, we set limits of IHα 0:024R and IHα 0:021R for the Draco and Ursa Minor dSphs, respectively, averaged ≤ ≤ over our 1◦ circular beam. Adopting a simple model for the ionized interstellar medium, these limits translate to upper bounds on the mass of ionized gas of .10% of the stellar mass, or 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor∼ dSphs could contain substantial amounts of interstellar gas, equivalent to all of the gas injected by dying stars since the end of their main star forming episodes &8 Gyr in the past, without violating these limits on the mass of ionized gas. -
![Arxiv:1806.06038V2 [Astro-Ph.GA] 31 Oct 2018 Gaia-Enceladus on the Basis of Their Orbits](https://docslib.b-cdn.net/cover/4386/arxiv-1806-06038v2-astro-ph-ga-31-oct-2018-gaia-enceladus-on-the-basis-of-their-orbits-124386.webp)
Arxiv:1806.06038V2 [Astro-Ph.GA] 31 Oct 2018 Gaia-Enceladus on the Basis of Their Orbits
The merger that led to the formation of the Milky Way's inner stellar halo and thick disk Amina Helmi1, Carine Babusiaux2, Helmer H. Koppelman1, Davide Massari1, Jovan Veljanoski1, Anthony G. A. Brown3 1Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, The Netherlands 2Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France and GEPI, Observatoire de Paris, Universit´ePSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France 3Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands The assembly process of our Galaxy can be retrieved using the motions and chemistry of individual stars.1, 2 Chemo-dynamical studies of the nearby halo have long hinted at the presence of multiple components such as streams,3 clumps,4 duality5 and correlations between the stars' chemical abundances and orbital parameters.6, 7, 8 More recently, the analysis of two large stellar sur- veys9, 10 have revealed the presence of a well-populated chemical elemental abun- dance sequence,7, 11 of two distinct sequences in the colour-magnitude diagram,12 and of a prominent slightly retrograde kinematic structure13, 14 all in the nearby halo, which may trace an important accretion event experienced by the Galaxy.15 Here report an analysis of the kinematics, chemistry, age and spatial distribution of stars in a relatively large volume around the Sun that are mainly linked to two major Galactic components, the thick disk and the stellar halo. We demon- strate that the inner halo is dominated by debris from an object which at infall was slightly more massive than the Small Magellanic Cloud, and which we refer to as Gaia-Enceladus. -
The Shape of the Galactic Halo with Gaia DR2 RR Lyrae
MNRAS 000,1{13 (2018) Preprint 16 October 2018 Compiled using MNRAS LATEX style file v3.0 The shape of the Galactic halo with Gaia DR2 RR Lyrae. Anatomy of an ancient major merger Giuliano Iorio1? and Vasily Belokurov1;2y 1Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 2Centre for Computational Astrophysics, Flatiron Institute, 162 5th Avenue, New York, NY 10010, USA Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We use the Gaia DR2 RR Lyrae sample to gain an uninterrupted view of the Galactic stellar halo. We dissect the available volume in slices parallel to the Milky Way's disc to show that within ∼ 30 kpc from the Galactic centre the halo is triaxial, with the longest axis misaligned by ∼ 70◦ with respect to the Galactic x-axis. This anatomical procedure exposes two large diffuse over-densities aligned with the semi- major axis of the halo: the Hercules-Aquila Cloud and the Virgo Over-density. We reveal the kinematics of the entire inner halo by mapping out the amplitudes and directions of the RR Lyrae proper motions. These are then compared to simple models with different anisotropies to demonstrate that the inner halo is dominated by stars on highly eccentric orbits. We interpret the shape of the density and the kinematics of the Gaia DR2 RR Lyrae as evidence in favour of a scenario in which the bulk of the halo was deposited in a single massive merger event. Key words: galaxies: individual (Milky Way) { Galaxy: structure { Galaxy: stellar content { Galaxy: stellar halo { stars: (RR Lyrae) { Galaxy: kinematics 1 INTRODUCTION Dav´eet al. -
Astrotalk: Behind the News Headlines
AstroTalk: Behind the news headlines Richard de Grijs (何锐思) (Macquarie University, Sydney, Australia) The Gaia ‘Sausage’ galaxy Our Milky Way galaxy has most likely collided or otherwise interacted with numerous other galaxies during its lifetime. Indeed, such interactions are common cosmic occurrences. Astronomers can deduce the history of mass accretion onto the Milky Way from a study of debris in the halo of the galaxy left as the tidal residue of such episodes. That approach has worked particularly well for studies of the most recent merger events, like the infall of the Sagittarius dwarf galaxy into the Milky Way’s centre a few billion years ago, which left tidal streamers of stars visiBle in galaxy maps. The damaging effects these encounters can cause to the Milky Way have, however, not been as well studied, and events even further in the past are even less obvious as they Become Blurred By the galaxy’s natural motions and evolution. Some episodes in the Milky Way’s history, however, were so cataclysmic that they are difficult to hide. Scientists have known for some time that the Milky Way’s halo of stars drastically changes in character with distance from the galactic centre, as revealed by the chemical composition—the ‘metallicity’—of the stars, the stellar motions, and the stellar density. Harvard astronomer Federico Marinacci and his colleagues recently analysed a suite of cosmological computer simulations and the galaxy interactions in them. In particular they analysed the history of galaxy halos as they evolved following a merger event. They concluded that six to ten Billion years ago the Milky Way merged in a head- on collision with a dwarf galaxy containing stars amounting to about one-to-ten billion solar masses, and that this collision could produce the character changes in stellar populations currently observed in the Milky Way’s stellar halo. -
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. -
Galactic Astronomy with AO: Nearby Star Clusters and Moving Groups
Galactic astronomy with AO: Nearby star clusters and moving groups T. J. Davidgea aDominion Astrophysical Observatory, Victoria, BC Canada ABSTRACT Observations of Galactic star clusters and objects in nearby moving groups recorded with Adaptive Optics (AO) systems on Gemini South are discussed. These include observations of open and globular clusters with the GeMS system, and high Strehl L observations of the moving group member Sirius obtained with NICI. The latter data 2 fail to reveal a brown dwarf companion with a mass ≥ 0.02M in an 18 × 18 arcsec area around Sirius A. Potential future directions for AO studies of nearby star clusters and groups with systems on large telescopes are also presented. Keywords: Adaptive optics, Open clusters: individual (Haffner 16, NGC 3105), Globular Clusters: individual (NGC 1851), stars: individual (Sirius) 1. STAR CLUSTERS AND THE GALAXY Deep surveys of star-forming regions have revealed that stars do not form in isolation, but instead form in clusters or loose groups (e.g. Ref. 25). This is a somewhat surprising result given that most stars in the Galaxy and nearby galaxies are not seen to be in obvious clusters (e.g. Ref. 31). This apparent contradiction can be reconciled if clusters tend to be short-lived. In fact, the pace of cluster destruction has been measured to be roughly an order of magnitude per decade in age (Ref. 17), indicating that the vast majority of clusters have lifespans that are only a modest fraction of the dynamical crossing-time of the Galactic disk. Clusters likely disperse in response to sudden changes in mass driven by supernovae and stellar winds (e.g. -
Does the Fornax Dwarf Spheroidal Have a Central Cusp Or Core?
Research Collection Journal Article Does the Fornax dwarf spheroidal have a central cusp or core? Author(s): Goerdt, Tobias; Moore, Ben; Read, J.I.; Stadel, Joachim; Zemp, Marcel Publication Date: 2006-05 Permanent Link: https://doi.org/10.3929/ethz-b-000024289 Originally published in: Monthly Notices of the Royal Astronomical Society 368(3), http://doi.org/10.1111/ j.1365-2966.2006.10182.x Rights / License: In Copyright - Non-Commercial Use Permitted This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library Mon. Not. R. Astron. Soc. 368, 1073–1077 (2006) doi:10.1111/j.1365-2966.2006.10182.x Does the Fornax dwarf spheroidal have a central cusp or core? , Tobias Goerdt,1 Ben Moore,1 J. I. Read,1 Joachim Stadel1 and Marcel Zemp1 2 1Institute for Theoretical Physics, University of Zurich,¨ Winterthurerstrasse 190, CH-8057 Zurich,¨ Switzerland 2Institute of Astronomy, ETH Zurich,¨ ETH Honggerberg¨ HPF D6, CH-8093 Zurich,¨ Switzerland Accepted 2006 February 8. Received 2006 February 7; in original form 2005 December 21 ABSTRACT The dark matter dominated Fornax dwarf spheroidal has five globular clusters orbiting at ∼1 kpc from its centre. In a cuspy cold dark matter halo the globulars would sink to the centre from their current positions within a few Gyr, presenting a puzzle as to why they survive undigested at the present epoch. We show that a solution to this timing problem is to adopt a cored dark matter halo. We use numerical simulations and analytic calculations to show that, under these conditions, the sinking time becomes many Hubble times; the globulars effectively stall at the dark matter core radius. -
HI in the M31/M33 Environment
HI in the M31/M33 Environment A thesis presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Master of Science Nicole L. Free November 2010 © 2010 Nicole L. Free. All Rights Reserved. 2 This thesis titled HI in the M31/M33 Environment by NICOLE L. FREE has been approved for the Department of Physics and Astronomy and the College of Arts and Sciences by Felix J. Lockman Adjunct Professor of Physics and Astronomy Joseph C. Shields Professor of Physics and Astronomy Benjamin M. Ogles Dean, College of Arts and Sciences 3 ABSTRACT FREE, NICOLE L., M.S., November 2010, Physics and Astronomy HI in the M31/M33 Environment (70 pp.) Director of Thesis: Felix J. Lockman and Joseph C. Shields With recent debate about a reported neutral hydrogen, HI, streamer between M33 and M31, we set out to determine the existence of the HI streamer. Using the National Radio Astronomy Observatory’s 100 m Green Bank Telescope, with 9.1´ angular resolution, we mapped the HI in the region from Wright’s Cloud and M33 through the location of the streamer features, as reported by Braun and Thilker (2004). To verify the findings of Braun and Thilker, we also performed pointed observations at two of the three local maxima within their maps. From our observations, we were able to confirm the existence of the three local maxima points. The three features have column densities ranging from 2.3 to 5.4 , with most being of the order of magnitude of the latter. -
ASKAP and Meerkat Surveys of the Magellanic Clouds
ASKAP and MeerKAT surveys of the Magellanic Clouds Jacco Th. van Loon Lennard-Jones Laboratories, Keele University, ST5 5BG, United Kingdom E-mail: [email protected] The GASKAP Team Hector Arce, Amanda Bailey, Indra Bains, Ayesha Begum, Kenji Bekki, Nadya Ben Bekhti, Joss Bland-Hawthorn, Kate Brooks, Chris Brunt, Michael Burton, James Caswell, Maria Cunningham, John Dickey, Kevin Douglas, Simon Ellingsen, Jayanne English, Robert Estalella, Alyson Ford, Tyler Foster, Bryan Gaensler, Jay Gallagher, Steven Gibson, José Girart, Paul Goldsmith, José F. Gómez, Yolanda Gómez, Anne Green, James Green, Matt Haffner, Carl Heiles, Fabian Heitsch, Patrick Hennebelle, Tomoya Hirota, Melvin Hoare, Hiroshi Imai, Hideyuki Izumiura, Gilles Joncas, Paul Jones, Peter Kalberla, Ji-hyun Kang, Akiko Kawamura, Jürgen Kerp, Charles Kerton, Bon-Chul Koo, Roland Kothes, Stan Kurtz, Maša Laki´cevi´c, Tom Landecker, Alex Lazarian, Nadia Lo, Felix Lockman, Loris Magnani, Naomi McClure-Griffiths, Karl Menten, Victor Migenes, Marc-Antoine Miville-Deschênes, Erik Muller, Akiharu Nakagawa, Hiroyuki Nakanishi, Jun-ichi Nakashima, David Nidever, Lou Nigra, Josh Peek, Miguel Pérez-Torres, Chris Phillips, Mary Putman, Anthony Remijan, Philipp Richter, Peter arXiv:1009.0717v1 [astro-ph.GA] 3 Sep 2010 Schilke, Yoshiaki Sofue, Snežana Stanimirovi´c, Daniel Tafoya, Russ Taylor, Wen-Wu Tian, Lucero Uscanga, Jacco van Loon, Maxim Voronkov, Bart Wakker, Andrew Walsh, Tobias Westmeier, Benjamin Winkel, Ellen Zweibel The MagiKAT Team Gemma Bagheri, Amanda Bailey, Sudhanshu Barway, -
Revealing the Ionization Properties of the Magellanic Stream Using Optical Emission
The Astrophysical Journal, 851:110 (26pp), 2017 December 20 https://doi.org/10.3847/1538-4357/aa992a © 2017. The American Astronomical Society. All rights reserved. Revealing the Ionization Properties of the Magellanic Stream Using Optical Emission K. A. Barger1,2 , G. J. Madsen3, A. J. Fox4 , B. P. Wakker5 , J. Bland-Hawthorn6 , D. Nidever7 , L. M. Haffner8,9 , Jacqueline Antwi-Danso1,10, Michael Hernandez1, N. Lehner2 , A. S. Hill11,12 , A. Curzons6, and T. Tepper-García6 1 Department of Physics and Astronomy, Texas Christian University, Fort Worth, TX 76129, USA 2 Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA 3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 4 Space Telescope Science Institute, Baltimore, MD 21218, USA 5 Supported by NASA/NSF, affiliated with Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA 6 Sydney Institute for Astronomy, School of Physics A28, University of Sydney, NSW 2006, Australia 7 National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ, 85719, USA 8 Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA 9 Space Science Institute, Boulder, CO 80301, USA 10 Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA 11 Departments of Physics and Astronomy, Haverford College, Haverford, PA 19041, USA 12 CSIRO Astronomy and Space Science, Marsfield, NSW 1710, Australia Received 2017 May 1; revised 2017 November 6; accepted 2017 November 6; published 2017 December 18 Abstract The Magellanic Stream, a gaseous tail that trails behind the Magellanic Clouds, could replenish the Milky Way (MW) with a tremendous amount of gas if it reaches the Galactic disk before it evaporates into the halo. -
National Optical Astronomy Observatories
E NATIONAL OPTICAL ASTRONOMY OBSERVATORIES Preprint Series NOAO Preprint No. 834 WFPC2 OBSERVATIONS OF THE URSA MINOR DWARF SPHEROIDAL GALAXY KENNETH J. MIGHELL CHRISTOPHER J. BURKE To Appear In: The Astrophysical Journal March 1999 Operated for the National Science Foundation by the Association of Universities for Research in Astronomy, Inc. To appear in the Astronomical Journal (accepted 1999 March 1) WFPC2 OBSERVATIONS OF THE URSA MINOR DWARF SPHEROIDAL GALAXY 1 KENNETH J. _'IIGHELL 2 AND CHRISTOPHER J. BURKE 3'4 Kitt Peak National Observatory, National Optical Astronomy Observatories 5, P. O. Box 2673:2, Tucson, AZ 85726 mighell@noao, edu, chrislopt_ r. burk_ @yale.cdu 1Based on observations made with tile NASA/ESA Hubble Space Telescope, obtained fl'om the data archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555. 2Guest User, Canadian Astronomy Data Centre, which is operated by the Dominion Astrophysical Observatory for the National Research Council of Canada's Herzberg Institute of Astrophysics. ZBased on research conducted at. NOAO as part of the Research Experiences for Undergraduates program. 4 Current address: Department of Astronomy, Yale University, P. O. Box 208101, New ttaven, CT 06520-8101 SNOAO is operated by the Association of Universilies for I/esearch in Astronomy, Inc., under cooperative agreelnent with the National Science Foundation. _ ABSTRACT \Ve present our analysis of archival Hubble Space Telescope Wide Field Planetary Canlera 2 (WFPC2) observations in F555W (,-_V) and F814W (_I) of the central region of the Ursa Minor dwarf spheroidal galaxy.