DOCSLIB.ORG

Denija Crnojević & Eva K. Grebel Texas Tech University & Heidelberg

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Denija Crnojević & Eva K. Grebel Texas Tech University & Heidelberg Denija Crnojević & Eva K. Grebel Texas Tech University & Heidelberg University Dr. Denija Crnojević (Texas Tech University) kindly agreed to present Dr. Eva Grebel’s talk slides during the Division H meeting when she had to cancel her participation in the IAU GA in Hawaii. A review paper focusing on Local Group globular clusters (not star clusters in general) will appear in the proceedings of IAU Symposium 312 (eds. R. Spurzem et al.): Grebel, E.K., “Globular Clusters in the Local Group”, to appear in IAU Symp. 312 on “Star Clusters and Black Holes in Galaxies Across Cosmic Time” held in Beijing 2014, Cambridge Univ. Press, in press. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 1 M31 and the Milky Way M31: Richest GC system in the LG. > 700 GCs! (MW: ~ 160 GCs). Also numerous young clusters. Huxor et al. 2014, MNRAS, 442, 2165 Halo GCs often still associated with tidal tails of disrupted dwarf Mackey et al. 2013, galaxies in which MNRAS, 429, 281 they formed. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 2 Globular Clusters in M31 and the Milky Way M31 and MW GC metallicity Galleti et al. 2009, distribution functions (here: A&A, 508, 1285; from Lick indices for M31): 245 GCs. 〈[Fe/H]〉M31 ≈ −0.9 dex. 〈[Fe/H]〉MW ≈ −1.3 dex. ➙ M31 GCs overall more metal-rich. 25% of M31 GCs > −0.5 dex. 7% of MW GCs > −0.5 dex. M31: No obvious bimodality like in MW, but 2-component fit with modes at −1.54 and −0.64 dex preferred (in MW: −1.60 and −0.59); also three- component fit possible. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 3 GCs in M31 Metal-rich GCs: Strongly centered, bulge. Follow HI rotation curve. A few deviant metal-rich GCs in outskirts. “Intermediate”: More widely distributed. “Metal-poor”: widest distribution. Larger velocity dispersion, but still clear rotation signature (contrary to MW GCs!). Galleti et al. 2009, 60’ ∝ 13.8 kpc A&A, 508, 1285 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 4 Cluster age-metallicity relation Clusters in M33 Beasley et al. 2015, MNRAS, 508, 1285 ! M33 disk clusters: Clear ! age-metallicity relation ! (but note large scatter). ! No radial age gradient ! in disk clusters (≤ 6 kpc). ! Clusters younger than 4 ! Gyr: rotate with disk of ! M33 (reduced rotation ! amplitude and increased velocity dispersion ! with higher cluster age; similar to MW). ! Mean metallicity of inner M33 GCs: high ! ( 〈[m/H]〉 = −1.12 ± 0.09 dex). Also kinem- Beasley et al. 2015, ! atics support association with thick disk. MNRAS, 508, 1285 ! At least six outer halo GCs with projected ! galactocentric radii of 10 – 50 kpc. ! Low number: M33 halo stripped in past ! encounters with M31? Age – velocity-dispersion relation Beasley et al. 2015, MNRAS, 508, 1285 Cockcroft et al. 2011, ApJ, 730, 112 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 5 (Globular) Clusters in M31 and the Milky Way Wang et al. 2013, AJ, 146, 20 Huxor et al. 2014, MNRAS, 442, 2165 ", ✕: M31 GCs #: MW GCs : M31 extended GCs Δ: M31 young clusters Trends: Tidal radii rt increase with (projected) galactocentric distance. On average larger half-light radii at Rgc > 30 kpc. Extended GCs may fill the gap between (ultrafaint) dSphs and GCs. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 6 Globular Clusters in the Milky Way , 504 355 rc depends on initial structural conditions of cluster. Little effect of tidal history, while rh quickly adjusts to new potential (Miholics et al. 2014). Similarity of structural parameters in GCs in dwarf satellites and MW halo: MackeyGilmore & 2004, MNRAS, Indication of possible accretion origin of “young” halo GCs. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 7 Globular cluster accretion from dwarf galaxies Assume: GC metallicity traces host galaxy metallicity at time of formation. ❏ Offset in MW GC age-metallicity relation: 0.6 dex (∝ stellar mass ❏ difference of ~ 2 dex). Leaman et al. 2013, ❏ Halo GCs on metal- MNRAS, 436, 122 ❏ poor branch: Well ❏ fitted by age-metal- ❏ licity relation of LG dIrrs. Much of MW halo GC system may have come from ~ 6 – 7 WLM- to LMC-sized dIrrs. ❏ Metal-rich branch: ❏ formed in situ in MW ❏ disk/bulge. See also Forbes & Bridges 2010, MNRAS, 404, 1203 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 8 GC disruption Additionally, GCs may get disrupted by disk and bulge crossings or internal relaxation. A few cases of ongoing dissolution were found in MW halo. (e.g., Odenkirchen et al. 2001, ApJ, 548, L165; Odenkirchen & Jordi & Grebel 2010, A&A, 522, 71). Grebel 2001 Quantifying contrib- ution to halo field stars by searching for field stars with light element abun- dance anomalies: Possible 2nd genera- tion stars from dis- Martell & Grebel 2010, A&A, 519, 14; solved GCs. Martell et al. 2011, A&A, 534, 136 ➙ ~ 17% of halo field stars originally from GCs. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 9 Specific GC frequency: S = N · 100.4 (Mv+15) GCs contributed by the Sgr dSph N GC ❏ 5 high-, 4 moderate, 2 low- Law & Majewski 2010, AJ, 718, 1128 ❏ confidence GC members. ❏ ~ 8 ± 2 genuine GCs. ❏ SN ~ 5 – 9 for initial Sgr ❏ luminosity of MV = −15. ❏ M54: GC at core of Sgr ❏ (formed elsewhere and sank to ❏ center via dynamical friction). ❏ In the (HB-type, [Fe/H] plane), ❏ Sgr is contributing “young halo” ❏ GCs with predominantly red HBs ❏ (Arp 2, NGC 4147) and “old halo” GCs (!) with mainly blue HBs. ❏ When fully disrupted, Sgr will (probably) have contributed up to 3 – 4 ❏ metal-rich, young objects to the Galactic halo, which have no counter- ❏ counterparts even among the “young halo” GCs. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 10 5 Globular Clusters in Fornax dSph GCs #1 – 3, #5 in Fornax: −2.5 dex −2.1 dex ~ indistinguishable in age; as old as oldest MW GCs. GC #4: ~ 3 Gyr younger, −1.9 dex. Buonanno et al. 1999, AJ, 118, 1671 −2.4 dex −2.2 dex Buonanno et al. 1998, ApJ, 501, L33 Note 2nd parameter effect in ~ coeval, metal- poor GCs! Smith et al. 1996, AJ, 111, 1596 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 11 NGC 185 Globular Clusters in M31’s Dwarf Ellipticals ! NGC 147: 8 – 10 GCs. Mainly old stellar populations, gas/dust free. ! NGC 185: ~ 7 GCs (incl. “young” and “old halo” GCs). Strong intermediate-age ! populations, some intermed.-age clusters (a few Gyr), nuclear cluster, gas, dust. ! NGC 205: ~ 6 GCs (incl. “young” and “old halo” GCs). 7 – 11 Gyr, −1.1 – −2 dex. ! Many intermed.-age clusters esp. ~ 1 – 2 Gyr; [m/H] > −0.8 dex. Nuclear cluster. Ellipse: B = 25 mag/arcsec2 isophote SN of dEs in Virgo & Fornax clusters consistent with those of M31’s dEs. Veljanoski et al. 2013, MNRAS, 435, 3654 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 12 Distribution of Star Clusters in the Magellanic Clouds ❏ “Old” LMC clusters (blue dots: > 4 Gyr) trace bar-like structure, slightly ❏ rotated against younger star cluster distribution. ❏ SMC disk and Bridge better traced by associations. ❏ LMC associations also trace leading edge, but its outer clusters ❏ form loose ring around entire LMC (not seen in associations). ❏ “Old” LMC clusters also in outer parts (not only in bar). ❏ “Old” SMC clusters preferentially found in outer parts. LMC Magellanic Bridge SMC Associations Bica et al. 2008, MNRAS 389, 678 Clusters 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 13 Recent Star Formation History of the LMC ❏ Ages of 1193 populous LMC star clusters from resolved CMDs taken from the ❏ Magellanic Clouds Photometric Survey (Glatt, Grebel, & Koch 2010, A&A 517, 50). ❏ Note how star formation migrates along the bar and how different disk regions ❏ become active at different times. Age < 20 Myr 20 Myr ≤ age < 50 Myr 30 Dor Ellipses show approximate location of supergiant shells. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 14 Recent Star Formation History of the LMC ❏ Ages of 1193 populous LMC star clusters from resolved CMDs taken from the ❏ Magellanic Clouds Photometric Survey (Glatt, Grebel, & Koch 2010, A&A 517, 50). 50 Myr ≤ age < 100 Myr 100 Myr ≤ age < 250 Myr 250 Myr: approx. one rotation period of the LMC. 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 15 Recent Star Formation History of LMC and SMC ❏ Ages of populous LMC and SMC star clusters from resolved CMDs from the ❏ Magellanic Clouds Photometric Survey (Glatt, Grebel, & Koch 2010, A&A 517, 50). 250 Myr ≤ age < 500 Myr LMC clusters Age histo- grams of populous LMC and SMC star SMC clusters clusters from re- solved CMDs: Similar peaks in the age distribution may Star clusters formed during the have been triggered by close encounters previous rotation period of the LMC. between the Clouds (and the MW). 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 16 Magellanic Cloud Cluster Core Radii vs. Ages ❏ Spread in cluster ❏ core radii (rc) ❏ increases with age. , 65 ❏ Young massive 386 4 ❏ (> 10 M!) clusters: , 138 ❏ rc ~ 1 – 2 pc; 138 ❏ oldest clusters: [pc] c ❏ up to 8 pc. r ❏ GCs in Fornax & ❏ Sgr dSphs also et al. 2009, AJ, AJ, et al.2009, ❏ fit this trend, as Mackey et al.2008,MNRAS Glatt ❏ do MW GCs (esp. ❏ “young” halo GCs). log (age) [yr] 08/07/2015 Crnojevic & Grebel: Local Group Star Clusters 17 LMC Star Cluster Survivability Cluster frequency divided by field SFH. LMC No. of clusters formed per unit stellar mass ~ constant up to 200 Myr. Then sharp drop − onset of et al.2013, MNRAS,430,676 dissolution.
Load more

Recommended publications
  • Groups of Galaxies in the Nearby Universe Held in Santiago De Chile, 5–9 December 2006
    Report on the Conference on Groups of Galaxies in the Nearby Universe held in Santiago de Chile, 5–9 December 2006 Ivo Saviane, Valentin D. Ivanov, Jura Borissova (ESO) n Bi r 10 For every galaxy in the field or in clusters, pe p there are about three galaxies in groups. ou Therefore, the evolution of most galax- Gr r ies actually happens in groups. The Milky pe Way resides in a group, and groups can be found at high redshift. The current xies 1 generation of 10-m-class telescopes and Gala space facilities allows us to study mem- of bers of nearby groups with exquisite de- tail, and their properties can be corre- –1 Number L < 41.7 Log (erg s ) lated with the global properties of their x L > 41.7 Log (erg s–1) host group. Finally, groups are relevant x for cosmology, since they trace large- scale structures better than clusters, and –22 –20 –18 –16 –14 Absolute Magnitude (M ) the evolution of groups and clusters may B be related. Figure 1: Cumulative B-band luminosity function of Strangely, there are three times fewer pa- 25 GEMS groups of galaxies grouped into X-ray- bright and X-ray-faint categories, fitted with one or pers on groups of galaxies than on clus- two Schechter functions, respectively (Miles et ters of galaxies, as revealed by an ADS al. 2004, MNRAS 355, 785; presented by Raychaud- search. Organising this conference was a hury). Mergers could explain the bimodality of the way to focus the attention of the com- luminosity function of X-ray-faint groups.
    [Show full text]
  • AAS Members Save on Annual Reviews Journals
    AAS Members Save on Annual Reviews Journals Annual Review of Astronomy and Astrophysics #1 JCR® Volume 50 • September 2012 • ISSN: 0066-4146 • ISBN: 978-0-8243-0950-2 • http://astro.annualreviews.org IMPACT FACTOR AAS Member Discounted Price: $62.30 (WORLDWIDE) Regular price: $89.00 (WORLDWIDE) RANKING Co-Editors: Sandra M. Faber, University of California, Santa Cruz and Ewine F. van Dishoeck, Sterrewacht Leiden Associate Editor: John Kormendy, University of Texas, Austin PLANNED TABLE OF CONTENTS AND AUTHORS (SUBJECT TO CHANGE): • Planet-Disk Interactions and Orbital Migration, W. Kley, R.P. Nelson • Adaptive Optics for Astronomy, Richard Davies, Markus Kasper • Pre-Supernova Evolution of Massive Single and Binary Stars, Norbert Langer • Advances in Submillimeter and Far-Infrared Detectors, Jonas Zmuidzinas • Ram-Pressure Stripping of Galaxy Gas, J.H. Van Gorkom • Collisionless Dissipation Processes in Astrophysical Plasma Turbulence, Stuart D. Bale • Relativistic Shocks, Anatoly Spitkovsky • Concensus Cosmology, John E. Carlstrom • Seeing Cosmology Grow, P.J.E. Peebles • Connecting Galactic Star Formation on Global and Local Scales, Robert C. Kennicutt • Solar Magnetic Field, Alan Title • Dynamical Evolution and Resonances of Planetary Systems, Gregory P. Laughlin • Solar Neutrinos, Wick C. Haxton • Formation of Galaxy Clusters, Andrey Kravtsov • Subpopulations in Globular Clusters, Giampaolo Piotto • Galactic Stellar Populations in the Era of Large Surveys, Željko Ivezic • Supermassive Black Holes in the HST Era, John Kormendy • High Redshift Galaxy Evolution, Garth Illingworth • The Formation and Early Evolution of Low-Mass Stars and Brown Dwarfs, • Large-Scale Heliosphere, Ed Stone Kevin L. Luhman • Magnetic Fields in Molecular Clouds, Richard M. Crutcher • The Gaseous Galactic Halo, M. Putman, Joshua E.G.
    [Show full text]
  • Commission H1 Annual Report (2019)
    COMMISSION H1 THE LOCAL UNIVERSE (L’UNIVERS LOCAL) PRESIDENT Dante Minniti VICE-PRESIDENT Grazina Tautvaisiene PAST PRESIDENT Eva K. Grebel SECRETARY Aoki Wako ORGANIZING COMMITTEE Evangelie Athanassoula, John Beckman, Maria-Rosa Cioni, Yasuo Fukui, Eva K. Grebel, Margaret Meixner, Dante Minniti, Grazina Tautvaisiene, Aoki Wako, Gang Zhao ANNUAL SUMMARY REPORT 2019 1. Introduction The IAU Commission H1 on “The Local Universe (L'Univers Local)” is one of the three commissions of Division H, “Interstellar Matter and Local Universe”. This Commission H1 was established in mid-2015, and it was presided by Eva Grebel (Germany) during its first triennial period. IAU Commission H1 presently counts with 331 members. Our Commission focuses on studies of the Milky Way and nearby galaxies, where we can resolve galaxies into stars. A range of observational and theoretical research on the stellar populations, interstellar medium, dark matter of local galaxies, etc. are covered in order to understand galaxy formation, history and evolution. Recent and future photometric, spectroscopic, and astrometric surveys (both ground-based and space- based) contribute to the knowledge revolution that this field is experiencing. Current and forthcoming facilities will yield an even deeper understanding of our local Universe. 2. Activities 2019 This past year 2019 organizing committee members attended several international meetings and workshops worldwide, representing the IAU and giving invited/contributed talks and posters. Among the major developments on the area of Milky Way and Nearby galaxies that occurred during the year 2019, we can mention as examples the data releases and important publications from the following large surveys (in random order, incomplete list): * Astrometry - Continuing research on the Gaia DR2 released on April 2018 yielding a number of publications.
    [Show full text]
  • Discovery of a Dwarf Spheroidal Galaxy Behind the Andromeda Galaxy
    Mirach’s Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy David Martínez-Delgado, Eva Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, Julio Carballo-Bello, Dmitry Makarov, Michael Beasley, Giuseppe Donatiello, Martha Haynes, et al. To cite this version: David Martínez-Delgado, Eva Grebel, Behnam Javanmardi, Walter Boschin, Nicolas Longeard, et al.. Mirach’s Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy. Astronomy and Astrophysics - A&A, EDP Sciences, 2018, 620, pp.A126. 10.1051/0004-6361/201833302. hal- 03152563 HAL Id: hal-03152563 https://hal.archives-ouvertes.fr/hal-03152563 Submitted on 27 Feb 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. A&A 620, A126 (2018) Astronomy https://doi.org/10.1051/0004-6361/201833302 & c ESO 2018 Astrophysics Mirach’s Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy David Martínez-Delgado1, Eva K. Grebel1, Behnam Javanmardi2, Walter Boschin3,4,5 , Nicolas Longeard6, Julio A. Carballo-Bello7, Dmitry Makarov8, Michael A. Beasley4,5, Giuseppe Donatiello9, Martha P. Haynes10, Duncan A. Forbes11, and Aaron J. Romanowsky12,13 1 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr.
    [Show full text]
  • The SPLASH Survey: Internal Kinematics, Chemical Abundances
    Draft version October 29, 2018 Preprint typeset using LATEX style emulateapj v. 2/19/04 THE SPLASH SURVEY: INTERNAL KINEMATICS, CHEMICAL ABUNDANCES, AND MASSES OF THE ANDROMEDA I, II, III, VII, X, AND XIV DSPHS1,2 Jason S. Kalirai3, Rachael L. Beaton4, Marla C. Geha5, Karoline M. Gilbert6,7, Puragra Guhathakurta7, Evan N. Kirby7,8,9, Steven R. Majewski4, James C. Ostheimer4, Richard J. Patterson4, and Joe Wolf10 Draft version October 29, 2018 ABSTRACT We present new Keck/DEIMOS spectroscopic observations of hundreds of individual stars along the sightline to Andromeda’s first three discovered dwarf spheroidal galaxies (dSphs) – And I, II, and III, and leverage recent observations by our team of three additional dSphs, And VII, X, and XIV, as a part of the SPLASH Survey (Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo). Member stars of each dSph are isolated from foreground Milky Way dwarf and M31 field contamination using a variety of photometric and spectroscopic diagnostics. Our final spectroscopic sample of member stars in each dSph, for which we measure accurate radial velocities with a median uncertainty (random plus systematic errors) of 4 – 5 km s−1, includes 80 red giants in And I, 95 in And II, 43 in And III, 18 in And VII, 22 in And X, and 38 in And XIV. The sample of confirmed members in the six dSphs are used to derive each system’s mean radial velocity, intrinsic central velocity dispersion, mean abundance, abundance spread, and dynamical mass. This combined data set presents us with a unique opportunity to perform the first systematic comparison of the global properties (e.g., metallicities, sizes, and dark matter masses) of one-third of Andromeda’s total known dSph population with Milky Way counterparts of the same luminosity.
    [Show full text]
  • Roadmap for Astronomy in Switzerland 2007-2016
    Roadmap for Astronomy in Switzerland 2007– 2016 Cover picture: Marsflash Till Credner, AlltheSky.com Contents 3 Preface The purpose and scope of this document 6 Executive Summary 8 Summary list of the Roadmap Statements, Findings and Recommendations Chapter 1 13 Why is astronomy important today? Chapter 2 20 The broader context of Swiss astrophysics Chapter 3 29 Building on a strong foundation: Swiss astronomy in the past decade Chapter 4 41 The future scientific development of Swiss astrophysics Chapter 5 71 Transforming professional astrophysics education in Switzerland Chapter 6 74 Making science possible: Technology development for astronomy Chapter 7 82 Sharing the excitement: Public education and outreach 86 Concluding Remarks Appendix A 88 Research Networks Appendix B 91 List of acronyms and project names Roadmap for Astronomy 2007-2016 1 A Hubble Space Telescope image of a small region of M27, the Dumbell Nebula, showing small dense knots of gas ejected by the dying star, each containing a few times the mass of the Earth. NASA/ESA Preface The purpose and scope of this document Who was this document prepared by? We are the College of Helvetic Astronomy Profes- sors (CHAPS) which represents the full range of This Roadmap for Astronomy 2007-2016 was pre- astronomical interests within our community, and is pared by the 21 elected Professors in Astrophys- small enough that all members were strongly in- ics at Swiss universities, plus representatives of volved in the production of the Roadmap. The three independent laboratories: IRSOL,
    [Show full text]
  • Sternwarten Und Schutzbauten
    www.vds-astro.de ISSN 1615-0880 I/2016 Nr. 56 Zeitschrift der Vereinigung der Sternfreunde e.V. Schwerpunktthema: Sternwarten und Aktuelle Astrofotografie Irisierende Wolken Simulation von PX Cephei Seite 62 Seite 74 Seite 120 Schutzbauten Editorial 1 Liebe Mitglieder, liebe Sternfreunde, wenn Sie dieses Heft aufblättern, wurde ein Rätsel gelöst. Denn Ende Novem- ber ist der Komet C/2013 US10 (Catalina) für Beobachter auf der Nordhalbkugel in der Morgendämmerung aufgetaucht. Sofort schossen die Spekulationen in die Höhe: Wie hell wird er werden? Wird man den Kometen mit bloßem Auge sehen können? Beschert uns der Himmel einen „Weihnachtskometen“? Jetzt, Unser Titelbild: Mitte Januar, kann man bequem die Prognosen der Kometen-Community ins Der Mai ist gekommen, die Schutz- eigene Auge fassen: „Catalina“ zieht an der Deichsel des Großen Wagens vor- bauten schlagen aus: Ob Schiebe- bei, er ist zirkumpolar und damit die ganze Nacht zu sehen. Zumindest einen dachhütte oder klassische Kuppel – schönen Fernglas-Kometen sollte man dann beobachten können. die Sternwarte im eigenen Garten ist nicht nur für die Beobachtung nützlich, Ganz abseits jeder Spekulation verlief hingegen die 32. VdS-Tagung und sie kann sogar der Gartengestaltung Mitgliederversammlung am 21./22. November 2015. Dank der hervorra- dienen, wie diese Aufnahme von Reiner genden Organisation durch die Sternfreunde Braunschweig-Hondelage und Guse zeigt. Den Bericht zu diesem Bild zahlreicher interessanter Vorträge werden die Teilnehmer der Tagung die- lesen Sie ab Seite 45. se Veranstaltung in sehr guter Erinnerung behalten. Als neuer Vorstand wurden die bisherigen Vorstandsmitglieder im Amt bestätigt. Einen kurzen Blick auf die Tagung wirft der Beitrag auf Seite 5.
    [Show full text]
  • 1 Introduction
    CONFERENCE SUM1V1ARY B.E.J. Pagel 1 1 NORD/TA, Copenhagen, Denmark. Abstract Some highlights of the conference are noted and commented on, especially abundances and chemical evolution and some problems relating to the overall cosmic abundance of heavy elements. 1 Introduction A previous meeting on dwarf galaxies was held at OHP nearly 5 years ago. At that meeting there were two concluding summaries, one from an observational point of view by Paul Hodge and the other from a theoretical point of view by Donald Lynden-Bell, who ended the conference with a disquisition on anti-tank weapons. Several of the issues discussed at that meeting have also come up at this one, e.g. dark matter, star formation histories, chemical abundances, gas distribution and dynamics, clustering properties and environmental effects. Apart from 5 years' worth of advances in these and other relatively traditional fields , the most striking change at the present meeting is a dramatic advance in the cosmological con­ nection. resulting from the CF and AAT red-shift surveys, HST observations including the Hubble Deep Field and the detailed studies of interveningiabsorption-line systems in front of quasars. Red-shift surveys have shown that irregular star-forming galaxies are the ones having the strongest cosmological evolution at moderate red-shifts, but to what extent these can- be classed as dwarfs is controversial. The maintopics covered at this meetingwere: Statistical properties of local dwarfs, Intrinsic properties reievant to cosmoiogy, Properties at significant iook-back times, ivi odeis and theory and Prospects with new instrumentation. In this brief summary I can only comment briefly on what s�ruck me being some of the highlights.
    [Show full text]
  • Issue 10 14 August 2015
    THE MILKY WAY Kai‘aleleiaka � Issue 10 � 14 August 2015 Wally Pacholka / AstroPics.com TABLE OF CONTENTS Resolution, Not Revolution, for the Next Triennium ............................................... 2 Hooray for Hands-on Science! ...................................................................................21 A New Tally of Individual IAU Members .................................................................... 3 Don’t Miss CAP 2016 in South America! .................................................................22 IAU Signs Agreements for Five New Coordinating Offices ................................. 5 Inspiring Every Child with Our Wonderful Universe .............................................23 On the ROAD in Armenia .............................................................................................. 6 The Social Network ......................................................................................................24 Astronomy Education and Development ...................................................................7 Exploring the Local Universe .....................................................................................25 Applause for Every Shiny Meteor ............................................................................... 9 The Intergalactic Medium ...........................................................................................26 New IAU Division Steering Committees .................................................................... 9 Hawaiian, Oceanic, and Global
    [Show full text]
  • Dwarf Galaxy Types (≤ 1/100 L ; MV ≥ –18) the Galaxy Content of the Local Group
    [copyrighted background image removed] 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 1 Dwarf Galaxy Types (≤ 1/100 L★; MV ≥ –18) The Galaxy Content of the Local Group ❏ Dwarf elliptical galaxies Certain or probable members: Early-type dwarfs. ≥ 104 galaxies within R ~ 1 Mpc. dEs ❏ Dwarf spheroidal galaxies Gas-deficient and now largely quiescent. 0 dIrrs § 3 spiral galaxies (~ 95% mass). dIrrs spirals ❏ Ultra-compact dwarf galaxies } High-density regions preferred. /dSphs § ≥ 101 dwarf and satellite galaxies ❏ Dwarf spirals / dwarf lenticulars Late-type dwarfs. (typically, MV ≥ –18). ❏ Dwarf irregular galaxies Gas-rich and usually star-forming. § Some satellites have own satellites... ❏ Blue compact dwarf galaxies Low-density regions preferred. } dE dSph dIrr dSphs ❏ Ultra-diffuse galaxies ❏ Tidal dwarf galaxies Pictures not on same scale dE dSph UCD dS0, dS dIrr BCD Gas-deficient, late-type dwarf galaxies: dwarf elliptical (dEs: 3; 1 cE) & dwarf spheroidal galaxies (dSphs: ≥ 83) Gas-rich, early-type dwarf galaxies: dwarf irregular galaxies (dIrrs: 9), transition types (dIrrs/dSphs: 5) 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 2 27.08.2018 Grebel: Dwarf Galaxies in the Local Group 3 New Satellites of Size – Luminosity Relation Morphology- the Milky Way density ❑ New discoveries mainly have mainly very low surface brightnesses. and M31 by Year relation ❑ Note overlap between GC −2 ❑ and dSph locus in L (M ) After Muñoz et al. 2018 of Publication V Blue points: GCs. −2 −2 Mainly thanks to large = 18 mag arcsec 26 mag V imaging surveys in the μ arcsec northern hemisphere 22 mag arcsec Grebel 2017 (esp.
    [Show full text]
  • 7. Dwarf Galaxies
    29.04.2018 I. Satellite Galaxies 1 1. DGs around the Milky Way The Magellanic Clouds: LMC and SMC 2 1 29.04.2018 1.1. The Magellanic System On the southern sky 2 large diffuse and faint patches are optically visible: 3 The Magellanic Clouds Small Magellanic Cloud (SMC); dIrr; dist.: ~ 58 kpc 4 2 29.04.2018 Large Magellanic Cloud (LMC), dIrr; dist.: ~ 58 kpc 5 optical : stars + lumin. gas 1.2. The many faces of the LMC Star-forming Regions: H 6 HI withl21cm 3 29.04.2018 (J. van Loon) 4/29/2018 Cosmic Matter Circuit 8 (J. van Loon) 4/29/2018 Cosmic Matter Circuit 9 4 29.04.2018 (J. van Loon) 4/29/2018 Cosmic Matter Circuit 10 1.3. The LMC, an gas-rich Dwarf Irregular Gakaxy (dIrr) 11 5 29.04.2018 (J. van Loon) 4/29/2018 Cosmic Matter Circuit 12 Panchromatic picture (J. van Loon) 4/29/2018 Cosmic Matter Circuit 13 6 29.04.2018 14 15 7 29.04.2018 The Magellanic Clouds Computer model of a small satellite galaxy orbiting a larger (edge-on) disk galaxy. As the satellite orbits, stars are stripped from the satellite and orbit in the halo of the larger galaxy. (Kathryn Johnston, Wesleyan): see the bending and tumbling of the satellite‘s figure axis! 17 8 29.04.2018 Further evidence for ram pressure: at its front-side LMC gas is compressed leading to molecular cloud formation triggered star formation Star-forming regions: H 18 Hot Supernova Gas: X-ray (J.
    [Show full text]
  • L33 an Internal Second-Parameter Problem in the Sculptor Dwarf Spheroidal Galaxy S. R. Majewski,1 M. H. Siegel, Richard J. Patte
    The Astrophysical Journal, 520:L33±L36, 1999 July 20 q 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. AN INTERNAL SECOND-PARAMETER PROBLEM IN THE SCULPTOR DWARF SPHEROIDAL GALAXY S. R. Majewski,1 M. H. Siegel, Richard J. Patterson, and R. T. Rood Department of Astronomy, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903-0818; [email protected], [email protected], [email protected], [email protected] Received 1999 March 1; accepted 1999 May 18; published 1999 June 22 ABSTRACT We present BV photometry of the Sculptor dwarf galaxy toV 5 22 . These data give evidence for a bimodality in Sculptor's metallicity distribution based on a discontinuity in the luminosities of horizontal-branch (HB) stars and by the presence of two distinct red giant branch (RGB) bumps. A consistent picture of the evolved stars in Sculptor is given by the presence of (1) a metal-poor population of[Fe/H] » 22.3 with an exclusively blue HB and that corresponds to the blueward side of the Sculptor RGB and the more luminous RGB bump, and (2) a less metal-poor population of[Fe/H] » 21.5 required to explain the less luminous red HB, the red side of the RGB, and a second, less luminous RGB bump. Best ®ts to the HB populations are obtained with enhanced oxygen abundances,[O/Fe] » 10.5 . Variations in the global HB and RGB morphology of Sculptor can be explained by differences in the radial distribution of the two different [Fe/H] populations. The presence of these two populations shows that the Sculptor dwarf galaxy has an internal second-parameter problem.
    [Show full text]