DOCSLIB.ORG

Galaxies 626

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Galaxies 626 GALAXIES 626 The Local Group: Why is the local group interesting? Can study the dynamics of the group and how it relates to the individual galaxies Can find the faintest galaxies and study their dark matter properties, stellar populations and star formation histories Can look in detail at the disruption and merging processes in galaxies GALAXIES 626 The Local Group is a fairly typical weak group so very characteristic of the environments in which many galaxies live ·Sparse group with zero- velocity radius of Local Group Substruct1u Mrpce ·M31 approaching at 120 km/s ·Reliable orbits unknown The Local Group of Galaxies · about 35-40 member galaxies · Milky Way and Andromeda subgroups 5 The least luminous galaxies known are in the local group 6 NGC 6822 Local Group LSB galaxy in near-IR. HI map has 20 pc resolution 7 Milky Way & M31 Satellites Galaxy Type Dist. (kpc) Galaxy Type Dist. (kpc) SMC SB(s)m 64 NGC 147 dE5 735 Sculptor dSph 92 And III dSph 889 Phoenix dIrr 490 NGC 185 dE3 705 Fornax dSph 153 M110 E5 889 LMC SB(s)m 55 And VIII dSph 828 Carina dSph 110 M32 E2 889 Canis Major dIrr 7.7 And I dSph 889 Leo A Ibm V 767 And V dSph 889 Leo I dE3 276 And II dSph 889 Sextans dSph 98 And VII dSph 797 Leo II dSph 230 And VI dSph 858 Ursa Minor dSph 74 Draco dSph 89 SagDEG dSph 27 Morphological Segregation Gas-poor, low-mass dwarfs (dSphs) tend to cluster around massive galaxies (Cetus & Tucana are exceptions) Gas-rich, high-mass dwarfs (dIs) are found to be widely distributed Observed in nearby groups and clusters as Grebel 2005 well as the Local Group Do these trends result from morphological transformations due to the influence of the massive primary galaxy? (i.e. tidal or ram pressure stripping) Dark Matter in M31 and the Milky Way The first thing we would like to do is see if there is more dark matter in the big spiral galaxies than we are inferring from the rotation curves. That is: do the dark halos extend beyond the maximum radius at which we can measure the rotation curve? 10 How large and massive are the dark halos of large spirals like the Milky Way ? Flat rotation curves => M(r) ~ r, like the isothermal sphere : ρ ~ r-2 This cannot go on for ever - the halo mass would be infinite. Halos must have a finite extent and mass, and their density distribution must truncate or be steeper than ρ ~ r-3 at very large radius 11 Tracers of dark matter in the Galaxy (rotation curve to ~ 20 kpc, kinematics of metal poor stars, globular clusters and satellites out to ~ 50 kpc) indicate that the halo mass M(r) = r(kpc) x 1010 solar masses. Again, this is what we expect if ρ ~ r-2 ie the rotation curve stays approximately flat at 220 km/s out to 50 kpc. How large are dark halos - how far in radius do they extend ? 12 M31 and the Milky Way are now M31 approaching at 118 km s -1. Their separation is about 750 kpc To acquire this velocity of approach in the life of the universe means that the total mass of the Milky Way is at least 13 x 10 11 M_sun. The stellar mass is about 6 x 1010 M_sun, so the ratio 118 km s -1 of dark to stellar mass is ~ 20 Milky Way The dark halo extends out to ~ 150 kpc, far beyond the disk©s radius of ~ 20 kpc 13 Timing argument M31 (Andromeda) is now approaching the Galaxy at 118 km s-1. Its distance is about 750 kpc. Assuming their initial separation was small and the age of the universe is say 18 Gyr, we can estimate a lower limit on the total mass of the Andromeda + Galaxy system. The Galaxy's share of this mass is (13 ± 2) x 1011 solar masses. A similar argument using the Leo I dwarf at a distance of about 230 kpc gives (12 ± 2) x 1011 solar masses. 14 The relation for the mass of the galactic halo M(r) = r (kpc) x 1010 solar masses out to r ~ 50 kpc then indicates that the dark halo extends out beyond r = 120 kpc if the rotation curve remains flat ie if ρ(r) ~ r -2 and possibly much further than 120 kpc if the density distribution declines more rapidly at large radius 15 This radius is much larger than the extent of any directly measured rotation curves, so this ªtiming argumentº gives a realistic lower limit on the total mass of the dark halo. For our Galaxy, the luminous mass (disk + bulge) is about 6 x 1010 solar masses The luminosity is about 2 x 1010 solar luminosities The ratio of total dark mass to stellar mass is then at least 120/6 = 20 and the total M/L ratio is at least 60 16 Satellites of disk galaxies can also be used to estimate the total mass and extent of the dark halos of other bright spirals Individual galaxies have only a few observable satellites each, but we can make a super-system by combining observations of many satellite systems and so get a measure of the mass of a typical dark halo. 17 Velocities |∆V| of 3000 satellites relative to their parent galaxy error bars show the velocity dispersion decreasing with radius out to ~ 300 kpc ! 18 With a careful treatment of interlopers, they find that the velocity dispersion of the super-satellite-system decreases slowly with radius The halos typically extend out to about 300 kpc but the density distribution at large radius is steeper than the isothermal: ρ(r) ~ r -3, like most cosmological models including NFW The total M/L ratios are typically 100-150, compared with the lower limit from the timing argument of 60 for our Galaxy. (The Prada galaxies are bright systems, comparable to the Galaxy) 19 M31 has a similar rotation amplitude so its total mass may be similar to the total mass of the Galaxy. Evans & Wilkinson (2000) used satellites and GCs +3.6 12 in M31 to derive a lower mass of 1.2 -1.7 x 10 M for M31 - similar to the Galaxy, within the uncertainties So the total mass of MW + M31 ~ 3 x 1012 M For comparison, from least action arguments, the likely mass of the local group is 4-8 x 1012 M Within the uncertainties, most of the mass in the Local Grou20 p could be in the two large spirals Conclusion The total mass of the Milky Way is ~ 1.5 x 1012 M The MW is one of the few galaxies for which we have an estimate of the total mass, rather than just the mass out to the end of a rotation curve. The stellar mass is about 6 x 1010 M So the stellar baryons are only about 4% of the total mass Ω Ω Compare this with the universal baryon / matter = 15% 21 GALAXIES 626 The satellite galaxies in the Local group can also be used to look at the issue of the dark matter halo substructure 23 Dark Halo Substructure In simulations of galaxy formation, the virialized halos are quite lumpy, with a lot of substructure - a lot more satellites and dwarf galaxies than observed. From simulations, we would expect a galaxy like the Milky Way to have ~ 500 satellites with bound masses > 108 M . These are not seen optically or in HI. What is wrong ? Could be a large number of baryon-depleted dark satellites, or some problem with details of CDM or could we missing lots of faint satellites? 24 The 21 known satellites of the MW - some discovered recently 25 Planar distribution! In dissipationless simulation, satellites are preferentially aligned along the major axes of the host©s triaxial mass distribution. Consistent with planarity of the MW satellite system, if major axis of the MW mass distribution is ~ perpendicular to the disk. The anisotropy is associated partly with accretion of satellites along filaments and partly due to evolution of satellites in the triaxial potential. Similar planar distribution for the early-type satellites around M31 26 Abundance predicted for CDM sub-halos vs. observed for Milky Way dwarfs 27 If the satellites are there, why haven't we found them? Very low surface brightness Accretion events High foreground extinction Unknown orbits for distant Local Group candidates Scarcity of stars¼ If the satellites are there, why haven't we found them? Found via data mining techniques mv=14.4, Mv=-10.1 DMW=775±50 kpc, DLG=615±40 kpc Fe/H = -1.9±0.2 If the satellites are there, why haven't we found them? Very low surface brightness Accretion events High foreground extinction (like ZOA) Unknown orbits for distant Local Group candidates Scarcity of stars¼ If the satellites are there, why haven't we found them? Canis Major Dwarf (?) Martin et al 2004 Evidence for Mergers & Accretion If primary mechanism for growth of large galaxies is accretion of low-mass dwarfs, we should find evidence of present-day merger events in the Local Group. Evidence for Mergers & Accretion On-going Accretion: · Sagittarius dSph galaxy · Metal-rich giants in M31 halo Stellar Overdensities: · Monoceros feature (possible tail connected to Canis Major overdensity) · Triangulum-Andromeda (possible tail of more distant dwarf) Twists & Distortions: · Ursa Minor shows distorted, S-shaped surf density profile If the satellites are there, why haven't we found them? Very low surface brightness Accretion events High foreground extinction (like ZOA) Unknown orbits for distant Local Group candidates Scarcity of stars¼ If the satellites are there, why haven't we found them? ● IInnccreased extinctnction and stellar foregroround near the galactic planeane limit our ability to dedetect dwarf galaxies there.
Load more

Recommended publications
  • A Revised View of the Canis Major Stellar Overdensity with Decam And
    MNRAS 501, 1690–1700 (2021) doi:10.1093/mnras/staa2655 Advance Access publication 2020 October 14 A revised view of the Canis Major stellar overdensity with DECam and Gaia: new evidence of a stellar warp of blue stars Downloaded from https://academic.oup.com/mnras/article/501/2/1690/5923573 by Consejo Superior de Investigaciones Cientificas (CSIC) user on 15 March 2021 Julio A. Carballo-Bello ,1‹ David Mart´ınez-Delgado,2 Jesus´ M. Corral-Santana ,3 Emilio J. Alfaro,2 Camila Navarrete,3,4 A. Katherina Vivas 5 and Marcio´ Catelan 4,6 1Instituto de Alta Investigacion,´ Universidad de Tarapaca,´ Casilla 7D, Arica, Chile 2Instituto de Astrof´ısica de Andaluc´ıa, CSIC, E-18080 Granada, Spain 3European Southern Observatory, Alonso de Cordova´ 3107, Casilla 19001, Santiago, Chile 4Millennium Institute of Astrophysics, Santiago, Chile 5Cerro Tololo Inter-American Observatory, NSF’s National Optical-Infrared Astronomy Research Laboratory, Casilla 603, La Serena, Chile 6Instituto de Astrof´ısica, Facultad de F´ısica, Pontificia Universidad Catolica´ de Chile, Av. Vicuna˜ Mackenna 4860, 782-0436 Macul, Santiago, Chile Accepted 2020 August 27. Received 2020 July 16; in original form 2020 February 24 ABSTRACT We present the Dark Energy Camera (DECam) imaging combined with Gaia Data Release 2 (DR2) data to study the Canis Major overdensity. The presence of the so-called Blue Plume stars in a low-pollution area of the colour–magnitude diagram allows us to derive the distance and proper motions of this stellar feature along the line of sight of its hypothetical core. The stellar overdensity extends on a large area of the sky at low Galactic latitudes, below the plane, and in the range 230◦ <<255◦.
    [Show full text]
  • Lecture 7: the Local Group and Nearby Clusters
    Lecture 7: the Local Group and nearby clusters • in this lecture we move up in scale, to explore typical clusters of galaxies – the Local Group is an example of a not very rich cluster • interesting topics include: – clusters and the structure of the Universe – the fate of galaxies: stable, destroyed or cannibals? Galaxies – AS 3011 1 the Local Group Galaxies – AS 3011 2 1 Inner Solar System Galaxies – AS 3011 3 Galaxies – AS 3011 4 2 some Local Group galaxies, roughly to the same physical scale: M31, Leo I LMC, M32 SMC MW M33 (images courtesy AAO) Galaxies – AS 3011 5 first impressions • there are some obvious properties of the Local Group: – it’s mostly empty, i.e. galaxies are quite distant from each other – with some exceptions like satellite galaxies – the three spirals are easily the biggest – dwarf galaxies are on the outskirts of the group • how typical is this of other galaxy groups? – turns out that the Local group is not very rich in galaxies Galaxies – AS 3011 6 3 groups and clusters • groups contain a smaller number of galaxies than clusters, and are more compact in both space and velocity spread: group: cluster: no. galaxies ~10+ >50 core radius ~300 kpc ~300 kpc median radius ~1 Mpc ~ 3Mpc v-dispersion 150 km/s 800 km/s M/L ~200 ~200 13 15 total mass few 10 Msolar few 10 Msolar Galaxies – AS 3011 7 classifying the Local Group • the Local Group has only about 10 significant galaxies 8 (L > 10 Lsolar), so does not qualify as a cluster – NB, dwarf spheroidals etc.
    [Show full text]
  • Introduction to Astronomy from Darkness to Blazing Glory
    Introduction to Astronomy From Darkness to Blazing Glory Published by JAS Educational Publications Copyright Pending 2010 JAS Educational Publications All rights reserved. Including the right of reproduction in whole or in part in any form. Second Edition Author: Jeffrey Wright Scott Photographs and Diagrams: Credit NASA, Jet Propulsion Laboratory, USGS, NOAA, Aames Research Center JAS Educational Publications 2601 Oakdale Road, H2 P.O. Box 197 Modesto California 95355 1-888-586-6252 Website: http://.Introastro.com Printing by Minuteman Press, Berkley, California ISBN 978-0-9827200-0-4 1 Introduction to Astronomy From Darkness to Blazing Glory The moon Titan is in the forefront with the moon Tethys behind it. These are two of many of Saturn’s moons Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA 2 Introduction to Astronomy Contents in Brief Chapter 1: Astronomy Basics: Pages 1 – 6 Workbook Pages 1 - 2 Chapter 2: Time: Pages 7 - 10 Workbook Pages 3 - 4 Chapter 3: Solar System Overview: Pages 11 - 14 Workbook Pages 5 - 8 Chapter 4: Our Sun: Pages 15 - 20 Workbook Pages 9 - 16 Chapter 5: The Terrestrial Planets: Page 21 - 39 Workbook Pages 17 - 36 Mercury: Pages 22 - 23 Venus: Pages 24 - 25 Earth: Pages 25 - 34 Mars: Pages 34 - 39 Chapter 6: Outer, Dwarf and Exoplanets Pages: 41-54 Workbook Pages 37 - 48 Jupiter: Pages 41 - 42 Saturn: Pages 42 - 44 Uranus: Pages 44 - 45 Neptune: Pages 45 - 46 Dwarf Planets, Plutoids and Exoplanets: Pages 47 -54 3 Chapter 7: The Moons: Pages: 55 - 66 Workbook Pages 49 - 56 Chapter 8: Rocks and Ice:
    [Show full text]
  • Winter Constellations
    Winter Constellations *Orion *Canis Major *Monoceros *Canis Minor *Gemini *Auriga *Taurus *Eradinus *Lepus *Monoceros *Cancer *Lynx *Ursa Major *Ursa Minor *Draco *Camelopardalis *Cassiopeia *Cepheus *Andromeda *Perseus *Lacerta *Pegasus *Triangulum *Aries *Pisces *Cetus *Leo (rising) *Hydra (rising) *Canes Venatici (rising) Orion--Myth: Orion, the great ​ ​ hunter. In one myth, Orion boasted he would kill all the wild animals on the earth. But, the earth goddess Gaia, who was the protector of all animals, produced a gigantic scorpion, whose body was so heavily encased that Orion was unable to pierce through the armour, and was himself stung to death. His companion Artemis was greatly saddened and arranged for Orion to be immortalised among the stars. Scorpius, the scorpion, was placed on the opposite side of the sky so that Orion would never be hurt by it again. To this day, Orion is never seen in the sky at the same time as Scorpius. DSO’s ● ***M42 “Orion Nebula” (Neb) with Trapezium A stellar ​ ​ ​ nursery where new stars are being born, perhaps a thousand stars. These are immense clouds of interstellar gas and dust collapse inward to form stars, mainly of ionized hydrogen which gives off the red glow so dominant, and also ionized greenish oxygen gas. The youngest stars may be less than 300,000 years old, even as young as 10,000 years old (compared to the Sun, 4.6 billion years old). 1300 ly. ​ ​ 1 ● *M43--(Neb) “De Marin’s Nebula” The star-forming ​ “comma-shaped” region connected to the Orion Nebula. ● *M78--(Neb) Hard to see. A star-forming region connected to the ​ Orion Nebula.
    [Show full text]
  • References and for Further Reading
    Contents Preface. vii Acknowledgements. ix About the Author . xi Chapter 1 A Short History of Planetary Nebulae. 1 Further Discoveries. 1 The Nature of the Nebulae and Modern Catalogues . 3 Chapter 2 The Evolution of Planetary Nebulae . 7 The Lives of the Stars . 7 Stages in the Life Cycle of a Sun-like Star . 9 The Asymptotic Giant Branch . 10 Proto-Planetary Nebulae and Dust. 12 Interactive Winds. 13 Emissions from Planetary Nebulae. 14 Central Stars. 16 Planetary Envelopes . 17 Binary Stars and Magnetic Fields . 19 Lifetimes of Planetary Nebulae . 21 Conclusion . 21 Chapter 3 Observing Planetary Nebulae . 23 Telescopes and Mountings . 23 Telescope Mounts. 26 Eyepieces. 27 Limiting Magnitudes and Angular Resolution . 29 Transparency and Seeing . 31 Dark Adaptation and Averted Vision . 32 Morphology of Planetary Nebulae . 33 Nebular Filters . 35 Star Charts, Observing and Computer Programs. 38 Observing Procedures. 42 Chapter 4 Photographing Planetary Nebulae. 45 Camera Equipment . 45 Software. 48 Filters for Astrophotography . 49 Contents Shooting . 50 Conclusion . 53 xiii Chapter 5 Planetary Nebulae Catalogues . 55 Main Planetary Nebulae . 56 Additional Planetary Nebulae . 58 Chapter 6 Planetary Nebulae by Constellation. 81 Andromeda. 83 Apus. 85 Aquarius . 87 Aquila . 90 Ara . 103 Auriga . 106 Camelopardalis . 108 Canis Major . 111 Carina . 113 Cassiopeia . 119 Centaurus . 123 Cepheus. 126 Cetus . 129 Chameleon . 131 Corona Australis . 133 Corvus. 135 Cygnus. 137 Delphinus . 154 Draco . 157 Eridanus . 160 Fornax . 162 Gemini. 164 Hercules . 170 Hydra. 174 Lacerta. 178 Leo . 180 Lepus . 182 Lupus . 184 Lynx . 190 Lyra . 192 Monoceros . 195 Musca. 198 Norma . 203 Ophiuchus. 205 Orion . 211 Pegasus . 214 Perseus. 219 Puppis .
    [Show full text]
  • Arxiv:0807.0009V2
    Draft version October 29, 2018 A Preprint typeset using LTEX style emulateapj v. 08/22/09 THE RESOLVED PROPERTIES OF EXTRAGALACTIC GIANT MOLECULAR CLOUDS Alberto D. Bolatto1, Adam K. Leroy2, Erik Rosolowsky3,4, Fabian Walter2, & Leo Blitz5 Draft version October 29, 2018 ABSTRACT We use high spatial resolution observations of CO to systematically measure the resolved size-line width, luminosity-line width, luminosity-size, and the mass-luminosity relations of Giant Molecular Clouds (GMCs) in a variety of extragalactic systems. Although the data are heterogeneous we analyze them in a consistent manner to remove the biases introduced by limited sensitivity and resolution, thus obtaining reliable sizes, velocity dispersions, and luminosities. We compare the results obtained in dwarf galaxies with those from the Local Group spiral galaxies. We find that extragalactic GMC properties measured across a wide range of environments are very much compatible with those in the Galaxy. The property that shows the largest variability is their resolved brightness temperature, although even that is similar to the average Galactic value in most sources. We use these results to investigate metallicity trends in the cloud average column density and virial CO-to-H2 factor. We find that these measurements do not accord with simple predictions from photoionization-regulated star formation theory, although this could be due to the fact that we do not sample small enough spatial scales or the full gravitational potential of the molecular cloud. We also find that the virial CO-to-H2 conversion factor in CO-bright GMCs is very similar to Galactic, and that the excursions do not show a measurable metallicity trend.
    [Show full text]
  • Naming the Extrasolar Planets
    Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named.
    [Show full text]
  • Long-Period Variables in NGC 147 and NGC 185⋆
    A&A 532, A78 (2011) Astronomy DOI: 10.1051/0004-6361/201116951 & c ESO 2011 Astrophysics Long-period variables in NGC 147 and NGC 185 D. Lorenz1, T. Lebzelter1,W.Nowotny1, J. Telting2, F. Kerschbaum1,H.Olofsson3,4, and H. E. Schwarz 1 University of Vienna, Department of Astronomy, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: [email protected] 2 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain 3 Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden 4 Onsala Space Observatory, 43992 Onsala, Sweden Received 24 March 2011 / Accepted 25 May 2011 ABSTRACT Context. Previous studies on the stellar content of the two nearby dwarf galaxies NGC 147 and NGC 185 reveal a rich population of late-type giants in both systems, including a large number of carbon-rich objects. These stars are known to show pronounced photo- metric variability, which can be used for a more detailed characterisation of these highly evolved stars. Owing to their well-studied parameters, these Local Group members are ideal candidates for comparative studies. Aims. Through photometric monitoring, we attempt to provide a catalogue of long-period variables (LPVs), including Mira variables, semi-regular variables, and even irregular variables in NGC 147 and NGC 185. We investigate the light variations and compare the characteristics of these two LPV populations with the results found for other galaxies, such as the LMC. Methods. We carried out time-series photometry in the i-band of the two target galaxies with the Nordic Optical Telescope (NOT), covering a time span of ≈2.5 years.
    [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]
  • Annual Report 2005
    Max Planck Institute t für Astron itu o st m n ie -I k H c e n id la e l P b - e x r a g M M g for Astronomy a r x e b P l la e n id The Max Planck Society c e k H In y s m titu no Heidelberg-Königstuhl te for Astro The Max Planck Society for the Promotion of Sciences was founded in 1948. It operates at present 88 Institutes and other facilities dedicated to basic and applied research. With an annual budget of around 1.4 billion € in the year 2005, the Max Planck Society has about 12 400 employees, of which 4300 are scientists. In addition, annually about 11000 junior and visiting scientists are working at the Institutes of the Max Planck Society. The goal of the Max Planck Society is to promote centers of excellence at the fore- front of the international scientific research. To this end, the Institutes of the Society are equipped with adequate tools and put into the hands of outstanding scientists, who Annual Report have a high degree of autonomy in their scientific work. 2005 Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. 2005 Public Relations Office Hofgartenstr. 8 80539 München Tel.: 089/2108-1275 or -1277 Annual Report Fax: 089/2108-1207 Internet: www.mpg.de Max Planck Institute for Astronomie K 4242 K 4243 Dossenheim B 3 D o s s E 35 e n h e N i eckar A5 m e r L a n d L 531 s t r M a a ß nn e he im B e e r r S t tr a a - K 9700 ß B e e n z - S t r a ß e Ziegelhausen Wieblingen Handschuhsheim K 9702 St eu b A656 e n s t B 37 r a E 35 ß e B e In de A5 r r N l kar ec i c M Ne k K 9702 n e a Ruprecht-Karls- ß lierb rh
    [Show full text]
  • Two Stellar Components in the Halo of the Milky Way
    1 Two stellar components in the halo of the Milky Way Daniela Carollo1,2,3,5, Timothy C. Beers2,3, Young Sun Lee2,3, Masashi Chiba4, John E. Norris5 , Ronald Wilhelm6, Thirupathi Sivarani2,3, Brian Marsteller2,3, Jeffrey A. Munn7, Coryn A. L. Bailer-Jones8, Paola Re Fiorentin8,9, & Donald G. York10,11 1INAF - Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy, 2Department of Physics & Astronomy, Center for the Study of Cosmic Evolution, 3Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI 48824, USA, 4Astronomical Institute, Tohoku University, Sendai 980-8578, Japan, 5Research School of Astronomy & Astrophysics, The Australian National University, Mount Stromlo Observatory, Cotter Road, Weston Australian Capital Territory 2611, Australia, 6Department of Physics, Texas Tech University, Lubbock, TX 79409, USA, 7US Naval Observatory, P.O. Box 1149, Flagstaff, AZ 86002, USA, 8Max-Planck-Institute für Astronomy, Königstuhl 17, D-69117, Heidelberg, Germany, 9Department of Physics, University of Ljubljana, Jadronska 19, 1000, Ljubljana, Slovenia, 10Department of Astronomy and Astrophysics, Center, 11The Enrico Fermi Institute, University of Chicago, Chicago, IL, 60637, USA The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, which can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for is dichotomy has slowly emerged in recent years from inspection of small samples of halo objects. Here we show that the halo is indeed clearly divisible into two broadly overlapping structural components -- an inner and an outer halo – that exhibit different spatial density profiles, stellar orbits and stellar metallicities (abundances of elements heavier than helium).
    [Show full text]
  • 1410.0681V1.Pdf
    ACCEPTED FOR PUBLICATION IN THE ASTROPHYSICAL JOURNAL Preprint typeset using LATEX style emulateapj v. 05/12/14 THE QUENCHING OF THE ULTRA-FAINT DWARF GALAXIES IN THE REIONIZATION ERA1 THOMAS M. BROWN2, JASON TUMLINSON2, MARLA GEHA3, JOSHUA D. SIMON4,LUIS C. VARGAS3,DON A. VANDENBERG5,EVAN N. KIRBY6, JASON S. KALIRAI2,7,ROBERTO J. AVILA2, MARIO GENNARO2,HENRY C. FERGUSON2 RICARDO R. MUÑOZ8,PURAGRA GUHATHAKURTA9, AND ALVIO RENZINI10 Accepted for publication in The Astrophysical Journal ABSTRACT We present new constraints on the star formation histories of six ultra-faint dwarf galaxies: Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I. Our analysis employs a combination of high-precision photometry obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, medium-resolutionspectroscopy obtained with the DEep Imaging Multi-Object Spectrograph on the W.M. Keck Observatory, and updated Victoria-Regina isochrones tailored to the abundance patterns appropriate for these galaxies. The data for five of these Milky Way satellites are best fit by a star formation history where at least 75% of the stars formed by z ∼ 10 (13.3 Gyr ago). All of the galaxies are consistent with 80% of the stars forming by z ∼ 6 (12.8 Gyr ago) and 100% of the stars forming by z ∼ 3 (11.6 Gyr ago). The similarly ancient populations of these galaxies support the hypothesis that star formation in the smallest dark matter sub-halos was suppressed by a global outside influence, such as the reionization of the universe. Keywords: Local Group — galaxies: dwarf — galaxies: photometry — galaxies: evolution — galaxies: for- mation — galaxies: stellar content 1.
    [Show full text]