DOCSLIB.ORG

The Milky Way As a Pure-Disk Galaxy Y the Bulge Is Simply the Bar Viewed Edge-On; It Is Part of the Disk, Not a Separate Component

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Milky Way As a Pure-Disk Galaxy Y the Bulge Is Simply the Bar Viewed Edge-On; It Is Part of the Disk, Not a Separate Component EANAM5 (Oct. 29 , 2012 @Kyoto) Structures,,y Dynamics, and Formation of the Milky Way: A Narrow Perspective Juntai Shen (Shanghai Astro. Obs.) 沈俊太 (上海天文台) 1 只 不 緣 識 身 廬 在 山 y . 此 真 山 面 蘇 東 中 目 坡 Outline There is no place like home! y Global properties y Components y Spiral structure y Bars in general y MW’s Bulge/Bar y Classical vs. pseudo bulges y Milkyyy Way’s bulg e y New developments y X-shaped structure 3 Components of the MW y Disk y Thin disk y Thick disk y Bulgg/e / Bar y Halo y Dark matter y Stellar y Gas y Spiral structure 5 Global properties of the MW y Rd ~ 2.5±0.5 kpc 10 y Ltot ~ 330X10 L⊙ y MI = -22.7 y Disk 85% vs. Bulge 15% 10 y Mdisk ~ 5X10 M⊙ y (Flynn et al 2006) 10 y Mtot (R) ~ R(kpc) X 10 M⊙ y Disk stellar (()M/L)R~ 2 (()M/L)⊙ 6 y SMBH ~ 4 X 10 M⊙ y Hubble type: SBbc 6 Solar neighborhood properties y R⊙ ~ 8.0-8.5 kpc y Vcirc ~ 220-245 km/s ? -3 y Disk ρ ~ 0.1 M⊙pc -2 y Disk Σ ~ 50 M⊙/pc y Disk thickness ~ 500 pc y Rotation period ~ 220 Myr y Vertical period ~ sqrt(4*pi*Gρ)~90 Myr 7 Component: thin disk y Scale-height ~ 300pc y Continuous on-going star formation for 10Gyr y Wide range of ages y Metal-rich y >~ solar metallicity 8 Component: thick disk y Scale-height ~ 1 kpc y Stars older; metal-poorer; alpha elements enhanced y Surface density ~ 7% of that of the thin disk y At midp lane, thin /thick stars ~ 50:1 y Created by thickening by an encounter with a smaller galaxy? y Quillen & Garnett 2001 y Is it really a distinct thick disk, z or just a thicker disk component? (Bovy et al. 2012) Gilmore & Reid (1983) 9 Component: stellar halo y Spherical y About 1% of the total stellar mass y Very metal-poor; 0.02Z⊙ y Little mean rotation y ρ~r-3 y Debris of disrupted stellar systems, globular clusters and small satellites? y Inner (<30kpc): in situ star formation? (Font et al. 2011) 10 CtComponent: gas hhlalo y Massive gaseous halo? y Ionized hydrogen at >106K, extends for 100s kpc y Shull et al (2009); Gupta et al (2012) y The missing baryons? 10 y Mass comparable to stars? >10 M⊙ y Reservo ir of gas to cool and fa ll in to the Gal axy y Observed high-speed clouds (HVCs)? y Stuff in and out: same things? y To be confirmed in follow-ups 11 Component : dark matter ha lo y The least well understood y Shape: spherical or triaxial? y Mass & Size y Kinematics of distant GCs and nearby galaxies 12 y Wilkinson & Evans (1999): 2X10 M⊙; rhalf ~ 100 kpc y Xue et al. (2008): blue horizontal-branch halo stars; 12 1X10 M⊙ 12 y Bovy et al. (2012): 0. 85X10 M⊙ 10 y Mtot (R) ~ R(kpc) X 10 M⊙ 12 Component: spiral arms y Very uncertain y How many arms y only two major stellar arms?: the Perseus arm and the Scutum- Centaurus arm (Benjamin et al. 2008) y BeSSel project 13 Spiral structure Contrast global and flocculent spiral structures M 51 NGC 5055 M 83 NGC 2841 14 Flocculent spiral structure y Easy to understand y Differential rotation; strong shear y “Spiral structures are quite natural. Every structural irregularity is likely to be drawn out into a part of a spiral” (Oort 1962) 15 Glo ba l “gran d-didesign” spiilrals y FtFact: observed spiilral arms are always trailing y The winding problem y Not material arms y They are density waves y Lin & Shu 1964 y Some of them are clearly driven by tidal interactions or perhaps bars 16 Self-excited global spirals y Quasi-steady modes y Lin & Shu y Persistence problem: group vel. not 0 y Anti-spiral theorem (Lynden- Bell & Ostriker 1967): y non-steady y dissipational y Short-lived, transient, recurrent y Today’s grand-design spirals have not been in M74 place in HDF. If a steady-state solution of a time- y reversible set of equations has the Swing amplifying of form of a trailing spiral, then there unsmooth distribution must be an identical solution in the func. (see Sellwood 2010) form of a leading spiral 17 Testing spiral structure theories y EtExpect to fifidnd a progression: y cold HI gas and CO y H2 and 24-μm emission from stars forming in clouds y the UV emission of fully formed and unobscured stars. y Both theories can have density waves surviving much longer than the TSF y Foyle et al. 2011: no systematic offsets y Observational evidence against long-lived spiral arms in galaxies? 18 BdBarred galilaxies y Bars: elongated cigar- shaped features in disk y CdComposed of old stars y Easier to detect bars in near infrared y Ubiquitous: ~ 2/3 of disk galaxies are barred y Latest NIR survey (Eskridge et al. 2000) y More normal than “normal” disk galaxies! y Bar pattern rotates rapidly 19 Impact of bars on galaxy evolution y Strongest internal disturber: influence disk, bulge, and dark matter halo y Drive gas flow inward y Ignite circum-nuclear starbursts y Build up pseudo-bulges y Different from classical bulges y Secular evolution (Kormendy + Kennicutt 2004) y Bars exchange angular momentum with dark matter halos via dynamical friction y Understanding bars is an integral part of understanding galaxy formation and evolution. 20 Making bars in simulations y Spontaneous bar instability y if ordered rotation dominates over random motion in the initial disk (dynamically “cold”) (Hohl 1971, Sellwood 1981) y Tidally-induced (e.g. Noguchi 1996) y Formation of real bars may be more sophisticated y Still lots of questions y HlHalo properties are itimportan t y Why 2/3 are barred? 21 Dynamics of bars y Bars are made of elongated x1 orbits y x1 are analogous to z-axis tubes y but veryyg elongated y They are nearly resonant (ILR) orbits that would precess exactly together like if Ωp= Ω –κ/2 y Since Ω –κ/2 is not qqjuite constant with R, it is the job of self-gravity to force the orbits precess exactly together. 22 Bars & ellipticals: fundamentally different! y Bars are tri-axial because of too much angular momentum y Giant ellipticals are tri-axial because of too little angular momentum y Supported by random motions y Mostly boxy orbits y Anggpular momentum is provided in z-axis tube orbits (not very elongated) Boxy O Boxy z -axis t u r bits bes Credit: J. Barnes23 BlBulges We do not fully understand them yet! y Classical bulges y Pseudo-bulges y ≈ Mini-elliptical y Extra light at small R; y Merger-made central thick comp. y Sersic n > 2 y Formed from disk by itinterna l secular y not rotation-dominated processes y Retain some memory of their disk origin y Rotation dominated y Young stars, gas, ddtust y Sersic index 1-2 y Including “boxy bulges” Kormendy & Kennicutt (ARAA, 2004) 24 B/Boxy/peanu t-shdhaped blbulges COBE Near IR image of the Milky Way y Most of bulge stars are old (>5 Gyr, Clarkson et al. 2008) y A wide range of metal abundances (McWilliam & Rich 1994; Fulbright et al. 2006; Zoccali et al. 2008) B/Boxy/peanu t-shdhaped blbulges HCG 87 y ~45% edge-on disks have peanut-shaped bulges (Lutticke et al. 2000) y Comparable to the fraction of bars 26 Boxy peanut-shaped bulges: side-on bars? y Simulation of bended/thickened bars y Buckling/firehose instability (Toomre 1966) σ Z ≤ 0.3σ R y Bar formation Æ Buckling instability Æ saturation Æ B/PS bulges (e.g. Raha, Sellwood et al. 1991) Buc kling inst abilit y and ellipti cal s y Possible explains why there are no ellipticals more elongated than E6 or E7, corresponding to a maximum axis ratio of about 3:1. y Sufficiently thick Æ low κz Æ disturbances damped Merritt & Hernquist 1991 Stellar Kinematics of the Bulge y BRAVA ((gBulge Radial Velocity Assay) y)y survey y ~10,000 M giants as targets y Stellar kinematics coveringgg the whole Bulge y Build a simple dynamical model to explain it The Milky Way in IR (COBE) 29 Modeling the Milky Way Bulge • A simple model of the Galactic bulge matches the BRAVA data extremely well in almost all aspects: – b = ‐4o major axis – b = ‐8o degree major axis – l = 0o degree minor axis – Surface density Shen, J., et al 2010, ApJL 30 Power of simplicity y High resolution N-body simulations with millions of particles y Cold massive disk, initial Q ~ 1.2 y A pseudo-isothermal rigid halo with a core which gives a nearly flat rotation curve of ~220 km/s from 5 to 20 kpc y Inside solar circle, Mdisk/Mhalo ~ 151.5, max disk y A good starting point 31 Modelinggyyg the Milky Way Bulge --- Surface Brightness Map Sun DIRBE Composite map – The bar ang le from kinema tic cons tra in t is a bou t ~ 20o – The bar’s axial ratio is about 0.5 to 0.6, andShen, its half-length J., et al 2010,is ~4kpc ApJL 32 Mo de ling the Milky Way Bu lge --- Match stellar kinematics in all strippgys strikingly well Black line = model; it is not a fit to data points Shen, J., et al 2010, ApJL 33 Modeling the Milky Way Bulge --- Constraining the Bar Angle • Bar angle consistent with other studies of star counts and surface brightness (Stanek et al.
Load more

Recommended publications
  • Capricorn (Astrology) - Wikipedia, the Free Encyclopedia
    מַ זַל גְּדִ י http://www.morfix.co.il/en/Capricorn بُ ْر ُج ال َج ْدي http://www.arabdict.com/en/english-arabic/Capricorn برج جدی https://translate.google.com/#auto/fa/Capricorn Αιγόκερως Capricornus - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Capricornus h m s Capricornus Coordinates: 21 00 00 , −20° 00 ′ 00 ″ From Wikipedia, the free encyclopedia Capricornus /ˌkæprɨˈkɔrnəs/ is one of the constellations of the zodiac. Its name is Latin for "horned goat" or Capricornus "goat horn", and it is commonly represented in the form Constellation of a sea-goat: a mythical creature that is half goat, half fish. Its symbol is (Unicode ♑). Capricornus is one of the 88 modern constellations, and was also one of the 48 constellations listed by the 2nd century astronomer Ptolemy. Under its modern boundaries it is bordered by Aquila, Sagittarius, Microscopium, Piscis Austrinus, and Aquarius. The constellation is located in an area of sky called the Sea or the Water, consisting of many water-related constellations such as Aquarius, Pisces and Eridanus. It is the smallest constellation in the zodiac. List of stars in Capricornus Contents Abbreviation Cap Genitive Capricorni 1 Notable features Pronunciation /ˌkæprɨˈkɔrnəs/, genitive 1.1 Deep-sky objects /ˌkæprɨˈkɔrnaɪ/ 1.2 Stars 2 History and mythology Symbolism the Sea Goat 3 Visualizations Right ascension 20 h 06 m 46.4871 s–21 h 59 m 04.8693 s[1] 4 Equivalents Declination −8.4043999°–−27.6914144° [1] 5 Astrology 6 Namesakes Family Zodiac 7 Citations Area 414 sq. deg. (40th) 8 See also Main stars 9, 13,23 9 External links Bayer/Flamsteed 49 stars Notable features Stars with 5 planets Deep-sky objects Stars brighter 1 than 3.00 m Several galaxies and star clusters are contained within Stars within 3 Capricornus.
    [Show full text]
  • Investigation Into the Spatial Distribution of AGN Companion Galaxies in Gravitationally Isolated Environments
    Investigation into the Spatial Distribution of AGN Companion Galaxies in Gravitationally Isolated Environments Janakan Sivasubramanium A Thesis Submitted to The Faculty Of Graduate Studies in Partial Fulfillment of the Requirements for the Degree Of Master of Science Graduate Program in Physics & Astronomy York University Toronto, Ontario September 2018 c Janakan Sivasubramanium, 2018 Abstract Active galaxies are an important subclass of galaxies, distinguished by an energetic core radiating an extraordinary amount of energy. These hyperactive cores, referred to as Active Galactic Nuclei (AGN), are driven by enhanced accretion onto a central supermassive black hole about a million to a billion times the mass of our Sun. Accre- tion onto a supermassive black hole may be a convincing mechanism to explain the extreme properties stemming from an active galaxy, but this proposal inevitably opens up another problem: what source provides the gaseous fuel for black hole accretion? In this research project, we examine the possibility that these active galaxies have engaged in some form of galactic \cannibalism" of their neighbouring galaxies to acquire a fuel supply to power their energetic cores. By using data from the Sloan Digital Sky Survey (SDSS), we conduct an environmental survey around active and non-active galaxies and map out the spatial distribution of their neighbouring galaxies. Our results show that, in gravitationally isolated environments, the local environment (< 0:5 Mpc) around active galaxies are seen to have an under-density or scarcity of neighbouring galaxies relative to the non-active control sample { a possible indication of a history of mergers and consumptions. ii Acknowledgments The past two years have been an incredible learning experience.
    [Show full text]
  • Issue 36, June 2008
    June2008 June2008 In This Issue: 7 Supernova Birth Seen in Real Time Alicia Soderberg & Edo Berger 23 Arp299 With LGS AO Damien Gratadour & Jean-René Roy 46 Aspen Instrument Update Joseph Jensen On the Cover: NGC 2770, home to Supernova 2008D (see story starting on page 7 Engaging Our Host of this issue, and image 52 above showing location Communities of supernova). Image Stephen J. O’Meara, Janice Harvey, was obtained with the Gemini Multi-Object & Maria Antonieta García Spectrograph (GMOS) on Gemini North. 2 Gemini Observatory www.gemini.edu GeminiFocus Director’s Message 4 Doug Simons 11 Intermediate-Mass Black Hole in Gemini South at moonset, April 2008 Omega Centauri Eva Noyola Collisions of 15 Planetary Embryos Earthquake Readiness Joseph Rhee 49 Workshop Michael Sheehan 19 Taking the Measure of a Black Hole 58 Polly Roth Andrea Prestwich Staff Profile Peter Michaud 28 To Coldly Go Where No Brown Dwarf 62 Rodrigo Carrasco Has Gone Before Staff Profile Étienne Artigau & Philippe Delorme David Tytell Recent 31 66 Photo Journal Science Highlights North & South Jean-René Roy & R. Scott Fisher Photographs by Gemini Staff: • Étienne Artigau NICI Update • Kirk Pu‘uohau-Pummill 37 Tom Hayward GNIRS Update 39 Joseph Jensen & Scot Kleinman FLAMINGOS-2 Update Managing Editor, Peter Michaud 42 Stephen Eikenberry Science Editor, R. Scott Fisher MCAO System Status Associate Editor, Carolyn Collins Petersen 44 Maxime Boccas & François Rigaut Designer, Kirk Pu‘uohau-Pummill 3 Gemini Observatory www.gemini.edu June2008 by Doug Simons Director, Gemini Observatory Director’s Message Figure 1. any organizations (Gemini Observatory 100 The year-end task included) have extremely dedicated and hard- completion statistics 90 working staff members striving to achieve a across the entire M 80 0-49% Done observatory are worthwhile goal.
    [Show full text]
  • Kinetic Effects on Turbulence Driven by the Magnetorotational Instability
    Kinetic Effects on Turbulence Driven by the Magnetorotational Instability in Black Hole Accretion Prateek Sharma A Dissertation Presented to the Faculty of Princeton University in Candidacy for the Degree of Doctor of Philosophy arXiv:astro-ph/0703542v1 20 Mar 2007 Recommended for Acceptance by the department of Astrophysical sciences September 2006 c Copyright by Prateek Sharma, 2018. All Rights Reserved Abstract Many astrophysical objects (e.g., spiral galaxies, the solar system, Saturn’s rings, and luminous disks around compact objects) occur in the form of a disk. One of the important astrophysical problems is to understand how rotationally supported disks lose angular momentum, and accrete towards the bottom of the gravitational potential, converting gravitational energy into thermal (and radiation) energy. The magnetorotational instability (MRI), an instability causing turbulent trans- port in ionized accretion disks, is studied in the kinetic regime. Kinetic effects are important because radiatively inefficient accretion flows (RIAFs), like the one around the supermassive black hole in the center of our Galaxy, are collisionless. The ion Larmor radius is tiny compared to the scale of MHD turbulence so that the drift kinetic equation (DKE), obtained by averaging the Vlasov equation over the fast gy- romotion, is appropriate for evolving the distribution function. The kinetic MHD formalism, based on the moments of the DKE, is used for linear and nonlinear stud- ies. A Landau fluid closure for parallel heat flux, which models kinetic effects like collisionless damping, is used to close the moment hierarchy. We show that the kinetic MHD and drift kinetic formalisms give the same set of linear modes for a Keplerian disk.
    [Show full text]
  • Space Based Astronomy Educator Guide
    * Space Based Atronomy.b/w 2/28/01 8:53 AM Page C1 Educational Product National Aeronautics Educators Grades 5–8 and Space Administration EG-2001-01-122-HQ Space-Based ANAstronomy EDUCATOR GUIDE WITH ACTIVITIES FOR SCIENCE, MATHEMATICS, AND TECHNOLOGY EDUCATION * Space Based Atronomy.b/w 2/28/01 8:54 AM Page C2 Space-Based Astronomy—An Educator Guide with Activities for Science, Mathematics, and Technology Education is available in electronic format through NASA Spacelink—one of the Agency’s electronic resources specifically developed for use by the educa- tional community. The system may be accessed at the following address: http://spacelink.nasa.gov * Space Based Atronomy.b/w 2/28/01 8:54 AM Page i Space-Based ANAstronomy EDUCATOR GUIDE WITH ACTIVITIES FOR SCIENCE, MATHEMATICS, AND TECHNOLOGY EDUCATION NATIONAL AERONAUTICS AND SPACE ADMINISTRATION | OFFICE OF HUMAN RESOURCES AND EDUCATION | EDUCATION DIVISION | OFFICE OF SPACE SCIENCE This publication is in the Public Domain and is not protected by copyright. Permission is not required for duplication. EG-2001-01-122-HQ * Space Based Atronomy.b/w 2/28/01 8:54 AM Page ii About the Cover Images 1. 2. 3. 4. 5. 6. 1. EIT 304Å image captures a sweeping prominence—huge clouds of relatively cool dense plasma suspended in the Sun’s hot, thin corona. At times, they can erupt, escaping the Sun’s atmosphere. Emission in this spectral line shows the upper chro- mosphere at a temperature of about 60,000 degrees K. Source/Credits: Solar & Heliospheric Observatory (SOHO). SOHO is a project of international cooperation between ESA and NASA.
    [Show full text]
  • Gas Kinematics of a Sample of Five Hickson
    A&A 402, 865–877 (2003) Astronomy DOI: 10.1051/0004-6361:20030034 & c ESO 2003 Astrophysics Gas kinematics of a sample of five Hickson Compact Groups?;?? The data P. Amram 1,H.Plana2, C. Mendes de Oliveira3,C.Balkowski4, and J. Boulesteix1 1 Observatoire Astronomique Marseille-Provence & Laboratoire d’Astrophysique de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 04, France 2 Observatorio Nacional MCT, Rua General Jose Cristino 77, S˜ao Crist´ov˜ao, 20921-400 Rio de Janeiro, RJ, Brazil 3 Universidade de S˜ao Paulo, Instituto de Astronomia, Geof´ısica e Ciˆencias Atmosf´ericas, Departamento de Astronomia, Rua do Mat˜ao 1226, Cidade Universit´aria, 05508-900, S˜ao Paulo, SP, Brazil 4 Observatoire de Paris, GEPI, CNRS and Universit´e Paris 7, 5 place Jules Janssen, 92195 Meudon Cedex, France Received 9 October 2002 / Accepted 19 December 2002 Abstract. We present Fabry Perot observations of galaxies in five Hickson Compact Groups: HCG 10, HCG 19, HCG 87, HCG 91 and HCG 96. We observed a total of 15 galaxies and we have detected ionized gas for 13 of them. We were able to derive 2D velocity, monochromatic, continuum maps and rotation curves for the 13 objects. Almost all galaxies in this study are late-type systems; only HCG 19a is an elliptical galaxy. We can see a trend of kinematic evolution within a group and among different groups – from strongly interacting systems to galaxies with no signs of interaction – HCG 10 exhibits at least one galaxy strongly disturbed; HCG 19 seems to be quite evolved; HCG 87 does not show any sign of merging but a possible gas exchange between two galaxies; HCG 91 could be accreting a new intruder; HCG 96 exhibits past and present interactions.
    [Show full text]
  • Introduction to Astronomy
    Introduction to Astronomy Prof. Sébastien R. A. Foucaud Department of Earth Sciences National Taiwan Normal University Unless noted, the course materials are licensed under Creative Commons 1 Attribution-NonCommercial-ShareAlike 3.0 Taiwan (CC BY-NC-SA 3.0) Credits: Chris Hetlage 2 Syllabus Astronomical techniques • Lecture 1: Finding its way on the night… • Lecture 2: Moving blindly and seeing the light… • Lecture 3: Eyes better than my eyes: the telescopes The solar system • Lecture 4: Home: Earth • Lecture 5: Our close friend: The Moon • Lecture 6: Our neighborhood: Rocky Planets • Lecture 7: The good Monsters: Giant Planets • Lecture 8: Dwarf Planets, minor bodies and scenario of solar system formation Stars and planets • Lecture 9: Our king: The Sun • Lecture 10: Shades of colors: so many stars… • Lecture 11: The life of a star: from its birth to its death • Lecture 12: The quest for another Earth: extrasolar planets The Milky-Way, galaxies and our Universe • Lecture 13: The cosmic carrousel: galactic structure & Galaxy formation • Lecture 14: Hubble, the expansion of the Universe and the Big-Bang Theory • Lecture 15: Einstein and the relativity 3 Lecture 13 The cosmic carrousel: galactic structure 4 Galaxies Spiral Galaxy NGC 253 Almost Sideways Credit & Copyright: Jean-Charles Cuillandre (CFHT) Hawaiian Starlight, CFHT APOD: 2003 May 25 • Star systems like our Milky Way •Few million to tens of billions of stars. • Large variety of shapes and sizes 5 Charles Messier (1730-1817) 6 M31 M51 M82 M82 New General Catalogue (NGC)/Johan Ludvig Emil Dreyer, William 7 Herschel, John Dunlop, Charles Messier M104 Messier Catalog, 1751 M31: The Andromeda Nebula 8 M51: The Whirlpool Galaxy 9 M82: An Exploding Galaxy 10 M1: The Crab Nebula 11 M57: The Ring Nebula 12 The Spiral Nebulae? • Nature unknown • Avoided the Milky Way • Immanuel Kant (1724 – 1804) speculated about “Island Universes”.
    [Show full text]
  • Multi-Species Measurements of the Firehose and Mirror Instability Thresholds in the Solar Wind C
    The Astrophysical Journal Letters, 825:L26 (5pp), 2016 July 10 doi:10.3847/2041-8205/825/2/L26 © 2016. The American Astronomical Society. All rights reserved. MULTI-SPECIES MEASUREMENTS OF THE FIREHOSE AND MIRROR INSTABILITY THRESHOLDS IN THE SOLAR WIND C. H. K. Chen1,2, L. Matteini1, A. A. Schekochihin3,4, M. L. Stevens5, C. S. Salem2, B. A. Maruca2, M. W. Kunz6, and S. D. Bale2,7 1 Department of Physics, Imperial College London, London SW7 2AZ, UK; [email protected] 2 Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA 3 Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, UK 4 Merton College, Oxford OX1 4JD, UK 5 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA 6 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA 7 Department of Physics, University of California, Berkeley, CA 94720, USA Received 2016 April 11; revised 2016 June 8; accepted 2016 June 8; published 2016 July 8 ABSTRACT The firehose and mirror instabilities are thought to arise in a variety of space and astrophysical plasmas, constraining the pressure anisotropies and drifts between particle species. The plasma stability depends on all species simultaneously, meaning that a combined analysis is required. Here, we present the first such analysis in the solar wind, using the long-wavelength stability parameters to combine the anisotropies and drifts of all major species (core and beam protons, alphas, and electrons). At the threshold, the firehose parameter was found to be dominated by protons (67%), but also to have significant contributions from electrons (18%) and alphas (15%).
    [Show full text]
  • Galaxy Groups in the COSMOS Survey
    Galaxy groups in the COSMOS survey: cosmic laboratories for galaxy evolution and feedback Stefania Giodini M¨unchen 2010 Galaxy groups in the COSMOS survey: cosmic laboratories for galaxy evolution and feedback DISSERTATION der Fakult¨at f¨ur Physik der Ludwigs-Maximilians-Universit¨at M¨unchen zur Erlangung des Grades Doktor der Naturwissenschaften Dr. rer. nat. vorgelegt von Stefania Giodini aus Erba, Italien M¨unchen, den 14 M¨arz 2010 Erstgutachter: Prof. Dr. Hans B¨ohringer Zweitgutachter: Prof. Dr. Joseph Mohr Tag der m¨undlichen Prufung: May 12th, 2010 iv Galaxy groups in the COSMOS survey: cosmic laboratories for galaxy evolution and feedback Abstract Groups and clusters of galaxies occupy a special position in the hierarchy of large–scale cos- mic structures, being the largest and most massive ( 1013 M for groups and 1015 M for ∼ ⊙ ∼ ⊙ clusters) objects in the universe evolved enough to reach a well defined equilibrium config- uration. In particular, since the growth of structures proceeds in a bottom–up sequence, galaxy groups are thought to be the clusters’ building blocks, thus they are important cosmic laboratories in which to investigate the physics of stucture formation through time. In this thesis I focus on the observational study of ordinary matter (baryons) in galaxy groups in the last 9 Gyr of the life of the Universe. The baryonic mass budget of galaxy groups consists mostly of stars and X–ray emitting hot gas. I use the unique multiwave- length database of the COSMOS 22◦ survey to investigate the groups’ baryonic content, and compare its properties to that of massive clusters of galaxies.
    [Show full text]
  • Issue 27, Dec. 2003
    December 2003 Issue 27 Energy, Life and Matter: The three major themes of Gemini’s future Science & Instrumentation Programs Inside This Issue • Aspen Conference Summary • Recent Science Highlights • Meet Gemini North’s Harlan Uehara • The New Gemini Science Archive • StarTeachers and PIO Highlights • Silver Coating Progress • Instrumentation Update • IRAF Report IMAGE FROM GMOS-SOUTH RIVALS VIEW FROM SPACE HCG 87 – Gemini GMOS-S The individual images captured by GMOS-South in g’, r’ and I’ were obtained in seeing conditions better than 0.4 arcseconds. HCG 87 – HST/WFPC2 Semester 2003A at Gemini South was highlighted by the swift and successful commissioning of GMOS-South. Supported by the expertise of the UK and GMOS-North commissioning teams, the GMOS-South team fully commissioned the instrument—including imaging, long slit, multi-object slitlets and Nod and Shuffle capabilities–– within a few months. Data taken by GMOS-South of the Hickson Compact Group 87 illustrate the point that, under excellent sky conditions, Gemini’s image quality rivals space facilities. Gemini’s image was released in mid-summer alongside an image of the same field obtained with Hubble Space Telescope’s WFPC2 that is also shown here. Published twice annually in June and December. Distributed to staff, users, organizations and others involved in the Gemini Observatory. FUTURE SCIENCE AT GEMINI New Horizons, New Science, New Tools stronomers are some of the most of the Aspen conference and now the real fortunate scientists in the world. work begins. AAfter all, we work in a field that has captured humanity’s attention and The results of the so-called “Aspen imagination for millennia.
    [Show full text]
  • 1. INTRODUCTION & Sulentic1991; Surace Et Al
    THE ASTROPHYSICAL JOURNAL, 497:89È107, 1998 April 10 ( 1998. The American Astronomical Society. All rights reserved. Printed in U.S.A. EFFECTS OF INTERACTION-INDUCED ACTIVITIES IN HICKSON COMPACT GROUPS: CO AND FAR-INFRARED STUDY L. VERDES-MONTENEGRO Instituto de Astrof•sica de Andaluc•a, CSIC, Apdo. 3004, 18080 Granada, Spain; lourdes=iaa.es M. S. YUN National Radio AstronomyObservatory,1 P.O. Box 0, Socorro, NM 87801; myun=nrao.edu J. PEREAAND A. DEL OLMO Instituto de Astrof•sica de Andaluc•a, CSIC, Apdo. 3004, 18080 Granada, Spain; jaime=iaa.es, chony=iaa.es AND P. T. P. HO Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138; pho=cfa.harvard.edu Received 1997 July 7; accepted 1997 November 14 ABSTRACT A study of 2.6 mm CO J \ 1 ] 0 and far-infrared (FIR) emission in a distance-limited (z \ 0.03) com- plete sample of Hickson compact group (HCG) galaxies was conducted in order to examine the e†ects of their unique environment on the interstellar medium of component galaxies and to search for a possible enhancement of star formation and nuclear activity. Ubiquitous tidal interactions in these dense groups would predict enhanced activities among the HCG galaxies compared to isolated galaxies. Instead, their CO and FIR properties (thus, ““ star formation efficiency ÏÏ) are surprisingly similar to isolated spirals. The CO data for 80 HCG galaxies presented here (including 10 obtained from the literature) indicate that the spirals globally show the sameH content as the isolated comparison sample, although 20% are deÐcient in CO emission. Because of their2 large optical luminosity, low metallicity is not likely the main cause for the low CO luminosity.
    [Show full text]
  • ROBERTO DE PROPRIS (ESO-SUOMEN KESKUS, UNIVERSITY of TURKU, FINLAND) the Cabal…
    THE NEW BULGE ROBERTO DE PROPRIS (ESO-SUOMEN KESKUS, UNIVERSITY OF TURKU, FINLAND) The Cabal… R. Michael Rich (UCLA), Andrea Kunder (Potsdam), Juntai Shen (Shanghai), Andreas Koch (Lancaster), David Nataf (Baltimore), Christian Johnson (CfA) … The Hubble Type of the Milky Way Our Galaxy is a relatively late-type multi-armed spiral galaxy Like all spirals it contains an inner bulge/spheroid component The Importance of the Bulge Robertson+ 2003 It is the only spheroidal-like population that we can resolve into stars to the level of the main sequence turnoff Models show bulges to be connected to the early phases of galaxy formation via mergers Bulges as small ellipticals Fundamental plane seems to indicate that bulges are like small ellipticals living in a disk However… There seems to be a fundamental difference between actual spheroids and bulges, with spiral bulges being more similar to disks and pseudobulges BULGE TYPES CLASSICAL VS. PSEUDOBULGES DE VAUCOULEURS EXPONENTIALS COBE BOXY/PEANUT BULGE HIGH EXTINCTION INFRARED IMAGING GALACTIC BAR FROM GAS MOTIONS AND LATER STELLAR COUNTS IN THE IR, THE MILKY WAY IS KNOWN TO CONTAIN A STELLAR BAR AS WELL RED CLUMP STARS USED AS DISTANCE INDICATORS MEAN LUMINOSITY OF RED CLUMP BRIGHTER AT L=+5 THAN AT L=-5 X-SHAPED STRUCTURE ORIGINALLY FROM DOUBLE RED CLUMP X-SHAPES SEEN IN EXTERNAL GALAXIES MOST COMMONLY ASSOCIATED WITH PSEUDOBULGES OUR GALAXY HAS A BAR AND X-SHAPE AND B/P BULGE LIKELY TO CONTAIN A PSEUDOBULGE. HOW IS EVERYTHING RELATED ? The Bulge Radial Velocity Assay Is there a bar ? Is there
    [Show full text]