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Dynamos on Galactic Scales, Or Dynamos Around Us
Dynamos on galactic scales, or Dynamos around us. Part I. Galaxies and galaxy clusters Anvar Shukurov School of Mathematics and Statistics, Newcastle University, U.K. 1. Introduction: basic facts and parameters 2. Spiral galaxies 2.1. Rotation 2.2. Hydrostatic equilibrium of the gas layer 2.3. Interstellar gas and its multi-phase structure 2.4. Interstellar turbulence 3. Elliptical galaxies 4. Galaxy clusters Warning cgs units will be used, 1 G = 10 -4 T, 1 µG = 10 -6 G = 0.1 nT. G ≈ 6.67 ×10 −8 cm 3 g−1 s−2; k ≈ 1.38 ×10 −16 erg K −1; ≈ × −24 ≈ × 7 ≈ × −12 mp 1.7 10 g, 1 year 3 10 s; 1 eV 1.6 10 erg. 1 parsec ≈ 3 × 10 18 cm ≈ 3.26 light years, 1 kpc = 10 3 pc; c ≈ 3×10 10 cm 3 cm s −1 (1 parsec distance: Earth orbit’s par allax = 1 sec ond of arc). Solar mass, radius and luminosity: ≈ × 33 ≈ × 10 ≈ × 33 −1 M 2 10 g; R 7 10 cm; L 4 10 erg s . Notation: HI = neutral hydrogen, HII = p+ = ionized hydrogen, CIV = triply ionized carbon, etc. Further reading R. G. Tayler, Galaxies: Structures and Evolution , Cambridge Univ. Press, 1993 (a high-level scientific popular book on galactic astrophysics, entertaining and informative, very well written). J.E Dyson and D.A Williams, The Physics of the Interstellar Medium , Second Edition (The Graduate Series in Astronomy), IOP, 1997 (a good textbook on interstellar medium, presents appropriate equations and their solutions together with clear qualitative arguments and explanations and order of magnitude estimates). -
Central Coast Astronomy Virtual Star Party May 15Th 7Pm Pacific
Central Coast Astronomy Virtual Star Party May 15th 7pm Pacific Welcome to our Virtual Star Gazing session! We’ll be focusing on objects you can see with binoculars or a small telescope, so after our session, you can simply walk outside, look up, and understand what you’re looking at. CCAS President Aurora Lipper and astronomer Kent Wallace will bring you a virtual “tour of the night sky” where you can discover, learn, and ask questions as we go along! All you need is an internet connection. You can use an iPad, laptop, computer or cell phone. When 7pm on Saturday night rolls around, click the link on our website to join our class. CentralCoastAstronomy.org/stargaze Before our session starts: Step 1: Download your free map of the night sky: SkyMaps.com They have it available for Northern and Southern hemispheres. Step 2: Print out this document and use it to take notes during our time on Saturday. This document highlights the objects we will focus on in our session together. Celestial Objects: Moon: The moon 4 days after new, which is excellent for star gazing! *Image credit: all astrophotography images are courtesy of NASA & ESO unless otherwise noted. All planetarium images are courtesy of Stellarium. Central Coast Astronomy CentralCoastAstronomy.org Page 1 Main Focus for the Session: 1. Canes Venatici (The Hunting Dogs) 2. Boötes (the Herdsman) 3. Coma Berenices (Hair of Berenice) 4. Virgo (the Virgin) Central Coast Astronomy CentralCoastAstronomy.org Page 2 Canes Venatici (the Hunting Dogs) Canes Venatici, The Hunting Dogs, a modern constellation created by Polish astronomer Johannes Hevelius in 1687. -
Teacher's Guide
Teacher’s guide CESAR Science Case – The secrets of galaxies Material that is necessary during the laboratory o CESAR Booklet o Computer with an Internet browser o CESAR List of Galaxies (.txt file) o Paper, pencil or pen o CESAR Student’s guide o o Introduction o o This Science Case provides an introduction to galaxies based on real multi-wavelength observations with space missions. It discusses concepts such as the Hubble Tuning Fork and the morphological classification of galaxies, stellar and ISM content of the different types of galaxies, and galaxy interaction and evolution. The activity is designed to encourage students to discover the properties of galaxies on their own. o During the laboratory, students make use of ESASky1, a portal for exploration and retrieval of space astronomical data, to visualise different galaxies and classify them according to their shapes and optical colours. Students can load different sky maps to see how the galaxies look like when they are observed at different wavelength ranges, and discuss how the presence of the ISM is affecting these observations. o Before starting this activity, students must be familiar with the properties of stars and of the interstellar medium, as well as have some basic concepts of stellar evolution. In particular, they must understand that young, massive stars display blue colors, while evolved stars look yellowish or reddish. They must also understand the relation between the ISM and young stars. o o Learning Outcomes o o By the end of this laboratory, students will be able to: 1. Explain how astronomers classify galaxies according to their shapes and contents. -
What Is an Ultra-Faint Galaxy?
What is an ultra-faint Galaxy? UCSB KITP Feb 16 2012 Beth Willman (Haverford College) ~ 1/10 Milky Way luminosity Large Magellanic Cloud, MV = -18 image credit: Yuri Beletsky (ESO) and APOD NGC 205, MV = -16.4 ~ 1/40 Milky Way luminosity image credit: www.noao.edu Image credit: David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration ~ 1/300 Milky Way luminosity MV = -14.2 Image credit: David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration ~ 1/2700 Milky Way luminosity MV = -11.9 Image credit: David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration ~ 1/14,000 Milky Way luminosity MV = -10.1 ~ 1/40,000 Milky Way luminosity ~ 1/1,000,000 Milky Way luminosity Ursa Major 1 Finding Invisible Galaxies bright faint blue red Willman et al 2002, Walsh, Willman & Jerjen 2009; see also e.g. Koposov et al 2008, Belokurov et al. Finding Invisible Galaxies Red, bright, cool bright Blue, hot, bright V-band apparent brightness V-band faint Red, faint, cool blue red From ARAA, V26, 1988 Willman et al 2002, Walsh, Willman & Jerjen 2009; see also e.g. Koposov et al 2008, Belokurov et al. Finding Invisible Galaxies Ursa Major I dwarf 1/1,000,000 MW luminosity Willman et al 2005 ~ 1/1,000,000 Milky Way luminosity Ursa Major 1 CMD of Ursa Major I Okamoto et al 2008 Distribution of the Milky Wayʼs dwarfs -14 Milky Way dwarfs 107 -12 -10 classical dwarfs V -8 5 10 Sun M L -6 ultra-faint dwarfs Canes Venatici II -4 Leo V Pisces II Willman I 1000 -2 Segue I 0 50 100 150 200 250 300 -
Asterion and Chara – the Confusion of the Chase
University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications, UNL Libraries Libraries at University of Nebraska-Lincoln July 2002 Asterion and Chara – the Confusion of the Chase Charles D. Bernholz University of Nebraska-Lincoln, [email protected] Michael J. Lyons Follow this and additional works at: https://digitalcommons.unl.edu/libraryscience Part of the Library and Information Science Commons Bernholz, Charles D. and Lyons, Michael J., "Asterion and Chara – the Confusion of the Chase" (2002). Faculty Publications, UNL Libraries. 7. https://digitalcommons.unl.edu/libraryscience/7 This Article is brought to you for free and open access by the Libraries at University of Nebraska-Lincoln at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications, UNL Libraries by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. SPECIAL FEATURE: DEVELOPING IDEAS OF SPACE www.iop.org/journals/physed Asterion and Chara—the confusion of the chase Charles D Bernholz1 and Michael J Lyons2 1 Memorial Library, State University of New York College at Cortland, Cortland, NY 13045, USA 2 Port Jervis High School, Port Jervis, NY 12771, USA E-mail: [email protected] Abstract The study of astronomy, as an important part of any science education programme, provides our students with insights into more than just the cosmos. It may also serve as a mechanism to link them to other natural and social sciences. This article examines equally valid interpretations of the constellation Canes Venatici as an example of how the study of astronomy may serve this multidisciplinary educational role. In addition, it is an extension of the thoughts of Stannard (2001) on communicating physics through story. -
Galaxies with Rows A
Astronomy Reports, Vol. 45, No. 11, 2001, pp. 841–853. Translated from Astronomicheski˘ı Zhurnal, Vol. 78, No. 11, 2001, pp. 963–976. Original Russian Text Copyright c 2001 by Chernin, Kravtsova, Zasov, Arkhipova. Galaxies with Rows A. D. Chernin, A. S. Kravtsova, A. V. Zasov, and V. P. Arkhipova Sternberg Astronomical Institute, Universitetskii˘ pr. 13, Moscow, 119899 Russia Received March 16, 2001 Abstract—The results of a search for galaxies with straight structural elements, usually spiral-arm rows (“rows” in the terminology of Vorontsov-Vel’yaminov), are reported. The list of galaxies that possess (or probably possess) such rows includes about 200 objects, of which about 70% are brighter than 14m.On the whole, galaxies with rows make up 6–8% of all spiral galaxies with well-developed spiral patterns. Most galaxies with rows are gas-rich Sbc–Scd spirals. The fraction of interacting galaxies among them is appreciably higher than among galaxies without rows. Earlier conclusions that, as a rule, the lengths of rows are similar to their galactocentric distances and that the angles between adjacent rows are concentrated near 120◦ are confirmed. It is concluded that the rows must be transient hydrodynamic structures that develop in normal galaxies. c 2001 MAIK “Nauka/Interperiodica”. 1. INTRODUCTION images were reproduced by Vorontsov-Vel’yaminov and analyze the general properties of these objects. The long, straight features found in some galaxies, which usually appear as straight spiral-arm rows and persist in spite of differential rotation of the galaxy 2. THE SAMPLE OF GALAXIES disks, pose an intriguing problem. These features, WITH STRAIGHT ROWS first described by Vorontsov-Vel’yaminov (to whom we owe the term “rows”) have long escaped the To identify galaxies with rows, we inspected about attention of researchers. -
Stsci Newsletter: 2011 Volume 028 Issue 02
National Aeronautics and Space Administration Interacting Galaxies UGC 1810 and UGC 1813 Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) 2011 VOL 28 ISSUE 02 NEWSLETTER Space Telescope Science Institute We received a total of 1,007 proposals, after accounting for duplications Hubble Cycle 19 and withdrawals. Review process Proposal Selection Members of the international astronomical community review Hubble propos- als. Grouped in panels organized by science category, each panel has one or more “mirror” panels to enable transfer of proposals in order to avoid conflicts. In Cycle 19, the panels were divided into the categories of Planets, Stars, Stellar Rachel Somerville, [email protected], Claus Leitherer, [email protected], & Brett Populations and Interstellar Medium (ISM), Galaxies, Active Galactic Nuclei and Blacker, [email protected] the Inter-Galactic Medium (AGN/IGM), and Cosmology, for a total of 14 panels. One of these panels reviewed Regular Guest Observer, Archival, Theory, and Chronology SNAP proposals. The panel chairs also serve as members of the Time Allocation Committee hen the Cycle 19 Call for Proposals was released in December 2010, (TAC), which reviews Large and Archival Legacy proposals. In addition, there Hubble had already seen a full cycle of operation with the newly are three at-large TAC members, whose broad expertise allows them to review installed and repaired instruments calibrated and characterized. W proposals as needed, and to advise panels if the panelists feel they do not have The Advanced Camera for Surveys (ACS), Cosmic Origins Spectrograph (COS), the expertise to review a certain proposal. Fine Guidance Sensor (FGS), Space Telescope Imaging Spectrograph (STIS), and The process of selecting the panelists begins with the selection of the TAC Chair, Wide Field Camera 3 (WFC3) were all close to nominal operation and were avail- about six months prior to the proposal deadline. -
Structural Parameters of Compact Stellar Systems
Structural Parameters of Compact Stellar Systems Juan Pablo Madrid Presented in fulfillment of the requirements of the degree of Doctor of Philosophy May 2013 Faculty of Information and Communication Technology Swinburne University Abstract The objective of this thesis is to establish the observational properties and structural parameters of compact stellar systems that are brighter or larger than the “standard” globular cluster. We consider a standard globular cluster to be fainter than M 11 V ∼ − mag and to have an effective radius of 3 pc. We perform simulations to further un- ∼ derstand observations and the relations between fundamental parameters of dense stellar systems. With the aim of establishing the photometric and structural properties of Ultra- Compact Dwarfs (UCDs) and extended star clusters we first analyzed deep F475W (Sloan g) and F814W (I) Hubble Space Telescope images obtained with the Advanced Camera for Surveys. We fitted the light profiles of 5000 point-like sources in the vicinity of NGC ∼ 4874 — one of the two central dominant galaxies of the Coma cluster. Also, NGC 4874 has one of the largest globular cluster systems in the nearby universe. We found that 52 objects have effective radii between 10 and 66 pc, in the range spanned by extended star ∼ clusters and UCDs. Of these 52 compact objects, 25 are brighter than M 11 mag, V ∼ − a magnitude conventionally thought to separate UCDs and globular clusters. We have discovered both a red and a blue subpopulation of Ultra-Compact Dwarf (UCD) galaxy candidates in the Coma galaxy cluster. Searching for UCDs in an environment different to galaxy clusters we found eleven Ultra-Compact Dwarf and 39 extended star cluster candidates associated with the fossil group NGC 1132. -
Constraining the Properties of Milky Way Dwarf Spheroidals with Surface Brightness & Velocity Dispersion Data Introduction Justin Craig, Casey R
Constraining the Properties of Milky Way Dwarf Spheroidals with Surface Brightness & Velocity Dispersion Data Introduction Justin Craig, Casey R. Watson Department of Physics & Astronomy, Millikin University, Decatur, IL, USA. Dark matter (DM) is the dominant form of matter in the universe [1]. Observations of Results Table 1. The star-related quantities derived from observations and steps I and II with the values for 푛, 훾, and 푅푒 from Ref. [7] and 푦푒 = 푅푒/푅∗. rotation curves (Fig. 1), suggest that every galaxy is embedded within a large DM halo (Fig. (B) (NFW) Abstract Galaxy 풏 휸 풚풆 푹풆/(pc) 푹∗/(pc) 휶 (B) 휶 (NFW) 휷ퟎ 휷ퟎ 휷∞ (B) 휷∞ (NFW) 푫 (B) 푫 (NFW) 2), that comprises, on average, 84% of the mass of each galaxy and the same fraction of CVI 5 0.60+0.08 0.785+0.050 452 ± 13 576 ± 17 1.0 ± 0.1 0.7 ± 0.1 0.27 ± 0.05 0.97 ± 0.01 -1.51 ± 0.57 -12.15 ± 0.01 7.7 ± 2.2 3.6 ± 1.2 Using a combination of surface brightness and velocity dispersion data, we simultaneously −0.06 −0.032 matter in the universe as a whole [1,2,3]. CVII 5 0.53+0.12 0.756+0.024 70.7 ± 11.2 93.6 ± 14.8 1.1 ± 0.1 0.9 ± 0.1 0.29 ± 0.05 0.93 ± 0.02 0.23 ± 0.20 −7.90 ± 1.16 3.5 ± 1.5 1.6 ± 0.7 constrain the velocity anisotropy and dark matter mass profiles of Milky Way dwarf spheroidals −0.10 −0.031 +0.02 +0.001 (dSphs). -
Canes Venatici I Cloud of Galaxies Seen in the Hα Line
A&A 479, 603–624 (2008) Astronomy DOI: 10.1051/0004-6361:20078652 & c ESO 2008 Astrophysics Canes Venatici I cloud of galaxies seen in the Hα line S. S. Kaisin and I. D. Karachentsev Special Astrophysical Observatory, Russian Academy of Sciences, N. Arkhyz, KChR, 369167, Russia e-mail: [email protected] Received 11 September 2007 / Accepted 25 September 2007 ABSTRACT We present results of Hα imaging for 42 galaxies in the nearby low-density cloud Canes Venatici I, populated mainly by late-type objects. Estimates of the Hα flux and integrated star formation rate (SFR) are now available for all 78 known members of this scattered system, spanning a large range in luminosity, surface brightness, HI content and SFR. Distributions of the CVnI galaxies versus their SFR, blue absolute magnitude and total hydrogen mass, are given in comparison with those for a population of the nearby virialized group around M 81. We found no essential correlation between star formation activity in a galaxy and its density environment. The bulk of CVnI galaxies had enough time to generate their baryon mass with the observed SFR. Most of them also possess a supply of gas that is sufficient to maintain their observed SFRs during the next Hubble time. Key words. galaxies: evolution – galaxies: ISM – galaxies: dwarf 1. Introduction 2. Observations and data reduction The distribution over the sky of 500 galaxies of the Local CCD images in the Hα-line and continuum were obtained for Volume, with distances within 10 Mpc, shows considerable in- 42 galaxies of the CVnI cloud during observing runs from March homogeneities due to the presence of groups and voids. -
M31 Andromeda Galaxy Aq
Constellation, Star, and Deep Sky Object Names Andromeda : M31 Andromeda Galaxy Lyra : Vega & M57 Ring Nebula Aquila : Altair Ophiuchus : Bernard’s Star Auriga : Capella Orion : Betelgeuse , Rigel & M42 Orion Nebula Bootes : Arcturus Perseus : Algol Cancer : M44 Beehive Cluster Sagittarius: Sagittarius A* Canes Venatici: M51 Whirlpool Galaxy Taurus : Aldebaran , Hyades Star Cluster , M1 Crab Nebula & Canis Major : Sirius M45 Pleiades Canis Minor : Procyon Tucana : Small Magellanic Cloud (SMC) Cassiopeia : Cassiopeia A & Tycho’s “Star” Ursa Minor : Polaris Centaurus : Proxima Centauri Virgo : Spica Dorado/Mensa : Large Magellanic Cloud (LMC) Milky Way Galaxy Gemini : Castor & Pollux Hercules : M13 Globular Cluster Characteristics of Stars (Compared with Sun) Class Color Temp. ( 1000 K) Absolute Magnitude Solar Luminosity Solar Mass Solar Diameter O Blue 60 -30 -7 1,000,000 50 100 to 1000 B Blue -White 30 -10 -3 10,000 10 10 to 100 A White 10 -7.5 +2 100 2 2 to 10 F White -Yellow 7.5 -6.5 +4 10 1.5 1 to 2 G Yellow 6.5 -4.5 +4.6 1 1 1 K Orange 4.5 -3.5 +11 1/100 0.5 0.5 M Red 3.5 -2.8 +15 1/100,000 0.08 0.1 Magnitude Magnitude scales: The smaller the magnitude number, the brighter the star Every 5 magnitudes = 100 times the brightness of object Every magnitude = 2.512 times the brightness of object Apparent magnitude = the brightness of object as seen from the viewer’s viewpoint (Earth) Absolute magnitude = “true brightness” – brightness as seen from 10 parsecs (32.6 light years) away Distance Measurement 1 astronomical unit = distance between Earth and Sun = 150 million kilometres or 93 million miles 1 light year ≈ 6 trillion miles / 9.5 trillion km Parsec = parallax second of arc – distance that a star “jumps” one second of a degree of arc in the sky as a result of the earth’s revolution around the sun. -
Gargantuan Galaxy NGC 1132 -- a Cosmic Fossil? 5 February 2008
Gargantuan galaxy NGC 1132 -- a cosmic fossil? 5 February 2008 together with the small dwarf galaxies surrounding it, are dubbed a “fossil group” as they are most likely the remains of a group of galaxies that merged together in the recent past. In visible light NGC 1132 appears as a single, isolated, giant elliptical galaxy, but this is only the tip of the iceberg. Scientists have found that NGC 1132 resides in an enormous halo of dark matter, comparable to the amount of dark matter usually found in an entire group of tens or hundreds of galaxies. It also has a strong X-ray glow from an abundant amount of hot gas – an amount normally only found in galaxy groups. Its X-ray glow extends over a region of space ten times larger than the 120,000 light-year radius it has in visible light. An X- ray glow that is equal in size to that of an entire group of galaxies. The origin of fossil group systems remains a puzzle. The most likely explanation is that they are The NASA/ESA Hubble Space Telescope has captured the end-products of a cosmic feeding frenzy in a new image of the galaxy NGC 1132 which is, most which a large cannibal galaxy devours all of its likely, a cosmic fossil -- the aftermath of an enormous neighbours. A less likely explanation is that they multi-galactic pile-up, where the carnage of collision after may be very rare objects that formed in a region or collision has built up a brilliant but fuzzy giant elliptical period of time where the growth of moderate-sized galaxy far outshining typical galaxies.