Young Globular Clusters and Dwarf Spheroidals
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Tidal Disruption of Globular Clusters in Dwarf Galaxies with Triaxial Dark Matter Haloes.” by J
“Tidal disruption of globular clusters in dwarf galaxies with triaxial dark matter haloes.” by J. Peñarrubia, M.J. Walker, and G. Gilmore University of Cambridge and University of Victoria MNRAS accepted Journal Club 5/15/09 Daniel Grin 1/19 Wednesday, September 2, 2009 1 Punchline 2/19 • Globular clusters (GCs) around dwarf spheroidal (dSph) galaxies may survive tidal encounters • Stellar substructure (morphology and kinematics) in dSph galaxies may be explained by past disruptions of GCs • Simulation techniques grossly over-simplify the problem, but useful first step Wednesday, September 2, 2009 2 Outline 3/19 • Motivation: subtructure in dSphs and existence of GCs near them. • Properties of systems modeled • Simulation techniques/caveats • Results Wednesday, September 2, 2009 3 Motivation: Substructure in dSph galaxies 4/19 • Milky Way (MW) dSph galaxies are DM dominated-- : • Ideal testbed for CDM scenario • Standing dispute about presence of cores (triaxiality? projection effect? see work by J. Simon) • dSph galaxies have substructure, contrary to expectation that it should be erased in a few crossing times (~100 Myr): • Morphology: Kinematically cold core in Sextans, kinematically distinct shell in Fornax, asymmetries across major/minor axes in Fornax (claims of butterfly shapes are sketchy) • Ages: 2 Gyr-old stellar populations in Fornax shell • Can prolong life of stellar substructure with cored density profile, challenge to CDM? • Can save CDM with formation of substructure that is not in situ • Blue stragglers in Sextans are mass segregated, not enough time for this in Sextans, do it elsewhere (like a merging G.C.) and disrupt? Wednesday, September 2, 2009 4 Motivation: Globular clusters in dSph 5/19 • Fornax (5) and Sagitarrius (4) contain GCs near : Name Angular sep. -
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. -
Authentic Data in the Classroom with the Sloan Digital Sky Survey
Proc. of the GHOU 2007 in Tokyo Authentic Data in the Classroom with the Sloan Digital Sky Survey M. Jordan Raddick* 1 Student engagement with the process of science is a proven part of highquality science education, but authentic science activities can be difficult in astronomy because of the difficulty students have in taking data. This paper describes how the Sloan Digital Sky Survey (SDSS) contributes to solving this problem by making its entire dataset available to students and the public, free of charge. The survey's SkyServer website (http://skyserver.sdss.org) includes simple tools to browse and search the data, as well as projects that use the data to teach science. The dataset is also a great source of independent research projects for students. 1. Introduction for each star or galaxy, including magnitudes and object types. Images are available as FITS files. Movements in science education reform in the The survey also measures followup spectra for United States and around the world frequently cite stars, galaxies and quasars. These spectra run from engagement with the process of science as a key 3800 to 9200 Ångstroms, and have a resolution of component of effective science learning, and 1.8 Ångstroms per pixel. They are available as GIF scientific inquiry as an important part of images or FITS files, and detailed line widths and understanding science [1,2]. strengths are available for each spectral line. Laboratory activities in other science subjects frequently make use of student inquiry labs, in which 3. SkyServer students make their own observations, interpret the results, and draw conclusions. -
Direct N-Body Simulations of Globular Clusters--III. Palomar\, 4 on An
MNRAS 000, 1–11 (2013) Preprint 14 September 2018 Compiled using MNRAS LATEX style file v3.0 Direct N-body simulations of globular clusters – III. Palomar4 on an eccentric orbit Akram Hasani Zonoozi1⋆, Hosein Haghi1, Pavel Kroupa2,3, Andreas H.W. K¨upper4†, Holger Baumgardt5 1Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), PO Box 11365-9161, Zanjan, Iran 2Helmholtz-Institut f¨ur Strahlen-und Kernphysik (HISKP), Universit¨at Bonn, Nussallee 14-16, D-53115 Bonn, Germany 3Charles University in Prague, Faculty of Mathematics and Physics, Astronomical Institute, V Holeˇsoviˇck´ach 2, CZ-180 00 Praha 8, Czech Republic 4Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA 5School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia Accepted .... Received ABSTRACT Palomar 4 is a low-density globular cluster with a current mass ≈ 30000 M⊙in the outer halo of the Milky Way with a two-body relaxation time of the order of a Hubble time. Yet, it is strongly mass segregated and contains a stellar mass function depleted of low-mass stars. Pal 4 was either born this way or it is a result of extraordi- nary dynamical evolution. Since two-body relaxation cannot explain these signatures alone, enhanced mass loss through tidal shocking may have had a strong influence on Pal 4. Here, we compute a grid of direct N-body simulations to model Pal4 on various eccentric orbits within the Milky Way potential to find likely initial conditions that reproduce its observed mass, half-light radius, stellar MF-slope and line-of-sight ve- locity dispersion. -
Science in the Urantia Papers
Science ¾ Scientific Validation of the UB z By Denver Pearson z By Phil Calabrese ¾ Seraphic Velocities ¾ Astronomy The Scientific Integrity of the Urantia Book by Denver Pearson As scientifically minded readers first peruse the Urantia Book, it soon occurs to them that many of its statements on the natural sciences conflict with currently held data and theories. In the minds of many this gives rise to doubts about the truthfulness of those statements. Wisdom would lead us to realize that nothing short of perfection is perfect, and anything touched by human hands has fingerprints. This should be our guiding thoughts as we contemplate the accuracy of the scientific content of the Urantia Papers. Several years ago, at the first scientific symposium, it was implied by one of the speakers that the revelation contains errors. This implication is alarming. More recently, at the second symposium held in Oklahoma, an interesting publication named "The Science Content of The Urantia Book" was made available (this document is obtainable from the Brotherhood of Man Library). In this publication is an article entitled "Time Bombs" in which the author suggests that the revelators planted certain inaccurate scientific statements in the book in order to prevent it from becoming a fetish. He states "...the revelators incorporated safeguards in the papers that would form The Urantia Book to diminish the tendency to regard it as an object of worship. What safeguards did they use? Suppose they decided to make sure that mortals reading it understood that some cosmological statements in the book would be found to be inaccurate". -
Galactic Metal-Poor Halo E NCYCLOPEDIA of a STRONOMY and a STROPHYSICS
Galactic Metal-Poor Halo E NCYCLOPEDIA OF A STRONOMY AND A STROPHYSICS Galactic Metal-Poor Halo Most of the gas, stars and clusters in our Milky Way Galaxy are distributed in its rotating, metal-rich, gas-rich and flattened disk and in the more slowly rotating, metal- rich and gas-poor bulge. The Galaxy’s halo is roughly spheroidal in shape, and extends, with decreasing density, out to distances comparable with those of the Magellanic Clouds and the dwarf spheroidal galaxies that have been collected around the Galaxy. Aside from its roughly spheroidal distribution, the most salient general properties of the halo are its low metallicity relative to the bulk of the Galaxy’s stars, its lack of a gaseous counterpart, unlike the Galactic disk, and its great age. The kinematics of the stellar halo is closely coupled to the spheroidal distribution. Solar neighborhood disk stars move at a speed of about 220 km s−1 toward a point in the plane ◦ and 90 from the Galactic center. Stars belonging to the spheroidal halo do not share such ordered motion, and thus appear to have ‘high velocities’ relative to the Sun. Their orbital energies are often comparable with those of the disk stars but they are directed differently, often on orbits that have a smaller component of rotation or angular Figure 1. The distribution of [Fe/H] values for globular clusters. momentum. Following the original description by Baade in 1944, the disk stars are often called POPULATION I while still used to measure R . The recognizability of globular the metal-poor halo stars belong to POPULATION II. -
Arxiv:1307.6035V1 [Astro-Ph.GA] 23 Jul 2013 Uaeydtriigterpoete,Ms Ftegalac- the of Most Properties, Their Determining Curately Et Ferraro the 1997; on Heggie 2012)
Draft version July 24, 2013 A Preprint typeset using LTEX style emulateapj v. 12/16/11 STAR COUNT DENSITY PROFILES AND STRUCTURAL PARAMETERS OF 26 GALACTIC GLOBULAR CLUSTERS P. Miocchi1, B. Lanzoni1, F.R. Ferraro1, E. Dalessandro1, E. Vesperini2, M. Pasquato3 , G. Beccari4, C. Pallanca1, and N. Sanna1 1Dipartimento di Fisica e Astronomia, Universit`adi Bologna, Viale Berti Pichat 6/2, 40127 Bologna, Italy 2Department of Astronomy, Indiana University, Bloomington, Indiana 47405, USA 3Department of Astronomy & Center for Galaxy Evolution Research, Yonsei University, and Yonsei University Observatory, Seoul 120-749, Republic of Korea 4European Organization for Astronomical Research in the Southern Hemisphere, K. Schwarzschild-Str. 2, 85748 Garching, Germany Draft version July 24, 2013 ABSTRACT We used a proper combination of high-resolution HST observations and wide-field ground based data to derive the radial star density profile of 26 Galactic globular clusters from resolved star counts (which can be all freely downloaded on-line). With respect to surface brightness (SB) profiles (which can be biased by the presence of sparse, bright stars), star counts are considered to be the most robust and reliable tool to derive cluster structural parameters. For each system a detailed comparison with both King and Wilson models has been performed and the most relevant best-fit parameters have been obtained. This is the largest homogeneous catalog collected so far of star count profiles and structural parameters derived therefrom. The analysis of the data -
Kiski Astronomers at Cherry Springs: Perseids - August, 2015
Kiski Astronomers at Cherry Springs: Perseids - August, 2015 After finishing my trip to the Lehigh Valley Amateur Astronomical Society ’s Pulpit Rock Observatory the weekend of August 7 th – 9th, I headed over to Cherry Springs to take in the annual Perseid Meteor shower with several other members of the Kiski Astronomers. Monday 08/10/2015: Leaving a damp Pulpit Rock behind, I made the 3 hour drive from Eastern PA to the Astronomers Paradise – Cherry Springs State Park. Arrived late afternoon to find Bob K already there, and setup my camp across from him. Assembled the telescope, but wasn’t able to do much more, as clouds rolled in at sunset. Headed inside to read and early to bed. Tuesday 08/11/2015: Spent the day setting up a few more camping items and visiting with Bob N from the Kiski Club and Mike P from Niagara Canada who arrived and setup with us, and planning for the observing that evening. The sky stayed clear for the afternoon, and once the sun went down, we all got to work. Using my StellaCam-3 videocamera and 8” SCT optical tube on a C-Gem mount, I started working thru my constellation survey, chasing faint galaxies in Ursa Major. These included NGC-3065 & 3066, 3259, 3348, and 3516. Would like to have gone after more galaxies in the Great Bear, but he was too low in the tree tops. Have to wait till next year to re -visit that dipper! I then chased down the faint and elusive globular cluster Palomar -12 in Capricornus. -
PALOMAR 12 AS a PART of the SAGITTARIUS STREAM: the EVIDENCE from ABUNDANCE RATIOS1 Judith G
The Astronomical Journal, 127:1545–1554, 2004 March A # 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A. PALOMAR 12 AS A PART OF THE SAGITTARIUS STREAM: THE EVIDENCE FROM ABUNDANCE RATIOS1 Judith G. Cohen2 Received 2003 November 7; accepted 2003 December 11 ABSTRACT We present a detailed abundance analysis for 21 elements based on high-dispersion, high spectral resolution Keck spectra for four members of the outer halo ‘‘young’’ Galactic globular cluster Palomar 12. All four stars show identical abundance distributions with no credible indication of any star-to-star scatter. However, the abundance ratios of the Pal 12 stars are very peculiar. There is no detected enhancement of the -elements; the mean of [Si/Fe], [Ca/Fe], and [Ti/Fe] is À0:07 Æ 0:05 dex, O/Fe is also solar, while Na is very deficient. The distribution among the heavy elements shows anomalies as well. These are inconsistent with those of almost all Galactic globular clusters or of field stars in the Galaxy. The peculiarities shown by the Pal 12 stars are, however, in good general agreement with the trends established by Smecker-Hane & McWilliam and by Bonifacio et al. for stars in the Sagittarius dwarf spheroidal (dSph) galaxy evaluated at the [Fe/H] of Pal 12. This reinforces earlier suggestions that Pal 12 originally was a cluster in the Sgr dSph galaxy that during the process of accretion of this galaxy by our own was tidally stripped from the Sgr galaxy to become part of the extended Sgr stream. Key words: globular clusters: general — globular clusters: individual (Palomar 12) — galaxies: individual (Sagittarius dSph) — stars: abundances On-line material: machine-readable table 1. -
Celestial Home of Stars Magda Streicher [email protected]
deep-sky delights Celestial Home of Stars Magda Streicher [email protected] In an�quity the Capricornus constella- �on was seen as a monster with the head and forelegs of a goat and the posterior of a fish. The creature could almost be compared to the so-called Mermaid but Image source: Stellarium.org could also some�mes, in the case of Cap- ricornus, refer to the Fishman. served towards the east it indicates the The name ‘Tropic of Capricornus’ origi- point of the winter sols�ce, this sols�ce nates from the fact that when first ob- at present being 33o to the west in the figure of Sagi�arius. The constella�on is special to the au- thor for two good reasons. Not only does she live right inside the old Tropic of Capricorn Circle, but the image also reflects a par�cular shape: it looks very much like a huge lopsided triangle, and special in the star composi�on. Heaven alone knows how anyone could see a sea goat with horns in that par�cular star pa�ern, but be that as it may … We will carefully unravel the constella�on, which holds a large number of bright stars to pleasure the eye. The constella�on occupies 414 square degrees of sky and is situated just east of Sagi�arius, but sadly it is not rich in Monument marking the tropic of Capricorn deep-sky objects. S�ll, it is an easily outside Polokwane, Limpopo province. recognisable compila�on, with several mnassa vol 72 nos 5 & 6 126 127 june 2013 capricornus: celestial home of stars look-alike double stars and is, famously, The lovely double star, alpha Capri- a close neighbour to the centre of the corni, also the star closest to the Sagit- Milky Way. -
Multiwavelength, Machine Learning, and Parallax Studies of X-Ray Binaries in Three Local Group Galaxies
Western University Scholarship@Western Electronic Thesis and Dissertation Repository 12-7-2018 1:30 PM Multiwavelength, Machine Learning, and Parallax Studies of X-ray Binaries in Three Local Group Galaxies Robin Arnason The University of Western Ontario Supervisor Barmby, Pauline The University of Western Ontario Graduate Program in Astronomy A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Robin Arnason 2018 Follow this and additional works at: https://ir.lib.uwo.ca/etd Part of the External Galaxies Commons Recommended Citation Arnason, Robin, "Multiwavelength, Machine Learning, and Parallax Studies of X-ray Binaries in Three Local Group Galaxies" (2018). Electronic Thesis and Dissertation Repository. 5931. https://ir.lib.uwo.ca/etd/5931 This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract X-ray binary stars are rare systems consisting of a black hole or neutron star and a main- sequence companion star. They are useful probes of galaxy properties and interesting labora- tories for extreme physical conditions. In this thesis, I investigated the X-ray binary population of three galaxies in the Local Group. The Sculptor Dwarf Spheroidal Galaxy offers the chance to study a primordial low-mass X-ray binary (LMXB) population in an isolated, low-metallicity environment. Combining X- ray, optical, and infrared observations, I have studied nine previously identified and discovered four additional LMXB candidates in this galaxy. -
Implications of Elemental Abundances in Dwarf Spheroidal Galaxies
A&A 447, 81–87 (2006) Astronomy DOI: 10.1051/0004-6361:20054120 & c ESO 2006 Astrophysics Implications of elemental abundances in dwarf spheroidal galaxies T. Tsujimoto National Astronomical Observatory, Mitaka-shi, Tokyo 181-8588, Japan e-mail: [email protected] Received 30 August 2005 / Accepted 17 September 2005 ABSTRACT Unusual elemental abundance patterns observed for stars belonging to nearby dwarf spheroidal (dSph) galaxies are discussed. Analysis of the [α/H] vs. [Fe/H] diagrams where α represents Mg or an average of α-elements reveals that Fe from type Ia supernovae (SNe Ia) does not contribute to the stellar abundances in the dSph galaxies where the member stars exhibit low α/Fe ratios except for the most massive dSph galaxy, Sagitarrius. The more massive dwarf (irregular) galaxy, the Large Magellanic Cloud, also has an SNe Ia signature in the stellar abundances. These findings suggest that whether SNe Ia contribute to chemical evolution in dwarf galaxies is likely to depend on the mass scale of galaxies. Unusual Mg abundances in some dSph stars are also found to be the origin of the large scatter in the [Mg/Fe] ratios and are responsible for a seemingly decreasing [Mg/Fe] feature with increasing [Fe/H]. In addition, the lack of massive stars in the dSph galaxies does not satisfactorily account for the low-α signature. Considering the assembly of deficient elements (O, Mg, Si, Ca, Ti and Zn), all of which are synthesized in pre-SN massive stars and in SN explosions, the low-α signature appears to reflect the heavy-element yields of massive stars with less rotation compared to solar neighborhood stars.