The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the Gev Excess
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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. -
Ray Emission from the Globular Cluster 47 Tucanae (Research Note)
A&A 499, 273–277 (2009) Astronomy DOI: 10.1051/0004-6361/200811564 & c ESO 2009 Astrophysics HESS upper limit on the very high energy γ-ray emission from the globular cluster 47 Tucanae (Research Note) F. Aharonian1,2, A. G. Akhperjanian3,G.Anton4, U. Barres de Almeida5,, A. R. Bazer-Bachi6, Y. Becherini7, B. Behera8, K. Bernlöhr1,9, C. Boisson10, A. Bochow1, V. Borrel6,I.Braun1,E.Brion11, J. Brucker4,P.Brun11, R. Bühler1,T.Bulik12, I. Büsching13, T. Boutelier14,P.M.Chadwick5, A. Charbonnier15,R.C.G.Chaves1, A. Cheesebrough5, L.-M. Chounet16,A.C.Clapson1, G. Coignet17, M. Dalton9,M.K.Daniel5,I.D.Davids18,13, B. Degrange16,C.Deil1, H. J. Dickinson5, A. Djannati-Ataï7, W. Domainko1, L. O’C. Drury2, F. Dubois17, G. Dubus14, J. Dyks12, M. Dyrda19,K.Egberts1, D. Emmanoulopoulos8, P. Espigat7, C. Farnier20, F. Feinstein20, A. Fiasson20, A. Förster1, G. Fontaine16,M.Füßling9,S.Gabici2,Y.A.Gallant20,L.Gérard7, B. Giebels16, J. F. Glicenstein11, B. Glück4,P.Goret11, D. Hauser8, M. Hauser8,S.Heinz4, G. Heinzelmann21,G.Henri14,G.Hermann1,J.A.Hinton22, A. Hoffmann23, W. Hofmann1, M. Holleran13, S. Hoppe1,D.Horns21, A. Jacholkowska15, O. C. de Jager13, I. Jung4, K. Katarzynski´ 24,U.Katz4, S. Kaufmann8, E. Kendziorra23, M. Kerschhaggl9, D. Khangulyan1, B. Khélifi16,D. Keogh5,Nu.Komin11, K. Kosack1,G.Lamanna17,J.-P.Lenain10, T. Lohse9, V. Marandon7, J. M. Martin10, O. Martineau-Huynh15 , A. Marcowith20, D. Maurin15,T.J.L.McComb5,M.C.Medina10, R. Moderski12, E. Moulin11, M. Naumann-Godo16, M. de Naurois15, D. Nedbal25, D. -
Star Clusters
Star Clusters • Eventually, photons and stellar winds clear out the remaining gas and dust and leave behind the stars. • Reflection nebulae provide evidence for remaining dust on the far side of the Pleiades Star Clusters • It may be that all stars are born in clusters. • A good question is therefore why are most stars we see in the Galaxy not members of obvious clusters? • The answer is that the majority of newly-formed clusters are very weakly gravitationally bound. Perturbations from passing molecular clouds, spiral arms or mass loss from the cluster stars `unbind’ most clusters. Star Cluster Ages • We can use the H-R Diagram of the stars in a cluster to determine the age of the cluster. • A cluster starts off with stars along the full main sequence. • Because stars with larger mass evolve more quickly, the hot, luminous end of the main sequence becomes depleted with time. • The `main-sequence turnoff’ moves to progressively lower mass, L and T with time. • Young clusters contain short-lived, massive stars in their main sequence • Other clusters are missing the high-mass MSTO stars and we can infer the cluster age is the main-sequence lifetime of the highest mass star still on the main- sequence. 25Mo 3million years 104 3Mo 500Myrs 102 1M 10Gyr L o 1 0.5Mo 200Gyr 10-2 30000 15000 7500 3750 Temperature Star Clusters Sidetrip • There are two basic types of clusters in the Galaxy. • Globular Clusters are mostly in the halo of the Galaxy, contain >100,000 stars and are very ancient. • Open clusters are in the disk, contain between several and a few thousand stars and range in age from 0 to 10Gyr Galaxy Ages • Deriving galaxy ages is much harder because most galaxies have a star formation history rather than a single-age population of stars. -
Adrienne M. Cool CURRICULUM VITAE Department
Adrienne M. Cool CURRICULUM VITAE Department of Physics and Astronomy San Francisco State University Tel: (415)338-6450 1600 Holloway Avenue Fax: (415)338-2178 San Francisco, CA 94132 E-mail: [email protected] Education Ph.D. Astronomy, Harvard University (1994) M.S. Electrical Engineering, Columbia University (1986) B.S. Physics, Yale University (1984) Employment 2006–present Professor, Department of Physics and Astronomy San Francisco State University 2000–06 Associate Professor, Department of Physics and Astronomy San Francisco State University 1996–00 Assistant Professor, Department of Physics and Astronomy San Francisco State University 1993–96 Postdoctoral Researcher, Department of Astronomy University of California, Berkeley 1988–93 Research Assistant, Department of Astronomy Harvard University 1988–90 Teaching Assistant, Department of Astronomy Harvard University 1987 Research Assistant, Astrophysics Laboratory Columbia University 1986 Teaching Assistant, Department of Electrical Engineering Columbia University 1985 Research Assistant, Department of Electrical Engineering Columbia University 1984 Private instructor in mathematics and physics 1981–84 Technical Assistant, Department of Nuclear Medicine Mount Sinai Medical Center, New York City Honors and Awards • Image of globular star cluster Omega Centauri chosen for Hubble Heritage web site (2008) • Affirmative Action Award, San Francisco State University (2005) • Image of globular star cluster NGC 6397 chosen for Hubble Heritage web site (2003) • Presidential Award for Professional Development of Probationary Faculty, San Francisco State University (2000) 1 • Outstanding Contributions to Teaching Certificate, San Francisco State University (1997) • Fellow, NASA Graduate Student Researchers Program (1992-93) • Harvard Merit Fellowship (1990) • Danforth Center Certificate for Teaching Excellence, Harvard University (1989) • Amelia Earhart Fellowship Award, Zonta International Foundation (1989, 1990) • Teaching Assistant/Scholar Award, Columbia University, Dept. -
Luminous Blue Variables
Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs. -
NGC 362: Another Globular Cluster with a Split Red Giant Branch⋆⋆⋆⋆⋆⋆
A&A 557, A138 (2013) Astronomy DOI: 10.1051/0004-6361/201321905 & c ESO 2013 Astrophysics NGC 362: another globular cluster with a split red giant branch,, E. Carretta1, A. Bragaglia1, R. G. Gratton2, S. Lucatello2, V. D’Orazi3,4, M. Bellazzini1, G. Catanzaro5, F. Leone6, Y. M om any 2,7, and A. Sollima1 1 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: [email protected] 2 INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy 3 Dept. of Physics and Astronomy, Macquarie University, Sydney, NSW, 2109 Australia 4 Monash Centre for Astrophysics, Monash University, School of Mathematical Sciences, Building 28, Clayton VIC 3800, Melbourne, Australia 5 INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy 6 Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 78, 95123 Catania, Italy 7 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile Received 16 May 2013 / Accepted 11 July 2013 ABSTRACT We obtained FLAMES GIRAFFE+UVES spectra for both first- and second-generation red giant branch (RGB) stars in the globular cluster (GC) NGC 362 and used them to derive abundances of 21 atomic species for a sample of 92 stars. The surveyed elements include proton-capture (O, Na, Mg, Al, Si), α-capture (Ca, Ti), Fe-peak (Sc, V, Mn, Co, Ni, Cu), and neutron-capture elements (Y, Zr, Ba, La, Ce, Nd, Eu, Dy). The analysis is fully consistent with that presented for twenty GCs in previous papers of this series. Stars in NGC 362 seem to be clustered into two discrete groups along the Na-O anti-correlation with a gap at [O/Na] ∼ 0 dex. -
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. -
The Impact of the Astro2010 Recommendations on Variable Star Science
The Impact of the Astro2010 Recommendations on Variable Star Science Corresponding Authors Lucianne M. Walkowicz Department of Astronomy, University of California Berkeley [email protected] phone: (510) 642–6931 Andrew C. Becker Department of Astronomy, University of Washington [email protected] phone: (206) 685–0542 Authors Scott F. Anderson, Department of Astronomy, University of Washington Joshua S. Bloom, Department of Astronomy, University of California Berkeley Leonid Georgiev, Universidad Autonoma de Mexico Josh Grindlay, Harvard–Smithsonian Center for Astrophysics Steve Howell, National Optical Astronomy Observatory Knox Long, Space Telescope Science Institute Anjum Mukadam, Department of Astronomy, University of Washington Andrej Prsa,ˇ Villanova University Joshua Pepper, Villanova University Arne Rau, California Institute of Technology Branimir Sesar, Department of Astronomy, University of Washington Nicole Silvestri, Department of Astronomy, University of Washington Nathan Smith, Department of Astronomy, University of California Berkeley Keivan Stassun, Vanderbilt University Paula Szkody, Department of Astronomy, University of Washington Science Frontier Panels: Stars and Stellar Evolution (SSE) February 16, 2009 Abstract The next decade of survey astronomy has the potential to transform our knowledge of variable stars. Stellar variability underpins our knowledge of the cosmological distance ladder, and provides direct tests of stellar formation and evolution theory. Variable stars can also be used to probe the fundamental physics of gravity and degenerate material in ways that are otherwise impossible in the laboratory. The computational and engineering advances of the past decade have made large–scale, time–domain surveys an immediate reality. Some surveys proposed for the next decade promise to gather more data than in the prior cumulative history of astronomy. -
PSR J1740-3052: a Pulsar with a Massive Companion
Haverford College Haverford Scholarship Faculty Publications Physics 2001 PSR J1740-3052: a Pulsar with a Massive Companion I. H. Stairs R. N. Manchester A. G. Lyne V. M. Kaspi Fronefield Crawford Haverford College, [email protected] Follow this and additional works at: https://scholarship.haverford.edu/physics_facpubs Repository Citation "PSR J1740-3052: a Pulsar with a Massive Companion" I. H. Stairs, R. N. Manchester, A. G. Lyne, V. M. Kaspi, F. Camilo, J. F. Bell, N. D'Amico, M. Kramer, F. Crawford, D. J. Morris, A. Possenti, N. P. F. McKay, S. L. Lumsden, L. E. Tacconi-Garman, R. D. Cannon, N. C. Hambly, & P. R. Wood, Monthly Notices of the Royal Astronomical Society, 325, 979 (2001). This Journal Article is brought to you for free and open access by the Physics at Haverford Scholarship. It has been accepted for inclusion in Faculty Publications by an authorized administrator of Haverford Scholarship. For more information, please contact [email protected]. Mon. Not. R. Astron. Soc. 325, 979–988 (2001) PSR J174023052: a pulsar with a massive companion I. H. Stairs,1,2P R. N. Manchester,3 A. G. Lyne,1 V. M. Kaspi,4† F. Camilo,5 J. F. Bell,3 N. D’Amico,6,7 M. Kramer,1 F. Crawford,8‡ D. J. Morris,1 A. Possenti,6 N. P. F. McKay,1 S. L. Lumsden,9 L. E. Tacconi-Garman,10 R. D. Cannon,11 N. C. Hambly12 and P. R. Wood13 1University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL 2National Radio Astronomy Observatory, PO Box 2, Green Bank, WV 24944, USA 3Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710, Australia 4Physics Department, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8, Canada 5Columbia Astrophysics Laboratory, Columbia University, 550 W. -
Arxiv:Astro-Ph/0606633V2 4 Jul 2006
submitted to Astrophysical Journal Letters Preprint typeset using LATEX style emulateapj v. 6/22/04 A CURIOUS NEW MILKY WAY SATELLITE IN URSA MAJOR0 D. B. Zucker1, V.Belokurov1, N.W.Evans1, J. T. Kleyna2, M. J. Irwin1,M.I.Wilkinson1,M.Fellhauer1,D.M.Bramich1,G.Gilmore1, H. J. Newberg3,B.Yanny4,J.A.Smith5,6,P.C.Hewett1,E.F.Bell7, H.-W. Rix7, O.Y. Gnedin8,S.Vidrih1,R.F.G.Wyse9,B.Willman10, E. K. Grebel11,D.P.Schneider12,T.C.Beers13,A. Y.Kniazev7,14 J.C. Barentine15,H.Brewington15,J.Brinkmann15,M.Harvanek15, S.J. Kleinman16,J.Krzesinski15,17,D.Long15,A.Nitta18,S.A.Snedden15 submitted to Astrophysical Journal Letters ABSTRACT In this Letter, we study a localized stellar overdensity in the constellation of Ursa Major, first identified in Sloan Digital Sky Survey (SDSS) data and subsequently followed up with Subaru imaging. Its color-magnitude diagram (CMD) shows a well-defined sub-giant branch, main sequence and turn-off, from which we estimate a distance of ∼ 30 kpc and a projected size of ∼ 250 × 125 pc. The CMD suggests a composite population with some range in metallicity and/or age. Based on its extent and stellar population, we argue that this is a previously unknown satellite galaxy of the Milky Way, hereby named Ursa Major II (UMa II) after its constellation. Using SDSS data, we find an absolute magnitude of MV ∼ −3.8, which would make it the faintest known satellite galaxy. UMa II’s isophotes are irregular and distorted with evidence for multiple concentrations; this suggests that the satellite is in the process of disruption. -
Report of Contributions
Mapping the X-ray Sky with SRG: First Results from eROSITA and ART-XC Report of Contributions https://events.mpe.mpg.de/e/SRG2020 Mapping the X- … / Report of Contributions eROSITA discovery of a new AGN … Contribution ID : 4 Type : Oral Presentation eROSITA discovery of a new AGN state in 1H0707-495 Tuesday, 17 March 2020 17:45 (15) One of the most prominent AGNs, the ultrasoft Narrow-Line Seyfert 1 Galaxy 1H0707-495, has been observed with eROSITA as one of the first CAL/PV observations on October 13, 2019 for about 60.000 seconds. 1H 0707-495 is a highly variable AGN, with a complex, steep X-ray spectrum, which has been the subject of intense study with XMM-Newton in the past. 1H0707-495 entered an historical low hard flux state, first detected with eROSITA, never seen before in the 20 years of XMM-Newton observations. In addition ultra-soft emission with a variability factor of about 100 has been detected for the first time in the eROSITA light curves. We discuss fast spectral transitions between the cool and a hot phase of the accretion flow in the very strong GR regime as a physical model for 1H0707-495, and provide tests on previously discussed models. Presenter status Senior eROSITA consortium member Primary author(s) : Prof. BOLLER, Thomas (MPE); Prof. NANDRA, Kirpal (MPE Garching); Dr LIU, Teng (MPE Garching); MERLONI, Andrea; Dr DAUSER, Thomas (FAU Nürnberg); Dr RAU, Arne (MPE Garching); Dr BUCHNER, Johannes (MPE); Dr FREYBERG, Michael (MPE) Presenter(s) : Prof. BOLLER, Thomas (MPE) Session Classification : AGN physics, variability, clustering October 3, 2021 Page 1 Mapping the X- … / Report of Contributions X-ray emission from warm-hot int … Contribution ID : 9 Type : Poster X-ray emission from warm-hot intergalactic medium: the role of resonantly scattered cosmic X-ray background We revisit calculations of the X-ray emission from warm-hot intergalactic medium (WHIM) with particular focus on contribution from the resonantly scattered cosmic X-ray background (CXB). -
1990Aj 100. .445V the Astronomical Journal
.445V THE ASTRONOMICAL JOURNAL VOLUME 100, NUMBER 2 AUGUST 1990 100. MEASURING AGE DIFFERENCES AMONG GLOBULAR CLUSTERS HAVING SIMILAR METALLICITIES: A NEW METHOD AND FIRST RESULTS Don A. VandenBerg 1990AJ Department of Physics and Astronomy, University of Victoria, P.O. Box 1700, Victoria, British Columbia V8W 2Y2, Canada Michael BoLTEa) and Peter B. STETSONa),b) Dominion Astrophysical Observatory, National Research Council of Canada, 5071 West Saanich Road, Victoria, British Columbia V8X 4M6, Canada Received 2 April 1990; revised 4 May 1990 ABSTRACT A new method is described for comparing observed color-magnitude diagrams to obtain accurate relative ages for star clusters having similar chemical compositions. It is exceedingly simple and straightforward: the principal sequence for one system is superimposed on that for another by applying whatever vertical and horizontal shifts are needed to make their main-sequence turnoff segments coin- cide in both V magnitude and B — V color. When this has been done, any apparent separation of the two lower giant branch loci can be interpreted in terms of an age disparity since, as is well known from basic theory, the color difference between the turnoff and the giant branch is a monotonie and inverse function of age. This diagnostic has the distinct advantage that it is strictly independent of distance, reddening, and the zero-point of color calibrations; and theoretical isochrones show it to be nearly independent of metallicity—particularly for [m/H] < — 1.2. (In fact, if the cluster photometry is secure and the metal abundance is accurately known, our technique provides an excellent way to determine relative reddenings.