279 research outputs found

    Mayall II = G1 in M31: Giant Globular Cluster or Core of a Dwarf Elliptical Galaxy ?

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    (Abridged version) Mayall II = G1 is one of the brightest globular clusters belonging to M31, the Andromeda galaxy. Our observations with HST/WFPC2 provide data for the (I vs. V-I) and (V vs. V-I) color-magnitude diagrams. From model fitting, we determine a rather high mean metallicity of [Fe/H] = --0.95 +- 0.09, somewhat similar to 47 Tucanae. We find a larger spread in V-I than can be explained by the measurement errors, and we attribute this to an intrinsic metallicity dispersion amongst the stars of G1. So far, only omega Centauri, the giant Galactic globular cluster, has been known to exhibit such an intrinsic metallicity dispersion. Three estimates of the total mass of this globular cluster can be obtained: King mass = 15 x 10^6 with M/Lv ~ 7.5, Virial mass = 7.3 x 10^6 with M/Lv ~ 3.6, and King-Michie mass range from 14 to 17 x 10^6. Although uncertain, all of these mass estimates make G1 more than twice as massive as omega Centauri. Such large masses relate to the metallicity spread whose origin is still unknown (either self-enrichment, an inhomogeneous proto-cluster cloud, or remaining core of a dwarf galaxy). When considering the positions of G1 in the different diagrams defined by Kormendy (1985), G1 always appears on the sequence defined by globular clusters, and definitely away from the other sequences defined by elliptical galaxies, bulges, and dwarf spheroidal galaxies. The same is true for omega Centauri and for the nucleus of the dwarf elliptical NGC 205. This does not prove that all (massive) globular clusters are the remnant cores of nucleated dwarf galaxies.Comment: 24 pages, 5 figures, accepted for publication in AJ (August 2001

    'Just open your eyes a bit more': The methodological challenges of researching black and minority ethnic students' experiences of physical education teacher education

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    In this paper we discuss some of the challenges of centralising 'race' and ethnicity in Physical Education (PE) research, through reflecting on the design and implementation of a study exploring Black and minority ethnic students' experiences of their teacher education. Our aim in the paper is to contribute to ongoing theoretical and methodological debates about intersectionality, and specifically about difference and power in the research process. As McCorkel and Myers notes, the 'researchers' backstage'-the assumptions, motivations, narratives and relations-that underpin any research are not always made visible and yet are highly significant in judging the quality and substance of the resulting project. As feminists, we argue that the invisibility of 'race' and ethnicity within Physical Education Teacher Education (PETE), and PE research more widely, is untenable; however, we also show how centralising 'race' and ethnicity raised significant methodological and epistemological questions, particularly given our position as White researchers and lecturers. In this paper, we reflect on a number of aspects of our research 'journey': the theoretical and methodological challenges of operationalising concepts of 'race' and ethnicity, the practical issues and dilemmas involved in recruiting participants for the study, the difficulties of 'talking race' personally and professionally and challenges of representing the experiences of 'others'. © 2012 Copyright Taylor and Francis Group, LLC

    The intrinsic shape of galaxy bulges

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    The knowledge of the intrinsic three-dimensional (3D) structure of galaxy components provides crucial information about the physical processes driving their formation and evolution. In this paper I discuss the main developments and results in the quest to better understand the 3D shape of galaxy bulges. I start by establishing the basic geometrical description of the problem. Our understanding of the intrinsic shape of elliptical galaxies and galaxy discs is then presented in a historical context, in order to place the role that the 3D structure of bulges play in the broader picture of galaxy evolution. Our current view on the 3D shape of the Milky Way bulge and future prospects in the field are also depicted.Comment: Invited Review to appear in "Galactic Bulges" Editors: Laurikainen E., Peletier R., Gadotti D. Springer Publishing. 24 pages, 7 figure
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