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ELLIPTICAL GALAXY MASSES OUT TO FIVE EFFECTIVE RADII: THE REALM OF DARK MATTER

Deason, AJ and Belokurov, V and Evans, NW and McCarthy, IG (2012) ELLIPTICAL GALAXY MASSES OUT TO FIVE EFFECTIVE RADII: THE REALM OF DARK MATTER. ASTROPHYSICAL JOURNAL, 748 (1). pp. 1-10. ISSN 0004-637X

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Abstract

We estimate the masses of elliptical galaxies out to five effective radii using planetary nebulae and globular
clusters as tracers. A sample of 15 elliptical galaxies with a broad variation in mass is compiled from the
literature. A distribution function-maximum likelihood analysis is used to estimate the overall potential slope,
normalisation and velocity anisotropy of the tracers. We assume power-law profiles for the potential and
tracer density and a constant velocity anisotropy. The derived potential power-law indices lie in between the
isothermal and Keplerian regime and vary with mass: there is tentative evidence that the less massive galaxies
have steeper potential profiles than the more massive galaxies. We use stellar mass-to-light ratios appropriate
for either a Chabrier/KTG (Kroupa, Tout & Gilmore) or Salpeter initial mass function to disentangle the stellar
and dark matter components. The fraction of dark matter within five effective radii increases with mass, in
agreement with several other studies. We employ simple models to show that a combination of star formation
efficiency and baryon extent are able to account for this trend. These models are in good agreement with both
our measurements out to five effective radii and recent SLACS measurements within one effective radii when
a universal Chabrier/KTG initial mass function is adopted.

Item Type: Article
Additional Information: Copyright IOP Publishing
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: IOP PUBLISHING LTD
Related URLs:
Date Deposited: 28 May 2015 14:15
Last Modified: 08 Sep 2015 13:51
DOI or Identification number: 10.1088/0004-637X/748/1/2
URI: http://researchonline.ljmu.ac.uk/id/eprint/1318

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