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  4. The outer halo of the nearest giant elliptical: a VLT/VIMOS survey of the resolved stellar populations in Centaurus A to 85 kpc
 
research article

The outer halo of the nearest giant elliptical: a VLT/VIMOS survey of the resolved stellar populations in Centaurus A to 85 kpc

Crnojevic, D.
•
Ferguson, A. M. N.
•
Irwin, M. J.
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2013
Monthly Notices Of The Royal Astronomical Society

We present the first survey of resolved stellar populations in the remote outer halo of our nearest giant elliptical (gE), Centaurus A (D = 3.8 Mpc). Using the VIsible Multi Object Spectrograph (VIMOS)/Very Large Telescope (VLT) optical camera, we obtained deep photometry for four fields along the major and minor axes at projected elliptical radii of similar to 30-85 kpc (corresponding to similar to 5-14R(eff)). We use resolved star counts to map the spatial and colour distribution of red giant branch (RGB) stars down to similar to 2 mag below the RGB tip. We detect an extended halo out to the furthermost elliptical radius probed (similar to 85 kpc or similar to 14R(eff)), demonstrating the vast extent of this system. We detect a localized substructure in these parts, visible in both (old) RGB and (intermediate-age) luminous asymptotic giant branch stars, and there is some evidence that the outer halo becomes more elliptical and has a shallower surface brightness profile. We derive photometric metallicity distribution functions for halo RGB stars and find relatively high median metallicity values (<Fe/H similar to -0.9 to -1.0 dex) that change very little with radius over the extent of our survey. Radial metallicity gradients are measured to be approximate to -0.002-0.004 dex kpc(-1), and the fraction of metal-poor stars (defined as [Fe/H] < -1.0) is approximate to 40-50 per cent at all radii. We discuss these findings in the context of galaxy formation models for the buildup of gE haloes.

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Type
research article
DOI
10.1093/mnras/stt494
Web of Science ID

WOS:000319524600082

Author(s)
Crnojevic, D.
Ferguson, A. M. N.
Irwin, M. J.
Bernard, E. J.
Arimoto, N.
Jablonka, P.  
Kobayashi, C.
Date Issued

2013

Publisher

Oxford Univ Press

Published in
Monthly Notices Of The Royal Astronomical Society
Volume

432

Issue

1

Start page

832

End page

847

Subjects

galaxies: evolution

•

galaxies: individual: Cen A

•

galaxies: photometry

•

galaxies: stellar content

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LASTRO  
Available on Infoscience
October 1, 2013
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/95292
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