The Outer Halo of the Nearest Giant Elliptical : A VLT/VIMOS Survey of the Resolved Stellar Populations in Centaurus A to 85 kpc
We present the first deep survey of resolved stellar populations in the remote outer halo of our nearest giant elliptical (gE), Centaurus A (D=3.8 Mpc). Using the VIMOS/VLT optical camera, we obtained deep photometry for four fields along the major and minor axes at projected elliptical radii of ~30-85 kpc (corresponding to ~5-14 R_{eff}). We use resolved star counts to map the spatial and colour distribution of red giant branch (RGB) stars down to ~2 magnitudes below the RGB tip. We detect an extended halo out to the furthermost elliptical radius probed (~85 kpc or ~14 R_{eff}), demonstrating the vast extent of this system. We detect a localised 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]_{med} -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 ~-0.002 to -0.004 dex/kpc and the fraction of metal-poor stars (defined as [Fe/H]
Item Type | Article |
---|---|
Additional information | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. © 2013 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Keywords | astro-ph.co |
Date Deposited | 15 May 2025 13:11 |
Last Modified | 31 May 2025 00:06 |
-
picture_as_pdf - 1303.4736.pdf
-
subject - Submitted Version