Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2012-02-20
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
To appear in ApJ, 15 pages, 9 figures
Scientific paper
We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107x107 sq arcsec), allowing us to achieve remarkably high signal-to-noise ratios of ~20-70 per pixel in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions sigma* > 150 km/s, we study the radial dependence in the equivalent widths (EWs) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by ~50%, and only a weak correlation between sigma* and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are approximately an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5R_e, while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high alpha-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.
Adams Joshua J.
Comerford Julia M.
Gebhardt Karl
Greene Jenny E.
Murphy Jeremy D.
No associations
LandOfFree
The Stellar Halos of Massive Elliptical Galaxies does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Stellar Halos of Massive Elliptical Galaxies, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Stellar Halos of Massive Elliptical Galaxies will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-422013