Bulgeless Galaxies at Intermediate Redshift: Sample Selection, Color Properties, and the Existence of Powerful Active Galactic Nuclei
Abstract
We present a catalog of bulgeless galaxies, which includes 19,225 objects selected in four of the deepest, largest multi-wavelength data sets available—COSMOS, AEGIS, GEMS, and GOODS—at intermediate redshift (0.4 <= z <= 1.0). The morphological classification was provided by the Advanced Camera for Surveys General Catalog (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyze the properties of the sample and the evolution of pure-disk systems with redshift. Very massive [log (M sstarf/M ⊙) > 10.5] bulgeless galaxies contribute to ~30% of the total galaxy population number density at z >= 0.7, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure disks appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogs were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 active galactic nuclei (AGNs) that reside in galaxies without a classical bulge. The finding of such peculiar objects at intermediate redshift shows that while AGN growth in merger-free systems is a rare event (0.2% AGN hosts in this sample of bulgeless galaxies), it can indeed happen relatively early in the history of the universe.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2014
- DOI:
- 10.1088/0004-637X/782/1/22
- arXiv:
- arXiv:1401.7767
- Bibcode:
- 2014ApJ...782...22B
- Keywords:
-
- catalogs;
- galaxies: evolution;
- galaxies: structure;
- X-rays: galaxies;
- Astrophysics - Galaxy Astrophysics
- E-Print:
- 49 pages, 13 figures