L. Bizzocchi, M. E. Filho, E. Leonardo, M. Grossi, R. L. Griffith, J. Afonso, C. S. Fernandes, J. Retrê, S. Antón, E. F. Bell, J. Brinchmann, B. Henriques, C. Lobo, H. Messias
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★/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.
catalogs – galaxies: evolution – galaxies: structure – X-rays: galaxies
The Astrophysical Journal
Volume 782, Number 1, Page 22_1