Bulgeless Galaxies at Intermediate Redshift: Sample Selection, Colour   Properties, and the Existence of Powerful AGN
  We present a catalogue of bulgeless galaxies, which includes 19225 objects selected in four of the deepest, largest multi-wavelength datasets available -- COSMOS, AEGIS, GEMS and GOODS -- at intermediate redshift ($0.4 \leq z \leq 1.0$). The morphological classification was provided by the Advanced Camera for Surveys General Catalogue (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 analyse the properties of the sample and the evolution of pure-disc systems with redshift. Very massive [$\log (M_\star/M_{\odot}) > 10.5$] bulgeless galaxies contribute to ~30% of the total galaxy population number density at $z \geq 0.7$, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure discs appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogues were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 AGN 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 Universe history. 
Luca Bizzocchi, Mercedes E. Filho, Elvira Leonardo, Marco Grossi,   Roger L. Griffith, Jos\'e Afonso, Cristina Fernandes, Jo...
astro-ph.GA