Title: Unbiased survey for Ly-alpha blobs at z~3-5 -- Direct probes for galaxy formation
Author(s): Tomoki Saito (Ehime Univ.), SXDS team, COSMOS team, (more than ten co-authors)
Abstract:

We present the results of unbiased survey for Ly-alpha blobs (LABs) 
in blank fields at z~3-5. We carried out wide-field, deep imaging survey 
with Subaru/Suprime-Cam and a set of intermediate-band filters 
in two blank fields, SXDS-S and COSMOS. The wide field-of-view and 
the large redshift coverages enable us to search selectively for 
objects with large equivalent widths over a large survey volume, 
~10^6 Mpc^3, giving a sample of ~60 LABs. 

We showed that LABs are common in the early universe, even in normal 
fields without protoclusters. Deep VLT/VIMOS spectroscopy 
showed that about a half of them are normal starbursts, and 
~30% have superwind activities. Excluding these, ~40% of our 
spectroscopic sample have large equivalent widths and no clear signatures 
of outflows. They clearly show positive correlation between the 
Ly-alpha luminosity and the velocity width, sugesting that their 
ionizing sources are possibly cold accretion of the primordial gas. 

Most of our objects do not show any signitures of overdensity, 
and have no NIR counterparts, unlike the known LABs in protoclusters. 
Thanks to our wide survey area, we detected 
both LABs with and without overdensity, and those in overdensity show 
high detection rate in Spitzer/IRAC data. This suggests that 
LABs in overdensity are likely to be stellar-massive, superwind galaxies. 
On the other hand, isolated LABs includes very good candidates for 
protogalaxies in very early phases of their assembly. 
Our blind search for LABs with intermediate-band filters is thus 
quite efficient way to find direct observational probes of galaxy formation.