Galaxy And Mass Assembly (GAMA): The input catalogue and star-galaxy separation

Abstract

We describe the spectroscopic target selection for the Galaxy And Mass Assembly (GAMA) survey. The input catalogue is drawn from the Sloan Digital Sky Survey (SDSS) and UKIRT Infrared Deep Sky Survey (UKIDSS). The initial aim is to measure redshifts for galaxies in three 4° × 12° regions at 9, 12 and 14.5 h, on the celestial equator, with magnitude selections r<19.4, z<18.2 and KAB < 17.6 over all three regions, and r<19.8 in the 12-h region. The target density is 1080 deg-2 in the 12-h region and 720 deg-2 in the other regions. The average GAMA target density and area are compared with completed and ongoing galaxy redshift surveys. The GAMA survey implements a highly complete star-galaxy separation that jointly uses an intensity-profile separator (Δsg = rpsf - rmodel as per the SDSS) and a colour separator. The colour separator is defined as Δsg,jk = J - K - f (g - i), where f (g - i) is a quadratic fit to the J - K colour of the stellar locus over the range 0.3 <g- i<2.3. All galaxy populations investigated are well separated with Δsg,jk > 0.2. From 2 yr out of a 3-yr AAOmega program on the Anglo-Australian Telescope, we have obtained 79 599 unique galaxy redshifts. Previously known redshifts in the GAMA region bring the total up to 98 497. The median galaxy redshift is 0.2 with 99 per cent at z<0.5. We present some of the global statistical properties of the survey, including K-band galaxy counts, colour-redshift relations and preliminary n(z). Show more