1202.3891 (S. Fleuren et al.)

Herschel-ATLAS: VISTA VIKING near-IR counterparts in the Phase 1 GAMA 9h data    [PDF]

S. Fleuren, W. Sutherland, L. Dunne, D. J. B. Smith, S. J. Maddox, J. González-Nuevo, J. Findlay, R. Auld, M. Baes, N. A. Bond, D. G. Bonfield, N. Bourne, A. Cooray, S. Buttiglione, A. Cava, A. Dariush, G. De Zotti, S. P. Driver, S. Dye, S. Eales, J. Fritz, M. L. P. Gunawardhana, R. Hopwood, E. Ibar, R. J. Ivison, M. J. Jarvis, L. Kelvin, A. Lapi, J. Liske, M. J. Michalowski, M. Negrello, E. Pascale, M. Pohlen, M. Prescott, E. E. Rigby, A. Robotham, D. Scott, P. Temi, M. A. Thompson, E. Valiante, P. van der Werf

We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm sources, using a preliminary object catalogue from the VISTA VIKING survey. The sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h field, which includes all objects detected at 250, 350 or 500 um with the SPIRE instrument. We apply and discuss a likelihood ratio (LR) method for VIKING candidates within a search radius of 10" of the 22,000 SPIRE sources with a 5 sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a best VIKING counterpart with a reliability $R\ge 0.8$, and the false identification rate of these is estimated to be 4.2%. We expect to miss ~5% of true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the reliable counterparts to SPIRE galaxies are marginally redder than the field population. We obtain photometric redshifts for ~68% of all (non-stellar) VIKING candidates with a median redshift of 0.405. Comparing to the results of the optical identifications supplied with the Phase I catalogue, we find that the use of medium-deep near-infrared data improves the identification rate of reliable counterparts from 36% to 51%.

View original: http://arxiv.org/abs/1202.3891