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

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

doi:10.1111/j.1365-2966.2012.21048.x

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 $Rge 0.8$, 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%.

Herschel-ATLAS: VISTA VIKING near-IR counterparts in the Phase 1 GAMA 9-h data / Fleuren, S.; Sutherland, W.; Dunne, L.; Smith, D. J. B.; Maddox, S. J.; González Nuevo, J.; Findlay, J.; Auld, R.; Baes, M.; Bond, N. A.; Bonfield, D. G.; Bourne, N.; Cooray, A.; Buttiglione, S.; Cava, A.; Dariush, A.; De Zotti, G.; Driver, S. P.; Dye, S.; Eales, S.; Fritz, J.; Gunawardhana, M. L. P.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Jarvis, M. J.; Kelvin, L.; Lapi, Andrea; Liske, J.; Michalowski, M. J.; Negrello, M.; Pascale, E.; Pohlen, M.; Prescott, M.; Rigby, E. E.; Robotham, A.; Scott, D.; Temi, P.; Thompson, M. A.; Valiante, E.; van der Werf, P.. - In: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - ISSN 0035-8711. - 423:3(2012), pp. 2407-2424. [10.1111/j.1365-2966.2012.21048.x]