Plausible Boosting of Millimeter-Galaxies in the COSMOS Field by Intervening Large-Scale Structure


Paper:	Plausible Boosting of Millimeter-Galaxies in the COSMOS Field by Intervening Large-Scale Structure
Volume:	446, Galaxy Evolution: Infrared to Millimeter Wavelength Perspective
Page:	89
Authors:	Aretxaga, I.; Wilson, G. W.; Aguilar, E.; Alberts, S.; Scott, K. S.; Scoville, N.; Yun, M. S.; Austermann, J.; Downes, T. D.; Ezawa, H.; Hatsukade, B.; Hughes, D. H.; Kawabe, R.; Kohno, K.; Oshima, T.; Perera, T. A.; Tamura, Y.; Zeballos, M.
Abstract:	The 0.72 sq. deg. contiguous 1.1mm survey in the central area of the COSMOS field, carried out to a 1σ≈1.26 mJy beam^-1 depth with the AzTEC camera mounted on the 10m Atacama Submillimeter Telescope Experiment (ASTE), shows number counts with a significant excess of sources when compared to the number counts derived from the ∼0.5 sq. deg. area sampled at similar depths in the Scuba HAlf Degree Extragalactic Survey (SHADES, Austermann et al. 2010). They are, however, consistent with those derived from fields that were considered too small to characterize the overall blank-field population. We identify differences to be more significant in the S_1.1mm ∼> 5 mJy regime, and demonstrate that these excesses in number counts are related to the areas where galaxies at redshifts ∼< 1.1 are more densely clustered. The positions of optical-IR galaxies in the redshift interval 0.6 ∼< z ∼< 0.75 are the ones that show the strongest correlation with the positions of the 1.1mm bright population (S_1.mm ∼>5 mJy), a result which does not depend exclusively on the presence of rich clusters within the survey sampled area. The most likely explanation for the observed excess in number counts at 1.1mm is galaxy-galaxy and galaxy-group lensing at moderate amplification levels, that increases in amplitude as one samples larger and larger flux densities.