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Published March 2009 | public
Journal Article

AzTEC millimetre survey of the COSMOS field - II. Source count overdensity and correlations with large-scale structure


We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg^2 AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z≲ 1.1. This portion of the COSMOS field shows a ~3σ overdensity of robust SMG detections when compared to a background, or 'blank-field', population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes S_(1.1 mm) > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an overdensity significance of ≫ 4σ . We find that the overdensity and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the z ≲ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the survey region, and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.

Additional Information

© 2009 RAS. Accepted 2008 November 21; received 2008 October 23; in original form 2008 August 9. We thank the referee for their thorough reading and helpful comments. Support for this work was provided in part by NSF grant AST 05-40852 and a grant from the Korea Science & Engineering Foundation (KOSEF) under a cooperative Astrophysical Research Center of the Structure and Evolution of the Cosmos (ARCSEC). IA and DHH acknowledge partial support by CONACyT from research grants 39953-F and 39548-F.

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August 21, 2023
October 18, 2023