TY - JOUR
T1 - Spatially unassociated galaxies contribute significantly to the blended submillimetre galaxy population
T2 - Predictions for follow-up observations of ALMA sources
AU - Hayward, Christopher C.
AU - Behroozi, Peter S.
AU - Somerville, Rachel S.
AU - Primack, Joel R.
AU - Moreno, Jorge
AU - Wechsler, Risa H.
PY - 2013/9
Y1 - 2013/9
N2 - There is anecdotal evidence that spatially and physically unassociated galaxies blended into a single submillimetre (submm) source contribute to the submm galaxy (SMG) population. This work is the first to theoretically predict the number counts of such sources. We generate mock SMG catalogues using light cones derived from the Bolshoi cosmological simulation; to assign submm flux densities to the mock galaxies, we use a fitting function previously derived from the results of dust radiative transfer performed on hydrodynamical simulations of isolated disc and merging galaxies. We then calculate submm number counts for different beam sizes and without blending. We predict that {similar or greater-than}50 per cent of blended SMGs have at least one spatially unassociated component with S850 > 1 mJy. For a 15-arcsec beam, blends of >2 galaxies in which at least one component is spatially unassociated dominate the blended sources with total S850 {similar or greater-than} 3mJy. The distribution of the redshift separations amongst the components is strongly bimodal. The typical redshift separation of spatially unassociated blended sources is ~1. Our predictions for the contributions of spatially unassociated components and the distribution of redshift separations are not testable with currently available data, but they will be easily tested once sufficiently accurate redshifts for the individual subcomponents (resolved by e.g. Atacama Large Millimeter/submillimeter Array) of a sufficient number of single-dish-detected blended SMGs are available.
AB - There is anecdotal evidence that spatially and physically unassociated galaxies blended into a single submillimetre (submm) source contribute to the submm galaxy (SMG) population. This work is the first to theoretically predict the number counts of such sources. We generate mock SMG catalogues using light cones derived from the Bolshoi cosmological simulation; to assign submm flux densities to the mock galaxies, we use a fitting function previously derived from the results of dust radiative transfer performed on hydrodynamical simulations of isolated disc and merging galaxies. We then calculate submm number counts for different beam sizes and without blending. We predict that {similar or greater-than}50 per cent of blended SMGs have at least one spatially unassociated component with S850 > 1 mJy. For a 15-arcsec beam, blends of >2 galaxies in which at least one component is spatially unassociated dominate the blended sources with total S850 {similar or greater-than} 3mJy. The distribution of the redshift separations amongst the components is strongly bimodal. The typical redshift separation of spatially unassociated blended sources is ~1. Our predictions for the contributions of spatially unassociated components and the distribution of redshift separations are not testable with currently available data, but they will be easily tested once sufficiently accurate redshifts for the individual subcomponents (resolved by e.g. Atacama Large Millimeter/submillimeter Array) of a sufficient number of single-dish-detected blended SMGs are available.
KW - Cosmology: theory
KW - Galaxies: abundances
KW - Galaxies: high-redshift
KW - Galaxies: luminosity function
KW - Large-scale structure of universe
KW - Mass function
KW - Submillimetre: galaxies
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U2 - https://doi.org/10.1093/mnras/stt1202
DO - https://doi.org/10.1093/mnras/stt1202
M3 - Article
SN - 1745-3925
VL - 434
SP - 2572
EP - 2581
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
IS - 3
ER -