Faint Submillimeter Galaxies Revealed by Multifield Deep ALMA Observations: Number Counts, Spatial Clustering, and A Dark Submillimeter Line Emitter

Understand

We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations.

• We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band 6 and Band 7 maps of 10 independent fields that reduce cosmic variance effects.
• The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy.
• Our number counts indicate that the faint (0.1-1.0 mJy, or SFR_IR ~ 30-300 Msun/yr) SMGs contribute nearly a half of the extragalactic background light (EBL), while the remaining half of the EBL is mostly contributed by very faint sources with flux densities of <0.1 mJy (SFR_IR <~ 30 Msun/yr).