Multi-wavelength Properties of Radio- and Machine-learning-identified Counterparts to Submillimeter Sources in S2COSMOS
Abstract
We identify multi-wavelength counterparts to 1147 submillimeter sources from the S2COSMOS SCUBA-2 survey of the COSMOS field by employing a recently developed radio+machine-learning method trained on a large sample of Atacama Large Millimeter/submillimeter Array (ALMA)-identified submillimeter galaxies (SMGs), including 260 SMGs identified in the AS2COSMOS pilot survey. In total, we identify 1222 optical/near-infrared (NIR)/radio counterparts to the 897 S2COSMOS submillimeter sources with S 850 > 1.6 mJy, yielding an overall identification rate of (78 ± 9)%. We find that (22 ± 5)% of S2COSMOS sources have multiple identified counterparts. We estimate that roughly 27% of these multiple counterparts within the same SCUBA-2 error circles very likely arise from physically associated galaxies rather than line-of-sight projections by chance. The photometric redshift of our radio+machine-learning-identified SMGs ranges from z = 0.2 to 5.7 and peaks at z = 2.3 ± 0.1. The AGN fraction of our sample is (19 ± 4)%, which is consistent with that of ALMA SMGs in the literature. Comparing with radio/NIR-detected field galaxy population in the COSMOS field, our radio+machine-learning-identified counterparts of SMGs have the highest star formation rates and stellar masses. These characteristics suggest that our identified counterparts of S2COSMOS sources are a representative sample of SMGs at z ≲ 3. We employ our machine-learning technique to the whole COSMOS field and identified 6877 potential SMGs, most of which are expected to have submillimeter emission fainter than the confusion limit of our S2COSMOS surveys ({S}850μ {{m}}≲ 1.5 mJy). We study the clustering properties of SMGs based on this statistically large sample, finding that they reside in high-mass dark matter halos ((1.2 ± 0.3) × 1013 h -1 {M}⊙ ), which suggests that SMGs may be the progenitors of massive ellipticals we see in the local universe.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2019
- DOI:
- 10.3847/1538-4357/ab4d53
- arXiv:
- arXiv:1910.03596
- Bibcode:
- 2019ApJ...886...48A
- Keywords:
-
- Observational astronomy;
- Starburst galaxies;
- High-redshift galaxies;
- Galaxy formation;
- Galaxy evolution;
- Submillimeter astronomy;
- Clustering;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 24 pages, 14 figures, 3 tables, resubmitted to ApJ