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arXiv · 2407.19881

The Nature of 500 micron Risers III: A Small Complete Sample

D. L. Clements·J. Cairns·J. Greenslade·G. Petitpas·Y. Ding·I. Pérez-Fournon·D. Riechers
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Abstract

Herschel surveys have found large numbers of sources with red far-IR colours, and spectral energy distributions (SEDs) rising from 250 to 500$\mu$m: 500 risers. The nature and role of these sources is not fully understood. We here present Submillimeter Array (SMA) interferometric imaging at 200 GHz of a complete sample of five 500 risers with F500 $>$ 44 mJy selected within a 4.5 square degree region of the XMMLSS field. These observations can resolve the separate components of multiple sources and allow cross identification at other wavelengths using the extensive optical-to-IR data in this field. Of our five targets we find that two are likely gravitationally lensed, two are multiple sources, and one an isolated single source. Photometric redshifts, using optical-to-IR data and far-IR/submm data, suggest they lie at redshifts $z \sim 2.5 - 3.5$. Star formation rates and stellar masses estimated from the SEDs show that the majority of our sources lie on the star-formation rate-stellar mass `main sequence', though with outliers both above and below this relation. Of particular interest is our most multiple source which consists of three submm emitters and one submm-undetected optical companion within a 7 arcsecond region, all with photometric redshifts $\sim$ 3. One of the submm emitters in this group lies above the `main sequence', while the optical companion lies well below the relation, and has an estimated stellar mass of 3.3$\pm 1.3 \times$10$^{11}$ M$_{\odot}$. We suggest this object is a forming brightest cluster galaxy (BCG) in the process of accreting actively star forming companions.

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D. L. Clements, J. Cairns, J. Greenslade, G. Petitpas, Y. Ding, I. Pérez-Fournon, D. Riechers. 2024-07-29. The Nature of 500 micron Risers III: A Small Complete Sample. https://arxiv.org/abs/2407.19881

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