WISE J044232.92+322734.9: A star-forming galaxy at redshift 1.1 seen through a Galactic dust clump?

TL;DR

This study identifies a star-forming galaxy at redshift 1.1 projected against a Galactic dust clump, using infrared and submillimetre data, and derives its physical properties suggesting it is an ultraluminous infrared galaxy and similar to submillimetre galaxies.

Contribution

First identification of a high-redshift star-forming galaxy projected onto a Galactic dust clump using multiwavelength data and spectral energy distribution modeling.

Findings

Redshift of the galaxy is approximately 1.13.

Galaxy's IR luminosity indicates it is ultraluminous.

Physical properties are consistent with submillimetre galaxy characteristics.

Abstract

Physically unassociated background or foreground objects seen towards submillimetre sources are potential contaminants of both the studies of young stellar objects embedded in Galactic dust clumps and multiwavelength counterparts of submillimetre galaxies (SMGs). We employed the near-infrared and mid-infrared data from the Wide-field Infrared Survey Explorer (WISE) and the submillimetre data from the Planck satellite, and uncovered a source, namely WISE J044232.92+322734.9, whose WISE infrared colours suggest that it is a star-forming galaxy (SFG), and which is seen in projection towards the Planck-detected dust clump PGCC G169.20-8.96. We used the MAGPHYS+photo-$z$ spectral energy distribution code to derive the photometric redshift and physical properties of J044232.92. The redshift was derived to be $z_{\rm phot}=1.132^{+0.280}_{-0.165}$, while, for example, the stellar mass, IR (8-1 000 $\mu$m) luminosity, and star formation rate were derived to be $M_{\star}=4.6^{+4.7}_{-2.5}\times10^{11}$ M$_{\odot}$, $L_{\rm IR}=2.8^{+5.7}_{-1.5}\times10^{12}$ L$_{\odot}$, and ${\rm SFR}=191^{+580}_{-146}$ ${\rm M}_{\odot}$ yr$^{-1}$. The derived value of $L_{\rm IR}$ suggests that J044232.92 could be an ultraluminous infrared galaxy, and we found that it is consistent with a main sequence SFG at a redshift of 1.132. Moreover, the estimated physical properties of J044232.92 are comparable to those of SMGs. Further observations, in particular high-resolution (sub-)millimetre and radio continuum imaging, are needed to better constrain the redshift and physical properties of J044232.92 and to see if the source really is a galaxy seen through a Galactic dust clump, in particular an SMG population member at $z\sim1.1$.