Resolving a dusty, star-forming SHiZELS galaxy at z = 2.2 with HST, ALMA, and SINFONI on kiloparsec scales

Abstract

ABSTRACT We present ∼0.15 arcsec spatial resolution imaging of SHiZELS-14, a massive ($M_{*}\sim 10^{11}\, \rm {M_{\odot }}$), dusty, star-forming galaxy at z = 2.24. Our rest-frame ${\sim}1\, \rm {kpc}$-scale, matched-resolution data comprise four different widely used tracers of star formation: the $\rm {H}\,\alpha$ emission line (from SINFONI/VLT), rest-frame UV continuum (from HST F606W imaging), the rest-frame far-infrared (from ALMA), and the radio continuum (from JVLA). Although originally identified by its modest $\rm {H}\,\alpha$ emission line flux, SHiZELS-14 appears to be a vigorously star-forming ($\rm {SFR}\sim 1000\, \rm {M_{\odot }\, yr^{-1}}$) example of a submillimetre galaxy, probably undergoing a merger. SHiZELS-14 displays a compact, dusty central starburst, as well as extended emission in $\rm {H}\,\alpha$ and the rest-frame optical and FIR. The UV emission is spatially offset from the peak of the dust continuum emission, and appears to trace holes in the dust distribution. We find that the dust attenuation varies across the spatial extent of the galaxy, reaching a peak of at least AH α ∼ 5 in the most dusty regions, although the extinction in the central starburst is likely to be much higher. Global star-formation rates inferred using standard calibrations for the different tracers vary from ${\sim}10\!-\!1000\, \rm {M_{\odot }\, yr^{-1}}$, and are particularly discrepant in the galaxy’s dusty centre. This galaxy highlights the biased view of the evolution of star-forming galaxies provided by shorter wavelength data.