A kpc-scale resolved study of unobscured and obscured star-formation activity in normal galaxies at z = 1.5 and 2.2 from ALMA and HiZELS

TL;DR

This study uses ALMA and HST observations to analyze star formation, stellar, and dust properties in high-redshift galaxies at kiloparsec scales, revealing links between galaxy mass, metallicity, and dust distribution.

Contribution

First detailed multi-wavelength, high-resolution analysis of star formation and dust in normal galaxies at z~1.5-2.2 combining ALMA, HST, and integral-field spectroscopy.

Findings

Higher ALMA detection rates in more massive and metal-rich galaxies.

Dust extends up to 8 kpc with smooth morphology, even in clumpy Hα galaxies.

Detected galaxies have dust half-light radii around 4.5 kpc, larger than similar submillimetre galaxies.

Abstract

We present Atacama Large Millimeter/Submillimeter Array (ALMA) continuum observations of a sample of nine star-forming galaxies at redshifts 1.47 and 2.23 selected from the High-$z$ Emission Line Survey (HiZELS). Four galaxies in our sample are detected at high significance by ALMA at a resolution of 0.25'' at rest-frame 355 $\mu$m. Together with the previously observed H$\alpha$ emission, from adaptive optics-assisted integral-field-unit spectroscopy (0.15'' resolution), and F606W and F140W imaging from the Hubble Space Telescope (0.2'' resolution), we study the star-formation activity, stellar and dust mass in these high-redshift galaxies at $\sim$kpc-scale resolution. We find that ALMA detection rates are higher for more massive galaxies ($M_*>10^{10.5}$ M$_\odot$) and higher [N {\sc ii}]/H$\alpha$ ratios ($>0.25$, a proxy for gas-phase metallicity). The dust extends out to a radius of 8 kpc, with a smooth structure, even for those galaxies presenting clumpy H$\alpha$ morphologies. The half-light radii ($R_{\rm dust}$) derived for the detected galaxies are of the order $\sim$4.5 kpc, more than twice the size of submillimetre-selected galaxies at a similar redshift. Our global star-formation rate estimates -- from far-IR and extinction-corrected H$\alpha$ luminosities -- are in good agreement. However, the different morphologies of the different phases of the interstellar medium suggest complex extinction properties of the high-redshift normal galaxies.