ALMA Lensing Cluster Survey: average dust, gas, and star formation properties of cluster and field galaxies from stacking analysis

Abstract: We develop new tools for continuum and spectral stacking of ALMA data, and apply these to the ALMA Lensing Cluster Survey (ALCS). We derive average dust masses, gas masses and star formation rates (SFR) from the stacked observed 260~GHz continuum of 3402 individually undetected star-forming galaxies, of which 1450 are cluster galaxies and 1952 field galaxies, over three redshift and stellar mass bins (over $z = 0$-1.6 and log $M_{} [M_{\odot}] = 8$-11.7), and derive the average molecular gas content by stacking the emission line spectra in a SFR-selected subsample. The average SFRs and specific SFRs of both cluster and field galaxies are lower than those expected for Main Sequence (MS) star-forming galaxies, and only galaxies with stellar mass of log $M_{} [M_{\odot}] = 9.35$-10.6 show dust and gas fractions comparable to those in the MS. The ALMA-traced average `highly obscured' SFRs are typically lower than the SFRs observed from optical to near-IR spectral analysis. Cluster and field galaxies show similar trends in their contents of dust and gas, even when field galaxies were brighter in the stacked maps. From spectral stacking we find a potential CO ($J=4\to3$) line emission (SNR $\sim4$) when stacking cluster and field galaxies with the highest SFRs.