We present a 1.1mm stacking analysis of moderately massive (log($M_{ *}$/$M_{ \odot}$) = 10.7 $\pm$ 0.2) quiescent galaxies (QGs) at $\langle z\rangle \sim1.5$, searching for cold dust continuum emission, an excellent tracer of dust and gas mass. Using both the recent GOODS-ALMA survey as well as the full suite of ALMA Band-6 ancillary data in the GOODS-S field, we report the tentative detection of dust continuum equivalent of dust mass log($M_{ dust}$/$M_{ \odot}$) = 7.47 $\pm$ 0.13 and gas mass log($M_{ gas}$/$M_{ \odot}$) = 9.42 $\pm$ 0.14. The emerging gas fraction is $f_{ gas}$ = 5.3 $\pm$ 1.8%, consistent with the results of previous stacking analyses based on lower resolution sub(mm) observations. Our results support the scenario where high-z QGs have an order of magnitude larger $f_{ gas}$ compared to their local counterparts and have experienced quenching with a non negligible gas reservoir in their interstellar medium - i.e. with gas retention. Subsequent analysis yields an anti-correlation between the $f_{ gas}$ and the stellar mass of QGs, especially in the high mass end where galaxies reside in the most massive haloes. The $f_{ gas}$ - $M_{ *}$ anti-correlation promotes the selection bias as a possible solution to the tension between the stacking results pointing towards gas retention in high-z QGs of moderate $M_{ *}$ and the studies of individual targets that favour a fully depleted ISM in massive (log($M_{ *}$/$M_{ \odot}$) high-z QGs.
Categories: astro-ph.GA