Molecular gas kinematics in local early-type galaxies with ALMA

TL;DR

This paper reviews a decade of ALMA observations revealing the distribution and movement of cold molecular gas in local early-type galaxies, challenging previous assumptions about their gas content and informing galaxy evolution models.

Contribution

It provides a comprehensive summary of ALMA's high-resolution studies of cold gas kinematics in early-type galaxies over the past ten years.

Findings

Detection of significant cold molecular gas in ETGs

Detailed kinematic maps of gas reservoirs

Insights into SMBH fueling and feedback processes

Abstract

Local early-type galaxies (ETGs) are mostly populated by old stars, with little or no recent star formation activity. For this reason, they have historically been believed to be essentially devoid of cold gas, that is the fuel for the formation of new stars. Over the past two decades, however, increasingly-sensitive instrumentation observing the sky at (sub-)mm wavelengths has revealed the presence of significant amounts of cold molecular gas in the hearts of nearby ETGs. The unprecedented capabilities offered by the Atacama Large Millimeter/submillimeter Array (ALMA), in particular, have allowed us to obtain snapshots of the central regions of these ETGs with unprecedented detail, mapping this gas with higher sensitivity and resolution than ever possible before. Studies of the kinematics of the observed cold gas reservoirs are crucial for galaxy formation and evolution theories, providing - e.g. - constraints on the fundamental properties and fuelling/feedback processes of super-massive black holes (SMBHs) at the centre of these galaxies. In this brief review, we summarise what the first ten years of ALMA observations have taught us about the distribution and kinematics of the cold molecular gas component in nearby ellipticals and lenticulars.