ALMA-FACTS: ALMA FundAmental CO 1-0 Transition Survey of Nearby Galaxies

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

Giant Molecular Clouds (GMCs) are huge concentrations of gas that are formed via the attractive force of gravity. Throughout cosmic time, the gas in GMCs has been converted into stars. This process is still under way, and we can see ongoing star formation within GMCs in the Milky Way and nearby galaxies. This research program investigates the evolution of molecular gas and GMCs in twelve nearby galaxies using the Atacama Large Millimeter/submillimeter Array (ALMA). It will study how the GMCs form and evolve and how they start forming stars in the galaxies. This program also integrates research and education by involving graduate and undergraduate students in the research activities, with a focus on recruiting students who discover a passion for science later in their academic careers. This program is built on the ALMA-FACTS survey (FundAmental CO 1-0 Transition Survey) of 12 nearby spiral galaxies. FACTS studies the evolution of molecular gas –by means of the systematic variations in the CO J=2-1/1-0 line ratio (R21) –on GMC scales within and among the galaxies. The galaxies are selected from the legacy surveys with a variety of telescopes (ALMA, HST, JWST, Spitzer, and Herschel), which provide rich ancillary data. FACTS utilizes the existing high-resolution CO(2-1) data of the same set of galaxies from ALMA, observing the same regions at the same physical resolution and mass sensitivity. Historically, CO(1-0) has been the yardstick of molecular gas observations, while CO(2-1) is now becoming a new standard due to its easier detectability. FACTS will characterize any systematic effects in R21 and bridge the gap between the historic CO(1-0) observations and the new standard. The main scientific goals are (1) to study systematic variations of R21 (i.e., the evolution of molecular gas) on GMC scales, in arms and interarm regions, bars, and from the centers to outskirts within/among galaxies, (2) to study the environmental conditions for SF at various stages, including GMCs on the verge of SF (i.e., having high R21, but no SF), and (3) to assess the capabilities and limitations of CO(2-1) with respect to CO(1-0), as CO(2-1) is becoming the new standard for tracing bulk molecular gas in galaxies. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.