Title: Probing the diffuse and translucent clouds with absorption lines

Speaker: Dr. Gan Luo

Affiliation: Institut de radioastronomie millimétrique (IRAM)

Abstract: Molecular gas is the raw material for forming stars. However, the process by which diffuse molecular gas transforms into dense cores is not fully understood. With the increasing capabilities of millimeter telescopes such as ALMA and NOEMA, we are able to probe diffuse and translucent molecular clouds with unprecedented sensitivity. In this talk, I will introduce our recent progress with molecular absorption lines against quasars. Our observations reveal the ubiquitous CO-dark molecular gas (DMG) in the solar neighborhood, highlighting a consistent DMG properties for clouds in both the solar neighborhood and low-metallicity outer disk region. Notably, we have detected DCN in low-density gas for the first time. The over-budget deuteration fraction, exceeding predictions from current chemical models, suggests a possible enhancement in low-density gas. By combining our observations with chemical models, we have successfully demonstrated the feasibility of using O-bearing molecules to infer the cosmic-ray ionization rate. Our findings coincide with the cosmic-ray attenuation models, offering a plausible explanation for the discrepancy in the cosmic-ray ionization rate between measurements obtained from Voyager and ions.

Time: 14:00 PM on July 26 (Friday)

Location: Room 5-516,PMO

欢迎大家参加！