Oral Presentation

Discovery of a [CI]-faint, CO-bright Galaxy: ALMA Observations of the Merging Galaxy NGC 6052

Author(s): Tomonari Michiyama (KIAA/PKU)

Presenter: Tomonari Michiyama (Kavli Institute for Astronomy and Astrophysics / Peking University)

We observed [CI] (3P1-3P0) and CO (4-3) in 35 Ultra/Luminous Infrared Galaxies (U/LIRGs) by using Band 8 receiver and Atacama Compact Array (ACA). Here, we report the result of a merging galaxy NGC 6052 that shows extremely weak [CI] (3P1-3P0) emission. In this galaxy, CO (4-3) is detection but [CI] (3P1-3P0) is non-detection with an upper limit of [CI] (3P1-3P0)/CO(4-3) < 0.07. It’s [CI] (3P1-3P0) emission is also weaker than expected given the molecular gas mass inferred from CO (1-0) and CO (2-1). This suggests that [CI] (3P1-3P0) may not be a reliable tracer of molecular gas mass in this galaxy. Dense (>10^5 cm-3) photodissociation regions may explain the unusual weakness [CI] (3P1-3P0) / CO (4-3) ratio, conditions that might arise naturally in the ongoing merging process. This result is published in Michiyama et al. 2020, ApJ, 897L, 19.