The Effect of Galaxy Interactions on Molecular Gas Properties
Hsi-An Pan1*, Lihwai Lin1, Bau-Ching Hsieh1, Ting Xiao2, Yang Gao3, Sara L. Ellison4, Jillian M. Scudder5, Jorge Barrera-Ballesteros6, Fangting Yuan3, Amelie Saintonge7, Christine D. Wilson8, Ho Seong Hwang9, Ilse De Looze7,10, Yu Gao11, Luis C. Ho12, Elias Brinks13, Angus Mok14, Toby Brown8, Timothy A. Davis15, Thomas G. Williams15, Aeree Chung16, Harriet Parsons17, Martin Bureau18, Mark T. Sargent19, Eun Jung Chung20, Eunbin Kim21, Tie Liu20, Micha􏰀l J. Micha􏰀lowski22, Tomoka Tosaki23
1Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
2Department of Physics, Zhejiang University, Hangzhou, China
3Shanghai Astronomical Observatory, Shanghai, China
4Department of Physics and Astronomy, University of Victoria, British Columbia, Canada
5Department of Physics and Astronomy, Oberlin College, Ohio, USA
6Department of Physics and Astronomy, Johns Hopkins University, Maryland, USA
7University College London, London, UK
8Department of Physics and Astronomy, McMaster University, Hamilton, Canada
9Quantum Universe Center, Korea Institute for Advanced Study, Seoul, Korea
10Sterrenkundig Observatorium, Ghent University, Gent, Belgium
11Purple Mountain Observatory & Key Laboratory for Radio Astronomy, Chinese Academy of Sciences, Nanjing, China
12Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing, China
13Centre for Astrophysics Research, University of Hertfordshire, Hatfield, UK
14Department of Physics & Astronomy, The University of Toledo, Ohio, USA
15School of Physics and Astronomy, Cardiff University, Cardiff, UK
16Department of Astronomy, Yonsei University, Seoul, Korea
17East Asian Observatory, Hawaii, USA
18Sub-Department of Astrophysics, University of Oxford, Oxford, UK
19Department of Physics and Astronomy, University of Sussex, Brighton, UK
20Korea Astronomy and Space Science Institute, Daejeon, Korea
21School of Space Research, Kyung Hee University, Gyeonggi, Korea
22Astronomical Observatory Institute, dam Mickiewicz University, Poznao, Poland
23Joetsu University of Education, Niigata, Japan
* Presenter:Hsi-An Pan,
Galaxy interactions are often accompanied by an enhanced star formation rate (SFR). Since molecular gas is essential for star formation, it is vital to establish whether, and by how much, galaxy interactions affect the molecular gas properties. We investigate the effect of interactions on global molecular gas properties by studying a sample of 58 galaxies in pairs and 154 control (isolated) galaxies. This is the first time that the dependence of molecular gas properties on merger configurations is probed statistically with a relatively large sample and with a carefully-selected control sample for individual galaxies.

Our results show that the SFR, gas mass, and gas fraction are all enhanced in galaxies in pairs compared to the controls matched in redshift, mass, and effective radius, while the enhancement of star formation efficiency is not significant. Moreover, the enhancements in SFR, gas mass and gas fraction increase with decreasing pair separation and are larger in systems with smaller stellar mass ratio. Conversely, the star formation efficiency is only enhanced in close pairs (separation < 20 kpc) and equal-mass systems. We conclude that galaxy interactions do modify the molecular gas properties, although the strength of the effect is merger configuration dependent.

Keywords: galaxies: interactions, galaxies: star formation, galaxies: ISM, ISM: molecules