The Effect of Galaxy Interactions on Molecular Gas Properties

Hsi-An Pan^1*, 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 Looze^7,10, 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, email:hapan@asiaa.sinica.edu.tw

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