University of Hertfordshire

From the same journal

From the same journal

By the same authors


  • Giulio Violino
  • S.L. Ellison
  • M. Sargent
  • Kristen Coppin
  • Jillian Scudder
  • Trevor Mendel
  • A. Saintonge
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Original languageEnglish
Pages (from-to)2591-2604
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Early online date10 Feb 2018
Publication statusPublished - 11 May 2018


We investigate the connection between star formation and molecular gas properties in galaxy mergers at low redshift (z ≤ 0.06). The study we present is based on IRAM 30-m CO(1-0) observations of 11 galaxies with a close companion selected from the Sloan Digital Sky Survey (SDSS). The pairs have mass ratios ≤4, projected separations r p ≤ 30 kpc and velocity separations ΔV ≤ 300 km s -1, and have been selected to exhibit enhanced specific star formation rates (sSFRs). We calculate molecular gas (H 2) masses, assigning to each galaxy a physically motivated conversion factor αCO, and we derive molecular gas fractions and depletion times. We compare these quantities with those of isolated galaxies from the extended CO Legacy Data base for the GALEX Arecibo SDSS Survey sample (xCOLDGASS; Saintonge et al.) with gas quantities computed in an identical way. Ours is the first study which directly compares the gas properties of galaxy pairs and those of a control sample of normal galaxies with rigorous control procedures and for which SFR and H 2 masses have been estimated using the same method. We find that the galaxy pairs have shorter depletion times and an average molecular gas fraction enhancement of 0.4 dex compared to the mass matched control sample drawn from xCOLDGASS. However, the gas masses (and fractions) in galaxy pairs and their depletion times are consistent with those of non-mergers whose SFRs are similarly elevated. We conclude that both external interactions and internal processes may lead to molecular gas enhancement and decreased depletion times.


This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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