Molecular and atomic gas in dust lane early-type galaxies - I. Low star formation efficiencies in minor merger remnants

Timothy A. Davis*, Kate Rowlands, James R. Allison, Stanislav S. Shabala, Yuan-Sen Ting, Claudia del P. Lagos, Sugata Kaviraj, Steve Eales, Rob. J. Ivison, Daniel J. B. Smith, Matthew W. L. Smith, Pasquale Temi, Nathan Bourne, Stephen Maddox, Loretta Dunne

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

In this work we present IRAM 30-m telescope observations of a sample of bulge-dominated galaxies with large dust lanes, which have had a recent minor merger. We find these galaxies are very gas rich, with H-2 masses between 4 x 10(8) and 2 x 10(10) M-circle dot. We use these molecular gas masses, combined with atomic gas masses from an accompanying paper, to calculate gas-to-dust and gas-to-stellar-mass ratios. The gas-to-dust ratios of our sample objects vary widely (between approximate to 50 and 750), suggesting many objects have low gas-phase metallicities, and thus that the gas has been accreted through a recent merger with a lower mass companion. We calculate the implied minor companion masses and gas fractions, finding a median predicted stellar mass ratio of approximate to 40:1. The minor companion likely had masses between approximate to 10(7) and 10(10) M-circle dot. The implied merger mass ratios are consistent with the expectation for low-redshift gas-rich mergers from simulations. We then go on to present evidence that (no matter which star formation rate indicator is used) our sample objects have very low star formation efficiencies (star formation rate per unit gas mass), lower even than the early-type galaxies from ATLAS(3D) which already show a suppression. This suggests that minor mergers can actually suppress star formation activity. We discuss mechanisms that could cause such a suppression, include dynamical effects induced by the minor merger.

Original languageEnglish
Pages (from-to)3503-3516
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Volume449
Issue number4
DOIs
Publication statusPublished - 1 Jun 2015

Keywords / Materials (for Non-textual outputs)

  • ISM: molecules
  • galaxies: elliptical and lenticular, cD
  • galaxies: evolution
  • galaxies: interactions
  • galaxies: ISM
  • CO-TO-H-2 CONVERSION FACTOR
  • SCIENCE DEMONSTRATION PHASE
  • MASS-METALLICITY RELATION
  • DIGITAL-SKY-SURVEY
  • ATLAS(3D) PROJECT
  • HERSCHEL-ATLAS
  • FORMING GALAXIES
  • ELLIPTIC GALAXIES
  • SAURON PROJECT
  • COLD GAS

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