TY - JOUR
T1 - Molecular and atomic gas in dust lane early-type galaxies - I
T2 - Low star-formation efficiencies in minor merger remnants
AU - Davis, Timothy A.
AU - Rowlands, Kate
AU - Allison, James R.
AU - Shabala, Stanislav S.
AU - Ting, Yuan-Sen
AU - Lagos, Claudia del P.
AU - Kaviraj, Sugata
AU - Bourne, Nathan
AU - Dunne, Loretta
AU - Eales, Steve
AU - Ivison, Rob J.
AU - Maddox, Steve
AU - Smith, Daniel
AU - Smith, Matthew W. L.
AU - Temi, Pasquale
PY - 2015/6/1
Y1 - 2015/6/1
N2 - In this work we present IRAM-30m 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 H2 masses between 4x10^8 and 2x10^10 Msun. 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 ~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 ~40:1. The minor companion likely had masses between ~10^7 - 10^10 Msun. 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 ATLAS3D 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.
AB - In this work we present IRAM-30m 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 H2 masses between 4x10^8 and 2x10^10 Msun. 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 ~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 ~40:1. The minor companion likely had masses between ~10^7 - 10^10 Msun. 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 ATLAS3D 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.
KW - astro-ph.GA
U2 - 10.1093/mnras/stv597
DO - 10.1093/mnras/stv597
M3 - Article
VL - 449
SP - 3503
EP - 3516
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -