TY - JOUR
T1 - ATLAS(3D) project - XI. Dense molecular gas properties of CO-luminous early-type galaxies
AU - Crocker, Alison
AU - Krips, Melanie
AU - Bureau, Martin
AU - Young, Lisa M.
AU - Davis, Timothy A.
AU - Bayet, Estelle
AU - Alatalo, Katherine
AU - Blitz, Leo
AU - Bois, Maxime
AU - Bournaud, Frédéric
AU - Cappellari, Michele
AU - Davies, Roger L.
AU - de Zeeuw, P. T.
AU - Duc, Pierre Alain
AU - Emsellem, Eric
AU - Khochfar, Sadegh
AU - Krajnović, Davor
AU - Kuntschner, Harald
AU - Lablanche, Pierre Yves
AU - Mcdermid, Richard M.
AU - Morganti, Raffaella
AU - Naab, Thorsten
AU - Oosterloo, Tom
AU - Sarzi, Marc
AU - Scott, Nicholas
AU - Serra, Paolo
AU - Weijmans, Anne Marie
PY - 2012/4
Y1 - 2012/4
N2 - Surveying 18 12CO-bright galaxies from the ATLAS 3D early-type galaxy sample with the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we detect 13CO(1-0) and 13CO(2-1) in all 18 galaxies, HCN(1-0) in 12/18 and HCO +(1-0) in 10/18. We find that the line ratios 12CO(1-0)/ 13CO(1-0) and 12CO(1-0)/HCN(1-0) are clearly correlated with several galaxy properties: total stellar mass, luminosity-weighted mean stellar age, molecular-to-atomic gas ratio, dust temperature and dust morphology. We suggest that these correlations are primarily governed by the optical depth in the 12CO lines; interacting, accreting and/or starbursting early-type galaxies have more optically thin molecular gas while those with settled dust and gas discs host optically thick molecular gas. The ranges of the integrated line intensity ratios generally overlap with those of spirals, although we note some outliers in the 12CO(1-0)/ 13CO(1-0), 12CO(2-1)/ 13CO(2-1) and HCN/HCO +(1-0) ratios. In particular, three galaxies are found to have very low 12CO(1-0)/ 13CO(1-0) and 12CO(2-1)/ 13CO(2-1) ratios. Such low ratios may signal particularly stable molecular gas which creates stars less efficiently than 'normal' (i.e. below Schmidt-Kennicutt prediction), consistent with the low dust temperatures seen in these galaxies.
AB - Surveying 18 12CO-bright galaxies from the ATLAS 3D early-type galaxy sample with the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we detect 13CO(1-0) and 13CO(2-1) in all 18 galaxies, HCN(1-0) in 12/18 and HCO +(1-0) in 10/18. We find that the line ratios 12CO(1-0)/ 13CO(1-0) and 12CO(1-0)/HCN(1-0) are clearly correlated with several galaxy properties: total stellar mass, luminosity-weighted mean stellar age, molecular-to-atomic gas ratio, dust temperature and dust morphology. We suggest that these correlations are primarily governed by the optical depth in the 12CO lines; interacting, accreting and/or starbursting early-type galaxies have more optically thin molecular gas while those with settled dust and gas discs host optically thick molecular gas. The ranges of the integrated line intensity ratios generally overlap with those of spirals, although we note some outliers in the 12CO(1-0)/ 13CO(1-0), 12CO(2-1)/ 13CO(2-1) and HCN/HCO +(1-0) ratios. In particular, three galaxies are found to have very low 12CO(1-0)/ 13CO(1-0) and 12CO(2-1)/ 13CO(2-1) ratios. Such low ratios may signal particularly stable molecular gas which creates stars less efficiently than 'normal' (i.e. below Schmidt-Kennicutt prediction), consistent with the low dust temperatures seen in these galaxies.
UR - http://www.scopus.com/inward/record.url?scp=84858447452&partnerID=8YFLogxK
U2 - 10.1111/j.1365-2966.2011.20393.x
DO - 10.1111/j.1365-2966.2011.20393.x
M3 - Article
AN - SCOPUS:84858447452
SN - 0035-8711
VL - 421
SP - 1298
EP - 1314
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -