TY - JOUR
T1 - The ATLAS3D project - XXII. Low-efficiency star formation in early-type galaxies
T2 - Hydrodynamic models and observations
AU - Martig, Marie
AU - Crocker, Alison F.
AU - Bournaud, Frédéric
AU - Emsellem, Eric
AU - Gabor, Jared M.
AU - Alatalo, Katherine
AU - Blitz, Leo
AU - Bois, Maxime
AU - Bureau, Martin
AU - Cappellari, Michele
AU - Davies, Roger L.
AU - Davis, Timothy A.
AU - Dekel, Avishai
AU - de Zeeuw, P. T.
AU - Duc, Pierre Alain
AU - Falcón-Barroso, Jesus
AU - Khochfar, Sadegh
AU - Krajnović, Davor
AU - Kuntschner, Harald
AU - Morganti, Raffaella
AU - McDermid, Richard M.
AU - Naab, Thorsten
AU - Oosterloo, Tom
AU - Sarzi, Marc
AU - Scott, Nicholas
AU - Serra, Paolo
AU - Griffin, Kristen Shapiro
AU - Teyssier, Romain
AU - Weijmans, Anne Marie
AU - Young, Lisa M.
PY - 2013/6
Y1 - 2013/6
N2 - We study the global efficiency of star formation in high-resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (typically above 104 cm-3) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and HI surface densities and their star formation rates as determined by their non-stellar 8 μm emission. As predicted by the simulations, we find that the early-type galaxies are offset from the Kennicutt relation compared to the spirals, with a twice lower efficiency. Finally, we validate our approach by performing a direct comparison between models and observations. We run a simulation designed to mimic the stellar and gaseous properties of NGC 524, a local lenticular galaxy, and find a gas disc structure and global star formation rate in good agreement with the observations. Morphological quenching thus seems to be a robust mechanism, and is also consistent with other observations of a reduced star formation efficiency in early-type galaxies in the COLD GASS survey. This lower efficiency of star formation is not enough to explain the formation of the whole red sequence, but can contribute to the reddening of some galaxies.
AB - We study the global efficiency of star formation in high-resolution hydrodynamical simulations of gas discs embedded in isolated early-type and spiral galaxies. Despite using a universal local law to form stars in the simulations, we find that the early-type galaxies are offset from the spirals on the large-scale Kennicutt relation, and form stars two to five times less efficiently. This offset is in agreement with previous results on morphological quenching: gas discs are more stable against star formation when embedded in early-type galaxies due to the lower disc self-gravity and increased shear. As a result, these gas discs do not fragment into dense clumps and do not reach as high densities as in the spiral galaxies. Even if some molecular gas is present, the fraction of very dense gas (typically above 104 cm-3) is significantly reduced, which explains the overall lower star formation efficiency. We also analyse a sample of local early-type and spiral galaxies, measuring their CO and HI surface densities and their star formation rates as determined by their non-stellar 8 μm emission. As predicted by the simulations, we find that the early-type galaxies are offset from the Kennicutt relation compared to the spirals, with a twice lower efficiency. Finally, we validate our approach by performing a direct comparison between models and observations. We run a simulation designed to mimic the stellar and gaseous properties of NGC 524, a local lenticular galaxy, and find a gas disc structure and global star formation rate in good agreement with the observations. Morphological quenching thus seems to be a robust mechanism, and is also consistent with other observations of a reduced star formation efficiency in early-type galaxies in the COLD GASS survey. This lower efficiency of star formation is not enough to explain the formation of the whole red sequence, but can contribute to the reddening of some galaxies.
KW - Galaxies: ISM
KW - Galaxies: elliptical and lenticular, cD
KW - Galaxies: star formation.
UR - http://www.scopus.com/inward/record.url?scp=84879568047&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84879568047&partnerID=8YFLogxK
U2 - 10.1093/mnras/sts594
DO - 10.1093/mnras/sts594
M3 - Article
AN - SCOPUS:84879568047
SN - 0035-8711
VL - 432
SP - 1914
EP - 1927
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -