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 - 2013/7/1
Y1 - 2013/7/1
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 H I 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 H I 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: elliptical and lenticular
KW - cD
KW - galaxies: ISM
KW - galaxies: star formation
U2 - 10.1093/mnras/sts594
DO - 10.1093/mnras/sts594
M3 - Article
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 -