||A Herschel Spectroscopic Survey of Warm Molecular Gas in Local Luminous
||477, Galaxy Mergers in an Evolving Universe
||Lu, N.; Xu, C. K.; Gao, Y.; Isaak, K.; Armus, L.; Appleton, P.; Charmandaris, V.; Diaz-Santos, T.; Evans, A.; Howell, J.; Iwasawa, K.; Leech, J.; Lord, S.; Mazzarella, J.; Petric, A.; Sanders, D.; Schulz, B.; Surace, J.; van der Werf, P.; Zhao, Y.
||We describe an on-going Herschel 200–700 μm spectroscopic
survey of a flux-limited sample of 125 local luminous infrared galaxies
(LIRGs), targeting primarily at CO line emission from warm and dense
molecular gas. The program will provide important statistical data
on the interplay between warm molecular gas, IR luminosity,
star formation rate and efficiency, AGN, and the diverse properties of
LIRGs. Of the 30 sample galaxies observed so far (18 by us; 12 taken
from Herschel archive), about 15% show
a dominant or significant hot CO
gas component emitting at J > 10, that is likely heated by AGN.
The other 85% is dominated by a warm gas component with CO line emission
peaking at J ≤ 8, likely powered by starburst.
While the spectral shapes of the warm gas component show little
overall dependence on the total IR luminosity LIR, the relative
contribution from the hot component appears to correlate positively
with LIR. The tightest one-to-one correlation between CO line
luminosity and LIR seems to be for CO(7-6), implying that the bulk
of LIR should be correlated with warm molecular gas of such density
and temperature that its CO line emission peaks around J ∼ 7.