TY - JOUR
T1 - DENSE GAS FRACTION and STAR FORMATION EFFICIENCY VARIATIONS in the ANTENNAE GALAXIES
AU - Bigiel, F.
AU - Leroy, A. K.
AU - Blitz, L.
AU - Bolatto, A. D.
AU - Da Cunha, E.
AU - Rosolowsky, E.
AU - Sandstrom, K.
AU - Usero, A.
PY - 2015/12/20
Y1 - 2015/12/20
N2 - We use the Combined Array for Research in Millimeter-wave Astronomy (CARMA) millimeter interferometer to map the Antennae Galaxies (NGC 4038/39), tracing the bulk of the molecular gas via the 12CO(1-0) line and denser molecular gas via the high density transitions HCN(1-0), HCO+(1-0), CS(2-1), and HNC(1-0). We detect bright emission from all tracers in both the two nuclei and three locales in the overlap region between the two nuclei. These three overlap region peaks correspond to previously identified "supergiant molecular clouds." We combine the CARMA data with Herschel infrared (IR) data to compare observational indicators of the star formation efficiency (star formation rate/H2 ∝ IR/CO), dense gas fraction (HCN/CO), and dense gas star formation efficiency (IR/HCN). Regions within the Antennae show ratios consistent with those seen for entire galaxies, but these ratios vary by up to a factor of six within the galaxy. The five detected regions vary strongly in both their integrated intensities and these ratios. The northern nucleus is the brightest region in millimeter-wave line emission, while the overlap region is the brightest part of the system in the IR. We combine the CARMA and Herschel data with ALMA CO data to report line ratio patterns for each bright point. CO shows a declining spectral line energy distribution, consistent with previous studies. HCO+ (1-0) emission is stronger than HCN (1-0) emission, perhaps indicating either more gas at moderate densities or higher optical depth than is commonly seen in more advanced mergers.
AB - We use the Combined Array for Research in Millimeter-wave Astronomy (CARMA) millimeter interferometer to map the Antennae Galaxies (NGC 4038/39), tracing the bulk of the molecular gas via the 12CO(1-0) line and denser molecular gas via the high density transitions HCN(1-0), HCO+(1-0), CS(2-1), and HNC(1-0). We detect bright emission from all tracers in both the two nuclei and three locales in the overlap region between the two nuclei. These three overlap region peaks correspond to previously identified "supergiant molecular clouds." We combine the CARMA data with Herschel infrared (IR) data to compare observational indicators of the star formation efficiency (star formation rate/H2 ∝ IR/CO), dense gas fraction (HCN/CO), and dense gas star formation efficiency (IR/HCN). Regions within the Antennae show ratios consistent with those seen for entire galaxies, but these ratios vary by up to a factor of six within the galaxy. The five detected regions vary strongly in both their integrated intensities and these ratios. The northern nucleus is the brightest region in millimeter-wave line emission, while the overlap region is the brightest part of the system in the IR. We combine the CARMA and Herschel data with ALMA CO data to report line ratio patterns for each bright point. CO shows a declining spectral line energy distribution, consistent with previous studies. HCO+ (1-0) emission is stronger than HCN (1-0) emission, perhaps indicating either more gas at moderate densities or higher optical depth than is commonly seen in more advanced mergers.
KW - galaxies: individual (NGC4038/39)
KW - galaxies: ISM
KW - galaxies: star formation
KW - infrared: galaxies
KW - ISM: molecules
KW - radio lines: galaxies
UR - http://www.scopus.com/inward/record.url?scp=84951790282&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/815/2/103
DO - 10.1088/0004-637X/815/2/103
M3 - Article
AN - SCOPUS:84951790282
SN - 0004-637X
VL - 815
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 103
ER -