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Molecular gas dynamics in luminous infrared galaxies observed with the SMA
Chris Wilson, McMaster UniversityC. Wilson et al. 2008(ApJS, in press),D. Iono et al. 2008(submitted to ApJ)
Molecular gas dynamics in luminous infrared galaxies
What are Luminous Infrared Galaxies?An SMA Legacy Project: Gas Morphology and Dynamics in U/LIRGsComparison to high redshift sourcesCO(3-2) correlates linearly with star formation rate (LFIR)Gas surface density versus star formation rateSizes and line widths
The SMA U/LIRG Legacy Survey
Chris Wilson, Brad Warren, Adam Atkinson, Jen Golding (McMaster)Glen Petitpas, Melanie Krips, T. J. Cox (CfA),Daisuke Iono(NAOJ), Alison Peck (ALMA)Andrew Baker (Rutgers), Lee Armus (IPAC), Paul Ho, Satoki Matsushita (ASIAA), Mike Juvela (U. Helsinki), Chris Mihos (Case Western), Ylva Pihlstrom (New Mexico), Min Yun (Umass)
ULIRGS are galaxy mergers
All galaxies with LFIR> 5x1011Loare interacting or close pairs(Sanders et al. 1987)
Figure from Galliano 2004
Scoville et al. 2000
Luminosity Source: Starbursts and AGN
70-80% predominantly starbursts20-30% predominantly AGN
Genzel et al. 1998
Gas Morphology and Dynamics in Luminous Infrared Galaxies:Sample Selection
Representative sample of 14 luminous (log(LFIR) > 11) and ultraluminous (log(LFIR) > 12) infrared galaxiesDL< 200 Mpc (resolution 1” ~ 1 kpc)log(LFIR) > 11.4All with previous interferometric observations in the CO J=1-0 line
The Nearby Luminous Infrared Galaxy Sample
The Submillimeter Array
8 x 6m antennas, maximum baseline 500 mDual frequency operation at 230, 345, 690 GHz2 GHz bandwidth = 1700 km/s at 345 GHz (880 micron)Angular resolution of our survey is 1-4” (CO 3-2 and 880 micron continuum)
Centrally compact CO 3-2 emission
(HST images of Arp55 andI10565+2448 fromEvans, Vavilkin, et al.,2008, in prep.)
Velocity Fields within R<1 kpc
Velocity dispersions within R<1 kpc
ULIRGs are best local analogs to dusty galaxies at high redshift
Cosmologically significant population of very luminous dusty galaxies discovered at submm wavelengthsFor z>0.5, 5 mJy at 850m implies L > 8x1012Lo
Tacconi et al. 2006
Ivison et al. 2000
High-redshift comparison sample
Select high-redshift objects with high resolution observations in CO(3-2) line12 submillimeter galaxies (SMGs) from z=2.2-3.1 (one at z=1.3)9 quasars from z=2.3-2.8 (one at z=6.4)2 Lyman Break Galaxies (LBGs) at z=2.7-3.1References for CO data:SMGs: Genzel et al. 2003, Downes & Solomon 2003, Sheth et al. 2004, Greve et al. 2005, Tacconi et al. 2006, Iono et al. 2006Quasars: Downes et al. 1995, Barvainis et al. 1998, Guilloteau et al. 1999, Weiss et al. 2003, Walter et al. 2004, Beelin et al. 2004, Hainline et al. 2004, Solomon & van den Bout 2005LBGS: Baker et al. 2004, Coppin et al. 2007
CO(3-2) tracesdense star forming gas
Slope (0.92+/-0.03) is similar to HCN (Gao & Solomon 2004) and significantly steeper than CO(1-0) (Yao et al. 2003)
Relation between gas surface density and far-infrared luminosity
Gas surface densities in Mo/pc2:1400 ± 350 U/LIRGs2290 ± 890 SMGs4280 ± 600 quasarsSurface density correlates with far-infrared luminosityL’CO(3-2)to M(H2) using M(H2)=0.8L’CO(3-2)assumes CO3-2/1-0=1Note surface densities are not corrected for inclination
Linewidths (FWHM) in four samples of galaxies
Average linewidths (FWHM, km/s)180 ± 10 local galaxies360 ± 30 U/LIRGs610 ± 90 SMGs310 ± 50 quasarsU/LIRG and quasar distributions similar (but no inclination corrections yet)
SMGs: larger diameters and line widths
SMGs: larger diameters and line widths
SMGs: larger diameters and line widths
Star-forming galaxies at z~2(Bouché et al. 2007)
SMGs have larger linewidths and are more compact than rest-frame optical and UV selected samples at z~2
Star-forming galaxies at z~2(Bouché et al. 2007)
SMGs have larger linewidths and are more compact than rest-frame optical and UV selected samples at z~2Our work confirms local compact U/LIRGs fall in a similar part of the diagram to SMGs
L’CO(3-2)and LFIRcorrelated over 5 orders of magnitudeCO(3-2) traces dusty star formation activityStar formation efficiency constant to within a factor of two

Molecular gas disks in local U/LIRGs are more compact than SMGs and SMGs have broader line widthsSMGs most similar to intermediate-stage mergers?broad lines due to violent mergers deep in massive halo potentialFuture Work:Spatially and velocity resolved physical conditions in gasComparison with merger simulations
Molecular gas in merging galaxies
Dynamical mass versus molecular gas mass
Average gas mass fraction:0.12+/-0.02 U/LIRGs0.37+/-0.09 SMGs2.0+/-0.5 QuasarsMdynuses R from gaussian fit and vc= vFWHM/2.4Inclination of 45 degrees assumed unless has been measured
Gas to dust ratio
Average gas-to-dust ratio179+/-44 U/LIRGs61+/-6 SMGs55+/-10 quasarsDust masses assume=1.5 cm2/gTD=40 K for SMGS/quasarsTDfrom SED fits for U/LIRGs





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