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Molecular gas dynamics in
luminous infrared galaxies
observed with the SMA
Chris Wilson, McMaster University
UGC5101
Mrk273
C. Wilson et al. 2008
(ApJS, in press),
D. Iono et al. 2008
(submitted to ApJ)
Molecular gas dynamics in
luminous infrared galaxies
1. What are Luminous Infrared Galaxies?
2. An SMA Legacy Project: Gas
Morphology and Dynamics in U/LIRGs
3. Comparison to high redshift sources
1. CO(3-2) correlates linearly with star
formation rate (LFIR)
2. Gas surface density versus star formation
rate
3. Sizes 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
Figure from Galliano 2004
Scoville et al. 2000
All galaxies with LFIR > 5x1011 Lo are interacting or close
pairs (Sanders et al. 1987)
Luminosity Source: Starbursts and AGN
• 70-80% predominantly starbursts
• 20-30% 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 galaxies
• DL < 200 Mpc (resolution 1” ~ 1 kpc)
• log(LFIR) > 11.4
• All 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 m
Dual frequency operation at 230, 345, 690 GHz
2 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
Mrk231
UGC5101
I10565+2448
Mrk273
Arp55
(HST images of Arp55 and
I10565+2448 from
Evans, Vavilkin, et al.,
2008, in prep.)
Velocity Fields within R<1 kpc
Mrk231
UGC5101
Mrk273
I10565+2448
Arp55(NE)
Arp55(SW)
Velocity dispersions within R<1 kpc
ULIRGs are best local analogs to
dusty galaxies at high redshift
Ivison et al. 2000
Tacconi et al. 2006
• Cosmologically significant population of very luminous dusty
galaxies discovered at submm wavelengths
• For z>0.5, 5 mJy at 850 m implies L > 8x1012 Lo
High-redshift comparison sample
• Select high-redshift objects with high resolution
observations in CO(3-2) line
– 12 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=2.7-3.1
• References 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. 2006
– Quasars: 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 2005
– LBGS: Baker et al. 2004, Coppin et al. 2007
CO(3-2) traces
dense 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/LIRGs
– 2290 ± 890 SMGs
– 4280 ± 600 quasars
• Surface density
correlates with farinfrared luminosity
– L’CO(3-2) to M(H2) using
M(H2)=0.8L’CO(3-2)
– assumes CO3-2/1-0=1
– Note surface densities are
not corrected for
inclination
Linewidths (FWHM) in four
samples of galaxies
• Average linewidths
(FWHM, km/s)
– 180 ± 10 local
galaxies
– 360 ± 30 U/LIRGs
– 610 ± 90 SMGs
– 310 ± 50 quasars
• U/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~2
• Our work confirms local
compact U/LIRGs fall in a
similar part of the diagram to
SMGs
Conclusions
• L’CO(3-2) and LFIR correlated over
5 orders of magnitude
• CO(3-2) traces dusty star formation
activity
• Star 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 widths
• SMGs most similar to intermediate-stage mergers?
• broad lines due to violent mergers deep in massive halo potential
• Future Work:
• Spatially and velocity resolved physical conditions in gas
• Comparison with merger simulations
Molecular gas in merging galaxies
end
Dynamical mass versus
molecular gas mass
• Average gas mass
fraction:
– 0.12+/-0.02 U/LIRGs
– 0.37+/-0.09 SMGs
– 2.0+/-0.5 Quasars
• Mdyn uses R from
gaussian fit and
vc = vFWHM/2.4
• Inclination of 45
degrees assumed
unless has been
measured
Gas to dust ratio
• Average gas-to-dust
ratio
– 179+/-44 U/LIRGs
– 61+/-6 SMGs
– 55+/-10 quasars
• Dust masses
assume
 =1.5 cm2/g
– TD=40 K for
SMGS/quasars
– TD from SED fits for
U/LIRGs