1. Chris Wilson, McMaster University
Molecular gas dynamics in luminous infrared galaxies observed with the SMA
Chris Wilson, McMaster University
C. Wilson et al. 2008
(ApJS, in press),
D. Iono et al. 2008
(submitted to ApJ)
UGC5101
Mrk273

2. Molecular gas dynamics in luminous infrared galaxies
What are Luminous Infrared Galaxies?
An SMA Legacy Project: Gas Morphology and Dynamics in U/LIRGs
Comparison to high redshift sources
CO(3-2) correlates linearly with star formation rate (LFIR)
Gas surface density versus star formation rate
Sizes and line widths

3. 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)

4. 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)

5. Luminosity Source: Starbursts and AGN
70-80% predominantly starbursts
20-30% predominantly AGN
Genzel et al. 1998

6. 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

7. The Nearby Luminous Infrared Galaxy Sample

8. 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)

9. Centrally compact CO 3-2 emission
Mrk231
Mrk273 I
UGC5101
Arp55
(HST images of Arp55 and
I from
Evans, Vavilkin, et al.,
2008, in prep.)

10. Velocity Fields within R<1 kpc
Mrk231
Mrk273 I
UGC5101
Arp55(NE)
Arp55(SW)

11. Velocity dispersions within R<1 kpc
Contour levels are 20 km/s for all but grey scales are not the same; left two are to 100 km/s and right two are to 200 km/s

12. 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

13. High-redshift comparison sample
Select high-redshift objects with high resolution observations in CO(3-2) line
12 submillimeter galaxies (SMGs) from z= (one at z=1.3)
9 quasars from z= (one at z=6.4)
2 Lyman Break Galaxies (LBGs) at z=
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

14. 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)

15. 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 far-infrared 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

16. 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)

17. SMGs: larger diameters and line widths

18. SMGs: larger diameters and line widths

19. SMGs: larger diameters and line widths

20. 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

21. 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

22. 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

23. Molecular gas in merging galaxies

24. end

25. 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

26. Gas to dust ratio Average gas-to-dust ratio Dust masses assume
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