1. From GMC-SNR interaction to gas-rich galaxy-galaxy merging Yu GAO Purple Mountain Observatory, Nanjing, China Chinese Academy of Sciences

2. SFR vs. M(H2): No Unique Slope:1, 1.4, 1.7? HI-dominated LSB galaxies HI ~ H2 H2-dominatedLIRGs/ULIRGs Gao & Solomon 2004b ApJExtragalactic SF=CO until 90’s

3. Bigiel’s talk @SFR50 SF thresholds may simply reflect the change of the dominant cold gas phase in galaxies from HI ->H2 & from H2->denseH2 Schruba+2011 ~linear in H2!

4. 13 HCN @high-zHCN @high-z Gao, Carilli, Solomon & Vanden Bout 2007 ApJ, 660, L93

5. Poster by Liu+ Liu & Gao 2011 arXiv:1106.2813 Dense H2 show the best correlation with SFR (linear Liu & Gao 2011).

6. Bi-modal SF laws in high-z gals (Daddi+2010; Genzel+2010) also exist in local gals

7. Introduction and Outline 1. R=CO/13CO line intensity ratios: R ~2-5 Galactic Ring Survey 13CO (Jackson+06; Simon+01) UMass-StonyBrook CO survey (Sanders+86), ~5-10 Galactic center GMCs + normal spirals, ~10-20 Starbursts (eg, Aalto+1995) ~30-50 (U)LIRGs (few 13CO published; Papadopoulos+11) high R 10 associated with small, warm but compact molecular clouds of low to moderate optical depth, or the high [ 12 CO/ 13 CO] abundance ratio 2. Best case studies: Arp220 (Greve+09; Matsushita+09), NGC6240(Greve+09; U+11) 3. Resolved measurements in Antennae galaxies (Gao+01; Zhu+03), Taffy (Gao+03; Braine+03; Zhu+07); nearby gals. (Tan+11) 4. Supernova remnant (SNR) IC 443: GMC-SNR interactions (Wang+Scoville92; Zhang+10) 5. Implications: the molecular gas conditions in (U)LIRGs

8. R~43 Greve+09 2. Best case studies

9. Matsushita+09

10. R~45 Greve+09

11. BIMA+12m CO on HST image VLA 20cm on HST Very tight FIR-radio continuum correlation 3. Resolved measurements in ongoing mergers

12. Gao+01, SFE (20cm/CO) contour map

13. Zhu+03 R 32 ~25 R 32 ~15

14. Zhu+03 R21 ~20-30@overlap ~15@Nuclei

15. Gao 2008 Zhang, Gao, Kong 2010 MNRAS

16. SCUBA: Zhu, Gao, Seaquist & Dunne 2007 CO: Gao, Zhu, Seaquist 2003 450um contours on 8um image 850um contours on CO image

17. R~15, 50 (The 12 CO line intensities are divided by 10, Braine+03) HII

18. Tan+11 arXiv1103.5540

19. Dame et al. 2001 Columnbia CO Survey CO (1-0) in Gem OB1 GMC Lee et al. 2008 1.4GHz Continuum 4. Supernova remnant (SNR) IC 443 -- the Jellyfish Nebula

20. Simultaneous observations: 12 CO, 13 CO & C 18 O (1-0) Typical T sys ~180-300K (rms noise ~0.2K in 0.4 km/s) Total obs. points >1000, total spectra~7000, 2Months Beam size and sampling grid: ~ 55” (~1’) Gateway 2 Lhasa by sky train Array 3x3 + OTF 2011

21. Zhang, Gao & Wang arXiv: 0911.4815

22. Zhang, Gao & Wang arXiv: 0911.4815 70um and 160um overlaid with CO(1-0)

23. Zhang, Gao & Wang arXiv: 0911.4815 HI and radio continuum images overlaid with CO(1-0)

24. CO/13CO Line Ratio & FIR Maps [FeII], [SI], H 2 0-0 S(0) [OI][CII] + Dust? Spitzer 24 um Spitzer 70 um Spitzer 160 um 1. Line ratios are much higher in shocked regions than in the rest regions. 2. Line ratio maps in IC443 are strikingly well matched with the FIR images.

25. SNR IC443 Yellow: 12 CO Blue: 13 CO Background: Spitzer 24μm Spectra Analysis

27. 5. Implications to (U)LIRGs Concentrated molecular gas of ~10^10Msun in ~1kpc (vs. >10 kpc 10^9 Msun H2 in the Galaxy) (~10^3) Packed with dense cores (HCN-FIR) and even intercloud (or inter-dense-core) medium is highly molecular SNe rates in ULIRGs ~100 times that of the Milky Way Most dense cores are shocked by SNRs in ULIRGs (~10^5xMW) besides strong galaxy-galaxy collisions Highly shocked regions  higher R=CO/13CO in LIRGs The abnormally high ratios of R (& CO/C18O) found in SNR IC443 of shock-origin are comparable to the observed values in starbursts and (U)LIRGs, likely implying their same physical origin. Gao & Solomon 04, Gao+07: Dense H 2  Dense Cores