from gmc-snr interaction to gas-rich galaxy-galaxy merging yu gao purple mountain observatory,...
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From GMC-SNR interaction to gas-rich galaxy-galaxy merging
Yu GAO
Purple Mountain Observatory, Nanjing, China
Chinese Academy of Sciences
SFR vs. M(H2): No Unique Slope:1, 1.4, 1.7?
HI-dominatedLSB galaxies
HI ~ H2
H2
-dom
ina
tedL
IRG
s/U
LIR
Gs
Gao & Solomon 2004b ApJExtragalactic SF=CO until 90’s
Big
iel’s
tal
k @
SF
R50
SF thresholds maysimply reflect the change of the dominant cold gas phase in galaxiesfrom HI ->H2 & from H2->denseH2
Schruba+2011~linear in H2!
Poster by Liu+
Liu & Gao 2011 arXiv:1106.2813
Dense H2 show the best correlation with SFR (linear Liu & Gao 2011).
Bi-modal SF laws in high-z gals (Daddi+2010; Genzel+2010) also exist in local gals
Introduction and Outline1. 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 R10 associated with small, warm but compact molecular clouds of low to
moderate optical depth, or the high [12CO/13CO] 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
R~43
Greve+09
2. Best case studies
Matsushita+09
R~45
Greve+09
BIMA+12m CO on HST image VLA 20cm on HST Very tight FIR-radio continuum correlation
3. Resolved measurements in ongoing mergers
Gao+01, SFE (20cm/CO) contour map
Zhu+03
R32~25R32~15
Zhu+03
R21~20-30@overlap ~15@Nuclei
Gao 2008
Zhang, Gao, Kong 2010 MNRAS
SCUBA: Zhu, Gao, Seaquist & Dunne 2007 CO: Gao, Zhu, Seaquist 2003
450um contours on 8um image 850um contours on CO image
R~15, 50 (The 12CO line intensities are divided by 10, Braine+03)
HII
Tan+11 arXiv1103.5540
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
Simultaneous observations: 12CO,13CO & C18O (1-0)Typical Tsys~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
Zhang, Gao & Wang arXiv: 0911.4815
Zhang, Gao & Wang arXiv: 0911.481570um and 160um overlaid with CO(1-0)
Zhang, Gao & Wang arXiv: 0911.4815HI and radio continuum images overlaid with CO(1-0)
CO/13CO Line Ratio & FIR Maps
[FeII], [SI], H2 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.
SNR IC443
Yellow: 12CO
Blue: 13CO
Background:
Spitzer 24μm
Spectra Analysis
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 H2 Dense Cores