Combining the 12CO(1-0),13CO(1-0),and C18O(1-0) data with IRAS four band data,we here estimate the physical parameters such as size,viral mass,and CO J=1-0 isotopic and infrared luminosities for 29 dense molecular clouds from two published CO samples. We further analyze the various correlations between CO J=1-0 isotopic luminosities and infrared luminosity(star formation rate,SFR) and discuss the relationships between the molecular gas tracers and SFR. The results show that 12CO(1-0),13CO(1-0) and C18O(1-0) luminosities have tight correlations with each other. CO J=1-0 isotopic luminosities and SFR show weak correlations with larger scatter than the HCN-IR correlations of 47 dense cores in the Galaxy and 65 external star-forming galaxies. This might be interpreted as that both the SFR and star formation efficiency are mainly determined by the molecular gas at high volume density rather than high column density.
SUN Yan & GAO Yu Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China
We present our initial results from a study of 14 （U）LIRGs with a doublenucleus （z 〈0.15） and an AGN signature in the Chandra archive.The goals of our study are to search for more possible cases of binary AGNs and to investigate the X-ray properties and energy sources of these energetic objects,a major effort devoted specifically to searching for binary AGNs from （U）LIRGs.Our studies suggest that Mrk 266 might be a new candidate in hosting binary AGNs supported by X-ray observations.Our analysis shows that most （U）LIRGs are essentially weak X-ray sources and are not dominated by AGNs,due to both the lack of Fe K line detections and weak emission in the hard X-ray band.We find evidence for thermal emission with temperature kT ～ 0.7keV in seven nuclear regions,and this component is possibly associated with the nuclear or circumnuclear starburst.The soft and hard X-ray to far-infrared ratios also suggest that most （U）LIRGs are not energetically dominated by AGNs.Therefore,this study only provides one additional candidate of binary AGNs.We cannot rule out the existence of low luminosity AGNs and thus binary AGNs in all of them,particularly,those highly obscured and spatially unresolved systems.Nine of 14 （U）LIRGs,including three previously known binary AGNs and a new candidate Mrk 266,clearly have obvious X-ray counterparts to their double optical/near-IR nuclei.whereas only two out of 14 have one obvious X-ray counterpart detected.Additionally,Arp 220 and Mrk 273 are not spatially resolved owing to their small nuclear separations （～ 1″）,and no
We present our 12CO and 13CO mapping observations of SNR IC 443 interacting with molecular clouds.It is the first largescale high-resolution 13CO mapping observation in the surrounding region.The morphologies of IC 443 in 12CO and 13 CO are compared with the optical,infrared,Spitzer far-infrared,X-ray,and neutral atomic gas(HI).We also make comparison and analysis in the kinematics,using the date-cubes of 12CO,13CO and HI,to help distinguish the complicated gas motions in the shocked regions.Based on the work of Wang & Scoville(1992),we present a new model to explain the coexistence of multiple shocks with different speeds in a pc-scale region at the central clump B.We test this new model by analyzing the HI and CO distribution in both velocity and space domain.We also establish the relationship between the dissociation rate of shocked molecular gas and the shock velocity in this region.Finally,we derive the optical depth of 12CO with the 13CO spectra in clump B,and discuss the validity of the assumption of optically thin emission for the shocked 12CO.
