The global star formation law of galaxies revisited in the radio continuum  

作　　者：LIU LiJie GAO Yu 

机构地区：[1]Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China [2]Graduate University of Chinese Academy of Sciences,Beijing 100039,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2012年第2期347-353,共7页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.10833006 and 10621303);the National Basic Research Program of China (Grant No.2007CB815406)

摘　　要：We study the global star formation law, the relation between the gas and star formation rate （SFR） in a sample of 130 local galaxies with infrared （IR） luminosities spanning over three orders of magnitude （109-1012 Lo）, which includes 91 normal spiral galaxies and 39 （ultra）luminous IR galaxies [（U）LIRGs]. We derive their total （atomic and molecular） gas and dense molecular gas masses using newly available HI, CO and HCN data from the literature. The SFR of galaxies is determined from total IR （8-1000 μm） and 1.4 GHz radio continuum （RC） luminosities. The galaxy disk sizes are defined by the de-convolved elliptical Gaussian FWHM of the RC maps. We derive the galaxy disk-averaged SFRs and various gas surface densities, and investigate their relationships. We find that the galaxy disk-averaged surface density of dense molecular gas mass has the tightest correlation with that of SFR （scatter -0.26 dex）, and is linear in log-log space （power-law slope of N=1.03±0.02） across the full galaxy sample. The correlation between the total gas and SFR surface densities for the full sample has a somewhat larger scatter （-0.48 dex）, and is best fit by a power-law with slope 1.45±0.02. However, the slope changes from -1 when only normal spirals are considered, to -1.5 when more and more （U）LIRGs are included in the fitting. When different CO-to-H2 conversion factors are used to infer molecular gas masses for normal galaxies and （U）LIRGs, the bi-modal relations claimed recently in CO observations of high-redshift galaxies appear to also exist in local populations of star-forming galaxies.We study the global star formation law,the relation between the gas and star formation rate (SFR) in a sample of 130 local galaxies with infrared (IR) luminosities spanning over three orders of magnitude (10 9-10 12 L),which includes 91 normal spiral galaxies and 39 (ultra)luminous IR galaxies [(U)LIRGs].We derive their total (atomic and molecular) gas and dense molecular gas masses using newly available HI,CO and HCN data from the literature.The SFR of galaxies is determined from total IR (8-1000 m) and 1.4 GHz radio continuum (RC) luminosities.The galaxy disk sizes are defined by the de-convolved elliptical Gaussian FWHM of the RC maps.We derive the galaxy disk-averaged SFRs and various gas surface densities,and investigate their relationships.We find that the galaxy disk-averaged surface density of dense molecular gas mass has the tightest correlation with that of SFR (scatter ～0.26 dex),and is linear in log-log space (power-law slope of N=1.03±0.02) across the full galaxy sample.The correlation between the total gas and SFR surface densities for the full sample has a somewhat larger scatter (～0.48 dex),and is best fit by a power-law with slope 1.45±0.02.However,the slope changes from ～1 when only normal spirals are considered,to ～1.5 when more and more (U)LIRGs are included in the fitting.When different CO-to-H 2 conversion factors are used to infer molecular gas masses for normal galaxies and (U)LIRGs,the bi-modal relations claimed recently in CO observations of high-redshift galaxies appear to also exist in local populations of star-forming galaxies.

关 键 词：galaxies： evolation galaxies： ISM radio lines： galaxies stars： fromation 

分 类 号：P145.3[天文地球—天体物理] TN927.2[天文地球—天文学]