赫歇尔时期下星系中(亚)毫米波谱线发射的研究进展

Progress of the Study on(Sub)millimeter Lines in Galaxies During the Herschel Period

目前,(亚)毫米波段探测到大量的谱线发射,例如简单分子(如CO,H_(2)O等)的转动发射以及原子(如C,O等)和离子(如C+,N+等)的基态精细结构跃迁。这些谱线是多种物理状态的星际介质(interstellar medium,ISM)的重要冷却剂,可以用于研究气体的物理性质和化学组成以及气体谱线发射的能量来源。首先介绍了文献中利用远红外(far-infrared,FIR)/(亚)毫米谱线测量星系中恒星形成性质的方法,如恒星形成率(sar formation rate,SFR)、恒星形成模式等;然后,介绍并比较了利用多条谱线示踪星系中的分子气体质量的方法,以及它们主要的依赖性;最后,介绍了利用多条CO谱线(CO谱线能量分布以及CO谱线与连续谱的比值),并结合其他谱线,来诊断星系中主导谱线发射能量来源的方法。

After the advent of the Herschel Space Observatory,there is much progress of the observational studies on the(sub)millimeter lines,such as the middle to high-J CO rotational transitions,multiple H2O lines,and fine-structure emissions of atoms(e.g.,C,O)and ions(e.g.,C+,N+).These lines are important coolants for the interstellar medium(ISM),and thus can be used to investigate the physical conditions and chemical compositions of the ISM,as well as the power sources.Therefore,it is important to study these(sub)millimeter lines in galaxies,which can provide key information of galaxy formation and evolution.In this paper,we first introduce how to explore the star formation properties(such as the calibration of star formation rate and the determination of the star formation mode)using different(sub)millimeter lines;Then we review for the different methods of measuring the total molecular mass with(sub)millimeter lines,and make comparison among these methods.Meanwhile we discuss the dependence of these methods on galactic properties.At last we summarize the use of CO(CO spectral line energy distribution and the ratio of mid-J CO emission to far-infrared continuum)and other lines to diagnose the power source in galaxies.