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报告题目：A Herschel Survey of the [NII] 205 micron Emisson in Local Luminous Infrared Galaxies

报告人：赵应和 博士

报告人单位：美国国家射电天文台

报告时间：11月18日(星期三)上午9：30-10：30

报告地点：Y12会议室

报告语言：中文

报告摘要：



The [NII] 205 micron emission ([NII]205) is a major coolant in ionized interstellar medium, and is expected to be a good star formation rate indicator. Here, for the first time, we present the flux measurements of the [NII]205 line for a flux-limited sample of 125 (ultra-)luminous infrared galaxies [(U)LIRGs] from the Great Observatories All-sky LIRG Survey and 20 additional normal galaxies, obtained with the Spectral and Photometric Image Receiver Fourier Transform Spectrometer of the Herschel Space Observatory (herschel). We explore the far-infrared (FIR) color dependence of the [NII]205 luminosity (LNII) to the total 8-1000 micron infrared luminosity (LIR) ratio, and find that LNII/LIR only depends modestly on the herschel-measured 70-to-160 micron flux density ratio (f70/f160) when f70/f160 <~ 0.6, whereas such dependence becomes much steeper for f70/f160> 0.6. We also investigate the relation between LNII and star formation rate (SFR), and show that LNII has a nearly linear correlation with SFR, albeit the intercept of such relation varies somewhat with f60/f100, suggesting that [NII]205 emission can serve as a useful SFR indicator with an accuracy of ~0.4 dex, or ~0.2 dex if f60/f100 is known independently. Furthermore, together with the previous ISO measurements of the [NII] 122 micron line, we use a total of ~200 galaxies to derive the local [NII]205 luminosity function (LF) by tying it to the known IR LF with a bivariate method. As a practical application, we also compute the local SFR volume density using the newly derived SFR calibrator and LF. The resulting SFR volume density agrees well with previous studies. Finally, we determine the electron densities (n_e) of the ionized medium for a subsample of 12 (U)LIRGs with both [NII]205 and [NII]122 data, and find that n_e is in the range of ~1-100 cm^{-3}, with a median value of 22 cm^{-3}.


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