Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7-6) and [N II] 205 mum Lines - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue The Astrophysical journal letters Année : 2015

Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7-6) and [N II] 205 mum Lines

Résumé

To better characterize the global star formation activity in a galaxy, one needs to know not only the star formation rate (SFR) but also the rest-frame, far-infrared color (e.g., the 60-100 mum color, C(60/100)) of the dust emission. The latter probes the average intensity of the dust heating radiation field and scales statistically with the effective SFR surface density in star-forming galaxies including (ultra-)luminous infrared galaxies ((U)LIRGs). To this end, here we exploit a new spectroscopic approach involving only two emission lines: CO(7-6) at 372 mum and [N ii] at 205 mum([N ii]205mum). For local (U)LIRGs, the ratios of the CO(7-6) luminosity (LCO(7-6)) to the total infrared luminosity (LIR; 8-1000 mum) are fairly tightly distributed (to within ˜0.12 dex) and show little dependence on C(60/100). This makes LCO(7-6) a good SFR tracer, which is less contaminated by active galactic nuclei than LIR and may also be much less sensitive to metallicity than LCO(1-0). Furthermore, the logarithmic [N ii]205mum/CO(7-6) luminosity ratio depends fairly strongly (at a slope of ˜ -1.4) on C(60/100), with a modest scatter (˜0.23 dex). This makes it a useful estimator on C(60/100) with an implied uncertainty of ˜0.15 (or ≲4 K in the dust temperature (Tdust) in the case of a graybody emission with Tdust ≳ 30 K and a dust emissivity index beta >= 1). Our locally calibrated SFR and C(60/100) estimators are shown to be consistent with the published data of (U)LIRGs of z up to ˜6.5.
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Dates et versions

hal-03786131 , version 1 (23-09-2022)

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Citer

Nanyao Lu, Yinghe Zhao, C. Kevin Xu, Yu Gao, Tanio Díaz-Santos, et al.. Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7-6) and [N II] 205 mum Lines. The Astrophysical journal letters, 2015, 802. ⟨hal-03786131⟩

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