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

Lu, Nanyao and Zhao, Yinghe and Xu, C. Kevin and Gao, Yu and Díaz-Santos, Tanio and Charmandaris, Vassilis and Inami, Hanae and Howell, Justin and Liu, Luie and Armus, Lee and Mazzarella, Joseph M. and Privon, George C. and Lord, Steven D. and Sanders, David B. and Schulz, Bernhard and van der Werf, Paul P. (2015) Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7–6) and [N II] 205 μm Lines. Astrophysical Journal Letters, 802 (1). Art. No. L11. ISSN 2041-8205. https://resolver.caltech.edu/CaltechAUTHORS:20150420-101224175

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Abstract

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 μm 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 μm and [N ii] at 205 μm([N ii]_(205μm)). For local (U)LIRGs, the ratios of the CO(7–6) luminosity (L_(CO(7–6))) to the total infrared luminosity (L_(IR); 8–1000 μm) are fairly tightly distributed (to within ~0.12 dex) and show little dependence on C(60/100). This makes L_(CO(7–6)) a good SFR tracer, which is less contaminated by active galactic nuclei than L_(IR) and may also be much less sensitive to metallicity than L_(CO(1–0)). Furthermore, the logarithmic [N ii]_(205μm)/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 (T_(dust)) in the case of a graybody emission with T_(dust) ≳30 K and a dust emissivity index β ≥ 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.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/2041-8205/802/1/L11DOIArticle
http://iopscience.iop.org/2041-8205/802/1/L11/PublisherArticle
http://arxiv.org/abs/1503.02052arXivDiscussion Paper
ORCID:
AuthorORCID
Lu, Nanyao0000-0002-8948-1044
Zhao, Yinghe0000-0002-9128-818X
Xu, C. Kevin0000-0002-1588-6700
Gao, Yu0000-0003-0007-2197
Díaz-Santos, Tanio0000-0003-0699-6083
Charmandaris, Vassilis0000-0002-2688-1956
Inami, Hanae0000-0003-4268-0393
Armus, Lee0000-0003-3498-2973
Mazzarella, Joseph M.0000-0002-8204-8619
Privon, George C.0000-0003-3474-1125
Sanders, David B.0000-0002-1233-9998
van der Werf, Paul P.0000-0001-5434-5942
Additional Information:© 2015 American Astronomical Society. Received 2015 January 22; accepted 2015 March 6; published 2015 March 23. This paper benefited from a number of thoughtful comments made by an anonymous referee. Support for this work was provided in part by NASA through an award issued by JPL/Caltech. Y.Z. and Y.G. acknowledge support by NSFC grants No. 11390373 and 11420101002, and CAS pilot-b program No. XDB09000000. T.D.-S. acknowledges support by ALMA-CONICYT No. 31130005.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
National Natural Science Foundation of China11390373
National Natural Science Foundation of China11420101002
Chinese Academy of SciencesXDB09000000
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)31130005
Subject Keywords:galaxies: active; galaxies: ISM; galaxies: star formation; infrared: galaxies; ISM: molecules; submillimeter: galaxies
Issue or Number:1
Record Number:CaltechAUTHORS:20150420-101224175
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150420-101224175
Official Citation:Measuring Star Formation Rate and Far-infrared Color in High-redshift Galaxies Using the CO(7–6) and [N II] 205 μm Lines Nanyao Lu et al. 2015 ApJ 802 L11
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:56771
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Apr 2015 18:38
Last Modified:05 Nov 2019 05:50

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