CaltechAUTHORS
Published March 20, 2015 | Version Published + Submitted
Journal Article Open

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

Creators

  • 1. ROR icon Infrared Processing and Analysis Center
  • 2. ROR icon Purple Mountain Observatory
  • 3. ROR icon Chinese Academy of Sciences
  • 4. ROR icon California Institute of Technology
  • 5. ROR icon Diego Portales University
  • 6. ROR icon University of Crete
  • 7. ROR icon National Observatory of Athens
  • 8. ROR icon Paris Observatory
  • 9. ROR icon NOIRLab
  • 10. ROR icon Max Planck Institute for Radio Astronomy
  • 11. ROR icon University of Concepción
  • 12. ROR icon Search for Extraterrestrial Intelligence
  • 13. ROR icon University of Hawaii at Manoa
  • 14. ROR icon Leiden University

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.

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.

Attached Files

Published - 2041-8205_802_1_L11.pdf

Submitted - 1503.02052v1.pdf

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Additional details

Identifiers

Eprint ID
56771
Resolver ID
CaltechAUTHORS:20150420-101224175

Related works

Describes
http://arxiv.org/abs/1503.02052 (URL)

Funding

NASA/JPL/Caltech
National Natural Science Foundation of China
11390373
National Natural Science Foundation of China
11420101002
Chinese Academy of Sciences
XDB09000000
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)
31130005

Dates

Created
2015-04-20
Created from EPrint's datestamp field
Updated
2021-11-10
Created from EPrint's last_modified field

Caltech Custom Metadata

Caltech groups
Infrared Processing and Analysis Center (IPAC)