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Published October 2013 | Published + Submitted
Journal Article Open

Encoding of the infrared excess in the NUVrK color diagram for star-forming galaxies


We present an empirical method of assessing the star formation rate (SFR) of star-forming galaxies based on their locations in the rest-frame color–color diagram (NUV − r) vs. (r − K). By using the Spitzer 24  μm sample in the COSMOS field (~16 400 galaxies with 0.2 ≤ z ≤ 1.3) and a local GALEX-SDSS-SWIRE sample (~700 galaxies with z ≤ 0.2), we show that the mean infrared excess ⟨IRX⟩ = ⟨ L_(IR)/L_(UV)⟩ can be described by a single vector, NRK , that combines the two colors. The calibration between ⟨IRX⟩ and NRK allows us to recover the IR luminosity, L_(IR), with an accuracy of σ ~ 0.21 for the COSMOS sample and 0.27 dex for the local one. The SFRs derived with this method agree with the ones based on the observed (UV+IR) luminosities and on the spectral energy distribution (SED) fitting for the vast majority (~85%) of the star-forming population. Thanks to a library of model galaxy SEDs with realistic prescriptions for the star formation history, we show that we need to include a two-component dust model (i.e., birth clouds and diffuse ISM) and a full distribution of galaxy inclinations in order to reproduce the behavior of the ⟨IRX⟩ stripes in the NUVrK diagram. In conclusion, the NRK method, based only on the rest-frame UV/optical colors available in most of the extragalactic fields, offers a simple alternative of assessing the SFR of star-forming galaxies in the absence of far-IR or spectral diagnostic observations.

Additional Information

© 2013 ESO. Article published by EDP Sciences. Published online 04 October 2013. Received 25 April 2013. Accepted 25 July 2013. We thank the anonymous referee for his useful comments. This work has been partially supported by the CNRS-INSU and the Progamme National de Cosmologie et Galaxies. J.C. acknowledges the support of the European Commission through the Marie Curie Initial Training Network ELIXIR under contract PITN-GA-2008-214227.

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Published - aa21768-13.pdf

Submitted - 1309.0008v1.pdf


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August 19, 2023
October 25, 2023