paper

Are CO lines good indicators of the star formation rate in galaxies?

arXiv:0906.2975 · doi:10.1111/j.1365-2966.2009.15258.x

Abstract

In this paper, we investigate the relevance of using the CO line emissions as indicators of star formation rates (SFR). For the first time, we present this study for a relatively large number of CO transitions (12) as well as over a large interval in redshift (from z0 to z6). For the nearby sources (D10 Mpc), we have used homogeneous sample of CO data provided by Bayet et al. (2004, 2006), mixing observational and modelled line intensities. For higher-z sources (z 1), we have collected CO observations from various papers and have completed the data set of line intensities with model predictions which we also present in this paper. Finally, for increasing the statistics, we have included recent CO(1-0) and CO(3-2) observations of intermediate-z sources. Linear regressions have been calculated for identifying the tightest SFR-CO line luminosity relationships. We show that the \emph{total} CO, the CO(5-4), the CO(6-5) and the CO(7-6) luminosities are the best indicators of SFR (as measured by the far-infrared luminosity). Comparisons with theoretical approaches from Krumholz and Thompson (2007) and Narayanan et al. (2008) are also performed in this paper. Although in general agreement, the predictions made by these authors and the observational results we present here show small and interesting discrepancies. In particular, the slope of the linear regressions, for J 4 CO lines are not similar between theoretical studies and observations. On one hand, a larger high-J CO data set of observations might help to better agree with models, increasing the statistics. On the other hand, theoretical studies extended to high redshift sources might also reduce such discrepancies.

10 pages, 3 figures and 4 tables, Accepted in MNRAS

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