%0 Generic %1 magnelli2012temperature %A Magnelli, B. %A Saintonge, A. %A Lutz, D. %A Tacconi, L. J. %A Berta, S. %A Bournaud, F. %A Charmandaris, V. %A Dannerbauer, H. %A Elbaz, D. %A Förster-Schreiber, N. M. %A Graciá-Carpio, J. %A Ivison, R. %A Maiolino, R. %A Nordon, R. %A Popesso, P. %A Rodighiero, G. %A Santini, P. %A Wuyts, S. %D 2012 %K conversion dust factor h2 temperature %T Dust temperature and CO-to-H2 conversion factor variations in the SFR-M* plane %U http://arxiv.org/abs/1210.2760 %X Deep Herschel imaging and 12CO(2-1) line luminosities from the IRAM PdBI are combined for a sample of 17 galaxies at z>1 from the GOODS-N field. The sample includes galaxies both on and above the main sequence (MS) traced by star-forming galaxies in the SFR-M* plane. The far-infrared data are used to derive dust masses, Mdust. Combined with an empirical prescription for the dependence of the gas-to-dust ratio on metallicity (GDR), the CO luminosities and Mdust values are used to derive for each galaxy the CO-to-H2 conversion factor, alpha_co. Like in the local Universe, the value of alpha_co is a factor of ~5 smaller in starbursts compared to normal star-forming galaxies (SFGs). We also uncover a relation between alpha_co and dust temperature (Tdust; alpha_co decreasing with increasing Tdust) as obtained from modified blackbody fits to the far-infrared data. While the absolute normalization of the alpha_co(Tdust) relation is uncertain, the global trend is robust against possible systematic biases in the determination of Mdust, GDR or metallicity. Although we cannot formally distinguish between a step and a smooth evolution of alpha_co with the dust temperature, we can conclude that in galaxies of near-solar metallicity, a critical value of Tdust=30K can be used to determine whether the appropriate alpha_co is closer to the starburst value (1.0 Msun(K kms pc^2)^-1, if Tdust>30K) or closer to the Galactic value (4.35 Msun (K kms pc^2)^-1, if Tdust<30K). This indicator has the great advantage of being less subjective than visual morphological classifications of mergers/SFGs, which can be difficult at high z because of the clumpy nature of SFGs. In the absence of far-infrared data, the offset of a galaxy from the main sequence (i.e., logSSFR(galaxy)/SSFR_MS(M*,z)) can be used to identify galaxies requiring the use of an alpha_co conversion factor lower than the Galactic value.

@misc{magnelli2012temperature, abstract = {Deep Herschel imaging and 12CO(2-1) line luminosities from the IRAM PdBI are combined for a sample of 17 galaxies at z>1 from the GOODS-N field. The sample includes galaxies both on and above the main sequence (MS) traced by star-forming galaxies in the SFR-M* plane. The far-infrared data are used to derive dust masses, Mdust. Combined with an empirical prescription for the dependence of the gas-to-dust ratio on metallicity (GDR), the CO luminosities and Mdust values are used to derive for each galaxy the CO-to-H2 conversion factor, alpha_co. Like in the local Universe, the value of alpha_co is a factor of ~5 smaller in starbursts compared to normal star-forming galaxies (SFGs). We also uncover a relation between alpha_co and dust temperature (Tdust; alpha_co decreasing with increasing Tdust) as obtained from modified blackbody fits to the far-infrared data. While the absolute normalization of the alpha_co(Tdust) relation is uncertain, the global trend is robust against possible systematic biases in the determination of Mdust, GDR or metallicity. Although we cannot formally distinguish between a step and a smooth evolution of alpha_co with the dust temperature, we can conclude that in galaxies of near-solar metallicity, a critical value of Tdust=30K can be used to determine whether the appropriate alpha_co is closer to the starburst value (1.0 Msun(K kms pc^2)^-1, if Tdust>30K) or closer to the Galactic value (4.35 Msun (K kms pc^2)^-1, if Tdust<30K). This indicator has the great advantage of being less subjective than visual morphological classifications of mergers/SFGs, which can be difficult at high z because of the clumpy nature of SFGs. In the absence of far-infrared data, the offset of a galaxy from the main sequence (i.e., log[SSFR(galaxy)/SSFR_MS(M*,z)]) can be used to identify galaxies requiring the use of an alpha_co conversion factor lower than the Galactic value.}, added-at = {2012-10-11T15:40:55.000+0200}, author = {Magnelli, B. and Saintonge, A. and Lutz, D. and Tacconi, L. J. and Berta, S. and Bournaud, F. and Charmandaris, V. and Dannerbauer, H. and Elbaz, D. and Förster-Schreiber, N. M. and Graciá-Carpio, J. and Ivison, R. and Maiolino, R. and Nordon, R. and Popesso, P. and Rodighiero, G. and Santini, P. and Wuyts, S.}, biburl = {https://www.bibsonomy.org/bibtex/2ff3a525c4a8a118f36fb81d91172ae8d/miki}, description = {[1210.2760] Dust temperature and CO-to-H2 conversion factor variations in the SFR-M* plane}, interhash = {7617f3425de133f769928d01e6525f41}, intrahash = {ff3a525c4a8a118f36fb81d91172ae8d}, keywords = {conversion dust factor h2 temperature}, note = {cite arxiv:1210.2760Comment: Accepted for publication in Astronomy and Astrophysics (A&A); 15 pages, 6 figures}, timestamp = {2012-10-11T15:40:55.000+0200}, title = {Dust temperature and CO-to-H2 conversion factor variations in the SFR-M* plane}, url = {http://arxiv.org/abs/1210.2760}, year = 2012 }