| The star formation history of redshift z ~ 2 galaxies： the role of the infrared prior |
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| 作者单位： | [1]Center for Astrophysics, University of Science and Technology of China, Hefei 230026, China [2]Key Laboratory for Research in Galaxies and Cosmology, Chinese Academy of Sciences, Hefei230026, China [3]Astrophysics Sector, SISSA, Via Bonomea 265, 34136 Trieste, Italy [4]Dip. Fisica, Univ. ＇Tor Vergata＇, Via Ricerca Scientifica 1, 00133 Roma, Italy [5]INAF-Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 40131 Trieste, Italy |
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| 基金项目： | Supported by the National Natural Science Foundation of China. |
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| 摘 要： | We build a sample of 298 spectroscopically-confirmed galaxies at redshift z - 2, selected in the z850-band from the GOODS-MUSIC catalog. By utilizing the rest frame 8 p.m luminosity as a proxy of the star formation rate （SFR）, we check the accuracy of the standard SED-fitting technique, finding it is not accurate enough to provide reliable estimates of the physical parameters of galaxies. We then develop a new SED-fitting method that includes the IR luminosity as a prior and a generalized Calzetti law with a variable Rv. Then we exploit the new method to re-analyze our galaxy sample, and to robustly determine SFRs, stellar masses and ages. We find that there is a general trend of increasing attenuation with the SFR. Moreover, we find that the SFRs range between a few to 103 M~ yr-1, the masses from 109 to 4 ~ 1011 Mo, and the ages from a few tens of Myr to more than 1 Gyr. We discuss how individual age measurements of highly attenuated objects indicate that dust must have formed within a few tens of Myr and already been copious at 〈 100 Myr. In addition, we find that low luminosity galaxies harbor, on average, significantly older stellar populations and are also less massive than brighter ones; we discuss how these findings and the well known ＇downsizing＇ scenario are consistent in a framework where less massive galaxies form first, but their star formation lasts longer. Finally, we find that the near-IR attenuation is not scarce for luminous objects, contrary to what is customarily assumed; we discuss how this affects the interpretation of the observed M,/L ratios.
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| 关 键 词： | 恒星形成率 星系红移 红外线 历史 红外光度 SFR 拟合技术 物理参数 |
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