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arXiv 1902.09172astro-ph.GA
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跨越宇宙时间尘埃恒星形成星系统计特性的多波长去混合赫歇尔观点

A multi-wavelength de-blended Herschel view of the statistical properties of dusty star-forming galaxies across cosmic time

L. Wang, W. J. Pearson, W. Cowley, J. W. Trayford, M. Bethermin, C. Gruppioni, P. Hurley, M. J. Michalowski

摘要:

我们的目标是研究尘埃恒星形成星系的统计特性,如它们的数量计数,光度函数(LF)和尘埃遮蔽的恒星形成率密度(SFRD)。我们在COSMOS领域使用最先进的去混合Herschel目录,通过结合贝叶斯源提取工具XID+和光谱能量分布的信息先验来生成,以测量远红外(FIR)和亚毫米(sub-mm)波长的数量计数和LF。得益于我们的去混淆技术和深度多波长测光,我们能够实现更精确的测量,同时探测比混淆极限低十倍。我们在250微米处的计数与以前的Herschel研究一致。然而,我们在350和500微米的计数大大低于以前的赫歇尔结果。这是由于以前的研究遭受源混淆,这使得波长更长。我们在450和870微米的计数显示出与以前的单碟和干涉观测结果非常一致。我们的单色LF和总IR LF的测量与以前的结果吻合得很好。我们测量的增加的动态范围使我们能够更好地测量LF的弱端斜率,并测量z~6的灰尘遮挡的SFRD。我们发现,尘埃遮蔽恒星形成活动的比例在z~1附近达到最高,然后向低和高红移方向降低。我们没有发现宇宙恒星形成历史中z~3和z~4之间的平衡从高红移的无遮蔽恒星形成为主到低红移的遮蔽恒星形成为主的变化。然而,我们确实发现3<z<4是一个有趣的过渡期,因为在较高的红移下,被尘埃遮蔽的总SFRD的比例显着降低。

英文摘要:

We aim to study the statistical properties of dusty star-forming galaxies, such as their number counts, luminosity functions (LF) and dust-obscured star-formation rate density (SFRD). We use state-of-the-art de-blended Herschel catalogue in the COSMOS field, generated by combining the Bayesian source extraction tool XID+ and informative prior on the spectral energy distributions, to measure the number counts and LFs at far-infrared (FIR) and sub-millimetre (sub-mm) wavelengths. Thanks to our de-confusion technique and deep multi-wavelength photometry, we are able to achieve more accurate measurements while probing ten times below the confusion limit. Our number counts at 250 microns agree well with previous Herschel studies. However, our counts at 350 and 500 microns are considerably below previous Herschel results. This is due to previous studies suffering from source confusion which worsens towards longer wavelength. Our number counts at 450 and 870 microns show excellent agreement with previous determinations derived from single dish and interferometric observations. Our measurements of the monochromatic LF and the total IR LF agree well with previous results. The increased dynamic range of our measurements allows us to better measure the faint-end slope of the LF and measure the dust-obscured SFRD out to z~6. We find that the fraction of dust obscured star-formation activity is at its highest around z~1 which then decreases towards both low and high redshift. We do not find a shift of balance between z~3 and z~4 in the cosmic star-formation history from being dominated by unobscured star formation at higher redshift to obscured star formation at lower redshift. However, we do find 3<z<4 to be an interesting transition period as the fraction of the total SFRD that is obscured by dust is significantly lower at higher redshifts.

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