论文标题
Z> 3的宇宙星形形成的隐藏面
The hidden side of cosmic star formation at z > 3: Bridging optically-dark and Lyman break galaxies with GOODS-ALMA
论文作者
论文摘要
我们目前对Z> 3处宇宙恒星形成历史的理解主要基于紫外线选择的星系（即LBG）。最近对H-漏斗的研究表明，我们可能缺少在Z> 3的大型星系中发生的大量恒星形成。在这项工作中，我们将H-Dropout Criterion扩展到较低的质量以选择光学深/微弱的星系（OFGS），以完成LBGS和H-Dropouts之间的人口普查。我们的标准（H> 26.5 mag＆[4.5] <25 mag）与DE融合技术相结合，不仅可以选择极度灰尘的大型星系，还可以选择正常的星形星系。我们总共确定了z_phot> 3（z_med = 4.1）的27个OFG，涵盖了具有log的恒星质量（$ m _ {\ star} $/$ m _ {\ odot} $）= 9.4-11.1。我们发现，具有LOG的OFG的最多75％（$ M _ {\ star} $/$ M _ {\ odot} $）= 9.5-10.5被以前的LBG和H-DropOut选择技术忽略了。进行堆叠分析后，OFG与典型的星形星系相比，OFG表现出较短的气体耗尽时间尺度，略低的气体部分和灰尘温度较低。他们的sfr_tot（sfr_ ir+sfr_uv）比sfr_uvcorr大得多（固定尘埃灭绝），带有sfr_tot/sfr_uvcorr = $ 8 \ pm1 $，这表明在OFG中存在隐藏的灰尘区域，从而吸收所有UV光子。通过圆形高斯模型拟合测得的平均灰尘尺寸为R_E（1.13毫米）= 1.01 $ \ pm $ 0.05 kpc。我们发现，大规模OFG贡献的Z> 3处的宇宙SFRD至少比同等大量LBG贡献的宇宙SFRD高两个数量级。最后，我们计算OFGS和LBG在z = 4-5时对宇宙SFRD的综合贡献为4 $ \ times $ 10 $^{ - 2} $ $ $ $ m _ {\ odot} $ yr $^{ - 1} $ MPC $^{ - 3} $ sypect yy 0.15 dex（43％）sheref（43％）在同一红移。
Our current understanding of the cosmic star formation history at z>3 is primarily based on UV-selected galaxies (i.e., LBGs). Recent studies of H-dropouts have revealed that we may be missing a large proportion of star formation that is taking place in massive galaxies at z>3. In this work, we extend the H-dropout criterion to lower masses to select optically dark/faint galaxies (OFGs), in order to complete the census between LBGs and H-dropouts. Our criterion (H> 26.5 mag & [4.5] < 25 mag) combined with a de-blending technique is designed to select not only extremely dust-obscured massive galaxies but also normal star-forming galaxies. In total, we identified 27 OFGs at z_phot > 3 (z_med=4.1) in the GOODS-ALMA field, covering a wide distribution of stellar masses with log($M_{\star}$/$M_{\odot}$) = 9.4-11.1. We find that up to 75% of the OFGs with log($M_{\star}$/$M_{\odot}$) = 9.5-10.5 were neglected by previous LBGs and H-dropout selection techniques. After performing stacking analyses, the OFGs exhibit shorter gas depletion timescales, slightly lower gas fractions, and lower dust temperatures than typical star-forming galaxies. Their SFR_tot (SFR_ IR+SFR_UV) is much larger than SFR_UVcorr (corrected for dust extinction), with SFR_tot/SFR_UVcorr = $8\pm1$, suggesting the presence of hidden dust regions in the OFGs that absorb all UV photons. The average dust size measured by a circular Gaussian model fit is R_e(1.13 mm)=1.01$\pm$0.05 kpc. We find that the cosmic SFRD at z>3 contributed by massive OFGs is at least two orders of magnitude higher than the one contributed by equivalently massive LBGs. Finally, we calculate the combined contribution of OFGs and LBGs to the cosmic SFRD at z=4-5 to be 4 $\times$ 10$^{-2}$ $M_{\odot}$ yr$^{-1}$Mpc$^{-3}$, which is about 0.15 dex (43%) higher than the SFRD derived from UV-selected samples alone at the same redshift.
