arXiv 2203.061852022-03-11astro-ph.GA

用HST grisms穿越绿谷：颜色演变，跨越时间尺度和$z=1.0-1.8$红色序列的增长

Across the Green Valley with HST grisms: colour evolution, crossing time-scales and the growth of the red sequence at $z=1.0-1.8$

Gaël Noirot, Marcin Sawicki, Roberto Abraham, Maruša Bradač, Kartheik Iyer, Thibaud Moutard, Camilla Pacifici, Swara Ravindranath, Chris J. Willott

备注：: 23 pages, 16 figures, 1 appendix. Accepted for publication in MNRAS
DOI：: 10.1093/mnras/stac668

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摘要：

我们测量的颜色演化和淬火的时间尺度的$z=1.0-1.8$星系在绿色的山谷。我们从CANDELS-GOODS-South和UDS多波段光度学的光谱能量分布模型中推导出静止坐标系$NUVrK$颜色，并选择了蓝云、绿谷和红序列星系。另外，我们约束这些星系的恒星形成历史（SFH）参数（年龄，$τ$），通过拟合他们的深档案HST棱镜光谱。我们推导出星系的颜色年龄关系，并表明，只有快速发展的星系的特征延迟$τ$ SFH时间尺度的$<0.5$陀螺仪达到红色序列在这些红移，经过一段时间的加速颜色演变的绿色山谷。这些结果表明，这些星系的恒星质量积累在离开蓝色云并进入绿色山谷后保持最小（即，它可能代表星系最终静止质量的$\lesssim 5\%$）。对叠加光谱中年龄敏感特征的目视检查也支持这样的观点，即这些星系沿着蓝云$\rightarrow$绿谷$\rightarrow$红序列轨道遵循猝灭序列。对于这个快速发展的人口，我们测量的绿谷穿越时间尺度为$0.99^{+0.42}_{-0.25}$ Gyr和穿越率在底部的绿色谷$0.82^{+0.27}_{-0.25}$ mag/Gyr。基于这些时间尺度，我们估计，大质量（$M_\star>10^{10} M_\odot$）的红序列星系的数量密度增加一倍，每个陀螺仪在这些红移，在显着的协议与静止星系恒星质量函数的演变。这些结果提供了一种新的方法来测量星系随时间的淬火，并代表了未来的JWST，欧几里得和罗马太空望远镜计划的探路者研究。

英文摘要：

We measure the colour evolution and quenching time-scales of $z=1.0-1.8$ galaxies across the green valley. We derive rest-frame $NUVrK$ colours and select blue-cloud, green-valley and red-sequence galaxies from the spectral energy distribution modelling of CANDELS GOODS-South and UDS multi-band photometry. Separately, we constrain the star-formation history (SFH) parameters (ages, $τ$) of these galaxies by fitting their deep archival HST grism spectroscopy. We derive the galaxy colour-age relation and show that only rapidly evolving galaxies with characteristic delayed-$τ$ SFH time-scales of $<0.5$ Gyr reach the red sequence at these redshifts, after a period of accelerated colour evolution across the green valley. These results indicate that the stellar mass build-up of these galaxies stays minimal after leaving the blue cloud and entering the green valley (i.e., it may represent $\lesssim 5\%$ of the galaxies' final, quiescent masses). Visual inspection of age-sensitive features in the stacked spectra also supports the view that these galaxies follow a quenching sequence along the blue-cloud $\rightarrow$ green-valley $\rightarrow$ red-sequence track. For this rapidly evolving population, we measure a green-valley crossing time-scale of $0.99^{+0.42}_{-0.25}$ Gyr and a crossing rate at the bottom of the green valley of $0.82^{+0.27}_{-0.25}$ mag/Gyr. Based on these time-scales, we estimate that the number density of massive ($M_\star>10^{10} M_\odot$) red-sequence galaxies doubles every Gyr at these redshifts, in remarkable agreement with the evolution of the quiescent galaxy stellar mass function. These results offer a new approach to measuring galaxy quenching over time and represent a pathfinder study for future JWST, Euclid, and Roman Space Telescope programs.

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