Title: A [CII]-158-micron Survey of DLA galaxies at z~4: Observations of Dense and Metal-Enriched Neutral Gas within the Circumgalactic Medium of Star-Forming Galaxies Show Chinese title

Title: 一个红移约为4的DLA星系[CII]-158微米调查：在恒星形成星系的星系际介质中致密和金属富集中性气体的观测

Abstract: We present a survey undertaken with the Atacama Large Millimeter/submillimeter Array (ALMA) to study the galaxies associated with a representative sample of 16 damped Ly-alpha absorbers (DLAs) at z~4.1-4.5, using the [CII]-158-micron ([CII]) line. We detect seven [CII]-emitting galaxies in the fields of 5 DLAs, all of which have absorption metallicity [M/H] > -1.5. We find that the detectability of these HI-selected galaxies with ALMA is a strong function of DLA metallicity, with a detection rate of 71^{+11}_{-20}% for DLAs with [M/H] > -1.5 and 0^{+18}% for DLAs with [M/H] <-1.5. The identified DLA galaxies have far-infrared properties similar to those of typical star-forming galaxies at z ~ 4, with estimated obscured star-formation rates ranging from ~6 Msun/yr to 110 Msun/yr. High-metallicity DLAs therefore provide an efficient way to identify and study samples of high-redshift, star-forming galaxies without preselecting the galaxies by their emission properties. The agreement between the velocities of the metal absorption lines of the DLA and the [CII] emission line of the DLA galaxy indicates that the metals within the DLA originated in the galaxy. With observed impact parameters between 14 and 59 kpc, this indicates that star-forming galaxies at z ~ 4 have a substantial reservoir of dense, cold neutral gas within their circumgalactic medium that has been enriched with metals from the galaxy. Show Chinese abstract

Abstract: 我们使用阿塔卡马大型毫米/亚毫米阵列（ALMA）进行了一项调查，研究与红移约为4.1-4.5的16个强吸收线（DLAs）代表性样本相关的星系，使用[ CII ]-158微米（[ CII ]）线。我们在5个DLA的区域中检测到7个[ CII ]发射星系，所有这些星系的吸收金属丰度[M/H] > -1.5。我们发现，用ALMA检测这些HI选择的星系是DLA金属丰度的强函数，对于[M/H] > -1.5的DLA检测率为71^{+11}_{-20}%，对于[M/H] < -1.5的DLA检测率为0^{+18}%。识别出的DLA星系的远红外特性与红移约4的典型恒星形成星系相似，估计的被遮蔽恒星形成率范围从约6 Msun/yr到110 Msun/yr。因此，高金属丰度的DLA提供了一种有效的方法来识别和研究高红移、恒星形成星系的样本，而无需通过其发射特性预先选择星系。DLA的金属吸收线速度与DLA星系的[ CII ]发射线速度之间的吻合表明，DLA中的金属起源于星系。观测到的投影距离在14到59 kpc之间，这表明红移约4的恒星形成星系在其星系晕介质中拥有大量密集、寒冷的中性气体，并且这些气体已被星系中的金属所富集。