标题： MeerKAT吸收线巡天（MALS）数据释放3：与银河系相关的冷原子气体 显示英文标题

标题： The MeerKAT Absorption Line Survey (MALS) data release 3: Cold atomic gas associated with the Milky Way

摘要： We present results of a blind search for Galactic HI 21-cm absorption lines toward 19130 radio sources, using 390 pointings of MALS, each pointing centered on a source brighter than 200 mJy. We detected 3640 HI absorption features. This represents the largest Galactic HI absorption line catalog to date. Based on the strong correlation between the HI 21-cm emission line column densities ($N_{HI}$) and the visual extinction ($A_V$) measured toward the pointing center, along with the confinement of the absorption features to a narrow range in radial velocities (-25$<v_{\rm LSR}$[kms$^{-1}$]$<$+25), we infer that the detected absorption lines form a homogeneous sample of HI clouds in the local interstellar medium (LISM). 21厘米氢吸收光学深度与$N_{HI}$和$A_V$呈线性相关，直到大约1mag的$A_V$。超过这个阈值，$A_V$追踪总氢含量，因此，$A_V$和$N_{HI}$以不同方式缩放。 $N_{HI}$分布的视线中心与 HI 21 厘米吸收检测和非检测之间的斜率在$>2\sigma$处有所不同。 类似的区别也出现在阻尼 Lya 系统中对于 H$_2$检测和非检测的情况，当$z$> 1.8 时，这表明湍流驱动的 WNM 到 CNM 转换是 HI 21 厘米和 H$_2$吸收存在的共同控制因素。 通过比较中心和轴外吸收特征，我们发现与 LISM 相关的平静气体中光学深度变化的均方根波动的斜率比盘中的早期测量值更浅。 从光学深度变化推断出的密度（20-30 cm$^{-3}$）典型于 CNM 值。 中心和轴外吸收剂之间可以忽略的多普勒频移与 CNM 和 LNM 云团从扩展的 WNM 相中冻结出来的假设一致。 显示英文摘要

摘要： We present results of a blind search for Galactic HI 21-cm absorption lines toward 19130 radio sources, using 390 pointings of MALS, each pointing centered on a source brighter than 200 mJy. We detected 3640 HI absorption features. This represents the largest Galactic HI absorption line catalog to date. Based on the strong correlation between the HI 21-cm emission line column densities ($N_{HI}$) and the visual extinction ($A_V$) measured toward the pointing center, along with the confinement of the absorption features to a narrow range in radial velocities (-25$<v_{\rm LSR}$[kms$^{-1}$]$<$+25), we infer that the detected absorption lines form a homogeneous sample of HI clouds in the local interstellar medium (LISM). The HI 21-cm absorption optical depth is linearly correlated to $N_{HI}$ and $A_V$, up to $A_V$ of about 1 mag. Above this threshold, $A_V$ traces the total hydrogen content, and consequently, $A_V$ and $N_{HI}$ scale, differently. The slopes of $N_{HI}$ distributions of central sight lines with HI 21-cm absorption detections and non-detection differ at $>2\sigma$. A similar difference is observed for H$_2$ detections and non-detections in damped Lyman-alpha systems at $z$ > 1.8, implying that turbulence-driven WNM-to-CNM conversion is the common governing factor for the presence of HI 21-cm and H$_2$ absorption. Through a comparison of central and off-axis absorption features, we find that the slope of rms fluctuations in the optical depth variations in the quiescent gas associated with LISM is shallower than the earlier measurements in the disk. The densities (20-30 cm$^{-3}$) inferred from the optical depth variations are typical of the CNM values. The negligible velocity shifts between central and off-axis absorbers are in line with the hypothesis that the CNM and LNM clouds freeze out of the extended WNM phase.