IRAS修订亮星系样本中南部星系的OH线探测
OH Line Detections in Southern Galaxies of the IRAS Revised Bright Galaxy Sample
中文总结 AI 辅助
该研究利用MeerKAT数据对186个南部星系开展OH线探测，明确了OH发射、吸收的探测率及相关影响因素，发现其与致密分子气体条件、恒星形成状态存在关联。
中文摘要 AI 辅助
我们利用MeerKAT快照档案数据，对IRAS修订亮星系样本中的186个南部星系进行了OH主线发射和吸收的系统研究。在38个星系中探测到OH特征，其中包括8个OH脉泽发射星系（3个为新发现）和30个OH吸收星系，这些吸收大多此前未被报道。有4个吸收系统呈现出叠加在强吸收之上的弱OH发射。OH发射区域通常比相关的射电连续谱更致密。大多数吸收轮廓可通过两个高斯成分（1667和1665 MHz）很好地拟合，平均积分线比约为1.5。LIRGs（红外亮星系）的OH发射探测率约为13%，而非LIRGs的探测率则显著更低。对于射电连续谱流量密度大于20 mJy的源，OH吸收探测率在LIRGs中达到约36%，在非LIRGs中达到约27%，而在射电连续谱流量密度较低的源中未探测到OH吸收特征，这表明足够的背景连续谱可能是探测OH吸收的重要因素。探测到的OH发射体遵循经验性的$L_{\rm OH}$-$L_{\rm FIR}$关系，与远红外泵浦机制一致，而未探测到的源的上限低于该关系。在红外光度或射电连续谱致密性方面，OH吸收体与未探测源之间未发现显著差异。未探测源的堆叠光谱未显示出显著的OH特征，表明仅灵敏度和取向无法完全解释吸收的缺失。相比之下，两个群体在中红外颜色（如W2-W3）和$q_{\rm TIR}$方面存在差异。OH吸收星系在$L_{\rm HCN}/L_{\rm CO}$中处于OH巨脉泽和未探测源之间的中间状态，这意味着OH吸收的可探测性与致密分子气体条件相关，极端恒星形成可能会抑制其出现。
英文摘要
We present a systematic study of OH main-line emission and absorption in 186 southern galaxies from the IRAS Revised Bright Galaxy Sample, using archival MeerKAT snapshot data. OH features are detected in 38 galaxies, including eight with OH maser emission (three new) and 30 showing OH absorption, mostly unreported previously. Four absorption systems exhibit weak OH emission superposed on strong absorption. OH-emitting regions are generally more compact than the associated radio continuum. Most absorption profiles are well fit by two Gaussian components (1667 and 1665 MHz), with an average integrated line ratio of $\sim$1.5. LIRGs show an OH emission detection rate of ~13\%, versus significantly lower rates in non-LIRGs. For sources with radio continuum flux densities >20 mJy, OH absorption detection rates reach ~36\% (LIRGs) and ~27\% (non-LIRGs), while no OH absorption features were detected among sources with lower radio continuum flux densities. This suggests that sufficient background continuum is likely an important factor for the detection of OH absorption. Detected OH emitters follow the empirical $L_{\rm OH}$--$L_{\rm FIR}$ relation, consistent with far-infrared pumping, while non-detections show upper limits below the relation. No significant differences are found between OH absorbers and non-detections in infrared luminosity or radio continuum compactness. Stacked spectra of non-detections reveal no significant OH features, suggesting that sensitivity and orientation alone do not fully explain the absence of absorption. In contrast, mid-infrared colors (e.g., W2--W3) and q_TIR differ between the two populations. OH absorption galaxies occupy an intermediate regime in L_HCN/L_CO between OH megamasers and non-detections, implying that OH absorption detectability is linked to dense molecular gas conditions, with extreme star formation potentially suppressing its occurrence.
