OH Line Detections in Southern Galaxies of the IRAS Revised Bright Galaxy Sample
4 affiliations
- 1Guizhou University
- 2Chinese Academy of Sciences
- 3Special Astrophysical Observatory of the Russian Academy of Science
- 4Xinjiang Astronomical Observatory
Abstract
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 maser emission (three new) and 30 showing absorption, mostly unreported previously. Four absorption systems exhibit weak OH emission superposed on strong absorption. OH-emitting regions are generally more compact than the radio continuum. Most absorption profiles are well fit by two Gaussian components, with an average integrated 1667/1665 MHz line ratio of ∼1.5. Luminous infrared galaxies (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 is detected below this threshold, suggesting that sufficient background continuum is important for absorption detection. OH emitters follow the empirical L OH – L FIR relation, consistent with far-infrared pumping, whereas nondetections show upper limits below the relation. Absorbers and nondetections show no significant differences in infrared luminosity or radio compactness. Stacked spectra of nondetections 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 nondetections, implying that the detectability of OH absorption is linked to dense molecular gas conditions, with extreme star formation potentially suppressing its occurrence.
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BibTeX
@article{zhao2026line,
title = {{OH Line Detections in Southern Galaxies of the IRAS Revised Bright Galaxy Sample}},
author = {Han Zhao and Zhongzu Wu and Bo Zhang and Timur Mufakharov and Yongjun Chen and Zhiqiang Shen and Yulia Sotnikova},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/ae9c2e},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/ae9c2e},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - OH Line Detections in Southern Galaxies of the IRAS Revised Bright Galaxy Sample
AU - Han Zhao
AU - Zhongzu Wu
AU - Bo Zhang
AU - Timur Mufakharov
AU - Yongjun Chen
AU - Zhiqiang Shen
AU - Yulia Sotnikova
PY - 2026
DA - 2026/10/01
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae9c2e
UR - https://iopscience.iop.org/article/10.3847/1538-4357/ae9c2e
AB - 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 maser emission (three new) and 30 showing absorption, mostly unreported previously. Four absorption systems exhibit weak OH emission superposed on strong absorption. OH-emitting regions are generally more compact than the radio continuum. Most absorption profiles are well fit by two Gaussian components, with an average integrated 1667/1665 MHz line ratio of ∼1.5. Luminous infrared galaxies (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 is detected below this threshold, suggesting that sufficient background continuum is important for absorption detection. OH emitters follow the empirical L OH – L FIR relation, consistent with far-infrared pumping, whereas nondetections show upper limits below the relation. Absorbers and nondetections show no significant differences in infrared luminosity or radio compactness. Stacked spectra of nondetections 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 nondetections, implying that the detectability of OH absorption is linked to dense molecular gas conditions, with extreme star formation potentially suppressing its occurrence.
SN - 0004-637X
SN - 1538-4357
ER -