OH megamasers as extragalactic diagnostics

Pihlström, Y. M.

doi:10.1017/s1743921307013579

Cited by 3 publications

(1 citation statement)

References 18 publications

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“…In general, OHM line emission has been observed in (U)LIRGs and it is likely that OHMs occur during a specific state, or stage of the merger, which are consequences of tidal density enhancements accompanying galaxy interactions (Darling et al 2007;Pihlström 2007). The hosts of OHM galaxies usually present features of starburst and AGN, and the radio continuum emission are produced from these phenomena.…”

Section: Nature Of the Radio Emission In Ohm Galaxiesmentioning

confidence: 99%

Radio properties of the OH megamaser galaxy IRAS 02524+2046

Han

Zhang

et al. 2020

A&A

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We present results from VLBI observations of continuum and OH line emission in IRAS 02524+2046 as well as arcsecond-scale radio properties of this galaxy using VLA archive data. We found that there is no significant detection of radio continuum emission from VLBI observations. The arcsecond-scale radio images of this source show no clear extended emission. The total radio flux density at L and C bands are approximately 2.9 mJy and 1.0 mJy, respectively, which indicates a steep radio spectral index between the two bands. A steep spectral index, low brightness temperature, and high q-ratio (i.e., the far-infrared to the radio flux density), which are three critical indicators in the classification of radio activity in the nuclei of galaxies, are all consistent with the classification of this source as a starburst galaxy from its optical spectrum. The high-resolution line profile reveals that we detected both the 1665 MHz and 1667 MHz OH maser lines, which show two and three clear components, respectively. The channel maps show that the maser emission are distributed in a region of ∼210 pc × 90 pc. The detected maser components in different regions indicate similar double spectral features, which might be evidence that this galaxy is at a stage of major merger as seen from the optical morphology.

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Section: Nature Of the Radio Emission In Ohm Galaxiesmentioning

confidence: 99%

Radio properties of the OH megamaser galaxy IRAS 02524+2046

Han

Zhang

et al. 2020

A&A

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Radio continuum and OH line emission of high-z OH megamaser galaxies

Sotnikova

Zhang

et al. 2023

A&A

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We present a study of the arcsecond-scale radio continuum and OH line emission of a sample of known OH megamaser (OHM) galaxies with z ≥ 0.15 using archival Very Large Array (VLA) data and also the results of our pilot Five-hundred-meter Aperture Spherical radio Telescope (FAST) observations of 12 of these OHM galaxies. The arcsecond-scale resolution images show that the OH emission is distributed in one compact structure and is spatially associated with radio continuum emission. Furthermore, nearly all the components we fit are likely smaller than the beam size (∼ 1.4"), which indicates that the broad OH line profiles of these sources originated from one masing region or that more components are distributed on subarcsecond scales. The radio parameters, including brightness temperature, spectral index, and q-index, show no significant differences with low-redshift OHM galaxies, which have significantly lower OH line luminosities. Because these parameters are indicators of the central power sources (active galactic nucleus, starburst, or both), our results indicate that the presence of a radio active galactic nucleus in the nuclei may not be essential for the formation of OH emission. Over one-third of OHMs in this sample (6 out of 17) show possible variable features that are likely caused by interstellar scintillation due to small angular sizes. We might underestimate this value because these sources are associated with the highest OH line flux densities of this sample. The sources with low OH line flux densities might need observations with higher sensitivity so that the variabilities can be studied. These results support the compact nature of OH maser emission and a starburst origin for the OHMs in our selected sample.

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The Hydroxyl–water Megamaser Connection. I. Water Emission Toward Oh Megamaser Hosts

Wiggins

Migenes

Smidt

2016

ApJ

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Questions surround the connection of luminous extragalactic masers to galactic processes. The observation that water and hydroxyl megamasers rarely coexist in the same galaxy has given rise to a hypothesis that the two species appear in different phases of nuclear activity. The detection of simultaneous hydroxyl and water megamaser emission toward IC694 has called this hypothesis into question, but, because many megamasers have not been surveyed for emission in the other molecule, it remains unclear whether IC694 occupies a narrow phase of galaxy evolution or whether the relationship between megamaser species and galactic processes is more complicated than previously believed. In this paper, we present results of a systematic search for 22 GHz water maser emission among OH megamaser hosts to identify additional objects hosting both megamasers. Our work roughly doubles the number of galaxies searched for emission in both molecules, which host at least one confirmed maser. We confirm with a high degree of confidence ( 8s > ) the detection of water emission toward IIZw96, firmly establishing it as the second object to cohost both water and hydroxyl megamasers after IC694. We find high luminosity, narrow features in the water feature in IIZw96. All dual megamaser candidates appear in merging galaxy systems suggestive that megamasers that coexistance may signal a brief phase along the merger sequence. A statistical analysis of the results of our observations provide possible evidence for an exclusion of H 2 O kilomasers among OH megamaser hosts.

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OH megamasers as extragalactic diagnostics

Cited by 3 publications

References 18 publications

Radio properties of the OH megamaser galaxy IRAS 02524+2046

Radio properties of the OH megamaser galaxy IRAS 02524+2046

Radio continuum and OH line emission of high-z OH megamaser galaxies

The Hydroxyl–water Megamaser Connection. I. Water Emission Toward Oh Megamaser Hosts

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