Properties of OH megamaser galaxies in the radio continuum. I. Observational data

Kandalyan, R. A.

doi:10.1007/s10511-005-0011-x

Cited by 3 publications

(1 citation statement)

References 17 publications

(19 reference statements)

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“…The properties of radio continuum emission, including spectral index and brightness temperature, can also be used to classify the central energy source of OHM galaxies (Kandalyan 2005a,b;Baan & Klöckner 2006;Sotnikova et al 2022). Kandalyan (2005a) and Baan & Klöckner (2006) obtained the radio structure of 30 and 51 OHM galaxies in the radio continuum based on VLA observations. They found that the OHM galaxies can be classified into different types, for instance, AGN and starburst-dominated sources.…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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

Sotnikova

Zhang

et al. 2023

A&A

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Radio continuum properties of OH megamaser galaxies

Sotnikova

Муфахаров

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We present a study of the radio continuum properties of two luminous/ultraluminous infrared galaxy samples: the OH megamaser (OHM) sample (74 objects) and the control sample (128 objects) without detected maser emission. We carried out pilot observations for 140 objects with the radio telescope RATAN-600 at 1.2, 2.3, 4.7, 8.2, 11.2, and 22.3 GHz in 2019–2021. The OHM sample has two times more flat-spectrum sources (32 per cent) than the control sample. Steep radio spectra prevail in both samples. The median spectral index at 4.7 GHz α4.7 = −0.59 for the OHM sample, and α4.7 = −0.71 for the non-OHM galaxies. We confirm a tight correlation of the far-infrared (FIR) and radio luminosities for the OHM sample. We found correlations between isotropic OH line luminosity LOH and the spectral index α4.7 (ρ=0.26, p-val.=0.04) and between LOH and radio luminosity P1.4 (ρ=0.35, p-val.=0.005). Reviewing subsamples of masers powered by active galactic nuclei and star formation revealed insignificant differences for their FIR and radio properties. Nonetheless, AGN-powered galaxies exhibit larger scatter in a range of parameters and their standard deviations. The similarities in the radio and FIR properties in the two samples are presumably caused by the presence of a significant amount of AGN sources in both samples (47 and 30 per cent in the OHM and control samples) and/or possibly by the presence of undetected OH emission sources in the control sample.

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Radio Variability and Broad-Band Spectra of Infrared Galaxies with and without OH Megamaser Emission

et al. 2022

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We study the radio variability of galaxies with and without sources of hydroxyl (OH) megamaser radiation based on the continuum radio measurements conducted in 2019-2022 with the radio telescope RATAN-600 at frequencies of 2.3, 4.7, 8.2, and 11.2 GHz. Presumably, radio continuum emission significantly affects the megamaser radiation brightness, therefore, such a characteristic as the variability of radio emission is important for determining the OHM galaxies parameters. With additional data from the literature, the parameters of radio variability on a time scale up to 30 years were estimated. The median values of the variability index for 48 OHM galaxies are in the range 𝑉 𝑆 = 0.08-0.17, and for 30 galaxies without OH emission they are 𝑉 𝑆 = 0.08-0.28. For some individual galaxies in both samples, flux density variations reach 30-50%. These sources either are commonly associated with AGNs or reveal active star formation. Generally, the variability of luminous infrared galaxies with and without OH megamaser emission is moderate and of the same order of magnitude on long time scales. From estimating the spectral energy distribution parameters in a broad frequency range (from MHz to THz), we determined the spectral index below 50 GHz and the color temperatures of dust components for megamaser and control sample galaxies. At a level of 𝜌 < 0.05, there are no statistically significant differences in the distribution of these parameters for the two samples, as well there are no statistically significant correlations between the dust color temperatures and the variability index or luminosity in the OH line.

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Properties of OH megamaser galaxies in the radio continuum. I. Observational data

Cited by 3 publications

References 17 publications

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

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

Radio continuum properties of OH megamaser galaxies

Radio Variability and Broad-Band Spectra of Infrared Galaxies with and without OH Megamaser Emission

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