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

Sotnikova, Yu. V.; Муфахаров, Т. В.; Михайлов, А. Г.; Stolyarov, V.; Wu, Zhibo; Мингалиев, М. Г.; Семенова, Т. А.; Erkenov, A. K.; Бурсов, Н. Н.; Udovitskiy, R. Yu.

doi:10.1134/s1990341322030117

Cited by 5 publications

(1 citation statement)

References 39 publications

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“…Based on the BLcat 4 RATAN-600 measurements at frequencies 1-22 GHz covering the period of observations 2006-2022 (Mingaliev et al 2014;Sotnikova et al 2022) and the CATS database 5 (Verkhodanov et al 1997(Verkhodanov et al , 2005, we calculated the averaged spectral flux density at a frequency of 5 GHz, radio spectral indices, and radio variability. The averaged spectral indices α were calculated for the 1-2, 2-5, 5-8, 5-11, 8-11, 11-22, 8-22, and 5-22 GHz ranges.…”

Section: Initial Datamentioning

confidence: 99%

Cluster Analysis of the Roma-BZCAT Blazars

Kudryavtsev,

Sotnikova,

Stolyarov

et al. 2024

Res. Astron. Astrophys.

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Based on the collected multiwavelength data, namely in the radio (NVSS, FIRST, RATAN-600), IR~(WISE), optical (Pan-STARRS), UV (GALEX), and X-ray (ROSAT, Swift-XRT) ranges, we have performed a cluster analysis for the blazars of the Roma-BZCAT catalog. Using two machine learning methods, namely a combination of PCA with k-means clustering and Kohonen's self-organizing maps, we have constructed an independent classification of the blazars (five classes) and compared the classes with the known Roma-BZCAT classification (FSRQs, BL Lacs, galaxy-dominated BL Lacs, and blazars of an uncertain type) as well as with the high synchrotron peaked blazars (HSP) from the 3HSP catalog and blazars from the TeVCat catalog. The obtained groups demonstrate concordance with the BL Lac/FSRQ classification along with a continuous character of the change in the properties. The group of HSP blazars stands out against the overall distribution. We examine the characteristics of the five groups and demonstrate distinctions in their spectral energy distribution shapes. The effectiveness of the clustering technique for objective analysis of multiparametric arrays of experimental data is demonstrated.

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Section: Initial Datamentioning

confidence: 99%

Cluster Analysis of the Roma-BZCAT Blazars

Kudryavtsev,

Sotnikova,

Stolyarov

et al. 2024

Res. Astron. Astrophys.

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GMRT observations of hydroxyl megamaser (OHM) candidates from the ALFALFA survey

Wang,

Wu,

Zhang

et al. 2024

A&A

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We present the results of our observations using the Giant Meterwave Radio Telescope (GMRT) to investigate the radio continuum and hydroxyl (OH) line emission of ten OH megamaser (OHM) candidates from the Arecibo Legacy Fast ALFA (ALFALFA) survey. Among these candidates, we identified two sources, AGC115713 and AGC249507, displaying compact OH line emission that is spatially associated with radio continuum emission. These characteristics are aligned with the typical properties of OHM galaxies. Furthermore, the infrared (IR) properties of these two galaxies are consistent with those of known OHM galaxies. Of the two sources, AGC 249507 has been confirmed through optical redshift, whereas AGC 115713 is aligned with a WISE color selection criterion in the literature, providing additional support for this source being an OHM galaxy, rather than a nearby galaxy. On the contrary, no significant spectral line emission was detected in the remaining eight OHM candidates using our full GMRT dataset. This suggests that the spectral line emission initially detected by the ALFALFA survey may have been significantly resolved in the high-resolution observations used in this work. Additionally, the absence of radio continuum emission in six candidates also distinguishes them from known OHM galaxies documented in the literature. These findings support the notion that OHM emission may be distributed on a subarcsecond scale, underscoring the utility of arcsecond-scale observations in confirming OHM candidates, particularly those lacking optical redshift data.

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Efficient selection of gravitationally lensed OH megamasers with MeerKAT and the Square Kilometre Array

Button,

Deane

2024

Monthly Notices of the Royal Astronomical Society

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There has been a recent resurgence in hydroxyl (OH) megamaser research driven by Square Kilometre Array (SKA) precursor/pathfinder telescopes. This will continue in the lead-up to the SKA mid-frequency array, which will greatly expand our view of OH megamasers and their cosmic evolution over ≳ 80 per cent of the age of the universe. This is expected to yield large scientific returns as OH megamasers trace galaxy mergers, extreme star formation, high molecular gas densities, and potentially binary/dual supermassive black hole systems. In this paper, we predict the distortion to the OH luminosity function that a magnification bias will inflict, and in turn, predict the distortion on the OH megamaser number counts as a function of redshift. We identify spectral flux density thresholds that will enable efficient lensed OH megamaser selection in large spectral line surveys with MeerKAT and SKA. The surface density of lensed galaxies that could be discovered in this way is a strong function of the redshift evolution of the OH megamaser luminosity function, with predictions as high as ∼1 lensed OH source per square degree at high redshifts (z ≳ 1) for anticipated SKA spectral line survey designs. This could enable efficient selection of some of the most highly-obscured galaxies in the universe. This high-redshift selection efficiency, in combination with the large survey speed of the SKA at ≲1 GHz frequencies and the high magnifications possible with compact OH emission regions (μOH ≫ 10), will enable a transformational view of OH in the universe.

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

Cited by 5 publications

References 39 publications

Cluster Analysis of the Roma-BZCAT Blazars

Cluster Analysis of the Roma-BZCAT Blazars

GMRT observations of hydroxyl megamaser (OHM) candidates from the ALFALFA survey

Efficient selection of gravitationally lensed OH megamasers with MeerKAT and the Square Kilometre Array

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