Radio Properties of the Low-Redshift Isolated Galaxies with Active Nuclei

Abstract

The properties of 61 isolated galaxies with active nuclei (isolated AGNs) in the radio frequency range at redshifts z < 0.05 have been studied. The sample is obtained by cross-matching of the 2MIG catalog (2MASS catalog of isolated galaxies based on the 2MASS) with the Véron-Cetty catalog of quasars/AGNs. The sample is limited to a stellar magnitude of 4^m < K_s ≤ 12^m, a radial velocity of V_r < 15 000 km/s, and the distance to the nearest large satellite galaxy. These limitations indicate that the isolated AGNs have not collided with other galaxies in at least 3 billion years, and the observed activity of their nuclei is due only to physical processes occurring in the torus–accretion disk–nuclear region–supermassive black hole system. This study systematized the radio parameters of isolated AGNs by using data from various databases and the archive of terrestrial and space telescopes. Such characteristics are necessary for the further comparative study of physical properties of regions with active star formation and the active nuclei of these galaxies with the properties that manifest themselves when observing other spectral ranges. As a result, the radio flux densities available from the databases at a frequency of 1.4 or 5 GHz for isolated AGNs from the 2MIG catalog are given. Among the 61 galaxies of the sample, flux densities at 1.4 GHz have been found for 51 galaxies. These values are in the range of 3–20 mJy for most isolated AGNs and in the range of 50–200 mJy for two galaxies PGC35009 and NGC6951, while two galaxies ESO483-009 and ESO097-013 have spectral flux densities of 352 and 1200 mJy, respectively. The flux densities of ten isolated AGNs are less than 3 mJy. Radio flux densities of NGC0157 are not related to the position of this galaxy. Ratio R of the spectral flux densities in the radio frequency range to those in the optical bands have been calculated. Since the flux densities at 5 GHz are measured only for eight isolated AGNs, the required values of spectral flux densities at 5 GHz on the basis of relationship S_ν ∝ ν^–α for galaxies of the Seyfert type have been calculated by using the radio flux density values at 1.4 GHz and assuming that the spectral index is equal to α = 0.7. The radio fluxes densities at 5 GHz are lower than 3 mJy for 27 isolated AGNs, are in the range of 4–15 mJy for 15 AGNs, and in the range of 15–55 mJy for seven AGNs, while two galaxies ESO097-013 and ESO483-009 have radio fluxes densities of 304 and 132 mJy, respectively. We have found that 51 isolated AGNs are radio quiet sources (R < 10), the radio properties of nine objects are absent, and ESO483-009 is a radio loud galaxy (R = 20.72, Sy3/LINER, and SAB00 pec). We propose the observational methods to determine the flux densities of radio quite isolated AGNs. In conclusion, the systematization of the properties of 61 low-redshift isolated AGNs in the radio frequency range, 36 of which are in the northern sky and 25 in the southern sky, is aimed at pursuing the future goal of establishing a program of radio astronomical observations for the assessment of radiation flux densities and setting up a monitoring study for more detailed mapping of the radio emission characteristics of these galaxies in comparison with their optical and X-ray properties. Observations in the radio frequency range are important since they make it possible to monitor and separate star formation regions of a galaxy and the central region with a supermassive black hole in the active nuclei that is free of absorption, thereby providing information about the nature of nuclear activity.