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تسجيل مستخدم جديدThe Parsec-scale Structure, Kinematics, and Polarization of Radio-Loud Narrow-Line Seyfert 1 Galaxies
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J. L. Richards
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Several narrow-line Seyfert 1 galaxies (NLS1s) have now been detected in gamma rays, providing firm evidence that at least some of this class of active galactic nuclei (AGN) produce relativistic jets. The presence of jets in NLS1s is surprising, as these sources are typified by comparatively small black hole masses and near- or super-Eddington accretion rates. This challenges the current understanding of the conditions necessary for jet production. Comparing the properties of the jets in NLS1s with those in more familiar jetted systems is thus essential to improve jet production models. We present early results from our campaign to monitor the kinematics and polarization of the parsec-scale jets in a sample of 15 NLS1s through multifrequency observations with the Very Long Baseline Array. These observations are complemented by fast-cadence 15 GHz monitoring with the Owens Valley Radio Observatory 40m telescope and optical spectroscopic monitoring with with the 2m class telescope at the Guillermo Haro Astrophysics Observatory in Cananea, Mexico.
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Most of the radio-loud narrow-line Seyfert 1 (NLS1) galaxies resemble compact steep-spectrum sources. However, the extremely radio-loud ones show blazar-like characteristics, like flat radio spectra, compact radio cores, substantial variability and h
igh brightness temperatures. These objects are thought to be similar to blazars as they possess relativistic jets seen at small angle to the line of sight. This claim has been further supported by the Fermi satellite discovery of gamma-ray emission from a handful of these sources. Using the Wide-Field Infrared Survey Explorer (WISE) data, we analyzed the mid-infrared variability characteristics of $42$ radio-loud NLS1 at $3.4$ and $4.6,mu$m. We found that $27$ out of the studied $42$ sources showed variability in at least one of the two infrared bands. In some cases, significant changes in the infrared colors can alter the location of the source in the WISE color-color diagram which might lead to different classification. More than $60$% of the variable sources also showed variability within a $1-1.5$ day interval. Such short time scales argue for a compact emission region like those associated with the jets. This connection is further strengthened by the fact that the brightest $gamma$-ray emitters of the sample ($6$ sources), all showed short time scale infrared variability.
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