High-resolution VLA Imaging of Obscured Quasars: Young Radio Jets Caught in a Dense ISM

Pallavi Patil, Kristina Nyland, Mark Whittle, Carol Lonsdale, Mark Lacy, Colin Lonsdale, Dipanjan Mukherjee, A. C. Trapp, Amy E. Kimball, Lauranne Lanz, Belinda J. Wilkes, Andrew Blain, Jeremy J. Harwood, Andreas Efstathiou, Catherine Vlahakis

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    We present new subarcsecond-resolution Karl G. Jansky Very Large Array (VLA) imaging at 10 GHz of 155 ultraluminous (L bol ∼ 1011.7-1014.2 L o˙) and heavily obscured quasars with redshifts z ∼ 0.4-3. The sample was selected to have extremely red mid-infrared-optical color ratios based on data from the Wide-Field Infrared Survey Explorer (WISE) along with a detection of bright, unresolved radio emission from the NRAO VLA Sky Survey (NVSS) or Faint Images of the Radio Sky at Twenty cm Survey. Our high-resolution VLA observations have revealed that the majority of the sources in our sample (93 out of 155) are compact on angular scales <0.″2 (≤1.7 kpc at z ∼ 2). The radio luminosities, linear extents, and lobe pressures of our sources are similar to young radio active galactic nuclei (e.g., gigahertz-peaked spectrum [GPS] and compact steep-spectrum [CSS] sources), but their space density is considerably lower. Application of a simple adiabatic lobe expansion model suggests relatively young dynamical ages (∼104-7 yr), relatively high ambient ISM densities (∼1-104 cm-3), and modest lobe expansion speeds (∼30-10,000 km s-1). Thus, we find our sources to be consistent with a population of newly triggered, young jets caught in a unique evolutionary stage in which they still reside within the dense gas reservoirs of their hosts. Based on their radio luminosity function and dynamical ages, we estimate that only ∼20% of classical large-scale FR I/II radio galaxies could have evolved directly from these objects. We speculate that the WISE-NVSS sources might first become GPS or CSS sources, of which some might ultimately evolve into larger radio galaxies.
    Original languageEnglish
    Article number18
    Number of pages38
    JournalThe Astrophysical Journal
    Issue number1
    Early online date9 Jun 2020
    Publication statusPublished - 10 Jun 2020


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