Astrometric Evidence for a Population of Dislodged AGNs

We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2017-02, Vol.835 (2), p.30-30
Main Authors: Makarov, Valeri V., Frouard, Julien, Berghea, Ciprian T., Rest, Armin, Chambers, Kenneth C., Kaiser, Nicholas, Kudritzki, Rolf-Peter, Magnier, Eugene A.
Format: Article
Language:English
Subjects:
Active galactic nuclei
astrometry
Confusion
Constraining
Displacement
Galaxies
galaxies: nuclei
Offsets
Parents
Perturbation methods
quasars: general
reference systems
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Summary:We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources and their optical counterparts is strongly non-Gaussian, with powerful wings extending beyond 1 arcsec. Limiting our analysis to only high-confidence difference detections, we find (and publish) a list of 188 objects with normalized variances above 12 and offsets below 1 arcsec. Pan-STARRS stacked and monochromatic images resolve some of these sources, indicating the presence of double sources, confusion sources, or pronounced extended structures. Some 89 high-quality objects, however, do not show any perturbations and appear to be star-like single sources, yet they are displaced by multiples of the expected error from the radio-loud AGN. We conclude that a fraction of luminous AGNs (more than 4%) can be physically dislodged from the optical centers of their parent galaxies.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/835/2/L30