Spatially offset AGN candidates in the CLASS survey

Skipper, Chris J.; Browne, I. W. A.

doi:10.1093/mnras/sty114

Cited by 27 publications

(31 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The angular resolution of Gaia is still much lower than that of VLBI, and the galactic substrates, blended cores of optical emission, gravitational lenses, and jets, can cause the optical photocenters to shift from the more constrained radio positions. A fraction of RORF objects can also be physically displaced with respect to their host galaxy centers (Skipper & Browne 2018). This may be the main explanation for relatively nearby AGNs (z 1), which are typically redder with a significant contribution of their host galaxies in the flux.…”

Section: Discussionmentioning

confidence: 99%

The Precious Set of Radio-optical Reference Frame Objects in the Light of Gaia DR2 Data

Макаров

Berghea

Frouard

et al. 2019

ApJ

View full text Add to dashboard Cite

We investigate a sample of 3413 International Celestial Reference Frame (ICRF3) extragalactic radio-loud sources with accurate positions determined by VLBI in the S/X band, mostly active galactic nuclei (AGN) and quasars, which are cross-matched with optical sources in the second Gaia data release (Gaia DR2). The main goal of this study is to determine a core sample of astrometric objects that define the mutual orientation of the two fundamental reference frames, the Gaia (optical) and the ICRF3 (radio) frames. The distribution of normalized offsets between the VLBI sources and their optical counterparts is non-Rayleigh, with a deficit around the modal value and a tail extending beyond the 3σ confidence level. A few filters are applied to the sample in order to discard double cross-matches, confusion sources, and Gaia astrometric solutions of doubtful quality. Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) and Dark Energy Survey (DES) stacked multicolor images are used to further deselect objects that are less suitable for precision astrometry, such as extended galaxies, double and multiple sources, and obvious misidentifications. After this cleaning, 2643 quasars remain, of which 20% still have normalized offset magnitudes exceeding 3, or a 99% confidence level. We publish a list of 2119 radio-loud quasars of prime astrometric quality. The observed dependence of binned median offset on redshift shows the expected decline at small redshifts, but also an unexpected rise at z ∼ 1.6, which may be attributed to the emergence of the C IV emission line in the Gaia's G band. The Gaia DR2 parallax zeropoint is found to be color-dependent, suggesting an uncorrected instrumental calibration effect.

show abstract

Section: Discussionmentioning

confidence: 99%

The Precious Set of Radio-optical Reference Frame Objects in the Light of Gaia DR2 Data

Макаров

Berghea

Frouard

et al. 2019

ApJ

View full text Add to dashboard Cite

show abstract

“…Ho et al 2003) corresponding to the red color, while we see such offsets predominantly in bluer sources in Figure 4 and Figure 6. Extinction of host galaxy emission by the dusty torus may lead to jet-aligned optical structure of the objects (Skipper & Browne 2018). However, the majority of sources in our sam-ple are blazars which have small viewing angles around 5 • (Savolainen et al 2010).…”

Section: Agn Classes With Different Host Galaxy -mentioning

confidence: 92%

Dissecting the AGN Disk–Jet System with Joint VLBI-Gaia Analysis

Plavin

Kovalev

Petrov

2019

ApJ

View full text Add to dashboard Cite

We analyze differences in positions of active galactic nuclei between Gaia data release 2 and VLBI and compare the significant VLBI-to-Gaia offsets in more than 1000 objects with their jet directions. Remarkably at least 3/4 of the significant offsets are confirmed to occur downstream or upstream the jet representing a genuine astrophysical effect. Introducing redshift and Gaia color into analysis can help distinguish between the contribution of the host galaxy, jet, and accretion disk emission. We find that strong optical jet emission at least 20-50pc long is required to explain the Gaia positions located downstream from VLBI ones. Offsets in the upstream direction of up to 2 mas are at least partly due to the dominant impact of the accretion disk on the Gaia coordinates and by the effects of parsec-scale radio jet. The host galaxy was found not to play an important role in the detected offsets. BL Lacertae object and Seyfert 2 galaxies are observationally confirmed to have a relatively weak disk and consequently downstream offsets. The disk emission drives upstream offsets in a significant fraction of quasars and Seyfert 1 galaxies when it dominates over the jet in the optical band. The observed behaviour of the different AGN classes is consistent with the unified scheme assuming varying contribution of the obscuring dusty torus and jet beaming.

show abstract

“…The sources plotted here include CLASS B1608+656 (red) and lower limits for CLASS B0712+472, and offset-AGN samples found in literature. Black empty circles indicate the sample of Skipper & Browne (2018), which consists of 345 galaxies with offsets estimated using SDSS and VLA observations. Green triangles indicate the offsets from Barrows et al (2016) estimated using X-ray Chandra imaging and SDSS.…”

Section: Tracing the Evolution Of Active Galaxies Using Large Samplesmentioning

confidence: 99%

Constraining VLBI−optical offsets in high redshift galaxies using strong gravitational lensing

Spingola

Barnacka

2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present a multi-wavelength analysis of two highly magnified strong gravitationally lensed galaxies, CLASS B0712+472 and CLASS B1608+656, at redshifts 1.34 and 1.394, respectively, using new VLBI and archival HST observations. We reconstruct the positions of the radio and optical emissions with their uncertainties using Monte Carlo sampling. We find that in CLASS B0712+472 the optical and radio emissions are co-spatial within 2 ± 5 mas (17 ± 42 pc at redshift of 1.34). But, in CLASS B1608+656, we reconstruct an optical-radio offset of 25 ± 16 mas (214 ± 137 pc at redshift of 1.394), the smallest offset measured for an AGN at such high redshift. The spectral features indicate that CLASS B1608+656 is a post-merger galaxy, which, in combination with the optical-VLBI offset reported here, makes CLASS B1608+656 a promising candidate for a high-z offset-AGN. Furthermore, the milliarcsecond angular resolution of the VLBI observations combined with the precise lens models allow us to spatially locate the radio emission at 0.05 mas precision (0.4 pc) in CLASS B0712+472, and 0.009 mas precision (0.08 pc) in CLASS B1608+656. The search for optical-radio offsets in high redshift galaxies will be eased by the upcoming synoptic all-sky surveys, including E-ELT and SKA, which are expected to find ∼ 10 5 strongly lensed galaxies, opening an era of large strong lensing samples observed at high angular resolution.

show abstract

Spatially offset AGN candidates in the CLASS survey

Cited by 27 publications

References 57 publications

The Precious Set of Radio-optical Reference Frame Objects in the Light of Gaia DR2 Data

The Precious Set of Radio-optical Reference Frame Objects in the Light of Gaia DR2 Data

Dissecting the AGN Disk–Jet System with Joint VLBI-Gaia Analysis

Constraining VLBI−optical offsets in high redshift galaxies using strong gravitational lensing

Contact Info

Product

Resources

About