Proper motion in lensed radio jets at redshift 3: A possible dual super-massive black hole system in the early Universe

Abstract

In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6 mas in the lensed images by comparing two Very Long Baseline Interferometric (VLBI) radio observations at 1.7 GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of µas. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-components separated by ∼ 175 pc, with proper motion of the order of tens µas yr −1 for the two components at highest magnification (µ ∼ 350) and of the order of a few mas yr −1 for the two components at lower magnification (µ ∼ 2). We propose single AGN and dual AGN scenarios to explain the source plane. Although, the latter interpretation is supported by the archival multi-wavelength properties of the object. In this case, MG B2016+112 would represent the highest redshift dual radio-loud AGN system discovered thus far, and would support the merger interpretation for such systems. Also, given the low probability (∼ 10 −5 ) of detecting a dual AGN system that is also gravitationally lensed, if confirmed, this would suggest that such dual AGN systems must be more abundant in the early Universe than currently thought.

Resolving Complex Inner X-ray Structure of the Gravitationaly Lensed AGN MGB2016+112

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We use a Chandra X-ray observation of the gravitationally lensed system MGB2016+112 at z=3.273 to elucidate presence of at least two X-ray sources. We find that these sources are consistent with the VLBI components measured by Spingola et al (2019), which are separated by ∼ 200 pc. Their intrinsic 0.5 -7 keV source frame luminosities are 2.6×10 43 and 4.2×10 44 erg s −1 .

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“…Such huge magnification is accompanied by spatial amplification that allows us not only to observe a source that would be otherwise too faint, but also to elucidate its structure as well as resolve spectra of individual lensed images of multiple sources. Radio observations reported by Spingola et al (2019) suggested possible dual-AGN-like structures with misaligned jets, and measured relative motions of components. If confirmed, MG B2016+112 would be the first gravitationally lensed dual AGN discovered to date.…”

“…Original X-ray detections by Hattori et al (1997) were interpreted as from the cluster, however Chandra observation by Chartas et al (2001) resolved three faint, point-like images consistent with the radio positions. Using the notation of Spingola et al (2019) we will call the X-ray images A1, B1 and C11.…”

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

“…However, 0402+379 is a very nearby source, located at redshift z = 0.055, which corresponds to luminosity distance of only ∼ 220 Mpc. Gravitational lensing can provide the necessary spatial resolution to resolve SMBH binary systems like 0402+379 even at high redshift (see also Spingola et al 2019c). We show that it is possible to confine the radio emission of the lensed AGN down to 0.4 pc (0.05 mas) for CLASS B0712+472 and 0.08 pc (9 µas) for CLASS B1608+656.…”

“…We use Monte Carlo simulations to estimate the uncertainty of the reconstructed source position at radio and optical wavelengths following the same approach explained in Spingola et al (2019c). We briefly outline the approach below.…”