Abstract
ABSTRACT Jets of high-redshift active galactic nuclei (AGNs) can be used to directly probe the activity of the black holes in the early Universe. Radio sources with jets misaligned with respect to the line of sight are expected to dominate the high-redshift AGN population. In this paper, we present the high-resolution imaging results of a z = 4.57 AGN J2102+6015 by analysing its multi-epoch dual-frequency very long baseline interferometry (VLBI) data. The 8.4-GHz VLBI images reveal two major features along the east–west direction separated by ∼10 mas. From the spectral index map, both features show flat/inverted spectra. The separation between the two features remains almost unchanged over an observation period of ∼13 yr, placing an upper limit of the separation speed as about 0.04 mas yr−1. Previous studies have classified the source as a GHz-peaked spectrum quasar. Our results indicate that J2102+6015 is most likely a young, compact symmetric object rather than a blazar-type core–jet source.
Highlights
Active galactic nuclei (AGNs) are the most luminous persistent radiation sources in the Universe
We present a detailed study of the mas-scale radio morphology, spectral index distribution, and component proper motion in this peculiar source, based on an extensive collection of archival and new dual-frequency very long baseline interferometry (VLBI) data
We reported and analysed new and archival VLBI observations of the high-redshift (z = 4.575) quasar J2102+6015
Summary
Active galactic nuclei (AGNs) are the most luminous persistent radiation sources in the Universe. They can be observed throughout almost the entire cosmic history from very high to low redshifts. AGNs are an important sub-class of the population. Their radio emission is dominated by synchrotron radiation from the relativistic jets which are closely related to the accretion of their central supermassive black holes (SMBHs) Blandford & Payne 1982; Bridle & Perley 1984). Radio-loud AGNs represent only ∼ 10 per cent of the population. This percentage becomes smaller when moving to high
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