Very long baseline interferometry observations of the high-redshift X-ray-bright blazar SRGE J170245.3+130104

¹ Shanghai Astronomical Observatory, CAS, 80 Nandan Road, Shanghai 200030, PR China
e-mail: antao@shao.ac.cn
² School of Astronomy and Space Sciences, University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, PR China
³ Key Laboratory of Radio Astronomy and Technology, Chinese Academy of Sciences, A20 Datun Road, Beijing 100101, PR China
⁴ Space Research Institute of RAS, Profsoyusnaya street, 84/32, Moscow 117997, Russia
⁵ Special Astrophysical Observatory of RAS, Nizhny Arkhyz 369167, Russia
⁶ Kazan Federal University, 18 Kremlyovskaya St, Kazan 420008, Russia
⁷ Institute of Applied Astronomy RAS, St. Petersburg 191187, Russia

Received: 30 January 2024
Accepted: 26 February 2024

Abstract

Aims. The X-ray luminous and radio-loud active galactic nucleus (AGN) SRGE J170245.3+130104 discovered at z ∼ 5.5 provides unique chances to probe the growth and evolution of a supermassice black hole (SMBH) with powerful jets in the early Universe.

Methods. We present 1.35 − 5.1 GHz Very Long Baseline Array (VLBA) results regarding the radio continuum emission and a spectral analysis of this quasar in a low-flux-density state.

Results. This source is unresolved at three frequencies, with total flux densities of 8.35 ± 0.09 Jy beam⁻¹, 7.47 ± 0.08 Jy beam⁻¹, and 6.57 ± 0.02 Jy beam⁻¹ at 1.73 GHz, 2.26 GHz, and 4.87 GHz, respectively. Meanwhile, the brightness temperature is higher than 10⁹ K.

Conclusions. Compared with previous radio observations with arcsecond-scale resolution, nearly all the radio emission from this source is concentrated in the very central milliarcsecond (mas) scale area. We confirm this source is a bright blazar at z > 5. This young AGN provides a great opportunity to understand the mechanisms behind the generation of strong jets in the early Universe.