Two Candidate High-Redshift X-ray Jets Without Coincident Radio Jets

TL;DR

This paper reports the discovery of two high-redshift quasars with X-ray jets that lack coincident radio jets, suggesting that such X-ray jets may be common at high redshifts due to inverse Compton scattering of the CMB.

Contribution

It presents the first evidence of high-redshift X-ray jets without radio counterparts, expanding understanding of jet emission mechanisms at early cosmic times.

Findings

Detected extended X-ray emission aligned with radio features.

X-ray jets could be common at high redshifts due to CMB effects.

These are among the first high-redshift quasars with X-ray jets lacking radio counterparts.

Abstract

We report the detection of extended X-ray emission from two high-redshift radio quasars. These quasars, J1405+0415 at $z$=3.208 and J1610+1811 at $z$=3.118, were observed in a Chandra snapshot survey selected from a complete sample of the radio-brightest quasars in the overlap area of the VLA-FIRST radio survey and the Sloan Digital Sky Survey. The extended X-ray emission is located along the line connecting the core to a radio knot or hotspot, favoring the interpretation of X-ray jets. The inferred rest frame jet X-ray luminosities from 2--30 keV would be of order 10$^{45}$ erg~s$^{-1}$ if emitted isotropically and without relativistic beaming. In the scenario of inverse Compton scattering of the cosmic microwave background (CMB), X-ray jets without a coincident radio counterpart may be common, and should be readily detectable to redshifts even beyond 3.2 due to the (1+$z$)$^4$ increase of the CMB energy density compensating for the (1+$z$)$^{-4}$ cosmological diminution of surface brightness. If these can be X-ray confirmed, they would be the second and third examples of quasar X-ray jets without detection of underlying continuous radio jets.