Relativistic Outflows in two quasars in the Chandra Deep Field South

TL;DR

This study confirms the presence of relativistic blueshifted X-ray emission/absorption lines in two quasars, indicating extremely fast outflows, and discusses their implications for jet and BAL outflows in quasars.

Contribution

It provides new 1 Ms Chandra spectra confirming relativistic outflows in two quasars and analyzes their properties over time, expanding the sample of such high-velocity outflows.

Findings

Relativistic blueshifted lines confirmed in one quasar and marginal in another.

Line energy decreased over 7 years, indicating possible velocity or ionization changes.

A total of 7 quasars with outflows v≥0.4c identified in literature.

Abstract

In this paper, we provide new 1 Ms $Chandra$ ACIS spectra of two quasars in the Chandra Deep Field South (CDF-S), which were previously reported to show strong and extremely blueshifted X-ray emission/absorption line features in previous 1 Ms spectra, with outflowing bulk velocity $v\sim$0.65-0.84c. In the new 1 Ms spectra, the relativistic blueshifted line feature is solidly confirmed in CXO CDFS J033225.3-274219 (CDFS 46, $z$ = 1.617), and marginally visible in CXO CDFS J033260.0-274748 (CDFS 11, $z$ = 2.579), probably due to the increased Chandra ACIS background in the new 1 Ms exposure. The new data rule out the possibility (though very tiny already based on the old 1Ms data) that the two sources were selected to be unusual due to noise spikes in the spectra. The only likely interpretation is extremely blueshifted iron absorption/emission line or absorption edge due to relativistic outflow. We find that the rest frame emission line center in CDFS 46 marginally decreased from 16.2 keV to 15.2 keV after 7 years. The line shift can be due to either decreasing outflowing velocity or lower ionization level. Including the two quasars reported in this paper, we collect from literature a total of 7 quasars showing blueshifted emission or absorption line feature with $v\geq0.4c$ in X-ray spectra, and discuss its connection to jet and/or BAL (broad absorption line) outflow.