A new apparent quasar pair: Q2225-403A,B

TL;DR

This paper reports the discovery of a new quasar pair at different redshifts, providing insights into quasar environments and halo gas, with detailed spectroscopic and imaging analysis.

Contribution

It presents the first identification of a quasar pair with different redshifts and analyzes their host galaxies and surrounding gas.

Findings

Discovered a quasar at z=2.410 near another at z=0.932

Detected absorption lines indicating gas within 80 kpc of the quasars

Estimated the probability of such a close pair to be less than 1%

Abstract

We report the serendipitous discovery of a previously unknown quasar at 10.5" from Q2225-403 (z=2.410). The observation of the broad emission line of MgII_2798 and of the surrounding FeII multiplets indicates that the companion quasar is at z=0.932. The spectrum of Q2225-403 shows a number of absorption lines, the most noteworthy is the MgII line at the same redshift of the companion, suggesting that we are probing the gas within the halo ~80 kpc from the closer quasar. From high resolution NIR images we were able to resolve the host galaxies of the two quasars. Basing on the known surface density of quasars in the 2dF survey we estimate that the probability of finding such a close pair is < ~1 per cent.