Mapping the ionised gas around the luminous QSO HE 1029-1401: Evidence for minor merger events?

TL;DR

This study maps the ionised gas around QSO HE 1029-1401, revealing complex gas dynamics and structures that suggest external origins and past minor merger events, providing insights into the galaxy's interaction history.

Contribution

First two-dimensional mapping of ionised gas around a luminous QSO, linking gas structures to minor merger signatures and nuclear activity.

Findings

Ionised gas distribution extends up to 16 kpc with complex morphology.

Gas metallicity lower than expected, indicating external origin.

Detection of rotating gas disc and disturbed velocity field suggestive of mergers.

Abstract

We present VIMOS integral field spectroscopy of the brightest radio-quiet QSO on the southern sky HE 1029-1401 at a redshift of z=0.086. Standard decomposition techniques for broad-band imaging are extended to integral field data in order to deblend the QSO and host emission. We perform a tentative analysis of the stellar continuum finding a young stellar population (<100Myr) or a featureless continuum embedded in an old stellar population (10Gyr) typical for a massive elliptical galaxy. The stellar velocity dispersion of sigma_*=320\pm90 km/s and the estimated black hole mass log(M_BH/M_sun)=8.7\pm0.3 are consistent with the local M_BH-sigma_* relation within the errors. For the first time we map the two-dimensional ionised gas distribution and the gas velocity field around HE 1029-1401. While the stellar host morphology is purely elliptical we find a highly structured distribution of ionised gas out to 16 kpc from the QSO. The gas is highly ionised solely by the QSO radiation and has a significantly lower metallicity than would be expected for the stellar mass of the host, indicating an external origin of the gas most likely due to minor mergers. We find a rotating gas disc around the QSO and a dispersion-dominated non-rotating gas component within the central 3 kpc. At larger distances the velocity field is heavily disturbed, which could be interpreted as another signature of past minor merger events. Alternatively, the arc-like structure seen in the ionised gas might also be indicative of a large-scale expanding bubble, centred on and possibly driven by the active nucleus.