We investigate the relationship between quasars (QSOs) and close companion galaxies using photometry and spectroscopy from the large dataset of the SDSS DR16 survey. Using the SDSS-QSO catalogue of quasars, we selected objects with 0.1 < z ≤ 0.35 and absolute magnitude M(r) < − 21.3. For all these targets, we searched for candidate companion galaxies located at a projected distance from the target of < 700 kpc and a radial velocity difference from the QSO of ΔV < 1000 km/s. We find that in 447 QSOs at least one companion galaxy was found to be associated. A total of 691 associated galaxies were found in these QSO fields. In the majority there was just one associated galaxy however in several cases a number of companion were also discovered and in two cases the QSO was found in a rich galaxy environments. We note that the possible contamination attributed to a chance projection of the companion galaxies is less than 5%. Based on the available data we expected to find on average ∼2 associated companion galaxies for each QSO. A small fraction (13%) of the companion galaxies exhibit OII emission lines as signature of recent star formation. However a similar fraction (16%) of unassociated galaxies in the same QSO fields exhibit OII emission. Overall this study suggests that there is no significant link between the presence of these close companion galaxies or the signature of recent star formation and QSO nuclear activity.
Bettoni et al. (Fri,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: