Inconsequential Dense Regions and Enhanced Star Formation in Quasar Host Galaxies in the Galaxy and Mass Assembly (GAMA) Survey
Acharya, Nischal (2020-01-10)
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Quasars (QSOs) are the brightest objects in the known universe which radiate across the electromagnetic spectrum. They are active nuclei of galaxies that have super- massive black holes (SMBH) at their center. It is believed that merger of gas rich galaxies results in the formation of an active galactic nucleus (AGN). Involved in this process is the obscuring of the central black hole pushing the gas and energy outward of the system through a series of negative feedback which consecutively leads to the quenching of Star Formation (SF) in the resulting galaxy. Science has so far led us to believe that these quiescent hosts are more likely to be found in overdense regions where the probability of mergers triggered AGNs would be higher than in low dense environments. We use the data of more than 330,000 galaxies in the GAMA database and identify the quasars among them using the Large Quasar Astrometric Catalogue-4 (LQAC-4) and study their environment. We aim to find the types of environment these quasar hosts live in, including their stellar parameters and compare their properties against a Monte Carlo simulation of random galaxies selected by the same mass range. We find no evidence of quenched star formation in 207 quasar hosts, but rather an enhanced star formation rate compared to that of inactive galaxies in the same mass range. We find these hosts to have almost twice the mean metallicity and hence a younger stellar population than normal galaxies. They have no direct correlation with the local density of their environments and the same can be said for their relation with the large scale structures they reside in.