Abstract
We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, $M_{200}$, and the normalized cluster-centric distance, $r/r_{200}$. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control for the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within an HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g., whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a binary variable. Furthermore, we demonstrate how an HBM can incorporate information of each particular galaxy morphological type in a unified framework. In elliptical galaxies, our analysis indicates a strong correlation of Seyfert-AGN activity with $r/r_{200}$, and a weaker correlation with the mass of the host. In spiral galaxies these trends do not appear, suggesting that the link between Seyfert activity and the properties of spiral galaxies are independent of the environment.
Highlights
For a long time it has been argued that active galactic nuclei (AGN) are powered by the accretion of gas into a supermassive black hole (SMBH) located at the centre of its host galaxy (e.g. Lynden-Bell 1969; Magorrian et al 1998; Orban de Xivry et al 2011)
We study how Seyfert-AGN activity in elliptical and spiral galaxies depends on local and global cluster properties, represented by the cluster-centric distance and the mass of the galaxy cluster
We used a sample of low redshift clusters (0.015 < z < 0.1), with at least 10 galaxy members each, and with 13.4 < log M200 < 14.6, from which we include galaxies up to 10· r200
Summary
For a long time it has been argued that active galactic nuclei (AGN) are powered by the accretion of gas into a supermassive black hole (SMBH) located at the centre of its host galaxy (e.g. Lynden-Bell 1969; Magorrian et al 1998; Orban de Xivry et al 2011). More recently Pimbblet et al (2013) using sample of cluster relatively free from mergers, which can locally enhance AGN activity, found a strong relation between AGN activity and r/r200, with significant increase of AGN fraction from the cluster centre to 1.5 Virial radii, with massive galaxies systematically hosting a larger fraction of AGN at any radial location It is well-known that many galaxy properties, such as stellar mass (M∗; Schawinski et al 2010), morphology (Dressler 1980; Calvi et al 2012), star formation rate (SFR; Abraham et al 1996; Hashimoto et al 1998; Gomez et al 2003; Kauffmann et al 2004; Harris et al 2016), and optical colours (Strateva et al 2001; Hogg et al 2004; Kauffmann et al 2004; Blanton et al 2005; Baldry et al 2006) are strongly correlated with the environment where the galaxy resides.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
