Browsing by Author "Conselice, Christopher J."
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- ItemGalaxy and Mass Assembly (GAMA): active galactic nuclei in pairs of galaxies(OXFORD UNIV PRESS, 2017) Gordon, Yjan A.; Owers, Matt S.; Pimbblet, Kevin A.; Croom, Scott M.; Alpaslan, Mehmet; Baldry, Ivan K.; Brough, Sarah; Brown, Michael J. I.; Cluver, Michelle E.; Conselice, Christopher J.; Davies, Luke J. M.; Holwerda, Benne W.; Hopkins, Andrew M.; Gunawardhana, Madusha L. P.; Loveday, Jonathan; Taylor, Edward N.; Wang, LingyuThere exist conflicting observations on whether or not the environment of broad-and narrowline active galatic nuclei (AGN) differ and this consequently questions the validity of the AGN unification model. The high spectroscopic completeness of the Galaxy and Mass Assembly (GAMA) survey makes it ideal for a comprehensive analysis of the close environment of galaxies. To exploit this, and conduct a comparative analysis of the environment of broad-and narrow-line AGN within GAMA, we use a double-Gaussian emission line fitting method to model the more complex line profiles associated with broad-line AGN. We select 209 type 1 (i.e. unobscured), 464 type 1.5-1.9 (partially obscured), and 281 type 2 (obscured) AGN within the GAMA II data base. Comparing the fractions of these with neighbouring galaxies out to a pair separation of 350 kpc h(-1) and triangle z < 0.012 shows no difference between AGN of different type, except at separations less than 20 kpc h(-1) where our observations suggest an excess of type 2 AGN in close pairs. We analyse the properties of the galaxies neighbouring our AGN and find no significant differences in colour or the star formation activity of these galaxies. Further to this, we find that Sigma(5) is also consistent between broad-and narrow-line AGN. We conclude that the observations presented here are consistent with AGN unification.
- ItemInvestigating the Effect of Galaxy Interactions on the Enhancement of Active Galactic Nuclei at 0.5 < z < 3.0(2020) Shah, Ekta A.; Kartaltepe, Jeyhan S.; Magagnoli, Christina T.; Cox, Isabella G.; Wetherell, Caleb T.; Vanderhoof, Brittany N.; Calabro, Antonello; Chartab, Nima; Conselice, Christopher J.; Croton, Darren J.; Donley, Jennifer; de Groot, Laura; de la Vega, Alexander; Hathi, Nimish P.; Ilbert, Olivier; Inami, Hanae; Kocevski, Dale D.; Koekemoer, Anton M.; Lemaux, Brian C.; Mantha, Kameswara Bharadwaj; Marchesi, Stefano; Martig, Marie; Masters, Daniel C.; McGrath, Elizabeth J.; McIntosh, Daniel H.; Moreno, Jorge; Nayyeri, Hooshang; Pampliega, Belen Alcalde; Salvato, Mara; Snyder, Gregory F.; Straughn, Amber N.; Treister, Ezequiel; Weston, Madalyn E.Galaxy interactions and mergers are thought to play an important role in the evolution of galaxies. Studies in the nearby universe show a higher fraction of active galactic nuclei (AGNs) in interacting and merging galaxies than in their isolated counterparts, indicating that such interactions are important contributors to black hole growth. To investigate the evolution of this role at higher redshifts, we have compiled the largest known sample of major spectroscopic galaxy pairs (2381 with Delta V < 5000 km s(-1)) at 0.5 < z < 3.0 from observations in the COSMOS and CANDELS surveys. We identify X-ray and IR AGNs among this kinematic pair sample, a visually identified sample of mergers and interactions, and a mass-, redshift-, and environment-matched control sample for each in order to calculate AGN fractions and the level of AGN enhancement as a function of relative velocity, redshift, and X-ray luminosity. While we see a slight increase in AGN fraction with decreasing projected separation, overall, we find no significant enhancement relative to the control sample at any separation. In the closest projected separation bin (< 25 kpc, Delta V < 1000 km s(-1)), we find enhancements of a factor of 0.94(-0.16)(+0.21) and 1.00(-0.31)(+0.58) for X-ray and IR-selected AGNs, respectively. While we conclude that galaxy interactions do not significantly enhance AGN activity on average over 0.5 < z < 3.0 at these separations, given the errors and the small sample size at the closest projected separations, our results would be consistent with the presence of low-level AGN enhancement.