Browsing by Author "Conselice, Christopher J."

Now showing 1 - 4 of 4
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    Galaxy 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, Lingyu
    There 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.
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    Investigating the Effect of Galaxy Interactions on Star Formation at 0.5 < z < 3.0
    (2022) Shah, Ekta A.; Kartaltepe, Jeyhan S.; Magagnoli, Christina T.; Cox, Isabella G.; Wetherell, Caleb T.; Vanderhoof, Brittany N.; Cooke, Kevin C.; Calabro, Antonello; Chartab, Nima; Conselice, Christopher J.; Croton, Darren J.; de la Vega, Alexander; Hathi, Nimish P.; Ilbert, Olivier; Inami, Hanae; Kocevski, Dale D.; Koekemoer, Anton M.; Lemaux, Brian C.; Lubin, Lori; Mantha, Kameswara Bharadwaj; Marchesi, Stefano; Martig, Marie; Moreno, Jorge; Pampliega, Belen Alcalde; Patton, David R.; Salvato, Mara; Treister, Ezequiel
    Observations and simulations of interacting galaxies and mergers in the local universe have shown that interactions can significantly enhance the star formation rates (SFRs) and fueling of active galactic nuclei (AGN). However, at higher redshift, some simulations suggest that the level of star formation enhancement induced by interactions is lower due to the higher gas fractions and already increased SFRs in these galaxies. To test this, we measure the SFR enhancement in a total of 2351 (1327) massive (M* > 10(10)M(?)) major (1 < M-1/M-2 < 4) spectroscopic galaxy pairs at 0.5 < z < 3.0 with delta V < 5000 km s-1 (1000 km s(-1)) and projected separation < 150 kpc selected from the extensive spectroscopic coverage in the COSMOS and CANDELS fields. We find that the highest level of SFR enhancement is a factor of 1.23 (-0.09) (+0.08) in the closest projected separation bin (< 25 kpc) relative to a stellar mass-, redshift-, and environment-matched control sample of isolated galaxies. We find that the level of SFR enhancement is a factor of similar to 1.5 higher at 0.5 < z < 1 than at 1 < z < 3 in the closest projected separation bin. Among a sample of visually identified mergers, we find an enhancement of a factor of 1.86 (-0.18) (+0.29) (similar to 3 sigma) for coalesced systems. For this visually identified sample, we see a clear trend of increased SFR enhancement with decreasing projected separation (2.40-+0.62versus + 0.37 1.58(-0.20) (+0.29) for 0.5 < z < 1.6 and 1.6 < z < 3.0, respectively). The SFR enhancements seen in our interactions and mergers are all lower than the level seen in local samples at the same separation, suggesting that the level of interaction-induced star formation evolves significantly over this time period.
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    Investigating 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.
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    The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814
    (2021) Kilpatrick, Charles D.; Coulter, David A.; Arcavi, Iair; Brink, Thomas G.; Dimitriadis, Georgios; Filippenko, Alexei, V; Foley, Ryan J.; Howell, D. Andrew; Jones, David O.; Kasen, Daniel; Makler, Martin; Piro, Anthony L.; Rojas-Bravo, Cesar; Sand, David J.; Swift, Jonathan J.; Tucker, Douglas; Zheng, WeiKang; Allam, Sahar S.; Annis, James T.; Antilen, Juanita; Bachmann, Tristan G.; Bloom, Joshua S.; Bom, Clecio R.; Bostroem, K. Azalee; Brout, Dillon; Burke, Jamison; Butler, Robert E.; Butner, Melissa; Campillay, Abdo; Clever, Karoli E.; Conselice, Christopher J.; Cooke, Jeff; Dage, Kristen C.; de Carvalho, Reinaldo R.; de Jaeger, Thomas; Desai, Shantanu; Garcia, Alyssa; Garcia-Bellido, Juan; Gill, Mandeep S. S.; Girish, Nachiket; Hallakoun, Na'ama; Herner, Kenneth; Hiramatsu, Daichi; Holz, Daniel E.; Huber, Grace; Kawash, Adam M.; McCully, Curtis; Medallon, Sophia A.; Metzger, Brian D.; Modak, Shaunak; Morgan, Robert; Munoz, Ricardo R.; Munoz-Elgueta, Nahir; Murakami, Yukei S.; Felipe Olivares, E.; Palmese, Antonella; Patra, Kishore C.; Pereira, Maria E. S.; Pessi, Thallis L.; Pineda-Garcia, J.; Quirola-Vasquez, Jonathan; Ramirez-Ruiz, Enrico; Rembold, Sandro Barboza; Rest, Armin; Rodriguez, Osmar; Santana-Silva, Luidhy; Sherman, Nora F.; Siebert, Matthew R.; Smith, Carli; Smith, J. Allyn; Soares-Santos, Marcelle; Stacey, Holland; Stahl, Benjamin E.; Strader, Jay; Strasburger, Erika; Sunseri, James; Tinyanont, Samaporn; Tucker, Brad E.; Ulloa, Natalie; Valenti, Stefano; Vasylyev, Sergiy S.; Wiesner, Matthew P.; Zhang, Keto D.
    We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star-black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg(2) for the 90th percentile best localization), covering a total of 51 deg(2) and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an r-band decline rate of 0.68 mag day(-1), similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most -17.8 mag (50% confidence). Our data are not constraining for "red" kilonovae and rule out "blue" kilonovae with M > 0.5 M (circle dot) (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles <17 degrees assuming an initial jet opening angle of similar to 5.degrees 2 and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources.