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Title: GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER

Abstract

We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2 < z < 3.2. These data, obtained for 387 fields, reach 3.6 and 4.5 {mu}m depths of [3.6]{sub AB} = 22.6 and [4.5]{sub AB} = 22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6] - [4.5] > -0.1 (AB), which efficiently selects high-redshift (z > 1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a {>=}2{sigma} level; 10% are overdense at a {>=}5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports anmore » association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.« less

Authors:
; ;  [1];  [2]; ;  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [10];  [11]
  1. Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)
  2. INAF-Osservatorio di Roma, Via Frascati 33, I-00040 Monteporzio (Italy)
  3. European Southern Observatory, Karl-Schwarzschildstr. 2, D-85748 Garching bei Muenchen (Germany)
  4. CASS, P.O. Box 76, Epping, NSW 1710 (Australia)
  5. Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States)
  6. Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)
  7. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)
  8. Astrophysics, Department of Physics, Keble Road, Oxford OX1 3RH (United Kingdom)
  9. Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)
  10. Physics Department, University of California, Davis, CA 95616 (United States)
  11. Centre for Astrophysics Research, STRI, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom)
Publication Date:
OSTI Identifier:
22126614
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 769; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CAMERAS; CORRELATIONS; DENSITY; EVOLUTION; GALAXY CLUSTERS; GALAXY NUCLEI; LUMINOSITY; ORIENTATION; QUASARS; RADIO GALAXIES; RED SHIFT; SOLIDS; SPACE; SURFACES; TELESCOPES

Citation Formats

Wylezalek, Dominika, Stern, Daniel, Eisenhardt, Peter R. M., Galametz, Audrey, Vernet, Joeel, De Breuck, Carlos, Seymour, Nick, Brodwin, Mark, Gonzalez, Anthony H., Hatch, Nina, Jarvis, Matt, Rettura, Alessandro, Stanford, Spencer A., and Stevens, Jason A. GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER. United States: N. p., 2013. Web. doi:10.1088/0004-637X/769/1/79.
Wylezalek, Dominika, Stern, Daniel, Eisenhardt, Peter R. M., Galametz, Audrey, Vernet, Joeel, De Breuck, Carlos, Seymour, Nick, Brodwin, Mark, Gonzalez, Anthony H., Hatch, Nina, Jarvis, Matt, Rettura, Alessandro, Stanford, Spencer A., & Stevens, Jason A. GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER. United States. https://doi.org/10.1088/0004-637X/769/1/79
Wylezalek, Dominika, Stern, Daniel, Eisenhardt, Peter R. M., Galametz, Audrey, Vernet, Joeel, De Breuck, Carlos, Seymour, Nick, Brodwin, Mark, Gonzalez, Anthony H., Hatch, Nina, Jarvis, Matt, Rettura, Alessandro, Stanford, Spencer A., and Stevens, Jason A. 2013. "GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER". United States. https://doi.org/10.1088/0004-637X/769/1/79.
@article{osti_22126614,
title = {GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER},
author = {Wylezalek, Dominika and Stern, Daniel and Eisenhardt, Peter R. M. and Galametz, Audrey and Vernet, Joeel and De Breuck, Carlos and Seymour, Nick and Brodwin, Mark and Gonzalez, Anthony H. and Hatch, Nina and Jarvis, Matt and Rettura, Alessandro and Stanford, Spencer A. and Stevens, Jason A.},
abstractNote = {We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2 < z < 3.2. These data, obtained for 387 fields, reach 3.6 and 4.5 {mu}m depths of [3.6]{sub AB} = 22.6 and [4.5]{sub AB} = 22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6] - [4.5] > -0.1 (AB), which efficiently selects high-redshift (z > 1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a {>=}2{sigma} level; 10% are overdense at a {>=}5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.},
doi = {10.1088/0004-637X/769/1/79},
url = {https://www.osti.gov/biblio/22126614}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 769,
place = {United States},
year = {Mon May 20 00:00:00 EDT 2013},
month = {Mon May 20 00:00:00 EDT 2013}
}