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Detection of the transverse proximity effect : radiative feedback from bright QSOs

Gonçalves, Thiago S. and Steidel, Charles C. and Pettini, Max (2008) Detection of the transverse proximity effect : radiative feedback from bright QSOs. Astrophysical Journal, 676 (2). pp. 816-835. ISSN 0004-637X. doi:10.1086/527313.

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Measuring the response of the intergalactic medium (IGM) to a blast of ionizing radiation allows one to infer the physical properties of the medium and, in principle, the lifetime and isotropy of the radiating source. The most sensitive such measurements can be made if the source of radiation is near the line of sight to a bright background QSO. We present results based on deep Keck HIRES observations of the QSO triplet KP 76, KP 77, and KP 78 at z ≃ 2.5, with separations of 2'-3' on the plane of the sky. Using accurate systemic redshifts of the QSOs from near-IR spectroscopy, we quantify the state of the IGM gas in the proximity regions where the expected ionizing flux from the foreground QSOs exceeds that of the metagalactic background by factors of 10-200, assuming constant and isotropic emission. Based on the unusual ionization properties of the absorption systems with detected H I, C IV, and O VI, we conclude that the gas has been significantly affected by the UV radiation from the nearby QSOs. Aided by observations of the galaxy density near the foreground QSOs, we discuss several effects that may explain why the transverse proximity effect has eluded most previous attempts to detect it. Our observations suggest that the luminosities of KP 76 and KP 77 have remained comparable to current values over timescales of, respectively, Δ t > 25 Myr and 16 Myr < Δ t < 33 Myr , consistent with typical QSO lifetimes estimated from independent, less direct methods. There is no evidence that the UV radiation from either QSO was significantly anisotropic during these intervals.

Item Type:Article
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Steidel, Charles C.0000-0002-4834-7260
Pettini, Max0000-0002-5139-4359
Additional Information:© 2008 The American Astronomical Society. Received 2007 August 16; accepted 2007 November 20. We would like to thank Dawn Erb, Naveen Reddy, and Alice Shapley for their collaboration in the large survey which supplied the LRIS spectroscopic redshifts of galaxies and AGNs in the field of Q1623+268. In addition, Dawn and Alice obtained the near-IR spectra used to determine the systemic redshifts of the QSOs, and Naveen kindly provided the Spitzer results on the QSOs prior to publication. Kurt Adelberger is thanked for many discussions and for his participation in the early stages of the project. We would also like to thank Tom Barlow, Rob Simcoe, George Becker, and Bob Carswell for assistance with the software used to reduce HIRES data. Rob Simcoe also provided us with measurements from his previous work, for which we are grateful. Wal Sargent provided us with his HIRES spectra of KP 76 and KP 77, which were combined with the new data presented here. An anonymous referee and Juna Kollmeier provided constructive comments which significantly improved the paper. Finally, we wish to extend thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. This work was supported by grants AST 03-07263 and AST 06-06912 from the US National Science Foundation and by the David and Lucile Packard Foundation.
Funding AgencyGrant Number
NSFAST 03-07263
NSFAST 06-06912
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:intergalactic medium; quasars: absorption lines; quasars: general
Issue or Number:2
Record Number:CaltechAUTHORS:GONapj08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13849
Deposited By: Tony Diaz
Deposited On:15 Jul 2009 20:49
Last Modified:08 Nov 2021 22:41

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