Discovery of Radio Jets in z ~ 2 Ultraluminous Infrared Galaxies with Deep 9.7 μm Silicate Absorption

Creators: Sajina, Anna; Yan, Lin; Lacy, Mark; Huynh, Minh

Abstract

Recent Spitzer observations have revealed a substantial population of z ~ 2 ultraluminous infrared galaxies (ULIRGs) with deep silicate absorption (τ_(9.7) > 1). This paper reports a 20 cm radio study of such a sample to elucidate their physical nature. We discover that a substantial fraction (40%) of deep silicate absorption ULIRGs at z ~ 2 are moderately radio-loud, with L_(1.4GHz) = 10^(25)-10^(26) W Hz^(-1). This is in strong contrast with z ≲ 1 radio galaxies and radio-loud quasars where none of the sources with available IRS spectra have τ_(9.7) > 1. In addition, we observe radio jets in two of our sources, with one having a double lobe structure ~200 kpc in extent and the other showing a one-sided jet extending ~90 kpc from the nucleus. The likely high inclination of the latter, coupled with its deep silicate absorption, implies the mid-IR obscuration does not share an axis with the radio jets. These sources are highly obscured quasars, observed in the transition stage after the birth of the radio source, but before feedback effects dispel the interstellar medium and halt the black hole accretion and starburst activity.

Additional Information

© 2007 American Astronomical Society. Print publication: Issue 1 (2007 September 20); received 2007 July 6; accepted for publication 2007 August 2; published 2007 August 31. Many thanks to Patrick Ogle for a critical reading of the manuscript prior to submission. We are also grateful to N. Seymour, K. Dasyra, B. Partridge, D. Lutz, and D. Scott for useful discussions.We are grateful to the anonymous referee for their helpful comments. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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