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

Abstract

Recent Spitzer observations have revealed a substantial population of z ~ 2 ultraluminous infrared galaxies (ULIRGs) with deep silicate absorption (τ9.7>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 L1.4GHz=1025-1026 W Hz-1. This is in strong contrast with z 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.