Discovery of Radio Jets in z~2 ULIRGs with Deep 9.7um Silicate Absorption

TL;DR

This study reveals that a significant portion of z~2 ULIRGs with deep silicate absorption exhibit radio jets and are moderately radio-loud, indicating a transitional phase in quasar evolution with complex obscuration and jet orientation.

Contribution

First detection of radio jets in z~2 ULIRGs with deep silicate absorption, highlighting their transitional nature and challenging assumptions about IR obscuration and jet alignment.

Findings

40% of deep silicate ULIRGs are moderately radio-loud.

Radio jets observed in two sources, including a 200kpc double lobe.

Mid-IR obscuration does not align with radio jet axes.

Abstract

Recent Spitzer observations have revealed a substantial population of z~2 ULIRGs with deep silicate absorption (\tau_{9.7}>1). This paper reports a 20cm 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}WHz^{-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 \tau_{9.7}>1. In addition, we observe radio jets in two of our sources where one has a double lobe structure ~200kpc in extent, and another shows a one-sided jet extending ~90kpc 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 ISM and halt the black hole accretion and starburst activity.