Deep Submillimeter and Radio Observations in the SSA22 Field. I. Powering Sources and the Lyα Escape Fraction of Lyα Blobs

Abstract

We study the heating mechanisms and Ly α escape fractions of 35 Ly α blobs (LABs) at z  ≈ 3.1 in the SSA22 field. Dust continuum sources have been identified in 11 of the 35 LABs, all with star formation rates (SFRs) above 100 M ⊙ yr −1 . Likely radio counterparts are detected in 9 out of 29 investigated LABs. The detection of submillimeter dust emission is more linked to the physical size of the Ly α emission than to the Ly α luminosities of the LABs. A radio excess in the submillimeter/radio-detected LABs is common, hinting at the presence of active galactic nuclei. Most radio sources without X-ray counterparts are located at the centers of the LABs. However, all X-ray counterparts avoid the central regions. This may be explained by absorption due to exceptionally large column densities along the line-of-sight or by LAB morphologies, which are highly orientation dependent. The median Ly α escape fraction is about 3% among the submillimeter-detected LABs, which is lower than a lower limit of 11% for the submillimeter-undetected LABs. We suspect that the large difference is due to the high dust attenuation supported by the large SFRs, the dense large-scale environment as well as large uncertainties in the extinction corrections required to apply when interpreting optical data.