出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We present initial results of wide-field Global VLBI 1.4-GHz observations of the Hubble Deep
Field North region (HDF-N) and Flanking Fields surrounding it with a spatial resolution of 4
milliarcseconds. These observations are both deeper and wider than any previous VLBI
observations of the field, attaining an r.m.s. noise level of 7.3 μJy/beam in the central field. Four
radio sources have been clearly detected in the inner part of the field and a search for additional
sources in the adjacent Hubble Flanking Field (HFF) is underway. Among the four detections in
the HDF-N, three (VLA J123642+621331, VLA J123644+621133, and VLA J123646+621404)
have already been detected in previous EVN 1.6-GHz observations, but the forth one, VLA
J123652+621444, is a new detection that clearly shows one-sided, jet-like radio structure. The
VLBI observations of VLA J123642+621331 – classified at other wavelengths as a distant,
dust-obscured starburst galaxy at z = 4.424 – reveal a resolved jet-like extension emanating from
a compact AGN core. These results demonstrate the power of high-resolution VLBI imaging in
discriminating between starburst and AGN activity in dust-obscured systems. We plan to
analyse 80 additional radio target fields in the HFF over the next few months1.
