Hydrogen recombination lines near 327 MHz - II: A galactic plane survey with a 2°x 6' beam

Abstract

In a previous paper we presented a low-resolution (2 deg × 2 deg) survey of radio recombination lines (RRLs) at 327 MHz in the longitude range l = 330 deg to 0 deg to 89 deg. In this paper, we present the results of a higher resolution (2 deg × 6 arcmin) survey of RRLs from seven 2 deg-wide fields and two 6 deg-wide fields in the same longitude range. Observations were made using the Ooty Radio Telescope (ORT). A total of 252 spectra that were obtained are presented. RRLs were detected in almost all the individual positions within the fields with l < 35 deg and at several individual positions within the fields in the longitude range l = 35 deg to 85 deg. Detailed analysis of the data towards the field centered at G45.5+0.0, shows that the line emission consists of discrete zones of ionized gas. The angular extent of these zones are likely to be one degree or more corresponding to a linear size of > 110 pc at the kinematic distance.