A survey of Radio Recombination Lines using Ooty Radio Telescope at 328 MHz in the Inner Galaxy

TL;DR

This survey used the Ooty Radio Telescope at 328 MHz to map radio recombination lines across a large part of the inner Galaxy, revealing the distribution of extended low-density warm-ionized medium.

Contribution

It provides the first extensive mapping of radio recombination lines in the inner Galaxy using the ORT with a new digital backend, improving understanding of ionized gas distribution.

Findings

Mapped the distribution of ELDWIM in the inner Galaxy

Determined kinematical distances of ionized gas clouds

Enhanced understanding of Galactic ionized medium structure

Abstract

A survey of radio recombination lines in the Galactic plane with longitude $-32^o < l < +80^o$ and latitude $b<\pm3^o$ using Ooty Radio Telescope(ORT) at 328 MHz has been reported. ORT observations were made using a New Digital Backend(NDB) augmented to it recently. With NDB ORT had a beam of $2^o.3 \times 2^o.2 sec(\delta)$ and a passband of $\sim$1 MHz in the spectral line mode. The above mentioned Galactic region was divided into $\sim 2^o \times 2^o$ patches with the ORT beam pointed to the center. The ORT observations form a study of distribution of extended low-density warm-ionized medium(ELDWIM) in the inner Galaxy using H271$\alpha$ RL. By obtaining kinematical distances using $V_{LSR}$ of the H271$\alpha$ RLs the distribution of ELDWIM clouds within the inner Galaxy has been deduced for the region given above.