EZOA: Nan\c{c}ay HI follow-up observations in the Zone of Avoidance

TL;DR

This study used the Nançay Radio Telescope to follow up on 99 galaxy candidates in the Zone of Avoidance, confirming most and improving the catalog with new and refined HI data, demonstrating enhanced sensitivity over previous surveys.

Contribution

First detailed follow-up observations of EZOA galaxy candidates with increased sensitivity, confirming detections and updating the catalog with improved HI parameters.

Findings

Confirmed 72 out of 99 sources, improving catalog accuracy.

Detected 5 serendipitous sources due to higher sensitivity.

Validated the correlation between catalog quality and detection success.

Abstract

We present follow-up 21cm HI line observations made with the Nan\c{c}ay Radio Telescope (NRT) of 99 weak or potential detections of galaxies from the EZOA catalogue in the northern Zone of Avoidance (ZoA), which were extracted from the shallow version of the EBHIS blind HI survey performed with the Effelsberg radio telescope. The new NRT observations are on average almost three times as sensitive as those from EBHIS. Of the 99 observed sources, we confirmed 72, while three yielded inconclusive results. We find that the quality assessment of the EZOA catalogue entries correlates well with the NRT recovery rate; for instance, only four of the 22 potential detections could be confirmed. Due to the higher sensitivity as well as the large north-south extent of the NRT beam, the NRT observations also yielded five serendipitous detections, which we include here. We updated the EZOA catalogue with the improved HI parameters and detections. To test mitigation of Radio Frequency Interference signals, we also observed selected sources using a dedicated receiver and data processing system.