EZOA: Nançay H I follow-up observations in the Zone of Avoidance

¹ Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching, Germany
² LUX, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 5 place Jules Janssen, 92190 Meudon, France
³ Observatoire Radioastronomique de Nançay, Observatoire de Paris, Université PSL, Université d’Orléans, 18330 Nançay, France
⁴ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
⁵ Université Paris-Cité, 143 avenue de Versailles, 75016 Paris, France

^⋆ Corresponding author; anja@mpe.mpg.de

Received: 2 December 2024
Accepted: 23 January 2025

Abstract

We present follow-up 21 cm H I line observations made with the Nançay 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 H I 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 H I parameters and detections. To test the mitigation of radio frequency interference signals, we also observed selected sources using a dedicated receiver and data processing system.