A blind HI survey in the Canes Venatici region

TL;DR

This paper presents a deep blind HI survey in the Canes Venatici region using the Westerbork telescope, discovering new low-mass HI objects and dwarf galaxy candidates, thereby constraining the low-mass end of the HI mass function.

Contribution

It provides the first deep blind HI survey in this region, detecting new low-mass HI sources and demonstrating the survey's ability to find dwarf galaxy candidates.

Findings

Detected 70 HI sources, 19 of which are new in this survey.

Found that 86% of detections are dwarf galaxy candidates.

Survey depth is about 10 times greater than previous surveys.

Abstract

We have carried out a blind HI survey using the Westerbork Synthesis Radio Telescope to make an inventory of objects with small HI masses (between 10^6 and 10^8 Msol) and to constrain the low-mass end of the HI mass function. The survey has been conducted in a part of the volume containing the nearby Canes Venatici groups of galaxies. The surveyed region covers an area on the sky of about 86 square degrees and a range in velocity from about -450 to about 1330 km/s. We find 70 sources in the survey by applying an automated searching algorithm. Two of the detections have not been catalogued previously, but they can be assigned an optical counterpart, based on visual inspection of the second generation Digital Sky Survey images. Only one of the HI detections is without an optical counterpart. This object is detected in the vicinity of NGC4822 and it has been already detected in previous HI studies. Nineteen of the objects have been detected for the first time in the 21-cm emission line in this survey. The distribution of the HI properties of our detections confirms our ability to find low mass objects. 86% of the detections have profile widths less than 130 km/s and can be considered dwarf galaxy candidates. The HI fluxes measured imply that this survey goes about 10 times deeper than any previous blind HI survey. The HI mass function and the optical properties of the detected sources will be discussed in future papers.