Pre-pilot survey explores dozens of candidate ultra-diffuse galaxies

By analyzing the information from the WALLABY pre-pilot survey, astronomers from the College of Western Australia and elsewhere, have inspected 78 candidate ultra-diffuse galaxies within the Eridanus supergroup. The research was detailed in a paper printed September 21 on the pre-print server arXiv.

Extremely-diffuse galaxies (UDGs) are extremely-low-density galaxies. The most important UDGs have sizes much like the Milky Way, however have solely about 1% as many stars as our house galaxy. The thriller of UDGs continues to be baffling scientists as they attempt to clarify why these faint however massive galaxies are usually not ripped aside by the tidal area of their host clusters.

Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a next-generation survey of impartial hydrogen (H I) within the native universe, working on the Australian Sq. Kilometer Array Pathfinder (ASKAP). Up to now, it has accomplished pilot observations of the Hydra, Norma, and NGC 4636 fields. WALLABY early science research have been in a position to get well many gas-rich low-mass dwarf galaxies.

Not too long ago, a group of astronomers led by Bi-Qing For, has analyzed the pre-pilot information from WALLABY to seek for impartial hydrogen in UDG candidates discovered within the Systematically Measuring Extremely-diffuse Galaxies survey (SMUDGes). They investigated candidate UDGs within the area of the Eridanus supergroup (positioned about 65 million gentle years away), which incorporates a bunch of galaxy teams that will finally merge to kind a cluster.

“On this paper, we current a pilot study of H I content material of optically recognized UDG candidates within the WALLABY pre-pilot Eridanus area and talk about implications for his or her formation mechanisms,” the researchers defined.

For’s group investigated the properties and derived the bodily parameters of 78 UDG candidates from the SMUDGes catalog. They discovered that six of them are putative UDGs, whereas the remaining are low-surface-brightness (LSB) dwarf galaxies.

In response to the research, many of the galaxies within the investigated pattern have efficient radii smaller than 4,900 light years. They’re additionally typically low-mass, with plenty lower than 100 million solar plenty, and are principally pink in colour.

The astronomers famous that impartial hydrogen has been detected in solely one of many studied galaxies—in a LSB dwarf designated WALLABY J033408−232125. Due to this fact, they anticipate about 22 neutral hydrogen detections because the decrease restrict for the complete WALLABY survey, noting that the detection price needs to be larger within the remoted and free group environments.

As a part of the research, the authors of the paper additionally investigated if tidal or ram-pressure stripping is a potential formation mechanism for UDGs within the Eridanus supergroup.

“We discover a putative UDG (SMDG 0345097−223826) that would have been shaped through tidal heating/interplay as it’s positioned on the tail finish of a stellar stream. If that was the case, this putative UDG would doubtless be a background UDG and wouldn’t be related to the Eridanus group,” the scientists concluded.

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