Discovery of a new ultra-diffuse dwarf galaxy

Spatial distribution of stars near NGC 55-dw1. Credit: McNanna et 

An international team of astronomers reports the discovery of a new faint ultradiffuse and diffuse dwarf galaxy as part of a systematic search over a large area for faint dwarf galaxies using how to use the Dark Energy Survey (DES). The newly discovered object, designated NGC 55-dw1, is a satellite of the galaxy NGC 55. The discovery is detailed in a paper published September 8 on the preprint server arXiv . Ultra-diffuse galaxies (UDG) are galaxies with extremely low density. The largest UDGs are similar in size to the Milky Way, but contain only about 1% more stars than our home galaxy. The mystery of UDG continues to perplex scientists as they try to explain why these faint but massive galaxies are not torn apart by the tidal fields of their host clusters. Recently, a team of astronomers led by Mitch McNanna of the University of Wisconsin-Madison discovered a new UDG, which turns out to be a satellite of NGC 55, a barred spiral galaxy located about 6 meters away. .5 million light years in the constellation Sculpture. . This finding is based on six years of DES large-scale survey observations (DES Y6).

“We searched the DES Y6 data for low-field dwarf galaxies with heliocentric separation D = 0.3−2 Mpc using a simple matching filter search algorithm. This algorithm identifies the galaxies The galaxy is so dense on the arc-minute scale of individually resolved stars,” the researchers explain. The new UDG, which received NGC 55-dw1, is only 47 arc minutes away from NGC 55. Therefore, assuming that the galaxy and its satellite are roughly the same distance apart, they are only 98,000 light years apart. NGC 55-dw1 has a V-band absolute magnitude of -8.0 mag, a half-light radius of about 7,200 light-years, and a total stellar mass of about 142,000 solar masses. The galaxy is estimated to be 6.5 billion years old and its metallicity is measured at -1.8. NGC 55-dw1’s large spatial extent relative to its luminosity makes it unusual among known dwarf galaxies in terms of local volume, being less than 36 million light-years from Earth. NGC 55-dw1 has one of the lowest surface luminosities (32.3 mag/arcsec2) and is the largest and most diffuse galaxy known at this luminosity.

The paper’s authors note that NGC 55-dw1’s highly diffuse nature, high ellipticity (0.56), and close distance to its potential host galaxy suggest tidal interaction with NGC 55 . However, further studies are needed to confirm this. “Tidal interactions are a possible explanation for its large size, high ellipticity and extremely low luminosity. (…) However, due to the depth limitations of our ground-based imagery, confirmation of tidal blocking will likely require further

Source: arXiv (2023). DOI: 10.48550/arxiv.2309.04467