New faint ultra-diffuse dwarf galaxy discovered

A world staff of astronomers studies the detection of a brand new faint ultra-diffuse dwarf galaxy as a part of a scientific wide-area seek for faint dwarf galaxies utilizing the Darkish Vitality Survey (DES). The newfound object, designated NGC 55-dw1, is a satellite of the galaxy NGC 55. The discovering was detailed in a paper revealed September 8 on the pre-print server arXiv.

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

Lately, a gaggle of astronomers led by Mitch McNanna of the College of Wisconsin-Madison has found a brand new UDG, which turned out to be a satellite of NGC 55—a barred spiral galaxy situated about 6.5 million light years away within the constellation Sculptor. The invention is predicated on the total six years of DES wide-area survey observations (DES Y6).

“We carried out a search over the DES Y6 knowledge for faint subject dwarf galaxies with heliocentric distances D = 0.3−2 Mpc utilizing the easy matched-filter search algorithm. This algorithm identifies galaxies as arcminute-scale overdensities of individually resolved stars,” the researchers defined.

The newfound UDG, which obtained NGC 55-dw1, is separated by solely 47 arcminutes from NGC 55. Subsequently, assuming that the galaxy and its satellite are roughly co-distant, they’re separated by solely 98,000 mild years.

NGC 55-dw1 has an absolute V-band magnitude of -8.0 magazine, half-light radius of about 7,200 mild years and total stellar mass of round 142,000 solar plenty. The galaxy is estimated to be 6.5 billion years outdated and its metallicity was measured to be at a stage of -1.8.

The massive spatial extent of NGC 55-dw1 relative to its luminosity makes it uncommon among the many recognized inhabitants of dwarf galaxies within the Native Quantity—inside 36 million mild years from the Earth. NGC 55-dw1 has one of many lowest floor brightness (32.3 magazine/arcsec²) and is the biggest, most diffuse galaxy recognized at this luminosity.

The authors of the paper famous that NGC 55-dw1’s giant, diffuse nature, excessive ellipticity (0.56), and proximity to its potential host galaxy recommend tidal interactions with NGC 55. Nonetheless, additional research are wanted to be able to verify this.

“Tidal interactions are a doable clarification for its giant measurement, excessive ellipticity, and very low floor brightness. (…) Nonetheless, as a result of depth limitations of our ground-based imaging, affirmation of tidal stripping will doubtless require additional follow-up,” the scientists concluded.

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