First ultra-compact dwarf galaxy in the group NGC 5044 found
https://phys.org/news/2017-02-ultra-compact-dwarf-galaxy-group-ngc.html
A team of astronomers led by Favio Faifer of the National University of La Plata, Argentina, has discovered the first ultra-compact dwarf (UCD) galaxy
in an X-ray bright galaxy group designated NGC 5044. The finding was presented Feb. 21 in a paper published online on the arXiv pre-print repository.
Located some 116 million light years away, NGC 5044 is an early-type massive elliptical galaxy residing at the center of an X-ray bright group also named
NGC 5044. This group contains about 150 members, most of which are dwarf galaxies. Although the group's center galaxy has been the subject of several past
studies, its globular cluster and UCD system remain unexplored.
UCDs are very compact galaxies with high stellar populations, containing about 100 million stars. They display masses, colors, and metallicities between
those of globular clusters and early-type dwarf galaxies. These ultra-compact stellar systems could provide important insights on the formation and evolution
of galaxies in the universe.
That is why Faifer's team observed the NGC 5044 with the Gemini Multi-Object Spectrograph (GMOS) at the Gemini South telescope in Chile. They obtained deep
images of several fields around NGC 5044, which allowed them to detect the presence of a UCD.
"From the photometric and spectroscopic analysis of a deep field taken with Gemini+GMOS, we have been able to detect and confirm the first UCD in the NGC 5044
group," the researchers wrote in the paper.
The radial velocity and angular proximity (2.83 arcmin) of this UCD indicate that this object is associated with galaxy NGC 5044. The newly discovered UCD
was designated NGC 5044-UCD1.
The researchers found that the metallicity of NGC 5044-UCD1 is within the range displayed by other UCD detected in constellations Virgo and Fornax, but
considerably lower than that of the confirmed stripped nuclei described in previous studies. They also studied the star formation history of this UCD and
found that this object is approximately 11.7 billion years old.