Observations shed more light on the star formation history of galaxy NGC 2915

Utilizing the Very Giant Telescope (VLT), Chinese language astronomers have investigated a close-by blue compact dwarf galaxy often called NGC 2915. Outcomes of the examine, offered in a paper printed October 12 on arXiv.org, yield vital insights concerning the star formation historical past of this galaxy.

Blue compact dwarfs (BCDs) are low-luminosity and low-metal content material dwarf galaxies experiencing violent bursts of star formation. They’re characterised by a compact optical look and H II-region-like spectra as a result of extremely concentrated starburst actions.

At a distance of some 13.4 million gentle years, NGC 2915 (often known as PGC 26761) is without doubt one of the closest BCDs to Earth. It’s an excessive case of BCDs within the native universe as its impartial atomic hydrogen (H I) gasoline content material may be very excessive and intensely prolonged in distribution. Furthermore, nearly all of the younger stellar populations and areas of ionized atomic hydrogen (H II) are situated close to the middle of this galaxy.

Nevertheless, though NGC 2915 is extraordinarily wealthy in gasoline, the star formation exercise is barely detected in its prolonged outer H I disk. Moreover, the triggering mechanism of the extremely concentrated star formation on this galaxy stays unclear.

Subsequently, with a view to additional examine the star formation exercise in NGC 2915, a gaggle of astronomers led by Yimeng Tang of the College of Science and Know-how of China in Hefei, China, carried out a complete evaluation of deep integral discipline spectroscopic observations of the galaxy’s central area made with VLT’s Multi Unit Spectroscopic Explorer (MUSE).

“To unveil the starburst-triggering thriller of NGC 2915, we carry out a complete evaluation of deep VLT/MUSE integral discipline spectroscopic observations that cowl the central kiloparsec star-forming area,” the researchers wrote within the paper.

The examine discovered that international star formation in NGC 2915 peaked round a few billion years in the past, when essentially the most huge star cluster was fashioned. The outcomes counsel that the newest episode of bursty star formation occurred round 50 million years in the past, has lasted for about 50–100 million years and was chargeable for the formation of some 3% of the galaxy’s total stellar mass.

Based on the analysis, episodes of bursty star formation just like the newest one could have recurred for lower than 4 instances in several places within the final billion years. Nevertheless, these episodes turned out to be largely confined throughout the galaxy’s central area (with a radius of roughly 1,300 gentle years).

The examine additionally discovered that the stellar disk of NGC 2915 reveals a comparatively weak however important rotation throughout the central 1,600 light years in radius and that the stellar rotation axis seems to be anti-parallel to that of the prolonged impartial H I disk. This discovering signifies that the latest episodes of bursty star formation have been sustained by externally accreted gasoline.

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