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Highly efficient star formation in NGC 5253 possibly from stream-fed accretion.

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  • 1Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, California 90095-1547, USA.

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Star formation in galaxies is inefficient, but a dense, dusty gas cloud in NGC 5253 shows over 50% efficiency. This high rate may be fueled by infalling gas, explaining ancient massive star cluster formation.

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Area of Science:

  • Astronomy
  • Astrophysics
  • Galaxy Evolution

Background:

  • Star formation efficiency in galaxies is generally low, impacting galaxy evolution and the survival of star clusters.
  • The existence of ancient globular clusters suggests higher star formation efficiencies in the early universe.
  • The dwarf galaxy NGC 5253 hosts a young, massive star cluster providing a potential case study for efficient star formation.

Purpose of the Study:

  • To investigate the properties of a gas cloud associated with a massive young star cluster in the dwarf galaxy NGC 5253.
  • To determine the star formation efficiency within this specific gas cloud.
  • To understand the conditions that may lead to highly efficient star formation.

Main Methods:

  • Detection of the J = 3→2 rotational transition of carbon monoxide (CO) using radio astronomy.
  • Analysis of the gas cloud's physical properties: temperature, density, and dust content.
  • Comparison of the gas-to-dust ratio with that of the Milky Way.

Main Results:

  • The gas cloud is characterized by high temperature, density, and extreme dust content.
  • The gas-to-dust ratio is significantly lower than the Galactic average, likely due to dust enrichment from the embedded star cluster.
  • The star formation efficiency within this cloud exceeds 50%, which is approximately tenfold higher than typical galactic values.

Conclusions:

  • The observed high star formation efficiency in NGC 5253's gas cloud is attributed to its unique physical conditions, including high density and dust content.
  • The low gas-to-dust ratio suggests enrichment by the young, massive star cluster.
  • Infalling gas streams ('force-feeding') are proposed as a mechanism driving this enhanced star formation, potentially mirroring conditions in the early universe.