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Inefficient star formation in extremely metal poor galaxies.
Yong Shi1, Lee Armus2, George Helou2
11] School of Astronomy and Space Science, Nanjing University, Nanjing 210093, China [2] Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, China.
Nature
|October 17, 2014
Summary
Star formation was highly inefficient in the early Universe. Observations of nearby metal-poor galaxies show star formation efficiencies less than one-tenth of those in metal-rich galaxies today.
Area of Science:
- Astronomy
- Astrophysics
- Cosmology
Background:
- Early galaxies formed stars from gas with very low metallicity (elements heavier than helium).
- Low metallicity is theoretically expected to hinder gas cooling and efficient star formation.
- This inhibition has not been directly observed in galaxies with oxygen abundance below 10% of the Sun's value.
Purpose of the Study:
- To investigate star formation efficiency in extremely metal-poor galaxies.
- To understand conditions in low-metallicity galaxies during the early Universe.
- To assess the reliability of gas tracers in low-metallicity environments.
Main Methods:
- Spatially resolved infrared observations of two extremely metal-poor galaxies (oxygen abundance < 10% of solar).
- Analysis of star formation in seven distinct star-forming clumps within these galaxies.
Main Results:
- Observed star formation efficiencies in the studied clumps were less than one-tenth of those in present-day metal-rich galaxies.
- Demonstrated highly inefficient star formation in these low-metallicity environments.
Conclusions:
- The findings support the hypothesis that star formation was significantly less efficient in the early Universe due to low metallicity.
- Extremely metal-poor galaxies serve as crucial local analogs for studying early cosmic epochs.
- Challenges with traditional gas tracers (CO, dust) at low metallicities highlight the need for advanced observational techniques.
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