New light shed on birth of the universe

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A faint blue galaxy about 30 million light-years from Earth and located in the constellation Leo Minor could shed new light on conditions at the birth of the universe.

Astronomers at Indiana University recently found that a galaxy nicknamed Leoncino, or "little lion," contains the lowest level of heavy chemical elements, or "metals," ever observed in a gravitationally bound system of stars.

The study appears today in the Astrophysical Journal. The lead author on the paper is Alec S. Hirschauer, a graduate student in the IU Bloomington College of Arts and Sciences' Department of Astronomy. Other IU authors on the paper are professor John J. Salzer and associate professor Katherine L. Rhode in the Department of Astronomy.

"Finding the most metal-poor galaxy ever is exciting since it could help contribute to a quantitative test of the Big Bang," Salzer said. "There are relatively few ways to explore conditions at the birth of the universe, but low-metal galaxies are among the most promising."

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You will find the paper on the physics ArXiv here:ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC 198691.

We have presented KPNO 4-m and MMT 6.5-m spectroscopic observations of the dwarf irregular galaxy AGC 198691 (a.k.a., the Leoncino Dwarf), which was discovered in the ALFALFA survey and included in the SHIELD sample of low HI mass systems. The analysis of our spectral data has resulted in the derivation of a "direct-method" oxygen abundance of 12+log(O/H) - 7.02 +/-0.03. This metallicity makes AGC 198691 the most metal-poor galaxy known in the local universe. The oxygen abundance of this system is a full 0.11 dex below that of SBS 0335-052W and 0.15 dex below I Zw 18. While the spectra in the current study were not suitable for providing an estimate of the helium abundance in this galaxy, we suggest that future observations would very likely be fruitful in yielding an estimate of the primordial helium abundance.
AGC 198691 is a small, high surface brightness system that we classify as a blue compact dwarf galaxy. It is one of the lowest luminosity members of the BCD class ever discovered. Its observed color of B-V = 0.29 is indicative of a galaxy dominated by a young stellar population. A secure distance to this system is not currently available.
Our analysis of the available data appears to constrain the distance to be within the range of 7 - 16 Mpc. If the distance is in the nearer portion of that range (7 -11 Mpc) it is located in the sparsely populated Leo Spur.
If it has a distance in the farther portion of this range (11 - 16 Mpc) then it is likely to be quite isolated, with no neighbors within 1 Mpc. The determination of an accurate distance for this object is a high priority. Regardless of its distance, it is clear that AGC 198691 is extremely gas rich.
The recent discoveries by the ALFALFA survey of two new XMD systems with 12+log(O/H) less than 7.20 speak to the power of the HI selection method for searching for metal poor systems. Both Leo P and AGC 198691 are extreme systems within the Local Supercluster that remained unrecognized until their detection in the blind HI survey carried out at Arecibo. Hundreds more ALFALFA detections remain to be explored

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