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Massive star formation within the Leo 'primordial' ring

Thilker, David A. and Donovan, Jennifer and Schiminovich, David and Bianchi, Luciana and Boissier, Samuel and Gil de Paz, Armando and Madore, Barry F. and Martin, D. Christopher and Seibert, Mark (2009) Massive star formation within the Leo 'primordial' ring. Nature, 457 (7232). pp. 990-993. ISSN 0028-0836.

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Few intergalactic, plausibly primordial clouds of neutral atomic hydrogen (H I) have been found in the local Universe, suggesting that such structures have either dispersed, become ionized or produced a stellar population on gigayear timescales. The Leo ring1,2, a massive (M_(HI)<1.8x10^9M_⊙, M_⊙ denoting the solar mass), 200-kpc-wide structure orbiting the galaxies M105 and NGC3384 with a 4-Gyr period, is a candidate primordial cloud. Despite repeated atttempts3,4, it has previously been seen only from HI emission, suggesting the absence of a stellar population. Here we report the detection of ultraviolet light from gaseous substructures of the Leo ring, which we attribute to recent massive star formation. The ultraviolet colour of the detected complexes is blue, implying the onset of a burst of star formation or continuous star formation of moderate (~10^8-yr) duration. Measured ultraviolet–visible photometry favours models with low metallicity (Z=Z_⊙/50–Z_⊙/5, Z_⊙ denoting the solar metallicity), that is, a low proportion of elements heavier than helium, although spectroscopic confirmation is needed. We speculate that the complexes are dwarf galaxies observed during their formation, but distinguished by their lack of a dark matter component5. In this regard, they resemble tidal dwarf galaxies, although without the enrichment preceding tidal stripping. If structures like the Leo ring were common in the early Universe, they may have produced a large, yet undetected, population of faint, metal-poor, halo-lacking dwarf galaxies.

Item Type:Article
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URLURL TypeDescription
Thilker, David A.0000-0002-8528-7340
Boissier, Samuel0000-0002-9091-2366
Gil de Paz, Armando0000-0001-6150-2854
Madore, Barry F.0000-0002-1576-1676
Martin, D. Christopher0000-0002-8650-1644
Seibert, Mark0000-0002-1143-5515
Additional Information:© 2009 Nature Publishing Group. Received 3 November 2008; Accepted 13 January 2009. GALEX is a NASA Small Explorer, launched in April 2003. We gratefully acknowledge NASA's support of the construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales, France, and the Korean Ministry of Science and Technology. This research draws upon data provided by B. Millis as distributed by the National Optical Astronomy Observatory (NOAO) Science Archive. NOAO is operated by the Association of Universities for Research in Astronomy under a cooperative agreement with the National Science Foundation. This research has made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. This research made use of NASA's Astrophysics Data System.
Group:Space Astrophysics Laboratory
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Ministry of Science and Technology (Korea)UNSPECIFIED
Issue or Number:7232
Record Number:CaltechAUTHORS:20090826-105346060
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15314
Deposited By: George Porter
Deposited On:11 Sep 2009 16:25
Last Modified:09 Mar 2020 21:00

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