A team of U.S. astronomers led by James Rhoads from the Space Telescope Science Institute, reports the discovery of extremely high rates of star formation in one of the most distant known galaxies in the universe. LALA J142442.24+353400.2, named for the survey in which it was discovered and its celestial coordinates, lies at a redshift of 6.535, which puts it 12.8 billion light-years away and appearing as it looked some 850 million years after the Big Bang. This faint, distant galaxy is fabricating stars at a rate of more than 11 solar masses per year, a frenetic pace among galaxies at this distance and epoch in the early universe. Astronomers traced the galaxy’s starburst activity by measuring light emitted in the so-called Lyman-alpha emission line, using deep multi-object spectroscopy conducted at Gemini Observatory with GMOS-N and the Keck Observatory with the Deep Imaging Multi-object Spectrograph (Deimos).
A team of U.S. astronomers led by James Rhoads from the Space Telescope Science Institute, reports the discovery of extremely high rates of star formation in one of the most distant known galaxies in the universe. LALA J142442.24+353400.2, named for the survey in which it was discovered and its celestial coordinates, lies at a redshift of 6.535, which puts it 12.8 billion light-years away and appearing as it looked some 850 million years after the Big Bang. This faint, distant galaxy is fabricating stars at a rate of more than 11 solar masses per year, a frenetic pace among galaxies at this distance and epoch in the early universe. Astronomers traced the galaxy’s starburst activity by measuring light emitted in the so-called Lyman-alpha emission line, using deep multi-object spectroscopy conducted at Gemini Observatory with GMOS-N and the Keck Observatory with the Deep Imaging Multi-object Spectrograph (Deimos).
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The properties of this line can be used to study the reionization process because neutral intergalactic hydrogen should scatter Lyman alpha light, hiding it from view in much the same way that a morning fog can obscure the Sun. The authors explore whether unusual effects in the gas within or around LALA J142442.24+353400.2 could facilitate the escape of Lyman-alpha emissions. For example, if the line is Doppler-shifted to longer wavelengths before it reaches the intergalactic gas (either by a drift velocity of the emitting galaxy or by interaction with gas internal to that galaxy), the intergalactic scattering can be reduced. Nonetheless, the properties of LALA J142442.24+353400.2 are most easily understood if the Universe is already mostly ionized at z = 6.5. A follow-on paper led by coauthor Sangeeta Malhotra strengthens this conclusion by showing that galaxies like LALA J142442.24+353400.2 are neither significantly rarer nor fainter than similar galaxies at lower redshifts.
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See the related press release from the National Optical Astronomy Observatory at: http://www.noao.edu/outreach/press/pr04/pr0405.html
For more details, see the paper "A Luminous Lyman-alpha Emitting Galaxy at Redshift z = 6.535: Discovery and Spectroscopic Confirmation", by James E. Rhoads, Chun Xu, Steve Dawson, Arjun Dey, Sangeeta Malhotra, JunXian Wang, Buell T. Jannuzi, Hyron Spinrad and Daniel Stern, in The Astrophysical Journal, vol. 611, pp. 59-67, 10 August 2004.
From the Dark Ages to the Re-Ionization Era
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