* Astronomy

"Dropouts" pinpoint earliest galaxies
Astronomers, conducting the broadest survey to date of galaxies from about 800 million years after the Big Bang, have found 22 early galaxies and confirmed the age of one by its characteristic hydrogen signature at 787 million years post Big Bang. The finding is the first age-confirmation of a so-called dropout galaxy at that distant time and pinpoints when an era called the reionisation epoch likely began. The research will be published in a December issue of the Astrophysical Journal.
With recent technological advancements, such as the Wide-Field Camera 3 on the Hubble Space Telescope, there has been an explosion of research of the reionisation period, the farthest back in time that astronomers can observe. The Big Bang, 13.7 billion years ago, created a hot, murky universe. Some 400,000 years later, temperatures cooled, electrons and protons joined to form neutral hydrogen, and the murk cleared. Some time before 1 billion years after the Big Bang, neutral hydrogen began to form stars in the first galaxies, which radiated energy and changed the hydrogen back to being ionised. Although not the thick plasma soup of the earlier period just after the Big Bang, this star formation started the reionisation epoch. Astronomers know that this era ended about 1 billion years after the Big Bang, but when it began has eluded them and intrigued researchers like lead author Masami Ouchi of the Carnegie Observatories.

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Title: Galaxy Zoo: Passive Red Spirals
Authors: Karen L. Masters (ICG, Portsmouth), Moein Mosleh (Sussex/Leiden), A. Kathy Romer (Sussex), Robert C. Nichol (ICG), Steven P. Bamford (Nottingham), Kevin Schawinski (Yale), Chris J. Lintott (Oxford), Dan Andreescu, Heather C. Campbell, Ben Crowcroft, Isabelle Doyle, Edward M. Edmondson, Phil Murray, M. Jordan Raddick, Anze Slosar, Alexander S. Szalay, Jan Vandenberg
(Version v2)

We study the spectroscopic properties and environments of red spiral galaxies found by the Galaxy Zoo project. By carefully selecting face-on, disk dominated spirals we construct a sample of truly passive disks (not dust reddened, nor dominated by old stellar populations in a bulge). As such, our red spirals represent an interesting set of possible transition objects between normal blue spirals and red early types. We use SDSS data to investigate the physical processes which could have turned these objects red without disturbing their morphology. Red spirals prefer intermediate density regimes, however there are no obvious correlations between red spiral properties and environment - environment alone is not sufficient to determine if a galaxy will become a red spiral. Red spirals are a small fraction of spirals at low masses, but dominate at large stellar masses - massive galaxies are red independent of morphology. We confirm that red spirals have older stellar populations and less recent star formation than the main spiral population. While the presence of spiral arms suggests that major star formation cannot have ceased long ago, we show that these are not recent post-starbursts, so star formation must have ceased gradually. Intriguingly, red spirals are ~4 times more likely than normal spirals to host optically identified Seyfert/LINER, with most of the difference coming from LINER-like emission. We find a curiously large bar fraction in the red spirals suggesting that the cessation of star formation and bar instabilities are strongly correlated. We conclude by discussing the possible origins. We suggest they may represent the very oldest spiral galaxies which have already used up their reserves of gas - probably aided by strangulation, and perhaps bar instabilities moving material around in the disk.

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Looking almost 11 billion years into the past, astronomers have measured the motions of stars for the first time in a very distant galaxy and clocked speeds upwards of one million miles per hour, about twice the speed of our Sun through the Milky Way.
The fast-moving stars shed new light on how these distant galaxies, which are a fraction the size of our Milky Way, may have evolved into the full-grown galaxies seen around us today. The results will be published in the August 6, 2009 issue of the journal Nature, with a companion paper in the Astrophysical Journal.

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Keck Laser Helps Astronomers Probe the Nature of Massive Galaxies in the Early Universe
Astronomers using the W. M. Keck Observatory have discovered distant galaxies as massive as the Milky Way yet ten to 1000 times more compact. The new results, announced June 9 at the 214th American Astronomical Society meeting in Pasadena, provide astronomers with surprising clues about early star and galaxy formation at a time when the Universe was just a few billion years old.

The shapes of these galaxies tell us that it is not reasonable to expect they could occur from mergers. Instead, the kind of disks were seeing and the constituent stars seemed to have formed all at once, directly from the gas. In the old lingo, this is monolithic galaxy formation - astronomer Alan Stockton of the University of Hawaii.

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