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TOPIC: Distant Galaxies


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Seeing the Birth of the Universe in an Atom of Hydrogen

An international team of scientists led by researchers at Tel Aviv University have developed a method for detecting galaxies of stars that formed when the universe was in its infancy, during the first 180 million years of its existence. The method is able to observe stars that were previously believed too old to find, says Prof. Rennan Barkana of TAU's School of Physics and Astronomy.
Published in the journal Nature, the researchers' method uses radio telescopes to seek out radio waves emitted by hydrogen atoms, which were abundant in the early days of the universe. Emitting waves measuring about eight inches (21 centimetres) long, the atoms reflect the radiation of the stars, making their emission detectable by radio telescopes, explains Prof. Barkana. This development opens the way to learning more about the universe's oldest galaxies.

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Title: Stars throw their weight in old galaxies
Authors: Nate Bastian

The observation that old, massive galaxies have a larger fraction of low-mass stars than their younger, lower-mass counterparts adds to mounting evidence that star formation may have been different in the early Universe.

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Under 'dark halo' old galaxies have many more stars

Some of the oldest galaxies in the Universe have three times more stellar mass, and so many more stars, than all current models of galaxy evolution predict. The finding comes from the Atlas3D international team, led by Michele Cappellari (Oxford), and including ASTRON astronomers Paolo Serra, Raffaella Morganti and Tom Oosterloo, who found a way to remove the 'halo' of dark matter that has clouded previous calculations.
The team's analysis means that all current models, which assumed for decades that the light we observe from a galaxy can be used to infer its stellar mass, will have to be revised. It also suggests that researchers have a new riddle to ponder: exactly how galaxies forming so early in the life of the Universe got to be massive so fast. A report of the research is published in this week's Nature.

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Under 'dark halo' old galaxies have many more stars

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VLT Observations of Gamma-ray Burst Reveal Surprising Ingredients of Early Galaxies

An international team of astronomers has used the brief but brilliant light of a distant gamma-ray burst as a probe to study the make-up of very distant galaxies. Surprisingly the new observations, made with ESOs Very Large Telescope, have revealed two galaxies in the young Universe that are richer in the heavier chemical elements than the Sun. The two galaxies may be in the process of merging. Such events in the early Universe will drive the formation of many new stars and may be the trigger for gamma-ray bursts.
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NASA's Spitzer Finds Distant Galaxies Grazed on Gas

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.
Astronomers have discovered that galaxies in the distant, early universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

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NASA's Spitzer Finds Distant Galaxies Grazed on Gas

Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.
Astronomers have discovered that galaxies in the distant, early universe continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

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H-ATLAS J090311.6+003906
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Title: Physical conditions of the interstellar medium of high-redshift, strongly lensed submillimetre galaxies from the Herschel-ATLAS
Authors: Ivan Valtchanov, J. Virdee, R. J. Ivison, B. Swinyard, P. van der Werf, D. Rigopoulou, E. da Cunha, R. Lupu, D. J. Benford, D. Riechers, Ian Smail, M. Jarvis, C. Pearson, H. Gomez, R. Hopwood, B. Altieri, M. Birkinshaw, D. Coia, L. Conversi, A. Cooray, G. De Zotti, L. Dunne, D. Frayer, L. Leeuw, A. Marston, M. Negrello, M. Sanchez Portal, D. Scott, M. A. Thompson, M. Vaccari, M. Baes, D. Clements, M. J. Michalowski, H. Dannerbauer, S. Serjeant, R. Auld, S. Buttiglione, A. Cava, A. Dariush, S. Dye, S. Eales, J. Fritz, E. Ibar, S. Maddox, E. Pascale, M. Pohlen, E. Rigby, G. Rodighiero, D. J. B. Smith, P. Temi, J. Carpenter, A. Bolatto, M. Gurwell

We present Herschel-SPIRE Fourier Transform Spectrometer (FTS) and radio follow-up observations of two Herschel-ATLAS (H-ATLAS) detected strongly lensed distant galaxies. In one of the targeted galaxies H-ATLAS J090311.6+003906 (SDP.81) we detect [OIII] 88\mum and [CII] 158\mum lines at a signal-to-noise ratio of ~5. We do not have any positive line identification in the other fainter target H-ATLAS J091305.0-005343 (SDP.130). Currently SDP.81 is the faintest sub-mm galaxy with positive line detections with the FTS, with continuum flux just below 200 mJy in the 200-600 \mum wavelength range. The derived redshift of SDP.81 from the two detections is z=3.043 ±0.012, in agreement with ground-based CO measurements. This is the first detection by Herschel of the [OIII] 88\mum line in a galaxy at redshift higher than 0.05. Comparing the observed lines and line ratios with a grid of photo-dissociation region (PDR) models with different physical conditions, we derive the PDR cloud density n ~ 2000 cm^{-3} and the far-UV ionising radiation field G_0 ~ 200 (in units of the Habing field -- the local Galactic interstellar radiation field of 1.6x10^{-6} W/m^2). Using the CO derived molecular mass and the PDR properties we estimate the effective radius of the emitting region to be 500-700 pc. These characteristics are typical for star-forming, high redshift galaxies. The radio observations indicate that SDP.81 deviates significantly from the local FIR/radio correlation, which hints that some fraction of the radio emission is coming from an AGN. The constraints on the source size from millimetre-wave observations put a very conservative upper limit of the possible AGN contribution to less than 33%. These indications, together with the high [OIII]/FIR ratio and the upper limit of [OI] 63\mum/[CII] 158\mum suggest that some fraction of the ionising radiation is likely to originate from an AGN.

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Herschel detects gigantic storms sweeping entire galaxies clean

In the distant and therefore younger Universe, many galaxies show much more activity than our Milky Way today. In commonly accepted evolutionary scenarios gas-rich galaxies merge, which triggers increased star formation ("starburst" galaxies) as well as the growth of supermassive black holes at their centres. This increased activity, however, seems to cease fairly suddenly, effectively stalling star formation and further growth of the black hole in as little as a few million years' time. What processes could be responsible for removing all the raw material powering this activity - around a billion solar masses - in such a (cosmologically) short timespan?
The solution to this riddle could be powerful winds that blow gas outwards from the centre of the galaxy. Powered by newly formed stars, shocks from stellar explosions or by the Black Hole in the galaxy's centre, these storms would remove all the gas supply from the galaxy thereby halting the same mechanisms that produced them in the first place.

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Huge storms sweep entire galaxies clean

Scientists examining data from the Herschel space observatory say they've detected gigantic storms of molecular gas in the centre of many galaxies.
Some of these outflows hit speeds of more than 1,000 kilometres per second. The more active galaxies contain stronger winds, which can blow away the entire gas reservoir in a galaxy, inhibiting further star formation and the growth of the central black hole.

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In Deep Galaxy Surveys, Astronomers Get a Boost - From Gravity

Astronomers who survey galaxies in the distant universe are getting some unexpected help from gravity, according to a new study.
In a presentation at the American Astronomical Society meeting this week and a related paper in the current issue of the journal Nature, researchers say that as many as 20 percent of the most distant galaxies currently detected appear brighter than they actually are, because of an effect called "strong gravitational lensing."
The discovery could change astronomers notions of how galaxies formed in the early universe.

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