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TOPIC: Distant Galaxies


L

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SDSS J1004+4112
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Hubble image of galaxy cluster SDSS J1004+4112 with 3 phenomena marked-
The blue circles show a five time gravitationally lensed Quasar.
The red circles indicate three different images of the same background galaxy 12 thousand million Ly's away.
The yellow circle marks a supernova found by comparing this image to a picture of the cluster taken by Hubble last year.

[youtube=http://youtube.com/watch?v=jt9muqN-E0I]

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Four Gravitationally Lensed Quasars
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Title: Discovery of Four Gravitationally Lensed Quasars from the Sloan Digital Sky Survey
Authors: Masamune Oguri, Naohisa Inada, Alejandro Clocchiatti, Issha Kayo, Min-Su Shin, Joseph F. Hennawi, Michael A. Strauss, Tomoki Morokuma, Donald P. Schneider, Donald G. York

We present the discovery of four gravitationally lensed quasars selected from the spectroscopic quasar catalogue of the Sloan Digital Sky Survey. We describe imaging and spectroscopic follow-up observations that support the lensing interpretation of the following four quasars: SDSS J0832+0404 (image separation \theta=1.98", source redshift z_s=1.115, lens redshift z_l=0.659); SDSS J1216+3529 (\theta=1.49", z_s=2.012); SDSS J1322+1052 (\theta=2.00", z_s=1.716); and SDSS J1524+4409 (\theta=1.67", z_s=1.210, z_l=0.320). Each system has two lensed images. We find that the fainter image component of SDSS J0832+0404 is significantly redder than the brighter component, perhaps because of differential reddening by the lensing galaxy. The lens potential of SDSS J1216+3529 might be complicated by the presence of a secondary galaxy near the main lensing galaxy.

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RE: Distant Galaxies
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By using gravitational lensing to increase the telescope's range, the scientists said they were able to see light generated by galaxies 13 billion years ago, when the universe was only 500 million years old. At that time, the universe was still in its "Dark Ages" because hydrogen atoms hadn't broken apart and stars hadn't yet formed.

babsbabs
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"We have detected six faint star-forming galaxies. We estimate the combined radiation output of this population could be sufficient to break apart the hydrogen atoms in space at that time, thereby ending the Dark Ages" - Dan Stark, graduate student.

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Astronomers say they may have detected the light from some of the earliest stars to form in the Universe.
They have pictures of what appear to be very faint galaxies that shone more than 13 billion years ago, a mere 500 million years after the Big Bang.
The remarkable claim dramatically exceeds the current, broadly accepted record for the most distant detection.
The Caltech-led team behind the work recognises there will be sceptics but says it believes its data is strong.

Richard Ellis
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It has published details in The Astrophysical Journal; and the group leader, Professor Richard Ellis, has been arguing the case at a conference in London, UK.

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Using natural "gravitational lenses," an international team of astronomers claim to have found the first traces of a population of the most distant galaxies yet seen-the light we see from them today left more than 13 billion years ago, when the universe was just 500 million years old.
Team leader Richard Ellis, the Steele Family Professor of Astronomy at the California Institute of Technology, will present images of these faint and distant objects in his talk on July 11 at the "From IRAS to Herschel and Planck" conference at the Geological Society in London. The meeting is being held to celebrate the 65th birthday of Royal Astronomical Society President Professor Michael Rowan-Robinson.

cosmic dawn2
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A selection of Hubble Space Telescope images show cluster fields with distant galaxy sources marked with circles. Each foreground cluster of galaxies acts as a natural telescope with particularly strong magnification along the `critical lines' indicated here with black curves.
Credit: Caltech\D. Stark, J. Richard, R. Ellis


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A high magnification scan of the heavens may have captured faint light from 13-billion-year-old galaxies
Astronomers say they have discovered a handful of relatively small galaxies that date to 500 million years after the big bang, or several hundred million years earlier than the previous oldest galaxies. The ancient objects may have initiated a key event called reionisation that led to the clumping of small galaxies into larger ones.

gal_distant_e5
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GRAVITATIONAL LENSING: Astronomers have spotted what may be the oldest galaxies yet (red circles) by training a powerful telescope on light passing near closer galaxies (dark spots), which focus the light along certain contours in the sky (black lines).
Credit STARK ET AL


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Astronomers using a giant telescope say they have found glimpses of the most distant - and oldest - galaxies ever seen, a finding that will help provide clues to the origins of the universe.
The light the researchers viewed originated when the universe was only 500 million years old and has been travelling through distant space for billions of years.
This means the team found galaxies further back in time than anyone has ever seen as scientists try to better understand how the universe was born some 13.5 billion years ago.

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Astronomers have spotted the most distant galaxies known, from an era when the universe was just 4% its present age. Objects like these could be responsible for lifting the veil on the so-called cosmic 'dark ages', by making the universe transparent to light.
Because it takes light from distant galaxies billions of years to reach us, we see them as they were long ago, when the universe was much younger. Astronomers gauge their distance using a metric called redshift, which measures how much the expansion of the universe has stretched out the wavelength of their light as it travelled to Earth.
Previously, the most distant galaxy known had been found at a redshift of 7 corresponding to a time when the universe was about 750 million years old.
Now, astronomers led by Daniel Stark of Caltech in Pasadena, California, US, have found several galaxies at a redshift of about 9. A redshift of 9 corresponds to an era just 500 million years after the big bang 4% the universe's present age of 13.7 billion years.

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The most distant galaxies ever detected have been detected by astronomers using the 10-meter Keck II telescope at Mauna Kea on the Big Island of Hawaii.
The galaxies were seen when they were only 500 million years old. They are more than 13 billion years away.
The six galaxies were detected using a natural "gravitational lens" of a nearby cluster of galaxies.

sixgal_1
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Credit: Caltech

"Gravitational lensing is the magnification of distant sources by foreground structures. By looking through carefully selected clusters, we have located six star-forming galaxies seen at unprecedented distances, corresponding to a time when the universe was only 500 million years old, or less than 4 percent of its present age" - Richard Ellis, Caltech astronomer

The team will present their findings tomorrow at a conference of the Geological Society in London.

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Star-forming galaxies
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Title: Presence of dust with a UV bump in massive, star-forming galaxies at 1 < z < 2.5
Authors: S. Noll, D. Pierini, M. Pannella, S. Savaglio

Fundamental properties of the extinction curve, like the slope in the rest-frame ultraviolet (UV) and the presence/absence of a broad absorption excess centred at 2175 A (the UV bump), are investigated for a sample of 108 massive, star-forming galaxies at 1 < z < 2.5, selected from the FDF Spectroscopic Survey, the K20 survey, and the GDDS. These characteristics are constrained from a parametric description of the UV spectral energy distribution (SED) of a galaxy, as enforced by combined stellar population and radiative transfer models for different geometries, dust/stars configurations and dust properties. In at least one third of the sample, there is a robust evidence for extinction curves with at least a moderate UV bump. The presence of the carriers of the UV bump is more evident in galaxies with UV SEDs suffering from heavy reddening. We interpret these results as follows. The sample objects possess different mixtures of dust grains and molecules producing extinction curves in between the average ones of the Small and Large Magellanic Cloud, where the UV bump is absent or modest, respectively. Most of the dust embeds the UV-emitting stellar populations or is distributed out of the galaxy mid-plane. Alternatively, even dust with a pronounced UV bump, as for the average Milky-Way extinction curve, can be present and distributed in the galaxy mid-plane. In this case, variations of the continuum scattering albedo with wavelength or an age-dependent extinction are not sufficient to explain the previous trend with reddening. Hence, additional extraplanar dust has to be invoked. The data suggest that the carriers of the UV bump are associated with intermediate-age stellar populations, while they survive in the harshest UV-radiation fields owing to dust self-shielding.

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