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TOPIC: Distant Galaxies
Blobrana


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Galaxies found to be flowing together
Hundreds of galaxy clusters are flowing toward the same spot in the sky beyond the observable universe, a University of Hawaii astronomer and NASA team members have discovered.
The clusters, each with hundreds of millions of stars, are moving at more than 1 million mph toward the constellations Centaurus and Vela, said Harald Ebeling, co-author of a paper on the baffling finding in the Astrophysical Journal Letters.

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Blobrana


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Early galaxy's magnetism surprises scientists
If there had been a gargantuan refrigerator in the early universe, it might have been plastered with little magnetic galaxies.
That's because the first direct measurement of an early galaxy's magnetic field has surprised astronomers by revealing a field 10 to 15 times stronger than that of our own Milky Way galaxy.

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Blobrana


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First detection of magnetic field in distant galaxy
Using a powerful radio telescope to peer into the early universe, a team of California astronomers has obtained the first direct measurement of a nascent galaxy's magnetic field as it appeared 6.5 billion years ago.
Astronomers believe the magnetic fields within our own Milky Way and other nearby galaxieswhich control the rate of star formation and the dynamics of interstellar gas--arose from a slow "dynamo effect." In this process, slowly rotating galaxies are thought to have generated magnetic fields that grew very gradually as they evolved over 5 billion to 10 billion years to their current levels.
But in the October 2 issue of Nature, the astronomers report that the magnetic field they measured in this distant "protogalaxy" is at least 10 times greater than the average value in the Milky Way.

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Blobrana


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Astronomers continue to puzzle over the recent discovery of a strange population of dense, compact galaxies that existed in the early universe but are nowhere to be seen today. They suspect the galaxies somehow puffed up into the bloated behemoths we see around us, but new research shortens the timescale during which this mysterious swelling could have happened.
In April, astronomers reported finding extremely compact galaxies as far back as 10 billion years ago, or 3.7 billion years after the big bang. The galaxies contained the same number of stars as modern, blob-shaped galaxies known as ellipticals but were two to three times smaller on average.

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Blobrana


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Barred Spiral Galaxies Are Latecomers to the Universe
In a landmark study of more than 2,000 spiral galaxies from the largest galaxy census conducted by NASA's Hubble Space Telescope, astronomers found that so-called barred spiral galaxies were far less plentiful 7 billion years ago than they are today, in the local universe. The study's results confirm the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. The observations are part of the Cosmic Evolution Survey (COSMOS).

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Blobrana


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New Hubble Space Telescope observations of six spectacular galaxy clusters acting as gravitational lenses have given significant insights into the early stages of the Universe. Scientists have found the largest sample of very distant galaxies seen to date: ten promising candidates thought to lie at a distance of 13 billion light-years (~redshift 7.5).

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Blobrana


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Mining the far reaches of the universe for clues about its past, a team of scientists including Philipp Kronberg of Los Alamos National Laboratory has proposed that magnetic fields of ancient galaxies like ours were just as strong as those existing today, prompting a rethinking of how our galaxy and others may have formed.
With powerful telescopes and sophisticated measurements, the team probed back in time to see the ancient universe as it existed some 8 to 9 billion years ago. Their research was published in the July 17 edition of Nature.

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Blobrana


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Title: Strong magnetic fields in normal galaxies at high redshifts
Authors: Martin L. Bernet, Francesco Miniati, Simon J. Lilly (ETHZ), Philipp P. Kronberg (LANL), Miroslava Dessauges-Zavadsky (Geneva)

The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It has recently been demonstrated that field strengths as traced by rotation measures of distant quasars are comparable to those seen today, but it was unclear whether the high fields were in the exotic environments of the quasars themselves or distributed along the line of sight. Here we demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Since MgII absorption occurs in the haloes of normal galaxies along the sightline to the quasars, this association requires that organised fields of surprisingly high strength are associated with normal galaxies when the Universe was only about one-third of its present age.

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Blobrana


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Light from distant quasarsearly galaxies that shine with tremendous brightnesshas given researchers a new clue to the origin of vast magnetic fields studding today's galaxies: They were running strong when the universe was only a third of its present age.
Astronomers had observed that radio emissions from quasars tend to be angled, or polarised, in such a way that powerful magnetic fields must have twisted them. The greater their distance from Earth, the more polarised their light. But researchers didn't know whether the magnetic fields were part of the quasar or were present in galaxies encountered by quasar light as it made its journey to our telescopes.

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Blobrana


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Galaxies beyond Redshift Seven
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Title: A Hubble & Spitzer Space Telescope Survey for Gravitationally-Lensed Galaxies: Further Evidence for a Significant Population of Low Luminosity Galaxies beyond Redshift Seven
Authors: Johan Richard (Caltech), Daniel P. Stark (Caltech), Richard S. Ellis (Caltech), Matthew R. George (Caltech), Eiichi Egami (Steward Observatory), Jean-Paul Kneib (LAM/OAMP), Graham P. Smith (U. Birmingham)
(Version v3)

We present the results of a systematic search for gravitationally-lensed continuum Lyman break `drop-outs' beyond a redshift 7 conducted via very deep imaging through six foreground clusters undertaken with the Hubble and Spitzer Space Telescopes. The survey has yielded 10 z-band and 2 J-band drop-out candidates to photometric limits of J_110~=26.2 AB (5sigma). Taking into account the magnifications afforded by our clusters (1-4 magnitudes), we probe the presence of z>7 sources to unlensed limits of J_{110}~=30 AB, fainter than those charted in the Hubble Ultradeep Field. To verify the fidelity of our candidates we conduct a number of tests for instrumental effects which would lead to spurious detections, and carefully evaluate the likelihood of foreground contamination by considering photometric uncertainties in the drop-out signature, the upper limits from stacked IRAC data and the statistics of multiply-imaged sources. Overall, we conclude that we can expect about half of our sample of z-band drop-outs are likely to be at high redshift. An ambitious infrared spectroscopic campaign undertaken with the NIRSPEC spectrograph at the WM Keck Observatory for seven of the most promising candidates failed to detect any Lyman-alpha emission highlighting the challenge of making further progress in this field. While the volume density of high redshift sources will likely remain uncertain until more powerful facilities are available, our data provides the first potentially interesting constraints on the UV luminosity function at z~=7.5 at intrinsically faint limits. We discuss the implications of our results in the context of the hypothesis that the bulk of the reionising photons in the era 7<12 arise in low luminosity galaxies undetected by conventional surveys.

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-- Edited by Blobrana at 14:22, 2008-06-16

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