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TOPIC: Distant Galaxies
Blobrana


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RE: Distant Galaxies
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Title: HST observations of gravitationally lensed QSOs
Authors: J.-F. Claeskens (1), D. Sluse (2), J. Surdej (1) ((1) Institut d'Astrophysique et de Géophysique, Université de Liège, Belgium; (2) Ecole Polytechnique Fédérale de Lausanne, Switzerland)

Thanks to its sharp view, HST has significantly improved our knowledge of tens of gravitationally lensed quasars in four different respects: (1) confirming their lensed nature; (2) detecting the lensing galaxy responsible for the image splitting; (3) improving the astrometric accuracy on the positions of the unresolved QSO images and of the lens; (4) resolving extended lensed structures from the QSO hosts into faint NIR or optical rings or arcs. These observations have helped to break some degeneracies on the lens potential, to probe the galaxy evolution and to reconstruct the true shape of the QSO host with an increased angular resolution.

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Blobrana


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RXJ1131-1231 and HE1104-1805
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Title: X-ray Microlensing in RXJ1131-1231 and HE1104-1805
Authors: G. Chartas, C. S. Kochanek, X. Dai, S. Poindexter, G. Garmire

We present results from a monitoring campaign performed with the Chandra X-ray Observatory of the gravitationally lensed quasars RXJ1131-1231 and HE1104-1805. We detect significant X-ray variability in all images of both quasars. The flux variability detected in image A of RXJ1131-1231 is of particular interest because of its high amplitude (a factor of ~ 30). We interpret it as arising from microlensing since the variability is uncorrelated with that of the other images and the X-ray flux ratios show larger changes than the optical as we would expect for microlensing of the more compact X-ray emission regions. The differences between the X-ray and optical flux ratios of HE1104-1805 are less dramatic, but there is no significant soft X-ray or dust absorption, implying the presence of X-ray microlensing in this system as well. Combining the X-ray data with the optical light curves we find that the X-ray emitting region of HE1104-1805 is compact with a half-light radius < 6r_g, where the gravitational radius is r_g = 3.6 x 10^14 cm, thus placing significant constraints on AGN corona models. We also find that the microlensing in HE1104-1805 favors mass models for the lens galaxy that are dominated by dark matter. Finally, we better characterise the massive foreground cluster near RXJ1131-1231, set limits on other sources of extended X-ray emission, and limit the fluxes of any central odd images to be 30-50 (3sigma) times fainter than the observed images.

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Blobrana


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RE: Distant Galaxies
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Astronomers have made use of ESO's Very Large Telescope to detect for the first time in the ultraviolet the carbon monoxide molecule in a galaxy located almost 11 billion light-years away, a feat that had remained elusive for 25 years. This detection allows them to obtain the most precise measurement of the cosmic temperature at such a remote epoch.

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Blobrana


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Title: The VVDS-Wide survey has been designed with the general aim of tracing the large-scale distribution of galaxies at z~1 on comoving scales reaching ~100Mpc/h, while providing a good control of cosmic variance over areas as large as a few square degrees. This is achieved by measuring redshifts with VIMOS at the ESO VLT to a limiting magnitude I_AB=22.5, targeting four independent fields with size up to 4 sq.deg. each. The whole survey covers 8.6 sq.deg., here we present the general properties of the current redshift sample. This includes 32734 spectra in the four regions (19977 galaxies, 304 type I AGNs, and 9913 stars), covering a total area of 6.1 sq.deg, with a sampling rate of 22 to 24%. The redshift success rate is above 90% independently of magnitude. It is the currently largest area coverage among redshift surveys reaching z~1. We give the mean N(z) distribution averaged over 6.1 sq.deg. Comparing galaxy densities from the four fields shows that in a redshift bin Deltaz=0.1 at z~1 one still has factor-of-two variations over areas as large as ~0.25 sq.deg. This level of cosmic variance agrees with that obtained by integrating the galaxy two-point correlation function estimated from the F22 field alone, and is also in fairly good statistical agreement with that predicted by the Millennium mocks. The variance estimated over the survey fields shows explicitly how clustering results from deep surveys of even ~1 sq.deg. size should be interpreted with caution.
This paper accompanies the public release of the first 18143 redshifts of the VVDS-Wide survey from the 4 sq.deg. contiguous area of the F22 field at RA=22h, publicly available at this http URL

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Blobrana


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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 v2)

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 at least 60% 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<z<12 arise in low luminosity galaxies undetected by conventional surveys.

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Blobrana


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Witnessing the Formation of Distant Galaxies
UK astronomers have produced the most sensitive infrared map of the distant Universe ever undertaken. Combining data over a period of three years, they have produced an image containing over 100,000 galaxies over an area four times the size of the full moon. Some of the first results from this project will be presented by Dr Sebastien Foucaud from the University of Nottingham on Friday 4th April at the RAS National Astronomy Meeting in Belfast.

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Blobrana


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Old Galaxies Stick Together in the Young Universe
Using the most sensitive images ever obtained with the United Kingdom Infra-Red Telescope (UKIRT), astronomers have found convincing evidence that galaxies which look old early in the history of the Universe reside in enormous clouds of invisible dark matter and will eventually evolve into the most massive galaxies that exist in the present day.
University of Nottingham PhD student Will Hartley, who led the study, will speak at the RAS National Astronomy Meeting in Belfast on Tuesday 1 April.

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Blobrana


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UK astronomers have developed the most sensitive infrared map of the distant universe ever produced, revealing the origins of the most massive galaxies in the cosmos.
Using images obtained with the United Kingdom Infra-Red Telescope (UKIRT), astronomers combined data over a period of three years. This produced a map encompassing more than 100,000 galaxies over an area of sky four times the size of the full moon.
As light from the far reaches of the universe takes so long to reach observers on Earth, UKIRT allows astronomers to look back in time more than ten billion years producing images of the galaxies' infancy. The image is so large and so deep that thousands of galaxies can be studied at these early epochs for the first time.
By observing these galaxies at the infrared wavelength, astronomers can now peer even further back in time as light is shifted towards the redder wavelength as it travels through the expanding universe.

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Blobrana


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 NASA's  Hubble and Spitzer space telescopes, with a boost from a natural "zoom lens," have uncovered what may be one of the youngest and brightest galaxies ever seen in the middle of the cosmic "dark ages," just 700 million years after the beginning of our universe.

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Blobrana


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Posts: 131433
Date:
A1689-zD1
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The NASA/ESA Hubble Space Telescope, with a boost from a natural "zoom lens," has found the strongest evidence so far for a galaxy with a redshift significantly above 7. It is likely to be one of the youngest and brightest galaxies ever seen right after the cosmic "dark ages," just 700 million years after the beginning of our universe (redshift ~7.6).
The detailed images from Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) reveal an infant galaxy, dubbed A1689-zD1, undergoing a firestorm of star birth during the dark ages, a time shortly after the Big Bang but before the first stars reheated the cold, dark universe. Images from NASA's Spitzer Space Telescope's Infrared Array Camera provided strong additional evidence that it was a young star- forming galaxy in the dark ages.

Source

A1689-zD1
Credit: NASA; ESA; L. Bradley (Johns Hopkins University); R. Bouwens (University of California, Santa Cruz); H. Ford (Johns Hopkins University); and G. Illingworth (University of California, Santa Cruz)

Abell1689
Position (J2000): R.A. 13h11m 34s.20, Dec. -01° 21' 56".0

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