* Astronomy

Images of the region around the 14 quasars where a previously hidden galaxy was detected via its hydrogen emission using the SINFONI instrument on ESO's Very Large Telescope. The contours show the quasars, while the arrow represents 1 arcsecond (~ 26 000 light-years at the distance of these galaxies, which is roughly 7 700 million light-years). North is up, East is left, and the colour-coding reflects the relative hydrogen fluxes of the sources.


[Preview - JPEG: 495 x 400 pix - 184k]
[Normal - JPEG: 990 x 800 pix - 648k]
[Full Res - JPEG: 2090 x 1689 pix - 1.5M]
[Full Res - TIFF: 2090 x 1689 pix - 10M]
Credit ESO

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An international team of researchers led by Natalia Boris of the University of São Paulo in Brazil has shown that quasar pairs may be excellent beacons for finding clusters of galaxies in the early universe.
Quasars are relatively rare astronomical objects. If, as evidence suggests, their spatial distribution follows that of galaxies then the presence of two or more quasars in the same small volume of space might indicate a region that is exceptionally rich in galaxies.
Deep multi-colour images of four fields around quasar pairs (QP0110-0219, QP1310+0007, QP1355-0032, and QP0114-3140) at redshift z~1 were obtained with the Gemini Multi-Object Spectrograph (GMOS) at both Gemini North and South. The quasar pairs were selected to have redshift differences smaller than 0.01 and projected angular separations less than 300 arcseconds, corresponding to projected physical separations less than 2.5 megaparsecs. Examination of the quasar spectra confirmed that these are bona fide pairs of quasars rather than gravitationally lensed systems.

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 NASA's Hubble and Spitzer Space Telescopes have joined forces to discover nine of the smallest, faintest, most compact galaxies ever observed in the distant universe. Blazing with the brilliance of millions of stars, each of the newly discovered galaxies is a hundred to a thousand times smaller than our Milky Way Galaxy.

"These are among the lowest mass galaxies ever directly observed in the early universe" - Nor Pirzkal of the Space Telescope Science Institute and the European Space Agency in Baltimore, Md.

The conventional model for galaxy evolution predicts that small galaxies in the early universe evolved into the massive galaxies of today by coalescing. These nine Lego-like "building block" galaxies initially detected by Hubble likely contributed to the construction of the universe as we know it.
Pirzkal was surprised to find that the galaxies' estimated masses were so small. Hubble's cousin observatory, NASA's Spitzer Space Telescope was called upon to make precise determinations of their masses. The Spitzer observations confirmed that these galaxies are some of the smallest building blocks of the universe.
These young galaxies offer important new insights into the universe's formative years, just one billion years after the Big Bang. Hubble detected sapphire blue stars residing within the nine pristine galaxies. The youthful stars are just a few million years old and are in the process of turning Big Bang elements (primarily hydrogen and helium) into heavier elements. The stars have probably not yet begun to pollute the surrounding space with elemental products forged within their cores.

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Position (J2000):      R.A. 03h 32m 40s.0 Dec. -27° 48' 00"

Title: The reddest ISO-2MASS quasar
Authors: C. Leipski (1), M. Haas (2), R. Siebenmorgen (3), H. Meusinger (4), M. Albrecht (5), C. Cesarsky (3), R. Chini (2), R. Cutri (6), H. Drass (2), J. P. Huchra (7), S. Ott (8), B. J. Wilkes (7) ((1) UCSB, CA, USA, (2) AIRUB, Bochum, Germany, (3) ESO, Garching, Germany, (4) TLS, Tautenburg, Germany, (5) UCN, Antofagasta, Chile, (6) IPAC, CA, USA, (7) CfA, MA, USA (8) Herschel Science Center, ESA, Noordwijk, The Netherlands)

In the course of the NIR/MIR AGN search combining the 6.7 mu ISOCAM Parallel Survey and 2MASS we have discovered 24 type-1 quasars about a third of which are too red to be discriminated by optical/UV search techniques. Here we report on a detailed case study of the reddest type-1 quasar of our sample (J2341) at redshift z=0.236 with M_K=-25.8 and J-K=1.95. We performed spectroscopy in the optical with VLT/FORS1 and in the MIR with Spitzer as well as NIR imaging with ISPI at CTIO. The optical and NIR observations reveal a star forming emission-line galaxy at the same redshift as the quasar with a projected linear separation of 1.8 arcsec (6.7 kpc). The quasar and its companion are embedded in diffuse extended continuum emission. Compared with its companion the quasar exhibits redder optical-NIR colours, which we attribute to hot nuclear dust. The MIR spectrum shows only few emission lines superimposed on a power-law spectral energy distribution. However, the lack of strong FIR emission suggests that our potentially interacting object contains much less gas and dust and is in a stage different from dust reddened ULIRG-AGN like Mrk 231. The optical spectrum shows signatures for reddening in the emission-lines and no post-starburst stellar population is detected in the host galaxy of the quasar. The optical continuum emission of the active nucleus appears absorbed and diluted. Even the combination of absorption and host dilution is not able to match J2341 with standard quasar templates. While the BLR shows only a rather moderate absorption of E_(B-V)=0.3, the continuum shorter than 4500 AA requires strong obscuration with E_(B-V)=0.7, exceeding the constraints from the low upper limit on the 9.7 mu silicate absorption. This leads us to conclude that the continuum of J2341 is intrinsically redder than that of typical quasars.

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