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TOPIC: LAB-1

Blobrana

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Posts: 131433

Date: Sep 21 11:19 2016

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ALMA Uncovers Secrets of Giant Space Blob An international team using ALMA, along with ESO's Very Large Telescope and other telescopes, has discovered the true nature of a rare object in the distant Universe called a Lyman-alpha Blob. Up to now astronomers did not understand what made these huge clouds of gas shine so brightly, but ALMA has now seen two galaxies at the heart of one of these objects and they are undergoing a frenzy of star formation that is lighting up their surroundings. These large galaxies are in turn at the centre of a swarm of smaller ones in what appears to be an early phase in the formation of a massive cluster of galaxies. The two ALMA sources are expected to evolve into a single giant elliptical galaxy. One of the largest Lyman-alpha Blobs known, and the most thoroughly studied, is SSA22-Lyman-alpha blob 1, or LAB-1. Embedded in the core of a huge cluster of galaxies in the early stages of formation, it was the very first such object to be discovered - in 2000 - and is located so far away that its light has taken about 11.5 billion years to reach us. Read more __________________

Blobrana

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Posts: 131433

Date: Sep 18 09:29 2012

LAB1 J21434423	Permalink

Title: Hot Gas, Cold Gas and Sub-Halos in a Lyman-alpha Blob at Redshift 2.38 Authors: Paul. J. Francis, Michael A. Dopita, James W. Colbert, Povilas Palunas, Claudia Scarlata, Harry Teplitz, Gerard M. Williger, Bruce E. Woodgate We present integral field spectroscopy of a Lyman-alpha blob at redshift 2.38, with a spectral resolution three times better than previous published work. As with previous observations, the blob has a chaotic velocity structure, much of which breaks up into multiple components. Our spectroscopy shows, however, that some of these multiple components are extremely narrow: they have velocity widths of less than 100 km/s. Combining these new data with previous observations, we argue that this Lyman-alpha blob resides in a dark-matter halo of around 10^13 solar masses. At the centre of this halo are two compact red massive galaxies. They are surrounded by hot gas, probably a super-wind from merger-induced nuclear starbursts. This hot gas has shut down star formation in the non-nuclear region of these galaxies, leading to their red-and-dead colours. A filament or lump of infalling cold gas is colliding with the hot gas phase and being shocked to high temperatures, while still around 30kpc from the red galaxies. The shock region is self-absorbed in Lyman-alpha but produces C IV emission. Further out still, the cold gas in a number of sub-halos is being lit up, most likely by a combination of tidally triggered star formation, bow-shocks as they plough through the hot halo medium, resonant scattering of Lyman-alpha from the filament collision, and tidal stripping of gas which enhances the Lyman-alpha escape fraction. The observed Lyman-alpha emission from the Blob is dominated by the sum of the emission from these sub-halos. On statistical grounds, we argue that Lyman-alpha blobs are not greatly elongated in shape, and that most are not powered by ionisation or scattering from a central active galactic nucleus or starburst. Read more (2558kb, PDF) __________________

Blobrana

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Posts: 131433

Date: Aug 18 06:33 2011

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Title: Central Powering of the Largest Lyman-alpha Nebula is Revealed by Polarised Radiation Authors: Matthew Hayes (1,2,3), Claudia Scarlata (4,5), Brian Siana (6) ((1) University of Toulouse, (2) CNRS, IRAP, (3) Geneva Observatory, (4) University of Minnesota, (5) Spitzer, (6) Caltech) High-redshift Lyman-alpha blobs are extended, luminous, but rare structures that appear to be associated with the highest peaks in the matter density of the Universe. Their energy output and morphology are similar to powerful radio galaxies, but the source of the luminosity is unclear. Some blobs are associated with ultraviolet or infrared bright galaxies, suggesting an extreme starburst event or accretion onto a central black hole. Another possibility is gas that is shock excited by supernovae. However some blobs are not associated with galaxies, and may instead be heated by gas falling into a dark matter halo. The polarisation of the Ly-alpha emission can in principle distinguish between these options, but a previous attempt to detect this signature returned a null detection. Here we report on the detection of polarised Ly-alpha from the blob LAB1. Although the central region shows no measurable polarisation, the polarised fraction (P) increases to ~20 per cent at a radius of 45 kpc, forming an almost complete polarised ring. The detection of polarised radiation is inconsistent with the in situ production of Ly-alpha photons, and we conclude that they must have been produced in the galaxies hosted within the nebula, and re-scattered by neutral hydrogen. Read more (1054kb, PDF) __________________

Blobrana

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Posts: 131433

Date: Aug 17 18:04 2011

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VLT finds primordial cloud of hydrogen to be centrally powered Observations from ESO's Very Large Telescope have shed light on the power source of a rare vast cloud of glowing gas in the early Universe. The observations show for the first time that this giant "Lyman-alpha blob" - one of the largest single objects known - must be powered by galaxies embedded within it. The results appear in the 18 August issue of the journal Nature. A team of astronomers has used ESO's Very Large Telescope (VLT) to study an unusual object called a Lyman-alpha blob. These huge and very luminous rare structures are normally seen in regions of the early Universe where matter is concentrated. The team found that the light coming from one of these blobs is polarised. In everyday life, for example, polarised light is used to create 3D effects in cinemas. This is the first time that polarisation has ever been found in a Lyman-alpha blob, and this observation helps to unlock the mystery of how the blobs shine. Read more __________________

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