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Enormous Fireworks Brighten Monster Hydrogen Blob

An international group of scientists with the help of Atacama Large Millimeter/sub-millimeter Array (ALMA) and other telescopes has found the power source lighting a so-called Lyman-alpha Blob, an uncommon brightly shining, and massive concentration of gas in the distant universe. Till now, astrophysicists doubted why these massive clouds of gas shined so brilliantly. The solution, in this example at least, seems to be two galaxies at the center of the blob suffering energetic star formation and illuminating up their surroundings. These huge galaxies, which are meant to eventually combine into a lone elliptical galaxy, are in the middle of a group of smaller galaxies. This seems to be an early stage in the formation of a huge cluster of galaxies.

Credit: J.Geach/D.Narayanan/R.Crain

Lyman-alpha Blobs (LABs) are huge clouds of hydrogen gas that can distance hundreds of thousands of light years and are found at very enormous cosmic distances. The name reveals the specific wavelength of ultraviolet light that they produce, known as Lyman-alpha radiation. Since their detection, the methods that give rise to LABs have been an astronomical mystery. New explanations with ALMA have now answered the mystery.

One of the biggest Lyman-alpha Blobs identified, and the most carefully studied is SSA22-Lyman-alpha blob 1, or LAB-1. Situated in the core of a gigantic cluster of galaxies in the early phases of formation, it was the actual first such object to be found, in 2000, and LAB-1 is found so far away that its light has taken nearly 11.5 billion years to reach us. A group of astronomers, commanded by Jim Geach, from the Center for Astrophysics Research of the University of Hertfordshire, UK, has now used ALMA's unparalleled capability to detect light from cool dust clouds in closest galaxies to peer intensely into LAB-1. This permitted them to determine and resolve numerous sources of sub-millimeter emission.

The astronomers then united the ALMA images with explanations from the Multi Unit Spectroscopic Explorer (MUSE) device fixed on ESO's Very Large Telescope (VLT), which map the Lyman-alpha light. This exposed that the ALMA sources are situated in the very center of the Lyman-alpha Blob, where they are making stars faster than 100 times that of the Milky Way Galaxy.

Deep imaging with the NASA/ESA Hubble Space Telescope and spectroscopy at the W. M. Keck Observatory also discovered that the ALMA sources are bounded by many dim companion galaxies that could be attacking the central ALMA sources with a material, helping to drive their great star formation rates. The group then turned to a classy imitation of galaxy formation, known as the Feedback in Realistic Environments (FIRE), to prove that the huge glowing cloud of Lyman-alpha emission can be described if ultraviolet light formed by star formation in the ALMA sources goes off the surrounding hydrogen gas. This would increase the Lyman-alpha Blob we see.

The lead writer of the new study accepted for publication in the Astrophysical Journal, Jim Geach,  explains: "Consider a streetlight on a foggy night, you see the diffuse light because light is spreading of the small water drops. The same thing is happening at this point, but the streetlight is an extremely star-forming galaxy and the fog is a gigantic cloud of intergalactic gas. The galaxies are lighting their surroundings".

Understanding how galaxies form and develop is a gigantic challenge. Scientists think Lyman-alpha Blobs are significant because they appear to be the places where the hugest galaxies in the universe form. In precise, the stretched Lyman-alpha glow delivers information on what is happening in the primeval gas clouds nearby young galaxies, the area that is very hard to study, but critical to comprehend.

Desika Narayanan of Haverford College in Pennsylvania and coauthor of the paper, said, "Entering the galaxies masked in LAB-1 did more than just put to bed the old issue of the gas cloud's spark. It delivered a rare chance to see how young, growing galaxies acted when the universe was quite young."

Jim Geach determines, "What is thrilling about these blobs is that we are getting an unusual hint of what is happening around these young, developing galaxies. For a long time, the source of the extended Lyman-alpha light has been debatable. But with the mixture of new observations and cutting-edge recreations, we consider we have answered a 15-year-old mystery: Lyman-alpha Blob-1 is the place of formation of a huge elliptical galaxy that will one day be the heart of a huge cluster. We are seeing a photo of the assembly of that galaxy 11.5 billion years from now".

The above post is re-printed from things provided by National Radio Astronomy Observatory.

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