ESO: “Band 5 Will Search for Water in the Local Universe”





"Band 5 will open up new possibilities to explore the Universe and bring new discoveries," explains ESO's Gianni Marconi, who is responsible for the integration of Band 5. "The frequency range of this receiver includes an emission line of water that ALMA will be able to study in nearby regions of star formation. The study of water is, of course, of intense interest because of its role in the origin of life."

After more than five years of development and construction, ALMA successfully opened its eyes on another frequency range after obtaining the first fringes with a Band 5 receiver, specifically designed to detect water in the local Universe. This band will also open up the possibility of studying complex molecules in star-forming regions and protoplanetary discs, and detecting molecules and atoms in galaxies in the early Universe, looking back about 13 billion years.

ALMA observes the Universe in radio waves: light that is invisible to the human eye. The weak electromagnetic glow from space is captured by the array of 66 antennas, each with diameters up to twelve metres. Their receivers transform this weak radiation into an electrical signal.

To scout a broad range of frequencies, each ALMA antenna is equipped with up to ten different receivers, each one specially designed to cover a specific range of wavelengths. The new Band 5 receiver is the eighth type to be integrated and covers a range of wavelengths from 1.4 to 1.8 millimetres (frequencies from 163 to 211 GHz), probing a part of the electromagnetic spectrum that has only been poorly explored before.

With Band 5 ALMA will also be able to probe the emission from ionised carbon from objects seen soon after the Big Bang, opening up the possibility of probing the earliest epoch of galaxy formation. "This band will also enable astronomers to study young galaxies in the early Universe about 500 million years after the Big Bang," added Gianni Marconi.




ALMA Band 5 first fringe. With a baseline of 1 kilometer, two antennas pointed to the Orion Molecular Cloud (above)detecting an H2O Maser at 183.3 GHz. When the signals from both antennas are correlated in phase, an emission line can be identified. Credit: ALMA (ESO/NAOJ/NRAO), Band 5 Integration Team.


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The Band 5 project is developed in collaboration between ESO, and the US National Radio Astronomy Observatory (NRAO)

Astronomers have found the most distant signs of water in the Universe to date: The water vapor is thought to be contained in a maser, a jet ejected from a supermassive black hole at the center of a galaxy, named MG J0414+0534. The Hubble image at the top of the page shows four lensed images of the dusty red quasar, connected by a gravitational arc of the quasar host galaxy. The lensing galaxy is seen in the center, between the four lensed images. The radiation from the water maser was emitted when the Universe was only about 2.5 billion years old, a fifth of its current age.

“The radiation that we detected has taken 11.1 billion years to reach the Earth, said Dr. John McKean of the Netherlands Institute for Radio Astronomy (ASTRON). “However, because the Universe has expanded like an inflating balloon in that time, stretching out the distances between points, the galaxy in which the water was detected is about 19.8 billion light years away.”

“This detection of water in the early Universe may mean that there is a higher abundance of dust and gas around the super-massive black hole at these epochs, or it may be because the black holes are more active, leading to the emission of more powerful jets that can stimulate the emission of water masers. We certainly know that the water vapour must be very hot and dense for us to observe a maser, so right now we are trying to establish what mechanism caused the gas to be so dense,” said Dr McKean.

The Daily Galaxy via ALMA Observatory


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