Galaxies

A measurement of the Hubble constant based on quasars suggests possible changes to cosmological models

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An article published in the journal “Nature Astronomy” describes the use of quasars as cosmic tracers to measure the expansion of the universe up to 12 billion years ago. Guido Risaliti of the University of Florence and Elisabeta Lusso of Durham University studied the X-ray and optical emissions of a number of quasars using the comparison between those emissions to accurately assess their distances. The results could explain the discrepancies between the different measurements carried out with other methods suggesting that the density of the mysterious dark energy isn’t constant over time.

Brightest quasar in the early universe discovered

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An article published in the journal “Astrophysical Journal Letters” reports the discovery of the brightest quasar in the early universe. A team of researchers used observations of the Hubble Space Telescope and some ground-based telescopes to identify the galaxy cataloged as J043947.08+163415.7 at a distance of about 12.8 billion light years from the Earth. The supermassive black hole at its center is surrounded by a lot of materials that emit the huge amount of light that allows it to be identified even at that enormous distance, but only thanks to a gravitational lensing effect. That activity dates back almost a billion years after the Big Bang.

A verification of dark matter heating

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An article published in the journal “Monthly Notices of the Royal Astronomical Society” reports confirmations to the hypothesis of the effect known as dark matter heating. A team of researchers looked for the effects of the presence of dark matter in dwarf galaxies relatively close to the Milky Way, finding the confirmation that star formation can heat it causing it to move outwards. It’s a new possibility to study dark matter to try to understand its nature.

The Abell S1063 galaxy cluster (Image NASA, ESA, and M. Montes (University of New South Wales, Sydney, Australia))

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An article published in the journal “Monthly Notices of the Royal Astronomical Society” describes a new method to detect and map the dark matter existing in galaxy clusters with a higher precision than those used so far. Mireia Montes of the University of New South Wales, Australia, and Ignacio Trujillo of the Canary Islands Institute of Astronomy, Spain, exploited the so-called intracluster light, the faint light within galaxy clusters produced by their interaction, detected in the Hubble Frontier Fields program, to map the distribution of dark matter within them.

The quasar 3C 273 (Image ESA/Hubble & NASA)

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An article published in the journal “Nature” describes the first detailed observation of the environment surrounding a supermassive black hole outside the Milky Way. A team of astronomers led by Professor Hagai Netzer of the Tel Aviv University used the GRAVITY instrument installed on ESO’s VLTI to examine the first quasar discovered, known as 3C 273, uncovering gas clouds that move quickly around the black hole that powers that quasar and forms its heart.