An astrophysicist announces her discovery that could rewrite the story of the death of galaxies

LAWRENCE – At the annual meeting of the American Astronomical Society in St. Louis, Missouri, Allison Kirkpatrick, Assistant Professor of Physics and Astronomy at the University of Kansas, will announce her discovery of "quasars cold "- galaxies containing an abundance of cold gas that can still produce new stars despite the quasar in the center – a discovery that reverses assumptions about the maturation of galaxies and can represent a phase of the life cycle of each galaxy unknown until Now.

His press conference entitled "A new Cold Quasar population" will take place on Wednesday, June 12 at 3 pm CDT on the 2nd floor of the St. Louis Union Station. It will be broadcast live on https: //aas.org /press /aas-press-conference-Webcasts

A quasar, or "quasi-stellar radio source", is essentially a supermassive black hole on steroids. Gases that fall to a quasar in the center of a galaxy form an "accretion disk" that can reject a bewildering amount of electromagnetic energy, often with a brightness hundreds of times greater than that of a planet. A typical galaxy. Generally, the formation of a quasar appears to be a galactic retreat. It has long been thought that this meant the end of a galaxy's ability to produce new stars.

"All the gas that accumulates on the black hole is heated and emits X-rays," Kirkpatrick said. "The wavelength of light that you emit is directly related to your heat, for example, we emit infrared light, but something that emits x-rays is one of the hottest things in the universe.This gas begins to accumulate On the black hole and begins to move at relativistic speeds, you also have a magnetic field around this gas, and it can be twisted. As you get solar flares, you can have jets of material through this magnetic field The jets smother the gas supply of the galaxy, thus preventing more gas from falling on the galaxy and forming new stars. 'a galaxy has stopped forming stars, we say it is passive … galaxy dead'

But in the Kirkpatrick poll, about 10% of the galaxies hosting supra massive black holes increased a reserve of cold gas after entering this phase and still created new stars.

"This in itself is surprising," she said. "All of this population is a bunch of different objects, some of the galaxies have very obvious fusion signatures, some of them very much like the Milky Way and have very obvious spiral arms, some of which are very compact. then 10% more, which is really unique and unexpected.They are very compact light sources, blue and bright, that look exactly like what you expect from a supermassive black hole at the end of the scene after turning off the whole star This formation is becoming a passive elliptical galaxy, but we found a lot of cold gas, the population I call cold quasars.

The astrophysicist of the KU suspected that the "cold quasars" in his survey represented a brief period to recognize in the final stages of life in a galaxy – in terms of human life, the ephemeral phase of " cold quasar "could look like a retirement party from the galaxy.

"These galaxies are rare because they are in a transition phase, we captured them just before star formation in the galaxy went out, and this transition period should be very short," she said. she declared.

Kirkpatrick first identified the objects of interest in an area of ​​the Sloan Digital Sky Survey, the most detailed digital map of the universe available. In an area called "Stripe 82", Kirkpatrick and his colleagues were able to visually identify quasars.

"Then we traveled this area with the XMM Newton telescope and examined it in the X-ray," she said. "X-rays are the key signature of growing black holes, from which we have studied the Herschel Space Telescope, a far-infrared telescope that can detect dust and gases in the host galaxy. we could find in x-rays and in the "infrared".

The KU researcher said her findings provide scientists with new insights and insights into how disintegration of star formation occurs in galaxies and reverse presumptions about quasars.

"We already knew the quasars were going through a darkening stage," Kirkpatrick said. "We knew that they were going through a heavily shrouded phase of dust surrounding the supermassive black hole – this is what we call the red quasar phase – but now we have found this unique transition regime that we do not Before, if you told anyone you had found a bright blue-colored optical quasar – but it still contained a lot of dust and gas, and a lot of star formation – the people would say: "No, that's not how it's going to look."

Kirkpatrick then hopes to determine if the "cold quasar" phase occurs in a specific class of galaxies or in all galaxies.

"We thought the way it was happening was that you have a growing black hole, it's shrouded in dust and gas, it's starting to blow this material," she said. "Then it becomes a luminous blue object, and we assumed that when it blew its own gas, it would also expel its host gas, but it does not seem to be the case for these objects. evaporated – so we see it as a blue object – but they have not yet cleared all the dust and gases from host galaxies – it's a transition phase, say 10 million years. At the universal time scale, it's really short – and it's hard to understand that – we do what we call a blind inquiry to find objects that we did not look for. these objects, yes, it could imply that this happens in all galaxies. "

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Kirkpatrick has collected data up to 2015 with the XMM Newton telescope, a high-speed X-ray telescope operated by the European Space Agency. His work is part of a collaboration called Accretion History of AGN (led by Yale University astrophysicist Meg Urry), which gathers archival data and performs a multi-stakeholder analysis. wavelengths.

Kirkpatrick's colleagues on this work and related work include Brandon Coleman and Michael Estrada of KU, Urry and Ananna Tonima of Yale University, Dave Sanders of the Hawaii Institute of Astronomy Jane Turner of the University of Maryland, Baltimore County, Stephanie LaMassa of Science Space Telescope. Middlebury College Institute and Eilat Glikman. The work is supported by NASA under number 80NSSC18K0418 at Yale University and National Science Foundation under grant number AST-1715512.