Winds of change: how hot and cold super winds change the fate of galaxies

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A team composed in large part of Italian astronomers, has used the Plateau de Bure interferometer in the French Alps, and data of X-ray satellites Chandra and NuStar, for mapping hot and cold superwinds in the galaxy Mrk 231. This ultra-luminous infrared galaxies emits energy equivalent to 1000 billion suns, and is situated at a distance of 500 million light-years away. His prodigious brightness is the result of a merging of two gas-rich galaxies, and of the super-massive black hole (80 million Suns) that houses in its core. Despite Mrk 231 is a very well studied source, has recently aroused the attention of astronomers since, in 2010, the same team found in this galaxy the first, prototypical galactic superwind. The amount of cold material (molecular gas, or carbon monoxide) that moves in this superwind amounts to at least 500 Solar masses per year, which move at a rate of about 1000 km/s over a region of approximately 3000 light years. It ’s easy to imagine how such a superwind has very high energy, capable of destroying everything that encounters on his path.

“Since the discovery of the molecular super wind in 2010, the central super-massive black hole was the #1 candidate driver of the wind, but only today’s the results give us the certainty. In fact we found out that it is the nuclear wind , which originates close to the central black hole with a speed of 20 thousand km / s and a temperature of about 10 million degrees, which transmits its energy to the cold gas which reisedes further out in the galactic disk. The hot superwind transmits such a strong impulse to the cold gas that forms the disk of the galaxy, to speed it up to 1000 km/s and then pushes a cold superwind stretching up to 1 kpc away from the galactic center”, explains Chiara Feruglio, researcher of the Cosmology Group of SNS who led the study.

3D rendering of the hot superwind due to stars and the cold superwind that expands to scales similar to the guest galaxy size.

3D rendering of the hot superwind due to stars and the cold superwind that expands to scales similar to the guest galaxy size.

This result is very important because it demonstrates what many years astronomers have suspected but could not prove, or that very energetic phenomena that occur in the immediate vicinity of the super massive black holes do not remain confined in these central regions, but they have a tremendous impact on the entire host galaxy on scales 100 thousand or even a million times larger.

“The hot uclear superwind had passed completely unnoticed until now. Comparing data from the two satellites Chandra and NuStar we found it in the data of both satellites, then we had no more doubts to have finally found the engine of galactic superwinds”, says Simonetta Puccetti, astronomer at ASI – ASDC who led the analysis of the X-ray data.

Detection in the CO(2-1) profile of winds exceeding 1000km/s

Detection in the CO(2-1) profile of winds exceeding 1000km/s

This discovery marks a turning point in the study of galaxies and their evolution . After years of research, we finally found observational evidence that black holes at the centers of galaxies are able , through very energetic super winds, to change the course of the life of a galaxy . In terms of size , it is like saying that a ladybug, by the flapping of wings , is capable of triggering tornadoes powerful enough to affect the climate of the entire planet, “ says Angela Bongiorno, researche at INAF-OAR, who partecipated in the study, “There are still many things to understand about this phenomenon, but this result is the first lighthouse on a road until now practically dark.

“Super winds represent one of the most important and mysterious way through which Super Massive Black Holes communicate with their host galaxies. A full understanding of these extremely energetic and spectacular phenomena can only be reached through the approach used in this work, namely giving voice both to the hot gas, shining as X-ray photons, and the cold gas, out of which stars in galaxies born, detectable at millimeter wavelengths”, says Simona Gallerani, astrophysicist at SNS.

This discovery was made ​​possible only by the uniquenes of the synergy between radio and and X-ray observatories, and paves the way for this type of study in even more extreme and distant objects. The future launch of new and more powerful satellites in the X-rays as ASTRO – H and ATHENA, used in synergy with ALMA and NOEMA, will make this field of research even more exciting.

Read more:    http://adsabs.harvard.edu/abs/2015arXiv150301481F

Author: Marcos Valdes

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