Supermassive black holes control star formation in large galaxies

[Disir]

Young galaxies blaze with bright new stars forming at a rapid rate, but star formation eventually shuts down as a galaxy evolves. A new study, published January 1, 2018, in Nature, shows that the mass of the black hole in the center of the galaxy determines how soon this "quenching" of star formation occurs.

Every massive galaxy has a central supermassive black hole, more than a million times more massive than the sun, revealing its presence through its gravitational effects on the galaxy's stars and sometimes powering the energetic radiation from an active galactic nucleus (AGN). The energy pouring into a galaxy from an active galactic nucleus is thought to turn off star formation by heating and dispelling the gas that would otherwise condense into stars as it cooled.

This idea has been around for decades, and astrophysicists have found that simulations of galaxy evolution must incorporate feedback from the black hole in order to reproduce the observed properties of galaxies. But observational evidence of a connection between supermassive black holes and star formation has been lacking, until now.

"We've been dialing in the feedback to make the simulations work out, without really knowing how it happens," said Jean Brodie, professor of astronomy and astrophysics at UC Santa Cruz and a coauthor of the paper. "This is the first direct observational evidence where we can see the effect of the black hole on the star formation history of the galaxy."

The new results reveal a continuous interplay between black hole activity and star formation throughout a galaxy's life, affecting every generation of stars formed as the galaxy evolves.

Led by first author Ignacio Martín-Navarro, a postdoctoral researcher at UC Santa Cruz, the study focused on massive galaxies for which the mass of the central black hole had been measured in previous studies by analyzing the motions of stars near the center of the galaxy. To determine the star formation histories of the galaxies, Martín-Navarro analyzed detailed spectra of their light obtained by the Hobby-Eberly Telescope Massive Galaxy Survey.


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That's another cool thang.

 

[Damaged Eagle]

Imagine the power...

*****CHUCKLE*****

 

[waltky]

Earliest galaxies found 'on our cosmic doorstep'...

Earliest galaxies found 'on our cosmic doorstep'
16 Aug.`18 - Some of the earliest galaxies to form in the Universe are sitting on our cosmic doorstep, according to a study.

These faint objects close to the Milky Way could be more than 13 billion years old, researchers from the universities of Durham and Harvard explain. They formed upwards of a hundred million years after the Big Bang and contained some of the first stars to light up the cosmos. The findings are published in the Astrophysical Journal. Our own galaxy, the Milky Way, is one of billions out there in the Universe. These sprawling cosmic neighbourhoods filled with stars and planets formed when many smaller building blocks - such as these galaxies - collided and merged. The discovery opens a window into what the Universe was like more than 13 billion years ago.

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A computer simulation of galaxy formation: White circles show some of the most ancient building blocks​

Prof Carlos Frenk, from Durham University, UK, said: "Finding some of the very first galaxies that formed in our Universe orbiting in the Milky Way's own backyard is the astronomical equivalent of finding the remains of the first humans that inhabited the Earth. It is hugely exciting." Lead author Dr Sownak Bose, from the Harvard-Smithsonian Center for Astrophysics in Cambridge, US, told BBC News: "For some of these tiny satellites, maybe 50% or even 90% of their mass was assembled at a time when the Universe was less than one billion years old. Their age today would be on the order of 13 billion years."

The data agree well with existing models of galaxy formation​

The astronomers looked at something called the "luminosity function" of small satellite galaxies that orbit the Milky Way and its neighbour Andromeda. Luminosity describes the total amount of energy radiated each second by an astronomical source. The "function" gives the abundance of galaxies for a given luminosity. When the researchers plotted the galaxies according to their luminosity function, they separated into two distinct populations. Prof Frenk, Dr Bose and co-author Dr Alis Deason from Durham found an existing model of galaxy formation explained the data, allowing them to infer the formation times of the satellite galaxies.

The Milky Way is surrounded by "dwarf" satellite galaxies​

The first population of galaxies appears to have been formed during the "cosmic dark ages", a period of cooling which began some 380,000 years after the Big Bang and lasted for 100 million years. The second population, consisting of slightly brighter galaxies, seems to have formed hundreds of millions of years after the first. The onset of the cosmic dark ages is tied to the formation of the very first atoms in the Universe. These were hydrogen atoms, the simplest element in the periodic table. As the hydrogen gathered into clouds, it began to cool. These hydrogen clouds then settled within small clumps of the enigmatic stuff known as dark matter, which emerged in the Big Bang. As the name suggests, dark matter neither reflects nor emits visible light, yet it makes up 85% of all matter in the Universe.

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[deanrd]

Did you watch that special, What is killing the Milky Way?

Something mysterious is killing 11,000 nearby galaxies

They said it's also happening in our Galaxy.