Astrophysicists discover new heating source in cosmological structure formation

May 15, 2012
A supermassive black hole is surrounded by a dust ring (torus). The collapse of gas onto the black hole launches an energetic jet of matter and radiation, which is transported over cosmological distances. A jet that is pointing into our direction is called a "blazar" (copyright: ESA/NASA, the AVO project and Paolo Padovani).

(Phys.org) -- So far, astrophysicists thought that super-massive black holes can only influence their immediate surroundings. A collaboration of scientists at the Heidelberg Institute for Theoretical Studies (HITS) and in Canada and the US now discovered that diffuse gas in the universe can absorb luminous gamma-ray emission from black holes, heating it up strongly. This surprising result has important implications for the formation of structures in the universe. The results have just been published in The Astrophysical Journal and Monthly Notices of the Royal Astronomical Society.

Every galaxy hosts a at its center. Such can emit high-energy gamma rays and are then called blazars. Whereas other radiation such as visible light and traverses the universe without problems, this is not the case for high-energy gamma rays. This particular radiation interacts with the that is emitted by galaxies, transforming it into the elementary particles electrons and positrons. Initially, these move almost at the speed of light. But as they are slowed down by the ambient diffuse gas, their energy is converted into heat, just like in other braking processes. As a result, the surrounding gas is heated efficiently. In fact, the temperature of the gas at mean density becomes ten times higher, and in underdense regions more than one hundred times higher than previously thought.

A Journey into the Cosmic Youth

"Blazars rewrite the thermal history of the universe", emphasizes Dr. Christoph Pfrommer (HITS), one of the authors. But how can this idea be tested? In the optical spectra of quasars there is a plethora of lines, called the "line forest". The forest originates from the absorption of ultra-violet light by neutral hydrogen in the young Universe. If the gas becomes hotter, weak lines in the forest are broadened. This effect represents an excellent opportunity to measure temperatures in the early Universe, while it was still growing up.

Simulated line forest of a quasar spectrum. The blue spectrum represents a universe without blazar heating, the red one a universe with blazar heating. It is evident that the additional heating process ionizes neutral hydrogen, implying less absorption of the UV light emitted by the quasar (Picture: HITS).

The astrophysicists at HITS checked this newly postulated heating process for the first time with detailed supercomputer simulations of the cosmological growth of structures. Surprisingly, the lines were broadened just enough so that their properties perfectly matched those of the observed lines. "This allows us to elegantly solve a long-standing problem with the quasar data", says Dr. Ewald Puchwein, who conducted the large simulations on the supercomputer at HITS.

How Black Holes Influence the Formation of Galaxies

What are the further consequences of this new heating process? The forest of lines in the quasar spectra originates from density fluctuations in the Universe. In the course of cosmic evolution, the densest fluctuations collapse to form galaxies and galaxy clusters, as observed in the local Universe. that is too hot cannot collapse. Hence, the formation of dwarf galaxies is slowed or even entirely suppressed. This could be the key to the solution of another long-standing problem in the theory of galaxy formation: why do we observe fewer dwarf galaxies in the vicinity of the Milky Way and in the underdense regions than predicted by cosmological simulations?

Prof. Volker Springel, scientific group leader at HITS, explains: "The process of blazar heating is especially exciting since this single effect is able to simultaneously solve several different puzzles in cosmological structure formation." The group plans to further improve their simulation models for a still deeper understanding of the nature of blazar heating and its implications for today's Universe.

Explore further: What lit up the universe?

More information: The series of scientific articles:

The Lyman-alpha forest in a blazar-heated Universe. E. Puchwein, C. Pfrommer, V. Springel, A. E. Broderick, and P. Chang, 2012, MNRAS, in print, arXiv:1107.3837
arxiv.org/abs/1107.3837

The Cosmological Impact of Luminous TeV Blazars III: Implications for Galaxy Clusters and the Formation of Dwarf Galaxies. C. Pfrommer, P. Chang, and A. E. Broderick, 2012, ApJ, in print, arXiv:1106.5505 arxiv.org/abs/1106.5505

The Cosmological Impact of Luminous TeV Blazars II: Rewriting the Thermal History of the Intergalactic Medium. P. Chang, A. E. Broderick, and C. Pfrommer, 2012, ApJ, in print, arXiv:1106.5504 arxiv.org/abs/1106.5504

The Cosmological Impact of Luminous TeV Blazars I: Implications of Plasma Instabilities for the Intergalactic Magnetic Field and Extragalactic Gamma-Ray Background. A. E. Broderick, P. Chang, and C. Pfrommer, 2012, ApJ, in print, arXiv:1106.5494 arxiv.org/abs/1106.5494

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User comments : 8

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Jeddy_Mctedder
1 / 5 (3) May 16, 2012
how's this for a science fantasy idea. alien god is a giant volitional black hole. he travels amidst the gasses of the universe choosing when and where to seed galaxy formation. lower alien god gaia then chooses which universes to seed with life. or as it goes, they also seed themselves with original life from time to time.
kevinrtrs
1 / 5 (11) May 16, 2012
The forest of lines in the quasar spectra originates from density fluctuations in the Universe. In the course of cosmic evolution, the densest fluctuations collapse to form galaxies and galaxy clusters, as observed in the local Universe.

the forest originates from the absorption of ultra-violet light by neutral hydrogen in the young Universe.

These two statements represent the very basis of most problems in cosmology right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint.
Baseline
5 / 5 (6) May 16, 2012
The forest of lines in the quasar spectra originates from density fluctuations in the Universe. In the course of cosmic evolution, the densest fluctuations collapse to form galaxies and galaxy clusters, as observed in the local Universe.

the forest originates from the absorption of ultra-violet light by neutral hydrogen in the young Universe.

These two statements represent the very basis of most problems in cosmology right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint.


Wow now there is the pot calling the kettle black.....
CardacianNeverid
5 / 5 (1) May 16, 2012
These two statements represent the very basis of most problems in cosmology right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint -KingTard

Ha, ha, ha, ha, ha! TardOfTards confuses science with his book of fairytales written by ignorant goat herders. Classic!
aroc91
5 / 5 (6) May 16, 2012
These two statements represent the very basis of most problems in cosmology right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint.


This statement represents the very basis of most problems in fundamental Christianity right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint.
stellar-demolitionist
not rated yet May 17, 2012
Kevin wrote:

These two statements represent the very basis of most problems in cosmology right here: The insidious coupling of present day observations with ardent attempts to uncover what happened in the past. Assumptions are made with regard to the past and then there's the extensive laboring to force current observations to fit in with them. Nevermind that the assumptions can be highly skewed to fit in with some a-priori philosophical viewpoint.


But they ARE modeling observations of things in the past!

The absorption spectra they are modeling are forming when the background light of a quasar is absorbed by galaxies with redshifts of 3 to 4, or so, probing the conditions at that epoch, long ago in the Universe's history.

The conditions sampled by these models, fit to existing observations, are definitely NOT of current conditions.

Origin
1 / 5 (3) May 17, 2012
..diffuse gas in the universe can absorb luminous gamma-ray emission from black holes, heating it up strongly..
Actually it's not so difficult to find it from available photos, something happens at the ends of black hole jets...

http://i.telegraph.co.uk/multimedia/archive/01902/black-hole-jets_1902547i.jpg

At first, we can see, how the material from jet condenses to brown (hydrogen? helium?) gas, which doesn't maintains the direction of jet. At second, we can see how the end of jet remains surrounded with faint blue glow, indicating the presence of hot ionized plasma, which is forming shock wave around jets.

IMO this process has its low temperature analogy at the case of sun corona, which gets heated with tiny jets (roentgen light spicules), which are emanated from the surface of sun. But the pressure of photons is not the only source of heating of corona, I presume the invisible flux of neutrinos contributes to it too. The neutrino flux can be expected at the case of BH too.
Origin
1 / 5 (2) May 17, 2012
Note that at the above picture the central black hole behaves pretty well like the asymmetric pulsar, which emanates jets outside of axis of its own rotation. Another pronounced feature is, these jets aren't symmetric. This effect can be attributed to relativistic red shift at the case of high relative difference in speed of both jets with respect to observer, in other case it could be attributed to CP-violation at the galactic scale as well.