What brought the dark ages directly following the Big Bang to an end? So-called "green pea" galaxies, which produce intensive UV radiation, are considered a possible explanation. Now researchers have examined a green pea in detail and found that it indeed emits sufficient radiation to explain cosmic reionization: The transition when most of the intergalactic hydrogen in the universe became separated into protons and electrons, starting 150 million years after the Big Bang. The result contributes to our knowledge about one of the least-known epochs of the universe, and has been published in the January 14 edition of the journal Nature.
After the Big Bang 13.8 billion years ago, the universe cooled down rapidly, and within less than a million years the cosmos became completely dark. The transition from this dark age to the epoch of the first stars and galaxies is one of the least-understood periods in cosmic history.
The "green pea" galaxy J0925+1403 as imaged with the Hubble Space Telescope. This is a smoothed-out false color image in the near-UV (HST/COS around 230 nm), colored green to evoke the green color the galaxy would have if imaged in visible light.
At about 6000 light-years, the diameter of the galaxy is less than 1/15 the diameter of the (visible parts of) the Milky Way Galaxy. Astronomers found that 8% of the intense UV radiation produced in this galaxy escaped into the surrounding space - enough for galaxies of this type to have caused the reionization of the universe shortly after the Big Bang.
Image: Ivana Orlitová, Astronomical Institute, Czech Academy of Sciences (Prague)
Now, astronomers including Gabor Worseck from the Max Planck Institute for Astronomy have confirmed that compact low-mass galaxies known as "green peas", which form new stars at impressive rates, could have been key players in that transition.
Such green peas are interesting candidates as drivers of reionization, which set in roughly 150 million years after the Big Bang, when most of the hydrogen atoms in the early universe were separated into electrons and protons. Star-forming galaxies like this should produce a significant number of massive stars, which in turn produce ultraviolet radiation sufficiently energetic to ionize hydrogen.
But so far, nobody had been able to show that galaxies of this type emit sufficient amounts of high-energy radiation to drive reionization - on the contrary, all previous observations had shown galaxies where most of the ultraviolet radiation is absorbed within the galaxy itself, with the remainder insufficient to account for reionization.
Moreover, direct observations of the escaping ultraviolet radiation are possible only in the nearby Universe: For really distant galaxies, almost all such radiation will be absorbed by intergalactic hydrogen before reaching Earth.
That is why the researchers, led by Yuri Izotov of the National Academy of Sciences of Ukraine, set out to find intensely star-forming green pea galaxies in the nearby universe, using data from the Sloan Digital Sky Survey (SDSS) to select promising candidates. The five top candidates were then observed with the Hubble Space Telescope.
This is where Gabor Worseck came in, a post-doctoral researcher at MPIA. As Worseck explains: "These observations were an ideal fit for a method of analyzing Hubble spectral data that I had developed over the last years. In this way, we were able to measure precisely the amount of ultraviolet radiation emitted by the five green pea galaxies."
One candidate galaxy in particular, with the designation J0925+1403, proved particularly efficient: a sizeable 8% of its ultraviolet radiation leak out into the surrounding space, where it should be able to ionize intergalactic hydrogen gas more than 40 times as massive than the galaxy itself.
The discovery shows that green pea galaxies should indeed be sufficiently powerful to have brought about reionization. Ancient specimens of this type of galaxy could well be responsible for lifting the universe out of its dark age directly after the Big Bang.
The work described here is published as Y. I. Izotov et al., "Lyman continuum leaking from the compact star-forming dwarf galaxy J0925+1403" in the January 14, 2016 edition of the journal Nature. Media representatives should contact email@example.com for access to the article.
Markus Pössel | Max Planck Institute for Astronomy, Heidelberg
New survey hints at exotic origin for the Cold Spot
26.04.2017 | Royal Astronomical Society
NASA's Fermi catches gamma-ray flashes from tropical storms
25.04.2017 | NASA/Goddard Space Flight Center
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
26.04.2017 | Earth Sciences
26.04.2017 | Health and Medicine
25.04.2017 | Physics and Astronomy