Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gamma bubbles of the Milky Way

04.02.2015

A new method for imaging unravels certain secrets of the galactic anatomy

The anatomy of the Milky Way as seen in gamma light is full of mysteries. For example, there are gigantic bubbles of unknown origin above and below the centre of the Milky Way that emit a lot of this high-energy radiation.


The Milky Way in gamma ray light: The left half shows the grainy raw data; the right half the processed data. The researchers have developed a statistical algorithm that helps remove the noise as well as instrumental artefacts and separates diffuse and point-like structures from each other. The images reveal interesting details such as the so-called Fermi bubbles (centre), extending over 50,000 light-years, about the origins of which astronomers are still puzzled.

© MPA / Marco Selig

A new method for imaging, developed at the Max Planck Institute for Astrophysics, now divided the Galactic gamma-radiation into three fundamental components: radiation from point sources, radiation from reactions of energetic protons with dense cold gas clouds, and radiation from electrons scattering light in the thin, hot, Galactic gas. The anatomic insights gained unravel some Galactic mysteries. Thus, it appears that the gamma-ray bubbles are simply outflows of ordinary, hot gas.

The sky in the light of gamma-radiation shows a variety of objects, structures, and astrophysical processes. It is most prominently illuminated by the Milky Way, which contributes a great part of the point sources as well as the major part of the diffuse gamma-radiation in the sky. The various radiation sources appear superimposed, which complicates their identification and interpretation. Furthermore, our measurement instruments, such as the Fermi satellite, record only individual gamma photons arriving at random times from random directions. These are highly energetic light particles, whose observation requires complex imaging algorithms in order to reconstruct sky maps. A new method for denoising, deconvolving, and decomposing photon observations, called D³PO (link: http://www.mpa-garching.mpg.de/mpa/research/current_research/hl2013-12/hl2013-12-en.html), developed at the Max Planck Institute for Astrophysics, has now created the by far most brilliant gamma-radiation map of the sky from the data of the Fermi satellite.

D³PO has decomposed the gamma-ray sky into point sources and diffuse radiation at nine photon energies. From these, a coloured image can be generated, which shows the diffuse sky as it would appear to an observer with gamma-eyes. The different astrophysical processes can be recognized therein via their different energy spectra, visible as different colours. The gamma-bubbles above (and below) the centre of the Milky Way appear blue-greenish, which indicates particularly high-energy gamma-radiation. This should have been mainly generated by collisions of electrons that are moving almost with the speed of light with starlight and other photons. The orange-brown areas on the right and left side are primarily caused by collisions of super-fast protons with nuclei in dense, cold gas clouds.

The big surprise was that the central bright Galactic disk, and virtually all other areas of the sky, shows essentially just a superposition of these two processes: collisions of protons with nuclei and of electrons with photons. If we decompose the diffuse gamma-radiation into only these two processes, more than 90% of the radiation is explained – and this at all studied sky locations and energies. The total diffuse galactic gamma-radiation is thus produced almost exclusively by two typical media: dense, cold gas clouds and the thin, hot gas between them. In fact, gamma-radiation coming from the clouds shows almost the same spatial distribution as the Galactic dust clouds as measured by the Planck satellite in the microwave range.

The gamma-radiation generated by electrons in the mysterious gamma-ray bubbles does not differ in colour from the electron-generated radiation from the Galactic disk. This suggests that we see the same material in both places: hot gas that has been enriched with electrons moving almost at the speed of light by supernova explosions. The gamma-bubbles are therefore simply rising hot gas masses, leaving the centre of our Milky Way.

In addition to unravelling the gamma-ray bubbles, the D³PO analysis of the anatomy of Galactic gamma-radiation has delivered a number of other scientific results. It was shown that the cold gas clouds that are illuminated by the gamma-radiation extend up to larger heights above the Galactic plane than the dust clouds measured by the Planck satellite. While this could have been expected due to the higher mass of dust particles in comparison with the gas particles, it is a nice confirmation of the astrophysical correctness of these anatomical dissections of the Galaxy in gamma light. Furthermore, a comprehensive catalogue of point sources was generated and searched for gamma-radiation from clusters of galaxies – unfortunately without success.

The D³PO algorithm that has made all this possible is now freely available and will in the future also provide astronomical images at other wavelengths of light. D³PO was developed by Marco Selig during his just-completed doctorate with honours at the Ludwigs-Maximilians-Universität München. The algorithm was derived within information field theory and implemented using the also freely available NIFTY- software for numerical information field theory. Information field theory deals with the mathematics of imaging complex data sets and is a central focus of the research group of Torsten Ensslin at the Max Planck Institute for Astrophysics.


Contact
Dr. Hannelore Hämmerle
Max Planck Institute for Astrophysics, Garching
Phone: +49 89 30000-3980
Fax: +49 89 30000-3569
Email: pr@mpa-garching.mpg.de
 
Dr. Torsten Enßlin
Max Planck Institute for Astrophysics, Garching
Phone: +49 89 30000-2243
Email: ensslin@mpa-garching.mpg.de
 
Dr. Marco Selig
Max Planck Institute for Astrophysics, Garching
Phone: +49 89 30000-2298
Email: mselig@mpa-garching.mpg.de


Original publication
Marco Selig, Valentina Vacca, Niels Oppermann, Torsten A. Enßlin
The Denoised, Deconvolved, and Decomposed Fermi γ-ray Sky – An Application of the D3PO Algorithm
Astronomy & Astrophysics

Source

Dr. Hannelore Hämmerle | Max Planck Institute for Astrophysics, Garching

More articles from Physics and Astronomy:

nachricht Major discovery in controlling quantum states of single atoms
20.02.2018 | Institute for Basic Science

nachricht Observing and controlling ultrafast processes with attosecond resolution
20.02.2018 | Technische Universität München

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Major discovery in controlling quantum states of single atoms

20.02.2018 | Physics and Astronomy

New printing technique uses cells and molecules to recreate biological structures

20.02.2018 | Life Sciences

New tech for commercial Lithium-ion batteries finds they can be charged 5 times fast

20.02.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>