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Planck Intermediate Results. IX. Detection of the Galactic haze with Planck

by d3mm
Tags: galactic center, jets
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d3mm
#1
Sep6-12, 05:40 PM
P: 139
Can someone explain to me this paper in laymans terms? I don't get it. They are claiming discovery of a new method of acceleration of cosmic rays in the centre of the galaxy.

URL: http://arxiv.org/abs/1208.5483

Paper: Planck Intermediate Results. IX. Detection of the Galactic haze with Planck

Author: Planck Collaboration

Summary: Using precise full-sky observations from Planck, and applying several methods of component separation, we identify and characterize the emission from the Galactic "haze" at microwave wavelengths. The haze is a distinct component of diffuse Galactic emission, roughly centered on the Galactic centre, and extends to |b| ~35 deg in Galactic latitude and |l| ~15 deg in longitude. By combining the Planck data with observations from the WMAP we are able to determine the spectrum of this emission to high accuracy, unhindered by the large systematic biases present in previous analyses. The derived spectrum is consistent with power-law emission with a spectral index of -2.55 +/- 0.05, thus excluding free-free emission as the source and instead favouring hard-spectrum synchrotron radiation from an electron population with a spectrum (number density per energy) dN/dE ~ E^-2.1. At Galactic latitudes |b|<30 deg, the microwave haze morphology is consistent with that of the Fermi gamma-ray "haze" or "bubbles," indicating that we have a multi-wavelength view of a distinct component of our Galaxy. Given both the very hard spectrum and the extended nature of the emission, it is highly unlikely that the haze electrons result from supernova shocks in the Galactic disk. Instead, a new mechanism for cosmic-ray acceleration in the centre of our Galaxy is implied.
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Dotini
#2
Sep6-12, 06:16 PM
PF Gold
P: 506
http://www.nasa.gov/mission_pages/GL...structure.html
A NASA article, with short video, about the discovery of the Fermi "bubbles".
Please see embedded link to view additional briefing materials.

And the NASA Planck mission index.
http://www.nasa.gov/mission_pages/planck/index.html

http://www.nasa.gov/mission_pages/pl.../pia15229.html
Here, dated March 1 of this year, NASA mentions gamma rays but not cosmic rays in a summary report.

In part, this little article makes the following hopefully pertinent comment,

"Synchrotron emission, a type of non-thermal radiation generated by charged particles, associated with the galactic haze seen by Planck, exhibits distinctly different characteristics from the synchrotron emission seen elsewhere in the Milky Way. Diffuse synchrotron emission in the galaxy is interpreted as radiation from highly energetic electrons that have been accelerated in shocks created by supernova explosions. Compared to this well-studied emission, the galactic haze has a "harder" spectrum, meaning that its emission does not decline as rapidly with increasing frequency.

Several explanations have been proposed for this unusual behavior, including enhanced supernova rates, galactic winds and even annihilation of dark-matter particles. Thus far, none of them have been confirmed and the issue remains open.
"

Apparently, the OP paper almost rules out the enhanced supernova explanation offered by NASA as a possibility.

http://phys.org/news/2012-05-ghostly...ky-center.html
PhysOrg reports on the gamma ray beams, a.k.a. "jets".

Respectfully,
Steve
Dotini
#3
Jan4-13, 08:12 AM
PF Gold
P: 506
New observations from the Parkes radio telescope seem to provide an explanation for the great bubbles and jets emanating from the galactic center.

http://www.csiro.au/Portals/Media/Ou...-of-power.aspx
"Monster" outflows of charged particles from the centre of our Galaxy, stretching more than halfway across the sky, have been detected and mapped with CSIRO's 64-m Parkes radio telescope.

------------

The WMAP, Planck and Fermi observations did not provide enough evidence to indicate definitively the source of the radiation they detected, but the new Parkes observations do.

"The options were a quasar-like outburst from the black hole at the Galactic Centre, or star-power — the hot winds from young stars, and exploding stars," said team member Dr Gianni Bernardi of the Harvard-Smithsonian Center for Astrophysics, in Cambridge, Massachusetts.


"Our observations tell us it's star-power."


http://arstechnica.com/science/2013/...the-milky-way/
In 2010, data from the Fermi Gamma-Ray Space Telescope revealed two huge gamma-ray-emitting bubbles extending 25,000 light-years in each direction from the Milky Way's center. Since this region of the galaxy is home both to a supermassive black hole and star formation activity, it was uncertain which of them produced the structures. A new analysis of radio and microwave observations has confirmed these bubbles exist—but found additional features suggestive of star formation, rather than black hole activity.

Respectfully submitted,
Steve


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