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

Abstract

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.

15 pages, 9 figures, submitted to Astronomy and Astrophysics

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Cited by in corpus (45)

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• A Unified Model of the Fermi Bubbles, Microwave Haze, and Polarized Radio Lobes: Reverse Shocks in the Galactic Center's Giant Outflows
• Suzaku observations of the diffuse x-ray emission across the fermi bubbles' edges
• Planck 2015 results. XXV. Diffuse low-frequency Galactic foregrounds
• Polarised radio filaments outside the Galactic plane
• Galaxy And Mass Assembly (GAMA): Assimilation of KiDS into the GAMA database
• Fingerprints of Galactic Loop I on the Cosmic Microwave Background
• The Fermi Bubbles as Starburst Wind Termination Shocks
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• Unveiling the Origin of the Fermi Bubbles
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• The Fermi Bubbles Revisited
• Constraints on dark matter annihilations from diffuse gamma-ray emission in the Galaxy
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• Fermi bubble edges: spectrum and diffusion function
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• The C-Band All-Sky Survey (C-BASS): Constraining diffuse Galactic radio emission in the North Celestial Pole region
• Origin of Galactic Spurs: New Insight from Radio/X-ray All-sky Maps
• Analytical and numerical studies of central galactic outflows powered by tidal disruption events -- a model for the Fermi bubbles?
• Fermi bubbles: high latitude X-ray supersonic shell
• Dark matter implications of the WMAP-Planck Haze
• The spectral index of polarized diffuse Galactic emission between 30 and 44 GHz
• A Perturbative Analysis of Synchrotron Spectral Index Variation over Microwave Sky
• The Important Role of Cosmic-Ray Re-Acceleration
• Cross Correlation of the Extragalactic Gamma-ray Background with Thermal Sunyaev-Zel'dovich Effect in the Cosmic Microwave Background
• A possible origin of gamma rays from the Fermi Bubbles
• Fermi bubble simulations: black hole feedback in the Milky Way