Planck intermediate results IX. Detection of the Galactic haze with Planck
MetadataShow full item record
Edp Sciencies S.A
nucleusGalaxy: nucleusISM: structureISM: bubblesRadio continuum: ISM
Ade, P. A. R., Aghanim, N., Arnaud, M., Ashdown, M., Atrio-Barandela, F., Aumont, J., ... & Bartlett, J. G. (2013). Planck intermediate results-IX. Detection of the Galactic haze with Planck. Astronomy & Astrophysics, 554, A139. [doi:10.1051/0004-6361/201220271]
SponsorshipEuropean Space Agency; Centre National D'etudes Spatiales; CNRS/INSU-IN2P3-INP (France); Agenzia Spaziale Italiana (ASI); Italian National Research Council; Istituto Nazionale Astrofisica (INAF); National Aeronautics & Space Administration (NASA); United States Department of Energy (DOE); Science & Technology Facilities Council (STFC); UKSA (UK); Consejo Superior de Investigaciones Cientificas (CSIC); Spanish Government; JA (Spain); Finnish Funding Agency for Technology & Innovation (TEKES); AoF (Finland); CSC (Finland); Helmholtz Association German Aerospace Centre (DLR); Max Planck Society; CSA (Canada); DTU Space (Denmark); SER/SSO (Switzerland); RCN (Norway); Science Foundation Ireland; Portuguese Foundation for Science and Technology; European Union (EU); National Aeronautics & Space Administration (NASA); Harvey L. Karp Discovery Award; Science & Technology Facilities Council (STFC) ST/G003874/1 ST/J00152X/1 ST/J001562/1 ST/J004812/1 ST/I005765/1 ST/J001538/1 ST/K000985/1 ST/K003674/1 ST/L001314/1
Using precise full-sky observations from Planck, and applying several methods of component separation, we identify and characterise the emission fromthe 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| ∼ 35−50◦ in Galactic latitude and |l| ∼ 15−20◦ in longitude. By combining the Planck data with observations from the Wilkinson Microwave Anisotropy Probe, we were able to determine the spectrum of this emission to high accuracy, unhindered by the strong systematic biases present in previous analyses. The derived spectrum is consistent with power-law emission with a spectral index of −2.56 ± 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◦, the microwave haze morphology is consistent with that of the Fermi gamma-ray “haze” or “bubbles”, while at b ∼ −50◦ we have identified an edge in the microwave haze that is spatially coincident with the edge in the gamma-ray bubbles. Taken together, this indicates 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 astrophysical mechanism for cosmic-ray acceleration in the inner Galaxy is implied.