Final Report Summary - P-WIND (New light on the gamma-ray sky: unveiling cosmic-ray accelerators in the Milky Way and their relation to pulsar wind nebulae)
Fermi's Large Area Telescope (LAT) scans the entire sky every three hours, continually deepening its portrait of the sky in gamma rays, the most energetic form of light. While the energy of visible light falls between about 2 and 3 electron volts, the LAT detects gamma rays with energies ranging from 20 million to more than 300 billion electron volts (GeV). Any object producing gamma rays at these energies is undergoing extraordinary astrophysical processes.
Before the start of the project, among all the sources detected by gamma-ray satellites and Cherenkov telescopes, hundreds of Galactic gamma-ray sources had no obvious counterpart at optical, radio, or X-ray wavelengths. We believed that many of them were pulsars or nebulae powered by pulsars. The complete analysis of these unidentified sources (focusing on pulsar wind nebulae) using multi-wavelength data, especially those obtained by the Large Area Telescope aboard Fermi was one of the main goal of this project.
During the project, an individual analysis of several pulsar wind nebulae was performed, showing that the emission from these sources can be very well modeled assuming that they are evolved pulsar wind nebulae in which the magnetic field has now decreased, thus suppressing the synchrotron emission. A more general analysis using Fermi-LAT data above 10 GeV of 58 TeV sources within 5 degrees of the Galactic Plane was also performed leading to the detection of 30 sources, among which 11 promising pulsar wind nebulae (PWNe) candidates and 5 PWNe clearly identified. This increased population of detected GeV sources provided a clear proof that evolved pulsar wind nebulae are a dominant class of sources in the gamma-ray range. In this context, our project brings new constraints on the properties of PWNe but also new clues on the nature of unidentified sources thanks to a parallel detection of one pulsar, one supernova remnant and one potential star forming region (W43).
Before the start of the project, among all the sources detected by gamma-ray satellites and Cherenkov telescopes, hundreds of Galactic gamma-ray sources had no obvious counterpart at optical, radio, or X-ray wavelengths. We believed that many of them were pulsars or nebulae powered by pulsars. The complete analysis of these unidentified sources (focusing on pulsar wind nebulae) using multi-wavelength data, especially those obtained by the Large Area Telescope aboard Fermi was one of the main goal of this project.
During the project, an individual analysis of several pulsar wind nebulae was performed, showing that the emission from these sources can be very well modeled assuming that they are evolved pulsar wind nebulae in which the magnetic field has now decreased, thus suppressing the synchrotron emission. A more general analysis using Fermi-LAT data above 10 GeV of 58 TeV sources within 5 degrees of the Galactic Plane was also performed leading to the detection of 30 sources, among which 11 promising pulsar wind nebulae (PWNe) candidates and 5 PWNe clearly identified. This increased population of detected GeV sources provided a clear proof that evolved pulsar wind nebulae are a dominant class of sources in the gamma-ray range. In this context, our project brings new constraints on the properties of PWNe but also new clues on the nature of unidentified sources thanks to a parallel detection of one pulsar, one supernova remnant and one potential star forming region (W43).