Fermi Gamma-ray Space Telescope

Deep View of the Large Magellanic Cloud with Six Years of Fermi-LAT Observations

P. Martin

Abstract:

The Large Magellanic Cloud (LMC) is a nearby satellite galaxy of the Milky Way, located at a distance of 50kpc. Its proximity and orientation offer excellent opportunities to study many astrophysical phenomena in detail. In particular, the LMC has a relatively high star-formation activity, attested by a large number of massive stars, supernova remnants, and superbubbles. These are expected to sustain a cosmic-ray population that may be studied through high-energy radiation seen by Fermi LAT, thereby providing a global view complementary with studies of the Milky Way. The LMC was detected in GeV gamma rays early in the Fermi mission, from 11 months of data. Extended emission spanning a part of the sky about the size of the LMC was detected, and it was found to be relatively strong in the direction of 30 Doradus, a star-forming region more active than any other in the Milky Way or in nearby galaxies of the Local Group. We revisited this result using 6 years of Fermi-LAT observations. The increased exposure and improved instrument performance allowed a dramatic enhancement of our view of the gamma-ray emission of the LMC. Point sources were detected, one of which turned out to be the first extragalactic gamma-ray pulsar and the most luminous gamma-ray pulsar known so far. Two other sources were found in spatial coincidence with the most energetic pulsar known and with a supernova remnant, two objects also detected at TeV energies. Extended emission still represents most of the gamma-ray signal from the LMC, but its morphology is at odds with expectations.