期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 730, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/730/1/L8
关键词
cosmic background radiation; galaxies: active; galaxies: jets; gamma rays: galaxies; quasars: individual (PKS 1222+21)
资金
- INFN Padova
- German BMBF
- MPG
- Italian INFN
- Swiss National Fund SNF
- Spanish MICINN
- Marie Curie program
- Spanish Consolider-Ingenio [CPAN CSD2007-00042, MultiDark CSD2009-00064]
- Bulgarian NSF [DO02-353]
- Academy of Finland [127740]
- YIP of the Helmholtz Gemeinschaft
- DFG Cluster of Excellence
- Polish MNiSzW [N N203 390834]
- NASA
- DOE in the United States
- CEA/Irfu
- CNRS in France [IN2P3/CNRS]
- ASI
- INFN in Italy
- MEXT
- KEK
- JAXA in Japan
- K. A. Wallenberg Foundation
- Swedish Research Council
- National Space Board in Sweden
- INAF in Italy
- CNES in France
- ICREA Funding Source: Custom
- Grants-in-Aid for Scientific Research [22840030] Funding Source: KAKEN
Very high energy (VHE) gamma-ray emission from the flat spectrum radio quasar (FSRQ) PKS 1222+ 21 (4C 21.35, z = 0.432) was detected with the MAGIC Cherenkov telescopes during a short observation (similar to 0.5 hr) performed on 2010 June 17. The MAGIC detection coincides with high-energy MeV/ GeV gamma-ray activity measured by the Large Area Telescope (LAT) on board the Fermi satellite. The VHE spectrum measured by MAGIC extends from about 70 GeV up to at least 400 GeV and can be well described by a power-law dN/dE proportional to E-Gamma with a photon index Gamma = 3.75 +/- 0.27(stat) +/- 0.2(syst). The averaged integral flux above 100 GeV is (4.6 +/- 0.5) x 10(-10) cm(-2) s(-1) (similar to 1 Crab Nebula flux). The VHE flux measured by MAGIC varies significantly within the 30 minute exposure implying a flux doubling time of about 10 minutes. The VHE and MeV/GeV spectra, corrected for the absorption by the extragalactic background light (EBL), can be described by a single power law with photon index 2.72 +/- 0.34 between 3 GeV and 400 GeV, and is consistent with emission belonging to a single component in the jet. The absence of a spectral cutoff constrains the gamma-ray emission region to lie outside the broad-line region, which would otherwise absorb the VHE gamma-rays. Together with the detected fast variability, this challenges present emission models from jets in FSRQs. Moreover, the combined Fermi/LAT and MAGIC spectral data yield constraints on the density of the EBL in the UV-optical to near-infrared range that are compatible with recent models.
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