The Radio-2 mm Spectral Index of the Crab Nebula Measured with Gismo
Abstract
We present results of 2 mm observations of the Crab Nebula, obtained using the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG bolometer array on the Green Bank Telescope are also presented. The integrated 2 mm flux density of the Crab Nebula provides no evidence for the emergence of a second synchrotron component that has been proposed. It is consistent with the radio power-law spectrum, extrapolated up to a break frequency of log (ν b [GHz]) = 2.84 ± 0.29 or ν b = 695+651 - 336 GHz. The Crab Nebula is well resolved by the ~16farcs7 beam (FWHM) of GISMO. Comparison to radio data at comparable spatial resolution enables us to confirm significant spatial variation of the spectral index between 21 cm and 2 mm. The main effect is a spectral flattening in the inner region of the Crab Nebula, correlated with the toroidal structure at the center of the nebula that is prominent in the near-IR through X-ray regime.
Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2011
- DOI:
- 10.1088/0004-637X/734/1/54
- arXiv:
- arXiv:1103.6225
- Bibcode:
- 2011ApJ...734...54A
- Keywords:
-
- ISM: individual objects: Crab Nebula;
- ISM: supernova remnants;
- radiation mechanisms: non-thermal;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Accepted for publication in the ApJ