Spitzer space telescope infrared imaging and spectroscqpy of the Crab Nebula

Tea Temim, Robert D. Gehrz, Charles E. Woodward, Thomas L. Roellio, Nathan Smith, Lawrence Rudnick, Elisha F. Polomski, Kris Davidson, Lunming Yuen, Takashi Onaka

Research output: Contribution to journalArticlepeer-review

77 Scopus citations

Abstract

We present 3.6, 4.5, 5.8, 8.0, 24, and 70 μm images of the Crab Nebula obtained with the Spitzer Space Telescope IRAC and MIPS cameras, low- and high-resolution Spitzer IRS spectra of selected positions within the nebula, and a near-infrared ground-based image made in the light of [Fe II] 1.644 μm. The 8.0 μm image, made with a bandpass that includes [Ar II] 7.0 μm, resembles the general morphology of visible Hα and near-IR [Fe II] line emission, while the 3.6 and 4.5 μm images are dominated by continuum synchrotron emission. The 24 and 70 μm images show enhanced emission that may be due to line emission or the presence of a small amount of warm dust in the nebula on the order of less than 1% of a solar mass. The ratio of the 3.6 and 4.5 μm images reveals a spatial variation in the synchrotron power-law index ranging from approximately 0.3 to 0.8 across the nebula. Combining this information with optical and X-ray synchrotron images, we derive a broadband spectrum that reflects the superposition of the flatter spectrum of the jet and torus with the steeper spectrum of the diffuse nebula. We also see suggestions of the expected pileup of relativistic electrons just before the exponential cutoff in the X-ray. The pulsar, and the associated equatorial toroid and polar jet structures seen in Chandra and Hubble Space Telescope images (Hester et al. 2002), can be identified in all of the IRAC images. We present the IR photometry of the pulsar. The forbidden lines identified in the high-resolution IR spectra are all double due to Doppler shifts from the front and back of the expanding nebula and give an expansion velocity of ≈1264 km s -1.

Original languageEnglish (US)
Pages (from-to)1610-1623
Number of pages14
JournalAstronomical Journal
Volume132
Issue number4
DOIs
StatePublished - Oct 2006
Externally publishedYes

Keywords

  • Acceleration of particles
  • Cosmic rays
  • ISM: individual (Crab Nebula)
  • Pulsars: individual (Crab Nebula)
  • Radiation mechanisms: nonthermal
  • Supernova remnants

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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