skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT

Abstract

We present the first Hubble Space Telescope Wide Field Planetary Camera-2 imaging survey of the entire Crab Nebula, in the filters F502N ([O III] emission), F673N ([S II]), F631N ([O I]), and F547M (continuum). We use our mosaics to characterize the pulsar wind nebula (PWN) and its three-dimensional structure, the ionizational structure in the filaments forming at its periphery, the speed of the shock driven by the PWN into surrounding ejecta (by inferring the cooling rates behind the shock), and the morphology and ionizational structure of the Rayleigh-Taylor (R-T) fingers. We quantify a number of asymmetries between the northwest (NW) and southeast (SE) quadrants of the Crab Nebula. The lack of observed filaments in the NW, and our observations of the spatial extent of [O III] emission lead us to conclude that cooling rates are slower, and therefore the shock speeds are greater, in the NW quadrant of the nebula, compared with the SE. We conclude that R-T fingers are longer, more ionizationally stratified, and apparently more massive in the NW than in the SE, and the R-T instability appears more fully developed in the NW.

Authors:
; ;  [1];  [2]
  1. School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States)
  2. Barrett, The Honors College, Arizona State University, P.O. Box 871612, Tempe, AZ 85287 (United States)
Publication Date:
OSTI Identifier:
22126965
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 765; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CAMERAS; COMPARATIVE EVALUATIONS; COOLING; CRAB NEBULA; FILTERS; OXYGEN IONS; PHOTON EMISSION; PULSARS; RAYLEIGH-TAYLOR INSTABILITY; SHOCK WAVES; STELLAR WINDS; TELESCOPES; VELOCITY

Citation Formats

Loll, A. M., Desch, S. J., Scowen, P. A., and Foy, J. P., E-mail: allison.loll@asu.edu. OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT. United States: N. p., 2013. Web. doi:10.1088/0004-637X/765/2/152.
Loll, A. M., Desch, S. J., Scowen, P. A., & Foy, J. P., E-mail: allison.loll@asu.edu. OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT. United States. doi:10.1088/0004-637X/765/2/152.
Loll, A. M., Desch, S. J., Scowen, P. A., and Foy, J. P., E-mail: allison.loll@asu.edu. 2013. "OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT". United States. doi:10.1088/0004-637X/765/2/152.
@article{osti_22126965,
title = {OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT},
author = {Loll, A. M. and Desch, S. J. and Scowen, P. A. and Foy, J. P., E-mail: allison.loll@asu.edu},
abstractNote = {We present the first Hubble Space Telescope Wide Field Planetary Camera-2 imaging survey of the entire Crab Nebula, in the filters F502N ([O III] emission), F673N ([S II]), F631N ([O I]), and F547M (continuum). We use our mosaics to characterize the pulsar wind nebula (PWN) and its three-dimensional structure, the ionizational structure in the filaments forming at its periphery, the speed of the shock driven by the PWN into surrounding ejecta (by inferring the cooling rates behind the shock), and the morphology and ionizational structure of the Rayleigh-Taylor (R-T) fingers. We quantify a number of asymmetries between the northwest (NW) and southeast (SE) quadrants of the Crab Nebula. The lack of observed filaments in the NW, and our observations of the spatial extent of [O III] emission lead us to conclude that cooling rates are slower, and therefore the shock speeds are greater, in the NW quadrant of the nebula, compared with the SE. We conclude that R-T fingers are longer, more ionizationally stratified, and apparently more massive in the NW than in the SE, and the R-T instability appears more fully developed in the NW.},
doi = {10.1088/0004-637X/765/2/152},
journal = {Astrophysical Journal},
number = 2,
volume = 765,
place = {United States},
year = 2013,
month = 3
}
  • Optical continuum images of the Crab Nebula are presented which reveal numerous, small dark spots across the face of the Crab's amorphous synchrotron nebula. These spots range in size from being unresolved at 0.8-arcsec resolution to about 5 arcsec, exhibit Delta(m)4470 = 0.08-0.44, and are most visible in the shorter-wavelength continuum images. Comparisons with images taken using interference filters centered on various emission lines indicate that these dark features are coincident with forbidden O I, C I, and S II bright cores of selected filaments. This positional coincidence plus a wavelength dependence similar to that exhibited by conventional interstellar dustmore » establishes the presence of dust within at least some of the Crab Nebula's filaments. 26 refs.« less
  • A deep, high-resolution forbidden O III image of the Crab Nebula's northern jet is presented which reveals considerably finer details than visible on previous photographs. The jet's small-scale structure appears composed of numerous emission-line filaments and knots which collectively exhibit a strong alignment having well-defined east-west boundaries. Comparison with an earlier published image suggests a proper motion northward for one of the jet's emission knots of 0.22 + or - 0.05 arcsec/yr. The jet's optical morphology is discussed and its properties compared to predictions of several proposed models. The shadowed flow model suggested by Morrison and Roberts (1985) appears tomore » explain best the jet's known properties. 35 references.« less
  • Chandra images of the Crab Nebula resolve the detailed structure of its 'inner ring', possibly a termination shock where pulsar-accelerated relativistic particles begin to emit X radiation. Analysis of these images finds that the center of the ellipse-presumably a circular ring in projection-lies about 0.''9 (10 light days at 2 kpc) from the pulsar's image, at a position angle of about 300 Degree-Sign (east of north). This analysis also measures properties of the ellipse: the position angle of the semi-major axis is about 210 Degree-Sign (east of north); the aspect ratio is 0.49. In a simple-albeit, not unique-de-projection of themore » observed geometry, a circular ring is centered on the axis of symmetry of the pulsar wind nebula. This ring is not equatorial but rather lies near +4.{sup 0}5 latitude in pulsar-centered coordinates. Alternative geometries are briefly discussed.« less
  • The Crab-like supernova remnant 3C 58 was observed with the VLA at frequencies of 1446 and 4886 MHz, with resolutions of 2.0 and 2.45 arcsec, respectively. It is found that 3C 58 has a considerably larger extent than previously realized, particularly at the eastern and western edges and above and below the central bulge. Some parts of the periphery are markedly confined while others are not; some confined-edge regions are slightly limb brightened. The fainter outer envelope contains extensive filamentation as do the brighter central regions. The filament profiles are nearly identical at 1446 and 4886 MHz. 33 references.