J/A+A/699/A319 EVLA and LOFAR images of Crab Nebula (Arias+, 2025)
The Crab Nebula at subarcsecond resolution with the International LOFAR
Telescope.
Arias M., Timmerman R., Sweijen F., van Weeren R.J., Bassa C.G.
<Astron. Astrophys. 699, A319 (2025)>
=2025A&A...699A.319A 2025A&A...699A.319A (SIMBAD/NED BibCode)
ADC_Keywords: Supernova remnants ; Radio sources
Keywords: radiation mechanisms: non-thermal - ISM: supernova remnants -
radio continuum: ISM - ISM: individual objects: Crab Nebula
Abstract:
We present International LOw Frequency ARray (LOFAR) Telescope (ILT)
observations of the Crab Nebula, the remnant of a core-collapse
supernova explosion observed by astronomers in 1054. The field of the
Crab Nebula was observed between 120 and 168MHz as part of the LOFAR
Two Meter Sky Survey (LoTSS), and the data were re-processed to
include the LOFAR international stations to create a high angular
resolution (0.43"x0.28") map at a central frequency of 145MHz.
Combining the ILT map with archival centimeter-range observations of
the Nebula with the Very Large Array (VLA) and LOFAR data at 54MHz,
we become sensitive to the effects of free-free absorption against the
synchrotron emission of the pulsar wind nebula. This absorption is
caused by the ionised filaments visible in optical and infrared data
of the Crab Nebula, which are the result of the pulsar wind nebula
expanding into the denser stellar ejecta that surrounds it and forming
Rayleigh-Taylor fingers. The LOFAR observations are sensitive to two
components of these filaments: their dense cores, which show electron
densities of ≥1000cm-3, and the diffuse envelopes, with electron
densities of ∼50-250cm-3. The denser structures have widths of
∼0.03pc, whereas the diffuse component is at one point as large as
0.2pc. The morphology of the two components is not always the same.
These finding suggests that the layered temperature, density, and
ionisation structure of the Crab optical filaments extends to larger
scales than previously considered.
Description:
The map was made by imaging calibrated visibilities downloaded from
the VLA archive Properties of the maps are given in Table 1 of the
paper, and in the headers of the FITS files.
Objects:
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RA (2000) DE Designation(s)
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05 34 31.77 +22 01 02.6 Crab Nebula = 1RXS J053431.2+220218
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 125 2 List of fits images
fits/* . 2 Individual fits images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 50 A21 "datime" Obs.date Observation date
52- 62 E11.6 Hz Freq Observed frequency
64- 69 I6 Kibyte size Size of FITS file
71- 90 A20 --- FileName Name of FITS file, in subdirectory fits
92-125 A34 --- Title Title of the FITS file
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Acknowledgements:
Maria Arias, maria.arias.de.saavedra(at)gmail.com
(End) Patricia Vannier [CDS] 25-Jun-2025