Orion Nebula with VLA/GBT
|Minimum credit line: Image courtesy of NRAO/AUI
(for details, see .|
The Orion Nebula is the defining Galactic HII region and has been well
studied over a wide range of wavelengths.
The top left image shows observations made with the Robert C. Byrd Green Bank Telescope (GBT) of extended emission at 3.6 cm wavelength from ionized gas in the Orion Nebula. The brightest feature with
a box around it is
M42 (NGC 1976), a thin blister of ionized gas on the surface of the
OMC-1 molecular cloud. Winds from luminous stars in the Trapezium
cluster ablate the surface of the cloud, ejecting cloud material into
the diffuse interstellar medium. M43 (NGC 1982) is just above the
northeastern rim of M42 (the circular feature above and slightly to the left of the box).
The top right image was made with the Very
Large Array (VLA) at the same wavelength as the GBT image. A wealth
of detail showing the complex inner structure of the ionized gas is
visible with the VLA. The bottom image was created by combining the
GBT and VLA images to get a better picture of what the center of the
nebula looks like. It combines the power of both instruments: the
GBT's sensitivity to extended structure and the VLA's ability to see
Investigator(s): Debra Shepherd, Ron Maddalena, and Joe McMullin
This image is available in the following downloadable versions:
- 502 x 576
- 916 x 1050
- 2063 x 2366
If you would like to obtain a higher resolution version of this image,
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Date of Observation
Type of Observation
Center of Image
RA: 05:35:17.40, Dec: -5:23:28.00 (J2000)
Field of View
0.6667 x 0.6667 degrees
The GBT image, made at a wavelength of 3.6 cm (8.435 GHz), was taken
in an 'on-the-fly' (OTF) mosaic raster mode on 2001 November 1. The
image was sampled every 25'' along a row while rows within the mosaic
were spaced by 30''. The bandwidth was 80 MHz. The primary beam of
the GBT is 1.46' at 8.4 GHz. The central region in the Orion Nebula
was imaged with the VLA in 3.6 cm continuum emission while the VLA was
in the compact D-array. Observations of the 3 x 3 field mosaic were
made on 2000 October 4; field centers were separated by 2.5' (slightly
better than Nyquist sampled). The band width was 50 MHz. The primary
beam of a single pointing was 5.4', the synthesized beam was 8.4''.
The GBT and VLA data were reduced and imaged using the AIPS++
Astronomical Information Processing System. The figure shows
the GBT image in the upper left displayed from 0 to 119.4 Jy/beam.
The OTF mosaic has an RMS of 10 mJy/beam and a maximum of 119.4
Jy/beam. The dynamic range of the image is 11,900 - the highest
dynamic range ever achieved by a single dish telescope. The total
flux is 430 Jy. The VLA image (upper right) is displayed on a linear
stretch from 0 to 0.83 Jy/beam. The mosaic has an RMS of 6.1
mJy/beam, a maximum of 0.83 Jy/beam, and a minimum of -0.027 Jy/beam.
The total flux is 189 Jy -- less than half the total flux measured
with the GBT. The combined GBT+VLA image (bottom center) was created
using an "image feathering'' technique in which each image was
automatically Fourier transformed to the uv-plane, weighted
appropriately, combined, and then Fourier transformed back to the
image plane. The resulting image has a peak flux density of 1.82
Jy/beam, an RMS of 10 mJy/beam, and a total flux of 415 Jy.
- Astronomical database entries for M42
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