J/A+A/711/A85 Extended Orion Nebula HI 21cm emission maps (Soler+, 2026)
The Neutral Atomic Hydrogen in the solar neighborhood (NeAtHood) project.
I. Ghost in the shell: Neutral atomic hydrogen in the extended Orion nebula.
Soler J.D., Beuther H., Glover S.C.O., Klessen R.S., Ott J., Rugel M.,
Teh J.W., Clark S.E., Goldsmith P., Hacar A., Socci A., Heyer M., Lee M.-Y.,
Murray C.E., Seifried D., Walch S., Godard B., Miville-Deschenes M.-A.
<Astron. Astrophys. 711, A85 (2026)>
=2026A&A...711A..85S 2026A&A...711A..85S (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; H I data ; Radio lines
Keywords: ISM: bubbles - HII regions - ISM: structure
Abstract:
The Orion nebula is the nearest site of ongoing and recent high-mass
star formation. It is a unique laboratory for studying the mass,
energy, and momentum input from high-mass stars. We present
21-centimeter emission line observations that resolve for the first
time the neutral atomic hydrogen (HI) gas in the extended Orion nebula
(EON) at a resolution of one arcminute, which corresponds to a
physical scale of 0.12 parsecs at the standard distance to the region.
Our HI emission maps reveal an expanding shell that matches the EON
contours delineated by recent observations of ionized carbon ([CII])
line emission. However, our combination of single-dish and
interferometric HI observations suggests 100 solar masses of material
for the front hemisphere of the shell, which is lower by roughly a
factor of ten than the mass inferred from [CII] observations. This
discrepancy suggests that the mass of the nearest wind-blown bubble
has been overestimated, although we do not rule out the possibility
that a significant amount of molecular hydrogen (H2) in the shell
may account for part of the difference. Our extended 21cm line maps
also reveal uncharted structures in and around the EON. They include a
probable secondary bubble and a linear protrusion extending roughly
four parsecs from the shell boundary. Our results illustrate the
potential of HI interferometric observations to elucidate key aspects
of the multiphase structure of star-forming regions and their
connection to their surroundings.
Description:
We present arcminute-resolution HI 21cm emission maps toward the
Extended Orion Nebula (EON) obtained from the combination of Karl G.
Jansky Very Large Array (VLA) and Five-hundred-meter Aperture
Spherical Radio Telescope (FAST) observations. The data reveal the
neutral atomic hydrogen counterpart to the expanding shell previously
identified in [CII] and X-ray observations. The combined VLA+FAST cube
samples the HI brightness temperature in Galactic coordinates and
radio velocity with respect to the Local Standard of Rest kinematic
frame (LSRK), with 10 arcsec pixels, 0.4km/s channels, and an
effective angular resolution of 1 arcmin FWHM.
The data consist of a three-dimensional FITS cube containing HI 21cm
brightness temperature observations toward the Orion nebula region.
The cube combines interferometric observations obtained with the VLA
D-array in project 19B-181 and single-dish observations from the FAST
CHiNA survey. The datasets were combined using Fourier-space
feathering.
The cube is sampled in Galactic coordinates and radio velocity with
respect to the Local Standard of Rest kinematic frame (LSRK).
The effective angular resolution is 1 arcmin FWHM. The spectral
resolution is 0.4km/s. The typical RMS noise level is approximately 2K
per velocity channel.
The central ONC/Trapezium region is affected by strong HI absorption
against bright continuum emission and by missing FAST single-dish
information. Users should treat the region within 120 arcsec of
Galactic coordinates l=209.06deg, b=-19.48deg with caution.
Scientific analysis in the paper excludes this central region.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 132 1 Information of fits data cube
fits/* . 1 Individual fits data cube
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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 A1 --- G [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude of center (J2000)
21- 23 I3 --- Nx Number of pixels along X-axis
25- 27 I3 --- Ny Number of pixels along Y-axis
29- 31 I3 --- Nz Number of pixels along Z-axis
33- 38 I6 m/s bVRAD Lower value of VRAD interval
40- 44 I5 m/s BVRAD Upper value of VRAD interval
46- 48 I3 m/s dVRAD VRAD resolution
50- 55 I6 Kibyte size Size of FITS file
57- 91 A35 --- FileName Name of FITS file, in subdirectory fits
93-132 A40 --- Title Title of the FITS file (1)
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Note (1):
FITS header keywords:
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Keyword Value Meaning
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CTYPE1 GLON-TAN Galactic longitude
CTYPE2 GLAT-TAN Galactic latitude
CTYPE3 VRAD Radio velocity
CUNIT1 deg Longitude unit
CUNIT2 deg Latitude unit
CUNIT3 m/s Velocity unit
CRVAL3 -25000 Reference velocity
CDELT3 400 Channel spacing
RESTFRQ 1420405751.77 HI rest frequency (Hz)
BUNIT K Brightness temperature
BMAJ 0.0166667 Beam major axis (deg)
BMIN 0.0166667 Beam minor axis (deg)
BPA 0.0 Beam position angle
SPECSYS LSRK Spectral reference frame
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Data characteristics:
Spatial sampling: 10 arcsec pixels
Velocity sampling: 0.4km/s channels
Velocity range: -25.0 to +24.6km/s
Effective angular resolution: 60 arcsec FWHM
Typical RMS noise: 2K
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Acknowledgements:
From Juan Diego Soler, juandiegosolerp(at)gmail.com
This work was funded in whole or in part by the Austrian
Science Fund (FWF) 10.55776/PAT6169824.
The data products distributed through CDS were prepared by
Dr. Juan Diego Soler.
The National Radio Astronomy Observatory is a facility
of the National Science Foundation operated under cooperative
agreement by Associated Universities, Inc.
FAST is operated by the National Astronomical Observatories,
Chinese Academy of Sciences.
License: CC-BY-4.0
(End) Patricia Vannier [CDS] 14-May-2026