J/A+A/327/1177 Kinematics and electron temperatures in Orion A (Wilson+ 1997)
Kinematics and electron temperatures in the core of Orion A
Wilson T.L., Filges L., Codella C., Reich W., Reich P.
<Astron. Astrophys. 327, 1177 (1997)>
=1997A&A...327.1177W 1997A&A...327.1177W (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Radial velocities ; Radio lines
Keywords: ISM: Orion A; HII regions; kinematics and dynamics; structure -
radio lines: ISM
Abstract:
A map of the core of Orion A, with a 42" resolution in the 64α
recombination line of hydrogen, covering ∼5' by ∼5', is presented. The
Vlsr distribution shows a complex variation about the center of the
ionized gas emission: From {DELTA}α=-200" to +300", the Vlsr
varies from -5km/s to +2km/s then to -4km/s, finally rising to +3km/s.
A search for cold (Te∼3000K) ionized gas toward the KL nebula has
revealed no measurable differences in Te between this region and
other parts of Orion A. The average Te from our data is 8300±200K.
We find no significant difference between Te values determined from
radio recombination lines and those determined from forbidden optical
lines of [O III], although the Te value from Balmer decrement data
is markedly lower. The turbulent velocity varies by <5% over the
region mapped. On the basis of our 2.45' resolution, high dynamic
range 6cm continuum map, we find that the emission falls off faster in
the East than in the West. We find support for the model in which
Orion A is ionization bounded in the East but density bounded in the
West. The ionized gas in the West is flowing in the direction of the
Sun, while the more positive Vlsr values in the east may be caused
by the flow of ionized gas off the foreground Dark Bay. This ionized
region may have little fine scale structure, since there is little
continuum emission in interferometer maps.
Objects:
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RA (2000) DE Designation(s)
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05 35 14 -05 22.5 Orion A = NGC 1976 = M 42
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1 71 261 H64α line parameters
table1.tex 95 805 LaTeX version of table1
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Byte-by-byte Description of file: table1
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Bytes Format Units Label Explanations
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1- 4 I4 arcsec DRA Offset relative to RA=05h 32min 48s (B1950) (1)
6- 9 I4 arcsec DDE Offset relative to DE=-05° 25' 23" (B1950)
11- 15 F5.2 10+3K Te ? LTE electron temperature
17- 19 F3.1 10+3K e_Te ? rms uncertainty on Te
21- 25 F5.3 --- TL/TC ? Line to continuum ratio, TL/TC (2)
27- 31 F5.3 --- e_TL/TC ? rms uncertainty on TL/TC
33- 37 F5.2 km/s DV1/2 FWHP linewidths, {DELTA}V1/2 (3)
39- 42 F4.2 km/s e_DV1/2 rms uncertainty on DV1/2
44- 47 F4.1 km/s RVlsr Radial velocity, with respect to the
Local Standard of Rest (3) (4)
49- 51 F3.1 km/s e_RVlsr rms uncertainty on RVlsr
53- 56 F4.1 km/s Vturb ? Turbulent velocity (5)
58- 60 F3.1 km/s e_Vturb ? rms uncertainty on Vturb
62- 67 F6.2 K.km/s TLdV Integrated main beam line brightness temperature
69- 71 F3.1 K.km/s e_TLdV rms uncertainty on TLdV
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Note (1): Nominal peak of the radio continuum (to obtain J2000 coordinates,
+2min 27.4s in RA, +2' 06.7" in DE.
Note (2): The line-to-continuum ratios were obtained from the peak intensities
of the H64α lines divided by he continuum intensities measured
at nearly the same time
Note (3): The radial velocities and FWHP linewidths were obtained from gaussian
fits to the line spectra.
Note (4): To obtain Heliocentric velocities, add 18.3 km/s.
Note (5): We take turbulent velocities to be the excess line widths after
removing the thermal broadening. Since the hydrogen linewidths are
found to be gaussian shaped, we can use
Vturb=sqrt[(ΔV1/2)2 - 0.046Te]
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(End) Patricia Bauer [CDS] 28-Jul-1997