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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 (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: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 05 35 14 -05 22.5 Orion A = NGC 1976 = M 42 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1 71 261 H64α line parameters table1.tex 95 805 LaTeX version of table1
Byte-by-byte Description of file: table1
Bytes Format Units Label Explanations
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, T_L_/T_C_ (2) 27- 31 F5.3 --- e_TL/TC ? rms uncertainty on TL/TC 33- 37 F5.2 km/s DV1/2 FWHP linewidths, DELTAV_1/2_ (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
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]

(End) Patricia Bauer [CDS] 28-Jul-1997
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