J/ApJS/138/63 H2CO and Hα observations of UC HII (Araya+, 2002)
Arecibo observations of formaldehyde and radio recombination lines toward
ultracompact H II regions.
Araya E., Hofner P., Churchwell E., Kurtz S.
<Astrophys. J. Suppl. Ser., 138, 63-74 (2002)>
=2002ApJS..138...63A 2002ApJS..138...63A
ADC_Keywords: H II regions ; Radio lines
Keywords: Galaxy: structure - ISM: H II regions - ISM: molecules -
radio lines: ISM
Abstract:
We report observations of the H110α radio recombination line and
H2CO (110-111) toward 21 ultracompact H II regions with the
Arecibo 305m radio telescope. We detect the H110α line in 20
sources, and for each of these we also detect a H2CO absorption
feature at nearly the same velocity, demonstrating the association
between molecular and ionized gas. We determine kinematic distances
and resolve the distance ambiguity for all observed HII regions, as
well as for 19 intervening molecular clouds. A plot of the Galactic
distribution of these objects traces part of the spiral structure in
the first Galactic quadrant. We compare flux densities and velocities
as measured with the Arecibo Telescope with interferometric
measurements of our sample of ultracompact HII regions. In general,
the single-dish fluxes exceed the interferometric values, consistent
with an extended component of radio continuum emission.
Description:
We performed observations toward 21 UC HII regions with 6cm flux
densities larger than 0.08Jy. The data were collected between 2000
September 15-18 with the 305m Arecibo Telescope. We observed the
H2CO (110-111) transition (ν0=4829.6594MHz for F=2-2), as
well as H110α (ν0=4874.1570MHz) toward the 21 UC HII regions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 40 21 Observed sources
table3.dat 76 21 H110α line (4874.16MHz)
table4.dat 80 69 Formaldehyde (H2CO, 4829.66MHz) results
table5.dat 73 43 Kinematic parameters
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See also:
J/A+AS/115/81 : A CS(2-1) survey of UC HII regions (Bronfman+, 1996)
J/A+AS/120/283 : Water maser features in UC HII regions (Hofner+ 1996)
J/A+A/336/339 : VLA observations of ultracompact HII regions (Molinari+ 1998)
J/MNRAS/301/640 : Ultracompact H II regions studies. II. (Walsh+, 1998)
J/ApJ/587/714 : H2CO and Halpha observations of UC HII (Watson+, 2003)
J/ApJS/155/123 : JHKs photometry of ultracompact HII regions (Alvarez+, 2004)
J/A+A/417/615 : Maser and outflows in UC HII region (Codella+, 2004)
J/A+A/453/1003 : SCUBA ultracompact HII regions (Thompson+, 2006)
J/ApJS/91/659 : Ultracompact HII regions radio images (Kurtz+ 1994)
J/MNRAS/420/1656 : RMS compact HII regions distances (Urquhart+, 2012)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name HII region designation, GLL.ll+D.dd
15- 16 I2 h RAh Right ascension (B1950)
18- 19 I2 min RAm Right ascension (B1950)
21- 24 F4.1 s RAs Right ascension (B1950)
26 A1 --- DE- Declination sign (B1950)
27- 28 I2 deg DEd Declination (B1950)
30- 31 I2 arcmin DEm Declination (B1950)
33- 34 I2 arcsec DEs Declination (B1950)
36 I1 --- Ref1 [1/9] Reference for UC HII region
flux density (2)
38 I1 --- Ref2 [1/9]? Reference for UC HII region velocity (2)
40 I1 --- Ref3 [1/9]? Reference for previously determined
distance (2)
42- 47 A6 --- OName Other name of the region (1)
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Note (1): Additional note:
S = Sharpless number (Sh 2 in Simbad);
ON = Onsala
K3 = Kohoutek faint planetary nebulae (PN K 3 in simbad)
Note (2): References as follows:
1 = Afflerbach et al., 1996ApJS..106..423A 1996ApJS..106..423A
2 = Kurtz et al., 1994, Cat. J/ApJS/91/659
3 = Wood & Churchwell, 1989ApJS...69..831W 1989ApJS...69..831W
4 = Kuchar & Bania, 1990ApJ...352..192K 1990ApJ...352..192K
5 = Downes et al., 1980A&AS...40..379D 1980A&AS...40..379D
6 = Lim & White, 1999, ed. T. Nakamoto (Nagano: Nobeyama Radio Obs.), 30
7 = Roelfsema et al., 1988A&A...207..132R 1988A&A...207..132R
8 = Churchwell et al., 1990A&AS...83..119C 1990A&AS...83..119C
9 = MacLeod et al., 1998AJ....116.1897M 1998AJ....116.1897M
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name HII region designation
13- 17 F5.3 Jy Sc ?=- Continum emission flux density
19- 23 F5.3 Jy e_Sc ? 1σ error on Sc
24 A1 --- n_Sc [a] a: Continum emission in off position
26- 30 F5.3 Jy SH110a ?=- Continum emission in off position
32- 36 F5.3 Jy e_SH110a ? 1σ error on SH110a (1)
37 A1 --- n_SH110a [b] b: No detection of H110α line
39- 43 F5.1 km/s VLSR ?=- Local Standard of Rest velocity
45- 47 F3.1 km/s e_VLSR ? 1σ error on VLSR (1)
48 A1 --- n_VLSR [b] b: No detection
50- 53 F4.1 km/s FWHM ?=- Full-Width at Half-Maximum
55- 57 F3.1 km/s e_FWHM ? 1σ error on FWHM (1)
58 A1 --- n_FWHM [b] b: No detection
60- 63 F4.2 Jy.km/s Sint ?=- Integrated H110α line flux
65- 68 F4.2 Jy.km/s e_Sint ? 1σ error on Sint (1)
69 A1 --- n_Sint [b] b: No detection
71- 75 F5.2 --- RS ?=- Flux density ratio HII to UCHII
76 A1 --- n_RS [a] a: Continum emission in off position
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Note (1): Calibration errors are approximately 30%.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name HII region designation
12 A1 --- m_Name [abc] Multiplicity index on Name
13- 15 A3 --- CName Intervening cloud identification
16 A1 --- m_CName [abcd] Multiplicity index on CName
18- 23 F6.3 Jy SH2CO ?=- H2CO flux density
25- 29 F5.3 Jy e_SH2CO ? rms uncertainty on SH2CO
31- 37 F7.3 km/s VLSR ?=- Local Standard of Rest velocity
39- 43 F5.3 km/s e_VLSR ? 1σ error on VLSR
44 A1 --- n_VLSR [b] b: No detection
46- 51 F6.3 km/s FWHM ?=- Line width
53- 57 F5.3 km/s e_FWHM ? 1σ error on Width
59- 65 F7.4 Jy.km/s Sint ?=- Integrated H110α line flux
67- 71 F5.3 Jy.km/s e_Sint ? 1σ error on Sint
73- 78 A6 --- Note Notes (1)
80 A1 --- f_Note [abc] Additional remarks (2)
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Note (1): Notes as follows:
MC = Intervening molecular cloud, arranged by decreasing line strength.
A = Asymmetric peak, not well fitted by Gaussian.
MP = Multipeak profile.
G = One Gaussian was used to fit the peak.
GMP = Number of Gaussians used to fit the multipeak line structure.
Gaussian line parameters for the strongest peak are presented here.
The other peaks fitted by the Gaussians could represent different
molecular clouds. Its line parameters are presented in the following
lines marked O (overlapped). If the Gaussian fit gave bad results
for weaker components, we only report the approximate flux density
and velocity of the overlapped line.
O = Overlapped with the previous peak.
V = Zero power width of the MP or A line is presented. The reported flux
density and VLSR correspond to the channel with deepest absorption.
If we observe more than one peak within the complex, we present the
approximate flux density and position of the overlapped peak in the
following lines.
E = Possible emission line in this complex.
Note (2): flag as follows:
a = For this spectrum, absorption is present in the off position.
b = The VLSR error presented is the channel width. The reported line width
error is twice the channel width.
c = No recombination line detected.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Name Source name
12 A1 --- n_Name [a] a: kinematic location
13- 15 A3 --- CName Intervening cloud identification
16 A1 --- m_CName [ac] Multiplicty index on CName
18- 23 F6.2 km/s VLSR The Local Standard of Rest velocity
24 A1 --- n_VLSR [i] Note on VLSR (1)
26- 29 F4.2 kpc DNear ?=- Inner Galaxy circular orbit near distance
31- 35 F5.2 kpc DFar ?=- Inner Galaxy circular orbit far distance
37- 40 F4.1 kpc VTP Distance derived to tangent point
42- 45 F4.2 kpc DTP Resolved Distance
47- 51 F5.2 kpc DLSR ? Distance derived from VLSR
52 A1 --- u_DLSR [?] Uncertainty flag on DLSR
54- 57 F4.2 kpc DGC Distance from the Galactic center
59- 71 A13 --- Near/Far Source distance (Near, Far, Tangent)
73 A1 --- n_Near/Far [bcdefhj] Note on Near/Far (1)
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Note (1): Notes as follows:
b = Velocities larger than the tangent point velocity imply strong noncircular
motions and/or undervalued velocities from the rotation curve. We
tentatively assign this molecular cloud to the tangent distance.
c = Kuchar & Bania (1990ApJ...352..192K 1990ApJ...352..192K) report HI absorption at a higher
velocity than the recombination line which implies the far kinematic
distance. We detect no corresponding H2CO absorption. Higher resolution
and sensitivity HI emission-absorption observations should be obtained
for confirmation.
d = Contradictory distances are reported in the literature. Our result agrees
with that of Churchwell et al. (1990ApJ...352..192K 1990ApJ...352..192K).
e = Radhakrishnan et al. (1972ApJS...24...49R 1972ApJS...24...49R) present a HI spectrum, which
shows absorption in the HI line wing up to 70km/s, which would argue for
the far distance (Downes et al., 1980A&AS...40..379D 1980A&AS...40..379D). We prefer to
assign the tangent distance.
f = Kurtz et al. (1994, cat. J/ApJS/91/659) summarize previous discrepant
distance determinations for this source. Our result agrees with the far
kinematic distance.
g = Churchwell et al. (1990ApJ...352..192K 1990ApJ...352..192K) prefer to assign the far kinematic
distance to G50.32+0.68 based on the trend of NH3 line width and UV
Luminosity as function of FIR Luminosity. We prefer to assign the near
kinematic distance.
h = Crampton et al. (1978A&A....66....1C 1978A&A....66....1C) estimated a distance of 2kpc to the
nearby S88A region, based on a possible optical detection. Our results
suggest that the kinematic position of S88B is at the tangent point.
i = No recombination line detected. We use the H2CO absorption line velocity.
j = MacLeod et al. (1998AJ....116.1897M 1998AJ....116.1897M) performed formaldehyde absorption
observations toward this source which agree with our spectrum. They report
the kinematic distance of this source as near. However, allowing for the
possibility of noncircular motion, we prefer to assign the distance of
tangent point.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 19-Feb-2014