J/ApJ/790/84 Ammonia in high-mass star formation regions (Lu+, 2014)
Very Large Array observations of ammonia in high-mass star formation regions.
Lu X., Zhang Q., Liu H.B., Wang J., Gu Q.
<Astrophys. J., 790, 84 (2014)>
=2014ApJ...790...84L 2014ApJ...790...84L (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Interstellar medium ; YSOs
Keywords: ISM: molecules - stars: formation
Abstract:
We report systematic mapping observations of the NH3(1, 1) and (2,
2) inversion lines toward 62 high-mass star-forming regions using the
Very Large Array (VLA) in its D and DnC array configurations. The VLA
images cover a spatial dynamic range from 40'' to 3'', allowing us to
trace gas kinematics from ∼1 pc scales to ≲ 0.1 pc scales. Based on
the NH3 morphology and the infrared nebulosity on 1 pc scales, we
categorize three subclasses in the sample: filaments, hot cores, and
NH3-dispersed sources. The ubiquitous gas filaments found on 1 pc
scales have a typical width of ∼0.1 pc and often contain regularly
spaced fragments along the major axis. The spacing of the fragments
and the column densities is consistent with the turbulent supported
fragmentation of cylinders. Several sources show multiple filaments
that converge toward a center where the velocity field in the
filaments is consistent with gas flows. We derive rotational
temperature maps for the entire sample. For the three hot core
sources, we find a projected radial temperature distribution that is
best fit by power-law indices from -0.18 to -0.35. We identify 174
velocity-coherent ∼0.1 pc scale dense cores from the entire sample.
The mean physical properties for these cores are 1.1 km/s in intrinsic
linewidth, 18 K in NH3 rotational temperature, 2.3x1015/cm2 in
NH3gas column density, and 67 M☉in molecular mass. The dense
cores identified from the filamentary sources are closer to being
virialized. Dense cores in the other two categories of sources appear
to be dynamically unstable.
Description:
We observed 54 high-mass star-forming regions during 2004 June
(project code: AC0733), using the NRAO5 VLA in D/DnC array
configurations, which constitute a good sample of high-mass protostars
given the large luminosity and association with molecular outflows and
dense NH3 gas (Molinari et al. 1996, J/A+A/308/573; Sridharan et al.
2002ApJ...566..931S 2002ApJ...566..931S; Beuther et al. 2002A&A...390..289B 2002A&A...390..289B; Wu et al.
2006A&A...450..607W 2006A&A...450..607W). The uv distances of the observations range from
2 kλ to ≥ 81 kλ, which yield ≲ 3 arcsec angular
resolution and ∼40 arcsec maximal detectable angular scales. The
correlator setup provided two independently tunable spectral windows
with a 48.8 kHz spectral channel spacing and a 3.125 MHz bandwidth,
corresponding to 0.618 km/s channel width and 39 km/s velocity
coverage for the NH3 (1, 1) transition. These two spectra windows
simultaneously covered the main and two inner satellite transitions of
the NH3 (1, 1) line, as well as the main and one inner satellite
transitions of the NH3 (2, 2) line.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 7 Summary of the VLA Observations
table2.dat 94 62 Observational Properties of the Sources
table6.dat 83 324 Dense core properties
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See also:
J/A+A/308/573 : Ammonia on YSOs IRAS sources (Molinari+ 1996)
J/A+AS/124/385 : Dense molecular cores. V. (Zinchenko+ 1997)
J/ApJS/125/161 : A database of dense cores mapped in ammonia (Jijina+, 1999)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Index [1/6] Project index
3- 8 A6 --- Project Project name
10- 23 A14 "date" Date Project date
25- 27 A3 --- Config [C,D,DnC ] VLA array configuration
29- 33 A5 --- Dist The uv-distance interval of the observation
(in klambda units)
35- 36 I2 --- Num [1/42] Number of samples
38- 54 A17 --- PhaseC Phase calibrator(s) used
56- 58 F3.1 mJy/beam rms rms level (per channel)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Source Source name
17 I1 --- Index [1/6] Project index defined in table 1
19- 20 I2 h RAh Hour of Right Ascension (J2000) (1)
22- 23 I2 min RAm Minute of Right Ascension (J2000) (1)
25- 29 F5.2 s RAs Second of Right Ascension (J2000) (1)
31 A1 --- DE- Sign of the Declination (J2000) (1)
32- 33 I2 deg DEd Degree of Declination (J2000) (1)
35- 36 I2 arcmin DEm Arcminute of Declination (J2000) (1)
38- 42 F5.2 arcsec DEs Arcsecond of Declination (J2000) (1)
44- 50 F7.3 deg GLON Galactic longitude (1)
52- 57 F6.3 deg GLAT Galactic latitude (1)
58- 69 A12 --- NH3 NH3 line(s) detection
71- 75 F5.1 km/s VLSR ? Local Standard of Rest velocity
77- 80 F4.1 kpc Dist ? Distance
82- 85 A4 --- n_Dist Note on Dist (2)
87- 91 E5.2 Lsun LIR ? IRAS point source luminosity
93- 94 I2 --- Ncore [0/15]? Number of core for this source in table6
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Note (1): Coordinates are phase centers of the VLA observations.
Note (2): Note as follows:
1 = Sridharan et al. (2002ApJ...566..931S 2002ApJ...566..931S);
2 = Niinuma et al. (2011PASJ...63....9N 2011PASJ...63....9N);
3 = At the tangential point or in the second or third quadrant of the Milky
Way;
4 = Wilking et al. (1989ApJ...345..257W 1989ApJ...345..257W);
5 = Fish et al. (2003ApJ...587..701F 2003ApJ...587..701F);
6 = Sato et al. (2010PASJ...62..287S 2010PASJ...62..287S);
7 = IRDC candidates;
8 = Anderson & Bania (2009, J/ApJ/690/706);
9 = Fazal et al. (2008ApJ...688L..41F 2008ApJ...688L..41F);
10 = Kurayama et al. (2011PASJ...63..513K 2011PASJ...63..513K);
11 = The far distance is applied because the derived near distance is too
small (≤1 kpc).
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- ID Core identifier
21- 22 I2 h RAh Hour of Right Ascension (J2000)
24- 25 I2 min RAm Minute of Right Ascension (J2000)
27- 31 F5.2 s RAs Second of Right Ascension (J2000)
33 A1 --- DE- Sign of the Declination (J2000)
34- 35 I2 deg DEd Degree of Declination (J2000)
37- 38 I2 arcmin DEm Arcminute of Declination (J2000)
40- 44 F5.2 arcsec DEs Arcsecond of Declination (J2000)
46- 49 F4.2 pc R Intrinsic core radius
51- 54 F4.2 km/s DelV Intrinsic line width
56- 59 F4.1 K TR ? Rotational temperature
61- 66 E6.1 cm-2 NNH3 NH3 column density
68- 73 F6.2 Msun Mcore Core mass
75- 79 F5.1 --- Ratio ? Ratio of virial to core masses
81- 83 A3 --- Multi [yes ] Multi-Velocity flag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 21-Mar-2017