J/AJ/154/140 MALT90 kinematic distances to molecular clumps (Whitaker+, 2017)
MALT90 kinematic distances to dense molecular clumps.
Whitaker J.S., Jackson J.M., Rathborne J.M., Foster J.B., Contreras Y.,
Sanhueza P., Stephens I.W., Longmore S.N.
<Astron. J., 154, 140 (2017)>
=2017AJ....154..140W 2017AJ....154..140W (SIMBAD/NED BibCode)
ADC_Keywords: Molecular clouds ; Surveys ; Millimetric/submm sources ;
Radial velocities ; Stars, distances
Keywords: ISM: clouds - stars: distances - stars: formation
Abstract:
Using molecular-line data from the Millimetre Astronomy Legacy Team
90 GHz Survey (MALT90), we have estimated kinematic distances to 1905
molecular clumps identified in the ATLASGAL 870 µm continuum survey
over the longitude range 295°<l<350°. The clump velocities were
determined using a flux-weighted average of the velocities obtained
from Gaussian fits to the HCO+, HNC, and N2H+ (1-0) transitions.
The near/far kinematic distance ambiguity was addressed by searching
for the presence or absence of absorption or self-absorption features
in 21 cm atomic hydrogen spectra from the Southern Galactic Plane
Survey. Our algorithm provides an estimation of the reliability of the
ambiguity resolution. The Galactic distribution of the clumps
indicates positions where the clumps are bunched together, and these
locations probably trace the locations of spiral arms. Several clumps
fall at the predicted location of the far side of the Scutum-Centaurus
arm. Moreover, a number of clumps with positive radial velocities are
unambiguously located on the far side of the Milky Way at galactocentric
radii beyond the solar circle. The measurement of these kinematic
distances, in combination with continuum or molecular-line data, now
enables the determination of fundamental parameters such as mass,
size, and luminosity for each clump.
Description:
This study employs the molecular-line velocities measured by the
MALT90 survey and described by Rathborne et al. (2016PASA...33...30R 2016PASA...33...30R).
MALT90 used the ATLASGAL 870 µm survey to select targets likely to be
dense clumps and used the ATNF Mopra 22 m telescope to map a 4'x4' region
around these targets; the central 3'x3' portion of each map has superior
noise characteristics due to the on-the-fly mapping process employed
by MALT90. The pixel size is 9", the angular resolution is 38", and
the spectral resolution is 0.11 km/s. Additional ATLASGAL targets
falling within the mapped regions were added to our source list: in a
total of 2014 MALT90 maps, we identified 3246 ATLASGAL targets.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 136 1905 Results of the kinematic distance analysis
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See also:
J/ApJS/197/25 : MALT90 pilot survey (Foster+, 2011)
J/ApJ/777/157 : 90GHz obs. of high-mass star-forming regions (Hoq+, 2013)
J/ApJ/815/130 : High-mass molecular clumps from MALT90 (Guzman+, 2015)
J/ApJ/824/29 : ATLASGAL clumps with IRAS flux and MALT90 data
(Stephens+, 2016)
J/MNRAS/473/1059 : Complete sample of Galactic clump properties
(Urquhart+, 2018)
http://malt90.bu.edu/ : MALT90 home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- --- [AGAL]
5- 20 A16 --- AGAL Clump name (AGAL LLL.lll+BB.bbb)
22- 28 F7.3 deg GLON [299.597/349.997] Galactic longitude
30- 35 F6.3 deg GLAT [-1.157/1.314] Galactic latitude
37- 43 F7.2 km/s RV [-137.64/35.56] Radial velocity
45- 51 F7.2 km/s TV [-169.7/-27.91] Tangent velocity
53- 57 F5.2 kpc Rgal [2.19/15.51] Galactocentric radius
59- 62 F4.2 kpc KDt [4.2/8.37] Kinematic distance to tangent point
64- 68 F5.2 kpc KDn [0.02/7.8]?=-9.99 Near kinematic distance
70- 73 F4.2 kpc b_KDn [0/7.49] Lower boundary range to KDn
75- 79 F5.2 kpc B_KDn [0.11/7.82]?=-9.99 Upper boundary range to KDn
81- 85 F5.2 kpc KDf [4.27/23.8] Far kinematic distance
87- 91 F5.2 kpc b_KDf [4.27/19.94] Lower boundary range to KDf
93- 97 F5.2 kpc B_KDf [4.27/31.23] Upper boundary range to KDf
99-102 F4.2 --- PHISA [0/0.96] Probability of a HISA absoprtion dip
104-110 F7.2 km/s Mabsv [-154.17/199] Minimum velocity of significant
absorption
112-113 I2 --- Dcode [1/24] Analysis process flag (1)
115-116 A2 --- Dflag Kinematic distance ambiguity resolution flag (1)
118 I1 --- Dqual [0/9] Integer flag for near/far ambiguity
resolution (2)
120-124 F5.2 kpc Dbest [0.02/23.8] Best guess for kinematic distance
126-130 F5.2 kpc b_Dbest [0/19.94] Lower boundary range to Dbest
132-136 F5.2 kpc B_Dbest [1/31.23] Upper boundary range to Dbest
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Note (1): Dcode and Dflag are defined as follows:
1 and FO = Velocity is off-sign but possible in rotation model;
KD beyond solar circle;
2 and BT = Velocity is beyond tangent velocity; KDn=KDf=KDt;
11 and N = Low continuum; highish HISA probability, near favored;
12 and F = Low continuum; lowish HISA probability, far favored;
21 and N = Significant continuum; absorption near source velocity,
near favored; single-velocity group;
22 and N = Significant continuum; absorption near source velocity,
near favored; multiple-velocity group, possible confusion;
23 and F = Significant continuum; absorption near tangent velocity,
far favored; single-velocity group;
24 and F = Significant continuum; absorption near tangent velocity,
far favored; multiple-velocity group, possible confusion.
Note (2): From 0 to 9 where a larger value indicating higher confidence in the
reliability of the near/far distance resolution. We consider the
ambiguity resolution for sources with Dqual less than 4 to be dubious.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 13-Jun-2018