J/A+A/579/A91 ATLASGAL inner Galaxy massive cold dust clumps (Wienen+, 2015)
ATLASGAL - Kinematic distances and the dense gas mass distribution of the
inner Galaxy.
Wienen M., Wyrowski F., Menten K.M., Urquhart J.S., Csengeri T.,
Walmsley C.M., Bontemps S., Russeil D., Bronfman L., Koribalski B.S.,
Schuller F.
<Astron. Astrophys., 579, A91-91 (2015)>
=2015A&A...579A..91W 2015A&A...579A..91W (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Milky Way ; Associations, stellar ; Stars, distances ;
Velocity dispersion
Keywords: surveys - submillimeter: general - radio lines: ISM - ISM: molecules -
ISM: kinematics and dynamics - stars: formation
Abstract:
The formation of high mass stars and clusters occurs in giant
molecular clouds. Objects in evolved stages of massive star formation
such as protostars, hot molecular cores, and ultracompact HII regions
have been studied in more detail than earlier, colder objects. Further
progress thus requires the analysis of the time before massive
protostellar objects can be probed by their infrared emission. With
this in mind, the APEX Telescope Large Area Survey of the whole inner
Galactic plane at 870µm (ATLASGAL) has been carried out to provide
a global view of cold dust and star formation at submillimetre
wavelengths. We derive kinematic distances to a large sample of
massive cold dust clumps from their measured line velocities. We
estimate masses and sizes of ATLASGAL sources, for which the kinematic
distance ambiguity is resolved. The ATLASGAL sample is divided into
groups of sources, which are located close together, mostly within a
radius of 2pc, and have velocities in a similar range with a median
velocity dispersion of ∼1km/s. We use NH3, N2H+, and CS
velocities to calculate near and far kinematic distances to those
groups. We obtain 296 groups of ATLASGAL sources in the first quadrant
and 393 groups in the fourth quadrant, which are coherent in space and
velocity. We analyse HI self-absorption and HI absorption to resolve
the kinematic distance ambiguity to 689 complexes of submm clumps.
They are associated with 12CO emission probing large-scale structure
and 13CO (1-0) line as well as the 870µm dust continuum on a
smaller scale. We obtain a scale height of ∼28±2pc and displacement
below the Galactic midplane of ~-7±1pc. Within distances from 2 to
18kpc ATLASGAL clumps have a broad range of gas masses with a median
of 1050M☉ as well as a wide distribution of radii with a median
of 0.4pc. Their distribution in galactocentric radii is correlated
with spiral arms. Using a statistically significant ATLASGAL sample we
derive a power-law exponent of -2.2±0.1 of the clump mass function.
This is consistent with the slope derived for clusters and with that
of the stellar initial mass function. Examining the power-law index
for different galactocentric distances and various source samples
shows that it is independent of environment and evolutionary phase.
Fitting the mass-size relationship by a power law gives a slope of
1.76±0.01 for cold sources such as IRDCs and warm clumps associated
with HII regions.
Description:
ATLASGAL clumps with observed radial velocities are divided into
groups of sources, which are coherent according to their location and
kinematics. We calculate kinematic distances to 689 groups of submm
clumps and distinguish between near and far distances using HI
self-absorption and HI absorption toward sources with strong radio
continuum emission. For each complex we give the group number, the
mean position, number of sources per group, the mean velocity, the
velocity dispersion, and the size of the groups. No velocity
dispersion and size are calculated for sources, which are not
associated with another ATLASGAL source within 0.3 deg and 10km/s. If
the number of sources is 0 in a complex, there were initially
velocities of sources, but the complex is not taken into account
because of missing HI data and no distance could be determined. In
addition, for each source within the groups, we list the ATLASGAL name
associated with the measurement, the observation name, the LSR
velocity, the KDA solution, the kinematic distance calculated from the
LSR velocity of each source, the distance of the group, in which the
clump is located, its errors, the logarithm of the gas mass, radius
and the group number with "n" for sources in the first quadrant and
"s" for clumps in the fourth quadrant. Some sources were observed, but
are not associated with an ATLASGAL source, because they have ammonia
spectra with low S/N ratio. To describe the KDA solution we denote the
near distance by "n", the far distance by "f" and the tangent point by
"t". The distance of the group is computed from the mean of all source
coordinates and velocities inside the group. To avoid any influence of
peculiar motion, we recommend the distance of the group, which is used
to determine gas masses and sizes. A few sources have velocities
inconsistent with the rotation model and we do not assign a distance
to them. Clumps with velocities close to 0km/s have large errors in
the distance. Because these sources are located at the near distance,
we give 0kpc and do not take them into account for further analysis
in the paper.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 45 709 Properties of complexes
table3.dat 95 1814 Kinematic distances, masses and radii of
ATLASGAL sources with observed radial velocities
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See also:
J/A+A/544/A146 : ATLASGAL cold high-mass clumps with NH3 (Wienen+, 2012)
J/A+A/549/A45 : ATLASGAL Compact Source Catalog: 330<l<21 (Contreras+, 2013)
J/A+A/568/A41 : ATLASGAL Compact Source Catalog: 280<l<60 (Urquhart+, 2014)
J/A+A/570/A65 : ATLASGAL massive clumps CO depletion (Giannetti+, 2014)
J/MNRAS/443/1555 : ATLASGAL massive star forming clumps sample (Urquhart+ 2014)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Complex Complex number
7- 14 F8.4 deg GLON Mean of Galactic longitude of sources in
the complex
17- 23 F7.4 deg GLAT Mean of Galactic latitude of clumps in
the complex
25- 27 I3 --- N Number of sources per complex
30- 35 F6.1 km/s <Vel> Mean of velocities of sources in the complex
38- 40 F3.1 km/s sigma ?=- Velocity dispersion of clumps in the complex
43- 45 I3 pc Size ?=- Size of the complex
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- ATLASGAL ATLASGAL name associated with the measurement
21- 38 A18 --- Source Observation name
41- 47 F7.2 km/s Vlsr LSR velocity
50 A1 --- KDA [nft] Solution of the kinematic distance
ambiguity (1)
53- 57 F5.2 kpc Dist ?=- Kinematic distance calculated from
the LSR velocity of each source
60- 64 F5.2 kpc Distcplx ?=- Distance of the complex computed from the
mean of all source coordinates and
velocities inside the complex
68- 71 F4.2 kpc e_Distcplx ?=- Error in the distance of the complex
(lower value)
73- 77 F5.2 kpc E_Distcplx ?=- Error in the distance of the complex
(upper value)
79- 83 F5.2 [Msun] log(Mgas) ?=- logarithm of the gas mass
85- 89 F5.2 pc Rad ?=- Radius
92- 95 A4 --- Complex Name of complex, where the source is located
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Note (1): kinematic distance ambiguity flag as follows:
n = for near distance
f = for far distance
t = for tangent point
--------------------------------------------------------------------------------
Acknowledgements:
Marion Wienen, mwienen(at)mpifr-bonn.mpg.de
References:
Schuller et al., 2009A&A...504..415S 2009A&A...504..415S
ATLASGAL-The APEX telescope large area survey of the galaxy at 870 micron
Contreras et al., 2013A&A...549A..45C 2013A&A...549A..45C, Cat. J/A+A/549/A45,
ATLASGAL-compact source catalogue: 330 deg < l < 21 deg
Urquhart et al., 2014A&A...568A..41U 2014A&A...568A..41U, Cat. J/A+A/568/A41,
ATLASGAL-Complete compact source catalogue: 280 deg < l < 60 deg
(End) Marion Wienen [MPIfR, Bonn], Patricia Vannier [CDS] 04-Feb-2016