J/A+A/632/A58 Physical properties of CHIMPS clumps (Rigby+, 2019)
CHIMPS: physical properties of molecular clumps across the inner Galaxy.
Rigby A.J., Moore T.J.T., Eden D.J., Urquhart J.S., Ragan S.E., Peretto N.,
Plume R., Thompson M.A., Currie M.J., Park G.
<Astron. Astrophys. 632, A58 (2019)>
=2019A&A...632A..58R 2019A&A...632A..58R (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Galactic plane ; Molecular clouds ; Carbon monoxide
Keywords: molecular data - surveys - stars: formation - ISM: molecules -
ISM: structure - Galaxy: structure
Abstract:
The latest generation of high-angular-resolution unbiased Galactic
plane surveys in molecular-gas tracers are enabling the interiors of
molecular clouds to be studied across a range of environments. The CO
Heterodyne Inner Milky Way Plane Survey (CHIMPS) simultaneously mapped
a sector of the inner Galactic plane, within 27.8<l<46.2° and
|b|<0.5°, in 13CO (3-2) and C18O (3-2) at an angular
resolution of 15 arcsec. The combination of the CHIMPS data with
12CO (3-2) data from the CO High Resolution Survey (COHRS) has
enabled us to perform a voxel-by-voxel local-thermodynamic-equilibrium
(LTE) analysis, determining the excitation temperature, optical depth,
and column density of 13CO at each l,b,v position. Distances to
discrete sources identified by FellWalker in the 13CO (3-2) emission
maps were determined, allowing the calculation of numerous physical
properties of the sources, and we present the first source catalogues
in this paper. We find that, in terms of size and density, the CHIMPS
sources represent an intermediate population between large-scale
molecular clouds identified by CO and dense clumps seen in thermal
dust continuum emission, and therefore represent the bulk transition
from the diffuse to the dense phase of molecular gas. We do not find
any significant systematic variations in the masses, column densities,
virial parameters, mean excitation temperature, or the turbulent
pressure over the range of Galactocentric distance probed, but we do
find a shallow increase in the mean volume density with increasing
Galactocentric distance. We find that inter-arm clumps have
significantly narrower linewidths, and lower virial parameters and
excitation temperatures than clumps located in spiral arms. When
considering the most reliable distance-limited subsamples, the largest
variations occur on the clump-to-clump scale, echoing similar recent
studies that suggest that the star-forming process is largely
insensitive to the Galactic-scale environment, at least within the
inner disc.
Description:
The two catalogues detailing the properties of the sources extracted
with FellWalker are made available via CDS. These catalogues contain
1) details of the sources extracted from the 13CO (3-2) data cubes and
2) the derived physical properties of the clumps, after the production
of the LTE-based excitation temperature and column density cubes.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 227 4999 Details of the sources extracted from the
13CO (3-2) data cubes
table1.fits 2880 273 FITS version of table1
table4.dat 370 4999 Derived physical properties of the clumps
table4.fits 2880 394 FITS version of table4
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- CHIMPS Source identifier, CHIMPSNNNN (CHIMPS_ID)
12- 26 A15 --- GAL Galactic designation, GLLL.lll+BB.bbb
(GAL_ID)
28 I1 --- Region Region number (REGION)
30- 33 I4 --- PIdent Clump pixel ID (PIDENT)
35- 48 F14.10 deg GLON Position of the 13CO centroid along l axis
(l_cen)
50- 62 F13.10 deg GLAT Position of the 13CO centroid along b axis
(b_cen)
64- 71 F8.4 km/s V Position of the 13CO centroid along v axis
(v_cen)
73- 86 F14.10 deg GLONp Position of the 13CO peak along l axis
(l_peak)
88-100 F13.10 deg GLATp Position of the 13CO peak along b axis
(b_peak)
102-109 F8.4 km/s Vp Position of the 13CO peak along v axis
(v_peak)
111-122 F12.8 arcsec sigGLON The rms size of the clump along l axis
(sigma_l)
124-135 F12.8 arcsec sigGLAT The rms size of the clump along b axis
(sigma_b)
137-142 F6.4 km/s sigV The rms size of the clump along v axis
(sigma_v)
144-162 F19.5 K Peak13CO The peak 13CO intensity in the clump
(Peak_13CO)
164-174 F11.5 K Sum13CO The sum of the 13CO intensity in the clump
(Sum_13CO) (1)
176-183 F8.5 K PeakC18O The peak C18O intensity in the clump
(Peak_C18O)
185-195 F11.5 K SumC18O The sum of the C18O intensity in the clump
(Sum_C18O) (2)
197-205 F9.5 --- PeakSN The peak S/N in the clump (at 27.4 arcsec)
(Peak_SN)
207-214 F8.5 --- MeanSN The mean S/N in the clump (at 27.4 arcsec)
(Mean_SN)
216-219 I4 --- Npix Total number of pixels in the clump area
(n_pixels)
221-225 I5 --- Nvox Total number of voxels in the clump volume
(n_voxels)
227 I1 --- FlagR [1/3] Reliability flag (Flag_R) (G1)
--------------------------------------------------------------------------------
Note (1): The values listed differ by a factor of 0.5km/s compared to the
similar quantity given in the print version. That version adopts the standard
convention for listing integrated intensities in units of K km/s, whereas the
values in the electronic table have not been multiplied by the 0.5km/s channel
width, and are simply the sum of the clump voxel values in units of K.
Note (2): The sum of C18O voxel values are presented with the same convention
as for the sum of the 13CO voxel values.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- CHIMPS Source identifier, CHIMPSNNNN (CHIMPS_ID)
12- 26 A15 --- GAL Galactic designation, GLLL.lll+BB.bbb
(GAL_ID)
28 I1 --- Region Region number (REGION)
30- 33 I4 --- PIdent Clump pixel ID (PIDENT)
35- 48 F14.10 deg GLON Position of the 13CO centroid along l axis
(l_cen)
50- 62 F13.10 deg GLAT Position of the 13CO centroid along b axis
(b_cen)
64- 71 F8.4 km/s V Position of the 13CO centroid along v axis
(v_cen)
73- 84 F12.8 arcsec sigGLON The rms size of the clump along l axis
(sigma_l)
86- 97 F12.8 arcsec sigGLAT The rms size of the clump along b axis
(sigma_b)
99-104 F6.4 km/s sigV The rms size of the clump along v axis
(sigma_v)
106-111 F6.4 km/s e_sigV Uncertainty on the rms velocity size
(sigmavErr)
113 A1 --- KDA Kinematic distance solution (KDA)
115-118 A4 --- KDAmeth Method used to determine kinematic distance
(KDA_method)
120-126 F7.4 kpc Dist ?=- Heliocentric distance (Dist)
128-133 F6.4 kpc e_Dist ?=- Uncertainty on the heliocentric distance
(Dist_Err)
135-141 F7.4 kpc RGC ?=- Galactocentric distance (R_GC)
143-148 F6.4 kpc e_RGC ?=- Uncertainty on the Galactocentric
distance (RGCErr)
150-153 A4 --- Arm Spiral arm assignment (Arm)
155-176 E22.15 Msun Mass ?=- Clump mass (Mass)
178-199 E22.15 Msun e_Mass ?=- Uncertainty on the clump mass (Mass_Err)
201-207 F7.4 pc Rsig ?=- Intensity-weighted rms radius (R_sig)
209-215 F7.4 pc Req ?=- Equivalent radius (R_eq)
217-238 E22.15 cm-3 nH2 ?=- Mean volume density (nH2)
240-261 E22.15 --- alpha ?=- Virial parameter (alpha)
263-284 E22.15 Msun/pc2 SurfDens ?=- Mean surface density (SurfDens) (1)
286-307 E22.15 K/cm3 Pturb ?=- Mean turbulent (non-thermal) pressure
(P_turb)
309-330 E22.15 K/cm3 Ptherm ?=- Mean thermal pressure (P_therm)
332-353 E22.15 cm-2 N13CO ?=- Mean 13CO column density (N13CO) (2)
355-362 F8.5 K Tex ?=- Mean excitation temperature (T_ex)
364-368 F5.3 --- Tau ?=- Mean 13CO (3-2) optical depth (Tau)
370 I1 --- FlagR [1/3] Reliability flag (Flag_R) (G1)
--------------------------------------------------------------------------------
Note (1): The surface density, which is not listed in the paper, is calculated
by dividing the total mass by π times the square of the equivalent radius.
Note (2): The listed mean 13CO column densities are the mean values of the
voxel distribution, and are therefore independent of the surface density as
calculated for column SurfDens.
--------------------------------------------------------------------------------
Global notes:
Note (G1): Reliability flag as follows:
3 = robust
2 = dubious
1 = poor
--------------------------------------------------------------------------------
Acknowledgements:
Andrew J. Rigby, rigbya(at)cardiff.ac.uk
(End) Andrew J. Rigby [Cardiff Univ.], Patricia Vannier [CDS] 18-Sep-2019