J/ApJS/144/47 Outer galaxy molecular cloud catalog (Brunt+, 2003)
An outer galaxy molecular cloud catalog.
Brunt C.M., Kerton C.R., Pomerleau C.
<Astrophys. J. Suppl. Ser. 144, 47 (2003)>
=2003ApJS..144...47B 2003ApJS..144...47B
ADC_Keywords: Interstellar medium ; Molecular clouds ; Radio lines ; Morphology
Keywords: catalogs - ISM: clouds - ISM: molecules - methods: miscellaneous -
radio lines: ISM
Description:
The Five College Radio Astronomy Observatory (FCRAO) Outer Galaxy
Survey (OGS) of 12CO(J=1-0) emission was carried out between 1994May
and 1997September, using the FCRAO focal plane array QUARRY (Erickson
et al. 1992, IEEE Trans. 40, 1), and initially described by Heyer et
al. (1998ApJS..115..241H 1998ApJS..115..241H). The OGS covers the Galactic area
102.5<l<141.5, -3<b<54, and the velocity range -152km/s<vlsr<40km/s,
at 45'' spatial resolution sampled every 50.22'', and 0.98km/s
velocity resolution (1.39km/s for l<106) sampled every 0.81km/s. The
typical sensitivity of the OGS at these resolutions is 0.6K (T*R
temperature scale).
The catalog was generated in a two-phase object identification
procedure. The first phase consists of grouping pixels into contiguous
structures above a radiation temperature threshold of 0.8K; the second
phase decomposes the first-phase objects by an enhanced version of the
CLUMPFIND algorithm, using dynamic thresholding, and again with a
threshold of 0.8K used for discrimination.
Basic attributes of the clouds (coordinates, bounding boxes,
integrated intensities, peak observed temperatures) are tabulated in
the catalog. A two-dimensional elliptical Gaussian is fitted to the
velocity- integrated map of each cloud; the major and minor axis sizes
and major axis position angles thus derived are included in the
catalog. To the spatially integrated emission line of each cloud, a
Gaussian profile is fitted to measure the global linewidth. Model
Gaussian clouds, truncated at 0.8K, are examined to determine the
effects of biases on measured quantities, induced by truncation.
Coupled with detailed analysis of the catalogued clouds, statistical
corrections for the effects of truncation on measured sizes,
linewidths, and integrated intensities are derived and applied, along
with corrections for the effects of finite resolution on the measured
attributes. The catalogued emission accounts for 76.4% of the total
emission in the Outer Galaxy Survey. The deficit is shown to arise
mainly from low-intensity emission on the periphery of larger objects,
rather than from a large number of small and/or low-intensity
features.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 211 14592 Properties of objects decomposed from the
Five College Radio Astronomy Observatory
12CO(J=1-0) Survey of the Outer Galaxy
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See also:
B/cgps : Canadian Galactic Plane Survey (CGPS) (CADC, 2001-)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- [BKP2003] Cloud Identification number (1)
7- 10 I4 --- OIN Cloud ID number (phase 1) (2)
12- 16 I5 --- Npix Number of pixels in cloud
18- 24 F7.3 deg GLON Galactic Longitude of cloud centroid (3)
26- 31 F6.3 deg GLAT Galactic Latitude of cloud centroid (3)
33- 39 F7.2 km/s Vlsr LSR velocity of cloud centroid (4)
41- 47 F7.3 deg GLONp Galactic Longitude of cloud peak
temperature (5)
49- 54 F6.3 deg GLATp Galactic Latitude of cloud peak
temperature (5)
56- 62 F7.2 km/s Vlsrp LSR velocity of cloud peak temperature (5)
64- 70 F7.3 deg GLONm Minimum Galactic Longitude of cloud (6)
72- 78 F7.3 deg GLONM Maximum Galactic Longitude of cloud (6)
80- 85 F6.3 deg GLATm Minimum Galactic Latitude of cloud (6)
87- 92 F6.3 deg GLATM Maximum Galactic Latitude of cloud (6)
94-100 F7.2 km/s Vlsrm Minimum LSR velocity of cloud (6)
102-108 F7.2 km/s VlsrM Maximum LSR velocity of cloud (6)
110-114 F5.2 K Tpeak Cloud peak temperature (7)
116-123 F8.2 K.km/s Int Cloud integrated intensity (8)
125-129 F5.2 arcmin s1 Raw fitted major axis diameter (9)
131-135 F5.2 arcmin s2 Raw fitted minor axis diameter (9)
137-141 F5.1 deg phi Raw fitted major axis position angle (10)
143-147 F5.2 km/s u Raw fitted linewidth (11)
149-156 F8.2 K.km/s Ic Corrected integrated intensity (12)
158-162 F5.2 arcmin s1cb Corrected major axis diameter (13)
164-168 F5.2 arcmin s2cb Corrected minor axis diameter (13)
170-174 F5.2 km/s ucb Corrected linewidth (14)
176-183 F8.2 K.km/s e_Ic Error on Ic (15)
185-189 F5.2 arcmin e_s1cb Error on s1cb (15)
191-195 F5.2 arcmin e_s2cb Error on s2cb (15)
197-201 F5.2 km/s e_ucb Error on ucb (15)
203-207 I5 --- Ns Number of spatial pixels in cloud (16)
209-211 I3 --- Flag Flag value (17)
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Note (1): Clouds with Subobject Identification Number (SIN) = 1,2,3
have been removed from the catalog, as they were determined to be
artifactual in nature.
Note (2): Clouds with a common OIN were contiguous after simple
thresholding above T=0.8K; OIN=423 does not exist.
Note (3): For clouds that are fitted with a 2D elliptical Gaussian, the
fitted central coordinates are recorded. If no fit was possible, the
temperature-weighted centroid coordinates are recorded (see Note 8).
Note (4): For clouds with fitted Gaussian line profiles, the fitted
central velocity is recorded. If no fit was possible, the
temperature-weighted centroid velocity is recorded (see Note 10).
Note (5): No fitting of the coordinates of the peak temperature position
was carried out; thus these coordinates are quantized on the data grid.
Note (6): The boundaries of the clouds are extended by 1/2 pixel
(50.22/2arcsec) from the pixel-centered coordinates of the cloud edges
in each direction.
Note (7): No fitting of peak temperature value was carried out.
Note (8): Summation over all temperature values * spectroscopic channel
width (0.82446km/s).
Note (9): 2D elliptical gaussian fits were attempted for all clouds with
Ns≥5 pixels. An entry of zero for the major and minor axis diameters
indicates that a fit was not attempted or the fit failed to converge.
Note (10): The reference point for position angles (phi=0) points along a
line of constant Galactic latitude towards lower Galactic longitude;
phi is measured clockwise from this point, and takes values
0≤phi≤180.
Note (11): A gaussian fit was attempted for all clouds defined over
at least 3 spectroscopic channels. An entry of zero for the linewidth
indicates that a fit was not attempted or the fit failed to converge.
Note (12): Integrated intensity corrected for the effects of truncation
at T=0.8K, based upon analysis of global signal recovery fractions.
The corrected values are derived only for clouds with Tp≥1.6K (see
discussion in paper).
Note (13): Major and minor axis diameters corrected for the effects of
truncation at T=0.8K and for the effects of beam-smearing. The
corrected values are derived only for clouds with Tp≥1.6K (see paper).
Note (14): Linewidth corrected for the effects of truncation at T=0.8K
and for the effects of instrumental broadening. The corrected values
are derived only for clouds with Tp≥1.6K (see paper).
Note (15): For the definition of these error estimates, see paper.
Note (16): Ns is the number of spatial pixels over which the
velocity-integrated cloud is defined. (Ns/pi)0.5 may be used as an
alternative definition of cloud 'size'. The pixel size is 0.837arcmin.
Note (17): Flags are multiplicative if non-zero.
(e.g. flag=35 means that flag=5 AND flag=7)
The bandpass ends are at +40km/s (+ve) and -152km/s (-ve).
0 : no flag
2 : Cloud adjoins longitude boundary of the data
3 : Cloud adjoins latitude boundary of the data
5 : Cloud adjoins velocity boundary of the data
7 : Possible artifacts in the spectral channels near the positive
VLSR bandpass end
11 : Possible artifacts in the spectral channels near the negative
VLSR bandpass end
13 : Anomalous spectral line intensities compared to the surrounding
emission; the affected block is rectangular in shape and
coincident with the FCRAO array pointing position
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 06-Feb-2003