J/ApJS/95/457 IRAS images of nearby dark clouds (Wood+ 1994)
IRAS images of nearby dark clouds
Wood D.O.S., Myers P.C., Daugherty D.A.
<Astrophys. J. Suppl. Ser. 95, 457 (1994)>
=1994ApJS...95..457W 1994ApJS...95..457W
ADC_Keywords: Infrared sources; Interstellar medium
Keywords: dust, extinction - infrared: ISM: continuum - ISM: molecules
Abstract:
We have investigated ∼100 nearby molecular clouds using the extensive,
all-sky database of IRAS. The clouds in this study cover a wide range
of physical properties including visual extinction, size, mass, degree
of isolation, homogeneity and morphology. IRAS 100 and 60 micrometre
co-added images were used to calculate the 100 micrometre optical
depth of dust in the clouds. These images of dust optical depth
compare very well with 12CO and 13CO observations, and can be
related to H2 column density. From the optical depth images we
locate the edges of dark clouds and the dense cores inside them. We
have identified a total of 43 "IRAS clouds" (regions with Av>2) which
contain a total of 255 "IRAS cores" (regions with Av>4) and we catalog
their physical properties. We find that the clouds are remarkably
filamentary, and that the cores within the clouds are often
distributed along the filaments. The largest cores are usually
connected to other large cores by filaments. We have developed
selection criteria to search the IRAS Point Source Catalog for stars
that are likely to be associated with the clouds and we catalog the
IRAS sources in each cloud or core. Optically visible stars associated
with the clouds have been identified from the Herbig and Bell catalog.
From these data we characterize the physical properties of the clouds
including their star-formation efficiency.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 43 16 Field studied
table3.dat 97 16 *Flat-fielding and background subtraction
table4.dat 82 43 IRAS clouds (Av > 2 mag)
table5.dat 127 261 IRAS cores (Av > 4 mag)
--------------------------------------------------------------------------------
Note on table3.dat : This table list the coordinates of the three points
and flux values that were used to calculate the flat field, and the
position where the background was measured and the flux that was
subtracted from the 100µm and 60µm images.
--------------------------------------------------------------------------------
See also:
II/125 : IRAS catalogue of Point Sources, Version 2.0 (IPAC 1986)
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Field name
10- 11 I2 h RAh Center right ascension (1950)
13- 14 I2 min RAm Center right ascension (1950)
16 A1 --- DE- Center declination sign
17- 18 I2 deg DEd Center declination (1950)
20- 21 I2 arcmin DEm Center declination (1950)
23- 28 F6.2 deg GLON Galactic longitude
30- 35 F6.2 deg GLAT Galactic latitude
37- 39 F3.1 deg Dim1 Dimension
40 A1 --- --- [x]
41- 43 F3.1 deg Dim2 Dimension
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Field name
9- 11 I3 arcmin oRA(1) ? Point 1 R.A. offset (1)
13- 16 I4 arcmin oDE(1) ? Point 1 Dec. offset (1)
18- 23 F6.2 MJy/sr S100(1) ? Point 1 100µm flux (1)
25- 30 F6.2 MJy/sr S60(1) ? Point 1 60µm flux (1)
32- 34 I3 arcmin oRA(2) ? Point 2 R.A. offset (1)
36- 39 I4 arcmin oDE(2) ? Point 2 Dec. offset (1)
41- 46 F6.2 MJy/sr S100(2) ? Point 2 100µm flux (1)
48- 52 F5.2 MJy/sr S60(2) ? Point 2 60µm flux (1)
54- 56 I3 arcmin oRA(3) ? Point 3 R.A. offset (1)
58- 61 I4 arcmin oDE(3) ? Point 3 Dec. offset (1)
63- 68 F6.2 MJy/sr S100(3) ? Point 3 100µm flux (1)
70- 74 F5.2 MJy/sr S60(3) ? Point 3 60µm flux (1)
76- 78 I3 arcmin oRA(b) Background subtraction R.A. offset
80- 82 I3 arcmin oDE(b) Background subtraction Dec. offset
84- 89 F6.2 MJy/sr S100(b) Background subtraction 100µm flux
91- 95 F5.2 MJy/sr S60(b) Background subtraction 60µm flux
--------------------------------------------------------------------------------
Note (1): Blank: no flat field subtraction
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Cloud Cloud name (1)
7- 10 I4 pc Dist Assumed distance to the cloud
12- 13 I2 h RA1h Bottom left field right ascension (1950)
15- 16 I2 min RA1m Bottom left field right ascension (1950)
18- 21 F4.1 s RA1s Bottom left field right ascension (1950)
23 A1 --- DE1- Bottom left field declination sign
24- 25 I2 deg DE1d Bottom left field declination (1950)
27- 28 I2 arcmin DE1m Bottom left field declination (1950)
30- 33 F4.1 arcsec DE1s Bottom left field declination (1950)
35- 36 I2 h RA2h Top right field right ascension (1950)
38- 39 I2 min RA2m Top right field right ascension (1950)
41- 44 F4.1 s RA2s Top right field right ascension (1950)
46 A1 --- DE2- Top right field declination sign
47- 48 I2 deg DE2d Top right field declination (1950)
50- 51 I2 arcmin DE2m Top right field declination (1950)
53- 56 F4.1 arcsec DE2s Top right field declination (1950)
58- 64 F7.2 pc+2 Area Total area of the cloud
66- 68 I3 10-6 tau100 Mean 100µm optical depth τ
70 A1 --- l_MH2 Limit flag on MH2
71- 76 I6 Msun MH2 H2 total mass
78- 82 A5 --- Note Notes (G1)
--------------------------------------------------------------------------------
Note (1): Name of the constellation where the cloud is located followed by
a single letter where A is the most massive cloud we identified in
that constellation, B is the second most massive and so on.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
-------------------------------------------------------------------------------
1- 5 A5 --- Cloud Cloud name (1)
7- 8 I2 --- m_Cloud Core name (1)
10- 11 I2 h RAP.h Peak 100um optical depth right ascension (1950)
13- 14 I2 min RAP.m Peak 100um optical depth right ascension (1950)
16- 19 F4.1 s RAP.s Peak 100um optical depth right ascension (1950)
21 A1 --- DEP.- Peak 100um optical depth declination sign
22- 23 I2 deg DEP.d Peak 100um optical depth declination (1950)
25- 26 I2 arcmin DEP.m Peak 100um optical depth declination (1950)
28- 29 I2 arcsec DEP.s Peak 100um optical depth declination (1950)
30- 35 I6 10-6 tauP Maximal optical depth in the core (in µneper)
37- 39 I3 K TP Dust temperature at the position of tauP
41- 42 I2 h RAh Ellipse right ascension (1950) (2)
44- 45 I2 min RAm Ellipse right ascension (1950) (2)
47- 50 F4.1 s RAs Ellipse right ascension (1950) (2)
52 A1 --- DE- Ellipse declination sign (2)
53- 54 I2 deg DEd Ellipse declination (1950) (2)
56- 57 I2 arcmin DEm Ellipse declination (1950) (2)
59- 60 I2 arcsec DEs [0/60] Ellipse declination (1950) (2)
62- 66 F5.2 pc MajAxis Ellipse major axis (2)
68- 72 F5.2 pc MinAxis Ellipse minor axis (2)
74- 76 I3 deg PA Ellipse position angle (deg E of N) (2)
78- 85 F8.4 pc+2 Area Core area
86 A1 --- l_Mcore Limit flag on Mcore
87- 94 F8.1 Msun Mcore Total mass of the core
96- 99 F4.1 10+21cm-2 N Mean core column density
101-102 I2 --- HD Number of associated stars from HD catalogue
104-105 I2 --- IRAS Numer of IRAS PSC associations
106 A1 --- l_M* Limit flag on M*
107-112 F6.2 Msun M* Total mass of all IRAS stars associated with
the core
113 A1 --- l_L* Limit flag on L*
114-121 F8.1 Lsun L* Total luminosity of all IRAS stars associated
with the core
123-127 A5 --- Note Notes (G1)
--------------------------------------------------------------------------------
Note (1): The name of the core is made from the parent cloud name (table4)
followed by a number where 1 is the most massive core in the cloud,
2 is the next most massive core, and so on.
Note (2): Parameters of an ellipse that fit to each core by eye.
--------------------------------------------------------------------------------
Global Notes:
Note (G1): the numbers have the following meaning:
1 = The cloud is truncated by one or more image edges.
2 = Part or all of the cloud lies in the region of overlap between
two images.
3 = Cloud mass is an upper limit due to significant heating by
embedded stars.
History: Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 25-Mar-1997