J/ApJ/603/584 Polarimetry toward Musca dark cloud (Pereyra+, 2004)
Polarimetry toward the Musca dark cloud. I. The catalog.
Pereyra A., Magalhaes A.M.
<Astrophys. J., 603, 584-594 (2004)>
=2004ApJ...603..584P 2004ApJ...603..584P
ADC_Keywords: Molecular clouds ; Polarization
Keywords: catalogs - ISM: clouds - ISM: magnetic fields - polarization -
ISM: individual (Chamaeleon-Musca Dark Cloud Complex) -
Abstract:
We have used CCD imaging polarimetry to obtain linear polarization
measurements of background stars toward the filamentary Musca dark
cloud. We present a catalog of 2497 objects with polarization
signal-to-noise ratio larger than 5. This allows us to build
polarization maps to infer the detailed geometry of the local magnetic
field. We show composite polarization maps along the cloud and explore
general correlations of the polarimetric data with the morphology of
the region. We find the overall field to be strikingly aligned with
the projected small axis of the filamentary cloud. We detect a lower
limit for the polarization across the cloud of ∼2%, with an enhanced
polarization of 6%-7% in the central region. We find evidence that the
polarization pattern is altered in the inner regions, those associated
with higher extinction.
Description:
The observations were made using IAGPOL, the IAG-USP imaging
polarimeter, at the f/13.5 Cassegrain focus of the 0.6m IAG
telescope at the Observatorio do Pico dos Dias, operated by the
Laboratorio Nacional de Astrofisica, Brazil. We obtained linear
polarization data for 35 CCD fields along the Musca dark cloud
obtained in runs in 1996 April and 1997 April through a standard V
filter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 45 35 Field CCD positions
table3.dat 59 2555 Field data
notes.dat 63 116 Notes
table5.dat 27 35 Analysis of 35 fields in Musca dark cloud
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See also:
J/A+AS/93/373 : uvby-beta photometry in SA 203 (Franco 1992)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- FNum Field number
4- 5 I2 h RAh Right ascension (J2000.0)
7- 8 I2 min RAm Right ascension (J2000.0)
10- 14 F5.2 s RAs Right ascension (J2000.0)
16 A1 --- DE- Declination sign (2000.0)
17- 18 I2 deg DEd Declination (2000.0)
20- 21 I2 arcmin DEm Declination (2000.0)
23- 27 F5.2 arcsec DEs Declination (2000.0)
29- 30 I2 --- Run Run number
32- 45 A14 --- Region Region
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- FNum Field number (1)
4- 6 I3 --- ID Object identification number (1)
8- 10 A3 --- n_ID Note detailled in file "notes.dat"
12- 13 I2 h RAh Hour of Right Ascension (J2000)
15- 16 I2 min RAm Minute of Right Ascension (J2000)
18- 22 F5.2 s RAs Second of Right Ascension (J2000)
24 A1 --- DE- Sign of the Declination (J2000)
25- 26 I2 deg DEd Degree of Declination (J2000)
28- 29 I2 arcmin DEm Arcminute of Declination (J2000)
31- 35 F5.2 arcsec DEs Arcsecond of Declination (J2000)
37- 41 F5.3 % PolV Percent linear polarization in the V band
43- 47 F5.3 % e_PolV Measured error in PolV (2)
49- 53 F5.1 deg PA Polarization position angle (3)
55- 59 F5.2 mag Vmag The V band magnitude
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Note (1): Objects are identified in Simbad as [PM2004] FNum ID
Note (2): The latter are obtained from the residuals of the observations at
each waveplate position angle (ψi) with respect to the expected
cos(4ψi) curve; they are consistent with the photon noise errors
(Magalhaes, Benedetti & Roland, 1984, ASP Conf. Ser. 97, 118).
Note (3): Measured from North to East.
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Byte-by-byte Description of file: notes.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Note Note designation
5- 64 A60 --- Text Text of the note
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- FNum Field number
4- 5 I2 --- N Number of objects with Pol/e_Pol>10 in the field
7- 10 F4.2 % Pol Mean polarization value
12- 15 F4.2 % e_Pol Associated error to Pol
17- 22 F6.2 deg PA Mean polarization position angle
24- 27 F4.2 deg e_PA Associated error to PA
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 07-May-2004