J/ApJ/665/369 Photopolarimetry of Southern Coalsack stars (Andersson+, 2007)
Observational constraints on interstellar grain alignment.
Andersson B.-G., Potter S.B.
<Astrophys. J., 665, 369-389 (2007)>
=2007ApJ...665..369A 2007ApJ...665..369A
ADC_Keywords: Interstellar medium ; Molecular clouds ; Photometry ; Polarization
Keywords: dust, extinction - ISM: individual (Southern Coalsack, Chamaeleon I,
Musca, rho Ophiuchus, R CrA, Taurus) - polarization
Abstract:
We present new multicolor photopolarimetry of stars behind the
Southern Coalsack. Analyzed together with multiband polarization data
from the literature, probing the Chamaeleon I, Musca, rho Opiuchus,
R CrA, and Taurus clouds, we show that the wavelength of maximum
polarization (λmax) is linearly correlated with the radiation
environment of the grains. Using far-infrared emission data, we show
that the large scatter seen in previous studies of λmax as a
function of Av is primarily due to line-of-sight effects causing some
Av measurements to not be a good tracer of the extinction (radiation
field strength) seen by the grains being probed.
Description:
We used the University of Cape Town Polarimeter on the 1.9m telescopes
of the South African Astronomical Observatory (SAAO) during 2005 April
6-8 and 13 to perform multiband observations of interstellar
polarization of stars background to the Southern Coalsack.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 136 15 Coalsack Polarimetry Results
table4.dat 129 141 Stars with data from archives and the literature
table5.dat 55 133 Polarization curve fits for stars from literature
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Star Star name
15- 18 F4.2 % p(U) Polarisation in U band
21- 24 F4.2 % e_p(U) Mean error on p(U)
27- 31 F5.1 deg pa(U) Position angle of U-band polarisation
34- 36 F3.1 deg e_pa(U) Mean error on pa(U)
40- 43 F4.2 % p(B) Polarisation in B band
46- 49 F4.2 % e_p(B) Mean error on p(B)
52- 56 F5.1 deg pa(B) Position angle of B-band polarisation
59- 61 F3.1 deg e_pa(B) Mean error on pa(B)
65- 68 F4.2 % p(V) Polarisation in V band
71- 74 F4.2 % e_p(V) Mean error on p(V)
77- 81 F5.1 deg pa(V) Position angle of V-band polarisation
84- 86 F3.1 deg e_pa(V) Mean error on pa(V)
90- 93 F4.2 % p(R) Polarisation in R band
96- 99 F4.2 % e_p(R) Mean error on p(R)
102-106 F5.1 deg pa(R) Position angle of R-band polarisation
109-111 F3.1 deg e_pa(R) Mean error on pa(R)
115-118 F4.2 % p(I) Polarisation in U band
121-124 F4.2 % e_p(I) Mean error on p(I)
127-131 F5.1 deg pa(I) Position angle of I-band polarisation
134-136 F3.1 deg e_pa(I) Mean error on pa(I)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Cloud Cloud name (1)
12- 22 A11 --- Star Star name
24- 36 A13 --- SpType MK Spectral Classification (2)
38- 43 F6.3 mag Vmag ? The V band magnitude
45- 48 F4.2 mag e_Vmag ? Uncertainty in Vmag
50- 55 F6.3 mag B-V Observed (B-V) color index
57- 60 F4.2 mag e_B-V Uncertainty in B-V
62- 66 F5.2 mag (B-V)0 ? Intrinsic (B-V) color index
68- 71 F4.2 mag e_(B-V)0 ? Uncertainty in (B-V)0
73- 78 F6.3 mag V-K ? Observed (V-K) color index
80- 84 F5.3 mag e_V-K ? Uncertainty in V-K
86- 90 F5.2 mag (V-K)0 ? Intrinsic (V-K) color index
92- 95 F4.2 mag e_(V-K)0 ? Uncertainty in (V-K)0
97-100 F4.2 --- Rv ? Ratio of total-to-selective extinction
102-105 F4.2 --- e_Rv ? Uncertainty in Rv
107 A1 --- f_Rv [d] Rv ignored in the analysis (3)
109-112 F4.2 mag Av ? The V band extinction
114-117 F4.2 mag e_Av ? Uncertainty in Av
119-127 A9 --- r_SpType Reference for SpType (4)
129 A1 --- S? Screened out? (5)
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Note (1): Based on comparisons of Figure 1 in Arnal et al.
(1993MNRAS.265....1A 1993MNRAS.265....1A) with the Aladin tool (Bonnarel et al.,
2000A&AS..143...33B 2000A&AS..143...33B) we have made the following target identifications
in Musca from Arnal et al. (1993MNRAS.265....1A 1993MNRAS.265....1A) (AMZ):
AMZ16 = CD-71 836 (= [AMR93] 16)
AMZ18 = CD-71 832 (= [AMR93] 18)
AMZ28 = CD-70 925 (= [AMR93] 28)
AMZ41 = CPD-69 1677 (= [AMR93] 41)
AMZ45 = CD-69 1024 (= [AMR93] 45)
Note (2): Estimated uncertainties given in parenthesis.
Note (3): d = The derived value is unphysical and is ignored in the analysis.
Note (4): Reference for SpType as follows:
KDH94 = Kenyon et al. (1994AJ....108..251K 1994AJ....108..251K)
M68 = Metreveli (1968AbaOB..38...93M 1968AbaOB..38...93M)
MSS = Houk & Cowley (1975, Cat. III/31)
N95 = Nesterov et al. (1995, Cat. III/182)
SSS80 = Slutskij et al. (1980SvAL....6..397S 1980SvAL....6..397S)
SM80 = Straizys & Meistas (1980AcA....30..541S 1980AcA....30..541S)
SCH85 = Straizys et al. (1985Ap&SS.112..251S 1985Ap&SS.112..251S)
U85 = Ungerer et al. (1985A&A...146..123U 1985A&A...146..123U)
VR84 = Vrba & Rydgren (1984ApJ...283..123V 1984ApJ...283..123V)
VR85 = Vrba & Rydgren (1985AJ.....90.1490V 1985AJ.....90.1490V)
VR93 = Vrba et al. (1993AJ....105.1010V 1993AJ....105.1010V)
W87 = Whittet et al. (1987MNRAS.224..497W 1987MNRAS.224..497W)
W01 = Whittet et al. (2001ApJ...547..872W 2001ApJ...547..872W)
Y = Yale observatory (1997)
Note (5): Sightlines that are screened out in the Hipparcos field star
based analysis. (see section 4.2)
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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- 10 A10 --- Cloud Cloud name
12- 22 A11 --- Star Star name (1)
24- 28 F5.2 % Pmax Maximum polarization
30- 33 F4.2 % e_Pmax Uncertainty in Pmax
35- 39 F5.3 um Wmax Wavelength of maximum polarization
41- 45 F5.3 um e_Wmax Uncertainty in Wmax
47- 50 F4.2 --- K ? Interstellar polarization K parameter (2)
52- 55 F4.2 --- e_K ? Uncertainty in K
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Note (1): For HD 107875 in Musca Arnal et al. (1993MNRAS.265....1A 1993MNRAS.265....1A) report
λmax=0.641±0.009. This is only case of a significant
discrepancy in λmax for our polarization curve fits compared
to the literature. This sightline is excluded from the analysis.
Note (2): Serkowski's K which relates the polarisation to wavelength:
p/pmax = exp[-K .ln2(λmax/λ)]
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History:
* 05-Sep-2009: From electronic version of the journal
* 16-Nov-2009: added table2.
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 05-Sep-2009