J/ApJ/749/71 Star polarization in the Galactic plane (Pavel+, 2012)
Testing Galactic magnetic field models using near-infrared polarimetry.
Pavel M.D., Clemens D.P., Pinnick A.F.
<Astrophys. J., 749, 71 (2012)>
=2012ApJ...749...71P 2012ApJ...749...71P
ADC_Keywords: Galactic plane ; Polarization ; Photometry, infrared
Keywords: dust - extinction - ISM: magnetic fields - polarization -
radiative transfer
Abstract:
This work combines new observations of NIR starlight linear
polarimetry with previously simulated observations in order to
constrain dynamo models of the Galactic magnetic field. Polarimetric
observations were obtained with the Mimir instrument on the Perkins
Telescope in Flagstaff, AZ, along a line of constant Galactic
longitude (ℓ=150°) with 17 pointings of the 10'x10' field of
view between -75°<b<10°, with more frequent pointings toward
the Galactic midplane. A total of 10962 stars were photometrically
measured and 1116 had usable polarizations. The observed distribution
of polarization position angles with Galactic latitude and the
cumulative distribution function of the measured polarizations are
compared to predicted values. While the predictions lack the effects
of turbulence and are therefore idealized, this comparison allows
significant rejection of A0-type magnetic field models. S0 and
disk-even halo-odd magnetic field geometries are also rejected by the
observations, but at lower significance. New predictions of
spiral-type, axisymmetric magnetic fields, when combined with these
new NIR observations, constrain the Galactic magnetic field spiral
pitch angle to -6°±2°.
Description:
Observations were made with the Mimir instrument in H-band (1.6um)
linear imaging polarimetry mode on the 1.8m Perkins Telescope outside
Flagstaff, AZ, on several nights from 2007 through 2009. A total of
10962 stars were detected in the combined photometric images, of which
332 had significant (P/σP>3) polarization detections, 784 had
"marginal" (1.25<P/σP<3) detections, and 194 had significant
upper limits (P/σP<1.25 and σP<1%). All of these 1310
polarization "targets" are listed in Table 2.
Most of the stars found have complementary NIR photometry from Two
Micron All Sky Survey (2MASS; Skrutskie et al. 2006, Cat. VII/233).
All polarization target coordinates were passed through SIMBAD to
search for previous spectral classifications, but only eight out of
the 1310 polarization targets had entries.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 72 1310 Starlight polarization observations
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/AJ/110/268 : Red and infrared polarimetry in galactic plane (Creese+ 1995)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg GLON Galactic longitude
11- 19 F9.5 deg GLAT Galactic latitude
21- 25 F5.2 % Pol [0/15.1] Polarization percentage (P) in H-band
27- 30 F4.2 % e_Pol [0.05/5] Uncertainty in Pol
32- 37 F6.2 deg GPA [0/180] Galactic position angle
39- 44 F6.2 deg e_GPA [0.5/180] Uncertainty in GPA (1)
46- 51 F6.3 mag Hmag [8.5/16.5]?=0 2MASS H-band magnitude
53 A1 --- u_Hmag [p] p: poor H photometry
54- 58 F5.3 mag e_Hmag ? Uncertainty in Hmag
60- 65 F6.3 mag Ksmag [8.3/15.9]?=0 2MASS Ks-band magnitude
67 A1 --- u_Ksmag [p] p: poor Ks photometry
68- 72 F5.3 mag e_Ksmag ? Uncertainty in Ksmag
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Note (1): An uncertainty of 180.0 indicates an upper limit.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 14-Nov-2013