J/ApJ/728/104 Optical polarization for 878 Hipparcos stars (Santos+ 2011)
Optical polarization mapping toward the interface between the Local Cavity and
Loop I.
Santos F.P., Corradi W., Reis W.
<Astrophys. J., 728, 104 (2011)>
=2011ApJ...728..104S 2011ApJ...728..104S
ADC_Keywords: Polarization ; Interstellar medium ; Stars, nearby
Keywords: dust, extinction - ISM: individual objects (Local Cavity, Loop I) -
ISM: magnetic fields - methods: data analysis -
techniques: polarimetric
Abstract:
The Sun is located inside an extremely low density and quite irregular
volume of the interstellar medium, known as the Local Cavity (LC). It
has been widely believed that some kind of interaction could be
occurring between the LC and Loop I, a nearby superbubble seen in the
direction of the Galactic center. As a result of such interaction, a
wall of neutral and dense material, surrounded by a ring-shaped
feature, would be formed at the interaction zone. Evidence of this
structure was previously observed by analyzing the soft X-ray emission
in the direction of Loop I. Our goal is to investigate the distance of
the proposed annular region and map the geometry of the Galactic
magnetic field in these directions. On that account, we have conducted
an optical polarization survey of 878 stars from the Hipparcos
catalog. Our results suggest that the structure is highly twisted and
fragmented, showing very discrepant distances along the annular
region: ∼100pc on the left side and 250pc on the right side,
independently confirming the indication from a previous photometric
analysis. In addition, the polarization vectors' orientation pattern
along the ring also shows a widely different behavior toward both
sides of the studied feature, running parallel to the ring contour on
the left side and showing no relation to its direction on the right
side. Altogether, these evidences suggest a highly irregular nature,
casting some doubt on the existence of a unique large-scale ring-like
structure.
Description:
The polarimetric data used in this work were collected at OPD
(Observatorio Pico dos Dias, LNA/MCT, Brazil) during 63 nights
distributed between 2007 August and 2009 February. We have used both
the 60cm and 1.6m telescopes, equipped with an imaging polarimeter
attached to a specially adapted CCD camera.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 50 878 Polarimetric data obtained at OPD
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See also:
J/MNRAS/405/2570 : Linear polarization of nearby bright stars (Bailey+, 2010)
J/A+A/346/955 : Magnetic field around the Local Bubble (Leroy, 1999)
J/A+AS/101/551 : Optical polarization of 1000 stars (Leroy 1993)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HIP Hipparcos identifier
8- 14 F7.3 deg GLON Galactic longitude
16- 22 F7.3 deg GLAT Galactic latitude
24- 26 I3 pc Dist Hipparcos trigonometric distance
28- 32 F5.3 % PV Polarization degree in V band
34- 38 F5.3 % e_PV Uncertainty in PV
40- 44 F5.1 deg PA Galactic polarization angle
46- 50 F5.1 deg e_PA Uncertainty in PA
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 06-Sep-2012