J/ApJ/783/1 VRI and H polarization toward Sh 2-29 (Santos+, 2014)
Optical/Near-infrared polarization survey of Sh 2-29: magnetic fields, dense
cloud fragmentations, and anomalous dust grain sizes.
Santos F.P., Franco G.A.P., Roman-Lopes A., Reis W., Roman-Zuniga C.G.
<Astrophys. J., 783, 1 (2014)>
=2014ApJ...783....1S 2014ApJ...783....1S (SIMBAD/NED BibCode)
ADC_Keywords: Interstellar medium ; H II regions ; Polarization
Keywords: dust, extinction - evolution - H II region -
ISM: individual(Sh 2-29) - ISM: magnetic fields - stars: formation -
techniques: polarimetric
Abstract:
Sh 2-29 is a conspicuous star-forming region marked by the presence of
massive embedded stars as well as several notable interstellar
structures. In this research, our goals were to determine the role of
magnetic fields and to study the size distribution of interstellar
dust particles within this turbulent environment. We have used a set
of optical and near-infrared polarimetric data obtained at OPD/LNA
(Brazil) and CTIO (Chile), correlated with extinction maps, Two Micron
All Sky Survey data, and images from the Digitized Sky Survey and
Spitzer. The region's most striking feature is a swept out
interstellar cavity whose polarimetric maps indicate that magnetic
field lines were dragged outward, piling up along its borders. This
led to a higher magnetic strength value (~400µG) and an
abrupt increase in polarization degree, probably due to an enhancement
in alignment efficiency. Furthermore, dense cloud fragmentations with
peak AV between 20 and 37mag were probably triggered by its
expansion. The presence of 24µm point-like sources indicates
possible newborn stars inside this dense environment. A statistical
analysis of the angular dispersion function revealed areas where field
lines are aligned in a well-ordered pattern, seemingly due to
compression effects from the HII region expansion. Finally, Serkowski
function fits were used to study the ratio of the total-to-selective
extinction, revealing a dual population of anomalous grain particle
sizes. This trend suggests that both effects of coagulation and
fragmentation of interstellar grains are present in the region.
Description:
The linear polarization data used in this work are a combination of
observations conducted at the Cerro Tololo Interamerican Observatory
(CTIO, Chile), using the 0.9m telescope, and also at the Observatorio
Pico dos Dias/Laboratorio Nacional de Astrofisica (OPD/LNA, Brazil),
using both the 0.6m and the 1.6m telescopes. The optical data (V, R,
and I Johnson-Cousins bands) were obtained with the CTIO-0.9m and
OPD-0.6m telescopes, while the near-IR data (H band) were collected
with the OPD-1.6m telescope.
The content and organization of the polarization values set is shown
in Table1.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 117 5254 Polarimetric data set for Sh 2-29 at optical
(V, R, I) and near-IR bands (H)
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See also:
VII/20 : Catalogue of HII Regions (Sharpless 1959)
J/ApJ/751/138 : VRIJHK photometry of IRAS 09149-4743 region (Santos+, 2012)
J/ApJ/728/104 : Optical polarization for 878 Hipparcos stars (Santos+ 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star [1/5254] Running sequence number of the star
6- 7 I2 h RAh Hour of Right Ascension (J2000)
9- 10 I2 min RAm Minute of Right Ascension (J2000)
12- 16 F5.2 s RAs Second of Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Degree of Declination (J2000)
22- 23 I2 arcmin DEm Arcminute of Declination (J2000)
25- 28 F4.1 arcsec DEs Arcsecond of Declination (J2000)
30- 34 F5.2 % PV [0.2/16]? The V band degree of polarization (1)
36- 39 F4.2 % e_PV [0.04/3.7]? Uncertainty in PV (1)
41- 45 F5.1 deg PAV [0.4/172.1]? The V band polarization angle (1)
47- 50 F4.1 deg e_PAV [2.5/14.5]? Uncertainty in PAV (1)
52- 56 F5.2 % PR [0.25/46]? The R Band degree of polarization (1)
58- 62 F5.2 % e_PR [0.01/12.75]? Uncertainty in PR (1)
64- 68 F5.1 deg PAR [0.2/180]? The R band polarization angle (1)
70- 73 F4.1 deg e_PAR [0.5/14.3]? Uncertainty in PAR (1)
75- 79 F5.2 % PI [0.1/17.9]? The I Band degree of polarization (1)
81- 84 F4.2 % e_PI [0.06/5.8]? Uncertainty in PI (1)
86- 90 F5.1 deg PAI [0.2/179.8]? The I band polarization angle (1)
92- 95 F4.1 deg e_PAI [1.8/14.2]? Uncertainty in PAI (1)
97-101 F5.2 % PH [0.1/13.8]? The H Band degree of polarization (1)
103-106 F4.2 % e_PH [0.01/5.2]? Uncertainty in PH (1)
108-112 F5.1 deg PAH [0.1/180]? The H band polarization angle (1)
114-117 F4.1 deg e_PAH [6/15.5]? Uncertainty in PAH (1)
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Note (1): Blank values indicates undeteced sources or objects excluded from the
sample.
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History:
From electronic version of the journal
(End) Prepared by [AAS]; Sylvain Guehenneux [CDS] 23-Mar-2016