Optical/near-infrared polarization survey of Sh 2-29: Magnetic fields, dense cloud fragmentations, and anomalous dust grain sizes

Journal Article · Sat Mar 01 04:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/783/1/1· OSTI ID:22351392

Santos, Fábio P.; Franco, Gabriel A. P.; Reis, Wilson ^[1]; Roman-Lopes, Alexandre ^[2]

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1. Departamento de Física, ICEx, UFMG, Caixa Postal 702, 30.123-970 Belo Horizote, MG (Brazil)
2. Departamento de Fisica-Universidad de La Serena, Cisternas 1200, La Serena (Chile)

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 (≈400 μG) and an abrupt increase in polarization degree, probably due to an enhancement in alignment efficiency. Furthermore, dense cloud fragmentations with peak A{sub V} between 20 and 37 mag were probably triggered by its expansion. The presence of 24 μm 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 H II 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.

• OSTI ID: 22351392
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 783; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CAVITIES
COMPRESSION
DISPERSIONS
DISTRIBUTION
EFFICIENCY
EVOLUTION
EXPANSION
GRAIN SIZE
INTERSTELLAR GRAINS
MAGNETIC FIELDS
MAPS
PARTICLE SIZE
POLARIZATION
SKY
STARS