A new optical polarization catalog for the Small Magellanic Cloud: The magnetic field structure

Journal Article · Wed Jun 10 04:00:00 EDT 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/806/1/94· OSTI ID:22883083

Gomes, Aiara Lobo ^[1]; Magalhães, Antônio Mário ^[2]; Pereyra, Antonio ^[3]

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1. Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany)
2. Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, 05508-900, São Paulo, SP (Brazil)
3. Instituto Geofísico del Perú, área Astronomía, Calle Badajoz, Lima 3, Lima, Per (Peru)

We present a new optical polarimetric catalog for the Small Magellanic Cloud (SMC). It contains a total of 7207 stars, located in the northeast (NE) and Wing sections of the SMC and part of the Magellanic Bridge. This new catalog is a significant improvement compared to previous polarimetric catalogs for the SMC. We used it to study the sky-projected interstellar magnetic field structure of the SMC. Three trends were observed for the ordered magnetic field direction at position angles (PAs) of (65° ± 10°), (115° ± 10°), and (150° ± 10°). Our results suggest the existence of an ordered magnetic field aligned with the Magellanic Bridge direction and SMC’s Bar in the NE region, which have PAs roughly at 115.°4 and 45°, respectively. However, the overall magnetic field structure is fairly complex. The trends at 115° and 150° may be correlated with the SMC’s bimodal structure, observed in Cepheids’ distances and HI velocities. We derived a value of B{sub sky}=(0.947±0.079) μG for the ordered sky-projected magnetic field, and δB=(1.465±0.069) μG for the turbulent magnetic field. This estimate of B{sub sky} is significantly larger (by a factor of ∼10) than the line of sight field derived from Faraday rotation observations, suggesting that most of the ordered field component is on the plane of the sky. A turbulent magnetic field stronger than the ordered field agrees with observed estimates for other irregular and spiral galaxies. For the SMC the B{sub sky}/δB ratio is closer to what is observed for our Galaxy than other irregular dwarf galaxies.

• OSTI ID: 22883083
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 806; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United Kingdom
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CATALOGS
CEPHEIDS
COMPARATIVE EVALUATIONS
DISTANCE
FARADAY EFFECT
INTERSTELLAR MAGNETIC FIELDS
MAGELLANIC CLOUDS
POLARIZATION