Three-dimensional B-fields in the Interstellar Medium and Star-forming Regions (3D-BLISS). I. Using Starlight Polarization in the Massive IRDC Filament G11.11-0.12

The Astrophysical Journal, vol. 1005, pp. 195

Abstract

Abstract Measuring three-dimensional magnetic fields (3D B -fields) is essential to understanding the formation and evolution of the interstellar medium and multiscale star formation; however, the accurate measurement of 3D B -fields is still challenging. The dust polarization angles induced by magnetically aligned grains provide the projected B -fields onto the plane of sky, while the dust polarization degree provides the B -field’s inclination angle with respect to the line of sight. Our previous theoretical studies proposed a new method of probing 3D B -fields using dust polarization combined with the radiative torque (RAT) alignment theory and demonstrated the accurate inference of B -field inclination angles using synthetic polarization data. In this paper, we report the first application of the new technique to study 3D B -fields and dust properties in the G11.11-0.12 filament (hereafter G11) from starlight polarization observations taken by ISRF/SIRPOL at 2.19 μ m. Using both observed starlight polarization and optical dust extinction curves from the Gaia mission, we constrained the maximum grain size of 0.25 μ m and the grain elongation with an axial ratio of s ≳ 1.4 in the outer regions of G11. We calculated the alignment properties in G11 by using the DustPOL_py code. The B -field’s inclination angles in G11 are then inferred from the observed starlight polarization efficiency when the grain alignment is included, with a mean angle of ∼48°. From these inferred inclination angles, we found evidence of the local 3D arc-shaped B -field structure toward the sightline. These findings are important for understanding 3D B -field’s roles in the formation and evolution of massive filamentary clouds.

Authors 6

1. Bao Truong corresponding

   Korea Astronomy and Space Science Institute

   Affiliation as printed

   Korea Astronomy and Space Science Institute

   University of Science and Technology

2. Thiem Hoang

   Korea Astronomy and Space Science Institute

   Affiliation as printed

   Korea Astronomy and Space Science Institute

   University of Science and Technology

3. Nguyen Bich Ngoc

   Vietnam Academy of Science and Technology

   Affiliation as printed

   Vietnam Academy of Science and Technology

4. Nguyen Chau Giang

   Korea Astronomy and Space Science Institute

   Affiliation as printed

   Korea Astronomy and Space Science Institute

   University of Science and Technology

5. Le Ngoc Tram Aachen

   Leiden University

   Affiliation as printed

   Leiden University

6. Ngân Lê

   Korea Astronomy and Space Science Institute

   Affiliation as printed

   Korea Astronomy and Space Science Institute