N131: A dust bubble born from the disruption of a gas filament^⋆

¹ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
e-mail: cpzhang@nao.cas.cn
² Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
³ University Observatory Munich, Scheinerstrasse 1, 81679 Munich, Germany
⁴ Purple Mountain Observatory & Key Laboratory for Radio Astronomy, Chinese Academy of Sciences, 2 West Beijing Road, Nanjing, 210008, PR China
⁵ NAOC-TU Joint Center for Astrophysics, Lhasa, 850000, PR China
⁶ University of the Chinese Academy of Sciences, Beijing, 100080, PR China

Received: 10 April 2015
Accepted: 16 October 2015

Abstract

Context. OB-type stars have strong ionizing radiation and drive energetic winds. The ultraviolet radiation from ionizing stars may heat dust and ionize gas to sweep up an expanding bubble shell. This shell may be the result of feedback leading to a new generation of stars.

Aims. N131 is an infrared dust bubble residing in a molecular filament. We study the formation and fragmentation of this bubble with multiwavelength dust and gas observations.

Methods. Towards the bubble N131, we analysed archival multiwavelength observations including 3.6, 4.5, 5.8, 8.0, 24, 70, 160, 250, 350, 500 μm, 1.1 mm, and 21 cm. In addition, we performed new observations of CO (2–1), CO (1–0), and ¹³CO (1–0) with the IRAM 30 m telescope.

Results. Multiwavelength dust and gas observations reveal a ring-like shell with compact fragments, two filamentary structures, and the secondary bubble N131-A. Bubble N131 is a rare object with a large hole at 24 μm and 21 cm in the direction of its centre. The dust and gas clumps are compact and might have been compressed at the inner edge of the ring-like shell, while they are extended and might be pre-existing at the outer edge. The column density, excitation temperature, and velocity show a potentially hierarchical distribution from the inner to outer edge of the ring-like shell. We also detected the front and back sides of the secondary bubble N131-A in the direction of its centre. The derived Lyman-continuum ionizing photon flux within N131-A is equivalent to an O9.5 star. Based on the above, we suggest that the bubble N131 might be triggered by the strong stellar winds from a group of massive stars inside the bubble.

Conclusions. We propose a scenario in which the bubble N131 forms from the disruption of a gas filament by the expansion of the H II region, strong stellar winds, and fragments under self-gravity.