The open cluster NGC 6823 and possible triggered star formation associated with SNR G59.5+0.1

¹ National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, PR China
e-mail: xujl@bao.ac.cn
² Graduate University of the Chinese Academy of Sciences, 100080 Beijing, PR China
³ NAOC-TU Joint Center for Astrophysics, 850000 Lhasa, PR China

Received: 20 February 2012
Accepted: 10 April 2012

Abstract

Aims. We investigate the environment in the vicinity of the supernova remnant (SNR) G59.5+0.1 and identify all the young stellar objects (YSOs) around the SNR, to derive the physical properties, obtain insight into the star-formation history, and determine whether SNR G59.5+0.1 can trigger star formation in this region.

Methods. We perform the submillimeter/millimeter observations in CO lines toward the southeast of SNR G59.5+0.1 with the KOSMA 3 m Telescope. High values of the integrated CO line-intensity ratio R_{ICO(3−2)/ICO(2−1)} is identified as one good signature of the SNR-MC (molecular cloud) interacting system. To investigate the impact of SNR G59.5+0.1 on the process of star formation, we use GLIMPSE I catalog to select YSOs (including Class I and Class II sources).

Results. The CO emission forming an arc-like shape and mid-infrared 8.28 μm emission are coincident with SNR G59.5+0.1, which has a total mass of 1.1 × 10⁴   M_⊙ and fully covers the open cluster NGC 6823. Three molecular clumps are identified in the CO molecular arc, each clump tracing the broad-line wing emission, indicating that there are three outflows in motion. The integrated CO line intensity ratio (R_{ICO(3 − 2)/ICO(2−1)}) for the whole molecular arc is between 0.48 and 1.57. The maximum value is 1.57, which is much higher than previous measurements of individual Galactic MCs. The CO molecular arc has a line-intensity ratio gradient. The SNR G59.5+0.1 is in adiabatic expansion phase. The age of the SNR is 8.6  ×  10⁴ yr. Based on the GLIMPSE I catalog, we select 625 YSOs candidates (including 176 Class I sources and 449 Class II sources). The timescales for Class 0, Class I and Class II sources are  ≤10⁴ yr,  ~10⁵ yr, and  ~10⁶ yr, respectively. The number of YSOs are significantly enhanced in the interacting regions, indicating the presence of some recently formed stars.