The Effect of Molecular Cloud Properties on the Kinematics of Stars Formed in the Trifid Region

Abstract

The dynamical states of molecular clouds may affect the properties of the stars they form. In the vicinity of the Trifid Nebula (d = 1180 ± 25 pc), the main star cluster (Trifid Main) lies within an expanding section of the molecular cloud; however, ∼0.°3 to the north (Trifid North), the cloud’s velocity structure is more tranquil. We acquired a Chandra X-ray observation to identify pre-main-sequence stars in Trifid North, complementing a previous observation of Trifid Main. In Trifid North, we identified 51 candidate pre-main-sequence stars, of which 13 are high-confidence Trifid members based on Gaia EDR3 parallaxes and proper motions. We also reanalyzed the membership of Trifid Main and separated out multiple background stellar associations. Trifid North represents a stellar population ∼10% as rich as Trifid Main that formed in a separate part of the cloud. The 1D stellar velocity dispersion in Trifid North (0.6 ± 0.2 km s−1) is 3 times lower than that in Trifid Main (1.9 ± 0.2 km s−1). Furthermore, in Trifid Main, proper motions indicate that the portion of the star cluster superimposed on the optical nebula is expanding. Expansion of the H ii region around the O-star HD 164492A, and the resulting gas expulsion, can explain both the motions of the stars and gas in Trifid Main. Contrary to previous studies, we find no evidence that a cloud–cloud collision triggered star formation in the region.

The cosmic DANCe of Perseus

“…the core and halo of Gorgophone), which has also been observed in other star-forming regions (e.g. Kuhn et al 2022;Lim et al 2022) and is predicted by the hierarchical star formation scenario (Ward & Kruijssen 2018).…”

Tracing the Layers of Photodissociated Gas in the Trifid Nebula

“…These data were observed with the APEX telescope between 2013 and 2016 with an angular resolution of 30″ and a 1σ sensitivity less than 1.0 K at 0.25 km s −1 velocity resolution. The SEGIDISM data were also used by Kuhn et al (2022).…”

“…The 12 CO(3-2) channel map shows similar emission features except for the component beyond 14 km s −1 . The 13 CO(2-1) SEDIGISM channel maps were also analyzed by Kuhn et al (2022), who write that the 13 CO emission is seen at almost any velocity between −4 and 28 km s −1 but the emission does not necessarily originate from gas at the same distance. In the Galactic spiral arm model from Reid et al (2016), gas near the Sagittarius Arm is expected to have v LSR ≈ 8 km s −1, and gas in the near Scutum Arm would have v LSR ≈ 18 km s −1 .…”

“…Sticking out of the boundaries of one of the cores, TC2 is a 22″ long irradiated jet HH 399, ending close to a bow shock ∼1 5 away, in a low-density environment (Cernicharo et al 1998;Rosado et al 1999;Yusef-Zadeh et al 2005). Millimeter-wavelength molecular line observations toward the nebula reveal several cloud components at velocities of v LSR ∼ 2 km s −1 (corresponding to the dark lanes crossing the optical nebula), v LSR ∼ 8 km s −1 (corresponding to dark features at the edge of the optical nebula), and v LSR ∼ 18 km s −1 (Cernicharo et al 1998;Torii et al 2011Torii et al , 2017Kuhn et al 2022). A bridging feature between the 2 and 8 km s −1 clouds is seen coincident with the optical nebula and indicates that these clouds are physically interacting and may have collided (Haworth et al 2015;Torii et al 2017;Kalari 2021).…”

“…Alternatively, the cloud kinematics could be interpreted as either an expanding H II region or turbulence (Fukuda & Hanawa 2000;Rho et al 2008). Kuhn et al (2022) used 13 CO(2-1) channel maps to suggest that the 18 km s −1 cloud, which is of much larger spatial extent, is likely to be in the background. Until now studies of photodissociated gas in M20 have only been for a small region around the TC2 globule using the far-and mid-infrared fine structure lines detected with the Long Wave Spectrometer (LWS) and Short Wave Spectrometer (SWS) on board ISO (Lefloch et al 2002).…”