Star and Cluster Formation in the Sh2-112 Filamentary Cloud Complex

Abstract

We present the star formation activity around the emission nebula Sh2-112. At a distance of ∼2.1 kpc, this H ii complex, itself 3 pc in radius, is illuminated by the massive star (O8 V) BD+45 3216. The associated molecular cloud extends in angular scales of 2.°0 × 0.°83, corresponding to linear sizes of 73 pc by 30 pc, along the Galactic longitude. The high-resolution (30″) extinction map reveals a chain of dust clumps aligned with the filament-like structure with an average extinction of A V ∼ 2.78 mag, varying up to a maximum of ∼17 mag. Our analysis led to identification of a rich population (∼500) of young (average age of ∼1 Myr) stars, plus a numerous number (∼350) of Hα emitters, spatially correlated with the filamentary clouds. Located near the edge of the cloud, the luminous star BD+45 3216 has created an arc-like pattern as the ionizing radiation encounters the dense gas, forming a blister-shaped morphology. We found three distinct young stellar groups, all coincident with relatively dense parts of the cloud complex, signifying ongoing star formation. Moreover, the cloud filament (excitation temperature ∼10 K) traced by the CO isotopologues and extending nearly ∼80 pc is devoid of ionized gas except at the dense cores (excitation temperature ∼28–32 K) wherein significant ionized emission excited by OB stars (dynamical age ∼0.18–1.0 Myr) pertains. The radial velocity is dynamic (median ∼−3.65 km s−1) along the main filament, increasing from Galactic east to west, indicating mass flow to form the massive stars/clusters at the central hubs.

Investigating the morphology and CO gas kinematics of Sh2-112 region

“…The RMS sources, though with wide wings, have nearly same mean velocities (∼ -4.0 km s −1 ), which is in agreement with the radial velocity for the Sh2-112 region in Blitz et al (1982); Stark & Brand (1989); Brand & Blitz (1993). Though our locations display a range of mean velocities, the overall distribution is consistent with other values cited in literature within error limits (Dobashi et al, 1994;Urquhart et al, 2008;Lumsden et al, 2013;Maud et al, 2015a,b;Panja et al, 2022).…”

“…According to Panja et al (2022), the column density of the molecular emission region has been calculated to be ∼10 22 cm −2 . Such regions have been designated as "hubs" in the context of hub-filament systems in literature (Myers, 2009).…”

“…This tallies with the linewidth map in Figure 3(h). For the above calculations, we take the excitation temperature T as 20 K (see Figure 15 in Panja et al, 2022). Furthermore, we also calculate Mach number (= σ nt /c s ) and the ratio of thermal to non-thermal pressure (P tnt = c 2 s /σ 2 nt ) (Lada et al, 2003) for each of the locations.…”

“…The Red MSX Source (RMS) survey by Lumsden et al (2013) -which aims to catalog massive young stellar population in the Galaxy -has identified two sources associated with the Sh2-112 region, namely G083.7962+03.3058 and G083.7071+03.2817, classified as H II region and YSO, respectively, in the catalog. Though the molecular cloud in this region has been subject to investigations in literature in various molec- ular transitions, such as HCN (J=1-0) (Burov et al, 1988), CO (Blitz et al, 1982), 13 CO (J=1-0) (Dobashi et al, 1994(Dobashi et al, , 1996, and CO isotopologues (Urquhart et al, 2008;Maud et al, 2015b;Panja et al, 2022), they have either been at a low resolution, and/or as a part of a large statistical study or a larger region encompassing Sh2-112. As such, a detailed examination of the molecular cloud associated with Sh2-112 H II region is pending, a void we try to fill in this paper.…”

Observational Evidence of the Merging of Filaments and Hub Formation in G083.097+03.270

“…The target of our study is G083.097+03.270 (hereafter G08; ℓ = 83°. 0970; b = + 03°.2700), which is a part of the large-scale area previously studied by Panja et al (2022) and therein referred to as Clump B. This complex, located in the Orion arm near the Cyg X system, was found by these authors associated with intense thermal dust emission (AKARI: 160 μm; Planck: 353 GHz), strong ionized gas emission (NVSS: 1.4 GHz), and dense molecular cloud (PMO: 12 CO, 13 CO, C 18 O).…”