Properties of Dense Cores Embedded in Musca Derived from Extinction Maps and ¹³CO, C¹⁸O, and NH₃ Emission Lines

Abstract

Using near-infrared data from the Two Micron All Sky Survey catalog and the Near Infrared Color Excess method, we studied the extinction distribution in five dense cores of Musca, which show visual extinction greater than 10 mag and are potential sites of star formation. We analyzed the stability in four of them, fitting their radial extinction profiles with Bonnor–Ebert isothermal spheres, and explored their properties using the J = 1–0 transition of 13CO and C18O and the J = K = 1 transition of NH3. One core is not well described by the model. The stability parameter of the fitted cores ranges from 4.5 to 5.7 and suggests that all cores are stable, including Mu13, which harbors one young stellar object (YSO), the IRAS 12322-7023 source. However, the analysis of the physical parameters shows that Mu13 tends to have larger A V, n c, and P ext than the remaining starless cores. The other physical parameters do not show any trend. It is possible that those are the main parameters to explore in active star-forming cores. Mu13 also shows the most intense emission of NH3. Its 13CO and C18O lines have double peaks, whose integrated intensity maps suggest that they are due to the superposition of clouds with different radial velocities seen in the line of sight. It is not possible to state whether these clouds are colliding and inducing star formation or are related to a physical process associated with the formation of the YSO.

Formation of the Musca filament: evidence for asymmetries in the accretion flow due to a cloud–cloud collision

“…It was shown by Nielbock et al (2012); Roy et al (2014) that the temperature in the dense interior of different clouds is at least 3 K lower than the Herschel dust temperature on the sky. Using a temperature of 10 K, which is actually also suggested by the LTE study of 13 CO(1-0) and C 18 O(1-0) by Machaieie et al (2017) for the filament crest, one gets a more probable typical density in the crest of n H 2 = 1.3±0.4 •10 4 cm −3 . Combining the obtained densities with the Herschel column densities, one can estimate the size of the dense gas along the line of sight as a function of the distance from the filament crest.…”

“…Figure 2 presents the column density map of the Musca filament combining 2MASS and Herschel data which shows that this high column density filament with its ambient cloud is in relative isolation in the plane of the sky. The Musca filament hosts one protostellar core (Vilas-Boas et al 1994;Juvela et al 2012;Machaieie et al 2017), and may contain a few prestellar cores (Kainulainen et al 2016) with an average core separation that could fit with gravitational fragmentation inside a filamentary crest. The filament is thus likely at a relatively early evolutionary stage and has indeed a relatively low line mass compared to other more active star forming filaments like B211/3 in Taurus (Palmeirim et al 2013;Cox et al 2016;Kainulainen et al 2016).…”

“…To construct the density profile, a RADEX grid of the 13 CO brightness temperature ratio was created with 40 points on a log scale between n H 2 = 10 2 and 10 5 cm −3 for three different kinetic temperatures: 10, 13 and 16 K. This covers the range of Herschel dust temperatures as well as kinetic gas temperatures put forward for Musca by Machaieie et al (2017). The FWHM and column density for 13 CO that are used in the RADEX calculations are 0.7 km s −1 and N13 CO = 1.1•10 16 cm −2 , respectively, which is obtained from N H 2 = 6•10 21 cm −2 using H 2 / 13 CO = 5.7•10 5 (from H 2 / 12 CO ∼ 10 4 and 12 CO / 13 CO ∼ 57 (Langer & Penzias 1990)).…”

Description of turbulent dynamics in the interstellar medium: multifractal-microcanonical analysis

“…Musca is a prominent filamentary structure, 6 pc in length, with a high aspect ratio at a distance of only 140-150 pc (Hacar et al 2016;Cox et al 2016;Kainulainen et al 2016;Gaia Collaboration 2018). It has a low average column density N, with N(max) ∼ 4-8 10 21 cm −2 (Bonne et al 2020b), and shows only one protostellar source located at the northern end of the filament (Juvela et al 2012;Machaieie et al 2017). Furthermore, Herschel observations reveal a network of striations orthogonal to the filament, which are thought to be indications of mass inflow along the magnetic field (Cox et al 2016).…”

Formation and evolution of protostellar accretion discs. I. Angular-momentum budget, gravitational self-regulation, and numerical convergence

“…The initial conditions for the star-and disc-formation processes have been observed extensively in molecular line emission (Myers & Benson 1983;Jijina et al 1999;Caselli et al 2002), infrared absorption (Teixeira et al 2005;Machaieie et al 2017), and submillimetre dust emission (Ward-Thompson et al 1994;Kirk et al 2005;Könyves et al 2015), which provide information on the mass, size, temperature, and rotation of pre-stellar cores. The morphology and Contact e-mail: wenruix@princeton.edu strength of the magnetic fields have also been inferred via observations of Zeeman splitting (e.g., Crutcher 1999;Falgarone et al 2008) and dust polarization (e.g., Ward-Thompson et al 2000;Crutcher et al 2004;Girart et al 2006;Maury et al 2018;Auddy et al 2019).…”