Formation of the Active Star-forming Region LHA 120-N 44 Triggered by Tidally Driven Colliding H i Flows

Abstract

N44 is the second active site of high mass star formation next to R136 in the Large Magellanic Cloud (LMC). We carried out a detailed analysis of Hi at 60 arcsec resolution by using the ATCA & Parkes data. We presented decomposition of the Hi emission into two velocity components (the L-and D-components) with the velocity separation of ∼60 km s −1 . In addition, we newly defined the I-component whose velocity is intermediate between the L-and D-components. The D-component was used to derive the rotation curve of the LMC disk, which is consistent with the stellar rotation curve (Alves & Nelson 2000). Toward the active cluster forming region of LHA 120-N 44, the three velocity components of Hi gas show signatures of dynamical interaction including bridges and complementary spatial distributions. We hypothesize that the L-and D-components have been colliding with each other since 5 Myrs ago and the interaction triggered formation of the O and early B stars ionizing N44. In the hypothesis the I-component is interpreted as decelerated gas in terms of momentum exchange in the collisional interaction of the Land D-components. In the N44 region the P lanck sub-mm dust optical depth is correlated with the Hi intensity, which is well approximated by a linear regression. We found that the N44 region shows a significantly steeper regression line than in the Bar region, indicating less dust abundance in the N44 region, which is ascribed to the tidal interaction between the LMC with the SMC 0.2 Gyrs ago.

Multiwavelength analysis of the X-ray spur and southeast of the Large Magellanic Cloud

“…Detailed numerical simulations of the galactic interaction by Bekki & Chiba (2007a) reproduced the asymmetry, lending support for the scenario. Additional evidence was presented by Tsuge et al (2019), who investigated N44, which is one of the most active star-forming regions in the LMC. They conclude that the collision between LMC gas and the L-component at the location of N44 was similar to R136, but it occurred earlier due to the geometry of the systems.…”

Star Clusters Near and Far

“…Stars and star clusters form due to the gravitational collapse of (parts of) GMCs (Kennicutt and Evans 2012; ). These GMCs mostly contain neutral (HI) and molecular (H 2 ) hydrogen at temperatures of 10-50 K. These temperatures make it necessary to observe star formation sites with radio telescopes, such as the Atacama Large Millimeter Array (ALMA) to understand the GMC dynamics by observing various CO transition lines of the cold interstellar medium (ISM, e.g., Yonekura et al 2005;Furukawa et al 2009;Heyer et al 2009a;Sun et al 2018;Tsuge et al 2019). The unprecedented high spatial resolution of radio telescopes also allows for the direct observation of protoplanetary and debris disks around young stars in the later stages of the star formation process (e.g., Brogan et al 2015;.…”

Coupling local to global star formation in spiral galaxies: the effect of differential rotation

“…This corresponds to values of A of 16 km s −1 kpc −1 . On the observational side, an increasing number of studies report star formation regions at the interface of colliding clouds (Dewangan et al 2018;Enokiya, Torii & Fukui 2019;Fukui et al 2019;Tsuge et al 2019). Fujita et al (2019) observe two colliding clouds with respective velocities of 16 and 25 km s −1 which makes their colliding velocity 8 km s −1 .…”