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ISM: Hii regions—Stars: formation—ISM: individual objects (NGC 602)

The formation of the open cluster NGC 602 in the Small Magellanic Cloud triggered by colliding Hi flows

Yasuo FUKUI11affiliation: Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan 22affiliation: Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan    Takahiro OHNO11affiliationmark:    Kisetsu TSUGE11affiliationmark:    Hidetoshi SANO33affiliation: National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588, Japan    Kengo TACHIHARA11affiliationmark: [email protected]
Abstract

NGC 602 is an outstanding young open cluster in the Small Magellanic Cloud. We have analyzed the new Hi data taken with the Galactic Australian Square Kilometre Array Pathfinder survey project at an angular resolution of 30\arcsec. The results show that there are three velocity components in the NGC 602 region. We found that two of them having ∼\sim20 km s-1 velocity separation show complementary spatial distribution with a displacement of 147 pc. We present a scenario that the two clouds collided with each other and triggered the formation of NGC 602 and eleven O stars. The average time scale of the collision is estimated to be ∼\sim8 Myr, while the collision may have continued over a few Myr. The red shifted Hi cloud extending ∼\sim500 pc flows possibly to the Magellanic Bridge, which was driven by the close encounter with the Large Magellanic Cloud 200 Myr ago (1990PASJ...42..505F; 2007MNRAS.381L..11M). Along with the RMC136 and LHA 120-N 44 regions the present results lend support for that the galaxy interaction played a role in forming high-mass stars and clusters.

1 Introduction

Dynamical interactions between galaxies are a common process in the Universe and exchange of the interstellar medium (ISM) between galaxies is often happening. It is also likely that the gas motion driven by the interaction produces shocks to trigger star formation, and drives the galaxy evolution. There are a number of interacting galaxies and in the most typical case, the Antennae Galaxies, many young massive clusters are probably formed under triggering by the interactions ([2000ApJ...542..120W, 2014ApJ...795..156W, 2019arXiv190905240T], \yearcite2020arXiv200504075T).

The Magellanic Clouds are a tidally interacting system with close encounters in the past.