Sanghyuk Moon (문상혁)
About
Hi! I am Sanghyuk Moon, a postdoctoral research associate at Princeton University. I study star formation using theory and numerical simulations. Questions that I am trying to answer include 1) what are the physical conditions that trigger the onset of the prestellar core collapse? 2) what physics determine the mass function of cores and how is it related to the initial mass function? 3) what controls the star formation at the centers of barred galaxies?
I grew up in South Korea, where I completed my Ph.D. in 2022 at Seoul National University (SNU) with my advisor Woong-Tae Kim.
Contact: sanghyuk.moon at princeton dot edu
Resume: Link to my CV
Publications: Link to ADS
Research
Quasi-equilibrium model for turbulent prestellar cores
A classical model for the structure and stability of prestellar cores is the Bonnor-Ebert sphere (BES).
However, the BES does not take into account the internal turbulent motions within the cores, which are inherited from their turbulent formation environments.
In Moon & Ostriker (2024), we obtain a family of quasi-equilibrium solutions for turbulent prestellar cores obeying power-law linewidth–size relations (which we call "turbulent equilibrium sphere" or TES) and propose a evolutionary scenario leading to collapse.
Critical conditions for collapse
Stars form from a dense molecular cloud core, but not every core forms stars.
To understand the physical conditions that determine the onset of the prestellar core collapse, in Moon & Ostriker (Paper I, submitted) we conduct a carefully constructed suite of numerical simulations and analyze the dynamical evolution of individual "cores" to identify the critical conditions for collapse.
In Moon & Ostriker (Paper II, submitted), we present physical properties of the cores at the onset of collapse and discuss the implications for the density threshold for star formation, massive prestellar cores, and core mass function.
Star formation in nuclear rings
Galactic centers occupy a unique junction in our understanding of galaxy evolution: They are the sites where the large-scale bar-driven inflows lead to strong starburst, with implications for the launching of galactic winds and the transport of gas into the vicinity of supermassive black holes.
They also provide the closest laboratory to study the star formation in extreme environments.
In a series of papers (Kim & Moon 2016, Moon et al. 2021, 2022, 2023), we use controlled numerical simulations to study the effects of various physical processes including gravitational instability, supernova feedback, (time-varying and spatially asymmetric) mass inflows along the bar, and magnetic fields on the star formation in nuclear rings at the barred galaxy centers.
Self-gravity solver for cylindrical mesh
Solving the Poisson equation under the open (vacuum) boundary conditions is a non-trivial problem.
In particular, there has been a lack of efficient algorithm that works in cylindrical/spherical grids.
In Moon, Kim, & Ostriker (2019), we show that the algorithm introduced by James (1977) (see also Lackner (1976)) can be generalized to cylindrical coordinate system, providing an efficient self-gravity solver in cylindrical coordinate system.
A version of the Athena++ code that implements this algorithm in 3D Cartesian and cylindrical grids can be found in https://github.com/sanghyukmoon/athena-public-version.