The VMC survey – XLVII. Turbulence-controlled hierarchical star formation in the Large Magellanic Cloud

Abstract

We perform a statistical clustering analysis of upper main-sequence stars in the Large Magellanic Cloud (LMC) using data from the Visible and Infrared Survey Telescope for Astronomy survey of the Magellanic Clouds. We map over 2500 young stellar structures at 15 significance levels across ∼120 square degrees centred on the LMC. The structures have sizes ranging from a few parsecs to over 1 kpc. We find that the young structures follow power-law size and mass distributions. From the perimeter–area relation, we derive a perimeter–area dimension of 1.44 ± 0.20. From the mass–size relation and the size distribution, we derive two-dimensional fractal dimensions of 1.50 ± 0.10 and 1.61 ± 0.20, respectively. We find that the surface density distribution is well-represented by a lognormal distribution. We apply the Larson relation to estimate the velocity dispersions and crossing times of these structures. Our results indicate that the fractal nature of the young stellar structures has been inherited from the gas clouds from which they form and that this architecture is generated by supersonic turbulence. Our results also suggest that star formation in the LMC is scale-free from 10 pc to 700 pc.

Structural and Dynamical Analysis of the Quiescent Molecular Ridge in the Large Magellanic Cloud

“…These values are higher than the D 2 = 1.36 ± 0.02 measured in galactic molecular clouds with 12 CO by Falgarone et al (1991) but are consistent with the range of 1.2-1.5 measured for HI emission in galactic clouds by Sánchez et al (2007). These values are also consistent with similar measurements made using stellar structures in the LMC (Miller et al 2022) and the Small Magellanic Cloud (SMC; Sun et al 2018), where both find D 2 = 1.44 ± 0.2.…”

Topography of the Young Galactic Disk: Spatial and Kinematic Patterns of Clustered Star Formation in the Solar Neighborhood

“…At smaller scales, where our analysis is relevant, turbulence is probably the main mechanism controlling the underlying structure where coherent star formation occurs. Our result is consistent with the recent detailed analysis of the distribution of ∼2500 young stellar structures in the Large Magellanic Cloud by Miller et al (2022), who derived a 2D fractal dimension of around 1.5-1.6 in the range of spatial scales from 10 pc to 700 pc. The value D c = 1.62 ± 0.05 implies that the corresponding 3D fractal dimension should be D f = 2.5 − 2.6 (see Table 1 in Sánchez & Alfaro 2008), which is similar to the range of values D f ∼ 2.5-2.7 obtained from emission maps of several spectral lines for different molecular clouds in the Milky Way (Sánchez et al 2005(Sánchez et al , 2007b) and for early-type stars in the GB (Sánchez et al 2007a).…”

Hierarchical star formation in the Magellanic Clouds with the VMC survey

“…We use point spread function photometry catalogues and deredden the magnitudes based on the extinction map provided by Skowron et al (2021). We construct (J − K s ) versus K s colour-magnitude diagrams and use them to select ∼ 400, 000 young upper main-sequence stars (see Figure 2 of Miller et al 2022). After binning the stars, we apply kernel density estimation (KDE) and make a surface density map with a resolution of 10 pc (see left panel of Figure 3 from Miller et al 2022).…”

“…We construct (J − K s ) versus K s colour-magnitude diagrams and use them to select ∼ 400, 000 young upper main-sequence stars (see Figure 2 of Miller et al 2022). After binning the stars, we apply kernel density estimation (KDE) and make a surface density map with a resolution of 10 pc (see left panel of Figure 3 from Miller et al 2022). From this map, we identify structures at 1 to 15σ above the median background density.…”

“…Their methodology was inspired by and incorporated work done by Gouliermis et al (2010Gouliermis et al ( , 2017. We applied their methodology to the entire LMC in Miller et al (2022). Our goals were to check for preferred scales of star formation, probe the dominant physical properties behind star formation, and to compare to the interstellar medium.…”