Investigating the structure of star-forming regions using INDICATE

TL;DR

This paper evaluates the INDICATE method for analyzing star-forming regions, demonstrating its ability to detect local clustering and mass segregation, and comparing it with other techniques across synthetic and real data.

Contribution

The paper introduces and tests INDICATE, a new method for quantifying local clustering tendencies of stars, and compares its effectiveness with existing methods on synthetic and observational data.

Findings

INDICATE effectively detects local clustering and mass segregation.

It shows limitations in quantifying overall region structure due to geometric degeneracies.

Applied to real regions, INDICATE reveals diverse clustering behaviors.

Abstract

The ability to make meaningful comparisons between theoretical and observational data of star-forming regions is key to understanding the star formation process. In this paper we test the performance of INDICATE, a new method to quantify the clustering tendencies of individual stars in a region, on synthetic star-forming regions with sub-structured, and smooth, centrally concentrated distributions. INDICATE quantifies the amount of stellar affiliation of each individual star, and also determines whether this affiliation is above random expectation for the star-forming region in question. We show that INDICATE cannot be used to quantify the overall structure of a region due to a degeneracy when applied to regions with different geometries. We test the ability of INDICATE to detect differences in the local stellar surface density and its ability to detect and quantify mass segregation. We then compare it to other methods such as the mass segregation ratio $\Lambda_{\rm{MSR}}$, the local stellar surface density ratio $\Sigma_{\rm{LDR}}$ and the cumulative distribution of stellar positions. INDICATE detects significant differences in the clustering tendencies of the most massive stars when they are at the centre of a smooth, centrally concentrated distribution, corresponding to areas of greater stellar surface density. When applied to a subset of the 50 most massive stars we show INDICATE can detect signals of mass segregation. We apply INDICATE to the following nearby star-forming regions: Taurus, ONC, NGC 1333, IC 348 and $\rho$ Ophiuchi and find a diverse range of clustering tendencies in these regions.