[Paper Review] Galactic Cold Cores VII: Filament Formation and Evolution - Methods & Observational Constraints

A. Rivera-Ingraham, I. Ristorcelli+16 more|arXiv (Cornell University)|Mar 30, 2016

Astrophysics and Star Formation Studies45 references16 citations

TL;DR

This study analyzes filament properties in 116 Herschel Galactic Cold Cores fields (D < 500 pc) using the getfilaments algorithm to extract and characterize filaments via Plummer-like profile fitting. It finds that filament mass components—core and wing—are strongly dependent on local environment, with higher background column densities driving increased core and wing mass densities, supporting an accretion-based evolution model; filaments with Mline,core ≥ 8.5 M⊙pc⁻¹ (∼Mcrit/2) are supercritical and likely to form stars.

ABSTRACT

The association of filaments with protostellar objects has made these structures a priority target in star formation studies. The datasets of the Herschel Galactic Cold Cores Key Programme allow for a statistical study of filaments with a wide range of intrinsic and environmental characteristics. Characterisation of this sample can be used to identify key physical parameters and quantify the role of environment in the formation of supercritical filaments. Filaments were extracted from fields at D<500pc with the getfilaments algorithm and characterised according to their column density profiles and intrinsic properties. Each profile was fitted with a beam-convolved Plummer-like function and quantified based on the relative contributions from the filament 'core', represented by a Gaussian, and 'wing' component, dominated by the power-law of the Plummer-like function. These parameters were examined for populations associated with different background levels. We find that filaments increase their core (Mcore) and wing (Mwing) contributions while increasing their total linear mass density (Mtot). Both components appear to be linked to the local environment, with filaments in higher backgrounds having systematically more massive Mcore and Mwing. This dependence on the environment supports an accretion-based model for filament evolution in the local neighbourhood (D<500pc). Structures located in the highest backgrounds develop the highest central Av, Mcore, and Mwing as Mtot increases with time, favoured by the local availability of material and the enhanced gravitational potential. Our results indicate that filaments acquiring a significantly massive central region with Mcore>Mcrit/2 may become supercritical and form stars. This translates into a need for filaments to become at least moderately self-gravitating in order to undergo localised star formation or become star-forming filaments.

Motivation & Objective

• To statistically characterize filament properties across diverse environments in the Herschel Galactic Cold Cores Key Programme.
• To quantify the influence of local background column density on filament structure and mass distribution.
• To identify observational constraints on filament formation and evolution, particularly for supercritical filaments.
• To test whether filament evolution is driven by accretion and gravitational potential in dense environments.

Proposed method

• Filaments were extracted from Herschel SPIRE and PACS maps (250–500 µm) using the getfilaments algorithm in fields within 500 pc.
• Column density profiles were fitted with a beam-convolved Plummer-like function to separate core (Gaussian-like) and wing (power-law) components.
• The relative contributions of core and wing to total linear mass density (Mline,tot) were quantified to assess structural and dynamical properties.
• Filament morphology and mass distribution were analyzed as functions of local background column density and distance.
• Three filament regimes were defined based on Mline,core: subcritical (≤4.2 M⊙pc⁻¹), transitional (4.2–8.4 M⊙pc⁻¹), and supercritical (>8.4 M⊙pc⁻¹).
• The critical mass per unit length (Mcrit ≈ 16.5 M⊙pc⁻¹ at T ≈ 10 K) was used as a reference for supercriticality.

Experimental results

Research questions

• RQ1 How does the local background column density influence the mass distribution in filament cores and wings?
• RQ2 What is the relationship between filament linear mass density and its structural components (core and wing)?
• RQ3 To what extent is filament evolution driven by accretion and gravitational potential in dense environments?
• RQ4 What threshold of core mass density (Mline,core) indicates supercriticality and potential for star formation?
• RQ5 How do filament widths and morphologies vary with distance and association with prestellar cores?

Key findings

• Filament core mass density (Mline,core) and wing mass density (Mline,wing) both increase with total linear mass density (Mline,tot), indicating a strong structural correlation.
• Filaments in higher background environments systematically exhibit higher Mline,core, Mline,wing, and Mline,tot, supporting environment-driven accretion.
• The most massive wing components are preferentially associated with the most massive cores and densest environments, suggesting gravitational accretion as a key driver.
• Filaments with Mline,core ≥ 8.5 M⊙pc⁻¹ (approximately half of Mcrit) are supercritical and likely to form stars.
• Core-scale filaments in the local neighborhood (D ≤ 300 pc) have a characteristic mean width of ∼0.13 pc, consistent with previous studies.
• Three distinct filament regimes were identified: core-dominated subcritical (≤4.2 M⊙pc⁻¹), transitional (4.2–8.4 M⊙pc⁻¹), and supercritical-only (>8.4 M⊙pc⁻¹), each with progressively higher background column densities.