Taking off the edge -- simultaneous filament and end core formation

Abstract

Simulations of idealised star-forming filaments of finite length typically show core growth which is dominated by two cores forming at its respective end. The end cores form due to a strong increasing acceleration at the filament ends which leads to a sweep-up of material during the filament collapse along its axis. As this growth mode is typically faster than any other core formation mode in a filament, the end cores usually dominate in mass and density compared to other cores forming inside a filament. However, observations of star-forming filaments often do not show this prevalence of cores at the filament edges. We use numerical simulations of accreting filaments forming in a finite converging flow to explore a possible mechanism which leads to a suppression of the end cores. While such a setup still leads to end cores that soon begin to move inwards, the continued accumulation of material outside of these makes a key difference: their positions now lie within the larger filamentary structure and not at its edges. This softens their inward gravitational acceleration as they are embedded by new material further out. As a result, these two cores do not grow as fast as expected for the edge effect and thus do not dominate over other core formation modes in the filament.

Filament collapse: A two phase process

“…This leads to a big puzzle: What suppresses the edge effect? A possible scenario is presented in Heigl et al (2021) where the filament is formed by a constant radial accretion and the end regions are continuously fed with new material. Therefore, no real edge effect occurs.…”

“…Although, such density distributions are not observed in low line-mass filaments (Roy et al 2015), the oscillations in cores have been detected (Redman et al 2006;Aguti et al 2007). In addition, there has been a recent study by Heigl et al (2021) where the edge effect is suppressed in a filament forming in a colliding flow, however, not every filament shows signs of accretion.…”

ArTéMiS imaging of the filamentary infrared dark clouds G1.75-0.08 and G11.36+0.80: Dust-based physical properties of the clouds and their clumps

“…A filament can also collapse along its long axis (longitudinal collapse) in such a way that the so-called gravitational focussing leads to the accumulation of gas at the ends of the filament, where gravitational collapse can then result in the formation of clumps (the so-called edge effect; e.g. Burkert & Hartmann 2004;Pon et al 2012;Clarke & Whitworth 2015;Heigl et al 2021;Hoemann et al 2022). This configuration is qualitatively consistent with the configuration observed in G1.75-0.08.…”