Different molecular filament widths as tracers of accretion onto filaments

TL;DR

This study investigates how different molecular tracers reflect gas accretion onto filaments by analyzing how their measured widths vary with environmental changes, proposing molecular width ratios as accretion rate indicators.

Contribution

It introduces a method to estimate filament accretion rates using ratios of molecular filament widths based on their formation timescales.

Findings

C2H, CO, CN, CS, and C3H2 widths are most sensitive to accretion effects.

N2H+, NH3, H2CO, HNC, CH3OH show less sensitivity and narrower widths.

Width ratios of different tracers can serve as proxies for accretion rates.

Abstract

We explore how dense filament widths, when measured using different molecular species, may change as a consequence of gas accretion toward the filament. As a gas parcel falls into the filament, it will experience different density, temperature, and extinction values. The rate at which this environment changes will affect differently the abundance of different molecules. So, a molecule that forms quickly will better reflect the local physical conditions a gas parcel experiences than a slower-forming molecule. Since these differences depend on how the respective timescales compare, the different molecular distributions should reflect how rapidly the environment changes, i.e., the accretion rate toward the filament. We find that the filament widths measured from time-dependent abundances for C2H, CO, CN, CS, and C3H2, are sensitive the most to this effect, being those molecules the ones presenting also the wider filament widths. On the contrary, molecules such as N2H+, NH3, H2CO, HNC or CH3OH are not so sensitive to accretion and present the narrowest filament widths. We propose that ratios of filament widths for different tracers could be a useful tool to estimate the accretion rate onto the filament.