Filamentary accretion flows in high-mass star-forming clouds

TL;DR

This study investigates filamentary accretion as a mechanism for feeding dense clumps in three high-mass star-forming clouds by combining dust continuum derived surface densities with velocity differences from HCO+ and H13CO+ line data. A simple inflow model relates $\Delta v$, $\Sigma$, and the inclination $i$ to estimate mass-flow rates along filaments and onto clumps. The results reveal filamentary mass flows reaching up to $\dot{M} \sim 10^{-3} M_{\odot}\,\mathrm{yr}^{-1}$ in G75 and $\dot{M} \sim 10^{-5}$ to $10^{-4} M_{\odot}\,\mathrm{yr}^{-1}$ in IRAS21078 and NGC7538, with flows often oriented toward clumps and enhanced near overdense regions; velocity gradients associated with H II region feedback can dominate local kinematics and complicate the inflow interpretation. The work demonstrates a practical method to quantify multi-scale filamentary accretion and highlights the role of feedback in shaping gas dynamics during the early stages of high-mass star formation.

Abstract

We quantify the gas flows from a scale of up to several parsecs down to the sub-parsec scale along filamentary structures in the three high-mass star-forming regions G75.78, IRAS21078+5211 and NGC7538 with data obtained from the IRAM 30 m telescope. The analysis is carried out using the surface density derived from 1.2 mm continuum emission and velocity differences estimated from HCO$^+$ and H$^{13}$CO$^+$ molecular line data.

Figures (46)

• Figure 1: Top row: NIKA2 1.2 mm dust continuum maps (see beuther2024) of the star-forming regions showing the clump and filament designations. The red and magenta markers indicate the data points used for the flow rate estimation in Section \ref{['sec:fila-flows']}. Triangular magenta markers indicate a separate section along a structure. Black contours outline the 1.2 mm continuum, ranging from 3$\sigma$ to 39$\sigma$ in steps of 3$\sigma$ (the RMS-values are presented in Table \ref{['tab:dust_hii_rms']}). The red contours in the upper panels mark the peak-positions of the continuum emission from 20% to 100% in steps of 20%. Designations used in the following refer to clumps and filament-structures, filaments are marked by an "F" in the designation; "CF" in G75 stands for "central filament", "CC" in IRAS21078 refers to "central clump" while the clumps in NGC7538 are the known objects IRS9, IRS1 and S (e.g. Beuther). G75 S1 is the object G75.78+0.34. We present the clump-designations together with their coordinates in Table \ref{['tab:clumps']}. Bottom row: The same dust-maps with red contour lines outlining the H$II$1.2ex-regions at 1.4 GHz (21 cm) (CondonVLA_1998); the contours range from 10% to 100% of the peak emission in steps of 10% (see Table \ref{['tab:dust_hii_rms']} for reference). The positions of the two main exciting sources of the H$II$1.2ex-region in NGC7538, NGC7538 IRS5 and NGC7538 IRS6, are marked in the lower right panel (Puga).
• Figure 2: First moment (intensity-weighted peak-velocity) maps for the HCO$^+$ ($1-0$)-line. The beam size is 27″ (lower left corner). The sources are labeled in each panel. The scale bar indicates the length of 1 parsec in each panel. Contour lines show the 1.2 mm dust continuum ranging from 3$\sigma$ to 39$\sigma$ in 3$\sigma$-steps.
• Figure 3: As for Fig. \ref{['fig:1stmoment_hco+']} but for H$^{13}$CO$^+$ ($1-0$)-transition.
• Figure 4: Dust temperature maps of G75 (left panel) and NGC7538 (right panel). Both maps were created using Herschel-data (Molinari2010) and free-free corrected dust continuum emission from the NIKA2 dataset. In the bottom left corner the 27″ beam of the final data product is shown. Black contours outline the free-free corrected 1.2 mm continuum emission at 27″ resolution in logarithmic scale from 5$\sigma$ to peak value.
• Figure 5: Spectra towards G75, showing molecular emission of HCO$^+$ ($1-0$) (red) and H$^{13}$CO$^+$ ($1-0$) (black). The left panel shows the emission at the clump position S1 in G75. The right panel shows the spectra for a position along the CF filament in G75 (see upper left panel of Fig. \ref{['fig:dusttags']}).