CASCADE: Filamentary accretion flows in Cygnus X DR20

TL;DR

This study investigates whether filamentary structures in Cygnus X DR20 funnel gas from cloud to core scales during high-mass star formation. It employs DisPerSE to identify filaments in high-resolution CASCADE data (HCO+(1-0) and H13CO+(1-0)) and uses Gaussian fits along filaments plus FilChaP width measurements to quantify kinematics and widths, cross-referencing with Herschel column maps. The results show projected velocity gradients of $0.4$–$2.4$ km s^-1 over about $0.1$ pc toward cores and filament widths predominantly around $\sim 0.1$ pc, with H13CO+(1-0) generally tracing narrower widths than HCO+(1-0); no strong dependence on evolutionary stage is detected. The findings support a picture of gas flowing along filaments onto cores and highlight a hierarchical connection between large-scale and small-scale filaments, justifying larger CASCADE-based statistical studies of high-mass filament properties.

Abstract

Aims. We investigate the role of filaments in high-mass star formation, whether gas flows from large to small scales along them, and what their properties might reveal about the region they are found in. Methods. The Max Planck IRAM Observatory Program (MIOP), the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE), includes high spatial resolution (~3'') data of HCO+(1-0) and H13CO+(1-0) emission in the star-forming DR20 region in the Cygnus X complex. In this data we identify filaments with the structure identification algorithm DisPerSE. We further analyze these filaments using Gaussian fits to the spectra to determine the line peak velocity and full width half maximum along them. The Python package FilChaP was used to determine filament widths. Results. We find projected velocity gradients inside several filaments between 0.4 to 2.4km/s over projected length-scales of 0.1pc toward star-forming cores. This can be interpreted as a sign of gas flowing along the filaments toward the cores. The filament width distributions exhibit median values between 0.06 and 0.14pc depending on the core, the tracer, and the method. Standard deviations are approximately 0.02 to 0.06pc. These values are roughly in agreement with the filament width of 0.1pc typically found in nearby low-mass star-forming regions. Conclusions. This first analysis of filamentary properties within the Cygnus X CASCADE program reveals potential signatures of gas flows along filaments onto star-forming cores. Furthermore, the characteristics of the filaments in this high-mass star-forming region can be compared to those of filaments in low-mass star-forming regions typically studied before. Extending such studies to the entire CASCADE survey will enhance our knowledge of high-mass filament properties on solid statistical grounds.

Figures (18)

• Figure 1: Overview of the DR20 region in Spitzer 8 $\mu$m emission in color-scale with white contours showing the hydrogen column density in five steps from 1 to 5 $\times$ 10$^{22}$ H$_2$ cm$^{-2}$, derived with Herschel data by marsh_multitemperature_2017. The red dots indicate the NOEMA 3.6 mm continuum intensity peaks, which are labeled from A to F beuther_cygnus_2022.
• Figure 2: Integrated intensities (from $-$8.4 km s$^{-1}$ to 6 km s$^{-1}$) for HCO$^+$$(1-0)$ (left) and H$^{13}$CO$^+$$(1-0)$ (right). The intensity peaks of the NOEMA 3.6 mm continuum emission (continuum sources) are labeled A to F. The NOEMA synthesized beam is shown in the bottom-right.
• Figure 3: Examples of the Gaussian fits to averaged spectra within filaments connected to core A in the combined NOEMA+30 m HCO$^+$$(1-0)$ data. The peak positions and FWHM seen in, for example, Figs. \ref{['plot_along_chosen_HCO']} result from such fits.
• Figure 4: Filaments identified with DisPerSE in all velocity channels (from -8.4 km s$^{-1}$ to 6 km s$^{-1}$) overlaid on the respective zeroth moment maps, i.e., the intensity integrated over all velocity channels, of all CASCADE data types. Top: Combined HCO$^+$$(1-0)$ (left) and H$^{13}$CO$^+$$(1-0)$ (right). Bottom: Single-dish HCO$^+$$(1-0)$ (left) and H$^{13}$CO$^+$$(1-0)$ (right). The intensity maxima of the 3.6 mm continuum emission are labeled A-F in the upper right panel. The beam is shown in the bottom-right of each panel.
• Figure 5: Filaments identified with DisPerSE in the Herschel hydrogen column density data marsh_multitemperature_2017. To also show the lower hydrogen column densities, the color scale bar is truncated at $3\times 10^{20}$ H$_2$ cm$^{-2}$, but the peak positions reach much higher column densities $>10^{22}$ cm$^{-2}$ (Fig. \ref{['plot_dr20_overview']}). The intensity maxima of the 3.6 mm continuum emission are labeled A-F. The beam is shown in the bottom-right.