Herschel/HIFI Observations of Molecular Lines Toward G10.47+0.03

TL;DR

This study uses archival Herschel/HIFI data to perform a wide-band spectral line census of the hot molecular core G10.47+0.03, addressing the chemical and physical state of a high-mass star-forming region in the far-IR regime inaccessible from the ground. Through line identification, LTE/MCMC analysis, non-LTE checks, and SED fitting, the authors derive molecular column densities, excitation temperatures, and global source parameters, uncovering two methanol temperature components and celebrating a broad inventory of species, including high-excitation CO and water isotopologues. The results reveal a chemically rich, dynamically complex environment with distinct outflow components, consistent with shock-driven ice mantle desorption and rapid gas-phase processing, thus advancing our understanding of warm, dense gas in massive star formation. The accompanying SED constraints provide essential context for interpreting the molecular emission and set benchmarks for future chemo-dynamical modeling of hot cores like G10.

Abstract

We present a spectral line analysis of the hot molecular core G10.47+0.03 (hereafter, G10). Our aim is to determine molecular abundances and excitation conditions across a wide spectral range inaccessible to ground-based observatories. We utilize archival data from the Herschel Space Observatory, obtained with the Heterodyne Instrument for the Far-Infrared (HIFI). We report here the detection of high-excitation CO, 13CO, and C18O, H2O isotopologues, HCO+, HCN, HNC, CS, C34S, SO, SO2, H2CS, and CH3OH. CO, p-H2O, CS, and HCN show similar velocity profiles with a narrow, blueshifted component, which may be linked to the outer outflow layer. Redshifted wings may indicate inner outflow activity. A Markov Chain Monte Carlo framework is employed to infer column densities and temperatures accurately. We also performed spectral energy distribution fitting to constrain the global physical parameters of G10, providing essential context for interpreting the molecular emission. The MCMC analysis revealed two excitation temperature components: a warm component (30-65 K) and a hot component (90-250 K). The higher temperatures indicate dense, hot gas typical of massive hot cores. The lower temperatures correspond to the warm, less dense envelope around the core. Transitions of H2O, high-excitation CO, and HCN indicate outflowing gas and high-density shocked regions. These findings highlight G10's complex dynamical environment.

Figures (7)

• Figure 1: SED fitting of G10. The fixed-aperture, background-subtracted SED data were fitted using the Zhang2018 protostellar model grid, and the best-fitting model is shown as a black line while all other"good” model fits (see text) are shown with colored lines (red to blue with increasing $\chi^2$). We define good models as those with $\chi^2$ values up to twice the minimum $\chi^2$ value, i.e., $\chi^2 < 2\,\chi^2_{\min}$Fedriani2023Telkamp2025.
• Figure 2: Comparison of key model parameters for each source: $\Sigma_{\mathrm{cl}}$ vs. $M_{\mathrm{c}}$ (left column), $m_{*}$ vs. $M_{\mathrm{c}}$ (center column), and $m_{*}$ vs. $\Sigma_{\mathrm{cl}}$ (right column). Only the "good" model fits are shown, color-coded by their $\chi^{2}$ values. The black cross marks the best-fitting model.
• Figure 3: G10 Spectra with identified species.
• Figure 4: Above two diagrams present the rotational spectrum for transitions occurring below and above 300 K for CH$_3$OH (vt=0-2). The vertical bars indicate the error margins for the measurements in each panel. Each panel provides the best-fitted values for the rotational temperature and column density.
• Figure 5: MCMC fitting of observed lines of CH$_{3}$OH (vt=0-2) below 300 K toward G10. Black lines represent the observed spectra and red lines the synthetic spectra.