Exploring the chemical evolution in hot molecular cores

Abstract

We present preliminary results of an extensive research project aimed at describing the physical and chemical conditions of hot molecular cores (HMCs). Using millimeter continuum and spectroscopic data extracted from the Atacama Large Millimeter Array (ALMA) archive, we have estimated rotational temperatures ($\rm T_{rot}$) and column densities of $\rm{CH_{3}CN}$, $\rm{CH_{3}CCH}$, and A-- and E--$\rm CH_{3}OH$ for a sample of molecular cores. We present a thermal characterization of these cores, revealing the existence of temperature gradients within them. These cores are, in turn, embedded in large molecular clouds. Additionally, we estimated molecular abundances that were evaluated as tracers of the chemical evolution of these cores. Finally, in a pilot study aimed to link observations with simulations, some of the obtained molecular abundances are compared with predictions from the Nautilus code.

Figures (4)

• Figure 1: Combined rotational diagram used to derive the T$\rm_{rot}$ towards SDC28.147$-$0.006 (source 7) from the four studied molecular species. The lines represent the best linear fits to the data.
• Figure 2: T$\rm_{rot}$ derived from the studied molecular species across the sample of ten regions. Horizontal dashed lines and shaded areas indicate the mean temperature and associated standard deviation ($\pm1\upsigma$), respectively, for each molecule.
• Figure 3: Obtained column densities and abundances (upper and bottom panels, respectively). Mean values are indicated with dashed lines, and shaded regions show the standard deviation around them ($\pm1\upsigma$).
• Figure 4: Chemical evolution of the studied molecular species simulated with the Nautilus gas-grain code in two stages: a cold phase ($\rm 15~K$) and a hot core phase ($\rm 100~K$). The solid lines represent the model predictions for the fractional abundances. The horizontal dashed lines show the mean logarithmic abundances derived from our ten-source sample (see Fig. \ref{['abundances']}). The vertical dotted grey line indicates the thermal jump.