Astrochemical Correlations in Molecular Clouds

TL;DR

This study uses hydrodynamic simulations and chemical networks to analyze spectral correlations among molecular cloud tracers, providing insights into how different species' emissions relate and how observational parameters affect these correlations.

Contribution

It introduces a comprehensive analysis of spectral correlation functions for multiple molecular tracers in simulated clouds, offering guidance for observational strategies.

Findings

C and CO have similar spectral correlation functions.

Beam size influences emission characteristics differently for each species.

Up to 10" beam size, SCF slopes remain relatively stable.

Abstract

We investigate the spectral correlations between different species used to observe molecular clouds. We use hydrodynamic simulations and a full chemical network to study the abundances of over 150 species in typical Milky Way molecular clouds. We perform synthetic observations in order to produce emission maps of a subset of these tracers. We study the effects of different lines of sight and spatial resolution on the emission distribution and perform a robust quantitative comparison of the species to each other. We use the Spectral Correlation Function (SCF), which quantifies the root mean squared difference between spectra separated by some length scale, to characterize the structure of the simulated cloud in position-position-velocity (PPV) space. We predict the observed SCF for a broad range of observational tracers, and thus, identify homologous species. In particular, we show that the pairs C and CO, C$^{+}$ and CN, NH$_3$ and H$_2$CS have very similar SCFs. We measure the SCF slope variation as a function of beam size for all species and demonstrate that the beam size has a distinct effect on different species emission. However, for beams of up to 10", placing the cloud at 1 kpc, the change is not large enough to move the SCF slopes into different regions of parameter space. The results from this study provide observational guidance for choosing the best tracer to probe various cloud length scales.