# The Molecular Gas Environment in the 20 km s$^{-1}$ Cloud in the Central Molecular Zone

## TL;DR

This study uses high-resolution molecular line observations to analyze the star-forming environment in the 20 km s$^{-1}$ cloud of the Central Molecular Zone, revealing shock activity, hot cores, and localized heating effects.

## Contribution

It provides detailed high-angular-resolution molecular line data and analysis of shock tracers, temperature, and heating mechanisms in a specific star-forming cloud in the Galactic Center.

## Key findings

- Detection of shock tracers correlated with dense cores.
- Gas temperatures exceeding 100 K at 0.1-pc scales.
- Identification of shock-heated regions and protostellar heating signatures.

## Abstract

We recently reported a population of protostellar candidates in the 20 km s$^{-1}$ cloud in the Central Molecular Zone of the Milky Way, traced by H$_2$O masers in gravitationally bound dense cores. In this paper, we report high-angular-resolution ($\sim$3'') molecular line studies of the environment of star formation in this cloud. Maps of various molecular line transitions as well as the continuum at 1.3 mm are obtained using the Submillimeter Array. Five NH$_3$ inversion lines and the 1.3 cm continuum are observed with the Karl G. Jansky Very Large Array. The interferometric observations are complemented with single-dish data. We find that the CH$_3$OH, SO, and HNCO lines, which are usually shock tracers, are better correlated spatially with the compact dust emission from dense cores among the detected lines. These lines also show enhancement in intensities with respect to SiO intensities toward the compact dust emission, suggesting the presence of slow shocks or hot cores in these regions. We find gas temperatures of $\gtrsim$100 K at 0.1-pc scales based on RADEX modelling of the H$_2$CO and NH$_3$ lines. Although no strong correlations between temperatures and linewidths/H$_2$O maser luminosities are found, in high-angular-resolution maps we notice several candidate shock heated regions offset from any dense cores, as well as signatures of localized heating by protostars in several dense cores. Our findings suggest that at 0.1-pc scales in this cloud star formation and strong turbulence may together affect the chemistry and temperature of the molecular gas.