The relation of H2CO, 12CO, and 13CO in molecular clouds

TL;DR

This study investigates the spatial distribution and relationship of H2CO, 12CO, and 13CO spectral lines in several molecular cloud regions, revealing that H2CO and 13CO trace similar dense regions.

Contribution

It provides the first detailed comparison of H2CO with 12CO and 13CO distributions across multiple regions, highlighting their correlation and similar tracing of dense molecular gas.

Findings

H2CO distribution closely matches 12CO and 13CO on large scales.

13CO correlates better with H2CO than 12CO does.

H2CO and 13CO trace similar dense regions with consistent spectral properties.

Abstract

Aims. We seek to understand how the 4.8 GHz formaldehyde absorption line is distributed in the MON R2, S156, DR17/L906, and M17/M18 regions. More specifically, we look for the relationship among the H2CO, 12CO, and 13CO spectral lines. Methods. The four regions of MON R2 (60'x90'), S156 (5'0x70'), DR17/L906 (40'x60'), and M17 /M18 (70'x80')were observed for H2CO (beam 10'), H110a recombination (beam 10'), 6 cm continuum (beam 10'), 12CO (beam 1'), and 13CO (beam 1'). We compared the H2CO,12CO,13CO, and continuum distributions, and also the spectra line parameters of H2CO,12CO, and 13CO. Column densities of H2CO,13CO, and H2 were also estimated. Results. We found out that the H2CO distribution is similar to the 12CO and the 13CO distributions on a large scale. The correlation between the 13 CO and the H2CO distributions is better than between the 12CO and H2CO distributions. The H2CO and the 13CO tracers systematically provide consistent views of the dense regions. T heir maps have similar shapes, sizes, peak positions, and molecular spectra and present similar centr al velocities and line widths. Such good agreement indicates that the H2CO and the 13CO arise from similar regions.