# The molecular environment of the pillar-like features in the HII region G46.5-0.2

## TL;DR

This study investigates the molecular environment of pillar-like structures in the HII region G46.5-0.2, revealing star formation activity and the influence of radiation, using molecular line and optical spectroscopic observations.

## Contribution

It provides new insights into the structure and star formation processes in pillar-like features influenced by an HII region, including evidence of molecular outflows and embedded YSOs.

## Key findings

- Detection of star formation indicators in the HCO+ cloud.
- Evidence of molecular outflows perpendicular to radiation flow.
- Confirmation that RDI process is not occurring in one pillar tip.

## Abstract

At the interface of HII regions and molecular gas peculiar structures appear, some of them with pillar-like shapes. Understanding their origin is important for characterizing triggered star formation and the impact of massive stars on the interstellar medium. In order to study the molecular environment and the influence of the radiation on two pillar-like features related to the HII region G46.5-0.2, we performed molecular line observations with the Atacama Submillimeter Telescope Experiment, and spectroscopic optical observations with the Isaac Newton Telescope. From the optical observations we identified the star that is exciting the HII region as a spectral type O4-6. The molecular data allowed us to study the structure of the pillars and a HCO+ cloud lying between them. In this HCO+ cloud, which have not any well defined 12CO counterpart, we found direct evidence of star formation: two molecular outflows and two associated near-IR nebulosities. The outflows axis orientation is perpendicular to the direction of the radiation flow from the HII region. Several Class I sources are also embedded in this HCO+ cloud, showing that it is usual that the YSOs form large associations occupying a cavity bounded by pillars. On the other hand, it was confirmed that the RDI process is not occurring in one of the pillar tips.