# Dusty Cloud Acceleration with Multiband Radiation

## TL;DR

This study uses simulations to analyze how dust clouds are accelerated by radiation pressure, revealing that infrared radiation efficiently drives acceleration while ultraviolet radiation can cause cloud disruption, affecting cloud survival and dynamics.

## Contribution

It provides new insights into the relative effects of ultraviolet and infrared radiation on dusty cloud acceleration and survival, highlighting the importance of infrared reprocessing in radiation-driven outflows.

## Key findings

- Infrared radiation dominates cloud acceleration and survival.
- Ultraviolet radiation can compress and disrupt clouds.
- Efficient infrared reprocessing enhances radiation pressure effectiveness.

## Abstract

We perform two-dimensional and three-dimensional simulations of cold, dense clouds, which are accelerated by radiation pressure on dust relative to a hot, diffuse background gas. We examine the relative effectiveness of acceleration by ultraviolet and infrared radiation fields, both independently and acting simultaneously on the same cloud. We study clouds that are optically thin to infrared emission but with varying ultraviolet optical depths. Consistent with previous work, we find relatively efficient acceleration and long cloud survival times when the infrared band flux dominates over the ultraviolet flux. However, when ultraviolet is dominant or even a modest percentage ($\sim 5-10$\%) of the infrared irradiating flux, it can act to compress the cloud, first crushing it and then disrupting the outer layers. This drives mixing of outer regions of the dusty gas with the hot diffuse background to the point where most dust is not likely to survive or stay coupled to the gas. Hence, the cold cloud is unable to survive for a long enough timescale to experience significant acceleration before disruption even though efficient infrared cooling keeps the majority of the gas close to radiative equilibrium temperature ($T \lesssim 100$K). We discuss implications for observed systems, concluding that radiation pressure driving is most effective when the light from star-forming regions is efficiently reprocessed into the infrared.