# An Infrared Study of the Dust Properties and Geometry of the Arched Filaments HII Region with SOFIA/FORCAST

## TL;DR

This study uses infrared observations from SOFIA/FORCAST to analyze dust properties and the influence of the Arches cluster on the surrounding interstellar medium in the Galactic center, revealing dust processing and PAH depletion.

## Contribution

It provides new insights into dust grain sizes, PAH abundance, and the environmental effects in the Arched Filaments region using multi-wavelength infrared data.

## Key findings

- Dust temperatures are relatively uniform at 70-100 K.
- Inferred dust grain sizes are smaller than typical ISM grains (~0.01 μm).
- PAH abundances are depleted by factors of 1.6-10 compared to diffuse ISM.

## Abstract

Massive stellar clusters provide radiation ($\mathrm{\sim 10^7-10^8~L_{\odot}}$) and winds ($\mathrm{\sim 1000~km/s}$) that act to heat dust and shape their surrounding environment. In this paper, the Arched Filaments in the Galactic center were studied to better understand the influence of the Arches cluster on its nearby interstellar medium (ISM). The Arched Filaments were observed with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, and 37.1 $\mu$m. Color-temperature maps of the region created with the 25.2 and 37.1 $\mu$m data reveal relatively uniform dust temperatures (70-100 K) over the extent of the filaments ($\sim 25$ pc). Distances between the cluster and the filaments were calculated assuming equilibrium heating of standard size ISM dust grains ($\sim$0.1 $\mu$m). The distances inferred by this method are in conflict with the projected distance between the filaments and the cluster, although this inconsistency can be explained if the characteristic grain size in the filaments is smaller ($\sim$0.01 $\mu$m) than typical values. DustEM models of selected locations within the filaments show evidence of depleted abundances of polycyclic aromatic hydrocarbons (PAHs) by factors of $\sim$1.6-10 by mass compared to the diffuse ISM. The evidence for both PAH depletion and a smaller characteristic grain size points to processing of the ISM within the filaments. We argue that the eroding of dust grains within the filaments is not likely attributable to the radiation or winds from the Arches cluster, but may be related to the physical conditions in the Galactic center.