PDR Emission from the Arched-Filaments and Nearby Positions

TL;DR

This study models the physical conditions of gas in the Galactic Center's filaments using PDR models, finding that observed intensities align with predictions and revealing insights into UV fields, densities, and cosmic-ray ionization rates.

Contribution

It applies PDR modeling to extreme Galactic Center conditions, providing new constraints on gas properties and line ratios in this unique environment.

Findings

Observed intensities match PDR model predictions.

Gas exposed to low UV fields (~10^2-10^3 Draine units).

Cosmic-ray ionization rates vary up to 10^-14 s^-1.

Abstract

We investigate the physical conditions of the gas, atomic and molecular, in the filaments in the context of Photo-Dissociation Regions (PDRs) using the KOSMA-PDR mode of clumpy clouds. We also compare the [CII] vs. [NII] integrated intensity predictions in Abel et al. 2005 for HII regions and adjacent PDRs in the Galactic disk, and check for their applicability under the extreme physical conditions present in the GC. Our preliminary results show that observed integrated intensities are well reproduced by the PDR model. The gas is exposed to a relatively low Far-UV field between 10^2 - 10^3 Draine fields. The total volume hydrogen density is well constrained between 10^4 - 10^5 cm^-3. The hydrogen ionization rate due to cosmic-rays varies between 10^-15 and 4x10^-15 s^-1, with the highest value ~ 10^-14 s^-1 found towards G0.07+0.04. Our results show that the line-of-sight contribution to the total distance of the filaments to the Arches Cluster is not negligible. The spatial distribution of the [CII]/[NII] ratio shows that the integrated intensity ratios are fairly homogeneously distributed for values below 10 in energy units. Calculations including variation on the [C/N] abundance ratio show that tight constraints on this ratio are needed to reproduce the observations.