AKARI Far-Infrared Spectroscopic Observations of the Galactic Center Region

Abstract

We have observed the Quintuplet- and Arches-cluster regions with the Fourier Transform Spectrometer (FTS) of the Far-Infrared Surveyor (FIS) aboard AKARI to investigate the physical conditions of interstellar matter around the clusters. The FIS-FTS mapping data reveal differences in the spatial distribution among the far-infrared [OIII], [NII], and [CII] line emissions near the Arches cluster; the emission of an ionic line with a higher ionization potential is distributed closer to the Arches cluster. This clearly indicates that UV photons from the Arches cluster are ionizing the surface of nearby molecular clouds, and penetrating deeper to dissociate the cloud. We have estimated the effective temperature of the Arches cluster to be about 34000K from the ratio of the [OIII]/[NII] lines.