Properties of dust in the Galactic center region probed by AKARI far-infrared spectral mapping - detection of a dust feature

TL;DR

This study maps far-infrared spectra of interstellar dust in the Galactic center, revealing two main dust temperature components and a new dust feature linked to specific gas and dust interactions.

Contribution

It presents the first detailed spectral mapping of dust in the Galactic center region, identifying a new dust feature and its association with specific gas components.

Findings

Two dust components at ~20 K and ~50 K explain most spectra.

A significant dust feature around 80-90 cm^-1 was detected.

The dust feature correlates with OH absorption and CO clouds.

Abstract

We investigate the properties of interstellar dust in the Galactic center region toward the Arches and Quintuplet clusters. With the Fourier Transform Spectrometer of the AKARI/Far-Infrared Surveyor, we performed the far-infrared (60 - 140 cm^-1) spectral mapping of an area of about 10' x 10' which includes the two clusters to obtain a low-resolution (R = 1.2 cm^-1) spectrum at every spatial bin of 30" x 30". We derive the spatial variations of dust continuum emission at different wavenumbers, which are compared with those of the [O III] 88 micron (113 cm^-1) emission and the OH 119 micron (84 cm^-1) absorption. The spectral fitting shows that two dust modified blackbody components with temperatures of ~20 K and ~50 K can reproduce most of the continuum spectra. For some spectra, however, we find that there exists a significant excess on top of a modified blackbody continuum around 80 - 90 cm^-1 (110 - 130 microns). The warmer dust component is spatially correlated well with the [O III] emission and hence likely to be associated with the highly-ionized gas locally heated by intense radiation from the two clusters. The excess emission probably represents a dust feature, which is found to be spatially correlated with the OH absorption and a CO cloud. We find that a dust model including micron-sized graphite grains can reproduce the observed spectrum with the dust feature fairly well.