Properties of dust at the Galactic center probed by AKARI far-infrared spectral mapping

Abstract

Aims. We investigate the properties of interstellar dust in the Galactic center region toward the Arches and Quintuplet clusters. Methods. 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 × 10 that includes both clusters to obtain a low-resolution (R = 1.2 cm −1 ) spectrum at every spatial bin of 30 × 30 . Results. We derive the spatial variations in the dust continuum emission at different wavenumbers, which are compared with those of the [OIII] 88 μm (113 cm −1 ) emission and the OH 119 μm (84 cm −1 ) absorption. The spectral fitting shows that two 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 is a significant excess on top of a modified blackbody continuum around 80-90 cm −1 (110-130 μm). Conclusions. The warmer dust component is spatially correlated with the [OIII] 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 quite closely reproduce the observed spectrum with the dust feature.

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

“…The need for a secondary cold dust component to match the continuum emission from the filaments was already noted by Kaneda et al (2012), who used AKARI observations of the Arched Filaments and the Sickle H II region to study the farinfrared fine-structure line emission of these regions. For our models of the filaments, an additional 20 K DUSTY model was used to fit the observed far-IR fluxes that exceeded the predictions of DUSTY models based on the 25/37 color temperatures.…”

The Properties of Dust Emission in the Galactic Center Region Revealed by Fis-FTS Observations

“…The differences suggest that the star-forming activity of the Arches cluster is at an earlier stage than that of the Quintuplet cluster. (Yasuda et al, 2009;Kaneda et al, 2012), and (b) cold dust with the contours of the integrated CO(J=1-0) emission (Oka et al, 1998).…”

Processing of Interstellar Dust Grains in Galaxies

“…For the Galactic center, we investigated spatial variations in the spectral shapes, focusing on dust continuum emission (Kaneda et al, 2012b). For this purpose, we reduced the spectral resolution to increase the signal-to-noise ratio of the dust continuum emission.…”

“…The excess emission probably represents a dust feature, which is found to be spatially correlated with the OH absorption and a CO cloud. Possible origins of the dust feature were discussed in Kaneda et al (2012b): carbon onions or micron-sized graphite grains, based on graphite materials. We find that the dust model including the large graphite grains can at least reproduce the observed spectrum with the dust feature fairly well.…”