11:45 AM - 12:00 PM
[PPS24-04] Small-scale structure of the zodiacal dust cloud observed in mid- and far-infrared with AKARI
Keywords:zodiacal light, interplanetary dust, AKARI, infrared
The zodiacal light emission (ZE) is the thermal emission from the interplanetary dust and the dominant diffuse radiation in the mid- to far-infrared wavelength region. The zodiacal dust cloud has a relatively smooth distribution. However, from the results of the Infrared Astronomy Satellite (IRAS) observations, it was found that there are many small-scale structures in the ZE distribution, such as asteroidal dust bands and a circumsolar resonance ring.
The Japanese infrared satellite AKARI, a dedicated satellite for infrared astronomical observations, is the mission to survey the whole sky in the mid- and far-infrared. AKARI detected the small-scale structure of the zodiacal cloud, such as the asteroidal dust bands and the circumsolar ring. There are three major bands (±1.4 degree, ±2.1 degree, and ±9.3 degree) among dust bands that form small-scale latitude features in the ZE. These three prominent asteroidal dust bands can be clearly seen in the AKARI far-infrared all-sky maps at 65 and 90 micron bands.
We also present spectra of the zodiacal light observed in mid-infrared wavelength region with Infrared Camera (IRC) onboard AKARI. The IRC spectra (5.5--12.5 micron) show a trapezoidal excess emission feature in 9--11 micron region which can be reasonably accounted for by a combination of amorphous and/or crystalline silicate. Although this excess feature is rather smooth and lacking sharp peaks, a possible 10.5 micron peak and small peaks around 9.3 and 11.35 micron can be seen at the shoulder of the trapezoidal excess. The spectrum around β=10 degree toward the asteroidal dust band seems to have a slight different shape of the silicate feature from those of other regions.
The Japanese infrared satellite AKARI, a dedicated satellite for infrared astronomical observations, is the mission to survey the whole sky in the mid- and far-infrared. AKARI detected the small-scale structure of the zodiacal cloud, such as the asteroidal dust bands and the circumsolar ring. There are three major bands (±1.4 degree, ±2.1 degree, and ±9.3 degree) among dust bands that form small-scale latitude features in the ZE. These three prominent asteroidal dust bands can be clearly seen in the AKARI far-infrared all-sky maps at 65 and 90 micron bands.
We also present spectra of the zodiacal light observed in mid-infrared wavelength region with Infrared Camera (IRC) onboard AKARI. The IRC spectra (5.5--12.5 micron) show a trapezoidal excess emission feature in 9--11 micron region which can be reasonably accounted for by a combination of amorphous and/or crystalline silicate. Although this excess feature is rather smooth and lacking sharp peaks, a possible 10.5 micron peak and small peaks around 9.3 and 11.35 micron can be seen at the shoulder of the trapezoidal excess. The spectrum around β=10 degree toward the asteroidal dust band seems to have a slight different shape of the silicate feature from those of other regions.