The Interstellar Medium viewed by
the AKARI Far-Infrared All-Sky Survey
121232Yasuo Doi , Satoshi Takita , Takafumi Ootsubo , Ko Arimatsu , Masahiro Tanaka , Yoshimi Kitamura ,24256,7Mitsunobu Kawada , Shuji Matsuura , Takao Nakagawa , Makoto Hattori , and Glenn J. White
1The University of Tokyo, Japan, 2Institute of Space and Astronautical Science, Japan, 3University of Tsukuba, Japan, 4Kwansei Gakuin University, Japan,5Tohoku University, Japan, 6The Open University, UK, 7The Rutherford Appleton Laboratory, UKAbstract
We present a far-infrared all-sky atlas made from a sensitive all-sky survey using the Japanese AKARI satellite. The survey covers > 99% of the sky in four photometric bands centred at65µm, 90µm, 140µm, and 160µm with spatial resolutions ranging from 1 to 1.5 arcmin. Having four to five times better spatial resolution as well as data at longer wavelengths comparedto IRAS, the data provide crucial information for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM). The comprehensive wavelength
coverage from 50 µm to 180 µm provides SED information at the peak of the dust continuum emission, enabling us to make a precise evaluation of its temperature, which leads to a detailed
investigation of the total amount of dust particles, and their irradiation environment. The large-scale distribution of dust in interstellar clouds, their temperatures and column densities, canbe investigated in great detail from the largest spatial scales of entire giant molecular clouds down to those as small as individual molecular cloud cores. In addition to the point source
distribution, the large-scale distribution of ISM cirrus emission, and its filamentary structure, are well traced. We have made the first public release of the full-sky data to provide a legacy
data set for use by the astronomical community. The AKARI FIR images are a new powerful resource from which to investigate the detailed nature of ISM from the smallest scales that
trace individual star forming cores, to the complex structures revealed that span the full sky.

The AKARI Far-Infrared All-Sky Survey

Full sky image in 4bands• All-sky photometric survey in 65µm, 90µm,140µm, and 160µm• Spatial resolution: 63”@65µm, 78”@90µm,88”@140µm & 160µm• improved spatial resolution and sensitivity,extended wavelength coverage comparing toIRAS (see comparison of η Car images below)

Images of η Car region. Left panel: three-colour composite of AKARI 65µm (blue), AKARI 90µm (green), andAKARI 140µm (red) images. Right panel: composite image of IRIS 60µm (cyan) and IRIS 100µm (red) images
for a comparison of spatial resolutions between IRAS and AKARI images.

IR cirrus spatial power spectra @ Polaris Flare

Evaluation of dust SED and column density
AKARI data give good evaluationof dust SED that show good consistency with IRAS and Planckdata. → Dust column with highspatial resolution.

As shown in the left figure, AKARI data trace
power-law spectra down to ∼ 20 @ 140µm, while
IRAS and Planck start losing their spatial information below ∼ 300. → Huge spatial dynamic
range of AKARI data.

Filament extraction @ Taurus

Access to the data and support informations

Typical width of filaments (∼ 0.1 pc) are approximately 2.50 @ 140pc → AKARI can trace
all the filamentary structures in near-by clouds and study their spatial distribution as wellas correlation with YSOs. In Taurus, we find that all the YSOs (30 sources) are on thefilaments, while TTSs show a lower, but still statistically significant association, with thefilaments.
Distance from the sources to thenearest filament (see figure below) is consistent with 0.1 [kms−1] random motion of TTSs
against their natal filaments.

AKARI data are open to the public and available at
http://www.ir.isas.jaxa.jp/AKARI/Archive/Images/FIS AllSkyMap/
Visit following site for the list of data mirror sites, detailed description ofdata and support informations: http://akari.c.u-tokyo.ac.jp/˜ doi/
Feel free to contact doi@ea.c.u-tokyo.ac.jp for more inquiries.

Summary: the AKARI FIR images• Multiple-waveband coverage at the peak of the dust SED– BGs colour temperature, dust column evaluation– Dust composition, evolution• Good spatial resolution, huge dynamic range– From global picture of diffuse ISM/giant molecular complex down to prestellar cores!!
– Structure formation, phase transition, radiative transfer in denser regions . . .
• A new powerful resource to investigate the detailed nature of ISM.

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