131 research outputs found
Far-infrared dust properties in the Galaxy and the Magellanic Clouds
A recent data analysis of the far-infrared (FIR) map of the Galaxy and the
Magellanic Clouds has shown that there is a tight correlation between two FIR
colours: the 60 um-100 um and 100 um-140 um colours. This FIR colour relation
called ``main correlation'' can be interpreted as indicative of a sequence of
various interstellar radiation fields with a common FIR optical property of
grains. In this paper, we constrain the FIR optical properties of grains by
comparing the calculated FIR colours with the observational main correlation.
We show that neither of the ``standard'' grain species (i.e. astronomical
silicate and graphite grains) reproduces the main correlation. However, if the
emissivity index at ~ 100--200 um is changed to ~ 1--1.5 (not ~ 2 as the above
two species), the main correlation can be successfully explained. Thus, we
propose that the FIR emissivity index is ~ 1--1.5 for the dust in the Galaxy
and the Magellanic Clouds at ~ 100--200 um. We also consider the origin of the
minor correlation called ``sub-correlation'', which can be used to estimate the
Galactic star formation rate.Comment: 12 pages, 8 figures, accepted for publication in MNRA
The ASTRO-F Mission : Large Area Infrared Survey
ASTRO-F is the first Japanese satellite mission dedicated for large area
surveys in the infrared. The 69cm aperture telescope and scientific instruments
are cooled to 6K by liquid Helium and mechanical coolers. During the expected
mission life of more than 500 days, ASTRO-F will make the most advanced all-sky
survey in the mid- to far-infrared since the Infrared astronomical Satellite
(IRAS). The survey will be made in 6 wavebands and will include the first all
sky survey at >100-160(mu)m. Deep imaging and spectroscopic surveys with
pointed observations will also be carried out in 13 wavelength bands from
2-160(mu)m. ASTRO-F should detect more than a half million galaxies tracing the
large-scale structure of the Universe out to redshifts of unity, detecting
rare, exotic extraordinarily luminous objects at high redshift, numerous brown
dwarfs, Vega-like stars, protostars, and will reveal the large-scale structure
of nearby galactic star forming regions. ASTRO-F is a perfect complement to
Spitzer Space Telescope in respect of its wide sky and wavelength coverage.
Approximately 30 percent of pointed observations will be allocated to an
open-time opportunity. Updated pre-flight ensitivities as well as the
observation plan including the large-area surveys are described.Comment: accepted for publication in Advances in Space Research, 15 pages, 7
Postscript figures, uses elsart.cl
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