102 research outputs found
Spatial Distributions of Cold and Warm Interstellar Dust in M101 Resolved with AKARI/Far-Infrared Surveyor (FIS)
The nearby face-on spiral galaxy M101 has been observed with the Far-Infrared
Surveyor (FIS) onboard AKARI. The far-infrared four-band images reveal fine
spatial structures of M101, which include global spiral patterns, giant HII
regions embedded in outer spiral arms, and a bar-like feature crossing the
center. The spectral energy distribution of the whole galaxy shows the presence
of the cold dust component (18 K) in addition to the warm dust component (55
K). The distribution of the cold dust is mostly concentrated near the center,
and exhibits smoothly distributed over the entire extent of the galaxy, whereas
the distribution of the warm dust indicates some correlation with the spiral
arms, and has spotty structures such as four distinctive bright spots in the
outer disk in addition to a bar-like feature near the center tracing the CO
intensity map. The star-formation activity of the giant HII regions that
spatially correspond to the former bright spots is found to be significantly
higher than that of the rest of the galaxy. The latter warm dust distribution
implies that there are significant star-formation activities in the entire bar
filled with molecular clouds. Unlike our Galaxy, M101 is a peculiar normal
galaxy with extraordinary active star-forming regions.Comment: 18 pages, 9 figures, accepted for publication in PASJ AKARI special
issu
Far-infrared all sky diffuse mapping with AKARI
We discuss the capability of AKARI in recovering diffuse far-infrared
emission, and examine the achieved reliability. Critical issues in making
images of diffuse emission are the transient response and long-term stability
of the far-infrared detectors. Quantitative evaluation of these characteristics
are the key to achieving sensitivity comparable to or better than that for
point sources (< 20 -- 95 MJy sr-1). We describe current activity and progress
toward the production of high quality images of the diffuse far-infrared
emission using the AKARI all-sky survey data.Comment: 4 pages, 8 figures, to appear in the Proceedings of the Conference
"AKARI, a light to illuminate the misty Universe", Fukutake Hall, The
University of Tokyo, Japan, 16-19 February 200
AKARI Far-Infrared All Sky Survey
We demonstrate the capability of AKARI for mapping diffuse far-infrared
emission and achieved reliability of all-sky diffuse map. We have conducted an
all-sky survey for more than 94 % of the whole sky during cold phase of AKARI
observation in 2006 Feb. -- 2007 Aug. The survey in far-infrared waveband
covers 50 um -- 180 um with four bands centered at 65 um, 90 um, 140 um, and
160 um and spatial resolution of 3000 -- 4000 (FWHM).This survey has allowed us
to make a revolutionary improvement compared to the IRAS survey that was
conducted in 1983 in both spatial resolution and sensitivity after more than a
quarter of a century. Additionally, it will provide us the first all-sky survey
data with high-spatial resolution beyond 100 um. Considering its extreme
importance of the AKARI far-infrared diffuse emission map, we are now
investigating carefully the quality of the data for possible release of the
archival data. Critical subjects in making image of diffuse emission from
detected signal are the transient response and long-term stability of the
far-infrared detectors. Quantitative evaluation of these characteristics is the
key to achieve sensitivity comparable to or better than that for point sources
(< 20 -- 95 [MJy/sr]). We describe current activities and progress that are
focused on making high quality all-sky survey images of the diffuse
far-infrared emission.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
A New Galactic Extinction Map of the Cygnus Region
We have made a Galactic extinction map of the Cygnus region with 5' spatial
resolution. The selected area is 80^\circ to 90^\circ in the Galactic longitude
and -4^\circ to 8^\circ in the Galactic latitude. The intensity at 140 \mum is
derived from the intensities at 60 and 100 \mum of the IRAS data using the
tight correlation between 60, 100, and 140 \mum found in the Galactic plane.
The dust temperature and optical depth are calculated with 5' resolution from
the 140 and 100 \mum intensity, and Av is calculated from the optical depth. In
the selected area, the mean dust temperature is 17 K, the minimum is 16 K, and
the maximum is 30 K. The mean Av is 6.5 mag, the minimum is 0.5 mag, and the
maximum is 11 mag. The dust temperature distribution shows significant spatial
variation on smaller scales down to 5'. Because the present study can trace the
5'-scale spatial variation of the extinction, it has an advantage over the
previous studies, such as the one by Schlegel, Finkbeiner, & Davis, who used
the COBE/DIRBE data to derive the dust temperature distribution with a spatial
resolution of 1^\circ. The difference of Av between our map and Schlegel et
al.'s is \pm 3 mag. A new extinction map of the entire sky can be produced by
applying the present method.Comment: 27 pages, 14 figures, accepted for publication in Ap
Observing H2 Emission in Forming Galaxies
We study the H2 cooling emission of forming galaxies, and discuss their
observability using the future infrared facility SAFIR. Forming galaxies with
mass >10^11 Msun emit most of their gravitational energy liberated by
contraction in molecular hydrogen line radiation, although a large part of
thermal energy at virialization is radiated away by the H Ly alpha emission.
For more massive objects, the degree of heating due to dissipation of kinetic
energy is so great that the temperature does not drop below 10^4 K and the
gravitational energy is emitted mainly by the Ly alpha emission. Therefore, the
total H2 luminosity attains the peak value of about 10^42 ergs/s for forming
galaxies whose total mass 10^11 Msun. If these sources are situated at redshift
z=8, they can be detected by rotational lines of 0-0S(3) at 9.7 micron and
0-0S(1) at 17 micron by SAFIR. An efficient way to find such H2 emitters is to
look at the Ly alpha emitters, since the brightest H2 emitters are also
luminous in the Ly alpha emission.Comment: 20 pages, 7 figures, ApJ accepte
Wide-Area Mapping of 155 Micron Continuum Emission from the Orion Molecular Cloud Complex
We present the results of a wide-area mapping of the far-infrared continuum
emission toward the Orion complex by using a Japanese balloon-borne telescope.
The 155-um continuum emission was detected over a region of 1.5 deg^2 around
the KL nebula with 3' resolution similar to that of the IRAS 100-um map.
Assuming a single-temperature model of the thermal equilibrium dust, maps of
the temperature and the optical depth were derived from the 155 um intensity
and the IRAS 100 um intensity. The derived dust temperature is 5 - 15 K lower
and the derived dust optical thickness were derived from the 155-um intensity
and the IRAS 100-um intensity. The derived dust temperature is 5 - 15 K lower
and the derived dust optical depth is 5 - 300 times larger than those derived
from the IRAS 60 and 100-um intensities due to the significant contribution of
the statistically heated very small grains to the IRAS 60-um intensity. The
optical-thickness distribution shows a filamentary dust ridge that has a 1.5
degrees extent in the north - south direction and well resembles the
Integral-Shaped Filament (ISF) molecular gas distribution. The gas-to-dust
ratio derived from the CO molecular gas distribution along the ISF is in the
range 30 - 200, which may be interpreted as being an effect of CO depletion due
to the photodissociation and/or the freezing on dust grains.Comment: 23 pages, 7 figures, 1 table, to appear in PASJ, Vol. 56, No.
The AKARI diffuse maps
We descibe the calibration of maps of diffuse Galactic Plane emission, and present detailed observations of several complexes. We put especial atention on Cygnus X region showing its temperature and density maps
The UV (GALEX) and FIR (ASTRO-F) All Sky Surveys: the measure of the dust extinction in the local universe
Before the end of 2002 will be launched the GALEX satellite (a NASA/SMEX
project) which will observe all the sky in Ultraviolet (UV) through filters at
1500 and 2300 A down to m(AB) 21. In 2004 will be launched the ASTRO-F
satellite which will perform an all sky survey at Far-Infrared (FIR)
wavelengths.
The cross-correlation of both surveys will lead to very large samples of
galaxies for which FIR and UV fluxes will be available. Using the FIR to UV
flux ratio as a quantitative tracer of the dust extinction we will be able to
measure the extinction in the nearby universe (z<0.2) and to perform a
statistically significant analysis of the extinction as a function of galactic
properties. Of particular interest is the construction of pure FIR and UV
selected samples for which the extinction will be measured as templates for the
observation of high redshift galaxies
ISO continuum observations of quasars at z=1-4 I.Spectral energy distributions of quasars from the UV to far-infrared
Eight luminous quasars with at z = 1.4 - 3.7 have been
observed in the mid- and far-infrared using ISO. All the quasars have been
detected in the mid-infrared bands of ISOCAM, while no far-infrared detections
have been made with ISOPHOT. Supplementing ISO observations with photometry in
the optical and near-infrared made from the ground mostly within 17 months
after the ISO observations, SEDs (Spectral Energy Distributions) from the UV to
far-infrared have been obtained. SEDs (Spectral Energy Distributions) from the
UV to far-infrared have been obtained while supplementing ISO observations with
photometry in the optical and near-infrared made from the ground within 17
months. The SEDs are compared with the MED (Mean spectral Energy Distributions)
of low-redshift quasars with . It is shown that our
far-infrared observations were limited by confusion noise due to crowded
sources.Comment: 9 pages, 3 figures: accepted for publication in Astronomy and
Astrophysic
Mid- to Far-Infrared spectroscopy of Sharpless 171
We have collected one-dimensional raster-scan observations of the active
star-forming region Sharpless 171 (S171), a typical HII region-molecular cloud
complex, with the three spectrometers (LWS, SWS, and PHT-S) on board ISO. We
have detected 8 far-infrared fine-structure lines, [OIII] 52um, [NIII] 57um,
[OI] 63um, [OIII] 88um, [NII] 122um, [OI] 146um, [CII] 158um, and [SiII] 35um
together with the far-infrared continuum and the H2 pure rotation transition
(J=5-3) line at 9.66um. The physical properties of each of the three phases
detected, highly-ionized, lowly-ionized and neutral, are investigated through
the far-infrared line and continuum emission. Toward the molecular region,
strong [OI] 146um emission was observed and the [OI] 63um to 146um line ratio
was found to be too small (about 5) compared to the values predicted by current
photodissociation region (PDR) models. We examine possible mechanisms to
account for the small line ratio and conclude that the absorption of the [OI]
63um and the [CII] 158um emission by overlapping PDRs along the line of sight
can account for the observations and that the [OI] 146um emission is the best
diagnostic line for PDRs. We propose a method to estimate the effect of
overlapping clouds using the far-infrared continuum intensity and derive the
physical properties of the PDR. The [SiII] 35um emission is quite strong at
almost all the observed positions. The correlation with [NII] 122um suggests
that the [SiII] emission originates mostly from the ionized gas. The [SiII]
35um to [NII] 122um ratio indicates that silicon of 30% of the solar abundance
must be in the diffuse ionized gas, suggesting that efficient dust destruction
is undergoing in the ionized region.Comment: 15 pages with 15 figures, accepted in Astronomy & Astrophysic
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