34 research outputs found
UA94/6/1 Folklore 566: Oral History Materials & Methods
Oral history assignment completed by Makiuti Tongia. 30 minute transcript of interview with Robert Wurster on the history of the WKU International Students\u27 Office Summary of Wurster interview part 2 Index of whole interview content Interpretative essa
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
Predicting dust extinction properties of star-forming galaxies from H-alpha/UV ratio
Using star-forming galaxies sample in the nearby Universe (0.02<z<0.10)
selected from the SDSS (DR7) and GALEX all-sky survey (GR5), we present a new
empirical calibration for predicting dust extinction of galaxies from
H-alpha-to-FUV flux ratio. We find that the H-alpha dust extinction (A(Ha))
derived with H-alpha/H-beta ratio (Balmer decrement) increases with increasing
H-alpha/UV ratio as expected, but there remains a considerable scatter around
the relation, which is largely dependent on stellar mass and/or H-alpha
equivalent width (EW(Ha)). At fixed H-alpha/UV ratio, galaxies with higher
stellar mass (or galaxies with lower EW(Ha)) tend to be more highly obscured by
dust. We quantify this trend and establish an empirical calibration for
predicting A(Ha) with a combination of H-alpha/UV ratio, stellar mass and
EW(Ha), with which we can successfully reduce the systematic uncertainties
accompanying the simple H-alpha/UV approach by ~15-30%. The new recipes
proposed in this study will provide a convenient tool for predicting dust
extinction level of galaxies particularly when Balmer decrement is not
available. By comparing A(Ha) (derived with Balmer decrement) and A(UV)
(derived with IR/UV luminosity ratio) for a subsample of galaxies for which
AKARI FIR photometry is available, we demonstrate that more massive galaxies
tend to have higher extra extinction towards the nebular regions compared to
the stellar continuum light. Considering recent studies reporting smaller extra
extinction towards nebular regions for high-redshift galaxies, we argue that
the dust geometry within high-redshift galaxies resemble more like low-mass
galaxies in the nearby Universe.Comment: 14 pages, 14 figures, Accepted for publication in MNRA
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.
AKARI-CAS --- Online Service for AKARI All-Sky Catalogues
The AKARI All-Sky Catalogues are an important infrared astronomical database
for next-generation astronomy that take over the IRAS catalog. We have
developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for
astronomers. The service includes useful and attractive search tools and visual
tools.
One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can
match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow
advanced queries to the databases, direct input of SQL is also supported. In
those queries, fast dynamic cross-identification between registered catalogs is
a remarkable feature. In addition, multiwavelength quick-look images are
displayed in the visualization tools, which will increase the value of the
service.
In the construction of our service, we considered a wide variety of
astronomers' requirements. As a result of our discussion, we concluded that
supporting users' SQL submissions is the best solution for the requirements.
Therefore, we implemented an RDBMS layer so that it covered important
facilities including the whole processing of tables. We found that PostgreSQL
is the best open-source RDBMS products for such purpose, and we wrote codes for
both simple and advanced searches into the SQL stored functions. To implement
such stored functions for fast radial search and cross-identification with
minimum cost, we applied a simple technique that is not based on dividing
celestial sphere such as HTM or HEALPix. In contrast, the Web application layer
became compact, and was written in simple procedural PHP codes. In total, our
system realizes cost-effective maintenance and enhancements.Comment: Yamauchi, C. et al. 2011, PASP..123..852
AKARI infrared imaging of reflection nebulae IC4954 and IC4955
We present the observations of the reflection nebulae IC4954 and IC4955
region with the Infrared Camera (IRC) and the Far-Infrared Surveyor (FIS) on
board the infrared astronomical satellite AKARI during its performance
verification phase. We obtained 7 band images from 7 to 160um with higher
spatial resolution and higher sensitivities than previous observations. The
mid-infrared color of the S9W (9um) and L18W (18um) bands shows a systematic
variation around the exciting sources. The spatial variation in the
mid-infrared color suggests that the star-formation in IC4954/4955 is
progressing from south-west to north-east. The FIS data also clearly resolve
two nebulae for the first time in the far-infrared. The FIS 4-band data from
65um to 160um allow us to correctly estimate the total infrared luminosity from
the region, which is about one sixth of the energy emitted from the existing
stellar sources. Five candidates for young stellar objects have been detected
as point sources for the first time in the 11um image. They are located in the
red S9W to L18W color regions, suggesting that current star-formation has been
triggered by previous star-formation activities. A wide area map of the size of
about 1 x 1 (deg^2) around the IC4954/4955 region was created from the AKARI
mid-infrared all-sky survey data. Together with the HI 21cm data, it suggests a
large hollow structure of a degree scale, on whose edge the IC4954/4955 region
has been created, indicating star formation over three generations in largely
different spatial scales.Comment: 23 pages, 7 figures, accepted for publication in PASJ AKARI special
issu
Calibration and Performance of the AKARI Far-Infrared Surveyor (FIS) -- Slow-Scan Observation Mode for Point Sources
We present the characterization and calibration of the Slow-Scan observation
mode of the Far-Infrared Surveyor (FIS) onboard the AKARI satellite. The FIS,
one of the two focal-plane instruments on AKARI, has four photometric bands
between 50--180 um with two types of Ge:Ga array detectors. In addition to the
All-Sky Survey, FIS has also taken detailed far-infrared images of selected
targets by using the Slow-Scan mode. The sensitivity of the Slow-Scan mode is
one to two orders of magnitude better than that of the All-Sky Survey, because
the exposure time on a targeted source is much longer. The point spread
functions (PSFs) were obtained by observing several bright point-like objects
such as asteroids, stars, and galaxies. The derived full widths at the half
maximum (FWHMs) are ~30'' for the two shorter wavelength bands and ~40'' for
the two longer wavelength bands, being consistent with those expected by the
optical simulation, although a certain amount of excess is seen in the tails of
the PSFs. The flux calibration has been performed by the observations of
well-established photometric calibration standards (asteroids and stars) in a
wide range of fluxes. After establishing the method of aperture photometry, the
photometric accuracy for point-sources is better than +-15% in all of the bands
expect for the longest wavelength.Comment: 25 pages, 7 figures, accepted publication in PAS
The Far-Infrared Properties of Spatially Resolved AKARI Observations
We present the spatially resolved observations of IRAS sources from the
Japanese infrared astronomy satellite AKARI All-Sky Survey during the
performance verification (PV) phase of the mission. We extracted reliable point
sources matched with IRAS point source catalogue. By comparing IRAS and AKARI
fluxes, we found that the flux measurements of some IRAS sources could have
been over or underestimated and affected by the local background rather than
the global background. We also found possible candidates for new AKARI sources
and confirmed that AKARI observations resolved IRAS sources into multiple
sources. All-Sky Survey observations are expected to verify the accuracies of
IRAS flux measurements and to find new extragalactic point sources.Comment: 11 pages, 7 figures, accepted publication in PASJ AKARI special issu
A deep ATCA 20cm radio survey of the AKARI Deep Field South near the South Ecliptic Pole
The results of a deep 20 cm radio survey at 20 cm are reported of the AKARI
Deep Field South (ADF-S) near the South Ecliptic Pole (SEP), using the
Australia Telescope Compact Array telescope, ATCA. The survey has 1 sigma
detection limits ranging from 18.7--50 microJy per beam over an area of ~1.1 sq
degrees, and ~2.5 sq degrees to lower sensitivity. The observations, data
reduction and source count analysis are presented, along with a description of
the overall scientific objectives, and a catalogue containing 530 radio sources
detected with a resolution of 6.2" x 4.9". The derived differential source
counts show a pronounced excess of sources fainter than ~1 mJy, consistent with
an emerging population of star forming galaxies. Cross-correlating the radio
with AKARI sources and archival data we find 95 cross matches, with most
galaxies having optical R-magnitudes in the range 18-24 mag, and 52 components
lying within 1" of a radio position in at least one further catalogue (either
IR or optical). We have reported redshifts for a sub-sample of our catalogue
finding that they vary between galaxies in the local universe to those having
redshifts of up to 0.825. Associating the radio sources with the Spitzer
catalogue at 24 microns, we find 173 matches within one Spitzer pixel, of which
a small sample of the identifications are clearly radio loud compared to the
bulk of the galaxies. The radio luminosity plot and a colour-colour analysis
suggest that the majority of the radio sources are in fact luminous star
forming galaxies, rather than radio-loud AGN. There are additionally five cross
matches between ASTE or BLAST submillimetre galaxies and radio sources from
this survey, two of which are also detected at 90 microns, and 41 cross-matches
with submillimetre sources detected in the Herschel HerMES survey Public Data
release.Comment: MNRAS accepted and in press 9 July 2012: 28 pages, 15 Figures, 17
Table
The Far-Infrared Surveyor (FIS) for AKARI
The Far-Infrared Surveyor (FIS) is one of two focal plane instruments on the
AKARI satellite. FIS has four photometric bands at 65, 90, 140, and 160 um, and
uses two kinds of array detectors. The FIS arrays and optics are designed to
sweep the sky with high spatial resolution and redundancy. The actual scan
width is more than eight arcmin, and the pixel pitch is matches the diffraction
limit of the telescope. Derived point spread functions (PSFs) from observations
of asteroids are similar to the optical model. Significant excesses, however,
are clearly seen around tails of the PSFs, whose contributions are about 30% of
the total power. All FIS functions are operating well in orbit, and its
performance meets the laboratory characterizations, except for the two longer
wavelength bands, which are not performing as well as characterized.
Furthermore, the FIS has a spectroscopic capability using a Fourier transform
spectrometer (FTS). Because the FTS takes advantage of the optics and detectors
of the photometer, it can simultaneously make a spectral map. This paper
summarizes the in-flight technical and operational performance of the FIS.Comment: 23 pages, 10 figures, and 2 tables. Accepted for publication in the
AKARI special issue of the Publications of the Astronomical Society of Japa