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Hideaki Fujiwara, Daisuke Ishihara,
Takashi Onaka,
Satoshi Takita,
Hirokazu Kataza,
Takuya Yamashita,
Misato Fukagawa,
Takafumi Ootsubo,
Takanori Hirao,
Keigo Enya,
Jonathan P. Marshall,
Glenn J. White,
Takao Nakagawa,
Hiroshi Murakami
[show abstract]
[hide abstract]
ABSTRACT: Context. Little is known about the properties of the warm (Tdust >~ 150 K)
debris disk material located close to the central star, which has a more direct
link to the formation of terrestrial planets than the low temperature debris
dust that has been detected to date. Aims. To discover new warm debris disk
candidates that show large 18 micron excess and estimate the fraction of stars
with excess based on the AKARI/IRC Mid-Infrared All-Sky Survey data. Methods.
We have searched for point sources detected in the AKARI/IRC All-Sky Survey,
which show a positional match with A-M dwarf stars in the Tycho-2 Spectral Type
Catalogue and exhibit excess emission at 18 micron compared to that expected
from the Ks magnitude in the 2MASS catalogue. Results. We find 24 warm debris
candidates including 8 new candidates among A-K stars. The apparent debris disk
frequency is estimated to be 2.8 +/- 0.6%. We also find that A stars and
solar-type FGK stars have different characteristics of the inner component of
the identified debris disk candidates --- while debris disks around A stars are
cooler and consistent with steady-state evolutionary model of debris disks,
those around FGK stars tend to be warmer and cannot be explained by the
steady-state model.
11/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We report Herschel and AKARI photometric observations at far-infrared (FIR)
wavelengths of the debris disk around the F3V star HD 15407A, in which the
presence of an extremely large amount of warm dust (~500-600 K) has been
suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux
densities of the debris disk at 60-160 micron are clearly above the
photospheric level of the star, suggesting excess emission at FIR as well as at
MIR wavelengths previously reported. The observed FIR excess emission is
consistent with the continuum level extrapolated from the MIR excess,
suggesting that it originates in the inner warm debris dust and cold dust
(~50-130 K) is absent in the outer region of the disk. The absence of cold dust
does not support a late heavy bombardment-like event as an origin of the large
amount of warm debris dust around HD 15047A.
10/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We present the characterization and calibration of the slow-scan observation
mode of the Infrared Camera (IRC) on-board AKARI. The IRC slow-scan
observations were operated at the S9W (9 $\mu$m) and L18W (18 $\mu$m) bands. We
have developed a toolkit for data reduction of the IRC slow-scan observations.
We introduced a "self-pointing reconstruction" method to improve the positional
accuracy to as good as 1". The sizes of the point spread functions were derived
to be $\sim6"$ at the S9W band and $\sim7"$ at the L18W bands in full width at
half maximum. The flux calibrations were achieved with the observations of 3
and 4 infrared standard stars at the S9W and L18W bands, respectively. The flux
uncertainties are estimated to be better than 20% from comparisons with the
AKARI IRC PSC and the WISE preliminary catalog.
09/2012;
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[show abstract]
[hide abstract]
ABSTRACT: With the Infrared Camera on board AKARI, we carried out near-infrared
(2.5-5.0 micron) spectroscopy of the central kiloparsec region of the barred
spiral galaxy, NGC1097, categorized as Seyfert 1 with a circumnuclear starburst
ring. Our observations mapped the area of ~50"*10" with the resolution of ~5",
covering about a half of the ring and the galactic center. As a result, we
spatially resolve the starburst ring in the polycyclic aromatic hydrocarbon 3.3
micron, the aliphatic hydrocarbon 3.4-3.6 micron features, and the hydrogen Br
alpha 4.05 micron emission. They exhibit spatial distributions significantly
different from each other, indicating that the environments vary considerably
around the ring. In particular, the aliphatic features are enhanced near the
bar connecting the ring with the nucleus, where the structure of hydrocarbon
grains seems to be relatively disordered. Near the center, the continuum
emission and the CO/SiO absorption features are strong, which indicates that
the environments inside the ring are dominated by old stellar populations. The
near-infrared spectra do not show any evidence for the presence of nuclear
activity.
04/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We report an intriguing debris disk towards the F3V star HD 15407A, in which
an extremely large amount of warm fine dust (~ 10^(-7) M_Earth) is detected.
The dust temperature is derived as ~ 500-600 K and the location of the debris
dust is estimated as 0.6-1.0 AU from the central star, a terrestrial planet
region. The fractional luminosity of the debris disk is ~ 0.005, which is much
larger than those predicted by steady-state models of the debris disk produced
by planetesimal collisions. The mid-infrared spectrum obtained by Spitzer
indicates the presence of abundant micron-sized silica dust, suggesting that
the dust comes from the surface layer of differentiated large rocky bodies and
might be trapped around the star.
03/2012;
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[show abstract]
[hide abstract]
ABSTRACT: We present the AKARI mid-infrared diffuse map of an area of about 4 deg x 3
deg near the Galactic center in the 9 um band. The band intensity is mostly
attributed to the aromatic hydrocarbon infrared emissions of carbonaceous
grains at wavelengths of 6.2, 7,7, 8.6, and 11.3 um. We detect the 9 um
emission structures extending from the Galactic plane up to the latitude of
about 2.5 deg, which have spatial correspondence to the molecular loops
revealed by the NANTEN 12CO (J=1-0) observations. We find that the surface
brightness at 9 um is suppressed near the foot points of the CO loops. The
ratios of the 9 um to the IRAS 100 um brightness show significant depression
near such bright regions in the CO emission. With the AKARI near-IR 2.5--5 um
spectroscopy, we find that the 3.3 um aromatic hydrocarbon emission is absent
in the region associated with the loop. These suggest the processing and
destruction of carbonaceous grains in the CO molecular loops.
10/2011;
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Fumihiko Usui,
Daisuke Kuroda,
Thomas G. Müller,
Sunao Hasegawa,
Masateru Ishiguro,
Takafumi Ootsubo, Daisuke Ishihara,
Hirokazu Kataza,
Satoshi Takita,
Shinki Oyabu,
Munetaka Ueno,
Hideo Matsuhara,
Takashi Onaka
[show abstract]
[hide abstract]
ABSTRACT: We present the results of an unbiased asteroid survey in the
mid-infrared wavelength region with the Infrared Camera (IRC) on board
the Japanese infrared satellite AKARI. About 20% of the point source
events recorded in the AKARI All-Sky Survey observations are not used
for the IRC Point Source Catalog (IRC-PSC) in its production process
because of a lack of multiple detection by position. Asteroids, which
are moving objects on the celestial sphere, remain in these ``residual
events''. We identify asteroids out of the residual events by matching
them with the positions of known asteroids. For the identified
asteroids, we calculate the size and albedo based on the Standard
Thermal Model. Finally we have a new brand of asteroid catalog, named
the Asteroid Catalog Using AKARI (AcuA), which contains 5120 objects,
about twice as many as the IRAS asteroid catalog. The catalog objects
comprise 4953 main belt asteroids, 58 near-Earth asteroids, and 109
Jovian Trojan asteroids. The catalog is publicly available via the
Internet.
Publications- Astronomical Society of Japan 09/2011; 63:1117-1138. · 2.44 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Context: The environmental conditions for asympotic giant branch (AGB) stars
to reach the carbon-rich (C-rich) phase are important to understand the
evolutionary process of AGB stars. The difference between the spatial
distributions of C-rich and oxygen-rich (O-rich) AGB stars is essential for the
study of the Galactic structure and the chemical evolution of the interstellar
medium (ISM). Aims: We quantitatively investigate the spatial distributions of
C-rich and O-rich AGB stars in our Galaxy. We discuss the difference between
them and its origin. Methods: We classify a large number of AGB stars newly
detected by the AKARI id-infrared all-sky survey. In the color-color diagrams,
we define their occupation zones based on the locations of known objects. We
then obtain the spatial distributions of C-rich and O-rich AGB stars, assuming
that they have the same luminosity for a given mass-loss rate. Results: We find
that O-rich AGB stars are concentrated toward the Galactic center and that the
density decreases with Galactocentric distance, whereas C-rich AGB stars show a
relatively uniform distribution within about 8kpc of Sun. Conclusion: Our
result confirms the trends reported in previous studies and extends them to a
Galactic scale. We discuss the relations between our result, the Galactic
metallicity gradient, and the chemical evolution of the ISM in our Galaxy.
08/2011;
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Tomotsugu Goto,
Stephane Arnouts,
Matthew Malkan,
Toshinobu Takagi,
Hanae Inami,
Chris Pearson,
Takehiko Wada,
Hideo Matsuhara,
Chisato Yamauchi,
Tsutomu T. Takeuchi,
Takao Nakagawa,
Shinki Oyabu, Daisuke Ishihara,
David B. Sanders,
Emeric Le Floc’h,
Hyung Mok Lee,
Woong-Seob Jeong,
Stephen Serjeant,
Chris Sedgwick
[show abstract]
[hide abstract]
ABSTRACT: By cross-correlating the AKARI all-sky survey in six infrared (IR) bands (9, 18, 65, 90, 140 and 160 μm) with the Sloan Digital Sky Survey (SDSS) galaxies, we identified 2357 IR galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial far-IR (FIR) bands for accurately measuring the galaxy spectral energy distribution (SED) across the peak of the dust emission at > 100 μ m. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (LIR) of individual galaxies.Using this LIR, we constructed the luminosity functions (LF) of IR galaxies at a median redshift of z= 0.031. The LF agrees well with that at z= 0.0082 (the Revised Bright Galaxy Sample), showing smooth and continuous evolution towards higher redshift LFs measured in the AKARI North Ecliptic Pole (NEP) deep field. By integrating the IR LF weighted by LIR, we measured the local cosmic IR luminosity density of ΩIR= (3.8+5.8−1.2) × 108 L⊙ Mpc−3. We separate galaxies into active galactic nuclei (AGN), star-forming galaxies (SFG) and composite by using the [N ii]/Hα versus [O iii]/Hβ line ratios. The fraction of AGN shows a continuous increase with increasing LIR from 25 to 90 per cent at 9 < log LIR < 12.5. The SFRHα and show good correlations with LIR for SFG and AGN, respectively. The self-absorption-corrected Hα/Hβ ratio shows a weak increase with LIR with a substantial scatter. When we separate IR LFs into contributions from AGN and SFG, the AGN contribution becomes dominant at LIR > 1011 L⊙, coinciding with the break of both the SFG and AGN IR LFs. At LIR≤ 1011 L⊙, SFG dominates IR LFs. Only 1.1 ± 0.1 per cent of ΩIR is produced by luminous infrared galaxies (LIR > 1011 L⊙), and only 0.03 ± 0.01 per cent by ultraluminous infrared galaxies (LIR > 1012 L⊙) in the local Universe. Compared with high-redshift results from the AKARI NEP deep survey, we observed a strong evolution of ΩSFGIR∝ (1 +z)4.1±0.4 and ΩAGNIR∝ (1 +z)4.1±0.5. Our results show that all of our measured quantities (IR LFs, L*, ΩAGNIR, ΩSFGIR) show smooth and steady increase from lower redshift (the Revised Bright Galaxy Sample) to higher redshift (the AKARI NEP deep survey).
Monthly Notices of the Royal Astronomical Society 06/2011; 414(3):1903 - 1913. · 4.90 Impact Factor
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Fumihiko Usui,
Daisuke Kuroda,
Thomas G. Mueller,
Sunao Hasegawa,
Masateru Ishiguro,
Takafumi Ootsubo, Daisuke Ishihara,
Hirokazu Kataza,
Satoshi Takita,
Shinki Oyabu,
Munetaka Ueno,
Hideo Matsuhara,
Takashi Onaka
[show abstract]
[hide abstract]
ABSTRACT: We present the results of an unbiased asteroid survey in the mid-infrared
wavelength with the Infrared Camera (IRC) onboard the Japanese infrared
satellite AKARI. About 20% of the point source events recorded in the AKARI
All-Sky Survey observations are not used for the IRC Point Source Catalog
(IRC-PSC) in its production process because of the lack of multiple detection
by position. Asteroids, which are moving objects on the celestial sphere,
remain in these "residual events". We identify asteroids out of the residual
events by matching them with the positions of known asteroids. For the
identified asteroids, we calculate the size and albedo based on the Standard
Thermal Model. Finally we have a brand-new catalog of asteroids, named the
Asteroid Catalog Using Akari (AcuA), which contains 5,120 objects, about twice
as many as the IRAS asteroid catalog. The catalog objects comprise 4,953 main
belt asteroids, 58 near Earth asteroids, and 109 Jovian Trojan asteroids. The
catalog will be publicly available via the Internet.
06/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present the spatial distributions of dust and polycyclic aromatic
hydrocarbons (PAHs) in the elliptical galaxy NGC 4125, revealed by AKARI
and Spitzer. NGC 4125 is relatively bright in dust and PAH emision for
elliptical galaxies, although it certainly possesses diffuse
interstellar hot plasma, indicated by the high spatial resolution X-ray
data of Chandra. We investigate how the dust and PAHs interact with the
X-ray plasma or avoid the interaction by comparing their spatial
distributions. We find that the distributions of the PAHs and dust are
different from each other, both showing a significant deviation from a
smooth stellar distribution. The PAH emission predominantly comes from a
dust lane, a compact dense molecular gas region in the galactic center,
where the PAHs are likely to have been protected from the interaction
with the X-ray plasma. The dust emission has more extended structures,
similar to the distribution of the X-ray plasma, suggesting their
interaction to some extent. We also discuss a possible origin of the
dust and PAHs in the galaxy.
Publications- Astronomical Society of Japan 05/2011; 63:601. · 2.44 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present the spatially-resolved near-infrared (2.5–5.0 µm) spectra of the edge-on starburst galaxy NGC 253 obtained with the Infrared Camera onboard AKARI. Near the center of the galaxy, we clearly detect the absorption features of interstellar ices (H 2 O: 3.05 µm, CO 2 : 4.27 µm, and XCN: 4.62 µm) and the emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 µm and hydrogen recombination line Brα at 4.05 µm. We find that the distributions of the ices differ from those of the PAH and gas. We calculate the column densities of the ices and derive the abundance ratios of N (CO 2)/N (H 2 O) = 0.17 ± 0.05. They are similar to those obtained around the massive young stellar objects in our Galaxy (0.17 ± 0.03), although much stronger interstellar radiation field and higher dust temperature are expected near the center of NGC 253.
03/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present the spatial distributions of dust and polycyclic aromatic
hydrocarbons (PAHs) in the elliptical galaxy NGC4125, revealed by AKARI and
Spitzer. NGC4125 is relatively bright in the dust and the PAH emision for
elliptical galaxies, although it certainly possesses diffuse interstellar hot
plasma indicated by the high spatial resolution X-ray data of Chandra. We
investigate how the dust and PAHs interact with the X-ray plasma or avoid the
interaction by comparing their spatial distributions. We find that the
distributions of the PAHs and dust are different from each other, both showing
a significant deviation from a smooth stellar distribution. The PAH emission
predominantly comes from a dust lane, a compact dense molecular gas region in
the galactic center, where the PAHs are likely to have been protected from the
interaction with the X-ray plasma. The dust emission has more extended
structures similar to the distribution of the X-ray plasma, suggesting their
interaction to some extent. We also discuss a possible origin of the dust and
PAHs in the galaxy.
03/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We evaluate the effects of high-energy ionizing particles on the Si:As
impurity band conduction (IBC) mid-infrared detector on board AKARI, the
Japanese infrared astronomical satellite. IBC-type detectors are known to be
little influenced by ionizing radiation. However we find that the detector is
significantly affected by in-orbit ionizing radiation even after spikes induced
by ionizing particles are removed. The effects are described as changes mostly
in the offset of detector output, but not in the gain. We conclude that the
changes in the offset are caused mainly by increase in dark current. We
establish a method to correct these ionizing radiation effects. The method is
essential to improve the quality and to increase the sky coverage of the AKARI
mid-infrared all-sky-survey map.
02/2011;
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[show abstract]
[hide abstract]
ABSTRACT: We present the spatially-resolved near-infrared (2.5-5.0 um) spectra of the
edge-on starburst galaxy NGC253 obtained with the Infrared Camera onboard
AKARI. Near the center of the galaxy, we clearly detect the absorption features
of interstellar ices (H_2O: 3.05 um, CO_2: 4.27 um, and XCN: 4.62 um) and the
emission of polycyclic aromatic hydrocarbons (PAHs) at 3.29 um and hydrogen
recombination line Br alpha at 4.05 um. We find that the distributions of the
ices differ from those of the PAH and gas. We calculate the column densities of
the ices and derive the abundance ratios of N(CO_2)/N(H_2O) = 0.17 +- 0.05.
They are similar to those obtained around the massive young stellar objects in
our Galaxy (0.17 +- 0.03), although much stronger interstellar radiation field
and higher dust temperature are expected near the center of NGC253.
02/2011;
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Tomotsugu Goto,
Stephane Arnouts,
Matthew Malkan,
Toshinobu Takagi,
Hanae Inami,
Chris Pearson,
Takehiko Wada,
Hideo Matsuhara,
Chisato Yamauchi,
Tsutomu T. Takeuchi,
Takao Nakagawa,
Shinki Oyabu, Daisuke Ishihara,
David B. Sanders,
Emeric Le Floc'h,
Hyung Mok Lee,
Woong-Seob Jeong,
Stephen Serjeant,
Chris Sedgwick
[show abstract]
[hide abstract]
ABSTRACT: By cross-correlating AKARI infrared (IR) sources with the SDSS galaxies, we
identified 2357 infrared galaxies with a spectroscopic redshift. This is not
just one of the largest samples of local IR galaxies, but AKARI provides
crucial FIR bands (9, 18, 65, 90, 140, and 160um) in accurately measuring
galaxy SED across the peak of the dust emission at ~100um. By fitting modern IR
SED models to the AKARI photometry, we measured the total infrared luminosity
(L_IR) of individual galaxies more accurately. Using this L_IR, we constructed
luminosity functions of infrared galaxies at a median redshift of z=0.031, with
4 times larger sample than previous work. The LF agrees well with that at
z=0.0082 (RBGS), showing smooth and continuous evolution toward higher redshift
LFs measured in the AKARI NEP deep field. The derived local cosmic IR
luminosity density is Omega_IR=3.8x10^8 LsunMpc^-3. We separate galaxies into
AGN, star-forming, and composite by using the [NII]/Ha vs [OIII]/Hb line
ratios. The fraction of AGN shows a continuous increase with increasing L_IR
from 25% to 90% at 9<log L_IR<12.5. The SFR_Ha and L_[OIII] show good
correlations with L_IR for SFG (star-forming galaxies) and AGN, respectively.
The self-absorption corrected Ha/Hb ratio shows a weak increase with L_IR with
a substantial scatter. When we separate IR LFs into contributions from AGN and
SFG, the AGN contribution becomes dominant at L_IR>10^11Lsun, coinciding the
break of the both SFG and AGN IR LFs. At L_IR<10^11Lsun, SFG dominates IR Lfs.
Only 1.1% of Omega_IR is produced by LIRG, and only 0.03% is by ULIRG in the
local Universe. This work also provides the most accurate infrared luminosity
density of the local Universe to date. Compared with high redshift results from
the AKARI NEP deep survey, we observed a strong evolution of Omega_IR^SFG
~(1+z)^4.1+-0.4 and Omega_IR^AGN ~(1+z)^4.1+-0.5 (abridged).
02/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Aims: We investigate the spatial distribution of dust emission around Tycho's SNR to understand its origin. We distinguish the dust associated with the SNR from that of the surrounding ISM. Methods: We performed mid- to far-infrared imaging observations of the remnant at wavelengths of 9, 15, 18, 24, 65, 90, 140, and 160um using the Infrared Camera and the Far-Infrared Surveyor onboard AKARI. We compared the AKARI images with the Suzaku X-ray image and the 12CO image of Tycho's SNR. Results: All the AKARI images except the 9, 140, and 160um band images show a shell-like emission structure with brightness peaks at the north east (NE) and north west (NW) boundaries, sharply outlining part of the X-ray shell. The 140 and 160um bands are dominated by cold dust emission from the surrounding ISM near the NE boundary. Conclusion: We conclude that the dust emission at the NE boundary comes from the ambient cloud interacting with the shock front, while the origin of the dust emission at the NW boundary is rather unclear because of the absence of prominent interstellar clouds near the corresponding region. We cannot rule out the possibility that the latter is mostly of an SN ejecta origin. Comment: Accepted for publication in A&A letter
09/2010;
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Tomotsugu Goto,
Stephane Arnouts,
Hanae Inami,
Hideo Matsuhara,
Chris Pearson,
Tsutomu T. Takeuchi,
Emeric Le Floc'h,
Toshinobu Takagi,
Takehiko Wada,
Takao Nakagawa,
Shinki Oyabu, Daisuke Ishihara,
Hyung Mok Lee,
Woong-Seob Jeong,
Chisato Yamauchi,
Stephen Serjeant,
Chris Sedgwick,
Ezequiel Treister
[show abstract]
[hide abstract]
ABSTRACT: Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and AGN evolution. The AKARI IR space telescope performed all sky survey in 6 IR bands (9, 18, 65, 90, 140, and 160um) with 3-10 times better sensitivity than IRAS, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L_TIR) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting IR SED models, we have re-measured L_TIR of the IRAS Revised Bright Galaxy Sample. We present mid-IR monochromatic luminosity to L_TIR conversions for Spitzer 8,24um, AKARI 9,18um, IRAS 12um, WISE 12,22um, and ISO 15um filters, with scatter ranging 13-44%. The resulting AKARI IR luminosity function (LF) agrees well with that from the IRAS. We integrate the LF weighted by L_TIR to obtain a cosmic IR luminosity density of Omega_TIR= (8.5^{+1.5}_{-2.3})x 10^7 L Mpc^-3, of which 7+-1% is produced by LIRGs, and only 0.4+-0.1% is from ULIRGs in the local Universe. Once IR contributions from AGN and star-forming galaxies (SFG) are separated, SFG IR LF shows a steep decline at the bright-end. Compared with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of Omega_TIRSF propto (1+z)^4.0+-0.5, and Omega_TIRAGN propto (1+z)^4.4+-0.4. For Omega_TIRAGN, the ULIRG contribution exceeds that from LIRG already by z~1. A rapid evolution in both Omega_TIRAGN and Omega_TIRSFG suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of Omega_TIRAGN to that of X-ray luminosity density. The Omega_TIRAGN/Omega_X-rayAGN ratio shows a possible increase at z>1, suggesting an increase of obscured AGN at z>1. Comment: Accepted for publication in MNRAS
08/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Aims: We search new T Tauri star (TTS) candidates with the mid-infrared (MIR) part of the AKARI All-Sky Survey at 9 and 18 um wavelengths. Methods: We used the point source catalogue (PSC), obtained by the Infrared Camera (IRC) on board AKARI. We combined the 2MASS PSC and the 3rd version of the USNO CCD Astrograph Catalogue (UCAC) with the AKARI IRC-PSC, and surveyed 517 known TTSs over a 1800-square-degree part of the Taurus-Auriga region to find criteria to extract TTSs. We considered asymptotic giant branch (AGB) stars, post-AGB stars, Planetary Nebulae (PNe), and galaxies, which have similar MIR colours, to separate TTSs from these sources. Results: Of the 517 known TTSs, we detected 133 sources with AKARI. Based on the colour-colour and colour-magnitude diagrams made from the AKARI, 2MASS, and UCAC surveys, we propose the criteria to extract TTS candidates from the AKARI All-Sky data. On the basis of our criteria, we selected 176/14725 AKARI sources as TTS candidates which are located around the Taurus-Auriga region. Comparing these sources with SIMBAD, there are 148 previously identified sources including 115 Young Stellar Objects (YSOs), and 28 unidentified sources. Conclusions: Based on SIMBAD identifications, we take the TTS-identification probability using our criteria to be ~75 %. We find 28 TTS candidates, of which we expect 21 to be confirmed once follow-up observations can be obtained. Although the probability of ~75 % is not so high, it is affected by the completeness of the SIMBAD database, and we can search for TTSs over the whole sky, over all star forming regions. Comment: 12 pages, 9 figures, accepted for publication in A&A
06/2010;
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[show abstract]
[hide abstract]
ABSTRACT: Spitzer and AKARI observations have found that polycyclic aromatic hydrocarbons (PAHs) are present in nearby elliptical galaxies, but their spatial distributions are still unknown. In order to investigate their distributions, we performed deep spectral mapping observations of the PAH-detected elliptical galaxy NGC 4589, a merger remnant with a minor-axis optical dust lane. As a result, we obtain clear evidence that the PAH 11.3 μm emission comes predominantly from the dust lane of the galaxy. We also detect molecular hydrogen line emissions from the dust lane. The PAH 17 μm emission is distributed differently from the PAH 11.3 μm emission, and more similarly to the dust continuum emission. From their distinctive distributions, we suggest that the PAHs responsible for the 11.3 μm feature are secondary products through the evolution of the interstellar medium brought in by the merger.
The Astrophysical Journal Letters 05/2010; 716(2):L161. · 5.53 Impact Factor
