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ABSTRACT: Aims. We investigate the properties of hydrocarbon grains in the galactic
superwind of M 82. Methods. With AKARI, we performed near-infrared (2.5 - 4.5
um) spectroscopic observations of 34 regions in M 82 including its northern and
southern halos. Results. Many of the spectra show strong emission at 3.3 um due
to polycyclic aromatic hydrocarbons (PAHs) and relatively weak features at 3.4
- 3.6 um due to aliphatic hydrocarbons. In particular, we clearly detect the
PAH 3.3 um emission and the 3.4 - 3.6 um features in halo regions, which are
located at a distance of 2 kpc away from the galactic center. We find that the
ratios of the 3.4 - 3.6 um features to the 3.3 um feature intensity
significantly increase with distance from the galactic center, while the ratios
of the 3.3 um feature to the AKARI 7 um band intensity do not. Conclusions. Our
results clearly confirm the presence of small PAHs even in a harsh environment
of the halo of M 82. The results also reveal that the aliphatic hydrocarbons
emitting the 3.4 - 3.6 um features are unusually abundant in the halo,
suggesting that small carbonaceous grains are produced by shattering of larger
grains in the galactic superwind.
03/2012;
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ABSTRACT: We assess the relationships between the surface densities of the gas and star formation rate (SFR) within spiral arms of the nearby late-type spiral galaxies M81 and M101. By analyzing these relationships locally, we derive empirically a kiloparsec scale Kennicutt-Schmidt Law. Both M81 and M101 were observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared bands at 65, 90, 140, and 160 um. The spectral energy distributions of the whole galaxies show the presence of the cold dust component (Tc~20 K) in addition to the warm dust component (Tw~60 K). We deconvolved the cold and warm dust emission components spatially by making the best use of the multi-band photometric capability of the FIS. The cold and warm dust components show power-law correlations in various regions, which can be converted into the gas mass and the SFR, respectively. We find a power-law correlation between the gas and SFR surface densities with significant differences in the power law index N between giant HII regions (N=1.0) and spiral arms (N=2.2) in M101. The power-law index for spiral arms in M81 is similar (N=1.9) to that of spiral arms in M101. Conclusions: The power-law index is not always constant within a galaxy. The difference in the power-law index can be attributed to the difference in the star formation processes on a kiloparsec scale. N~2 seen in the spiral arms in M81 and M101 supports the scenario of star formation triggered by cloud-cloud collisions enhanced by spiral density wave, while N~1 derived in giant HII regions in M101 suggests the star formation induced by the Parker instability triggered by high velocity HI gas infall. The present method can be applied to a large galaxy sample for which the AKARI All Sky Survey provides the same 4 far-infrared band data. Comment: 12 pages, 8 figures, accepted for publication in A&A
06/2010;
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ABSTRACT: The edge-on starburst galaxy M82 exhibits complicated distributions of gaseous materials in its halo, which include ionized superwinds driven by nuclear starbursts, neutral materials entrained by the superwinds, and large-scale neutral streamers probably caused by a past tidal interaction with M81. We investigate detailed distributions of dust grains and polycyclic aromatic hydrocarbons (PAHs) around M82 to understand their interplay with the gaseous components. We performed mid- (MIR) and far-infrared (FIR) observations of M82 with the Infrared Camera and Far-Infrared Surveyor on board AKARI. We obtain new MIR and FIR images of M82, which reveal both faint extended emission in the halo and very bright emission in the center with signal dynamic ranges as large as five and three orders of magnitude for the MIR and FIR, respectively. We detect MIR and FIR emission in the regions far away from the disk of the galaxy, reflecting the presence of dust and PAHs in the halo of M82. We find that the dust and PAHs are contained in both ionized and neutral gas components, implying that they have been expelled into the halo of M82 by both starbursts and galaxy interaction. In particular, we obtain a tight correlation between the PAH and H$\alpha$ emission, which provides evidence that the PAHs are well mixed in the ionized superwind gas and outflowing from the disk. Comment: 12 pages, 8 figures, accepted for publication in A&A
02/2010;
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[show abstract]
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ABSTRACT: Aims: We assess the relationships between the surface densities of the gas and star formation rate (SFR) within spiral arms of the nearby late-type spiral galaxies M 81 and M 101. By analyzing these relationships locally, we empirically derive a kiloparsec scale Kennicutt-Schmidt Law (SigmaSFR ∝ SigmagasN). Methods: Both M 81 and M 101 were observed with the Far-Infrared Surveyor (FIS) aboard AKARI in four far-infrared bands at 65, 90, 140, and 160 mum. Results: The spectral energy distributions of the whole galaxies show the presence of the cold dust component (TC ~ 20 K) in addition to the warm dust component (TW ~ 60 K). We deconvolved the cold and warm dust emission components spatially by making the best use of the multi-band photometric capability of the FIS. The cold and warm dust components show power-law correlations in various regions, which can be converted into the gas mass and the SFR, respectively. We find a power-law correlation between the gas and SFR surface densities with significant differences in the power-law index N between giant H ii regions (N = 1.0 ± 0.5) and spiral arms (N = 2.2 ± 0.2) in M 101. The power-law index for spiral arms in M 81 is similar (N = 1.9 ± 0.4) to that of spiral arms in M 101. Conclusions: The power-law index is not always constant within a galaxy. The difference can be attributed to the difference in the star formation processes on a kiloparsec scale. N ~= 2 seen in the spiral arms in M 81 and M 101 supports the scenario of star formation triggered by cloud-cloud collisions enhanced by a spiral density wave, while N ~= 1 derived in giant H ii regions in M 101 suggests the star formation induced by the Parker instability triggered by high-velocity H i gas infall. The present method can be applied to a large galaxy sample for which the AKARI All Sky Survey provides the same 4 far-infrared band data.
Astronomy & Astrophysics - ASTRON ASTROPHYS. 01/2010; 521.
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I. Sakon,
T. Onaka,
T. Wada,
Y. Ohyama,
H. Kaneda,
D. Ishihara,
T. Tanabé,
T. Minezaki,
Y. Yoshii,
N. Tominaga, [......],
T. Nozawa,
T. Kozasa,
M. Tanaka, T. Suzuki,
H. Umeda,
S. Ohyabu,
F. Usui,
H. Matsuhara,
T. Nakagawa,
and H. Murakami
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ABSTRACT: We present our latest results on near- to mid-infrared (MIR) observation of supernova (SN) 2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board AKARI. The near-infrared (2-5 μm) spectrum of SN 2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800 ± 10 K with the mass of 6.9 ± 0.5 × 10–5 M ☉ that was formed in the SN ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust-forming core-collapse supernovae based on recent observations (i.e., 10–3-10–5 M ☉). MIR photometric data with AKARI/IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800 K. This MIR excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320 ± 10 K with the mass of 2.7+0.7 –0.5 × 10–3 M ☉ rather than by the band emission of astronomical silicate and/or silica grains. This warm amorphous carbon dust is expected to have been formed in the mass-loss wind associated with the Wolf-Rayet stellar activity before the SN explosion. Our result suggests that a significant amount of dust is condensed in the mass-loss wind prior to the SN explosion.
The Astrophysical Journal 02/2009; 692(1):546. · 6.02 Impact Factor
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ABSTRACT: We performed mid-infrared spectroscopic observations of 18 local dusty elliptical galaxies by using the Infrared Spectrograph (IRS) on board Spitzer. We have significantly detected polycyclic aromatic hydrocarbon (PAH) features from 14 out of the 18 galaxies, and thus found that the presence of PAHs is not rare but rather common in dusty elliptical galaxies. Most of these galaxies show an unusually weak 7.7 um emission feature relative to 11.3 um and 17 um emission features. A large fraction of the galaxies also exhibit H2 rotational line and ionic fine-structure line emissions, which have no significant correlation with the PAH emissions. The PAH features are well correlated with the continuum at 35 um, whereas they are not correlated with the continuum at 6 um. We conclude that the PAH emission of the elliptical galaxies is mostly of interstellar origin rather than of stellar origin, and that the unusual PAH interband strength ratios are likely to be due to a large fraction of neutral to ionized PAHs. Comment: 26 pages, 6 figures, accepted for publication in the ApJ
05/2008;
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I. Sakon,
T Wada,
Y Ohyama,
D. Ishihara,
T. Tanabé,
H Kaneda,
T Onaka,
N Tominaga,
M Tanaka, T Suzuki, [......],
K Nomoto,
T Nozawa,
T. Kozasa,
T. Minezaki,
Y Yoshii,
S. Ohyabu,
F. Usui,
H. Matsuhara,
T Nakagawa,
H Murakami
[show abstract]
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ABSTRACT: We present our latest results on near- to mid- infrared observation of SN2006jc at 200 days after the discovery using the Infrared Camera (IRC) on board $AKARI$. The near-infrared (2--5$\mu$m) spectrum of SN2006jc is obtained for the first time and is found to be well interpreted in terms of the thermal emission from amorphous carbon of 800$\pm 10$K with the mass of $6.9\pm 0.5 \times 10^{-5}M_{\odot}$ that was formed in the supernova ejecta. This dust mass newly formed in the ejecta of SN 2006jc is in a range similar to those obtained for other several dust forming core collapse supernovae based on recent observations (i.e., $10^{-3}$--$10^{-5}$$M_{\odot}$). Mid-infrared photometric data with {\it{AKARI}}/IRC MIR-S/S7, S9W, and S11 bands have shown excess emission over the thermal emission by hot amorphous carbon of 800K. This mid-infrared excess emission is likely to be accounted for by the emission from warm amorphous carbon dust of 320$\pm 10$K with the mass of 2.7$^{+0.7}_{-0.5} \times 10^{-3}M_{\odot}$ rather than by the band emission of astronomical silicate and/or silica grains. This warm amorphous carbon dust is expected to have been formed in the mass loss wind associated with the Wolf-Rayet stellar activity before the SN explosion. Our result suggests that a significant amount of dust is condensed in the mass loss wind prior to the SN explosion. A possible contribution of emission bands by precursory SiO molecules in 7.5--9.5$\mu$m is also suggested. Comment: 28 pages, 9 figures. Submitted to the Astrophysical Journal
11/2007;
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ABSTRACT: 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.
09/2007;
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H Murakami,
H Baba,
P. Barthel,
D. L. Clements,
M Cohen,
Y Doi,
K. Enya,
E. Figueredo,
N. Fujishiro,
H Fujiwara, [......],
F. Usui,
E. Verdugo,
T Wada,
L Wang,
T Watabe,
H Watarai,
G. J. White,
I. Yamamura,
C Yamauchi,
A Yasuda
[show abstract]
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ABSTRACT: AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from the mid- to far-infrared. The instruments also have the capability for imaging and spectroscopy in the wavelength range 2 - 180 micron in the pointed observation mode, occasionally inserted into the continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90 percent of the whole sky with higher spatial resolution and wider wavelength coverage than that of the previous IRAS all-sky survey. Point source catalogues of the All-Sky Survey will be released to the astronomical community. The pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission. Comment: 13 pages, 4 figures, and 3 tables. Accepted for publication in the AKARI special issue of the Publications of the Astronomical Society of Japan
08/2007;
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H Kaneda, T Suzuki,
T Onaka,
Y Doi,
M Kawada,
B. -C. Koo,
S. Makiuti,
T Nakagawa,
Y Okada,
S. Serjeant,
H Shibai,
M Shirahata
[show abstract]
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ABSTRACT: Far-infrared (IR) images of the nearby Sb galaxy NGC2841 and the Sc galaxy NGC2976 at wavelengths of 65, 90, 140, and 160 um have been obtained with the Far-Infrared Surveyor (FIS) onboard AKARI. Both galaxies reveal similar morphologies of dust rings. They are, however, significantly different in the dust temperature: a cold (21 K) ring for NGC2841 and a warm (30 K) ring for NGC2976, which presumably reflects the difference in the origin of the ring structure for the different Hubble type of the galaxy. In addition to the dust ring structure, a warm dust component is detected from the central region of NGC2841, which may be attributed to the heating by its Low-Ionization Nuclear Emission-line Region nucleus. As for NGC2976, an extended dust component is observed along the minor axis, which shows a distribution somewhat asymmetrical to the galactic disk; this might be associated with the HI bridge in the M81/M82 group that NGC2976 belongs to. By taking advantage of a wealth of the far-IR bands of the FIS, it is demonstrated that the spectral energy distribution of NGC2841 is spatially more variable than that of NGC2976.
07/2007;
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ABSTRACT: The low-temperature specific heat and Mössbauer spectra have been measured for Sr3Fe2O7−y. The iron sites are subdivided into two electronically nonequivalent sites, that is, one is a tetravalent site and the other a trivalent one. The concentration and the isomer shift of tetravalent site depend on the oxygen vacancies. The electronic specific heat of Sr3Fe2O6.92 is smaller by one order than those of Sr3Fe2O7−y above y = 0.2. It is concluded that the electronic state of Sr3Fe2O7−y changes around y ∼ 0.15.
Physica B Condensed Matter 01/1997; 237:105-107. · 1.06 Impact Factor
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International Journal of Legal Medicine - INT J LEGAL MED. 01/1983; 91(1):33-35.
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ABSTRACT: Far-infrared (FIR) properties of 57 nearby galaxies are studied using
the Far-Infrared Surveyor (FIS) on AKARI. Among them, this paper focuses
on the results obtained for the three famous nearby edge-on galaxies,
NGC~3079, M82, and NGC253, which show prominent galactic superwinds in
the X-ray and Hα. These galaxies exhibit very bright nuclei in the
FIR due to starburst activity. We have spatially resolved the central
regions of these galaxies, among which we have detected FIR dust
emission in the haloes of M~82 and NGC~253. We discuss similarities and
differences in the FIR properties among the three galaxies.
1:91-97.
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ABSTRACT: We performed mid- to far-IR observations of 20 nearby dusty elliptical galaxies with AKARI and Spitzer. We have detected PAHs and extended dust emission from many of our sample galaxies.
http://dx.doi.org/10.1051/eas:0831037.
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http://dx.doi.org/10.1051/0004-6361/200913769.
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H Kaneda, T Suzuki,
T Onaka,
Y Doi,
M Kawada,
B. -C. Koo,
S. Makiutu,
T Nakagawa,
Y Okada,
S. Serjeant,
H Shibai,
M Shirahata
