79 research outputs found
A survey of T Tauri stars with AKARI toward the Taurus-Auriga region
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&
Physical Relation of Source I to IRc2 in the Orion KL Region
We present mid-infrared narrow-band images of the Orion BN/KL region, and
N-band low-resolution spectra of IRc2 and the nearby radio source "I." The
distributions of the silicate absorption strength and the color temperature
have been revealed with a sub-arcsecond resolution. The detailed structure of
the 7.8 micron/12.4 micron color temperature distribution was resolved in the
vicinity of IRc2. A mid-infrared counterpart to source I has been detected as a
large color temperature peak. The color temperature distribution shows an
increasing gradient from IRc2 toward source I, and no dominant temperature peak
is seen at IRc2. The spectral energy distribution of IRc2 could be fitted by a
two-temperature component model, and the "warmer component" of the infrared
emission from IRc2 could be reproduced by scattering of radiation from source
I. IRc2 itself is not self-luminous, but is illuminated and heated by an
embedded luminous young stellar object located at source I.Comment: 20 pages, 11 figures. Minor corrections had been done in the ver.2.
Accepted for publication in PAS
Ionization of Polycyclic Aromatic Hydrocarbon Molecules around the Herbig Ae/Be environment
We present the results of mid-infrared N-band spectroscopy of the Herbig
Ae/Be system MWC1080 using the Cooled Mid-Infrared Camera and Spectrometer
(COMICS) on board the 8m Subaru Telescope. The MWC1080 has a geometry such that
the diffuse nebulous structures surround the central Herbig B0 type star. We
focus on the properties of polycyclic aromatic hydrocarbons (PAHs) and PAH-like
species, which are thought to be the carriers of the unidentified infrared
(UIR) bands in such environments. A series of UIR bands at 8.6, 11.0, 11.2, and
12.7um is detected throughout the system and we find a clear increase in the
UIR 11.0um/11.2um ratio in the vicinity of the central star. Since the UIR
11.0um feature is attributed to a solo-CH out-of-plane wagging mode of cationic
PAHs while the UIR 11.2um feature to a solo-CH out-of-plane bending mode of
neutral PAHs, the large 11.0um/11.2um ratio directly indicates a promotion of
the ionization of PAHs near the central star.Comment: accepted for publication in Advances in Geoscienc
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