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Infrared, UV/VIS and Raman Spectroscopy of Comet Wild-2 Samples Returned by the Stardust Mission
Results from the preliminary examination of Stardust samples obtained using various spectroscopic methods will be presented
Photoelectric sensor output controlled by eyeball movements
The difference between the infrared absorption of the iris and infrared reflectivity of the eyeball controls the operation of a device consisting of an infrared source and amplifier, a cadmium selenide infrared sensor, and an infrared filter
Mid Infrared Polarisation of Ultraluminous Infrared Galaxies
The mid infrared polarisation properties of four Ultraluminous Infrared
Galaxies (ULIRGs) have been investigated by broad band filter observations with
the ISOCAM instrument on board the Infrared Space Observatory (ISO). The
wavelength region from 5 to 18 mic. was selected where the emission from the
putative torus peaks. We report detection of polarisation for all ULIRGs
studied. The fractional polarisation ranges from about 3% up to 8%. The highest
polarisation is recorded in Mrk231 which has a clear AGN signature, whereas the
lowest is for Arp220, which is generally thought to be powered predominantly by
star formation. We discuss the various mechanisms that could give rise to the
polarisation and conclude that the most likely interpretation is that it is due
to magnetically aligned elongated dust grains. This is the same mechanism
believed to be operating in a number of galactic sources. The position angle of
polarisation could give the projected magnetic field direction and therefore
constrain models for the formation of the tori.Comment: Accepted by A&A (Letter
The luminosity function of the brightest galaxies in the IRAS survey
Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume
Near-infrared and Mid-infrared Spectroscopy with the Infrared Camera (IRC) for AKARI
The Infrared Camera (IRC) is one of the two instruments on board the AKARI
satellite. In addition to deep imaging from 1.8-26.5um for the pointed
observation mode of the AKARI, it has a spectroscopic capability in its
spectral range. By replacing the imaging filters by transmission-type
dispersers on the filter wheels, it provides low-resolution (lambda/d_lambda ~
20-120) spectroscopy with slits or in a wide imaging field-of-view
(approximately 10'X10'). The IRC spectroscopic mode is unique in space infrared
missions in that it has the capability to perform sensitive wide-field
spectroscopic surveys in the near- and mid-infrared wavelength ranges. This
paper describes specifications of the IRC spectrograph and its in-orbit
performance.Comment: 13 pages, 7 figures, accepted for publication on PAS
AKARI IRC 2.5-5 um Spectroscopy of Infrared Galaxies over a Wide Luminosity Range
We present the result of a systematic infrared 2.5-5 um spectroscopic study
of 22 nearby infrared galaxies over a wide infrared luminosity range (10 <
log(L_IR / Lsun) < 13) obtained from AKARI Infrared Camera (IRC). The unique
band of the AKARI IRC spectroscopy enables us to access both the 3.3 um
polycyclic aromatic hydrocarbon (PAH) emission feature from star forming
activity and the continuum of torus-dust emission heated by an active galactic
nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover
14 buried AGNs. The large fraction of buried AGNs suggests that AGN activity
behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies
(U/LIRGs). We also find that both the fraction and energy contribution of
buried AGNs increase with infrared luminosity from 10 < log(L_IR / Lsun) < 13,
including normal infrared galaxies with log (L_IR / Lsun) < 11. The energy
contribution from AGNs in the total infrared luminosity is only ~7% in LIRGs
and ~20% in ULIRGs, suggesting that the majority of the infrared luminosity
originates from starburst activity. Using the PAH emission, we investigate the
luminosity relation between star formation and AGN. We find that these infrared
galaxies exhibit higher star formation rates than optically selected Seyfert
galaxies with the same AGN luminosities, implying that infrared galaxies could
be an early evolutionary phase of AGN.Comment: 13 pages, 8 figures, accepted for publication in Ap
Near-Infrared Colours of Active Galactic Nuclei
We propose near-infrared colour selection criteria to extract Active Galactic
Nuclei (AGNs) using the near-infrared Colour-Colour Diagram (CCD) and predict
near-infrared colour evolution with respect to redshift. First, we
cross-identify two AGN catalogues with the 2MASS Point Source Catalogue, and
confirm both the loci of quasars/AGNs in the near-infrared CCD and
redshift-colour relations. In the CCD, the loci of over 70 - 80% of AGNs can be
distinguished from the stellar locus. To examine the colours of quasars, we
simulate near-infrared colours using Hyperz code. Assuming a realistic quasar
SED, we derive simulated near-infrared colours of quasars with redshift (up to
z ~ 11). The simulated colours can reproduce not only the redshift-colour
relations but also the loci of quasars/AGNs in the near-infrared CCD. We
finally discuss the possibility of contamination by other types of objects. We
compare the locus of AGNs with the other four types of objects (namely,
microquasars, CVs, LMXBs, and MYSOs) which have a radiation mechanism similar
to that of AGNs. In the near-infrared CCD, each type of object is located at a
position similar to the stellar locus. Accordingly, it is highly probable that
the four types of objects can be distinguished on the basis of the locus in a
near-infrared CCD. We additionally consider contamination by distant normal
galaxies. The near-infrared colours of several types of galaxies are also
simulated using the Hyperz code. Although galaxies with z ~ 1 have
near-infrared colours similar to those of AGNs, these galaxies are unlikely to
be detected because they are very faint. In other words, few galaxies should
contaminate the locus of AGNs in the near-infrared CCD. Consequently, we can
extract reliable AGN candidates on the basis of the near-infrared CCD.Comment: 7 pages, 6 figures, Accepted for publication in A&
AKARI Near-Infrared Spectroscopy of Luminous Infrared Galaxies
We present the AKARI near-infrared (NIR; 2.5-5 micron) spectroscopic study of
36 (ultra)luminous infrared galaxies [(U)LIRGs] at z=0.01-0.4. We measure the
NIR spectral features including the strengths of 3.3 micron polycyclic aromatic
hydrocarbon (PAH) emission and hydrogen recombination lines (Br\alpha. and
Br\beta), optical depths at 3.1 and 3.4 micron, and NIR continuum slope. These
spectral features are used to identify optically elusive, buried AGN. We find
that half of the (U)LIRGs optically classified as non-Seyferts show AGN
signatures in their NIR spectra. Using a combined sample of (U)LIRGs with NIR
spectra in the literature, we measure the contribution of buried AGN to the
infrared luminosity from the SED-fitting to the IRAS photometry. The
contribution of these buried AGN to the infrared luminosity is 5-10%, smaller
than the typical AGN contribution of (U)LIRGs including Seyfert galaxies
(10-40%). We show that NIR continuum slopes correlate well with WISE
[3.4]-[4.6] colors, which would be useful for identifying a large number of
buried AGN using the WISE data.Comment: ApJ, accepted. 37 pages, 11 figure
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