49 research outputs found
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
Systematic infrared 2.5-5 micron spectroscopy of nearby ultraluminous infrared galaxies with AKARI
We report on the results of systematic infrared 2.5-5 micron spectroscopy of
45 nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.3 using IRC onboard
the AKARI satellite. This paper investigates whether the luminosities of these
ULIRGs are dominated by starburst activity, or optically elusive buried AGNs
are energetically important. Our criteria include the strengths of the 3.3
micron polycyclic aromatic hydrocarbon (PAH) emission features and the optical
depths of absorption features at 3.1 micron due to ice-covered dust grains and
at 3.4 micron from bare carbonaceous dust grains. Because of the AKARI IRC's
spectroscopic capability in the full 2.5-5 micron wavelength range, unaffected
by Earth's atmosphere, we can apply this energy diagnostic method to ULIRGs at
z > 0.15. We estimate the intrinsic luminosities of extended (several kpc),
modestly obscured (Av < 15 mag) starburst activity based on the 3.3 micron PAH
emission luminosities measured in AKARI IRC slitless spectra, and confirm that
such starbursts are energetically unimportant in nearby ULIRGs. In roughly half
of the observed ULIRGs classified optically as non-Seyferts, we find signatures
of luminous energy sources that produce no PAH emission and/or are more
centrally concentrated than the surrounding dust. We interpret these energy
sources as buried AGNs. The fraction of ULIRGs with detectable buried AGN
signatures increases with increasing infrared luminosity. Our overall results
support the scenario that luminous buried AGNs are important in many ULIRGs at
z < 0.3 classified optically as non-Seyferts, and that the optical
undetectability of such buried AGNs occurs merely because of a large amount of
nuclear dust, which can make the sightline of even the lowest dust column
density opaque to the ionizing radiation of the AGNs.Comment: 48 pages, 7 figures, accepted for publication in PASJ (AKARI special
issue
A Spitzer IRS Low-Resolution Spectroscopic Search for Buried AGNs in Nearby Ultraluminous Infrared Galaxies - A Constraint on Geometry between Energy Sources and Dust -
We present the results of Spitzer IRS low-resolution infrared 5-35 micron
spectroscopy of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. We
focus on the search for the signatures of buried active galactic nuclei (AGNs)
in the complete sample of ULIRGs classified optically as non-Seyferts (LINERs
or HII-regions). In addition to polycyclic aromatic hydrocarbon (PAH) emission
features at 6.2 micron, 7.7 micron, and 11.3 micron, the conventional tool of
starburst-AGN separation, we use the optical depths of the 9.7 micron and 18
micron silicate dust absorption features to infer the geometry of energy
sources and dust at the nuclei of these ULIRGs, namely, whether the energy
sources are spatially well mixed with dust(a normal starburst) or are more
centrally concentrated than the dust (a buried AGN). Infrared spectra of at
least 30%, and possibly 50%, of the observed optical non-Seyfert ULIRGs are
naturally explained by emission consisting of (1) energetically insignificant,
modestly obscured (Av < 20-30 mag) PAH-emitting normal starbursts, and (2)
energetically dominant, highly dust-obscured, centrally concentrated energy
sources with no PAH emission. We interpret the latter component as a buried
AGN. The fraction of ULIRGs showing some buried AGN signatures is higher in
LINER ULIRGs than in HII-region ULIRGs. Most of the luminous buried AGN
candidates are found in ULIRGs with cool far-infrared colors. Where the
absorption-corrected intrinsic AGN luminosities are derivable with little
uncertainty, they are found to be of the order of 10^12Lsun, accounting for the
bulk of the ULIRGs' luminosities. The 5-35 micron spectroscopic starburst/AGN
classifications are generally consistent with our previous classifications
based on 3-4 micron spectra for the same sample.Comment: 67 pages, 13 figures, accepted for publication in Ap
Mid and Far Infrared Properties of a Complete Sample of Local AGNs
We investigate the mid- (MIR) to far-infrared (FIR) properties of a nearly
complete sample of local Active Galactic Nuclei (AGNs) detected in the
Swift/BAT all sky hard X-ray (14-195 keV) survey, based on the cross
correlation with the AKARI infrared survey catalogs complemented by those with
IRAS and WISE. Out of 135 non-blazer AGNs in the Swift/BAT 9 month catalog, we
obtain the MIR photometric data for 128 sources either in the 9, 12, 18, 22,
and/or 25 um band. We find good correlation between their hard X-ray and MIR
luminosities over 3 orders of magnitude (42< log lambda L_{lambda}(9, 18 um)<
45), which is tighter than that with the FIR luminosities at 90 um. This
suggests that thermal emission from hot dusts irradiated by the AGN emission
dominate the MIR fluxes. Both X-ray unabsorbed and absorbed AGNs follow the
same correlation, implying isotropic infrared emission, as expected in clumpy
dust tori rather than homogeneous ones. We find excess signals around 9 um in
the averaged infrared spectral energy distribution from heavy obscured "new
type" AGNs with small scattering fractions in the X-ray spectra. This could be
attributed to the PAH emission feature, suggesting that their host galaxies
have strong starburst activities.Comment: 14 pages, 8 figures, accepted for publication in Ap
Large-scale identification and characterization of alternative splicing variants of human gene transcripts using 56 419 completely sequenced and manually annotated full-length cDNAs
We report the first genome-wide identification and characterization of alternative splicing in human gene transcripts based on analysis of the full-length cDNAs. Applying both manual and computational analyses for 56ā419 completely sequenced and precisely annotated full-length cDNAs selected for the H-Invitational human transcriptome annotation meetings, we identified 6877 alternative splicing genes with 18 297 different alternative splicing variants. A total of 37 670 exons were involved in these alternative splicing events. The encoded protein sequences were affected in 6005 of the 6877 genes. Notably, alternative splicing affected protein motifs in 3015 genes, subcellular localizations in 2982 genes and transmembrane domains in 1348 genes. We also identified interesting patterns of alternative splicing, in which two distinct genes seemed to be bridged, nested or having overlapping protein coding sequences (CDSs) of different reading frames (multiple CDS). In these cases, completely unrelated proteins are encoded by a single locus. Genome-wide annotations of alternative splicing, relying on full-length cDNAs, should lay firm groundwork for exploring in detail the diversification of protein function, which is mediated by the fast expanding universe of alternative splicing variants
Integrative Annotation of 21,037 Human Genes Validated by Full-Length cDNA Clones
The human genome sequence defines our inherent biological potential; the realization of the biology encoded therein requires knowledge of the function of each gene. Currently, our knowledge in this area is still limited. Several lines of investigation have been used to elucidate the structure and function of the genes in the human genome. Even so, gene prediction remains a difficult task, as the varieties of transcripts of a gene may vary to a great extent. We thus performed an exhaustive integrative characterization of 41,118 full-length cDNAs that capture the gene transcripts as complete functional cassettes, providing an unequivocal report of structural and functional diversity at the gene level. Our international collaboration has validated 21,037 human gene candidates by analysis of high-quality full-length cDNA clones through curation using unified criteria. This led to the identification of 5,155 new gene candidates. It also manifested the most reliable way to control the quality of the cDNA clones. We have developed a human gene database, called the H-Invitational Database (H-InvDB; http://www.h-invitational.jp/). It provides the following: integrative annotation of human genes, description of gene structures, details of novel alternative splicing isoforms, non-protein-coding RNAs, functional domains, subcellular localizations, metabolic pathways, predictions of protein three-dimensional structure, mapping of known single nucleotide polymorphisms (SNPs), identification of polymorphic microsatellite repeats within human genes, and comparative results with mouse full-length cDNAs. The H-InvDB analysis has shown that up to 4% of the human genome sequence (National Center for Biotechnology Information build 34 assembly) may contain misassembled or missing regions. We found that 6.5% of the human gene candidates (1,377 loci) did not have a good protein-coding open reading frame, of which 296 loci are strong candidates for non-protein-coding RNA genes. In addition, among 72,027 uniquely mapped SNPs and insertions/deletions localized within human genes, 13,215 nonsynonymous SNPs, 315 nonsense SNPs, and 452 indels occurred in coding regions. Together with 25 polymorphic microsatellite repeats present in coding regions, they may alter protein structure, causing phenotypic effects or resulting in disease. The H-InvDB platform represents a substantial contribution to resources needed for the exploration of human biology and pathology
Fast simulation of flexible multibody dynamics with electric-hydraulic drive system
AbstractHardware in the loop simulation (HILS) has been investigated in the field of the multibody dynamics (MBD), which combined the MBD simulation with the actual mechanical system. The fast simulation is necessary for the HILS system in order to require the real time simulation. This paper presents a fast simulation technique using the domain decomposition method with the iteration in the flexible multibody system in which flexible linkage system and electro-hydraulic drive system are coupled with each other