41 research outputs found
レーザーピーニングの衝撃力のAE法による評価
学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 榎 学, 東京大学教授 小関 敏彦, 東京大学准教授 井上 純哉, 東京大学教授 佐藤 英一, 東京大学教授 酒井 信介University of Tokyo(東京大学
Plastic brain structure changes associated with the division of labour and ageing in termites
Division of labour is a prominent feature of social insect societies, where different castes engage in different specialised tasks. As brain differences are associated with behavioural differences, brain anatomy may be linked to caste polymorphism. Here, we show that termite brain morphology changes markedly with caste differentiation and age in the termite, Reticulitermes speratus. Brain morphology was shown to be associated with reproductive division of labour, with reproductive individuals (alates and neotenic reproductives) having larger brains than non-reproductives (workers and soldiers). Micro-computed tomography (CT) imaging and dissection observations showed that the king's brain morphology changed markedly with shrinkage of the optic lobes during their long life in the dark. Behavioural experiments showed that mature primary kings lose visual function as a result of optic lobe shrinkage. These results suggested that termites restructure their nervous systems to perform necessary tasks as they undergo caste differentiation, and that they also show flexible changes in brain morphology even after the final moult. This study showed that brain morphology in social insects is linked to caste and ageing, and that the evolution of the division of labour is underpinned by the development of diverse neural systems for specialised tasks. This article is protected by copyright. All rights reserved
The Subaru/XMM-Newton Deep Survey (SXDS). IV. Evolution of Lya Emitters from z=3.1 to 5.7 in the 1 deg^2 Field: Luminosity Functions and AGN
We present luminosity functions (LFs) and various properties of Lya emitters
(LAEs) at z=3.1, 3.7, and 5.7, in a 1 deg^2 sky of the Subaru/XMM-Newton Deep
Survey (SXDS) Field. We obtain a photometric sample of 858 LAE candidates based
on deep Subaru/Suprime-Cam imaging data, and a spectroscopic sample of 84
confirmed LAEs from Subaru/FOCAS and VLT/VIMOS spectroscopy in a survey volume
of ~10^6 Mpc^3 with a limiting Lya luminosity of ~3x10^42 erg/s. We derive the
LFs of Lya and UV-continuum (~1500 \AA) for each redshift, taking into account
the statistical error and the field-to-field variation. We find that the
apparent Lya LF shows no significant evolution between z=3.1 and 5.7 within
factors of 1.8 and 2.7 in L* and phi*, respectively. On the other hand, the UV
LF of LAEs increases from z=3.1 to 5.7, indicating that galaxies with Lya
emission are more common at earlier epochs. We identify six LAEs with AGN
activities from our spectra combined with VLA, Spitzer, and XMM-Newton data.
Among the photometrically selected LAEs at z=3.1 and 3.7, only ~1 % show AGN
activities, while the brightest LAEs with logL(Lya) >~ 43.4-43.6 erg/s appear
to always host AGNs. Our LAEs are bluer in UV-continuum color than dropout
galaxies, suggesting lower extinction and/or younger stellar populations. Our
stacking analyses provide upper limits to the radio luminosity and the
f(HeII)/f(Lya) line fraction, and constrain the hidden star formation
(+low-luminosity AGN) and the primordial population in LAEs.Comment: 75 pages, 27 figures; ApJS in press. High resolution version at
http://www.ociw.edu/~ouchi/work/astroph/sxds_LAEs/ouchi_SXDSLAE_ApJS.pd
The Subaru-XMM-Newton Deep Survey (SXDS) VIII.: Multi-wavelength Identification, Optical/NIR Spectroscopic Properties, and Photometric Redshifts of X-ray Sources
We report the multi-wavelength identification of the X-ray sources found in
the Subaru-XMM-Newton Deep Survey (SXDS) using deep imaging data covering the
wavelength range between the far-UV to the mid-IR. We select a primary
counterpart of each X-ray source by applying the likelihood ratio method to
R-band, 3.6micron, near-UV, and 24micron source catalogs as well as matching
catalogs of AGN candidates selected in 1.4GHz radio and i'-band variability
surveys. Once candidates of Galactic stars, ultra-luminous X-ray sources in a
nearby galaxy, and clusters of galaxies are removed there are 896 AGN
candidates in the sample. We conduct spectroscopic observations of the primary
counterparts with multi-object spectrographs in the optical and NIR; 65\% of
the X-ray AGN candidates are spectroscopically-identified. For the remaining
X-ray AGN candidates, we evaluate their photometric redshift with photometric
data in 15 bands. Utilising the multi-wavelength photometric data of the large
sample of X-ray selected AGNs, we evaluate the stellar masses, M*, of the host
galaxies of the narrow-line AGNs. The distribution of the stellar mass is
remarkably constant from z=0.1 to 4.0. The relation between M* and 2--10 keV
luminosity can be explained with strong cosmological evolution of the
relationship between the black hole mass and M*. We also evaluate the scatter
of the UV-MIR spectral energy distribution (SED) of the X-ray AGNs as a
function of X-ray luminosity and absorption to the nucleus. The scatter is
compared with galaxies which have redshift and stellar mass distribution
matched with the X-ray AGN. The UV-NIR SEDs of obscured X-ray AGNs are similar
to those of the galaxies in the matched sample. In the NIR-MIR range, the
median SEDs of X-ray AGNs are redder, but the scatter of the SEDs of the X-ray
AGN broadly overlaps that of the galaxies in the matched sample.Comment: Accepted for publication in PASJ Subaru special issue. 42 pages, 22
figures. Entire contents of Tables 3, 8, 9, 10, and 11, and ASCII format
tables are available from
http://www.astr.tohoku.ac.jp/~akiyama/SXDS/index.htm
Hyper-luminous Dust Obscured Galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE
We present the photometric properties of a sample of infrared (IR) bright
dust obscured galaxies (DOGs). Combining wide and deep optical images obtained
with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR
(MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we
discovered 48 DOGs with and , where
, , and [22] represent AB magnitude in the -band,
-band, and 22 m, respectively, in the GAMA 14hr field
( 9 deg). Among these objects, 31 ( 65 %) show power-law
spectral energy distributions (SEDs) in the near-IR (NIR) and MIR regime, while
the remainder show a NIR bump in their SEDs. Assuming that the redshift
distribution for our DOGs sample is Gaussian, with mean and sigma = 1.99
0.45, we calculated their total IR luminosity using an empirical relation
between 22 m luminosity and total IR luminosity. The average value of the
total IR luminosity is (3.5 1.1) L, which
classifies them as hyper-luminous infrared galaxies (HyLIRGs). We also derived
the total IR luminosity function (LF) and IR luminosity density (LD) for a
flux-limited subsample of 18 DOGs with 22 m flux greater than 3.0 mJy and
with -band magnitude brighter than 24 AB magnitude. The derived space
density for this subsample is log = -6.59 0.11 [Mpc]. The
IR LF for DOGs including data obtained from the literature is well fitted by a
double-power law. The derived lower limit for the IR LD for our sample is
3.8 10 [L Mpc] and
its contributions to the total IR LD, IR LD of all ultra-luminous infrared
galaxies (ULIRGs), and that of all DOGs are 3 %, 9 %, and 15 %,
respectively.Comment: 15 pages, 15 figures, and 3 tables, accepted for publication in PASJ
(Subaru special issue
Subaru high-z exploration of low-luminosity quasars (SHELLQs). I. Discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9
We report the discovery of 15 quasars and bright galaxies at 5.7 < z < 6.9.
This is the initial result from the Subaru High-z Exploration of Low-Luminosity
Quasars (SHELLQs) project, which exploits the exquisite multiband imaging data
produced by the Subaru Hyper Suprime-Cam (HSC) Strategic Program survey. The
candidate selection is performed by combining several photometric approaches
including a Bayesian probabilistic algorithm to reject stars and dwarfs. The
spectroscopic identification was carried out with the Gran Telescopio Canarias
and the Subaru Telescope for the first 80 deg2 of the survey footprint. The
success rate of our photometric selection is quite high, approaching 100 % at
the brighter magnitudes (zAB < 23.5 mag). Our selection also recovered all the
known high-z quasars on the HSC images. Among the 15 discovered objects, six
are likely quasars, while the other six with interstellar absorption lines and
in some cases narrow emission lines are likely bright Lyman-break galaxies. The
remaining three objects have weak continua and very strong and narrow Ly alpha
lines, which may be excited by ultraviolet light from both young stars and
quasars. These results indicate that we are starting to see the steep rise of
the luminosity function of z > 6 galaxies, compared with that of quasars, at
magnitudes fainter than M1450 ~ -22 mag or zAB ~24 mag. Follow-up studies of
the discovered objects as well as further survey observations are ongoing.Comment: Published in ApJ (828:26, 2016
First Data Release of the Hyper Suprime-Cam Subaru Strategic Program
The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered
imaging survey aimed at addressing some of the most outstanding questions in
astronomy today, including the nature of dark matter and dark energy. The
survey has been awarded 300 nights of observing time at the Subaru Telescope
and it started in March 2014. This paper presents the first public data release
of HSC-SSP. This release includes data taken in the first 1.7 years of
observations (61.5 nights) and each of the Wide, Deep, and UltraDeep layers
covers about 108, 26, and 4 square degrees down to depths of i~26.4, ~26.5, and
~27.0 mag, respectively (5sigma for point sources). All the layers are observed
in five broad bands (grizy), and the Deep and UltraDeep layers are observed in
narrow bands as well. We achieve an impressive image quality of 0.6 arcsec in
the i-band in the Wide layer. We show that we achieve 1-2 per cent PSF
photometry (rms) both internally and externally (against Pan-STARRS1), and ~10
mas and 40 mas internal and external astrometric accuracy, respectively. Both
the calibrated images and catalogs are made available to the community through
dedicated user interfaces and database servers. In addition to the pipeline
products, we also provide value-added products such as photometric redshifts
and a collection of public spectroscopic redshifts. Detailed descriptions of
all the data can be found online. The data release website is
https://hsc-release.mtk.nao.ac.jp/.Comment: 34 pages, 20 figures, 7 tables, moderate revision, accepted for
publication in PAS
Down-Sizing in Galaxy Formation at z~1 in the Subaru/XMM-Newton Deep Survey (SXDS)
We use the deep wide-field optical imaging data of the Subaru/XMM-Newton Deep
Survey (SXDS) to discuss the luminosity (mass) dependent galaxy colours down to
z'=25.0 (5 x 10^9 h_{70}^{-2} Msun) for z~1 galaxies in colour-selected high
density regions. We find an apparent absence of galaxies on the red
colour-magnitude sequence below z'~24.2, corresponding to ~M*+2 (~10^{10} Msun)
with respect to passively evolving galaxies at z~1. Galaxies brighter than
M*-0.5 (8 x 10^{10} Msun), however, are predominantly red passively evolving
systems, with few blue star forming galaxies at these magnitudes.
This apparent age gradient, where massive galaxies are dominated by old
stellar populations while less massive galaxies have more extended star
formation histories, supports the `down-sizing' idea where the mass of galaxies
hosting star formation decreases as the Universe ages. Combined with the lack
of evolution in the shape of the stellar mass function for massive galaxies
since at least z~1, it appears that galaxy formation processes (both star
formation and mass assembly) should have occurred in an accelerated way in
massive systems in high density regions, while these processes should have been
slower in smaller systems. This result provides an interesting challenge for
modern CDM-based galaxy formation theories which predict later formation epochs
of massive systems, commonly referred to as ``bottom-up''.Comment: proof corrected version (MNRAS in press), 10 pages, 12 figures (of
which 3 are in jpg format