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M. Ando

Publications and source records attributed to M. Ando.

At least 109 records · Page 6Linked to original sources
arXiv2019

Vibration isolation system with a compact damping system for power recycling mirrors of KAGRA

A vibration isolation system called Type-Bp system used for power recycling mirrors has been developed for KAGRA, the interferometric gravitational-wave observatory in Japan. A suspension of the Type-Bp system passively isolates an optic from seismic vibration using three main pendulum stages equipped with two vertical vibration isolation systems. A compact reaction mass around each of the main stages allows for achieving sufficient damping performance with a simple feedback as well as vibration isolation ratio. Three Type-Bp systems were installed in KAGRA, and were proved to satisfy the requirements on the damping performance, and also on estimated residual displacement of the optics.

physics.ins-det↗
arXiv2018

KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector

The recent detections of gravitational waves (GWs) reported by LIGO/Virgo collaborations have made significant impact on physics and astronomy. A global network of GW detectors will play a key role to solve the unknown nature of the sources in coordinated observations with astronomical telescopes and detectors. Here we introduce KAGRA (former name LCGT; Large-scale Cryogenic Gravitational wave Telescope), a new GW detector with two 3-km baseline arms arranged in the shape of an "L", located inside the Mt. Ikenoyama, Kamioka, Gifu, Japan. KAGRA's design is similar to those of the second generations such as Advanced LIGO/Virgo, but it will be operating at the cryogenic temperature with sapphire mirrors. This low temperature feature is advantageous for improving the sensitivity around 100 Hz and is considered as an important feature for the third generation GW detector concept (e.g. Einstein Telescope of Europe or Cosmic Explorer of USA). Hence, KAGRA is often called as a 2.5 generation GW detector based on laser interferometry. The installation and commissioning of KAGRA is underway and its cryogenic systems have been successfully tested in May, 2018. KAGRA's first observation run is scheduled in late 2019, aiming to join the third observation run (O3) of the advanced LIGO/Virgo network. In this work, we describe a brief history of KAGRA and highlights of main feature. We also discuss the prospects of GW observation with KAGRA in the era of O3. When operating along with the existing GW detectors, KAGRA will be helpful to locate a GW source more accurately and to determine the source parameters with higher precision, providing information for follow-up observations of a GW trigger candidate.

gr-qc↗
arXiv2017

Imaging the Molecular Outflows of the Prototypical ULIRG NGC 6240 with ALMA

We present 0".97 $\times$ 0".53 (470 pc $\times$ 250 pc) resolution CO ($J$ = 2-1) observations toward the nearby luminous merging galaxy NGC 6240 with the Atacama Large Millimeter/submillimeter Array. We confirmed a strong CO concentration within the central 700 pc, which peaks between the double nuclei, surrounded by extended CO features along the optical dust lanes ($\sim$11 kpc). We found that the CO emission around the central a few kpc has extremely broad velocity wings with full width at zero intensity $\sim$ 2000 km s$^{-1}$, suggesting a possible signature of molecular outflow(s). In order to extract and visualize the high-velocity components in NGC 6240, we performed a multiple Gaussian fit to the CO datacube. The distribution of the broad CO components show four extremely large linewidth regions ($\sim$1000 km s$^{-1}$) located 1-2 kpc away from both nuclei. Spatial coincidence of the large linewidth regions with H$α$, near-IR H$_2$, and X-ray suggests that the broad CO (2-1) components are associated with nuclear outflows launched from the double nuclei.

astro-ph.GA↗
arXiv2017

Construction of KAGRA: an Underground Gravitational Wave Observatory

Major construction and initial-phase operation of a second-generation gravitational-wave detector KAGRA has been completed. The entire 3-km detector is installed underground in a mine in order to be isolated from background seismic vibrations on the surface. This allows us to achieve a good sensitivity at low frequencies and high stability of the detector. Bare-bones equipment for the interferometer operation has been installed and the first test run was accomplished in March and April of 2016 with a rather simple configuration. The initial configuration of KAGRA is named {\it iKAGRA}. In this paper, we summarize the construction of KAGRA, including the study of the advantages and challenges of building an underground detector and the operation of the iKAGRA interferometer together with the geophysics interferometer that has been constructed in the same tunnel.

gr-qc↗
arXiv2017

The status of KAGRA underground cryogenic gravitational wave telescope

KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial phase operation of the interferometer with a simple 3-km Michelson configuration have been completed. The first cryogenic operation is expected in 2018, and the observing runs with a full interferometer are expected in 2020s. The basic interferometer configuration and the current status of KAGRA are described.

gr-qc↗
arXiv2013

Elliptic genera of Landau-Ginzburg models over nontrivial spaces

In this paper, we discuss elliptic genera of (2,2) and (0,2) supersymmetric Landau-Ginzburg models over nontrivial spaces, i.e., nonlinear sigma models on nontrivial noncompact manifolds with superpotential, generalizing old computations in Landau-Ginzburg models over (orbifolds of) vector spaces. For Landau-Ginzburg models in the same universality class as nonlinear sigma models, we explicitly check that the elliptic genera of the Landau-Ginzburg models match that of the nonlinear sigma models, via a Thom class computation of a form analogous to that appearing in recent studies of other properties of Landau-Ginzburg models on nontrivial spaces.

hep-th↗
arXiv2010

Two-dimensional topological field theories as taffy

In this paper we use trivial defects to define global taffy-like operations on string worldsheets, which preserve the field theory. We fold open and closed strings on a space X into open strings on products of multiple copies of X, and perform checks that the "taffy-folded" worldsheets have the same massless spectra and other properties as the original worldsheets. Such folding tricks are a standard method in the defects community; the novelty of this paper lies in deriving mathematical identities to check that e.g. massless spectra are invariant in topological field theories. We discuss the case of the B model extensively, and also derive the same identities for string topology, where they become statements of homotopy invariance. We outline analogous results in the A model, B-twisted Landau-Ginzburg models, and physical strings. We also discuss the understanding of the closed string states as the Hochschild homology of the open string algebra, and outline possible applications to elliptic genera.

hep-th↗
arXiv2007

Adaptive Optics Rest-Frame V-band Imaging of Lyman Break Galaxies at z~3: High-surface Density Disk-like Galaxies ?

In order to reveal the rest-frame V-band morphology of galaxies at z~3, we conducted AO-assisted K-band imaging observations of z~3 LBGs with Mv*-0.5 to Mv*+3.0 mag. LBGs brighter than Mv* have larger rHL (0.40") than the fainter LBGs (0.23") on average, and there is no bright LBGs with a small rHL. The LBGs brighter than Mv* have red rest-frame U-V colors (average of 0.2 mag) and most of the fainter LBGs show blue rest-frame U-V colors (average of -0.4 mag). The K-band peaks of some of the LBGs brighter than K=22.0 mag show significant shift from those in the optical images. The images of all but one of the LBGs with K<21.5 mag are fitted well with Sersic profile with n index less than 2, similar to disk galaxies in the local universe. Assuming that the LBGs have a disk-shape, we compared their size-luminosity and size-stellar mass relation with those of z=0 and z=1 disk galaxies. The LBGs are brighter than z=0 and z=1 disk galaxies at the same effective radius. The rest-frame V-band surface brightness of the LBGs are 2.2-2.9 mag and 1.2-1.9 mag brighter than the disk galaxies at z=0 and z=1, respectively. The size-stellar mass relation of the LBGs shows that the effective radii of the LBGs do not depend on their stellar mass. For the LBGs brighter than Mv*, the average surface stellar mass density is 3-6 times larger than those of the z=0 and z=1 disk galaxies. We also examine the profiles of the serendipitously observed DRGs. They are also fitted with the Sersic profiles with n<2. The implications of the dominance of n<2 population among galaxies at z~3 and the presence of the high surface stellar mass density disk systems are discussed.

astro-ph↗
arXiv2007

Differential Evolution of the UV Luminosity Function of Lyman Break Galaxies from z~5 to 3

(abridged) We report the UV luminosity function (LF) of Lyman break galaxies at z~5 derived from a deep and wide survey using the Subaru/Suprime-Cam. Target fields consist of two blank regions of the sky (the HDF-N and J0053+1234), and the total effective surveyed area is 1290 sqarcmin. Applications of carefully determined colour selection criteria in V-I and I-z' yield a detection of 853 candidates with z'AB<26.5 mag. The derived UVLF at z~5 shows no significant change in the number density of bright (L>=L*_z=3) LBGs from that at z~3, while there is a significant decline in the LF's faint end with increasing lookback time. This result means that the evolution of the number densities is differential with UV luminosity: the number density of UV luminous objects remains almost constant from z~5 to 3 while the number density of fainter objects gradually increases with cosmic time. This trend becomes apparent thanks to the small uncertainties in number densities both in the bright and faint parts of LFs at different epochs that are made possible by the deep and wide surveys. We discuss the origins of this differential evolution and suggest that our observational findings are consistent with the biased galaxy evolution scenario: a galaxy population hosted by massive dark haloes starts active star formation preferentially at early cosmic time, while less massive galaxies increase their number density later. We also calculated the UV luminosity density by integrating the UVLF and at z~5 found it to be 38.8% of that at z~3 for the luminosity range L>0.1 L^*_z=3. By combining our results with those from the literature, we find that the cosmic UV luminosity density marks its peak at z=2-3 and then slowly declines toward higher redshift.

astro-ph↗
arXiv2006

Balmer Absorption Lines in FeLoBALs

We discovered non-stellar Balmer absorption lines in two many-narrow-trough FeLoBALs (mntBALs) by the near-infrared spectroscopy with Subaru/CISCO. Presence of the non-stellar Balmer absorption lines is known to date only in the Seyfert galaxy NGC 4151, thus our discovery is the first cases for quasars. Since all known active galactic nuclei with Balmer absorption lines share characteristics, it is suggested that there is a population of BAL quasars which have unique structures at their nuclei or unique evolutionary phase.

astro-ph↗
arXiv2006

Luminosity Dependent Evolution of Lyman Break Galaxies from redshift 5 to 3

In this contribution we briefly describe our recent results on the properties of Lyman break galaxies at z~5 obtained from deep and wide blank field surveys using Subaru telescope, and through the comparison with samples at lower redshift ranges we discuss the evolution of star-forming galaxies in the early universe.

astro-ph↗
arXiv2006

Cluster decomposition, T-duality, and gerby CFT's

In this paper we study CFT's associated to gerbes. These theories suffer from a lack of cluster decomposition, but this problem can be resolved: the CFT's are the same as CFT's for disconnected targets. Such theories also lack cluster decomposition, but in that form, the lack is manifestly not very problematic. In particular, we shall see that this matching of CFT's, this duality between noneffective gaugings and sigma models on disconnected targets, is a worldsheet duality related to T-duality. We perform a wide variety of tests of this claim, ranging from checking partition functions at arbitrary genus to D-branes to mirror symmetry. We also discuss a number of applications of these results, including predictions for quantum cohomology and Gromov-Witten theory and additional physical understanding of the geometric Langlands program.

hep-th↗
arXiv2005

Evolution of Lyman Break Galaxies From z=5 to 3

We report the updated UV luminosity function (LF) of Lyman break galaxies (LBGs) at z~5. Combining with lower redshift data, we found that the evolution of UV LF is differential depending on the UV luminosity; i.e., the number density of luminous LBGs does not change significantly from z=5 to 3, while the number density of faint (L<L*) galaxies increases by a factor of five. We also found the signs of differential evolution within other observational results for LBGs at z~5. UV-luminous objects show strong clustering, and they have weak or no Lyman-alpha emissions while showing prominent metal absorption lines. There is also a clear deficiency of objects with blue UV-optical colors for those bright in rest-frame optical bands (from the Spitzer/IRAC data obtained by the GOODS project). By the SED fitting using rest-frame optical to near-infrared photometry data it is suggested that most luminous objects at z~5 have already accumulated stellar mass more than 10^10 Msun. We discuss that this differential evolution might be understood as a consequence of the biased galaxy evolution.

astro-ph↗
arXiv2005

Deep Spectroscopic Survey of Lyman Break Galaxies at z~5

We report results of deep optical spectroscopy with Subaru/FOCAS for Lyman Break Galaxy (LBG) candidates at z~5. So far, we made spectroscopic observations for 24 LBG candidates among ~200 bright (z'<25.0) LBG sample and confirmed 9 objects to be LBGs at z~5. Intriguingly, these bright LBGs show no or a weak Ly-alpha emission and relatively strong low ionization interstellar metal absorption lines. We also identified 2 faint (z'>25.0) objects to be at z~5 with their strong (EW_rest>20AA) Ly-alpha emission. Combining our results with other spectroscopic observations of galaxies at the similar redshift range, we found a clear luminosity dependence of EW_rest of Ly-alpha emission, i.e., the lack of strong Ly-alpha emission in bright LBGs. If the absence of Ly-alpha emission is due to dust absorption, these results suggest that bright LBGs at z~5 are in dusty and more chemically evolved environment than faint ones. This interpretation implies that bright LBGs started star formation earlier than faint ones, suggesting biased star formation.

astro-ph↗
arXiv2004

Stabilization of a Fabry-Perot interferometer using a suspension-point interferometer

A suspension-point interferometer (SPI) is an auxiliary interferometer for active vibration isolation, implemented at the suspension points of the mirrors of an interferometric gravitational wave detector. We constructed a prototype Fabry-Perot interferometer equipped with an SPI and observed vibration isolation in both the spectrum and transfer function. The noise spectrum of the main interferometer was reduced by 40 dB below 1 Hz. Transfer function measurements showed that the SPI also produced good vibration suppression above 1 Hz. These results indicate that SPI can improve both the sensitivity and the stability of the interferometer.

gr-qc↗
arXiv2003

Lyman Break Galaxies at z~5: Luminosity Function

(abridged) We present results of a search for Lyman break galaxies (LBGs) at z ~ 5 in a 618 square-arcmin field including the HDF-N taken by Subaru Prime Focus Camera. Utilizing the published redshift data of the HDF-N and its flanking fields, the color selection criteria are chosen so that LBGs are picked out most efficiently and least contaminated by foreground objects. The numbers of LBG candidates detected are 310 in 23.0 < I_c < 25.5. The rest-frame UV luminosity function(LF) of LBGs at z ~ 5 is derived statistically. The fraction of contamination is estimated to be ~50% in the faintest magnitude range. The completeness of the survey is ~80% at the bright part of the sample, and ~20% in the faintest magnitude range (25.0 < I_c <= 25.5). The LF of LBG candidates at z ~ 5 does not show a significant difference from those at z ~ 3 and 4, though there might be a slight decrease in the fainter part. The UV luminosity density within the observational limit is 0.56 - 0.69 times smaller than that obtained for LBGs at z ~ 3, depending on the adopted cosmology and the integration range of the LF. The similarity of the LFs at redshifts 5 to 3 implies that most of LBGs at z ~ 5 should have faded out at z ~ 3 and LBGs at z \~ 5 are different galaxies from those seen at z ~ 3, if we take face values for ages of the LBGs at z ~ 3 obtained by the SED fitting in which a continuous star formation in an individual galaxy is assumed. However, if the star formation in LBGs is sporadic, the similarity of the LF at z ~ 3 and 5 would be explained. Such sporadic star formation has been suggested by hydrodynamical simulations and semi-analytic models with collisional starbursts, and the trend of the cosmic star formation history predicted by these studies resembles to that estimated from the UV luminosity density within the observational limit.

astro-ph↗
arXiv2000

The patching of critical points using quantum group

Following our recent conjecture to model the phenomenona of antiferromagnetism and superconductivity by quantum symmetry groups, we discuss in the present note how to construct a workable scenario using this symmetry. In particular we propose to patch the relevant critical points. This means we identify fixed points, corresponding to various $k$ or $q$ [since the two are related] and make expansion around these points, to control these expansion we can impose gauge structure and we thus arrive at quantum group based gauge theory or collection of classical gauge theories which represent the condensed matter system such as cuprates. This is different than ordinary gauge theories in several ways, for in ordinary field theory one has well-defined critical point here the critical points are not unique or simple. In short the real transition than in condensed matter system is represented by collection or {\it ensemble average} of the several chosen critical points which come from ordinary field theory [gauge theory]. This idea may reveal the connection between Hubbard model and gauge theory and string theory. In short it can lead to the non-perturbative formualtion of Hubbard and other condensed matter Hamiltonians.

cond-mat.supr-con↗