Chisato Yamauchi
Japan Aerospace Exploration Agency
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Chisato Yamauchi.
Monthly Notices of the Royal Astronomical Society | 2003
Tomotsugu Goto; Chisato Yamauchi; Y. Fujita; Sadanori Okamura; Maki Sekiguchi; Ian Smail; Mariangela Bernardi; Percy Luis Gomez
We have studied the morphology-density relation and morphology-cluster-centric-radius relation using a volume-limited sample (0.05 < z < 0.1, Mr* < -20.5) of the Sloan Digital Sky Survey (SDSS) data. Major improvements compared with previous work are: (i) automated galaxy morphology classification capable of separating galaxies into four types; (ii) three-dimensional local galaxy density estimation; and (iii) the extension of the morphology-density relation into the field region. We found that the morphology-density and morphology-cluster-centric-radius relation in the SDSS data for both of our automated morphological classifiers, Cin and Tauto, as fractions of early-type galaxies increase and late-type galaxies decrease toward increasing local galaxy density. In addition, we found that there are two characteristic changes in both the morphology-density and the morphology-radius relations, suggesting that two different mechanisms are responsible for the relations. In the sparsest regions (below 1 Mpc - 2 or outside of 1 virial radius), both relations become less noticeable, suggesting that the physical mechanisms responsible for galaxy morphological change require a denser environment. In the intermediate-density regions (density between 1 and 6 Mpc - 2 or virial radius between 0.3 and 1), intermediate-type fractions increase toward denser regions, whereas late-disc fractions decrease. Considering that the median size of intermediate-type galaxies is smaller than that of late-disc galaxies, we propose that the mechanism is likely to stop star formation in late-disc galaxies, eventually turning them into intermediate-type galaxies after their outer discs and spiral arms become invisible as stars die. For example, ram-pressure stripping is one of the candidate mechanisms. In the densest regions (above 6 Mpc - 2 or inside 0.3 virial radii), intermediate-type fractions decrease radically and early-type fractions increase in turn. This is a contrasting result to that in intermediate regions and it suggests that yet another mechanism is more responsible for the morphological change in these regions. We also compared the morphology-density relation from the SDSS (0.01 < z < 0.054) with that of the MORPHS data (z ∼ 0.5). Two relations lie on top of each other, suggesting that the morphology-density relation was already established at z ∼ 0.5 as in the present Universe. A slight sign of an excess elliptical/S0 fraction in the SDSS data in dense regions might suggest the additional formation of elliptical/S0 galaxies in the cluster core regions between z = 0.5 and 0.05.
Publications of the Astronomical Society of Japan | 2007
Hiroshi Murakami; Hajime Baba; Peter D. Barthel; D. L. Clements; Martin Cohen; Yasuo Doi; Keigo Enya; Elysandra Figueredo; Naofumi Fujishiro; Hideaki Fujiwara; Mikio Fujiwara; Pedro Garcia-Lario; Tomotsugu Goto; Sunao Hasegawa; Yasunori Hibi; Takanori Hirao; Norihisa Hiromoto; Seung Soo Hong; Koji Imai; Miho Ishigaki; Masateru Ishiguro; Daisuke Ishihara; Yoshifusa Ita; Woong-Seob Jeong; Kyung Sook Jeong; Hidehiro Kaneda; Hirokazu Kataza; Mitsunobu Kawada; Toshihide Kawai; Akiko Kawamura
AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from mid- to far-infrared. The instruments also have a capability for imaging and spectroscopy in the wavelength range 2-180 mu m in the pointed observation mode, occasionally inserted into a continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90% of the whole sky with a higher spatial resolution and a wider wavelength coverage than that of the previous IRAS all-sky survey. Point-source catalogues of the All-Sky Survey will be released to the astronomical community. Pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission.
Publications of the Astronomical Society of Japan | 2007
Mitsunobu Kawada; Hajime Baba; Peter D. Barthel; D. L. Clements; Martin Cohen; Yasuo Doi; Elysandra Figueredo; Mikio Fujiwara; Tomotsugu Goto; Sunao Hasegawa; Yasunori Hibi; Takanori Hirao; Norihisa Hiromoto; Woong-Seob Jeong; Hidehiro Kaneda; Toshihide Kawai; Akiko Kawamura; Do Kester; Tsuneo Kii; Hisato Kobayashi; Suk Minn Kwon; Hyung Mok Lee; Sin’itirou Makiuti; Hiroshi Matsuo; Shuji Matsuura; Thomas Müller; Noriko Murakami; Hirohisa Nagata; Takao Nakagawa; Masanao Narita
The Far-Infrared Surveyor (FIS) is one of two focal-plane instruments on the AKARI satellite. FIS has four photometric bands at 65, 90, 140, and 160 mu m, and uses two kinds of array detectors. The FIS arrays and optics are designed to sweep the sky with high spatial resolution and redundancy. The actual scan width is more than eight arcminutes, and the pixel pitch matches the diffraction limit of the telescope. Derived point-spread functions (PSFs) from observations of asteroids are similar to those given by the optical model. Significant excesses, however, are clearly seen around tails of the PSFs, whose contributions are about 30% of the total power. All FIS functions are operating well in orbit, and the performance meets the laboratory characterizations, except for the two longer wavelength bands, which are not performing as well as characterized. Furthermore, the FIS has a spectroscopic capability using a Fourier transform spectrometer (FTS). Because the FTS takes advantage of the optics and detectors of the photometer, it can simultaneously make a spectral map. This paper summarizes the in-flight technical and operational performance of the FIS.
Publications of the Astronomical Society of Japan | 2003
Tomotsugu Goto; Sadanori Okamura; Maki Sekiguchi; Mariangela Bernardi; J. Brinkmann; Percy Luis Gomez; Michael Harvanek; S. J. Kleinman; Jurek Krzesinski; Dan Long; Jon Loveday; Christopher J. Miller; Eric H. Neilsen; Peter R. Newman; Atsuko Nitta; Ravi K. Sheth; Stephanie A. Snedden; Chisato Yamauchi
In previous work on galaxy clusters, several authors reported the discovery of an unusual population of galaxies, which have spiral morphologies, but do not show any star-formation activity. These galaxies are called “passive spirals”, and have been interesting since it has been difficult to understand the existence of such galaxies. Using a volume-limited sample (0.05 <z <0. 1a ndMr ∗ < −20.5; 25813 galaxies) of the Sloan Digital Sky Survey data, we found 73 (0.28±0.03%) passivespiral galaxiesand studied their environments. It is found that passivespiral galaxies exist in a local galaxy density of 1–2Mpc −2 and have a 1–10 cluster-centric virial radius. Thus, the origins of passive spiral galaxies are likely to be cluster-related. These characteristic environments coincide with a previously reported environment where the galaxy star-formation rate suddenly declines and the so-called morphology–density relation turns. It is likely that the same physical mechanism is responsible for all of these observational results. The existence of passive spiral galaxies suggests that a physical mechanism that works calmly is preferred to dynamical origins such as major merger/interaction since such a mechanism would destroy the spiral-arm structures. Compared with the observed cluster galaxy evolution such as the Butcher–Oemler effect and the morphological Butcher–Oemler effect, passive spiral galaxies are likely to be a key galaxy population in transition between red, elliptical/S0 galaxies in low-redshift clusters and blue, spiral galaxies more numerous in higher-redshift clusters.
Monthly Notices of the Royal Astronomical Society | 2011
Tomotsugu Goto; S. Arnouts; Hanae Inami; Hideo Matsuhara; Chris Pearson; Tsutomu T. Takeuchi; Emeric Le Floc'h; Toshinobu Takagi; Takehiko Wada; Takao Nakagawa; Shinki Oyabu; Daisuke Ishihara; Hyung Mok Lee; Woong-Seob Jeong; Chisato Yamauchi; S. Serjeant; Chris Sedgwick; Ezequiel Treister
Infrared (IR) luminosity is fundamental to understanding the cosmic star formation history and active galactic nuclei (AGN) evolution, since their most intense stages are often obscured by dust. However, local IR luminosity function estimates today are still based on the IRAS survey in the 1980s, with wavelength coverage only up to 100 μm. The AKARI IR space telescope performed an all-sky survey in six IR bands (9, 18, 65, 90, 140 and 160 μm) with 3–10 times better sensitivity, covering the crucial far-IR wavelengths across the peak of the dust emission. Combined with a better spatial resolution, AKARI can much more precisely measure the total infrared luminosity (L_(TIR)) of individual galaxies, and thus, the total infrared luminosity density in the local Universe. By fitting modern IR spectral energy distribution (SED) models, we have remeasured L_(TIR) of the IRAS Revised Bright Galaxy Sample, which is a complete sample of local galaxies with S_(60μm) > 5.24 Jy. We present mid-IR monochromatic luminosity (νL_ν) to L_(TIR) correlations for Spitzer 8 μm, AKARI 9 μm, IRAS 12 μm, WISE 12 μm, ISO 15 μm, AKARI 18 μm, WISE 22 μm and Spitzer 24 μm filters. These measures of L_(MIR) are well correlated with L_(TIR), with scatter in the range 13–44 per cent. The best-fitting L_(MIR)-to-L_(TIR) conversions provide us with estimates of L_(TIR) using only a single MIR band, in which several deep all-sky surveys are becoming available such as AKARI MIR and WISE. Although we have found some overestimates of L_(TIR) by IRAS due to contaminating cirrus/ sources, the resulting AKARI IR luminosity function (LF) agrees well with that from IRAS. We integrate the LF weighted by L_(TIR) to obtain a cosmic IR luminosity density of Ω_(TIR) = (8.5^(+1.5)_(−2.3)) × 10^7 L_⊙ Mpc^(−3), of which 7 ± 1 per cent is produced by luminous infrared galaxies (LIRGs) (L_(TIR) > 10^(11) L_⊙), and only 0.4 ± 0.1 per cent is from ultraluminous infrared galaxies (ULIRGs) (L_(TIR) > 10^(12) L_⊙) in the local Universe, in stark contrast to high-redshift results. We separate the contributions from AGN and star-forming galaxies (SFGs). The SFG IR LF shows a steep decline at the bright end. Combined with high-redshift results from the AKARI NEP deep survey, these data show a strong evolution of Ω^(SF)_(TIR) ∝ (1 + z)^(4.0 ± 0.5) and Ω^(AGN)_(TIR) ∝ (1 + z)^(4.4 ± 0.4). For Ω^(AGN)_(TIR), the ULIRG contribution exceeds that from LIRGs already by z ~ 1. A rapid evolution in both Ω^(AGN)_(TIR) and Ω^(SFG)_(TIR) suggests the correlation between star formation and black hole accretion rate continues up to higher redshifts. We compare the evolution of Ω^(AGN)_(TIR) to that of X-ray luminosity density. The Ω^(AGN)_(TIR)/Ω^(AGN)_(X-ray) ratio shows a possible increase at z > 1, suggesting an increase of obscured AGN at z > 1.
The Astronomical Journal | 2005
Chisato Yamauchi; Shin Ichi Ichikawa; Mamoru Doi; Naoki Yasuda; Masafumi Yagi; Masataka Fukugita; Sadanori Okamura; Osamu Nakamura; Maki Sekiguchi; Tomotsugu Goto
We devise improved photometric parameters for the morphological classification of galaxies using a bright sample from the First Data Release of the Sloan Digital Sky Survey. In addition to using an elliptical aperture concentration index for classification, we introduce a new texture parameter, coarseness, which quantifies deviations from smooth galaxy isophotes. The elliptical aperture concentration index produces morphological classifications that are in appreciably better agreement with visual classifications than those based on circular apertures. With the addition of the coarseness parameter, the success rate of classifying galaxies into early and late types increases to 88% with respect to the reference visual classification. A reasonably high success rate (68%) is also attained in classifying galaxies into three types, early-type galaxies (E+S0) and early-type (Sa+Sb) and late-type (Sc+Sdm+Im) spiral galaxies.
Monthly Notices of the Royal Astronomical Society | 2011
Tomotsugu Goto; S. Arnouts; Matthew A. Malkan; Toshinobu Takagi; Hanae Inami; Chris Pearson; Takehiko Wada; Hideo Matsuhara; Chisato Yamauchi; Tsutomu T. Takeuchi; Takao Nakagawa; Shinki Oyabu; Daisuke Ishihara; David B. Sanders; Emeric Le Floc’h; Hyung Mok Lee; Woong-Seob Jeong; S. Serjeant; Chris Sedgwick
By cross-correlating the AKARI all-sky survey in six infrared (IR) bands (9, 18, 65, 90, 140 and 160 μm) with the Sloan Digital Sky Survey (SDSS) galaxies, we identified 2357 IR galaxies with a spectroscopic redshift. This is not just one of the largest samples of local IR galaxies, but AKARI provides crucial far-IR (FIR) bands for accurately measuring the galaxy spectral energy distribution (SED) across the peak of the dust emission at > 100 μ m. By fitting modern IR SED models to the AKARI photometry, we measured the total infrared luminosity (L_(IR)) of individual galaxies. Using this L_(IR), we constructed the luminosity functions (LF) of IR galaxies at a median redshift of z= 0.031. The LF agrees well with that at z= 0.0082 (the Revised Bright Galaxy Sample), showing smooth and continuous evolution towards higher redshift LFs measured in the AKARI North Ecliptic Pole (NEP) deep field. By integrating the IR LF weighted by L_(IR), we measured the local cosmic IR luminosity density of Ω_(IR_= (3.8^(+5.8)_(−1.2)) × 10^8 L_⊙ Mpc^(−3). We separate galaxies into active galactic nuclei (AGN), star-forming galaxies (SFG) and composite by using the [N ii]/Hα versus [O iii]/Hβ line ratios. The fraction of AGN shows a continuous increase with increasing L_(IR) from 25 to 90 per cent at 9 10^(11) L_⊙, coinciding with the break of both the SFG and AGN IR LFs. At L_(IR)≤ 10^(11) L_⊙, SFG dominates IR LFs. Only 1.1 ± 0.1 per cent of Ω_(IR) is produced by luminous infrared galaxies (L_(IR) > 10^(11) L_⊙), and only 0.03 ± 0.01 per cent by ultraluminous infrared galaxies (L_(IR) > 10^(12) L_⊙) in the local Universe. Compared with high-redshift results from the AKARI NEP deep survey, we observed a strong evolution of Ω^(SFG)IR^∝ (1 +z)^(4.1±0.4) and Ω^(AGN)IR^∝ (1+z)^(4.1±0.5). Our results show that all of our measured quantities (IR LFs, L^*, Ω^(AGN)IR, Ω^(SFG)IR) show smooth and steady increase from lower redshift (the Revised Bright Galaxy Sample) to higher redshift (the AKARI NEP deep survey).
Monthly Notices of the Royal Astronomical Society | 2004
Chisato Yamauchi; Tomotsugu Goto
Passive spiral galaxies – unusual galaxies with spiral morphology without any sign of on-going star formation – have recently been found to exist preferentially in cluster infalling regions (at about the virial radius, or at a local galaxy density of ∼1 Mpc−2). The discovery directly connects passive spiral galaxies to cluster galaxy evolution studies such as the Butcher–Oemler effect or the morphology–density relation, i.e. passive spiral galaxies are likely to be transition objects between high-z blue, spiral galaxies and low-z red, cluster early-type galaxies. Thus, detailed study of passive spiral galaxies could potentially bring new insight into the underlying physical mechanisms governing cluster galaxy evolution. However, in previous work, passive spiral galaxies were selected from low-resolution optical images with ∼1.5 arcsec of seeing. Therefore, passive spirals could be a misidentification of S0 galaxies; or dusty starburst galaxies which are not passive at all. To answer these questions, we performed deep, high-resolution, near-infrared imaging of 32 passive spiral galaxies. Our high-resolution K-band images show clear spiral-arm structures. Thus, passive spirals are not S0s. Optical–infrared colour does not show any signs of dusty starburst at all. Therefore, it is likely that they are truly ‘passive’ and ‘spiral’ galaxies in the midst of cluster galaxy evolution.
The Astrophysical Journal | 2014
Yoshiki Toba; Shinki Oyabu; Hideo Matsuhara; Matthew A. Malkan; P. Gandhi; Takao Nakagawa; Naoki Isobe; Mai Shirahata; Nagisa Oi; Youichi Ohyama; Satoshi Takita; Chisato Yamauchi; Kenichi Yano
In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) (i) on the mid-infrared (MIR) luminosity and (ii) on the redshift. We constructed 12- and 22-micron luminosity functions (LFs) at 0.006 < z < 0.3 using the Wide-field Infrared Survey Explorer} (WISE) data. Combining the WISE catalog with the Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 micron and 25,721 galaxies at 22 micron for spectroscopic classification. We then identified 16,355 AGNs at 12 micron and 4,683 AGNs at 22 micron by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that (i) the CF decreased with increasing MIR luminosity, regardless of the choice of type 2 AGN classification criteria, and (ii) the CF did not change significantly with the redshift for z < 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed similar dependences exist even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the modified receding torus model gives a slightly better fit, as suggested by Simpson.
Publications of the Astronomical Society of the Pacific | 2011
Chisato Yamauchi; S. Fujishima; N. Ikeda; K. Inada; M. Katano; Hirokazu Kataza; S. Makiuti; K. Matsuzaki; Satoshi Takita; Y. Yamamoto; Issei Yamamura; Daisuke Ishihara; Shinki Oyabu
ABSTRACT.The AKARI All-Sky Catalogues are an important infrared astronomical database for next-generation astronomy that take over the IRAS catalog. We have developed an online service, AKARI Catalogue Archive Server (AKARI-CAS), for astronomers. The service includes useful and attractive search tools and visual tools. One of the new features of AKARI-CAS is cached SIMBAD/NED entries, which can match AKARI catalogs with other catalogs stored in SIMBAD or NED. To allow advanced queries to the databases, direct input of SQL is also supported. In those queries, fast dynamic cross-identification between registered catalogs is a remarkable feature. In addition, multiwavelength quick-look images are displayed in the visualization tools, which will increase the value of the service. In the construction of our service, we considered a wide variety of astronomers’ requirements. As a result of our discussion, we concluded that supporting users’ SQL submissions is the best solution for the requirements. Therefore, w...