 | 井上 開輝 （イノウエ カイキ）
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宇宙論について研究しています。特に重力レンズや重力波など一般相対論的効果によって生じる宇宙論的現象や、重力による天文学的現象の探究を専門としています。報道関連出演・掲載一覧
＜報道関連出演・掲載一覧＞ ●2020/4/12 NHK大阪放送局 関西のニュース 「星誕生の鍵 ブラックホール撮影」 ブラックホール噴出物質が星間ガスに及ぼす影響について
研究者情報
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ホームページURL
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プロフィール
研究分野
観測的宇宙論、一般相対性理論、銀河天文学
研究テーマ
重力レンズ、重力波などの宇宙論的スケールにおける一般相対論的現象の解析から未知の物理学に迫る。特に、ダークマターやダークエネルギーの起源の解明に焦点をあてて研究を進めている。また近年は電波観測による活動銀河核や銀河形成に関する研究にも力を注いでいる。
研究キーワード
- 一般相対性理論 ダークエネルギー ブラックホール 活動銀河核 銀河形成 電波天文学 ダークマター 重力レンズ 宇宙マイクロ波背景輻射 宇宙論 宇宙物理 重力波
現在の研究分野（キーワード）
- 宇宙論について研究しています。特に重力レンズや重力波など一般相対論的効果によって生じる宇宙論的現象や、重力による天文学的現象の探究を専門としています。
研究分野
経歴
- 2019年04月 - 現在 近畿大学教授
- 2007年04月 - 2019年03月 近畿大学理工学部准教授
- 2011年09月 - 2012年08月 英国オックスフォード大学客員研究員
- 2004年04月 - 2006年03月 近畿大学理工学部講師
- 2002年04月 - 2004年03月 日本学術振興会(国立天文台)特別研究員（PD）
- 1998年04月 - 2001年03月 日本学術振興会(基礎物理学研究所)特別研究員 (DC1)
学歴
所属学協会
研究活動情報
論文
- Kaiki Taro Inoue; Takeo Minezaki; Satoki Matsushita; Kouichiro NakanishiThe Astrophysical Journal 954 2 197 - 197 2023年09月 [査読有り]
Abstract The lensing power spectra for gravitational potential, astrometric shift, and convergence perturbations are powerful probes to investigate dark matter structures on small scales. We report the first lower and upper bounds of these lensing power spectra on angular scale ∼1″ toward the anomalous quadruply lensed quasar MG J0414+0534 at a redshift z = 2.639. To obtain the spectra, we conducted observations of MG J0414+0534 using the Atacama Large Millimeter/submillimeter Array with high angular resolution (0.″02–0.″05). We developed a new partially nonparametric method in which Fourier coefficients of potential perturbation are adjusted to minimize the difference between linear combinations of weighted mean de-lensed images. Using positions of radio-jet components, extended dust emission on scales >1 kpc, and mid-infrared flux ratios, the range of measured convergence, astrometric shift, and potential powers at an angular scale of ∼1.″1 (corresponding to an angular wavenumber of l = 1.2 × 106 or ∼9 kpc in the primary lens plane) within 1σ are Δκ = 0.021–0.028, Δα = 7–9 mas, and Δψ = 1.2–1.6 mas2, respectively. Our result is consistent with the predicted abundance of halos in the line of sight and subhalos in cold dark matter models. Our partially nonparametric lens models suggest the presence of a clump in the vicinity of object Y, a possible dusty dwarf galaxy, and some small clumps in the vicinity of other lensed quadruple images. Although much fainter than the previous report, we detected weak continuum emission possibly from object Y with a peak flux of ∼100 μJy beam−1 at the ∼4σ level. - Yoshiki Toba; Teng Liu; Tanya Urrutia; Mara Salvato; Junyao Li; Yoshihiro Ueda; Marcella Brusa; Naomichi Yutani; Keiichi Wada; Atsushi J. Nishizawa; Johannes Buchner; Tohru Nagao; Andrea Merloni; Masayuki Akiyama; Riccardo Arcodia; Bau-Ching Hsieh; Kohei Ichikawa; Masatoshi Imanishi; Kaiki T. Inoue; Toshihiro Kawaguchi; Georg Lamer; Kirpal Nandra; John D. Silverman; Yuichi TerashimaAstronomy and Astrophysics 661 A15 - A15 2022年05月 [査読有り]
Aims. We investigate the physical properties – such as the stellar mass (M*), star-formation rate, infrared (IR) luminosity (LIR), X-ray luminosity (LX), and hydrogen column density (NH) – of mid-IR (MIR) galaxies and active galactic nuclei (AGN) at z < 4 in the 140 deg2 field observed by eROSITA on SRG using the Performance-and-Verification-Phase program named the eROSITA Final Equatorial Depth Survey (eFEDS). Methods. By cross-matching the WISE 22 μm (W4)-detected sample and the eFEDS X-ray point-source catalog, we find that 692 extragalactic objects are detected by eROSITA. We have compiled a multiwavelength dataset extending from X-ray to far-IR wavelengths. We have also performed (i) an X-ray spectral analysis, (ii) spectral-energy-distribution fitting using X-CIGALE, (iii) 2D image-decomposition analysis using Subaru Hyper Suprime-Cam images, and (iv) optical spectral fitting with QSFit to investigate the AGN and host-galaxy properties. For 7088 WISE 22 μm objects that are undetected by eROSITA, we have performed an X-ray stacking analysis to examine the typical physical properties of these X-ray faint and probably obscured objects. Results. We find that (i) 82% of the eFEDS–W4 sources are classified as X-ray AGN with log LX > 42 erg s−1 ; (ii) 67 and 24% of the objects have log(LIR/L⊙) > 12 and 13, respectively; (iii) the relationship between LX and the 6 μm luminosity is consistent with that reported in previous works; and (iv) the relationship between the Eddington ratio and NH for the eFEDS–W4 sample and a comparison with a model prediction from a galaxy-merger simulation indicates that approximately 5.0% of the eFEDS–W4 sources in our sample are likely to be in an AGN-feedback phase, in which strong radiation pressure from the AGN blows out the surrounding material from the nuclear region. Conclusions. Thanks to the wide area coverage of eFEDS, we have been able to constrain the ranges of the physical properties of the WISE 22 μm-selected sample of AGNs at z < 4, providing a benchmark for forthcoming studies on a complete census of MIR galaxies selected from the full-depth eROSITA all-sky survey. - Yiping Shu; Raoul Cañameras; Stefan Schuldt; Sherry H. Suyu; Stefan Taubenberger; Kaiki Taro Inoue; Anton T. Jaelani2022年01月We carry out a search for strong-lens systems containing high-redshift lens galaxies with the goal of extending strong-lensing-assisted galaxy evolutionary studies to earlier cosmic time. Two strong-lens classifiers are constructed from a deep residual network and trained with datasets of different lens-redshift and brightness distributions. We classify a sample of 5,356,628 pre-selected objects from the Wide-layer fields in the second public data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) by applying the two classifiers to their HSC $gri$-filter cutouts. Cutting off at thresholds that correspond to a false positive rate of $10^{-3}$ on our test set, the two classifiers identify 5,468 and 6,119 strong-lens candidates. Visually inspecting the cutouts of those candidates results in 735 grade-A or B strong-lens candidates in total, of which 277 candidates are discovered for the first time. This is the single largest set of galaxy-scale strong-lens candidates discovered with HSC data to date, and nearly half of it (331/735) contains lens galaxies with photometric redshifts above 0.6. Our discoveries will serve as a valuable target list for ongoing and scheduled spectroscopic surveys such as the Dark Energy Spectroscopic Instrument, the Subaru Prime Focus Spectrograph project, and the Maunakea Spectroscopic Explorer.
- R. Canameras; S. Schuldt; Y. Shu; S. H. Suyu; S. Taubenberger; T. Meinhardt; L. Leal-Taixe; D. C. -Y. Chao; K. T. Inoue; A. T. Jaelani; A. MoreASTRONOMY & ASTROPHYSICS 653 2021年09月 [査読有り]
We have carried out a systematic search for galaxy-scale strong lenses in multiband imaging from the Hyper Suprime-Cam (HSC) survey. Our automated pipeline, based on realistic strong-lens simulations, deep neural network classification, and visual inspection, is aimed at efficiently selecting systems with wide image separations (Einstein radii theta(E) similar to 1.0-3.0 ''), intermediate redshift lenses (z similar to 0.4-0.7), and bright arcs for galaxy evolution and cosmology. We classified gri images of all 62 5 million galaxies in HSC Wide with i-band Kron radius >= 0.8" to avoid strict preselections and to prepare for the upcoming era of deep, wide-scale imaging surveys with Euclid and Rubin Observatory. We obtained 206 newly-discovered candidates classified as definite or probable lenses with either spatially-resolved multiple images or extended, distorted arcs. In addition, we found 88 high-quality candidates that were assigned lower confidence in previous HSC searches, and we recovered 173 known systems in the literature. These results demonstrate that, aided by limited human input, deep learning pipelines with false positive rates as low as-='0.01% can be very powerful tools for identifying the rare strong lenses from large catalogs, and can also largely extend the samples found by traditional algorithms. We provide a ranked list of candidates for future spectroscopic confirmation. - Yoshiki Toba; Teng Liu; Tanya Urrutia; Mara Salvato; Junyao Li; Yoshihiro Ueda; Marcella Brusa; Naomichi Yutani; Keiichi Wada; Atsushi J. Nishizawa; Johannes Buchner; Tohru Nagao; Andrea Merloni; Masayuki Akiyama; Riccardo Arcodia; Bau-Ching Hsieh; Kohei Ichikawa; Masatoshi Imanishi; Kaiki T. Inoue; Toshihiro Kawaguchi; Georg Lamer; Kirpal Nandra; John D. Silverman; Yuichi Terashima2021年06月 [査読有り]
We investigate the physical properties--such as the stellar mass, SFR, IR luminosity, X-ray luminosity, and hydrogen column density--of MIR galaxies and AGN at $z < 4$ in the 140 deg$^2$ field observed by SRG/eROSITA through the eFEDS survey. By cross-matching the WISE 22 $\mu$m (W4)-detected sample and the eFEDS X-ray point-source catalog, we find that 692 extragalactic objects are detected by eROSITA. We have compiled a multiwavelength dataset. We have also performed (i) an X-ray spectral analysis, (ii) SED fitting using X-CIGALE, (iii) 2D image-decomposition analysis using Subaru HSC images, and (iv) optical spectral fitting with QSFit to investigate the AGN and host-galaxy properties. For 7,088 WISE W4 objects that are undetected by eROSITA, we have performed an X-ray stacking analysis to examine the typical physical properties of these X-ray faint and/or probably obscured objects. We find that (i) 82% of the eFEDS-W4 sources are classified as X-ray AGN with $\log\,L_{\rm X} >$ 42 erg s$^{-1}$; (ii) 67% and 24% of the objects have $\log\,(L_{\rm IR}/L_{\odot}) > 12$ and 13, respectively; (iii) the relationship between $L_{\rm X}$ and the 6 $\mu$m luminosity is consistent with that reported in previous works; and (iv) the relationship between the Eddington ratio and $N_{\rm H}$ for the eFEDS-W4 sample and a comparison with a model prediction from a galaxy-merger simulation indicates that approximately 5% of the eFEDS-W4 sources in our sample are likely to be in an AGN-feedback phase, in which strong radiation pressure from the AGN blows out the surrounding material from the nuclear region. Thanks to the wide area coverage of eFEDS, we have been able to constrain the ranges of the physical properties of the WISE W4 sample of AGNs at $z < 4$, providing a benchmark for forthcoming studies on a complete census of MIR galaxies selected from the full-depth eROSITA all-sky survey. - Yoshiki Toba; Marcella Brusa; Teng Liu; Johannes Buchner; Yuichi Terashima; Tanya Urrutia; Mara Salvato; Masayuki Akiyama; Riccardo Arcodia; Andy D. Goulding; Yuichi Higuchi; Kaiki T. Inoue; Toshihiro Kawaguchi; Georg Lamer; Andrea Merloni; Tohru Nagao; Yoshihiro Ueda; Kirpal NandraAstronomy & Astrophysics 649 L11 - L11 2021年04月 [査読有り]
In this study, we investigate the X-ray properties of WISE J090924.01+000211.1 (WISEJ0909+0002), an extremely luminous infrared (IR) galaxy (ELIRG) at $z_{\rm spec}$= 1.871 in the eROSITA final equatorial depth survey (eFEDS). WISEJ0909+0002 is a WISE 22 $\mu$m source, located in the GAMA-09 field, detected by eROSITA during the performance and verification phase. The corresponding optical spectrum indicates that this object is a type-1 active galactic nucleus (AGN). Observations from eROSITA combined with Chandra and XMM-Newton archival data indicate a very luminous ($L$ (2--10 keV) = ($2.1 \pm 0.2) \times 10^{45}$ erg s$^{-1}$) unobscured AGN with a power-law photon index of $\Gamma$ = 1.73$_{-0.15}^{+0.16}$, and an absorption hydrogen column density of $\log\,(N_{\rm H}/{\rm cm}^{-2}) < 21.0$. The IR luminosity was estimated to be $L_{\rm IR}$ = (1.79 $\pm$ 0.09) $\times 10^{14}\, L_{\odot}$ from spectral energy distribution modeling based on 22 photometric data (X-ray to far-IR) with X-CIGALE, which confirmed that WISEJ0909+0002 is an ELIRG. A remarkably high $L_{\rm IR}$ despite very low $N_{\rm H}$ would indicate that we are witnessing a short-lived phase in which hydrogen gas along the line of sight is blown outwards, whereas warm and hot dust heated by AGNs still exist. As a consequence of eROSITA all-sky survey, $6.8_{-5.6}^{+16}\times 10^2$ such X-ray bright ELIRGs are expected to be discovered in the entire extragalactic sky ($|b| > 10^\circ$). This can potentially be the key population to constrain the bright-end of IR luminosity functions. - Anton T Jaelani; Cristian E Rusu; Issha Kayo; Anupreeta More; Alessandro Sonnenfeld; John D Silverman; Malte Schramm; Timo Anguita; Naohisa Inada; Daichi Kondo; Paul L Schechter; Khee-Gan Lee; Masamune Oguri; James H H Chan; Kenneth C Wong; Kaiki T InoueMonthly Notices of the Royal Astronomical Society 2021年01月 [査読有り]
Abstract We present spectroscopic confirmation of three new two-image gravitationally lensed quasars, compiled from existing strong lens and X-ray catalogs. Images of HSC J091843.27–022007.5 show a red galaxy with two blue point sources at either side, separated by 2.26 arcsec. This system has a source and a lens redshifts zs = 0.804 and zℓ = 0.459, respectively, as obtained by our follow-up spectroscopic data. CXCO J100201.50+020330.0 shows two point sources separated by 0.85 arcsec on either side of an early-type galaxy. The follow-up spectroscopic data confirm the fainter quasar has the same redshift with the brighter quasar from the SDSS fiber spectrum at zs = 2.016. The deflecting foreground galaxy is a typical early-type galaxy at a redshift of zℓ = 0.439. SDSS J135944.21+012809.8 has two point sources with quasar spectra at the same redshift zs = 1.096, separated by 1.05 arcsec, and fits to the HSC images confirm the presence of a galaxy between these. These discoveries demonstrate the power of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP)’s deep imaging and wide sky coverage. Combined with existing X-ray source catalogues and follow-up spectroscopy, the HSC-SSP provides us unique opportunities to find multiple-image quasars lensed by a foreground galaxy. - Anton T. Jaelani; Anupreeta More; Masamune Oguri; Alessandro Sonnenfeld; Sherry H. Suyu; Cristian E. Rusu; Kenneth C. Wong; James H. H. Chan; Issha Kayo; Chien-Hsiu Lee; Dani C. -Y. Chao; Jean Coupon; Kaiki T. Inoue; Toshifumi FutamaseMonthly Notices of the Royal Astronomical Society 495 1 1291 - 1310 2020年04月 [査読有り]
We report the largest sample of candidate strong gravitational lenses belonging to the Survey of Gravitationally-lensed Objects in HSC Imaging for group-to-cluster scale (SuGOHI-c) systems. These candidates are compiled from the S18A data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) Survey. We visually inspect $\sim39,500$ galaxy clusters, selected from several catalogs, overlapping with the Wide, Deep, and UltraDeep fields, spanning the cluster redshift range $0.05Kaiki Taro Inoue; Satoki Matsushita; Kouichiro Nakanishi; Takeo MinezakiThe Astrophysical Journal 892 2 L18 - L18 2020年03月Yuichi Higuchi; Kaiki Taro InoueMonthly Notices of the Royal Astronomical Society 488 4 5811 - 5822 2019年10月 [査読有り]
ABSTRACT The cosmic microwave background (CMB) contains an anomalous cold spot with a surrounding hot ring, known as the Cold Spot. Inoue & Silk proposed that this feature could be explained by postulating a supervoid: if such a large underdense region exists, then the growth of matter perturbing around the spot might differ from the average value in the Universe and the differences might affect weak lensing analysis of peak statistics. To investigate environmental effects on halo number count and peak statistics, we used a publicly available ray-tracing simulation for a box size of 2250 h−1 Mpc on a side. We found that the number count for massive haloes towards the largest underdense region in the simulation decreases and the corresponding significance of the difference, based on a cosmic average, is ≥3σ. On the basis of the results of peak statistics analysis, the number of high peaks decreases with the decrement of massive haloes, but the number of low peaks increases with the lack of matter in the line of sight. The highest significance of the decrement in peak counts in large underdense regions is 5σ in the total signal-to-noise ratio. Our result implies that environmental effects on halo abundance and weak lensing peak statistic can be used to probe the presence and properties of supervoids.Anton T. Jaelani; Anupreeta More; Alessandro Sonnenfeld; Masamune Oguri; Cristian E. Rusu; Kenneth C. Wong; James H. H. Chan; Sherry H. Suyu; Issha Kayo; Chien-Hsiu Lee; Kaiki T. InoueMonthly Notices of the Royal Astronomical Society 494 3 3156 - 3165 2019年08月 [査読有り]
We report the serendipitous discovery of HSC J0904$-$0102, a quadruply-lensed Lyman break galaxy (LBG) in the Survey of Gravitationally-lensed Objects in Hyper Suprime-Cam Imaging (SuGOHI). Owing to its point-like appearance, the source was thought to be a lensed active galactic nucleus. We obtained follow-up spectroscopic data with the Gemini Multi-Object Spectrographs on the Gemini South Telescope, which confirmed this to be a lens system. The deflecting foreground galaxy is a typical early-type galaxy at a high redshift of $z_{\ell} = 0.957$ with stellar velocity dispersion $\sigma_v=259\pm56$ km~s$^{-1}$. The lensed source is identified as an LBG at $z_{\rm s} = 3.403$, based on the sharp drop bluewards of Ly$\alpha$ and other absorption features. A simple lens mass model for the system, assuming a singular isothermal ellipsoid, yields an Einstein radius of $\theta_{\rm Ein} = 1. 23^{\prime\prime}$ and a total mass within the Einstein radius of $M_{\rm Ein} = (5.55\pm 0.24) \times 10^{11}M_{\odot}$ corresponding to a velocity dispersion of $\sigma_{\rm SIE}= 283\pm 3$ km~s$^{-1}$, which is in good agreement with the value derived spectroscopically. The most isolated lensed LBG image has a magnification of $\sim 6.5$. In comparison with other lensed LBGs and typical $z\sim4$ LBG populations, HSC J0904$-$0102 is unusually compact, an outlier at $>2\sigma$ confidence. Together with a previously discovered SuGOHI lens, HSC J1152$+$0047, that is similarly compact, we believe that the HSC Survey is extending LBG studies down to smaller galaxy sizes.Kawamura, S.; Nakamura, T.; Ando, M.; Seto, N.; Akutsu, T.; Funaki, I.; Ioka, K.; K; a, N.; Kawano, I.; Musha, M.; Nakazawa, K.; Sato, S.; Takashima, T.; Tanaka, T.; Tsubono, K.; Yokoyama, J.; Agatsuma, K.; Aoyanagi, K.-S.; Arai, K.; Araya, A.; Aritomi, N.; Asada, H.; Aso, Y.; Chen, D.; Chiba, T.; Ebisuzaki, T.; Eguchi, S.; Ejiri, Y.; Enoki, M.; Eriguchi, Y.; Fujimoto, M.-K.; Fujita, R.; Fukushima, M.; Futamase, T.; Gondo, R.; Harada, T.; Hashimoto, T.; Hayama, K.; Hikida, W.; Himemoto, Y.; Hirabayashi, H.; Hiramatsu, T.; Hong, F.-L.; Horisawa, H.; Hosokawa, M.; Ichiki, K.; Ikegami, T.; Inoue, K.T.; Ishihara, H.; Ishikawa, T.; Ishizaki, H.; Ito, H.; Itoh, Y.; Izumi, K.; Kanemura, S.; Kawashima, N.; Kawazoe, F.; Kishimoto, N.; Kiuchi, K.; Kobayashi, S.; Kohri, K.; Koizumi, H.; Kojima, Y.; Kokeyama, K.; Kokuyama, W.; Kotake, K.; Kozai, Y.; Kunimori, H.; Kuninaka, H.; Kuroda, K.; Kuroyanagi, S.; Maeda, K.-I.; Matsuhara, H.; Matsumoto, N.; Michimura, Y.; Miyakawa, O.; Miyamoto, U.; Miyoki, S.; Morimoto, M.Y.; Morisawa, T.; Moriwaki, S.; Mukohyama, S.; Nagano, S.; Nakamura, K.; Nakano, H.; Nakao, K.; Nakasuka, S.; Nakayama, Y.; Nishida, E.; Nishizawa, A.; Niwa, Y.; Noumi, T.; Obuchi, Y.; Ohishi, N.; Ohkawa, M.; Okada, K.; Okada, N.; Okutomi, K.; Oohara, K.; Sago, N.; Saijo, M.; Saito, R.; Sakagami, M.; Sakai, S.-I.; Sakata, S.; Sasaki, M.; Sato, T.; Shibata, M.; Shibata, K.; Shimo-Oku, A.; Shinkai, H.; Shoda, A.; Somiya, K.; Sotani, H.; Suemasa, A.; Sugiyama, N.; Suwa, Y.; Suzuki, R.; Tagoshi, H.; Takahashi, F.; Takahashi, K.; Takahashi, K.; Takahashi, R.; Takahashi, R.; Takahashi, H.; Akiteru, T.; Takano, T.; Tanaka, N.; Taniguchi, K.; Taruya, A.; Tashiro, H.; Torii, Y.; Toyoshima, M.; Tsujikawa, S.; Ueda, A.; Ueda, K.-I.; Ushiba, T.; Utashima, M.; Wakabayashi, Y.; Yagi, K.; Yamamoto, K.; Yamazaki, T.; Yoo, C.-M.; Yoshida, S.; Yoshino, T.International Journal of Modern Physics D 28 12 2019年Yuichi Higuchi; Kaiki Taro InoueMonthly Notices of the Royal Astronomical Society 476 1 359 - 365 2018年05月 [査読有り]Kaiki Taro InoueNew Astronomy 58 47 - 52 2018年01月 [査読有り]
By monitoring a large number of stars in the Local Group galaxies, we can detect nanolensing events by sub-lunar mass compact objects (SULCOs) such as primordial black holes (PBHs) and rogue (free-floating) dwarf planets in the Milky Way halo. In contarst to microlensing by stellar-mass objects, the finite-source size effect becomes important and the lensing time duration becomes shorter (∼101−4s). Using stars with V < 26 in M33 as sources, for one-night observation, we would be able to detect 103−4 nanolensing events caused by SULCOs in the Milky Way halo with a mass of 10−9M⊙ to 10−7M⊙ for sources with S/N > 5 if SULCOs constitute all the dark matter components. Moreover, we expect 101−2 events in which bright blue stars with S/N > 100 are weakly amplified due to lensing by SULCOs with a mass range of 10−11M⊙ to 10−9M⊙. Thus the method would open a new window on SULCOs in the Milky Way halo that would otherwise not be observable.Ayuki Kamada; Kaiki Taro Inoue; Kazunori Kohri; Tomo TakahashiJournal of Cosmology and Astroparticle Physics 2017 11 008 - 008 2017年11月 [査読有り]
We investigate anomalous strong lens systems, particularly weak lens effects of structures in the line of sight, in models with long-lived electrically charged massive particles (CHAMPs). In such models, matter density perturbations are suppressed through the acoustic damping and the flux ratios in lens systems are impacted, from which we can constrain the nature of CHAMPs. For this purpose, we perform N-body simulations and develop a fitting formula to obtain non-linear matter power spectra in models where cold neutral dark matter and CHAMPs coexist in the early Universe. By using the observed anomalous quadruple lens samples, we obtained the constraints on the lifetime (τCh) and the mass density fraction (rCh) of CHAMPs. We show that, for rCh=1, the lifetime is bounded as τCh < 0.96 yr at the 95% confidence level, while a longer lifetime τCh = 10 yr is allowed when rCh < 0.5 at the 95% confidence level. Implications of our result for particle physics models are also discussed.井上 開輝天文月報 = The astronomical herald 110 5 341 - 349 日本天文学会 2017年05月井上開輝天文月報 110 5 341‐349 2017年04月Kaiki Taro Inoue; Satoki Matsushita; Takeo Minezaki; Masashi ChibaAstrophysical Journal Letters 835 2 L23 - L23 2017年02月 [査読有り]
We report the 4s detection of a faint object with a flux of ∼0.3 mJy, in the vicinity of the quadruply lensed QSO MG 0414+0534 using the Atacama Large Millimeter/submillimeter array (ALMA) Band 7. The object is most probably a dusty dark dwarf galaxy, which has not been detected in either the optical, near-infrared, or radio (centimeter) bands. An anomaly in the flux ratio of the lensed images observed in Band 7 and the mid-infrared band and the reddening of the QSO light color can be simultaneously explained if we consider the object as a lensing substructure with an ellipticity of ∼0.7 at a redshift of 0.5 ≲ z ≲ 1. Using the best-fit lens models with three lenses, we find that the dark matter plus baryon mass associated with the object is ∼109 Mo, the dust mass is ∼107 Mo, and the linear size is ≳5 kpc. Thus, our findings suggest that the object is a dusty dark dwarf galaxy. A substantial portion of faint submillimeter galaxies (SMGs) in the universe may be attributed to such dark objects.Atsushi J. Nishizawa; Kaiki Taro InoueMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 462 1 588 - 600 2016年10月 [査読有り]
In the cosmic microwave background or galaxy density maps, missing fluctuations in masked regions can be reconstructed from fluctuations in the surrounding unmasked regions if the original fluctuations are sufficiently smooth. One reconstruction method involves applying a harmonic expansion iteratively to fluctuations in the unmasked region. In this paper, we discuss how well this reconstruction method can recover the original fluctuations depending on the prior of fluctuations and property of the masked region. The reconstruction method is formulated with an asymptotic expansion in terms of the size of mask for a fixed iteration number. The reconstruction accuracy depends on the mask size, the spectrum of the underlying density fluctuations, the scales of the fluctuations to be reconstructed and the number of iterations. For Gaussian fluctuations with the Harrison-Zel'dovich spectrum, the reconstruction method provides more accurate restoration than naive methods based on brute-force matrix inversion or the singular value decomposition. We also demonstrate that an isotropic non-Gaussian prior does not change the results but an anisotropic non-Gaussian prior can yield a higher reconstruction accuracy compared to the Gaussian prior case.Kaiki Taro InoueMonthly Notices of the Royal Astronomical Society 461 1 164 - 175 2016年09月 [査読有り]Kamada, A.; Inoue, K.T.; Takahashi, T.Physical Review D 94 2 2016年07月 [査読有り]Kaiki Taro Inoue; Takeo Minezaki; Satoki Matsushita; Masashi ChibaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 457 3 2936 - 2950 2016年04月 [査読有り]
We present an analysis of the Atacama Large Millimeter/submillimeter Array long baseline science verification data of the gravitational lens system SDP. 81. We fit the positions of the brightest clumps at redshift z = 3.042 and a possible active galactic nucleus component of the lensing galaxy at redshift z = 0.2999 in the band 7 continuum image using a canonical lens model, a singular isothermal ellipsoid plus an external shear. Then, we measure the ratio of fluxes in some apertures at the source plane where the lensed images are inversely mapped. We find that the aperture flux ratios of band 7 continuum image are perturbed by 10-20 per cent with a significance at 2 similar to 3 sigma level. Moreover, we measure the astrometric shifts of multiply lensed images near the caustic using the CO(8-7) line. Using a lens model best fitted to the band 7 continuum image, we reconstruct the source image of the CO(8-7) line by taking linear combination of inverted quadruply lensed images. At the 50th channel (rest-frame velocity 28.6 km s(-1)) of the CO(8-7) line, we find an imprint of astrometric shifts of the order of 0.01 arcsec in the source image. Based on a semi-analytic calculation, we find that the observed anomalous flux ratios and the astrometric shifts can be explained by intergalactic dark structures in the line of sight. A compensated homogeneous spherical clump with a mean surface mass density of the order of 10(8) M(circle dot)h(-1) arcsec(-2) can explain the observed anomaly and astrometric shifts simultaneously.Nishizawa, A.J.; Inoue, K.T.Monthly Notices of the Royal Astronomical Society 462 1 2016年 [査読有り]
In the cosmic microwave background or galaxy density maps, missing
fluctuations in masked regions can be reconstructed from fluctuations in the
surrounding unmasked regions if the original fluctuations are sufficiently
smooth. One reconstruction method involves applying a harmonic expansion
iteratively to fluctuations in the unmasked region. In this paper, we discuss
how well this reconstruction method can recover the original fluctuations
depending on the prior of fluctuations and property of the masked region. The
reconstruction method is formulated with an asymptotic expansion in terms of
the size of mask for a fixed iteration number. The reconstruction accuracy
depends on the mask size, the spectrum of the underlying density fluctuations,
the scales of the fluctuations to be reconstructed and the number of
iterations. For Gaussian fluctuations with the Harrison--Zel'dovich spectrum,
the reconstruction method provides more accurate restoration than naive methods
based on brute--forth matrix inversion or the singular value decomposition. We
also demonstrate that an isotropic non-Gaussian prior does not change the
results but an anisotropic non-Gaussian prior can yield a higher reconstruction
accuracy compared to the Gaussian prior case.Kaiki Taro Inoue; Ryuichi Takahashi; Tomo Takahashi; Tomoaki IshiyamaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 448 3 2704 - 2716 2015年04月 [査読有り]
We investigate the weak lensing effect by line-of-sight structures with a surface mass density of less than or similar to 10(8) M-circle dot arcsec(-2) in QSO-galaxy quadruple lens systems. Using high-resolution N-body simulations in warm dark matter (WDM) models and observed four quadruple lenses that show anomalies in the flux ratios, we obtain constraints on the mass of thermal WDM, m(WDM) >= 1.3 keV (95 per cent CL) assuming that the density of the primary lens is described by a singular isothermal ellipsoid (SIE). The obtained constraint is consistent with those from Lyman alpha forests and the number counts of high-redshift galaxies at z > 4. Our results show that WDM with a free-streaming comoving wavenumber k(fs) <= 27 h Mpc(-1) is disfavoured as the major component of cosmological density at redshifts 0.5 less than or similar to z less than or similar to 4 provided that the SIE models describe the gravitational potentials of the primary lenses correctly.Inoue, K.T.Monthly Notices of the Royal Astronomical Society 447 2 1452 - 1459 2015年02月 [査読有り]Ryuichi Takahashi; Kaiki Taro InoueMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 440 1 870 - 888 2014年05月 [査読有り]
We investigate the weak lensing effects of line-of-sight structures on quadruple images in quasar-galaxy strong lens systems based on N-body and ray-tracing simulations that can resolve haloes with a mass of similar to 10(5) M-circle dot. The intervening haloes and voids disturb the magnification ratios of lensed images as well as their relative positions due to lensing. The magnification ratios typically change by O(10 per cent) when the shifts of relative angular positions of lensed images are constrained to < 0.004 arcsec. The constrained amplitudes of projected density perturbations due to line-of-sight structures are O(10(8)) M-circle dot arcsec(- 2). These results are consistent with our new analytical estimate based on the two-point correlation of density fluctuations. The observed mid-infrared flux ratios for six quasar-galaxy lens systems with quadruple images agree well with the numerically estimated values without taking into account subhalos residing in the lensing galaxies. We find that the constrained mean amplitudes of projected density perturbations in the line of sight are negative, which suggests that the fluxes of lensed images are perturbed mainly by minivoids and minihaloes in underdense regions. We derive a new fitting formula for estimating the probability distribution function of magnification perturbation. We also find that the mean amplitude of magnification perturbation roughly equals the standard deviation regardless of the model parameters.Kaiki Taro Inoue; Valery Rashkov; Joseph Silk; Piero MadauMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 435 3 2092 - 2098 2013年11月 [査読有り]
A galaxy halo may contain a large number of intermediate mass black holes (IMBHs) with masses in the range of 10(2) M-circle dot less than or similar to M-BH less than or similar to 10(6) M-circle dot. We propose to directly detect these IMBHs by observing multiply imaged QSO-galaxy or galaxy-galaxy strong lens systems in the submillimetre bands with high angular resolution. The silhouette of an IMBH in the lensing galaxy halo would appear as either a monopole-like or a dipole-like variation at the scale of the Einstein radius against the Einstein ring of the dust-emitting region surrounding the QSO. We use a particle tagging technique to dynamically populate a Milky Way-sized dark matter halo with black holes (BHs), and show that the surface mass density and number density of IMBHs have power-law dependences on the distance from the centre of the host halo if smoothed on a scale of similar to 1 kpc. Most of the BHs orbiting close to the centre are freely roaming as they have lost their dark matter hosts during infall due to tidal stripping. Next generation submillimetre telescopes with high angular resolution (less than or similar to 0.3 mas) will be capable of directly mapping such off-nuclear freely roaming BHs with a mass of less than or similar to 10(6) M-circle dot in a lensing galaxy that harbours an O(10(9)) M-circle dot supermassive black hole in its nucleus.Kaiki Taro Inoue; Ryuichi TakahashiMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 426 4 2978 - 2993 2012年11月 [査読有り]
We explore the weak lensing effect by line-of-sight haloes and subhaloes with a mass of M ? 107?M? in Quasi-Stellar Object (QSO)galaxy strong lens systems with quadruple images in a concordant ? cold dark matter universe. Using a polynomially fitted non-linear power spectrum P(k) obtained from N-body simulations that can resolve haloes with a mass of M similar to 105?M?, or structures with a comoving wavenumber of k similar to 3 x 102?h?Mpc-1, we find that the ratio of magnification perturbation due to intervening haloes to that of a primary lens is typically similar to 10 per cent and the predicted values agree well with the estimated values for six observed QSOgalaxy lens systems with quadruple images in the mid-infrared band without considering the effects of substructures inside a primary lens. We also find that the estimated amplitudes of convergence perturbation for the six lenses increase with the source redshift as predicted by theoretical models. Using an extrapolated matter power spectrum, we demonstrate that small haloes or subhaloes in the line of sight with a mass of M = 10(3)-10(7)?M?, or structures with a comoving wavenumber of k = 3 x 10(2) -10(4)?h?Mpc-1, can significantly affect the magnification ratios of the lensed images. Flux-ratio anomalies in QSOgalaxy strong lens systems offer us a unique probe into the clustering property of minihaloes with a mass of M < 106?M circle dot.Inoue, K.T.Monthly Notices of the Royal Astronomical Society 421 3 2731 - 2736 2012年04月 [査読有り]Kawamura, S.; Ando, M.; Seto, N.; Sato, S.; Nakamura, T.; Tsubono, K.; K; a, N.; Tanaka, T.; Yokoyama, J.; Funaki, I.; Numata, K.; Ioka, K.; Takashima, T.; Agatsuma, K.; Akutsu, T.; Aoyanagi, K.-S.; Arai, K.; Araya, A.; Asada, H.; Aso, Y.; Chen, D.; Chiba, T.; Ebisuzaki, T.; Ejiri, Y.; Enoki, M.; Eriguchi, Y.; Fujimoto, M.-K.; Fujita, R.; Fukushima, M.; Futamase, T.; Harada, T.; Hashimoto, T.; Hayama, K.; Hikida, W.; Himemoto, Y.; Hirabayashi, H.; Hiramatsu, T.; Hong, F.-L.; Horisawa, H.; Hosokawa, M.; Ichiki, K.; Ikegami, T.; Inoue, K.T.; Ishidoshiro, K.; Ishihara, H.; Ishikawa, T.; Ishizaki, H.; Ito, H.; Itoh, Y.; Izumi, K.; Kawano, I.; Kawashima, N.; Kawazoe, F.; Kishimoto, N.; Kiuchi, K.; Kobayashi, S.; Kohri, K.; Koizumi, H.; Kojima, Y.; Kokeyama, K.; Kokuyama, W.; Kotake, K.; Kozai, Y.; Kunimori, H.; Kuninaka, H.; Kuroda, K.; Kuroyanagi, S.; Maeda, K.-I.; Matsuhara, H.; Matsumoto, N.; Michimura, Y.; Miyakawa, O.; Miyamoto, U.; Miyoki, S.; Morimoto, M.Y.; Morisawa, T.; Moriwaki, S.; Mukohyama, S.; Musha, M.; Nagano, S.; Naito, I.; Nakamura, K.; Nakano, H.; Nakao, K.; Nakasuka, S.; Nakayama, Y.; Nakazawa, K.; Nishida, E.; Nishiyama, K.; Nishizawa, A.; Niwa, Y.; Noumi, T.; Obuchi, Y.; Ohashi, M.; Ohishi, N.; Ohkawa, M.; Okada, K.; Okada, N.; Oohara, K.; Sago, N.; Saijo, M.; Saito, R.; Sakagami, M.; Sakai, S.-I.; Sakata, S.; Sasaki, M.; Sato, T.; Shibata, M.; Shinkai, H.; Shoda, A.; Somiya, K.; Sotani, H.; Sugiyama, N.; Suwa, Y.; Suzuki, R.; Tagoshi, H.; Takahashi, F.; Takahashi, K.; Takahashi, K.; Takahashi, R.; Takahashi, R.; Takahashi, T.; Takahashi, H.; Akiteru, T.; Takano, T.; Tanaka, N.; Taniguchi, K.; Taruya, A.; Tashiro, H.; Torii, Y.; Toyoshima, M.; Tsujikawa, S.; Tsunesada, Y.; Ueda, A.; Ueda, K.-I.; Utashima, M.; Wakabayashi, Y.; Yagi, K.; Yamakawa, H.; Yamamoto, K.; Yamazaki, T.; Yoo, C.-M.; Yoshida, S.; Yoshino, T.; Sun, K.-X.Classical and Quantum Gravity 28 9 2011年EVIDENCE OF QUASI-LINEAR SUPER-STRUCTURES IN THE COSMIC MICROWAVE BACKGROUND AND GALAXY DISTRIBUTIONKaiki Taro Inoue; Nobuyuki Sakai; Kenji TomitaASTROPHYSICAL JOURNAL 724 1 12 - 25 2010年11月 [査読有り]
Recent measurements of hot and cold spots on the cosmic microwave background (CMB) sky suggest the presence of super-structures on (> 100 h(-1) Mpc) scales. We develop a new formalism to estimate the expected amplitude of temperature fluctuations due to the integrated Sachs-Wolfe (ISW) effect from prominent quasi-linear structures. Applying the developed tools to the observed ISW signals from voids and clusters in catalogs of galaxies at redshifts z < 1, we find that they indeed imply a presence of quasi-linear super-structures with a comoving radius of 100 similar to 300 h(-1) Mpc and a density contrast vertical bar delta vertical bar similar to O(0.1). We also find that the observed ISW signals are at odds with the concordant. cold dark matter model that predicts Gaussian primordial perturbations at greater than or similar to 3 sigma level. We confirm that the mean temperature around the CMB cold spot in the southern Galactic hemisphere filtered by a compensating top-hat filter deviates from the mean value at similar to 3 sigma level, implying that a quasi-linear supervoid or an underdensity region surrounded by a massive wall may reside at low redshifts z < 0.3 and the actual angular size (16 degrees-17 degrees) may be larger than the apparent size (4 degrees-10 degrees) discussed in literature. Possible solutions are briefly discussed.Ando, M.; Kawamura, S.; Seto, N.; Sato, S.; Nakamura, T.; Tsubono, K.; Takashima, T.; Funaki, I.; Numata, K.; K; a, N.; Tanaka, T.; Ioka, K.; Agatsuma, K.; Aoyanagi, K.-S.; Arai, K.; Araya, A.; Asada, H.; Aso, Y.; Chiba, T.; Ebisuzaki, T.; Ejiri, Y.; Enoki, M.; Eriguchi, Y.; Fujimoto, M.-K.; Fujita, R.; Fukushima, M.; Futamase, T.; Harada, T.; Hashimoto, T.; Hayama, K.; Hikida, W.; Himemoto, Y.; Hirabayashi, H.; Hiramatsu, T.; Hong, F.-L.; Horisawa, H.; Hosokawa, M.; Ichiki, K.; Ikegami, T.; Inoue, K.T.; Ishidoshiro, K.; Ishihara, H.; Ishikawa, T.; Ishizaki, H.; Ito, H.; Itoh, Y.; Izumi, K.; Kawano, I.; Kawashima, N.; Kawazoe, F.; Kishimoto, N.; Kiuchi, K.; Kobayashi, S.; Kohri, K.; Koizumi, H.; Kojima, Y.; Kokeyama, K.; Kokuyama, W.; Kotake, K.; Kozai, Y.; Kunimori, H.; Kuninaka, H.; Kuroda, K.; Maeda, K.-I.; Matsuhara, H.; Mino, Y.; Miyakawa, O.; Miyamoto, U.; Miyoki, S.; Morimoto, M.Y.; Morisawa, T.; Moriwaki, S.; Mukohyama, S.; Musha, M.; Nagano, S.; Naito, I.; Nakamura, K.; Nakamura, M.; Nakano, H.; Nakao, K.; Nakasuka, S.; Nakayama, Y.; Nakazawa, K.; Nishida, E.; Nishiyama, K.; Nishizawa, A.; Niwa, Y.; Noumi, T.; Obuchi, Y.; Ohashi, M.; Ohishi, N.; Ohkawa, M.; Okada, K.; Okada, N.; Oohara, K.; Sago, N.; Saijo, M.; Saito, R.; Sakagami, M.; Sakai, S.-I.; Sakata, S.; Sasaki, M.; Sato, T.; Shibata, M.; Shinkai, H.; Somiya, K.; Sotani, H.; Sugiyama, N.; Suwa, Y.; Suzuki, R.; Tagoshi, H.; Takahashi, F.; Takahashi, K.; Takahashi, K.; Takahashi, R.; Takahashi, R.; Takahashi, T.; Takahashi, H.; Akiteru, T.; Takano, T.; Taniguchi, K.; Taruya, A.; Tashiro, H.; Torii, Y.; Toyoshima, M.; Tsujikawa, S.; Tsunesada, Y.; Ueda, A.; Ueda, K.-I.; Utashima, M.; Wakabayashi, Y.; Yagi, K.; Yamakawa, H.; Yamamoto, K.; Yamazaki, T.; Yokoyama, J.; Yoo, C.-M.; Yoshida, S.; Yoshino, T.; Sun, K.-X.Classical and Quantum Gravity 27 8 2010年坂井 伸之; 井上 開輝; 冨田 憲二素粒子論研究 118 1 A179 - A184 素粒子論グループ 素粒子論研究 編集部 2010年Kenji Tomita; Kaiki Taro InouePHYSICAL REVIEW D 79 10 2009年05月 [査読有り]
Recent observational data of supernovae point to Lambda-dominated flat cosmological models. However, an alternative model in which we happen to live in an underdense region requires no dark energy or modification of gravity. This challenges the Copernican principle. We show that the integrated Sachs-Wolfe (ISW) effect is an excellent discriminator between anti-Copernican inhomogeneous models and the standard Copernican models. As a reference model, we consider an anti-Copernican inhomogeneous model that consists of two inner negatively curved underdense regions and an outer flat Einstein-de Sitter region. We assume that these regions are connected by two thin walls at redshifts z=0.067 and z=0.45. In the inner two regions, the first-order ISW effect is dominant and comparable to that in the concordant flat-Lambda models. In the outer Einstein-de Sitter region, the first-order ISW effect vanishes but the second-order ISW effect plays a dominant role, while the first-order ISW effect is dominant in the flat-Lambda models at moderate redshifts. This difference can discriminate the anti-Copernican models from the concordant flat-Lambda model. At high redshifts, the second-order ISW effect is dominant both in our inhomogeneous model and in the concordant model. In the outer region, moreover, the ISW effect due to large-scale density perturbations with a present matter density contrast epsilon(m0)< 0.37 is negligible, while the effect due to small-scale density perturbations (such as clusters of galaxies, superclusters, and voids) with epsilon(m0)> 0.37 would generate anisotropies which are larger than those generated by the ISW effect in the concordant model.Takeo Minezaki; Masashi Chiba; Nobunari Kashikawa; Kaiki Taro Inoue; Hirokazu KatazaASTROPHYSICAL JOURNAL 697 1 610 - 618 2009年05月 [査読有り]
We present mid-infrared imaging at 11.7 mu m for the quadruple lens systems, MG0414+0534 and Q2237+030, using the cooled mid-infrared camera and spectrometer attached on the Subaru telescope. MG0414+0534 is characterized by a bright pair of lensed images (A1, A2) and their optical flux ratio A2/A1 deviates significantly from the prediction of a smooth-lens model. Q2237+030 is "the Einstein Cross" being comprised of four lensed images, which are significantly affected by microlensing in a foreground lensing galaxy. Our mid-infrared observations of these lensed images have revealed that the mid-infrared flux ratio for A2/A1 of MG0414+0534 is nearly unity (0.90 +/- 0.04). We find that this flux ratio is systematically small, at 4-5 sigma level, compared with the prediction of a best smooth-lens model (1.09) represented by a singular isothermal ellipsoid and external shear. The smooth-lens model, which also considers the additional lensing effect of the possible faint satellite, object X, still provides a large flux ratio of A2/A1=1.06, thereby suggesting the presence of more substructures that can explain our observational result. In contrast, for Q2237+030, our high signal-to-noise observation indicates that the mid-infrared flux ratios between all the four images of Q2237+030 are virtually consistent with the prediction of a smooth-lens model. Based on the size estimate of the dust torus surrounding the nuclei of these QSOs, we set limits on the mass of a substructure in these lens systems, which can cause anomalies in the flux ratios. For MG0414+0534, since the required mass of a substructure inside its Einstein radius is greater than or similar to 360 M(circle dot), millilensing by a cold dark matter substructure is most likely. If it is modeled as a singular isothermal sphere, the mass inside a radius of 100 pc is given as greater than or similar to 1.0 x 10(5) M(circle dot). For Q2237+030, there is no significant evidence of millilensing, so the reported anomalous flux ratios in shorter wavelengths are entirely caused due to microlensing by stars.Ando, M.; Kawamura, S.; Sato, S.; Nakamura, T.; Tsubono, K.; Araya, A.; Funaki, I.; Ioka, K.; K; a, N.; Moriwaki, S.; Musha, M.; Nakazawa, K.; Numata, K.; Sakai, S.-I.; Seto, N.; Takashima, T.; Tanaka, T.; Agatsuma, K.; Aoyanagi, K.-S.; Arai, K.; Asada, H.; Aso, Y.; Chiba, T.; Ebisuzaki, T.; Ejiri, Y.; Enoki, M.; Eriguchi, Y.; Fujimoto, M.-K.; Fujita, R.; Fukushima, M.; Futamase, T.; Ganzu, K.; Harada, T.; Hashimoto, T.; Hayama, K.; Hikida, W.; Himemoto, Y.; Hirabayashi, H.; Hiramatsu, T.; Hong, F.-L.; Horisawa, H.; Hosokawa, M.; Ichiki, K.; Ikegami, T.; Inoue, K.T.; Ishidoshiro, K.; Ishihara, H.; Ishikawa, T.; Ishizaki, H.; Ito, H.; Itoh, Y.; Kawashima, N.; Kawazoe, F.; Kishimoto, N.; Kiuchi, K.; Kobayashi, S.; Kohri, K.; Koizumi, H.; Kojima, Y.; Kokeyama, K.; Kokuyama, W.; Kotake, K.; Kozai, Y.; Kudoh, H.; Kunimori, H.; Kuninaka, H.; Kuroda, K.; Maeda, K.-I.; Matsuhara, H.; Mino, Y.; Miyakawa, O.; Miyoki, S.; Morimoto, M.Y.; Morioka, T.; Morisawa, T.; Mukohyama, S.; Nagano, S.; Naito, I.; Nakamura, K.; Nakano, H.; Nakao, K.; Nakasuka, S.; Nakayama, Y.; Nishida, E.; Nishiyama, K.; Nishizawa, A.; Niwa, Y.; Noumi, T.; Obuchi, Y.; Ohashi, M.; Ohishi, N.; Ohkawa, M.; Okada, N.; Onozato, K.; Oohara, K.; Sago, N.; Saijo, M.; Sakagami, M.; Sakata, S.; Sasaki, M.; Sato, T.; Shibata, M.; Shinkai, H.; Somiya, K.; Sotani, H.; Sugiyama, N.; Suwa, Y.; Suzuki, R.; Tagoshi, H.; Takahashi, F.; Takahashi, K.; Takahashi, K.; Takahashi, R.; Takahashi, R.; Takahashi, T.; Takahashi, H.; Akiteru, T.; Takano, T.; Taniguchi, K.; Taruya, A.; Tashiro, H.; Torii, Y.; Toyoshima, M.; Tsujikawa, S.; Tsunesada, Y.; Ueda, A.; Ueda, K.-I.; Utashima, M.; Wakabayashi, Y.; Yamakawa, H.; Yamamoto, K.; Yamazaki, T.; Yokoyama, J.; Yoo, C.-M.; Yoshida, S.; Yoshino, T.Classical and Quantum Gravity 26 9 2009年Shigenori Ohashi; Masashi Chiba; Kaiki Taro InoueAPPROACHING MICRO-ARCSECOND RESOLUTION WITH VSOP-2: ASTROPHYSICS AND TECHNOLOGY 402 290 - 292 2009年Hierarchical clustering models of cold dark matter (CDM) predict that about 5% - 10% of a galaxy-sized halo with mass similar to 10(12) solar masses (M-circle dot) resides in substructures (CDM subhalos) with masses less than or similar to 10(8)M(circle dot). To directly identify such substructures, we propose to observe radio continuum emission from multiply imaged QSOs using VSOP-2 with a high angular resolution.Nobuyuki Sakai; Kaiki Taro InouePhysical Review D - Particles, Fields, Gravitation and Cosmology 78 6 2008年09月 [査読有り]
We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large (100Mpc) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance 10-5K in the CMB sky. © 2008 The American Physical Society.Nobuyuki Sakai; Kaiki Taro InouePHYSICAL REVIEW D 78 6 2008年09月 [査読有り]
We study the cosmic microwave background (CMB) anisotropy due to spherically symmetric nonlinear structures in flat universes with dust and a cosmological constant. By modeling a time-evolving spherical compensated void/lump by Lemaitre-Tolman-Bondi spacetimes, we numerically solve the null geodesic equations with the Einstein equations. We find that a nonlinear void redshifts the CMB photons that pass through it regardless of the distance to it. In contrast, a nonlinear lump blueshifts (or redshifts) the CMB photons if it is located near (or sufficiently far from) us. The present analysis comprehensively covers previous works based on a thin-shell approximation and a linear/second-order perturbation method and the effects of shell thickness and full nonlinearity. Our results indicate that, if quasilinear and large (greater than or similar to 100 Mpc) voids/lumps would exist, they could be observed as cold or hot spots with temperature variance greater than or similar to 10(-5) K in the CMB sky.Kaiki Taro Inoue; Paolo Cabella; Eiichiro KomatsuPHYSICAL REVIEW D 77 12 2008年06月 [査読有り]
We develop a new interpolation scheme, based on harmonic inpainting, for reconstructing the cosmic microwave backgroundtemperature data within the Galaxy mask from the data outside the mask. We find that, for scale-invariant isotropic random Gaussian fluctuations, the developed algorithm reduces the errors in the reconstructed map for the odd-parity modes significantly for azimuthally symmetric masks with constant galactic latitudes. For a more realistic Galaxy mask, we find a modest improvement in the even-parity modes as well.Kenji Tomita; Kaiki Taro InouePhysical Review D - Particles, Fields, Gravitation and Cosmology 77 10 2008年05月 [査読有り]
We study second order gravitational effects of local inhomogeneities on the cosmic microwave background radiation in flat universes with matter and a cosmological constant Λ. We find that the general relativistic correction to the Newtonian approximation is negligible at second order provided that the size of the inhomogeneous region is sufficiently smaller than the horizon scale. For a spherically symmetric top-hat type quasilinear perturbation, the first order temperature fluctuation corresponding to the linear integrated Sachs-Wolfe effect is enhanced (suppressed) by the second order one for a compensated void (lump). As a function of redshift of the local inhomogeneity, the second order temperature fluctuations due to evolution of the gravitational potential have a peak before the matter-Λ equality epoch for a fixed comoving size and a density contrast. The second order gravitational effects from local quasilinear inhomogeneities at a redshift z∼1 may significantly affect the cosmic microwave background. © 2008 The American Physical Society.Kenji Tomita; Kaiki Taro InouePHYSICAL REVIEW D 77 10 2008年05月 [査読有り]
We study second order gravitational effects of local inhomogeneities on the cosmic microwave background radiation in flat universes with matter and a cosmological constant Lambda. We find that the general relativistic correction to the Newtonian approximation is negligible at second order provided that the size of the inhomogeneous region is sufficiently smaller than the horizon scale. For a spherically symmetric top-hat type quasilinear perturbation, the first order temperature fluctuation corresponding to the linear integrated Sachs-Wolfe effect is enhanced (suppressed) by the second order one for a compensated void (lump). As a function of redshift of the local inhomogeneity, the second order temperature fluctuations due to evolution of the gravitational potential have a peak before the matter-Lambda equality epoch for a fixed comoving size and a density contrast. The second order gravitational effects from local quasilinear inhomogeneities at a redshift z similar to 1 may significantly affect the cosmic microwave background.Kaiki Taro InoueScience and Technology No.19 p 11-14 RIST, Kinki University (2007) 2007年10月It has been argued that the large-angle cosmic microwave background
anisotropy has anomalies at 3-sigma level. We review various proposed ideas to
explain the origin of the anomalies and discuss how we can constrain the
proposed models using future observational data.Kaiki Taro Inoue; Joseph SilkAstrophysical Journal 664 2 I 650 - 659 2007年08月 [査読有り]
We explore the large angular scale temperature anisotropics in the cosmic microwave background (CMB) due to homogeneous local dust-filled voids in a flat Friedmann-Robertson-Walker universe with a cosmological constant. In comparison with the equivalent dust-filled void model in the Einstein-de Sitter background, we find that the anisotropy for compensated asymptotically expanding local voids can be larger, because second-order effects enhance the linear integrated Sachs-Wolfe (ISW) effect. However, for local voids that expand sufficiently faster than the asymptotic velocity of the wall, the second-order effect can suppress the fluctuation due to the linear ISW effect. A pair of quasi-linear compensated asymptotic local voids with radius (2-3) × 102 h-1 Mpc and a matter density contrast δm ∼ -0.3 can be observed as cold spots with a temperature anisotropy ΔT/T ∼ O(10-5) that might help explain the observed large-angle CMB anomalies. We predict that the associated anisotropy in the local Hubble constant in the direction of the voids could be as large as a few percent. © 2007. The American Astronomical Society. All rights reserved.H. Sugai; A. Kawai; A. Shimono; T. Hattori; G. Kosugi; N. Kashikawa; K. T. Inoue; M. ChibaASTROPHYSICAL JOURNAL 660 2 1016 - 1022 2007年05月 [査読有り]
We have observed the quadruply lensed quasar 1RXS J1131-1231 with the integral field spectrograph mode of the Kyoto Tridimensional Spectrograph II mounted on the Subaru telescope. Its field of view has simultaneously covered the three brighter lensed images A, B, and C, which are known to exhibit anomalous flux ratios in their continuum emission. We have found that the [O III] line flux ratios among these lensed images are consistent with those predicted by smooth- lens models. The absence of both microlensing and millilensing effects on this [O III] narrow- line region sets important limits on the mass of any substructures along the line of sight, which is expressed as M-E < 10(5) M-circle dot for the mass inside an Einstein radius. In contrast, the H beta line emission, which originates from the broad-line region, shows an anomaly in the flux ratio between images B and C, i. e., a factor 2 smaller C/B ratio than predicted by smooth- lens models. The ratio of A/B in the H beta line is well reproduced. We show that the anomalous C/B ratio for the H beta line is most likely caused by micro-/millilensing of image C. This is because other effects, such as the differential dust extinction and/or arrival time difference between images B and C, or the simultaneous lensing of another pair of images A and B, are all unlikely. In addition, we have found that the broad H beta line of image A shows a slight asymmetry in its profile compared with those in the other images, which suggests the presence of a small microlensing effect on this line emitting region of image A.Junji Hisano; Kaiki Taro Inoue; Tomo TakahashiPHYSICS LETTERS B 643 3-4 141 - 146 2006年12月 [査読有り]
We propose to observe QSO-galaxy strong lens systems to give a new constraint on the damping scale of the initial fluctuations. We find that the future observation of submilliarc scale astrometric shifts of the multiple lensed images of QSOs would find similar to 10((3-9))M(circle dot) subhalos inside the macrolens halo. The superweakly interacting massive particles (superWIMPs) produced from a WIMP decay and the warm dark matter (WDM) particles that predict a comoving damping scale larger than similar to 2 kpc can be constrained if similar to 10(3) M(circle dot) subhalos are detected. (c) 2006 Elsevier B.V. All rights reserved.Kaiki Taro Indue; Joseph SilkAstrophysical Journal 648 1 I 23 - 30 2006年09月 [査読有り]
We explore the large angular scale temperature anisotropies in the cosmic microwave background due to expanding homogeneous local voids at redshift z ≲ 1. A compensated spherically symmetric homogeneous dust-filled void with radius ∼3 × 102 h-1 Mpc and density contrast δ ∼ -0.3 can be observed as a cold spot with a temperature anisotropy ΔT/T ∼ -1 × 10-5 surrounded by a slightly hotter ring. We find that a pair of these circular cold spots separated by ∼50° can account both for the planarity of the octopole and for the alignment between the quadrupole and the octopole in the cosmic microwave background (CMB) anisotropy. The cold spot in the Galactic southern hemisphere, which is anomalous at the ∼3 σ level, can be explained by such a large void at z ∼ 1. The observed north-south asymmetry in the large-angle CMB power can be attributed to the asymmetric distribution of these local voids between the two hemispheres. The statistical significance of the low quadrupole is further reduced in this interpretation of the large angular scale CMB anomalies. © 2006. The American Astronomical Society. All rights reserved.Kawamura, S.; Nakamura, T.; Ando, M.; Seto, N.; Tsubono, K.; Numata, K.; Takahashi, R.; Nagano, S.; Ishikawa, T.; Musha, M.; Ueda, K.-I.; Sato, T.; Hosokawa, M.; Agatsuma, K.; Akutsu, T.; Aoyanagi, K.-S.; Arai, K.; Araya, A.; Asada, H.; Aso, Y.; Chiba, T.; Ebisuzaki, T.; Eriguchi, Y.; Fujimoto, M.; Fukushima, M.; Futamase, T.; Ganzu, K.; Harada, T.; Hashimoto, T.; Hayama, K.; Hikida, W.; Himemoto, Y.; Hirabayashi, H.; Hiramatsu, T.; Ichiki, K.; Ikegami, T.; Inoue, K.T.; Ioka, K.; Ishidoshiro, K.; Itoh, Y.; Kamagasako, S.; K; a, N.; Kawashima, N.; Kirihara, H.; Kiuchi, K.; Kobayashi, S.; Kohri, K.; Kojima, Y.; Kokeyama, K.; Kozai, Y.; Kudoh, H.; Kunimori, H.; Kuroda, K.; Maeda, K.; Matsuhara, H.; Mino, Y.; Miyakawa, O.; Miyoki, S.; Mizusawa, H.; Morisawa, T.; Mukohyama, S.; Naito, I.; Nakagawa, N.; Nakamura, K.; Nakano, H.; Nakao, K.; Nishizawa, A.; Niwa, Y.; Nozawa, C.; Ohashi, M.; Ohishi, N.; Ohkawa, M.; Okutomi, A.; Oohara, K.; Sago, N.; Saijo, M.; Sakagami, M.; Sakata, S.; Sasaki, M.; Sato, S.; Shibata, M.; Shinkai, H.; Somiya, K.; Sotani, H.; Sugiyama, N.; Tagoshi, H.; Takahashi, T.; Takahashi, H.; Takahashi, R.; Takano, T.; Tanaka, T.; Taniguchi, K.; Taruya, A.; Tashiro, H.; Tokunari, M.; Tsujikawa, S.; Tsunesada, Y.; Yamamoto, K.; Yamazaki, T.; Yokoyama, J.; Yoo, C.-M.; Yoshida, S.; Yoshino, T.Classical and Quantum Gravity 23 8 2006年Kaiki Taro Inoue; Masashi ChibaAnnual reports by Research Institute for Science and Technology, (2006) 18, p.11-14 2005年12月A galaxy-sized halo may contain a large number of intermediate mass (10^{2-4}
solar mass) compact objects (IMCOs), which can be intermediate mass black holes
(IMBHs) or the CDM subhalos. We propose to directly detect the IMBHs by
observing multiply imaged QSO-galaxy lens systems with a high angular
resolution (~ 0.03mas), which would be achieved by the next-VLBI space
missions. The silhouette of the IMBHs would appear as an either monopole-like
or dipole-like variation at the scale of the Einstein radius against the QSO
jets. As a byproduct, we can also directly detect the 10^{4-5} solar mass CDM
subhalos. From a measurement of the local distortion in the surface brightness
of the QSO jet, we can make a distinction between a point mass (corresponding
to an IMBH) and an extended structure (corresponding to a CDM subhalo). It
would be a unique probe of the IMCOs whose nature has been under the veil of
mistery.Kaiki Taro Inoue; Masashi ChibaAstrophysical Journal 634 1 I 77 - 89 2005年11月 [査読有り]
We investigate the extended source size effects on gravitational lensing in which a lens consists of a smooth potential and small mass clumps ("substructure lensing"). We first consider a lens model that consists of a clump modeled as a singular isothermal sphere (SIS) and a primary lens modeled as an external background shear and convergence. For this simple model, we derive analytic formulae for (de)magnification of circularly symmetric tophat sources with three types of parity for their lensed images, namely, positive, negative, and doubly negative parities. Provided that the source size is sufficiently larger than the Einstein radius of the SIS, we find that in the positive (doubly negative) parity case, an extended source is always magnified (demagnified) in comparison with the unperturbed macrolens system, whereas in the negative parity case, the (de)magnification effect, which depends on the sign of convergence minus unity, is weaker than those in other parities. It is shown that a measurement of the distortion pattern in a multiply lensed image enables us to break the degeneracy between the lensing effects of clump mass and those of clump distance if the lensing parameters of the relevant macrolens model are determined from the position and flux of multiple images. We also show that an actual density profile of a clump can be directly measured by analyzing the "fine structure" in a multiply lensed image within the Einstein radius of the clump. © 2005. The American Astronomical Society. All rights reserved.Kaiki Taro Inoue; Masashi ChibaAstrophysical Journal 633 1 I 23 - 28 2005年11月 [査読有り]
The cold dark matter (CDM) structure formation model predicts that about 5%-10% of a typical galactic halo of mass ∼ 1012 M⊙ is in substructures with masses ≲108 M⊙. To directly detect such substructures, we propose to observe dust continuum emission from a strongly lensed QSO host galaxy using a large submillimeter interferometer array with a high angular resolution of ∼0″.01, such as the planned Atacama Large Submillimeter Array (ALMA). To assess their observational feasibility, we numerically simulate millilensing of an extended circular source by a CDM substructure modeled as a tidally truncated singular isothermal sphere (SIS) embedded in a typical QSO-galaxy lens system, B1422+231, modeled as a singular isothermal ellipsoid (SIE) with an external constant shear and a constant convergence. Assuming an angular resolution of 0″.01, we find that the angular positions of ∼108 M⊙ substructures at several kpc from the center of the macrolens halo can be directly measured if the size of the dust continuum emission region and the gradient of the surface brightness at the position of the perturber are sufficiently large. From the astrometric shift on a scale of a few times 10 mas of an image perturbed by a subhalo with respect to an unperturbed macrolensed image, we can break the degeneracy between subhalo mass and distance provided that macrolensing parameters are determined from positions and fluxes of multiple images. © 2005. The American Astronomical Society. All rights reserved.Masashi Chiba; Takeo Minezaki; Nobunari Kashikawa; Hirokazu Kataza; Kaiki Taro InoueAstrophysical Journal 627 1 I 53 - 61 2005年07月 [査読有り]
We present mid-infrared imaging at 11.7 μm for the quadruple lens systems PG 1115+080 and B1422+231 using the cooled mid-infrared camera and spectrometer (COMICS) attached on the Subaru Telescope. These lensed QSOs are characterized by their anomalous optical and radio flux ratios, as obtained for Al and A2 images of PG 1115 + 080 and A, B, and C images of B1422+231, respectively, i.e., such flux ratios are hardly able to be reproduced by lens models with a smooth mass distribution. Our mid-infrared observations for these images have revealed that the mid-infrared flux ratio A2/A1 of PG 1115+080 is virtually consistent with smooth lens models (but inconsistent with the optical flux ratio), whereas for B1422+231, the mid-infrared flux ratios among the A, B, and C images are in good agreement with the radio flux ratios. We also identify a clear infrared bump in the spectral energy distributions of these QSOs, thereby indicating that the observed mid-infrared fluxes originate from a hot dust torus around a QSO nucleus. Based on the size estimate of the dust torus, we place limits on the mass of a substructure in these lens systems causing the anomalous optical or radio flux ratios. For PG 1115+080, the mass of a substructure inside an Einstein radius ME is ≲16 M ⊙, corresponding to either a star or a low-mass CDM subhalo having a mass of M100SIS ≲ 2.2 × 104 Ṁ inside a radius of 100 pc if modeled as a singular isothermal sphere (SIS). For B1422+231, we obtain ME ≳ 209 M ̇, indicating that a CDM subhalo is more likely, having a mass of M100SIS ≳ 7.4 × 104 M ⊙. © 2005. The American Astronomical Society. All rights reserved.Motohiro Enoki; Kaiki T. Inoue; Masahiro Nagashima; Naoshi SugiyamaThe Astrophysical Journal 615 1 19 - 28 2004年11月 [査読有り]Motohiro Enoki; Kaiki Taro Inoue; Naoshi Sugiyama; Masahiro NagashimaProgress of Theoretical Physics Supplement 155 323 - 324 2004年 [査読有り]
We investigate expected gravitational wave spectrum from coalescing supermassive black hole (SMBH) binaries resulting from mergers of host galaxies. When galaxies merge, the central SMBHs sink to the center of the new merged galaxy and they finally coalesce producing low-frequency gravitational waves (GWs). Using a semi-analytic model of galaxy and quasar formations, we estimate the SMBH coalescence rate and find that the characteristic strain amplitude of the expected GW background spectrum is hc(f) ∼ 10 -16(f/yr-1)-2/3 just below the detection limit from measurements of pulsar timing.KT Inoue; M ChibaDARK MATTER IN GALAXIES 220 139 - 140 2004年We propose a method for directly detecting MASsive Compact Objects (MASCOs) in extragalactic halos, using VLBI techniques with extremely high resolution similar to 0.01 milli-arcsec. If a galactic halo comprising a large number of MASCOs produces multiple images of a background radio-loud QSO by gravitational lensing, then a high-resolution radio map of each macro-lensed image should reveal microlensing effects by MASCOs. Based on the size, position, and magnified or demagnified patterns of images, we shall be able to determine the mass and density profile of an individual MASCO as well as its spatial distribution and abundance in a galactic halo.Kaiki Taro Inoue; Masashi ChibaAstrophysical Journal 591 2 L83 - L86 2003年07月 [査読有り]
A significant fraction of nonbaryonic or baryonic dark matter in galactic halos may consist of massive compact objects (MASCOs) with mass M = 10 1-104 M⊙. Possible candidates for such compact objects include primordial black holes or remnants of primordial (Population III) stars. We propose a method for directly detecting MASCOs in extragalactic halos, using the VLBI techniques with extremely high resolution that would be achieved by the next-generation mission of the VLBI Space Observatory Program such as VSOP-2. If a galactic halo comprising a large number of MASCOs produces multiple images of a background radio-loud QSO by gravitational lensing, then a high-resolution radio map of each macrolensed image should reveal microlensing effects by MASCOs. To assess their observational feasibility, we simulate microlensing of the radio-loud, four-image lensed QSO, B1422+231, assuming angular resolution of ∼0.01 mas. MASCOs are represented by point masses. For comparison, we also simulate microlensing of B1422+231 by singular isothermal spheres. We find that the surface brightness of the macrolensed images shows distinct spatial patterns on the scale of the Einstein radius of the perturbers. In the case of point-mass perturbers, many tiny dark spots also appear in the macrolensed images associated with a decrease in the surface brightness toward the fringe of the original QSO image, whereas no such spots are available in the SIS models. Because such spatial patterns in each macrolensed image cannot be linearly mapped to those in other macrolensed images if they are relevant to lensing perturbers, it is fairly easy to discriminate them from intrinsic substructures within a QSO. Based on the size, position, and magnified or demagnified patterns of images, we shall be able to determine the mass and density profile of an individual MASCO as well as its spatial distribution and abundance in a galactic halo.KT Inoue; T TanakaPHYSICAL REVIEW LETTERS 91 2 2003年07月 [査読有り]
In many brane world models, gravity is largely modified at the electroweak scale similar to1 TeV. In such models, primordial black holes (PBHs) with a lunar mass Msimilar to10(-7)M(circle dot) might have been produced when the temperature of the Universe was at similar to1 TeV. If a significant fraction of the dark halo of our galaxy consists of these lunar mass PBHs, a huge number of BH binaries will exist in our neighborhood. Third generation detectors such as EURO can detect gravitational waves from these binaries, and can also determine their chirp mass. With a new detector designed to be sensitive at high frequency bands greater than or similar to1 kHz, the existence of extradimensions could be confirmed.KT Inoue; N SugiyamaPHYSICAL REVIEW D 67 4 2003年02月 [査読有り]
We reexamine constraints on the spatial size of closed toroidal models with cold dark matter and the cosmological constant from a cosmic microwave background. We carry out Bayesian analyses using the Cosmic Background Explorer (COBE) data properly taking into account the statistically anisotropic correlation, i.e., off-diagonal elements in the covariance. We find that the COBE constraint becomes more stringent in comparison with that using only the angular power spectrum, if the likelihood is marginalized over the orientation of the observer. For some limited choices of orientations, the fit to the COBE data is considerably better than that of the infinite counterpart. The best-fit matter normalization is increased because of large-angle suppression in the power and the global anisotropy of the temperature fluctuations. We also study several deformed closed toroidal models in which the fundamental cell is described by a rectangular box. In contrast with the cubic models, the large-angle power can be enhanced in comparison with the infinite counterparts if the cell is sufficiently squashed in a certain direction. It turns out that constraints on some slightly deformed models are less stringent. We comment on how these results affect our understanding of the global topology of our Universe.Kaiki Taro Inoue; Masahiro NagashimaAstrophysical Journal 574 1 I 9 - 18 2002年07月 [査読有り]
We revisit the cloud-in-cloud problem for non-Gaussian density fluctuations. We show that the extended Press-Schechter (EPS) formalism for non-Gaussian fluctuations has a flaw in describing mass functions regardless of the type of filtering. As an example, we consider non-Gaussian models in which density fluctuations at a point obey a χ2 distribution with ν degrees of freedom. We find that mass functions predicted by using an integral formula proposed by Jedamzik and Yano, Nagashima, and Gouda, properly taking into account correlation between objects at different scales, deviate from those predicted by using the EPS formalism, especially for strongly non-Gaussian fluctuations. Our results for the mass function at large mass scales are consistent with those by Avelino and Viana obtained from numerical simulations.Kaiki Taro InoueProgress of Theoretical Physics 106 1 39 - 61 2001年07月 [査読有り]
We revisit the observational constraints on compact (closed) hyperbolic (CH) models from a cosmic microwave background (CMB). We carry out Bayesian analyses for CH models with volume comparable to the cube of the present curvature radius using the COBE-DMR data and show that a slight suppression in the large-angle temperature correlations owing to the non-trivial topology explains rather naturally the observed anomalously small quadrupole which is incompatible with the prediction of the standard infinite Friedmann-Robertson-Walker models. While most positions and orientations are ruled out, the likelihoods of CH models are found to be much greater than those of infinite counterparts for some specific positions and orientations of the observer, leading to less stringent constraints on the volume of the manifolds. Even if the spatial geometry is as nearly flat as Ωtot = 0.9 -0.95, suppression of the angular power on large angular scales is still prominent for CH models with volume much less than the cube of the present curvature radius if the cosmological constant is dominant at present.Kaiki Taro InoueClassical and Quantum Gravity 18 10 1967 - 1978 2001年05月In this paper, the cosmic microwave background (CMB) anisotropy in a multiply connected compact flat 3-torus model with the cosmological constant is investigated. Using the COBE-DMR four-year data, a full Bayesian analysis revealed that the constraint on the topology of the flat 3-torus model with low matter density is less stringent. As in compact hyperbolic models, the large-angle temperature fluctuations can be produced as the gravitational potential decays at the Λ-dominant epoch well after the last scattering. The maximum allowed number of images of the cell, N (fundamental domain), within the observable region at present is approximately 49 for Ωm = 0.1 and ΩΛ = 0.9, whereas N ∼ 8 for Ωm = 1.0 and ΩΛ = 0.Kaiki Taro Inoue2001年03月We study the effect of global topology of the spatial geometry on the cosmic
microwave background (CMB) for closed flat and closed hyperbolic models in
which the spatial hypersurface is multiply connected. If the CMB temperature
fluctuations were entirely produced at the last scattering, then the
large-angle fluctuations would be much suppressed in comparison with the simply
connected counterparts which is at variance with the observational data.
However, as we shall show in this thesis, for low matter density models the
observational constraints are less stringent since a large amount of
large-angle fluctuations could be produced at late times. On the other hand, a
slight suppression in large-angle temperature correlations in such models
explains rather naturally the observed anomalously low quadrupole which is
incompatible with the prediction of the "standard"
Friedmann-Robertson-Walker-Lemaitre models. Interestingly, moreover, the
development in the astronomical observation technology has made it possible to
directly explore the imprint of the non-trivial topology by looking for
identical objects so called "ghosts" in wide separated directions. For the CMB
temperature fluctuations identical patterns would appear on a pair of circles
in the sky. Another interesting feature is the non-Gaussianity in the
temperature fluctuations. Inhomogeneous and anisotropic Gaussian fluctuations
for a particular choice of position and orientation are regarded as
non-Gaussian fluctuations for a homogeneous and isotropic ensemble.Numerical study of length spectra and low-lying eigenvalue spectra of compact hyperbolic 3-manifoldsKaiki Taro InoueClassical and Quantum Gravity 18 4 629 - 652 2001年02月 [査読有り]
In this paper, we investigate numerically the length spectra and the low-lying eigenvalue spectra of the Laplace-Beltrami operator for a large number of small compact (closed) hyperbolic (CH) 3-manifolds. The first non-zero eigenvalues have been computed successfully using the periodic orbit sum method, which are compared with various geometric quantities such as the volume, diameter and length of the shortest periodic geodesic of the manifolds. The deviation of low-lying eigenvalue spectra of manifolds converging to a cusped hyperbolic manifold from the asymptotic distribution has been measured using the ζ-function and spectral distance.Kaiki Taro Inoue2000年11月We have investigated the cosmic microwave background (CMB) anisotropy in
closed multiply connected universes
(flat and hyperbolic) with low matter density. We show that the COBE
constraints on these low matter density models with non-trivial topology are
less stringent since a large amount of CMB anisotropy on large angular scales
can be produced due to the decay of the gravitational potential at late time.Kaiki Taro Inoue; Kenji Tomita; Naoshi SugiyamaMonthly Notices of the Royal Astronomical Society 314 4 L21 - L25 2000年06月 [査読有り]
The effect of a non-trivial topology on the temperature correlations of the cosmic microwave background (CMB) in a small compact hyperbolic universe with volume comparable to the cube of the curvature radius is investigated. Because the bulk of large-angle CMB fluctuations are produced at the late epoch in low-Ω0 models, the effect of a long-wavelength cut-off owing to the periodic structure does not lead to significant suppression of large-angle power as in compact flat models. The angular power spectra are consistent with COBE data for Ω0 ≥ 0.1.Kaiki Taro InouePhysical Review D - Particles, Fields, Gravitation and Cosmology 62 10 16 2000年 [査読有り]
In this paper, the Gaussianity of eigenmodes and non-Gaussianity in the cosmic microwave background (CMB) temperature fluctuations in the two smallest compact hyperbolic (CH) models are investigated. First, it is numerically found that the expansion coefficients of low-lying eigenmodes on the two CH manifolds behave as if they are Gaussian random numbers in almost all places. Next, the non-Gaussianity of the temperature fluctuations in the (Formula presented) space in these models is studied. Assuming that the initial fluctuations are Gaussian, the real expansion coefficients (Formula presented) of the temperature fluctuations in the sky are found to be distinctively non-Gaussian. In particular, the cosmic variances are found to be much larger than for Gaussian models. On the other hand, the anisotropic structure is vastly erased if one averages the fluctuations at a number of different observation points because of the Gaussian pseudorandomness of the eigenmodes. Thus the dominant contribution to the two-point correlation functions comes from the isotropic terms described by the angular power spectra (Formula presented) Finally, topological quantities, the total length and the genus of isotemperature contours are investigated. The variances of total length and genus at high and low threshold levels are found to be considerably larger than that of Gaussian models while the means almost agree with them. © 2000 The American Physical Society.Kaiki Taro InoueClassical and Quantum Gravity 16 10 3071 - 3094 1999年10月 [査読有り]
Measurements of cosmic microwave background (CMB) anisotropy are ideal experiments for discovering the non-trivial global topology of the universe. To evaluate the CMB anisotropy in multiply-connected compact cosmological models, one needs to compute the eigenmodes of the Laplace-Beltrami operator. Using the direct boundary element method, we obtain numerically the low-lying eigenmodes on a compact hyperbolic 3-space called the Thurston manifold which is the second smallest in the known compact hyperbolic 3-manifolds. The computed eigenmodes are expanded in terms of eigenmodes on the unit three-dimensional pseudosphere. We find numerically that the expansion coefficients behave as Gaussian pseudo-random numbers for low-lying eigenmodes. The observed Gaussianity in the CMB fluctuations can partially be attributed to the Gaussian pseudo-randomness of the expansion coefficients assuming that the Gaussian pseudo-randomness is the universal property of the compact hyperbolic spaces.KT Inoue3 K COSMOLOGY 476 343 - 347 1999年Measurements of CMB anisotropy are ideal experiments for discovering the non-trivial global topology of the universe. To evaluate the CMB anisotropy in multiply-connected compact cosmological models, one needs to compute eigenmodes of the Laplace-Beltrami operator. We numerically obtain the eigenmodes on a compact 3-hyperbolic space cataloged as m003(-2, 3) in SnapPea (1) using the direct boundary element method, which enables one to simulate the CMB in multiply-connected compact models with high precision. The angular power spectra C-l's (2 less than or equal to l less than or equal to 18) are calculated using computed eigenmodes for 5.4 less than or equal to k < 10 and Gaussian random approximation for the expansion coefficients for 10 less than or equal to k < 20. Assuming that the initial power spectrum is the Harrison-Zeldovich spectrum, the computed C-l's are consistent with the COBE data for 0.1 less than or equal to Ohm(0) less than or equal to 0.6. In low Ohm(0) models, the large-angular fluctuations can be produced at periods after the last scattering as the curvature perturbations decay in the curvature dominant era.講演・口頭発表等
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- 弱重力レンズ効果による超ボイドの重力的撮像 [通常講演]井上開輝; 西澤淳; 浜名崇; 樋口祐一; 宮武広直日本天文学会年会講演予稿集 2016年08月
- 4重像レンズにおけるフラックス比異常の起源について [通常講演]井上開輝日本天文学会年会講演予稿集 2016年02月
- Kaiki Taro InoueMNRAS (2016) 461 (1), p164-175 2016年01月 口頭発表（一般）We explore the origin of flux ratio anomaly in quadruple lens systems. Using a semi-analytic method based on $N$-body simulations, we estimate the effect of possible magnification perturbation caused by subhaloes with a mass scale of <$\sim 10^9\,h^{-1} \textrm{M}_\odot$ in lensing galaxy haloes. Taking into account astrometric shifts, assuming that the primary lens is described by a singular isothermal ellipsoid, the expected change to the flux ratios per a multiply lensed image is just a few percent and the mean of the expected convergence perturbation at the effective Einstein radius of the lensing galaxy halo is $ 0.003$, corresponding to the mean of the ratio of a projected dark matter mass fraction in subhaloes at the effective Einstein radius $0.006$. In contrast, the expected change to the flux ratio caused by line-of-sight structures is typically $\sim 10$ percent and the mean of the convergence perturbation is $0.008$, corresponding to $0.017$. The contribution of magnification perturbation caused by subhaloes is $\sim 40$ percent of the total at a source redshift $z_S= 0.7$ and decreases monotonically in $z_S$ to $\sim 20$ percent at $z_S= 3.6$. Assuming statistical isotropy, the convergence perturbation estimated from observed 11 quadruple lens systems has a positive correlation with the source redshift $z_S$, which is much stronger than that with the lens redshift $z_L$. This feature also supports an idea that the flux ratio anomaly is caused mainly by line-of-sight structures rather than subhaloes. We also discuss about a possible imprint of line-of-sight structures in demagnification of minimum images due to locally underdense structures in the line of sight.
- 井上開輝; 峰崎岳夫; 松下聡樹; 千葉柾司日本天文学会年会講演予稿集 2015年08月
- 4重像重力レンズを用いた温かいダークマターの質量の制限 [通常講演]井上開輝; 高橋龍一; 高橋智; 石山智明日本天文学会年会講演予稿集 2015年02月
- 安東正樹; 川村静児; 瀬戸直樹; 中村卓史; 坪野公夫; 佐藤修一; 田中貴浩; 船木一幸; 沼田健司; 神田展行; 井岡邦仁; 高島健; 横山順一; 阿久津智忠; 武者満; 上田暁俊; 麻生洋一; 新谷昌人; 坂井真一郎; 青柳巧介; 我妻一博; 浅田秀樹; 新井宏二; 池上健; 石川毅彦; 石崎秀晴; 石原秀樹; 和泉究; 市來淨與; 伊東宏之; 伊藤洋介; 井上開輝; 植田憲一; 牛場崇文; 歌島昌由; 江口智士; 江尻悠美子; 榎基宏; 戎崎俊一; 江里口良治日本物理学会講演概要集 2014年08月
- ”Probing the origin of flux-ratio anomalies in quadruple lenses with ALMA” [通常講演]井上 開輝日本天文学会 2014年03月 口頭発表（一般）
- INOUE Kaiki; MATSUSHITA Satoki; CHIBA Masashi; MINEZAKI Takeo; TAKAHASHI Ryuichi日本天文学会年会講演予稿集 2014年02月
- ”系外銀河ハロー内にある中間質量ブラックホールの重力的直接撮像” [通常講演]井上 開輝日本天文学会 2013年11月 口頭発表（一般）
- ”ミニ重力レンズで探るダークマターの起源” [招待講演]井上 開輝東大天文センター談話会 2013年06月 口頭発表（一般）
- ”Weak Lensing by Line-of-sight Halos as the Origin of Flux-ratio Anomalies in Quadruply Lensed QSOs” [通常講演]井上 開輝日本天文学会 2013年03月 口頭発表（一般）
MISC
- ALMA2 Project -アルマ望遠鏡が切り拓く2020年代の科学のフロンティア-大石雅寿他37名 49 -51 2019年03月 [招待有り]
- 坂井 伸之; 井上 開輝; 冨田 憲二 日本物理学会講演概要集 65 (1) 105 -105 2010年03月
- 井上 開輝; 冨田 憲二; 坂井 伸之 日本物理学会講演概要集 64 (2) 46 -46 2009年08月
- Masashi Chiba; Takeo Minezaki; Kaiki T. Inoue; Nobunari Kashikawa; Hirokazu Kataza; Hajime Sugai PANORAMIC VIEWS OF GALAXY FORMATION AND EVOLUTION, PROCEEDINGS 399 98 -101 2008年
- Motohiro Enoki; Kaiki T. Inoue; Masahiro Nagashima; Naoshi Sugiyama 2005年02月
共同研究・競争的資金等の研究課題
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2017年04月 -2021年03月代表者 : 井上 開輝10kpc以下の小スケールにおいて構造形成に関する理論と観測が一致しない「小スケール問題」が知られている。この問題を解決するため、我々は、多重像としてみえるレンズ像のそれぞれの位置は理論モデルの予測と合うが、それらのフラックス比が予測と合わない「フラックス比異常」を示す重力レンズ系に着目する。「フラックス比異常」の原因として、レンズ銀河ハロー内のダークマターサブハローと視線方向のハローという2つの候補が挙げられているが、何が真の原因なのかはまだ分かっていない。我々はフラックス比異常の原因を解明する新手法を確立し、4重像重力レンズ系を用いて様々なダークマターモデルに対する観測的な制限を付けることを目的としている。本年度の成果は以下の通りである。 1)宇宙の構造形成を用いて様々なダークマターモデルを観測的に制限するため、2017年4月に、ALMA望遠鏡による4重像重力レンズクエーサーMG0414+0534の観測計画を提案し、提案が採択され、2017年11月に天体が観測された。2018年2月にデータにアクセスすることが可能になった。 2)長寿命荷電大質量粒子(CHAMP)をダークマターとする宇宙モデルに対して、N体シミュレーションを実行し、ダークマターによる非線形構造を計算した。得られた非線形構造が既存の4重像レンズ系におけるフラックス比異常を説明できるかどうか調べた。その結果、ダークマターの全てがCHAMPであり、レンズ銀河ハロー内のサブハローの効果が視線方向のサブハローの効果より小さい場合、その寿命は0.96年より小さい必要があることが判明した。
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2013年04月 -2016年03月代表者 : 井上 開輝; 千葉 柾司; 峰崎 岳夫; 高橋 龍一; 松下 聡樹4重像をもつ重力レンズを用いて、レンズ銀河内のサブハロー（小質量のハロー）もしくは視線方向のダークマターの構造によるレンズ効果を理論および観測的に求めた。その結果、以下の事が判明した。1)観測データはコールドダークマター(CDM)に基づく宇宙モデルと矛盾しない。2)ウォームダークマター(WDM)から成る宇宙モデルでは、観測データを説明することが難しく、粒子の質量は電子の質量の約400分の1より大きくなければならない。これらの結果から、原始銀河の母体であると考えられる始原ミニハローの起源はCDMである可能性が高まった。一方で、近傍矮小銀河の観測データはCDMモデルの予言と矛盾することが分かった。
- 日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)研究期間 : 2009年07月 -2014年03月代表者 : 服部 誠; 大坪 貴文; 土井 靖生; 松元 亮治; 田村 元秀; 井上 開輝マイクロ波偏光観測データから宇宙マイクロ波背景放射と銀河系内星間物質からのマイクロ波放射の分離を高精度で行う成分分離スキームの完成を目指して活動した。分離スキームとして、階層ベイズ法を応用した独自のスキームの開発した。銀河系内星間物質からのマイクロ波域での偏光放射の物理的理解の深化に繋がる研究も遂行した。その一つが、日本の赤外線観測衛星「あかり」が取得した遠赤外線全天探査データからの遠赤外線宇宙地図の作成である。衛星が取得した一次データを処理し全天地図を作成する作業に、当科研費で購入した高速クラスター計算機を活用することで作業効率を飛躍的に向上させ研究期間内に完成させること出来た。
- 日本学術振興会：科学研究費助成事業 若手研究(B)研究期間 : 2008年 -2011年代表者 : 井上 開輝宇宙マイクロ波背景輻射(CMB)の大角度温度揺らぎの異常の原因として加速宇宙における超大規模構造の重力ポテンシャル進化が重要な役割を果たしていることが明らかになった。特に半径200-300h/Mpcの大きさをもつ低密度領域の効果が重要であり、低密度領域の総量に関するΛCDMモデルとの不一致は3σ以上の有意性を持つことが判明した。
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2008年 -2010年代表者 : 千葉 柾司; 井上 開輝; 峰崎 岳夫; 齋藤 正雄; 亀野 誠二; 菅井 肇; 住 貴宏冷たい暗黒物質(CDM)の階層的合体過程に基づく宇宙の構造形成理論によると、銀河系のような明るい銀河の周囲に数千に及ぶ暗黒物質のサブストラクチャー(CDMサブハロー)が存在することが示唆されている。そこで、この暗黒物質サブハローを実際に検出して標準理論に重要な制限を付けるために、本研究において重力レンズ天体の高空間分解能天体観測に基づいた暗黒物質分布の新しい導出方法を開発した。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2006年 -2009年代表者 : 坂井 伸之; 中尾 憲一; 石原 秀樹; 玉置 孝至; 井上 開輝; 冨田 憲二1987年にFarhi & Guthが提起した「実験室で宇宙を作れるか?」という問題について、初期特異点なしに古典的過程のみで(準)定常な粒子がインフレーション宇宙に転移する理論モデルを2つ発見した。1つは定常な磁気モノポールが、もう1つは振動する偽真空泡が進化してインフレーション宇宙になるモデルである。また、素粒子場のソリトン解の基礎研究として、カタストロフィー理論を用いた新しい安定性解析の方法を定式化した。
- 日本学術振興会：科学研究費助成事業 若手研究(B)研究期間 : 2005年 -2007年代表者 : 井上 開輝非線形重力ポテンシャルの進化による温度ゆらぎ生成機構の解明 「薄い殻」近似、摂動論、Lemaitre-Tolman-Bondi時空モデルの3つの計算方法を駆使して明らかになったのは以下の四点である。 (1)宇宙項入りの平坦Friedmann-Robertoson-Walker(FRW)モデルでは、Einsten-de Sitter宇宙の場合と異なり、温度ゆらぎに対して、密度コントラストの一次の項も寄与する。又、密度コントラストの一次の項と二次の項はボイドの場合相関する。 (2)二次の項はポテンシャルの符号によらず、常に温度を下げる働きがある。従って、低赤方偏移では、ボイド領域を通過した宇宙背景輻射光子は、より低温になり、質量集中の領域を通過した光子は高温になる。しかし、二次の効果がより効くとやや温度が下がる。又、高赤方偏移の質量集中を通過した光子に対しては一次の効果より二次の効果が利くため、温度揺らぎは負になる。 (3)標準モデル(宇宙項入りの平坦FRWモデル)の予測する大角度スケールにおける非線形重力ポテンシャル進化による温度揺らぎの平均値のオーダーは大き目に見積もって1億分の1程度であり、その効果は線形積分Sachs-Wolfe効果に比べて無視できる。 (4)しかしながら、高赤方偏移の天体のみの寄与を考えると、その線形積分Sachs-Wolfe効果は質量優勢期において消滅するため、一次の効果対する二次の効果は高赤方偏移では無視できなくなる。
- 銀河における暗黒物質構造の解明日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2005年 -2006年代表者 : 千葉 柾司; 高田 昌広; 峰崎 岳夫; 柏川 伸成; 井上 開輝本研究では、現在の宇宙構造形成理論の標準理論である冷たい暗黒物質理論において、その予測する暗黒物質サブハローが銀河周辺領域においてどのような状態で存在し、さらに銀河形態の形成とどのように関連しているのかを、理論と観測の両面から総合的に解明することを主眼とした。そこで、暗黒物質サブハローが銀河円盤の動力学構造に与える影響を詳しく研究するとともに、重カレンズ現象に基づくサブハローの研究を行った。まず、詳細な数値実験に基づいて、暗黒物質サブハローによってどのように銀河円盤が厚くなるか、そして、現在観測される薄い円盤を維持するためには、サブハローの分布にどのような制限が付くかを考察した。さらに研究を進めて、いわゆる厚い円盤構造の起源との関連を調べ、観測される厚い円盤構造がサブハローとの力学相互作用による可能性がはじめて明らかになった。また、すばる望遠鏡によって相互フラックス比の異常を示す4重クエーサーの観測を遂行し、手前のレンズ銀河における暗黒物質サブハローの分布に関して新たな知見を得た。さらに、本研究チームの組織により、銀河スケールにおける暗黒物質(冷たい暗黒物質、ブラックホール)の存在形態を導く新しい方法論の確立、現有の観測装置に基づく暗黒物質の探査の実施とその解析方法の確立、暗黒物質の存在形態に関する理論的理解の確立、の3本柱を基にして、銀河における暗黒物質の存在形態を解明するための研究を進めた。そして、暗黒物質と銀河形成と進化と関係について新しい知見を獲得することができた。これらの研究成果は6編の論文掲載紙に発表し、さらに2編の論文が投稿済みとなっている。
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