Y. Toba - Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

Y. Toba
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Y. Toba
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

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Astrophysics of Galaxies (22)
Cosmology and Nongalactic Astrophysics (10)
High Energy Astrophysical Phenomena (4)
Instrumentation and Methods for Astrophysics (2)
Solar and Stellar Astrophysics (1)
Earth and Planetary Astrophysics (1)

Publications Authored By Y. Toba

Authors: H. Aihara1, N. Arimoto2, R. Armstrong3, S. Arnouts4, N. A. Bahcall5, S. Bickerton6, J. Bosch7, K. Bundy8, P. L. Capak9, J. H. H. Chan10, M. Chiba11, J. Coupon12, E. Egami13, M. Enoki14, F. Finet15, H. Fujimori16, S. Fujimoto17, H. Furusawa18, J. Furusawa19, T. Goto20, A. Goulding21, J. P. Greco22, J. E. Greene23, J. E. Gunn24, T. Hamana25, Y. Harikane26, Y. Hashimoto27, T. Hattori28, M. Hayashi29, Y. Hayashi30, K. G. Hełminiak31, R. Higuchi32, C. Hikage33, P. T. P. Ho34, B. -C. Hsieh35, K. Huang36, S. Huang37, H. Ikeda38, M. Imanishi39, A. K. Inoue40, K. Iwasawa41, I. Iwata42, A. T. Jaelani43, H. -Y. Jian44, Y. Kamata45, H. Karoji46, N. Kashikawa47, N. Katayama48, S. Kawanomoto49, I. Kayo50, J. Koda51, M. Koike52, T. Kojima53, Y. Komiyama54, A. Konno55, S. Koshida56, Y. Koyama57, H. Kusakabe58, A. Leauthaud59, C. -H. Lee60, L. Lin61, Y. -T. Lin62, R. H. Lupton63, R. Mandelbaum64, Y. Matsuoka65, E. Medezinski66, S. Mineo67, S. Miyama68, H. Miyatake69, S. Miyazaki70, R. Momose71, A. More72, S. More73, Y. Moritani74, T. J. Moriya75, T. Morokuma76, S. Mukae77, R. Murata78, H. Murayama79, T. Nagao80, F. Nakata81, M. Niida82, H. Niikura83, A. J. Nishizawa84, Y. Obuchi85, M. Oguri86, Y. Oishi87, N. Okabe88, Y. Okura89, Y. Ono90, M. Onodera91, M. Onoue92, K. Osato93, M. Ouchi94, P. A. Price95, T. -S. Pyo96, M. Sako97, S. Okamoto98, M. Sawicki99, T. Shibuya100, K. Shimasaku101, A. Shimono102, M. Shirasaki103, J. D. Silverman104, M. Simet105, J. Speagle106, D. N. Spergel107, M. A. Strauss108, Y. Sugahara109, N. Sugiyama110, Y. Suto111, S. H. Suyu112, N. Suzuki113, P. J. Tait114, T. Takata115, M. Takada116, N. Tamura117, M. M. Tanaka118, M. Tanaka119, M. Tanaka120, Y. Tanaka121, T. Terai122, Y. Terashima123, Y. Toba124, J. Toshikawa125, E. L. Turner126, T. Uchida127, H. Uchiyama128, K. Umetsu129, F. Uraguchi130, Y. Urata131, T. Usuda132, Y. Utsumi133, S. -Y. Wang134, W. -H. Wang135, K. C. Wong136, K. Yabe137, Y. Yamada138, H. Yamanoi139, N. Yasuda140, S. Yeh141, A. Yonehara142, S. Yuma143
Affiliations: 1HSC Collaboration, 2HSC Collaboration, 3HSC Collaboration, 4HSC Collaboration, 5HSC Collaboration, 6HSC Collaboration, 7HSC Collaboration, 8HSC Collaboration, 9HSC Collaboration, 10HSC Collaboration, 11HSC Collaboration, 12HSC Collaboration, 13HSC Collaboration, 14HSC Collaboration, 15HSC Collaboration, 16HSC Collaboration, 17HSC Collaboration, 18HSC Collaboration, 19HSC Collaboration, 20HSC Collaboration, 21HSC Collaboration, 22HSC Collaboration, 23HSC Collaboration, 24HSC Collaboration, 25HSC Collaboration, 26HSC Collaboration, 27HSC Collaboration, 28HSC Collaboration, 29HSC Collaboration, 30HSC Collaboration, 31HSC Collaboration, 32HSC Collaboration, 33HSC Collaboration, 34HSC Collaboration, 35HSC Collaboration, 36HSC Collaboration, 37HSC Collaboration, 38HSC Collaboration, 39HSC Collaboration, 40HSC Collaboration, 41HSC Collaboration, 42HSC Collaboration, 43HSC Collaboration, 44HSC Collaboration, 45HSC Collaboration, 46HSC Collaboration, 47HSC Collaboration, 48HSC Collaboration, 49HSC Collaboration, 50HSC Collaboration, 51HSC Collaboration, 52HSC Collaboration, 53HSC Collaboration, 54HSC Collaboration, 55HSC Collaboration, 56HSC Collaboration, 57HSC Collaboration, 58HSC Collaboration, 59HSC Collaboration, 60HSC Collaboration, 61HSC Collaboration, 62HSC Collaboration, 63HSC Collaboration, 64HSC Collaboration, 65HSC Collaboration, 66HSC Collaboration, 67HSC Collaboration, 68HSC Collaboration, 69HSC Collaboration, 70HSC Collaboration, 71HSC Collaboration, 72HSC Collaboration, 73HSC Collaboration, 74HSC Collaboration, 75HSC Collaboration, 76HSC Collaboration, 77HSC Collaboration, 78HSC Collaboration, 79HSC Collaboration, 80HSC Collaboration, 81HSC Collaboration, 82HSC Collaboration, 83HSC Collaboration, 84HSC Collaboration, 85HSC Collaboration, 86HSC Collaboration, 87HSC Collaboration, 88HSC Collaboration, 89HSC Collaboration, 90HSC Collaboration, 91HSC Collaboration, 92HSC Collaboration, 93HSC Collaboration, 94HSC Collaboration, 95HSC Collaboration, 96HSC Collaboration, 97HSC Collaboration, 98HSC Collaboration, 99HSC Collaboration, 100HSC Collaboration, 101HSC Collaboration, 102HSC Collaboration, 103HSC Collaboration, 104HSC Collaboration, 105HSC Collaboration, 106HSC Collaboration, 107HSC Collaboration, 108HSC Collaboration, 109HSC Collaboration, 110HSC Collaboration, 111HSC Collaboration, 112HSC Collaboration, 113HSC Collaboration, 114HSC Collaboration, 115HSC Collaboration, 116HSC Collaboration, 117HSC Collaboration, 118HSC Collaboration, 119HSC Collaboration, 120HSC Collaboration, 121HSC Collaboration, 122HSC Collaboration, 123HSC Collaboration, 124HSC Collaboration, 125HSC Collaboration, 126HSC Collaboration, 127HSC Collaboration, 128HSC Collaboration, 129HSC Collaboration, 130HSC Collaboration, 131HSC Collaboration, 132HSC Collaboration, 133HSC Collaboration, 134HSC Collaboration, 135HSC Collaboration, 136HSC Collaboration, 137HSC Collaboration, 138HSC Collaboration, 139HSC Collaboration, 140HSC Collaboration, 141HSC Collaboration, 142HSC Collaboration, 143HSC Collaboration

Hyper Suprime-Cam (HSC) is a wide-field imaging camera on the prime focus of the 8.2m Subaru telescope on the summit of Maunakea. A team of scientists from Japan, Taiwan and Princeton University is using HSC to carry out a 300-night multi-band imaging survey of the high-latitude sky. Read More

We have measured the clustering of galaxies around active galactic nuclei (AGN) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from 250deg$^{2}$ S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0. Read More

We present the environmental dependence of colour, stellar mass, and star formation (SF) activity in H-alpha-selected galaxies along the huge cosmic web at z=0.4 hosting twin clusters in DEEP2-3 field, discovered by Subaru Strategic Programme of Hyper Suprime-Cam (HSC SSP). By combining photo-z selected galaxies and H-alpha emitters selected with broad-band and narrow-band data of the recent internal data release of HSC SSP (DR1), we confirm that galaxies in higher-density environments or galaxies in the cluster central regions show redder colours. Read More

We construct a sample of X-ray bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. 53 X-ray sources satisfying i band magnitude fainter than 23.5 mag and X-ray counts with EPIC-PN detector larger than 70 are selected from 9. Read More

We investigate the galaxy overdensity around <2 pMpc-scale quasar pairs at high (z>3) and low (z~1) redshift based on the unprecedentedly wide and deep optical survey of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). Using the first-year survey data covering effectively ~121 deg2 in full-color and depth, we find two luminous pairs at z~3.6 and 3. Read More

We present the luminosity function of z=4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg^2. From stellar objects, 1666 z~4 quasar candidates are selected by the g-dropout selection down to i=24. Read More

We investigate the star forming activity of a sample of infrared (IR)-bright dust-obscured galaxies (DOGs) that show an extreme red color in the optical and IR regime, $(i - [22])_{\rm AB} > 7.0$. Combining an IR-bright DOG sample with the flux at 22 $\mu$m $>$ 3. Read More

The identification of high-redshift massive galaxies with old stellar populations may pose challenges to some models of galaxy formation. However, to securely classify a galaxy as quiescent, it is necessary to exclude significant ongoing star formation, something that can be challenging to achieve at high redshift. In this letter, we analyse deep ALMA/870um and SCUBA-2/450um imaging of the claimed "post-starburst" galaxy ZF-20115 at z=3. Read More

In order to investigate the physical relationship between strong Ly-alpha absorbers (logN_HI>20.0 cm^-2) such as damped Ly-alpha absorption systems (DLAs) and young star-forming galaxies at high redshift, we have conducted narrow-band observations of Ly-alpha emitters (LAEs) in a concentrated region of strong Ly-alpha absorbers at z= 2.3, the J1230+34 field. Read More

Authors: Hiroaki Aihara, Robert Armstrong, Steven Bickerton, James Bosch, Jean Coupon, Hisanori Furusawa, Yusuke Hayashi, Hiroyuki Ikeda, Yukiko Kamata, Hiroshi Karoji, Satoshi Kawanomoto, Michitaro Koike, Yutaka Komiyama, Robert H. Lupton, Sogo Mineo, Hironao Miyatake, Satoshi Miyazaki, Tomoki Morokuma, Yoshiyuki Obuchi, Yukie Oishi, Yuki Okura, Paul A. Price, Tadafumi Takata, Manobu M. Tanaka, Masayuki Tanaka, Yoko Tanaka, Tomohisa Uchida, Fumihiro Uraguchi, Yousuke Utsumi, Shiang-Yu Wang, Yoshihiko Yamada, Hitomi Yamanoi, Naoki Yasuda, Nobuo Arimoto, Masashi Chiba, Francois Finet, Hiroki Fujimori, Seiji Fujimoto, Junko Furusawa, Tomotsugu Goto, Andy Goulding, James E. Gunn, Yuichi Harikane, Takashi Hattori, Masao Hayashi, Krzysztof G. Helminiak, Ryo Higuchi, Chiaki Hikage, Paul T. P. Ho, Bau-Ching Hsieh, Kuiyun Huang, Song Huang, Masatoshi Imanishi, Ikuru Iwata, Anton T. Jaelani, Hung-Yu Jian, Nobunari Kashikawa, Nobuhiko Katayama, Takashi Kojima, Akira Konno, Shintaro Koshida, Alexie Leauthaud, C. -H. Lee, Lihwai Lin, Yen-Ting Lin, Rachel Mandelbaum, Yoshiki Matsuoka, Elinor Medezinski, Shoken Miyama, Rieko Momose, Anupreeta More, Surhud More, Shiro Mukae, Ryoma Murata, Hitoshi Murayama, Tohru Nagao, Fumiaki Nakata, Hiroko Niikura, Atsushi J. Nishizawa, Masamune Oguri, Nobuhiro Okabe, Yoshiaki Ono, Masato Onodera, Masafusa Onoue, Masami Ouchi, Tae-Soo Pyo, Takatoshi Shibuya, Kazuhiro Shimasaku, Melanie Simet, Joshua Speagle, David N. Spergel, Michael A. Strauss, Yuma Sugahara, Naoshi Sugiyama, Yasushi Suto, Nao Suzuki, Philip J. Tait, Masahiro Takada, Tsuyoshi Terai, Yoshiki Toba, Edwin L. Turner, Hisakazu Uchiyama, Keiichi Umetsu, Yuji Urata, Tomonori Usuda, Sherry Yeh, Suraphong Yuma

The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is a three-layered imaging survey aimed at addressing some of the most outstanding questions in astronomy today, including the nature of dark matter and dark energy. The survey has been awarded 300 nights of observing time at the Subaru Telescope. The survey started in March 2014. Read More

We present measurements of the clustering properties of a sample of infrared (IR) bright dust-obscured galaxies (DOGs). Combining 125 deg$^2$ of wide and deep optical images obtained with the Hyper Suprime-Cam on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer, we have discovered 4,367 IR-bright DOGs with $(i - [22])_{\rm AB}$ $>$ 7.0 and flux density at 22 $\mu$m $>$ 1. Read More

We systematically investigate the near- (NIR) to far-infrared (FIR) photometric properties of a nearly complete sample of local active galactic nuclei (AGN) detected in the Swift/Burst Alert Telescope (BAT) all-sky ultra hard X-ray (14-195 keV) survey. Out of 606 non-blazar AGN in the Swift/BAT 70-month catalog at high galactic latitude of $|b|>10^{\circ}$, we obtain IR photometric data of 604 objects by cross-matching the AGN positions with catalogs from the WISE, AKARI, IRAS, and Herschel infrared observatories. We find a good correlation between the ultra-hard X-ray and mid-IR (MIR) luminosities over five orders of magnitude ($41 < \log (L_{14-195}/{\rm erg}~{\rm s}^{-1})< 46$). Read More

One of the unsettled, important problems in active galactic nuclei (AGNs) is the major ionization mechanism of gas clouds in their narrow-line regions (NLRs). In order to investigate this issue, we present our $J$-band spectroscopic observations for a sample of 26 nearby Seyfert galaxies. In our study, we use the flux ratio of the following two forbidden emission lines, [Fe II]1. Read More

Recent studies have derived quasar luminosity functions (QLFs) at various redshifts. However, the faint side of the QLF at high redshifts is still too uncertain. An accurate estimate of the survey completeness is essential to derive an accurate QLF for use in studying the luminosity-dependent density evolution of the quasar population. Read More

Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths, with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. Among the X-ray sources listed in the second release of the MAXI all-sky X-ray source catalog, 100 ones are currently identified as a non-blazar-type active galactic nucleus. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. Read More

We aim to search for hyperliminous infrared (IR) galaxies (HyLIRGs) with IR luminosity $L_{{\rm IR}}$ $>$ 10$^{13}$ $L_{\odot}$ by applying the selection method of Dust Obscured Galaxies (DOGs). They are spatially rare but could correspond to a maximum phase of cosmic star formation and/or active galactic nucleus (AGN) activity, hence they are a crucial population for understanding the star formation and mass assembly history of galaxies. Combining the optical and IR catalogs obtained from Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE), we performed the extensive HyLIRGs survey; we selected 5,311 IR-bright DOGs with $i$ -- [22] $>$ 7. Read More

We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90 micron) sources located at |b|>10 deg to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. Read More

We present the photometric properties of a sample of infrared (IR) bright dust obscured galaxies (DOGs). Combining wide and deep optical images obtained with the Hyper Suprime-Cam (HSC) on the Subaru Telescope and all-sky mid-IR (MIR) images taken with Wide-Field Infrared Survey Explorer (WISE), we discovered 48 DOGs with $i - K_\mathrm{s} > 1.2$ and $i - [22] > 7. Read More

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. Read More

Affiliations: 1Graduate School of Science, Nagoya University, 2Graduate School of Science, Nagoya University, 3Department of Physics and Astronomy, University of California, Los Angeles, 4Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 5Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 6Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 7Academia Sinica, Institute of Astronomy and Astrophysics, 8Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 9Department of Astronomy, University of Tokyo, 10Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 11Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 12Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 13Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency

We present a new sample of active galactic nuclei (AGNs) identified using the catalog of the AKARI Mid-infrared(MIR) All-Sky Survey. Our MIR search has an advantage in detecting AGNs that are obscured at optical wavelengths due to extinction. We first selected AKARI 9micron excess sources with F(9micron)/F(K_S)>2 where K_S magnitudes were taken from the Two Micron All Sky Survey. Read More

We present Subaru observations of the newly discovered luminous quasar AKARI J1757+5907, which shows an absorption outflow in its spectrum. The absorption consists of 9 distinct troughs, and our analysis focuses on the troughs at ~ -1000$ km s^{-1} for which we can measure accurate column densities of He I*, Fe II and Mg II. We use photoionization models to constrain the ionization parameter, total hydrogen column density, and the number density of the outflowing gas. Read More