arXiv subjects

Ryuji Suzuki

Publications and source records attributed to Ryuji Suzuki.

62 records · Page 4Linked to original sources

arXiv2010

The Infrared Imaging Spectrograph (IRIS) for TMT: Instrument Overview

We present an overview of the design of IRIS, an infrared (0.85 - 2.5 micron) integral field spectrograph and imaging camera for the Thirty Meter Telescope (TMT). With extremely low wavefront error (<30 nm) and on-board wavefront sensors, IRIS will take advantage of the high angular resolution of the narrow field infrared adaptive optics system (NFIRAOS) to dissect the sky at the diffraction limit of the 30-meter aperture. With a primary spectral resolution of 4000 and spatial sampling starting at 4 milliarcseconds, the instrument will create an unparalleled ability to explore high redshift galaxies, the Galactic center, star forming regions and virtually any astrophysical object. This paper summarizes the entire design and basic capabilities. Among the design innovations is the combination of lenslet and slicer integral field units, new 4Kx4k detectors, extremely precise atmospheric dispersion correction, infrared wavefront sensors, and a very large vacuum cryogenic system.

astro-ph.IM↗

arXiv2010

The infrared imaging spectrograph (IRIS) for TMT: spectrograph design

The Infra-Red Imaging Spectrograph (IRIS) is one of the three first light instruments for the Thirty Meter Telescope (TMT) and is the only one to directly sample the diffraction limit. The instrument consists of a parallel imager and off-axis Integral Field Spectrograph (IFS) for optimum use of the near infrared (0.84um-2.4um) Adaptive Optics corrected focal surface. We present an overview of the IRIS spectrograph that is designed to probe a range of scientific targets from the dynamics and morphology of high-z galaxies to studying the atmospheres and surfaces of solar system objects, the latter requiring a narrow field and high Strehl performance. The IRIS spectrograph is a hybrid system consisting of two state of the art IFS technologies providing four plate scales (4mas, 9mas, 25mas, 50mas spaxel sizes). We present the design of the unique hybrid system that combines the power of a lenslet spectrograph and image slicer spectrograph in a configuration where major hardware is shared. The result is a powerful yet economical solution to what would otherwise require two separate 30m-class instruments.

astro-ph.IM↗

arXiv2010

MOIRCS Deep Survey. VI. Near-Infrared Spectroscopy of K-Selected Star-Forming Galaxies at z~2

We present near-infrared (NIR) spectroscopy for 37 BzK-color-selected star-forming galaxies with MOIRCS on Subaru. The sample is drawn from the Ks-band selected catalog of the MOIRCS Deep Survey (MODS) in the GOODS-N region. About half of our samples are selected from the MIPS 24um-source catalog. Ha emission lines are detected from 23 galaxies, of which the median redshift is 2.12. We derived the star formation rates (SFRs) from extinction-corrected Ha luminosities. The extinction correction is estimated from the SED fitting of multi-band photometric data covering UV to NIR wavelengths. The Balmer decrement of the stacked emission lines shows that the amount of extinction for the ionized gas is larger than that for the stellar continuum. From a comparison of the extinction corrected Ha luminosity and other SFR indicators we found that the relation between the dust properties of stellar continuum and ionized gas is different depending on the intrinsic SFR. The comparison between the Ha SFR and stellar mass estimated from SED fitting shows no correlation between them. Some galaxies with stellar mass smaller than ~10^10 Msun show SFRs higher than ~100 Msun/yr. The specific SFRs (SSFRs) of these galaxies are remarkably high. The average stellar-population age of these high-SSFR galaxies is younger than 100 Myr, which is consistent with the implied high SSFR. The large SFR implies the possibility that the high SSFR galaxies significantly contribute to the cosmic SFR density of the universe at z~2. The total SFR density estimated from the Ha emission line galaxies is 0.089-0.136 Msun/yr/Mpc^3, which is consistent with the total SFR densities in the literature. The metallicity of the high-SSFR galaxies is larger than that expected from the mass-metallicity relation of UV-selected galaxies at z~2 by Erb et al. (2006a). [Abridged]

astro-ph.CO↗

arXiv2010

Search for Outer Massive Bodies around Transiting Planetary Systems: Candidates of Faint Stellar Companions around HAT-P-7

We present results of direct imaging observations for HAT-P-7 taken with the Subaru HiCIAO and the Calar Alto AstraLux. Since the close-in transiting planet HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as giant planets, brown dwarfs, or a binary star are expected to exist in the outer region of this system. We show that there are indeed two candidates for distant faint stellar companions around HAT-P-7. We discuss possible roles played by such companions on the orbital evolution of HAT-P-7b. We conclude that as there is a third body in the system as reported by Winn et al. (2009, ApJL, 763, L99), the Kozai migration is less likely while planet-planet scattering is possible.

astro-ph.EP↗

arXiv2009

Discovery of the Coldest Imaged Companion of a Sun-Like Star

We present the discovery of a brown dwarf or possible planet at a projected separation of 1.9" = 29 AU around the star GJ 758, placing it between the separations at which substellar companions are expected to form by core accretion (~5 AU) or direct gravitational collapse (typically >100 AU). The object was detected by direct imaging of its thermal glow with Subaru/HiCIAO. At 10-40 times the mass of Jupiter and a temperature of 550-640 K, GJ 758 B constitutes one of the few known T-type companions, and the coldest ever to be imaged in thermal light around a Sun-like star. Its orbit is likely eccentric and of a size comparable to Pluto's orbit, possibly as a result of gravitational scattering or outward migration. A candidate second companion is detected at 1.2" at one epoch.

astro-ph.EP↗

arXiv2008

Subaru/MOIRCS Near-Infrared Imaging in the Proto-Cluster Region at z=3.1

We present the results of deep near-infrared imaging observations of the z=3.1 proto-cluster region in the SSA22a field taken by MOIRCS mounted on the Subaru Telescope. We observed a 21.7 arcmin^2 field to the depths of J=24.5, H=24.3, and K=23.9 (5 sigma). We examine the distribution of the K-selected galaxies at z~3 by using the simple color cut for distant red galaxies (DRGs) as well as the photometric-redshift selection technique. The marginal density excess of DRGs and the photo-z selected objects are found around the two most luminous Ly alpha blobs (LABs). We investigate the correlation between the K-selected objects and the LABs, and find that several galaxies with stellar mass M_* = 10^9-10^11 M_solar exist in vicinity of LABs, especially around the two most luminous ones. We also find that 7 of the 8 LABs in the field have plausible K_s-band counterparts and the sum of the stellar mass possibly associated with LABs correlates with the luminosity and surface brightness of them, which implies that the origin of Ly alpha emission may be closely correlated with their stellar mass or their previous star formation phenomena.

astro-ph↗

arXiv2007

MOIRCS Deep Survey. II. Clustering Properties of K-band Selected Galaxies in GOODS-North Region

We present the first measurement of clustering properties of low mass galaxies with a stellar mass down to M_*~10^9 Msun at 1 1.3 show a large bias of b~7.2+-1.3 on scales up to θ~100" or 3.1 comoving Mpc, while blue galaxies with 0.5 ~10^{10} Msun, we estimate a correlation length and bias to be r_0~4.5 h^{-1} Mpc and b=1.9-3.5, which are much larger than those of low mass (M_*~10^9-10^{10} Msun) galaxies. The comparison of our measurements with analytic CDM models constrains the properties of hosting dark halos, and indicates that the low mass galaxies would be progenitors of galaxies with a typical luminosity of L<~L_* in the local Universe. The blue galaxies in low mass samples are more strongly clustered in more massive halos with higher occupation numbers than low mass red galaxies. This fact suggests an environment effect due to the halo mass on star formation activity at high-z.

astro-ph↗

arXiv2006

MOIRCS Deep Survey. I: DRG Number Counts

We use very deep near-infrared imaging data taken with Multi-Object InfraRed Camera and Spectrograph (MOIRCS) on the Subaru Telescope to investigate the number counts of Distant Red Galaxies (DRGs). We have observed a 4x7 arcmin^2 field in the Great Observatories Origins Deep Survey North (GOODS-N), and our data reach J=24.6 and K=23.2 (5sigma, Vega magnitude). The surface density of DRGs selected by J-K>2.3 is 2.35+-0.31 arcmin^-2 at K<22 and 3.54+-0.38 arcmin^-2 at K<23, respectively. These values are consistent with those in the GOODS-South and FIRES. Our deep and wide data suggest that the number counts of DRGs turn over at K~22, and the surface density of the faint DRGs with K>22 is smaller than that expected from the number counts at the brighter magnitude. The result indicates that while there are many bright galaxies at 2 22 suggest that the mass-dependent color distribution, where most of low-mass galaxies are blue while more massive galaxies tend to have redder colors, had already been established at that epoch.

astro-ph↗