Satoshi Kawanomoto

Hyper Suprime-Cam

Hyper Suprime-Cam (HSC) is an 870 Mega pixel prime focus camera for the 8.2 m Subaru telescope. The wide field corrector delivers sharp image of 0.25 arc-sec FWHM in r-band over the entire 1.5 degree (in diameter) field of view. The collimation of the camera with respect to the optical axis of the primary mirror is realized by hexapod actuators whose mechanical accuracy is few microns. As a result, we expect to have seeing limited image most of the time. Expected median seeing is 0.67 arc-sec FWHM in i-band. The sensor is a p-ch fully depleted CCD of 200 micron thickness (2048 x 4096 15 μm square pixel) and we employ 116 of them to pave the 50 cm focal plane. Minimum interval between exposures is roughly 30 seconds including reading out arrays, transferring data to the control computer and saving them to the hard drive. HSC uniquely features the combination of large primary mirror, wide field of view, sharp image and high sensitivity especially in red. This enables accurate shape measurement of faint galaxies which is critical for planned weak lensing survey to probe the nature of dark energy. The system is being assembled now and will see the first light in August 2012.

Behavior of Sulfur Abundances in Metal-poor Giants and Dwarfs

LTE and non-LTE (NLTE) abundances of sulfur in six metal-poor giants and 61 dwarfs (62 dwarfs including the Sun) were explored in the range of -3 [Fe/H] +0.5 using high-resolution, high signal-to-noise ratio spectra of the S I 8693.9 and 8694.6 A lines observed by us and measured by Francois and Clegg, Lambert, & Tomkin. NLTE effects in S abundances are found to be small and practically negligible. The behavior of [S/Fe] versus [Fe/H] exhibits a linear increasing trend without plateau with decreasing [Fe/H]. Combining our results with those available in the literature, we find that the slope of the increasing trend is -0.25 in the NLTE behavior of [S/Fe], which is comparable to that observed in [O/Fe]. The observed behavior of S may require chemical evolution models of the Galaxy, in which scenarios of hypernovae nucleosynthesis and/or time-delayed deposition into interstellar medium are incorporated.

Photospheric Abundances of Volatile and Refractory Elements in Planet-Harboring Stars

By using the high-dispersion spectra of 14 bright planet-harboring stars (along with 4 reference stars) observed with the new coude echelle spectrograph at Okayama Astrophysical Observatory, we investigated the abundances of volatile elements (C, N, O, S, Zn; low condensation temperature Tc) in order to examine whether these show any significant difference compared to the abundances of other refractory elements (Si, Ti, V, Fe, Co, Ni; high Tc) which are known to be generally overabundant in those stars with planets, since a Tc-dependence is expected if the cause of such a metal-richness is due to the accretion of solid planetesimals onto the host star. We found, however, that all elements we studied behave themselves quite similarly to Fe (i.e., [X/Fe]~0) even for the case of volatile elements, which may suggest that the enhanced metallicity in those planet-bearing stars is not so much an acquired character (by accretion of rocky material) as rather primordial.

PROPERTIES OF WEAK LENSING CLUSTERS DETECTED ON HYPER SUPRIME-CAM's 2.3 deg2 FIELD

We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks exceeding a signal-to-noise ratio (S/N) of 4.5 are identified on the convergence S/N map of a 2.3 deg2 field observed during the early commissioning phase of the camera. Multi-color photometric data are used to generate optically selected clusters using the Cluster finding algorithm based on the Multiband Identification of Red-sequence galaxies algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters is evaluated by adopting the Singular Isothemal Sphere fit to the tangential shear profiles, yielding virial mass estimates,

Chemical Composition of Carbon-Rich, Very Metal-Poor Subgiant LP 625-44 Observed with the Subaru/HDS

{M}_{{500}_{c}}

THE NEW DETECTIONS OF 7Li/6Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA*

, of the clusters which range from 2.7 × 1013 to 4.4 × 10

A low upper-limit on the lithium isotope ratio in HD140283

{}^{14}\ {M}_{\odot }

High-dispersion spectrograph (HDS) for Subaru Telescope

. The number of peaks is considerably larger than the average number expected from ΛCDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account. We could, however, safely argue that the peak count strongly favors the recent Planck result suggesting a high

Lithium 6104 Å in Population II stars

{\sigma }_{8}

Hyper Suprime-Cam: development of the CCD readout electronics

value of 0.83. The ratio of stellar mass to the dark matter halo mass shows a clear decline as the halo mass increases. If the gas mass fraction, fg, in halos is universal, as has been suggested in the literature, the observed baryon mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.