Tomonori Usuda

A NEW MILKY WAY SATELLITE DISCOVERED IN THE SUBARU/HYPER SUPRIME-CAM SURVEY

We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5 sigma) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in their color-magnitude diagram. The significance of this overdensity increases to 10.8 sigma when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main sequence turn-off at r ~ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M_V = -0.8 +/- 0.9 mag. This stellar system has an extended spatial distribution with a half-light radius of 38 +12/-11 pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of VirgoI is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the Milky Way.

Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

We report the current status of the Infrared Doppler (IRD) instrument for the Subaru telescope, which aims at detecting Earth-like planets around nearby M darwfs via the radial velocity (RV) measurements. IRD is a fiber-fed, near infrared spectrometer which enables us to obtain high-resolution spectrum (R~70000) from 0.97 to 1.75 μm. We have been developing new technologies to achieve 1m/s RV measurement precision, including an original laser frequency comb as an extremely stable wavelength standard in the near infrared. To achieve ultimate thermal stability, very low thermal expansion ceramic is used for most of the optical components including the optical bench.

SPOTS: The Search for Planets Orbiting Two Stars - I. Survey description and first observations

Direct imaging surveys for exoplanets commonly exclude binary stars from their target lists, leaving a large part of the overall planet demography unexplored. To address this gap in our understanding of planet formation and evolution, we have launched the first directimaging survey dedicated to circumbinary planets: SPOTS, the Search for Planets Orbiting Two Stars. We discuss the theoretical context, scientific merit, and technical feasibility of such observations, describe the target sample and observational strategy of our survey, and report on the first results from our pilot survey of 26 targets with the VLT NaCo facility. While we have not found any confirmed substellar companions to date, a number of promising candidate companions remain to be tested for common proper motion in upcoming follow-up observations. We also report on the astrometry of the three resolved binaries in our target sample. This pilot survey constitutes a successful proof of concept for our survey strategy and paves the way for a second stage in the exploratory observations with VLT SPHERE.

An optically-selected cluster catalog at redshift 0.1 < z < 1.1 from the Hyper Suprime-Cam Subaru Strategic Program S16A data

We present an optically-selected cluster catalog from the Hyper Suprime-Cam (HSC) Subaru Strategic Program. The HSC images are sufficiently deep to detect cluster member galaxies down to

Hyper-luminous dust-obscured galaxies discovered by the Hyper Suprime-Cam on Subaru and WISE

M_*sim 10^{10.2}M_odot

A new quadruple gravitational lens from the Hyper Suprime-Cam Survey: the puzzle of HSC J115252+004733

even at

Clustering of Infrared-Bright Dust-Obscured Galaxies Revealed by the Hyper Suprime-Cam and Wise

zsim 1

Sumo Puff: Tidal debris or disturbed ultra-diffuse galaxy?

, allowing a reliable cluster detection at such high redshifts. We apply the CAMIRA algorithm to the HSC Wide S16A dataset covering

A WEAK LENSING VIEW OF THE DOWNSIZING OF STAR-FORMING GALAXIES*

sim 232

Constraining the Movement of the Spiral Features and the Locations of Planetary Bodies Within the AB Aur System

deg