Tomoyuki Taguchi

Subaru Deep Survey I. Near-Infrared Observations

Deep near-infraredimages of a blank 2 � ×2 � section of skynear the galactic north pole taken by Subaru Telescope are presented. The total integration times of the J and Kbands were 12.1 hr and 9.7 hr, resulting in 5 σ limiting magnitudes of 25.1 and 23.5 mag, respectively. The numbers of sources within these limiting magnitudes found with an automated detection procedure are 385 in the J band and 350 in K � . Based on photometric measurements of these sources, we present number count vs. magnitude relations, color vs. magnitude diagrams, size vs. color relationships, etc. The slope of the galaxy number count plotted against the AB magnitude scale is about 0.23 in the 22 to 26 AB magnitude range of both bands. The spatial number density of galaxies as well as the slopes in the faint-end region given by the Subaru Deep Field (SDF) survey are consistent with those given by HST-NICMOS surveys, as expressed on the AB magnitude diagram. Several sources having very large J − Kcolor have been found, including a few Kobjects without detection at J. In addition, a number of faint galactic stars were also

Near-Infrared Spectroscopy of the Cool Brown Dwarf, SDSS 1624+00

Using the Subaru Telescope, we have obtained multiple near-infrared spectra of the cool brown dwarf, SDSS 1624 + 00 (J162414.37+002915.8), in search of spectral variability in an 80 minute time span. We have found the suspected variability of water vapor absorption throughout the observations, which requires a confirmation with a longer time baseline. After coadding the spectra, we have obtained a high-quality spectrum covering from 1.05 to 1.8 /im. There are three kinds of spectral indicators, the water vapor bands, methane band and Kl lines at 1.243 and 1.252 //m, which can be used to study the temperature and the presence of dust. We compare the spectra of SDSS 1624+00 and Gliese 229B, while paying special attention to these indicators. The shallower water vapor absorption of SDSS 1624+00 indicates that it is warmer and/or dustier. The shallower methane absorption suggests that SDSS 1624+00 is warmer. We interpret the deeper KI lines in SDSS 1624+00 as being the result of its higher temperature. With the help of model spectra, we conclude that SDSS 1624+00 is warmer and dustier than Gliese 229B. For the first time in a cool brown dwarf, a finite flux is seen at the bottom of the water vapor band between 1.34 and 1.42 /im, which means that the 1.4 /xm band of water can be completely observed from the ground.

Superwind-Driven Intense H2 Emission in NGC 6240

We have performed a long-slit K band spectroscopic observation of the luminous infrared galaxy NGC 6240. Spatially extended H2 emission is detected over 3.3 kpc around the two nuclei. The peak position of the H2 v = 1 − 0 S(1) emission in the slit is located ∼ 0. 3 − 0. 4 north of the southern nucleus. It is almost the midpoint between the southern nucleus and the peak position of the 12 CO (J = 1 − 0) emission. Based on the line-ratio analyses, we suggest the excitation mechanism of H2 is pure thermal at

Near-Infrared Emission-Line Galaxies in the Hubble Deep Field North

We present the 2.12 yum narrow-band image of the Hubble Deep Field North taken with the nearinfrared camera (CISCO) on the Subaru telescope. Among five targets whose Ha or [O III] emission lines are redshifted into our narrow-band range expected from their spectroscopic redshift, four of them have strong emission lines, especially for the two [O III] emission-line objects. The remaining one target shows no Ha emission in spite of its bright rest-UV luminosity, indicating that this object is already under the post-starburst phase. The volume-averaged SFR derived from the detected two Ha emission is roughly consistent with that evaluated from the rest-UV continuum.

JHK Spectra of the z = 2.39 Radio Galaxy 53W002^1

We present low-resolution, near-IR JHK spectra of the weak z =2 .39 radio galaxy 53W002, obtained with the OH-airglow Suppressor spectrograph (OHS) and Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru Telescope. They cover rest-frame wavelengths of 3400–7200 u A, and the emission lines of [O II] λ3727, Hβ ,[ OIII] λλ4959, 5007, Hα ,[ NII] λλ6548, 6583 and [S II] λλ6716, 6731 were detected. Using the Hα/Hβ line ratio, we find an extinction of E(B − V )=0 .14. The emission-line ratios are reproduced by a cloud of electron density ne =1 × 10 3−4 cm −3 with solar metallicity, ionized by an α = −0.7 power-law continuum with ionizing parameter U =1 ×10 −3 . In addition to these emission lines, we make the first spectroscopic confirmation of the Balmer discontinuity in a high-z radio galaxy. Together with rest-frame UV photometry from the literature, we show that at least 1/3 of the present stellar mass was formed in the current starburst. The stellar mass was estimated

High-Resolution Near-Infrared Imaging of the Powerful Radio Galaxy 3C 324 at z = 1.21 with the Subaru Telescope

We have obtained high-resolution K ′ -band images of the powerful z = 1.206 radio galaxy 3C 324 with the Subaru telescope under seeing conditions of 0 ′′ .3–0 ′′ .4. We clearly resolved the galaxy and directly compared it to the optical images obtained with the Hubble Space Telescope. The host galaxy of 3C 324 is revealed to be a moderately luminous elliptical galaxy with a smooth light profile. The effective radius of the galaxy, as determined by profile fitting, is 1.3± 0 ′′ .1 (1.2 kpc), which is significantly smaller than the value of 2 ′′ .2 published in Best et al. (1998, MNRAS, 292, 758). The peak of the K ′ -band light coincides with the position of the radio core, which implies that the powerful AGN lies at the nucleus of the host galaxy. The peak also coincides with the gap in the optical knotty structures which may be a dust lane hiding the UV-optical emission of the AGN from our line of sight; it is very likely that we are seeing the obscuring structure almost edge-on. We clearly detected the ‘aligned component’ in the K ′ -band image by subtracting a model elliptical galaxy from the observed image. The red RF702W K color of the outer region of the galaxy avoiding the aligned component indicates that the near infrared light of the host galaxy is dominated by an old stellar population.