202 research outputs found
OHS: OH-airglow Suppressor for the Subaru Telescope
This paper describes an OH-airglow Suppressor (OHS) for the infrared Nasmyth
focus of the Subaru telescope. OHS has the capability of eliminating 224
airglow-lines in the - and -bands, which are major sources of background
radiation at near-infrared wavelengths up to 2 m. Specifically, it is a
pre-optics system installed between the telescope and an infrared
camera/spectrograph (CISCO). The suppressor reduces sky background emissions to
1/25 and its throughput is 40%. As a result, the S/N gain achieved with OHS is
more than 1 mag compared to the typical spectroscopic approach. The limiting
magnitude measured during a test observing run was found to be = 21.1 mag
( = 210, S/N = 5) in the standard 4000 s exposure
sequence.Comment: 6 pages, 9 figures. Accepted for publication in PASJ(2001
JHK Spectra of the z=2.39 Radio Galaxy 53W002
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 A, and the emission
lines of [O II]3727, Hb, [O III]4959, 5007, Ha, [N II]6548, 6583 and [S
II]6716, 6731 were detected. Using the Ha/Hb line ratio, we find an extinction
of E(B-V)=0.14. The emission-line ratios are reproduced by a cloud of electron
density n_e=1x10^{3-4}(/cm3) with solar metallicity, ionized by an alpha=-0.7
power-law continuum with ionizing parameter U=1x10^-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 to be
(1-1.4)x10^11 M_sol by one-component model fitting, which is smaller than that
of typical z~1 B2/6C radio galaxies. We suggest that 53W002 is currently
assembling a large part of its stellar mass through merger events with the
surrounding sub-galactic clumps, some of which can be identified with the Lya
emitters detected in narrow-band imaging. After a few such events over the next
few Gyr, 53W002 will evolve into a massive elliptical galaxy.Comment: 10 pages, including 11 figures. Accepted for publication in
PASJ(2001). Revised 5/15/200
Infrared Imaging of the Gravitational Lens PG 1115+080 with the Subaru Telescope
We present high spatial resolution images of the gravitational-lens system PG
1115+080 taken with the near-infrared camera (CISCO) on the Subaru telescope.
The FWHM of the combined image is in the -band, yielding spatial
resolution of after a deconvolution procedure. This is a first
detection of an extended emission adjacent to the A1/A2 components, indicating
the presence of a fairly bright emission region with a characteristic angular
radius of 5 mas (40 pc). The near-infrared image of the Einstein ring
was extracted in both the and bands. The color is found to be
significantly redder than that of a synthetic model galaxy with an age of 3
Gyr, the age of the universe at the quasar redshift.Comment: 11 pages, 6 figures. Accepted for publication in PASJ(2000
Spectral Classification and Effective Temperatures of L and T Dwarfs Based of Near-Infrared Spectra
We have obtained near-infrared spectra of L dwarfs, L/T transition objects
and T dwarfs using Subaru. Resulting spectra are examined in detail to see
their dependence on the spectral types. We have obtained bolometric
luminosities of the objects with known parallaxes in our sample, first by
integrating the spectra and second by K band bolometric correction. We derive
the relation between effective temperature and spectral type.Comment: To appear in May 20, 2004 issue of ApJ There is a companion paper by
Tsuji, Nakajima and Yanagisaw
An Observational Pursuit for Population III Stars in a Ly_alpha Emitter at z=6.33 through HeII Emission
We present a very deep near-infrared spectroscopic observation of a strong
Ly_alpha emitter at z=6.33, SDF J132440.6+273607, which we used to search for
HeII 1640. This emission line is expected if the target hosts a significant
number of population III stars. Even after 42 ksec of integration with the
Subaru/OHS spectrograph, no emission-line features are detected in the JH band,
which confirms that SDF J132440.6+273607 is neither an active galactic nucleus
nor a low- emission-line object. We obtained a 2sigma upper-limit of
9.06e-18 ergs/s/cm^2 on the HeII 1640 emission line flux, which corresponds to
a luminosity of 4.11e42 ergs/s. This upper-limit on the HeII 1640 luminosity
implies that the upper limit on population III star-formation rate is in the
range 4.9--41.2 M_sun/yr if population III stars suffer no mass loss, and in
the range 1.8--13.2 M_sun/yr if strong mass loss is present. The non-detection
of HeII in SDF J132440.6+273607 at z=6.33 may thus disfavor weak feedback
models for population III stars.Comment: 13 pages, 3 figures, to appear in The Astrophysical Journal Letter
[OII]3727 Emission from the Companion to the Quasar BR 1202-0725 at z=4.7
Results of a narrow-band imaging for the redshifted [OII]3727 emission around
a quasar at z=4.7 obtained with the Subaru telescope and CISCO (a Cassegrain
near infrared camera) are presented. A significant emission line is detected in
the narrow-band H_2 (v=1-0 S(1)) filter at a location 2.4" northwest from the
quasar, where the presence of a companion has been reported in Lyman alpha
emission and the rest-frame UV continuum. We identify this line as [OII]3727
emission and confirm that the source really is a companion at z=4.7. The
[OII]3727 flux from the companion is estimated to be 2.5 x 10^{-17} erg s^{-1}
cm^{-2}. If the companion is a star forming object, the inferred star formation
rate is as high as 45-230 M_{solar} yr^{-1} even without assuming the
extinction correction. This value is higher than those derived from the Lyman
alpha emission or from the UV continuum. Thus, provided that the difference is
caused by dust extinction, the extinction corrected star formation rate is
calculated to be 45 to 2300 M_{solar} yr^{-1} depending on the assuming
extinction curves.Comment: 15 pages including 3 figures. Accepted for publication in PAS
Characterization of the distribution of the Lly\alpha emitters in the 53W002 field at z = 2.4
We present the results of our wide-field narrow band imaging of the field
around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom
made filter NB413 centered at 4140 \AA\ with the width of 83 \AA\ is used to
observe the 31' x 24' area around the radio galaxy. We detected 204 Ly\alpha
emitters (LAEs) at z = 2.4 with a rest frame equivalent width larger than 25
\AA\ to the depth of 26 AB mag (in NB413). The entire LAE population in the
53W002 field has an average number density and distributions of equivalent
width and size that are similar to those of other fields at z ~ 2. We identify
a significant high density region (53W002F-HDR) that spreads over ~ 5' x 4'
near 53W002 where the LAE number density is nearly four times as large as the
average of the entire field. Using the probability distribution function of
density fluctuation, we evaluate the rareness probability of the 53W002F-HDR to
be 0.9^{+2.4}_{-0.62}%, which corresponds to a moderately rich structure. No
notable environmental dependency at the comoving scale of 10 Mpc is found for
the distributions of the Ly\alpha equivalent width and luminosity in the field.
We also detected 4 Ly\alpha blobs (LABs), one of which is newly discovered.
They are all found to be located in the rims of high density regions. The
biased location and unique morphologies in Ly\alpha suggest that galaxy
interaction play a key role in their formation.Comment: 26 pages, 12 figure
Near-Infrared Observations of Powerful High-Redshift Radio Galaxies: 4C 40.36 and 4C 39.37
We present near-infrared imaging and spectroscopic observations of two FR II
high-redshift radio galaxies (HzRGs), 4C 40.36 (z=2.3) and 4C 39.37 (z=3.2),
obtained with the Hubble, Keck, and Hale Telescopes. High resolution images
were taken with filters both in and out of strong emission lines, and together
with the spectroscopic data, the properties of the line and continuum emissions
were carefully analyzed. Our analysis of 4C 40.36 and 4C 39.37 shows that
strong emission lines (e.g., [O III] 5007 A and H alpha+[N II]) contribute to
the broad-band fluxes much more significantly than previously estimated (80%
vs. 20-40%), and that when the continuum sources are imaged through line-free
filters, they show an extremely compact morphology with a high surface
brightness. If we use the R^1/4-law parametrization, their effective radii
(r(e)) are only 2-3 kpc while their restframe B-band surface brightnesses at
r(e) are I(B) ~ 18 mag/arcsec^2. Compared with z ~ 1 3CR radio galaxies, the
former is x3-5 smaller, while the latter is 1-1.5 mag brighter than what is
predicted from the I(B)-r(e) correlation. Although exponential profiles produce
equally good fits for 4C 40.36 and 4C 39.37, this clearly indicates that with
respect to the z~1 3CR radio galaxies, the light distribution of these two
HzRGs is much more centrally concentrated. Spectroscopically, 4C 40.36 shows a
flat (fnu=const) continuum while 4C 39.37 shows a spectrum as red as that of a
local giant elliptical galaxy. Although this difference may be explained in
terms of a varying degree of star formation, the similarities of their surface
brightness profiles and the submillimeter detection of 4C 39.37 might suggest
that the intrinsic spectra is equally blue (young stars or an AGN), and that
the difference is the amount of reddening.Comment: 30 pages, 6 tables, 10 figures; Accepted for publication in
Astronomical Journa
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