16 research outputs found
An Intermediate-band imaging survey for high-redshift Lyman Alpha Emitters: The Mahoroba-11
We present results of our intermediate-band optical imaging survey for
high- Ly emitters (LAEs) using the prime focus camera, Suprime-Cam,
on the 8.2m Subaru Telescope. In our survey, we use eleven filters; four
broad-band filters (, , , and ) and seven
intermediate-band filters covering from 500 nm to 720 nm; we call this imaging
program as the Mahoroba-11. The seven intermediate-band filters are selected
from the IA filter series that is the Suprime-Cam intermediate-band filter
system whose spectral resolution is . Our survey has been made in a
sky area in the Subaru XMM Newton Deep Survey
field. We have found 409 IA-excess objects that provide us a large photometric
sample of strong emission-line objects. Applying the photometric redshift
method to this sample, we obtained a new sample of 198 LAE candidates at . We found that there is no evidence for evolution of the number density
and the star formation rate density for LAEs with between and 5.Comment: 46 pages, 15 figures, PASJ, Vol.57, No.6, in pres
The Intermediate-band Dropout Method: A New Method to Search for High-Redshift Galaxies
We propose a new method to search for high-redshift galaxies that is based on
an intermediate-band dropout technique rather than the usual broad-band dropout
one. In this method, we use an intermediate-band filter whose central
wavelength is longer than 7000 \AA. This new method makes it possible to
distinguish both very late-type stars such as L and T dwarfs and dusty galaxies
at intermediate redshift from real high- Lyman break galaxies. The reason
for this is that such interlopers do not show strong intermediate-band
depression although they have very red broad-band colors that are indicative of
Lyman break galaxies. Applying our new method to imaging data sets obtained
with the Suprime-Cam on the Subaru Telescope, we find a new sample of Lyman
break galaxies at .Comment: 15 pages, 5 figures, PASJ, Vol.57, No.2, in pres
Detection of Polarized Broad Emission in the Seyfert 2 Galaxy Mrk 573
We report the discovery of the scattered emission from a hidden broad-line
region (BLR) in a Seyfert 2 galaxy, Mrk 573, based on our recent
spectropolarimetric observation performed at the Subaru Telescope. This object
has been regarded as a type 2 AGN without a hidden BLR by the previous
observations. However, our high quality spectrum of the polarized flux of Mrk
573 shows prominent broad (~3000 km/s) H_alpha emission, broad weak H_beta
emission, and subtle Fe II multiplet emission. Our new detection of these
indications for the presence of the hidden BLR in the nucleus of Mrk 573 is
thought to be owing to the high signal-to-noise ratio of our data, but the
possibility of a time variation of the scattered BLR emission is also
mentioned. Some diagnostic quantities such as the IRAS color, the radio power,
and the line ratio of the emission from the narrow-line region of Mrk 573 are
consistent with the distributions of such quantities of type 2 AGNs with a
hidden BLR. Mrk 573 is thought to be an object whose level of the AGN activity
is the weakest among the type 2 AGNs with a hidden BLR. In terms of the
systematic differences between the type 2 AGNs with and without a hidden BLR,
we briefly comment on an interesting Seyfert 2 galaxy, Mrk 266SW, which may
possess a hidden BLR but has been treated as a type 2 AGNs without a hidden
BLR.Comment: 9 pages including 6 figures, to appear in The Astronomical Journa
Strong Emission-Line Galaxies at Low Redshift in the Field around the Quasar SDSSp J104433.04-012502.2
We discuss observational properties of strong emission-line galaxies at low
redshift found by our deep imaging survey for high-redshift Ly alpha emitters.
In our surveys, we used the narrowband filter, NB816 (lambda_center=8150A with
FWHM = 120A), and the intermediate-band filter, IA827 (lambda_center = 8270A
with FWHM = 340A). In this survey, 62 NB816-excess (> 0.9 mag) and 21
IA827-excess (> 0.8 mag) objects were found. Among them, we found 20
NB816-excess and 4 IA827-excess Ly alpha emitter candidates. Therefore, it
turns out that 42 NB816-excess and 17 IA827-excess objects are strong
emission-line objects at lower redshift. Since 4 objects in the two low-z
samples are common, the total number of strong low-z emitters is 55. Applying
our photometric redshift technique, we identify 7 H alpha emitters at z~0.24,
20 H beta-[OIII] ones at z~0.65, and 11 [OII] ones at z~1.19. However, we
cannot determine reliable photometric redshifts of the remaining 17 emitters.
The distributions of their rest frame equivalent widths are consistently
understood with recent studies of galaxy evolution from z~1 to z~0.Comment: 28 pages, 8 figures, PASJ, Vol. 58, No. 1, in pres
A Subaru Search for Lyman-Alpha Emitters at z=5.8 with an Intermediate-Band Filter
We present the results of a survey for Ly-alpha emitters at z ~ 5.8 using a
new intermediate-band filter centered at lambda_c = 8275 AA with
Delta-lambda_FWHM = 340 AA (i.e., the spectroscopic resolution is R ~ 23) with
a combination with a traditional narrow-band centered at lambda_c = 8150 AA
with
Delta-lambda_FWHM = 120 AA (R ~ 68). Our observations were made with use of
the Subaru Prime Focus Camera, Suprime-Cam, on the 8.2 m Subaru telescope in a
sky area surrounding the high redshift quasar, SDSSp J104433.04-012522.2 at
z=5.74, covering an effective sky area with ~ 720 arcmin^2. In this survey, we
have found four Ly-alpha-emitter candidates from the intermediate-band image (z
\~ 5.8 with Delta z ~ 0.3). Combined with our previous results based on the
NB816 imaging, we discuss the star formation activity in galaxies between z ~
5.7 and z ~ 5.9.Comment: 8 pages, 8 figures. Accepted for publication in PAS
A survey of NB921 dropouts in the Subaru Deep Field
In order to search for high-redshift galaxies beyond in the Subaru
Deep Field, we have investigated NB921-dropout galaxies where NB921 is the
narrowband filter centered at 919.6 nm with FWHM of 13.2 nm for the Suprime-Cam
on the Subaru Telescope. There are no secure NB921-dropout candidates brighter
than . Based on this result, we discuss the UV luminosity
function of star-forming galaxies at .Comment: 10 pages, 5 figures, PASJ, Vol.57, No.5, in pres
Subaru Spectropolarimetry of Mrk 573: The Hidden High-Ionization Nuclear Emission-Line Region inside the Dusty Torus
We report on the result of our high quality spectropolarimetric observation
for the narrow-line region in a nearby Seyfert 2 galaxy, Mrk 573, by the Subaru
Telescope. The polarized flux spectrum of Mrk 573 shows not only prominent
scattered broad H emission but also various narrow forbidden emission
lines. We find that the measured polarization degree of the observed forbidden
emission lines is positively correlated with the ionization potential of the
corresponding ions and the critical density of the corresponding transitions.
We discuss some possible origins of these correlations, and then we point out
that the correlations are caused due to the obscuration of the stratified
narrow-line region in Mrk 573 by the optically and geometrically thick dusty
torus, just similar to the previous study on NGC 4258.Comment: 10 pages including 8 figures, to appear in The Astronomical Journa