245 research outputs found
The Discovery of Two Lyman Emitters Beyond Redshift 6 in the Subaru Deep Field
We have performed a deep optical imaging survey using a narrowband filter
() centered at 9196 \AA ~ together with and
broadband filters covering an 814 arcmin area of the Subaru Deep
Field. We obtained a sample of 73 strong -excess objects based on the
following two color criteria; and . We then obtained optical spectroscopy of nine objects in our
-excess sample, and identified at least two Ly emitters
at and , each of which shows the
characteristic sharp cutoff together with the continuum depression at
wavelengths shortward of the line peak. The latter object is more distant than
HCM-6A at and thus this is the most distant known object found so far.
These new data allow us to estimate the first meaningful lower limit of the
star formation rate density beyond redshift 6; yr Mpc. Since it is expected that the actual
density is higher by a factor of several than this value, our new observation
reveals that a moderately high level of star formation activity already
occurred at 6.6.Comment: 13 pages, 3 figures. PASJ (Letters), 55, vol.2, in pres
Influence of polymer-pore interactions on translocation
We investigate the influence of polymer-pore interactions on the
translocation dynamics using Langevin dynamics simulations. An attractive
interaction can greatly improve translocation probability. At the same time, it
also increases translocation time slowly for weak attraction while exponential
dependence is observed for strong attraction. For fixed driving force and chain
length the histogram of translocation time has a transition from Gaussian
distribution to long-tailed distribution with increasing attraction. Under a
weak driving force and a strong attractive force, both the translocation time
and the residence time in the pore show a non-monotonic behavior as a function
of the chain length. Our simulations results are in good agreement with recent
experimental data.Comment: 4 pages, 5 figures, Submitted to Phys. Rev. Let
Young Brown Dwarfs in the Core of the W3 Main Star-Forming Region
We present the results of deep and high-resolution (FWHM ~ 0".35) JHK NIR
observations with the Subaru telescope, to search for very low mass young
stellar objects (YSOs) in the W3 Main star-forming region. The NIR survey
covers an area of ~ 2.6 arcmin^2 with 10-sigma limiting magnitude exceeding 20
mag in the JHK bands. The survey is sensitive enough to provide unprecedented
details in W3 IRS 5 region and reveals a census of the stellar population down
to objects below the hydrogen-burning limit. We construct JHK color-color (CC)
and J-H/J and H-K/K color-magnitude (CM) diagrams to identify very low
luminosity YSOs and to estimate their masses. Based on these CC and CM
diagrams, we identified a rich population of embedded YSO candidates with
infrared excesses (Class I and Class II), associated with the W3 Main region. A
large number of red sources (H-K > 2) have also been detected around W3 Main.
We argue that these red stars are most probably pre-main-sequence (PMS) stars
with intrinsic color excesses. Based on the comparison between theoretical
evolutionary models of very low-mass PMS objects with the observed CM diagram,
we find there exists a substantial substellar population in the observed
region. The mass function (MF) does not show the presence of cutoff and sharp
turnover around the substellar limit, at least at the hydrogen-burning limit.
Furthermore, the MF slope indicates that the number ratio of young brown dwarfs
and hydrogen-burning stars in the W3 Main is probably higher than those in
Trapezium and IC 348. The presence of mass segregation, in the sense that
relatively massive YSOs lie near the cluster center, is seen. The estimated
dynamical evolution time indicates that the observed mass segregation in the W3
Main may be the imprint of the star formation process.Comment: 39 pages, 15 figures. Accepted for publication in the Astrophysical
Journa
Spectroscopy of i-Dropout Galaxies with an NB921-Band Depression in the Subaru Deep Field
We report new spectroscopy of two star-forming galaxies with strong Ly_alpha
emission at z=6.03 and z=6.04 in the Subaru Deep Field. These two objects are
originally selected as i'-dropouts (i'-z' > 1.5) showing an interesting
photometric property, the ``NB921 depression''. The NB921-band (centered at
9196A) magnitude is significantly depressed with respect to the z'-band
magnitude. The optical spectra of these two objects exhibit asymmetric
emission-lines at lambda_obs ~ 8540A and ~ 8560A, suggesting that these objects
are Ly_alpha emitters at z~6. The rest-frame equivalent widths of the Ly_alpha
emission of the two objects are 94A and 236A; the latter one is the Ly_alpha
emitter with the largest Ly_alpha equivalent width at z > 6 ever
spectroscopically confirmed. The spectroscopically measured Ly_alpha fluxes of
these two objects are consistent with the interpretation that the NB921
depression is caused by the contribution of the strong Ly_alpha emission to the
z'-band flux. Most of the NB921-depressed i'-dropout objects are thought to be
strong Ly_alpha emitters at 6.0 < z < 6.5; Galactic L and T dwarfs and
NB921-dropout galaxies at z > 6.6 do not dominate the NB921-depressed
i'-dropout sample. Thus the NB921-depression method is very useful for finding
high-z Ly_alpha emitters with a large Ly_alpha equivalent width over a large
redshift range, 6.0 < z < 6.5. Although the broadband-selected sample at z ~ 3
contains only a small fraction of objects with a Ly_alpha equivalent width
larger than 100A, the i'-dropout sample of the Subaru Deep Field contains a
much larger fraction of such strong Ly_alpha emitters. This may imply a strong
evolution of the Ly_alpha equivalent width from z > 6 to z ~ 3.Comment: 21 pages, 6 figures, to appear in The Astrophysical Journa
A Potential Galaxy Threshing System in the Cosmos Field
We report on the discovery of a new potential galaxy threshing system in the
COSMOS 2 square degree field using the prime-focus camera, Suprime-Cam, on the
8.2 m Subaru Telescope. This system consists of a giant elliptical galaxy with
and a tidally disrupted satellite galaxy with at a photometric redshift of . This redshift is
consistent with the spectroscopic redshift of 0.079 for the giant elliptical
galaxy obtained from the Sloan Digital Sky Survey (SDSS) archive. The
luminosity masses of the two galaxies are
and , respectively. The distance between the
two galaxies is greater than 100 kpc. The two tidal tails emanating from the
satellite galaxy extend over 150 kpc. This system would be the second
well-defined galaxy threshing system found so far.Comment: 17 pages, 7 figures, accepted for the COSMOS special issue of ApJ
Chaperone-assisted translocation of a polymer through a nanopore
Using Langevin dynamics simulations, we investigate the dynamics of
chaperone-assisted translocation of a flexible polymer through a nanopore. We
find that increasing the binding energy between the chaperone and
the chain and the chaperone concentration can greatly improve the
translocation probability. Particularly, with increasing the chaperone
concentration a maximum translocation probability is observed for weak binding.
For a fixed chaperone concentration, the histogram of translocation time
has a transition from long-tailed distribution to Gaussian distribution with
increasing . rapidly decreases and then almost saturates with
increasing binding energy for short chain, however, it has a minimum for longer
chains at lower chaperone concentration. We also show that has a minimum
as a function of the chaperone concentration. For different , a
nonuniversal dependence of on the chain length is also observed.
These results can be interpreted by characteristic entropic effects for
flexible polymers induced by either crowding effect from high chaperone
concentration or the intersegmental binding for the high binding energy.Comment: 10 pages, to appear in J. Am. Chem. So
The Subaru COSMOS 20: Subaru Optical Imaging of the HST COSMOS Field with 20 Filters
We present both the observations and the data reduction procedures of the
Subaru COSMOS 20 project that is an optical imaging survey of the HST COSMOS
field, carried out by using Suprime-Cam on the Subaru Telescope with the
following 20 optical filters: 6 broad-band (B, g', V, r', i', and z'), 2
narrow-band (NB711 and NB816), and 12 intermediate-band filters (IA427, IA464,
IA484, IA505, IA527, IA574, IA624, IA679, IA709, IA738, IA767, and IA827). A
part of this project is described in Taniguchi et al. (2007) and Capak et al.
(2007) for the six broad-band and one narrow-band (NB816) filter data. In this
paper, we present details of the observations and data reduction for remaining
13 filters (the 12 IA filters and NB711). In particular, we describe the
accuracy of both photometry and astrometry in all the filter bands. We also
present optical properties of the Suprime-Cam IA filter system in Appendix.Comment: 15 pages, 8 figures, 7 tables; accepted for publication in PASJ on
October 2, 201
Electron-phonon renormalization of the absorption edge of the cuprous halides
Compared to most tetrahedral semiconductors, the temperature dependence of
the absorption edges of the cuprous halides (CuCl, CuBr, CuI) is very small.
CuCl and CuBr show a small increase of the gap with increasing
temperature, with a change in the slope of vs. at around 150 K: above
this temperature, the variation of with becomes even smaller. This
unusual behavior has been clarified for CuCl by measurements of the low
temperature gap vs. the isotopic masses of both constituents, yielding an
anomalous negative shift with increasing copper mass. Here we report the
isotope effects of Cu and Br on the gap of CuBr, and that of Cu on the gap of
CuI. The measured isotope effects allow us to understand the corresponding
temperature dependences, which we also report, to our knowledge for the first
time, in the case of CuI. These results enable us to develop a more
quantitative understanding of the phenomena mentioned for the three halides,
and to interpret other anomalies reported for the temperature dependence of the
absorption gap in copper and silver chalcogenides; similarities to the behavior
observed for the copper chalcopyrites are also pointed out.Comment: 14 pages, 5 figures, submitted to Phys. Rev.
Low- and Medium-Dispersion Spectropolarimetry of Nova V475 Sct (Nova Scuti 2003): Discovery of an Asymmetric High-Velocity Wind in a Moderately Fast Nova
We present low-resolution () and medium-resolution ()
spectropolarimetry of Nova V475 Sct with the HBS instrument, mounted on the
0.91-m telescope at the Okayama Astrophysical Observatory, and with FOCAS,
mounted on the 8.2-m Subaru telescope. We estimated the interstellar
polarization toward the nova from the steady continuum polarization components
and H line emission components. After subtracting the interstellar
polarization component from the observations, we found that the H
emission seen on 2003 October 7 was clearly polarized. In the polarized flux
spectrum, the H emission had a distinct red wing extending to km s and a shoulder around km s, showing a
constant position angle of linear polarization \theta_{\rm *}\simeq
155\arcdeg\pm 15\arcdeg. This suggests that the nova had an asymmetric outflow
with a velocity of km s or more, which is six
times higher than the expansion velocity of the ionized shell at the same
epoch. Such a high-velocity component has not previously been reported for a
nova in the `moderately fast' speed class. Our observations suggest the
occurrence of violent mass-loss activity in the nova binary system even during
the common-envelope phase. The position angle of the polarization in the
H wing is in good agreement with that of the continuum polarization
found on 2003 September 26 (--0.6 %), which disappeared
within the following 2 d. The uniformity of the PA between the continuum
polarization and the wing polarization on October 7 suggests that the axis of
the circumstellar asymmetry remained nearly constant during the period of our
observations.Comment: 27 pages, 7 figures, accepted for publication in A
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