39 research outputs found
Twists in views on RB functions in cellular signaling, metabolism and stem cells
One-quarter of a century ago, identification of the human retinoblastoma gene (RB) loci proved Knudson\u27s \u27two-hit theory\u27 that tumor suppressor genes exist. Since then, numerous works delineated crucial roles for the RB protein (pRB)-E2F transcription factor complex in G1-S phase transition. In addition, discovering the relationship between pRB and tissue-specific transcription factors enabled a better understanding of how cell cycle exit and terminal differentiation are coupled. Recent works provoked many exciting twists in views on pRB functions during cancer initiation and progression beyond its previously well-appreciated roles. Various mitogenic and cytostatic cellular signals appeared to modulate pRB functions and thus affect a wide variety of effector molecules. In addition, genetic studies in mice as well as other creatures incessantly force us to revise our views on pRB functions. This review will focus particularly on the roles of pRB in regulating intracellular signaling, cell metabolism, chromatin function, stem cells and cancer stem cells. © 2012 Japanese Cancer Association
High-redshift Ly alpha emitters with a large equivalent width: Properties of i-dropout galaxies with an NB921-band depression in the Subaru Deep Field
We report new follow-up spectroscopy of i-dropout galaxies with an NB921-band
depression found in the Subaru Deep Field. The NB921-depressed i-dropout
selection method is expected to select galaxies with large equivalent width Ly
alpha emission over a wide redshift range, 6.0<z<6.5. Two of four observed
targets show a strong emission line with a clear asymmetric profile, identified
as Ly alpha emitters at z=6.11 and 6.00. Their rest-frame equivalent widths are
153A and 114A, which are lower limits on the intrinsic equivalent widths.
Through our spectroscopic observations (including previous ones) of
NB921-depressed i-dropout galaxies, we identified 5 galaxies in total with a
rest-frame equivalent width larger than 100A at 6.0<z<6.5 out of 8 photometric
candidates, which suggests that the NB921-depressed i-dropout selection method
is possibly an efficient way to search for Ly alpha emitters with a large Ly
alpha equivalent width, in a wider redshift range than usual narrow-band excess
techniques. By combining these findings with our previous observational
results, we infer that the fraction of broad-band selected galaxies having a
rest-frame equivalent width larger than 100A is significantly higher at z~6
(the cosmic age of ~1 Gyr) than that at z~3 (~2 Gyr), being consistent with the
idea that the typical stellar population of galaxies is significantly younger
at z~6 than that at z~3. The NB921-depressed i-dropout galaxies may be
interesting candidates for hosts of massive, zero-metallicity Population III
stars.Comment: 9 pages, 5 figures, accepted for publication in A&
Definitive Identification of the Transition between Small- to Large-Scale Clustering for Lyman Break Galaxies
We report angular correlation function (ACF) of Lyman Break Galaxies (LBGs)
with unprecedented statistical quality on the basis of 16,920 LBGs at z=4
detected in the 1 deg^2 sky of the Subaru/XMM-Newton Deep Field. The ACF
significantly departs from a power law, and shows an excess on small scale.
Particularly, the ACF of LBGs with i'<27.5 have a clear break between the small
and large-scale regimes at the angular separation of ~7'' whose projected
length corresponds to the virial radius of dark halos with a mass of 10^11-12
Mo, indicating multiple LBGs residing in a single dark halo. Both on small
(2''<theta<3'') and large (40''<theta<400'') scales, clustering amplitudes
monotonically increase with luminosity for the magnitude range of i'=24.5-27.5,
and the small-scale clustering shows a stronger luminosity dependence than the
large-scale clustering. The small-scale bias reaches b~10-50, and the outskirts
of small-scale excess extend to a larger angular separation for brighter LBGs.
The ACF and number density of LBGs can be explained by the cold dark matter
model.Comment: Accepted for publication in ApJL. 5 pages, 4 figures. The text and
Figures 2-4 have been revised. There is no major change which affects to the
main discussion shown in the original preprint. This paper with high
resolution figures is available at
http://www-int.stsci.edu/~ouchi/work/astroph/sxds_z4LBG/ouchi_highres.pdf
(PDF
Dusty ERO Search behind Two Massive Clusters
We performed deep K'-band imaging observations of 2 massive clusters, MS
0451.6-0305 at z = 0.55 and MS 0440.5+0204 at z = 0.19, for searching
counterparts of the faint sub-mm sources behind these clusters, which would
provide one of the deepest extremely red object(ERO) samples. Comparing our
near-infrared images with optical images taken by the Hubble Space Telescope
and by the Subaru Telescope, we identified 13 EROs in these fields. The sky
distributions of EROs are consistent with the previous results, that there is a
sign of strong clustering among detected EROs. Also, the surface density with
corrected lensing amplification factors in both clusters are in good agreement
with that derived from previous surveys. We found 7 EROs and 3 additional very
red objects in a small area (\sim 0.6 arcmin^2) of the MS 0451.6-0305 field
around an extended SCUBA source. Many of their optical and near-infrared colors
are consistent with dusty star-forming galaxies at high redshifts(z \sim
1.0-4.0), and they may be constituting a cluster of dusty starburst galaxies
and/or lensed star-forming galaxies at high redshift. Their red J-K' colors and
faint optical magnitudes suggest they are relatively old massive stellar
systems with ages(>300 Mega years) suffering from dust obscuration. We also
found a surface-density enhancement of EROs around the SCUBA source in the MS
0440.5+0204 field.Comment: 19 pages, 11 figures, Latex(using pasj00.cls). To be published in
PASJ vol 55, No. 4(Aug 2003
Subaru Spectroscopy of the Gravitational Lens HST 14176+5226: Implications for a Large Cosmological Constan
We present new optical spectroscopy of the lens elliptical galax in the
``Einstein Cross'' lens system HST 14176+5226, using the Faint Object Camera
and Spectrograph (FOCAS) of the Subaru t Our spectroscopic observations are
aimed at measuring the stella dispersion of the lens galaxy, located at high
redshift of z_L= as an important component to lens models. We have measured
this 230 +- 14 km s^{-1} (1 sigma) inside 0.35 effective radi based on the
comparison between the observed galaxy spectrum and templates of three G-K
giants by means of the Fourier cross-corr To extract the significance of this
information on the geometry universe which also affects the lensing of the
background image, to fit three different lens models to the available data of
the Provided that the lens galaxy has the structural and dynamical p (i.e., its
radial density profile, core radius, and velocity ani similar to those of local
elliptical galaxies, we calculate the function for the simultaneous
reproduction of both the observed and newly measured velocity dispersion of the
lens. Although the interval depends rather sensitively on the adopted lens
models o parameters, our experiments suggest the larger likelihood for a
cosmological constant, Omega_Lambda: formal 1 sigma lower Omega_Lambda in the
flat universe ranges 0.73 to 0.97, where lower limit is basically unavailable.
This method for determinin model is thus dependent on lens models but is
insensitive to oth ambiguities, such as the dust absorption or the evolutionary
eff galaxies. Exploring spectroscopic observations of more lens gala redshift
may minimize the model uncertainties and thus place a m constraint on
Omega_Lambda.Comment: 23 pages, 5 figures, accepted for publication in The Astronomical
Journa
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
A photometric survey for Lyalpha-HeII dual emitters: Searching for Population III stars in high-redshift galaxies
We present a new photometric search for high-z galaxies hosting Population
III (PopIII) stars based on deep intermediate-band imaging observations
obtained in the Subaru Deep Field (SDF), by using Suprime-Cam on the Subaru
Telescope. By combining our new data with the existing broad-band and
narrow-band data, we searched for galaxies which emit strongly both in Ly_alpha
and in HeII 1640 (``dual emitters'') that are promising candidates for
PopIII-hosting galaxies, at 3.93<z<4.01 and 4.57<z<4.65. Although we found 10
``dual emitters'', most of them turn out to be [OII]-[OIII] dual emitters or
H_beta-(H_alpha+[NII]) dual emitters at z<1, as inferred from their broad-band
colors and from the ratio of the equivalent widths. No convincing candidate of
Ly_alpha-HeII dual emitter of SFR_PopIII > 2 Msun/yr was found by our
photometric search in 4.03 x 10^5 Mpc^3 in the SDF. This result disfavors low
feedback models for PopIII star clusters, and implies an upper-limit of the
PopIII SFR density of SFRD_PopIII < 5 x 10^-6 Msun/yr/Mpc^3. This new selection
method to search for PopIII-hosting galaxies should be useful in future
narrow-band surveys to achieve the first observational detection of
PopIII-hosting galaxies at high redshifts.Comment: 24 pages, 10 figures, accepted for publication in Ap
Decomposition of the Superwind in M82
We present new optical images (, , and H) of the archetypical
starburst/superwind galaxy M82 obtained with the 8.2 m Subaru Telescope to
reveal new detailed structures of the superwind-driven nebula and the
high-latitude dark lanes. The emission-line nebula is decomposed into (1) a
ridge-dominated component comprising numerous filament/loop sub-structures
whose overall morphology appears as a pair of narrow cylinders, and (2) a
diffuse component extended over much wider opening angle from the nucleus. We
suggest that these two components have different origins. The ridge-dominated
component appears as a pair of cylinders rather than a pair of cones. Since
this morphological property is similar to that of hot plasma probed by soft
X-ray, this component seems to surround the hot plasma. On the other hand, the
diffuse component may arise from dust grains which scatter stellar light from
the galaxy. Since inner region of this component is seen over the prominent ^^
^^ X"-shaped dark lanes streaming out from the nuclear region and they can be
reproduced as a conical distribution of dust grains, there seems to be a dusty
cold outflow as well as the hot one probed by soft X-ray and shock-excited
optical emission lines. If this is the case, the presence of such high-latitude
dust grains implies that neutral gaseous matter is also blown out during the
course of the superwind activity.Comment: 12 pages, 6 figures. Accepted for publication in PAS
A Shock-Induced Pair of Superbubbles in the High-Redshift Powerful Radio Galaxy MRC 0406-244
We present new optical spectroscopy of the high-redshift powerful radio
galaxy MRC 0406244 at redshift of 2.429. We find that the two extensions
toward NW and SE probed in the rest-frame ultraviolet image are heated mainly
by the nonthermal continuum of the active galactic nucleus. However, each
extension shows a shell-like morphology, suggesting that they are a pair of
superbubbles induced by the superwind activity rather than by the interaction
between the radio jet and the ambient gas clouds. If this is the case, the
intense starburst responsible for the formation of superbubbles could occur
yr ago. On the other hand, the age of the radio jets may
be of the order of yr, being much shorter than the starburst age.
Therefore, the two events, i.e., the starburst and the radio-jet activities,
are independent phenomena. However, their directions of the expanding motions
could be governed by the rotational motion of the gaseous component in the host
galaxy. This idea appears to explain the alignment effect of MRC 0406244.Comment: 4 pages (emulateapj.sty), Fig. 1 (jpeg) + Fig.2 (eps). Accepted for
publications in ApJ (Letters