162 research outputs found
FeII/MgII Emission Line Ratios of QSOs. II. z>6 Objects
Near-infrared spectra of four QSOs located at are obtained with the
OH-airglow suppressor mounted on the Subaru telescope. The FeII/MgII
emission-line ratios of these QSOs are examined by the same fitting algorithm
as in our previous study of QSOs. The fitting results show that two out
of the four QSOs have significant FeII emission in their rest-UV spectra,
while the other two have almost no FeII features. We also applied our fitting
algorithm to more than 10,000 SDSS QSOs and found two trends in the
distribution of FeII/MgII against redshift: (1) the upper envelope of the
FeII/MgII distribution at shows a probable declination toward high
redshift, and (2) the median distribution settles into lower ratios at with small scatter compared to the other redshift. We discuss an Fe/Mg
abundance evolution of QSOs with a substantial contribution from the diverse
nature of the broad-line regions in high-redshift QSOs.Comment: 12 pages, 2 figures. Accepted for publication in ApJ (10 October
2004, v614
Diffuse Extragalactic Background Light versus Deep Galaxy Counts in the Subaru Deep Field: Missing Light in the Universe?
Deep optical and near-infrared galaxy counts are utilized to estimate the
extragalactic background light (EBL) coming from normal galactic light in the
universe. Although the slope of number-magnitude relation of the faintest
counts is flat enough for the count integration to converge, considerable
fraction of EBL from galaxies could still have been missed in deep galaxy
surveys because of various selection effects including the cosmological dimming
of surface brightness of galaxies. Here we give an estimate of EBL from galaxy
counts, in which these selection effects are quantitatively taken into account
for the first time, based on reasonable models of galaxy evolution which are
consistent with all available data of galaxy counts, size, and redshift
distributions. We show that the EBL from galaxies is best resolved into
discrete galaxies in the near-infrared bands (J, K) by using the latest data of
the Subaru Deep Field; more than 80-90% of EBL from galaxies has been resolved
in these bands. Our result indicates that the contribution by missing galaxies
cannot account for the discrepancy between the count integration and recent
tentative detections of diffuse EBL in the K-band (2.2 micron), and there may
be a very diffuse component of EBL which has left no imprints in known galaxy
populations.Comment: ApJ Letters in press. Two new reports on the diffuse EBL at 1.25 and
2.2 microns are added to the reference list and Table
Hyper Extremely Red Objects in the Subaru Deep Field: Evidence for Primordial Elliptical Galaxies in the Dusty Starburst Phase
We report observational analyses and theoretical interpretations of unusually
red galaxies in the Subaru Deep Field (SDF). A careful analysis of the SDF data
revealed a population with unusually red near-infrared (NIR) colors of J - K >~
3-4, with higher confidence than the previous SDF result. Their surface number
density drastically increases at K >~ 22 and becomes roughly the same with that
of dusty starburst galaxies detected by submillimeter observations in recent
years. These colors are even redder than the known population of the extremely
red objects (EROs), and too red to explain by passively evolving elliptical
galaxies which are the largest population of EROs. Hence these hyper extremely
red objects (HEROs) should be considered as a distinct population from EROs. We
discuss several possible interpretations of these enigmatic objects, and we
show that these red NIR colors, K-band and sub-mm flux, and surface number
density are quantitatively best explained by primordial elliptical galaxies
reddened by dust, still in the starburst phase of their formation at z ~ 3.Comment: Accepted by ApJ Letter
The apelin‑apelin receptor signaling pathway in fibroblasts is involved in tumor growth via p53 expression of cancer cells
Cancer-associated fibroblasts (CAFs) are pivotal in tumor progression. TP53-deficiency in cancer cells is associated with robust stromal activation. The apelin-apelin receptor (APJ) system has been implicated in suppressing fibroblast-to-myofibroblast transition in non-neoplastic organ fibrosis. The present study aimed to elucidate the oncogenic role of the apelin-APJ system in tumor fibroblasts. APJ expression and the effect of APJ suppression in fibroblasts were investigated for p53 status in cancer cells using human cell lines (TP53-wild colon cancer, HCT116, and Caco-2; TP53-mutant colon cancer, SW480, and DLD-1; and colon fibroblasts, CCD-18Co), resected human tissue samples of colorectal cancers, and immune-deficient nude mouse xenograft models. The role of exosomes collected by ultracentrifugation were also analyzed as mediators of p53 expression in cancer cells and APJ expression in fibroblasts. APJ expression in fibroblasts co-cultured with p53-suppressed colon cancer cells (HCT116sh p53 cells) was significantly lower than in control colon cancer cells (HCT116sh control cells). APJ-suppressed fibroblasts treated with an antagonist or small interfering RNA showed myofibroblast-like properties, including increased proliferation and migratory abilities, via accelerated phosphorylation of Sma- and Mad-related protein 2/3 (Smad2/3). In addition, xenografts of HCT116 cells with APJ-suppressed fibroblasts showed accelerated tumor growth. By contrast, apelin suppressed the upregulation of phosphorylated Smad2/3 in fibroblasts. MicroRNA 5703 enriched in exosomes derived from HCT116sh p53 cells inhibited APJ expression, and inhibition of miR-5703 diminished APJ suppression in fibroblasts caused by cancer cells. APJ suppression from a specific microRNA in cancer cell-derived exosomes induced CAF-like properties in fibroblasts. Thus, the APJ system in fibroblasts in the tumor microenvironment may be a promising therapeutic target.Saiki H., Hayashi Y., Yoshii S., et al. The apelin‑apelin receptor signaling pathway in fibroblasts is involved in tumor growth via p53 expression of cancer cells. International Journal of Oncology 63, 139 (2023); https://doi.org/10.3892/ijo.2023.5587
The Type Ic Hypernova SN 2002ap
Photometric and spectroscopic data of the energetic Type Ic supernova (SN)
2002ap are presented, and the properties of the SN are investigated through
models of its spectral evolution and its light curve. The SN is
spectroscopically similar to the "hypernova" SN 1997ef. However, its kinetic
energy [ erg] and the mass ejected (2.5-5
) are smaller, resulting in a faster-evolving light curve. The SN
synthesized of Ni, and its peak luminosity was
similar to that of normal SNe. Brightness alone should not be used to define a
hypernova, whose defining character, namely very broad spectral features, is
the result of a high kinetic energy. The likely main-sequence mass of the
progenitor star was 20-25 , which is also lower than that of both
hypernovae SNe 1997ef and 1998bw. SN 2002ap appears to lie at the low-energy
and low-mass end of the hypernova sequence as it is known so far. Observations
of the nebular spectrum, which is expected to dominate by summer 2002, are
necessary to confirm these values.Comment: 10 pages, 4 figures, accepted for publication in ApJL, 30 April 2002
(minor changes to match the accepted version, with figures being colored
- …