6,245 research outputs found
Fossil group origins V. The dependence of the luminosity function on the magnitude gap
In nature we observe galaxy aggregations that span a wide range of magnitude
gaps between the two first-ranked galaxies of a system (). There
are systems with gaps close to zero (e.g., the Coma cluster), and at the other
extreme of the distribution, the largest gaps are found among the so-called
fossil systems. Fossil and non-fossil systems could have different galaxy
populations that should be reflected in their luminosity functions. In this
work we study, for the first time, the dependence of the luminosity function
parameters on using data obtained by the fossil group origins
(FOGO) project. We constructed a hybrid luminosity function for 102 groups and
clusters at . We stacked all the individual luminosity functions,
dividing them into bins of , and studied their best-fit
Schechter parameters. We additionally computed a relative luminosity function,
expressed as a function of the central galaxy luminosity, which boosts our
capacity to detect differences, especially at the bright end. We find trends as
a function of at both the bright and faint ends of the
luminosity function. In particular, at the bright end, the larger the magnitude
gap, the fainter the characteristic magnitude . We also find
differences at the faint end. In this region, the larger the gap, the flatter
the faint-end slope . The differences found at the bright end support a
dissipationless, dynamical friction-driven merging model for the growth of the
central galaxy in group- and cluster-sized halos. The differences in the faint
end cannot be explained by this mechanism. Other processes, such as enhanced
tidal disruption due to early infall and/or prevalence of eccentric orbits, may
play a role. However, a larger sample of systems with is
needed to establish the differences at the faint end.Comment: 11 pages, 10 figures, accepted for publication in A&
Fossil Groups Origins III. The relation between optical and X-ray luminosities
This study is part of the FOssil Groups Origin (FOGO) project which aims at
carrying out a systematic and multiwavelength study of a large sample of fossil
systems. Here we focus on the relation between the optical luminosity (Lopt)
and X-ray luminosity (Lx). Out of a sample of 28 candidate fossil systems, we
consider a sample of 12 systems whose fossil classification has been confirmed
by a companion study. They are compared with the complementary sample of 16
systems whose fossil nature is not confirmed and with a subsample of 102 galaxy
systems from the RASS-SDSS galaxy cluster survey. Fossil and normal systems
span the same redshift range 0<z<0.5 and have the same Lx distribution. For
each fossil system, the Lx in the 0.1-2.4 keV band is computed using data from
the ROSAT All Sky Survey. For each fossil and normal system we homogeneously
compute Lopt in the r-band within the characteristic cluster radius, using data
from the SDSS DR7. We sample the Lx-Lopt relation over two orders of magnitude
in Lx. Our analysis shows that fossil systems are not statistically
distinguishable from the normal systems both through the 2D KS test and the fit
of the Lx-Lopt relation. The optical luminosity of the galaxy system does
strongly correlate with the X-ray luminosity of the hot gas component,
independently of whether the system is fossil or not. We conclude that our
results are consistent with the classical "merging scenario" of the brightest
galaxy formed via merger/cannibalism of other group galaxies, with conservation
of the optical light. We find no evidence for a peculiar state of the hot
intracluster medium.Comment: A&A, 12 pages, 4 figures, 3 tables, typos corr. and paper re-numbe
Fossil Groups Origins III. Characterization of the sample and observational properties of fossil systems
(Abridged) Fossil systems are group- or cluster-sized objects whose
luminosity is dominated by a very massive central galaxy. In the current cold
dark matter scenario, these objects formed hierarchically at an early epoch of
the Universe and then slowly evolved until present day. That is the reason why
they are called {\it fossils}. We started an extensive observational program to
characterize a sample of 34 fossil group candidates spanning a broad range of
physical properties. Deep band images were taken for each candidate and
optical spectroscopic observations were obtained for 1200 galaxies. This
new dataset was completed with SDSS DR7 archival data to obtain robust cluster
membership and global properties of each fossil group candidate. For each
system, we recomputed the magnitude gaps between the two brightest galaxies
() and the first and fourth ranked galaxies ()
within 0.5 . We consider fossil systems those with mag or mag within the errors. We find
that 15 candidates turned out to be fossil systems. Their observational
properties agree with those of non-fossil systems. Both follow the same
correlations, but fossils are always extreme cases. In particular, they host
the brightest central galaxies and the fraction of total galaxy light enclosed
in the central galaxy is larger in fossil than in non-fossil systems. Finally,
we confirm the existence of genuine fossil clusters. Combining our results with
others in the literature, we favor the merging scenario in which fossil systems
formed due to mergers of galaxies. The large magnitude gap is a
consequence of the extreme merger ratio within fossil systems and therefore it
is an evolutionary effect. Moreover, we suggest that at least one candidate in
our sample could represent a transitional fossil stage.Comment: 14 pages, 11 figures, accepted for publication in A&
Observations of velocities, sand concentrations, and fluxes under velocity-asymmetric oscillatory flows
Peer reviewedPublisher PD
Fossil group origins : VII. Galaxy substructures in fossil systems
This work has been partially funded by the MINECO (grant AIA2013-43188-P). M.G. acknowledges financial support from MIUR PRIN2010-2011 (J91J12000450001). Funding for the Sloan Digital Sky Survey (SDSS) and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the US Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, and the Max Planck Society, and the Higher Education Funding Council for England.Context. Fossil groups (FG) are expected to be the final product of galaxy merging within galaxy groups. In simulations, they are predicted to assemble their mass at high redshift. This early formation allows for the innermost M galaxies to merge into a massive central galaxy. Then, they are expected to maintain their fossil status because of the few interactions with the large-scale structure. In this context, the magnitude gap between the two brightest galaxies of the system is considered a good indicator of its dynamical status. As a consequence, the systems with the largest gaps should be dynamically relaxed. Aims. In order to examine the dynamical status of these systems, we systematically analyze, for the first time, the presence of galaxy substructures in a sample of 12 spectroscopically-confirmed fossil systems with redshift z 0:25. Methods. We apply a number of tests to investigate the substructure in fossil systems in the two-dimensional space of projected positions out to R200. Moreover, for a subsample of five systems with at least 30 spectroscopically-confirmed members we also analyze the substructure in the velocity and in the three-dimensional velocity-position spaces. Additionally, we look for signs of recent mergers in the regions around the central galaxies. Results. We find that an important fraction of fossil systems show substructure. The fraction depends critically on the adopted test, since each test is more sensitive to a particular type of substructure. Conclusions. Our interpretation of the results is that fossil systems are not, in general, as relaxed as expected from simulations. Our sample of 12 spectroscopically-confirmed fossil systems need to be extended to compute an accurate fraction, but our conclusion is that this fraction is similar to the fraction of substructure detected in nonfossil clusters. This result points out that the magnitude gap alone is not a good indicator of the dynamical status of a system. However, the subsample of five FGs for which we were able to use velocities as a probe for substructures is dominated by high-mass FGs. These massive systems could have a different evolution compared to low-mass FGs, since they are expected to form via the merging of a fossil group with another group of galaxies. This merger would lengthen the relaxation time and it could be responsible for the substructure detected in present-time massive FGs. If this is the case, only low-mass FGs are expected to be dynamically old and relaxed.Publisher PDFPeer reviewe
Pd-(L)1 inhibitors as monotherapy for the first-line treatment of non-small-cell lung cancer patients with high pd-l1 expression : A network meta-analysis
Altres ajuts: RocheProgrammed cell death-ligand 1 (PD-L1) has emerged as a potential biomarker for selec-tion of patients more likely to respond to immunotherapy and as a prognostic factor in non-small cell lung cancer (NSCLC). In this network meta-analysis, we aimed to evaluate the efficacy of first-line anti-PD-(L)1 monotherapy in advanced NSCLC patients with high PD-L1 expression (â„50%) compared to platinum-based chemotherapy. We also evaluated efficacy outcomes according to tumor mutational burden (TMB). To that end, we conducted a systematic review. Six clinical trials with 2111 patients were included. In head-to-head comparisons, immunotherapy showed a significant improvement in progression-free survival (PFS: HRpooled = 0.69, 95% CI: 0.52-0.90, p = 0.007), overall survival (OS: HRpooled = 0.69, 95% CI: 0.61-0.78; p < 0.001) and overall response rate (ORR) (Risk ratio (RR)pooled = 1.354, 95% CI: 1.04-1.762, p = 0.024). In the assessment of relative efficacy for PFS through indirect comparisons, pembrolizumab (results from KEYNOTE-024) ranked highest followed by cemiplimab and atezolizumab, with statistical significance determined for some of the drugs. In terms of OS, cemiplimab ranked highest followed by atezolizumab and pembrolizumab, although non-significant OS was determined for these drugs. In conclusion, PD-(L)1 inhibitor mon-otherapy improves efficacy outcomes in the first line setting of advanced NSCLC patients with high PD-L1 expression. Evaluations with longer follow up are still needed to determine the superiority of any specific drug
Fossil Groups Origins: I. RX J105453.3+552102 a very massive and relaxed system at z~0.5
The most accepted scenario for the origin of fossil groups (FGs) is that they
are galaxy associations in which the merging rate was fast and efficient. These
systems have assembled half of their mass at early epoch of the Universe,
subsequently growing by minor mergers. They could contain a fossil record of
the galaxy structure formation. We have started a project in order to
characterize a large sample of FGs. In this paper we present the analysis of
the fossil system RX J105453.3+552102. Optical deep images were used for
studying the properties of the brightest group galaxy and for computing the
photometric luminosity function of the group. We have also performed a detail
dynamical analysis of the system based on redshift data for 116 galaxies. This
galaxy system is located at z=0.47, and shows a quite large line-of-sight
velocity dispersion \sigma_{v}~1000 km/s. Assuming the dynamical equilibrium,
we estimated a virial mass of M ~ 10^{15} h_{70} M_{\odot}. No evidence of
substructure was found within 1.4 Mpc radius. We found a statistically
significant departure from Gaussianity of the group members velocities in the
most external regions of the group. This could indicate the presence of
galaxies in radial orbits in the external region of the group. We also found
that the photometrical luminosity function is bimodal, showing a lack of M_{r}
~ -19.5 galaxies. The brightest group galaxy shows low Sersic parameter (n~2)
and a small peculiar velocity. Indeed, our accurate photometry shows that the
difference between the brightest and the second brightest galaxies is 1.9 mag
in the r-band, while the classical definition of FGs is based on a magnitude
gap of 2. We conclude that this fossil system does not follow the empirical
definition of FGs. Nevertheless, it is a massive, old and undisturbed galaxy
system with little infall of L^{*} galaxies since its initial collapse.Comment: 17 pages, 14 figures, accepted for publication at A&
Final results from TAIL: updated long-term efficacy of atezolizumab in a diverse population of patients with previously treated advanced non-small cell lung cancer
In patients with previously treated advanced or metastatic non-small cell lung cancer (NSCLC), atezolizumab therapy improves survival with manageable safety. The open-label, single-arm phase III/IV TAIL study (NCT03285763) evaluated atezolizumab monotherapy in patients with previously treated NSCLC, including those with Eastern Cooperative Oncology Group performance status of 2, severe renal impairment, prior anti-programmed death 1 therapy, autoimmune disease, and age & GE;75 years. Patients received atezolizumab intravenously (1200 mg) every 3 weeks. At data cut-off for final analysis, the median follow-up was 36.1 (range 0.0-42.3) months. Treatment-related (TR) serious adverse events (SAEs) and TR immune-related adverse events (irAEs) were the coprimary endpoints. Secondary endpoints included overall survival (OS), progression-free survival (PFS), overall response rate, and duration of response. Safety and efficacy in key patient subgroups were also assessed. TR SAEs and TR irAEs occurred in 8.0% and 9.4% of patients, respectively. No new safety signals were documented. In the overall population, median OS and PFS (95% CI) were 11.2 months (8.9 to 12.7) and 2.7 months (2.3 to 2.8), respectively. TAIL showed that atezolizumab has a similar risk-benefit profile in clinically diverse patients with previously treated NSCLC, which may guide treatment decisions for patients generally excluded from pivotal clinical trials
Detecting microRNA binding and siRNA off-target effects from expression data.
Sylamer is a method for detecting microRNA target and small interfering RNA off-target signals in 3' untranslated regions from a ranked gene list, sorted from upregulated to downregulated, after a microRNA perturbation or RNA interference experiment. The output is a landscape plot that tracks occurrence biases using hypergeometric P-values for all words across the gene ranking. We demonstrated the utility, speed and accuracy of this approach on several datasets
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