Abstract Background Radical cystectomy (RC) represents the mainstay of treatment in patients with muscle-invasive urinary bladder cancer but how it compares with the best organ preservation approach ...is not known. Materials and methods The objective of our review is to compare the 5-year overall survival (OS) rates from retrospective and prospective studies of RC and trimodality treatment (TMT), i.e. concurrent delivery of chemotherapy and radiotherapy after a transurethral resection of bladder tumor (TURBT), involving a total of 10,265 and 3131 patients, respectively. We used random-effect models to pool outcomes across studies and compared event rates of combined outcomes for TMT and RC using an interaction test. Results The median 5-year OS rate was 57% in the TMT group, when compared with 52% ( P = 0.04), 51% ( P = 0.02) and 53% ( P = 0.38) in the whole group receiving RC or the group treated with RC alone or RC + chemotherapy, respectively. The hazard risk (HR) of mortality of patients treated with TMT or RC was 1.22 (95% CI = 1.13–1.32) with an absolute benefit of 5% in favor of the former. The HR of mortality from TMT persisted significantly better not only versus the group treated with RC alone (HR = 1.22; 95% CI = 1.12–1.32), but also versus the group receiving RC + chemotherapy (HR = 1.22; 95% CI = 1.09–1.36). Multivariate analysis confirmed TMT as a significant prognostic variable for both RC alone and RC + chemotherapy. Conclusion Compared with RC, TMT seems to be associated with a better outcome for patients with muscle-invasive bladder cancer (MIBC). The addition of chemotherapy may improve the RC outcome in some subgroups of patients with a higher probability of micrometastases. Prospective randomized trials are urged to verify these findings and better define the role of organ preservation and radical treatment strategy in the management of patients with MIBC.
We present the results of a search for unidentified emission lines in deep Suzaku X-ray spectra of the central regions of the X-ray brightest galaxy clusters: Perseus, Coma, Virgo and Ophiuchus. We ...analyse an optimized energy range (3.2–5.3 keV) that is relatively free of instrumental features, and a plasma emission model incorporating the abundances of elements with the strongest expected emission lines at these energies (S, Ar, Ca) as free parameters. For the Perseus Cluster core, employing this model, we find evidence for an additional emission feature at an energy
$E=3.51^{+0.02}_{-0.01}$
keV with a flux of
$2.87_{-0.38}^{+0.33}\times 10^{-7}\,{\rm photons}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcmin}^{-2}$
. At slightly larger radii, we detect an emission line at 3.59 ± 0.02 keV with a flux of
$4.8_{-1.4}^{+1.7}\times 10^{-8}\,{\rm photons}\,{\rm s}^{-1}\,{\rm cm}^{-2}\,{\rm arcmin}^{-2}$
. The properties of these features are broadly consistent with previous claims, although the radial variation of the line strength appears in tension with dark matter (DM) decay model predictions. Assuming a decaying DM origin for these features allows us to predict the energies and detected line fluxes for the other clusters. We do not detect an emission feature at the predicted energy and line flux in the Coma, Virgo and Ophiuchus clusters. The formal 99.5 per cent upper limits on the line strengths in each cluster are well below the decaying DM model predictions, disfavouring a decaying DM interpretation. The results of further analysis suggest that systematic effects associated with modelling the spectra for the Perseus Cluster, details of the assumed ionization balance and errors in the predicted spectral line emissivities may be largely responsible for the ∼3.55 keV feature.
We perform a search for stellar streams around the Milky Way using the first 3 yr of multiband optical imaging data from the Dark Energy Survey (DES). We use DES data covering ∼5000 deg2 to a depth ...of g > 23.5 with a relative photometric calibration uncertainty of <1%. This data set yields unprecedented sensitivity to the stellar density field in the southern celestial hemisphere, enabling the detection of faint stellar streams to a heliocentric distance of ∼50 kpc. We search for stellar streams using a matched filter in color-magnitude space derived from a synthetic isochrone of an old, metal-poor stellar population. Our detection technique recovers four previously known thin stellar streams: Phoenix, ATLAS, Tucana III, and a possible extension of Molonglo. In addition, we report the discovery of 11 new stellar streams. In general, the new streams detected by DES are fainter, more distant, and lower surface brightness than streams detected by similar techniques in previous photometric surveys. As a by-product of our stellar stream search, we find evidence for extratidal stellar structure associated with four globular clusters: NGC 288, NGC 1261, NGC 1851, and NGC 1904. The ever-growing sample of stellar streams will provide insight into the formation of the Galactic stellar halo, the Milky Way gravitational potential, and the large- and small-scale distribution of dark matter around the Milky Way.
Abstract
We present
Magellan
/IMACS spectroscopy of the recently discovered Milky Way satellite Eridanus II (Eri II). We identify 28 member stars in Eri II, from which we measure a systemic radial ...velocity of
and a velocity dispersion of
. Assuming that Eri II is a dispersion-supported system in dynamical equilibrium, we derive a mass within the half-light radius of
, indicating a mass-to-light ratio of
/
and confirming that it is a dark matter-dominated dwarf galaxy. From the equivalent width measurements of the Ca triplet lines of 16 red giant member stars, we derive a mean metallicity of Fe/H = −2.38 ± 0.13 and a metallicity dispersion of
. The velocity of Eri II in the Galactic standard of rest frame is
v
GSR
= −66.6
, indicating that either Eri II is falling into the Milky Way potential for the first time or that it has passed the apocenter of its orbit on a subsequent passage. At a Galactocentric distance of ∼370 kpc, Eri II is one of the Milky Way’s most distant satellites known. Additionally, we show that the bright blue stars previously suggested to be a young stellar population are not associated with Eri II. The lack of gas and recent star formation in Eri II is surprising given its mass and distance from the Milky Way, and may place constraints on models of quenching in dwarf galaxies and on the distribution of hot gas in the Milky Way halo. Furthermore, the large velocity dispersion of Eri II can be combined with the existence of a central star cluster to constrain massive compact halo object dark matter with mass ≳10
.
Abstract
We present Magellan/IMACS spectroscopy of the recently discovered Milky Way satellite Tucana III (Tuc III). We identify 26 member stars in Tuc III from which we measure a mean radial ...velocity of
v
hel
= −102.3 ± 0.4 (stat.) ± 2.0 (sys.)
, a velocity dispersion of
, and a mean metallicity of
. The upper limit on the velocity dispersion is
σ
< 1.5
at 95.5% confidence, and the corresponding upper limit on the mass within the half-light radius of Tuc III is 9.0 × 10
4
M
⊙
. We cannot rule out mass-to-light ratios as large as 240
M
⊙
/
L
⊙
for Tuc III, but much lower mass-to-light ratios that would leave the system baryon-dominated are also allowed. We measure an upper limit on the metallicity spread of the stars in Tuc III of 0.19 dex at 95.5% confidence. Tuc III has a smaller metallicity dispersion and likely a smaller velocity dispersion than any known dwarf galaxy, but a larger size and lower surface brightness than any known globular cluster. Its metallicity is also much lower than those of the clusters with similar luminosity. We therefore tentatively suggest that Tuc III is the tidally stripped remnant of a dark matter-dominated dwarf galaxy, but additional precise velocity and metallicity measurements will be necessary for a definitive classification. If Tuc III is indeed a dwarf galaxy, it is one of the closest external galaxies to the Sun. Because of its proximity, the most luminous stars in Tuc III are quite bright, including one star at
V
= 15.7 that is the brightest known member star of an ultra-faint satellite.
ABSTRACT
Indirect detection strategies of particle dark matter (DM) in Dwarf spheroidal satellite galaxies (dSphs) typically entail searching for annihilation signals above the astrophysical ...background. To robustly compare model predictions with the observed fluxes of product particles, most analyses of astrophysical data – which are generally frequentist – rely on estimating the abundance of DM by calculating the so-called J factor. This quantity is usually inferred from the kinematic properties of the stellar population of a dSph using the Jeans equation, commonly by means of Bayesian techniques that entail the presence (and additional systematic uncertainty) of prior choice. Here, extending earlier work, we develop a scheme to derive the profile likelihood for J factors of dwarf spheroidals for models with five or more free parameters. We validate our method on a publicly available simulation suite, released by the Gaia Challenge, finding satisfactory statistical properties for bias and probability coverage. We present the profile likelihood function and maximum likelihood estimates for the J-factor of 10 dSphs. As an illustration, we apply these profile likelihoods to recently published analyses of γ-ray data with the Fermi Large Area Telescope to derive new, consistent upper limits on the DM annihilation cross-section. We do this for a subset of systems, generally referred to as classical dwarfs. The implications of these findings for DM searches are discussed, together with future improvements and extensions of this technique.
ABSTRACT We search for excess γ-ray emission coincident with the positions of confirmed and candidate Milky Way satellite galaxies using six years of data from the Fermi Large Area Telescope (LAT). ...Our sample of 45 stellar systems includes 28 kinematically confirmed dark-matter-dominated dwarf spheroidal galaxies (dSphs) and 17 recently discovered systems that have photometric characteristics consistent with the population of known dSphs. For each of these targets, the relative predicted γ-ray flux due to dark matter annihilation is taken from kinematic analysis if available, and estimated from a distance-based scaling relation otherwise, assuming that the stellar systems are DM-dominated dSphs. LAT data coincident with four of the newly discovered targets show a slight preference (each 2 local) for γ-ray emission in excess of the background. However, the ensemble of derived γ-ray flux upper limits for individual targets is consistent with the expectation from analyzing random blank-sky regions, and a combined analysis of the population of stellar systems yields no globally significant excess (global significance ). Our analysis has increased sensitivity compared to the analysis of 15 confirmed dSphs by Ackermann et al. The observed constraints on the DM annihilation cross section are statistically consistent with the background expectation, improving by a factor of ∼2 for large DM masses ( and ) and weakening by a factor of ∼1.5 at lower masses relative to previously observed limits.
The dwarf spheroidal satellite galaxies (dSphs) of the Milky Way are some of the most dark matter (DM) dominated objects known. We report on γ-ray observations of Milky Way dSphs based on six years ...of Fermi Large Area Telescope data processed with the new Pass8 event-level analysis. None of the dSphs are significantly detected in γ rays, and we present upper limits on the DM annihilation cross section from a combined analysis of 15 dSphs. These constraints are among the strongest and most robust to date and lie below the canonical thermal relic cross section for DM of mass ≲100 GeV annihilating via quark and τ-lepton channels.
Abstract
Line-of-sight integrals of the squared density, commonly called the J-factor, are essential for inferring dark matter (DM) annihilation signals. The J-factors of DM-dominated dwarf ...spheroidal satellite galaxies (dSphs) have typically been derived using Bayesian techniques, which for small data samples implies that a choice of priors constitutes a non-negligible systematic uncertainty. Here we report the development of a new fully frequentist approach to construct the profile likelihood of the J-factor. Using stellar kinematic data from several classical and ultra-faint dSphs, we derive the maximum likelihood value for the J-factor and its confidence intervals. We validate this method, in particular its bias and coverage, using simulated data from the Gaia Challenge. We find that the method possesses good statistical properties. The J-factors and their uncertainties are generally in good agreement with the Bayesian-derived values, with the largest deviations restricted to the systems with the smallest kinematic data sets. We discuss improvements, extensions, and future applications of this technique.
Recent analysis of the second data release of Gaia has revealed a number of new stellar streams surrounding the Milky Way. It has been suggested that one of these streams, Gjöll, is associated with ...the globular cluster NGC 3201, but thus far the association has only been based on kinematics of the stream stars. In this work we identify five likely stream members in the Gaia data that are bright enough for high-resolution spectroscopic follow-up with the Harlan J. Smith telescope at McDonald Observatory. One star is ruled out as a member based on its radial velocity. Abundance analysis of the remaining four kinematic members reveals a good chemical match to NGC 3201 for two of the stars, driven by their similar Al and -element abundances. Of the remaining two, one shows no chemical similarity to NGC 3201 and is likely an unassociated Milky Way halo field star, while the other exhibits a similar Al abundance but has somewhat lower -element abundances. The chemical tagging of stars in the Gjöll stream to NGC 3201 confirms this association and provides direct proof of the hierarchical formation of the Milky Way.
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