81 research outputs found
Large scale distribution of total mass versus luminous matter from Baryon Acoustic Oscillations: First search in the SDSS-III BOSS Data Release 10
Baryon Acoustic Oscillations (BAOs) in the early Universe are predicted to
leave an as yet undetected signature on the relative clustering of total mass
versus luminous matter. A detection of this effect would provide an important
confirmation of the standard cosmological paradigm and constrain alternatives
to dark matter as well as non-standard fluctuations such as Compensated
Isocurvature Perturbations (CIPs). We conduct the first observational search
for this effect, by comparing the number-weighted and luminosity-weighted
correlation functions, using the SDSS-III BOSS Data Release 10 CMASS sample.
When including CIPs in our model, we formally obtain evidence at of
the relative clustering signature and a limit that matches the existing upper
limits on the amplitude of CIPs. However, various tests suggest that these
results are not yet robust, perhaps due to systematic biases in the data. The
method developed in this Letter, used with more accurate future data such as
that from DESI, is likely to confirm or disprove our preliminary evidence.Comment: 6 pages, 2 figures, accepted for publication in PR
Statistical Determination of Bulk Flow Motions
We present here a new parameterization for the bulk motions of galaxies and
clusters (in the linear regime) that can be measured statistically from the
shape and amplitude of the two-dimensional two-point correlation function. We
further propose the one-dimensional velocity dispersion (v_p) of the bulk flow
as a complementary measure of redshift-space distortions, which is
model-independent and not dependent on the normalisation method. As a
demonstration, we have applied our new methodology to the C4 cluster catalogue
constructed from Data Release Three (DR3) of the Sloan Digital Sky Survey. We
find v_p=270^{+433}km/s (also consistent with v_p=0) for this cluster sample
(at z=0.1), which is in agreement with that predicted for a WMAP5-normalised
LCDM model (i.e., v_p(LCDM=203km/s). This measurement does not lend support to
recent claims of excessive bulk motions (\simeq1000 km/s) which appear in
conflict with LCDM, although our large statistical error cannot rule them out.
From the measured coherent evolution of v_p, we develop a technique to
re-construct the perturbed potential, as well as estimating the unbiased matter
density fluctuations and scale--independent bias.Comment: 8 pages, 5 figure
First results on monolithic CMOS detector with internal gain
: In this paper we report on a set of characterisations carried out on the first monolithic
LGAD prototype integrated in a customised 110 nm CMOS process having a depleted active volume
thickness of 48 μm. This prototype is formed by a pixel array where each pixel has a total size of
100 μm × 250 μm and includes a high-speed front-end amplifier. After describing the sensor and
the electronics architecture, both laboratory and in-beam measurements are reported and described. Optical characterisations performed with an IR pulsed laser setup have shown a sensor internal gain of
about 2.5. With the same experimental setup, the electronic jitter was found to be between 50 ps and
150 ps, depending on the signal amplitude. Moreover, the analysis of a test beam performed at the
Proton Synchrotron (PS) T10 facility of CERN with 10 GeV/c protons and pions indicated that the
overall detector time resolution is in the range of 234 ps to 244 ps. Further TCAD investigations, based
on the doping profile extracted from C(V) measurements, confirmed the multiplication gain measured
on the test devices. Finally, TCAD simulations were used to tune the future doping concentration of
the gain layer implant, targeting sensors with a higher avalanche gain. This adjustment is expected
to enhance the timing performance of the sensors of the future productions, in order to cope with
the high event rate expected in most of the near future high-energy and high-luminosity physics
experiments, where the time resolution will be essential to disentangle overlapping events and it
will also be crucial for Particle IDentification (PID
Delivery of costimulatory blockade to lymph nodes promotes transplant acceptance in mice
The lymph node (LN) is the primary site of alloimmunity activation and regulation during transplantation. Here, we investigated how fibroblastic reticular cells (FRCs) facilitate the tolerance induced by anti-CD40L in a murine model of heart transplantation. We found that both the absence of LNs and FRC depletion abrogated the effect of anti-CD40L in prolonging murine heart allograft survival. Depletion of FRCs impaired homing of T cells across the high endothelial venules (HEVs) and promoted formation of alloreactive T cells in the LNs in heart-transplanted mice treated with anti-CD40L. Single-cell RNA sequencing of the LNs showed that anti-CD40L promotes a Madcam1+ FRC subset. FRCs also promoted the formation of regulatory T cells (Tregs) in vitro. Nanoparticles (NPs) containing anti-CD40L were selectively delivered to the LNs by coating them with MECA-79, which binds to peripheral node addressin (PNAd) glycoproteins expressed exclusively by HEVs. Treatment with these MECA-79-anti-CD40L-NPs markedly delayed the onset of heart allograft rejection and increased the presence of Tregs. Finally, combined MECA-79-anti-CD40L-NPs and rapamycin treatment resulted in markedly longer allograft survival than soluble anti-CD40L and rapamycin. These data demonstrate that FRCs are critical to facilitating costimulatory blockade. LN-targeted nanodelivery of anti-CD40L could effectively promote heart allograft acceptance
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey : baryon acoustic oscillations in the Data Releases 10 and 11 Galaxy samples
We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations (BAO) in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey, which is part of the Sloan Digital Sky Survey III. Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2 < z < 0.7. We also compare these results with those from the publicly released DR9 and DR10 samples. Assuming a concordance Λ cold dark matter (ΛCDM) cosmological model, the DR11 sample covers a volume of 13 Gpc3 and is the largest region of the Universe ever surveyed at this density. We measure the correlation function and power spectrum, including density-field reconstruction of the BAO feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid = 149.28 Mpc in our fiducial cosmology. We find DV = (1264 ± 25 Mpc)(rd/rd,fid) at z = 0.32 and DV = (2056 ± 20 Mpc)(rd/rd,fid) at z = 0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line of sight yields measurements at z = 0.57 of DA = (1421 ± 20 Mpc)(rd/rd,fid) and H = (96.8 ± 3.4 km s−1 Mpc−1)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat CDM model with a cosmological constant.Publisher PDFPeer reviewe
Measurements of the Cherenkov effect in direct detection of charged particles with SiPMs
In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been
tested with charged particles to characterize the Cherenkov light produced in
the sensor protection layer. A careful position scan of the SiPM response has
been performed with different prototypes, confirming the large number of firing
cells and proving almost full efficiency, with the SiPM filling factor
essentially negligible. This study also allowed us to study the time resolution
of such devices as a function of the number of firing cells, reaching values
below 20 ps. These measurements provide significant insight into the
capabilities of SiPM sensors in direct detection of charged particles and their
potential for several applications
Star/galaxy separation at faint magnitudes: application to a simulated Dark Energy Survey
We address the problem of separating stars from galaxies in future large photometric surveys. We focus our analysis on simulations of the Dark Energy Survey (DES). In the first part of the paper, we derive the science requirements on star/galaxy separation, for measurement of the cosmological parameters with the gravitational weak lensing and large-scale structure probes. These requirements are dictated by the need to control both the statistical and systematic errors on the cosmological parameters, and by point spread function calibration. We formulate the requirements in terms of the completeness and purity provided by a given star/galaxy classifier. In order to achieve these requirements at faint magnitudes, we propose a new method for star/galaxy separation in the second part of the paper. We first use principal component analysis to outline the correlations between the objects parameters and extract from it the most relevant information. We then use the reduced set of parameters as input to an Artificial Neural Network. This multiparameter approach improves upon purely morphometric classifiers (such as the classifier implemented in SExtractor), especially at faint magnitudes: it increases the purity by up to 20 per cent for stars and by up to 12 per cent for galaxies, at i-magnitude fainter than 2
The DESI survey validation : results from visual inspection of bright galaxies, luminous red galaxies, and emission line galaxies
Funding: TWL was supported by the Ministry of Science and Technology (MOST 111-2112-M-002-015-MY3), the Ministry of Education, Taiwan (MOE Yushan Young Scholar grant NTU-110VV007), National Taiwan University research grants (NTU CC-111L894806, NTU- 111L7318), and NSF grant AST-1911140. DMA acknowledges the Science Technology and Facilities Council (STFC) for support through grant code ST/T000244/1. This research is supported by the Director, Office of Science, Office of High Energy Physics of the U.S. Department of Energy under Contract No. DE–AC02–05CH11231, and by the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility under the same contract; additional support for DESI is provided by the U.S. National Science Foundation, Division of Astronomical Sciences under Contract No. AST-0950945 to the NSF’s National Optical-Infrared Astronomy Research Laboratory; the Science and Technologies Facilities Council of the United Kingdom; the Gordon and Betty Moore Foundation; the Heising-Simons Foundation; the French Alternative Energies and Atomic Energy Commission (CEA); the National Council of Science and Technology of Mexico (CONACYT); the Ministry of Science and Innovation of Spain (MICINN), and by the DESI Member Institutions: https://www.desi.lbl.gov/ collaborating-institutions.The Dark Energy Spectroscopic Instrument (DESI) Survey has obtained a set of spectroscopic measurements of galaxies for validating the final survey design and target selections. To assist these tasks, we visually inspect (VI) DESI spectra of approximately 2,500 bright galaxies, 3,500 luminous red galaxies, and 10,000 emission line galaxies, to obtain robust redshift identifications. We then utilize the VI redshift information to characterize the performance of the DESI operation. Based on the VI catalogs, our results show that the final survey design yields samples of bright galaxies, luminous red galaxies, and emission line galaxies with purity greater than 99%. Moreover, we demonstrate that the precision of the redshift measurements is approximately 10 km/s for bright galaxies and emission line galaxies and approximately 40 km/s for luminous red galaxies. The average redshift accuracy is within 10 km/s for the three types of galaxies. The VI process also helps to improve the quality of the DESI data by identifying spurious spectral features introduced by the pipeline. Finally, we show examples of unexpected real astronomical objects, such as Lyman α emitters and strong lensing candidates, identified by VI. These results demonstrate the importance and utility of visually inspecting data from incoming and upcoming surveys, especially during their early operation phases.Publisher PDFPeer reviewe
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