Ref Arxiv: 2210.07210
DOI: 10.1093/mnras/stad512
Ref. & Cit.: NASA ADS
Résumé:

Line-of-sight effects in strong gravitational lensing have long been treated as a nuisance. However, it was recently proposed that the line-of-sight shear could be a cosmological observable in its own right, if it is not degenerate with lens model parameters. Using the formalism introduced by Fleury et al. (2021a), we firstly demonstrate that the line-of-sight shear can be accurately measured from a simple simulated strong lensing image with percent precision. We then extend our analysis to more complex simulated images and stress test the recovery of the line-of-sight shear when using deficient fitting models, finding that it escapes from degeneracies with lens model parameters, albeit at the expense of the precision. Lastly, we check the validity of the tidal approximation by simulating and fitting an image generated in the presence of many line-of-sight dark matter haloes, finding that an explicit violation of the tidal approximation does not necessarily prevent one from measuring the line-of-sight shear.

Commentaires: 16 + 3 pages, 14 figures, prepared for submission to MNRAS

Ref Arxiv: 2206.03059
DOI: 10.1088/1475-7516/2022/09/076
Ref. & Cit.: NASA ADS
Résumé:

We analyse the clustering of matter on large scales in an extension of the concordance model that allows for spatial curvature. We develop a consistent approach to curvature and wide-angle effects on the galaxy 2-point correlation function in redshift space. In particular we derive the Alcock-Paczynski distortion of $f\sigma_{8}$, which differs significantly from empirical models in the literature. A key innovation is the use of the `Clustering Ratio', which probes clustering in a different way to redshift-space distortions, so that their combination delivers more powerful cosmological constraints. We use this combination to constrain cosmological parameters, without CMB information. In a curved Universe, we find that $\Omega_{{\rm m}, 0}=0.26\pm 0.04$ (68\% CL). When the clustering probes are combined with low-redshift background probes -- BAO and SNIa -- we obtain a CMB-independent constraint on curvature: $\Omega_{K,0} = 0.0041\,_{-0.0504}^{+0.0500}$. We find no Bayesian evidence that the flat concordance model can be rejected. In addition we show that the sound horizon at decoupling is $r_{\rm d} = 144.57 \pm 2.34 \; {\rm Mpc}$, in agreement with its measurement from CMB anisotropies. As a consequence, the late-time Universe is compatible with flat $\Lambda$CDM and a standard sound horizon, leading to a small value of $H_{0}$, {\em without} assuming any CMB information. Clustering Ratio measurements produce the only low-redshift clustering data set that is not in disagreement with the CMB, and combining the two data sets we obtain $\Omega_{K,0}= -0.023 \pm 0.010$.

Commentaires: 40 pages; 13 figures; Version accepted by JCAP. Réf Journal: JCAP09(2022)076

DOI: 10.1103/PhysRevD.105.063525
Résumé:

Recent weak lensing surveys have revealed that the direct measurement of the parameter combination S8≡σ8(Ωm/0.3)0.5S8​≡σ8​(Ωm​/0.3)0.5-- where σ8σ8​ is a measure of the amplitude of matter fluctuations on 8 h−1h−1Mpc scales -- is ∼3σ∼3σ discrepant with the value reconstructed from cosmic microwave background (CMB) data assuming the ΛΛCDM model. In this article, we show that it is possible to resolve the tension if dark matter (DM) decays with a lifetime of Γ−1≃55 GyrsΓ−1≃55 Gyrs into one massless and one massive product, and transfers a fraction ε≃0.7 %ε≃0.7 % of its rest mass energy to the massless component. The velocity-kick received by the massive daughter leads to a suppression of gravitational clustering below its free-streaming length, thereby reducing the σ8σ8​ value as compared to that inferred from the standard ΛΛCDM model, in a similar fashion to massive neutrino and standard warm DM. Contrarily to the latter scenarios, the time-dependence of the power suppression and the free-streaming scale allows the 2-body decaying DM scenario to accommodate CMB, baryon acoustic oscillation, growth factor and un-calibrated supernova Ia data. We briefly discuss implications for DM model building, galactic small-scale structure problems and the recent Xenon-1T excess. Future experiments measuring the growth factor to high accuracy at 0≲z≲10≲z≲1 can further test this scenario.

Résumé:

We study regions in the parameter space of the NMSSM which are able to simultaneously explain the current measured values for the W mass MW and the muon anomalous magnetic moment aμ, and provide a dark matter relic density consistent with the observations as well as constraints from detection experiments. The corresponding regions feature light charginos, sleptons and staus in the 100-600 GeV range, at least some of them with masses below 150 GeV such that the electroweakly-interacting SUSY particles generate sufficiently large contributions to MW. The LSP is always singlino-like with a mass below 140 GeV, and could possibly remain invisible even at future detection experiments. De- cays of electroweak sparticles proceed through cascades via staus and/or sleptons which makes their detection challenging. The lightest CP-even scalar may have a mass in the 95-98 GeV range with, however, modest signal rates in view of the mild excesses reported in this range at LEP and by CMS at the LHC.

Ref HAL: hal-03622519,_v2
Ref Arxiv: 2203.07440
Ref INSPIRE: 2052488
DOI: 10.1103/PhysRevD.106.023516
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote

DOI: 10.1088/1475-7516/2022/10/021
Résumé:

Gamma-ray observations have long been used to constrain the properties of dark matter (DM), with a strong focus on weakly interacting massive particles annihilating through velocity-independent processes. However, in the absence of clear-cut observational evidence for the simplest candidates, the interest of the community in more complex DM scenarios involving a velocity-dependent cross-section has been growing steadily over the past few years. We present the first systematic study of velocity-dependent DM annihilation (in particular $p$-wave annihilation and Sommerfeld enhancement) in a variety of astrophysical objects, not only including the well-studied Milky Way dwarf satellite galaxies, but nearby dwarf irregular galaxies and local galaxy clusters as well. Particular attention is given to the interplay between velocity dependence and DM halo substructure. Uncertainties related to halo mass, phase-space and substructure modelling are also discussed in this velocity-dependent context. We show that, for $s$-wave annihilation, extremely large subhalo boost factors are to be expected, up to $10^{11}$ in clusters and up to $10^6-10^7$ in dwarf galaxies where subhalos are usually assumed not to play an important role. Boost factors for $p$-wave annihilation are smaller but can still reach $10^3$ in clusters. The angular extension of the DM signal is also significantly impacted, with e.g. the cluster typical emission radius increasing by a factor of order 10 in the $s$-wave case. We also compute the signal contrast of the objects in our sample with respect to annihilation happening in the Milky Way halo. Overall, we find that the hierarchy between the brightest considered targets depends on the specific details of the assumed particle-physics model.

Ref HAL: hal-03625359_v1
Ref Arxiv: 2203.16491
Ref INSPIRE: 2060145
DOI: 10.1088/1475-7516/2023/02/004
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote