PETAC Mihael
Position : PostDoctorant
Team: LUPM/Particules, Astroparticules, Cosmologie : Théorie
petac
lupm.in2p3.fr
0467143770
Room: 21, Floor: 1, Build.: 13
Research Topics:  sdu/sdu.astr/sdu.astr.co
 sdu/sdu.astr/sdu.astr.ga
 sdu/sdu.astr/sdu.astr.he
 phys/phys.grqc
 phys/phys.astr/phys.astr.ga
 phys/phys.astr/phys.astr.co
 phys/phys.hphe
 phys/phys.astr
 phys/phys.hexp
 sdu/sdu.astr

Scientific productions :


Microlensing constraints on clustered primordial black holes
Author(s): Petac M., Lavalle J., Jedamzik K.
(Article) Published:
Physical Review D, vol. 105 p.083520 (2022)
Links openAccess full text :
Ref Arxiv: 2201.02521
DOI: 10.1103/PhysRevD.105.083520
Ref. & Cit.: NASA ADS
Abstract: The discovery of blackholebinary mergers through their gravitational wave (GW) emission has reopened the exciting possibility that dark matter is made, at least partly, of primordial black holes (PBHs). However, this scenario is challenged by many observational probes that set bounds on the relative PBH abundance across a broad range of viable PBH masses. Among these bounds, the ones coming from microlensing surveys are particularly severe in the mass range from $\sim 10^{10}$ to a few M$_{\odot}$. The upper part of this range precisely corresponds to the mass window inside which the formation of PBHs should be boosted due to the QCD phase transition in the early Universe, which makes the microlensing probes particularly important. However, it has been argued that taking into account the inevitable clustering of PBH on small scales can significantly relax or entirely remove these bounds. While the impact of PBH clustering on the GW event rate has been studied in detail, its impact on the microlensing event rate has not yet been fully assessed. In this Letter, we address this issue, and show that clusters arising from PBH formed from Gaussian initial curvature perturbations do not alter the current microlensing constraints, as they are not sufficiently dense nor massive.
Comments: 9 pages, 1 figure. Comments are welcome!



Testing the predictions of axisymmetric distribution functions of galactic dark matter with hydrodynamical simulations
Author(s): Petac M., Lavalle J., Nunezcastineyra Arturo, Nezri Emmanuel
(Article) Published:
Journal Of Cosmology And Astroparticle Physics, vol. p.031 (2021)
DOI: 10.1088/14757516/2021/08/031
Abstract: Signal predictions for galactic dark matter (DM) searches often rely on assumptions regarding the DM phasespace distribution function (DF) in halos. This applies to both particle (e.g. pwave suppressed or Sommerfeldenhanced annihilation, scattering off atoms, etc.) and macroscopic DM candidates (e.g. microlensing of primordial black holes). As experiments and observations improve in precision, better assessing theoretical uncertainties becomes pressing in the prospect of deriving reliable constraints on DM candidates or trustworthy hints for detection. Most reliable predictions of DFs in halos are based on solving the steadystate collisionless Boltzmann equation (e.g. Eddingtonlike inversions, actionangle methods, etc.) consistently with observational constraints. One can do so starting from maximal symmetries and a minimal set of degrees of freedom, and then increasing complexity. Key issues are then whether adding complexity, which is computationally costy, improves predictions, and if so where to stop. Clues can be obtained by making predictions for zoomedin hydrodynamical cosmological simulations in which one can access the true (coarsegrained) phasespace information. Here, we test an axisymmetric extension of the Eddington inversion to predict the full DM DF from its density profile and the total gravitational potential of the system. This permits to go beyond spherical symmetry, and is a priori well suited for spiral galaxies. We show that axisymmetry does not necessarily improve over spherical symmetry because the (observationally unconstrained) angular momentum of the DM halo is not generically aligned with the baryonic one. Theoretical errors are similar to those of the Eddington inversion though, at the 1020% level for velocitydependent predictions related to particle DM searches in spiral galaxies. We extensively describe the approach and comment on the results.



Equilibrium axisymmetric halo model for the Milky Way and its implications for direct and indirect dark matter searches
Author(s): Petac M.
(Article) Published:
Phys.rev.d, vol. 102 p.123028 (2020)
Links openAccess full text :
Ref Arxiv: 2008.11172
Ref INSPIRE: 1813244
DOI: 10.1103/PhysRevD.102.123028
Ref. & Cit.: NASA ADS
Abstract: We for the first time provide selfconsistent axisymmetric phasespace distribution models for the Milky Way’s dark matter (DM) halo which are carefully matched against the latest kinematic measurements through Bayesian analysis. By using broad priors on the individual galactic components, we derive conservative estimates for the astrophysical factors entering the interpretation of direct and indirect DM searches. While the resulting DM density profiles are in good agreement with previous studies, implying ρ⊙≈10⁻² M⊙/pc3, the presence of baryonic disc leads to significant differences in the local DM velocity distribution in comparison with the standard halo model. For direct detection, this implies roughly 30% stronger cross section limits at DM masses near detectors maximum sensitivity and up to an order of magnitude weaker limits at the lower end of the mass range. Furthermore, by performing Monte Carlo simulations for the upcoming DARWIN and DarkSide20k experiments, we demonstrate that upon successful detection of heavy DM with coupling just below the current limits, the carefully constructed axisymmetric models can eliminate bias and reduce uncertainties by more then 50% in the reconstructed DM coupling and mass, but also help in a more reliable determination of the scattering operator. Furthermore, the velocity anisotropies induced by the baryonic disc can lead to significantly larger annual modulation amplitude and sizable differences in the directional distribution of the expected DMinduced events. For indirect searches, we provide the differential J factors and compute several moments of the relative velocity distribution that are needed for predicting the rate of velocitydependent annihilations. However, we find that accurate predictions are still hindered by large uncertainties regarding the DM distribution near the galactic center.
