LAVALLE Julien
Fonction : CR1 CNRS
Thème de Recherche: LUPM/Interactions fondamentales, Astroparticules et Cosmologie
lavalle
in2p3.fr
39 61
Bureau: 23, Etg: 1, Bât: 13
Administration Nationale: 
Administration Locale: Direction/codirection de laboratoire
 Direction d'équipe

Activités de Recherche: 
Aspects théoriques/phénoménologiques de la matière sombre et du rayonnement cosmique. Theoretical/phenomenological aspects of dark matter and cosmic rays. 
Participation(s) à Projets: 

Domaines de Recherche:  Physique/Astrophysique/Phénomènes cosmiques de haute energie
 Physique/Astrophysique/Cosmologie et astrophysique extragalactique
 Physique/Physique des Hautes Energies  Phénoménologie
 Physique/Astrophysique/Astrophysique galactique
 Physique/Astrophysique
 Planète et Univers/Astrophysique/Cosmologie et astrophysique extragalactique
 Planète et Univers/Astrophysique/Astrophysique galactique
 Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
 Physique/Physique des Hautes Energies  Expérience
 Planète et Univers/Astrophysique

Dernieres productions scientifiques :


Statistics for dark matter subhalo searches in gamma rays from a kinematically constrained population model. I: FermiLATlike telescopes
Auteur(s): Facchinetti G., Lavalle J., Stref M.
(Document sans référence bibliographique) 20200720
Résumé: Cold dark matter subhalos are expected to populate galaxies in numbers. If dark matter
selfannihilates, these objects turn into prime targets for indirect searches, in particular
with gammaray telescopes. Incidentally, the FermiLAT catalog already contains many unidentified
sources that might be associated with subhalos. In this paper, we infer the statistics of those
subhalos which could be identified as gammaray pointlike sources from their predicted
distribution properties. We use a semianalytical model for the Galactic subhalo population,
which, in contrast to cosmological simulations, can be made fully consistent with current
kinematic constraints in the Milky Way and has no resolution limit. The model incorporates
tidal stripping, predicted from a realistic distribution of baryons in the Milky Way. The same
baryonic distribution contributes a diffuse gammaray foreground, which adds up to that, often
neglected, induced by the smooth dark matter and the unresolved subhalos. This idealized
configuration, as viewed by an idealized telescope \`a la FermiLAT, implies a correlation between
pointlike subhalo signals and diffuse background. Based on this modeling, we compute the
full statistics semianalytically, and accurately determine the distribution properties of the
most luminous subhalos in the sky (relative to background). We find a number of
visible subhalos of order ${\cal O}(01)$ for optimistic model parameters and a WIMP mass of
100~GeV, maximized for a cored host halo. This barely provides support to the current
interpretation of several Fermi unidentified sources as subhalos. We also find that it is more
likely to detect the smooth Galactic halo itself before subhalos, should dark matter
in the GeVTeV mass range selfannihilate through $s$wave processes.



Predicting the dark matter velocity distribution in galactic structures: tests against hydrodynamic cosmological simulations
Auteur(s): Lacroix T., Nunezcastineyra Arturo, Stref M., Lavalle J., Nezri Emmanuel
(Article) Publié:
Journal Of Cosmology And Astroparticle Physics, vol. p.031 (2020)
DOI: 10.1088/14757516/2020/10/031
Résumé: Reducing theoretical uncertainties in Galactic dark matter (DM) searches is an important challenge as several experiments are now delving into the parameter space relevant to popular (particle or not) candidates. Since many DM signal predictions rely on the knowledge of the DM velocity distributiondirect searches, capture by stars, $p$wavesuppressed or Sommerfeldenhanced annihilation rate, microlensing of primordial black holes, \etcit is necessary to assess the
accuracy of our current theoretical handle. Beyond Maxwellian approximations or adhoc extrapolations of fits on cosmological simulations, approaches have been proposed to selfconsistently derive the DM phasespace distribution only from the detailed mass content of the Galaxy and some symmetry assumptions (\eg~the Eddington inversion and its anisotropic
extensions). Although theoretically sound, these methods are still based on simplifying assumptions and their relevance to real galaxies can be questioned. In this paper, we use zoomedin cosmological simulations to quantify the associated uncertainties. Assuming isotropy, we predict the speed distribution and its moments from the DM and baryonic content measured in simulations, and compare them with the true ones. We reach a predictivity down to $\sim 10$\% for some observables, significantly better than some Maxwellian models. This moderate theoretical error is particularly encouraging at a time when stellar surveys like the \textit{Gaia} mission should
allow us to improve constraints on Galactic mass models.



Galactic halo size in the light of recent AMS02 data
Auteur(s): Weinrich N., Boudaud M., Derome L., Genolini Y., Lavalle J., Maurin D., Salati P., Serpico P., Weymanndespres G.
(Article) Publié:
Astronomy & Astrophysics, vol. 639 p.A74 (2020)
Texte intégral en Openaccess :
Ref Arxiv: 2004.00441
DOI: 10.1051/00046361/202038064
Ref. & Cit.: NASA ADS
1 citation
Résumé: Context. The vertical diffusive halo size of the Galaxy, $L$, is a key parameter for dark matter indirect searches. It can be better determined thanks to recent AMS02 data.
Aims. We set constraints on $L$ from Be/B and $^{10}$Be/Be data, and we performed a consistency check with positron data. We detail the dependence of Be/B and $^{10}$Be/Be on $L$ and forecast on which energy range better data would be helpful for future $L$ improvements.
Methods. We used USINE V3.5 for the propagation of nuclei, and e+ were calculated with the pinching method.
Results. The current AMS02 Be/B (∼3% precision) and ACECRIS $^(10)$Be/Be (∼10% precision) data bring similar and consistent constraints on $L$. The AMS02 Be/B data alone constrain $L = 5_{−2}^{+3}$ kpc at a 68% confidence level (spanning different benchmark transport configurations), a range for which most models do not overproduce positrons. Future experiments need to deliver percentlevel accuracy on 10Be/9Be anywhere below 10 GV to further constrain $L$.
Conclusions. Forthcoming AMS02, HELIX, and PAMELA $^{10}Be/$^{9}$Be results will further test and possibly tighten the limits derived here. Elemental ratios involving radioactive species with different lifetimes (e.g. Al/Mg and Cl/Ar) are also awaited to provide complementary and robuster constraints.



Dynamically constrained model of galactic subhalos and impact on dark matter searches
Auteur(s): Stref M., Lavalle J.
Conference: 15th International Conference on Topics in Astroparticle and Underground Physics (Sudbury, CA, 20170724)
Actes de conférence: J.Phys.Conf.Ser., vol. 1342 p.012079 (2020)
Texte intégral en Openaccess :



AMS02 antiprotons are consistent with a secondary astrophysical origin
Auteur(s): Boudaud Mathieu, Génolini Yoann, Derome Laurent, Lavalle J., Maurin David, Salati Pierre, Serpico Pasquale Dario
(Article) Publié:
Physical Review Research, vol. 2 p.023022 (2020)
Texte intégral en Openaccess :

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