KIAS workshop 2014 3 rd November 2014 Evolution

KIAS workshop (2014) 3 rd November, 2014 Evolution of perturbations and cosmological constraints in decaying dark matter models with arbitrary decay mass products Shohei Aoyama Nagoya University Collaborators: Toyokazu Sekiguchi, Kiyotomo Ichiki & Naoshi Sugiyama JCAP 07(2014)021, ar. Xiv: 1402. 2972

CDM and its problem • The ΛCDM model can predict numerous cosmological observations on large scales about temperature anisotropy of the CMB Cl. TT http: //cdn. arstechnica. net/wpand the large scale structure. content/uploads/2013/03/Planck_cosmic_recipe. png • However the nature of dark matter (eg. the mass or interactions ) is still unknown. • In addition, observations on the small scale, the discrepancies between the observations and theoretical predictions. (eg. missing satellite problem)

Planck anomaly Planck collaborations pointed out that σ8 which is estimated from Cl. TT is larger than that from the number counts of cluster by SZ effect on CMB by more than 2σ CL. Planck Collaboration(2013, XX)[1303. 5080]

A prescription of these problems Some mechanisms that suppress small scale structure formation may rescue these problems. (Ostriker & Steinhardt (2003) [astro-ph/0306402]). Decaying dark matter (DDM) is a candidate of these problems because product particles are generated with large momentum and smear out of the gravitational potential which was originated by progenitor particles. Moore+ (1999) [astro-ph/9907411] Planck Collaboration(XX)[1303. 5080]

Our model of DDM • We consider the DDM which decays into two product dark matter particles. In this case, the decaying process and the time evolutions of distribution functions of dark matter particles can be characterized by 4 parameters. • In our calculation, by solving Boltzmann equations for these product particles directly, one can take the mass of one of daughter particles arbitrary and obtain the time evolutions of density perturbations, Cl. TT and σ8. • • •

The effect on Cl. TT peak shift integrated SW

Our model of DDM • We consider the DDM which decays into two product dark matter particles. In this case, the decaying process and the time evolutions of distribution functions of dark matter particles can be characterized by 4 parameters. • In this work, we set the constraint on the lifetime of DDM from σ8 estimated from BOSS III data. 　 σ8=0. 80± 0. 02 Sánchez et al. (2012)[ar. Xiv: 1203. 6616])

The constraint on the lifetime of DDM This SDSS data excluded σ8 < 0. 76 on 2 σ CL. 2σ anomaly The lifetime of the DDM should be longer than 200 Gyr in the case relativistic decay. This constraint is consistent with previous works (Ichiki et al. (2004), [astro-ph: astro-ph/0403164]).

Planck anomaly Favored region The DDM whose lifetime of DDM is around 200 Gyr and which decays into two relativistic particles can explain observational Cl. TT and the number of clusters.

The power spectrum of CMB lens potential Clφφ ―m. D 1/m. M=0. 3 ―m. D 1/m. M=0. 9 ― ΛCDM The DDM which decays into two relativistic particles is not ruled out from the current CMB lensing observation.

Conclusion • We consider the decaying dark matter which decays two particles and its effect on the cosmological observables. • Even in the case that the finite mass of one of product particles, the lifetime should be larger than 200 Gyr. • DDM may reconcile the tension between the observed σ8 estimated from Cl. TT and that from number counts of 　 cluster from SZ effect.