The discovery of neutrino masses through the observation of oscillations boosted the importance of neutrinoless double beta decay ( 0 ν β β ). In this paper, we review the main features of this ...process, underlining its key role from both the experimental and theoretical point of view. In particular, we contextualize the 0 ν β β in the panorama of lepton number violating processes, also assessing some possible particle physics mechanisms mediating the process. Since the 0 ν β β existence is correlated with neutrino masses, we also review the state of the art of the theoretical understanding of neutrino masses. In the final part, the status of current 0 ν β β experiments is presented and the prospects for the future hunt for 0 ν β β are discussed. Also, experimental data coming from cosmological surveys are considered and their impact on 0 ν β β expectations is examined.
We perform an extensive suite of N-body simulations of the matter power spectrum, incorporating massive neutrinos in the range M
ν= 0.15-0.6 eV, probing the non-linear regime at scales k < 10 h Mpc−1 ...at z < 3. We extend the widely used halofit approximation to account for the effect of massive neutrinos on the power spectrum. In the strongly non-linear regime, halofit systematically overpredicts the suppression due to the free streaming of the neutrinos. The maximal discrepancy occurs at k∼ 1h Mpc−1, and is at the level of 10 per cent of the total suppression. Most published constraints on neutrino masses based on halofit are not affected, as they rely on data probing the matter power spectrum in the linear or mildly non-linear regime. However, predictions for future galaxy, Lyman α forest and weak lensing surveys extending to more non-linear scales will benefit from the improved approximation to the non-linear matter power spectrum we provide. Our approximation reproduces the induced neutrino suppression over the targeted scales and redshifts significantly better. We test its robustness with regard to changing cosmological parameters and a variety of modelling effects.
We present results of cosmological N-body hydrodynamic chemistry simulations of primordial structure growth and evolution in a scenario with warm dark matter (WDM) having a mass of 3 keV (thermal ...relic) and compare with a model consisting of standard cold dark matter (CDM). We focus on the high-redshift universe (z > 6), where the structure formation process should better reflect the primordial (linear) differences in terms of matter power spectrum. We find that early epochs can be exceptional probes of the dark matter nature. Non-linear WDM power spectra and mass functions are up to 2 dex lower than in CDM and show spreads of factor of a few persisting in the whole first Gyr. Runaway molecular cooling in WDM haloes results severely inhibited because of the damping of power at large k modes and hence cosmic (Populations III and II-I) star formation rate (SFR) is usually suppressed with respect to CDM predictions. Luminous objects formed in a WDM background are very rare at z > 10, due to the sparser and retarded evolution of early WDM minihaloes during the dark ages and their lack can be fitted with a simple analytical formula depending only on magnitude and redshift. Future high-z observations of faint galaxies have the potential to discriminate between CDM and WDM scenarios by means of cosmic stellar mass density and specific SFR, as well. When compared to the effects of alternative cosmologies (e.g. non-Gaussian or dark energy models) or of high-order corrections at large z (e.g. primordial streaming motions or changes in the pristine initial mass function) the ones caused by WDM are definitely more dramatic.
ABSTRACT
We present a comprehensive analysis of atomic hydrogen (H i) properties using a semi-analytical model of galaxy formation and N-body simulations covering a large cosmological volume at high ...resolution. We examine the H i mass function and the H i density, characterizing both their redshift evolution and their dependence on hosting halo mass. We analyse the H i content of dark matter haloes in the local Universe and up to redshift z = 5, discussing the contribution of different galaxy properties. We find that different assembly history plays a crucial role in the scatter of this relation. We propose new fitting functions useful for constructing mock H i maps with halo occupation distribution techniques. We investigate the H i clustering properties relevant for future 21 cm intensity mapping (IM) experiments, including the H i bias and the shot-noise level. The H i bias increases with redshift and it is roughly flat on the largest scales probed. The scale dependence is found at progressively larger scales with increasing redshift, apart from a dip feature at z = 0. The shot-noise values are consistent with the ones inferred by independent studies, confirming that shot noise will not be a limiting factor for IM experiments. We detail the contribution from various galaxy properties on the H i power spectrum and their relation to the halo bias. We find that H i poor satellite galaxies play an important role at the scales of the one-halo term. Finally, we present the 21 cm signal in redshift space, a fundamental prediction to be tested against data from future radio telescopes such as Square Kilometre Array.
Abstract
We present high signal-to-noise galaxy–galaxy lensing measurements of the Baryon Oscillation Spectroscopic Survey constant mass (CMASS) sample using 250 deg2 of weak-lensing data from ...Canada–France–Hawaii Telescope Lensing Survey and Canada–France–Hawaii Telescope Stripe 82 Survey. We compare this signal with predictions from mock catalogues trained to match observables including the stellar mass function and the projected and two-dimensional clustering of CMASS. We show that the clustering of CMASS, together with standard models of the galaxy–halo connection, robustly predicts a lensing signal that is 20–40 per cent larger than observed. Detailed tests show that our results are robust to a variety of systematic effects. Lowering the value of
$S_{\rm 8}=\sigma _{\rm 8} \sqrt{\Omega _{\rm m}/0.3}$
compared to Planck Collaboration XIII reconciles the lensing with clustering. However, given the scale of our measurement (r < 10 h
−1 Mpc), other effects may also be at play and need to be taken into consideration. We explore the impact of baryon physics, assembly bias, massive neutrinos and modifications to general relativity on ΔΣ and show that several of these effects may be non-negligible given the precision of our measurement. Disentangling cosmological effects from the details of the galaxy–halo connection, the effect of baryons, and massive neutrinos, is the next challenge facing joint lensing and clustering analyses. This is especially true in the context of large galaxy samples from Baryon Acoustic Oscillation surveys with precise measurements but complex selection functions.
Cosmological neutrinos strongly affect the evolution of the largest structures in the Universe, i.e. galaxies and galaxy clusters. We use large box-size full hydrodynamic simulations to investigate ...the non-linear effects that massive neutrinos have on the spatial properties of cold dark matter (CDM) haloes. We quantify the difference with respect to the concordance ΛCDM model of the halo mass function and of the halo two-point correlation function. We model the redshift-space distortions and compute the errors on the linear distortion parameter β introduced if cosmological neutrinos are assumed to be massless. We find that, if not taken correctly into account and depending on the total neutrino mass M
ν, these effects could lead to a potentially fake signature of modified gravity. Future nearly all-sky spectroscopic galaxy surveys will be able to constrain the neutrino mass if M
ν≳ 0.6 eV, using β measurements alone and independently of the value of the matter power spectrum normalization σ8. In combination with other cosmological probes, this will strengthen neutrino mass constraints and help breaking parameter degeneracies.
PDF
