The observational cosmology with distant Type Ia supernovae (SNe) as standard candles claims that the Universe is in accelerated expansion, caused by a large fraction of dark energy. In this paper we investigate the SN Ia environment, studying the impact of the nature of their host galaxies on the Hubble diagram fitting. The supernovae (192 SNe) used in the analysis were extracted from Joint-Light-curves-Analysis (JLA) compilation of high-redshift and nearby supernovae which is the best one to date. The analysis is based on the empirical fact that SN Ia luminosities depend on their light curve shapes and colors. We confirm that the stretch parameter of Type Ia supernovae is correlated with the host galaxy type. The supernovae with lower stretch are hosted mainly in elliptical and lenticular galaxies. No significant correlation between SN Ia colour and host morphology was found.We also examine how the luminosities of SNe Ia change depending on host * Corresponding author Email addresses: henne-vincent@wanadoo.fr (V. Henne), pruzhinskaya@gmail.com (M. V. Pruzhinskaya), philippe.rosnet@clermont.in2p3.fr (P. Rosnet), pierre-francois.leget@clermont.in2p3.fr (P.-F. Léget), emille.ishida@clermont.in2p3.fr (E. E. O. Ishida), ciulli@clermont.in2p3.fr (A. Ciulli), philippe.gris@clermont.in2p3.fr (P. Gris), louis-pierre.says@clermont.in2p3.fr (L.-P. Says), emmanuel.gangler@clermont.in2p3.fr (and E. Gangler) Preprint submitted to New AstronomyAugust 15, 2016 galaxy morphology after stretch and colour corrections. Our results show that in old stellar populations and low dust environments, the supernovae are slightly fainter. SNe Ia in elliptical and lenticular galaxies have a higher α (slope in luminosity-stretch) and β (slope in luminosity-colour) parameter than in spirals. However, the observed shift is at the 1-σ uncertainty level and, therefore, can not be considered as significant. We confirm that the supernova properties depend on their environment and that the incorporation of a host galaxy term into the Hubble diagram fit is expected to be crucial for future cosmological analyses.

Context. Type Ia Supernovae (SNe Ia) are widely used to measure the expansion of the Universe. To perform such measurements the luminosity and cosmological redshift (z) of the SNe Ia have to be determined. The uncertainty on z includes an unknown peculiar velocity, which can be very large for SNe Ia in the virialized cores of massive clusters. Aims. We determine which SNe Ia exploded in galaxy clusters. We then study how the correction for peculiar velocities of host galaxies inside the clusters improves the Hubble residuals. Methods. Using 145 SNe Ia from the Nearby Supernova Factory we found 11 candidates for membership in clusters. To estimate the redshift of a cluster we applied the bi-weight technique. Then, we use the galaxy cluster redshift instead of the host galaxy redshift to construct the Hubble diagram. Results. For SNe Ia inside galaxy clusters the dispersion around the Hubble diagram when peculiar velocities are taken into account is smaller in comparison with a case without peculiar velocity correction, with a wRMS =0.130 ± 0.038 mag instead of wRMS =0.137 ± 0.036 mag. The significance of this improvement is 3.58 σ. If we remove the very nearby Virgo cluster member SN2006X (z < 0.01) from the analysis, the significance decreases to 1.34 σ. The peculiar velocity correction is found to be highest for the SNe Ia hosted by blue spiral galaxies, with high local specific star formation rate and smaller stellar mass, seemingly counter to what might be expected given the heavy concentration of old, massive elliptical galaxies in clusters. Conclusions. As expected, the Hubble residuals of SNe Ia associated with massive galaxy clusters improve when the cluster redshift is taken as the cosmological redshift of the SN. This fact has to be taken into account in future cosmological analyses in order to achieve higher accuracy for cosmological redshift measurements. Here we provide an approach to do so.

In this article we discuss some consequences of the well-known proposition of Fritz Zwicky [1], published in the nineteen thirties, that Dark Matter 'mimics' the inertiagravitational behaviour of usual matter. In particular, we consider some special dynamical regions such as those of the Ring Systems of the gaseous giants at the edge of the Planetary System. This article is a continuation of an earlier paper [2], where it was shown that gravitationally interacting particles may remain near the Lagrange Points L4 and L5 for many thousands of years. This provides enough time for the Dark Matter, if present there, to interact with the usual matter. We discuss also a number of questions related to places which might be considered singular in the mathematical sense.