We measure F814W surface brightness fluctuations (SBFs) for a sample of distant shell galaxies with radial velocities ranging from 4000 to 8000 km s À1 . The distance at galaxies is then evaluated by using the SBF method. For this purpose, theoretical SBF magnitudes for the HST ACS filters are computed for single-burst stellar populations covering a wide range of ages (t ¼ 1:5Y14 Gyr) and metallicities (Z ¼ 0:008Y0:04). Using these stellar population models, we provide the firstM F814W versus ( F475W À F814W ) 0 calibration and we extend the previous M 1 versus (B À I ) 0 color relation to colors (B À I ) 0 2:0 mag. Coupling our SBF measurements with the theoretical calibration we derive distances with a statistical uncertainty of $8%, and systematic error of $6%. The procedure developed to analyze data ensures that the indetermination due to possible unmasked residual shells is well below $12%. The results suggest that optical SBFs can be measured at d ! 100 Mpc with HST ACS imaging. SBF-based distances coupled with recession velocities corrected for peculiar motion, allow us obtain H 0 ¼ 76 AE 6 (statistical) AE5 (systematic) km s À1 Mpc À1 .

Aims. We present optical and near-infrared (NIR) photometry of supernova (SN) 2008fv and a brief investigation of SN type Ia to search for possible correlations between the properties of NIR light curves and the optical decline rate. Methods. We analyse our BVRI and JHK observations to derive light curves (LCs), colour curves, and the bolometric behaviour of SN 2008fv. Data range from about five days before to two months after maximum. We also collect a database of the main characteristics of NIR LCs of SNe Ia available in literature. Results. We find close similarities between the observed LCs of the SN event studied here and SN 2000E. SN 2008fv is a slow-declining SNe Ia with a post-maximum decline of Δm 15,B = 0.96 ± 0.08 mag and a B-band maximum luminosity of M B,0 = −19.40 ± 0.1 mag, close to the value of normal SNe Ia. The optical and NIR data allow us to constrain the host galaxy reddening of NGC 3147, E(B−V) = 0.22 ± 0.05 mag and its distance μ = 33.2 ± 0.1 mag. Furthermore, we derive a synthesized 56 Ni mass of about 0.7 M , by using the well-known relation between the maximum luminosity of the uvoir bolometric light curve and the initial content of 56 Ni. We investigate the correlation between the NIR characteristics of LCs and optical properties by collecting data of a sample of 40 SNe. We derive quantitative relationships involving the epoch of the secondary maximum in the JHK bands and the decline rate Δm 15 (B). Further, we find no correlations between Δm 15 measured in the JHK bands and the optical Δm 15 (B). In contrast, quite evident correlations with the Δm 15 (B) and Δm 40 (J)/Δm 15 (H).

Aims. We study the characteristics of field stars in the two bright ellipticals NGC 4621 and NGC 4374 in the Virgo cluster to derive distances and stellar population properties. Moreover, since the target galaxies have hosted three type Ia Supernova events, we investigate the correlations between the SNe Ia properties and their host stellar systems. Methods. Using deep imaging BV R data, obtained with the FORS2 camera mounted at the VLT, we analyse the Surface Brightness Fluctuations (SBF) properties of the targets. We adopt our measurements and existing empirical or theoretical calibrations to estimate the distance of the NGC 4621 and NGC 4374. For stellar population analysis, we measured SBF amplitudes in different galaxy regions, allowing to study the changes in field star properties. The three band coverage of present data, coupled with existing SBF measures available from literature, provides us with the largest wavelength coverage of SBF magnitudes for single objects. We present a detailed comparison between SBF data and models to constrain the physical characteristics of the dominant stellar components at i) various galactic radii, and ii) in the regions where SNe Ia events were recorded. Results. Our V and R SBF measures provide distances in agreement with literature estimates. The median of our and literature SBF-based distances agrees with the one from non-SBF methods, indicating the absence of any systematic effect in the SBF technique. Comparing either the SBF versus integrated colour diagrams, or the SBF versus SBF colour diagrams, with models, we find that stellar populations properties do not change significantly along galactic radius, with a dominant population having old age and solar chemical composition. The galaxies appear similar in all properties analysed, except for B-band SBF. Since the SBF magnitudes in this band are sensitive to the properties of the hot stellar component, we speculate that such behaviour is a consequence of different diffuse hot stellar components in the galaxies. Using specific models we find that the presence of a percentage of hot-HB stars in old and metal rich stellar populations could be at the origin of the observed differences. We find a good uniformity in the V and R SBF and integrated colours in the regions where the three SNe Ia, presenting different absolute luminosities, exploded. On the other hand, the B-band SBF signal shows intriguing differences.