We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low-and high-redshift SN Ia surveys. Within the framework of the mlcs2k2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, R V = 2.18 ± 0.14 stat ± 0.48 syst , and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P (A V) = exp(−A V /τ V), with τ V = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and Ω M , assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon Ω M and Ω Λ for a cosmological constant model (ΛCDM) with w = −1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia,

Constraining dynamo theories of magnetic field origin by observation is indispensable but challenging, in part because the basic quantities measured by observers and predicted by modelers are different. We clarify these differences and sketch out ways to bridge the divide. Based on archival and previously unpublished data, we then compile various important properties of galactic magnetic fields for nearby spiral galaxies. We consistently compute strengths of total, ordered, and regular fields, pitch angles of ordered and regular fields, and we summarize the present knowledge on azimuthal modes, field parities, and the properties of non-axisymmetric spiral features called magnetic arms. We review related aspects of dynamo theory, with a focus on mean-field models and their predictions for large-scale magnetic fields in galactic discs and halos. Further, we measure the velocity dispersion of H I gas in arm and inter-arm regions in three galaxies, M 51, M 74, and NGC 6946, since spiral modulation of the root-mean-square turbulent speed has been proposed as a driver of non-axisymmetry in large-scale dynamos. We find no evidence for such a modulation and place upper limits on its strength, helping to narrow down the list of mechanisms to explain magnetic arms. Successes and remaining challenges of dynamo models with respect to explaining observations are briefly summarized, and possible strategies are suggested. With new instruments like the Square Kilometre Array (SKA), large data sets of magnetic and non-magnetic properties from thousands of galaxies will become available, to be compared with theory.

Galaxy evolution is driven to a large extent by interactions and mergers with other galaxies and the gas in galaxies is extremely sensitive to the interactions. One method to measure such interactions uses the quantified morphology of galaxy images. Well‐established parameters are Concentration, Asymmetry, Smoothness, Gini and M20 of a galaxy image. Thus far, the application of this technique has mostly been restricted to rest‐frame ultraviolet and optical images. However, with the new radio observatories being commissioned [South African Karoo Array Telescope (MeerKAT), Australian SKA Pathfinder (ASKAP), Extended Very Large Array (EVLA), Westerbork Synthesis Radio Telescope/APERture Tile In Focus instrument (WSRT/APERTIF) and ultimately the Square Kilometer Array (SKA)], a new window on the neutral atomic hydrogen gas (H i) morphology of large numbers of galaxies will open up. The quantified morphology of gas discs of spirals can be an alternative indicator of the level and frequency of interaction. The H i in galaxies is typically spatially more extended and more sensitive to low‐mass or weak interactions. In this paper, we explore six morphological parameters calculated over the extent of the stellar (optical) disc and the extent of the gas disc for a range of wavelengths spanning ultraviolet (UV), optical, near‐ and far‐infrared and 21 cm (H i) of 28 galaxies from The H i Nearby Galaxy Survey (THINGS). Although the THINGS sample is small and contains only a single ongoing interaction, it spans both non‐interacting and post‐interacting galaxies with a wealth of multi‐wavelength data. We find that the choice of area for the computation of the morphological parameters is less of an issue than the wavelength at which they are measured. The signal of interaction is as good in the H i as at any of the other wavelengths at which morphology has been used to trace the interaction rate to date, mostly star formation dominated ones (near‐ and far‐ultraviolet). The Asymmetry and M20 parameters are the ones that show the most promise as tracers of interaction in 21 cm line observations.

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