Integral-field high spatial resolution spectroscopy of the giant Hii region NGC5461

We present preliminary results obtained from integral-field (IFU) data of the giant extragalactic Hii region NGC5461, located in a spiral arm (RA=14^h03^m41.4^s, dec=+54°19′05″) of M101. The spatial and spectral information obtained with IFUs allows us to decompose the Hii region and analyze it at high resolution.     

TNOs are Cool: A Survey of the Transneptunian Region

Over one thousand objects have so far been discovered orbiting beyond Neptune. These trans-Neptunian objects (TNOs) represent the primitive remnants of the planetesimal disk from which the planets formed and are perhaps analogous to the unseen dust parent-bodies in debris disks observed around other main-sequence stars. The dynamical and physical properties of these bodies provide unique and important constraints on formation and evolution models of the Solar System. While the dynamical architecture in this region (also known as the Kuiper Belt) is becoming relatively clear, the physical properties of the objects are still largely unexplored. In particular, fundamental parameters such as size, albedo, density and thermal properties are difficult to measure. Measurements of thermal emission, which peaks at far-IR wavelengths, offer the best means available to determine the physical properties. While Spitzer has provided some results, notably revealing a large albedo diversity in this population, the increased sensitivity of Herschel and its superior wavelength coverage should permit profound advances in the field. Within our accepted project we propose to perform radiometric measurements of 139 objects, including 25 known multiple systems. When combined with measurements of the dust population beyond Neptune (e.g. from the New Horizons mission to Pluto), our results will provide a benchmark for understanding the Solar debris disk, and extra-solar ones as well.     

39Ar‐40Ar “ages” and origin of excess 40Ar in Martian shergottites

Abstract— We report new ³⁹Ar‐⁴⁰Ar measurements on 15 plagioclase, pyroxene, and/or whole rock samples of 8 Martian shergottites. All age spectra suggest ages older than the meteorite formation ages, as defined by Sm‐Nd and Rb‐Sr isochrons. Employing isochron plots, only Los Angeles plagioclase and possibly Northwest Africa (NWA) 3171 plagioclase give ages in agreement with their formation ages. Isochrons for all shergottite samples reveal the presence of trapped Martian ⁴⁰Ar (⁴⁰Ar_xs), which exists in variable amounts in different lattice locations. Some ⁴⁰Ar_xs is uniformly distributed throughout the lattice, resulting in a positive isochron intercept, and other ⁴⁰Ar_xs occurs in association with K‐bearing minerals and increases the isochron slope. These samples demonstrate situations where linear Ar isochrons give false ages that are too old. After subtracting ⁴⁰Ar*that would accumulate by ⁴⁰K decay since meteorite formation and small amounts of terrestrial ⁴⁰Ar, all young age samples give similar ⁴⁰Ar_xs concentrations of ?1–2 × 10^?6cm³/g, but a variation in K content by a factor of ?80. Previously reported NASA Johnson Space Center data for Zagami, Shergotty, Yamato (Y‐) 000097, Y‐793605, and Queen Alexandra Range (QUE) 94201 shergottites show similar concentrations of ⁴⁰Ar_xs to the new meteorite data reported here. Similar ⁴⁰Ar_xs in different minerals and meteorites cannot be explained as arising from Martian atmosphere carried in strongly shocked phases such as melt veins. We invoke the explanation given by Bogard and Park (2008) for Zagami, that this ⁴⁰Ar_xs in shergottites was acquired from the magma. Similarity in ⁴⁰Ar_xs among shergottites may reveal common magma sources and/or similar magma generation and emplacement processes.     

The Compatibility of Flare Temperatures Observed with AIA,GOES, and RHESSI

We test the compatibility and biases of multi-thermal flare DEM (differential emission measure) peak temperatures determined with AIA with those determined by GOES and RHESSI using the isothermal assumption. In a set of 149 M- and X-class flares observed during the first two years of the SDO mission, AIA finds DEM peak temperatures at the time of the peak GOES 1?–?8 Å flux to have an average of T _p=12.0±2.9 MK and Gaussian DEM widths of log₁₀(σ _T )=0.50±0.13. From GOES observations of the same 149 events, a mean temperature of T _p=15.6±2.4 MK is inferred, which is systematically higher by a factor of T _GOES/T _AIA=1.4±0.4. We demonstrate that this discrepancy results from the isothermal assumption in the inversion of the GOES filter ratio. From isothermal fits to photon spectra at energies of ?≈6?–?12 keV of 61 of these events, RHESSI finds the temperature to be higher still by a factor of T _RHESSI/T _AIA=1.9±1.0. We find that this is partly a consequence of the isothermal assumption. However, RHESSI is not sensitive to the low-temperature range of the DEM peak, and thus RHESSI samples only the high-temperature tail of the DEM function. This can also contribute to the discrepancy between AIA and RHESSI temperatures. The higher flare temperatures found by GOES and RHESSI imply correspondingly lower emission measures. We conclude that self-consistent flare DEM temperatures and emission measures require simultaneous fitting of EUV (AIA) and soft X-ray (GOES and RHESSI) fluxes.     

On the thermal regeneration rate for light gravitinos in the early Universe

We investigate the light gravitino regeneration rate in the early Universe in models based on N = 1 supergravity. Motivated by a recent claim by Fischler, we evaluate finite-temperature effects on the gravitino regeneration rate due to the hot primordial plasma for a wide range of the supersymmetry-breaking scale F. We find that the leading thermal corrections to the gravitino pole mass and to the Goldstino coupling are negligible for a wide range of temperatures, thereby justifying the extension of the equivalence theorem for the helicity-1/2 gravitino and Goldstino to a hot primordial plasma background. Utilizing the Braaten-Pisarski resummation method, and assuming that the other particles are close to thermal equilibrium, the helicity-1/2 gravitino regeneration rate is found to be insensitive to magnetic Debye screening and of order _s(T) log(1/_s(T))¦m_soft/ F ¦²T³(1_s(T) log(1/_s(T))T²/¦F ¦) up to a calculable, model-dependent O(1) numerical factor. We review the implications of this regeneration rate for supergravity cosmology, focusing in particular on scenarios for baryogenesis.     

The effect of magnetic fields on the formation of circumstellar discs around young stars

We present first results of our simulations of magnetic fields in the formation of single and binary stars using a recently developed method for incorporating Magnetohydrodynamics (MHD) into the Smoothed Particle Hydrodynamics (SPH) method. An overview of the method is presented before discussing the effect of magnetic fields on the formation of circumstellar discs around young stars. We find that the presence of magnetic fields during the disc formation process can lead to significantly smaller and less massive discs which are much less prone to gravitational instability. Similarly in the case of binary star formation we find that magnetic fields, overall, suppress fragmentation. However these effects are found to be largely driven by magnetic pressure. The relative importance of magnetic tension is dependent on the orientation of the field with respect to the rotation axis, but can, with the right orientation, lead to a dilution of the magnetic pressure-driven suppression of fragmentation.     

Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse

As a part of a study of the cause of solar coronal heating, we searched for high-frequency (1 Hz) intensity oscillations in coronal loops in the [Fexiv] coronal green line. We summarize results from observations made at the 11 August 1999 total solar eclipse from Râmnicu-Vâlcea, Romania, through clear skies. We discuss the image reduction and analysis through two simultaneous series of coronal CCD images digitized at 10 Hz for a total time of about 140 s. One series of images was taken through a 3.6 Å filter isolating the 5303 Å[Fexiv] coronal green line and the other through a 100 Å filter in the nearby K-corona continuum. Previous observations, described in Pasachoff et al. (2000), showed no evidence for oscillations in the [Fexiv] green line at a level greater than 2% of coronal intensity. We describe several improvements made over the 1998 eclipse that led to increased image clarity and sensitivity. The corona was brighter in 1999 with the solar maximum, further improving the data. We use Fourier analysis to search in the [Fexiv] channel for intensity oscillations in loops at the base of the corona. Such oscillations in the 1-Hz range are predicted as a result of density fluctuations from the resonant absorption of MHD waves. The dissipation of a significant amount of mechanical energy from the photosphere into the corona through this mechanism could provide sufficient energy to heat the corona. A Monte Carlo model of the data suggests the presence of enhanced power, particularly in the 0.75–1.0 Hz range, and we conclude that MHD waves remain a viable method for coronal heating.     

Fitting the integrated spectral energy distributions of galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details of dust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.