Projectile fragmentation reactions and production of nuclei near the neutron drip-line

The reaction mechanism of projectile fragmentation at intermediate energies has been investigated observing the target dependence of the production cross sections of very neutron-rich nuclei. Measurement of longitudinal momentum distributions of projectile-like fragments within a wide range of fragment mass and its charge was performed using a hundred-MeV/n $^{40}$Ar beam incident on Be and Ta targets. By measurement of fragment momentum distribution, a parabolic mass dependence of momentum peak shift was observed in the results of both targets, and a phenomenon of light-fragment acceleration was found only in the Be-target data. The analysis of production cross sections revealed an obvious enhancement of the target dependence except target size effect when the neutron excess is increased. This result implies the breakdown of factorization (BOF) of production cross sections for very neutron-rich nuclei near the drip line.Comment: 16 pages, 18 figures, submitted to Phys. Rev.

Source finding, parametrization and classification for the extragalactic Effelsberg-Bonn HI Survey

Context. Source extraction for large-scale HI surveys currently involves large amounts of manual labor. For data volumes expected from future HI surveys with upcoming facilities, this approach is not feasible any longer. Aims. We describe the implementation of a fully automated source finding, parametrization, and classification pipeline for the Effelsberg-Bonn HI Survey (EBHIS). With future radio astronomical facilities in mind, we want to explore the feasibility of a completely automated approach to source extraction for large-scale HI surveys. Methods. Source finding is implemented using wavelet denoising methods, which previous studies show to be a powerful tool, especially in the presence of data defects. For parametrization, we automate baseline fitting, mask optimization, and other tasks based on well-established algorithms, currently used interactively. For the classification of candidates, we implement an artificial neural network which is trained on a candidate set comprised of false positives from real data and simulated sources. Using simulated data, we perform a thorough analysis of the algorithms implemented. Results. We compare the results from our simulations to the parametrization accuracy of the HI Parkes All-Sky Survey (HIPASS) survey. Even though HIPASS is more sensitive than EBHIS in its current state, the parametrization accuracy and classification reliability match or surpass the manual approach used for HIPASS data.Comment: 13 Pages, 13 Figures, 1 Table, accepted for publication in A&

Acoustic scale from the angular power spectra of SDSS-III DR8 photometric luminous galaxies

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872,921 galaxies over ~ 10,000 deg^2 between 0.45<z<0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey (BOSS) luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, Ho et al. 2011, to derive the location of Baryon acoustic oscillations (BAO) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D_A/r_s= 9.212 + 0.416 -0.404 at z=0.54, and therefore, D_A= 1411+- 65 Mpc at z=0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D_A is 1.4 \sigma higher than what is expected for the concordance LCDM (Komatsu et al. 2011), in accordance to the trend of other spectroscopic BAO measurements for z >~ 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS (Percival et al. 2010) and WiggleZ (Blake et al. 2011). We refer to our companion papers (Ho et al. 2011; de Putter et al. 2011) for investigations on information of the full power spectrum.Comment: 16 pages, 14 figures, 3 tables, submitted to Ap

Mean-field calculations of exotic nuclei ground states

We study the predictions of three mean-field theoretical approaches in the description of the ground state properties of some spherical nuclei far from the stability line. We compare binding energies, single particle spectra, density distributions, charge and neutron radii obtained with non-relativistic Hartree-Fock calculations carried out with both zero and finite-range interactions, and with a relativistic Hartree approach which uses a finite-range interaction. The agreement between the results obtained with the three different approaches indicates that these results are more related to the basic hypotheses of the mean-field approach rather than to its implementation in actual calculations.Comment: 16 pages, 12 figures, 2 tables, accepted for publication in Physical Review

On the dark matter profile in Sculptor: Breaking the β\beta degeneracy with Virial shape parameters

We present a new method for studying tracers in gravitational systems where higher moments of the line-of-sight velocity distribution are introduced via Virial equations rather than the Jeans equations. Unlike the fourth order Jeans equations, the fourth order Virial equations can simply be added to the standard second order Jeans equation without introducing a new anisotropy parameter $\beta^{\prime}$. We introduce two new global shape parameters $\zeta_A$ and $\zeta_B$ which replace the kurtosis as a more statistically robust measure of the shape of the line of sight velocity distribution. We show that in the case of stars in dwarf spheroidal galaxies these new parameters can significantly reduce the range of density profiles that are otherwise consistent with the observed stellar kinematics (a problem sometimes known as the $\beta$ degeneracy). Specifically, we find that $\zeta_A$ focuses tightly on a subset of solutions where cusped density profiles are degenerate with more concentrated cored dark matter halos. If the number density of stars $\nu(r)$ is fixed, then introducing $\zeta_B$ can further reduce the space of solutions by constraining the outer slope of the dark matter density profile. Assuming a Plummer profile for $\nu(r)$ we recover the surprising result that the dark matter in Sculptor may be cuspy after all, in contrast to the conclusions of other approaches.Comment: 19 pages, 15 figures. Matches version accepted in MNRAS. Minor additions to text. Conclusions unchange