Internal kinematics of isolated modelled disk galaxies

We present a systematic investigation of rotation curves (RCs) of fully hydrodynamically simulated galaxies, including cooling, star formation with associated feedback and galactic winds. Applying two commonly used fitting formulae to characterize the RCs, we investigate systematic effects on the shape of RCs both by observational constraints and internal properties of the galaxies. We mainly focus on effects that occur in measurements of intermediate and high redshift galaxies. We find that RC parameters are affected by the observational setup, like slit misalignment or the spatial resolution and also depend on the evolution of a galaxy. Therefore, a direct comparison of quantities derived from measured RCs with predictions of semi-analytic models is difficult. The virial velocity V_c, which is usually calculated and used by semi-analytic models can differ significantly from fit parameters like V_max or V_opt inferred from RCs. We find that V_c is usually lower than typical characteristic velocities derived from RCs. V_max alone is in general not a robust estimator for the virial mass.Comment: 9 pages, 15 figures, accepted for publication in A&

Historical roots of Agile methods: where did “Agile thinking” come from?

The appearance of Agile methods has been the most noticeable change to software process thinking in the last fifteen years [16], but in fact many of the “Agile ideas” have been around since 70’s or even before. Many studies and reviews have been conducted about Agile methods which ascribe their emergence as a reaction against traditional methods. In this paper, we argue that although Agile methods are new as a whole, they have strong roots in the history of software engineering. In addition to the iterative and incremental approaches that have been in use since 1957 [21], people who criticised the traditional methods suggested alternative approaches which were actually Agile ideas such as the response to change, customer involvement, and working software over documentation. The authors of this paper believe that education about the history of Agile thinking will help to develop better understanding as well as promoting the use of Agile methods. We therefore present and discuss the reasons behind the development and introduction of Agile methods, as a reaction to traditional methods, as a result of people's experience, and in particular focusing on reusing ideas from histor

Internal kinematics of modelled interacting disc galaxies

We present an investigation of galaxy-galaxy interactions and their effects on the velocity fields of disc galaxies in combined N-body/hydrodynamic simulations, which include cooling, star formation with feedback, and galactic winds. Rotation curves (RCs) of the gas are extracted from these simulations in a way that follows the procedure applied to observations of distant, small, and faint galaxies as closely as possible. We show that galaxy-galaxy mergers and fly-bys disturb the velocity fields significantly and hence the RCs of the interacting galaxies, leading to asymmetries and distortions in the RCs. Typical features of disturbed kinematics are significantly rising or falling profiles in the direction of the companion galaxy and pronounced bumps in the RCs. In addition, tidal tails can leave strong imprints on the rotation curve. All these features are observable for intermediate redshift galaxies, on which we focus our investigations. We use a quantitative measure for the asymmetry of rotation curves to show that the appearance of these distortions strongly depends on the viewing angle. We also find in this way that the velocity fields settle back into relatively undisturbed equilibrium states after unequal mass mergers and fly-bys. About 1 Gyr after the first encounter, the RCs show no severe distortions anymore. These results are consistent with previous theoretical and observational studies. As an illustration of our results, we compare our simulated velocity fields and direct images with rotation curves from VLT/FORS spectroscopy and ACS images of a cluster at z=0.53 and find remarkable similarities.Comment: 13 pages, 14 figures, accepted for publication in A&A, some improvements and changes, main conclusions are unaffecte

Spin dynamics in copper metaborate CuB2O4CuB_2 O_4 studied by muon spin relaxation

Copper metaborate CuB$_2$O$_{4}$ was studied by muon spin relaxation measurements in order to clarify its static and dynamic magnetic properties. The time spectra of muon spin depolarization suggest that the local fields at the muon site contain both static and fluctuating components in all ordered phases down to 0.3 K. In the weak ferromagnetic phase (20 K~$>T>$~9.3 K), the static component is dominant. On the other hand, upon cooling the fluctuating component becomes dominant in the incommensurate helix phase (9.3K > T > 1.4K). The dynamical fluctuations of the local fields persist down to 0.3K, where a new incommensurate phase (T < 1.4K) is expected to appear. This result suggests that spins fluctuate even at T \to 0. We propose two possible origins of the remnant dynamical spin fluctuations: frustration of the exchange interactions and the dynamic behavior of the soliton lattice

Neutrino Physics and Nuclear Axial Two-Body Interactions

We consider the counter-term describing isoscalar axial two-body currents in the nucleon-nucleon interaction, L1A, in the effective field theory approach. We determine this quantity using the solar neutrino data. We investigate the variation of L1A when different sets of data are used.Comment: 8 pages with 4 figures. To be published in the Proceedings of the Conference "Blueprints For The Nucleus: From First Principles to Collective Motion" held at Feza Gursey Institute, Istanbul, Turkey; May 17 -22, 200

Investigations of fast neutron production by 190 GeV/c muon interactions on different targets

The production of fast neutrons (1 MeV - 1 GeV) in high energy muon-nucleus interactions is poorly understood, yet it is fundamental to the understanding of the background in many underground experiments. The aim of the present experiment (CERN NA55) was to measure spallation neutrons produced by 190 GeV/c muons scattering on carbon, copper and lead targets. We have investigated the energy spectrum and angular distribution of spallation neutrons, and we report the result of our measurement of the neutron production differential cross section.Comment: 19 pages, 11 figures ep

Kinematics of disk galaxies in (proto-)clusters at z=1.5

We observed star-forming galaxies at z~1.5 selected from the HyperSuprimeCam Subaru Strategic Program. The galaxies are part of two significant overdensities of [OII] emitters identified via narrow-band imaging and photometric redshifts from grizy photometry. We used VLT/KMOS to carry out Halpha integral field spectroscopy of 46 galaxies in total. Ionized gas maps, star formation rates and velocity fields were derived from the Halpha emission line. We quantified morphological and kinematical asymmetries to test for potential gravitational (e.g. galaxy-galaxy) or hydrodynamical (e.g. ram-pressure) interactions. Halpha emission was detected in 36 targets. 34 of the galaxies are members of two (proto-)clusters at z=1.47, confirming our selection strategy to be highly efficient. By fitting model velocity fields to the observed ones, we determined the intrinsic maximum rotation velocity Vmax of 14 galaxies. Utilizing the luminosity-velocity (Tully-Fisher) relation, we find that these galaxies are more luminous than their local counterparts of similar mass by up to ~4 mag in the rest-frame B-band. In contrast to field galaxies at z<1, the offsets of the z~1.5 (proto-)cluster galaxies from the local Tully-Fisher relation are not correlated with their star formation rates but with the ratio between Vmax and gas velocity dispersion sigma_g. This probably reflects that, as is observed in the field at similar redshifts, fewer disks have settled to purely rotational kinematics and high Vmax/sigma_g ratios. Due to relatively low galaxy velocity dispersions (sigma_v < 400 km/s) of the (proto-)clusters, gravitational interactions likely are more efficient, resulting in higher kinematical asymmetries, than in present-day clusters. (abbr.)Comment: Accepted for publication in A&A. 11 pages, 8 figures, 1 tabl

Self-interacting dark matter and Higgs bosons in the SU(3)_C x SU(3)_L x U(1)_N model with right-handed neutrinos

We investigate the possibility that dark matter could be made from CP-even and CP- odd Higgs bosons in the SU(3)_C X SU(3)_L X U(1)_N (3-3-1) model with right-handed neutrinos. This self-interacting dark matters are stable without imposing of new symmetry and should be weak-interacting.Comment: 7 pages, Latex, To appear in Europhys. Let