Galaxy And Mass Assembly (GAMA): linking star formation histories and stellar mass growth

We present evidence for stochastic star formation histories in low-mass (M* < 1010 M⊙) galaxies from observations within the Galaxy And Mass Assembly (GAMA) survey. For ˜73 000 galaxies between 0.05 < z < 0.32, we calculate star formation rates (SFR) and specific star formation rates (SSFR = SFR/M*) from spectroscopic Hα measurements and apply dust corrections derived from Balmer decrements. We find a dependence of SSFR on stellar mass, such that SSFRs decrease with increasing stellar mass for star-forming galaxies, and for the full sample, SSFRs decrease as a stronger function of stellar mass. We use simple parametrizations of exponentially declining star formation histories to investigate the dependence on stellar mass of the star formation time-scale and the formation redshift. We find that parametrizations previously fit to samples of z ˜ 1 galaxies cannot recover the distributions of SSFRs and stellar masses observed in the GAMA sample between 0.05 < z < 0.32. In particular, a large number of low-mass (M* < 1010 M⊙) galaxies are observed to have much higher SSFRs than can be explained by these simple models over the redshift range of 0.05 < z < 0.32, even when invoking mass-dependent staged evolution. For such a large number of galaxies to maintain low stellar masses, yet harbour such high SSFRs, requires the late onset of a weak underlying exponentially declining star formation history with stochastic bursts of star formation superimposed

Theoretical and experimental investigation of the physics of crystalline surfaces Quarterly status report, 1 Aug. - 31 Oct. 1968

Particle densities, elastic and inelastic scattering, electron diffraction patterns, and adsorbate influence on surface structure and work function changes on crystalline surface

Theoretical and Experimental Investigations of the Physics of Crystalline Surfaces Second Quarterly Status Report, 1 May - 31 Jul. 1966

Single crystal metal film formation on alkali halides, crystal structure and electron emission properties of work functions, and relativistic effects on slow electron scatterin

Theoretical and experimental investigation of the physics of crystalline surfaces Quarterly report, 1 Feb. - 30 Apr. 1967

Theoretical and experimental investigation of physics of crystalline surface

Microscopic Approach to Nucleon Spectra in Hypernuclear Non-Mesonic Weak Decay

A consistent microscopic diagrammatic approach is applied for the first time to the calculation of the nucleon emission spectra in the non-mesonic weak decay of Lambda-hypernuclei. We adopt a nuclear matter formalism extended to finite nuclei via the local density approximation, a one--meson exchange weak transition potential and a Bonn nucleon-nucleon strong potential. Ground state correlations and final state interactions, at second order in the nucleon--nucleon interaction, are introduced on the same footing for all the isospin channels of one- and two-nucleon induced decays. Single and double--coincidence nucleon spectra are predicted for 12_Lambda^C and compared with recent KEK and FINUDA data. The key role played by quantum interference terms allows us to improve the predictions obtained with intranuclear cascade codes. Discrepancies with data remain for proton emission.Comment: 11 pages, 6 figures, 2 tables. To be published in Physics Letters

On some derivatives of phenylethers, 2

Products and the synthesis of chloronitrobenzol with certain phenolates are discussed, as is the p-oxyphenylether occasionally produced. Yield, melting point, and physical description are given for each product. The products include 2,4'-dinitrophenylether; 2,2'-dinitrophenylether; p-nitrophenylether-p-oxybenzoic acid and its methylester; p-aminophenylether-p-oxybenzoic acid, its sulfate, and its barium salt; and p-oxypenylether

On the role of ground state correlations in hypernuclear non-mesonic weak decay

The contribution of ground state correlations (GSC) to the non--mesonic weak decay of $^{12}_\Lambda$C and other medium to heavy hypernuclei is studied within a nuclear matter formalism implemented in a local density approximation. We adopt a weak transition potential including the exchange of the complete octets of pseudoscalar and vector mesons as well as a residual strong interaction modeled on the Bonn potential. Leading GSC contributions, at first order in the residual strong interaction, are introduced on the same footing for all isospin channels of one-- and two--nucleon induced decays. Together with fermion antisymmetrization, GSC turn out to be important for an accurate determination of the decay widths. Besides opening the two--nucleon stimulated decay channels, for $^{12}_\Lambda$C GSC are responsible for 14% of the rate $\Gamma_1$ while increasing the $\Gamma_{n}/\Gamma_{p}$ ratio by 4%. Our final results for $^{12}_\Lambda$C are: $\Gamma_{\rm NM}=0.98$, $\Gamma_{n}/\Gamma_{p}=0.34$ and $\Gamma_2/\Gamma_{\rm NM}=0.26$. The saturation property of $\Gamma_{\rm NM}$ with increasing hypernuclear mass number is clearly observed. The agreement with data of our predictions for $\Gamma_{\rm NM}$, $\Gamma_n/\Gamma_p$ and $\Gamma_2$ is rather good.Comment: 32 pages, 9 figure