Review of SIS Experimental Results on Strangeness

>A review of meson emission in heavy ion collisions at incident energies around 1 -- 2 $A\cdot$GeV is presented. It is shown how the shape of the spectra and the various particle yields vary with system size, with centrality and with incident energy. A statistical model assuming thermal and chemical equilibrium and exact strangeness conservation (i.e. strangeness conservation per collision) explains most of the observed features. Emphasis is put onto the study of $K^+$ and $K^-$ emission. In the framework of this statistical model it is shown that the experimentally observed equality of $K^+$ and $K^-$ rates at threshold corrected energies $\sqrt{s} - \sqrt{s_{th}}$ is due to a crossing of two excitation functions. Furthermore, the independence of the $K^+$ to $K^-$ ratio on the number of participating nucleons observed between 1 and 10 $A\cdot$GeV is consistent with this model. The observed flow effects are beyond the scope of this model.Comment: 10 pages, 9 figures, Strangeness 2000, V International Conference on Strangeness in Quark Matter, July, 2000, Berkeley, Californi

The Evolution of Radio Galaxies at Intermediate Redshift

We describe a new estimate of the radio galaxy 1.4 GHz luminosity function and its evolution at intermediate redshifts (z~0.4). Photometric redshifts and color selection have been used to select Bj<23.5 early-type galaxies from the Panoramic Deep Fields, a multicolor survey of two 25 sq deg fields. Approximately 230 radio galaxies have then been selected by matching early-type galaxies with NVSS radio sources brighter than 5 mJy. Estimates of the 1.4 GHz luminosity function of radio galaxies measure significant evolution over the observed redshift range. For an Omega_M=1 cosmology the evolution of the radio power is consistent with luminosity evolution where P(z)=P(0)(1+z)^{k_L} and 3<k_L<5. The observed evolution is similar to that observed for UVX and X-ray selected AGN and is consistent with the same physical process being responsible for the optical and radio luminosity evolution of AGN.Comment: 26 pages, 9 Figures, Accepted for Publication in A

Avoiding spurious breaks in binned luminosity functions

We show that using either the method of Page & Carrera or the well-known $1/V_a$ method to construct the binned luminosity function (LF) of a flux limited sample of Active Galactic Nuclei (AGN) can produce an artificial flattening (or steepening in the case of negative evolution) of the binned LF for bins intersected by the flux cutoff of the sample. This effect is more pronounced for samples with steep and strongly evolving parent LFs but is still present even for non-evolving LFs. As a result of this distortion of the true LF, fitting a model LF to binned data may lead to errors in the estimation of the parameters and may even prompt the erroneous use of broken power law functions. We compute the expected positions of apparent breaks in the binned LF. We show that these spurious breaks in the binned LFs can be avoided if the binning is done in the flux--redshift plane instead of the typically used luminosity--redshift plane. Binning in the flux--redshift plane can be used in conjunction with the binning in the luminosity--redshift plane to test for real breaks in the binned LFs and to identify the features that are the result of binning biases. We illustrate this effect for most typical forms of luminosity dependence and redshift evolution and show how the proposed method helps address this problem. We also apply this method to the MOJAVE AGN sample and show that it eliminates an apparent break in the binned LF.Comment: 7 pages and 7 figures. Accepted for publication in Ap

Shock-Induced Texture in Lunar Mg-Suite Apatite and its Effect on Volatile Distribution

The lunar Mg-suite are plutonic rocks which represent an episode of crustal building following primordial differentiation of the Moon. They range in crystallization ages from 4.43-4.1 Ga. This suite of rocks includes dunites, troctolites, and norites and comprises 20-30% of the lunar crust up to a depth of ~ 50-60 km. Apatite is the most common volatile-bearing mineral in lunar rocks, which made them an ideal target for in-situ studies of volatiles. This study focusses on pristine highland samples that have experienced different levels of shock metamorphism. Therefore, they are valuable samples for understanding how the content of water and other volatiles, as well as their isotopic signature respond to shock

Many-body theory of gamma spectra from positron-atom annihilation

A many-body theory approach to the calculation of gamma spectra of positron annihilation on many-electron atoms is developed. We evaluate the first-order correlation correction to the annihilation vertex and perform numerical calculations for the noble gas atoms. Extrapolation with respect to the maximal orbital momentum of the intermediate electron and positron states is used to achieve convergence. The inclusion of correlation corrections improves agreement with experimental gamma spectra.Comment: 25 pages, 9 figures, submitted to J. Phys.

The Global Star Formation Rate from the 1.4 GHz Luminosity Function

The decimetric luminosity of many galaxies appears to be dominated by synchrotron emission excited by supernova explosions. Simple models suggest that the luminosity is directly proportional to the rate of supernova explosions of massive stars averaged over the past 30 Myr. The proportionality may be used together with models of the evolving 1.4 GHz luminosity function to estimate the global star formation rate density in the era z < 1. The local value is estimated to be 0.026 solar masses per year per cubic megaparsec, some 50% larger than the value inferred from the Halpha luminosity density. The value at z ~ 1 is found to be 0.30 solar masses per year per cubic megaparsec. The 10-fold increase in star formation rate density is consistent with the increase inferred from mm-wave, far-infrared, ultra-violet and Halpha observations.Comment: 10 pages, 2 figures, Astrophysical Journal Letters (in press); new PS version has improved figure placemen

Breaking the Redshift Deadlock - I: Constraining the star formation history of galaxies with sub-millimetre photometric redshifts

Future extragalactic sub-millimetre and millimetre surveys have the potential to provide a sensitive census of the level of obscured star formation in galaxies at all redshifts. While in general there is good agreement between the source counts from existing SCUBA (850um) and MAMBO (1.25mm) surveys of different depths and areas, it remains difficult to determine the redshift distribution and bolometric luminosities of the sub-millimetre and millimetre galaxy population. This is principally due to the ambiguity in identifying an individual sub-millimetre source with its optical, IR or radio counterpart which, in turn, prevents a confident measurement of the spectroscopic redshift. Additionally, the lack of data measuring the rest-frame FIR spectral peak of the sub-millimetre galaxies gives rise to poor constraints on their rest-frame FIR luminosities and star formation rates. In this paper we describe Monte-Carlo simulations of ground-based, balloon-borne and satellite sub-millimetre surveys that demonstrate how the rest-frame FIR-sub-millimetre spectral energy distributions (250-850um) can be used to derive photometric redshifts with an r.m.s accuracy of +/- 0.4 over the range 0 < z < 6. This opportunity to break the redshift deadlock will provide an estimate of the global star formation history for luminous optically-obscured galaxies [L(FIR) > 3 x 10^12 Lsun] with an accuracy of 20 per cent.Comment: 14 pages, 22 figures, submitted to MNRAS, replaced with accepted versio