Dark Matter Halos: The Dynamical Basis of Effective Empirical Models

We investigate the dynamical basis of the classic empirical models (specifically, Sersic-Einasto and generalized NFW) that are widely used to describe the distributions of collisionless matter in galaxies. We submit that such a basis is provided by our \alpha-profiles, shown to constitute solutions of the Jeans dynamical equilibrium with physical boundary conditions. We show how to set the parameters of the empirical in terms of the dynamical models; we find the empirical models, and specifically Sersic-Einasto, to constitute a simple and close approximation to the dynamical models. Finally, we discuss how these provide an useful baseline for assessing the impact of the small-scale dynamics that may modulate the density slope in the central galaxy regions.Comment: 11 pages, 2 figures, Accepted by Advances in Astronom

Marine Fungi of Iceland: A Preliminary Account of Ascomycetes

This paper reports, for the first time, 25 species of marine pyrenomycetes from Icelandic waters. Taxonomic notes are included for certain species. Surtsey, a submarine volcanic upthrust off the south coast of Iceland (Thorarinsson, 1967), is a current center for cooperative geophysical, geochemical, and biological investigations on an international scale. The mycological portion of the total biological research effort of the Surtsey project has emphasized a survey of the marine and freshwater mycoflora on the mainland of Iceland itself as a necessary prerequisite to ecological studies on Surtsey. With the exception of two reports on aquatic phycomycetes (Larsen, 1931, and Johnson, 1966), the aquatic mycoflora of Iceland is unknown. Thus Iceland, rather than Surtsey, has become the immediate focal point for mycological investigations

The History of Cosmic Baryons: X-ray Emission vs. Star Formation Rate

We relate the star formation from cold baryons in virialized structures to the X-ray properties of the associated diffuse, hot baryonic component. Our computations use the standard ``semi-analytic'' models to describe i) the evolution of dark matter halos through merging after the hierarchical clustering, ii) the star formation governed by radiative cooling and by supernova feedback, iii) the hydro- and thermodynamics of the hot gas, rendered with our Punctuated Equilibria model. So we relate the X-ray observables concerning the intra-cluster medium to the thermal energy of the gas pre-heated and expelled by supernovae following star formation, and then accreted during the subsequent merging events. We show that at fluxes fainter than $F_X\approx 10^{-15}$ erg/cm$^2$ s (well within the reach of next generation X-ray observatories) the X-ray counts of extended extragalactic sources (as well as the faint end of the luminosity function, the contribution to the soft X-ray background, and the $L_X-T$ correlation at the group scales) increase considerably when the star formation rate is enhanced for z>1 as indicated by growing optical/infrared evidence. Specifically, the counts in the range 0.5-2 keV are increased by factors $\sim 4$ when the the feedback is decreased and star formation is enhanced as to yield a flat shape of the star formation rate for 2<z<4.Comment: 11 pages, 8 figures, accepted for publication in MNRA

Two New Species of Leafblight Fungi on Kalmia Latifolia

The evergreen shrub, Kalmia latifolia L., commonly known as mountain laurel, calico bush, or sheep-kill, grows widely on rocky, acid soils in the eastern United States. Whether growing in its natural habit or in cultivation, mountain laurel appears to be equally subject to attack by fungi. The following account characterizes and discusses two of these fungi. One of them has not been described previously and additional observations have been made regarding the developmental morphology of the other one. Both pathogens are Pyrenomycetes, one a Physalospora and the other a Diaporthe. Each produces a leafblight disease. Tiny brown discolorations on young leaves characterize the early stages of attack by both organisms. These small lesions gradually enlarge and become irregular brown spots that may encompass the major portion of the leaf surface. The invaded tissues are darkest near the margins of the lesions, but a reddish zone lies between the darker border and the surrounding green tissues. Severely attacked leaves are deformed and shed prematurely. The reproductive structures of the Physalospora occur on the lower surface and begin to develop before the leaves are shed. The pycnidial stromata of the Diaporthe elevate the epidermis and caticle, and consequently produce grayish spots on the leaf surface. Both fungi continue to develop after the leaves have fallen, and since the mycelia extend beyond the margins of the lesions, perithecia ultimately may occupy most of the leaf surface. [excerpt

The SZ Effect as a Probe of Non-Gravitational Entropy in Groups and Clusters of Galaxies

We investigate how strongly and at what scales the Sunyaev- Zel'dovich effect reflects the shifting balance between the two processes that compete for governing the density and the thermodynamic state of the hot intra-cluster medium pervading clusters and groups of galaxies: the hierarchical clustering of the DM; the non-gravitational energy and momentum fed back into the ICM by the condensing baryons. We base on a SAM of galaxy formation and clustering to describe how the baryons are partitioned among the hot, the cool and the stellar phase; the partition shifts as the galaxies cluster hierarchically, and as the feedback by stellar winds and SN explosions follows the star formation. Their impact is amplified by the same large scale accretion shocks that thermalize the gravitational energy of gas falling into the growing potential wells. We compute the Compton parameter $y$, and find a relation of $y$ with the ICM temperature, the $y-T$ relation, which departs from the self-similar scaling and bends down at temperatures typical of galaxy groups. We model-independently relate this with the analogous behaviour of the L_x - T relation, and discuss to what extent our results are generic of the hierarchical models of galaxy formation and clustering.Comment: 24 pages, 6 figures, submitted to MNRAS; typos correcte

Imbedding estimates and elliptic equations with discontinuous coefficients in unbounded domains

In this paper we deal with the multiplication operator u ∈ W^{k,p} (Ω) → gu ∈ L^q (Ω), with g belonging to a space of Morrey type. We apply our results in order to establish an a-priori bound for the solutions of the Dirichlet problem concerning elliptic equations with discontinuous coefficients