Modelling the Pan-Spectral Energy Distributions of Starburst & Active Galaxies

We present results of a self-consistent model of the spectral energy distribution (SED) of starburst galaxies. Two parameters control the IR SED, the mean pressure in the ISM and the destruction timescale of molecular clouds. Adding a simplified AGN spectrum provides mixing lines on IRAS color : color diagrams. This reproduces the observed colors of both AGNs and starbursts.Comment: Poster Paper for IAU 222: The Interplay among Black Holes, Stars and ISM in Galactic Nucle

Storm Deposition of Pisoids in the Humboldt Oolite Member of the Gilmore City Formation (Mississippian), North-Central Iowa

Pisoids (concentrically laminated carbonate grains, \u3e 2 mm in diameter) are abundant in the upper Humboldt Oolite Member of the Gilmore City Formation (Mississippian). Their cortices are isopachous and nuclei include both intraclasts and fragments of preexisting pisoids. They occur both as floating grams m a fine grainstone matrix and concentrated at the bases of distinct layers that may be crudely graded beds. Sorting characteristics and the presence of broken and abraded pisoids suggest not only their origin as primary free grams, but also storm influence in the deposition of local pisolite layers. Regionally, the upper Humboldt Oolite is characterized by pisolite with birdseyes, fenestrae, evaporite cements, evaporite solution-collapse breccias and tepee structures, a recurrent facies association that has been documented m both ancient and modern arid, peritidal, carbonate depositional environments

Dust in dwarf galaxies: The case of NGC 4214

We have carried out a detailed modelling of the dust heating and emission in the nearby, starbursting dwarf galaxy NGC 4214. Due to its proximity and the great wealth of data from the UV to the millimeter range (from GALEX, HST, {\it Spitzer}, Herschel, Planck and IRAM) it is possible to separately model the emission from HII regions and their associated photodissociation regions (PDRs) and the emission from diffuse dust. Furthermore, most model parameters can be directly determined from the data leaving very few free parameters. We can fit both the emission from HII+PDR regions and the diffuse emission in NGC 4214 with these models with "normal" dust properties and realistic parameters.Comment: 4pages, 3 figures. To appear in 'The Spectral Energy Distribution of Galaxies' Proceedings IAU Symposium No 284, 201

The Use of Lanthanum Hexaboride Cathodes in Electron Beam Lithography

Lanthanum Hexaboride (LaB6) is best known as a thermionic electron emitter with high brightness and long lifetime. It is used in a variety of electron optical instruments, including systems for electron beam lithography of integrated circuits. The major limitation in present-day electron beam lithography systems is throughput, or the ability to process a wafer or mask in a reasonable time. The design of the electron optics is, therefore, governed by a desire to make the writing time as short as possible, together with the other system overhead times. This places inevitable constraints on the electron source. The simplest systems employ a Gaussian round beam of minimal size, requiring maximum brightness. The fastest systems in use today employ the variable shaped beam concept. For these systems brightness is a minor consideration; however the illumination must be highly uniform. For all systems it is desirable to minimize the energy spread. This minimizes the chromatic aberration, which causes a deterioration of edge acuity of the focussed spot. For minimum energy spread one must use the largest possible fraction of the total emission current to form the writing probe. Most shaped beam systems employ Koehler illumination, in which typically one percent of the total emission reaches the target. By using a flat, single crystal cathode with critical illumination it is possible to use nearly all of the emission current, thereby reducing the energy spread by roughly an order of magnitude

K 3-22: a D-type symbiotic star

A goal of the IPHAS survey is to determine the frequency and nature of emission-line sources in the Galactic plane. According to our selection criteria, K 3-22 is a candidate symbiotic star, but it was previously classified as a planetary nebula. To determine its nature, we acquired a low-resolution optical spectrum of K 3-22. Our analysis of our spectroscopy demonstrates that K 3-22 is indeed a D-type symbiotic star, because of its high excitation nebular spectrum and the simultaneous presence of Raman-scattered O VI emission at 6825 and 7082 angstrom, which is detected primarily in symbiotic stars.Comment: 3 pages, 1 figure. Accepted for publication on Astronomy and Astrophysic

Stress-Energy Tensor for the Massless Spin 1/2 Field in Static Black Hole Spacetimes

The stress-energy tensor for the massless spin 1/2 field is numerically computed outside and on the event horizons of both charged and uncharged static non-rotating black holes, corresponding to the Schwarzschild, Reissner-Nordstrom and extreme Reissner-Nordstr\"om solutions of Einstein's equations. The field is assumed to be in a thermal state at the black hole temperature. Comparison is made between the numerical results and previous analytic approximations for the stress-energy tensor in these spacetimes. For the Schwarzschild (charge zero) solution, it is shown that the stress-energy differs even in sign from the analytic approximation. For the Reissner-Nordstrom and extreme Reissner-Nordstrom solutions, divergences predicted by the analytic approximations are shown not to exist.Comment: 5 pages, 4 figures, additional discussio

Variations of the ISM Compactness Across the Main Sequence of Star-Forming Galaxies: Observations and Simulations

(abridged) The majority of star-forming galaxies follow a simple empirical correlation in the star formation rate (SFR) versus stellar mass ($M_*$) plane, usually referred to as the star formation Main Sequence (MS). Here we combine a set of hydro-dynamical simulations of interacting galactic disks with state-of-the-art radiative transfer codes to analyze how the evolution of mergers is reflected upon the properties of the MS. We present \textsc{Chiburst}, a Markov Chain Monte Carlo (MCMC) Spectral Energy Distribution (SED) code that fits the multi-wavelength, broad-band photometry of galaxies and derives stellar masses, star formation rates, and geometrical properties of the dust distribution. We apply this tool to the SEDs of simulated mergers and compare the derived results with the reference output from the simulations. Our results indicate that changes in the SEDs of mergers as they approach coalescence and depart from the MS are related to an evolution of dust geometry in scales larger than a few hundred parsecs. This is reflected in a correlation between the specific star formation rate (sSFR), and the compactness parameter $\mathcal{C}$, that parametrizes this geometry and hence the evolution of dust temperature ($T_{\rm{dust}}$) with time. As mergers approach coalescence, they depart from the MS and increase their compactness, which implies that moderate outliers of the MS are consistent with late-type mergers. By further applying our method to real observations of Luminous Infrared Galaxies (LIRGs), we show that the merger scenario is unable to explain these extreme outliers of the MS. Only by significantly increasing the gas fraction in the simulations are we able to reproduce the SEDs of LIRGs.Comment: 18 pages, 10 figures, accepted in Ap