Molecular transitions as probes of the physical conditions of extragalactic environments

Ab initio grids of time dependent chemical models, varying in gas density, temperature, cosmic ray ionization rate, and radiation field, are used as input to RADEX calculations. Tables of abundances, column densities, theoretical line intensities, and line ratios for some of the most used dense gas tracers are provided. The degree of correlation as well as degeneracy inherent in molecular ratios is discussed. Comparisons of the theoretical intensities with example observations are also provided. We find that, within the parameters space explored, chemical abundances can be constrained by a well defined set of gas density-gas temperature-cosmic ray ionization rate for the species we investigate here. However, line intensities, as well as, more importantly, line ratios, from different chemical models can be very similar leading to a clear degeneracy. We also find that the gas subjected to a galactic cosmic ray ionization rate will not necessarily have reached steady state by 1 Myr. The species most affected by time dependency effects are HCN and CS, both high density tracers. We use our method to fit an example set of data from two galaxies. We find that (i) molecular line ratios can be easily matched even with erroneous individual line intensities; (ii) no set of species can be matched by a one-component ISM; (iii) a species may be a good tracer of an energetic process but only under specific density and temperature conditions. We show that by taking into consideration the chemistry behind each species and the individual line intensities, many degeneracies that arise by just using molecular line ratios can be avoided. Finally we show that using a species or a ratio as a tracer of an individual energetic process (e.g. cosmic rays, UV) ought to be done with caution.Comment: A&A in press (in press version will be different from this one as tables will be either in appendix or on the journal online site) This is revised version as figure was wron

He Said, She Said: A Feminist Approach to Teaching the Twentieth-Century Novel in the Twenty-First Century

The question of women\u27s relationship to the literary canon is still pertinent today and is particularly significant for those of us who are both guided by feminist pedagogy and constrained by departmental limitations. How do we give an overview of the novel without either diminishing the importance of certain male novelists or eliminating female writers altogether? The author suggest that a thematic approach in which pairs of texts make explicit two different gender perspectives is useful. This approach underscores the notion that gender informs writing as well as reading and, equally significant, introduces feminist theory as a tool for literary analysis

Phase separation and interface structure in two dimensions from field theory

We study phase separation in two dimensions in the scaling limit below criticality. The general form of the magnetization profile as the volume goes to infinity is determined exactly within the field theoretical framework which explicitly takes into account the topological nature of the elementary excitations. The result known for the Ising model from its lattice solution is recovered as a particular case. In the asymptotic infrared limit the interface behaves as a simple curve characterized by a gaussian passage probability density. The leading deviation, due to branching, from this behavior is also derived and its coefficient is determined for the Potts model. As a byproduct, for random percolation we obtain the asymptotic density profile of a spanning cluster conditioned to touch only the left half of the boundary.Comment: 12 pages, 3 figures; published version, references adde

Annie Ernaux\u27s Passion Simple and Se Perdre: Proust\u27s \u27Amour-Maladie\u27 Revisited and Revised

At first blush it may seem that Marcel Proust and Annie Ernaux have little in common. The author a A la recherche du temps perdu depends extensively on metaphor and serpentine sentences which culminate in a three-thousand-page work while the more contemporary writer rejects prolixity and imagery and produces dramatically briefer texts. [excerpt

Four-point boundary connectivities in critical two-dimensional percolation from conformal invariance

We conjecture an exact form for an universal ratio of four-point cluster connectivities in the critical two-dimensional $Q$-color Potts model. We also provide analogous results for the limit $Q\rightarrow 1$ that corresponds to percolation where the observable has a logarithmic singularity. Our conjectures are tested against Monte Carlo simulations showing excellent agreement for $Q=1,2,3$.Comment: 29 pages, 9 Figures. Published version: improved discussion, additional numerical tests and reference

Chemical Tracers of Pre-Brown Dwarf Cores Formed Through Turbulent Fragmentation

A gas-grain time dependent chemical code, UCL\_CHEM, has been used to investigate the possibility of using chemical tracers to differentiate between the possible formation mechanisms of brown dwarfs. In this work, we model the formation of a pre-brown dwarf core through turbulent fragmentation by following the depth-dependent chemistry in a molecular cloud through the step change in density associated with an isothermal shock and the subsequent freefall collapse once a bound core is produced. Trends in the fractional abundance of molecules commonly observed in star forming cores are then explored to find a diagnostic for identifying brown dwarf mass cores formed through turbulence. We find that the cores produced by our models would be bright in CO and NH$_3$ but not in HCO$^+$. This differentiates them from models using purely freefall collapse as such models produce cores that would have detectable transitions from all three molecules.Comment: 7 page, 3 figures, Accepted for publication in MNRA

Chemistry of dense clumps near moving Herbig-Haro objects

Localised regions of enhanced emission from HCO+, NH3 and other species near Herbig-Haro objects (HHOs) have been interpreted as arising in a photochemistry stimulated by the HHO radiation on high density quiescent clumps in molecular clouds. Static models of this process have been successful in accounting for the variety of molecular species arising ahead of the jet; however recent observations show that the enhanced molecular emission is widespread along the jet as well as ahead. Hence, a realistic model must take into account the movement of the radiation field past the clump. It was previously unclear as to whether the short interaction time between the clump and the HHO in a moving source model would allow molecules such as HCO+ to reach high enough levels, and to survive for long enough to be observed. In this work we model a moving radiation source that approaches and passes a clump. The chemical picture is qualitatively unchanged by the addition of the moving source, strengthening the idea that enhancements are due to evaporation of molecules from dust grains. In addition, in the case of several molecules, the enhanced emission regions are longer-lived. Some photochemically-induced species, including methanol, are expected to maintain high abundances for ~10,000 years.Comment: 7 pages, 3 figure

Local logarithmic correlators as limits of Coulomb gas integrals

We will describe how logarithmic singularities arise as limits of Coulomb Gas integrals. Our approach will combine analytic properties of the time-like Liouville structure constants, together with the recursive formula of the Virasoro conformal blocks. Although the Coulomb Gas formalism forces a diagonal coupling between the chiral and antichiral sectors of the Conformal Field Theory (CFT), we present new results for the multi-screening integrals which are potentially interesting for applications to critical statistical systems described by Logarithmic CFTs. In particular our findings extend and complement previous results, derived with Coulomb Gas methods, at $c=0$ and $c=-2$.Comment: 38 pages, 12 figure