Three-dimensional extinction mapping using Gaussian random fields

We present a scheme for using stellar catalogues to map the three-dimensional distributions of extinction and dust within our Galaxy. Extinction is modelled as a Gaussian random field, whose covariance function is set by a simple physical model of the ISM that assumes a Kolmogorov-like power spectrum of turbulent fluctuations. As extinction is modelled as a random field, the spatial resolution of the resulting maps is set naturally by the data available; there is no need to impose any spatial binning. We verify the validity of our scheme by testing it on simulated extinction fields and show that its precision is significantly improved over previous dust-mapping efforts. The approach we describe here can make use of any photometric, spectroscopic or astrometric data; it is not limited to any particular survey. Consequently, it can be applied to a wide range of data from both existing and future surveys.Comment: 16 pages, 12 figures. Submitted for publication in MNRAS. Text revise

Marginal likelihoods of distances and extinctions to stars: computation and compact representation

We present a method for obtaining the likelihood function of distance and extinction to a star given its photometry. The other properties of the star (its mass, age, metallicity and so on) are marginalised assuming a simple Galaxy model. We demonstrate that the resulting marginalised likelihood function can be described faithfully and compactly using a Gaussian mixture model. For dust mapping applications we strongly advocate using monochromatic over bandpass extinctions, and provide tables for converting from the former to the latter for different stellar types.Comment: 14 pages, 12 figures. Accepted for publication in MNRAS. Source code is available at https://github.com/stuartsal

A 3D extinction map of the northern Galactic plane based on IPHAS photometry

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.We present a 3D map of extinction in the northern Galactic plane derived using photometry from the INT/WFC Photometric Hα Survey of the northern Galactic plane. The map has fine angular (~10 arcmin) and distance (100 pc) sampling allied to a significant depth (≳5 kpc). We construct the map using a method based on a hierarchical Bayesian model described in a previous article by Sale. In addition to mean extinction, we also measure differential extinction, which arises from the fractal nature of the interstellar medium, and show that it will be the dominant source of uncertainty in estimates of extinction to some arbitrary position. The method applied also furnishes us with photometric estimates of the distance, extinction, effective temperature, surface gravity, and mass for ~38 million stars. Both the extinction map and the catalogue of stellar parameters are made publicly available via http://www.iphas.org/extinction.Peer reviewe

The Appalachian Model Teaching Consortium: Preparing Teachers for Rural Appalachia

The Appalachian Model Teacher Consortium is a partnership involving Radford University, Wytheville Community College, and the Grayson County (Virginia) School System. Its purpose is to prepare highly qualified teachers for rural southwest Virginia. The model was developed in response to the growing teacher shortage facing school districts in rural southwest Virginia. Poorer, more rural districts often have weaker tax bases that provide limited, and at times inadequate, financial support for their school districts. This lack of local resources often results in lower salaries and benefits when compared to many districts that compete for the shrinking pool of potential teachers. Additionally, rural communities are often geographically isolated areas and have fewer amenities that attract young teachers from outside the district. The Appalachian Model Teacher Consortium attempts to naturalize shortages by recruiting potential teachers from the local area, and providing incentives for them to stay and teach in their home community

Measurement of the cross-section ratio 3H(d,γ)5He/3H(d,α)n at 100 keV

The cross-section ratio for 3H(d,γ)5He relative to 3H(d,α)n has been measured at an effective deuteron bombarding energy of 100 keV with a NaI pair spectrometer and a tritiated-titanium target. The ratio was determined to be (1.2±0.3)×10^-4 by comparing the spectra and count rates for 3H(d,γ)5He and 3H(d,α)n with 2H(3He,γ)5Li and 2H(3He,α)1H

A NuRD Complex from Xenopus laevis Eggs Is Essential for DNA Replication during Early Embryogenesis.

DNA replication in the embryo of Xenopus laevis changes dramatically at the mid-blastula transition (MBT), with Y RNA-independent random initiation switching to Y RNA-dependent initiation at specific origins. Here, we identify xNuRD, an MTA2-containing assemblage of the nucleosome remodeling and histone deacetylation complex NuRD, as an essential factor in pre-MBT Xenopus embryos that overcomes a functional requirement for Y RNAs during DNA replication. Human NuRD complexes have a different subunit composition than xNuRD and do not support Y RNA-independent initiation of DNA replication. Blocking or immunodepletion of xNuRD inhibits DNA replication initiation in isolated nuclei in vitro and causes inhibition of DNA synthesis, developmental delay, and embryonic lethality in early embryos. xNuRD activity declines after the MBT, coinciding with dissociation of the complex and emergence of Y RNA-dependent initiation. Our data thus reveal an essential role for a NuRD complex as a DNA replication factor during early Xenopus development