Cold galaxies

We use 350 mu angular diameter estimates from Planck to test the idea that some galaxies contain exceptionally cold (10-13 K) dust, since colder dust implies a lower surface brightness radiation field illuminating the dust, and hence a greater physical extent for a given luminosity. The galaxies identified from their spectral energy distributions as containing cold dust do indeed show the expected larger 350 mu diameters. For a few cold dust galaxies where Herschel data are available we are able to use submillimetre maps or surface brightness profiles to locate the cold dust, which as expected generally lies outside the optical galaxy.Comment: 9 pages, 15 figures. Accepted for publication MNRA

Modelling the Spoon IRS diagnostic diagram

We explore whether our models for starbursts, quiescent star-forming galaxies and for AGN dust tori are able to model the full range of IRS spectra measured with Spitzer. The diagnostic plot of 9.7 mu silicate optical depth versus 6.2 mu PAH equivalent width, introduced by Spoon and coworkers in 2007, gives a good indication of the age and optical depth of a starburst, and of the contribution of an AGN dust torus. However there is aliasing between age and optical depth at later times in the evolution of a starburst, and between age and the presence of an AGN dust torus. Modeling the full IRS spectra and using broad-band 25-850 mu fluxes can help to resolve these aliases. The observed spectral energy distributions require starbursts of a range of ages with initial dust optical depth ranging from 50-200, optically thin dust emission ('cirrus') illuminated by a range of surface brightnesses of the interstellar radiation field, and AGN dust tori with a range of viewing angles.Comment: Accepted for publication by MNRAS. 8 pages, 10 figure

Users and non-users of next generation broadband

This paper explores the contexts and motivations that underpin the uptake of Australia’s National Broadband Network (NBN). The findings are drawn from a mixed-methods research study of households using surveys and interviews conducted in 2011 and 2012 in an early release site of the NBN rollout. Whilst use and non-use have traditionally been treated as questions of digital access, inequality and exclusion, there is evidence for emerging forms of non-use characterized by more critical and discriminating approaches. We contribute to this evidence, but our findings suggest that use and non-use of high speed broadband do not occur in isolation or as an expression of individual choice, but as part of increasingly dense household media ecologies of digital infrastructures, devices, services and knowledge

Detections and Constraints on White Dwarf Variability from Time-Series GALEX Observations

We search for photometric variability in more than 23,000 known and candidate white dwarfs, the largest ultraviolet survey compiled for a single study of white dwarfs. We use gPhoton, a publicly available calibration/reduction pipeline, to generate time-series photometry of white dwarfs observed by GALEX. By implementing a system of weighted metrics, we select sources with variability due to pulsations and eclipses. Although GALEX observations have short baselines (< 30 min), we identify intrinsic variability in sources as faint as Gaia G = 20 mag. With our ranking algorithm, we identify 49 new variable white dwarfs (WDs) in archival GALEX observations. We detect 41 new pulsators: 37 have hydrogen-dominated atmospheres (DAVs), including one possible massive DAV, and four are helium-dominated pulsators (DBVs). We also detect eight new eclipsing systems; five are new discoveries, and three were previously known spectroscopic binaries. We perform synthetic injections of the light curve of WD 1145+017, a system with known transiting debris, to test our ability to recover similar systems. We find that the 3{\sigma} maximum occurrence rate of WD 1145+017-like transiting objects is < 0.5%.Comment: 17 pages, 13 figure

Panchromatic radiation from galaxies as a probe of galaxy formation and evolution

I review work on modelling the infrared and submillimetre SEDs of galaxies. The underlying physical assumptions are discussed and spherically symmetric, axisymmetric, and 3-dimensional radiative transfer codes are reviewed. Models for galaxies with Spitzer IRS data and for galaxies in the Herschel-Hermes survey are discussed. Searches for high redshift infrared and submillimetre galaxies, the star formation history, the evolution of dust extinction, and constraints from source-counts, are briefly discussed.Comment: to be published in IAU Symposium 284 'The Spectral Energy Distribution of Galaxies', Preston 2012, eds. R.J.Tiffs and C.C.Popesc