Talk at the University of Cambridge

I gave the following talk here at the University of Cambridge:

Abstract:

Observed broad-band radio spectra of both galactic and extra-galactic
objects contain valuable information about their energetics, dynamics
and the physical processes involved in the radio emission. Extracting
this information is however complicated by the fact that there are often
several alternative models for the radio emission; and, by the many
parameters in these models which are only approximately a-priori
constrained.

I will describe a computer program for straightforward Bayesian analysis
of radio spectra based on the nested sampling algorithm. Such an
analysis provides for objective model selection, easy handling of
nuisance parameters, and of course a natural way to handle a-priori
constraints on parameters. I will show some example analyses: a
supernova remnant, a star-forming region in a near-by spiral, and a
number of nearby (U)LIRGs.

PDF: http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-11-02-Cambridge.pdf

Talk at the ALMA EU FP6 Enhancement meeting at RAL, UK

This talk reviews some of the progress in the last year in our work on
advanced techniques for radiometric phase correction for ALMA (i.e., WP5
of the ALMA Enhancement programme). The PDF is available here:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-10-14-Annual.pdf

Talks at the Observatory of Cagliari

Recently I gave three talks at the observatory of Cagliari:

* Fitting and Comparison of Models of Radio Spectra, with updated slides
on the modelling of spinning dust emission:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-09-Sardinia.pdf

* The OOF Holography Technique: Correcting the Effects of Gravity and
Thermal Gradients on Large Filled-Aperture Telescopes:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/Sardinia10.pdf

* OOF Software: Its Structure and How to Extend It

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-09-OOFSoftware.pdf

Talk on the Oxygen sounder thermal profiler for ALMA

The PDF is available at:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-08-General.pdf

--
Bojan Nikolic Tel: +44 1223 746432
Astrophysics Group Mob: +44 7894 223621
Cavendish Laboratory Fax: +44 1223 354599
Cambridge CB3 0HE

Anomalous dust emission in NGC 6946

New paper out today...

The abstract:

We report new cm-wave measurements at five frequencies between 15 and
18 GHz of the continuum emission from the reportedly anomalous
"region 4" of the nearby galaxy NGC 6946. We find that the emission
in this frequency range is significantly in excess of that measured at
8.5 GHz, but has a spectrum from 15-18 GHz consistent with optically
thin free-free emission from a compact H II region. In combination
with previously published data we fit four emission models
containing different continuum components. These fits show that, in
combination with data at other frequencies, a model with a spinning
dust component is slightly preferred above those which possess more
well established emission mechanisms.

PDF:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/N6946.pdf

Software:

http://www.mrao.cam.ac.uk/~bn204/galevol/speca/index.html

Talk on fitting of radio spectra at the JAO, Santiago, Chile

The PDF is available at:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010-JAO-intro.pdf

Introductory talk at the Kavli Institute for Cosmology, Cambridge

This is the brief introductory talk that I gave at the Kavli Institute for Cosmology, Cambridge:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010FebCambIntro.pdf

Talk at NRAO/Charlottesville: First Tests of Atmospheric Phase Correction for ALMA with 183 GHz Water Vapour Radiometers

You can get PDF of the talk at:

http://www.mrao.cam.ac.uk/~bn204/publications/2010/2010JanNRAO.pdf

ALMA Memo 590: Atmospheric dispersion and the implications for phase calibration

This memo was posted in December.

Abstract:

The success of any ALMA phase-calibration strategy, which incorporates
phase transfer, depends on a good understanding of how the atmospheric
path delay changes with frequency (e.g. Holdaway & Pardo 2001). We
explore how the wet dispersive path delay varies for realistic
atmospheric conditions at the ALMA site using the ATM transmission
code. We find the wet dispersive path delay becomes a significant
fraction (5 per cent) of the non-dispersive delay for the high-frequency
ALMA bands (160 GHz, Bands 5 to 10). Additionally, the variation in
dispersive path delay across ALMA's 4-GHz contiguous band- width is not
significant except in Bands 9 and 10. The ratio of dispersive path delay
to total column of water vapour does not vary significantly for typical
amounts of water vapour, water vapour scale heights and ground pressures
above Chajnantor. However, the temperature profile and particularly the
ground-level temperature are more important. Given the likely
constraints from ALMA's ancillary calibration devices, the uncertainty
on the dispersive-path scaling will be around 2 per cent in the worst
case and should contribute about 1 per cent overall to the wet path
fluctuations at the highest frequencies.

Full text:

http://www.mrao.cam.ac.uk/~bn204/publications/2009/ALMAMemo590.pdf