Oxford astro-ph Coffee

A star with a mid-IR excess (circumstellar disk?) that vanishes in a 2-year interval.

Paper discussing how lensing can bias your reconstruction of reionisation field.

The first detection of a filament.

Very nice. I'm a little surprised that it's the first detection - I swear some people working on this a few years ago. But maybe their detection wasn't significant enough. At least, they didn't get a Nature paper out of it!

Interesting letter discussing re-ionizing the universe through accretion shocks around massive halos in the early universe.

They show that the mean redshift-magnitude relation from a spectroscopic survey can be used to infer peculiar velocities.

More dipoles!

WMAP confirmation of Planck's SZ-mass relation

I've not read the whole thing (it's 44 pages!) but Yu Lu is, IMO, doing the Right Thing in this field - he takes a Semi Analytic Model of galaxy formation, and *actually fits* all the parameters to the data (in this case, the observed K-band luminosity function). Some parameters are well-constrained (implying we may have learnt something about galaxies), while others show strong degeneracies, indicating what new physics needs to be included. Seems like the models in most of the parameter volume fail to predict some other datasets, giving more clues on how to improve the model. The key thing is that by doing the inference properly, Lu has elevated SAM study to a quantified learning process.

The authors find a dipole in the variance of the Hubble flow, which they attribute to the effects of local structure. They find that local structure induces a ~0.5% variation in the distance to last scattering over the sky.

Andy Lawrence suggests that the unaccounted for UV flux in AGN spectra could be coming from "clouds" of gas orbiting the black hole at ~10 Schwarzschild radii, and reflecting light as UV line emission which all gets blurred together to make a broad continuum due to the insane speeds involved.

I saw Andy yesterday at the Edinburgh sims workshop - he agreed that his clouds were probably shreds, but all that really matters is the filling factor and ionisation state, and the code he used to play around with it all is called "cloudy"... I told him we found the model pretty plausible (stuff comes off accretion disks and stays in orbit, absorbing and emitting, fine), his hope is that someone makes a more detailed model, checks his results and does some inference. That'll be Lance then...

The authors construct exact instanton solutions for tunneling over very small barriers in the presence of gravity, and demonstrate matching between previous results, and with the flat potential and no gravity case. Confusingly, it seems that for consistency one should include the tunneling effect along side the rolling of a field on a flat potential, even when there is no barrier. I'm not sure quite what this means operationally, but I think it may have effects for models of quintessence where the asymptotic future is a big crunch. Here it seems we may not be able to consider simple scalar field rolling, but may also have to include the instanton effects. More excuses to go back and read Coleman-DeLuccia again are always good.

A sampler, new in both algorithm and code, from Hogg and co. They claim speed ups over Metropolis Hastings and easy shared-memory parallelism using an ensemble method.

CosmoMC gets upgraded by the Cavendish inference team (Hobson, Feroz, and now Graff) - they approximate complex likelihood functions with neural networks, which are then much much faster to evaluate. Could be a real time-saver

Recommended by Jo.

First kSZ detection! From ACT and BOSS together.

Kelly and Kirshner look at the SDSS images and spectra of the host galaxies of more than 500 nearby supernovae. Seems like an interesting complement to the SNLS host studies, I'd be interested to hear from Mark where this one fits. They can resolve the galaxies very well, so can make statements like "the SN Ic-BL and SN IIb explode in exceptionally blue locations" :-)

Hada et al reckon they can position the black hole to +/- 20 microarcsec, and resolve jet emission 100 Schwarzschild radii away!

Suyu et al combine strong gravitational lensing and stellar kinematics data for a spiral galaxy to measure the mass of both the disk and the dark matter halo. The constraints are very strong - they find an oblate, flattened halo, and get a disk stellar mass with small uncertainty (0.1dex); when they compare this with the stellar mass from the disk colours and K-band magnitude they find that stellar population models with Chabrier IMF work, and Salpeter does not - the opposite to the case of massive elliptical galaxies.

As soon as you move away from a perfectly homogeneous and isotropic cosmological model, what is meant by the "acceleration" of spacetime becomes ambiguous. It's important to be clear on what type of acceleration is being considered in any given observational or theoretical study, since different types can have very different cosmological implications.