A new blog

I'm going to be posting about my astro-ph reading. It will mostly be abstract summaries (if that's possible) and what I've learned from them.



http://arxiv.org/abs/1105.5139
The Morphology of the Thermal Sunyaev-Zel'dovich Sky
Munshi, Smidt, Joudaki, Coles


tSZ effect (in CMB at high angular frequencies) is the large scale pressure fluctuations in the baryonic distribution, and estimates the properties of the projected 3d pressure fluctuations.  It is a sensitive probe of the density fluctuations, and its bias associated with pressure can be separated from bispectrum (or the one-point statistics analogue, the skewness).


The morphological properties (I assume we're talking about the power spectra), in addition to skewness, is probed by the Minkowski Functionals (which at low order is identical to skewness).  Generalized skewness parameters can be extended to define a set of 3 associated generalized skew-spectra.  Use skew-spectra to probe the morphology of the tSZ sky.  The skew-spectra can be recovered from the data when mask and noise present using Pseudo-Cl (PCL) approach.


This will allow mode by mode estimation and will help differentiate various other sources of non-Gaussianity.


* This abstract is not very clear in what they mean by "morphology" (IMO)
* I guess this is about how to sort out tSZ from the primordial non-G effects


http://arxiv.org/abs/1105.5292
The linear power spectrum of observed source number counts
Challinor, Lewis

* What in the world do they mean by linear power spectra of source number counts?


Gives: the exact results on observer number of galaxies per solid angle and redshift to the underlying proper source density and velocity, BG evolution and LOS potentials, based on linear perturbations assuming GR.  Correctly incorporates clustering, z-space distortions, magnification, radial displacement, and other linear terms on sub-horizon scales.  Gives result for amgnitude-limited survey at low z; discuss angular power spectrum of total count distribution (nb: I think they mean what the powser spectrum is given these selection effects).  Also calculates X-corr with the CMB polarization and temperatures (magnification and velocity effects for the sources). Contribution of z-space distortions is generally small.  Also relate source counts to line radiation (e.g., 21-cm) from sources.


* Are they going to include NL effects, so that it can model the real Universe?  
* What is the significance of this paper?

== this is how far I got in about one hour today.  BBC news is on its third cycle. ==