Day 4 of Nice vacation and astroph abstract blog. Today I made breakfast for my family (parents & sister) and took a day off from vacation to work on a paper I need to referee.
http://arxiv.org/abs/1105.5642
The evolution of early-type galaxies selected by their spatial clustering
Padilla, Christlein, Gawiser, Marchesini
* I wonder how clustering can probe evolution of red galaxies?
To follow a progenitor-to-descendant relationship, combine clustering with luminosity or stellar mass functions at different redshifts [ah, this is similar to Eric G's research]. This then can be used to infer merger rates. The clustering is used to infer the halo mass of a galaxy at a given redshift; then combine with LCDM prediction and follow the haloes down to their descendant. This shows that MUSYC early type galaxies evolve into brighter galaxies, indicating increase in stellar mass over time [by merger?]; and also indicates that stellar mass selection at different redshifts does not provide samples of progenitor-descendant relationship. They find that the progenitor number density is factor of 5 (with error of +/-4) higher, so infer that there must have been mergers. The luminosity densities of progenitors and descendants are consistent, showing no significant star formation in the early type galaxies since z=1.
* Answer: use galaxy-halo mass relation. This would be a good paper to compare with gg lensing results.
http://arxiv.org/abs/1105.5649
Defrosting in an emergent Galileon cosmology
Levasseur, Brandenberger, Davis
* Why am I doing this to myself? What is Galileon cosmology anyway? I know I looked it up before, and I've already forgotten.
They are talking about before-the-reheating phase of the universe, after inflation but before today's known particles have emerged. This is the "defrosting" or "preheating" phase they're talking about. They mention a "Galileon condensate." Preheating occurs when matter couples to the coherent inflaton [is this the Galileon?] condensate. This coupling has been shown to generate a scale-invariant spectrum of matter fluctuations. Expansion of the universe affects the coupling of the matter to the Galileon condensate. They talk about the defrosting mechanism.
* I guess a Galileon is a type of inflaton? Or something that is responsible for dark energy?
http://arxiv.org/abs/1105.5885
Connecting synchrotron, cosmic rays, and magnetic field in the plane of the galaxy
Jaffe, Banday, Leahy, Leach, Strong
* Ooh, what's the origin of CR's and magnetic fields?
Use synchrotron emission in total and polarized to infer and model the galactic magnetic field in the plane. Extend previous work by including realistic CR e- to match the high-energy data available. This reduces degeneracy, and allows low-energy end of CR e- spectrum to be studied. Assuming pure diffusion propagation, some numbers on the CR e- spectra and synchrotron brightness are predicted, showing CR re-acceleration process to be incompatible with synchrotron data.
* Oh, it's just some extension on the CR modeling they've done. I guess the origin of these things are still not well understood.
http://arxiv.org/abs/1105.5916
Reconstruction of the primordial power spectrum from CMB data
Guo, Schwarz, Zhang
* How did they do the reconstruction?
Use WMAP7 plus ACT data, and a binning method of cubic spline interpolation in log-log space [???]. They find a power-law spectrum [what in the world did they do with the transfer function???]. They find Harrison-Zel'dovich spectrum to be inconsistent with data at 95% confidence.
* The abstract is unclear about how the reconstruction was done.
* The Harrison-Zel'dovich spectrum is the scale-free matter perturbation, P_primordial(k) = Ak (i.e., n=1).
* The transfer function T(k) conveys information about the pre-recombination evolution and the nature of the matter content: P(k) = T^2(k) P_primordial(k).
http://arxiv.org/abs/1105.5644
Direct detection and CMB constraints on light DM scenario of top quark asymmetry and dijet excess at Tevatron
Hektor, Hütsi, Kadastik, Kannike, Raidal, Straub
* Crossover between HEP and cosmology. What do they mean by "light DM"? They all have to be pretty massive, I thought.
Tevatron experiment show Top quark fwd-bkwd asymmetry [mass of top quark is 172 GeV] that can be explained by GeV scale DM [wiki says sub-GeV particles are considered light-DM, I thought it had to be more massive than a GeV], which also improve agreement of the W+jj theory and data. Assuming this particle to be real, they calculate the predicted DM thermal relic density, the nutralino-nucleon cross section, and the CMB constraints on Dirac and Majorana neutralino DM direct detection experiments. They find that DM direct detection experiments and CMB constraints exclude the possibility of stable neutralino, unless local DM density is several times smaller than expected, in which case ~3GeV Dirac DM may be stable. This particle can be tested by the Planck mission, but predicts too broad excess in dijet distribution and strong modification of the missing E distribution in the W+jj events.
* It sounds like real science with both HEP and cosmology, but unfortunately it doesn't sound like a neutralino detection.
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