Do we need extra radiation?

A theory of extra radiation in the Universe

Kazunori Nakayamaa, Fuminobu Takahashib and Tsutomu T. Yanagidab


Abstract
Recent cosmological observations, such as the measurement of the primordial
4He abundance, CMB, and large scale structure, give preference to the existence of extra radiation component. The extra radiation may be accounted for
by particles which were in thermal equilibrium and decoupled before the big bangnucleosynthesis. Broadly speaking, there are two possibilities: 1) there are about 10 particles which have very weak couplings to the standard model particles and decoupled much before the QCD phase transition; 2) there is one or a few light particles with a reasonably strong coupling to the plasma and it decouples after the QCD phase transition.

Are we back to square one with dark matter?

From here (http://arxiv.org/abs/1010.4290):

General relativistic effects on non-linear matter power spectrum

Authors calculated the matter power spectrum based on next to the linear order perturbation theory (3rd order perturbation theory, 3PT) fully taking GR effect into account.
Basically, P_{3PT}=P_L+P_{22}+P_{13}, where non linear contributions cancel each other at large scale (P_{22}+P_{13}~0, or linear Pk is good enough), but boost up the Pk at small scale ( P_{22}+P_{13}>0).
P_{3PT} has been calculated for decades using Newtonian approximation, but this work is the first result to include genuine GR effect. As naively expected, correction due to GR is negligible, and the use of Newtonian approximation is verified.
arXiv:1010.3489

Falling into Virgo

The preferred direction of infalling satellite galaxies in the Local Group

Authors: Noam I Libeskind, Alexander Knebe, Yehuda Hoffman, Stefan Gottloeber, Gustavo Yepes, Matthias Steinmetz

http://arxiv.org/abs/1010.1531

"It becomes apparent from this figure, that as the MW and M31 travel towards virgo they scoop up subhalos in their path. These subhalos reside in a filamentary like structure that also points in the direction of Virgo."

Dark Matter Halo Density Profile

From arXiv:0810.1522

Title: The Diversity and Similarity of Simulated Cold Dark Matter Halos

From arXiv:1010.2539

Title: The Origin of Dark Matter Halo Profiles

Constraining the expansion rate of the Universe using low-redshift ellipticals as cosmic chronometers arXiv:1010.0831v1

Authors used a spectral feature around 4000A of Early Type Galaxies (ETG) to measure the Hubble constant. The result, H_0 = 72.3 \pm 2.8 (68% confidence), is in a good agreement to that of WMAP, and the error (systematic dominated?) is comparable to the one from SNIa.
Since the method is a direct measurement of the age of galaxies, it will be very useful for cross checking the values of w(z) etc... measured from other types of future DE missions.

Constraints on the Dark Matter Particle Mass from the Number of MilkyWay Satellites

http://arxiv.org/abs/1004.1459

Interesting numerical simulation and maybe one explanation to the satellite problem.

Quantum gravitational contributions to QED

This was a paper Joel (and I) briefly touched on this morning. It talks about how quantum gravitational affects can affect the running of other coupling constants (and potentially the scale of a Grand Unified Theory). This graph from this paper (which is probably not quite right) shows how couplings might evolve.

The M_BH-M_star relation of obscured AGNs at high redshift

J.E. Sarria, R. Maiolino, F. La Franca, F. Pozzi, F. Fiore, A. Marconi, C. Vignali, A. Comastri

http://arxiv.org/abs/1010.0768

These authors present the first sample of x-ray selected obscured (in the optical) high-z AGN. Using near-infreared spectra obtained with VLT and a SED fitting code, they infer AGN and stellar masses. They discuss their results in the context of the black hole mass - stellar mass relation (Magorrian relation, Magorrian et al. 1998).

From their abstract:
"All of these obscured high-z AGNs are fully consistent with the local M_BH-M_star relation. This result is in contrast with other samples of AGNs in the same redshift range, whose M_BH/M_star ratio departs significantly from the value observed in local galaxies."

Dark cores shining bright

The Ubiquity of Micrometer-Sized Dust Grains in the Dense Interstellar Medium

Pagani et al,

Science 24 September 2010:
Vol. 329. no. 5999, pp. 1622 - 1624

Dark (in Spitzer IRAC 8.0 micrometer, right) molecular cores shining bright (in Spitzer IRAC 3.6 micrometer, left). The white bar in the bottoms is 4000 AU.


From their abstract:

Cold molecular clouds are the birthplaces of stars and planets, where dense cores of gas collapse to form protostars. The dust mixed in these clouds is thought to be made of grains of an average size of 0.1 micrometer. We report the widespread detection of the coreshine effect as a direct sign of the existence of grown, micrometer-sized dust grains. This effect is seen in half of the cores we have analyzed in our survey, spanning all Galactic longitudes, and is dominated by changes in the internal properties and local environment of the cores, implying that the coreshine effect can be used to constrain fundamental core properties such as the three-dimensional density structure and ages and also the grain characteristics themselves.

Nice picture showing the masses of standard model quarks and leptons, as well as neutrinos

From http://arxiv.org/abs/1009.5870v1.