Day 26

Saturday.  Actually going to do astroph today (and intend to do it tomorrow too).


1106.4621
Effects of P-wave annihilation on the Angular power spectrum of extragalactic gamma-rays from DM annihilation


* P-wave annihilation:  The orbital angular momentum of the initial state is p-wave.


DM annihilation with general velocity-dependent cross section, producing gamma rays: p-wave annihilation cross section is sigma v = a + b v^2.  Increases gamma ray power if b/a >> 1e6.  Important effect for a given b/a is largely determined yb the cosmic DM distribution.  Some speculations about how DM would behave if it were produced thermally from strong p-wave theories (whatever that is).


* the velocity that they talk about--is that the the motion of observer relative to the DM halo?


1106.4722
Dusty explosions from dusty progenitors:  The physics of SN2008S and the 2008 NGC300-OT
Kochanek


Explosive transients of stars self-obscured by very dense, dusty stellar winds.  1e10 Lsun required to render the transients little obscured and visible in the optical at their peaks---indicating cool red supergiant progenitor (~9Msun) extreme AGB stars.  Produce shock luminosity in soft X-rays, powering the long-lived luminosity of the transients.  The progenitor winds are optically thick to soft X-rays, easily absorb radio emission and rapidly reform dust destroyed by the peak luminosity of the transients.  Energy ultimately radiated by the reformed dust (only visible in the mid-IR after 3 years, although significantly luminous than the progenitor stars).  


* AGB:  Asymptotic Giant Branch:  evolving low to medium-mass stars (0.6-10 Msun), late in their lives.  
* AGB phases:  (1) "early": He fusion, CO core.   Becomes a red giant.  (2) He runs out, H burns, He accumulates, He flash.  The thermal pulsation phase.  Pulse mixes material from core region into the outer layers.  


1010.1065
ACT: SZ selected galaxy cluster at 148GHz in the 2008 survey
Marriage, et al.


23 clusters detected in 455 square-degree map.  All have optical counterparts.  10 are new.  One really massive, high z (z~0.75) cluster found.  100% pure, 80% complete (for M500>6e14 Msun) subsample.  Agrees well with self-similar and non-adiabatic, simulation-derived scaling laws.


1106.3312
Cosmology of the Galileon from massive gravity
de Rham, Heisenberg


Hubble parameter corresponds to the graviton mass.


* that's the only sentence that made sense to me.


1106.4313
An improved forecast of patchy reionization reconstruction with CMB
Yu, Yadav, McQuinn, Yoo, Zaldarriaga


* I read this one two days ago, apparently.


S/N is not as good as previously reported to get patchy reionization from angular variation in tau. It was report to be S/N~10, but it's probably more like S/N~1 because gravitational lensing signal completely dominates this signal.  Derived a better estimator to do the tau business.


* apparently I remembered what it was about.


1001.2333
Shape measurement biases from underfitting and ellipticity gradients
Bernstein


When measuring galaxy shapes, methods that rely on fitting elliptical isophote methods have two biases:  (1) when galaxies do not match the models being fit ("underfitting bias")---these methods attempt to use information at high frequencies destroyed by the convolution with the PSF and/or sampling.  Propose new technique confined to observable regions of k-space.  (2) if there is ellipticity variation with radius ("ellipticity gradient bias")--most shape measurement methods are subject to this bias.  These biases can be reduced by x20-100 with the new method.  Resulting shear estimator has <1 part in 1e3 for high S/N images, even for highly asymmetric galaxies.  Without any training or calibration, new method obtains Q=3000 in the GREAT08 Challenge.


* I got to read this paper.


MNRAS 382, 315 (2007)
Bayesian galaxy shape measurement for weak lensing surveys -- I. Methodology and a fast-fitting algorithm
Miller, Kitching, Heymans, Heavens and Van Waerbeke


Measuring the shapes of galaxies by a model-fitting approach (in context of WL).  Need maximum S/N along with measurement error estimates.  Distinction between likelihood-based and Bayesian methods discussed.  Systematic biases in the Bayesian method may be evaluated as a part of the fitting process.  Overall such an approach should yield unbiased shear estimation w/o external calibrations.  Drawback is computing time, but a new algorithm introduced that is suitable for large-scale surveys.  Method tested on STEP.


MNRAS 390, 149 (2008)
Bayesian galaxy shape measurement for weak lensing surveys -- II. Application to simulations
Kitching, Miller, Heymans, van Waerbeke, Heavens


Extend the Bayesian model fitting shape measurement (above) and estimate shear using STEP simulations.  Describe method: model fitting, fast, realistic, analytical marginalization over position and amplitude (done in Fourier space).  Full posterior probability in ellipticity.  Then find shear in Bayesian way from this posterior probability surface.  Iterative algorithm that can be used to estimate the intrinsic ellipticity prior.  (COOL!!!!  ...I'm such a geek.)  Shape noise estimation is accurate and stable.
Results:  Shear bias 0.006 pm 0.005; additive offset 0.0002 (STEP 1), 0.002 pm 0.016 and offset -0.0007 (STEP2).  Bias and offset stable to changes in magnitude and size of the galaxies.  Pretty robust in systematic effects, at least in terms of shape measurements.  
Present alternative to STEP parameterization: quality factor---relates intrinsic shear variance in a simulation to the variance in shear that is measured.  Q>100 for this method, x10 better than others.


* Might have to read this a bit.