Day 425

Thursday.

1305.0005

Discovery of spectral curvature in the shock downstream region: CIZA J2242.8+5301
Stroe et al

[what's a radio phoenix?]

1305.0008
Probing dark energy through scale dependence
Motta et al

Consider consequences of having no prior knowledge of the true DE model for the interpretation of cosmological observations.  The magnitude of z-space distortions and WL shear is determined by the metric on the geodesics of which galaxies and light propagate.  Show that these data can be used to completely reconstruct the metric on our past lightcone and therefore to measure the scale- and time-dependence of the anisotropic stress and the evolution of the gravitational potentials in a model-independent manner.  Since both DM and DE affect the visible sector only through the gravitational field they produce, they are inseparable without a model for DE: galaxy bias cannot be measured and therefore the distribution of DM determined; the peculiar velocity of DM can be identified with that of galaxies only when the equivalence principle holds.  Given these limitations, show how one can nonetheless build tests for classes of DE models which depend on making measurements at multiple scales at a particular redshift.  They are null tests on the model-independent observables, do not require modeling evolution in time and do not require any parameterization of the free functions of these models, such as the sound speed.  Show how one can rule out or constrain the whole class of the most-general scalar-tensor theories even without assuming the quasi-static limit.

1305.0088
The galactic center: not an active galactic nucleus
An et al

10um-35um Spitzer spectra of central molecular zone (CMZ), the central 210 pc x 60 pc of the Galactic center (GC).  Maps of CMZ in ionic and H2 emission; radial velocities and intensities of ionic lines and H2 suggest that most of the H2 0-0 S(0) emission comes from gas along the LoS, as found by previous work.  Compare diagnostic line ratios meausured in the Spitzer Infrared Nearby Galaxies Survey; GC line ratios agree with SF galaxies and not with INERs or AGNs.

1305.0116
Reconstruction of missing data in the sky using iterative Harmonic expansion
Nishizawa, Inoue

As the title says; more accurate restoration than naive methods using the brute-force matrix inversion or SVD.

1305.0210
A new method to directly measure the Jeans scale of the intergalactic medium using close quasar pairs
Rorai, Hennawi, White

Small-scale (~100 kpc) fluctuation of baryons (IGM) suppressed by pressure support, analogous to the classical Jeans argument.  Cosmological implications: it provides a thermal record of heat injected by UV photons during reionization events, determines the clumpiness of the IGM, and sets the minimum mass scale for gravitational collapse, a key quantity in galaxy formation.  But, extremely challenging to measure via the standard analysis of purely longitudinal Lya forest spectra, because the thermal Doppler broadening of absorption lines is highly degenerate with Jeans pressure smoothing.  Show that the Jeans scale can be directly measured by characterizing the coherence of correlated Lya absorption in quasar pairs with separations small enough to resolve it.  New technique: PDF of phase angle differences of homologous longitudinal Fourier modes in close quasar pair spectra.  Bayesian formalism is introduced based on the phase angle PDF, and MCMC techniques are used to characterize the precision of a future Jeans scale measurement, and explore degeneracies with other thermal parameters governing the IGM.  A semi-analytical model of the IGM is used to generate a grid of 500 thermal models from DM simulation.  Full parameter study indicates that a realistic sample of only 20 close quasar pair spectra can pinpoint the Jeans scale to ~5% precision, independent of the parameters governing the T-density relation of the IGM.  Show that this new method is insensitive to a battery of systematics such as continuum fitting errors, imprecise knowledge of the noise and spectra resolution, and metal-line absorption.