Day 547

Monday.  A full week behind.

1311.1888
D3PO - Denoising, deconvolving, and decomposing photon observations
Selig, Enßlin

[no matter how many times I read the abstract, I cannot understand what's going on]  D3PO algorithm addresses the inference problem of denoting, deconvolving, and decomposing photon observations.  Goal: simultaneous reconstruction of the diffuse and point-like photon flux from a given photon count image.  In order to discriminate between these morphologically different signal components, a probabilistic algorithm is derived in the language of information field theory based on a hierarchical Bayesian parameter model.  The signal inference exploits prior information on the spatial correlation structure of the diffuse component and the brightness distribution of the spatially uncorrelated point-like sources.  A maximum a posteriori solution and a solution minimizing the Gibbs free energy of the inference problem using variational Bayesian methods are discussed.  Since the derivation of the solution does not depend on the underlying position space, the implementation of the D3PO algorithm uses the NIFTY package [?] to ensure operationally on various spatial grids and at any resolution.  The fidelity of the algorithm is validated by the analysis of simulated data, including a realistic high energy photon count image showing a 32x32 arcmin^2 observation with a spatial resolution of 0.1 arcmin.  In all tests the D3PO algorithm successfully denoised, deconvolved, and decomposed the data into a diffuse and a point-like signal estimate for the respective photon flux components.

1311.2073
Galaxies on FIRE (Feedback in Realistic Environments): stellar feedback explains cosmologically inefficient star formation
Hopkints, Keres, Onorbe, Faucher-Giguere, Quataert, Murray, Bullock

[77 votes!  highest I've ever seen]  High-res cosmo sim of galaxy formation to z=0, spanning halo masses 1e8 to 13 Msun, and stellar masses 1e4-11 Msun.  Include both multi-phase ISM (molecular through hot) and stellar feedback (energy, momentum, mass, and metal fluxes), taken directly from stellar population models.  These sources of feedback, with zero adjusted parameters, reproduce the observed relation between stellar and halo mass up to M_halo~1e12 Msun (including dwarfs, satellites, MW-mass disks, and small groups).  By extension, this leads to reasonable agreement with the stellar mass function for M*<1e11 Msun.  Predict weak redshift evolution in the M*-M_halo relation, consistent with current constraints to z>6.  Find that the M*-M_halo relation is insensitive to numerical details, but is sensitive to the feedback physics.  Simulations with only SN feedback fail to reproduce the observed stellar masses, particularly in dwarf and high-z galaxies: radiative feedback (photo-heating and radiation pressure) is necessary to disrupt GMCs and enable efficient coupling of later SNe to the gas.  SFRs agree well with the observed Kennicutt relation at all redshifts.  THe galaxy-averaged Kennicutt relation is very different from the numerically imposed law for converting gas into stars in the simulation, and is instead determined by self-regulation via stellar feedback.  Feedback reduces SFRs considerably and produces a reservoir of gas that leads to rising late-time SFHs significantly different from the halo accretion history.  Fieedback also produces large short-timescale variability in galactic SFRs, especially in dwarfs.  Many of these properties are not captured by common 'sub-grid' galactic wind models.

1311.2583
Mapping compound cosmic telescopes containing multiple, projected cluster-scale halos
Ammons, Wong, Zabludoff, Keeton

"Compound cosmic telescopes": cluster-scale haloes along the line of sight with boosted magnification (entendue) makes detection of faint BG sources more likely than elsewhere.  Identified LoS with highest integrated mass densities (>3e15Msun along the LoS), as traced by LRGs.  2-3 group- and cluster-scale halos in 0.1<z<0.7, all of which are well-traced by LRGs.  Find V-dropout source at z=5.03.  ...

1311.2597
Sloan Digital Sky Survey III photometric quasar clustering: probing the initial conditions of the universe using the largest volume
Ho, et al

Clustering of 1.6M quasars in ~11k sq. deg, between 0.5<z<2.5, classified from imaging.  Measure angular clustering using an optimal quadratic estimator in four redshift slices with accuracy of ~25% over delta(l)~10-15 on scales corresponding to matter-radiation equality and larger (ell~2-30).  Observational systematics can strongly bias clustering measurements on large scales, which can mimic cosmologically relevant signals such as deviations from Gaussianity in the spectrum of primordial perturbations.  Constrain local primordial non-Gaussianity to f_NL=2pm65 (1 sigma) after removing systematics from data and removing angular bins that are contaminated by unknown systematics.

1311.2603
Short-duration gamma-ray bursts
Berger

GRB display a bimodal duration distribution, with separation between short- and long-duration bursts at about 2 sec.  The progenitors of long GRBs have been identified as massive stars based on their association with Type Ic core-collapse SNe, their exclusive location in SF galaxies, and their strong correlation with bright UV regions within their host galaxies.  Short GRBs have long been suspected on theoretical grounds to arise from compact object binary mergers (NS-NS or NS-BH).  The discovery of short GRB after glows in 2005, provided the first insight into their energy scale and environments, established a cosmological origin, a mix of host galaxy types, and an absence of associated SNe.  In this review review, summarize nearly a decade of short GRB afterglow and host galaxy observations, and use this information to shed light on the nature and properties of their progenitors, the energy scale and collimation of the relativistic outflow, and the properties of the circumburst [?] environments.  The preponderance of the evidence points to compact object binary progenitors, although some open questions remain.  Based on this association, observations of short GRBs and their afterglows can shed light on the on- and off-axis EM counterparts of GW sources from the Advanced LIGO/Virgo experiments.

1311.2896
A tale of cosmic rays narrated in gamma rays by Fermi
Tibaldo, Fermi LAT collaboration

CRs: charged particles scrambled by B-fields, combining direct measurements with other observations necessary to understand their origin and propagation.  As energetic particles traverse matter and EM fields, they leave marks in the form of neutral interaction products.  Among those, gamma rays trace interactions of nuclei that inelastically collide with interstellar gas, as well as of leptons that undergo Bremsstrahlung and inverse-Compton scattering.  Data collected by the Fermi LAT tell story of CRs along their path from sources through their home galaxies.  SN remnants emerge as a notable gamma-ray source population, and older remnants interacting with interstellar matter show strong evidence of the presence of accelerated nuclei.  Yet the maximum energy attained by shock accelerators is poorly constrained.  Cygnus X, a massive SF region established by the LAT as housing CR sources, provides a test case to study the impact of wind-driven turbulence on the early propagation.  Interstellar emission resulting from the large-scale propagation of CRs in the MW is revealed in unprecedented detail that challenges some of the simple assumptions used for the modeling.  Moreover, the CR induced gamma-ray luminosities of galaxies scale quasi-linearly with their massive-star formation rates, and suggests that for most systems a substantial fraction of energy in CRs escapes into the intergalactic medium.  The nuclear production models and the distribution of target gas and radiation fields, not determined precisely enough yet, are key to exploiting the full potential of gamma-ray data.  Nevertheless, data being collected by Fermi and complementary observations are bringing us closer to solving the CR mystery.