Day 153

Friday, already.  Catch up with work today.

1112.1692

The 3-D distribution of dust in NGC 891

Schechtman-Rook, Bershady, Wood

Produce 3d Monte-Carlo radiative transfer models of the edge-on spiral galaxy NGC 891 (similar to MW).  Fit models to HST B/I images.  The 30 best-fit models have strong preference for spirality and clumpiness, with average face-on attenuation decreasing from 0.24 to 0.03 in the B band between 0.5 and 2 radial scale-lengths.  Most attenuation comes from high-density clumps with low filling factors [?].  Fraction of dust in clumps broadly consistent with results from fitting NGC 891's spectral energy distribution.  Attenuation curve fitting--higher attenuation at low inclinations than previous models.

1112.1693

Fables of reconstruction: controlling bias in the dark energy equation of state

Crittenden, Zhao, Pogosian, Samushia, Zhang

Develop non-parametric Bayesian method for reconstructing the time evolution of DE equation of state w(z) from observational data.  Choice of prior: minimize variance and bias in the reconstruction.  Using PCA, show how a correlated prior can be used to create a smooth reconstruction, and also avoid bias in the mean behaviour of w(z).  Test method using Wiener reconstructions based on Fisher matrix projections.  Accuracy depends on the smoothness of the assumed w(z); relative error of typical DE models is <10% out to redshift z=1.5.

1112.1697

Radio monitoring of the tidal disruption event Swift J164449.3+573451. I. Jet Energetics and the pristine parsec-scale environment of a supermassive black hole

Berger et al

Radio observations of the tidal disruption event extending to ~216 days after discovery.  Part of a long-term program to monitor the expansion and energy scale of the relativistic outflow, and to trace the parsec-scale environment around a previously-dormant SMBH.  Increase in energy cannot be explained with continuous injection from an L~t^-5/3 tail, which is observed in X-rays.  Relativistic jet must have been launched with a wide range of Lorentz factors, obeying E(>Gamma) ~ Gamma^-2.5.  Since this even is similar to GRB ratio of duration to dynamical timescale, it may be applicable to regular GRBs as well.  Show radial density profile around SMBH of r^-3.2 out to 1.2 pc, with significant flattening at 0.4-0.6 pc; this may be indicative of the Bondi accretion, with inferred flattening at r~0.5pc in good agreement with Bondi radius for a 1e6 Msun BH.  Density at ~0.5 pc is 30x less than MW center, potentially due to a smaller number of mass-shedding massive stars.  

1112.1698

Confronting simulations with the observed CGM at z=0

Stinson, Brook, Prochaska, Hennawi, ... etal

Model circumgalactic medium (metallicity out to virial radius) of two galaxies at L~0.1 and 1 L*, each at two different SNe feedback models (HF--high and LF--low feedback).  Only the HF models give sufficient OVI and HI gas in the CGM to reproduce observed distributions, as well as other galaxy observables (stellar mass-halo mass relation).  LF models are what are typically used in the literature.  Infer CGM holdes the dominant reservoir of baryons for galaxy halos.

1112.1705

Baryon content of massive galaxy clusters at z=0-0.6

(Yen-TIng) Lin, Stanford, Eisenhardt, Vikhlinin, Maughan, Kravtsov

Relationship between stars and ICM ionized gas in galaxies, using 94 clusters that span the redshift range 0-0.6.  Total and ICM masses from Chandra; stellar masses from wide-field IR survey explorer and 2MASS trace the evolution of cluster baryon content in a self-consistent fashion.  Find that, within r_500, the evolution of ICM mass-total mass relation is consistent with the expectation of self-similar model, while there is no evidence for redshift evolution in the stellar mass-total mass relation.  Suggests that the stellar mass and ICM mass in the inner parts of clusters evolve differently.

* I should read this.

1112.1717

Relativistic iron K X-ray reverberation in NGC 4151

Zaghbi, Fabian, Reynolds, Cackett

Reverberation delay of 2000s in Fe K band in AGN.  Peak of lag spectra shifts to lower energies at higher frequencies, consistent with the red wing of the line being emitted at smaller radii.

1112.1729

Investigating MgII Absorption in paird quasar sight-lines

Rogerson, Hall

Tinker & Chen model of MgII absorption due to gaseous halo around a galaxy: reproduce absorption in quasar pairs, which show total of 38 MgII systems spanning z=0,043-2.066.  Generate simulated sight-lines, marginalize unknown parameters of the absorbing galaxies: DM halo mass, impact parameter, azimuthal angle on the sky. ...

1112.1732

The X-factor in Galaxies: I. Dependence on environment and scale

Feldmann, Gnedin, Kravtsov

Conversion factor between CO emission and column density of molecular hydrogen (X_CO) crucial in studying the gaseous content of galaxies, evolution, and relation to SF.  Usually assumed to be similar to giant molecular clouds (GMCs) in MW, except for mergers and star bursting galaxies.  Physically, it should also depend on metallicity, surface density, and strength of interstellar radiation field; it may also depend on the scale on which CO emission is averaged due to effects of limited resolution.  Combine sub-pc scale MHD sims and on gas distribtion from self-consistent cosmo sims of galaxy formation--model predicts a value of X_CO that is consistent with Galactic value for ISM conditions typical for the MW, no strong dependence on surface density in the range of 50-500 Msun/pc^2.  Scale of GMC predicted, and X_CO is a strong function of metallicity; depends on the column density and interstellar UV flux.  Show explicitly that neglecting these dependencies in observational estimates can strongly bias the inferred distribution of H2 column densities of molecular clouds to have a harrower and offset range compared to true distribution.  Averaged kpc scales of X-factor depends only weakly on radiation field and column density, but is still a strong function of metallicity.  

1112.1754

The new horizon run cosmological N-body simulations

Kim, Park, Rossi, Lee, Gott

New N-body simulation with 6000^3 and 7210^3 particles, of volumes (7.2Gpc/h)^ 3 and (10.8Gpc/h)^3.  For simulating the BOSS geometry.

1112.1820

The kinetic SZ signal from inhomogeneous reionization: a parameter space study

Mesinger, McQuinn, Spergel

Inhomogeneous reionization acts as a source of arcminute-scale anisotropies in the CMB, the most important of which is the kSZ [really?].  ACT and SPT are poised to detect his signal for the first time.  Use 21cmFAST and compute kSZ signal from a suite of ~100 reionization models.  Parameterize by ionizing efficiency of high-z galaxies, minimum virial temperature of haloes capable of hosting stars, and ionizaing photon mean free path.  Predict contribution of patchy reionzation signal, P_patchy~1.5-3.5 uK^2.  None of the models consistent with the aggressive 2sigma SPT bound that does not include correlations.  Implies either (i) the early stages of reinozatin occurred in a much more homogenous manner than suggested by the stellar-driven scenarios explored (by very high energy X-rays or exotic particles), and/or (ii) there is a significant correlation between the CIB and the tSZ.  The conservative SPT bound is compatible with all models.

1112.1862

Constraints on the CMB temperature redshift dependence from SZ and distance measurements

Avgoustidis, Luzzi, Martins, Monteiro

Relation between redshift and CMB temperature: key prediction in standard cosmology, but violated in many non-standard models.  If photons can be created or destoyed, not only does the T-z relation change, but so does the distance duality relation.  ...

1112.1922

Tides in colliding galaxies

Duc, Renaud

Review of galactic tides.  Numerical simulations, theoretical aspects, observations and the need for multi-wavelength data.  Tidal tails are not just stellar structures, but contain all components usually found in galactic disks (atomic/molecular gas and dust).  Host star-forming complexes and are able to form star-clusters or even second-generation dwarf galaxies.  What it reveals about structure and content of present-day galaxies, probe past evolution of galaxies and mass assembly history.