Day 341

Tuesday.

1211.5601
Blocking low-eccentricity EMRIs: A statistical direct-summation N-body study of the Schwarzschild barrier
Brem et al

Extreme-mass ratio inspiral (EMRI), the capture of a compact object by SMBH in a galactic nucleus, is the best way to map space and time around it.  "Schwarzschild barrier": stellar dynamics phase space complot [what is this word?] in phase space acting on low-eccentricity captures (rates decrease significantly by the presence of a blockade in the rate at which L change takes place).  Result of the impact of relativistic precession on to the stellar potential torques, and thus it affects the enhancement on lower-eccentricity EMRIs that one would expect from resonant relaxation.  Confirm and quantify the existence of this barrier with 2500 direct-summation N-body sims; use post-Newtonian and geodesic approximation for the relativistic orbits.  The existence of the barrier prevents low-eccentricity EMRIs from approaching the central MBH, but high-eccentricity EMRIs ignore the presence of the barrier, because they are driven by 2-body relaxation.  Since the rates are significantly affected in the case of low-eccentricity EMRIs, predict that a LISA-like observatory will predominantly detect high-e EMRIs.

1211.5603
Planets near mean-motion resonances
Petrovich, Malhotra, Tremaine

Multiple planets found by Kepler: planet pairs near first-order mean-motion resonances prefer orbits just outside the nominal resonance, while avoiding those just inside the resonance.  Simple dynamical model for planet formation where planets grow in mass at a prescribed rate without orbital migration or dissipation.  Develop an analytic version of this model for 2 planet systems in 2 limiting cases: the planet mass grows quickly or slowly relative to the characteristic resonant libration time.  In both cases the distribution of systems in period ratio develops a characteristic asymmetric peak-trough structure around the resonance, qualitatively similar to that observed in the Kepler sample.  Verify this result with numerical integrations of the restricted 3-body problem.  Show: for 3:2 resonance (where the observed peak-trough structure is strongest), the simple model is consistent with the observations for a range of mean planet masses 20-100 M_earth.  This mass range is higher than expected, by at least a factor of three, from the few Kepler planets with measured masses, but part of this discrepancy could be due to oversimplifcations in the dynamical model or uncertainties in the planetary mass-radius relation.

1211.5605
The WiggleZ dark energy survey: probing the epoch of radiation domination using large scale structure
Poole, Blake, et al

Find the turnover of MPS at k_0=0.016pm0.004 h/Mpc.

1211.5607
The colors of central and satellite galaxies in zCOSMOS out to z~0.8 and implications for quenching
Knobel, Lilly, et al

Examine the red fraction of central and satellite galaxies in zCOSMOS group catalog out to z~0.8, correcting for both the incompleteness in stellar mass and for the less than perfect purities of the central and satellite samples.  Show: at all masses and z, the fraction of satellite galaxies that have been quenched (i.e., are red), is systematically higher than that of centrals, as seen locally in the SDSS.  The satellite quenching efficiency, which is the probability that a satellite is quenched because it is a satellite rather than a central, is, as locally, independent of stellar mass.  Furthermore, the average value is about 0.5, which is also very similar to that seen in the SDSS.  Also construct the mass functions of blue and red centrals and satellites and show that these broadly follow the predictions of the Peng+2012 analysis of the SDSS groups.  Together, these results indicate that the effect of the group environment in quenching satellite galaxies was very similar when the Universe was about half its present age.

1211.5619
Correlating features in the primordial spectra
Achucarro, Gong (Jinn-Ouk!), Palma, Patil

Heavy fields coupled to the inflation reduce the speed of sound in the effective theory of the adiabatic mode each time the BG inflationary trajectory deviates from a geodesic; this can result in features in the primordial spectra.  Compute corresponding bispectrum and show that if a varying speed of sound induces features in the power spectrum, the change in the bispectrum is given by a simple formula involving the change in the PS and its derivatives.  In this manner, provide a uniquely discriminable signature of a varying sound speed for the adiabatic mode during inflation that indicates the influence of heavy fields.  Find that features in the bispectrum peak in the equilateral limit and, in particular, in the squeezed limit we find considerable enhancement entirely consistent with the single field consistency relation.  From the perspective of the underlying effective theory, results can be generalized to incorporate a wide variety of inflationary models where features are sourced by the time variation of BG quantities.

1211.5709
Magnetic white dwarf stars in the SDSS
Kepler, et al

Look for Zeeman splittings in H lines of WD atmosphere; about 4% of them were split, with fields from 1 MG to 733 MG.  

1211.5743
PHIBSS: molecular gas content and scaling relations in a~1-3 normal star forming galaxies
Tacconi, ... Genzel,... et al

High-z blue sequence CO 3-2 survey of molecular gas properties in normal SFGs near the cosmic SF peak.  52 CO detections in 2 redshift slices z~1.2 and 2.2, with log (M*/Msun)>10.4, and log(SFR/(Msun/yr))>1.5.  Include correction for the incomplete coverage of M*-SFR plane, infer average gas fractions of ~0.33 at z~1.2 and ~0.47 at z~2.2.  Gas fractions drop with stellar mass, in agreement with cosmological simulations including strong SF feedback.  Most of the z~1-3 SFGs are rotationally supported turbulent disks.  The sizes of CO and UV/optical emission are comparable.  The molecular gas-SF relation for the z=1-3 SFGs is near-linear, with a ~0.7 Gyrs gas depletion timescale; changes in depletion time are only a secondary effect.  Since this timescale is much less than the Hubble time in all SFGs between z~0 and 2, fresh gas must be supplied with a fairly high duty cycle over several billion years.  At given z and M*, gas fractions correlate strongly with the specific SFR.  The variation of specific SFR between z~0 and 3 is mainly controlled by the fraction of baryonic mass that resides in cold gas.

1211.5854
Feedback from high-mass X-ray binaries on the high redshift intergalactic medium : model spectra
Power, James, Combet, Wynn

Massive stars at z>6 plays a major role in cosmological reionization as luminous sources of UV photons.  Remnants of these stars can be equally important as x-ray luminous high-mass X-ray binaries (HMXBs).  Absorption cross section of neutral H decreases sharply with photon energy (propto inverse cube), X-rays can escape more freely than UV photons from SF regions in which they are produced, allowing HMXBs to make a potentially significant contribution to the ionizing X-ray background during reionization.  Explore the ionization power of HMXBs at z>6 using MC model for a coeval stellar population of MS stars and HMXBs.  Using the archetypal galactic HMXB Cygnus X-1 as template, propose a composite HMXB SED consisting of BB and power-law components, whose contributions depend on the accretion state of the system.  Determine the time-dependent ionizing power of a combined population of UV-luminous stars and X-ray luminous HMXBs, and deduce fitting formulae for the boost in the population's ionizing power arising from HMXBs; these fits allow for simple implementation of HMXB feedback in numerical simulations.  Based on this analysis, estimate the contribution of high-z HMXBs to the present-day soft X-ray BG, and show that it is a factor of ~100-1000 smaller than the observed limit.  Finally, discuss the implications of our results for the role of HMXBs in reionization and in high z galaxy formation.

1211.5966
Measuring the mass distribution of voids with stacked weak lensing
Higuchi, Oguri, Hamana

Study the prospects of measuring the DM distribution of voids with stacked WL.  Select voids from a large set of N-body simulations, and explore their lensing signals with the full ray-tracing simulations, including the effect of the large-scale structure along the LoS.  The lensing signals are compared with simple void model predictions to reconstruct the 3d mass distribution of voids.  Show that the stacked WL signals are detected at significant level (S/N >= 5) for a 5000 deg^2 survey area, for a wide range of void radii up to ~ 50 Mpc.  The error from the shape noise little affects lensing signals at large scale.  Also found that dense ridges around voids have a great impact on the WL signal, suggesting that proper modeling of the void density profile including surrounding ridges is essential for extracting the average total mass of voids.

1211.5376
Measuring dark matter profiles non-parametrically in dwarf spheroidals: an application to Draco
Jardel et al

Use stellar kinematics to map DM distribution, find it to be pretty cuspy for Draco, a dSph.  The profile for 20 < r < 700 pc well-fit by a power law with slope alpha=-1.0 pm 0.2, consistent with CDM simulations.  Despite its low baryon content, Draco lives in a massive halo.