Day 651

Friday.

1405.1414
Stars as resonant absorbers of gravitational waves
McKernan, Ford, Kocsis, Haiman

Quadrupole oscillation modes in stars can resonate with indecent GWs, and grow NL at the expense of GW energy.  Stars near MBHB (massive BH binaries) can act as GW-charged batteries, cooling radiatively.  Mass-loss from these stars can prompt MBHB accretion at near-Eddington rates.  GW opacity is independent of amplitude, so distant resonating stars can eclipse GW sources.  Absorption by the Sun of GWs from Galactic WD binaries may be detectable with second-generation space-based GW detectors as a shadow within a complex diffraction pattern.

1405.1418
Properties of galaxies reproduced by a hydrodynamic simulation
Vogelsberger, … Springel, Xu, Hernquist, et al

Previous simulations of cosmic structures failed to create a mixed population of elliptical and spiral galaxies due to numerical inaccuracies and incomplete physical models.  Because of computational constraints, they were unable to track the small locale evolution of gas and stars to the present epoch within a representative portion of the Universe.  Report a simulation that starts 12 Myrs after BB, and traces 13 Byrs of cosmic evolution with 12 billion resolution elements in a volume of (106.5Mpc)^3.  Yields a reasonable population of ellipticals and spirals, reproduces the distribution of galaxies in clusters and statistics of hydrogen on large scales, and at the same time the metal and hydrogen content of galaxies on small scales.

1405.1427
Gone with the wind: where is the missing stellar wind energy from massive star clusters?
Rosen et al

Star clusters larger than ~1e3 Msun contain multiple hot stars that launch fast stellar winds.  The integrated kinetic energy carried by these winds is comparable to that delivered by SN explosions, suggesting that at early times winds could be an important form of feedback on the surrounding cold material from which the star cluster formed.  However, the interaction of these winds with the surrounding clumpy, turbulent, cold gas is complex and poorly understood.  Investigate this problem via an accounting exercise: use empirically determined properties of four well-studied massive stars clusters to determine where the energy injected by stellar winds ultimately ends up.  Consider a range of kinetic energy loss channels, including radiative cooling, mechanical work on the cold interstellar medium, thermal conduction, heating of dust via collisions by the hot gas, and bulk advection of thermal energy by the hot gas.  Show that, for at least some of the clusters, none of these channels can account for more than a small fraction of the injected energy.  Suggest that turbulent mixing at the hot-cold interface or physical leakage of the hot gas from the HII region can efficiently remove the kinetic energy injected by the massive stars in young star clusters.  Even for the clusters where it is able to account for all the injected kinetic energy, show that accounting sets strong constraints on the importance of stellar winds as a mechanism for feedback on the cold ISM.

1405.1432
Delensing galaxy surveys
Chang, Jain

WL can cause displacements, magnification, rotation and shearing of the images of distant galaxies.  Most studies focus on the shear and magnification effects since they are more easily observed.  IN this paper, focus on the feet of lensing displacements on wide field images.  Galaxies at 0.5<z<1 are typically displaced by 1 arc minute, and the displiacemtns are cohenereng over degree-size patches.  HOwever the displacement effect is z-dependent, so there is a visible relative shift between galaxies at different redshifts, even if they are close on the sky.  SHow that the reconstruction of the original galaxy position is now feasible with lensing surveys that cover many hundreds of square degrees.  Test with simulations two approaches to "delensing": one uses shear measurements and the other uses the FG galaxy distribution as a proxy for the mass.  Also estimate the effect of FG deflections on gg lensing measurements and find it is relevant only for LSST and Euclid-era surveys.

1405.1447
Understanding higher-order nonlocal halo bias at large scales by combining the power spectrum with the bispectrum
Saito, Baldauf, Vlah, Seljak, Okumura, McDonald

Understanding the relation between underlying matter distriubiton and biased tracers such as galaxy or DM halo is essential to extract cosmological information from ongoing or future galaxy redshift surveys.  At sufficiently large scales such as the BAO scale, a standard approach for the bias problem on the basis of the PT is to assume the 'local bias' model in which the density field of biased tracers is deterministically expanded in terms of matter density field at the same position.  The higher-order bias parameters are then determined by combining the PS with higher-order statistics such as the bispectrum.  As is pointed out by recent studies, however, NL gravitational evolution naturally includes nonlocal bias terms even if initially starting only with purely local bias.  Previous works showed that the second-order nonlocal bias term, which corresponds to the gravitational tidal field, is important to explain the characteristic scale-dependence of the bispectrum.  In this paper, extend the non-local bias term up to 3rd order, and investigate whether the PT-based model including NL bias terms can simultaneously explain the PS and the bispectrum of simulated haloes in N-body simulations.  Show that the PS, including density and momentum, and the bispectrum between halo and matter in N-body simulations can be simultaneously well explained by the model including up to 3rd order nonlocal bias terms up to k~0.1h/Mpc.  Also, the results seem in a good agreement with theoretical predictions of a simple coevolution picture, although the agreement is not perfect.  These demonstration clearly shows a failure of the local bias model even at such large scales, and conclude that nonlocal bias terms should be consistently included in order to model statistics of haloes.

1405.1539
A new method of weak lensing shear measurement using 0th order ellipticity and ERA
Okura, Futamase

Developed a new method for WL shear analysis using the ellipticity defined by the 0th order moment of the image and a new method of PSF correction called the ERA method.  Although there is a strong correlation between the ellipticity calculated using this approach and the usual ellipticity defined by the 2nd order moment, the ellipticity calculated here has a higher S/N ratio because it is weighted to the central region of the image.  These results were confirmed using data for A1689 from the Subaru telescope.  The new PSF correction technique developed is also applied here, which uses an artificial image with the same ellipticity as the lensed images, and avoids the systematic error associated with the approximation used in previous approaches for PSF correction.  Therefore it is expected that this new method measures the shear more accurately than the previous moment method.  Tested and confirmed this expectation using simulated images.

1405.1566
Detection of a super void aligned with the cold spot of the cosmic microwave background
Szapudi et al

Use the WISE-2MASS IR galaxy catalog matched with PS1 galaxies to search for a super void in the direction of the CMB cold spot.  Imaging catalog has median z~0.14, and we obtain photometric z from PS1 optical colors to create a tomographic map of the galaxy distribution.  The radial profile centered on the Cold Spot shows a large low density region, extending over 10's of degrees.  Motivated by previous CMB results, test for under densities within two angular radii, 5 and 15 deg.  The counts in photo-z bins show significantly low densities at high significance, >5 sigma and >6 sigma, respectively, for the two fiducial radii. The line-of-sight position of the deepest region of the void is z~0.15-0.25.  Data combined with an earlier measurement are consistent with a large R_void=192pm15 Mpc/h (2sigma) super void with delta~-0.13pm0.03 centered at z=0.22pm0.01.  Such a super void, constituting a ~3.5-5 sigma fluctuation in a Gaussian distribution of the LCDM model, is a plausible cause for the Cold Spot.

1405.1604
Jupiter as a giant cosmic ray detector
RImmer, Stark, Helling

In order to be observed, air showers in Jupiter's atmosphere would need to be oriented toward the Earth, and would need to occur sufficiently high in the atmosphere that the gamma rays an penetrate.  Demonstrate that under these assumptions, Jupiter provides an effective CR "detector" area of 3.3e7 km^2.  Predict that Fermi-LAT should be able to detect events of energy>1e21 eV with fluence 1e-7 erg/cm2 at a rate of about one per month.  THe observed number of air showers may provide an indirect measure of the flux of CRs > 1e20 eV.  Extensive air showers also produce a synchrotron signature that may be measurable by ALMA.  Simultaneous observations of Jupiter with ALMA and Fermi-LAT could be used to provide broad constraints on the energies of the initiating CRs.

1405.1910
Optical spectra of 73 stripped-envelope core-collapse supernovae
Modjaz, et al

Present 645 optical spectra of 73 SNe of types IIb, Ib, Ic and broad-lined Ic.  All of these types are attributed to the core collapse of massive stars, with varying degrees of intact H and He envelopes before explosion.  The SNe in the sample have a mean redshift <cz>=4200 km/s.  Most of these spectra were gathered at the Harvard-Smithsonian CfA between 2004 and 2009.  For 53 SNe, these are the first published spectra.  The data coverage range from mere identification (1-3 spectra) for a few SNe to extensive series of observations (10-30 spectra) that trace the spectral evolution for others, with an average of 9 spectra per SN.  For 44 SNe of the 73 SNe presented here, have well-determined dates of maximum light to determine the phase of each spectrum.  Sample constitutes the most extensive spectral library of stripped-envelope SNe to date.  Provide very early coverage (as early as 30 days before V-band max) for photospheric spectra, as well as late-time nebular coverage when the innermost regions of the SNe are visible (as late as 2 years after explosion, while for SN1993J, there are data as late as 11.6 years).  This data set has homogeneous observations and reductions that allow us to study the spectroscopic diversity of these classes of stripped SNe and to compare these to SNe associated with gamma-ray bursts.  Undertake these matters in follow-up papers.

1405.2020
Generalized slow roll for tensors
Hu

The recent BICEP2 detection of degree scale CMB B-mode polarization, coupled with a deficit of observed power in large angle temperature anisotropy, suggest that the slow-roll parameter epsilon_H, the fractional variation in the Hubble rate per e-fold, is both relatively large and may evolve from an even larger value on scales greater than the horizon at recombination.  The relatively large tensor contribution implied also requires finite matching features in the tensor PS for any scalar PS feature proposed to explain anomalies in the temperature data.  Extend the generalized slow-roll approach for computing power spectra, appropriate for such models where the slow-roll parameters vary, to tensor features where scalar features are large.  This approach also generalizes the tensor-scalar consistency relation to be between the ratio of tensor and scalar sources and features in the two power spectra.  Features in the tensor spectrum are generically suppressed by e_H relative those in the scalar spectrum and by the smoothness of the Hubble rate, which must obey covariant conservation of energy, versus its derivatives.  Their detection in near future CMB data would indicate a fast roll period of inflation where e_H approaches order unity, allowed but not required by inflationary explanations of temperature anomalies.

1405.2035
Shape profiles and orientation bias for weak and strong lensing cluster haloes
Groener, Goldberg

Study the intrinsic shape and alignment of isodensities of galaxy cluster haloes extracted from the MultiDark MDR1 cosmological simulation.  Find that the simulated haloes are extremely prolate on small scales, and increasingly spherical on larger ones.  Due to this trend, projection along the LoS produces an overestimate of the concentration index as a decreasing function of radius.  Based on this result, predict that the selection of clusters based upon their strong lensing features will tend to produce a larger over-concentration bias when compared with WL of this same population, a difference of ~17%.  Isodensities are found to be fairly well-aligned throughout the entirety of the radial scale of each halo population.  However, major axes of individual halos have been found to deviate by as much as ~30deg.  Also present a value-added catalog of our analysis results, which have made publicly available to download.