1307.2571
Cosmology with void-galaxy correlations
Hamaus et al
Galaxy bias is a major hurdle for cosmological inference from large-scale structure. While traditional analysis focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs, demonstrate that cross-correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a standard ruler thanks to the observable geometric nature of voids. Illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross-correlations reveals a concordance with the mass-density profile of voids.
1307.2573
Simulating intergalactic quasar scintillation
Pallottini, Ferrara, Evoli
Intergalactic scintillation of distant quasars [don't understand exactly what is scintillating] is sensitive to free electrons and therefore complements Lya absorption line experiments probing the neutral IGM. Present a new scheme to compute IGM refractive scintillation effects on distant sources in combination with AMR cosmo sims. First validate model by reproducing the well-known interstellar scintillation (ISS) of galactic sources. The simulated cosmic density field is then used to infer the statistical properties of intergalactic scintillation. Find (contrary to previous claims) that the scattering measure of the simulated IGM at z<2 is 3.8, almost 40x larger than for the usually assumed smooth IGM. This yield an average modulation index ranging from 0.01 (nu_s=5 GHz) to 0.2 (nu_s=50 GHz); above 30 GHz the IGM contribution dominates over ISS modulation. ...Possibility of using IGM scintillation as a tool to pinpoint the presence of intervening high-z groups/clusters along the LoS, thus making it a probe suitably complementing SZ data.
1307.2632
Imprint of primordial non-Gaussianity on dark matter halo profiles
Dizgah, Dodelson, Riotto
Impact of primordial non-Gaussianity on the density profile of DM haloes by using the SAM by Dalal+, which relates the peaks of the initial linear density field to the final density profile of DM haloes. Models with primordial non-Gaussianity typically produce an initial density field that differs from that produced in Gaussian models. Use the path integral formulation of excursion set theory to calculate the non-Gaussian corrections to the peak profile and derive the statistics of the peaks of non-Gaussian density field. In the context of the SM for halo profiles, currently allowed values for primordial non-Gaussianity would increase the shapes of the inner DM profiles [wth do they mean by "increase the shape"?], but only at the sub-percent level except in the very innermost regions.
1307.2638
Determining the Hubble constant from gravitational wave observations of merging compact binaries
Nissanke, Holz, Dalal, Hughes, Sievers, Hirata [wow]
SGRBs probably associated with NS binary mergers; indicate association with G signal corresponding to the final inspiral of the compact binary. The radioactive decay of elements produced in NS binary mergers may result in transients visible in the optical and IR with peak luminosities on hours-days timescales. Simultaneous observations of the GWs and signatures in the EM band may allow directly and independently determine both the luminosity distance and redshift to a binary. These standard sirens (GW analog of standard candles) have the potential to provide an accurate measurement of the low-z Hubble flow. In addition, these systems are absolutely calibrated by GR, and therefore do not experience the same set of astrophysical systematics found in traditional standard candles, nor do the measurements rely on a distance ladder. Show that 15 observable GW and EM events should allow the Hubble constant to be measured with 5% precision using a network of detectors that includes advanced LIGO and Virgo. Measuring 30 beamed GW-SGRB events could constrain H_0 to better than 1%. When comparing to standard Gaussian likelihood analysis, find that each event's non-Gaussian posterior in H_0 helps reduce the overall measurement errors in H_0 for an ensemble of NS binary mergers. [so do NS binary mergers give a clean correspondence between GW and radioactive decay (hence EM wave) production?]
1307.2721
SN 2011fe: a laboratory for testing models of type Ia supernovae
Chomiuk
SN 2011fe is the nearest SNIa discovered in the modern multi-wavelength telescope era with the earliest discovery [I assume they mean that the lightcurve was detected way before it peaked]. This review covers 4 questions: (1) what explodes in SNIa? (2) how does it explode? (3) what is the progenitor of this SNe? (4) How accurate are SNIa as standardizable candles? Most aspects of SN 2011fe are consistent with the canonical picture of a massive CO white dwarf undergoing a deflagration-to-detonation transition. However, there is minimal evidence for a non-degenerate companion star, so SN 2011fe may have marked the merger of two WDs.
1307.2886
Direct imaging of a cold Jovian exoplanet in orbit around the sun-like star GJ 504
Kuzuhara et al
As the title says. Has the potential of providing novel insights into the origins of giant planets, as well as their atmospheric properties.
1307.2890
The stability of tidally deformed neutron stars to three- and four-mode coupling
Venumadhav, Zimmerman, Hirata [wow]
Recently suggested: the tidal deformation of a NS excites daughter p- and g-modes [what modes?] to large amplitudes via a quasi-static instability. This would remove energy from the tidal bulge, resulting in dissipation and possibly affecting the phase evolution of inspirialling binary NSs and hence the extraction of binary parameters form gravitational wave observations. This instability appears to arise because of a large 3-mode interaction among the tidal mode and high-order p- and g-modes of similar radial wavenumber. We show that additional four-mode interactions enter into the analysis at the same order as the 3-mode terms previously considered. Compute these 4-mode couplings by finding a volume-preserving coordinate transformation that relates the energy of a tidally deformed star to that of a radially perturbed spherical star. Using this method, relate the 4-mode coupling to 3-mode couplings and show that there is a near-exact cancellation between the destabilizing effect of the 3-mode interactions and the stabilizing effect of the 4-mode interaction. Show that the equilibrium tide is stable against the quasi-static decay into daughter p- and g-modes to leading order. The leading deviation from the quasi-static approximation due to orbital motion of the binary is considered; while it may slightly spoil the near-cancellation, any resulting instability timescale is at least of order the gravitational-wave inspiral time. Conclude that the p-/g-mode coupling does not lead to a quasi-static instability, and does not impact the phase evolution of gravitational waves from binary NSs.
Cosmology with void-galaxy correlations
Hamaus et al
Galaxy bias is a major hurdle for cosmological inference from large-scale structure. While traditional analysis focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs, demonstrate that cross-correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a standard ruler thanks to the observable geometric nature of voids. Illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross-correlations reveals a concordance with the mass-density profile of voids.
1307.2573
Simulating intergalactic quasar scintillation
Pallottini, Ferrara, Evoli
Intergalactic scintillation of distant quasars [don't understand exactly what is scintillating] is sensitive to free electrons and therefore complements Lya absorption line experiments probing the neutral IGM. Present a new scheme to compute IGM refractive scintillation effects on distant sources in combination with AMR cosmo sims. First validate model by reproducing the well-known interstellar scintillation (ISS) of galactic sources. The simulated cosmic density field is then used to infer the statistical properties of intergalactic scintillation. Find (contrary to previous claims) that the scattering measure of the simulated IGM at z<2 is 3.8, almost 40x larger than for the usually assumed smooth IGM. This yield an average modulation index ranging from 0.01 (nu_s=5 GHz) to 0.2 (nu_s=50 GHz); above 30 GHz the IGM contribution dominates over ISS modulation. ...Possibility of using IGM scintillation as a tool to pinpoint the presence of intervening high-z groups/clusters along the LoS, thus making it a probe suitably complementing SZ data.
1307.2632
Imprint of primordial non-Gaussianity on dark matter halo profiles
Dizgah, Dodelson, Riotto
Impact of primordial non-Gaussianity on the density profile of DM haloes by using the SAM by Dalal+, which relates the peaks of the initial linear density field to the final density profile of DM haloes. Models with primordial non-Gaussianity typically produce an initial density field that differs from that produced in Gaussian models. Use the path integral formulation of excursion set theory to calculate the non-Gaussian corrections to the peak profile and derive the statistics of the peaks of non-Gaussian density field. In the context of the SM for halo profiles, currently allowed values for primordial non-Gaussianity would increase the shapes of the inner DM profiles [wth do they mean by "increase the shape"?], but only at the sub-percent level except in the very innermost regions.
1307.2638
Determining the Hubble constant from gravitational wave observations of merging compact binaries
Nissanke, Holz, Dalal, Hughes, Sievers, Hirata [wow]
SGRBs probably associated with NS binary mergers; indicate association with G signal corresponding to the final inspiral of the compact binary. The radioactive decay of elements produced in NS binary mergers may result in transients visible in the optical and IR with peak luminosities on hours-days timescales. Simultaneous observations of the GWs and signatures in the EM band may allow directly and independently determine both the luminosity distance and redshift to a binary. These standard sirens (GW analog of standard candles) have the potential to provide an accurate measurement of the low-z Hubble flow. In addition, these systems are absolutely calibrated by GR, and therefore do not experience the same set of astrophysical systematics found in traditional standard candles, nor do the measurements rely on a distance ladder. Show that 15 observable GW and EM events should allow the Hubble constant to be measured with 5% precision using a network of detectors that includes advanced LIGO and Virgo. Measuring 30 beamed GW-SGRB events could constrain H_0 to better than 1%. When comparing to standard Gaussian likelihood analysis, find that each event's non-Gaussian posterior in H_0 helps reduce the overall measurement errors in H_0 for an ensemble of NS binary mergers. [so do NS binary mergers give a clean correspondence between GW and radioactive decay (hence EM wave) production?]
1307.2721
SN 2011fe: a laboratory for testing models of type Ia supernovae
Chomiuk
SN 2011fe is the nearest SNIa discovered in the modern multi-wavelength telescope era with the earliest discovery [I assume they mean that the lightcurve was detected way before it peaked]. This review covers 4 questions: (1) what explodes in SNIa? (2) how does it explode? (3) what is the progenitor of this SNe? (4) How accurate are SNIa as standardizable candles? Most aspects of SN 2011fe are consistent with the canonical picture of a massive CO white dwarf undergoing a deflagration-to-detonation transition. However, there is minimal evidence for a non-degenerate companion star, so SN 2011fe may have marked the merger of two WDs.
1307.2886
Direct imaging of a cold Jovian exoplanet in orbit around the sun-like star GJ 504
Kuzuhara et al
As the title says. Has the potential of providing novel insights into the origins of giant planets, as well as their atmospheric properties.
1307.2890
The stability of tidally deformed neutron stars to three- and four-mode coupling
Venumadhav, Zimmerman, Hirata [wow]
Recently suggested: the tidal deformation of a NS excites daughter p- and g-modes [what modes?] to large amplitudes via a quasi-static instability. This would remove energy from the tidal bulge, resulting in dissipation and possibly affecting the phase evolution of inspirialling binary NSs and hence the extraction of binary parameters form gravitational wave observations. This instability appears to arise because of a large 3-mode interaction among the tidal mode and high-order p- and g-modes of similar radial wavenumber. We show that additional four-mode interactions enter into the analysis at the same order as the 3-mode terms previously considered. Compute these 4-mode couplings by finding a volume-preserving coordinate transformation that relates the energy of a tidally deformed star to that of a radially perturbed spherical star. Using this method, relate the 4-mode coupling to 3-mode couplings and show that there is a near-exact cancellation between the destabilizing effect of the 3-mode interactions and the stabilizing effect of the 4-mode interaction. Show that the equilibrium tide is stable against the quasi-static decay into daughter p- and g-modes to leading order. The leading deviation from the quasi-static approximation due to orbital motion of the binary is considered; while it may slightly spoil the near-cancellation, any resulting instability timescale is at least of order the gravitational-wave inspiral time. Conclude that the p-/g-mode coupling does not lead to a quasi-static instability, and does not impact the phase evolution of gravitational waves from binary NSs.
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