Tuesday. Met with Felicite and her friends last night. Tonight is Okonomiyaki night!
MPIfR Master Colloquium (Oct 27 15:15)
The molecular envelope of the Archetypical red supergiant Alpha Orionis (Betelgeuse)
Elisavet Proedrou
Betelgeuse is the closest red supergiant, has been studied extensively throughout the whole EM spectrum, yet understanding of some of this object's key properties remain limited. The outflowing circumstellar envelope (CSE) is of special interest as study of its structure can give us a record of the star's mass loss history and deepen our knowledge of the physical conditions and the chemical processes at work. Lost mass contributes to the enrichment of the interstellar medium with molecules and dust. New observations of sub-mm CO emission in CSE show (almost all of them being) never-before observed excited levels. Radiative transfer modeling of lines yielded in a viable wind model and estimates of the main physical parameters of the cool molecular envelope. Outline future observations that will shed further light on the properties of this object.
1110.4888
The effects of alignment and ellipticity on the clustering of galaxies
van Daalen, Angulo, SDM White
Investigate the effects of halo ellipticity and alignment with LSS on the galaxy correlation function. Analysis based on galaxy formation models from Guo et al, run on Millenium Simulations. Quantify importance by: randomizing angular positions of satellite galaxies within halos, either coherently or individually, while keeping the distance to their respective central galaxies fixed. Find: effect of disrupting the alignment with larger-scale structure is a 2% decrease in galaxy correlation function around r=1.8Mpc/h. Sphericalizing the ellipsoidal distributions of galaxies within haloes decreases the correlation function by up to 20% for r<1Mpc/h. Similar results apply to power spectra and z-space correlation functions. Models such as those based on HOD (which adopt a spherically averaged profile for the galaxy distributions within haloes) will therefore significantly underestimate the clustering on sub-Mpc scales.
* Hmm, is this going to be a problem with my gg-lensing project? I plan to use HOD modeling to get to the DM distribution around stacked galaxies...
1110.4889
The dynamical fingerprint of gas-expulsion: insights into the assembly of the MW's old GC system
Marks, Kroupa
Globular clusters (GCs) were exposed to the likely evolving potential of our Galaxy. The expulsion of the residual-gas from the GCs embedded progenitors is sensitive to the conditions in the pre-MW gas cloud. From N-body sims, show that gas throw-out from initially mass-segragated GCs affect the shape of the low-mass stellar mass function (MF) and that its imprint might still be visible in the present-day MF (PDMF). Strength of the tidal-field at birth influences the degree of gas-expulsion driven low-mass-star depletion, and therefore the PDMF probes the MW potential at the time of GC formation. Argue: among the old GC population in the MW, younger GCs show stronger low-mass-star loss than older GCs, shown to be consistent with a contracting and self-gravitating cloud in which fluctuations in the pre-MW potential grow with time. An initially relatively smooth tidal field evolved into a grainy potential within a dynamical time-scale of the collapsing cloud.
* Should have clearly stated whether deeper or shallower MW potential results in more gas-loss in the GC progenitors. Not mentioned in the abstract, but only by inference (deeper has more mass loss)!
1110.4894
Gravitational lensing with three-dimensional ray tracing
Killedar, Lasky, Lewis, Fluke
High-z sources suffer from (de)magnification due to WL by LSS. One consequence: the distance-redshift relation (widely used for cosmological tests) suffers lensing-induced scatter. Quantify this by magnification probability distribution, which requires ray-tracing through N-body sims. Standard methods apply multiple thin-lens approximation; to quantify the accuracy of this method, develop code that performs ray-tracing without the use of this approximation. Efficiency and accuracy of this approach can be improved by careful choices of numerical parameters [what kind of parameters? what do they do?]; the results ae analysed for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and NFW lenses. Preliminary comparisions drawn with the multiple lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of z_s=0.5.
1110.4913
The impact of high spatial frequency atmospheric distortions on WL measurements
Heymans, Rowe, Hoekstra, Miller, Erben, Kitching, Van Waerbeke
Precise measure of the PSF across the imaging data required for WL: accuracy to which high spatial frequency variation can be modeled is limited by the stellar number density across the field. Analyse dense stellar fields imaged at the CFHT to quantify the degree of high spatial frequency variation in ground-based imaging PSFs and compare our results to models of atmospheric turbulence [really? why?--for short exposures, apparently]. Data shows anisotropic turbulence pattern with an orientation independent of the wind direction and wind speed. Find amplitude of the high spatial frequencies to decrease with increasing exposure time as t^{-1/2}, and find a negligibly small atmospheric contribution to the PSF ellipticity variation for exposure times t>180 seconds. For future surveys analysing shorter exposure data, this anisotropic turbulence will need to be taken into account as the amplitude of the correlated atmospheric distortions becomes comparable to a cosmological lensing signal on scales less than ~10 arcminutes. This effect could be mitigated, however, by correlating galaxy shear measured on exposures imaged with a time separation greater than 50 seconds, for which we find the spatial turbulence patterns to be uncorrelated.
1110.4916
A VLA survey of radio-selected SDSS BAL Quasars
DiPompeo, Brotherton, De Breuck, Laurent-Muehleisen
AL quasars are indeed generally compact, at least at arcsecond resolutions. Majority not significantly variable at 1.4 GHz. Found 2 BAL quasars that may fit into the "polar" BAL category. Find significant favoring of steeper radio spectral index (statistical indicator of viewing angle) for BAL, compared to non-BAL quasars. Suggests BAL quasars have a range of orientations, but are more often observed farther from the jet axis compared to normal quasars.
* wait, i don't understand how they got to the "away from jet angle" conclusion. From the radio spectral index? Steep index means away from jet angle? Does that make sense?
1110.4986
Using observations of distant quasars to constrain quantum gravity
Perlman, Ng, Floyd, Christiansen
If space is foamy on the Planck scale, photons emitted from distant objects will accumulate uncertainties in distance and propagation directions thus affecting the expected angular size of a compact object as a function of redshift. Discuss geometry of foamy spacetime, and the appropriate distance measure for calculating the expected angular broadening. Discuss mechanics of such a test. [!] When calculating the light path one must use comoving distance, not luminosity distance [duh!]. Also the appropriate distance to use to calculate angular broadening. Previous paper by Tomburini et al. overstates constraints on spacetime foam by their use of luminosity distance. Consider impact of different ways of parameterizing and measuring the effects of spacetime foam. Important to select and document carefully the comparison stars [what, not galaxies? and what about astrometry?] as well as the methods used to compute the Strehl ratio.
* Strehl ratio: a measure of the optical quality of telescopes and other imaging instruments. Defined as the ratio of the observed peak intensity at the detection plane from a point source as compared to the theoretical maximum peak intensity of a perfect imaging system working at the diffraction limit. Closely related to the sharpness criteria for optics. S == exp[(-2\pi\sigma/\lambda)^2], with sigma being the root mean square deviation of the wavefront and lambda being the wavelength. The Strehl ratio is usually calculated at the best focus of the imaging system under study.
1110.5019
Mass of the universe in a black hole
Poplawski
* Wha?
If spacetime torsion couples to the intrinsic spin of matter (ECSK gravity theory), then the resulting gravitational repulsion at supranuclear densities prevents the formation of singularities in black holes. Consequently, the interior of every BH becomes a new universe that expands from a nonsingular bounce. Consider gravitational collapse of fermionic spin-fluid matter with the stiff equation of state in a stellar BH. Such a collapse increases the mass of the matter... [some non-memorable, non-comprehensive stuff] ... Show that the universe in a BH of mass M_BH at the bounce has a mass M_b ~ M^2_BH m^1/2_n / m^3/2_Pl, where M_n is the mass of a neutron and m_Pl is the reduced Planck mass. For a typical stellar BH, M_b is about 1e32 solar masses, which is 1e6 larger than the mass of our universe. As the relativistic black-hole universe expands, its mass decreases until the universe becomes dominated by non-relativistic heavy particles.
* Interesting, in a sense that I used to dream up such a scenario too. (hahaha! no, really!)
* so how small does the mass decrease to? Can it be comparable to our universe? What kind of mass would the BH need to generate our universe?
1110.5026
The missing matter problem: from the DM search to alternative hypothesis
Capozziello, Consiglio, De Laurentis, De Rosa, Di Donato
Review the status of DM search at theoretical and experimental level discussing alternative hypothesis.
1110.5048
TeVeS/MOND is in harmony with gravitational redshifts in galaxy clusters
Bekenstein, Sanders
Wojtak, Hansen and Hjorth: claim TeVeS ruled out based on gravitational redshifts in 7800 clusters. But modeling of gravitational field where the sources reside with NFW profile justified out to the necessary radii in clusters, nor relevant in the case of TeVeS. Using MONDian isothermal sphere models consistently constructed within MOND, determined redshifts do just as well as GR. WHH also confuses primitive mu-functions of TeVeS and the MOND interpolation function.
1110.5060
Holographic dynamics as way to solve the basic cosmological problems
Bolotin, Lemets, Yerokhin, Zazunov
* holographic principle: a property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region--preferably a light-like boundary like a gravitational horizon. String theory admits a lower dimensional description in which gravity emerges from it in what would now be called a holographic way.
* (quantum) entanglement: occurs when electrons, molecules even as large as buckyballs, photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description (state), which is indefinite in terms of important factors such as position, momentum, spin, polarization, etc. Their shared state is indefinite until measured; quantum entanglement is a form of quantum superposition. When a measurement is made and it causes one member of such a pair to take on a definite value, the other member of this entangled pair will at an subsequent time be found to have taken the complementary value. Thus, there is a correlation between the results of measurements performed on entangled pairs, and this occurs even though the entangled pair may have been separated by arbitrarily large distances.
Review recent results on the cosmological models based on the holographic principle which were proposed to explain the most of the problems occurring in the Standard cosmological model. Solves cosmological constant problem and coincidence problem. Show model of the universe consisting of dark matter interacting with a scalar field on the agegraphic background can explain the transient acceleration. Study impact of ideas on the physics of entangled states in these models. Entanglement entropy of the universe gives holographic dark energy with the equation of state consistent with current observational data.
1110.5065
Deformed distance duality relations and SNe dimming
JAS Lima, JV Cuhna, VT Zanchin (i.e., not the Lima and Cuhna I know)
Etheringon cosmic distance duality relation: eta == D_L / D_A / (1+z)^2 == 1. Show that under certain conditions such expressions (deformed original Etherington's relation with phenomenological expressions) can be derived from a more fundamental approach with the parameters appearing in the eta(z) expression defining the cosmic absorption parameter as recently discussed by Chen and Kontowski. Find latest SNe data can also be explained in the framework of a pure CDM model (EdS): two different scenarios with cosmic absorption are discussed. Only if cosmic opacity is fully negligible, the description of an accelerating universe powered by DE must be invoked.
* I'm sure there are evidences other than SNe supporting DE... (but I cannot pinpoint what)
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