Day 71

Tuesday.  Lucas' PhD celebration bash was last night.  Might still be hung over.


1108.5176
Simulatios of early baryonic structure formation with stream velocity: I. Halo abundance
Naoz, Yoshida, Gnedin


Relative velocity between the DM and baryons (v_bc) at the time of recombination can affect the structure formation in the early universe (Tseliakhovich+Hirata 2010).  Statistically quantify using large cosmological simulations: separate transfer functions for baryons and dark matter; three different high resolution sets of simulations that vary the value of relative velocity.  The total number of halos suppressed by 20% at z=25 for vbc = 1 sigma(vbc) and 50% for vbc = 3.4 sigma (vbc), remaining above 30% to z=11.  High abundance of "empty halos" (halos with half the gas fraction of cosmic mean) found: for vbc = 1sigma(vbc), all new halos below 1e5Msun are empty at z=19.  The high abundance of empty halos results in significant delay in the formation of gas rich mini-halos and the first galaxies.


1108.5282
Rating growth of scientific knowledge and risk from theory bubbles
Loeb


Advocate the need for a website operated by graduate students that will use various measures of publicly available data (e.g., growth rate of research grants, publications, faculty jobs) to gauge the future dividends of various research frontiers.  Analysis can benefit from past experience; aim to alert the community of the risk from future theory bubbles.


1108.5211
Experimental test of airplane boarding methods
Steffen, Hotchkiss


Report experimental comparison of different airplane boarding methods.  757 mock with 12 rows of 6 seats and a single aisle; 5 methods with 72 passengers of various ages; significan reduction of boarding time found in optimized methods over traditional methods.  


1108.2506
Only marginal alignment of disc galaxies
Andrae, Jahnke


Angular-momentum acquisition of rotationally supported disc galaxies: key to understand formation of this type of galaxies.  Tidal-torque theory: tries to explain the angular momentum acquisition in a cosmological framework, predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness on distances of 1Mpc/h.  Disc alignment also an IA contamination to WL signal.  Explain how to propagate the important errors (redshift, ellipticity, morphological classifications).  From SDSS, positive autocorrelations of spiral-arm handedness and angular momentum orientations on distances of 1Mpc/h are plausible but not statistically significant.  (Local Group shows not evidence of alignment either.)  Ellipticity estimates based on second moments are strongly biased by galactic bulges, corrupts correlation estimates.  Overestimates the impact of disc alignment on WL studies.  Discuss the potential of future sky surveys--PanSTARRS and LSST cannot be used for photoz (to measure...?)


* IA is marginal for disc galaxies.  Bulge may produce some correlation signals.
* I want to understand what alignment they're talking about--it doesn't seem like they're talking about alignment to LSS, but rather the angular momentum of the galaxy to the spiral arm structure...


1108.2635
The WIggleZ Dark Energy Survey: mapping the distance-redshift relation with BAO
Blake, Kazin, etal


BAO measurements at z=0.44, 0.6, 0.73 with WiggleZ.  Combine with 6dFGS and SDSS, BAO significance of 4.9 sigma.  Fit cosmological models with 6 distance-redshift data points; compare results to SNe and CMB data.  BAO and SNe produce consistent measurements of w of DE.  Provides check for systematic errors in either of these distance probes when combined separately with CMB (?).  Combining all, find w=-1.03 pm 0.08 for a flat universe.  Assume w=-1, find Omega_k = -0.004 pm 0.006.


1108.2637
The WiggleZ DE survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant SNe
Blake, Glazebrook, et al


Combine distant SNe observations with geometrical analysis of galaxy clustering within the WiggleZ DE survey; using the AP test to measure the distortion of standard spheres.  Constitutes a robust and non-parametric measurement of the Hubble expansion rate as a fn of time with 4 bins in 0.1<z<0.9.  Demonstrate that cosmic expansion is accelerating, in a manner independent of the parameterization of the cosmological model (although assuming cosmic homogeneity).  Expansion history is consistent with a w=-1.


* how do they use the AP test to determine Hubble rate?  


1108.2657
Measuring large-scale structure with quasars in narrow-band filter surveys
Abramo, Strauss, Lima, Hernandez-Monteagudo, Lazkoz, Moles, de Oliveira, Sendra, Sodra


Show that large-area imaging survey using narrow-band filters can detect quasars in sufficiently high number densities to turn them into suitable tracers of large-scale structure.  Narrow-band optical survey that can detect to i=23 could reach volumetric number densities as high as 1e-4 h^3 Mpc^-3 (comoving) at z~1.5, leading to precision measurements of the power spectrum up to z~3-4.  Possible to employ quasars to measure BAO at high z, where the uncertainties from z distortions and nonlinearities are much (?) smaller than at z<1.  Study the future impact of J-PAS: narrowband (100A fwhm) 42 filter survey of 1/5 of unobscured sky.  Due to broad emission line, get excellent photo-z of sigma_z = 0.002(1+z).


1108.2700
It was twenty years ago today...
Ginsparg


20th anniversary of hep-th@xxx.lanl.gov (now arXiv.org).  Trace some historical context and early developement of the resousrce, its later trajectory; close with thoughts about future.