Day 98

Tuesday.  I'm going lax on the housing search.


1109.6656
Spherically averaging ellipsoidal galaxy clusters in X-ray and SZ studies: II. Biases
Buote, Humphrey


Quantify orientation-average bias and scatter in observables that result from spherically averaging clusters described by ellipsoidal generalizations of the NFW profile or a nearly scale-free logarithmic potential.  Althoug hthe mean biases are small and mostly <1%, the flattest cluster models generally have a significant mean bias; i.e., averaging over all orientations does not always eliminate projection biases.  large biases results form different viewing orientations, where the integrated Compton-y parameter (Y_SZ) has the largest scatter (~10%), and the emission-weieghted temperature (T_Z) has the smallest (<0.5%).  The very small scatter for T_Z leads to Y_X and M_gas having virtually the same orientation bias.   Substantial scatter is expected for individual clusters (up to ~8%) in the correlation between Y_SZ and Y_Z in comparison to the small mean bias (sigma<1%).  For ellipsoidal NFW models the orientation bias for the total cluster mass attains a minimum near the radius r_2500 so that the spherically averaged mass computed at this radius is always within 0.5% of the true value for any orientation.  Provide cubic polynomial approximations to the mean orientation bias and 1 sigma scatter for each cluster observable as a function of axial ratio for the ellipsoidal NFW models.  


1109.6741
The Dark Energy Survey Data management System
Sevilla, ... et al for the DES collaboration


DES: 74 CCD camera at the Blanco telescope to study DE/cosmic acceleration.  5k sq. deg. coverage of the southern hemisphere and will record the positions and shapes of 300 million galaxies up to redshift 1.4.  Survey completed using 525 nights during a 5yr period starting 2012. About O(1TB) of raw data produced every night (incl. science and calibration images).  DES data management system has been designed for the processing, calibration and archiving of these data. Developed by collaborating institutions, led by NCSA.  Describe the basic functions of the system, what kind of scientific codes are involved, how the Data Challenge process works, to improve simultaneously the Data Management system algorithms and the Science WOrking Group analysis codes.


1109.6793
Variation of fundamental parameters and dark energy: a principal component approach
Amendola, Leite, Martins, Nunes, Pedrosa, Seganti


Methods based on PCA for reconstructing the DE equation of state and constraining its evolution, using a combination of Type Ia supernovae at low redshift and spectroscopic measurements of varying fundamental couplings at higher redshifts.  


1109.6828
A new automatic method to identify galaxy mergers I. Description and application to the STAGES survey
Hoyos, Aragon-Salamanca, Gray, Maltby, Bell, Barazza, Boehm, Haussler, Jahnke, Jogee, Lane, McIntosh, Wolf


Method to automatically identify galaxy mergers using morphological information contained in the residual images of galaxies after the subtraction of a Sersic model.  Removal of bulk signal for detecting the fainter minor mergers.  Residual flux fraction and asymmetry of the residuals used in merger diagnostic.  Contamination by non-mergers is also high.  [what the hey is the CAS system?  is it this system, or some other method?]  This method best used as a negative merger test.  Still lots of non-merger contaminants.  Uses HST images.


1109.6921
Spherically averaging ellipsoidal galaxy clusters in X-ray and SZ studies: I.  Analytical relations
Buote, Humphrey


First of two papers investigating the deprojection and spherical averaging of ellipsoidal galaxy clusters.  Specifically consider applications to hydrostatic X-ray and SZ studies.  many results also apply to isotropic dispersion-supported stellar dynamical systems.  Present analytical formulas for galaxy clusters described by gravitational potential that is triaxial ellipsoid of constant shape and orientation.   For this model, show that the mass bias dues to spherically averaging X-ray observations is independent of the temperature profile, and for the scale-free logarithmic potential, there is exactly zero mass bias for any shape, orientation, and temperature profile.  Ratio of spherically averaged ICM pressures obtained from SZ and X-ray measurements depends only on the ICM intrinsic shape and projection orientation, which provides another illustration of how cluster geometry can be recovered through a combination of X-ray and SZ measurements.  Also demonstrate that Y_SZ and Y_Z have different biases owing to spherical averaging, which leads to an offset in the spherically averaged Y_SZ - Y_X relation.  Potentially useful application of the analytical formulas presented is to asses the error range of an observable accounting for deviations from assumed spherical symmetry, without having to perform the ellipsoidal deprojection explicitly.  For dedicated ellipsoidal studies, we also generalize the spherical onion peeling method to the triaxial case for a given shape and orientation.  


MPIfR Lunch Colloquium
Shining a light on the galactic magnetic field with pulsars
Aris Noutsos (MPIfR Bonn)


Complex and irregular topology of the MW's magnetic field.  Pulsar surveys in the last decade helped make a new leap forward, an opportunity to reconstruct the 3d structure of the large-scale galactic magnetic field.  Present the current state of affairs in our efforts to study the galactic magnetic field with pulsars and give an outlook on what is expected from state-of-the-art surveys with LOFAR and SKA.


MPIfR Bonn Astronomisches Kolloquium
The cosmological impact of Blazars: from plasma instabilities to structure formation
Christoph Pfrommer, Heidelberg


Atmospheric imaging Cherenkov telescopes: reveal a plethora of blazars that populate the extragalactic gamma-ray sky at TeV energies.  Blazars: a subclass of accreting SMBH with powerful relativistic outflows directed at us, allowing us to detect the Doppler-boosted radiation.    The universe is opaque to extragalctic TeV-gamma rays because they annihilate and pair produce on the CMB.  The resulting ultra-relativistic pairs are commonly assumed to lose energy primarily through inverse Compton scattering of CMB photons, reprocessing the original emission from TeV to GeV energies.  However, argue that this is not the case; powerful plasma instabilities driven by the highly anisotropic nature of the ultra-relativistic pair distribution provide a plausible way to dissipate the kinetic energy of he TeV-generated pairs locally, heating the IGM.  This has important implications for origin of the extragalactic gamma-ray BG and recent estimate of intergalactic magnetic field strengths from blazar spectra; also significantly alters the thermal history of the IGM, imprinting a unique signal into the Lyman-alpha forest.  Finally, the substantially increased temperatures of the IGM have dramatic consequences for the thermodynamic structure of forming galaxy groups and dwarf galaxies.  This may help resolve the "missing satellite problem" in the MW and the "void phenomenon" of the low observed abundances of dwarf satellites compared to CDM simulations and may bring the observed early star formation histories into agreement with galaxy formation models.  


* i want to see this talk.