Day 76

Wednesday.  Gotta push the a2218 through the pipeline, and copy data and code to my laptop today.


UCB Astro Theory Lunch
Galaxy kinematics and DM halos with VIRUS-P
Jeremy Murphy (UT Austin)


Elliptical galaxies: process of galaxy formation and evolution takes place in the centers of DM halos.  Observational methods: estimate the mass and radial extent of these halos.  Extended stellar halos of M87 and M49 in the Virgo cluster discussed; show if they agree with other (DM) mass tracers.


1109.0285
MOKA: a new tool for Strong Lensing Studies
Giocoli, Meneghetti, Bartelmann, Moscardini, Boldrin


* compare with Gravlens


New algorithm for simulating gravitational lensing signal from cluster-sized halos (NFW profile, concentration decreasing with mass, large amount of substructures).  Create realistic lenses based on numerical simulations with properties independent of numerical resolution.  Perform systematic studies of strong lensing cross section in dependence of halo structure; find dependence on concentration and the inner slope of density profile of a halo; then halo triaxiality and the presence of a BCG.


* can this be used to look at data?  no, it seems like it's just a calculation based on simulation...


1109.0529
Neutral Hydrogen Tully Fisher Relation: The case for Newtonian Gravity
Chakraborti, Khedekar


TF relation: intrinsic luminosities related to rotation velocities of disk galaxies.  Baryonic TF relation explained by both DM+Newtonian and MOND.  But BTF relation ignores contribution from hot gas and oversimplifies galaxy-scale physics.  Advocate use of Hydrogen TF (HITF), free of dust obscuration and stellar evolution effects.  Incorporate physics of hot gas from SNe feedback, which drives porosity of the ISM.  Simple model with SNe feedback generalized to include parameterized effective gravitational force law.  Kennicutt-Schmidt (KS) law for star formation and simple Newtonian gravity adequate for explaining observed HI scaling relations.  Data rules out MOND-like theories in this model.


* How does the model rule out MOND??


1109.0548
Substructure in the lens HE 0435-1223
Fadely, Keeton


Investigate properties of DM substructure for HE 0435 (z_l=0.455) through its effects on the positions and flux ratios of the quadruply-imaged BG quasar (z_s=1.689).  Examine individual substructure placement, and a full population of substructure assuming clump masses follow a mass function dN/dM~M^-1.9.


1109.0549
An enhanced cosmological Li6 abundance as a potential signature of residual dark matter annihilations
Ellis, Fields, Luo, Olive, Spanos


Constrained minimal supersymmetric extension of the standard model (CMSSM) with late-time DM annihilations (after BBN) can affect primordial element abundance: not much with He3, He4 and Li7, but Li6 is enhanced, but given LHC constraints, not by much.  Similar enhancement can also be given for non-universal Higgs mass (NUHM1) models.


* Li7 is low compared to BBN predictions, unclear if due to astrophysics.  Li6 is also lower observed.


1109.0850
Galaxy cluster searches based on photometric redshifts of the four CFHTLS wide fields
Durret, Adami, Cappi, Maurogordato, Marquez, Ilbert, Coupon, Arnouts, ...Le Fevre, ...McCracken, Mellier, ... etal


Developed a method for detecting clusters in large imaging surveys: based on structures in slices of photometric redshifts.  Detection rate validity estimated by applying method to Millennium simulation.  Detect 4061 candidate clusters at >3 sigma (6k for >2sigma) in 0.1<z<1.15.  Estimated mean masses of 1.3e14 and 1.3e15 M_sun.  Catalog available via VizieR online.  Check cluster characteristics (color-mag relation, luminosity function); cluster-cluster correlation function compared to other reports; analyze large scale filamentary galaxy distributions.  


1109.0873
Model-independent reconstruction of the expansion history of the universe from SNe Ia
Benitez-Herrera, Roepke, Hillebrandt, Mignone, Bartelmann, Weller


Model-independent reconstruction of the expansion history based on Union2 sample.  Tests geometry of the universe without any assumptions made on the energy content.  Better suited to constrain DE and non-standard cosmological models.  Can also be used for pointing out systematic errors in SNe data, and planning future SNe Ia cosmology campaigns.


* How do they do this??


1109.0953
ACT: ACT-CL J0102-4215 "El Gordo", a massive merging cluster at z=0.87
Menanteau, Hughes, Sifon, Hilton, Gonzalez... Das, Devlin, ... Marsden, ... Page, Reese, Sehgal, ... Spergel ... et al.


Most likely the most massive, hottest, most X-ray luminous and brightest SZ effect cluster known at z>0.6.  Discovered in the ACT SZ survey of 755 sq. degrees.  89 members have spectra with cluster redshift of 0.870; sigma_v = 1321 km/s.  Chandra: Tx=14.5 keV, Lx=2e45 erg/s (at 0.5-2.0 keV band).  Cluster mass estimates: M_200=2e15M_sun.  Optical and Chandra data show evidence of major merger (2:1).  Shows temperature variations from 6.6 keV (cool core) to 22 keV.  Wake in X-ray surface brightness; estimate merger speed of around 1300 km/s with assumed merger timescale of 1Gyr.  Rare massive cluster, but allowed in LCDM; but unlikely to be reproduced in N-body sims.


Bonn MPIfR Lunch Colloquium
IRAS 16293-2422: a very young FU Orionis analog entering a phase of enhanced accretion?
Laurent Loinaird (MPIfR Bonn/UNAM Mexico)


IRAS 16293 underwent (possibly one-sided) ejection in 2011, after 40% increase in accretion rate.  Unambiguous evidence of the direct coupling (presumably magnetic) between accretion and ejection processes during the earliest stages of stellar evolution.  Validates claims of accretion history reconstruction of young stellar objects from fossil record of ejection imprinted on their outflow systems.  Excess accretion approximately 3x the ejection mass, in good agreement with theory.  Since 1980s, only the 2006 and 2011 events are recorded ejection events.  


Bonn Promotions-Kolloquium
Study of two radio gravitational lenses: insight into the high-redshift universe and properties of mass distribution
Filomena Volino


Astrophysical applications of GL, concentrate on lensing as tool to study the intervening mass distribution in the lens system MG J0414+0534.  Results of VLBI at 1.7GHz and lens modeling results, full set of constraints from observations.


* I have to hear about the intervening mass distribution.


* three talks today, and a Skype con.


Bonn MPIfR Special Colloquium
A multiwavelength view of the microquasar Cyg X-1: spectral variability, Gamma-ray polarization, and jets
Victoria Grinberg (Remeis Observatory & ECAP)


Cyg X-1: discovered in 1965, persistent high mass X-ray binary of O supergiant + stellar mass BH; i.e., a down-scaled versions of AGN, supported by observations of radio jets.  Shows distinct X-ray states (spectral and timing properties), and correlated radio behaviour.  Campaign of X-ray and gamma-ray observations has goal to understand the inflow/outflow connection for BHs on all mass-scales.  Shows Gamma-ray polarization of an X-ray binary; emission component is produced in jets.


Bonn MPIfR Special Colloquium
Astrometry Lost and Regained: from a modest experiment in Copenhagen in 1925 to the Hipparcos and Gaia space missions
Erik Hoeg (Niels Bohr Institute)


Astrometry!  Important for celestial phenomena, control of telescopes and satellites, and monitoring Earth's rotation.  Hipparcos made astrometry flourish, soon to be followed by Gaia mission.  Hipparcos in 1980: one star detected at a time (photoelectric detectors); Roemer mission in 1992: CCD detectors (10k stars simultaneous), rotating satellite, systematic scan.  Gaia in 1993-1997: interferometric option (but direct imaging of CCDs was considered to be better, and was used for SGaia mission).


1107.1378
Estimate of halo ellipticity as a function of radius with flexions
Xinzhong Er, Mao, Xu, Cao


Triaxial DM halos: radial distribution of halo ellipticity depends on baryonic processes and the nature of DM particles.  Use lensing flexion ratios to measure halo ellipticity as a function of radius.  Use weight function, study relationship between first and second order statistics of flexion ratios (?), use both the reduce bias in ellipticity estimation.  Perform numerical tests and demonstrate bias reduction.  Minimum mean flexion ratio can be used to trace the centers of galaxy clusters.