Day 345

Tuesday.  Sick.

1212.0009
Daniel, Linder

Can surveys such as BigBOSS fit simultaneously for time varying DE EoS and time- and scale-dependent gravity?  The simultaneous fit avoids potential bias from assuming LCDM expansion or GR and leads to only modest degradation in constraints.  Galaxy bias, fit freely in z bins, is self calibrated by spectroscopic measurements of z space distortions and causes little impact.  The combination of galaxy z, CMB, and SNe distance data can deliver 5-10% constraints on 6 model independent modified gravity quantities.  

1212.0026
CX Lyrae 2008 observing campaign
de Ponthiere, Le Borgne, Hambsch

* Blazhko effect: long-term modulation in period and amplitude in RR Lyrae type variable stars.  Hypothesis: (1) resonance model: fundamental or the first overtone pulsation mode of the star, and the higher order mode, resonating non-linearly.  (2) magnetic model: assumes variation to be caused by the B-field being inclined to the rotational axis, deforming the main radial mode.  (3) cycles in the convection causes alternations and the modulations.  

4-month observing campaign (59 nights): Blazhko period of 62 +/- 2 days suggested; previously 128 or 227 days also suggested.  Need more densely sampled measurements.

1212.0034
GEOS RR Lyr survey: Blazhko peroid measurement of three RRab stars - CZ Lyrae, NU Aurigae and VY Corono Borealis

3 stars with strong Blazhko effect.

1212.0095
THe halo mass function through the cosmic ages
Watson, Iliev, D'Aloisio, Knebe, Shapiro, Yepes

With N-body sims: halo catalogue spans 0<z<30, allows generating mass function from dark ages to present.  Use both FoF and SO halo finding methods to compare the mass function derived.  SO mass functions exhibits a clear evolution with z, especially during the recent era of DE dominance (z<1).  Provide a z-parameterised fit for the SO MF valid for the entire z range within ~20% as well as a scheme to calculate the MF for haloes with arbitrary overdensities.  The FoF MF displays a weaker evolution with z.  Also provide a 'universal' fit for the FoF MF across all z, and observe z evolution in the data versus this fit.  The relative evolution of the MF derived via the 2 methods is compared and we find that the MFs most closely match at z=0.  The disparity at z=0 between the FoF and SO MF resides in their high mass tails where the collapsed fraction of mass in SO haloes is ~80% of that in FoF haloes.  This difference grows with z so that, by z>20, the SO algorithm finds a ~50-80% lower collapsed fraction in high mass haloes than does the FoF algorithm, due in part to the significant over-linking effects known to affect the FoF method.

 1212.0113
On the probability of habitable planets
Forget

Significant fraction of stars should harbor terrestrial planets; how many of them are habitable (suitable for life and its evolution)?  Liquid water (internal to planetary bodies, but more likely surface water interacting with rocks and light necessary for environmental modification and evolution.  First key issue: understand the climatic conditions allowing surface liquid water, assuming a suitable atmosphere.  3d climate models available---accurately explore climate regimes that could locally allow liquid water.  Second key issue: Composition and the evolution of the atmospheres of exoplanets need to be understood; in particular the geophysical feedbacks that seems to be necessary to maintain a continuously habitable climate.  It is possible that Earth's case may be very special and uncommon.  [Wording!]

1212.0238
On the formation of cD galaxies and their parent clusters
Tovmassian, Andernach

* Bautz-Morgan classification: type I cluster is dominated by a bright, large, supermassive cD galaxy (e.g., Abell 2029, 2199); type III contains no remarkable members, and type II contains elliptical galaxies whose brightness relative to the cluster is intermediate to that of type I and II.

Study the formation of cD galaxies: search for possible dependencies between the L_K and the parameters of their host clusters of BM type I.  As a comparison, use cD galaxies in clusters where they are not dominant ("NBMI" type clusters).  For 71 BMI clusters, the absolute K-band L of cDs depends on the cluster richness, but less strongly on the cluster velocity dispersion.  The 35 NBMI clusters have L and richness correlation weaker, and L and sigma_v correlation absent.  In addition, find that the luminosity of the cD galaxy hosted in BMI clusters tends to increase with the cD's peculiar velocity with respect to the cluster mean velocity.  In contrast, for NBMI clusters the cD luminosity decreases with increasing peculiar velocity.  The X-ray luminosity of BMI clusters depends on the cluster velocity dispersion, while in NBMI clusters such a correlation is absent.  These findings favour the cannibalism scenario for the formation of cD galaxies [not sure how the x-ray "evidence" works this way].  Suggest that cDs in clusters of BMI type were formed and evolved preferentially in one and the same cluster.  In contrast, cDs in NBMI type clusters were either originally formed in clusters that later merged with groups or clusters to form the current cluster, or are now in the process of merging.

1212.0261
The drivers of AGN activity in galaxy clusters: AGN fraction as a function of mass and environment
Pimbblet et al

Optical spectroscopically-id'ed AGN to M*+1 in a sample of 6 self-similar SDSS galaxy clusters at z=0.07.  Clusters selected to lack significant substructure "at bright limits" [?] in their central regions (eliminate local action of merging clusters on the frequency of AGN).  Demonstrate that the AGN fraction increases significantly from the cluster centre to 1.5 R_virial, but tails off at larger radii.  If only comparing the cluster core region to regions at ~2 R_virial, no significant variation would be found.  Compute the AGN fraction by mass and show that massive galaxies (M*>1e10.7 Msun) are host to a systematically higher fraction of AGN than lower mass galaxies at all radii from the cluster centre.  Attribute this deficit of AGN in the cluster center to the changing mix of galaxy types with radius: The 'retired' AGN ('retired' galaxies are those whose main ionization mechanism comes from old stellar populations) are found at all radii, while the mass effect is more pronounced: find that massive galaxies are more likely to be in the retired class. Show that AGN have no special position inside galaxy clusters--they are neither preferentially located in the infall regions, nor situated at local maxima of galaxy density.  However, find that the most powerful AGN reside at significant velocity offsets in the cluster, and brings analysis into agreement with previous work on X-ray selected AGN.  Results suggest that if interactions with other galaxies are responsible for triggering AGN activity, the time-lag between trigger and AGN enhancement must be sufficiently long to obfuscate the encounter site and wipe out the local galaxy density signal.

1212.0274
Particle interactions in matter at the terascale: the cosmic-ray experience
Klein (Spencer)

CR with energies up to 3e20 eV have been observed, as have astrophysical neutrinos with energies above 1 PeV (1e15 eV).  Discuss some of the unique phenomena that occur when particles with TeV energies and above interact with matter; emphasis on lepton interactions.  The cross-sections for electron bremsstrahlung and photon pair conversion are suppressed at high E by the Landau-Pomeranchuk-Migdal (LPM) effect, lengthening EM showers.  At still higher energies (>1e20 eV), photonuclear and electronuclear interactions dominate, and showers become predominantly hadronic.  Muons interact much less strongly, so can travel long distances through solids before losing energy.  Tau leptons behave similarly, although their short lifetime limits how far they can travel.  The hadronic interaction cross-section is believed to continue to increase slowly with rising energy; measurements of CR air showers support this prediction.

1212.0307
Detection of far infrared emission from galaxies and quasars in the galactic extinction map by stacking analysis
Kashiwagi, Yahata, Suto

Stacking image analysis of galaxies over the Galactic extinction map of SFD98.  1e7 galaxies from SDSS DR7 photometric catalog; detect clear signatures of the enhancement of the extinction in r-band (Delta A_r) around galaxies, indicating that the extinction map is contaminated by FIR emission [how?].  The average amplitude of the contamination per galaxy is well fitted to Delta A_r(m_r) = 0.64e0.17(18-m_r) [mmag].  While this value is very small, it is directly associated with galaxies and may have a systematic effect on galaxy statistics.  Indeed this correlated contamination leads to a relatively large anomaly of galaxy surface number densities against the SFD extinction A_SFD previously discovered. Model the radial profiles of stacked galaxy images, find that the FIR signal around each galaxy does not originate from the central galaxy alone, but is dominated by the contributions of nearby galaxies via galaxy angular clustering [how did they figure this out?].  The separation of the single galaxy and the clustering terms enables us to infer the statistical relation of the FIR and r-band fluxes of galaxies, and also to probe the flux-weighted cross-corerlation of galaxies, down to the magnitudes that are difficult to probe directly for individual objects. Repeat the same stacking analysis for SDSS DR6 photometric quasars, and discover similar signatures but with weaker amplitudes.  The implications of the present results for galaxy and quasar statistics and for correction to the Galactic extinction map are briefly discussed.

* must know that: SFD98 "dust map" was generated assuming a linear relation between FIR flux at 100um and dust column density, with a temperature correction for dust emissivity.  (it's not absorption weighted, but rather emission weighted)