Day 409

Thursday.

1304.2764
Neutron-capture element deficiency of the Hercules dwarf spheroidal galaxy
Koch et al

Study low Ba abundances in this dSph galaxy, in contrast with the high dispersions in Fe and Ca in this galaxy.  The latter spreads are typical of the very low luminosity, DM-dominated dSphs, a high level of depletion in heavy elements suggests that chemical enrichment in Hercules was governed by very massive stars, coupled with a very low star formation efficiency.  While very low abundances of some heavy elements are also found in individual stars of other dwarf galaxies, this is the first time that a very low Ba abundance is found within an entire dSph over a broad metallicity range.

1304.2765
Rotational signature of the Milky Way stellar halo
Fermani, Schönrich

Measure the rotation of MW stellar halo that reach out to ~50 kpc in galactocentric distance; on two samples of blue horizontal branch (BHB) field halo stars from SDSS, with 4 different methods.  Find: all 4 methods agree on a weakly prograde or non-rotating halo.  Further, observe no duality in the rotation of sub-samples with different metallicities or at different radii.  Trace the rotation gradient across metallicity measured by Deason+ on a similar sample of BHB stars back to the inclusion of regions in the apparent magnitude-surface gravity plane [that are] known to be contaminated.  In the spectroscopically selected sample of Xue+, flag ~500 hot metal-poor stars for their peculiar kinematics wrt to both their cooler metal-ppor counterparts and o the metal-rich stars in the same sample.  They show a seemingly retrograde behavior in LoS velocities, which is not cofirmed by the 3d estimators. THeir anomalous vertical motion hints at either a pipeline problem or a stream-like component rather than a smooth retrograde population.

13034.2774
The simplest model of galaxy formation I: a formation history model of galaxy stellar mass growth
Mutch, Croton, Poole

Introduce a simple model to self-consistently connect the growth of galaxies to the formation history of their host DM haloes.  Model defined by 2 simple functions: "baryonic growth function" which controls the rate at which new baryonic material is made available for SF, and the "physics function" which controls the efficiency with which this material is converted into stars.  Using simple, phenomenologically motivated forms for both functions that depend only on a single halo property, demonstrate the model's ability to reproduce the z=0 red and blue stellar mass functions.  Add redshift as a 2nd input variable to the physics function, show that the reproduction of the global stellar mass function out to z=3 is improved.  Conclude by discussing the general utility of new model, highlighting its usefulness for creating mock galaxy samples which have a number of key advantages over those generated by other techniques.


1304.2776
Investigating the relationship between AGN acidity and stellar mass in zCOSMOS galaxies at 0<z<1 using emission line diagnostic diagrams
Vitale, ... Lilly,  et al

Stacked spectra show AGN signatures above log (M*/M_sun) > 10.2 threshold; stellar populations of AGN hosts are found to be older with respect to SF and composite galaxies.  Could be due to the tendency of AGN to reside in massive hosts.  The dependence of the AGN classification on the stellar mass is in agreement with previous studies.  Consistent with the downsizing scenario: an evolutionary scenario where the AGN-feedback is capable of quenching the SF in the most massive galaxies.  AGN-feedback is the best candidate for initiating the passive evolutionary phase of galaxies.

1304.2785
Inflationary paradigm in trouble after Planck2013
Ijjas, Steinhardt, Loeb

Results favor models with a single scale field; while all the simplest inflation models are disfavored by the data while the surviving models (those with plateau-like potentials) are problematic.  Restriction to plateau-like models leads to 3 independent problems: exacerbates both the initial conditions problem and the multiverse-unpredictability problem, and it creates a new difficulty dubbed the inflationary "unlikeliness problem".  Comment on problems reconciling inflation with a standard model Higgs, as suggested by recent LHC results.  Find that recent experimental data disfavors all the best-motivated inflationary scenarios and introduces new, serious difficulties that cut to the core of the inflationary paradigm.  Forthcoming searches for B-modes, non Gaussianity and new particles should be decisive [?].  

1304.2873
Mask effects on cosmological studies with weak lensing peak statistics
Liu, Fan

Find: high peak fractions systematically enhanced due to masks---the larger the masked area, the higher the enhancement.  For 13% masked fraction, fraction of peaks with SNR > 3 is ~13, in comparison with ~9 of the mask-free case.  Induces large bias on cosmological studies with WL peak statistics.  For survey area of 9 deg sq, the bias is ~3sigma.  Most affected peaks are close to the masked regions.  Excluding peaks in those regions can reduce the bias, but at the expense of losing usable survey areas.  Enhancement of high peak number can be largely attributed to higher noise led by the fewer number of galaxies usable in the reconstruction.  Develop a 2-noise-level model that treats the areas close to and away from the masked regions separately.  Shown that the model can account for the mask effect very well, and the parameter bias is significantly reduced.  Analyze the systematic effects on peak statistics resulting from NL convergence reconstruction, including the smoothing order problem and the mass-sheet degeneracy.