Day 209

Wednesday.  Did an OK Journal Club yesterday.  Annoyed Aaron further.  Now I am 5 days behind.


1202.4755
Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity
Marks, Kroupa, Dabringhausen, Pawlowski


From observation of globular cluster masses, radii, metallcity, and PDMF, find: IMF is required to become more top-heavy the lower the cluster metallicity and the larger the pre-GC cloud-core density are; in agreement with theoretical expectation.  GCs and UCDs might have formed along te same channel, or UCDs formed via mergers of GCs.  Find fundamental plane which describes the variation of the IMF with density and metallicity of the pre-GC cloud-cores simultaneously.  Major implications to evolution of galaxies, and chemical enrichment.


1202.4758
Spatial variation in the fine-structure constant -- new results from VLT/UVES
King, Webb, Murphy, Flambaum, Carswell, Bainbridge, Wilczynska, Koch


From 154 (VLT) and 141 (Keck) quasar absorbers:  VLT shows alpha increases with increasing cosmological distance from Earth.  Keck show some evidence fro smaller alpha in the distant absorption clouds.  Combine samples: apparent variation of alpha across the sky emerges by an angular dipole model at R=17.3 hr = 259 deg, dec = -61 deg, with amplitude of 0.97e-5 at 4 sigma.  Data consistent with cuts, VLT vs. Keck.  Dipole effect does not originate from a small subset of the absorbers or spectra.  


1202.4761
Relativistic resonant relations between massive BH binary and extreme mass ratio inspiral
Seto


MBHB can capture a small third body, forming a triple system; analyze evolution of the triple initially with small eccentricities.  Find: a new resonant relation can arise, where GR effects crucial.  Relativistic resonances can significantly change the orbit of the inner small body.


1202.4767
Evolution of group galaxies from the first red-sequence cluster (RCS) survey
Li, Yee, Hsieh, Gladders


* Butcher-Oemler effect: distant clusters contain more blue galaxies than nearby ones.


Study red fraction in RCS1 clusters, find BO effect in groups, from 0.15<z<0.52.  Luminous red sequence galaxies are already in place by z~0.5, formation epoch of z>2.  Study evolution of f_red as a function of (1) Stellar mass, (2) total group stellar mass, (3) normalized group-centric radius, and (4) local galaxy density.  M* (1) strongest effect on f_red, then environment (2,3,4).  Once massive (M>1e11 Msun), little dependence seen on the parameters; dependence mostly seen in M*<1e10.6 Msun galaxies.  Observe an apparent 'group downsizing' effect.  At fixed size (3), significant dependence on f_red on local density (4), and f_red gradients seen for fixed (4); indicates galaxy group environment has a residual effect over that of local galaxy density (or vice versa), both params need to be considered.  Red galaxy state are caused both by local galaxy density (harassment and mergers) and accretion onto larger group halo (ram pressure and strangulation).


1202.4770
The physics of the fundamental metallicity relation
Dayal, Ferrara, Dunlop


* FMR: Metallicity, mass, SFR relation in a plane.


Show: physics of the FMR summarised as follows: Massive galaxies with M*>1e11 Msun has low metallicity gas inflow, and retains high metallicity gas outflow, leading to a constant value of the gas metallicity with SFM.  Less massive galaxies have smaller SFR, produce less heavy elements, more efficiently ejected due to shallower potential: as a result, the gas metallicity decreases with SFR for a given stellar mass; the outflow efficiency determines the slope and the knee of the metallicity-SFR relation.  Model successfully matched to results from numerical simulations including metal enrichment and feedback at higher z.


1202.4783
The contribution of TP-AGB and RHeB stars to the Near-IR luminosity of local galaxies: Implications for stellar mass measurements of high redshift galaxies
Melbourne, et al


HST imaging of resolved stellar populations in 23 nearby galaxies show that TP-AGB starns and red helium burning (RHeB) stars contribute to 1.6 um NIR luminosity by up to 20% each.  The NIR mass-to-light ratio should be therefore be expected to vary significantly due to fluctuations in the star formation rate over timescales from 25 Myr to several Gyr.  Compare observational results to derived SFH and SPS models.  The SPS models generally reproduce the expected numbers of TP-AGB stars, but give larger discrepancy in the flux contribution, overpredicting by factor of 2.3; offset driven by the modest numbers of TP-AGB stars at young (<300 Myrs) ages.  Best-fit SPS models tend to under-predict the numbers and fluxes of HReB stars by a factor of 2.  These two discrepancies result in NIR M/L largely unchanged for a rapid SFR, but NIR-to-optical flux ratio of galaxies could be significantly smaller than AGB-rich models would predict.


1202.4790
The H I environment of counter-rotating gas hosts: gas accretion from cold gas blobs
Chung, Bureau, van Gorkom, Koribalski


H I gas that is counter-rotating wrt the galaxy is most likely due to the gas flowing in from each of the neighboring galaxies, for the 3 galaxies studied.


1202.4804
Characterizing the nature of fossil groups with XMM
La Barbera, Paolillo, De Fiippis, de Carvalho


6 Fossil group candidates from SDSS and RASS studied with X-ray follow up, 4 confirmed; 2 have x-ray bright AGN or blending of distinct x-ray sources.  Find r-band magnitude gap between seed elliptical and the second-rank galaxy; but gap value can change/wrong if using SDSS magnitudes.  Bright ellipticals in FGs do not represent a distinct population of galaxies (seed FGs and non-fossil ellipticals have similar properties).  FGs don't seem to necessarily form a population of true fossils.


1202.4870
Evolutionary synthesis models as a tool and guild towards the first galaxies
Schaerer


Summarize the principles and fundamental ingredients of evolutionary synthesis models: stellar evolution, stellar atmospheres, the IMF, SFH, nebular emission, and attenuation from ISM and IGM.  Importance for predictions of metal-poor and Pop III dominated galaxies.  Predicted observables: rest-frame UV-to-optical domain with continuum emission from stars and the ionized ISM, plus emission lines from H, He, and metals.  Based on these predictions, summarize the main observational signatures (colors, emission lines, etc) which can be used to distinguish "normal" stellar populations from very metal-poor objects or even Pop III.  


1202.4890
Non-Gaussian isocurvature perturbations in dark radiation
Kawakami, Kawasaki, Miyamoto, Nakayama, Sekiguchi


Study non-G properties of the isocurvature perturbations in the dark radiation (active neutrinos and possible extra light species).  First derive bispectra of primordial perturbations (mixture of curvature and dark radiation isocurvature perturbations).  Also discuss CMB bispectra produced in this model, and their constraints.  Some concrete particle physics models give neutrino density (or light species) isocurvature perturbations.


1202.4927
Multimodality in galaxy clusters from SDSS DR8: substructure and velocity distribution
Einasto, et al


Study galaxy clusters with at least 50 member galaxies from SDSS DR8.  >80% have substructure, median value of peculiar velocities of the main galaxies in clusters is 206 km/s (41% of the rms velocity); the velocities of galaxies in more than 20% of the clusters show significant non-Gausisanity.  Richer, larger and more luminous clusters have larger amount of substructure and larger peculiar velocities of the main galaxies.  PCA of both substructure indicators and physical parameters of clusters show that galaxy clusters are complicated objects (cannot be explained by a small number of parameters).  The presence of substructure, the non-G velocity distributions, as well as the large peculiar velocities of the main galaxies, shows that most of the clusters in our sample are dynamically young.


1202.4936
Rip/singularity free cosmology models with bulk viscosity
Meng, Ma


Universe with a non-perfect fluid with bulk viscosity to interpret the observed cosmic accelerating expansion.  Fits observations.


1202.5004
Intermediate old star clusters in a young starburst: the case of NGC 5253
Harbeck, Gallagher, Crnojevic


Found high global SFR at 1-2 Gyr-aged massive star clusters.  Current star burst is just one episode in an very active galaxy.