1201.0748
Relativistic model on pulsar radio emission and polarization
Kumar, Gangadhara
Developed a relativistic model for pulsar radio emission and polarization by taking into account of detailed geometry of emission region, rotation and modulation. "Sparks" activity on the polar cap leads to plasma columns in the emission region and modulated emission. Considering relativistic plasma bunches streaming out along the rotating dipolar field lines as source of "curvature radiation," deduce the polarization state of the radiation field in terms of the Stokes parameters.
1201.0753
Fermi-LAT constraints on dark matter annihilation cross section with the Fornax cluster
Ando, Nagai
1-100 GeV photos from 49 clusters of galaxies, and find no excess gamma-ray emission towards directions of the galaxy clusters. Use baryonic contraction models to model DM contraction and substructures. Obtain upper limits on annihilation cross section for DM particle of 10 GeV of <1e-25 cm^3/s: only x3 larger than a value theoretically preferred to explain the DM relic density. More robust than the annihilation boost dues to substructure.
1201.0754
The effects of anisotropic viscosity on turbulence and heat transport in the intracluster medium
Parrish, McCourt, Quataert, Sharma
In the ICM of galaxy clusters, heat and momentum are transported almost entirely along (but not across) magnetic field lines. Perform the first fully self-consistent Braginskii-MHD simulations of galaxy clusters including both of these effects. Perform local and global simulations of the magnetothermal instability (MTI) and the head-flux-driven buoyance instability (HBI) and assess the effects of viscosity on their saturation and astrophysical implications. Find that viscosity has only a modest effect on the saturation of the MTI. MTI can generate nearly sonic turbulent velocities in the outer parts of galaxy clusters (somewhat damped by viscosity). At smaller radii in cool-core clusters, viscosity can decrease the linear growth rates of HBI, but has less effect on the HBI's nonlinear saturation. HBI robustly inhibits radial radial thermal conduction and thus precipitates a cooling catastrophe (in simulations). For high-entropy cluster, viscosity is more important: contribute to the global transition from cool-core to non cool-core states. AGN or galactic wakes can suppress HBI, heating the cluster core by thermal conduction, making ICM more viscous, slows HBI, thus heating the core further.
* what is a typical magnetic field-line structure in cluster of galaxies?
1201.0755
The bright end of the UV luminosity function at z~8: new constraints from CANDELS data
Oesch, Bouwens,... Gonzalez, Trenti, van Dokkum, ... et al
Search over 95 arcmin sq for z~8 galaxy candidates with WFC3/IR, to determine the bright end of the UV luminosity function (LF) of SF galaxies at z~8. Search for bright (M_UV < -19.5) z~8 galaxy candidates using Lyman Break technique. 11 candidate galaxies, showing UV LF is x2 lower than previously determined. M*=-19.8 mag, faint end slope alpha = -2.1.
1201.0757
Concordance models of reionization: implications for faint galaxies and escape fraction evolution
Kuhlen, Faucher-Giguere
* escape fraction: of ionizing photons
UV luminosity function up to z~10 has been constrained, but allow for a wide range of reionization scenarios due to uncertainties in abundance of faint galaxies and the escape fraction of ionizing photons. If one requires continuity with post reionization (z<6) measusrements where the Lya forest probes the cosmological emissivity of ionizing photons, this significantly reduces the permitted parameter space. Models that are simultaneously consistent with the measured UV luminosity function, the Thomson optical depth to the CMB, and the Lya forest data require either (1) extrapolation of the galaxy luminosity function down to very faint UV magnitudes M_lim ~ -10, corresponding roughly to the UV background suppression scale, (2) an increase of f_esc by a factor >~10 from z=4 to z=9, or (3) a hybrid solution in which undetected galaxies contribute significantly and f_esc increases more modestly. [i don't understand what tension the data has with theory... UV luminosity function must be pretty low compared to the expected number of faint galaxies? or too high? wait... there seems to be more ionization than expected from UV luminosity function. That must be it. Unclear abstract!] Models in which star formation is strongly suppressed in low-mass, reionization-epoch haloes of mass up to 1e10 Msun (owing to a metallicity dependence) are only allowed for extreme assumptions for the "extreme assumptions" [what the heck does *that* mean?] for the evolution of f_esc. Assuming an earlier or higher metallicity floor are in better agreement with the data. 50% reionization at around z~10. Duration of reionization sensitive to the relative contribution of bright versus faint galaxies, with scenarios dominated by faint galaxies predicting a more extended reionization event. SZ measurements prefer a short reionization history.
1201.0758
Masses of nearby SMBH with VLBI
Johannsen, et al
Mass measurement of Sgr A* has degeneracy with distance, where M~D^2. Future VLBI observations will build a bright and narrow ring surrounding the shadow of the SMBH, if its accretion flow is optically thin. Show that the combination of dynamical meausrements and VLBI imaging of the ring of Sgr A* breaks the degeneracy between mass and distance, from the expected size of the ring image, and existing data of stellar ephemerides.
1201.0763
Astrophysically motivated bulge-disk decompositions of SDSS galaxies
Lackner, Gunn
71k SDSS galaxies in the range 0.003<z<0.05, bulge-disk decomposed into deV or exponential bulge, and an exponential disk. 2d Sersic fits performed when the 2 component fits are not statistically significant, or when the fits are poor. Study robustness of 2 component fit: systematics of fits with decreasing resolution and S/N. 30% of sample fit with 2 component fits in which both components are non-zero. g-r and g-i colors of each component of the two-component models are determined using linear templates derived from the r-band model. Petrosian concentration is a good indicator of B/T, while overall Sersic index is not. Find: majority of green valley galaxies are bulge+disk galaxies. In the transition from green to red B+D galaxies, the total galaxy colour is most strongly correlated with the disk colour.
1201.0765
The self-calibrating Hubble diagram
Feindt, Kowalski, Paech
Primary reference spectrum (which is the main contributor to the systematic uncertainty budget), perturbation is consistent with 0 at the 1% level. For future surveys, ~3500 SNe required for self-calibration to outperform the standard method of deriving cosmo parameters.
1201.0780
Relative merits of different types of rest-frame optical observations to constrain galaxy physical parameters
Pacifici, Charlot, Blaizot, Brinchmann
New approach to constraint galaxy physical parameters from the combined interpretation of stellar and nebular emission in wide ranges of observations. Bayesian analysis of any type of galaxy SED using comprehensive library of synthetic spectra (star formation, chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust). 12k SDSS SF galaxies using this approach yields likelihood distributions of stellar mass, gas-phase oxygen abundance, optical depth of the dust and specific star formation rate similar to past studies of stellar and nebular emission with the original (x2 better) SDSS resolution.
1201.0783
The Carnegie-Spitzer-IMACS redshift survey of galaxy evolution since z=1.5: I. Description and Methodology
Kelson, et al
CSI: new spectrophotometric survey, efficiently tracing stellar mass of average galaxies to z~1.5. Survey selection, observations, processing of photometry and spectrophotometry. Photoz, stellar masses, emission line luminosities, and coarse info on recent SF. Photoz sigma/(1+z) < 0.015. Comparable redshift uncertainties and success rates for both red and blue galaxies.
1201.0835
New Lithium Measurements in metal-poor stars
Schaeuble, King
Li 6708A measurements in 37 metal-poor stars with high resolution, high S/N spectroscopy. Li depletion mechanism can be studied.
1201.0866
Clearing out a galaxy
Zubovas, King
What is the observable properties required for AGN to sweep galaxies clear of gas? kinetic luminosities ~0.05 L_edd and momentum rates ~ 20 L_edd/c. Creates expanding two-phase medium in which molecular species coexist with hot gas, which can persist after the central AGN has switched off. Predicts outflow velocities of 1000 to 1500 km/s, and mass outflow rates up to 4000 M_sun/yr on kpc scales. All these features agree with outflows observed in galaxies. Suggests AGn is what sweeps galaxies clear of their gas.
1201.0885
Simulations of binary galaxy mergers and the link with fast rotators, slow rotators, and kinematically distinct cores
Bois et al
GalMer simulation project: disk 3:1 and 6:1 mergers are Fast Rotators (they preserve the structure of the input fast rotating spiral progenitors). Major disc mergers (2:1 and 1:1) lead to both fast and slow rotators. Most slow rotators hold a kinematically distinct core (KDC) in their central 1-3 kpc, build from stellar components of the progenitors.
1201.0922
A low-frequency study of two asymmetric large radio galaxies
Pirya, Nandi, Saikia, Singh
Two asymmetric, Mpc-scale radio sources: multifrequency observations. FRI: brightest toward the center, FRII: brightest toward the edges. ...
1201.0926
On the discriminating power of f_NL
Hazra, Sriramkumar, Martin
Calculate f_NL for a variety of single field inflationary models that lead to features in the scalar power spectrum. Find that different behavior of the slow roll parameters can lead to a reasonably large difference in f_NL^eq generated by the models.
1201.0991
The Atacama cosmology telescope: dynamical masses and scaling relations for a sample of massive SZ effect selected galaxy clusters
Sifon,... Marriage, Hughes, ... Das, Devlin, Dunkley, ... et al
From 16 massive clusters detected with ACT over 455 sq deg, use kinematics over ~60 galaxies per cluster to estimate mass, using simulations to scale between velocity dispersion and mass. Sample has median redshift of z=0.5 and a median mass M200c=1.1e15 Msun/h_70 with lower limit 5e14 Msun/h_70. Compared mass to ACT SZE properties SZ amplitude y0, Compton signal within 0.5': y_0.5', and integrated Compton signal Y_200c. All SZE estimators correlate with dynamical mass with low intrinsic scatter (11-16%), in agreement with numerical simulations. Influence of dynamically distributed clusters on the scaling relations considered. Divide sample in to relaxed and disturbed clusters, find that ~50% of the clusters are disturbed. Conclude that disturbed systems do not significantly bias the scaling relations, but might modestly boost their scatter.
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