1204.2261
Electron beam induced radio emission from ultracool dwarfs
Yu, Doyle, Kuznetsov, Hallinan, Antonova, MacKinnon, Golden
Attempt to understand recently discovered intense radio emission from ultra cool dwarfs: simulate e-beam-driven and loss-cone-driven electron-cyclotron maser (ECM) with different plasma parameters and different magnetic field strengths in a relatively small region and short time-scale. A rapidly developed high-energy tail of electrons in velocity space (resulting from the heating process of the ECM) may produce the radio continuum depending on the initial strength of the external magnetic field and the electron beam current. Both significant linear polarization and circular polarization of EM waves can be obtained from the simulations. The SED of the simulated radio waves show that harmonics may appear from 10 to 70 nu_pc (nu_pc == electron plasma frequency) in the non-relativistic case and from 10 to 6000 nu_pc in the relativistic case ,which makes it difficult to find the fundamental cyclotron frequency in the observed radio frequencies. A wide frequency band should therefore be covered by future radio observations.
1204.2263
Disc scalelengths out to redshift 5.8
Fathi, Gatchell, Hatziminaoglou, Epinat
Compute the exponential disk scale length for 686 disc galaxies with spec-z's out to 5.8 based on HST archival data. Compare results with previous measurements based on 30k nearby galaxies from SDSS. Confirm the presence of dominated exponential component in galaxies out to this redshift. At the highest redshifts, the disc scale length for the brightest galaxies with absolute magnitude between -24 and -22 is up to a factor 8 smaller compared to that in the local Universe. This observed scale length decrease is significantly greater than the value predicted by a cosmological picture in which baryonic disk scale length scales with the virial radius of the DM halo.
1204.2264
Separating intrinsic alignment and galaxy-galaxy lensing
Blazek, Mandelbaum, Seljak, Nakajima
No coherent alignment of IA in gg lensing, at least not in SDSS LRGs. Solve for IA and lensing signal simultaneously, find IA signal consistent with zero.
1204.2265
Polar bulges and polar nuclear discs: the case of NGC4698
Corsini, et al
Early-type spiral: known to host a nuclear disk of gas and stars rotating perpendicularly with respect to the galaxy main disc; bulge and main disc are characterized by a remarkable geometrical decoupling (they appear elongated orthogonally to each other. Investigate complex structure by a detailed photometric decomposition of optical and near-IR images. Intrinsic shape of bulge constrained; actually elongated perpendicular to the main disc and is equally likely to be triaxial or axisymmetric. The nuclear disk's size, orientation and location do not depend on the observed passband. Support a scenario in which the nuclear disc is the end result of the acquisition of external gas by the pre-existing triaxial bulge on the principal plane perpendicular to its shortest axis and perpendicular to the galaxy main disc. The subsequent SF either occurred homogeneously all over the extension of the nuclear disc or through an inside-out process that ended more than 5 Gyr ago.
1204.2266
Effects of thermohaline instability and rotation-induced mixing on the evolution of light elements in the Galaxy : D, 3He and 4He
Lagarde et al
Inclusion of thermohaline mixing in stellar models provides a solution to the long-standing "3He problem" on a Galctic scale, also reproduces D and 4He observations. Thermonaline mixing is likely the dominating process that governs the photospheric composition of low-mass red giant branch stars and has been shown to drastically reduce the net 3He production in these stars.
1204.2272
Gaussian process cosmography
Shafieloo, Kim, Linder
Gaussian processes provide a method for extracting cosmological information from observations without assuming a cosmological model. Cosmography in a model-independent manner using kinematic variables and a geometric probe of cosmology. Using Union2.1, constrain H0 and deceleration parameter as a function of redshift. Extraction of these relations tested successfully against models with features on various coherence scales, subject to certain statistical cautions. [I'm not sure what they did]
1204.2280
Bonsai: A GPU Tree-Code
Bedorf, Gaburov, Zwart
N-body hierarchical code on GPUs; algorithm on GPU, eliminating the need for data transfer between the CPU and GPU; outperforms tuned CPU code for all parts of the algorithm, show and overall performance improvement of more than 20x.
1204.2305
A highly magnified candidate for a young galaxy seen when the Universe was 500 Myrs old
Zheng, Postman, Zitrin, Moustakas, ... et al
Discovery of an object found in the multi-band observations of the cluster MACS1149+22 that is likely from z=9.6pm0.2, detected above 1.2 um. 15x magnification, constrain stellar mass, SFR and age. Must be <200 Myr old! Formation z~14. Bright enough for JWST spectroscopy!
1204.2308
Near-infrared observations of type Ia supernovae: the best known standard candle for cosmology
Barone-Nugent et al
Suggest: SNe Ia observed in the NIR are the best known standard candles (0.03<z<0.09).
1204.2417
Metallicity effects on the cosmic SNIb/c and GRB rates
Grieco et al
SN Ib/c are likely to be associated to long GRBs; compare SN rate in galaxies with the GRB rate. Results: (1) ratio is 1e-2 to 1e-4: only a small fraction of all the Type Ib/c gives rise to GRBs. (2) Metallicity dependence of progenitors produces lower cosmic SN Ib/c rates at early times for any SFR, (3) Different theoretical cosmic star formation rates produce SN I/c cosmic rates which differ mainly at very high z. (4) GRBs can be important tracers of SF at high z if their luminosity function does not vary with redshift.
1204.2455
Magnetic field amplification by shocks in galaxy clusters: application to radio relics
Iapichino, Brüggen
Radio relics: merger shocks inducing turbulence in ICM, accelerating electrons to relativistic velocities, which generate radio emission. Found mostly at the periphery of galaxy clusters, and appear to have B-field of uG level. Origins of B-field: turbulence from shock insufficient, vorticity generated by compressive and baroclinic effects across the shock discontinuity can lead to a sufficient amplification of the B-field.
1204.2510
Cosmological lepton asymmetry with a nonzero mixing angle theta_13
Castorina, et al
Bounds on the lepton asymmetry in the form of neutrinos very weak. Consider cosmo data and flavor oscillation. For large theta_13 the limits on the total neutrino asymmetry become more stringent, diluting even large initial flavor asymmetries. Find that the present bounds are still dominated by the limits coming from BBN, while the limits on the total neutrino mass from cosmological data are essentially independent of theta_13. Forecast for COrE: could improve the limits on the total lepton asymmetry approximately by 5x.
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