Saturday: fly out to Berkeley. Still somewhat jet lagged here. Yookyung picked me up at Berkeley train station, Petra gave me the keys to Uros' apartment (part of his house), met up with Tommy and Rahan for tea, then Anthony joined us for dinner at Finfine.
Sunday: must read one astro-ph today....but didn't. Rented a car (ran down Marin to get to Hertz before they closed at noon). Went to lunch with YK and Hee-Jong. Grocery shopping with YK, SooMi+hubby. Movie (Hunger Games) with YK, HJ and Tommy.
Monday: Got my old badge back.
1204.5742
Ionization structure and chemical abundances of the Wolf-Rayet nebula NGC6888 with integral field spectroscopy
Fernandez-Martin, Martin-Gordon, Vilchez, Montero, Riera, Sanchez
* crescent nebula.
* WR star: evolved, massive stars (initially, >20 Msun) which is losing mass by means of a very strong stellar wind (2000 km/s).
Interaction between ISM and stellar winds in the WR nebula (ionization structure, chemical composition, kinematics) Maps of extinction structure and electron density. Shock models describes a localized SW region. Electron temperature 7700K to 10200K. Strong variation (x10) between different regions in the nitrogen abundance. N/H appears lower than the solar abundance (lower at edges, and very enhanced in the inner parts). Structure model of multiple shells.
1204.5749
Diagnostics of baryonic cooling in lensing galaxies
Leier, Ferreras, Saha
Theory: inverse proportionality between the concentration of DM haloes and virial mass, confirmed for Mvir > 6e12 Msun with X-ray observation. Alternative approach: Concentration of DM halo in 18 early-type systems. c-Mvir relation consistent with the X-ray analysis, extending towards lower virial masses, covering the range from 4e11 Msun up to 5e12 Msun. Combination of lensing with photometric data constrain the baryon fraction within a few effective radii, which is compared with prescriptions for adiabatic contraction (AC) of the dark matter haloes. Find: standard methods for AC are strongly disfavored, requiring additional mechanisms, such as mass loss during the contraction process, to play a role during the phases following the collapse of the haloes.
1204.5753
Detection of dark galaxies and circum-galactic filaments fluorescently illuminated by a quasar at z=2.4
Cantalupo, Lilly, Haehnelt
98 LyA candidates in 5500 Mpc^3 (comoving) at z=2.4, centered on the hyperluminous quasar HE0109-3518. A large fraction of these are fluorescently "illuminated" by this quasar; verified by radiative transfer simulations. 18 objects have LyA emission limit for Pop II star formation, and 12 sources among those do not have any continuum counterpart in a deep V-band imaging of the same field. Stacking analysis rules out LyA powered by internal SF. These sources are thus the best candidates for proto-galactic clouds or "dark" galaxies at high-redshift, whose existence has recently been suggested by several theoretical studies; gas mass of 1e9 Msun; SFE < 4e-12 /yr, 1 order magnitude below the SFE of most gas-rich dwarf galaxies locally, and five hundred times lower than typical massive star-forming galaxies at z~2. Also discovered extended, filamentary gas, also likely illuminated by the quasar, around some of the brightest continuum-deteted sources. Emission compatible with the expectations for circum-galactic cold-streams, but other origins (tidal stripping) possible.
1204.5754
Carbon-rich dust production in metal-poor galaxies in the local group
Sloan et al
A study of the carbon budget in these stars reinforces previous considerations that the dredge-up of sufficient quantities of carbon from the stellar cores may trigger the final super wind phase, ending a star's lifetime on the asymptotic giant branch.
1204.5761
Using galaxy pairs as cosmological tracers
Belloso, Pettinari, Meures, Percival
AP test: constrains the product of the Hubble parameter and the angular diameter distance. But expansion of the universe in inhomogeneous, and local curvature depends on density, distorting AP effect on small scales. Study dynamics of galaxy pairs in Millennium, find an interplay between peculiar velocities, galaxy properties and local density that affects how pairs trace cosmological expansion--only low mass, isolated galaxy pair trace the average expansion with minimum "correction" for peculiar velocities.
1204.5770
Halo sampling, local bias and loop corrections
Chan, Scoccimarro
New test of local bias: construct locally biased halo density field from sampling the DM halo distribution. Preserves full scatter in the bias relation (does not rely on perturbation theory). Automatically include the running of bias parameters, give vanishingly small loop corrections at low-k. Better agreement of the sampling and perturbation theory results with original simulations. Does not produce constant power at very large scales, like perturbation theory. Demonstrate nonlocal bias effects discovered recently in simulations impact the power spectrum only at the few percent level in the weakly NL regime.
1204.5771
NGC 5466: a unique probe of the galactic halo shape
Lux, Read, Lake, Johnston
Longer tidal stream provide cleaner measurements of galactic potentials. Find evidence for triaxial halo of MW.
1204.5861
Thermalisation of light sterile neutrinos in the early universe
Hannestad, Tamborra, Tram
Cosmo data favor additional relativistic degrees of freedom beyond the 3 active neutrinos and photons ("dark" radiation). Light sterile neutrinos is one of the prime candidates for such additional radiation. But constraints on sterile neutrinos based on the current cosmo data have been derived using simplified assumptions about the thermalization of the sterile neutrino at BBN; not necessarily justified. Solve the full quantum kinetic equations in the (1 active + 1 sterile) scenario, and derive the number of thermalized species just before BBN (T~1Mev) for null and large initial lepton asymmetry, and for a range of possible mass-mixing parameters. Find: full thermalization assumption during the BBN epoch is justified for initial small lepton asymmetry only. Partial or null thermalization occurs when the initial lepton asymmetry is large.
1204.5869
Selected results from the ANTARES neutrino telescope
ANTARES collaboration
Cherenkov light produced in Mediterranean Seak by neutrino-induced muons. Tri-dim array of 885 photomultipliers on 12 vertical lines; located at a depth of 2.475 km, 40km off the French coast. Probe the universe by means for neutrino events, nature of HE astro sources, ID of CR sources, and to explore the nature of dark matter. Searching for astrophysical sources.
1204.5927
Modelling the correlation between the thermal Sunyaev Zel'dovich effect and the cosmic infrared background
Addison, Dunkley, Spergel
Calculate, in halo model framework, the correlation between tSZ from galaxy clusters and dust emission from CIB sources. Size of cross-correlation is approximately 10% at 150 GHz. Contribution to the total angular power spectrum is of order -1 mu K^2 at ell=3000; this value is uncertain by a factor of two to three, because of CIB source modeling uncertainties. Expect the large uncertainty in this component to degrade upper limits on the kSZ, due to similarity in the frequency dependence of the tSZxCIB and kSZ across the frequency range probed by current CMB missions. Find that the degree of tSZxCIB correlation is higher for mmxsub-mm spectra than mmxmm, because more of the sub-mm CIB originates at lower redshifts (z<2), where most tSZ clusters are found.
1204.5947
Constraining multiple systems with GAIA
Beauvalet, Lainey, Arlot, Bancelin, Binzel, Marchis
GAIA will provide observations of some multiple asteroid and dwarf systems. These observations are a way to determine and improve the quantification of dynamical parameters, such as masses and gravity fields in these systems. Investigate this problem in the cases of Pluto's and Eugenia's system. Developed a numerical model reproducing the specific behavior of multiple asteroid system around the Sun and fit it to the simulated observations, giving the uncertainties on the fitted parameters. Find that GAIA will improve significantly the precision of Pluto's and Charon's mass, as well as Petit Prince's orbital elements and Eugenia's polar oblateness.
1204.6005
Cold fronts and gas sloshing in galaxy clusters with anisotropic thermal conduction
ZuHone, Markevitch, Ruszkowski, Lee
Cold fronts in cluster cool cores should be erased on short timescales by thermal conduction, unless protected by magnetic fields that are "draped" parallel to the front surfaces, suppressing conduction perpendicular to the fronts. MHD simulations of cold from formation in the core with anisotropic thermal conduction, exploring a parameter space of coeducation strengths parallel and perpendicular to the fields lines. Field geometry is such that the cold gas below the front surfaces can be connected to hotter regions outside via fields lines along directions perpendicular to the plane of the sloshing motions and along sections of the front which are not perfectly draped; results in heating of this gas below the front on a timescale of Gyr. Conduction may indirectly aid in suppressing Kelvin-Helmoholtz instabilities; if conduction along field lines is unsuppressed, find that the characteristic shape jumps in x-ray emission seen in observations of clusters do not form. This suggests that the presence of sharp cold fronts in hot clusters could be used to place upper limits on conduction in the bulk of the ICM. Combination of sloshing and anisotropic thermal conduction can result in a larger flux of heat to the core than either process in isolation, reducing significantly the mass of cool gas that accumulates outside those radii.
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