1203.4232
Improved limits on short-wavelength gravitational waves from the cosmic microwave background
Sendra, Smith
GW at the time of recombination will mimic massless non-intereacting neutrinos, but its effect would be distinct. Present observational bounds for both [?] initial conditions using the latest CMB data at small scales from SPT and WMAP, BAO, and H0. Adiabatic bound on CGWB improves by a factor of 1.7 (Omega_gw<8.7e-6); comer to upper limit on the tension of horizon-sized cosmic strings that could generate this GW component Gmu<2e-7.
1203.4234
The formation of the extremely primitive star SDSS J102915+172927 relies on dust
Schneider, Omukai, Limongi, Ferrara, Salvaterra, Chievvi, Bianchi
The relative importance of metals and dust grains in the formation of the first low-mass stars has been a subject of debate. Investigate origin of this star (Galactic halo star, Z=4.5e-5 Zsun, 0.8 Msun) by reconstruction the physical conditions in birth cloud; observed abundance can be all fitted by the yields of core-collapse SNe with metal-free progenitors of 20 Msun and 35 Msun. Compute dust yields. 0.05-0.1 Msun mass fragments lead to the formation of low-mass stars can occur, provided that mass fraction of dust grains in the birth cloud exceeds 0.01 of the total mass of metals and dust. This requires that at least 0.4 Msun of dust condense in the first supernovae (moderate destruction by the refers shock).
1203.4240
Dark matter concentrations and a search for cores in Milky Way dwarf satellites
Wolf, Bullock
Investigate the mass distributions within eight classical MW dSphs using an equilibrium Jeans analysis and compare results to the mass distributions predicted for sub haloes in dissipation less LCDM simulations. In order to match the DM density concentrations predicted, the stars in these galaxies must have a fairly significant tangential velocity dispersion anisotropy (if isotropic velocity dispersion, then haloes are less concentrated than LCDM predictions). To dSphs live in haloes with constant density cores? Not all dSphs prefer large constant-density cores. Can the density profiles for these 8 MW dSphs be quantified by a common DM halo?
1203.4248
A phase space diagram for gravity
Hernandez
In modified theories of gravity including a critical acceleration scale, a0, a critical length scale, r_M=(GM/a0)^1/2 will naturally arise. This makes the second critical scale to gravity, after the Schwarzschild radius r_S=2GM/c^2. Non-trivial phenomenology in the (mass, length) plane for astrophysical structures.
1203.4251
Star formation in metal-poor gas clouds
Glover, Clark
Observations of molecular clouds in metal-poor environments typically find that they have much higher star formation rates than one would expected based on their observed CO luminosities and the molecular gas masses that are inferred from them [well, it's low metallicity, so CO concentration would probably be low too, duh?]. The finding can be understood if one assumes that the conversion factor between CO luminosity and H2 mass is much larger in these low metallicity systems than in nearby molecular clouds [duh??]. But it is unclear whether the SFR of the clouds is directly sensitive to the metallicity, or if there are other factors at work [true; there must be other factors at work]. Numerical simulations of coupled dynamical, chemical and thermal evolution of model clouds with 0.01 Zsun to 1 Zsun; find SFR have little sensitivity to metallicity. Reducing the metallicity of the gas by two orders of magnitude delays the onset of SF in the clouds by no more than a cloud free-fall time and reduces the time-averaged SFR by at most a factor of two. On the other hand, the chemical state of the clouds is highly sensitive to the metallicity, and at the lowest meatllicities, the clouds are completely dominated by atomic gas. Results confirm that the CO-to-H2 conversion factor in these systems depends strongly on the metallicity, but also show that the precise value is highly time-dependent, as the integrated CO luminosity of the most metal-poor clouds is dominated by emission from short-lived gravitationally collapsing regions. Find evidence that the SFR per unit H2 mass increases with decreasing metallicity, owing to the much smaller H2 fraction present in the low metallicity clouds. [compared to observation?]
1203.4260
Lagrangian perturbations and the matter bispectrum I: fourth-order model
Ramph, Buchert
Derive perturbation theory solutions to fourth order (for Lagrangian matter bispectrum). Focus on the fastest growing modes. Find exact relations between the series in Lagrangian and Eulerian perturbation theory, leading to identical predictions for the density contrast and the peculiar-velocity divergence up to the fourth order.
1203.4261
Lagrangian perturbations and the matter bispectrum II: the resumed one-loop correction to the matter bispectrum
Ramph, Wong
LPT to study the non-linear evolution of the LSS distribution in the universe. Apply above method to find a resumed one-loop bispectrum that compares favorably with results from N-body simulations. Generalize resummation to redshift-space bispecturm, up to one loop.
1203.4265
Detailed optical and near-infrared polarimetry, spectroscopy and broadband photometry of the afterglow of GRB 091018: polarization evolution
Wiersema et al
Dust-induced polarization in the host galaxy is likely negligible; 0-3% linear polarization; achromatic break corresponding to polarimetric curve features. Data can be reproduced by jet break models only if an additional polarized component of unknown nature is present in the polarimetric curve. P_circ<0.15%, ordered fields are weak, if at all present.
1203.4284
Structure and dynamics of galaxies with a low surface-birghtness disk - II. Stellar populations of bulges
Morelli, Corsini, Pizzella, Bonta, Coccato, Mendez-Abreu, Cesetti
Radial profiles of Hb, Mg and Fe line-strength indices presented for 8 low surface-brightness stellar disk spirals, with bulges. Bulge properties consistent with known early-type galaxies and bulges of other spirals. Almost all sample bulges characterized by a young stellar populations, on-going SF, and a solar alpha/Fe enhancement; spans high to sub-solar metallicities. Observations suggest that a pure dissipative collapse is not able to explain formation of all the sample bulges, and other phenomena (mergers or acquisition events) need to be invoked; this is also supported by lack of correlation between the central value and gradient of the metallicity in bulges with very low metallicity. Stellar populations of the bulges host by low mu discs share many properties with those of high mu galaxies, so they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that in spite of being hosted by discs with extremely different properties, the bulges of low and high surface-brightness discs are remarkably similar.
1203.4291
Recent glitches detected in the Crab pulsar
Wang, Wang, Tong, Yuan
* not clear on the glitch characteristics
Persistent change in pulse frequency and pulse frequency derivative after each glitch; 9 glitches from 2000 to 2010.
1203.4298
Synthesized grain size distribution in the interstellar medium
Hirashita, Nozawa
A synthetic way of constructing the grain size distribution in the ISM: Start with 3 grain size distributions, processed by (i) grain growth by accretion and coagulation in dense clouds, (ii) SNe shock destruction by sputtering in diffuse ISM, and (iii) shattering driven by turbulence in diffuse ISM (all common processes in MW). Compare with MW grain size distribution. Deficiency of small grains due to (i) and (ii) is compensated by the production of small grains by (iii).
1203.4304
Modelling chemical abundance anticorrelations on globular cluster spectra
Coelho, Percival, Salaris
Individual Galactic globular clusters harbor two coeval generations of stars: the first one born with the 'standard' alpha-enhanced metal mixture observed in field Halo objects; the second one characterized by an anti correlated CN-ONa abundance pattern over imposed on the first generation. Investigate how the second generation of stars affects the integrated spectrum of typical metal rich Galactic globular cluster. Conclusions: (1) the age-sensitive Balmer one, Fe line and MgFe indices widely used to determine age, Fe and total metallicity of extragalactic systems are largely insensitive to the second generation population; (2) enhanced He in second generation stars affects the Balmer line indices of the integrated spectra, through the change of the turn off temperature and the HB morphology of the underlying isochrones, which translate into a bias towards slightly younger ages.
1203.4372
The super-Eddington nature of super massive stars
Dotan, Shiva
* Polytrope: In astrophysics, a polytrope refers to a solution of the Lane-Emden equation in which the pressure depends upon the density in the form P=K rho^{(n+1)/n}
Supermassive stars (SMS) are massive hydrogen objects, slowly radiating their gravitational binding energy (hypothetical objects; may have been the seed of massive BHs). Approximately n=3 polytropes; shine extremely close to their Eddington luminosity. Study super-Eddington possibilities. Find: the evolution of SMSs is hastened due to their increase energy release; accelerate continuum driven winds. If no rotational stabilization, winds are insufficient to "evaporate" objects, and can collapse to form a SMBH, but prevent SMSs from emitting a copious amount of ionizing radiation. If rotationally stabilized, the winds "evaporate" objects until a normal sub-Eddington star remains after losing a few 100 Msun mass.
1203.4429
A fast empirical method for galaxy shape measurements in weak lensing surveys
Tewes, Cantale, Courbin, Kitching, Meylan
Q=142 in GREAT10; use a trained look-up table to correct for PSF effects. Very efficient.
1203.4437
Turbulence and fossil turbulence lead to live in the universe
Gibson
* ...something about "Because spontaneous life formation according to the standard cosmological model is virtually impossible, the existence of life falsifies the standard cosmological model." Other than this sentence, he talks about fossil turbulence.
1203.4440
Lythium in M67: from the main sequence to the red giant branch
Pace, Castro, Melendez, Theado, do Nascimento
Li abundances in open clusters are very effective probe of mixing processes; study can help understand the large depletion of Li in the Sun. Study M67, because its metallicity and age is interesting [what is its metallicity and age? Wiki: stars in M67 are younger than the sun; is a relatively old cluster (but not the oldest), turn-off at F stars]. Compare model with observational data. Li in M67 is a tight function of mass for stars more massive than the Sun. Significant scatter in Li abundances for M<1.1Msun. Model reproduce observations, except depletion of Li is 0.45 dex smaller than observed for masses in the plateu region (1.1<M/Msun<1.28). No firm conclusion of Li depletion.
1203.4479
Local and non-local measures of acceleration in cosmology
Bull, Clifton
For inhomogeneous space times that do not display statistical homogeneity and isotropy, find little correlation between acceleration inferred from observations and the acceleration of the averaged space-time. Observations made in an inhomogeneous universe can imply acceleration without the existence of DE.
1203.4505
The life and death of dense molecular clumps in the large Magellanic cloud
Seale, Loney, Wong, Ott, Klein, Pineda
2/3 of the massive YSOs are no longer located in molecular clumps; estimate that these found stars/clusters have destroyed their natal clumps on a time scale of at least 3e5 yrs.
1203.4509
Radio spectra and polarization properties of a bright sample of radio-loud broad absorption line quasars
Bruni, Mack, Salerno, Montenegro-Montes, Carballo, Benn, Gonzalez-Serrano, Holt, Jiminez-Lujan
Origin of BAL QSOs (values~20% of QSO population) still an open issue: broad absorption lines from outflows with velocities up to 0.2c. Does 'orientation' or 'evolutionary' models of BAL model best describe the phenomenon? Age of non-BAL and BAL similar; both show large range of spectral indices (consistent with broad range of orientations). Weak evidence that spectral indices of BAL QSOs are steeper than those of non-BAL, mildly favoring edge-on orientations. [decide orientation from spectra? how?] Polar orientation not preferred.
1203.4517
Reconstructing f(R) model from Holographic DE: using the observational evidence
Saaidi, Aghamohammadi
* holographic principle: property of quantum gravity and string theories which states that the description of a volume of space can be thought of as encoded on a boundary to the region (preferably a light-like boundary like a gravitational horizon).
Investigate relation between f(R) gravity and an interacting holographic DE. Find a viable f(R) model which can explain the present universe. Obtain explicit evolutionary forms of the corresponding scalar field, potential and scale factor of universe.
1203.4521
Spectral energy distributions of quasars selected in the mid-infrared
Lacy, Sajina, Ridgway, Nielsen, Urrutia, Farrah, Gates
142 z>1 quasars selected in the mid-IR. Highly obscured type-2 to lightly reddened type 1 quasars and normal type-1s. No build systematic offset between the far IR properties of dusty and normal quasars. Hosts of type-2 quasars have stellar masses comparable to those of radio galaxies at similar redshifts. Many of type 1s and one of type-2s require a very hot dust component in addition to the normal torus emission.
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