1301.0024
Relative velocity of dark matter and baryons in clusters of galaxies and measurements of their peculiar velocities
Dolag, Sunyaev
Peculiar velocities of individual clusters of galaxies might be measured using the kinematic SZ effect. Next generation of X-ray telescopes promise first detections of motion of the ICM within clusters. Use cosmo sims with many clusters and very high resolution on some clusters to investigate how the presence of baryons and their associated physical processes like cooling and SF are affecting the systematic difference between mass averaged velocities of DM and the ICM inside a cluster. Quantify the peculiar motion of galaxy clusters as function of the large scale environment; demonstrate that in very massive systems, the relative velocity of the ICM compared to the cluster peculiar velocity add significant scatter onto the inferred peculiar velocity, especially when measurements are limited to the central regions of the cluster. Depending on the aperture used, this scatter varies between 50% and 20%, when going from the core (<10% r_vir) to the full cluster (~r_vir).
1301.0060
On the validity of the perturbative approach for strong lensing: local distortion for pseudo-elliptical models
Dumet-Montoya, ... Gill, et al
The perturbative approach (PA) provides analytic solutions for gravitational arcs by solving the lens equation linearized around the Einstein ring solution, a method for lens inversion and simulations that can be used for generic lens models. In this paper, aim to quantify the domain of validity of this method for caustics, critical curves, and the deformation cross section (the arc cross set ion in the infinitesimal circular source approximation). Consider lens models with elliptical potentials (Singular Isothermal Elliptic Potential and Pseudo-Elliptical NFW models). Show that the PA is exact for the first model. For the second, obtain contraints on the model parameter space (given by the potential ellipticity parameter \epsilon and characteristic convergence \kappa_s) such that the PA is accurate for the aforementioned quantities. In this process, obtain analytic expressions for several lensing functions, which are valid for the PA in general. The determination of this domain of validity could have significant implications for the use of the PA, but it still needs to be probed with extended sources.
1301.0163
Lithium-rich field giants in the Sloan digital sky survey
Martell, Shetrone
A search for post-main sequence field stars in the Galaxy with atypically large Li abundances. Using SDSS spectra along with high-res followup, identify 23 post-turnoff stars with log epsilon(Li) > 1.95, including 14 with >2.3 and 8 with >3.0, well above the low level expected for evolved stars. Comparison with theoretical isochrones indicates that some of these Li-rich stars are affiliated with the upper red giant branch, the AGB and the red clump rather than the RGB bump, which is a challenge to existing models of Li production in evolved stars.
1301.0217
Characterization of potentially habitable planets: retrieval of atmospheric and planetary properties from emission spectra
von Paris, Hedelt, Selsis, Schreier, Trautmann
Sear for atmospheric signatures to establish planetary habitability and the presence of life: want to quantify the accuracy of retrieved atmospheric parameters which might be obtained from IR emission spectroscopy. Use synthetic observations of hypothetical habitable planets constructed with a parameterized atmosphere model, a high-res radiative transfer model and a simplified noise model. ... find that emission spectroscopy could provide weak limits on surface conditions of terrestrial planets, hence their potential habitability; although unlikely to allow characterization of the composition of the atmosphere of a habitable planet. CO2 content to <2 orders of magnitude, O3 biosignature remains marginal. Other methods such as transmission spectroscopy or orbital photometry are probably needed in order to give additional constraints and break degeneracies.
1301.0235
Hot moons and cool stars
Heller, Barnes
Kepler photometry can detect extrasolar moons. First review observational and analytical techniques recently proposed for exomoon detection. Then discuss the prospects of characterizing potentially habitable extrasolar satellites. With moons being much more numerous than planets in the solar system and with most exoplanets found in the stellar habitable zone being gas giants, habitable moons could be as abundant as habitable planets. However, satellites orbiting planets in the habitable zones of cool stars will encounter strong tidal heating and likely appear as hot moons.
1301.0285
The equations of magnetoquasigeostrophy
Umurhan
"Magneto quasi geo strophy": Dynamics contain in magnetized layers of exoplanet atomospheres. Framework development.
1301.0311
Venus transits: history and opportunities for planetary, solar and gravitational physics
Sigismondi, Wang, Rocher, Reis-Neto
Compare 2012 transit to 2004. Thickness of the atmosphere of Venus, its aureole and the effect of oblateness and other asphericities in the figure of the Sun are taken into consideration, as well as the black drop effect. A new extrapolation method for the contact times is presented. The next Mercury transit in 2016 will be fully visible from Europe, and the data will be gathered in view of this new method of analysis, to obtain the solar diameter.
1301.0320
The radial distribution of star formation in galaxies at z~1 from the 3D-HST survey
Nelson, van Dokkum, et al
The assembly of galaxies can be described by the distribution of their star formation as a function of cosmic time. Thanks to the WFC3 grism on HST, it is now possible to measure this beyond the local Universe. Present the spatial distribution of Halpha emission for a sample of 54 strongly SF galaxies at z~1 in the 3D-HST Treasury survey. By stacking the Halpha emission, find that SF occurred in approximately exponential distributions at z~1, with median Sersic index of n=1.0pm0.2. The stacks are elongated with median axis ratios of b/a=0.58pm0.09 in Halpha, consistent with (possibly thick) disks at random orientation angles. Keck spectra obtained for a subset of 8 of the galaxies show clear evidence for rotation, with inclination-corrected velocities of 90 to 330 km/s. The most straightforward interpretation of our results is that SF in strongly SF galaxies at z~1 generally occurred in disks. The disks appear to be "scaled-up" versions of nearby spiral galaxies: they have EW(Ha)~100 Angstroms out to the solar orbit and they have SF surface densities above the threshold for driving galactic scale winds.
1301.0321
Strontium and Barium in early-type galaxies
Conroy, van Dokkum, Graves
Abundance pattern 'chronometers' include the alpha and Fe-peak elements, which are created on short and long timescales, respectively. These two clocks have been widely used to estimate SF timescales from moderate-resolution spectra of early-type galaxies. Elements formed via s-process neutron captures (eg., Sr and Ba) comprise a third type of chronometer, as the site of the main s-process is believed to be intermediate and low-mass asymptotic giant branch stars. The [alpha/Ba] ratio in particular should provide a powerful new constraint on the SFH of galaxies, in part because it is insensitive to the uncertain distribution of SNIa detonation times and the overall Ia rate. Present new measurements of the abundance of Sr and Ba in nearby early-type galaxies by applying SPS tools to high S/N optical spectra. Find a strong anti-correlation between [Mg/Fe] and [Ba/Fe], and a strong positive correlation between [Mg/Ba] and galaxy velocity dispersion. These trends are consistent with the idea that more massive galaxies formed their stars on shorter timescales compared to less massive galaxies, and rule out several outer proposed explanations for the observed super-solar [Mg/Fe] values in massive galaxies. In contrast, [Sr/Fe]~0, with no strong variation across the sample. It is difficult to interpret the Sr trends without detailed chemical evolution models owing to the multiplicity of proposed nucleosynthetic sites for Sr.
1301.0360
Gravitational lensing effects on sub-millimetre galaxy counts
Er, Li, Mao, Cao
Study of effect on the number counts of SMG due to gravitational lensing. Explore the effects on the magnification cross section due to halo density profiles, ellipticity and cosmological parameter (sigma_8). Show that the ellipticity does not strongly affect the magnification cross section in gravitational lensing while the halo radial profiles do. Since the baryonic cooling effect is stronger in galaxies than in clusters, galactic haloes are more concentrated. In light of this, a new scenario of two halo population model is explored where galaxies are modeled as a singular isothermal sphere profile and clusters as a NFW profile. Find the transition mass between the two has modest effects on the lensing probability. The cosmological parameter sigma_8 alters the abundance of haloes and therefore affects our results. Compared with other methods, this model is simpler and more realistic. The conclusions of previous works is confirm that gravitational lensing is a natural explanation for the number count excess at the bright end.
1301.0371
Cool gas in high redshift galaxies
Carilli, Walter
Molecular gas has now been observed in ~200 galaxies at z>1, including numerous AGN host-galaxies out to z~7, highly SF galaxies (median z ~ 2.5), and increasing samples of 'main-sequence' SF galaxies at z~1.5-2.5. Studies have moved well beyond simple detections to dynamical imaging to kpc-scale resolution, and multi-line, multi-species studies that determine the physical conditions in the interstellar medium. Observations of the cool gas are the required complement to studies of the stellar density and SFH of the Universe, as they reveal the phase of the interstellar medium that immediately precedes SF. Current observations suggest that the order of magnitude increase in the cosmic SFR density from z~0 to 2 is commensurate with a similar increase in the gas to stellar mass ratio in SF disk galaxies. Progress has been made on determining the CO luminosity to H2 mass conversion factor at high-z, and the dichotomy between high versus low depletion time values for main sequence versus starburst galaxies, respectively with a likely dependence on metallicity and other local physical conditions. Studies of atomic fine structure line emission are rapidly progressing, with some tens of galaxies detected in the exceptionally bright CII 158 micron line to date. This line is proving to be a unique tracer of galaxy dynamics in the early Universe and has the potential to be the most direct means of obtaining spectroscopic redshifts for the first galaxies during cosmic reionization.
1301.0462
Searching for neutral hydrogen haloes around z ~ 2.1 and z ~ 3.1 Ly-alpha emitting galaxies
Feldmeier, ... Gawiser, ... Acquiaviva, ... et al
Stack 187 LAEs at z=2.1, and 241 LAEs at z=3.10, and 179 LAEs at z=3.12, obtain mean surface brightness maps that reach 9.9, 8.7, 6.2e-19 ergs/cm^2/s/arcsec^2 in the emission line. Find that limits are 5-10 times larger than what is expected from Poisson BG fluctuations; these uncertainties are often underestimated in the literature. At z~3.1, find marginal evidence for extended haloes with scale lengths of 5-8 kpcs, and demonstrate that sub-samples of galaxies with low equivalent widths and brighter continuum magnitudes are more likely to posses such haloes. At z~2.1, find no evidence of extended Lya emission down to detection limits. Compare these findings to other measurements, discuss possible instruemental and astrophysical reasons for the discrepancies, including possible evolution of Lya halo properties from z~3.1 to 2.1.
1301.0475
Cross-correlation of WMAP7 and the WISE full data release
Kovacs et al
Cross correlate WMAP7 temperature map to WIde-field Infrared SUrvey Explorer galaxy map; find a positive cross-correlation signal [at what significance?]. Results are fully consistent with a LCDM universe, although not statistically significant. Findings are robust against changing the galactic latitude cut from |b|>10 to |b|>20 and no color dependence was detected. Confirm higher significance correlations found in the preliminary data release. The change in significance is consistent with cosmic variance.
1301.0530
The origin and optical depth of ionizing radiation in the "Green Pea" galaxies
Jaskot, Oey
Observations of SF galaxies at low-z generally indicate low LyC (Lyman continuum) escape fractions, though at high-z they likely caused reionization of the universe. However, the extreme [OIII]/[O II] ratios of the z=0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, compare nebula photoionization and stellar population models with observed emission lines in the Peas' SDSS spectra. Focus on the 6 most extreme Green Peas. The Balmer line equivalent widths and He I emission in the extreme Peas support young ages of 3-5 Myr, and He II emission in 5 extreme Peas signals the presence of hard ionizing sources. Ionization by AGN or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no WR features, tentatively detect WR features in the SDSS spectra of 3 extreme Peas. Based on the Peas' ages and line ratios, find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of Lyman-continuum radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.
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