1205.0806
Precision astrometry of the exoplanet host candidate GD 66
Farihi, Subasavage, Nelan, Harris, Dahn, Nordhaus, Spiegel
A WD thought to harbor a giant planet between 2 and 3 AU based on stellar pulsation arrival times. Implications for both the survival and possible regeneration of planets during post-MS stellar evolution. Use IR data, precision measurements rule out all stellar-mass and BD companions, implying that only a planet remains plausible, if orbital motion is the cause of variations in pulsation timing.
1205.0812
The properties and prevalence of galactic outflows at z=1 in the extended Groth strip
Kornei, Shapley, Martin, Coil, Lotz, Schiminovich, Bundy, Noeske
Galactic-scale outflowing winds in 72 SF galaxies at z~1 in EGS investigated; DEEP2 survey with follow-up LRIS spectra, covering SiII, CIV, FeII, MgII, and MgI lines in the rest-frame UV. Use GALEX, HST and Spitzer imaging, examine galaxies on a per-object basis to understand both the prevalence of galactic winds at z~1 and the SF and structural properties of objects experiencing outflows. Gas velocities, measured from the centroids of FeII interstellar absorption lines, span the interval [-200, +150] km/s. Find ~40% (~10%) of the sample exhibits blue shifted FeII lines at the 1-sigma (3-sigma) level. Maximal outflow velocities from FeII and MgII; show MgII frequently traces higher velocity gas than FeII. Quantitative morphological parameters derived from HST imaging suggest that mergers are not a prerequisite for driving outflows. More face-on galaxies also show stronger winds than highly-inclined systems, consistent with the canonical picture of winds emanating perpendicular to galactic disks. Using SF rates from GALEX data and HST imaging areas, detect ~3sigma correlation between outflow velocity and SF rate surface density, but only a weak 1-sigma trend between outflow velocity and SFR. Higher resolution data needed in order to test the scaling relation between outflow velocity and both SFR and SFR surface density predicted by theory.
1205.0823
Cosmology and the Hubble constant: on the megamaser cosmology project (MCP)
Henkel, Braatz, Reid, Condon, Lo, Impellizzeri, Kuo
Recent measurements of H0 anchored on Cepheid observations have reached a precision of several percent. A direct method for comparison: H2O masers orbiting nuclear SMBH for distance measurements, out to local galaxies in Hubble flow.
1205.0847
Reconstruction of the Dark Energy equation of state
Vasquez, Bridges, Hobson, Lasenby
DE characterized as: a perfect fluid with (potentially) time-dependent w(z). Investigate evolution of this parameter with z by performing a Bayesian analysis of current cosmo observations. Model temporal evolution piecewise linear in redshift between 'nodes'. The optimal number of nodes is chosen by the Bayesian evidence; determine the complexity supported by current data and locate any features present in w(z). Compare this node-based reconstruction with other methods: CPL and JBP models. Compare Bayesian evidence for all these; find indication towards possible time-dependence in w(z). Also worth noting that the CPL and JBP models are significantly disfavored when compared to the node-based reconstruction, and also to a simple w=-1 constant.
1205.0868
A new cosmic accelerating scenario without dark energy
Lima, Basilakos, Costa
An alternative (non-singular) scenario based on gravitationally-induced particle production: attempt to evade the coincidence and cosmological constant problems of LCDM; connect early and late-time accelerating stages of the universe. Space-time emerges from a pure initial de Sitter stage; instability provoked by production of massless particles; evolution to standard radiation-dominated era, ending the production of radiation required by conformal invariance. Radiation becomes subdominant as CDM dominates, then negative pressure associated with the creation of cold dark matter (CCDM model) particles accelerates the expansion and drives the universe to a final de-Sitter stage. ...
1205.0932
Quantifying the role of bars in the build-up of central mass concentrations in disk galaxies
Wang, Kauffmann, ... et al
SDSS DR7 3757 face-on disk galaxies at 0.01<z<0.05. 1555 galaxies with bars identified. Galaxies with strong bars have centrally enhanced SF; the degree of enhancement depends primarily on the ellipticity of the bar, and not on the size of the bar, or the mass or structure of host galaxy. Fraction of galaxies with strong bars is highest at stellar masses > 3e10 Msun; stellar surface densities < 3e8Msun, and concentration indices < 2.5. Galaxies with strong bars either have enhanced central SFR, or SF that is suppressed compared to the mean. Suggests that bars may play a role in the eventual quenching of SF in galaxies. Only 50% of galaxies with strongly concentrated SF have strong bars, indicating that other processes such as galaxy interactions also induce central star-bursts. Also find ratio of the size of bar to that of the disk depends mainly on the color of the galaxy, suggesting that growth and destruction of bars are regulated by gas accretion.
1205.1040
Variability of the infrared excess of extreme debris disks
Meng, Rieke, Su, Ivanov, Vanzi, Rujopakarn
Debris disks with extremely large IR excesses (>1e-2 fractional luminosity) are rare. There might be collisions (e.g., between two protoplanets, causing Si-rich vapor, produced in a series of violent collisions), such as that similar to what happened for the early Earth-Moon system. Major collision may be relatively common in this age range.
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