Day 666

Tuesday.

1405.6237
Characterizing the galactic warp with Gaia: I. the tilted ring model with a twist
Abedi, Mateu, Aguilar, Figueras, Romero-Gomez

Explore the possibility of detecting and characterizing the warp of the stellar disk of MW using synthetic Gaia data.  The availability of proper motions and, for the brightest stars radial velocities, adds a new dimension to this study.  A family of Great Circle Cell Counts (GC3) methods is used.  They are ideally used to find the tilt and twist of a collection of rings, which allow us to detect and measure the warp parameters.  To test them, use random realizations of test particles which evolve in a realistic Galactic potential warped adiabatically to various final configurations.  In some cases, a twist is introduced additionally.  The Gaia selection function, its errors model and a realistic 3d extinction map are applied to mimic 3 tracer populations: OB, A and Red Clump stars.  Show how the use of kinematics improves the accuracy in the recovery of the warp parameters.  The OB stars are demonstrated to be the best tracers [why?] determining the tilt angle with accuracy better than ~0.5 up to Galctocentric distance of ~16 kpc.  Using data with good astrometric quality, the same accuracy is obtained for A type stars up to ~13 kpc and for Red Clump up to the expected stellar cut-off.  Using OB stars the twist angle is recovered to within <3deg for all distances.

1405.6336
The origins and concentrations of water, carbon, nitrogen and noble gases on Earth
Marty

They sot pic compositions of terrestrial H and N are clearly different from those of the nebular gas from which the solar system formed, and also differ from most of cometary values.  Terrestrial N and H isotopic compositions are in the range of values characterizing primitive meteorites, which suggests that H2O, N and other volatile elements on Earth originated from a cosmochemical reservoir that also sourced the parent bodies of primiteve meteorites.  Remnants of the proto-solar nebula (PSN) are still present in the mantle, presumably signing the sequestration of PSN gas at an early stage of planetary growth.  The contribution of cometary volatiles appears limited to a few percents at most of the total volatile inventory of the Earth.  The isotope signatures of H, N, Ne and Ar can be explained by mixing between two end-members of solar and chondritic compositions, respectively, and do not require isotropic fractionation during hydrodynamic escape of an early atmosphere.  The terrestrial inventory of 40Ar (produced by the decay of 40K throughout the Earth's history) suggests that a significant fraction of radiogenic Ar may be still trapped in the silicate Earth.  By normalizing other volatile element abundances to this isotope, it is proposed that the Earth is not as volatile-poor as previously thought.  Our planet may indeed contain up to ~3000 ppm H2O (preferred range: 1000-3000 ppm), and up to ~500 ppm C, both largely sequestrated in the solid Earth.  This volatile content is equivalent to a ~2 (pm1)% contribution of carbonaceous chondrite (Cl-CM) material to a dry proto-Earth, which is higher than the contribution of chondritic material advocated to account for the platinum group element budget of the mantle.  Such a (relatively) high contribution of volatile-rich matter is consistent with the accretion of a few wet planetesimals during Earth accretion.

1405.6568
Lensing reconstruction from a patchwork of polarization maps
Namikawa, Nagata

The lensing signals imvolved in CMB polarization maps have already been measured with ground-based experiments such as SPTpol and POLARBEAR, and would become important as a probe of cosmological and astrophysical issues in the near future.  Sizes of polarization maps from ground-based experiments are, however, limited by contamination of long wavelength modes of observational noise.  To further extract the lensing signals, explore feasibility of measuring lensing signals from a collection of small sky maps each of which is observed separately by a ground-based large telescope, i.e., lensing reconstruction from a patchwork map of large sky coverage organized from small sky patches.  Show that, although the B-mode PS obtained from the patchwork map is biased due to baseline uncertainty, bias on the lensing potential would be negligible if the B-mode on scales larger than the blowup scale of 1/f noise is removed in the lensing reconstruction.  As examples of cosmological applications, also show 1) the cross-correlations between the reconstructed lensing potential and full-sky temperature/polarization maps from satellite missions such as PLANCK and LiteBIRD, and 2) the use of the reconstructed potential for delousing B-mode polarization of LiteBIRD observation.

1405.6701
Warming early Mars with CO2 and H2
Ramirez et al

Early Mars had flowing water, current Mars is below freezing temperature.  The above freezing temperatures required to explain valley formation could have been transient, in response to frequent large meteorite impacts on early Mars, or they could have been caused by long-lived greenhouse warming.  Climate models that consider only the greenhouse gases CO2 and H2O vapor have been unable to recreate warm surface conditions, given the lower solar luminosity at that time.  Use 1d climate model to demonstrate that an atmosphere containing 1.3-4 bar of CO2 and H2O vapor, along with 5 to 20% H2, could have raised the mean surface temperature of early mars above the freezing point of water.  Vigorous volcanic outgassing from a highly reduced early martian mantle is expected to provide sufficient atmospheric H2 and CO2, the latter from the photochecmial oxidation of outgassed CH4 and CO, to form a CO2-H2 greenhouse.  Such a dense early martian atmosphere is consistent with independent estimates of surface pressed based on cratering data.