Day 716

Tuesday.  Wednesday.

1408.0797
Microlens masses from 1-D parallaxes and heliocentric proper motions
Gould

1D microlens parallaxes can be combined with heliocentric lens-source relative proper motion measurements to derive the lens mass and distance, as suggested by Ghosh+2004.  Present the first mathematical analysis of this procedure, which can be shown to be represented as a quadratic equation.  It is formally subject to a 2-fold degeneracy.  Show that this degeneracy can be broken in many cases using the relatively crude 2D parallax information that is often available for microlensing events.  Also develop an explicit formula for the region of parameter space where it is more difficult to break this degeneracy.  Although no mass/distance measurements have yet been made using this technique, it is likely to become quite common over the next decade.

1408.0799
Mapping the cosmic web with the largest all-sky surveys
Bilicki, Peacock, et al

In order to reliably map the Universe to cosmologically significant depth over the full celestial sphere, one must draw on multi wavelength datasets and photo-z techniques.  Cross-match the largest photometric all-sky surveys (2MASS, WISE and SuperCOSMOS) to obtain accurate redshift estimates of millions of galaxies.  The first is the 2MASS Photometric Redshift Catalog (2MPZ, Bilicki+2014) is public and includes almost 1e6 galaxies with <z>=0.08.  Summarize how this catalog was constructed, and how using the WISE MIR sample together with SuperCOSMOS optical data allows to push to redshift shells of z~0.2-0.3 on unprecedented angular scales.  The catalogs, with ~20M sources in total, provide access to cosmological volumes crucial for studies of local galaxy flows (clustering dipole, bulk flow) and cross-correlations with the CMB such as ISW or lensing.

1408.0816
Molecular gas content in strongly-lensed z~1.5-3 star-forming galaxies with low IR luminosities
Dessauges-Zavadsky, ...Egami, ... Rex, Kneib, ... et al

To extend the molecular gas measurements to typical SFGs with SFR<40Msun/yr and M*<2.5e10 Msun at z~1.5-3, observe CO emission for 5 strongly lensed galaxies selected from the Herschel Lensing Survey.  Combine with a compilation of CO measurements from the literature.  Infer luminosity correction factors of the CO rotational levels J=2 and 3, valid for SFGs and sub-mm galaxies at z>1.  The combined sample of CO-detected SFGs at z>1 shows a large spared in SF efficiency (SFE), such that SFE extend beyond the low values of local spirals and overlap the distribution of z>1 submm galaxies.  Find that the spread in SFE (or equivalently in molecular gas depletion timescale) is due to primarily the sSFR, but also stellar mass and redshift.  Correlations of SFE with the offset from the MS and the compactness of the starburst are less clear.  The increase of the molecular gas depletion timescale with M* now revealed by low M* SFGs at z>1 is opposed to the admitted constant molecular gas depletion timescale and the linear KS relation.  Confirm an increase of the molecular gas fraction (fgas) from z~0.2 to z~1.2, followed by a quasi non-evolution toward higher redshifts.  At each redshift fgas shows a large dispersion due to the dependence on fgas on M*, producing a gradient of increasing fgas with decreasing M*.  Provide the first measure of fgas of z>1 SFGs at the low-M* end (1e9.4 < M*/Msun < 1e9.9), reaching a mean fgas=0.67pm0.20 which shows a clear fgas upturn.  Finally, find evidence for a non-universal dust-to-gas ratio among high-z SFGs and sub-mm galaxies, local spirals and ULIRGs with near solar metallicities.

1408.1081
Super-sample signal
Li, Hu, Takada

PS measurements extracting cosmo params require consideration of the impact of super-sample density fluctuations, larger than the survey scale.  These modes contribute to the mean density fluctuations delta_b in the survey and change the PS in the same was as a change in the cosmological background.  They can be simply included in cosmo param estimation and forecasts by treating delta_b as an additional cosmological parameter enabling efficient exploration of its impact.  Verify that the minimum variance estimator of delta_b is both unbiased and has the predicted variance using sub-volumes of large-volume N-body sims for PS measured wrt either the global or local mean density, e.g., for WL or galaxy clustering.  Parameter degeneracies arise since the response of the PS to delta_b and cosmological parameters share similar properties in changing the growth of structure and dilating the scale of features, especially in the local case.  In the absence of external constraints in the variance of delta_b, degeneracies can lead to a factor of 4-5 degradation in the errors of certain combinations of LCDM cosmo params for a wide range of survey volumes when using info out to k<~2h/Mpc.  Even with perfect info on the variance, the degradation can be a factor of 2-3 for one combination in the global case though its impact on individual parameters is smaller.  These techniques can easily extended to other parameter spaces and cosmological observables or to include baryonic effects.