Day 818

Monday.

1501.03822
Real time cosmology - a direct measure of the expansion rate of the Universe
Klöckner et al

The SKA enables an ultimate test in cosmology by measuring the expansion rate of the Universe in real time.  This can be done by a rather simple experiment of observing the neutral hydrogen (HI) signal of galaxies at two different epochs.  The signal will encounter a change in frequency imprinted as the Universe expands over time and thus monitoring the drift in frequencies will provide a real time measure of the cosmic acceleration.  Over a period of 12 years, one would expect a frequency shift of the order 0.1 Hz assuming a standard LCDM cosmology.  Based on the sensitivity estimates of the SKA and the number counts of the expected HI galaxies, it is shown that the number counts are sufficiently high to compensate for the observational uncertainties of the measurements and hence allow a statistical detection of the frequency shift.

1501.03828
Weak gravitational lensing with the Square Kilometre Array
Brown, Bacon, .. Harrison, Joachim, Metcalfe, ... Zuntz, Abdalla, Bridle, Jarvis, Kitching, Miller, et al

Investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys.  Outline a way forward to develop the tools needed for pursuing weak lensing in the radio band.  Identify the key analysis challenges and the key pathfinder experiments that will allow to address them in the run up to the SKA.  Identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of WL.  These include the use of polarization and rotational velocity information to control IA, and the new area of WL using intensity mapping experiments.  Show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of WL to high z.

1501.03848
Cross correlation surveys with the Square Kilometre Array
Kirk, Benoit-Lévy, Abdalla, Bull, Joachimi

SKA will be able to perform state of the art LSS as well as WL measurements of the distribution of matter in the Universe.  Concentrate on the synergies that result from cross-correlating these different SKA data products as well as external correlation with the WL measurements available from CMB missions.  Show that the DE FoM obtained individually from WL/LSS measurements and their independent combination is significantly increased when their full cross-correlations are taken in to account.  This is due to the increased knowledge of galaxy bias as a function of z as well as the extra information from the different cosmological dependences of the cross-correlations.  Show that the cross-correlation between a spectroscopic LSS sample and a WL sample with photometric z can calibrate these same photometric z, and their scatter, to high accuracy by modeling them as nuisance parameters and fitting them simultaneously.  Finally, show that Modified Gravity parameters are greatly constrained by this cross-correlations because WL and z-space distortions (from LSS survey) break strong degeneracies in common parameterizations of modified gravity.

1501.03977
Synergy between the Large Synoptic Survey Telescope and the Square Kilometer Array
Bacon, Bridle, Abdalla, ... et al

Describe how WL and galaxy clustering studies with LSST and SKA can provide improved constraints on the causes of the cosmological acceleration.  Summarize the benefits to galaxy evolution studies of combining deep optical multi-band imaging with radio observations.  Discuss the excellent match between one of the most unique features of the LSST, its temporal cadence in the optical waveband, and the time resolution of the SKA.

1501.03978
Euclid & SKA Symergies
Kitching, et al

The two experiments are synergistic in several respects, both through the scientific objectives and through the control of systematic effects.  SKA Phase-1 and Euclid will be commissioned on similar timescales offering an exciting opportunity to exploit synergies between these facilities.