Square Kilometre Array key science: a progressive retrospective

Abstract

I summarize the science drivers presented at the workshop for Phase I of the Square Kilometre Array: 'Advancing Astrophysics with the Square Kilometre Array'. I build from the historical perspective of the original Key Science programs: 'Science with a Square Kilometre Array', and consider progress in astrophysics since 2004. I then present my 'score card' of the primary science drivers proposed by the Science Working Groups, and further developed in the white papers and presentations at the meeting, assuming a conservative high frequency of 3GHz. The science case for the SKA phase I is compelling, with the right mix of killer applications (eg. pulsars and gravity, 21cm cosmology), foundational radio astronomy (eg. cosmic magnetism, baryon cycle, high energy phenomena), and high risk-high return 'game-changing' programs (eg. fast radio bursts, BAO intensity mapping, SETI). A strong case was made at the conference for band 5 (4 to 15GHz), in particular in the area of planet formation and exobiology. Such a capability engages the rapidly growing exoplanet community, and enables fundamental break-throughs in most of the key science areas. The case for real-time data spigots that allow for commensal observing is also strong. Ultimately, the greatest discoveries that will come from the SKA are likely even richer still, and beyond prognostication.

Cosmic X-ray surveys of distant active galaxies

“…However, substantially deeper radio surveys are now being undertaken over > ∼ 1,000 deg 2 and many aim to cover the majority of the visible sky (e.g., at low < ∼ 200 MHz frequencies: GMRT-TGSS; LOFAR; MWA; at mid ≈ 1 GHz frequencies: Apertif-WODAN; ASKAP-EMU; MeerKAT-MIGHTEE; VLA-VLASS; see Norris et al 2011Norris et al , 2013Lazio et al 2014 for a recent summary). Many of these surveys are pre-cursors and pathfinders to the Square Kilometer Array (SKA; e.g., Dewdney et al 2009;Carilli 2014), an international project to build the world's largest radio telescope, planned to start operations over the next ≈ 10-20 yr. The SKA is designed to operate over a very broad range of frequencies (≈ 50 MHz to 20 GHz) down to sub-µJy levels at sub-arcsec resolution, sufficient to detect essentially all of the X-ray sources at radio frequencies and provide an independent method of AGN selection (i.e., radio bright AGNs undetected at X-ray energies) in addition to sensitive SFR constraints; see Fig.…”

Gravitational waves: Classification, methods of detection, sensitivities and sources

“…106 In Table 5, we compile the projected sensitivities for IPTA, FAST 107 and SKA 108 for an observation span of 20 years, 50 years and 100 years respectively. To obtain a fiducial sensitivity of IPTA, we take the MTG canonical PTA [103], but extend the observation time span to 20 yrs.…”

“…In obtaining a fiducial sensitivity, we assume the FAST PTA to observe 50 pulsars with 50 ns timing accuracy for a 50 yr time span. The Square Kilometre Array (SKA) 108 in South Africa and Australia will certainly improve on existing limits and we assume pulsar timing measurements every 2 weeks for 100 pulsars with 20 ns timing accuracies for 100 yrs. Table 5 lists the basic assumptions for IPTA, FAST and SKA and their projected sensitivities in Byr on the characteristic strain.…”

Studying topological structure of 21-cm line fluctuations with 3D Minkowski functionals before reionization

“…Dillon et al (2015)). The Square Kilometre Array low (SKA-low), a future project of a lowfrequency radio interferometer, will start observations in the near future (Carilli 2015) and it will have enough sensitivity to image the 21cm-line signal at scales from several arcminutes to several degrees (Mellema et al 2015;Wyithe et al 2015).…”