SKA

The Square Kilometre Array (SKA) will be an aperture synthesis telescope with one square kilometre of collecting area and separations between antennas of several thousands of km. After the so-called rebaselining of SKA in 2014, the approved first phase includes two arrays: SKA1-MID, in South Africa, and SKA1-LOW, in Australia. SKA1-MID will be the outcome of the current MeerKAT (the South African SKA pathfinder), and will consist mainly of traditional dishes of about 12 m in diameter, and will observe at frequencies 350 to 14000 MHz. The SKA1-LOW will be the final stage of the current ASKAP (Australian SKA Pathfinder), and will include standard dipoles and low-frequency phased aperture arrays, which will observe at frequencies in the range 50 – 350 MHz. When finished, by 2023, the SKA will have a sensitivity, survey speed and angular resolution at all frequencies about two orders of magnitude better than any currently existing radio interferometric facility. Even during phase 1, its sensitivity and survey speed will be higher by almost one and two orders of magnitude, respectivley, than the currently best observatories working at similar frequencies (LOFAR and the JVLA, which are two of the SKA precursors).

In the past years, the IAA has participated in large international cooperations and developed some initiatives to coordinate the participation of the Spanish astronomical community in the SKA Key Science Projects (workshop organization, coordination of a SKA science network -- RIA workshop on "Science and opportunities in the SKA era", 9/10 May 2011). We were also members of VIA-SKA, a feasibility study to define the technological-industrial participation of the spanish scientific institutions and industries in the project SKA. VIA-SKA was lead by the IAA (PI: Lourdes Verdes-Montenegro) and was funded by the ``Subprograma de Actuaciones Científicas relativas a Infraestructuras Cientificas Internacionales“. Simultaneously, a scientific academic network (SKA-Spain) was defined, under the leadership of the UV (PI: José Carlos Guirado) to coordinate the Spanish scientific participation in the SKA precursors (ASKAP, MeerKAT) and SKA in the future. One of the milestones of those efforts was the organization of a RIA meeting in Granada, the Spanish SKA Day, that took place on October 23rd, 2014, with the participation of Prof. Phil Diamond, Director General of SKA, and more than 80 scientists and industry representatives.

We have been very active in participating in the science cases of the SKA. Namely, we contributed in several science cases to the SKA (“Core-Collapse and Type Ia supernovae with the SKA”, Pérez-Torres, Alberdi et al. 2015, arXiv:1409.1827; “SKA studies of nearby galaxies: star-formation, accretion processes and molecular gas across all environments”, Beswick, Brinks, Pérez-Torres et al. 2015, arXiv:1412.5810; “Very Long Baseline Interferometry with the SKA”, Paragi et al. 2015, arXiv:1412.5971 [including Alberdi, Pérez-Torres]; “The connection between radio and high energy emission in black hole powered systems in the SKA era”, Giroletti et al. 2015, arXiv:1501.03330 [including Alberdi]). We also devoted very significant efforts to promote the use of the SKA by Spanish astronomers, as well as their participation in the SKA science working groups. The milestone of those efforts has been the publication of The Spanish Square Kilometre Array White Book (Eds. Pérez-Torres, Verdes-Montenegro, Guirado, Alberdi et al.), which is the result of the coordinated effort of 120 astronomers. This White Book clearly shows the strong interest of the Spanish astrophysical community in the SKA. It also shows the scientific capability of the research groups and the synergies between them, as well as the synergies of the SKA with other astronomical observatories. All of this indicates a very promising potential for an optimum scientific exploitation of the SKA by Spanish astronomers.

We have been successful in getting observing time from the SKA1-LOW precursor, LOFAR. Since Spain is not part of LOFAR, getting observing time is a daunting task, as just 10% of the observing time is offered to the entire community. Taking advantage of our international collaboration with Prof. John Conway (Chalmers, Onsala), we pushed the submission of two LOFAR proposals to study M82 and Arp 220 (PI: Conway, Co-Is: Pérez-Torres, Ramírez-Olivencia, Alberdi), both of which were awarded time. The publication of our LOFAR observations on M82 (Varenius et al. 2015, A&A, 574, 114) represented a milestone, as this was the first LOFAR paper including data from long baselines. We demonstrated the feasibility of using those international baselines for LOFAR, thus opening the possibility to obtain high angular resolution observations (0.3 arcsec) for future observations. Scientifically, we constrained the low-frequency spectra of compact and diffuse emission in the central starburst region of M82 via high-resolution radio imaging at low frequencies.