February 13 th, 2014 German SKA Science Meeting, Bielefeld J. Anton Zensus, Andrei P. Lobanov, E. Ros. J.A. Zensus - GESKA - SKA & VLBI

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1 February 13 th, 2014 German SKA Science Meeting, Bielefeld J. Anton Zensus, Andrei P. Lobanov, E. Ros

2 SKA, from 1991 to now VLBI community pushing for the SKA (USA, Canada, Europe, later also China, Australia, India, and South Africa) Bonn, December 2001: Workshop on Highresolution options for the SKA

3 Outlook High-resolution options for the SKA Out of nishes: general scientific purposes (and room for serendipity) Survey mode: importance of array design SKA & VLBI synergy High-resolution science

4 SKA imaging SKA developments: imaging capability is often viewed as a tradeoff against survey speed hence core-spread array configurations are envisaged and long baselines are downgraded SKA will survey crowded fields with resolved objects High-fidelity imaging becomes an essential feature rather than a tradeoff : the FoM A eff /T sys is not good for estimating the survey speed SKA needs to have the capability of imaging adequately all spatial frequencies at which there is more than one sky object per primary beam Number of FIRST sources (S>0.4 mjy) within the primary beam of a 12-meter antenna.

5 Survey speed vs imaging Optimisation for survey speed as expressed by A eff /T sys is based on two implicit assumptions 1. Small number of objects in primary beam N sources (B max /D ant ) 2 2. All sources essentially unresolved by array θ source source 2 HPBW/SNR 1/2 This is generally not the case for the SKA. Primary beam of a 12-m dish: ~50 objects over 0.4mJy larger than θ source Optimising for dynamic range and highfidelity image is then also required

6 Figure of merit for imaging Uniform structural sensitivity provided by For non-uniform uv-coverages Structural sensitivity Gap between adjacent baselines Δu/u=(u 2 -u 1 )/u 2 Scale-dependent image noise Structural sensitivity η uv =1 for filled aperture (Δu/u=0) Scale-dependent noise reduced by improving η uv, i.e., by reducing Δu/u

7 Pixel fidelity and resolution Existing trend on pixel fidelity as a function of resolution needs to be improved to reach the noise specs for SKA surveys existing instruments SKA Pathfinders SKA Needed to achieve noise specs for SKA Surveys

8 Configuration choices Compare to a corespread array, a Gaussian array of the same extent will have: ~3 worse brightness sensitivity on scales of 0.1B max ~30% lower noise in snapshot images ~2 lower side level A fair array configuration is a necessity for large area surveys The factor η uv2 (A eff /T sys ) should be used in optimisation calculations Core-spread Gaussian scale-dependent noise for a 10-minute snapshot Scale arcsec Observing time with core-spread configuration: ~1hr to reach down to 5% above the thermal noise spec ~12 hr to reach down to 0.5% above the normal noise spec

9 Pixel fidelity for fair arrays Choice of fair array configuration will enable imaging adequately all angular scales of interest necessary both for science and confusing source extraction. existing instruments SKA Pathfinders SKA

10 SKA with VLBI Add VLBI dishes (aka radio telescopes) to the SKA Long-baseline, pointed elements to the array Add the SKA to existing VLBI arrays Phased? Phased by areas?

11 SKA+VLB arrays VLBI ARRAYS SKA DESIGN To Australia LBA (Western VLBA, Asia) To Southern Africa: EVN (Asia, Eastern VLBA) To all: Geodetic 2.3 GHz antennas (small dishes) Res. down to 10 mas Dishes ( GHz) Res mas Only possible at 90cm (327 MHz), but with big difficulties, remote antennas Res. down to 30 mas Aperture array ( GHz & GHz) Res mas

12 Available antennas, 327 MHz MK_VLBA KP_VLBA FD_VLBA OV_VLBA PT_VLBA LA_VLBA NL_VLBA HN_VLBA BR_VLBA SC_VLBA GBT JB1 Arecibo WSRT Noto Urumqi Simeiz GMRT 6700km 6500km 9500km Image: Google Maps & ER

13 Available antennas 1.4/1.6 GHz MK_VLBA KP_VLBA FD_VLBA OV_VLBA PT_VLBA LA_VLBA NL_VLBA HN_VLBA BR_VLBA SC_VLBA GBT JB1 Arecibo WSRT Noto Urumqi Simeiz GMRT Parkes ATCA Mopra Parkes Hobart Kashima EVLA Effelsberg Arecibo Cambridge Medicina Torun Shanghai Hartebeesthoek Onsala Auckland Image: Google Maps & ER

14 Available antennas, 2.3 GHz Yaragadee MK_VLBA KP_VLBA FD_VLBA OV_VLBA PT_VLBA LA_VLBA WSRT Jodrell Effelsberg Medicina Noto Onsala Robledo VERA-Mizusawa VERA-Iriki VERA-Ogasawara VERA-Ishigakijima Hobart Mopra Ceduna Tidbinbilla O Higgins Parkes Katherine ATCA Auckland NL_VLBA Metsähovi HN_VLBA BR_VLBA SC_VLBA GBT EVLA Arecibo Yebes Wettzell Ny Alesund Matera Simeiz Hartebeesthoek Urumqi TIGO Shanghai Itapetinga La Plata Usuda Kashima Image: Google Maps & ER

15 Uptime SKA (S. Africa) VLBI Decl East AUS JP CN NZ CL USA- HI USA- NM USA- PR Europ e

16 Uptime SKA (W. Austr.) VLBI Decl. ZA JP CN NZ CL USA- HI USA- NM USA- PR Europe

17 High-resolution + highsensitivity SKA science (i) Astrometry of AGN (post-gaia) Pulsar proper motions Stellar astrometry (search for exoplanets) Supernovae and starburst processes in galaxies PSR J proper motion (Deller et al. 2009)

18 High-resolution + highsensitivity SKA science (i) High sensitivity on long baselines needed Astrometry of AGN (post-gaia) Pulsar proper motions Stellar astrometry (search for exoplanets) Supernovae and starburst processes in galaxies Supernova factory Arp 299-A (Pérez-Torres et al. 2009)

19 High-resolution + highsensitivity SKA science (ii) Nuclear gas in galaxies (megamasers and nuclear absorption) Radio-quiet QSOs Outflows from the cores of galaxies (both ultra- and mildly relativistic) OH megamaser emission in Arp 220 (Rovilos et al. 2003)

20 High-resolution + highsensitivity SKA science (ii) Nuclear gas in galaxies (megamasers and nuclear absorption) Radio-quiet QSOs Outflows from the cores of galaxies (both ultra- and mildly relativistic) Radio-quiet BALQSO (Kunert-Bajrazewska et al. 2010)

21 High-resolution + highsensitivity SKA science (iii) Post-merger processes in galaxies (weak AGN radio emission) Physics of the vicinity of SMBH by polarisation and brightness temperature measurements Centaurus A as seen by the TANAMI project (Müller et al. 2011)

22 High-resolution + high-sensitivity SKA science (iii) Relativistic jet VLBI core Corona Subrelativistic outflow BLR 2 (outflow) BLR 1 (disk) VHE continuum -ray continuum Optical continuum Outflows and relativistic shocks are likely to be dominant sites of non-thermal continuum production. Hard X-ray continuum Soft X-ray continuum SKA will be essential for understanding the physics of highenergy emission production in AGN. Chatterjee et al. 2009, Arshakian et al. 2010, Leon-Tavares et al. 2010, Jorstad et al. 2010, Schinzel et al. 2010

23 Summary: SKA as VLBI SKA with high-resolution radio observations will address: Supernova studies, providing a good account of starburst activity in galaxies Probing nuclear in galaxies via megamaseras and nuclear absorption Understanding the physics of (ultra- and mildly relativistic) outflows and their connection to nuclear regions in galaxies Searching for radio emission from weaker AGN and secondary BH in post-merger galaxies Studying physics of the vicinity of SMBH by measuring the brightness temperature and polarisation of compact radio emission Reliable high-resolution imaging is needed for the lowresolution SKA science, most notably the science considered as the very selling point of the instrument

24 High-resolution SKA science Astrometry Pulsar proper motions Supernovae Astrophysical masers Nuclear regions of AGN Physics of relativistic and mildly relativistic outflows Kinetic feedback from AGN SMBH and galaxy evolution

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26 OH Megamasers (λ6cm) Mrk 321 Klöckner et al. 2003

27 Nuclear absorption Absorption due to several species, most notably HI, CO, OH, and HCO + HI and OH absorption toward compact continuum sources is an unique tool to probe nuclear regions on pc-scales still beating resolution and accuracy of optical integral field spectroscopic studies Studies of nuclear absorption will benefit by high sensitivity baselines by the SKA alone or as part of a VLBI array NGC pc Mundell et al. 2003

28 Extragalactic jets Probing physical conditions in low-energy tail of outflowing plasma Mildly relativistic and subrelativistic components of outflows Stratification of outflows and interaction with ambient medium; kinetic feedback Strongly evolved plasma in extended lobes, cavities and halos produced by jets AGN relics and duty cycles; tracers of BBH and BH mergers Merritt & Ekers 2002 courtesy F. Owen

29 Mergers and NGC2207 & IC2163 AGN Most powerful AGN produced by galactic /SMBH mergers (Hähnelt & Kaufmann 2002, Di Matteo et al. 2004) Activity is reduced when a loss cone is formed and most of nuclear gas is accreted onto SMBH (Dokuchaev 1991, Merritt 2003). Having a secondary SMBH helps maintaining activity of the primary. Evolution of nuclear activity can be connected to the dynamic evolution of binary SMBH in galactic centres (Lobanov 2008) Secondary BH in post-merger galaxies a needle in a haystack NGC6240 Centaurus A

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