February 13 , 2014 German SKA Science Meeting, Bielefeld J ... · February 13th, 2014 German SKA...

February 13th, 2014German SKA Science Meeting, Bielefeld

J. Anton Zensus, Andrei P. Lobanov, E. Ros

13feb14 J.A. Zensus - GESKA - SKA & VLBI

SKA, from 1991 to nowVLBI community pushing for the SKA (USA, Canada, Europe, later also China, Australia, India, and South Africa)


Bonn, 11-12 December 2001: Workshop on “High-resolution options for the SKA”

OutlookHigh-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


SKA imagingSKA developments: imaging capability is often viewed as a ‘tradeoff’ against survey speed – hence ‘core-spread’array configurations are envisaged and long baselines are downgradedSKA will survey crowded fields with resolved objectsHigh-fidelity imaging becomes an essential feature rather than a ‘tradeoff’: the FoM Aeff/Tsys 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.

Survey speed vs imagingOptimisation for ‘survey speed’ as expressed by Aeff/Tsys is based on two implicit assumptions1. Small number of objects in primary beam

NNsourcessources ≤≤ (B(Bmaxmax/D/Dantant))22

2. All sources essentially unresolved by arrayθθsourcesource ≤≤ 22××HPBW/SNRHPBW/SNR1/21/2

This is generally not the case for the SKA. Primary beam of a 12-m dish: ~50 objects over 0.4mJy larger than θsourceOptimising for dynamic range and high-fidelity image is then also required


Figure of merit for imagingUniform structural sensitivity provided by

For non-uniform uv-coverages

Structural sensitivity

Scale-dependent image noise


Structural sensitivity ηuv=1 for filled aperture (Δu/u=0)Scale-dependent noise reduced by improving ηuv, i.e., by reducing Δu/u

Gap between adjacent baselines

Δu/u=(u2-u1)/u2

Pixel fidelity and resolutionExisting 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

Configuration choicesCompare to a ‘core-spread’ array, a ‘Gaussian’array of the same extent will have:

~3× worse brightness sensitivity on scales of ≤0.1Bmax~30% lower noise in snapshot images~2× lower side level

A ‘fair’ array configuration is a necessity for large area surveys

The factor ηuv2(Aeff/Tsys)

should be used in optimisation calculations

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


1.05

1.1

1.15

1.2

1.25

1.3

1.35Core-spread

Gaussian

scale-dependent noise for a 10-minute snapshot20 40 60 80Scale �arcsec�

Pixel fidelity for fair arraysChoice 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

SKA with VLBIAdd VLBI dishes (aka radio telescopes) to the SKA

Long-baseline, pointed elements to the array

Add the SKA to existing VLBI arraysPhased?Phased by areas?


SKA+VLB arraysVLBI ARRAYS

To AustraliaLBA (Western VLBA, Asia)

To Southern Africa:EVN (Asia, Eastern VLBA)

To all: Geodetic 2.3 GHz antennas (small dishes)Res. down to 10 mas

Only possible at 90cm (327 MHz), but with big difficulties, remote antennas

Res. down to 30 mas

SKA DESIGN

Dishes (0.5−20 GHz)Res. 50-1400 mas

Aperture array (0.07−0.2 GHz &0.2-0.5 GHz)

Res. 1000-8000 mas


Available antennas, 327 MHz

MK_VLBAKP_VLBAFD_VLBAOV_VLBAPT_VLBALA_VLBANL_VLBAHN_VLBABR_VLBASC_VLBAGBTJB1AreciboWSRTNotoUrumqiSimeizGMRT


9500km

6500km

6700km

Image: Google Maps & ER

Available antennas 1.4/1.6 GHzMK_VLBAKP_VLBAFD_VLBAOV_VLBAPT_VLBALA_VLBANL_VLBAHN_VLBABR_VLBASC_VLBAGBTJB1AreciboWSRTNotoUrumqiSimeizGMRTParkes


ATCAMopraParkesHobartKashima

EVLAEffelsbergAreciboCambridgeMedicina

TorunShanghaiHartebeesthoekOnsalaAuckland


Available antennas, 2.3 GHzMK_VLBAKP_VLBAFD_VLBAOV_VLBAPT_VLBALA_VLBANL_VLBAHN_VLBABR_VLBASC_VLBAGBTEVLAAreciboTIGOItapetingaLa Plata


WSRTJodrellEffelsbergMedicinaNotoOnsalaRobledoMetsähoviYebesWettzellNy AlesundMateraSimeizHartebeesthoekUrumqiShanghaiUsudaKashima

HobartMopraCeduna

TidbinbillaO’HigginsParkes

YaragadeeKatherineATCAAuckland


VERA-MizusawaVERA-IrikiVERA-OgasawaraVERA-Ishigakijima

Uptime SKA (S. Africa) –VLBI

DeclEast AUS JP CN NZ CL

USA-HI

USA-NM

USA-PR

Europe

+45 0.0 2.2 5.4 0.0 0.0 0.0 1.5 3.6 5.4+30 0.0 2.7 7.6 0.0 0.4 0.0 1.8 4.4 8.0+15 0.0 2.7 7.3 0.0 2.3 0.0 1.8 4.8 9.4

0 0.8 2.5 6.8 0.6 3.7 0.0 1.7 5.0 9.1−15 2.0 2.1 6.3 1.9 4.9 0.0 1.4 5.1 7.8−30 3.0 1.2 5.4 3.1 6.2 0.0 0.9 5.2 3.0−45 4.0 0.0 0.0 5.2 7.9 0.0 0.0 5.2 0.0−60 5.5 0.0 0.0 11.8 11.6 0.0 0.0 0.0 0.0−75 12.9 0.0 0.0 24.0 24.0 0.0 0.0 0.0 0.0−90 24.0 0.0 0.0 24.0 24.0 0.0 0.0 0.0 0.0


Uptime SKA (W. Austr.) –VLBI

Decl. ZA JP CN NZ CLUSA-

HIUSA-NM

USA-PR

Euro-pe

+45 0.0 5.3 5.3 0.0 0.0 4.0 1.3 0.0 5.3+30 2.0 7.9 7.9 3.2 0.0 4.8 1.7 0.0 4.5+15 3.5 8.6 9.2 5.2 0.0 5.1 1.7 0.0 3.8

0 4.5 8.5 6.7 6.6 0.0 5.3 1.6 0.0 3.2−15 5.5 7.8 8.3 7.8 0.4 5.4 1.3 0.0 2.3−30 9.0 5.1 6.2 9.1 1.9 5.5 0.8 0.0 0.4−45 7.7 0.0 0.0 10.8 5.2 5.4 0.0 0.0 0.0−60 11.5 0.0 0.0 14.1 11.7 5.1 0.0 0.0 0.0−75 24.0 0.0 0.0 24.0 24.0 0.0 0.0 0.0 0.0−90 24.0 0.0 0.0 24.0 24.0 0.0 0.0 0.0 0.0


High-resolution + high-sensitivity SKA science (i)

Astrometry of AGN (post-GAIA)Pulsar proper motionsStellar astrometry (search for exoplanets)Supernovae and starburst processes in galaxies


PSR J1459−4438 proper motion (Deller et al. 2009)

High-resolution + high-sensitivity SKA science (i)

Astrometry of AGN (post-GAIA)Pulsar proper motionsStellar astrometry (search for exoplanets)Supernovae and starburst processes in galaxies


Supernova factory Arp 299-A (Pérez-Torres et al. 2009)

High sensitivity on long baselines needed

High-resolution + high-sensitivity SKA science (ii)

Nuclear gas in galaxies (megamasers and nuclear absorption)Radio-quiet QSOsOutflows from the cores of galaxies (both ultra- and mildly relativistic)


OH megamaser emission in Arp 220 (Rovilos et al. 2003)

High-resolution + high-sensitivity SKA science (ii)

Nuclear gas in galaxies (megamasers and nuclear absorption)Radio-quiet QSOsOutflows from the cores of galaxies (both ultra- and mildly relativistic)


Radio-quiet BALQSO 1045+352 (Kunert-Bajrazewska et al. 2010)

High-resolution + high-sensitivity 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)

High-resolution + high-sensitivity SKA science (iii)


Corona BLR 1 (disk)

Subrelativistic outflow

VLBI “core” BLR 2 (outflow)

Relativistic jet

Outflows and relativistic shocks are likely to be dominant sites of non-thermal continuum production.

Chatterjee et al. 2009, Arshakian et al. 2010,Leon-Tavares et al. 2010, Jorstad et al. 2010, Schinzel et al. 2010

SKA will be essential for understanding the physics of high-energy emission production in AGN.

Optical continuumSoft X-ray continuum

Hard X-ray continuum

� -ray continuum

VHE continuum

Summary: SKA as VLBISKA with high-resolution radio observations will address:

Supernova studies, providing a good account of starburst activity in galaxiesProbing nuclear in galaxies via megamaseras and nuclear absorptionUnderstanding the physics of (ultra- and mildly relativistic) outflows and their connection to nuclear regions in galaxiesSearching for radio emission from weaker AGN and secondary BH in post-merger galaxiesStudying 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 low-resolution SKA science, most notably the science considered as the very ‘selling point’ of the instrument


High-resolution SKA science

AstrometryPulsar proper motions SupernovaeAstrophysical masersNuclear regions of AGNPhysics of relativistic and mildly relativistic outflowsKinetic feedback from AGNSMBH and galaxy evolution


OH Megamasers (λ6cm)


Mrk 321

Klöckner et al. 2003

Nuclear absorptionAbsorption 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 studiesStudies of nuclear absorption will benefit by high sensitivity baselines by the SKA alone or as part of a VLBI array


Mundell et al. 2003

NGC 4151

0.6pc

Extragalactic jetsProbing physical conditions in low-energy tail of outflowing plasmaMildly relativistic and sub-relativistic components of outflowsStratification of outflows and interaction with ambient medium; kinetic feedbackStrongly evolved plasma in extended lobes, cavities and halos produced by jetsAGN relics and duty cycles; tracers of BBH and BH mergers


courtesy F. Owen

Merritt & Ekers 2002

Mergers and 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


NGC2207 & IC2163

NGC6240

Centaurus A

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