The SKA Molonglo Prototype (SKAMP) progress & first results. Anne Green University of Sydney

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1 The SKA Molonglo Prototype (SKAMP) progress & first results Anne Green University of Sydney SKA2010

2 SKAMP Objectives & Goals Project Goal: A new low-frequency spectral line & polarisation instrument. Objectives: (1) Technology flexible, high speed wideband digital signal transport and processing; rapid response to triggers; pipeline for real-time data calibration, RFI mitigation & analysis. (2) Science survey of redshifted HI absorption; transients search & monitoring; OH megamasers; cosmic magnetism; to complement ASKAP, MWA projects.

3 Specifications for the SKAMP project Area 18,000 m 2, aperture efficiency ~50%, Tsys 55K Highly redundant array Angular resolution 43 x43 cosecδ (confusion limit 0.12 mjy beam -1 ) Centre frequency 843 MHz Field of View 4 deg 2 Redshift coverage (HI 1420 MHz) z = to (OH 1665/1667 MHz) z = to Channel width 15 khz Velocity resolution 5 km sec -1 per channel gives 12 hour sensitivity of 0.8 mjy beam -1 Staged development to allow continous science operations

4 Overview diagram of SKAMP signal pathway Complete Prototype Design

5 Spectral line capability stage 2 Correlator & fibre network in shielded room BW MHz Hz (5 km sec -1 ) >4000 baselines (131 independent) Sensitivity (12 hr) 1σ 0.15 mjy beam -1 Sensitivity per channel 0.8 mjy beam Gbps Pipeline for real-time calibration & compression

6 Correlator board & early image 800 FPGAs 30,000 correlation cells Design BW 100 MHz 2-stage PFB (coarse/fine) SKAMP digital system provided to MWA project Sensitivity ~1 mjy beam -1

7 Stage 3: wideband feed (prototype) 8-element module, 1.4 m length Wide-band dipoles no moving parts Polarisation axes oriented along & across axis of feed Range tested for MHz (Leung)

8 SKAMP science projects linked to SKA key goals 1. Blind survey of HI absorption in high redshift galaxies (z~0.7). 2. Transient & variable sky surveys 3. Search for OH megamasers in disks around super-massive black holes (z ~1). 4. Cosmic magnetism studies diffuse Galactic polarisation and Rotation Measure.

9 1. How does a galaxy accrete gas? Cosmic starformation rate Reasonable idea of the cosmic star-formation history, but know little about how (and when) the gas is assembled into galaxies. (Heavens et al. 2004) At present, there are few observations to test the predictions for the gas mass assembly history of galaxies. For ~70% cosmic time, HI content unknown (Johnston et al. 2008)

10 Blind HI absorption survey Radio surveys very sensitive to cold neutral hydrogen (T<200K) 80% radio sources have z > % chance a source will have detectable HI absorption in our redshift band Need to observe 10,000 sources to get sample of ~60 Lane et al (z = galaxy) Typically 20 sources (S 50 mjy) per field need to survey 2400 deg 2

11 2. Transients & variable sources Combination of blind surveys & close monitoring of known objects. New algorithms for intelligent source detection & classification. Targets orphan radio afterglows of GRBS, magnetars, new transient phenomena. Cadence of observing days to months. Can piggyback on other surveys. Link to MWA & ASKAP projects. Preliminary results: >50 sources varying by >40% and 16 sources detected once, then absent (Bannister & Murphy). A new transient Epoch 1 Epoch 2 Quotient map

12 3. OH megamasers in starburst galaxies Characteristics: low amplification, broad lines, unpolarised, not saturated, hosts ULIRGs, interacting galaxies Predict gigamasers with flux 1 mjy (maybe 10 mjy) at z~1 IRAS most distant OH megamaser to date at z = (883 Mpc) Baan et al. (1992) Townsend et al. (2001)

13 4. Cosmic Magnetism Mapping the Milky Way s magnetic field probes the creation process SKAMP will produce Faraday rotation data for 20,000 background galaxies to give a 3D view of our Galaxy s magnetism Faraday Rotation Magnetism is one of the fundamental forces But its role and origins are largely unknown

14 Summary of SKAMP Project status Stage 1: Narrowband correlator operational data pipeline under test. First light images. Stage 2: Signal pathway partly implemented; imminent production of digital system (SKAMP and MWA). Commissioning by end Stage 3: Dual polarization 8-element feed module installed on test telescope with double-meshing. Production model & LNAs to be finalised.

15 A new lease on life for a mature instrument

16 Molonglo Observatory Google Map

17 Observing Parameters for MOST Strengths - large collecting area, large extent, highly redundant array Single frequency MHz continuum 3 MHz bandwidth, RHC polarisation 43" spatial resolution (the beam ) Field of view (since 1997): > 5 square degrees Sensitivity (1σ rms in 12 hrs): 0.8 mjy/beam Tsys ~55K

18 70% of cosmic time not tested Redshift evolution of the neutral hydrogen (HI) mass density. Time evolution of the neutral hydrogen (HI) mass density

19 Confusion limits for 843 MHz (10 beams/source) at δ = 60 Flux Density (mjy) beam size: 112 x 112 csc δ Rengelink et al 1997 WENSS 325 MHz beam size: 43 x 43 csc δ Bock et al 1999 SUMSS 843 MHz Frequency (MHz) beam size: 26 x 26 csc δ Wall MHz 43 spatial resolution: total intensity confusion limit is 0.12 mjy Not for spectroscopy or polarimetry discrimination via another parameter

20 Expected source density and spectral index distribution Spectral Index Distribution: At least 80% of sources with S>50mJy have redshifts above z~0.7 Radio 843 MHz: Mostly very distant radio galaxies (median z~1) (SUMSS Survey; Mauch et al. 2003)

21 Masers & dusty star formation history OH and H 2 O masers are found in many ULIRGs. Maser luminosity ~correlates with FIR luminosity analogues of Milky Way massive star-forming regions? (Henkel et al. 2005) Determine redshift distribution of distant dusty starburst galaxies using masers. e.g. at z~3, expected S OH = 0.4 mjy H 2 O for z~1-10 is in range 2-11 GHz For HLIRGs, OH maser flux ~1 mjy at z 4 Townsend et al. (2001) Separation higher z & luminosity) may be real or selection effects