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Future radio observations of the high redshift universe

Future radio observations of the high redshift universe. Open Questions in Cosmology Munich Aug 22-26 2005 Ron Ekers CSIRO. Overview of new facilities at radio wavelengths. Many other talks on mm and submm results so I will concentrate on cm and m wavelengths ie freq < 30GHz

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Future radio observations of the high redshift universe

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  1. Future radio observations of the high redshift universe Open Questions in Cosmology Munich Aug 22-26 2005 Ron Ekers CSIRO

  2. Overview of new facilities at radio wavelengths • Many other talks on mm and submm results so I will concentrate on cm and m wavelengths • ie freq < 30GHz • GMRT (3x VLA at low frequency) • LOFAR (very low frequency, multibeaming, multi-user) • EVLA (VLA with bandwidth) • ATA (16x VLA field of view, multi-user) • SKA – all of above and some • Continued role for special purpose experiments • Mainly at very high and very low frequencies

  3. SKA

  4. Unique SKA traits for cosmology • sensitivity  106 m2. HI out to z=3 • cost of collecting area reduced by consumer electronics • FoV - at least 1 deg2, maybe 100 deg2 • Moores law • Simultaneous observations at all frequencies • specs call for 0.1 to 25GHz • more likely is (0.1-0.7) + (0.7-2) + (2-20) GHz • driven by the antenna technology EVLA I first LOFAR

  5. { SKA Key Science Goals • Probing the dark ages before the first stars • Evolution of galaxies and large scale structure in the universe • Origin and evolution of cosmic magnetism • The cradle of life (terrestrial planets) • Strong field tests of gravity via pulsars and black holes • and... Exploration of the unknown

  6. SKA 6cm HST SKA’s 1o field-of-view SKA 20 cm and x100 possible! 15 Mpc at z = 2 ALMA

  7. Why use HI for Surveys? • Most abundant element in the Universe • Simplest constituent of the Universe • We may be able to understand it • Provides the fuel for star formation • Hence necessary to interpret star formation rates • Simultaneous velocities and line widths • Bias’s surveys to late type galaxies • Avoids some of the non-linear effects of clustering

  8. Parkes multibeam The 10 Gyr gap in the Gas Evolution History of the Universe No data Models imply HI(1+z)2-3 (+Pei et al 1999) DLAs HIPASS

  9. Zwaan et al. (2001) A2218 z=0.18 WSRT 12x18 hr Why collecting area is critical for HI... Sensitivity: SNR A.t for a radio telescope (background-noise limited) with collecting area A, integration time t. Approximate time needed to detect an M* spiral galaxy (MHI = 6 x 109 Msun) at z=0.1: Parkes (3200 m2) 120 hours (5 days) 0.1 SKA (100,000 m2) 7 minutes Full SKA (1,000,000 m2) 5 seconds For any given collecting area, there is an effective zmaxbeyond which HI emission is effectively undetectable.

  10. CMB acoustic peaks

  11. Simulation of Evolution of Acoustic Oscillations TIME

  12. Probing Dark Energy with the SKA • Standard ruler based on baryonic oscillations (wriggles) • Need to reach z ~ 1 • Current limit z = 0.2 so > x25 in sensitivity • Optimum strategy is the survey the largest area • Minimise cosmic variance • Large FoV makes this practical • HI selection  strong bias to late type galaxies • SKA FoV=1sq deg in 1 year • 109 galaxies, 0 < z < 1.5 Δω =0.01 • Or 1/10 SKA pathfinder with FoV=100sq deg   $1B and 2020 $0.2B and 2012

  13. Epoch of Re-ionization at radio wavelengths • Look at effects of the re-ionization on the HI • Look at the sources of re-ionization

  14. High Redshift HI Experiments • Bebbington (1985); Uson; et alia • Current generation: • PAST 21CMA (Pen, Peterson, Wang: China) • LOFAR(de Bruyn et alia: The Netherlands) • MWA (Lonsdale, Hewitt et alia: WA) • PAPER (Backer, Bradley: NRAO GBWA?) • CORE (Ekers, Subramanian, Chippendale: WA) • Next generation: • SKA (International) $$ $$$ $$ $$ $ $$$$$ Don Backer

  15. D.H.O. Bebbingtona radio search for primordial pancakes Redshift not known Technology well developed Black~60 mJy/beam Mon. Not. R. astr. Soc. (1986) 218, 577-585 Don Backer

  16. Shaver et al. “Can the reionization epoch be detected as a global signature in the cosmic background?” P.A. Shaver, R.A. Windhorst, P. Madau, and A.G. de Bruyn Astron. Astrophys.345, 380–390 (1999) Don Backer

  17. A Global EoR Experiment • Cosmological Re-Ionization Experiment – CoRE • Ekers, Subramanian, Chippendale - ATNF • Measurement of any mK spectral features in the global low-frequency radio background • Antenna with one steradian beam • 110-230 MHz band : corresponding to z = 5-12 Ravi Subramanyan

  18. Global EoR is challenging • Cant use spatial structure to remove foregrounds • Needs 50,000:1 spectral dynamic range over an octave bandwidth • Spectral contaminants (additive) • Bandpass calibration (multiplicative) • Quality is important here: not quantity. • The telescope required is a precision instrument, not a big bucket. Ravi Subramanyan

  19. Need a design with minimum frequency dependence 3D beam shape of the pyramidal spiral antenna Antenna modeling: Ravi Subramanyan

  20. 2-arm log-spiral winding 4 arm variation is possible Support structure Styrofoam pyramid Foam, glue and paint tested using the Australia Telescope interferometer CoRE Antenna Ravi Subramanyan

  21. Iwo-Jima to EoR

  22. Interference environment in Australia Sydney : 4 million people Narrabri : 7000 Mileura : 4 80 --- 1600 MHz Ravi Subramanyan

  23. PAPER @ Mileura? Walsh Homestead CSIRO RFI van at SKA core site PAPER site to south? Don Backer

  24. 21cm fluctuationsObservability PAST LOFAR SKA • Zaldarriaga et al • ApJ 608, 622 (2004) • 4w integration noise power Cleaned foreground ! LOFAR Error in noise power SKA

  25. MIT Telescope and Mileura Sunset The best way to search for HI in the epoch of re-ionization? • HI redshifted to z=6 (200MHz) to z=17 (80MHz) • Global signal • Easily detectable but needs spectral dynamic range of >105 : 1 • Statistical detection of fluctuations • PAPER (1o) • PAST, MWA, LOFAR (3’) • Extreme control of foreground leakage necessary • Direct detection of structure • Needs full SKA Ekers - Bali

  26. Some comments on foregrounds • Foreground is 103 - 105 x EoR signal • depending on resolution and z • Continuum - both discrete and diffuse • Some line • Search in frequency removes most of the problem • Frequency structure due to Faraday Rotation in the polarized galactic synchrotron emission • Need full polarization, and polarization purity • Frequency structure in the array sidelobes • Keep antenna sidelobes low • Model and subtract source sidelobes (over whole sky) Very different to CMB Very different to CMB

  27. SKA observation of HI absorption in the EoR Cyg A at z =10 S = 20mJy SKA: 10days, 1kHz Carilli 2002

  28. 1’’~ 7 kpc foreground object ATCA 16-26 GHz CO(1-0) 80-100 GHz CO(5-4) van Breugel et al. 1999 TN J0924-2201 z=5.2CO detection • Compact 1.2’’ double • Under-luminous Lya • Protocluster cD

  29. CO(5-4) CO(1-0) 10 CO(5-4) Flux Density (mJy beam-1) 5 0 -5 TN J0924-2201RESULTS CO(1-0): peak 0.5 mJy/beam width=250-400 km/sec Ico = 0.087Jy/beam km/sec CO(5-4): peak 10 m Jy/beam width=200-300 km/sec Ico = 1.14 Jy/beam km/sec

  30. Derived parameters1.Temperature & Density J2 • Optically thick & thermally excited gas goes as J2 (1/25) • Single-component LVG model (C. Henkel & A. Weiss) • Observations of J>5 to constrain excitation conditions • Solid line (best match): log(n)= 3.4 cm-3, T=50K • Higher order transitions are biased to high density regions dashed: log(n) = 4.4cm-3, T = 30K dotted: log(n) = 2cm-3, T = 150K

  31. Searching for redshifted CO with the SKA • CO is redshifted into the cm bands • 20Ghz  CO(1-0) at z=5, CO (2-1) at z=10 • very complimentary to ALMA • ALMA can only study high transitions at high redshift • (CO7-6 at z=8) • low excitation transitions are more likely at high z • easier to compare with observations in the local universe • SKA sensitivity more than compensates for transition strength • Blind searching becomes possible with SKA • wide FoV at cm wavelength • Relatively wider bandwidth • eg SKA blind survey (Carilli and Blain 2002) • 15 sources/hr with z>4 using redshifted CO (1-0) at 20GHz Also ACTA and EVLA I

  32. VLA SKA Future Sensitivity HST

  33. Starburst Radio galaxy/AGN VLA B2 3C SKA Radio Source Counts ?

  34. 1202-0725 (z = 4.7) 1335-0415 (z = 4.4) 1335-0415 (z = 4.4) Synchrotron Dust Free-free Radiometric Redshifts • M82 Spectrum Condon Ann Rev. 30: 576-611 (1992) • Radiometric redshifts Carilli Ap J513 (1999) • Positions SKA ALMA R. Ekers - Square Km Array

  35. How to find a radio galaxy at z>3 • Redshift - spectral index correlation (Miley et al) • Use spectral index culling to find potential galaxies at high redshift. • Technique has been very successful • Conventional explanation is the negative K correction • This turns out to be wrong! steep spectra may be tracing high density regions (Klamer 2005) • Much more of the high z universe is at high density steep flat Ilana Klamer - ASA

  36. Radio Galaxy - 4C41.17redshift 3.8 • Alignment of radio jets (contours) with other tracers of star formation • VLA radio image • HST F702 • HST F569 • Ly-α van Breugel (1985) R D Ekers

  37. HST K-band Radio VLA CO(2-1) Hu et. al. 1996 ApJ Carilli et. al. 2002 Carilli et. al. 2002 BR 1202-0725 Redshift 4.69 • Radio – CO – Ly alpha – Optical are all aligned ! Klamer, Ekers, et al, ApJ 612, L97 R D Ekers

  38. Alignment with Radio Axis Radio PA Dust PA CO PA Predicted an alignment in 4C41.17 Observed Δpa = 8o Klamer et al. 2004 R D Ekers

  39. CMB – special purpose instruments DASI with sun dogs

  40. CMB foregrounds – role for ground based telescopes? • Acknowledged as the main problem for future experiments (Bouchet, Lawrence) • Measure structures to better understand the physics • Eg spinning dust, galactic polarization • Look after the point source foregrounds • Here we can take advantage of higher angular resolution to separate out and measure the point source foreground • AT20G all sky survey at 20GHz with ATCA • 1/3 southern sky completed to 50-100mJy • Less variability than expected • No power law spectra! • No new class of objects

  41. S-Z • Clusters • Excellent for S-Z because non-thermal confusion can be subtracted • 10<ν<20GHz • Optimum sensitivity • Optimum resolution • Protospheroids • Few μK (very hard with current telescopes) • Only SKA has adequate sensitivity

  42. Stokes I Stokes V Magnetism and Radio Astronomy Most of what we know about cosmic magnetism is from radio waves! • Faraday rotation → B|| • Synchrotron emission → orientation, |B| • Zeeman splitting → B|| Kazès et al (1991) Fletcher & Beck (2004)

  43. The Origin and Evolution of Cosmic Magnetism: • all-sky radio continuum survey with SKA • measure rotation measures for 108 polarized extragalactic sources, with an average spacing between sightlines of ~60”. • This will completely characterize the evolution of magnetic fields in galaxies and clusters from redshifts z > 3 to the present. • Is there a connection between the formation of magnetic fields and the formation of structure in the early Universe? • When and how are the first magnetic fields in the Universe generated?

  44. Advanced LIGO Pulsars LISA SKA Pulsars as Gravitational Wave Detectors • Millisecond pulsars act as arms of huge detector: QSO astrometry too! Pulsar Timing Array: Look for global spatial pattern in timing residuals! • Complementary in Frequency! Kramer - Leiden retreat (updated)

  45. Exploring the unknown The universe is not only queerer than we suppose, but queerer than we CAN suppose. J.B.S.Haldane

  46. Exploring the unknown • Astronomy is not an experimental science • Experiments which open new parameter space are most likely to make transformational discoveries • cm radio astronomy has opened all the available parameter space • space, time, frequency, polarization • but the SKA greatly enlarges the volume of parameter space explored • sensitivity and FoV  106 x VLA • New classes of rare objects • Access to the high redshift universe

  47. Key Discoveries in Radio Astronomy# # This is a short list covering only metre and centimetre wavelengths. Wilkinson, Kellermann, Ekers, Cordes & Lazio (2004)

  48. Key Discoveries :Type of instrument • The number of discoveries made with special purpose instruments has declined

  49. Proposed SKA Timeline 2011 2006 2007 2008 2009 2020 2013 SKA Pathfinder construction Demonstrator developments 2070+ SKA Construction Site bid Full SKA operational Technology selection SKA production readiness review Site ranking

  50. A possible SKA Pathfinder • One possibility • 1000 x 15m dishes • 0.6 – 2 GHz • Wide field-of-view (35deg2) • 10 x 10 Focal Plane Array • 10% SKA area • Construction 2009-2012 • International collaboration a fundamental component

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