Science with the Square Kilometer Array
Total Page:16
File Type:pdf, Size:1020Kb
Science with the Square Kilometer Array edited by: A.R. Taylor and R. Braun March 1999 Cover image: The Hubble Deep Field Courtesy of R. Williams and the HDF Team (ST ScI) and NASA. Contents Executive Summary 6 1 Introduction 10 1.1 ANextGenerationRadioObservatory . 10 1.2 The Square Kilometre Array Concept . 12 1.3 Instrumental Sensitivity . 15 1.4 Contributors................................ 18 2 Formation and Evolution of Galaxies 20 2.1 TheDawnofGalaxies .......................... 20 2.1.1 21-cm Emission and Absorption Mechanisms . 22 2.1.2 PreheatingtheIGM ....................... 24 2.1.3 Scenarios: SKA Imaging of Cosmological H I .......... 25 2.2 LargeScale Structure and GalaxyEvolution . ... 28 2.2.1 A Deep SKA H I Pencil Beam Survey . 29 2.2.2 Large scale structure studies from a shallow, wide area survey 31 2.2.3 The Lyα forest seen in the 21-cm H I line............ 32 2.2.4 HighRedshiftCO......................... 33 2.3 DeepContinuumFields. .. .. 38 2.3.1 ExtragalacticRadioSources . 38 2.3.2 The SubmicroJansky Sky . 40 2.4 Probing Dark Matter with Gravitational Lensing . .... 42 2.5 ActivityinGalacticNuclei . 46 2.5.1 The SKA and Active Galactic Nuclei . 47 2.5.2 Sensitivity of the SKA in VLBI Arrays . 52 2.6 Circum-nuclearMegaMasers . 53 2.6.1 H2Omegamasers ......................... 54 2.6.2 OHMegamasers.......................... 55 2.6.3 FormaldehydeMegamasers. 55 2.6.4 The Impact of the SKA on Megamaser Studies . 56 2.7 TheStarburstPhenomenon . 57 2.7.1 TheimportanceofStarbursts . 58 2.7.2 CurrentRadioStudies . 58 2.7.3 The Potential of SKA for Starburst Studies . 61 3 4 CONTENTS 2.8 InterstellarProcesses . 63 2.8.1 HII Regions: High Resolution Imaging of Thermal Emission . 64 2.8.2 Centimetre Wavelength Molecular Probes of the ISM . .. 66 2.8.3 SupernovaRemnants . 68 2.8.4 TheOriginofCosmicRays . 74 2.8.5 Interstellar Plasma Turbulence . 76 2.8.6 RecombinationLines . 77 2.9 MagneticFields.............................. 78 2.9.1 RotationMeasureSynthesis . 78 2.9.2 Polarization Studies of the Interstellar Medium in the Galaxy andinNearbyExternalGalaxies . 80 3 Formation and Evolution of Stars 86 3.1 ContinuumRadioEmissionfromStars . 86 3.2 ImagingtheSurfacesofStars . 90 3.2.1 RedGiantsandSupergiantStars . 90 3.2.2 Complementarity to Planned Optical-IR Interferometers ... 97 3.3 StarFormation .............................. 98 3.3.1 ProtostellarCores. 99 3.3.2 ProtostellarJets . .. .. 102 3.3.3 Uncovering the Evolutionary Sequence . 105 3.3.4 Magnetic Fields in Frotostellar Objects . 107 3.4 CoolStarAstronomy . .. .. 109 3.4.1 TheRadioSun .......................... 111 3.4.2 Observing Solar Analogs at Radio Wavelengths . 114 3.4.3 WherearethemanyotherRadioSuns?. 115 3.4.4 ProspectsfortheSKA . 117 3.4.5 FlaresandMicroflares . 118 3.4.6 Summary of Scientific Objectives . 120 3.5 Imaging of Circumstellar Phenomena . 121 3.6 StellarAstrometry ............................ 121 3.7 Supernovae ................................ 122 3.7.1 RadioSupernovae. 123 3.7.2 New Observations Possible with the SKA . 127 3.7.3 SummaryandConclusions . 129 3.8 TheRadioAfter-GlowsofGamma-rayBursts . 132 3.9 Pulsars................................... 135 3.9.1 PulsarSearcheswiththeSKA . 136 3.9.2 PulsarTimingwiththeSKA . 137 3.9.3 Radio Pulsar Timing and General Relativity . 138 3.9.4 Summary ............................. 139 CONTENTS 5 4 Solar System Science 141 4.1 Thermal Emission from Small Solar System Bodies . ... 141 4.1.1 Asteroids ............................. 142 4.1.2 PlanetarySatellites . 145 4.1.3 KuiperBeltObjects . 146 4.2 RadarImagingofNearEarthAsteroids. 149 4.3 The Atmosphere and Magnetosphere of Jupiter . 152 4.4 CometStudies............................... 153 4.5 SolarRadar ................................ 153 4.6 CoronalScattering ............................ 154 5 Formation and Evolution of Life 155 5.1 DetectionofExtrasolarPlanets . 155 5.2 Pre-BioticChemistry . .. .. 157 5.3 The Search for Extraterrestrial Intelligence . ....... 157 Bibliography 161 List of Tables 1.1 SKADesignGoals ............................ 14 1.2 Instrumental Sensitivity per Polarisation in 8 hours . ........ 16 2.1 Detectable H I Masses for an SKA Deep Pencil Beam Survey . 30 2.2 CODetectionsatHighRedshift . 35 3.1 Some Current and Planned Optical-IR Interferometers . ...... 97 4.1 SKA Specifications for Imaging Small Solar System Bodies ...... 141 5.1 Parameters of Selected SETI Surveys . 159 6 List of Figures 1.1 ComparisonofFieldsofView . 12 1.2 TheSquareKilometreArray. 13 1.3 SpectralLineSensitivity . 16 1.4 ContinuumSensitivity . .. .. 17 2.1 Detectability of fluctuations in H I brightness temperature. 27 2.2 H I emission from the region surrounding a QSO source . 27 2.3 The Local H I MassFunction....................... 30 2.4 Properties of Galaxy Redshift Surveys . .. 32 2.5 Observable CO Transitions as a Function of Redshift . ..... 34 2.6 CO Luminosity as a Function of Redshift . 36 2.7 CO Flux Density as a Function of Redshift . 36 2.8 Signal to Noise Ratio as a Function of Redshift . ... 37 2.9 Simulated Continuum Observation of a region the size and shape of theHubbleDeepField .......................... 41 2.10 Instrumental Distortion of HST Field Stars . ..... 44 2.11 Smoothed Distortion Field toward CL 1358+62 . ... 45 2.12 Dependence of peak VLA power on distance for 374 UGC galaxies . 48 2.13 H I absorptionin3C236.......................... 49 2.14 DeepVLBIImageof3C84 ....................... 50 2.15 Compact Component Luminosity as a Function of Redshift ...... 52 2.16 ThecenterofNGC4258 ......................... 54 2.17 A λ6cmMERLIN/VLAimageofM82 . 60 2.18 ExpansionofaYoungSNRinM82 . 61 2.19 Brightness Temperature – Angular Size Space . .... 65 2.20 RotationMeasureofPulsarJ0214+4232 . .. 79 2.21 Effects of the Diffuse Faraday Screen in our Galaxy . .... 82 3.1 TheRadioHRDiagram ......................... 87 3.2 Distribution of Stellar Radio Luminosities . ..... 88 3.3 DetectionofMiraPhotospheres . 89 3.4 Non-thermallyEmittingStars . 90 3.5 HST and Interferometer Images of Mira and Betelgeuse . ..... 91 3.6 Image and Model of UV emission from Betelgeuse . .. 92 7 8 LIST OF FIGURES 3.7 Flux Density and Size for a Mira-like Red Giant Star versus Distance andFrequency............................... 93 3.8 Flux Density and Size for a Red Supergiant Star versus Distance and Frequency ................................. 94 3.9 VLAImageoftheBetelguese . 96 3.10 Angular Resolution of the SKA and Planned Optical-IR Inteferometers 98 3.11 Dust and Ionized Wind from the Protostellar Object HL Tau..... 99 3.12 OpacityofaSphericalDustCloud . 101 3.13 Collimated Outflows in Young Stellar Objects . .... 103 3.14 A λ3.6cmImageofDouble? JetsinL1551. 104 3.15 Proper Motion of the Ionized Jet of HH80-81. ... 104 3.16L1498 ................................... 106 3.17 TMC1, Rosetta Stone forstar formation?. ... 106 3.18TheRadioSun .............................. 112 3.19 DynamicSpectrumofaSolarRadioBurst . 113 3.20 Radiospectraoftheactive dMestarUVCet. 115 3.21 Dynamic Spectrum of a Coherent Radio Burst from the dMe Star AD Leo..................................... 116 3.22 Expected sensitivity range of the SKA . 119 3.23 Light curves at multiple radio frequencies for several extragalactic SN 125 3.24 Light curves at multiple radio frequencies for SN 1993J ........ 126 3.25 Peak 6 cm luminosity, L6 cm peak of RSNe vs. time........... 128 3.26 Peak RSNe λ6cmfluxversusredshift. 130 3.27 The radio luminosity vs. age for a number of young radio supernovae 131 3.28 The broad-band radio/IR/optical/X-ray spectrum of GRB980703 . 133 4.1 HSTImageoftheVesta ......................... 143 4.2 Light Curve of Vesta at λ2mm...................... 144 4.3 Kuiper Belt like Phenomena Around Nearby Stars . ... 147 4.4 RadarImagesofAsteroid4769Castalia. 150 4.5 RadarImagesofAsteroid4179Toutatis . 151 5.1 Angular Motion of the Sun-Jupiter System . 156 5.2 Predicted and Observed Abundance of Carbon-chain Species ..... 158 Executive Summary The Square Kilometre Array New developments in all fields of astronomy have brought the current generation of astronomers to the brink of probing the origin and evolution of the Universe as a whole. Planning for the next generation of facilitiies leads to the conclusion that a revolutionary new instrument at radio wavelengths is needed, one with an effective collecting area more than 30 times greater than the largest telescope ever built. Such a telescope will reveal the dawn of galaxy formation, as well as a plethora of other new discoveries in all fields of astronomy. Vigorous technological developments in computing and radio frequency devices make it possible for such a telescope to be built within the next decade, and the international radio astronomical community is proposing that such a telescope, with a million square metres of collecting area, be the next major radio telescope to be built. The project has acquired the appellation, the Square Kilometre Array (SKA). The driving ambition for this new facility, indeed of the next generation of as- tronomers, is no less than to chart a complete history of time. This imperative demands a frequency coverage from several meters to about one centimetre, with a sensitivity of 100 times that of the Very Large Array. Using new technologies, the SKA will become the premier imaging instrument of its generation in any wavelength region. With a spatial resolution better than the Hubble Telescope, a field of view larger than the full Moon, and the ability to simultaneously image a wide range of red shift (as