Interferometry and Synthesis in Radio Astronomy

910 Pages·2017·18.88 MB·English

by  A. Richard Thompson

Astronomy and Astrophysics Library
A. Richard Thompson
James M. Moran
George W. Swenson Jr.
Interferometry
and Synthesis in
Radio Astronomy
Third Edition
Serieseditors MartinA.Barstow,Heidelberg,Germany
GerhardBörner,Garching,Germany
AndreasBurkert,München,Germany
W.B.Burton,Mathews,VA,USA
A.Coustenis,Meudon,France
MichaelA.Dopita,WestonCreek,ACT,Australia
BrunoLeibundgut,Garching,Germany
GeorgesMeynet,Versoix,Switzerland
PeterSchneider,Bonn,Germany
VirginiaTrimble,Irvine,CA,USA
DerekWard-Thompson,Preston,UK
IanRobson,Edinburgh,UK
Moreinformationaboutthisseriesathttp://www.springer.com/series/848
An image from the Karl G. Jansky Very Large Array of the Galaxy Hercules
A (also known as 3C348) showing powerful synchrotron jets emerging from its
core, the site of a supermassive black hole of 109 solar masses. The field center
is RA = 16h51m8.147s, Dec. = 4ı 590 33.3200 (2000), and the field of view is 3.3
(cid:2) 2.4 arcmin. The image has been rotated clockwise by 36 degrees. The data set
comprised70 hoursof observationsacquiredin 2010and 2011in bandsfrom 4.2
to 9 GHz inall fourarrayconfigurationswith baselinesfrom36m to 36km.The
image resolution is 0.300, corresponding to a linear scale of 800 pc at a distance
of 730 Mpc, and the image contains about 10.7 Mpixels. The dynamic range is
about 1200. The image has been reconstructed with a multiresolution CLEAN
algorithmandself-calibrationproceduresdescribedinChapter11.Colorcodedby
intensity.ImagefromtheNRAO, courtesyofB. Saxton,W. Cotton,andR. Perley
(NRAO/AUI/NSF).©NRAO.
A. Richard Thompson (cid:129) James M. Moran (cid:129)
George W. Swenson Jr.
Interferometry and Synthesis
in Radio Astronomy
Third Edition
A.RichardThompson JamesM.Moran
NationalRadioAstronomyObservatory HarvardSmithsonianCenterfor
Charlottesville Astrophysics
Virginia,USA Cambridge
Massachusetts,USA
GeorgeW.SwensonJr.
UniversityofIllinoisUrbanaChampaign
Champaign
Illinois,USA
PreviouseditionpublishedbyJohnWiley&Sons2001,ISBN:978-0-471-25492-8
ISSN0941-7834 ISSN2196-9698 (electronic)
AstronomyandAstrophysicsLibrary
ISBN978-3-319-44429-1 ISBN978-3-319-44431-4 (eBook)
DOI10.1007/978-3-319-44431-4
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Coverillustration:TheAtacamaLargeMillimeter/submillimeterArrayontheChajnantorPlateauofthe
AtacamaDesertinnorthernChileat5000mabovesealevel.
Credit:ALMA(ESO/NAOJ/NRAO)/W.Garnier(ALMA).©ESO.
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Preface to the Third Edition
Theadvancesin radioastronomy,especiallyininstrumentationforinterferometry,
over the past 15 years since the second edition have been remarkable. With the
commissioning of the Atacama Large Millimeter/submillimeter Array (ALMA),
high-resolution radio astronomy has reached the high-frequency limit of ground-
based observations of about 1 THz. There has been a revitalization of interest
at low frequencies, with multiple new instruments such as the LOw Frequency
ARray(LOFAR),theLongWavelengthArray(LWA),andtheMurchisonWidefield
Array(MWA).Tremendousadvancesinsignal-processingcapabilitieshaveenabled
the first instruments with multiple fields of view, the Australian SKA Pathfinder
(ASKAP)andAPERITIFontheWesterborkarray.VLBIhasreachedsubmillimeter
wavelengths and is being used by the Event Horizon Telescope (EHT) to resolve
thestructureoftheemissionsurroundingtheblackholeinthecenterofourgalaxy.
VLBIwiththeelementsinEarthorbit,RadioAstronandVSOP,hasgreatlyextended
thebaselinesavailable.
Much new material has been added to this edition. In Chap. 1, the historical
perspective has been brought up to date. An appendix has been added where the
radiometerequation,whichgivesthefundamentallimitationin thesensitivityofa
radiotelescope,hasbeenderivedfrombasicprinciples.InChap.2,anewappendix
gives an overview of the Fourier transform theory used throughout the book.
Chapter 4 includes a description of the so-called measurement equation, which
providesaunifiedframeworkforarraycalibration.Chapter5includesadescription
of the new instruments available, including the fast Fourier Transform Telescope.
The discussion of system design has been substantially expanded in Chap. 7.
In Chap. 8, which deals with digital signal processing, the coverage of FX-type
correlatorshas been greatly expandedand the operation of polyphase filter banks
explained.Theanalysisofsensitivitylossduetoquantizationhasbeengeneralized.
An appendix describing the basic properties of the discrete Fourier transform has
been added. Chapter 9 on VLBI has been updated to reflect the conversion from
datastorageontapetodatastorageondiskmedia.Withtheprevalenceofdirectdata
transmissiontocorrelationfacilities,thedistinctionbetweenVLBIandconnected-
elementinterferometrycontinuestodiminish.InChap.10,thediscussionofmodel
ix
x PrefacetotheThirdEdition
fitting in the .u;v/ plane has been greatly expanded to reflect a trend in the field
toward fitting the fundamental interferometric data even though image fidelity
continuestoimprovedramatically.Thephaseandamplitudeclosureconditionsare
exploredingreaterdepthbecauseoftheirunderlyingimportanceindatacalibration.
InChap.11,advancesinimageprocessingalgorithmsaredescribed,includingthe
applicationofcompressedsensingtechniques.Chapter12describesthetechniques
underlyingthetremendousadvanceinastrometry.Precisionsof10microarcseconds
arenowroutineasaresultofprogressinphase-referencingmethods.Inthisedition,
discussionofthepropagationoftheneutralatmosphereandtheionizedmediafrom
the ionosphere to the interstellar medium has been separated into two chapters,
Chaps.13and14,becauseofthegrowthininformationintheseareas.Overthelast
15 years, enormous amounts of data have been acquired on site characterization,
whicharedescribedinChap.13.Becauseoftheimportanceofbothtwo-andthree-
dimensionalturbulenceinthetroposphere,adetailedanalysisofthetworegimesis
given.Chapter17,onrelatedtechniques,includesnewmaterialontheuseofradio
arraystotracksatellitesandspacedebris.Italsodescribestheapplicationofradio
interferometrytoremotesensingoftheEarth.Suchapplicationprovidesimportant
informationonsoilmoistureandoceansalinity.
In the early days of radio interferometry, measurements of the distribution of
source intensity were usually referred to as “maps” and the associated technique
as“mapping.”Withthe maturityofthefield,itseemsmoreappropriateto referto
the results as “images.” We have done so, except in a few cases where the term
“map”still seemsappropriate,asin the determinationofthe distributionofmaser
spotpositionsfromfringeratemeasurements.
Readerswhoarenewtothefieldofradioastronomyarestronglyencouragedto
study the basic principles of the field from other sources. Some of the numerous
textbooks are listed under Further Reading at the end of Chap. 1. Of particular
usefulnessisthebookTheFourerTransformandItsApplicationsbyRonBracewell,
a radio astronomer and mathematician, because of its practical approach to the
subject.Theintellectualrootsofthisapproachcanbetracedtothelecturenotesof
J.A.RatcliffeofCambridgeUniversity,whichinspiredthebookFourierTransforms
andConvolutionsfortheExperimentalistbyRogerJennison.
Theauthorswouldbegratefulforanyfeedbackfromthereadersofthisbookin
regardtopedogogical,technical,orgrammaticalissuesortypographicalerrors.
We havebenefitedgreatlyfrommanyofourcolleagueswhohavehelpedinthe
preparationofthisedition.TheyincludeBetseyAdams,KazunoriAkiyama,Subra
Ananthakrishnan,YoshiharuAsaki,JaapBaars,DenisBarkats,NorbertBartel,Leo
Benkevitch,MarkBirkinshaw,KatieBouman,GeoffBower,MichaelBremer,John
Bunton, Andrew Chael, Barry Clark, Tim Cornwell, Pierre Cox, Adam Deller,
Hélène Dickel, Phil Edwards, Ron Ekers, Pedro Elosegui, Phil Erickson, Hugh
Garsden, John Gibson, Lincoln Greenhill, Richard Hills, Mareki Honma, Chat
Hull, Michael Johnson, Ken Kellermann, Eric Keto, Robert Kimberk, Jonathon
Kocz, Vladimir Kostenko, Yuri Kovalev, Laurent Loinard, Colin Lonsdale, Ryan
Loomis, Chopo Ma, Dick Manchester, Satoki Matsushita, John McKean, Russ
McWhirter, Arnaud Mialon, George Miley, Eric Murphy, Tara Murphy, Ramesh
PrefacetotheThirdEdition xi
Narayan,ScottPaine,NimeshPatel,MichaelPearlman,RichardPlambeck,Danny
Price, Rurik Primiani, Simon Radford, Mark Reid, Maria Rioja, Luis Rodríguez,
Nemesio Rodríguez-Fernández, Alan Rogers, Jon Romney, Katherine Rosenfeld,
Jean Rüeger, Marion Schmitz, Fred Schwab, Mamoru Sekido, T. K. Sridharan,
Anjali Tripathi, Harish Vedantham, Jonathan Weintroub, Alan Whitney, David
Wilner,RobertWilson,andAndreYoung.
JMtaughtagraduatecourseinradioastronomyatHarvardUniversitybiannually
for 40 years. He thanks the hundreds of students who took this course for the
feedback,stimulation,andchallengestheyposed.
ThepublicationofthiseditionunderanOpenAccesslicensewasmadepossible
bygrantsfromtheD.H.MenzelFundatHarvardUniversityandtheNationalRadio
AstronomyObservatory.WeareparticularlygratefultoCharlesAlcock,directorof
theHarvard–SmithsonianCenterforAstrophysics,andAnthonyBeasley,directorof
theNationalRadioAstronomyObservatory,fortheirgeneroussupportofallaspects
ofthisproject.
We thank John Lewis for much help with the graphics and other creative
contributions that improved the presentation of material in this book. We are
also grateful to Tania Burchell, Maureen Connors, Christopher Erdmann, Muriel
Hodges,CarolynHunsinger,ClintonLeite,RobertReifsnyder,andLarrySelterfor
theirvaluablesupport.
Thepublicationofthiseditionwouldnothavebeenpossiblewithoutthetireless
and expert assistance of Carolann Barrett of Harvard University. An experienced
editor with a degree in mathematics, she completed both our sentences and our
equations.Hercapacitytoholdeverydetailofthebookinherbrainistrulyamazing.
Charlottesville,VA,USA A.RichardThompson
Cambridge,MA,USA JamesM.Moran
Urbana,IL,USA GeorgeW.SwensonJr.
June2016