Observational Molecular Astronomy: Exploring the Universe using Molecular Line Emissions

192 Pages·2013·4.933 MB·English

by  Williams D.A., Viti S.

ObservationalMolecularAstronomy
ExploringtheUniverseUsingMolecularLineEmissions
Molecularlineemissionsofferresearchersexcitingopportunitiestolearnaboutthe
evolutionarystateoftheMilkyWayanddistantgalaxies.Thistextprovidesadetailed
introductiontomolecularastrophysicsandanarrayofusefultechniquesforobserving
astronomicalphenomenaatmillimetreandsubmillimetrewavelengths.After
discussingthetheoreticalunderpinningsofmolecularobservation,theauthors
cataloguesuitablemoleculartracersformanytypesofastronomicalregionsinlocal
anddistantpartsoftheUniverse,includingcoldgasreservoirsprimedforthe
formationofnewstars,regionsofactivestarformation,giantphoton-dominated
regions,andnearactivegalacticnuclei.Furtherchaptersdemonstratehowtoobtain
usefulastronomicalinformationfromrawtelescopedatawhileproviding
recommendationsforappropriateobservingstrategies.Repletewithmaps,charts,and
referencesforfurtherreading,thishandbookwillsuitresearchastronomersand
graduatestudentsinterestedinbroadeningtheirskillstotakeadvantageofthenew
facilitiesnowcomingonline.
david a.williamsistheEmeritusPerrenProfessorofAstronomyatUniversity
CollegeLondon.AformerpresidentoftheRoyalAstronomicalSociety(2000–2002)
andrecipientoftheRAS’sGoldMedal(2009),hehasledresearchgroupsin
ManchesterandLondonandhasco-authoredanumberoftextsonastrophysicsand
astrochemistry.Hisresearchinterestscentreonastrochemistryandusingmolecular
lineemissionstodescribeandunderstandtheevolutionofastronomicalregions.
serena vitiisaprofessorofastrophysicsatUniversityCollegeLondon.Shebegan
hercareerworkingonthespectroscopyofverycoolstarsbutsoonbecameinterested
instarformationandastrochemistry.SheisthesecretaryoftheEuropean
AstronomicalSocietyandroutinelyservesonnationalandinternationalscientific
panelsandcommittees.

CambridgeObservingHandbooksforResearchAstronomers
Today’sprofessionalastronomersmustbeabletoadapttousetelescopesand
interpretdataatallwavelengths.Thisseriesisdesignedtoprovidethemwith
acollectionofconcise,self-containedhandbooks,whichcoverthebasicprin-
ciplespeculiartoobservinginaparticularspectralregion,ortousingaspecial
techniqueortypeofinstrument.Thebookscanbeusedasanintroductionto
thesubjectandasahandyreferenceforuseatthetelescopeorintheoffice.
SeriesEditors
Professor Richard Ellis, Department of Astronomy, California Institute of
Technology
ProfessorSteveKahn,DepartmentofPhysics,StanfordUniversity
ProfessorGeorgeRieke,StewardObservatory,UniversityofArizona,Tucson
Dr.PeterB.Stetson,HerzbergInstituteofAstrophysics,DominionAstrophysi-
calObservatory,Victoria,BritishColumbia
Bookscurrentlyavailableinthisseries:
1. HandbookofInfraredAstronomy
I.S.Glass
4. HandbookofPulsarAstronomy
D.R.LorimerandM.Kramer
5. HandbookofCCDAstronomy,SecondEdition
SteveB.Howell
6. IntroductiontoAstronomicalPhotometry,SecondEdition
EdwinBuddingandOsmanDemircan
7. HandbookofX-rayAstronomy
EditedbyKeithArnaud,RandallSmith,andAnetaSiemiginowska
8. PracticalStatisticsforAstronomers,SecondEdition
J.V.WallandC.R.Jenkins
9. IntroductiontoAstronomicalSpectroscopy
ImmoAppenzeller
10. ObservationalMolecularAstronomy
DavidA.WilliamsandSerenaViti

Observational Molecular Astronomy
Exploring the Universe Using Molecular
Line Emissions
DAVID A. WILLIAMS
UniversityCollegeLondon
SERENA VITI
UniversityCollegeLondon
32AvenueoftheAmericas,NewYork,NY10013-2473,USA
CambridgeUniversityPressispartoftheUniversityofCambridge.
ItfurtherstheUniversity’smissionbydisseminatingknowledgeinthepursuitofeducation,
learning,andresearchatthehighestinternationallevelsofexcellence.
www.cambridge.org
Informationonthistitle:www.cambridge.org/9781107018167
©DavidA.WilliamsandSerenaViti2013
Thispublicationisincopyright.Subjecttostatutoryexception
andtotheprovisionsofrelevantcollectivelicensingagreements,
noreproductionofanypartmaytakeplacewithoutthewritten
permissionofCambridgeUniversityPress.
Firstpublished2013
PrintedintheUnitedStatesofAmerica
AcataloguerecordforthispublicationisavailablefromtheBritishLibrary.
LibraryofCongressCataloguinginPublicationdata
Williams,D.A.(DavidArnold),1937–author.
Observationalmolecularastronomy:exploringtheuniverseusingmolecularline
emissions/DavidA.Williams,UniversityCollegeLondon,SerenaViti,
UniversityCollegeLondon.
pages cm.–(Cambridgeobservinghandbooksforresearchastronomers;10)
Includesbibliographicalreferencesandindexes.
ISBN978-1-107-01816-7(hardcover:alk.paper)
1.Molecularastrophysics. I.Viti,Serena,author. II.Title. III.Series:Cambridge
observinghandbooksforresearchastronomers;10.
QB462.6.W55 2013
523(cid:2).02–dc23 2013013585
ISBN978-1-107-01816-7Hardback
CambridgeUniversityPresshasnoresponsibilityforthepersistenceoraccuracyofURLs
forexternalorthird-partyInternetwebsitesreferredtointhispublicationanddoesnot
guaranteethatanycontentonsuchwebsitesis,orwillremain,accurateorappropriate.
Contents
ListofIllustrations pagexi
ListofTables xiii
Preface xv
1 Introduction 1
1.1 WhyAreMoleculesImportantinAstronomy? 1
1.2 AVeryBriefHistoryoftheDiscoveryofMolecules
inSpace 3
1.3 GasandDust 9
1.4 What’sinThisBook 14
1.5 FurtherReading 15
2 SpectraandExcitationofInterstellarMolecules 16
2.1 MolecularSpectroscopy 16
2.2 RadiativeTransportintheInterstellarMedium 20
2.3 DeterminingtheLevelPopulations 21
2.4 FurtherReading 23
3 AstrochemicalProcesses 24
3.1 WhatDrivesCosmicChemistry? 24
3.2 ChemistryInitiatedbyElectromagneticRadiation 25
3.3 ChemistryInitiatedbyCosmicRays 30
3.4 ChemistryandDust 37
3.5 ChemistryInitiatedbyGasDynamics 42
3.6 IsotopesinInterstellarChemistry 46
3.7 Conclusions 48
3.8 FurtherReading 48
vii
viii Contents
4 PhysicalProcessesinDifferentAstronomicalEnvironments 50
4.1 VaryingtheIntensityofElectromagneticRadiation 51
4.2 VaryingtheCosmicRayIonisationRate 53
4.3 VaryingtheDust:GasRatioandtheMetallicity 54
4.4 VaryingShockSpeedsinInterstellarGas 56
4.5 Timescales 57
4.6 Conclusions 58
4.7 FurtherReading 61
5 MolecularTracersintheMilkyWayGalaxy 62
5.1 MolecularClouds 62
5.2 Star-FormingRegionsandTheirOutflows 69
5.3 FormationofLow-MassStars 80
5.4 FormationofHigh-MassStars 85
5.5 CircumstellarMaterial 88
5.6 TheGalacticCentre 95
5.7 FurtherReading 98
6 MolecularTracersinExternalGalaxies 99
6.1 MulticomponentGalaxies 101
6.2 CharacterisationofGalaxiesviaMolecules 111
6.3 RecentMolecularLineStudiesofGalaxies 115
6.4 StarFormationandtheInitialMassFunction 123
6.5 MoleculesinthePerseusClusterofGalaxies 125
6.6 Conclusions 126
6.7 FurtherReading 127
7 TheEarlyUniverseandtheFirstGalaxies 128
7.1 ThePregalacticEra 128
7.2 FormationoftheFirstStars 132
7.3 FormationoftheFirstGalaxies 134
7.4 FurtherReading 140
8 RecipesforMolecularSubmillimetreAstronomy 141
8.1 TheAntennaTemperature 142
8.2 LocalThermodynamicEquilibrium 143
8.3 Non-LTE 149
8.4 FurtherReading 151