CO in late-type galaxies within the central region of Abell 1367

21 Pages·2013·5.11 MB·English

MNRAS429,221–241(2013) doi:10.1093/mnras/sts328
CO in late-type galaxies within the central region of Abell 1367
T. C. Scott,1,2‹ A. Usero,3 E. Brinks,2 A. Boselli,4 L. Cortese5 and H. Bravo-Alfaro6
1InstitutodeAstrof´ısicadeAndaluc´ıa(CSIC),Apartado3004,E-18080Granada,Spain
2CentreforAstrophysicsResearch,UniversityofHertfordshire,CollegeLane,HatfieldAL109AB
3ObservatorioAstrono´micoNacional,C/AlfonsoXII3,E-28014Madrid,Spain
4Laboratoired’AstrophysiquedeMarseille,OAMP,Universite´Aix–Marseille8CNRS,38RueFre´de´ricJoliot–Curie,F-13388Marseille,France
5ESO,Karl–Schwarzschild–Str.2,D-85748GarchingbeiMu¨nchen,Germany
6DepartamentodeAstronom´ıa,UniversidaddeGuanajuato,Apdo.Postal144,Guanajuato36000,Mexico
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Accepted2012October31.Received2012October6;inoriginalform2012July20 loa
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ABSTRACT
h
Wepresent12CO(J=1–0)and12CO(J=2–1)spectrafor19bright,late-typegalaxies(spirals) ttp
inthecentralregionofthegalaxyclusterAbell1367(z=0.02)fromobservationsmadewith s://a
theIRAM30-mtelescope.All19spiralswereobservedatthepositionoftheiropticalcentre ca
d
andforasubset,atmultiplepositions.ForeachspiraltheintegratedCO(J=1–0)intensity em
fromthecentralpointing,infewcasessupplementedwithintensitiesfromoffsetpointings,was ic.o
u
usedtoestimateitsmolecularhydrogenmassandH2 deficiency.Acceptingtheconsiderable p.c
uncertainties involved in determining H deficiencies, spirals previously identified by us o
2 m
to have redder colours and higher HI deficiencies as a result of environmental influence /m
n
were found to be more H2 deficient compared to members of the sample in less advanced ras
evolutionarystates.Foreightoftheobservedspiralsmultiplepointingobservationsweremade /a
toinvestigatethedistributionoftheirmoleculargas.ForthesespiralswefittedGaussiansto rticle
the CO intensities projected in a line across the galaxy. In two cases, CGCG 097−079 and -a
b
CGCG097−102(N),theoffsetbetweentheCOandopticalintensitymaximawassignificantly stra
c
largerthanthepointinguncertainty,andthefullwidthathalf-maximumvaluesofthefitswere t/4
2
significantlygreaterthanthoseoftheotherspirals,irrespectiveofopticalsize.Bothsignatures 9
are indicators of an abnormal molecular gas distribution. In the case of CGCG 097−079, /1/2
2
whichisconsideredanarchetypeforram-pressurestripping,ourobservationsindicatethatthe 1/1
COintensitymaximumlies∼15.6±8.5arcsec(6kpc)north-westoftheopticalcentreatthe 01
8
sameprojectedpositionastheHIintensitymaximum. 04
1
b
Keywords: galaxies:clusters:individual:Abell1367–galaxies:ISM. y
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N
&Rhee1997).Incontrast,themoleculargasisusuallyconcentrated o
1 INTRODUCTION v
inspiralarmswellinsidetheopticaldisc(Dickey&Kazes1992; em
Two principal classes of mechanisms are invoked to explain the Leroyetal.2008,2009),beingmoretightlyboundgravitationally b
e
rapidevolutionoftheinterstellarmedium(ISM)oflate-typegalax- than HI. In the absence of a recent major interaction, the stellar, r 2
0
ies (spirals) in galaxy clusters: hydrodynamic interactions (Gunn HIandmoleculardiscsareexpectedtobe,tofirstorder,distributed 18
&Gott1972;Nulsen1982;Bekki,Couch&Shioya2002;Fujita axisymmetrically with the centres of the HI and molecular discs
&Goto2004)andfasttidalencounters(Mooreetal.1996,1999; coincidingwiththeopticalcentre.
Bekki1999;Natarajan,Kneib&Smail2002).Theseprocessesare IntheclusterenvironmentHIdeficiencieshavebeeninterpreted
extensivelydiscussedandcomparedinBoselli&Gavazzi(2006). as evidence of past gas loss (van Gorkom 2004), due to removal
The sensitivity and spatial resolution of current instruments limit ofHIbeyondapositionwhereitisnotexpectedtofallbackinto
detailedobservationalstudiesoftheeffectofthesetypesofinter- the spiral’s potential and/or conversion of HI to other hydrogen
actionontheISMtonearbyclusters(z(cid:2)0.05). phases.Ingeneraltodeterminewhetheraspiralcontainsanormal
Typically,theradiusofanunperturbedspiral’sHIdiscextends amount of cold ISM, its HI and H2 masses are compared to the
∼1.8timesfurtherthantheopticaldisc(Cayatteetal.1994;Broeils meanHIandH2contentofisolatedspiralsofsimilarsizeandHub-
bletype.Aspiral’sdeficiency(inHIorH2)isdefinedasthelog
oftheratiooftheexpectedtoobservedgasmass(Haynes&Gio-
(cid:2)E-mail:[email protected] vanelli1984;Bosellietal.1997;Boselli,Lequeux&Gavazzi2002).
(cid:3)C 2012TheAuthors
PublishedbyOxfordUniversityPressonbehalfoftheRoyalAstronomicalSociety
222 T.C.Scottetal.
TheH deficiency(Def )ofaclusterspiralisthenetresultofsev- Table1. Evolutionarystatesofspirals.
2 H2
eralcompetingprocesseswhichdeterminethemassofitsobserved
H2 reservoir, e.g. depletion of H2 by star formation, dissociation State HI Colour
bytheultraviolet(UV)radiationemittedbyhigh-massstars,direct deficiency SDSSg−i
removalduringinteractionsandreplenishmentofH byconversion
2 A <0.7 <0.76
ofHItoH2(Krumholz,McKee&Tumlinson2008,2009). B <0.7 ≥0.76and<1.1
Wecanconsiderstarformationinspiralsasbeingtheendresult C <0.7 ≥1.1
ofacontinuousprocessofconvertingHI→H2→stars.Howthe D ≥0.7 Any
relativeproportionsofthesecomponentsisalteredduringandasa
resultofeithertidalorhydrodynamicinteractionsispoorlyunder-
in distinguishing between interaction mechanisms (Vollmer et al.
stood,primarilybecauseofthelimitedavailabilityanduncertainties
2001, 2008). It is generally thought that molecular discs remain
surroundingtheH data.Modelspredictincreasedstarformation
2 largelyundisturbedbyhydrodynamicinteractions(Lucero,Young D
rates(SFRs)inclusterspiralsduringbothhydrodynamicandtidal o
& van Gorkom 2005; Vollmer et al. 2008). This may, in part, be w
interactions.Thesemodelsindicatethatbothtypesofinteractionare becausethebeststudiedcasesareexperiencingrelativelylowram nlo
capable,inspecificcircumstances,ofenhancingstarformationby pressures,e.g.NGC4522whichis∼1Mpcfromitscluster’score, ade
uptoanorderofmagnitude(Kapfereretal.2008,2009;Kronberger d
etal.2008;Martig&Bournaud2008).Alternativeexplanationsfor wopitthica7l5dpiescrcaenndtoshfothweinmgoalencuSlFaRrgoafs0re.1mMain(cid:6)inygr−c1os(pVaotilalmlweritehttahle. from
H2deficienciesincludestarvationunderwhichaspiral’sHIhalois 2008).However,ESO137−001,projected180kpcfromthecentre h
strippedbyinteractionwiththecluster’sintraclustermedium(ICM). ttp
ofAbell3627,appearstobeexperiencinganorderofmagnitude s
Inthisscenario,aspiral’scoldmolecularreservoirisdepletedby greater ram pressure than NGC 4522. ESO 137−001 has a re- ://a
acombinationofnormalstarformationandreducedavailabilityof c
centlydiscoveredwarmmoleculartail,implyingtheinteractionhas ad
HItoconverttoH2 (e.g.Larson,Tinsley&Caldwell1980;Bekki resulted in a significant mass of cold molecular gas downstream em
esttaarvl.at2io0n02e)f.feItctsshiosusldevberealnoGtyedr,(Bhoowseelvlie&r, tGhaatvathzezit2im00e6-s;cBaloesefollri o2f01th0e).oTphteicaclasdeisocf(ESSivOan1a3n7d−am00,1Riheikgehl&ighRtsietkheat2t0h1e0r;eSlautnionetbael-. ic.oup
etal.2006). tweenthemagnitudeofahydrodynamicinteractionanditseffect .co
Previousstudiesofmoleculardeficienciesinclusters,e.g.Young m
&Knezek(1989)fortheVirgoclusterandCasolietal.(1991)for onthedistributionofdiscandextraplanarmoleculargasremains /m
poorlyconstrained. n
the Coma supercluster, concluded that cluster spirals are not de- ra
Weareinvestigatingtheimpactoftheclusterenvironmentonthe s
fiotchieenrtLFinIR-Hse2leccotmedpasraemdptloestharoesebiiansetdheagfiaeilnds.tHfinodwinevgeHr,2t-hdeesfieciaenndt IwSiMthinofaacseanmtraplleraodfiu2s6(o1p.5tiMcapllcy)soeflethcetendebarribgyhctlluastete-rtyApebegllal1a3x6ie7s, /article
galaxies, because of the strong correlation between MH2 per unit begunwithaprogrammeofVeryLargeArray(VLA)HIobserva- -ab
smaamspslea,ndBoLsFeIRlli(eBtoasle.ll(i20e0t2a)l.re1a9c9h7e)d. Uthseinsgamaencoopntciclualsliyons.elTehcetesde tions(Scottetal.2010,hereafterPaperI).Themajorityofspirals stra
results have been used to support the argument that the observed from this sample imaged so far with the VLA show asymmetric ct/4
HIdeficienciesinclustersprimarilyarisefromhydrodynamicstrip- sHigIndifiisctrainbtuitniotenrsacatniodnHsoIfdseofimcieeknicnieds., implying they are suffering 29/1
pingonthebasisthatrampressurestripsHIwhileleavingtheH2 In this paper, we report on the CO (J = 1–0) and CO (J = /22
componentunperturbed(Boselli&Gavazzi2006).Giventhatstar 1
2–1) emission from 19 of the 26 galaxies from Paper I. The /1
formation in cluster spirals is lower than in the field (Kennicutt 0
seven galaxies from the Paper I sample which were not ob- 1
8
1983; Gavazzi et al. 2002; Koopmann & Kenney 2004), the lack 0
served in CO were principally those with the smallest diame- 4
of overall H deficiency is surprising as it implies a typical clus- 1
2 ter optical discs. The most extensive previous CO observations b
terspiralhassuppressedstarformationdespitehavingnormalH y
2 covering the central region of Abell 1367 were carried out with g
content.Todate,onlyafewH -deficientclusterspiralshavebeen u
2 the National Radio Astronomy Observatory (NRAO) Kitt Peak e
reported(e.g.Fumagallietal.2009),butthismayreflectthebias 12-m telescope (Boselli et al. 1997). Several spirals within the st o
inmostprevioussurveysagainstfindingsuchdeficiencies(Boselli n
central region have previously been observed with the IRAM1 1
etal.1997,2002). 6
30m(e.g.Casolietal.1991;Dickey&Kazes1992;Bosellietal. N
How ongoing interactions (tidal or hydrodynamic) impact the o
1994;Lavezzietal.1999).IncomparisonwithpreviousCOstudies v
amountanddistributionofcoldmoleculargasinclusterspiralsis withinthecentralregionourcurrentobservationsincludealarger em
mofuscphirlaelsssiwnveolllvsetuddiinedsttrhoanngfotirdathleinnteeuratrcatlioantosmraincggeasf.roCmObiamr-algikees numberofgalaxies,oftenhavinghigherangularresolution,andin ber 2
casesofre-observations,almostallaremoresensitive. 0
to triple-lobed distributions (e.g. Kaufman et al. 2002; Iono, Yun 1
InPaper Iwe distinguishedfourbroad evolutionary states (A– 8
&Ho2005;Corte´s,Kenney&Hardy2006;Combesetal.2009).
D)forthespiralsusingrangesofHIdeficiencyandSloanDigital
Ionoetal.(2005)reportedoffsetsbetweenHIandopticalintensity Sky Survey (SDSS) colour. We continue to use the same defini-
maximain50percentofasampleoftidallyinteractinggalaxies,
tionsofevolutionarystateinthecurrentpaper,withtheparameters
buttheirstudy(theirtable9)indicatestheimpactonthedistribution
giveninTable1.Theclassificationassumesthatinteraction-induced
ofmolecularandHIcomponentsmaybequitedifferentdepending removal/consumptionofISMgas(HI)willeventuallyleadtosup-
ontheparametersoftheinteraction.
pressionofstarformationandachangeofopticalcolour.
Most hydrodynamic interaction simulations do specifically BasedonaredshifttoAbell1367of0.022andassuming(cid:3) =
modelthecoldmolecularISM(Roediger&Hensler2005;Roedi- 0.3,(cid:3) =0.7andH =72kms−1Mpc−1(Spergeletal.2007)M,the
ger&Bru¨ggen2007;Kronbergeretal.2008;Kapfereretal.2009). (cid:4) 0
In the few cases where spatially resolved molecular observations
havebeenutilizedincombinationwithdatafromotherwavelengths 1IRAMissupportedbyCNRS/INSU(France),theMPG(Germany)and
andstickyparticlesimulations,theyhaveprovedextremelyfruitful theIGN(Spain).
COinAbell1367 223
Table2. Observationalparameters.
Restfrequency Wavelength FWHP FWHPa Receivers Filterbank Tsysb Tmbc
(GHz) (mm) (arcsec) (kpc) (MHz) (K) (K)
115.3 2.6 22 8.8 A100,B100 1 239 1.28T∗
A
230.5 1.3 11 4.4 A230,B230 4 679 1.70T∗
A
aFullwidthhalfpower(FWHP)beamatthedistanceofA1367of92Mpc.
bTypicalTsys(Tmbscale).
cConversiontomainbeambrightnessTmb=TA∗ηfs/ηmb,whereTmbisthemainbeamtemperature,ηfsis
theforwardscatteringandspilloverefficiencyandηmb istheapertureefficiency,withηfs/ηmb fromthe
IRAMwebsitehttp://www.iram.fr.Themain-beamtemperaturescanbeconvertedintofluxdensitiesby
applyingafactorof4.95JyK−1. D
o
w
n
distancetotheclusteris92Mpcwithanangularscaleof1arcmin orotherabnormalitieswerediscarded.Tomeasurelinefluxeswe lo
≈24.8kpc.Allα andδ positionsreferredtothroughoutthepaper definedavelocitywindowinwhichthelinewaseitherdetectedor, ad
e
areInJ2S0e0c0t.i0o.n 2 we describe the observations and reduction. The itnhethHeIcavseeloocfitnyonw-iddetthe.ctTiohniss,wwinasdoewxpewcatesdtytopibcealdlyeteccetnetdrebdasoendtohne d from
observationalresultsaresetoutinSection3anddiscussedinSection opticalvelocityandwas150–300kms−1wide.Theuseofwobbler h
4,followedbyconcludingremarksinSection5. switching produced a flat baseline for each spectrum, allowing a ttp
s
linearfittothetworegionsofthespectrumadjacenttothewindow ://a
c
2 OBSERVATIONS whichwasthensubtractedfromtherawspectrumtoproducethe a
d
finalspectrum. em
Theobservationswerecarriedoutin2008JulyusingtheIRAM30-
ic
mtelescopeatPicoVeleta,Spain,withsimultaneousobservations .o
u
oanfd121C2COO(J(J==12––01))––rreessttffrreeqquueennccyy121350..257318GGHHzz,,2121--aarrccsseeccbbeeaamm 3 OBSERVATIONAL RESULTS p.com
–withthereceiverstunedtotheredshiftedfrequenciescorrespond- The positions of the observed galaxies are shown in Fig. 1, and /m
n
ingtotheopticalvelocityofeachsource.Themainobservational detailsofalltheobservedspectraaretabulatedinTable4,together ra
s
parametersaresetoutinTable2.Wecheckedcalibrationagainst with definitions of the properties derived from measurements of /a
the CN (1–0) line in IRC+10216. The calibration was consistent the spectra. The central pointing CO (J = 1–0) and CO (J = 2– rtic
within 15–20 per cent with the intensities measured by Mauers- 1) spectra for each galaxy are shown in Figs 2 and 3. In these le-a
berger et al. (1989). After every two scans (∼15min) a chopper figures, the CO (J = 2–1) spectra have been scaled so that their bs
wheelcalibrationwascarriedout.Pointingwascheckedatbetween peak main beam temperature T is equal to the CO (J = 1–0) tra
mb c
1- and 2-h intervals using the broad-band continuum from Mars, maximum. The scaling factor to achieve this is shown at the top t/4
2
3caCte2s7a3n,a4vCera2g9e.4p5oianntdin4gCac0c1u.r2a8cy.Tofh∼eI2RaArcMsec3o0r-mbetwteerb.pTahgisevianlduie- ArigrehctibabooGvealaexacyhEsnpveicrotrnumme.nWtShuerrveeyth(eAreGiEsSa;nCHorItedseeteecttaiol.n2f0r0o8m) 9/1/2
2
is in good agreement with the differences in pointing corrections ortheNRAOVLAforthegalaxy,itsvelocityandvelocitywidth, 1
/1
thatwefoundbetweenconsecutivepointingmeasurements.Allob- W ,areindicatedwithabarbelowthesespectra(purple). 0
20 1
servationsweremadeinwobblerswitchingmodewithafrequency For eight of the spirals, CGCG 097−062, CGCG 097−068, 80
of0.5Hzandanon–offthrowof±220arcsecinazimuth.Forthe CGCG 097−072, CGCG 097−079, CGCG 097−092(S), 41
galaxywiththelargestopticalmajoraxis,CGCG097−129(W),the CGCG 097−102(N), CGCG 097−120 and CGCG 097−129(W), by
g
on–offthrowisestimatedtoleaveaseparationbetweentheouter samplemapsweremadewiththreetosixpointings.Theintensities u
e
eodffg-epoosfittihoenoopft∼ica5l5dkipscc.aTnhdeo1u-tearnedd4g-eMoHftzhbea2c.k6e-nmdmswbeeraemusinedthaet aarnedgpiovienntiinngcooflfusmetnssfo2rathneds3esopfiTraalbsl,ere3l.aAtivpepteontdhiexcAe,nFtriaglspAoi1n–tiAn8g,, st on
1
2.6and1.3mm,respectively.Thisgaveavelocityresolutionforthe showthespectraandpointingpositionsforthesespirals.Where,for 6
rawdataof∼2.6kms−1at2.6mmand∼5.2kms−1at1.3mm,but oneoftheemissionlines,thereweremorethanthreedetectionspro- No
v
forouranalysisthechannelswerebinnedtoavelocitywidthof10 jectedlinearlyacrossthespiral,wefittedaGaussiantotheintensity e
m
or20kms−1.Theweatherconditionsweregenerallyfairlygood distributionasafunctionofprojectedposition.TheGaussianfits b
e
withzenithopacityτ rangingfrom0.1to0.4at225GHz. forCGCG097−079andCGCG097−102(N)producedsignificant r 2
0
Alistoftheobservedgalaxiesandtheirbasiccharacteristicsis indicationsofasymmetricmoleculargasdistributions(Seesection 1
8
giveninTable3.AsingleCOobservationwasmadeattheoptical 4.4andAppendixA).
centre(centralpointing)ofeachofthe19observedgalaxies.Addi-
tionally,foreightofthegalaxieswhichhadinteractionsignatures,
e.g.disturbedmorphologiesatotherwavelengths,wetriedtodeter- 4 DISCUSSION
mine,withinthelimitsofsensitivityandpointingerrors,whether
theirCOdistributionwasasymmetricornot.Todothis,wemade Section4.1considerswhethertheobservedspiralsaredeficientin
maps with three to six pointings, typically with offsets along the molecular hydrogen, based on the CO (J = 1–0) intensities. The
opticalmajoraxis,instepsof11arcsec(halfthe2.6-mmbeam). H2 and HI deficiencies of the observed spirals are considered in
The data reduction was carried out with the CLASS software Section 4.2, while their SFRs relative to their H2 reservoirs are
package2.Allscanswerereviewedandthosewithpoorbaselines analysed in Section 4.3. In Section 4.4 we assess, for the subset
oftheobservedspiralswithmultiplepointings,whatevidencethe
pointingsprovideaboutthedistributionofthemoleculargasinthose
2http://www.iram.fr/IRAMFR/GILDAS spirals.
224 T.C.Scottetal.
Table3. Generalcharacteristicsoftheobservedgalaxies.
Galaxya RA(2000)b Dec.(2000)c Typed Velocitye Majoraxisf Minoraxis HTf VHIg W20h Statey EWj
(Hα+[NII])
CGCG (hms) (◦(cid:10)(cid:10)(cid:10)) (kms−1) ((cid:10)) ((cid:10)) (mag) (kms−1) (kms−1) (Å)
97−062 114214.55 195833.61 Pec 7815 1.01 0.40 12.95 7774 246 A 37
97−063 114215.70 200255.16 Pec 6102 0.58 0.34 13.56 6087 173 A 22
97−068 114224.48 200709.90 Sbc 5974 1.23 0.76 11.26 5979 353 B 41
97−072 114245.20 200156.60 Sa 6332 1.21 0.54 11.36 6338 307 B 9
97−076 114302.17 193859.87 Sb 6987 1.20 0.54 11.39 – D 1
97−079 114313.40 200017.00 Pec 7000 0.75 0.45 13.15 7073 238 A 129
97−078 114316.22 194456.18 Sa 7542 1.88 0.92 11.22 – – D –
97−082 114324.49 194459.95 Sa 6100 1.30 0.64 10.50 – – D – Do
97−092(S) 114358.20 201108.00 Sbc 6487 0.76 0.54 12.57 – – B 28 wn
97−091 114359.00 200437.00 Sa 7368 1.12 0.81 11.07 7372 273 B 23 loa
97−093 114401.77 194703.54 Pec 4909 0.96 0.39 12.90 – – D 9 de
9977−−111012((SN)) 111144442157..9210 220001630293..7900 ISrar 76433668 01..4058 00..3605 1121..7470 637–0 32–5 CC –2 d from
97−121 114447.06 200729.10 Sab 6571 1.20 0.83 10.64 6583 408 C 4 h
97−114 114447.80 194624.31 Pec 8293 0.54 0.49 13.19 – – – 36 ttp
s
97−120 114449.16 194742.14 Sa 5595 1.32 0.85 10.55 – – D 4 ://a
97−122 114452.23 192715.12 Pec 5468 0.47 0.47 11.74 5478 456 B 45 c
a
97−125 114454.85 194635.18 S0a 8271 0.84 0.59 11.53 8225 425 – 23 de
97−129(W) 114503.91 195825.51 Sb 5085 2.36 1.27 9.77 5091 494 C 14 m
ic
aIdentifier from the Zwicky catalogue. The letters in parenthesis indicate relative position of the pair member. The equivalents in the NED are .ou
CGCG097−092(S)=CGCG097−092(NED01),CGCG097−102(N)=CGCG097−102(NED02),CGCG097−111(S)=CGCG097−111(NED01)and p.c
CGCG097−129(W)=CGCG097−129(NED01). om
bFromNED. /m
cHubbletypefromGOLDMine(http://goldmine.mib.infn.it/;Gavazzietal.2003)orifunavailableNED. nra
dOpticalvelocityfromNED. s/a
efTOoptatilceaxltmraapjoolraatexdisHfr-obmanGdOmLagDnMituindeeofrroimfuGnaOvLaiDlaMblieneN.ED. rticle
gHIvelocityfromAGESwiththeexceptionofCGCG097−079whichisfromPaperI. -ab
hiEHvIovluetlioocniatyryrasntagtee,fWro2m0fPraopmerAIG. ESexceptforCGCG097−079whichistakenfromPaperI. strac
jEW(Hα+[NII])fromGOLDMine. t/42
9
/1
/2
2
4.1 H deficiency were essentially the same as those used by Haynes & Giovanelli 1
2 /1
WeaimtodeterminewhethertheobservedspiralsareH deficient (1984)tocalibrateHIdeficiencies. 01
o(1r9n9o7t).aAsspiral’sH2 deficiency(DefH2)isdefinedinBo2sellietal. toWcaelchualavteeuthseedexthpeecBtoedseHlli2emtaasl.s,(2(M00H22))er,elia.et.ion(theirequation8) 8041 b
log10(MH2)e=3.28+0.51log10(LH), (2) y gu
Def =log (M ) −log (M ) , (1) es
H2 10 H2 e 10 H2 o log (L )=11.36−0.4H +2log D, (3) t on
10 H T 10 1
wH2hemreas(sM.H2)e istheexpectedH2 massand(MH2)o istheobserved 2w0h0e0re),HDT==ditshtaengcaelainxyM’spctoatanldHM-banadndmLagnairteudeexp(rGesasveadzzini estolaalr. 6 Nov
ItiscriticalinderivingtheH2 deficiencyofaspiralthat(MH2)e units. H2 H em
iassdpeotsesrimblienefrdofmroimtscaugrarelanxtymcohleacrauclaterrcisotnictewnth,ibcuhtiissasstrionndgelpyecnodrerne-t Each spiral’s actual (MH2)o was determined from its observed ber 2
I(CO), which incorporates a luminosity-dependent X-factor from 0
latedtotheM containedinisolatedspiralsofsimilarHubbletype 1
H2 Bosellietal.(2002),andassumingthesourcewasunresolvedinthe 8
andsize.Usingasampleofopticallyselectednon-HI-deficientspi- CO(J=1–0)beam(seeAppendixB),i.e.
ralsandthestandardconversionfactor(alsoknownastheX-factor) (cid:2)
betweenI(CO)andH2,Bosellietal.(1997)determinedsuchare- M(H2)o=7950χcoD2 Si(cid:10)V, (4)
lationbetweenMH2 andLH(andalternativelywithlinearsize)with i
no significant residuals attributable to Hubble type. However, the (cid:2)
goodcorrelationbetweenaspiral’stotalLHanditsdynamicalmass Si(cid:10)V =I(CO)×G, (5)
(Gavazzi & Scodeggio 1996; Boselli et al. 2001) implies we are i
relyingonamorefundamentalrelationbetweenaspiral’s(M ) wherethecoefficient7950isderivedinAppendixB;
H2 e
anditsdynamicalmass.Subsequently,Bosellietal.(2002)modi- G(cid:3)=4.95JyK−1isthetelescopegainderivedinAppendixB;
fiedtherelationtodetermineM derivedfromanL -dependent S(cid:10)VisthefluxinJykms−1;
H2 H i i
conversion factor, again using an optically selected sample of HI χco = XCHO / XCO, where XCHO is the LH-dependent con-
non-deficient spirals (HI deficiency ≤0.3). Their sample galaxies version factor from table 5 in Boselli et al. (2002), i.e.
COinAbell1367 225
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Figure1. Positionsofbrightlate-typegalaxiesinthecentralregionofAbell1367fromPaperI.OurCOdetectionsplusCGCG097−073andCGCG097−087 16
fromBosellietal.(1994)areshownwithblackopensquares.Thecolourofthesymbol(redorblue)usedforeachspiralindicatesitsSDSSg−icolour:blue N
o
(≤1.1)andred(>1.1).AGESHIdetectionsaremarked(whitecircles).ThesymbolusedforeachspiralindicatesitsevolutionarystatefromPaperIasfollows: ve
A–asterisk,B–opencircle,C–filledcircleandD–opensquare.SpiralsthatbelongtoBIGaremarkedwithacrossandunclassifiedspiralswithadiamond. m
b
RofOTSaAbTleX.3-r.ayintensitiesfromarchivedata(yellowcontours)areoverlaidonanSDSSi-bandimage.Detailsforthegalaxyidentifiersaregiveninfootnotea er 20
1
8
log10(XCHO)=−0.38log10(LH) + 24.23 and XCO = 2.3 × impactoftemporaryinteraction-inducedenhancementsinLB and
1020moleculecm−2(Kkms−1)−1(Strongetal.1988); ofextinction.
DisthedistanceinMpc; In calculating (M ) we have assumed that the CO (J =
I(CO)istheCOintensityinKkms−1(T scale); 1–0) emission was uHn2reosolved in the 2.6-mm IRAM beam. CO
mb
H isthetotalH-bandmagnitudefromGalaxyOnlineDatabase emission from a spiral’s disc is generally understood to decline
T
MilanoNetwork(GOLDMine;Gavazzietal.2003). exponentially (Young et al. 1995; Leroy et al. 2009) with radius
Our calculations of (M ) and (M ) are both based on fromtheopticalcentre.Fromasampleofbarredandunbarredspi-
H2 e H2 o
H-band luminosity (L ), rather than L , in order to minimize the rals,Nishiyama,Nakai&Kuno(2001)foundameanscalelength
H B
226 T.C.Scottetal.
Table4. COobservations.
J=1–0 J=2–1
Galaxy (cid:10)RAa (cid:10)Dec.a rmsb I(CO)c,d Ve W20f rmsb I(CO)c,d Ve W20f
CGCG ((cid:10)(cid:10)) ((cid:10)(cid:10)) (mK) (Kkms−1) (kms−1) (kms−1) (mK) (Kkms−1) (kms−1) (kms−1)
97062 0 0 2.5 1.26±0.13 7832±42 224±84 5.6 2.28±0.28 7796±27 171±54
97062 −7.8 −7.8 2.8 0.54±0.14 7731±21 86±42 4.5 0.79±0.17 7807±53 192±106
97062 7.8 7.8 3.6 <0.38±0.14 – – 5.6 0.98±0.23 7879±13 99±21
97063 0 0 3.1 <0.43±0.16 – – 9.4 <1.37±0.48 – –
97068 0 0 3.8 13.72±0.25 5970±4 350±8 7.7 20.52±0.50 5976±12 297±24
97068 0 11 3.2 7.17±0.2 5959±19 329±38 6.9 3.77±0.45 5992±85 329±170
97068 0 −11 3.2 10.29±0.2 5986±3 318±6 8.4 9.9±0.53 5976±23 339±46
97068 0 −22 3.2 1.14±0.21 5965±81 318±162 10.5 <1.48±0.59 – – Do
97068 0 22 3.1 1.11±0.18 5991±67 329±134 6.6 <0.03±0.37 – – wn
97072 0 0 2.9 4.16±0.18 6317±26 287±52 6.0 4.51±0.37 6308±37 266±74 loa
97072 −8.9 6.5 3.6 3.65±0.23 6334±38 276±76 7.2 2.22±0.47 6345±52 234±104 de
9977007762 8.09 −6.05 22..10 12..6432±±00..1142 66929533±±3162 317539±±7224 65..22 11..7552±±00..4207 66829293±±2198 118318±±5386 d from
97079 0 0 3.0 1.29±0.15 6985±26 159±52 6.1 2.36±0.30 7008±42 202±84 h
97079 −7.8 7.8 2.6 1.31±0.13 7033±17 149±34 6.1 2.32±0.31 7029±51 202±102 ttp
s
9977007799 −−151.16 151.16 33..67 11..6366±±00..1188 77004343±±297 117409±±1584 56..85 10..2981±±00..2383 77009038±±538 22062±±1916 ://ac
a
97078 0 0 2.1 <0.30±0.12 – – 4.9 <0.70±0.28 – – de
97082 0 0 2.4 <0.34±0.14 – – 5.8 <0.81±0.32 – – m
97091 0 0 2.6 7.18±0.15 7385±12 267±24 4.1 12.51±0.22 7381±26 235±52 ic.o
97092(S) 0 0 3.8 3.37±0.19 6472±5 159±10 6.7 5.71±0.33 6473±7 159±14 up
97092(S) 0 −11 2.8 2.1±0.12 6493±2 117±4 7.4 1.54±0.31 6495±5 74±10 .co
97092(S) 0 11 3.3 2.06±0.15 6483±12 138±24 6.3 1.78±0.29 6452±14 117±28 m/m
97092(S) 11 0 4.4 1.65±0.2 6493±32 159±64 7.0 <0.98±0.39 – – n
97092(S) −11 0 4.0 2.38±0.19 6472±8 159±16 7.6 2.72±0.35 6473±43 159±86 ra
s
97092(S) 0 22 4.6 0.99±0.21 6430±14 74±28 11.4 <1.61±0.64 – – /a
97093 0 0 2.5 1.35±0.15 4873±28 201±56 6.4 2.3±0.33 4895±41 201±82 rtic
97102(N) 0 0 2.8 2.35±0.18 6369±53 297±106 7.0 2.62±0.43 6381±78 276±156 le-a
97102(N) 7.2 −8.3 4.6 1.72±0.26 6491±9 95±18 10.5 <1.48±0.59 – – bs
97102(N) −7.2 8.3 3.3 2.61±0.21 6369±42 297±84 7.3 2.31±0.45 6391±53 255±106 tra
97111(S) 0 0 2.5 <0.35±0.14 – – 7.3 <1.0±0.40 – – ct/4
97114 0 0 3.4 1.94±0.16 8481±15 139±30 6.3 4.29±0.29 8461±8 139±16 2
9
97120 0 0 3.2 8.66±0.22 5622±23 413±46 4.7 11.32±0.32 5571±25 308±50 /1
97120 −6.8 −8.7 5.6 7.69±0.38 5633±32 392±64 10.7 4.38±0.56 5762±23 138±46 /22
97120 6.8 8.7 5.5 6.9±0.38 5495±15 159±30 10.3 5.87±0.71 5454±9 75±18 1/1
97120 9.2 11.8 9.1 5.24±0.63 5464±15 96±30 15.9 <2.24±0.90 – − 01
97121 0 0 2.4 1.58±0.17 6572±77 383±154 4.4 2.19±0.30 6584±96 404±196 80
4
97122 0 0 3.1 6.67±0.21 5522±19 360±38 4.7 9.67±0.30 5502±11 233±22 1
97125 0 0 2.1 2.85±0.16 8224±72 481±144 4.8 5.92±0.36 8236±70 502±140 by
97129(W) 0 0 3.9 4.05±0.3 5134±89 412±178 8.7 1.97±0.57 5108±143 381±286 gu
97129(W) −2.3 −10.8 3.7 2.74±0.27 5044±77 380±154 8.1 2.17±0.46 5098±120 402±240 es
97129(W) 2.3 10.8 4.5 3.13±0.36 5155±110 455±220 7.5 2.9±0.38 5172±54 254±108 t on
1
aPointingoffsetfromthegalaxycentreinarcsec. 6
brmsnoise;(cid:3)channelwidth(δVCO)was10.6kms−1. No
cI(CO)= Ti (cid:10)V withthesummationcarriedoutacrossavelocitywindowdeterminedfromtherangeofvelocitiesoverwhichemissionwasobserved. ve
i mb m
Fornon-detectionswegiveupperlimitsbasedon2.5timesthermswithinthevelocitywindow[i.e.δI(CO);seebelow]. b
dδI(CO)=σ(cid:10)VN1/2,whereδVCO =channelvelocitywidth–10kms−1,σ=rmsbrightnesstemperature(inchannelsofδVCOwidth)andN=numberof er 2
channelswithinthevelocitywindow. 0
eV=themeanofthelowerandupperW20velocitylimitsfromthespectrumsmoothedto20kms−1.Theuncertainty,σ(V)=(W20−W50)(S/N)−1isbased 18
onSchneideretal.(1990),exceptwhereW20=W50inwhichcaseσ(V)=(2×δVCO)(S/N)−1.W20andW50arethelinewidthsat20and50percentof
thepeakintensity.TheS/Nisdefinedasthespectrum’speakfluxoverthermsnoise.Inthecaseofmarginaldetections(S/N∼2.5–3)themeanvelocitywas
determinedfromthemeanofasingleGaussianfittotheemissionwithinthevelocitywindow.Theuncertaintythenistakenasthe1σ uncertaintyofthefit.
fW20asdefinedintablefootnoteewithW20uncertainty=2σ(V),theexceptionbeingthemarginaldetectionswherethevelocitywidthanduncertainties
aretheFWHManditsuncertaintyfromtheGaussianfitreferredtointablefootnotee.
r (CO)/r =0.22±0.12(r =2.5±1.6kpc).TheFiveCollege spiralshaveanopticalmajoraxisdiameterof∼60arcsec(24.8kpc),
e 25 e
RadioAstronomyObservatory(FCRAO)surveyfoundadeclineto implyingCOisophotalradiiof∼6.2kpc,ordiametersof∼12.4kpc,
1 K km s−1 (CO isophotal radius) at ∼52 per cent of the optical i.e.somewhatlargerthantheIRAM30-mbeamat2.6mmof22arc-
radius based on D (Young et al. 1995). Typically, our observed sec(9kpc).10ofthespiralsofoursamplehavebeenpreviously
25
COinAbell1367 227
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Figure2. CO(J=1–0)(black)andCO(J=2–1)(red)spectraatthepositionoftheopticalcentreofeachgalaxy.δVCO=10kms−1,exceptCGCG097−063,
CGCG097−076,CGCG097−078,CGCG097−082andCGCG097−092(S)whereitis20kms−1.TheCO(J=2–1)spectraarescaledsothattheCO(J=
2–1)TmbmaximumhasthesamevalueastheCO(J=1–0)maximum;thescalingfactorisshownatthetoprightabovethespectrum.Theverticalscaleis
TmbinKandthehorizontalscaleisthevelocityinkms−1.WherethereisanHIdetection(AGESorVLAPaperI)forthegalaxy,itscentralvelocityandW20
velocitywidthisshownbelowthespectra(purple).
228 T.C.Scottetal.
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Figure3. CO(J=1–0)(black)andCO(J=2–1)(red)spectraatthepositionoftheopticalcentreofeachgalaxy.δVCO=10kms−1,exceptCGCG097−102(N),
CGCG097−111(S)andCGCG097−129(W)whereitis20kms−1.FurtherdetailsforthesespectraaregiveninthecaptiontoFig.2.
COinAbell1367 229
Table5. H2deficienciesfromCO(J=1–0)andSFRs.
HI H2
Galaxya ExpectedMb Defc ExpectedM ObservedMd I(CO)e Deff SFRg H2depletionh
time-scale
CGCG (×109M(cid:6)) (×109M(cid:6)) (×109M(cid:6)) (Kkms−1) (M(cid:6)yr−1) (Gyr)
97062 3.93 0.35 0.27 0.47 1.26 −0.22 0.32 1.48
97063 1.50 0.01 0.20 ≤0.20 ≤0.43 ≥0.01 0.16 1.23
97068 4.48 -0.28 0.60 2.87 13.72 −0.68 1.35 2.13
97072 3.22 0.55 0.57 0.90 4.16 −0.20 0.23 3.84
97076 4.59 ≥0.88 0.56 0.36 1.63 0.20 0.02 15.94
97078 5.44 ≥0.96 0.61 ≤0.06 ≤0.30 ≥0.99 – –
97079 2.34 0.25 0.25 1.07 2.65 −0.64 1.06 1.01 Do
97082 3.51 ≥0.77 0.86 ≤0.05 ≤0.34 ≥1.20 – – wn
97091 2.94 −0.23 0.66 1.40 7.18 −0.33 0.59 2.39 loa
97092(S) 2.49 0.62 0.32 1.11 3.37 −0.54 0.21 5.22 de
9977100923(N) 32..8519 ≥00..4718 00..5268 00..5520 21..3355 −00..2064 00..1056 38..4737 d from
97111(S) 0.96 ≥0.21 0.29 ≤0.12 ≤0.35 ≥0.38 – – h
97114 1.32 ≥0.34 0.24 0.80 1.94 −0.52 0.28 2.86 ttp
s
97120 3.57 ≥0.78 0.84 1.41 8.66 −0.23 0.27 5.25 ://a
97121 3.19 0.38 0.8 0.27 1.58 0.48 0.20 1.30 c
a
97122 7.36 0.47 0.48 1.65 6.67 −0.54 1.08 1.52 de
97125 2.09 ≥−0.14 0.53 0.65 2.85 −0.09 0.43 1.54 m
97129(W) 10.7 −0.07 1.21 0.98 4.05 0.09 1.58 0.61 ic.o
97073* 2.39 0.02 0.24 0.94 2.30 −0.59 1.08 0.87 up
97087* 12.89 0.39 0.67 2.03 11.7 −0.48 3.67 0.55 .co
m
aTheCGCG097−073andCGCG097−087I(CO)dataarefromBosellietal.(1994)andmarkedinthetablewithanasterisk. /m
bFromPaperI. nra
cFromPaperI. s/a
dBoMseHl2liisetdaelr.iv(1e9d9f7ro).mThoeurIRIRAAMM-dCeOriv(eJd=m1a–ss0)foerxCceGpCtfGor0C9G7−C1G290W97−is102.94W8×w1h0i9chMi(cid:6)sd.erivedfromtheKittPeak12-mobservationsby rticle
eTheI(CO)Tmb forCGCG097−079isthesumoftheCO(J=1–0)fluxfromthecentralpointingplusthatfromthe[−15.6,15.6] -ab
pfoorinCtiGnCg,Gw0h9ic7h−w08as7itnhceluflduexdibsetchaeussuemthoefflfluuxxietsdferotemctethdeli[e−s2b1e,y2o1n]danthdecFeWntrHalMpooifntthinegCsOfro(mJ=Bo1s–e0ll)iceetnatlr.a(l1p9o9i4n)ti.nTghbeeCamO.(SJim=il1a–r0ly) strac
detectionforCGCG097−063wasmarginalandtherewerenodetectionsforCGCG097−078,CGCG097−082andCGCG097−111(S), t/4
2
sothevaluesgivenareupperlimits(seeSection4.1). 9
ofguSsbDeFsedeRfrtHvo=2atciiasoSlnFdcsueRrlb(aiHyvteeαBdD)ofesurfeosHlmiln2i.geotutharleI.R(m1Ae9Mt9h7oC)d.OTfrh(oJemI=RBA1o–Ms0e)-lldoiebersitveaervld.aD(ti2oe0nf0Hs22e).xfocCreopCrtrGefocCrtGioCnG0s9C7(dG−e1p02e9n97dW−e1ni2ts9o0Wn.4m.wSoheriepchhSoeilscotdgioeicnriav4le.t1dypfforeor)mdwetethareeilsKmoiatftdtPeheefaomkre1[tN2h-oImId] /1/221/1018
0
contaminationandinternalextinctionasperBosellietal.(2001).Noadjustmenthasbeenmadeforgasrecyclingastheappropriaterate 4
1
touseinthecentralclusterenvironmentisunknownanditisthoughtanyexpelledgasreturningtoagalaxywouldbeunlikelytoremain b
y
molecular. g
ohbMseHr2v/aStiFoRn(sHbαy)B.MosHe2lliisedtearli.v(e1d99fr7o)m.TohuerMIRHA2M/SFCRO(H(Jα=)fo1r–0C)GeCxcGep0t9f7o−rC12G9CWGd0e9r7iv−ed12u9sWingwhheicIhRiAsMderCivOed(Jfr=om1–th0e)KobitstePrveaatkio1n2s-mis uest o
0.3Gyr. n 1
6
N
o
observedinCO(J=1–0)withtheNRAOKittPeak12-mtelescope this being by far the largest observed spiral (D25 =2.3 arcmin), vem
whichhasa55-arcsecbeambyBosellietal.(1997)whichmeans nearlytwicetheopticalsizeofthenextlargestobservedspiral(see b
e
thatwecanchecktowhatextentwemightbeunderestimatingtheir Table 3). CGCG 097−129W shows evidence that its CO is dis- r 2
COflux(seeAppendixC).ThisanalysisconfirmsthattheCO(J= tributedacrossalargefractionofitsopticaldisc(seeAppendixC). 01
1–0)emissionfillsasubstantialfractionoftheIRAM30-mbeam Forthisreasonthe(M ) showninTable5forCGCG097−129W 8
H2 o
and,inthosecaseswhereweonlyhaveasinglepointingmightbe hasbeenderivedfromtheKittPeakCO(J=1–0)fluxratherthe
systematicallyunderestimatingtheirCOfluxbyupto30percent. IRAM30-mCO(J=1–0)flux.
Forsometargets,inparticularthelargestones,wemightbeoffby
uptoafactorof2.
4.2 H content–results
WhereCO(J=1–0)emissionextendsbeyondthe(22arcsec) 2
full width at half-maximum (FWHM) of the IRAM 30-m beam TheH2deficienciesforoursample,determinedfromourCO(J=
at the central pointing position (large or extended objects), the 1–0) pointings (in most cases from the central pointings alone),
(M ) mass shown in Table 5 is a lower limit. In the case of andforCGCG097−129WfromtheKittPeakpointing,aregiven
H2 o
cClGudCeGem09is7s−io0n8d7eatencdteCdGbCeyGon0d97th−e027.96,-mthme(cMenHt2r)aolcpaolicnutliantgiobnesaimn-, itnecTtiaobnlsei5n.oTuhresmameapnleaannddsCtaGndCaGrd0d9e7v−ia0ti7o3nainndDCeGfHC2,Gfo0r9t7h−e0d8e7-
i.e.frommultiplepointings.CGCG097−129Wisaspecialcase, from Boselli et al. (1994) [excluding spirals in the blue infalling
230 T.C.Scottetal.
Fig.5comparesDef andDef foreachoftheobservedspirals
H2 HI
withsymbolsindicatingtheirevolutionarystatefromPaperI(Table
6).WeusedtheestimatesofnaturalvariationinDef (±0.3dex
HI
fromPaperI)andDef (±0.4dex),indicatedbydashedvertical
H2
lines and horizontal lines, respectively in Fig. 5, to identify the
following classes of spirals, defined in Table 7: HI deficient, H2
deficientandgasdeficient,i.e.spiralswithbothanHIandH2defi-
ciency.WheninterpretingthedeficienciesinFig.5,itisimportant
tonotethatthevalueofthedeficiencyissubjecttomeasurement
errors (e.g. beam filling factor, CO to H conversion and obser-
2
vationalerrorsinthereferencesample).Anadditionaluncertainty
inassessinganindividualdeficiencyarisesfromthelargenatural
D
variationinHIandH2contentofspiralsofthesamemorphological ow
typeinthereferencefieldsample.ThismeansthatthefurtheranHI nlo
orH2deficiencyvalueisfromthedeficiency/excessthreshold(mea- ad
e
surementandnaturalvariation),delineatedbythedashedrectangle d
inthefigure,themoreconfidentwecanbethatitistrulydeficient. fro
m
Thisisthecaseirrespectiveofwhetherthedeficiencyisdetermined h
basedonadetectionoralowerlimitfromanon-detection.Kendall’s ttp
s
τ correlationcoefficient,takingintoaccountthefactthatbothdefi- ://a
cienciescontaincensoreddata,forH2andHIdeficienciesis0.064, ca
d
indicatingH2 andHIdeficienciesarenotcorrelated.However,in- em
terestinglythesametestforcorrelationbetweenH2deficiencyand ic
evolutionary type has a Kendall’s τ of 0.27 which would reject .ou
p
thenullhypothesisofnocorrelationatthe10percentlevel.The .c
o
FanigduCreGC4.GH0297d−efi0c7i3enicnieesacfohretvhoeluotbiosnearvryedstsapteir,ailnscpluludsinCgGnConG-d0e9te7c−ti0o8n7s cgo−rreilactoiolonubreatnwdeeDneHfH2I)deafincdielancckyaonfdcoervroelluattiioonnawryitthypDee(fbHaIsaerdgoune m/mn
butexcludingspiralsintheBIG.Thehorizontalthickerblacklinewithin for a connection between H2 deficiency and a process connected ras
eeadcghesboofxtshheogwresythbeomxeesdiinadnicHa2tidnegfitchieeunpcypefroranthdelostwateer,qwuiathrtiulepsp.eTrhaendenlodwsoerf wanidthacgoalionusrtdeviroelcuttiroenm(opvoaslsoibflmyaolbeucrusltaorfgeanshbayncraemd-sptarersfsourrmeasttiroinp)- /artic
le
theverticallinesshowtheupperandlowerrange(inclusiveoflowerlimits) ping.However,almostallofthepointsinFig.5areonorbelow -a
ofH2deficiencyforspiralsineachevolutionarystate. tthhee eonnvei-rtoon-omneenctothrraenlaHtioIn.,WchoantfiervmerintghethpahtyHsi2cailsmleescshaafnfiescmte,dthbiys bstrac
group (BIG); Cortese et al. 2006 is −0.26 ± 0.35. 32 per cent supports a scenario in which the H is more tightly bound to the t/4
2 2
of the observed spirals have H2 excesses (negative deficiencies) galaxyandlessaffectedbyexternalmechanisms. 9/1
<−0.2comparedto17percentintheBosellietal.(1997)sam- Thecalculationof(MH2)o issensitivetodistanceerrors,butas /22
pleofisolatedgalaxies(theirfig.7).EvenlargerH excesseshave thedistancealsoentersthecalculationof(M ) viaL (equation 1
2 H2 e H /1
beenreportedinspiralsofasampleoflessevolvedHicksonCom- 2), Def is much less sensitive to errors in D. Furthermore, by 0
pactGroups(Martinez-Badenesetal.2012)whichwascalibrated adoptingH2the same conversion factor (X-factor) between CO (J = 180
4
to a different isolated galaxy sample [Analysis of the interstel- 1–0)andM whendeterminingboth(M ) and(M ) ,itmeans 1
H2 H2 e H2 o b
larMediumofIsolatedGAlaxies(AMIGA);Lisenfeldetal.2011]. thatuncertaintiesattributabletotheconversionfactoraretoagreat y
g
Furtherobservationsarerequired,mappingthefullextentoftheCO extentcancelledout.Theratiobetweentheluminosity-dependent u
e
distribution,todeterminetowhatextenttheseapparentsurplusesin and the standard, 2.3 × 1020moleculecm−2 (K km s−1)−1 (Polk st o
boththeMartinez–Badenesandourownsamplesaregenuine,for etal.1988;Strongetal.1988),X-factorsfortheobservedgalaxies n
1
exampleduetotheobjectsbeingperturbedandasaresultofthisthe rangesfrom0.35to1.32. 6
N
balanceintheISMbeingskewedtotheformationofH2,orifthey NotableresultsregardingtheirH2 content,includingsignificant ov
fallwithintherangeofuncertaintythatistypicalindeterminingH2 differenceswithpreviousresults,arethefollowing. em
deficiencies. be
Fig.4showsboxplotsoftheH2deficienciesorlowerlimitsfor (i) CGCG 097−082 was not detected in CO at either 2.6 or r 20
the observed spirals plus CGCG 097−073 and CGCG 097−087 1.3mm,givinganupperH masslimitof4×107 M(cid:6).However, 1
2 8
in each of the four evolutionary states from Paper I and defined Bosellietal.(1997)reportedanindicativeH massof4.8×108
2
in terms of HI deficiency and SDSS g − i colour (Table 1). De- M(cid:6)andavelocityof6057kms−1usingtheNRAOKittPeak12m.
spitetheuncertaintiesabouttheabsoluteH deficiencies,whichare WehaveconfirmedourpointingpositionwithNASA/IPACExtra-
2
discussedfurtherinAppendixC,Fig.4showsaclearrelativedif- galactic Database (NED) and GOLDMine and our observations
ferenceinthedistributionofH deficienciesbetweenspiralsinless werecentredattheopticalvelocityof6100kms−1.Toexplainthe
2
evolvedevolutionarystates,AandB,andthosewithmoreadvanced discrepancyintermsofapointingerroritwouldrequireapointing
evolutionarystates,CandD.Thisrelativedifferenceisreflectedin error5–6timesgreaterthanourestimatedpointinguncertaintyof
the mean deficiencies for the galaxies in each evolutionary state 2arcsec.Whilewebelieveourresultstobecorrect,anindependent
shown in Table 6 as well as the log rank (Mantel–Haenszel) test observationisrequiredtosettletheissue.
forsamplescontainingcensoreddata(non-detections),whichgives (ii) TheH massderivedfromtheCO(J=1–0)centralpointing
2
a probability of the AB and CD samples coming from the same CGCG097−129WKittPeak12mis0.98×109,nearlydoublethat
populationofonly0.04percent(pvalue=0.0004). derived from the CO (J = 1–0) central pointing with the IRAM