Determining an accurate position for a submm galaxy (SMG) is the crucial step that enables us to move from the basic properties of an SMG sample - source counts and 2-D clustering - to an assessment of their detailed, multi-wavelength properties, their con

Identi cationofsubmillimetregalaxiesintheSHADESSourceCatalogue

7

Table3.Mid-IRpropertiesofSMGsintheLHSHADESSourceCatalogue.

Nickname

Positionat24µmIDa

S24µmOffPb

αJ2000δJ2000

/µJy-set

hms ′′′

′′

LOCK850.01105201.30+572446.11934217±163.200.024LOCK850.02105257.07+572102.919460545±313.510.010LOCK850.03

105238.66+572443.71745173.7±21.37.900.196105238.31+572439.520054183±333.000.026105238.31+572434.820603175±231.810.012LOCK850.04

105204.21+572655.615970261±733.270.020105204.04+572658.315971179±681.190.006105203.67+572707.037071,104±33(9.10)(0.026)LOCK850.05105302.86+571823.91192158.6±15.13.640.107LOCK850.06

105204.12+572525.81192275.1±12.70.550.005105203.51+572517.117409379±18(10.5)(0.107)105205.19+572522.920753540±48(9.22)(0.060)LOCK850.07105300.97+572552.25670341±214.050.021LOCK850.08105153.69+571834.91811481±255.050.021LOCK850.09105215.73+572501.713577159±733.760.043105215.65+572504.513578466±743.560.012LOCK850.10105247.39+573257.91608865.9±11.1(9.82)(0.429)105248.27+573251.01760479.6±10.8(8.05)(0.313)LOCK850.11

105129.16+572406.88740112±573.390.053105129.39+572410.38741177±515.220.063105129.81+572416.38742111±17(11.3)(0.349)LOCK850.12105227.60+572512.43757263±190.690.001LOCK850.13105131.45+573129.111931240±17(9.09)(0.137)105131.77+573141.211932172±147.880.110LOCK850.14105230.72+572209.45560188±167.880.102105229.06+572221.85563103±13(10.5)(0.343)LOCK850.15105319.26+572108.33834353±202.390.009105318.99+572115.6383670.4±12.15.240.141LOCK850.16105151.67+572636.03626314±242.020.008LOCK850.17105158.48+571801.21338764.2±26.11.900.040105157.96+571759.917315239±182.520.015LOCK850.18105229.06+572221.85563103±13(11.8)(0.381)LOCK850.19

105236.09+573119.613661118±153.120.045105235.52+573111.717536242±197.510.076105235.06+573123.717539221±367.000.075LOCK850.21105256.79+573037.9283297.9±14.10.570.004105257.80+573035.32833124±18(8.07)(0.218)LOCK850.22105137.09+573316.92895402±217.410.045105136.68+573332.82896377±20(11.8)(0.127)LOCK850.23105212.83+573200.52722116±17(9.70)(0.288)105214.71+573154.71751657.3±11.37.860.213LOCK850.24105200.45+572039.71842455±212.450.007LOCK850.26105241.13+572319.823975.9±12.77.920.193105240.66+572309.75601195±163.290.029LOCK850.27105203.45+571819.31984106±155.930.117105204.77+571805.91986196±13(12.3)(0.247)LOCK850.28105257.69+573058.613901252±14(10.2)(0.154)LOCK850.29105131.65+572040.818689111±147.630.149LOCK850.30105207.68+571904.12004233±192.630.016LOCK850.31105215.96+571619.23434467±192.060.005LOCK850.33105155.40+572312.91917104±144.790.091LOCK850.34

105213.66+573321.3293293.5±12.06.960.153105214.21+573327.9293384.9±16.75.700.134105213.97+573332.82934128±195.990.101LOCK850.35

105246.46+572056.815351.0±12.73.720.124105245.94+572051.415952161±14(9.26)(0.206)105246.42+572106.615953110±38(11.1)(0.346)105246.91+572106.115954108±34(9.85)(0.309)105247.94

+572101.3

1955575.0±11.4(9.71)(0.393)LOCK850.36———5σ<60——LOCK850.37105124.60+572331.01870250±175.420.047105124.27+572341.417334126±166.640.116LOCK850.38105307.06

+572431.6

5682260±160.410.001LOCK850.39———5σ<60——LOCK850.40105201.54+571915.9199491.9±15.03.840.077105203.07+571923.5199785.2±14.0(11.5)(0.422)LOCK850.41

105200.24+572421.513508475±373.710.013105159.81+572425.113509651±461.560.002105159.27+572413.317394108±15(11.4)(0.358)105200.19+572415.317395212±22(8.72)(0.147)LOCK850.43105256.64+572351.45780261±244.300.031105256.61+572358.05781456±357.660.042LOCK850.47

105234.85

+572504.6

17453107±16(11.3)(0.359)

a)UsedtoidentifysourcesinFig.A1.

b)Pwascalculatedusingasearchradiusof8arcsec.Forpossiblecounterpartswith8–15-arcsecoffsets,Pwascalculatedusingasearchradiusof15arcsec—thesevaluesarelistedinparentheses.Reliableidenti cations(P 0.05)within8arcsecarelistedinbold.

c0000RAS,MNRAS000,000–000Table3.Cont...

Nickname

Positionat24µmID

S24µmOffP

αJ2000δJ2000

/µJy

-set

hms ′′′

′′

LOCK850.48105256.03+573242.318826203±173.900.035105255.37+573246.52010585.2±13.77.030.165LOCK850.52105246.16+573120.218804561±865.360.019105245.76+573120.620079310±352.280.009LOCK850.53105240.29+571924.413519168±154.330.050LOCK850.60

105143.50+572435.81941150±15(10.2)(0.247)105143.90+572443.61351287.8±12.03.490.070105143.08+572452.21351382.5±13.47.440.176105143.81+572454.913514109±15(9.12)(0.282)LOCK850.63

105153.43+572506.2192553.0±13.04.010.130105154.27+572502.71931236±173.780.029105155.24+572459.3193279.1±12.0(12.2)(0.461)LOCK850.64

105251.67+573248.7274088.5±12.56.560.150105252.57+573248.9274153.1±11.8(9.06)(0.454)105252.32+573233.012103425±25(10.1)(0.089)LOCK850.66105139.57+572027.11336571.2±12.1(12.2)(0.484)LOCK850.67105208.07+572348.02044102±14(10.4)(0.340)105208.87+572356.32045108±141.560.017LOCK850.70105147.88+573044.62571106±125.530.108LOCK850.71105219.10+571857.33487181±207.570.100105219.53+571904.8348854.3±16.07.460.212LOCK850.73105141.92+572218.61855278±192.320.011LOCK850.75

105315.19+572645.95713147±175.960.089105315.02+572653.25714150±16(10.7)(0.260)105315.52+572637.116059262±18(8.99)(0.124)LOCK850.76105149.12+572840.12512592±265.070.016LOCK850.77

105156.99+572208.4360251.7±13.11.670.042105157.57+572213.43603154±155.660.080105156.23+572212.3360855.4±13.56.650.199LOCK850.78105143.93+571744.9173485.6±14.7(13.0)(0.462)LOCK850.79105151.22+572127.8188492.8±13.17.160.158105152.63+572124.41892292±185.200.037LOCK850.81105231.52+571751.6173533,667±51(9.59)(0.007)LOCK850.83105307.17+572840.02815344±256.260.041LOCK850.87105153.36+571730.51975399±222.920.011LOCK850.100

105138.76

+571504.7

1623118±135.650.101

thelimitwherecentroidinguncertaintydominatesoversystematicastrometryerrorsandforuncorrelatedGaussiannoise.Here, αand δarether.m.s.errorsinR.A.andDec.,respectively,θistheFWHMofthesubmmbeamandSNRisthesignal-to-noiseratioaftercorrectionfor uxboosting(seeAppendixBforderivations).

Wecanuseourradioassociations,whichshouldprovidenear-perfectpositions,tocheckwhethertheuncertaintiesinsubmmpo-sitionareconsistentwiththistheoreticalexpectation,giventhesizeoftheJCMT’sbeamandtheSNRofthe850-µmsources.

ForaGaussiandistributionofdistributionofradialoffsets(re r2errorsinR.A.andDec.,the

/2σ2

)peaksatσ(= α= δ).Thispeakboundsonly39.3percentofsources,with68percentoftheanticipatedradial√offsetslyingwithin1.51σ(closeto,butnotpreciselyequalto

α2+δ2.ThevalueofσobservedinFig.

2isapproximately3arcsecsoouradoptedsearchradiusof8arcsec(§3)correspondsto～2.5σandshouldthusinclude～95percentofallgenuinera-dioidenti cations;moreover,sincethetypicaldeboostedSNRofthesubmmsourcesis～3(Coppinetal.2006),thetheoreticalex-pectationisalsoσ～3arcsec(fromequation2ofAppendixBforθ=14.5arcsecandSNR=3).Itisclear,therefore,thattheob-serveddistributionofradialoffsetsfortheradioidenti cationsisatleastcomparablewiththeoreticalexpectations.