I. NGC 2623

26 Pages·2004·1.16 MB·English

Mon.Not.R.Astron.Soc.348,369–394(2004) doi:10.1111/j.1365-2966.2004.07319.x
Infrared mergers and infrared quasi-stellar objects with galactic
winds – I. NGC 2623: nuclear outflow in a proto-elliptical candidate
(cid:3)
S. L´ıpari,1,2 E. Mediavilla,3,2 R. J. D´ıaz,4 B. Garc´ıa-Lorenzo,5,2 J. Acosta-Pulido,3
M. P. Agu¨ero4 and R. Terlevich6
1Co´rdobaObservatoryandCONICET,Laprida854,5000Co´rdoba,Argentina
2VisitingastronomeratEuropeanNorthernObservatory,LaPalma,Spain
3InstitutodeAstrofisicadeCanarias,38205LaLaguna,Tenerife,Spain
4Co´rdobaObservatoryandSeCyT,UniversidadNacionaldeCo´rdoba,Argentina D
5IsaacNewtonGroupofTelescopes,AC321,38700S/C,LaPalma,Spain ow
6InstituteofAstronomy,MadingleyRoad,CambridgeCB30HA nlo
a
d
e
d
Accepted2003October17.Received2003September19;inoriginalform2003March17 fro
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ABSTRACT ://a
c
Wepresentthefirstresultsofastudyofthemorphology,kinematicsandionizationstructure a
d
e
ofinfrared(IR)mergers/quasi-stellarobjects(QSOs)withgalacticwinds.Thisstudyisbased m
ic
mainlyonINTEGRALtwo-dimensional(2D)fibrespectroscopy[obtainedonthe4.2-mWilliam .o
u
HerschelTelescope(WHT),LaPalma]combinedwithhigh-resolutionHubbleSpaceTelescope p
.c
(HST)observations. om
Clearevidenceofoutflow(OF)fromthenucleusoftheluminousinfraredmergerNGC2623 /m
n
isreported.Specifically:(i)theINTEGRAL2DHα,[NII]and[SII]emissionlinemapsdepict ras
1a0c0o◦n±e-s5h◦aapneddreexatcehnidnegdandeibsutalanctehaotfe∼m3e.r2gkepscfrforommththeennuuccleleuuss,;w(iiit)hinasnidaeptehretunreebaunlgalaenθdi=n /article
thecentralregion,alltheemission-lineWHTspectrashowlowvelocityblue/OFcomponents, -ab
s
with (cid:6)VOF(cid:7) =(−405 ± 35) km s−1; and (iii) in the OF nebula, the emission line ratios are tra
c
consistent with ionization by a dusty nuclear starburst plus shock heating. These results are t/3
4
consistentwithagalacticwindprocesspoweredmainlybyanuclearstarburst. 8
/2
The INTEGRAL 2D Hα and [N II] λ6583 velocity field (VF) maps for the main body of /36
NGC2623(16.4×12.3arcsec2;∼5.9×4.4kpc2)showoutflowmotioninthenuclearand 9/9
theHα+[NII]nebularregionssuperposedonageneralcircularmotion.Thiscircularmotion 840
prevails inside r ∼ 1.5 kpc, and for larger radii we detected non-circular motions. In the 00
b
centralregion,theaverageobservedrotationcurvewasfittedwithamodelcorrespondingto y
g
a single-component Plummer spherical potential. After the subtraction of the Plummer and ue
s
anaxisymmetricpolynomialmodel,theresiduesoftheVFinbothcasesindicateejectionas t o
n
theoriginoftheconenebula.ThefittedPlummermodelimpliesatotalmassofMT =1.5× 07
1010M(cid:11)andasphericaldistributionofmatterinthecentralregion. A
p
Thehigh-resolutionHSTWFPC2F555W(∼V)andF814W(∼I)broad-bandimagesdisplay ril 2
astronglyobscurednucleusintheapexofasmallnuclearcone,anasymmetricalclumpyspiral 01
9
arm located to the east of the nucleus, a ring plus an arc to the west and several large-scale
filaments of dust. A good r1/4-law fit to the HST WFPC2 I band luminosity profile was
found.
In 85 per cent of the INTEGRAL 2D field we measure very high values (>1) of the [N II]
λ6583/Hαand[SII]λ6717+31/Hαratios,suggestingthatshocksareimportantonlargescales
(inalmostallthemainbody).Furthermore,the2DfullwidthathalfmaximumFWHM–[NII]
andVFresidualmapsshowagoodspatialcorrelation,suggestingthattheOFshocksionize
thegasandbroadentheemissionlines.However,closetothenucleus,theOFnebulashows
(cid:3)
E-mail:[email protected]
(cid:12)C 2004RAS
370 S.L´ıparietal.
low values of the [N II]λ6583/Hα ratio (in the range 0.1–0.4), indicating that photoioniza-
tion by a dusty nuclear starburst also plays a significant role in the excitation of the nebula.
ThecharacteristicsofthenucleusofNGC2623couldbeassociatedwithastarburst-related
LINER.
ThepropertiesfoundinIRmergers/QSOswithgalacticwindsmainlyunderlinetheimpor-
tanceofstudyingthepossiblelinkbetweenIRmergerswithstarburst+galacticwind→IR
QSOswithcompositenature+galacticwind,andellipticalgalaxies.
Keywords:ISM:bubbles–galaxies:individual:NGC2623–galaxies:interactions–galaxies:
kinematicsanddynamics–quasars:general–galaxies:starburst.
D
o
w
(LIR(cid:1)1013L(cid:11)),whicharestrongcandidatesforprimaevalgalaxies nlo
a
intheprocessofamajorepisodeofstarformation(Rowan-Robinson d
1 INTRODUCTION e
2000). d
Infrared(IR)mergersofdiscgalaxiesshowhighgasdensitiesplus These results strongly suggest that it is important to make a fro
m
starburstandactivegalacticnuclei(AGNs)characteristicsintheir detailed study of possible links among mergers, ULIRGs, QSOs h
nuclearregions(Joseph&Wright1985;Riekeetal.1985;Sanders and elliptical galaxies (Toomre & Toomre 1972; Larson 1974; ttp
s
etal.1988a;Scoville&Soifer1991;L´ıpari1994;Lutz,Veilleux& Toomre 1977; Schweizer 1982; Joseph & Wright 1985; Sanders ://a
Genzel1999;Veilleux,Kim&Sanders1999;L´ıparietal.2000a, etal.1988a,b;L´ıpari1994;L´ıparietal.2003;Colinaetal.2001). ca
d
2003andothers).Theoreticalworksuggestedthatinmergersand Inaddition,itisalsoimportanttoanalysetheroleofthesesystems e
m
galaxycollisionstheinterstellarmedium(ISM)experiencesstrong intheformationandevolutionofgalaxies/AGNs(Rowan-Robinson ic
.o
torques and loss of angular momentum. As a consequence, inter- 2000;Sanders&Mirabel1996). u
p
stellar gas is transported towards the nuclear/circumnuclear envi- Animportant,commonphenomenonassociatedwiththesystems .c
o
ronmentandisconcentratedandcompressedthere(Noguchi1991; described is galactic wind: there is strong observational evidence m
/m
Barnes&Hernquist1992,1996;Hernquist&Mihos1995;Mihos, for galactic wind (GW) features from starburst and/or AGNs in
n
Richstone&Bothun1992).Thisprocessfrequentlygeneratesmas- LIRGs(Ulrich1972,1978;Heckman,Armus&Miley1987,1990; ra
s
sivestarformation,accordingtotheconditionsoftheISM(Mihos& McCarthy, Heckman& van Breugel1987; Taniguchi etal. 1988; /a
Hernquist1994a,b,1996;Mihos,Bothun&Richstone1993;Olson Fabbiano 1988; Phillips 1993; L´ıpari 1994; L´ıpari, Tsvetanov & rtic
le
&Kwan1990;Taniguchi&Wada1996).Inthesenuclearstarbursts, Macchetto 1997; L´ıpari et al. 2000a, 2003; Veilleux et al. 1994; -a
b
verylowangularmomentumgasmayfallintothenucleusitselfand Rupke,Veilleux&Sanders2002,andothers).Thereissubstantial s
accrete on to the central massive black hole (Norman & Scoville theoreticalliteratureaboutGWsassociatedwithstarbursts(Larson trac
1988;Taniguchi,Ikeuchi&Shioya1999;Kawakatu,Umemura& 1974; Ostriker & Cowie 1981; Chevalier & Clegg 1985; Ikeuchi t/3
4
8
Mori2003). & Ostriker 1986; Tomisaka & Ikeuchi 1988; Norman & Ikeuchi /2
Inaddition,theoreticalandobservationalstudiesindicatethatin 1989;Suchkovetal.1994;Strickland&Stevens2000,andothers) /3
6
somemergersbetweendiscgalaxies,dynamicalfrictionandsubse- and with AGNs (see Murray et al. 1995; Rupke et al. 2002, for 9/9
quentrelaxationwillproduceellipticalgalaxies,i.e.systemswith references). 84
0
massandlightdistributionssimilartothoseofellipticals(Toomre The discovery and study of IR QSOs (Beichman et al. 1986; 0
0
1977; White 1979; Schweizer 1980, 1982, 1990; Negroponte Vader et al. 1987; Lawrence et al. 1988; Low et al. 1988, 1989; b
y
& White 1983; Joseph & Wright 1985; Barnes 1989; Barnes & L´ıpari,Macchetto&Golombeck1991a;L´ıpari1994;L´ıparietal. g
u
Hernquist 1992; Kormendy & Sanders 1992; Hibbard & van 2003andothers)raisesseveralinterestingquestions,inparticular es
Gorkom1996;Shier&Fischer1998;Genzeletal.2001andothers). whether they form a special class of QSOs. We have found – or t o
n
InthecentreofluminousIRmergers,theextremelylargemolecu- confirmed–thathighpercentageofIRQSOsshowextremeGWs 0
7
lar+ionizedgasdensities(∼102–103M(cid:11)pc−3)arecomparableto withgiantsgalacticshells,mergerfeatures,broadabsorptionline A
p
thestellardensitiesinthecompactcoresofellipticals(Sanders& (BAL)systemsandextremeFeIIemission,andareradio-quiet(see ril 2
Mirabel1996;Solomon,Downes&Radford1992). L´ıparietal.2003).Wehavesuggestedthattheseobjectscouldbe 0
1
LuminousIRgalaxies(LIRGs;L (cid:1)1011L(cid:11))aredustystrong youngIRactivegalaxiesattheendphaseofanextremestarburst, 9
IR
IRemitters(L /L ∼5–300)whereanenhancementofstarforma- i.e.composite(starburst+AGN)andtransitionIRQSOs(L´ıpari,
IR B
tionisfrequentlytakingplace(Riekeetal.1980,1985;Lonsdale, Terlevich&Macchetto1993;L´ıpari1994;L´ıparietal.2003;L´ıpari,
Persson&Matthews1984;Joseph&Wright1985;Schweizer1990; Colina&Macchetto1994).
Norris et al. 1990; Hutching & Neff 1991; Condon et al. 1991; Atthefinalstageofan‘extremestarburst’;i.e.theTypeIISN
L´ıpari 1994; L´ıpari et al. 2000a; Lutz et al. 1996, 1999; Genzel phase[(8–60)×106yrfromtheinitialburst;Terlevichetal.1992,
etal.1998;Downes&Solomon1998;Alonso-Herreroetal.2002). 1993] powerful GWs, giant galactic arcs, BAL systems and ex-
Ontheotherhand,imagingsurveysofultraluminousIRgalaxies treme Fe II emission can appear (Norman & Ikeuchi 1989; Perry
(ULIRGs, L (cid:1) 1012 L(cid:11)) show that ∼100 per cent are mergers &Dyson1992;L´ıparietal.1993;L´ıpari1994;L´ıparietal.2003;
IR
or interacting systems (Sanders et al. 1988a; Melnick & Mirabel Suchkov et al. 1994; Taniguchi et al. 1994; Scoville & Norman
1990;Clementsetal.1996).Theluminositiesandspacedensities 1996. Terlevich, L´ıpari & Sodre, in preparation). In addition, the
ofULIRGsinthelocalUniversearesimilartothoseofquasi-stellar early starburst phase dominated by H II regions is associated
objects(QSOs;Soifer,Houck&Neugebauer1987).Inaddition,an with a large amount of dust and IR emission (Terlevich et al.
interestingsubgroupofULIRGsarethehyperluminousIRgalaxies 1993).
(cid:12)C 2004RAS,MNRAS348,369–394
InfraredmergersandQSOswithGWs–I 371
2 THE PROGRAMME AND OBSERVATIONS In addition, it is worth to remember that evidence for OF in
nearbyobjectsismainlykinematical,morphologicalandphysical
2.1 Theprogrammeandmaingoals (seeHeckmanetal.1990).However,fordistantgalaxiesandQSOs
thisevidenceismainlyintheformofthepresenceofhighvelocity
Wehavestartedastudyofthemorphology,kinematicsandioniza-
componentsinthekinematicdata.
tion structure of IR mergers and IR QSOs, especially those with
For 2D spectroscopic observations we have selected mainly
GWs(L´ıpari1994;L´ıparietal.2000a,2003;L´ıpari,Macchetto&
‘nearby’ IR mergers/QSOs from Table 1. More specifically, we
Golombeck1991a;L´ıparietal.1993;Colina,L´ıpari&Macchetto
selected nearby IR systems in different phases of the collision
1991a,b).ThisprogrammeincludesthestudyofMrk231,Arp220,
process in order to study the evolution of the relation between
NGC 2623, NGC 3256, NGC 3690, NGC 4038/39 (the Anten-
mergersandstarburst+GWs(usingourimagesandthemorpho-
nae),IRAS01003–2238,04505–2958,07598+6508,13218+0552,
logical/interaction classification presented in Table 1, column 8).
14026+4341,17002+5153,18508–7815,19254–7245(theSuper
Furthermore,wealsoselectednearbyIRmergerswhereweprevi-
Antennae),22419–6049,PHL1092,IZw1andothers.
Inthispaperwepresentthefirstresultsfromanewpartofthis ouslyobservedstarburstoractivityinthenuclearandextranuclear D
regions,andmergersbetweenequalandunequalmassgalaxies(us- ow
observationalprogramme:thestudywith2Dspectroscopyofase- n
lectedsequenceoftheseIRsystemswithoutflow(OF),whichin- ingspectrafromoursurveys).Therefore,thegeneralgoalofthis loa
programme is to study the properties of the different states of IR d
cludenewOFobjects(suchasNGC2623)andalsotheprototypes e
mergers/QSOs,extremestarburstsandGWs(andtheirrelations) d
of IR mergers/QSOs with OF (Arp 220 and Mrk 231). We have Detailednew-technologyinterferometric(IRAMandVLT)and fro
observed(mainlyonLaPalma)∼10nearbyobjectsfromourdata m
spectroscopic (ISO) studies have recently confirmed the presence h
baseof43IRmergers/QSOswithGWorcandidates.InTable1we ofextremestarburstsinIRmergersandIRQSOswithGWs:one ttp
psyressteemnts.aWsuememmparhyasoizfeththeamtianinthperloapstertwtieoscooflutmhensseoofrtihgiisnatalb4l3ewIRe thousandtimesasmanyOBstarsas30DorintheIRmergers/QSOs s://a
Mrk 231, Arp 220 and Mrk 273 (see Downes & Solomon 1998; ca
presentforeachobjectthetypeofOFdetectionandthereference d
Smith et al. 1998; Genzel et al. 1998). In addition, using Hubble e
fromwhichthevalueoftheOFwasobtained. m
SpaceTelescope(HST)andESONTTnew-technologydata,L´ıpari ic
AsTable1willbealsousedinSection4.4.2(forthestudyofthe .o
etal.(2000a)showedthatNGC3256isanotherexampleofanearby u
‘general’propertiesofIRmergers/QSOswithGWs)itisimportant p
IR merger with an extreme and extended massive star formation .c
toexplainindetailhowtheselectionofthese43IRsystemswas o
processunderwaywithapowerfulassociatedGW. m
performed.First,weselectedIRMergersandQSOswithkinematic /m
Someoftheparticulargoalsofthisprogrammemaybeenumer-
and/ormorphologicalevidenceofOFobtainedfromourprevious atedasfollows. nra
studiesof: s/a
(i) Tostudytheprocessofextremestarbursts,inducedbymerger rtic
(i) ‘ExtremeGalacticWindsintheIRAS1Jycompletesample’ le
(L´ıparietal.2000b,2003); events.Thesestarburstscouldbeassociatedwithahighconcentra- -a
b
tionofmoleculargas,andhighlyenergeticGWsthatmighthave s
Sam(iip)le‘S’p(SecatnrdoescrsopeticalS.u1r9v9e5y);ofthecompleteIRASBrightGalaxy tcrliigkgeesrterducsttuarrefsor(mLaartsioennientsahl.el2l0s0o2f;sHwoepdtg-eup19g6a7s)a.nIdngaedndeirtiaotend,tahre- tract/3
(iii) ‘SpectroscopicSurveyofWarmIRASGalaxies’(L´ıparietal. 4
1991b,a); blueasymmetricalspiralarmsofyoungmassivestarformation(ob- 8/2
servedinIRmergers;L´ıparietal.2000a)couldbegeneratedbythe /3
(iv) GW in individual objects, such as Mrk 231, NGC 3256 6
and the Super Antennae (L´ıpari et al. 2000a, 1994; Colina dynamicaleffectsofthemergerprocess(Mihos&Hernquist1994b, 9/9
etal.1991a). 1996;Taniguchi&Wada1996). 84
0
Specifically,ourpurposeistostudythespatialdistribution,and 0
0
Inaddition,Table1alsoincludestheresultsofthemainstudies thekinematicandphysicalpropertiesoftheionizedgas,starsand b
y
ofGWs(inIRMergers/QSOs)alreadypublishedbyUlrich(1972), dust,allofwhichprovideinformationabouttheevolutionarycon- g
u
Heckmanetal.(2000,1990,1987),Rupkeetal.(2002)andothers. ditionsandthepossibleoriginsofthestarformationprocesses. es
WenotethatinourdatabasetheIRsystemsselectedasOFcan- (ii) Toinvestigatethepresence,properties,originandimportance t o
n
didatesareobjectsforwhichtheevidenceforOFisambiguousor of GWs in IR mergers and IR QSOs. In particular, our aim is to 0
7
needsconfirmationwithhigherresolutionorsignal-to-noiseratio analyse the spatial distribution, kinematics and properties mainly A
p
(S/N)data(fordetails,seeL´ıparietal.2003). oftheionizedgasanddust.Thesedatawillallowustostudythe ril 2
Itisimportanttorecallthataverysimpleapproachtothestudy evolutionarystateandtheoriginoftheGWs. 0
1
ofOFprocessesistoseparatelowandhigh/extremevelocitycases ItisimportanttostudyindetailthehostgalaxiesofIRQSOs, 9
(LVOFandEVOF,respectively;L´ıparietal.2003).Forthedefinition especially the presence of GWs, Wolf–Rayet features, arcs/shells
of the velocity limit between LVOF and EVOF systems (700 km andyoungstellarpopulations.
s−1),weused–inthispreviouswork–thesimplefactthatmainly (iii) To study in general possible links or evolutionary paths
low values of GWs were observed in starbursts, which lie in the amongmergers,starbursts,GWs,QSOsandgalaxies.Morespecif-
velocityrangeof100kms−1 (cid:2)V (cid:2)700kms−1.Specifically, ically,toanalysethepossibleconnectionbetweenIRmergerswith
OF
thisresultisbasedon:(a)observationalandtheoreticalstudiesof extremestarburst+GWleadingtoIRcompositeQSOswithGW
GWsandshocksassociatedwithstarburstspublishedby(Viegas, andellipticalgalaxies(forreferencesseeSection4.4.2).
Contini&Contini1999);and(b)ourstudiesanddatabaseofGWs We have a special interest in studying the evolutionary role of
inIRmergerswithstarbursts(L´ıparietal.2003,2000a).Wethen IRQSOswithGW+giantgalacticshells(plusBALsystemsand
found that below this limit ‘only’ systems with LVOF associated strongFeIIemission).TheseIRQSOsweredefinedascomposite
with starburst processes were detected, whereas the EVOF were andtransitionobjectsbetweenULIRGsandstandardQSOsinthe
observedmainlyinobjectswithIRQSOs/AGNs+starbursts(for IRAScolour–colourdiagram(L´ıpari1994fig.5;e.g.Mrk231,IRAS
details,seeL´ıparietal.2003). 07598+6508,IRAS17002+5153andothers).
(cid:12)C 2004RAS,MNRAS348,369–394
372 S.L´ıparietal.
Table1. IRMergersandIRQSOs/AGNswithLVOFandEVOF.
Object VOF1 VOF2 z LIR LIR/LB Nuclear Morpholog. OF OF
kms−1 kms−1 log LIR/L(cid:11) activity Type Type Reference
LowvelocityOF
Arp220 −450 – 0.01825 12.18 87 L+SB PM EL Heckmanetal.(1987)
IRAS00182-7112 −450 – 0.3270 12.90 (200) L+SB (M) EL Heckmanetal.(1990)
IRAS03250+1606 −431 – 0.129 12.06 – L M AL Rupkeetal.(2002)
IRAS03514+1546 −200 – 0.02100 11.10 – SB M AL Heckmanetal.(2000)
IRAS09039+0503 −656 – 0.125 12.07 – L M AL Rupkeetal.(2002)
IRAS11387+4116 −511 – 0.149 12.18 – SB OM AL ”
IRAS23128-5919 −300 – 0.04490 12.60 8 L+SB M EL L´ıparietal.(2003)
Mrk266 −300 – 0.02900 11.37 8 SB PM EL Wangetal.(1997)
Mrk273 −600 – 0.03850 12.14 36 L+SB PM EL Colina,Arribas&Borne(1999) Do
NGC1614 −400 – 0.01550 11.61 18 L+SB M EL Ulrich(1972) w
n
NGC2623 −405 – 0.01846 11.55 17 L+SB M EL Thispaper lo
a
NGC3256 −370 – 0.00940 11.57 9 SB MM EL L´ıparietal.(2000a) de
NNGGCC34609309 −−330605 –– 00..0010052650 1110..9919 236 L+SBSB PPMM EELL HL´ıepcakrmieatnael.t(a2l0.0(139)90) d fro
m
NGC5514 −320 – 0.02453 10.70 1 L+SB PM EL Thisprogramme h
High/ExtremeOF ttp
IIRRAASS0051002043--12924318 −−1767706 −1–520 00..1191280 1122..4234 –67 QSOS+2SB OMM AELL LR´ıuppakreieettaall..((22000032)) s://ac
a
IRAS05189-2524 −849 – 0.042 12.07 – S2 M AL ” d
e
IRAS10378+1108 −1517 – 0.136 12.26 – L M AL ” m
IRAS11119+3257 −1300 (−2120) 0.1873 12.58 – S1+SB M EL L´ıparietal.(2003) ic.o
IRAS13218+0552 −1800 (−3438) 0.2048 12.63 96 QSO+SB OM EL ” up
IRAS14394+5332 −880 (−1650) 0.1050 12.04 – S2 MM EL ” .co
IRAS15130-1958 −780 (−1200) 0.1093 12.09 – S2 M EL ” m
IRAS15462-0450 −1000 (−1760) 0.1001 12.16 – S1 M EL ” /mn
IRAS19254-7245 −800 – 0.05970 12.04 30 QSO+SB PM EL Colinaetal.(1991a) ra
s
Mrk231 −1000 – 0.04220 12.53 32 QSO+SB M EL L´ıparietal.(1994) /a
NGC3079 −1600 – 0.00400 10.49 2 L+SB Sp EL Heckmanetal.(1990) rtic
NGC6240 −930 – 0.02425 11.83 15 L+SB PM EL ” le-a
b
s
OFcandidates tra
c
AIRrApS10903275-2859 –– –– 00..0227292 1112..6504 179 QSOSB+SB PPMM EELL Thispaper ” t/34
8
IRAS04505-2958 GWarc – 0.2863 12.55 20 QSO+SB PM – L´ıparietal.(2003) /2
IRAS07598+6508 (PaαOF) – 0.1483 12.41 5 QSO+SB M EL L´ıpari(1994) /36
9
IRAS13305-1739 [OIII]MC – 0.148 12.21 – S2 OM EL L´ıparietal.(2003) /9
IRAS13451+1232 [OIII]MC – 0.122 12.28 – S2 PM EL ” 84
IRAS14026+4341 (GWarcs) – 0.320 12.55 40 QSO M – ” 00
IRAS17002+5153 GWarcs – 0.2923 12.58 5 QSO+SB PM – ” 0 b
y
IRAS18508-7815 – – 0.162 12.0 8 QSO M EL Thispaper g
IRAS21219-1757 – – 0.110 11.98 89 QSO OM EL ” ue
IRAS22419-6049 WRQSO – 0.1133 11.30 – QSO+SB M EL L´ıpari&Macchetto(1992) st o
IRAS23389+0300 [OIII]MC – 0.145 12.09 – S2 PM EL L´ıparietal.(2003) n 0
NGC1222 – – 0.009 10.46 6 SB (M) EL Heckmanetal.(1990) 7
NGC4194 – – 0.009 10.87 6 SB M EL ” Ap
PHL1092 – – 0.396 ∼12.3 – QSO – EL Thispaper ril 2
0
Notes.Columns2and3:OFvaluesobtainedfromthereferencesincludedincolumn10.Valuesbetweenparenthesisarepossibledetections.[OIII]MC 19
indicatesemissionline[OIII]λ5007withmultiplecomponents.Column5:theLIRwereobtainedfor[8–1000µm],usingtherelationgivenbySanders&
Mirabel(1996).Column7:thepropertiesofthenuclearactivitywereobtainedfromVeilleuxetal.(1999),Canalizo&Stockton(2001)andL´ıparietal.(2003).
S1:Seyfert1,S2:Seyfert2,L:LinersandSB:starburst.Column8:forthemorphologicalorinteractiontypeweusedtheclassificationcriteriaofVeilleux,
Kim&Sanders(2002b)andSuraceetal.(1998);PM:pre-merger,M:merger,OM:oldmerger,MM:multiplemerger,Sp:spirals.Column9:ELandAL
indicateOFderivedfromemissionandabsorptionlines,respectively.
(iv) ToanalysethedynamicalstateoftheseIRsystemsandtheir IR systems, especially the presence and origin of rotation
relationwithgalacticoutflow/inflow,starburstsandAGNs.Wenote curves with ‘sinusoidal’ shapes in mergers (for references see
thatourspectroscopicobservationswereoptimizedforthemapping Section4.2).
ofthekinematicpropertiesoftheionizedgas.Thiscomponentof (v) TostudytheoriginoflowionizationBALsystemsobservedin
theISMisagoodtracerofpotentialperturbationsandOF/inflow; IRQSOs(Boroson&Meyers1992;L´ıpari1994;L´ıparietal.1994).
itrespondsquicklytogravitationalvariations. Theseabsorptionsystemscanbeexplainedwithintheframework
In particular, our purpose is to study in detail the 2D ofthecomposite(starburst+AGN)outflowscenario.Wearepar-
VFs, the rotation curves and mass–luminosity ratios of these ticularly interested in making a detailed study of our proposition
(cid:12)C 2004RAS,MNRAS348,369–394
InfraredmergersandQSOswithGWs–I 373
Table2. JournalofobservationsofNGC2623.
Date Telescope/ Spectralregion Expos.time Comments
instrument [s]
2001Apr12 4.2mWHT/Integral λλ6000–7500Å 1800×3 (cid:6)FWHM(cid:7)=1.0arcsec
2000Sep20 HST/WFPC2 F555W,λλ5407/1236Å 320 (cid:6)FWHM(cid:7)=0.1arcsec,archival
F814W,λλ7970/1531Å 320 ”
1997Nov19 HST/NICMOS F110W,λλ1.10/0.60µm 352 (cid:6)FWHM(cid:7)=0.22arcsec,archival,NIC2
F160W,λλ1.60/0.40µm 352 ”
F222M,λλ2.22/0.14µm 480 ”
D
o
w
thatsomeBALsystemscouldbeassociatedwithGWsthatproduce TheHSTWideFieldPlanetaryCamera2(WFPC2)archivalob- n
lo
dustyexpandingshells. servationsincludebroad-bandimagespositionedonthePlanetary a
d
(vi) Itisimportanttostressthatweareworkingonastudyofstar Camera(PC)chipwithapixelscaleof0.046arcsecpixel−1,using e
d
formation, GW and galaxy evolution at high redshift (z > 3; e.g. theF555WandF814Wfilters(Table2),whichcorrespondclosely fro
Macchettoetal.1993).However,thefirststepinthisprogrammeis tothestandardJohnsonVandCousinsIfilters(seeHoltzmanetal. m
h
tounderstandstarformationandGWinnearbygalaxies,wherewe 1995a,b;Baggetetal.2002).Measurementofthefullwidthathalf- ttp
caanndoIRbtaQinSOmsoareredeextacielelldenatnldabuonraamtobriigeusoautsloinwforermdsahtiifotnf.oIrRthmeesrtguedrys minatxhiemPuCmF(5F5W5WHMan)dofFth8e14HWSTimWaFgPesCg2ipvoesinatsrpesreoaludtfiuonncbtieottne(rPthSaFn) s://ac
ofGWsandextremestarformationprocesses(seeSection4.4.2). 0.1 arcsec (∼20–30 pc). In addition HST NICMOS archival data ad
e
wereobtained(mainlyfortheastrometryofthenucleus)inthenear- m
NGC2623(Arp243,UGC4509,IRAS08354+2555)isanearby ic
luminousIRgalaxy(z=0.01846,LIR[8−1000µm]=3.56×1011L(cid:11)), FIR1,6w0Whic(h1.i6n0clµumde,(cid:10)imλag0e.4sµwmith)athnedFF121202WM((21..2100µµmm,,(cid:10)(cid:10)λλ00..164µµmm)), .oup
whichistheresultofamajormergerbetweentwogas-richgalaxies filters using camera 2 (with pixel scales of 0.0762 arcsec pixel−1 .co
(Toomre1977;Joseph&Wright1985).Thisobjectshowsacompact m
and0.0755arcsecpixel−1 inxandy,respectively).Thedatawere /m
nucleus,anellipticalmainbody,aloop/extensiontothesouthofthe n
main body and two extended tidal tails. Throughout this paper, a reducedattheSpaceTelescopeInstitute,usingthestandardprocess ra
NHGubCbl2e6c2o3nswtaentadoofpHte0d=a7d5isktamncse−o1fM∼p7c4−1Mwpilcl(bVesaysss=um5e5d3.9Fo±r fyosreTathhrecehIdRivaAatalF.o1Tbshsoeefrtvrweaadtiruoecnptsiao.cnkoagfethwea2sDusWedHmTaisnpleycttororsecdoupciecaonbdsearnvaal-- s/article
10kms−1,seeSection3.3),andtheangularscaleis1(cid:14)(cid:14)≈358pc. -a
tionsconsistsoftwomainsteps:(I)reductionofthespectraforeach b
s
ofthe219fibres,and(II)thegenerationof2Dmapsbyinterpolating tra
c
2.2 Observationsandreductions theselectedparameter(e.g.emission-lineintensity,continuumin- t/3
tensity,radialvelocity,etc.)fromthegridvaluesdefinedbythefibre 48
Ttawinoe-ddidmureinnsgioanpahlo(t2oDm)eotrpitcicnailghspteinctAropsrciol2p0y0o1faNtGthCe42.622m3Wwailslioabm- bundle.Step(I)wasbasicallydonewithIRAFinthesamewayas /2/3
HvaetrosrcyhoenlTtheeleissclaonpdeo(WfLHaTP)alamttah(eTRabolqeu2e).dTehloesWMHuTchwaacshousseOdbwseitrh- finoirtiloonnga-nsdlittrsapceec,trsotrsacyo-plyig,hintcsluubdtirnagctbioians,seuxbtrtaracctitoionno,faptheertuspreecdteraf-, 69/984
wavelength calibration, throughput correction and cosmic-ray re- 0
FthOeSINsTpEeGcRtrAoLgfirabpreho(Bptiincgshsaymsteemta(lA.1rr9ib9a4s).eTtahle.1se9e9i8n)gawndasthtyepWicYalFly- jection.Weobtainedtypicalwavelengthcalibrationerrorsof0.1Å, 00 b
1.0arcsec. whichgivevelocityuncertaintiesof5kms−1.Forstep(II)weused y g
INTEGRALlinksthef/11NasmythfocusoftheWHTwiththeslit thesoftwarepackageINTEGRAL,2with2Dinterpolationroutines.In ues
of WYFFOS via three optical fibre bundles. A detailed technical particular,wetransformedASCIIfileswiththepositionsofthefi- t o
dreecsaclrlipotniloyniotsfmINaTiEnGcRhAaLraiscpterroivstiidcesd.TbyheAtrhrriebeasbeutnadll.e(s19h9av8e).dHifefreerewnet bstraensdaanrddtFhIeTScofirrleessp.oMndaipnsggsepneecrtartaeldfeiantuthreisswinatoyraergeuplarrelsyenstpeadceidn n 07 A
spatialconfigurationsonthefocalplaneandcanbeinterchanged tshoeftwneaxret.s3ection. For studying the kinematics we used the ADHOC pril 2
depending on the scientific programme or the seeing conditions. 0
PhotometriccalibrationoftheHSTWFPC2wasperformedusing 1
At the focal plane, the fibres of each bundle are arranged in two 9
publishedphotometricsolutionfortheF555WandF814Wfilters.
groups, one forming a rectangle and the other an outer ring (for
Specifically, the fluxes and magnitudes were obtained following
collectingbackgroundlight,inthecaseofsmall-sizedobjects).The
theproceduredescribedintheSTScIHST/WFPC2DataHandbook
dataanalysedinthispaperwereobtainedwithstandardbundle2
(version4.0;Baggetetal.2002).First,thefluxeswerederivedfrom
(219fibres,each0.9arcsecindiameterprojectedonthesky).The
thenumberofcountsperarcsec2 (C),whichweredividedbythe
centralrectangleisformedby189fibres,coveringafieldofview
of16.4×12.3arcsec2,andtheother30fibresformaring90arcsec exposuretime(ET)andmultipliedbythevalueofthePHOTFLAM
keyword in the HST image header (which is the flux of a source
indiameter.
TheWYFFOSspectrographwasequippedwitha1200linemm−1
grating,coveringtheλλ6000–7500Årange.ATekCCDarrayof
1IRAFisareductionandanalysissoftwarefacilitydevelopedbytheNOAO.
1124 × 1124 pixels of 24 µm × 24 µm size was used, giving a 2INTEGRALisa2Dspectroscopicanalysissoftwarefacilitydevelopedbythe
lineardispersionofabout1.4Åpixel−1 (∼2.8Åeffectiveresolu- InstitutodeAstrofisicadeCanarias(IAC).
tion,∼100kms−1).Withthisconfigurationwetookthree1800s 3ADHOCisthe2DkinematicanalysissoftwarefacilitydevelopedbyMar-
exposuresofthecentralregionofNGC2623. seillesObservatory.
(cid:12)C 2004RAS,MNRAS348,369–394
374 S.L´ıparietal.
Table3. GeneralPropertiesofNGC2623andnearbyIRmergers/QSOswithGWs.
Parameters NGC2623 NGC4038/9 NGC3256 NGC3690 Arp220 NGC6240 Mrk231 I19254-7245
Parametersadopted:
D(Mpc,H0=75) 74 22 35 41 77 98 170 236
Scale(pc/0.1arcsec) 36 11 18 20 37 48 81 114
Inclination 47◦ – 42◦ – – – – 20◦–30◦
Parametersderived:
SystemicVelocity(kms−1) 5539 1650 2817 3080 5450 7300 12450 17900
log LIR(L(cid:11)) 11.55 10.99 11.57 11.91 12.18 11.83 12.53 12.04
LIR/LB 17 6 9 23 87 15 32 30
MB −20.3 −22.4 −22.6 −20.9 −20.8 −21.5 −22.3 −23.3
VOF(kms−1) −405 −365 −370 −300 −450 −930 −1000 −800
SFR(M(cid:11)yr−1) 90 5 80 50 300 100 ∼1000 150–500 Do
SNrate(yr−1) 2 0.1 2 1 3 1.0 5 4 w
n
Tidaltails(kpc) 28,27 90,50 50,60 – (33) (28,27) (27,22) 192,123 lo
a
Typenucl. L+SB L+SB SB SB L+SB L+SB QSO+SB QSO+SB de
A(cid:10)Vrnnuuccll((mkapgc),H0=75) (cid:1)0.05 67.04 43.54 11.70 1000-.14000 200-.540 (cid:1)0.200 (cid:1)9.140 d from
MassesoftheISMandtotal: h
AMIotnooilmzeecid.cHHH2IIImmmaaassssss((×(××111000997MMM(cid:11)(cid:11)(cid:11)))) ∼53..981 39–..48 30––.9 126–..83 149–..01 19––.1 (cid:2)128–2.0.4 ∼30–1.01 ttps://ac
a
Dustmass(×107M(cid:11)) 1.6 1.4 (2.0) 2.6 7.4 2.8 8.0 1.5 d
e
m
Dyn.totalMass(×1010M(cid:11)) 1.5 8.0 ∼5 – (cid:1)2.6 (8) (cid:1)3.0 – ic.o
Mass(gas+dust)/Mdyn ∼0.4 ∼0.2 (cid:1)0.3 – – ((cid:1)0.3) – – up
LIR/mass(H2) 60 29 12 68 79 35 210 37 .co
MNuacslse(aHr2H)/2mmasass(sH(×I)109M(cid:11)) ∼15.6.9 10..05 –– 4–.1 156.0.3 19–.1 (cid:1)180..07 –– m/mn
Massnewstars(×109M(cid:11)) – – – – 2.3 – 3.8 – ras
/a
rtic
Note–Valuesinparenthesesaremainlypreliminaryresultsthatrequireconfirmation.ThedatawereobtainedfromYoungetal.(1989),Mirabeletal.(1990), le
Heckmanetal.(1990),Sandersetal.(1991),L´ıpari(1994,2000,2003),Hibbard(1995),Kimetal.(1995),Prugnieletal.(1998),Downes&Solomon(1998) -a
b
andthispaper. stra
c
wPHithOTcoFnLsAtaMnt(flPuFx)pvearluuensitawreav2e.5le0n8gt×h,1in0−e1r8gfso−r1thcme−F281Å4−W1).fiTltheer 3.1 Themorphologyofthemainbody(HSTimages) t/348/2
and3.483×10−18forF555W.Thenthemagnitudeswereobtained The Palomar 103a-0 (∼B band) image (Fig. 1) shows the whole /36
–intheHST/WFPC2STMAGsystem–usingtherelation: merger.Thisgalaxyconsistsofamainbody(r∼5kpc∼15arcsec), 9/9
(cid:1) (cid:2) twoextendedtidaltails(∼50kpc)andseveralouterloops.ThisB 84
C 0
mSTMAG=−21.1−2.5log(PF)−2.5log ET . (1) oimfadguestdeinpitchtsetmwoaibnribgohdtystroufctthueremsseerpgaerra,taenddbyalvseoryalbarriggehfitllaomoepnttos 00 b
y
TotransformSTMAGF814WmagnitudetoCousinsIweadded thesouth.InseveralcataloguesthesethreebrightBstructureswere g
u
theconstant–1.27mag,whiletoconvertSTMAGF555Wmagnitude associatedwithatriplesystemincollision. es
toJohnsonVweadoptedaconstant0.00mag(Baggetetal.2002). TheHST WFPC2F555WandF814Wbroad-bandobservations t o
n
FromtheNASAExtragalacticDatabase(NED;CaliforniaInsti- show at sub-arcsec scale (better than 0.1 arcsec) very interesting 0
7
tuteofTechnology)weobtainedacopyofthePalomar5mtelescope structuresofthemainbodyofthisIRmerger(Figs2a,b,candd): A
p
Gimaalagxeieosf’N(AGrCp12966263a(,bA)r.4pT2h4i3s)pphuobtoligsrhaepdhiicnitmheag‘Ae–tlaosfo3f0-Pmecinuleixar- (wi)haicnhobemsceurrgeedsnaunclaesuysmcmloesetrtiocathlespaipreaxlaorfma,samrailnlgnuacnldeafirlcaomneenftrsoomf ril 20
1
posure–wasobservedusinga103a-Oplate(∼broad-bandBinthe dust;(ii)aclumpyasymmetricalspiralarmtotheeastofthenucleus 9
Cousinssystem). thatreachestheouterregionsofthemainbody;(iii)aringplusan
arc–tothewestofthenucleus–whichareprobablyaprojection
3 RESULTS ofasecondspiralarmorcouldbeshellsassociatedwiththeGW;
and(iv)severalverylargeandwidefilamentsofdust.
Here,wepresentforNGC2623(i)high-resolution HST WFPC2
ThenucleusofNGC2623iscompletelyobscuredatbluewave-
broad-bandimages;(ii)strongevidenceofnuclearOFassociated
lengths(fordetailsseethebroad-bandBcontourimagereportedby
withaGWand(iii)detailedstudiesofthe2Dkinematicsandionized
Joy&Harvey1987,theirfig.4).TheHSTF555Wimage(Fig.2b)
structure.ThegeneralpropertiesofNGC2623andsimilarnearby
shows that the nucleus is still strongly obscured in the V band.
IRmergersandIRQSOswithGWarepresentedinTable3.
However,inthenuclearareawedetectedafaintcoreclosetothe
apex of a small emission cone. Furthermore, several knots in the
asymmetricalspiralarmarebrighterthanthiscore(Fig.2b).Oth-
4Wehaveobtainedthepermissionoftheauthor,theAstrophysicalJournal erwise,theHST WFPC2F814Wimage(Figs2candd)displaysa
andtheCaliforniaInstituteofTechnologytoreproduceandusethesedata. brightandcompactnucleusclosetotheapexofthesmallnuclear
(cid:12)C 2004RAS,MNRAS348,369–394
InfraredmergersandQSOswithGWs–I 375
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Figure1. Palomar5-mtelescope∼B(photograpic/103aO)imageofthewholeIRmergerNGC2623.Northistothetop,eastistotheleft.Thisimagewas le-a
obtainedfromtheNASAExtragalacticDatabaseoftheCaliforniaInstituteofTechnology(andpublishedbyArp1966a,b). b
s
tra
c
t/3
cone. This HST image is clearly less obscured than the previous Inorderatleasttocomparethepositionsoftheemissionpeaks 4
8
one.Thesmallnuclearemissionconehasanapertureangleθ=60◦ intheHST optical(WFPC2/F814W)andnear-IR(NICMOS)im- /2
/3
±6◦,aprojectedaxisatpositionanglePA=10◦±6◦,andextends ages,weusedSTSDAS,ADHOCandVTTsoftware.5Wehavemeasured 69
uptor∼400pcfromthenucleus.TheHST F814Wcontourmap the position of the nuclear emission peaks in the Planetary Cam- /9
8
ofthenuclearregion(2×2arcsec2;Fig.2d)showsthatthereisa era chip of WFPC2 and Camera 2 of NICMOS with a precision 40
0
knotveryclosetothenucleus(0.25arcsec∼90pctotheeast)that closetothepixelsize(±0.8pixel),thusanupperlimitforourer- 0
b
isbrighterthanthenucleusintheF555Wimageandisconnected rors is ±0.1 arcsec. In the HST/WFPC2 F814W band image the y
g
withtheasymmetricalspiralarm. position of the nuclear peak was found to be [RA 8h38m24s.115, u
e
Interestingresultswereobtainedfortheneareststronglyobscured Dec.+25◦45(cid:14)16(cid:14).(cid:14)5],inJ2000.0equatorialcoordinates.Forthethree st o
IRnucleus(NGC4945)fromadetailedcomparisonoftheoptical, HST/NICMOSnear-IRimageswefound,withintheerrors,thesame n
0
near-IR and radio emission peaks (L´ıpari et al. 1997). However, positionforthenucleuspeak[RA8h38m24s.14,Dec.+25◦45(cid:14)16(cid:14).(cid:14)1]. 7
A
forNGC2623–amoredistantstronglyobscuredIRnucleus–it Previously,Condonetal.(1991)hadreportedforthenucleusaradio p
isdifficulttoperformthistypeofstudybecausethedifferencesin position(fromhigh-resolution8.44-GhzVLAobservations,witha ril 2
thepositionsofthepeaksaresimilartotheresolutionoftheimages beamof0.25arcsec)[RA8h38m24s.08,Dec.+25◦45(cid:14)16(cid:14).(cid:14)1].Fig.2(d) 01
9
and/ortotheerrorsintheastrometry.ProbablyforthisreasonSoifer showsthesethreepositions(plusthelocationofthekinematiccen-
etal.(2001)assumedforNGC2623that,toafirstapproximation,the tre, see Section 3.3); we will comment mainly on the difference
brightestcompactnuclearpeaksinthenear-IR[theKband(2.2µm); foundinthepeaksoftheHST opticalandnear-IRimagesbecause
Scovilleetal.2000],mid-IR[theN band(12.5µm);Soiferetal. theirpositionswereobtainedwiththesameprocedureandthesame
2001]andradio(8.44GHz;Condonetal.1991)arecoincidentand telescope. A difference of ∼180 pc (≡ 0.5 arcsec) was detected
definethenucleusposition.However,thisassumptionisonlyafirst betweenthesetwo(opticalandnear-IR)emissionpeaksinthedi-
approximation, because, for example, in NGC 4945 we detected rectiontotheapexofthesmallemissionnuclearcone.Thisresult
anoffsetof70pc(≡4arcsec)betweenthepositionoftheoptical isconsistentwiththatobtainedforthenearestobscuredIRnucleus,
HαandKemissionpeaks,and∼110pc(∼6arcsec)fortheoptical
and radio peaks (see L´ıpari et al. 1997 their figure/plate 2). It is
interestingtohighlightthatthesethreepeaksarealignedandpoint 5STSDASandVTTarereductionandanalysissoftwarefacilitiesdeveloped
towardstheobscuredapexofanemissionnuclearcone(andtothe bytheSpaceTelescopeScienceInstituteandNASAGoddardSpaceFlight
kinematiccentre). Centre,respectively.
(cid:12)C 2004RAS,MNRAS348,369–394
376 S.L´ıparietal.
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Figure2. HST WFPC2broad-bandimagesandcontourmapofNGC2623,throughtheF555WandF814Wfilters.Therangesoffluxesineachimage 00
are:[0.09,0.80],[0.09,1.27],[0.07,2.82]and[1.31,3.73],respectivelyandinunitsof[×10−16ergcm−2s−1Å−1arcsec−2].Thecorrespondingrangesof 0 b
tVh-eJosthenpso–ninanflduxI-–Ciosu0s.i3n1sm×a1g0a−r1c6s,eacn−d2tahree:m[e2a1n.5u0n,c1e9r.t1a4in(tiVe)s]i,n[2th1e.5I0,,n1e8a.r6-4IR(,Va)n]d,[k2i0n.e6m0,a1ti6c.a5l1p(eIa)k]sa/cnedn[t1re7s.3a5re,1±60.2.015(,I±)],0.r1esapnedct±iv0e.l8y.aIrncstehce,creosnptoecutrivpelolyt y gu
e
(seethetext). st o
n
0
7
in NGC 4945. On the other hand, we note that because the posi- (L´ıparietal.2000a,seefordetailthenextparagraph).Figs2(b)and A
toifon0.o2f5tharecrsaedci,oapnedatkhweasspaotbiatalirneesdolfurotimonoibnsethrveantieoanrs-IwRitihmaagbeesamis (toc)thdeepwicetsat orifngthweinthucpleroujse)c,tpedlusdiaamfaeitnetradrc∼w7h0i0chpcis(cpoonsicteionntreidc pril 20
∼0.2 arcsec, we consider that, within the errors, the positions of andconnectedwiththering,with d ∼1.4kpc.Figs2(b)and(c) 19
thesetwopeakscouldbeveryclose,orevencoincident(inagree- indicatethatthefaintasymmetricalspiralarmandthering+arc
mentwiththeassumptionmadebySoiferetal.2001).Furthermore, aremoreintenseintheF555Wimage,suggestingbluecoloursfor
thepositionsofthekinematiccentreandthenear-IRpeaksarealso thesestructures.Inaddition,thebroad-bandBimage,reportedby
locatedveryclosetogether(withintheuncertainties). Joy&Harvey(1987,theirfig.4),alsosuggestastrongbluecolour
The HST WFPC2 images reveal two interesting structures, the forthearmandthering(forfurtherdetailsseethelastparagraph
asymmetricalspiralarmandthering+arc.However,wenotethat in this section). In Fig. 2(d), the nuclear contour map shows that
thesestructures(observedwithhighresolutionbutthroughthedust) bothstructures(thearmandring)areconnectedwiththecompact
weredetectedusingbothHSTimageswithdifferentspatialandflux nucleus.
scales,andafteradetailedstudy.TheHSTF555Wimage(Fig.2b) ItisinterestingtonotethatforthenearbyIRmergerNGC3256
shows a faint asymmetrical spiral arm (r ∼ 3 kpc located to the wefoundthreeblueasymmetricalspiralarmsconnectedwiththree
east of the nucleus) superposed on a large filament of dust (this nuclei,andweassociatedthesearmswiththetrajectoryofthenuclei
filament is probably in front of the arm). This asymmetrical arm oftheoriginaldiscgalaxiesthatcollidedtogeneratenewepisodesof
shows a very similar morphology to that detected in NGC 3256 starformation(fromthecompressionofthehighdensityISM;L´ıpari
(cid:12)C 2004RAS,MNRAS348,369–394
InfraredmergersandQSOswithGWs–I 377
etal.2000a;Mihos&Hernquist1994b,1996;Taniguchi&Wada
1996).Thisinterpretationisalsoconsistentwiththeprobablenature
oftheasymmetricalspiralarmsdetectedinNGC2623.However,
forthecaseofthewesternring+arc,wealsoneedtoconsiderother
options,e.g.tidalrings,orarcs/shellsassociatedwithGWs.
AnotherinterestingfeatureinthemainbodyofNGC2623isthe
presenceofseverallarge-scalewidefilamentsofdustwithextension
of∼2–3kpc(Figs2aandb).Twooftheseemergefromtheborders
ofthesmallnuclearcone(tothenorth),andbothreachtheouter
regionsofthismerger.Therearealsoseverallargefilamentsofdust
crossing different parts of this main body and reaching the more
externalareas.Similartypesofdustfilamentswereclearlydetected
intheOFregionsofM82,NGC3079,NGC3256andothergalaxies D
usingmainlyhigh-resolutionHSTWFPC2images(e.g.Ceciletal. ow
n
2001). lo
ThecolourmapofF814W/F555W(Fig.3)isusefulfordisplay- ad
e
ingthegeometryofthemainbody.Themoststronglyobscuredside, d
probablythefarthest,isthenorthernone.Asthisfigureshows,the fro
m
dustseemstobeuniformlydistributedinthemainbody,generating h
theobservedfadingofthenorthside.Wedetectedasimilarredden- ttp
s
ingeffectinthemainbodyofNGC3256.Furthermore,thereare ://a
dustfilamentsovertheequatorialplaneofNGC2623–especially ca
d
attheborderofthenuclearconearea–whicharesuperposedonthe e
m
farside. ic
The position of the optical photometric major axis was anal- Figure4. HSTWFPC2Cousins–Isurfacebrightness(magarcsec−2)plot- .ou
ysedbyfittingellipsestothehigh-resolutionHSTWFPC2(F555W, tedagainstthefourthrootoftheradius.Thelineisthefitofanr1/4law. p.c
o
F814W)imagesandtotheWHTnarrowcontinuumλλ6540–6630 m
/m
map(seeSection3.2).Wefoundthefollowingpositionanglesfor
n
the photometric major axis: PA = 85◦ ± 3◦ for 1 kpc (cid:2) r majoraxisPAinthethreeimagesinthenuclearandcircumnuclear ra
F814W s
(cid:2)2.5kpc,PA =90◦ ±2◦ for2.3kpc(cid:2)r (cid:2)4.3kpcand regions(forr(cid:2)1kpc)andalsointhecentralareaoftheF555W /a
PA =92◦W±HT8c◦onftor3.5kpc(cid:2)r(cid:2)5.5kpc.Theseradialranges image,whichcouldbecausedmainlybythepresenceofdustand rtic
F555W le
correspondtotheregionswherethemajoraxisPAsshowrelatively severalbluestructures. -a
b
constantvalues.Wedetectedstrongvariationsofthephotometric Adetailedstudyhasbeenperformedoftheluminosityprofileof s
thebroad-bandHSTWFPC2F814W(∼I)image.Wefittedellipses tra
c
0.14-arcsecwide(3pixels)andweextractedthesurfacebrightness t/3
4
along the major axes of the ellipse at each radius. The obtained 8
/2
profilethencorrespondstothesurfacebrightnessacrossthephoto- /3
6
metricmajoraxis.AgoodfitoftheI surfacebrightnesswiththe 9
/9
r1/4lawwasobtainedintworadialrangessimultaneously:1kpc(cid:2) 8
4
r(cid:2)2.5kpcand3.7kpc(cid:2)r(cid:2)5.0kpc(seeFig.4).Forthefitting 00
0
omft(hre)l=awm (r )+8.327(cid:3)(cid:4)r (cid:5)1/4−1(cid:6) (2) by gue
I I e re st o
n
weobtainedtheparametersm (r )=21.7±0.2magarsec−2 and 0
I e 7
r =11±2kpc.Weverifiedthatonlyforverysmallradialranges A
e p
could the WFPC2 I surface brightness also be fitted well by an ril 2
exponential/spirallaw(seeScovilleetal.2000).ThedropintheI 0
1
surfacebrightnessintherangesr(cid:2)1kpc,and2.5kpc(cid:2)r(cid:2)3.7kpc 9
(withanabsorptionpeakatr∼3.1kpc)couldbeexplainedbythe
presence of dust in these regions. Previous studies using near-IR
images of NGC 2623 also provided a good fit to the luminosity
profilebyanr1/4law,for0.8kpc(cid:2)r(cid:2)4kpc(Wrightetal.1990;
Scovilleetal.2000).ThepresentstudyoftheHSTWFPC2I-band
imageextendsthesepreviousstudiestoopticalwavelengths,aswell
astotheouterandfaintregionsofthissystem,reachingadistance
of∼5.3kpc.Therefore,forthemainbodyofNGC2623,theoptical
(I band) and near-IR (1.1-, 1.6- and 2.2-µm bands) photometric
Figure3. HSTWFPC2(I−V)colourimage,fromtheF814WandF555W
profilescorrespondmainlytoaspheroidalsystem.Wenotethatour
filters.Thecalibratedrangeofcolours(usingI-CousinsandV-Johnsonmag)
inthisplotis:(0.01,−2.85).Themoreobscuredregionisthesmallnuclear fitoftheopticalluminosityprofilebyanr1/4lawforNGC2623is
cone(seethetext),withareddeningpeakatthepositionofthenucleusof verysimilartothatpresentedfortheIRmerger/QSOMrk231by
(V−I)=2.75. Hamilton&Keel(1987,theirFig.6a).
(cid:12)C 2004RAS,MNRAS348,369–394
378 S.L´ıparietal.
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Figure5. WHT+INTEGRALspectraofthemainbodyofNGC2623(atthewavelengthregionofHα+[NII]).Thenumberoneachspectrumindicatesthe /98
4
fibrenumber(thenucleuswaspositionedonthefibre94).Thecentreofthefibrebundledefinethezero(0,0)position. 0
0
0
Thepresenceoftwolargetidaltailsinthissystemwithatotal 5.9 × 4.4 kpc2) are shown in Fig. 5. These data represent only a by
extensionof∼50kpc(Fig.1)requiresthatthecollisionoftheorig- smallpart(∼100Å)ofthefullspectralcoverage(6000–7500Å)at gu
e
inalgalaxiesoccurasprogrademergers(Barnes&Hernquist1992, eachofthe189fibrelocations.Thenucleuswaspositionedrelatively s
1996). closetothecentreofthefield,2.4arcseceastand0.2arcsecnorth t on
AtaresolutionofFWHM∼1arcsec,broad-bandBcontourdig- ofcentre(thispositionofthenucleuswasobtainedfromtheWHT 07
italimages(Joy&Harvey1987)showsimilarstructurestothose narrowcontinuumλλ6540–6630map).EveninFig.5thepresence Ap
detectedinFig.1.Inparticular:(i)therearetwobright‘compact’B of ‘extended’ LINER emission, with strong [N II] lines is clearly ril 2
knotsinthecentralregions,(ii)thereisathirdBknotintheexter- noted. 01
nalareaand(iii)thenucleusiscompletelyobscuredintheBband. Fig.6(a)showstheHαadjacentcontinuumλλ6540–6630Å,and 9
Morespecifically,thecentralBknotsarelocatedonbothsidesand Figs6(b),(c)and(d)depicttheHα,[NII]and[SII]emissionline
close(∼2–3arcsec)tothepositionoftheobscurednucleusinthe mapsforthemainbodyofNGC2623.Acompactnucleusisevident
east–westdirection,andthethirdliesinthesouthernloop.TheHST inthecontinuummap(Fig.6a),fromwhichanextendedconenebula
WFPC2imagessuggestthatthetwoBknotslocatedonbothsides ofHα,[NII]and[SII]emissionemerges(Figs6b,candd).This
ofthenucleuscouldbepartoftheringandtheasymmetricalspiral conenebula–withacleareroutlineinHα–hasanapertureangle
armsthatemergefromthenucleus,whilethethirdBknotispartof θ =100◦±5◦andaprojectedaxisatPA=50◦±6◦,andextends
asystemofsmallblueknotsinthesouthernloop/extension(Figs2a outtor∼9arcsec(∼3.1kpc)fromthenucleus.TheindividualHα
andb). and[NII]emissionlinemapsshowtheconewithasimilarshape.
Inparticular,bothmapsdepictafilamentarystructure.Ontheother
hand,inthenuclearandcircumnuclearregions(r(cid:2)4.0arcsec)the
3.2 Detectingandmappingthenuclearoutflow(GW)
[SII]emissionlinemapshowsashapesimilartothatobservedinthe
TheHα+[NII]emissionlineprofilesobtainedsimultaneouslywith Hα and[NII]maps.Inaddition,thismap(Fig.6d)clearlyshows
INTEGRALforthecentralregionofNGC2623(16.4×12.3arcsec2, several filaments of [S II] emission; specifically, the brighter and
(cid:12)C 2004RAS,MNRAS348,369–394