Tracing the origin of the AGN fuelling reservoir in MCG–6-30-15

20 Pages·2016·2.89 MB·English

MNRAS464,4227–4246(2017) doi:10.1093/mnras/stw2635
AdvanceAccesspublication2016October13
(cid:2)
Tracing the origin of the AGN fuelling reservoir in MCG–6-30-15
S. I. Raimundo,1† R. I. Davies,2 R. E. A Canning,3,4 A. Celotti,5,6,7 A. C. Fabian8
and P. Gandhi9
1DarkCosmologyCentre,NielsBohrInstitute,UniversityofCopenhagen,DK-2100CopenhagenØ,Denmark
2Max-Planck-Institutfu¨rextraterrestrischePhysik,Postfach1312,D-85741Garching,Germany
3KavliInstituteforParticleAstrophysicsandCosmology(KIPAC),StanfordUniversity,452LomitaMall,Stanford,CA94305-4085,USA
4DepartmentofPhysics,StanfordUniversity,452LomitaMall,Stanford,CA94305-4085,USA
5SISSA–ScuolaInternazionaleSuperiorediStudiAvanzati,ViaBonomea265,I-34135Trieste,Italy
6INFN–SezionediTrieste,viaValerio2,I-34127Trieste,Italy
7INAF–OsservatorioAstronomicodiBrera,viaBianchi46,I-23807Merate,Italy
8InstituteofAstronomy,UniversityofCambridge,MadingleyRoad,CambridgeCB30HA,UK
9DepartmentofPhysicsandAstronomy,UniversityofSouthampton,Highfield,SouthamptonSO171BJ,UK
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Accepted2016October11.Received2016October10;inoriginalform2016August3 lo
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ABSTRACT m
h
The active galaxy MCG–6-30-15 has a 400 pc diameter stellar kinematically distinct core, ttp
counter-rotatingwithrespecttothemainbodyofthegalaxy.Ourprevioushighspatialresolu- ://m
n
tion(0.1arcsec)H-bandobservationsofthisgalaxymappedthestellarkinematicsand[FeII] ras
1.64 µm gas dynamics though mainly restricted to the spatial region of the counter-rotating .ox
fo
core.Inthiswork,weprobethestellarkinematicsonalargerfieldofviewanddeterminethe rd
jo
ionizedandmoleculargasdynamicstostudytheformationofthecounter-rotatingcoreandthe u
rn
implicationsforactivegalacticnucleus(AGN)fuelling.Wepresentintegralfieldspectroscopy als
.o
observations with SINFONI in the H and K bands in the central 1.2 kpc and with VIMOS rg
HR-blue in the central 4 kpc of the galaxy. Ionized gas outflows of vout ∼ 100kms−1 are at U/
tracedbythe[CaVIII]2.32µmcoronallineandextendouttoatleastaradiusof r∼140pc. niv
Themoleculargas,tracedbytheH22.12µmemission,isalsocounter-rotatingwithrespectto ers
themainbodyofthegalaxy,indicatingthattheformationofthedistinctcorewasassociated ity
o
with inflow of external gas into the centre of MCG–6-30-15. The molecular gas traces the f C
a
availablegasreservoirforAGNfuellingandisdetectedascloseasr∼50–100pc.External m
b
gasaccretionisabletosignificantlyreplenishthefuellingreservoirsuggestingthattheevent rid
g
e
whichformedthecounter-rotatingcorewasalsothemainmechanismprovidinggasforAGN o
n
fuelling. Ja
n
u
a
Keywords: galaxies:active–galaxies:individual:MCG–6-30-15–galaxies:kinematicsand ry
1
dynamics–galaxies:nuclei–galaxies:Seyfert. 2, 2
0
1
7
accretioniscurrentlyoneofthemostimportantquestionsinAGN
1 INTRODUCTION
andgalaxyevolutionstudies.
Theobservedcorrelationsbetweenpropertiesofsupermassiveblack TounderstandthephysicsofAGNfuelling,itisessentialtostudy
holesandtheirhostgalaxies(Magorrianetal.1998;Ferrarese& notonlytheblackholeaccretionphysicsbutalsotheenvironment
Merritt2000;Gebhardtetal.2000;Marconi&Hunt2003;Ha¨ring ofthehostgalaxies,inparticulartheircentralregions.Duetothe
& Rix2004) suggest a co-evolution in which the active galactic higherspatialresolutionachievable,severalsignaturesoffuelling
nucleus (AGN) phase may play a central role in regulating gas havebeenobservedinthelow-redshiftUniverse,providingthebest
accretionandstarformationinthegalaxy.Understandinghowthe laboratorytostudyAGNfuelling.ThemoleculargassurveyNUclei
host galaxy fuels the AGN and how the AGN in turn affect gas ofGAlaxies(NUGA)forexamplehasfoundawidevarietyoffu-
ellingtracersontheformofdynamicalperturbationsintherange
0.1–1 kpc in lower luminosity AGN (Seyferts and low-ionization
nuclear emission-line regions, LINERs; e.g. Garc´ıa-Burillo et al.
(cid:2)BasedonobservationscollectedattheEuropeanOrganisationforAstro-
2003;Garc´ıa-Burillo&Combes2012).Theionizedgasinthecen-
nomicalResearchintheSouthernhemisphere,Chile,duringprogramme
tral kiloparsec also seems to be more disturbed in Seyfert host
093.B-0734andonobservationsmadewithESOTelescopesattheLaSilla
ParanalObservatoryunderprogramme073.B-0617. galaxies than in inactive galaxies (Dumas et al. 2007). For even
†E-mail:[email protected] smallerphysicalscales,Hicksetal.(2013)andDaviesetal.(2014)
(cid:3)C 2016TheAuthors
PublishedbyOxfordUniversityPressonbehalfoftheRoyalAstronomicalSociety
4228 S.I.Raimundoetal.
comparedfivepairsofmatchedactiveandinactivegalaxiesatares- ingisolatedgalaxies(Katkov,Sil’chenko&Afanasiev2014)which
olutionof∼50pcusinginfraredintegralfieldspectroscopy.They is consistent with an external origin for the counter-rotating gas
foundthatatthescalesof<200–500pc,wherethedynamicaltime (Bertola, Buson & Zeilinger 1992). Pizzella et al. (2004) argue
approachestheAGNactivitytime-scale,therearesystematicdif- that the formation of counter-rotating gas discs is favoured in S0
ferencesbetweenpropertiesofstarsandgasforactiveandinactive galaxiesduetotheirlowgasfraction.Inspiralgalaxieswhichare
galaxies,associatedwiththeblackholefuellingprocess.Theactive more gas rich, the acquired external gas can be swept away due
galaxiesintheirsampleshowanuclearstructureinstarsandgas, to the interactions with the pre-existing gas which would make
composedofarelativelyyoungstellarpopulationandofasignif- thecounter-rotatingdiscobservableonlywhenitsmassishigher
icantgasreservoir,whichcouldcontributetofueltheblackhole. than the one of the pre-existing gas. The difference between the
This nuclear structure is not observed in the quiescent galaxies. fractionofS0galaxieswithobservedcounter-rotatinggasandob-
Thepresenceofcircumnucleardiscsofmoleculargasseemstobe servedcounter-rotatingstarsmaybeduetotheinherentdifficulty
requiredfornuclearactivity,withgasinflowsandoutflowsbeing ofdetectingsmallnumbersofcounter-rotatingstars(e.g.Bureau&
detectedonlyinactivegalaxies.Gasinflow/outflowstructuresare Chung2006).
commonlydetectedintheinnerregionsofAGNhostgalaxies(e.g. The presence of large kinematic misalignments of counter-
Storchi-Bergmann et al. 2007 ; Davies et al.2009, 2014 ; Mu¨ller- rotatinggas,inparticularinS0galaxies,hasbeentakenasstrong
Sa´nchez et al. 2011), and usually most of the inflow and outflow evidenceoftheexternaloriginofthegas(e.g.Bertolaetal.1992;
massisintheformofmoleculargas.Athigherspatialresolution,the Davis&Bureau2016).Ifthegasoriginatesfromstellarmasslossin D
o
AtacamaLargeMillimeter/submillimeterArrayhasalsoprovided thegalacticdisc,thenstarsandgasareexpectedtocorotate.Inter- w
n
anewviewofthesmallspatialscalesaroundtheAGN,withtracers nalphysicalprocessessuchasweakbarsorspiralscancausemild lo
a
d
ofmoleculargasinflowandoutflowbeingdetectedinmostofthe kinematicmisalignmentsbetweengasandstars(uptoanangular e
d
AGNobserved(e.g.Combesetal.2013,2014;Garc´ıa-Burilloetal. difference (cid:4) PA (cid:2) 55 deg; Dumas et al. 2007). However, large fro
2014;Smajic´etal.2014).Consideringtherecentworkinthisfield, kinematicmisalignmentsorcounter-rotatinggas((cid:4)PA=180deg) m
h
ithasbecomeclearthatthecentralhundredsofparsecsofgalaxies wouldrequireasignificantamountofenergytochangetheangular ttp
areessentialtounderstandtheAGNfuellingprocess. momentumofthecorotatinggas,whichisunlikelytobeprovided ://m
TheS0galaxyMCG–6-30-15isanarrow-lineSeyfert1galaxy, byinternalprocesses,especiallyforlargegasmasses(e.g.Dumas nra
with an AGN luminosity of LX(2–10keV)∼4×1042 erg s−1 etal.2007;Daviesetal.2014).Simulationsofinternaldynamical s.ox
(Vasudevan et al. 2009; Winter et al. 2009) and a total bolomet- perturbations, for example of nuclear spirals generated by asym- fo
ricluminosityof∼3×1043ergs−1(Liraetal.2015).Thisgalaxy metriesinthegalacticpotential(Maciejewski2004)orgasflowin rdjo
u
hasbeenparticularlytargetedbyX-raystudies,sinceitwasthefirst barredspiralgalaxies(Regan,Sheth&Vogel1999),donotseemto rn
sourceforwhichthebroadenedFeKαemissionlinewasobserved, generatecounter-rotatinggasstructures. als
.o
showingthatthislinewasbeingemittedfromtheveryinnerregions ThemaintheoriesfortheformationofKDCsinvolvetheinflow rg
of the accretion disc (Tanaka et al. 1995). Our study of the inner ofmaterial(stars/gas)withadistinctangularmomentumintothe a/
500 pc of MCG–6-30-15 in Raimundo et al. (2013) was the first centreofthegalaxy.However,thereismorethanonemechanism t U
n
integralfieldspectroscopystudyonthisgalaxy.Duetotheunprece- thancandrivethismaterialinwardstoproducetheKDCsandcan ive
dentedspatialresolutionreached(0.1arcsec∼16pcintheHband), result in two different KDC populations. In optical wavelengths, rsity
wediscoveredapreviouslyunknownstellarkinematicallydistinct McDermidetal.(2006)foundthatthereisonepopulationofKDCs o
core (KDC) in the centre of MCG–6-30-15 counter-rotating with whicharetypicallylarge(diameter≥1kpc)witholdstellarpopu- f C
a
respecttothemainbodyofthegalaxy.Wefirstestimatedasizeof lations(age≥10Gyr)foundinslow-rotatingearly-typegalaxies. mb
R∼125pcforthedistinctcoreduetothelimitedfieldofviewofour Inthiscase,thestellarpopulationwithintheKDCandinthemain rid
g
initialobservations;wewillshowinthisworkthatthedistinctcore body of the galaxy show little or no difference. This can be ex- e o
hasasizeofR∼200pc.Theageofthestarsinthecounter-rotating plained if the distinct core was formed a long time ago and the n J
a
corewasestimatedtobe<100Myr(Raimundoetal.2013),which differencesinoriginhavealreadybeendilutedoriftheKDCisa nu
a
isinlinewiththefindingsofBonattoetal.(2000),whodetermined superposition of stellar orbits and caused by the geometry of the ry
that>35percentofthestellarpopulationistheresultofburstsof galaxy.Ithasbeensuggested(e.g.Hernquist&Barnes1991)and 12
, 2
starformationdistributedinagebetween2.5and75Myr. shownfromsimulations(Boisetal.2011;Tsatsietal.2015)that 0
1
Stellar KDCs such as the one in MCG–6-30-15 are character- theselargeKDCscanbeformedbyhighmassratiomergers(1:1 7
izedbythepresenceofastellarcorewithkinematicsandangular or 2:1) between disc galaxies with prograde or retrograde orbits.
momentumdistinctfromthemainbodyofthegalaxy.KDCscan Anon-mergerscenariohasalsobeensuggestedfromsimulations,
be defined by an abrupt change of more than 30 deg in the local wherecounter-rotatingstellardiscsareformedearlyinthehistory
kinematic orientation of the galaxy (e.g. McDermid et al. 2006; ofthegalaxyfromtheinfallofgaswithmisalignedspinthrough
Krajnovic´ et al.2011), with counter-rotating cores having angles large-scalefilaments(Algorryetal.2014).Thesecondpopulationof
of180deg.TheATLAS3D projectfoundthatKDCsarepresentin KDCsfoundbyMcDermidetal.(2006)consistsofsmallerstruc-
a small fraction (∼ 7 per cent) of early-type galaxies (Krajnovic´ tures (diameter < 1 kpc), found mostly in fast rotators, typically
et al. 2011), and seem to be more common in slow rotators than closetocounter-rotatinginrelationtotheouterpartsofthegalaxy
in fast rotators (Emsellem et al. 2011). In spiral galaxies, stellar andshowingyoungerstellarpopulations.TheseKDCswerelikely
counter-rotating discs are present in < 8 per cent of the galaxies formedbyrecentaccretionofgaswhichthenformedstarsinsitu.
andarerarerthancounter-rotatinggasdiscs(<12percent;Pizzella ThefactthatthedistinctcorehasananglePA ∼180◦inrelation
kin
etal.2004).InS0galaxiessuchasMCG–6-30-15,itisestimated totheouterpartsofthegalaxymayindicatethatinfactdissipation
that <10 per cent host counter-rotating stars (Kuijken, Fisher & processesareimportantintheformationofthesesmallerKDCs.
Merrifield1996)and∼25–40percenthostacounter-rotatinggas MCG–6-30-15isoneofthegalaxieswithhigherAGNluminosity
disc(Kuijken et al. 1996; Kannappan &Fabricant 2001; Pizzella amongthegalaxieswithknownstellardistinctcores,andtherefore
etal.2004;Bureau&Chung2006),or∼70percentifconsider- weareinterestedinunderstandingtheimpactwhichtheformation
MNRAS464,4227–4246(2017)
TheAGNfuelling reservoirinMCG–6-30-15 4229
oftheKDCmayhaveonAGNfuelling.Daviesetal.(2014)studied Thepointspreadfunction(PSF)isdeterminedfromtheintensity
asampleofS0galaxiesandfoundthattheoneswithAGNtypically ofthebroadcomponentoftheatomichydrogenBrackettrecombi-
have gas detected on large scales (> 1 kpc), while the inactive nationlines.Thebroad-lineregionwheretheselinesareproduced
ones do not. They also find a fraction of sources with counter- isunresolvedinourobservationsandthereforethelinewidthofthe
rotatinggasconsistentwithwhatisexpectedforexternalaccretion. broad hydrogen emission provides a method to estimate the PSF.
TheseobservationssuggestthatinS0galaxies,AGNaretypically SeveraltransitionsofthisBrackettseriesareobservedbothintheH
fuelledbyexternalaccretion.Theyhavealsoshownthatintwoof andKbands.IntheHband,therearefivestronglineswhichweuse
thegalaxiestheyobserved(IC5267andNGC3368),theexternal tomeasurethePSFandalsolaterinthissectiontoremovetheAGN
counter-rotatinggascanreachtheinnertensofparsecsofthegalaxy. contributionfromthespectra.IntheKband,weusethestrongest
In our previous work (Raimundo et al. 2013), we studied the lineofthe(7–4)λ=2.166µmtransition(Brγ).Wefittheselines
stellar kinematics out to r < 250 pc in MCG–6-30-15. Since our withadoubleGaussian(onenarrowGaussiantomodelthecoreand
datawerelimitedtotheHbandandtoa3arcsec× 3arcsecfield onebroaderGaussiantomodeltheextendedemission),toempiri-
ofview,weonlyhadonetracerfortheionizedgasontheformof callymodelthePSF.Thefullwidthhalf-maximumofeachofthe
[FeII]1.64µmemission,mainlyrestrictedtothespatialregionof GaussiansisfortheHband(FWHM=3.6pixels∼0.4arcsec)and
thecounter-rotatingcore.Inthepresentwork,ourgoalisforemost (FWHM=6.7pixels∼0.8arcsec)andfortheKband(FWHM=
to probe the dynamics of the molecular gas, for which there are 3.9pixels∼0.5arcsec)and(FWHM=8.6pixels∼1arcsec).Asa
no previous observations. In this work, we will investigate if the secondcheck,wealsousetheunresolvednon-stellarcontinuumto D
o
formationofthecounter-rotatingcoreisassociatedwithinflowof determinethePSF.TheFWHMoftheGaussiansforthenon-stellar w
n
gasintothecentralregionsofthegalaxyandifthisgascancreate continuumis,asexpected,similartowhatwasdeterminedwiththe lo
a
orreplenishthemoleculargasreservoirforAGNfuelling.Wewill broadBrackettemission:Hband(FWHM=3.3pixels∼0.4arc- de
d
firstdescribetheSINFONIandVIMOSobservationsandthedata sec) and (FWHM = 5.4 pixels ∼0.7 arcsec); K band (FWHM = fro
reductionandanalysis.Wewillthenpresenttheresultsonthestellar, 3.9pixels∼0.5arcsec)and(FWHM=8.7pixels∼1.1arcsec). m
h
ionizedandmoleculargaspropertiesinthegalaxy.Usingthestellar Theinstrumentalbroadeningiscalculatedbyselectingandmea- ttp
andgasdynamics,wesetnewconstraintsontheblackholemass. suringthespectralbroadeningofanunblendedskyemissionline. ://m
Finally,wewilldiscuss,basedontheseobservations,theoriginof Thebroadeningvariesasafunctionofwavelengthandspatialpo- nra
thestellarcounter-rotatingcoreanditseffectonAGNfuelling. sitioninourdatacube;therefore,weselectskylinesclosetothe s.o
70Wkmesa−d1oMptpcth−e1, (cid:5)stamnd=ar0d.2c7oasmndol(cid:5)og(cid:6)ic=al0p.7a3ra.mTehteersscaoleffHor0ou=r twhaisveclaelncgutlhatoiofninftoerressktyfolrinoeusrcmloesaesutoretmheenwtsa.vFeolernthgethKobfatnhde,[wSeiVdIo] xfordjo
measurements is approximately 0.158 kpc arcsec−1 at a redshift 1.963 µm, Brγ 2.166 µm, 1–0 S(1) H2 2.1218 µm and [Ca VIII] urn
z=0.0077(Fisheretal.1995valuequotedattheNASA/IPACEx- 2.3211 µm emission lines for every spaxel in the sky emission als
.o
tragalacticDatabase).ThedistancetoMCG–6-30-15usedinthis cube.Theinstrumentalbroadeningatthewavelengthofeachline rg
paperis33.2Mpc(Wright2006). isdeterminedbydoingafield-of-viewspatialaverageofthebest- a/
fittingGaussianσ.Weobtainvalueswhichvarybetweenσ ∼42 t U
inst n
and48kms−1 intheKband.Thespectralresolutionatthewave- ive
2 DATA ANALYSIS lengthofthe1–0S(1)H2emissionisHalfwidthathalfmaximum rsity
(HWHM)∼3.3Å.FortheHband,weobtainvaluesofσ ∼44– o
2.1 SINFONIdatareduction 54kms−1whichatthewavelengthofthe[FeII]1.644µminesmt ission f Ca
TheSINFONI/VLTH-banddatawithR∼3000weretakenonthe correspondstoHWHM∼3.2ÅandaresolutionofR∼2500. mb
nightof2014June2withapixelscaleof0.25arcsec×0.125arcsec, Asmentionedabove,thebroadhydrogenrecombinationlinesof rid
g
samplingafieldofviewof8arcsec×8arcsec.Eachexposurewas the Brackett series are present in both the H and K bands. In the e o
n
of 300 s, in an object (O) and sky (S) sequence of OSO. The Hband,severaloftheselinesoverlapwithstellarabsorptionlines J
a
total on-source exposure time was 55 min. The SINFONI/VLT of interest and therefore it was necessary to remove them before nu
a
K-band data with R∼4000 were taken on four nights (2014 June determining the stellar kinematics. The procedure was similar to ry
4, 12 and July 2, 3) with a pixel scale 0.25 arcsec×0.125 arcsec theonedescribedinRaimundoetal.(2013),wherethebroademis- 12
and also sampling a field of view of 8 arcsec× 8 arcsec. Each sionlineswerefittedsimultaneously,whilefixingtheirrest-frame , 20
1
exposure was of 300 s, in an object (O) and sky (S) sequence of wavelengths to a common redshift and relative intensities to the 7
OSO.Thetotalon-sourceexposuretimewas2h30min.Thedata ones predicted theoretically using as an approximation Hummer
reductionwasdonewiththeEuropeanSouthernObservatory(ESO) & Storey (1987) for case B recombination. In the K band, only
pipeline for SINFONI ESOREX version 3.10.2 and complemented twobroademissionlineswereobservedandtheydidnotoverlap
with independent IDL routines. The two main extra routines used withthewavelengthrangeoftheCOstellarabsorptionlinesorthe
weretheimplementationoftheskyemissionsubtractiondescribed emissionlines.FortheKband,itwasnotnecessarytoremovethe
in Davies et al. (2007) and a bad pixel removal routine for 3D AGNbroadhydrogenemissionpriortotheanalysisofthestellar
datacubes(Daviesetal.2010)–a3DversionofLAcosmic(van properties.
Dokkum2001).Fortheanalysis,thecubeswereshiftedconsidering Thefluxcalibrationisdoneusingthe2MASSmeasuredfluxes
theoffsetsrecordedintheirheaders,combinedandre-sampledtoa in the H band and Ks band for a 5 arcsec diameter aperture. To
spatialscaleof0.125arcsec×0.125arcsec.Theobservationswere determinethe2MASSfluxes,weusethezero-magnitudecalibra-
taken with a rotation angle of 25 deg to obtain a better spatial tionsinCohen,Wheaton&Megeath(2003).Wethencomparethe
sampling along the major axis of the galaxy. In the plots in this 2MASS fluxes with the median number counts of the integrated
paper,thex-axiswillbeparalleltothemajoraxisofthegalaxy.The spectrainourdatacubes,forthesameaperture.Inourdatacubes,
compassineachoftheplotsindicatestherelativepositioninthe themediannumbercountsaredeterminedwithinthewavebandof
sky.Amoredetaileddescriptionofthetypicaldatareductionsteps [1.504–1.709] µm for the H band and [1.989–2.316] µm for the
fortheHbandcanbefoundinRaimundoetal.(2013). Kband.Thesewavebandscorrespondtothewavelengthsatwhich
MNRAS464,4227–4246(2017)
4230 S.I.Raimundoetal.
thetransmissioninthe2MASSfiltersishigherthan0.2.Byusing component and a more spatially extended narrow component is
differentaperturesin2MASS,wedeterminethatourcalibrationis also detected. Stellar absorption lines albeit with a lower signal-
consistentto∼20percent. to-noise ratio (S/N) are also observed. The broad Hβ component
originatesfromtheAGNandisthereforeunresolvedinourdata.
WeuseitsfluxdistributiontoobtainanestimateforthePSFand
2.2 VIMOSdatareduction thespatialresolution.FittingthebroadHβfluxspatialdistribution
Toinvestigatetheemissionintheopticalwavelengths,weanalysed withacircularGaussian,wefindFWHM=1.7pixelwhichforour
archivalIntegralFieldUnit(IFU)dataofMCG–6-30-15from2004 scaleof0.67arcsecpixel−1correspondstoFWHM=1.1arcsec.
usingVIMOS/VLT.ThedataweretakenwiththeoldHR-bluegrism
(replacedbyanewsetofgrismsin2012)withawavelengthrange
2.3 AGNandstellarcontinuum
4200–6150Åandapixelscaleof0.67arcsecpixel−1 inafieldof
viewof27arcsec×27arcsec.Wereducedthedataineachofthe Theobservednear-infrared(near-IR)continuumisacombinationof
four quadrants using the ESO VIMOS pipeline and the standard stellarandnon-stellarcontributions.Toevaluatethecontributionof
recipesfordoingthebiassubtractionandflat-fieldcorrection,bad eachofthesecomponentstothetotalcontinuumintheHband,we
pixelremoval,wavelengthcalibrationandrelativefluxcalibration usetheequivalentwidthoftheCO(4–1)1.578µmstellarabsorption
withvmbias,vmifucalib,vmifustandardandvmifuscience.Inquad- line, while in the K band we use the 12CO (3–1) 2.323 µm line
rantthree,weobservedthattherewerezig-zaggingpatternsonits (Fig.1).ClosetotheAGN,thestellarabsorptionlinewillbediluted Do
w
reconstructedimageaftervmifusciencewhichiscausedbyafibre andweexpecttheequivalentwidthtodecreaseasthedistancefrom n
misidentificationduringvmifucalib.Thishasbeenobservedinother the AGN decreases. In the regions further away from the centre loa
d
datasets(e.g.Rodr´ıguez-Zaur´ınetal.2011).Tosolvethisproblem, of the galaxy (r (cid:3) 1.3 arcsec), where the AGN contribution is ed
we did not use a fibre identification file but ran the recipe with a negligible,theequivalentwidthwillbeduetostellarprocessesonly fro
m
‘firstguess’fibreidentificationmethod;specifically,thearclamp and determines the intrinsic line equivalent width (Wintr; Davies h
linesareidentifiedusingmodelsofthespectraldistortionsasfirst et al. 2007; Burtscher et al. 2015). The plots in Fig. 1 give us ttp
guesses.Doingsuchafibreidentificationimprovedtheresultbut theobservedequivalentwidthasafunctionofradius(W ).The ://m
obs n
didnotcompletelysolvetheproblem.Wethendecidedtochange fractionofthecontinuumwhichisduetonon-stellarprocesseswill ra
s
themaximumpercentageofrejectedpositionsinthefibrespectra thenbe .o
x
tpriaxceilngpotsoitaiocnosnwsearsvamtiovreevtahlaune,1i7.ep.ewrhceenntt,htehefraficbtrioenwoafsrflejaegcgteedd fAGN(r)=1− WWobs(r), (1) fordjo
as ‘dead’. As we only have one exposure for each quadrant, this intr urn
a
resultsinsomefibresbeingexcluded(havingnoassociateddata) and we can determine the AGN contribution to the continuum at ls
.o
in the final data cube which is not ideal but preferable to having eachradialposition.Thetotalcontinuumateachpositionofthefield rg
mvieiswidaenndtitfiheedfifinablrecsu.bTehweerfienoabltareinceodnsbtyruccotmedbiinminaggethoefrethdeucfieedlddaotaf otifnuvuiemwiisscfiatltceudlautseidngbyamseuclotinpdly-dineggrteheeptootlaylncoomnitainl.uTuhmebAyGfANGNco(rn)-. at Un/
onthefourquadrantsusingvmifucombineandvmifucombinecube, Thestellarcontinuum isdeterminedfromthedepthofthestellar ive
respectively.Finalfibre-to-fibretransmissioncorrectionsweredone absorptionlinespresentinourspectra.Thecontinuumdecompo- rsity
vtuheseirnisfgykydtheldeiniwceaaotvefed[leOIDnLgI]trhoλuc5ta5iln7ibe7sraÅatni.odTnhthaenesdfiatmboreed-esttokey-rfimlbiinrneeeiwnthtaeesgiranalsstteorduumflsueedxntitanol snaiotsinmo-nsatleflolrlreagrthicoeonnHctilnoaunseudmtKoitsbhaeansndsuoscciliseautseshdo(rww(cid:2)nithi0nt.h5Fe–i0gA..8G2aN.rcAassnedce)xi.spTelhicmeteisdtte,edltlhtaoer of Camb
broadeningwhichisσ =22kms−1.Thescopeofouranalysisis continuumshowsamoreextendeddistribution. ridg
e
todeterminetherelativelineintensitymapandvelocityprofilefor o
n
the[OIII]emissionandthereforenoabsolutefluxcorrectionswere Ja
3 RESULTS AND DISCUSSION n
done. Sky lines are observed in the spectra; however, as they are ua
not confused with the object emission, they are not subtracted in IntheHband,aftersubtractingthebroadhydrogenemissionlines, ry 1
thedatacube. variousstellarabsorptionlinefeaturessuchastheCOabsorption 2, 2
Severalemissionlinesareobservedinthespectra:thestrongest bands,SiIandMgIareobservedinthespectra.Theonlyemission 01
emission is [O III] 5007 Å but Hβ 4861 Å with a nuclear broad lineobserved,apartfromthehydrogenrecombinationlines,isthe 7
Figure1. Left:equivalentwidthoftheCO(4–1)1.578µmlineintheHbandasafunctionofradius.Right:equivalentwidthofthe12CO(3–1)2.3227µm
lineasafunctionofradius.ThecentreindicatesthepositionoftheblackholeandismeasuredfromthepeakofthebroadhydrogenBrackettemission.The
equivalentwidthsaremeasuredinannuliof1pixel(0.125arcsec)width.Theredlinesineachoftheplotsarethebest-fittingGaussiancurvestothedata
points.TheyareusedinthesubsequentdecompositionofAGNandstellarcontinuumfortheHandKbands.
MNRAS464,4227–4246(2017)
TheAGNfuelling reservoirinMCG–6-30-15 4231
Figure2. Non-stellarandstellarcontinuummapsafterthecontinuumdecompositionbasedonthestellarabsorptionlines’equivalentwidths.Thetwoplots
ontheleftshowtheH-bandcontinuumandthetwoplotsontherightshowtheK-bandcontinuum.ThepositionoftheAGNisindicatedbytheblackcross.
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Figure4. Spectrumofthenuclearregionintegratedina0.625arcsecradius ls
aperture.Theinnerr<0.25arcsecareexcluded.Theregionsingreyindicate .org
thepresenceofresidualsfromthetelluricabsorptioncorrection. a/
t U
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method,andofouranalysis,istorecovertheline-of-sightvelocity ive
distribution from the stellar absorption features of our observed rsity
spectra.Thismethodassumesaparametrizationforthestellarline- o
Figure 3. H2 2.1218 µm emission from four regions of 5 × 5 pixels of-sightvelocitydistributionontheformofaGauss–Hermiteseries f Cam
(0.625arcsec× 0.625 arcsec) in the field of view. From top to bottom: expansion, with thefirsttwo moments being thevelocity and the b
north-east,south-west,south-eastandnorth-westfromthenucleus.Relative velocity dispersion (V, σ). It then uses a set of stellar templates rid
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totheimagesinFig.2,theseregionsarelocatedattheleft,right,topand andapolynomialcomponenttoaccountfortheAGNcontinuum, e o
bottomoftheAGNposition.ThewavelengthrangeintheplotshowstheH2 to find the best-weighted template combination and line-of-sight n J
a
gasemissionline.TheemissionattheSEandNWofthenucleusshowsa velocitydistributiontofittheinputgalaxyspectra.Duetothelimited nu
clearredshiftandblueshift.Theverticaldashedlinesindicatetheposition S/Nofourdata,weonlyfitthefirsttwomomentsofthevelocity ary
ofthepeakoftheemissionineachofthesetworegions.Thex-axisisthe 1
distribution. 2
observedwavelength. , 2
In the H band, we use the stellar templates of Le et al. (2011) 0
1
at a resolution of R ∼ 5000. This library contains only 10 G, K 7
[FeII]1.64µmemissionline.IntheKband,wedetectseveralstellar and M giant stars, but as described in Raimundo et al. (2013), K
absorptionfeatures,includingtheCOabsorptionbandswhichare
andMstarsprovideagoodmatchtoourstellarabsorptionfeatures.
thestrongestabsorptionlinesinourspectra.TherovibrationalH
2 IntheKband,weusethestellartemplatesfromWinge,Riffel&
2.12 µm emission is also detected and a tracer of the molecular
Storchi-Bergmann(2009)inthenear-IRwavelengthrangeof2.24–
gasdistribution(Fig.3).Inaddition,therearethreeotheremission 2.43 µm, at a resolution of R = 5900 obtained with GNIRS. We
linesfromionizedgaswhichareobserved([SiVI]1.963µm,Brγ convolvethesespectrawithaGaussianofσ =2.3Åtomatchthem
2.166 µm and [Ca VIII] 2.3211 µm) and will be analysed in the tothelowerresolutionofourdata.
followingsections.ThenuclearspectrumofMCG–6-30-15inthe
ThestellarkinematicsfromboththeHandKbandsareconsistent
KbandshowingtheBrγ andcoronalemissionlinescanbeseenin
withwhatwasfoundinRaimundoetal.(2013).InRaimundoetal.
Fig.4.H2isnotsignificantlydetectedinthenuclearregion. (2013),weonlyhadH-banddataina3arcsec×3arcsecfieldof
view,whichallowedustodiscoverthecounter-rotatingcorebutnot
tostudythemainbodyofthegalaxyextensively.Withthelarger
3.1 Stellarkinematics
field of view of our new H - andK-band observations (8arcsec×
Thestellarkinematicsareobtainedbyfittingtheobservedgalaxy 8arcsec), we are able to probe larger distances from the nucleus.
spectrausingthePenalizedPixel-Fitting(pPXF)method(vander Fig.5showsthefittotheintegratedemissionintheHandKbands.
Marel&Franx1993;Cappellari&Emsellem2004).Thegoalofthis Theblacklineshowstheintegratedgalaxyspectrumandtheredline
MNRAS464,4227–4246(2017)
4232 S.I.Raimundoetal.
Figure5. Data(blackline),best-fittingmodel(redline)andresiduals(bottomgreyspectrumshiftedbyaconstantfactortobevisibleintheplot)forthe
galacticspectrumfitwithpPXF.Left:H-bandintegratedemissioninanr<2arcsecregion,excludingtheinnerr<0.5arcsec.Right:K-bandintegrated D
emissioninanr<2.5arcsecregionexcludingthecentralr<0.25arcsec.Theverticalshadedbandsindicatethewavebandsexcludedfromthefit.Thex-axis ow
istherest-framewavelengthaftercorrectingforthesystemicvelocityofthegalaxy. nlo
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Figure6. Stellarline-of-sightvelocityandvelocitydispersionmapsfortheHband(top)andKband(bottom).Left:line-of-sightvelocityfieldcorrectedfor ry 1
thegalaxy’ssystemicvelocityof2410kms−1.Right:velocitydispersioncorrectedfortheinstrumentalbroadening.ThemapwasbinnedtoaminimumS/N 2, 2
of5.ThecentralregionsweremaskedoutduetothelowS/Nofthestellarabsorptionfeaturesandtheouterregionsweremaskedoutduetoacombinationof 0
1
lowfluxandlowS/N. 7
showsthebest-fittingmodelfrompPXF.Theresidualsareshown of-sightvelocityandvelocitydispersionfortheHandKbandsare
inlightgreyatthebottomoftheplot.Regionswithemissionlines showninFig.6.TheKDC,characterizedbyachangeintherotation
andtelluricsubtractionresidualsweremaskedoutofthefitandare directionofthevelocityfield,isclearlyobservedinthecentreof
identifiedbytheverticalshadedbars. boththevelocityfieldmaps.DespitethelowerS/NintheKband,
EachspatialpixelwasthenfittedusingpPXFinasimilarpro- theK-bandvelocityandvelocitydispersionmaps(Fig.6,bottom
ceduretowhatwasdonefortheintegratedspectruminFig.5.The panels)areconsistentwiththeonesfortheHbandconsideringthat
mapswerefirstbinnedtoaminimumS/N∼5betweenthedepthof the velocities measured in the K band have larger error bars (see
theCOstellarabsorptionlinesandthenoiseinaline-freeregionof below).Althoughforthefinalresultsweonlyfitforthefirsttwo
thespectrausingtheVoronoibinningtechniquedescribedinCap- momentsofthevelocitydistribution,wetestedadeterminationof
pellari&Copin(2003).ThestellarfeaturesintheKbandareweaker theparameterh3,whichisassociatedwithasymmetricdeviations
andthemaphastobemoresignificantlybinnedtoachievethetarget from a Gaussian shape for the line-of-sight velocity distribution.
S/N;furthermore,theinnerregionsshowahighnoiseleveldueto Theh3mapshowedananti-correlationwiththevelocitystructure
thepresenceoftheAGNemission,andthereforeweremaskedout. ofthedistinctcore.
The outer regions of both maps where the flux is low (less than UsingMonteCarlosimulationswherethewavelengthrangesfor
1percentofthepeakflux)werealsomaskedout.Themapsofline- thefitandinitialparametersarechangedrandomly,weestimatethe
MNRAS464,4227–4246(2017)
TheAGNfuelling reservoirinMCG–6-30-15 4233
starsprovidetheonlyexcitationmechanismforBrγ (e.g.Panuzzo
etal.2003;Valenciaetal.2012;Smajic´etal.2014).Inthecaseof
MCG–6-30-15,thespatialdistributionofBrγ whencomparedwith
thestellardistributionprofileleadsustobelievethatthisemission
is mainly associated with the AGN, although some smaller con-
tributionfromstarformationisalsopossible.AsnotedbySmajic´
etal.(2014),assumingthatallofthecentralBrγ emissionisdue
tostarformationisanunlikelyscenarioforaSeyfertgalaxy.We
canhoweverusetheequivalentwidthofthenarrowBrγ linetoset
upperlimitsonthestarformation.Intheintegratedcentralregionof
0.625arcsec×0.625arcsec,thewidthofthenarrowlineis∼15Å.
Thisisalowvalue(similarvalueshavebeenfoundforotherSeyfert
galaxies;Daviesetal.2007),whichindicatesthatthereislittlestar
Figure7. FittothehydrogenBrackettemissionlineintheKbandwhich
formationongoinginthisgalaxy.Ifstarformationisoccurring,it
consists of two components: a broad one associated with the AGN and
ispossiblyintheformofshortbursts,inlinewithwhatisobserved
a narrow one which may have a contribution from star formation. The
emissionintheplotcorrespondstoanintegratedregionof5×5pixels intheultravioletspectra(Bonattoetal.2000).
(0.625arcsec×0.625arcsec)centredatthespatialpositionoftheAGN. Do
w
Thex-axisistherest-framewavelength. 3.2.2 [FeII]emission nlo
a
errorsintheH-bandvelocitymaptobetypically6kms−1exceptin Theforbidden[FeII]emissionlineat1.644µmwasfirstdetected ded
thecentralregionsclosetotheblackholewhereitreaches13kms−1. in the H-band observations in Raimundo et al. (2013), extending fro
Theerrorsinthevelocitydispersionare∼7and15kms−1 inthe outtoaradiusofr<0.8arcsec.Withthenewdatainthepresent hm
centre.IntheK-bandmap,weestimatetheerrorinthevelocityand workcoveringawiderfieldofviewandatahigherS/N,wewere ttp
velocitydispersiontobe<10kms−1outtor<2arcsec.Theouter abletostudythedistributionofionizedgasfurtheroutinthegalaxy ://m
regions(r>2arcsec)andthecentralmaskedregionhaveerrorsof (Fig.8,secondrow).Fortheanalysisoftheionizedgasemission, nra
∼20–25kms−1inbothvelocityandvelocitydispersion. we use the code LINEFIT (appendix B of Davies et al. 2011 ) to s.o
x
The systemic velocity and position angle (PA) are determined fit the emission line at each spatial position of our field of view. fo
usingthemethodoutlinedinKrajnovic´etal.(2006).Thekinematic LINEFITusesaskyemissionlineobservedclosetothewavelengthof rdjo
u
PA for the distinct core is determined from the H-band velocity interestasatemplatefortheemission,andthenconvolvesitwitha rn
a
maplimitedtotheregionofr<1.1arcsec.WefindPA=118± Gaussiankerneltomatchtheobservedlineprofile.Theinstrumental ls
.o
22deg(3σ error)measuredfromnorthtoeast.Theregionoutside broadeningisthereforeautomaticallyaccountedforwhenfittingthe rg
wtheefidnisdtinPAct=cor1e1i2s±mo8ddeellged(3sσetetirnrogrr).>Th1e.2siamndilarr<ity3b.5etawrecesenct,haensde alinndest.hIenrdmivsidnuoaislepoixfetlhsewciotnhtiSn/uNum<)3w(ebreetwmeaesnketdheopuetaokftohfethimealignee. at Un/
angles combined with the observation of the shift in the velocity Weobservethatthe[FeII]linefluxdoesnotpeakattheposition ive
fieldindicatethatthedistinctcoreismisalignedfromthemainbody of the nucleus but at a position north-west of the nucleus, as in rsity
o(1f8t0hedeggalsahxiyftwiniththaenveolroiecnittyatoiornienctoantisoisntewntithwirtehspceocutnttoert-hroetamtiaoinn tmheapfiirnstditcimateesitawnaosvdeeratellctbeudlk(Rroaitmatiuonndaolvetelaolc.i2ty01d3i)r.ecTthioenvseilmociiltayr of Ca
m
bodyofthegalaxy). totheoneofthestellarcounter-rotatingcore,albeitwithahigher b
rotationalvelocity[−70,60]kms−1.Wecannowdistinguishfurther rid
g
structureinthevelocitydispersionmap.Theforbiddentransition e o
3.2 Ionizedgas of [Fe II] is excited by electron collisions. To achieve the right n Ja
3.2.1 HydrogenBrγ emission conditionsforthislineemission,itisnecessarytohaveazoneof nua
partiallyionizedhydrogenwhereFe+ ande− coexist.InAGNin ry
BclroosaedtohtyhderoAgGeNn,Barnγdi2t.i1s6s6paµtimalleymuinsrseiosonlviseddebtyecotuerddiantat.hTehreegBiorγn tphaertciceunltarra,l[AFeGINI]eomribsysisohnoccaknsb(ceaguesneedrabtyedthbeyipnhteortaocitoionnizaotfiornadbiyo 12, 20
1
emissionalsoshowsanarrowcomponentwhichcanbeseparated jetswiththemedium,bynuclearmassoutflowshockswithambient 7
fromtheunderlyingbroadcomponent.Fig.7showstheintegrated cloudsorbysupernova-drivenshocks;Mouri,Kawara&Taniguchi
emission in a region of 0.625 arcsec × 0.625 arcsec centred at 2000;Rodr´ıguez-Ardilaetal.2004).Correlationshavebeenfound
thenucleus.Thislineshowsablueshiftof∼100–150kms−1 with betweentheradiopropertiesofSeyfertsandthepresenceof[FeII]
respecttothesystemicvelocityofthegalaxy,asfoundinReynolds (Forbes&Ward1993;RamosAlmeidaetal.2006;Riffel,Storchi-
etal.(1997).ThebroadBrackettemissionwasusedtodeterminethe Bergmann&Nagar2010)whichindicatesthatshocksassociated
instrumentalPSFandthecentreofthePSFistakenasthespatial with radio jets may be the main excitation mechanism in some
position of the AGN. Although the narrow emission may have a active galaxies. Mundell et al. (2009) analysis of radio data on
contribution from star formation, it is not detected significantly MCG–6-30-15 find a possible elongation in the extended radio
outsidethePSFregion.Thevelocity,dispersionandfluxmapsare emissionapproximatelyperpendiculartotheorientationofthe[OIII]
showninFig.8(toprow).Fig.9showsthestellarandgasemission emissionwhichmayindicatethepresenceofajet-likeordiscwind
velocityprofilesalongthemajoraxisofthegalaxy,averagedina component.However,the[FeII]emissionhasasimilarorientationto
pseudo-slitof3pixel(∼0.4arcsec)width.ThekinematicsofBrγ the[OIII]emissionandthereforeitisunlikelythatshocksassociated
resemblearotationpatternandisverysimilartotheoneofthestars withapossibleradiojetarethemainexcitationmechanismfor[FeII]
intermsofthevelocitygradientandlowdispersion. emissioninthisgalaxy.
The Brγ narrow-line flux can be used to estimate the star for- Inourpreviouswork(Raimundoetal.2013),wehypothesized
mation rate or to determine upper limits for it in galaxies where that the [Fe II] emission was caused mainly by supernova shocks
MNRAS464,4227–4246(2017)
4234 S.I.Raimundoetal.
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Figure8. Velocity,velocitydispersionandfluxmapsoftheionizedgasemissionlinesinourspectra.Toptobottom:narrowBrγ,[FeII],[SiVI]and[CaVIII]. am
TThheevwehloitceiteilelsipwseeriencthoerretocptepdafnoerltihnedsicyastteesmtihcevseilzoecoitfytohfetshteelglaarlaKxDyCan.dinstrumentalbroadening.MinimumS/Nis3.0.ThecrossindicatestheAGNposition. bridg
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1
2
, 2
0
1
7
Figure9. HorizontalcutsalongthemajoraxisofthegalaxytomeasuretheionizedgasandtheH-bandmeasuredstellardynamicsasafunctionofradius
fromtheAGNposition.Left:velocity.Right:velocitydispersion.
fromapreviousstarformationeventandournewobservationssup- in our data, the dynamics of [Fe II] resembles a rotation pattern
portthisscenario.Thespatialdistributionofthe[FeII]coincides andisdistinctfromthe[CaVIII]dynamics(Fig.9).Thefollowing
with the region where we see the strongest S/N in the stellar ab- additionalindicationsarepresentinthedata.First,weobservethat
sorption features and although we detect an AGN-driven outflow the [Fe II] emission extends further out than the [Si VI] and Brγ
MNRAS464,4227–4246(2017)
TheAGNfuelling reservoirinMCG–6-30-15 4235
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Figure10. H22.12µmdistributionanddynamics.Topleft:velocitymap.Topright:velocitydispersion.Bottomleft:fluxmap.Bottomright:fluxresiduals from
acthfoteuesnretsecure-bnrtotrrtaaaclttipinnigxgeceloslrlweip.etTircehaemlmiassoakppehdwoaotesustb.oiTnfnhtehedeHtiom2aarogmtea.itnioimnudmireSc/tNionofi5s.tIhnetshaemceenatsraflorregthioencso,uthneteHr-2roetmatiisnsgiocnoirse.nTothdeestepcatteiadlaetxatesnigtnoifficthaentHS2/Nislelavregle;rthtehraenfotrhee, http://m
n
ra
s
emission(Fig.8). Secondly, the [FeII] emissionis not centred at .ox
thenucleusandseemstotraceasimilardistributiontowhatisseen ford
forthemoleculargas(tracedbytheH emissioninFig.10),which jo
2 u
would be expected if both these lines originate from regions of rn
a
star formation. Thirdly, the velocity dispersion map shows peaks ls.o
ithnevlaorcioaulsdyrengaimonicssoafntdhebe[FaessIoI]cieamteidsswiointhwlohcicahtiocnosulodfbmeatjroarcisnug- at Urg/
pernovaevents.Thegeneral[FeII]velocitydispersionprofilealong niv
themajoraxis,ascanbeseenintheright-handpanelofFig.9,is ers
lowerthanforthestarsortheotherionizedspecies,butcloserto ity
o
thedispersionprofileofH2,furtherindicatingthatthesetwolines f C
maybetracingthesameregionsofstarformationandsupernova a
m
events. It would be expected that if [Fe II] and H2 are being ex- brid
cshitoewdimnothreedsiasmtuerbreedgikoinnse,mthaeticiosn(ihziegdhegrasvetrloacceitdybdyisp[FeersiIIo]nw)othualdn Figure 11. [Ca VIII] emission integrated in a 1arcsec × 1arcsec region ge o
n
theItmisoloefcucloaurrgseaslitkraeclyedthbaytHA2G.Nphotoionizationalsocontributes cshenowtresdthaetotbhseenrvuecdlesupsecatsruamfuinncbtliaocnk,otfhreetsot-tafrlalmineefiwta(vreeldelnignteh).aTndhethfiegtuwroe Janua
to the [Fe II] emission, even if it is not the dominant mechanism Gthaeuvseslioancitcyombipnosnuesnetdsfoofrththeefitto(mbolugeraapnhdygarneeanly)s.iTsh(e−v1e2r5ti,c−al2l5in,e+s2i5n,d+ic1a2t5e ry 12
(Rodr´ıguez-Ardilaetal.2004).The[FeII]emissionwillthenpro- and+190kms−1).Thenumbers1to4indicatethecorrespondingpanelsof , 2
videanupperlimitforthenumberofsupernovaevents.Withour Fig.12. 017
newobservations,wecanprobethe[FeII]emissionwithinthefull
extent of the KDC and improve the [Fe II] flux measurement in
hasalowerionizationpotential(IP=127eV),anditisobserved
Raimundoetal.(2013).Integratingfortheregionswithemission
S/N>3,weobtainF =3.0×10−15ergs−1cm−2andL = atahigherS/Nthan[SiVI].Itsemissioniscompactbutresolved,
[Feii] [Feii]
4×1038ergs−1. slightly more extended than [Si VI] and asymmetric with its flux
emissionpeaknorth-westofthenucleus.Theshapeofthe[CaVIII]
emissionlineiscomplex,ascanbeseeninFig.11.Thisplotshows
thelineprofileintegratedina1arcsec×1arcsecregioncentredat
3.2.3 Coronallineemission
thenucleus.TheemissionlinecanbefittedusingtwoGaussians,
Twohigh-ionizationcoronallinesaredetectedintheK-bandobser- andthatholdstrueformostofthepixelsinthemapwithobserved
vations:[SiVI]1.963µmand[CaVIII]2.321µm.Theselinesarea emission.Thetwolinesareblueshiftedandredshiftedwithrespect
goodtracerofAGNactivityduetotheirhighionizationpotential tothesystemicvelocityofthegalaxyandobservedsimultaneously
(IP > 100 eV). [Si VI] (IP = 167 eV) is mainly detected in the ateachspatialposition,whichisanindicationthatweareseeingthe
nucleuswithaspatialextentoftheorderoftheinstrumentalPSF. approachingandrecedingsidesofasingleionizationcone.Tobetter
ThevelocityandvelocitydispersionmapswithaminimumS/N∼3 understandthepropertiesofthisemission,wemeasuredthefluxat
arepresentedinFig.8(thirdrow).Theregionswithfluxlessthan variousvelocitybins(‘velocitytomography’)andplottheresultin
5percentofthatofthepeakweremaskedoutofthemaps.[CaVIII] Fig.12.Wecanseethatthe[CaVIII]dynamicsisdominatedbyan
MNRAS464,4227–4246(2017)
4236 S.I.Raimundoetal.
Figure12. Velocitytomographyofthe[CaVIII]line.Velocityintervalsindicatedatthebottomcorrespondtodeviationsfromthesystemicvelocityofthe
galaxyandcorrespondtotheregions(1to4)delimitedbytheverticallinesinFig.11.ThespatialscaleisarcsecandtheorientationisthesameasinFig.8.
Thefirstandthirdpanelsshowtheblueshiftedandredshiftedcomponentsoftheoutflow,respectively.Thissuggeststhatweareseeingtheapproachingand
recedingsidesofaone-sidedionizationcone.
D
Table1. Theradialextentismeasuredinradiusfromthenucleus. inMCG–6-30-15fromX-raystudiesofwarmabsorbers(Sakoetal. o
w
2003;Blustinetal.2005;Chiang&Fabian2011).Theseoutflows nlo
Spatialextentofthecoronallineemissionregion present blueshifted velocities of vout = −1900 and −150kms−1 ade
[[ESCmiaiVsVIs]IIiIo1]n.29l.63i3n2e1µmµm 11IP2677eeVV 00E..x97teaanrrcctss(eeraccd((i∼∼al11)4100ppcc)) aaamtlctachdyeoilsbuetergaahnatcisniestgosicwsoiafintneo0ddt.0(wcB3l6iletuahsarttnihindfeet[5thC.ae7al.tpV2wcI0IoI0]f5rooo)uu.mttTflflhoothewweosauntatuflsrcecolaweplueasssra,totrfosefmrsp<tahelelc1ts4iscv0aaemllpeyecs, http://md from
othuetfloouwtfl.oTwheatfiurspttpolo−t1o2n5thkemlesf−t1m.Taphsetnhuecbleluaerschoimftepdonceonmtpisosneeenntoinf waAhsdsiicurehmcwtincegootnhbnasetectrthvioeenfianbsettehtwrisoeuwetnfloorskuw;chahtoarw∼leavr0ge.er0,3riat6nipsgcedwiofofifucpluhdlytlsotiosceaelvsetsalcobacllieistsyh. nras.ox
ItshneeeFnsiegicn.o8tnh,dewptheloisrtdhforpwolomtthftehroermelestufhtletasnleodfftt,hfiwettsiintthrgovntehgleorce[CidtsiaehsVifIutIeIp]dteocmo1im2ss5piooknnmewns−titi1hs. taosrietpprroodpuacgeattehse,oitustvfleolwocwityeowbosuelrdvehainve[CtoadVeIIcI]reaatsre∼as1v4o0utp∝c.r−0.4 fordjourn
a
asingleGaussianline.Althoughtheshapeoftherealemissionis ls
.o
mredosrehicftoemdpcloemx,ptohneesnetmoauptflsorweflinegctatthveedloycniatimesic∼s1o0f0thkemdso−m1.inating 3.2.4 Opticalemissionlines arg/
The [Si VI] emission could also have a redshifted outflowing IntheVIMOSdatacube,wedetecttwostrongemissionlines:[OIII] t Un
component,asthevelocitiesnorth-westofthenucleusareslightly 5007andHβ 4861Å(withanuclearbroadcomponentandaspa- ive
higher than expected based solely on rotation and the dispersion tiallyextendednarrowcomponent).Tostudythegasdynamics,we rsity
ishigherthanthatobservedinthenarrowBrγ emission(Fig.9). firstusethestellarabsorptionlinestodeterminethegalaxy’ssys- o
However,duetoitshigherionizingpotential,thisoutflowingcom- temic velocity. We integrate the data cube spatially in the region f C
a
m
ponentisnotasstrongasin[CaVIII].Thevelocitytomographyfor of the field of view with highest contribution from the galaxy to b
[Si VI] shows a very centrally concentrated emission, which does determineanintegratedspectrum.WethenusepPXFandasetof ridg
notextend beyondthePSF.Theextent ofthecoronallineregion stellaropticaltemplates(Vazdekis1999)todeterminethesystemic e o
n
forboththeselinesisshowninTable1.Wedefinetheextentofthe velocity.Thisvelocityisthenusedasareferenceforthestudyofthe J
a
coronallineregionatthepositionwherethefluxofthelinedrops gasdynamics.ToanalysetheHβ narrowcomponent,wesubtract nu
a
to5percentofitspeakvalue. thebroadHβcomponentfromthespectra.Asnotedpreviouslyby ry
Whencomparingtheprofilesoftheionizedgasemissionwiththe Reynoldsetal.(1997),thebroadHβlinecanbefittedbytwocom- 12
oneofthestars,weseeclearlythatnarrowBrγ hasaprofilesimilar ponents,withthestrongestfluxbeinginacomponentblueshifted , 20
1
tothestars.[SiVI]and[CaVIII]showaredshiftinrelationtothe by ∼150–200kms−1 with respect to the systemic velocity of the 7
stellarrotation.Theredshiftofthe[SiVI]issmallanditisclosetothe galaxy.InFig.13,weshowthelineemissionmapsforthe[OIII]and
rangeoferrorsexpectedforthestellarvelocity.[CaVIII]hasaclearly thenarrowHβ.PixelswithS/N<5betweenthepeakoftheline
distinctvelocityprofile,dominatedbytheredshiftedcomponentof andthenoiseinaline-freeregionofthecontinuumweremasked
theoutflow.Althoughalsoslightlydistinctfromthestellar,theBrγ out.TheHβemissionextendsouttor∼400pc,significantlymore
and the [Si VI] profiles, the velocity gradient of [Fe II] is clearly extendedthanthecoronallinesdetectedinthenear-IR.Itsvelocity
differentfrom[CaVIII]whichisanotherindicationthatthe[FeII] map shows a rotation pattern counter-rotating with respect to the
emissionisnotpartoftheAGNoutflowbuttracingstarformation mainbodyofthegalaxy.
inthedisc.ThestudyofRodr´ıguez-Ardilaetal.(2006)onthesize The[OIII]emissionisthemostextendedgasemissionwedetect.
ofthecoronallineregioninMCG–6-30-15showsthatthe[FeVII] Thelineisdetectedouttor<10arcsec∼1.5kpcaboveaS/Nof5.
linewithanionizationpotentialofIP=100eVclosetotheoneof Thedynamicsintheregiontothesouth-eastofthenucleusmatch
[CaVIII](IP=127eV)showsanextentof(cid:2)140pc(afterconverting what we observe in the molecular gas (in terms of the rotational
to our cosmological parameters) similar to the spatial extent we velocity expected and counter-rotation). To the north-west of the
observeinourstudy(Table1).Rodr´ıguez-Ardilaetal.(2006)also nucleus,thevelocitydispersionincreasesandthevelocitydoesnot
findthatthebroadcomponentof[FeVII]isblueshiftedandhasa match the rotational pattern. We are likely observing the large-
FWHM∼670kms−1,whichhasbeeninterpretedassignatureof scale counterpart of the gas outflow observed in [Ca VIII]. In this
anoutflowingwind.Blueshiftedoutflowshavealsobeendetected region to the north-west of the nucleus, we observe velocities of
MNRAS464,4227–4246(2017)