Feeding Versus Feedback in AGNs from Near-Infrared IFU Observations: The Case of Mrk79

0.92 MB·English

by  Rogemar A. Riffel

Mon.Not.R.Astron.Soc.000,1–14(2011) Printed11December 2013 (MNLATEXstylefilev2.2)
Feeding Versus Feedback in AGNs from Near-Infrared IFU
Observations: The Case of Mrk 79
3 Rogemar. A. Riffel1⋆, Thaisa Storchi-Bergmann2 and Claudia Winge3
1
1UniversidadeFederaldeSantaMaria,DepartamentodeF´ısica,CentrodeCieˆnciasNaturaiseExatas,97105-900,SantaMaria,RS,Brazil
0
2UniversidadeFederaldoRioGrandedoSul,InstitutodeF´ısica,CP15051,PortoAlegre91501-970,RS,Brazil
2
3GeminiObservatory,c/oAura,Inc.,Casilla603,LaSerena,Chile

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11December 2013
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ABSTRACT
O
C
We have mapped the gaseous kinematics and the emission-line flux distributions and
. ratiosfromtheinner≈680pcradiusoftheSeyfert1galaxyMrk79,usingtwo-dimensional
h
p (2D)near-IRJ−andKl−bandspectraobtainedwiththeGeminiinstrumentNIFSataspatial
- resolution of ≈100 pc and velocity resolution of ≈40kms−1. The molecular hydrogen H2
o fluxdistributionpresentstwospiralarmsextendingby≈700pc,onetothenorthandanother
r
tothesouthofthenucleus,with anexcitationindicatingheatingbyX-raysfromthecentral
t
s source.Thelowvelocitydispersion(σ ≈ 50kms−1)androtationpatternsupportsalocation
a
of the H gas in the disk of the galaxy. Blueshifts observed along the spiral arm in the far
[ 2
sideofthegalaxyandredshiftsinthespiralarminthenearside,suggestthatthespiralarms

1 arefeedingchannelsofH totheinner200pc.FromchannelmapsalongtheH λ2.1218µm
2 2
2v emission-line profile we estimate a mass inflow rate of M˙H2 ≈ 4×10−3M⊙yr−1, which is
one order of magnitude smaller than the mass accretion rate necessary to power the AGN
4 ofMrk79.Theemissionfromtheionizedgas(tracedbyPaβand[Feii]λ1.2570µmemission
2
lines) is correlated with the radio jet and with the narrow-band [Oiii] flux distribution. Its
1
kinematicsshowsbothrotationandoutflowstothenorthandsouthofthenucleus.Theionized
.
1 gas mass outflow rate through a cross section with radius ≈320pc located at a distance of
30 ≈455pc from the nucleusis M˙out ≈ 3.5M⊙yr−1, which is much largerthanthe AGN mass
accretionrate,indicatingthatmostoftheoutflowinggasoriginatesintheinterstellarmedium
1
surroundingthegalaxynucleus,whichispushedawaybyanuclearjet.
:
v
i Key words: galaxies: individual (Mrk79) – galaxies: Seyfert – galaxies: ISM – infrared:
X
galaxies–galaxies:kinematicsanddynamics
r
a
1 INTRODUCTION somecases,streamingmotionstowardsthenucleus,whilethelat-
ter presents emission from outflowing material at high latitudes
This work is part of a large project, in which our group (Ac-
above the plane and usually is associated to the radio emission
tive Galactic Nuclei Integral Field Spectroscopy - AGNIFS) has
(Riffeletal.2006,2008,2009;Riffel,Storchi-Bergmann&Nagar
been observing the inner kiloparsec of nearby activegalaxies us-
2010; Riffel&Storchi-Bergmann 2011a; Storchi-Bergmannetal.
ing optical and near-infrared (hereafter near-IR) high-spatial res-
2009,2010).Wehaveconcluded thatthemoleculargasisagood
olution (afew to tensof pc) integral fieldspectroscopy. Wehave
tracer of the nuclear feeding and the ionized gas of its feedback.
obtained the gaseous flux distributions, kinematics and excita-
Nevertheless, the sample observed so far comprises only half a
tion, with the main goal of mapping gas inflows and outflows
dozen objects and more integral fieldobservations in the near-IR
and constraining the corresponding mass flow rates and power.
arerequiredinordertohaveamorecompletecensusofthesepro-
Whenever the signal-to-noise ratio in the continuum and absorp-
cessesinAGNsandtorelatethemassflowratestotheAGNpower.
tion lines is high enough we also map the stellar kinematics and
ages. In the near-IR, our main results so far can be summarized Inthiswork,wepresentthegaseousfluxdistributionandkine-
as follows. We have found that the molecular (H2) and ionized matics of the inner 680 pc of the active galaxy Mrk79 obtained
gases present distinct flux distributions and kinematics, with the fromobservationsusingtheGemini-North’sNear-InfraredIntegral
former restricted to the plane of the galaxy and presenting, in Field Spectrograph (NIFS McGregoretal. 2003) in the J and K-
bands. Thisobject wasselectedfor thisstudy because itpresents
extendedradioand[Oiii]emission(e.g.Ulvestad&Wilson1984;
⋆ E-mail:[email protected] Nagaretal. 1999; Schmittetal. 2003) allowing us to explore the
2 Riffel,Storchi-Bergmann& Winge
relationbetweentheradiojetandtheNarrowLineRegion(NLR) els.ThefinalIFUdatacubeineachbandcontains∼4000spectra,
kinematics,aswellasitseffectintheexcitationofthenear-IRlines. eachspectrumcorrespondingtoanangularcoverageof0′.′05×0′.′05,
Mrk79isaSBbgalaxy(deVaucouleursetal.1991)locatedat whichtranslatesinto∼23×23pc2atthegalaxyandcoveringthein-
adistanceof93.8Mpc(e.g.Kraemeretal.2011),forwhich1arc- ner3′′×3′′(∼1.35×1.35kpc2).
seccorrespondsto455pcatthegalaxy.Itsnucleusisclassifiedas Inordertoincreasethesignaltonoiseratioandallowthefit-
Seyfert1withacentralblackholewithamassof5.2±1.44×107M⊙ ting of the emission line profiles, we have replaced each spatial
(Petersonetal.2004).Itpresentsextendedradio-continuumemis- pixelbythemedianofitsvalueandthatofitsfirst8neighbors.Af-
sionalongpositionangle(PA)11◦(Schmittetal.2001;Nagaretal. terthisprocedure,theangularresolution,obtainedfromtheFWHM
1999; Ulvestad&Wilson 1984), which can be described as an ofthespatialprofileofthebroadcomponentsofBrγandPaβemis-
asymmetric triple radio structure with the northern source being sion lines fluxes, is 0′.′25±0′.′05 for both bands, corresponding to
located at a distance of 800pc from the nucleus and the south- ∼100pcatthegalaxy.
ern source at 460pc from it (Schmittetal. 2001). In the opti-
cal,Mrk79presents extended [Oiii] lineemissionasobserved in
ground-based(e.g.Haniffetal.1988)andHubbleSpaceTelescope
(HST)images(Schmittetal.2003).The[Oiii]λ5007emissionex-
tends to about 4.6 arcsec from the nucleus in the north-south di-
rection, being co-spatial with the radio emission and presenting
severalblobsofenhanced emission(Schmittetal.2003).Anout-
3 RESULTS
flowinggascomponent issuggestedbythedetectionoftwocom-
ponents in the [Oiii]λ5007 mission-line profile withvelocities of In order toillustrate thespatial coverage of our observations, we
+100kms−1and−50kms−1relativetothesystemicvelocityofthe show in the top-left panel of Figure1 a V-band optical image of
galaxy. Thiscomponent seemstobeassociatedwiththenorthern Mrk79obtainedwiththewiththe1-mtelescopeoftheLickOb-
radio structure (Whittleetal. 1988). The modeling of the optical servatory (Huntetal. 1999). In the top-right panel we present an
andinfraredspectralenergydistribution(SED)ofMrk79,includ- [Oiii]λ5007Å narrow-band image obtained with the HST Wide
ingtheemissionbydustinatoroidal-likestructureheatedbyacen- Field Planetary Camera 2 (WFPC2) through the filter FR533N
tralAGNsuggeststhatthedustytorushasamassof7.30×102M⊙ (Schmittetal. 2003). This image shows extended emission up to
(Fritz,Franceschini&Hatziminaoglou2006). 4′′from the nucleus of Mrk79, being more elongated along po-
Thispaperisorganizedasfollows.InSec.2wedescribethe sition angle (PA) 15◦ and presenting several blobs of emission.
observations and data reduction procedures. The results are pre- Schmittetal.(2003) suggest that the[Oiii] emissionisrelatedto
sentedinSec.3anddiscussedinSec.4.Wepresentourconclusions theradiojet.The3.6cmradiocontinuumimageobtainedwiththe
inSec.5. VeryLargeArraybySchmittetal.(2001)isshowninthebottom-
left panel of this figure, and can be described as an asymmetric
tripleradiostructurealongPA=11◦.Thegreenboxoverplotedon
this panel represents the NIFS field of view and shows that the
2 OBSERVATIONSANDDATAREDUCTION
north-eastern radio structure is beyond its borders. The Paβ flux
The J and Kl-band observations of Mrk 79 were obtained us- mapobtainedfromourNIFSdatacubeisshowninthebottom-right
ing the NIFS instrument (McGregoretal. 2003) operating with panelinunitsof10−17ergs−1cm−2.
theGeminiNorthAdaptiveOpticssystemALTAIRinSeptember Allspectra inthedatacube werefirstcorrectedfor redshift.
2010 under the programme GN-2010B-Q-42, following the stan- In Figure2 we present the J and K spectra extracted within an
l
dard Object-Sky-Sky-Object dither sequence, withoff-source sky 0′.′25×0′.′25 aperture centered on the the nucleus in the top pan-
positionssincethetargetisextended,andindividualexposuretimes els. The middle panels show the spectra extracted at 1′.′1 south-
of520sfortheJbandand550sfortheK band.Sixon-sourcein- southeastofthenucleusatthelocationwhereitisobservedaknot
l
dividual exposureswereobtainedforeachband, totalizing3120s withenhanced emissioninthe[Oiii]imageinthetop-rightpanel
and3300sfortheJandK-band,respectively. of Figure1, whilethe bottom panels show the spectra for a loca-
l
The J-band observations covered the spectral region from tionco-spatialwiththesouthernradiohotspotseeninbottom-left
1.14µmto1.36µm,centeredat1.25µmwithaspectralresolution panel of Figure1at1′.′1south-southwest ofthenucleus. Someof
of≈ 1.8Å,asobtainedfromthemeasurementofthefullwidthat thestrongestemissionlinesareidentifiedinthetoppanels.
half maximum (FWHM)of the ArXecalibration lamplines. The We have detected about 4 dozen of emission lines at the J
K-bandobservations werecenteredat2.3µm,covering thespec- andK-bands aslistedinTable1,which presentsthecorrespond-
l l
tral range from 2.10µm to 2.53µm with a spectral resolution of ingfluxesofthelinesforthethreepositionsabove.Theobserved
FWHM≈ 3.5Å. In velocity space, the resolution of the observa- emissionlinesincludemolecular(H )linesaswellaslinesofion-
2
tionsis≈45kms−1fortheK-bandand35kms−1fortheJ-band. ized gas from a range of ionization levels, e.g. from [Feii] up to
l
The data reduction was accomplished using tasks contained [Six].ThelinefluxesweremeasuredbyfittingaGaussiantoeach
in the nifs package which is part of gemini iraf package, as well emission-line profile using the iraf splot task. The uncertainties
asgenericiraftasks.Thereductionprocedureincludedtrimming quotedinthetablearethestandarddeviationsfromtheaverageof
of the images, flat-fielding, sky subtraction, wavelength and s- several measurements (typically 6) and do not include uncertain-
distortioncalibrations.Wehavealsoremovedthetelluricbandsand tiesinthefluxcalibrationofthespectra.Fluxvaluesfollowedby
fluxcalibratedtheframesbyinterpolatingablackbodyfunctionto “?”indicatethatthelineisonlymarginallydetected,withalarge
the spectrum of the telluric standard star. The six individual dat- uncertainty, oftheorder ofthelineflux.Thepresence oftheline
acubes of each band were median combined toasingle datacube issupportedbythefactthatithastheexpectedcentralwavelength
usingthegemcombinetaskofthegeminiirafpackage,withasig- andthefactthatthewidthissimilartothatoftheother emission
clipalgorithmtoeliminatetheremainingcosmicraysandbadpix- lines.
Feedingvs.FeedbackinMrk79 3
Figure 1. Top-left: V-band optical image of Mrk79 obtained with the with the 1-m telescope of the Lick Observatory (Huntetal. 1999). Top-right:
[Oiii]λ5007Å image obtained with the HST (Schmittetal. 2003). Bottom-left: 3.6cm radio continuum image obtained with the VLA by Schmittetal.
(2001).Thegreenboxoverlaid tothispanelrepresents theNIFSfieldofview.Bottom-right: Paβfluxmapobtained fromourNIFSdatacube inunitsof
10−17ergs−1cm−2.ThepositionslabeledasN,RSandOSmarkthelocationofthenucleus,thesouthernradiospotandthesouthern[Oiii]southernblob,
respectively.
3.1 Emission-LineFluxDistributions in the bottom-left panel of Fig. 1. The lower flux level shown in
eachpanelcorrespondsto3σ,whereσisthenoiseintheadjacent
Inordertoconstructmapsforthefluxdistributionofthestrongest continuumtotheline.
emissionlines,weusedtheprofitroutine(Riffel2010)tointegrate
thefluxesundertheprofilesof[Pii]λ1.1886µm,[Six]λ1.2526µm, The coronal line [Six]λ1.2526µm (top-middle panel of
[Feii]λ1.2570µm,Paβ,H λ2.1218µmandBrγemissionlinesand Fig.3) emission ismarginally resolved by our observations (with
2 FWHM≈0′.′35) being more extended along the north-south direc-
subtracttheunderlyingcontinuum.Theseparticularlineshavebeen
chosen because theyhave thehighest signal-to-noise (S/N)ratios tionwithfluxpeakatthenucleus.Asimilarbehaviorisobserved
for the [Pii] flux distribution (top-left panel), with an additional
amongtheirspecies(coronallines,forbiddenandpermittedionized
emission from a region located at 1′.′1 south of the nucleus, al-
gaslinesandmolecularlines).Wewereunabletoconstructmaps
forthefluxdistributionsofHei,Heiiand[Caviii] emissionlines mostco-spatialwiththesouthernradiohotspotseeninFig.1.The
[Feii] emission is extended up to 1′.′4 from the nucleus, showing
because theyaredetectedonlyatafewlocationsoftheobserved
field.ThebroadcomponentsforPaβandBrγwerefittedandsub- twostructuresatthehighestfluxlevels:oneatthenucleusandan-
otherco-spatialwiththesouthernradiohotspot.Lowerlevelemis-
tractedbeforetheconstructionofthefluxmapsintheseemission
sionisobservedsurroundingthesestructures.
lines.
Figure3showstheresultingfluxmapsforeachemissionline ThePaβandBrγfluxmapsshowextendedemissionuptothe
(identifiedinthetopofeachpanel).Thecentralcrossmarksthepo- bordersoftheNIFSfieldtothenorthandtothesouth,whileinthe
sitionofthenucleusdefinedasthepeakofthenear-IRcontinuum east-westdirectionitextendsonlyto≈0′.′5fromthenucleus.The
emission,thecyancontoursoverlaidtothe[Feii]maparefromthe Hiemissionseemstobewellcorrelatedwiththe[Oiii]structures,
radio continuum image from Schmittetal. (2001), shown in the as evidenced by the contours of the [Oiii] image overlaid on the
top-right panel of Fig. 1. The green contours overlaid to the Paβ Paβfluxmap.Finally,theH alsopresentsextendedemissionmore
2
fluxmaparefromthe[Oiii]imageofSchmittetal.(2003),shown elongatedinthenorth-southdirection,butwithadistinctfluxdis-
4 Riffel,Storchi-Bergmann& Winge
Figure2.SampleofspectraforMrk79extractedwithinsquareapertures of0′.′25×0′.′25,withthestrongeremission-lines identified.Toppanelsshowthe
nuclearJ(left)andK(right)spectrum,middlepanelsshowaspectrumforalocationat1′.′2south-southeastofthenucleus,co-spatialwithan[Oiii]emission
knotandthebottom panels presentaspectrum extracted attheposition oftheradiostructure at1′.′2south-southwest ofthenucleus. Thesepositions are
identifiedinfigure1as”N”,”OS”and”RS”,respectively.
tributionthanthoseobservedfortheotheremissionlines.TheH Cardelli,Clayton&Mathis (1989) and adopted the intrinsic ra-
2
mapclearlyshowstwospiralarmsextendingupto1′.′5arcsecfrom tio F /F = 5.88 corresponding to case B recombination
Paβ Brγ
thenucleus,whichseemtooriginatefromthetipsofanuclearbar- (Osterbrock&Ferland2006).TheresultingE(B−V)mapisshown
shapedstructureorientedapproximatelyalongeast-west,observed intheleftpanelofFig.4.Thismapshowsaverycomplexstructure
atthehighestfluxlevels. withseveralknotsofhigherextinction,inwhichE(B−V)reaches
valuesofupto2.
The excitation mechanism of the [Feii] lines can be in-
3.2 Line-RatioMaps vestigated using the [Feii]λ1.2570µm/Paβ line ratio, shown in
Line ratios can be used to study the extinction and the middle panel of Fig. 4. Typical values for this ratio are
the excitation mechanisms of the near-IR lines in the [Feii]λ1.2570µm/Paβ ≈0.6,observed over most of thefield.The
NLR (e.g. Dorsetal. 2012; Riffel&Storchi-Bergmann lowestvaluesareobservedatthenucleus(≈0.15),whilethehigh-
2011b; Riffel,Storchi-Bergmann&Nagar estvaluesofupto2areobservedtothesouthwestat≈0′.′4fromthe
2010; Riffel,Rodr´ıguez-Ardila,&Pastoriza nucleus and in anarc-shaped structure at ≈1′′. At thelocation of
2006; Storchi-Bergmannetal. 2009; thesouthernratiohotspot(cyancontoursarefromtheradioimage)
Rodr´ıguez-Ardila,Riffel&Pastoriza2005;Rodr´ıguez-Ardilaetal. theaveragevalueforthisratiois1.2.
2006). Anusefullineratiotostudytheexcitationmechanismofthe
ThereddeningcanbeestimatedfromthePaβ/Brγlineratioas near-IRH linesisH λ2.1218µm/Brγ.Wepresentamapforthis
2 2
ratiointherightpanelofFig.4.Thehighestvaluesofupto4.5are
5.88
E(B−V)=4.74log , (1) observedalongthetwospiralarmsseenintheH fluxmapshown
F /F ! 2
Paβ Brγ inthebottom-middlepanelofFig.3,overlaidasgreencontoursin
where F and F are the fluxes of Paβ and Brγ emis- theline-ratiomap.Thelowestvalues,around0.6,areobservedat
Paβ Brγ
sion lines, respectively. We have used the reddening law of thenucleusandatlocationsawayfromthespiralstructures.
Feedingvs.FeedbackinMrk79 5
Table1.J-bandemission-linefluxesforthenucleus,thepositionofan[Oiii]blob(at1′.′1south-southeastofthenucleus)andthepositionoftheradiohotspot
(at1′.′2south-southwestofthenucleus)integratedwithin0′.′25×0′.′25apertures.Thelocationwhereeachspectrumwasextractedisidentifiedinthebottom-left
panelofFig.1asN(forthenucleus),OS([Oiii]structure)andRS(radiostructure).Thefluxesarein10−17ergs−1cm−2units.A”?”bythesideoftheflux
valueindicatesthatthelineisdetectedbuttheuncertaintyinthemeasurementisoftheorderofthefluxoftheline.
λvac(µm) ID Nucleus [Oiii]peak Radiopeak
1.12708 [Feii]b2F5/2−b4F5/2 – – 2.45±1.18
1.13488 [Feii]b2D3/2−a2F7/2 – 1.54? 3.17±0.84
1.14276 [Feii]b4D5/2−b4F9/2 – – 0.61?
1.14713 [Pii]1D3−3P1 32.39±1.97 – 1.87?
1.15841 [Feii]b2F5/2−a2D3/2 7.13? 1.95?
1.16296 Heii7−5 43.71±7.75 – 5.23±1.51
1.18363 [Feii]b4D5/2−b4F5/2 5.29? 0.76? –
1.18552 Heii29−7 – 1.28? –
1.18693 [Feii]b4D3/2−b4F5/2 – 1.44? –
1.18861 [Pii]1D2−3P2 17.30±5.85 3.00±0.28 4.57±0.77
1.20370 Heii26−7 – 0.77? 1.18?
1.20545 [Feii]a4D3/2−a6F7/2 5.73? – –
1.22263 [Feii]a4D1/2−a6D5/2 8.78? 2.02? 1.19?
1.24414 [Feii]c2G9/2−a4G11/2 – – 0.97?
1.25235 [Six]3P1−3P2 161.97±7.91 3.99±0.25 2.55±0.71
1.25702 [Feii]a4D7/2−a6D9/2 26.79±7.33 8.12±1.99 13.20±0.29
1.27069 [Feii]a4D1/2−a6D1/2 – 1.32? –
1.27912 [Feii]a4D3/2−a6D3/2/HeI? – 1.39? 0.71?
1.28216 HiPaβ(broad) 5666.25±164.06 – –
1.28216 HiPaβ(narrow) 154.28±15.41 16.34±0.61 16.56±1.04
1.28495 Hei3S1−3Po1 – 1.40? 0.87?
1.29812 [Feii]a4D3/2−a6D1/2 11.85±3.30 – 0.39?
1.30529 [Feii]c2G9/2−a4G9/2 – 1.46? 0.59?
1.31958 [Feii]b2G7/2−b4F9/2 – – 1.36?
1.32092 [Feii]a4D7/2−a6D7/2 – 2.46? 3.50?
2.12183 H2 1-0S(1) 89.89±23.19 4.42±0.09 8.85±0.74
2.15420 H21-0S(2) – – 0.80?
2.16612 HiBrγ(broad) 1054.40±159.49 – –
2.16612 HiBrγ(narrow) 48.96±9.36 4.08±0.72 3.21±0.27
2.17661 [Feii]b2G7/2−b2H11/2 22.06? – –
2.18911 Heii10−7 – 1.53±0.08 –
2.22344 H21-0S(0) 19.51±6.74 1.35±0.13 2.14±0.35
2.24776 H22-1S(1) – 1.39±0.34
2.26647 [Feii]b2G7/2−b2H9/2 – 0.59? –
2.32204 [Caviii]2P0 −2P0 165.60±38.37 – 3.50±0.65
3/2 1/2
2.36760 [Feii]a4G9/2−a4H9/2 – 2.43? –
2.39901 [Feii]b4D7/2−a2F7/2 – 3.90±0.21 4.79?
2.40847 H21-0Q(1) – 2.75±0.22 6.81±0.50
2.41367 H21-0Q(2) – 1.01? –
2.42180 H21-0Q(3) – 4.28±0.06 5.20±0.21
2.43697 H21-0Q(4) – 2.61? –
2.46075 Heii18−9 – 8.20±1.41 –
3.3 CentroidVelocityandVelocityDispersionMaps than 15kms−1 for all emission lines at all locations of the field.
WhiteregionsinthisfigurerepresentlocationswheretheS/Nwas
Theprofitroutine (Riffel2010) wasused tofittheemissionline not high enough to allow the fitting of the line profiles. We sub-
profilesbyGaussian curvesinorder toobtainthecentroidveloc- tractedtheheliocentricsystemicvelocity(V ≈ 6636kms−1),ob-
s
ity(V)andvelocitydispersion(σ),whichhavebeenusedtomap tained from the fitting of the H velocity field by a rotating disk
2
of the gaskinematics intheinner region of Mrk79. Weused the model (e.g. Riffel&Storchi-Bergmann 2011a,b). The thick con-
[Feii]λ1.2570µm,PaβandtheH2λ2.1218µmemissionlinestorep- tours overlaid to the H2 velocity map are from the H2λ2.12 flux
resentthekinematicsoftheionizedandmoleculargas.Wedonot image,showninFig.3.Thesemapsshowthatthe[Feii]andPaβ
showkinematicmapsforthe[Pii],[Six]andBrγlines(asdonefor emittinggaspresentsimilarvelocityfields,withredshiftsofabout
fluxmaps) because theselinesaredetectedonly inafew regions 40kms−1 atthenucleusandblueshiftsofupto−150kms−1 both
andtheBrγkinematicsisthesameasthatofPaβ. tothenorthandtothesouth.ThePaβmapalsoshowssomered-
shiftsinaregionlocatedat≈1′.′0arcsecnorthwestofthenucleus,
In Figure 5 we present the velocity fields obtained from the
centroidwavelengthof[Feii]λ1.2570µm(leftpanel),Paβ(middle) withvelocitiesof150kms−1,similartothevaluesseenintheH2
velocityfieldatthesamelocation.TheH velocityfieldshowsan
andH λ2.1218µm(right).Theuncertaintiesinvelocityaresmaller 2
2
6 Riffel,Storchi-Bergmann& Winge
Figure3.Emission-linefluxdistributionsfor[Pii]λ1.1886µm,[Six]λ1.2526µm,[Feii]λ1.2570µm,Paβ,H2λ2.1218µmandBrγemissionlines.Thecolor
barsshowthefluxscaleinunitsof10−17ergs−1cm−2.Thecentralcrossmarksthepositionofthenucleus,thecyancontoursoverlaidtothe[Feii]mapare
fromthe3.6cmradio-continuumimageofSchmittetal.(2001)andthegreencontoursoverlaidtothePaβmaparefromthe[Oiii]imageofSchmittetal.
(2003).
Figure4.Emission-lineratiomaps.Left:E(B-V)obtainedfromPaβ/Brγlineratio.Middle:[Feii]λ1.2570µm/Paβ.Right:H2λ2.1218µm/Brγ.Thecontours
overlaidtothe[Feii]λ1.2570µm/PaβarefortheradioimageandtotheH2λ2.1218µm/BrγfortheH2fluxmapofFig.3.
approximaterotationpattern,withthehighest blueshifts,of upto seeninsidethehighestlevelcontourdelimitingthespiralstructure
−150kms−1,tothesoutheast of thenucleus, andthehighest red- tothesouthofthenucleus.
shifts,ofupto150kms−1,tothenorthwest.Thecontoursoverlaid In Figure 6 we show the velocity dispersion maps for the
asthicklinesarefromtheH2 fluxdistribution,showingthatdevi- [Feii]λ1.2570µm (left panel), Paβ (middle) and H2λ2.1218µm
ationsfromtherotationpatternareassociatedwiththespiralarms. (right) emittinggas.Typical uncertaintiesinσ are15kms−1. For
Inparticular,aregionofhigherblueshiftsthanthesurrounding is the[Feii]andPaβtheσvaluesrangefrom40kms−1to180kms−1,
presentingthehighestvaluesinsomeknotslocatedawayfromthe
Feedingvs.FeedbackinMrk79 7
Figure5.Centroidvelocityfieldsforthe[Feii]λ1.2570µm(left),Paβ(middle)andH2λ2.1218µm(left)emittinggas.Thecentralcrossesmarktheposition
ofthenucleus,NorthisupandEastleftandthethickcontoursoverlaidtotheH2maparefromtheH2fluximageofFig.3.Onlytheinner1′.′2arcsecinthe
East-Westdirectionisshown.
Figure6.σmapsforthesameemissionlinesofFig.5.Thecyancontoursoverlaidtothe[Feii]maparefromthe3.6cmradio-continuumimageofSchmittetal.
(2001)andthegreencontoursoverlaidtothePaβmaparefromthe[Oiii]imageofSchmittetal.(2003).
nucleus.Inordertocomparethe[Feii]σandradiomaps,wehave 3.4 VelocityChannelMaps
overlaid the contours from the radio image on the [Feii] σ map
(cyancontoursinFig.6).Thiscomparisonshowsthatthehighestσ In order to map the flux distributions at all velocities covered
valuesareobservedinregionssurroundingtheradiostructures.The bytheemission-lineprofiles,includingthewings,weconstructed
nuclearσfor[Feii]andPaβarebothoftheorderof≈110kms−1. channel mapsalongtheprofilesofthe[Feii]λ1.2570µm, Paβand
TheH2 σmap isshown intheright panel of Fig. 6and presents H2λ2.1218µmemissionlines,showninFigures7,8and9,respec-
smaller values than those observed for the Paβ and [Feii], with tively.Eachpanelpresentsthefluxdistributioninlogarithmicunits
typical values being 75kms−1. The smallest values (∼60kms−1) integratedwithinthevelocitybincenteredatthevelocityshownin
are observed in locations co-spatial with the spiral structure ob- thetop-leftcorner(relativetothesystemicvelocityofthegalaxy)
servedintheH fluxmap(Fig.3),whilethehighestvaluesofup andthecentralcrossmarksthepositionofthenucleus.
2
to130kms−1areobservedinsomeknotstosouthandsouthwestof In Figure 7, the channel maps along the [Feii] emission-
thenucleus. line profile show the flux distributions integrated within veloc-
ity bins of 50 kms−1(corresponding to two spectral pixels). The
8 Riffel,Storchi-Bergmann& Winge
Figure7.Channelmapsalongthe[Feii]emission-lineprofileforavelocitybinof50kms−1andcenteredatthevelocityshowninthetop-leftcornerofeach
panel.ThegreencontoursarefromtheradioimageofSchmittetal.(2003)andthecrossmarksthepositionofthenucleus.
greencontoursoverlaidtosomepanelsarefromtheradioimageof atvelocitiesrangingfrom−175to−54kms−1,thespiralarmcurves
Schmittetal.(2003).Thehighest blueshiftsofupto−200kms−1 inthedirectionofthenucleus,resemblingthearmseenintheH
2
andthehighestredshifts,withsimilarvelocities,areobservedatthe flux distribution of Fig.3. At zero velocities there is emission to
nucleusandfromaregioncenteredat∼1′.′0tothesouth,whereitis bothsidesofthenucleusandasthevelocitiesincreaseandreach
approximatelycoincidentwiththesouthernradiostructure.Atin- positive values another spiral arm appears to the northwest. The
termediateandzerovelocitiesthe[Feii]emissionisobservedfrom highestredshiftsofupto400kms−1areobservedatthenucleus.
thenucleusdownto≈1′.′4tothesouth,stillpresentingthesametwo
peaks,atthenucleusandat1′.′0tothesouth.
Figure8showsthechannelmapsforthePaβemittinggasfor 4 DISCUSSION
thesamevelocitybinasfor[Feii].Thegreencontoursoverlaidto
somepanelsarefromthe[Oiii]imageofSchmittetal.(2001).At 4.1 GaseousExcitation
thehighestblueshifts(velocitiesof∼ −200kms−1)thePaβemis- What is the origin of the near-IR lines of [Feii]
sionarisesfromthreestructures:a“blob”atthenucleus,one0′.′7 and H from AGNs? This question has been inves-
2
to the south and another 1′.′1 to the southeast (see channel maps tigated by several studies (e.g. Black&vanDishoeck
centeredat−166and−215kms−1)whilethehighestredshiftsare 1987; Hollenbach&McKee 1989; Forbes&Ward 1993;
observedatthenucleusand0′.′7tothesouth.Atvelocitiesbetween Mouri 1994; Maloney,Hollenbach&Tielens 1996;
≈ −160 and ≈ −80kms−1an additional structure is seen at 0′.′8 Simpsonetal. 1996; Larkinetal. 1998; Rodr´ıguez-Ardilaetal.
northofthenucleus.Atthesevelocities,thePaβemissionisthus 2004; Rodr´ıguez-Ardila,Riffel&Pastoriza 2005;
observedtobothsides(northandsouth)ofthenucleus,presenting Riffeletal. 2006; Riffel,Storchi-Bergmann&Nagar 2010;
4knotsofenhancedemission,whicharecorrelatedtostructuresob- Riffel&Storchi-Bergmann 2011b; Storchi-Bergmannetal.
servedinthe[Oiii]image,ascanbeseenfromthe[Oiii]contours 2009; Hicksetal. 2009; Sa´nchezetal. 2009;
overlaidtothepanelsatvelocitiesrangingfrom−66to80kms−1. RamosAlmeida,Pe´rezGarc´ıa&Acosta-Pulido 2009). In sum-
The channel maps along the H emission-line profile are mary,theH emissionlinescanbeexcitedbytwomechanisms:(i)
2 2
showninFigure9foravelocitybinof60kms−1 (corresponding fluorescentexcitationthroughabsorptionofsoft-UVphotons(912–
to two spectral pixels). At the highest blueshifts (−235 to −175 1108 Å) in the Lyman and Werner bands (Black&vanDishoeck
kms−1), the H emission originates in a spiral arm extending for 1987) and (ii) collisional excitation due to the heating of the gas
2
about1′.′0andlocatedsoutheastofthenucleus.Forpanelscentered by shocks, due to interaction of a radio jet with the interstellar
Feedingvs.FeedbackinMrk79 9
Figure8.SameasFig.7forthePaβemissionline.Thegreencontoursarefromthe[Oiii]imagefromSchmittetal.(2001).
medium(Hollenbach&McKee1989)orbyX-raysfromtheAGN morerestrictedtotheplaneofthegalaxy.The[Feii]emittinggas
(Maloney,Hollenbach&Tielens 1996). The second mechanism, presentsamoredisturbedvelocityfield,higherσvaluesandaflux
usually refereed as thermal processes, is also the responsible for distribution well correlated with the radio structures, indicating
theexcitationofthenear-IRlinesofthe[Feii].Mostofthestudies interactionwiththeradiojet.Thepresenceofbothblueshiftsand
aboveinvestigatetheoriginofbothH and[Feii]usinglineratios, redshiftstothesouthofthenucleusatthelocationofthesouthern
2
such as [Feii]λ1.2570µm/Paβ and H λ2.1218µm/Brγ, and a radio structure, suggests that the [Feii] emitting gas extends to
2
commonconclusionamongthesestudiesisthatthermalprocesses high galactic latitudes. The Hi recombination lines present a
dominatetheH emissioninthecentralregionofactivegalaxies, similarvelocityfieldtothatof[Feii],butpresentsmallerσvalues
2
while the fluorescent excitation can contribute only with a small (intermediatevalues betweenthoseof [Feii] andH )anddistinct
2
fractionoftheobservedH emission. flux distributions, being more associated to the [Oiii] emission
2
The main difficulty in the study of the excitation of the H thantotheradioemission,asseenintheFigs.3and8.Thus,the
2
and [Feii] in AGNs regards the distinction between X-ray and [Feii] kinematics supports thepresence of shocks contributing to
shock mechanisms. Recent detailed studies using integral field itsexcitation.
spectroscopy – most of them by our AGNIFS group – indicate Theemission-lineratioscanalsobeusedtoinvestigatethegas
thattheH and[Feii]emittinggashavedistinctfluxdistributions excitation.The[Feii]λ1.25µm/PaβandH λ2.12µm/Brγemission-
2 2
and kinematics, with the former being considered a tracer of line ratios can be used to distinguish between Seyferts, LINERS
the feeding of the AGN and the latter a tracer of its feedback and Starbursts (e.g. Larkinetal. 1998; Rodr´ıguez-Ardilaetal.
(e.g. Riffeletal. 2006; Riffel,Storchi-Bergmann&Nagar 2010; 2004; Rodr´ıguez-Ardila,Riffel&Pastoriza 2005). Seyfert
Riffel&Storchi-Bergmann 2011a,b; Storchi-Bergmannetal. nuclei have values in the range 0.6.[Feii]/Paβ.2.0 and
2009,2010;Hicksetal.2009;Sa´nchezetal.2009).Thisscenario 0.6.H /Brγ.2.0, while Starburst galaxies have smaller val-
2
isalso favored in the case of Mrk79. TheH flux distributionin ues for both ratios and LINERs have higher values (e.g.
2
theshapeoftwospiralarms(Fig.3),observedalsointhechannel Rodr´ıguez-Ardila,Riffel&Pastoriza 2005). From the middle
maps (Fig.9) supports a location of the molecular gas in the panelofFig.4itcanbeseenthatthe[Feii]/Paβratiomappresents
plane of the galaxy. Additionally, the H velocity field, shown typical Seyfert values for most of the observed field. The only
2
in Fig.5, presents a clear rotation pattern with the southeast side exception is the nucleus, where [Feii]/Paβ≈ 0.15, for which the
approachingandthenorthwestsiderecedingfromus.Thesmaller Paβ flux can be increased due to contamination of the narrow
velocitydispersionvaluesobservedforH (seeFig.6),relativeto componentbythebroadprofileandthus,decreasingthisratio.The
2
thoseoftheionizedgas,alsosupportsthattheH emittinggasis H /Brγlineratio,shownintherightpanelofFig.4,presentsmost
2 2
10 Riffel,Storchi-Bergmann& Winge
Figure9.SameasFig.7fortheH2emissionlineforavelocitybinof60kms−1.
values in the range expected for Seyfert galaxies. Nevertheless, distribution and the radio emission, as well as an increase of the
highervaluesareobservedintheregionswherethespiralstructures [Feii]σinlocationsco-spatialwiththeradiostructures.Thiscor-
areseenintheH fluxdistribution(Fig.3)reachingH /Brγ≈4.5. relationisparticularly clear inthe channel maps shown inFig. 7
2 2
These ratios can be understood by an enhancement of the H for velocities ranging from −61 to 91 kms−1 – enhancements in
2
emissioninthespiral armsdue totheincreaseof thegasdensity thefluxareobservedatthelocationsofthetwomainradiostruc-
duetothespiralstructure. tures:ahotspotatthenucleusandanotherat≈1′.′2tothesouthof
In a recent study, Dorsetal. (2012) built photoionization thenucleus.Thisresultsuggestthattheradiojethasanimportant
models considering a two-component continuum, one to account roleinthe[Feii]emission,eitherbyreleasingironfromdustgrains
for the Big Bump component peaking at 1 Ryd and another to via shocks and increasing itsabundance in the gas phase as well
representtheX-raysourcethatdominatesthecontinuumemission asbyenhancingthe[Feii]emittinggasdensityduetocompression
at high energies in order to reproduce the [Feii]λ1.25µm/Paβ producedbytheradiojet.
and H2λ2.12µm/Brγ line ratios of AGNs. The authors compared The correlation between the NLR gas emission and radio
their models with the line ratios observed for a large sample structureshasbeenquestionedindetailedstudiesofnearbySeyfert
of AGN from long-slit and IFU spectroscopy. They concluded galaxies. Examples are the studies of the NLR kinematics of
that typical Seyfert values for these ratios, as those observed NGC4151 (Kaiseretal. 2000; Dasetal 2005) and NGC1068
for Mrk79, are well reproduced by the model and concluded (Dasetal2006),usinghigh-spatialresolutionlongslitspectraob-
that the heating by X-rays produced by active nuclei can be tainedwithSpaceTelescopeImagingSpectrograph(STIS).Theab-
considered a common and very important mechanism of ex- sence of any clear correlation between the optical emission lines
citation of [Feii] and H lines. In the case of Mrk79, such and radio structures led the authors to conclude that there is no
2
conclusion must be taken with caution since the H and [Feii] connection between the kinematics of the NLR and radio jets.
2
have distinct flux distribution and kinematics, suggesting that The argument is that, even though these structures are approxi-
their emission originate from gas located at distinct regions of matelyaligned asthey originate inthe same AGN,when the tar-
the galaxy, as discussed above. This may also be the case of getsarecloseenough,highspatialresolutiondatashowsthatthere
the extended emission of other Seyfert galaxy (e.g. Riffeletal. is no correlation between the NLR gas kinematics and the radio
2006, 2008, 2009; Riffel,Storchi-Bergmann&Nagar 2010; jet.Although webelieve that thismay happen insome cases, we
Riffel&Storchi-Bergmann 2011a,b,c; Storchi-Bergmannetal. would like to point out that in the case of NGC4151, our study
2009,2010;Storchi-Bergmann2010). (Storchi-Bergmannetal.2010)oftheNLRkinematicsusingadap-
Wehaveobservedagoodcorrelationbetweenthe[Feii]flux tiveopticsnear-IRintegralfieldspectroscopy,atsimilarspatialres-