Evidence of bar--driven secular evolution in the gamma--ray narrow--line Seyfert 1 galaxy FBQS J164442.5+261913

2.7 MB·

by  A. Olguín-Iglesias

MNRAS000,1–12(2015) Preprint5January2017 CompiledusingMNRASLATEXstylefilev3.0
Evidence of bar–driven secular evolution in the gamma–ray
narrow–line Seyfert 1 galaxy FBQS J164442.5+261913
A. Olgu´ın–Iglesias,1,2(cid:63) J. K. Kotilainen,2 J. Leo´n Tavares,3 V. Chavushyan1 C. An˜orve4
1Instituto Nacional de Astrof´ısica O´ptica y Electr´onica (INAOE), Apartado Postal 51 y 216, 72000 Puebla, M´exico;
2Finnish Centre for Astronomy with ESO (FINCA), University of Turku, V¨ais¨al¨antie 20, FI-21500 Piikki¨o, Finland
3Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281-S9, B-9000 Gent, Belgium
4Facultad de Ciencias de la Tierra y del Espacio de la Universidad Aut´onoma de Sinaloa, Blvd. de las Am´ericas y Av.
7 Universitarios S/N, Ciudad Universitaria, C.P. 80010, Culiac´an Sinaloa, M´exico
1
0
2

n AcceptedXXX.ReceivedYYY;inoriginalformZZZ
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4 ABSTRACT
We present near–infrared (NIR) imaging of FBQS J164442.5+261913, one of the few

] γ–ray emitting Narrow Line Seyfert 1 (NLSy1) galaxies detected at high significance
A
level by Fermi–LAT. This study is the first morphological analysis performed of this
G source and the third performed of this class of objects. Conducting a detailed two–
. dimensional modeling of its surface brightness distribution and analysing its J −Ks
h
colour gradients, we find that FBQS J164442.5+261913 is statistically most likely
p
hostedbyabarredlenticulargalaxy(SB0).Wefindevidencethatthebulgeinthehost
-
o galaxy of FBQS J164442.5+261913 is not classical but pseudo, against the paradigm
r of powerful relativistic jets exclusively launched by giant ellipticals. Our analysis,
t
s also reveal the presence of a ring with diameter equalling the bar length (rbar =
a 8.13kpc±0.25),whoseoriginmightbeacombinationofbar–drivengasrearrangement
[
andminormergers,asrevealedbytheapparentmergerremnantintheJ–bandimage.

1 In general, our results suggest that the prominent bar in the host galaxy of FBQS
v J164442.5+261913 has mostly contributed to its overall morphology driving a strong
1 secular evolution, which plays a crucial role in the onset of the nuclear activity and
1 the growth of the massive bulge. Minor mergers, in conjunction, are likely to provide
9 the necessary fresh supply of gas to the central regions of the host galaxy.
0
0 1 INTRODUCTION (RL–NLSy1) by the Large Area Telescope (LAT) on board
.
1 the Fermi satellite, suggesting that highly beamed and
0 Narrow line Seyfert 1 (NLSy1) galaxies are type 1 active stronglycollimatedrelativisticjetscanbelaunchedbyRL–
7 galactic nuclei (AGN) characterized by narrower Balmer NLSy1 AGN. The latter, challenge the paradigm that such
1 lines (FWHM(Hβ) < 2000 km s−1) than in normal jets are launched exclusively by blazars hosted by giant el-
: Seyferts,fluxratios[OIII]/Hβ <3,strongopticalFeIIlines lipticalgalaxies(Laor2000;Marscher2009)withblackholes
v
i (FeII bump) and a soft X-ray excess (Osterbrock & Pogge withmassesMBH (cid:38)108M(cid:12) accretingatlowrates(McLure
X 1985;Pogge2000).Basedonthefullwidthathalfmaximum et al. 2004; Sikora et al. 2007). Therefore, a thorough anal-
r (FWHM) of their Broad Line Region (BLR) lines and the ysisofthehostgalaxiesofthisnewclassofAGN(hereafter
a continuumluminosity(Kaspietal.2000),theircentralblack γ–NLSy1, Abdo et al. 2009), becomes a priority.
holesmasses(M )areestimatedtorangefrom∼106M(cid:12)
BH
to∼107M(cid:12)(Mathuretal.2012a,althoughBaldietal.2016 Sofar,onlytwoγ–NLSy1hostgalaxieshavebeenchar-
show that these low M estimates might be seriously af- acterized, 1H 0323+342 (Anto´n et al. 2008; Leo´n Tavares
BH
fectedbytheorientationoftheBLR).Theirlow–massblack et al. 2014) and PKS 2004-447 (Kotilainen et al. 2016).
holes suggest that their accretion rates are close to the Ed- These studies reveal characteristics such as the presence of
dingtonlimitandtheirhostgalaxiesareinanearlyphaseof disks, rings, bars and pseudobulges, which are expected in
galaxyevolution(Ohtaetal.2007).Unfortunately,relatively normal NLSy1s, however, do not fit with the common be-
little is known about their host galaxies. lief that powerful relativistic jets are launched exclusively
by giant ellipticals.
Some studies find that their morphologies resemble
those of inactive spirals with a regular presence of stel- As part of our ongoing imaging survey of the com-
lar bars (Crenshaw et al. 2003a), and pseudobulges (Orban plete sample of γ–NLSy1 galaxies detected so far, we con-
de Xivry et al. 2011; Mathur et al. 2012b). However, γ– ductedNIR(J andK –bands)observationstotheγ–NLSy1
s
rayemissionhavebeendetectedinsevenradio–loudNLSy1 FBQSJ164442.5+261913.Thisisoneofthesourcesdetected
(cid:13)c 2015TheAuthors
2 A. Olgu´ın–Iglesias et al.
by Fermi–LAT with high significance, having test statistic 3 IMAGE ANALYSIS
TS > 25 (∼ 5σ, Mattox et al. 1996) and given its redshift
(z=0.145,Badeetal.1995),itisthesecondclosestafter1H 3.1 Photometric decomposition
0323+342 (z =0.061), making it an excellent candidate for
We perform a 2D modeling of the galaxy using the image
accurate morphological studies to its host galaxy. With the
decomposition code GALFIT (Peng et al. 2011). We fol-
aim of achieving a better understanding of the mechanisms
lowtheproceduredescribedinourpreviousstudiesofAGN
needed to form and develop highly collimated relativistic
hostgalaxies(Leo´nTavaresetal.2014;Olgu´ın-Iglesiasetal.
jets, in this paper we present the results from our thorough
2016), which is described below.
analysis to FBQS J164442.5+261913.
The first, and most important part of the analysis is
This paper is structured as follows: Observations and
the modeling of the point spread function (PSF) by fitting
data reduction are presented in Section 2; the methods
selectedstarsofthefieldofview(FOV,Fig.1).Thesestars
we adopt to analyse the data are explained in Section 3.
arenon-saturated,withnosourceswithin∼7(cid:48)(cid:48) radius,more
Our results and discussion are presented in Section 4 and
than ∼ 10(cid:48)(cid:48) away from the border of the FOV and with a
5. In Section 6 we summarize our findings. Throughout
rangeofmagnitudesthatallowusapropercharacterization
the manuscript we adopt a concordance cosmology with
of core and wings. Stars 2, 5, 6, 8 and 9 fulfil these criteria
Ω = 0.3, Ω = 0.7 and a Hubble constant of H = 70
m Λ 0 (see Figure 1) and thus are used to derive our PSF model.
Mpc−1 km s−1.
On the other hand, star 1 is saturated, stars 3 and 10 are
very close to the border of the FOV and stars 4 and 7 have
close companions.
2 OBSERVATIONS AND DATA REDUCTION Eachselectedstariscenteredina50(cid:48)(cid:48)×50(cid:48)(cid:48) box,where
all extra sources are masked out by implementing the seg-
The J– and K–band observations of FBQS mentation image process of SExtractor (Bertin & Arnouts
J164442.5+261913 were conducted at the 2.5 m Nordic 1996). The stars are simultaneously modeled, using one
Optical Telescope (NOT) during the night of May 1, 2015 Gaussianfunction(intendedtofitthecoreofthestars)then,
using the Wide–Field near–infrared camera NOTcam with the resulting model is added with an exponential function
CCDdimensionsof1024pix×1024pixandapixelscaleof (intendedtofitthewingsofthestars).Similarly,depending
0.234(cid:48)(cid:48)/pix,givingafieldofviewof∼4×4arcmin2).During on the residuals, we add extra Gaussians and exponential
thenight,theseeingwasverygood,withanaverageFWHM functions until the core and wings are satisfactorely fitted.
of ∼0.75(cid:48)(cid:48) and ∼0.63(cid:48)(cid:48) for J– and Ks–bands, respectively. For our imagery, six Gaussians and six exponentials (and a
The target was imaged using the NOTcam standard J flat plane, that fits the sky background) were enough. The
(λcentral = 1.246µm) and Ks (λcentral = 2.140µm) filters resultisconsideredasasuitablePSFmodelforouranalysis
with a dithering technique with individual exposures of once it successfully fits all the stars individually (Figure 2).
30 seconds and a typical offset of ∼ 10(cid:48)(cid:48). A total of 85
Next, we fit FBQS J164442.5+261913 with the scaled
individualexposuresforJ−bandand72forK −bandwere
s
version of our derived PSF as the only component, to con-
obtained, giving a total exposure time of 2550 seconds and
straintheunresolvedAGNcontributionatthecentreofthe
2160 seconds, respectively.
galaxy. Since the residuals of the single PSF model (here-
The data reduction was performed using the NOTcam after model 1) are considerable (χ2 =4.148±0.01 for
reduction package1 for IRAF2. First we corrected for the J–band and χ2 = 3.171±0.0m2ofdoerl1K –band), we con-
optical distortion of the Wide–Field camera using distor- model1 s
tinue our analysis by adding extra functions to the model.
tion models based on high quality data of a stellar–rich
We use the S´ersic profile, expressed such that
field. Then, bad pixels were masked out using a file avail-
able in the NOTCam bad pixel mask archive. A normal-
ized flat field was created from evening and morning sky
frames to account for the thermal contribution. Using field (cid:34) (cid:32)(cid:18) R (cid:19)1/n (cid:33)(cid:35)
stars as reference points, the dittered images were aligned I(R)=Ieexp −κn R −1 (1)
and co-added to obtain the final reduced image used in our e
analysis.Inordertoperformphotometriccalibrationtothe
whereI(R)isthesurfacebrightnessattheradiusR,andκ
images, we retrieved J– and K – band magnitudes from n
s
is a parameter coupled to the S´ersic index n in such a way
2MASS (Skrutskie et al. 2006) resulting in an accuracy of
that I is the surface brightness at the effective radius R ,
∼ 0.10 mag. The derived integrated magnitudes in circular e e
wherethegalaxycontainshalfofthelight(Graham&Driver
aperturesarem =15.35±0.10(M =−23.84±0.10)and
J J
2005).TheS´ersicprofilehastheabilitytorepresentdifferent
m = 13.44±0.10 (M = −25.86±0.10). Galactic ex-
Ks Ks
stellardistributionssuchasellipticalgalaxies,classical–and
tinction for J and K bands are negligible (A [J] = 0.058
s λ
pseudo–bulges and bars, just by varying its S´ersic index n.
and A [K ]=0.025).
λ s
Hence, when n = 4, the S´ersic funtion is known as the de
Vaucouleursprofile(widelyusedtofitellipticalgalaxiesand
classical bulges); when n=1, it is an exponential function,
1 www.not.iac.es/instruments/notcam/ and when n=0.5, it is a Gaussian.
2 IRAFisdistributedbytheNationalOpticalAstronomyObser-
vatories,whichareoperatedbytheAssociationofUniversitiesfor GiventhatNLSy1sareknowntobetypicallyhostedin
Research in Astronomy, Inc., under cooperative agreement with discgalaxies(Crenshawetal.2003b),wealsoexploremodels
theNationalScienceFoundation that include the exponential function, expressed as:
MNRAS000,1–12(2015)
Bar–driven secular evolution in the γ −NLSy1 galaxy FBQS J164442.5+261913 3
1
N 3
E
4
6
10
5
9
7
FBQS J164442.5+261913
2
8
50 arcsec

Figure 1. J–band NOTcam image of FBQS J164442.5+261913. The large green vertical arrow indicates the location of the target.
Horizontalarrowsshowthesuitable(bluethickarrows)andunsuitable(redthinarrows)starsforthePSFconstruction.
alesserextent(yetsignificantly),thestructuralparameters
(cid:18) (cid:19) of the galaxy model. Even though, our imagery is in NIR
R
I(R)=I0exp h (2) bandsandthustheskycountsareSKYCOUNTS≈0,they
r
may show large variations. To account for this, we run sev-
where I(R) is the surface brightness at the radius R, I0 is eral sky fits in separated regions of 300 pixels × 300 pixels
thecentralsurfacebrightnessandhr isthediscscalelength. (70(cid:48)(cid:48)×70(cid:48)(cid:48))andusethemeanand±1σ oftheresultantval-
uestofitthegalaxy.Theoutcomesaremodelswithslightly
differentmagnitudeswhichareassumedtobetheerrorsdue
3.1.1 Uncertainties to the sky background.
Since the error bars produced by GALFIT are purely sta- Model magnitudes are also affected by uncertainties in
tistical and thus, unrealistically small (H¨aussler et al. 2007; the zero-point, estimated from magnitudes retrieved from
Bruce et al. 2012), we follow Kotilainen et al. (2011) and 2MASS. Thus, zero-point magnitude variations (±0.1mag)
Le´onTavaresetal.(2014)toderivetheuncertaintiesofour arealsoaddedaserrorsinthemagnitudesofourfinalmod-
fittings.Weidentifymodelparametersthatcouldcontribute els.
mostsignificantlytoerrors.RegardingthePSF,spatialvari-
ations might affect the structural parameters of the galaxy
model and, to a lesser extent, its magnitudes. To account 3.2 Fit of the isophotes
for this, we compare the brightness distribution of our PSF
Additionally to the morphological decomposition, we per-
model with the brightness distribution of each star in the
form an analysis based on the ellipse fit to the galaxy
field, whose only difference is assumed to lie in their posi-
isophotes (Wozniak et al. 1995; Knapen et al. 2000; Laine
tions.
et al. 2002; Sheth et al. 2003; Elmegreen et al. 2004; Mari-
On the other hand, sky background can affect magni- nova & Jogee 2007; Barazza et al. 2008). We perform this
tudesinalargerextent(whencomparedtothePSF)andto analysisusingtheELLIPSE taskinIRAF.Thisprocedure
MNRAS000,1–12(2015)
4 A. Olgu´ın–Iglesias et al.
14 Star2
] PSF model
2
− 16
c
e
s
c
ar 18
g
a
m
20
[
µ
22
0.5
µ
∆ 0.0

0.5
0 1 2 3 4 5
radius[arcsec]
15 16
16 Star5 17 Star6
2]− 17 PSF model 2]− 18 PSF model
c c
e 18 e
cs cs 19
ar 19 ar
g g20
a20 a
m m
[ 21 [ 21
µ µ
22 22
23 23
0.5 0.5
µ µ
∆ 0.0 ∆ 0.0
0.5 0.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.5 1.0 1.5 2.0
radius[arcsec] radius[arcsec]
16 18
Star 8 Star9
17
19
] PSF model ] PSF model
2− 18 2−
c c
cse 19 cse20
r r
a a
ag20 ag 21
m m
[ 21 [
µ µ22
22
23 23
0.5 0.5
µ µ
∆ 0.0 ∆ 0.0
0.5 0.5
0.0 0.5 1.0 1.5 2.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
radius[arcsec] radius[arcsec]
Figure 2. Test of the PSF model (top left image). Each star is fitted with our final PSF model in order to ensure its reliability. The
topsubpanelofeachplotshowstheazimuthallyaveragedsurfacebrightnessprofilesofthePSFmodel(magentaline)andthefittedstar
(blackdatapoints).Thelowersubpanelshowstheresidualsofthefit.
readsa2–dimensionalimagetofitisophotestoitslightdis- galaxyandthemodelsderivedfromthephotometricdecom-
tribution.Thefitsstartfromaninitialguessofxandycen- position.Furthermore,thesampleofisophotesextractedare
ter, ellipticity ((cid:15)) and position angle (PA). Each extracted used to identify changes in PA and ellipticity that could be
isophote is represented by its surface brightness (µ), semi– associatedtodifferentstructureswithinthegalaxymorphol-
major axis length (R), PA and (cid:15). ogy.
The fitted isophotes are used to represent and analyse
the azimuthally averaged surface brightness profiles of the
MNRAS000,1–12(2015)
Bar–driven secular evolution in the γ −NLSy1 galaxy FBQS J164442.5+261913 5
5" 5"
5" 5"
radius[kpc] radius[kpc]
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
16 14
17 Galaxy 15 Galaxy
] ]
2− 18 Model 2− 16 Model
sec 19 Bulge sec 17 Bulge
c Nucleus c Nucleus
ar20 ar 18
g g
a 21 a 19
m m
[22 [20
µ µ
23 21
24 22
0.5 0.5
µ µ
∆ 0.0 ∆ 0.0
0.5 0.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
radius[arcsec] radius[arcsec]
Figure 3. Model 2 (AGN+Bulge). North is up and east is to the left. Left column shows the J–band and right column shows the
Ks–band.Toprowshowstheobservedimages.Middlerowshowsthemodelsimages.Lowerrowshowstheazimuthallyaveragedsurface
brightnessprofilesofthetarget,themodelandthesubcomponentsofthemodel(toppanel)anditsresiduals(bottompanel).Symbols
areexplainedintheplots.
4 STRUCTURE OF FBQS J164442.5+261913 n>2, whereas most disk-like bulges have n<2 (Fisher &
Drory 2008; Gadotti 2009).
By means of a χ2 test, we find that the improvement
In order to characterize the morphology of FBQS
of this model (hereafter model 2) is equal for the J− and
J164442.5+261913, we first assume that it is hosted by an
the Ks−bands (χ2 /χ2 = 0.42 for J–band and
ellipticalgalaxy,sinceonlythesetypeofgalaxiesareknown model2 model1
χ2 /χ2 = 0.42 for K band). The images of the
to launch powerful relativistic jets able to produce γ−rays model2 model1 s
galaxy and the models, as well as the azimuthally average
(Marscher2009).Thus,weaddaS´ersicprofiletothesingle
surface brightness profiles of the galaxy, the model and the
PSF model that represents the AGN contribution. We con-
sub-components of the model for each band are shown in
strain the S´ersic index to n > 2.0, given the observational
Figure 3.
evidence that the light profiles of most ellipticals and clas-
sical bulges, are better described by a S´ersic function with The residual image of the J–band from model 2 (top
MNRAS000,1–12(2015)
6 A. Olgu´ın–Iglesias et al.
Model1 Model2 Model3 Model4a
Parameter
J Ks J Ks J Ks Ks
15.65 14.28 16.67 14.39 16.67 14.80 14.38
mAGN (0.33) (0.34) (0.38) (0.41) (0.43) (0.38) (0.24)
- - 15.70 13.86 17.77 14.55 14.97
m
bulge - - (0.37) (0.39) (0.40) (0.39) (0.32)
- - - - 16.28 14.33 14.90
m
disc - - - - (0.35) (0.38) (0.25)
- - - - - - 15.32
m
bar - - - - - - (0.42)
- - 0.95/2.40 0.82/2.07 0.38/0.96 0.30/0.76 0.43/1.10
R [”/kpc]
eff - - (0.23/0.58) (0.27/0.68) (0.13/0.32) (0.14/0.35) (0.14/0.34)
- - - - 2.62/6.65 3.04/7.68 3.19/8.10
hr [”/kpc] - - - - (0.45/1.14) (0.40/1.01) (0.47/1.20)
- - 2.58 2.71 1.80 1.95 1.90
n
bulge - - (0.40) (0.42) (0.31) (0.38) (0.35)
- - - - - - 1.17
n
bar - - - - - - (0.30)
- - - - - - 0.59
(cid:15)
bar - - - - - - (0.06)
4.250 3.927 1.785 1.645 1.160 1.300 1.181
χ2
ν (0.032) (0.033) (0.030) (0.031) (0.027) (0.029) (0.022)
Table 1. Best–fit parameters for model 1 (PSF only), model 2 (PSF+bulge), model 3 (PSF+bulge+disk) and model 4
(PSF+bulge+disk+bar).Parametererrorsappearinparenthesesb.
aModel4isonlyshownforKs−band,sincenostellarbarisdetectedinJ−band.
bParametererrorsareestimatedfollowingprocedurefromsection3.1.1.
panel of Figure 4), shows a ring like feature interrupted in evident. The upper panels of Figure 7 shows an image of
theeasternpart.Neithertheresidualsnorthesurfacebright- FBQS J164442.5+261913 in Ks–band, with the AGN and
ness profiles of the stars fitted with our PSF model show bulge contribution subtracted (using a bulge+AGN+disc
similar features. Moreover, its radius (∼ 3.5(cid:48)(cid:48)) exceeds by model),revealinganelongatedandsymmetricalfeaturethat
far the FWHM of our PSF (∼ 0.75(cid:48)(cid:48)). Hence, we consider resembles a stellar bar over the underlying disk.
the ring as a real component of the host galaxy.
TheK –bandresidual(toppanelofFigure5)showsan In order to confirm the existence of a bar in the host
s
elongated and roughly symmetric structure with a length galaxy of FBQS J164442.5+261913, we perform another
similar to the diameter of the ringed feature (∼ 3.2(cid:48)(cid:48)/ ∼ widely used method for detecting and describing bars; the
8.1kpc). In both bands a not-fitted bump in the light dis- ellipsefitofthegalaxyisophotes(seeplotinthelowerpanel
tributionofthegalaxyisobserved(from∼2.8(cid:48)(cid:48) to∼3.7(cid:48)(cid:48)), of Figure 7). When (cid:15) and PA are plotted against radius, a
whichisconsistentwiththeringandthetwolightenhance- bar is characterized by a local maximum in (cid:15) and a con-
ments close to the ends of the elongated structure. Since stant PA (typically ∆PA (cid:46) 20◦) along the bar (Wozniak
residuals are still considerable, we include an extra com- et al. 1995; Jogee et al. 1999; Men´endez-Delmestre et al.
ponent into the last model (Figure 6). We choose an ex- 2007). We can see a region that fulfil these criteria (from
ponential function, since it is able to represent the likely ∼ 2.6(cid:48)(cid:48) < radius < ∼ 3.2(cid:48)(cid:48) and PA ∼ 78◦) suggesting again
presence of a disk in the host galaxy of a typical NLSy1 the presence of a bar. Since the method of the ellipses fit
galaxy(wecallitmodel3).Theimprovementovermodel2is also hints at the presence of a bar, we proceed to charac-
χ2 /χ2 = 0.65 for J–band and χ2 /χ2 = terized its morphology (Figure 8). We add a S´ersic profile
model3 model2 model3 model2
0.79forK –band.Fromtheresidualimages,weobservethat to model 3 of K –band to fit the light distribution of the
s s
theringinJ–band(bottompanelofFigure4)seemsbetter stellar bar (we call it model 4). We use as initial guesses
defined. Moreover, in K –band (middle panel of Figure 5), a S´ersic index n = 0.5 (Greene et al. 2008) and the (cid:15) and
s
hintsofthisstructureemerge,whereastheelongatedstruc- PA derived from the ellipse fit of Figure 7. The improve-
ture disappear. ment with respect to the model where no bar is included is
The elongated feature and the light enhancements χ2 /χ2 =0.90. From the residual image (shown in
model4 model3
might be explained by the presence of a stellar bar show- lowerpaneloffigure5)wecanseethatingeneral,theresid-
ing their ansae (bright regions at the ends of bars observed ualsdecrease,thehintsoftheringremainandtheansaeare
in ∼ 40% of SB0 galaxies, as found by Martinez-Valpuesta better defined. The bump remains unfitted with the func-
et al. 2007; Laurikainen et al. 2007). Such a bar could be tions included in the model, which is expected given that
more likely detected in K −band since neither young lumi- it is caused by a ring and the bar ansae. The parameters
s
nousstarsorduststronglyaffectitsobservedemission(Rix derived from every model analysed are shown in table 1.
&Rieke1993).Nevertheless,apowerfulAGN,abrightbulge
andadisc,mightoutshinethebar,makingitspresenceless
MNRAS000,1–12(2015)
Bar–driven secular evolution in the γ −NLSy1 galaxy FBQS J164442.5+261913 7
Light
enhancements
5''
Figure 4. Residuals of the J−band model 2 (AGN+Bulge, top
panel)andmodel3(AGN+Bulge+Disc,bottompanel).Northis
up and east is to the left. To enhance S/N and to detect faint
structures, the residuals were smoothed to <1(cid:48)(cid:48) resolution. The
segmentedwhitecirclehasa3.2(cid:48)(cid:48) radiusandguidesthroughthe
ringfeature.Bluearrowsshowthelightenhancementsattheends
ofthebar(ansae).Alikelyminormergereventfeatureisobserved
intheeastpartofthegalaxy(fromR≈3(cid:48)(cid:48)uptoR≈5(cid:48)(cid:48)),witha
surfacebrightnessinJ–bandµ=21.0±0.5mag/arcsec2,which
originates the blue region at 3(cid:48)(cid:48) in the J −Ks colour profile of
figure9.
4.1 NIR colour gradient

Figure 9 shows the J−K colour profile of the host galaxy
s
of FBQS J164442.5+261913. The AGN contribution has
been subtracted using the best fit model for each band. In
general, as we move from the center to the outer parts of
the host galaxy, we can see that the colour decreases from Figure5.ResidualsfortheKs–bandmodel2(AGN+Bulge,top
J−K =4.33magdowntoJ−K =3.45magatR=1.20(cid:48)(cid:48), panel), model 3 (AGN+Bulge+Disc, middle panel) and model 4
s s
showingthatthecentralregion(bulge)isthereddestofthe (AGN+Bulge+Disc+Bar, bottom panel). North is up and east
hostgalaxy.FromR=1.20(cid:48)(cid:48)towardslargerradii,thecolour is to the left. To enhance S/N and to detect faint structures,
the residuals were smoothed to <1(cid:48)(cid:48) resolution. The segmented
increases up to a local maximum of J −K = 3.63 mag
s whitecirclehasa3.2(cid:48)(cid:48)radiusandguidesthroughtheringfeature.
at R = 1.55(cid:48)(cid:48). We link this increase in color to the bar,
Blue arrows show the light enhancements at the ends of the bar
since here is where it has its maximum influence (see Fig-
(ansae).Theresidualsofmodel2showshintsofthebar,whereas
ure 8). A second increase in colour is observed in the bar the residuals of the models where we include a disc and a bar
(model 3 and 4), show hints of the ring and the likely minor
MNRAS000,1–12(2015) merger(easternpartofthegalaxy,insidethewhitecircle,)shown
inJ−band.
8 A. Olgu´ın–Iglesias et al.
5" 5"
5" 5"
radius[kpc] radius[kpc]
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
16 14
17 Galaxy 15 Galaxy
] Model ] Model
2− 18 2− 16
c Bulge c Bulge
se 19 Nucleus se 17 Nucleus
c c
ar20 Disc ar 18 Disc
g g
a 21 a 19
m m
[22 [20
µ µ
23 21
24 22
0.5 0.5
µ µ
∆ 0.0 ∆ 0.0
0.5 0.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
radius[arcsec] radius[arcsec]
Figure 6. Model 3 (AGN+Bulge+Disc) for FBQS J164442.5+261913. Left column shows the J–band and right column shows the
Ks–band.Toprowshowstheobservedimages.Middlerowshowstheimagesofourmodels.Lowerrowshowstheazimuthallyaveraged
surface brightness profiles of the target, the model and the subcomponents of the model (top panel) and its residuals (bottom panel).
Symbolsareexplainedintheplots.
region from R = 2.20(cid:48)(cid:48) to R = 2.85(cid:48)(cid:48), with a maximum of 5 THE HOST GALAXY OF FBQS
J −K = 3.80 mag. Between 2.85(cid:48)(cid:48) < R < 3.15(cid:48)(cid:48), a blue J164442.5+261913
s
regionisobservedwhichcorrespondstoeasternfeature(in-
side the ring) in figures 4 and 5. We observe a last local According to the results shown in table 1, the host of
minimum at R = 3.30(cid:48)(cid:48) with a colour J −Ks = 3.80 mag. FBQSJ164442.5+261913canbeclassifiedasabarredlentic-
We associate this colour to the ring, with no influence of ular galaxy (SB0). In addition to the ansae morphology,
the ansae since, according to observations by (Martinez- that is frequent in S0 galaxies (∼ 40% of S0) as found
Valpuesta et al. 2007), ansae do not show any colour en- by Laurikainen et al. (2007), both the bulge and the disc
hancement(probablybecausetheyareadynamicalphenom- fulfil the characteristics for lenticular galaxies presented
ena). Finally, as we move outward, the disk becomes bluer, in Laurikainen et al. (2010). They also find that, as in
reaching an average colour J−Ks =3.70 mag. spirals (Hunt et al. 2004; Noordermeer & van der Hulst
2007), the luminosity of the bulge in S0s correlate to
MNRAS000,1–12(2015)
Bar–driven secular evolution in the γ −NLSy1 galaxy FBQS J164442.5+261913 9
0.25
0
Ellipticity
PA 5"

0.20 20
40
0.15
Ellipticity 60 PA[deg]
0.10
80
0.05
100
0.00 120
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Radius[arcsec] 5"
Figure 7.IntoppanelswecomparetheobservedKs–bandim-
age (top left), with an image in Ks–band where the AGN and
bulgemodelshavebeensubtracted(topright).Thebarbecomes radius[kpc]
visibleontheunderlyingdiskiftheAGNandbulgecontributions
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
aresubtracted.Inthelowerpanelweshowtheaverageprofilesof 14
ellipticity(cid:15)(blueline)andpositionanglePA(redline)obtained Galaxy
15
withELLIPSE fromKs–bandplottedagainsttheisophotema- ] Model
joraxis. 2− 16 Bulge
c
e 17 Bar
s
c Nucleus
the luminosity of their discs. According to such correla- ar 18 Disc
tion (MK,disk = 0.63MK,bulge +9.3), the bulge of FBQS ag 19
J164442.5+261913shouldhaveadiskwithanabsolutemag- m
nitude M = −24.55±0.20, consistent with the abso- [20
K,disk µ
lute magnitude derived through the morphological analysis 21
in this work (MK,disk =−24.85±0.25). 22
0.5
The parameters derived in this work for the compo-
µ
nentsofFBQSJ164442.5+261913areconsistentwiththose ∆ 0.0
ofpseudobulges.Weinzirletal.(2009)findaconnectionwith 0.5
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pseudobulges and small S´ersic indeces (n < 2.0), consis-
radius[arcsec]
tent with n = 1.8±0.31 for J–band and n = 1.9±0.35
for Ks–band, derived for FBQS J164442.5+261913. Inde- Figure 8.Model4(AGN+Bulge+Disc+Bar)fortheKs−band.
pendently, Fisher & Drory (2008) find that pseudobulges Top panel shows the observed image. Middle panel shows our
and their discs are associated through their effective radius modelimage.Lowerrowshowstheazimuthallyaveragedsurface
and scale lengths as r /h = 0.21±0.10 consistent with brightness profiles of the target, the model and the subcompo-
eff r
FBQSJ164442.5+261913(r /h =0.14±0.07forJ–band nentsofthemodel(toppanel)anditsresiduals(bottompanel).
eff r
and r /h = 0.14±0.06 for K –band). On the contrary, Symbolsareexplainedintheplots.
eff r s
they found that classical bulges have large r /h ratios
eff r
(r /h =0.45±0.28).Additionally,whenwecomparethe
eff r
luminosity(Minniti&Rix1996),thentheJ−K colorgra-
structuralparametersoftable1,withtheresultsinLaBar- s
dient of the host galaxy of FBQS J164442.5+261913, is in
bera et al. (2010), we find that FBQS J164442.5+261913
agreementwiththelatterpseudobulgeclassificationcriteria,
lies below the Kormendy relation (either for J– as for K –
s
where we see that, in the central region, K –band luminos-
band), consistent with Gadotti (2009) who find that pseu- s
ity is stronger in comparison to J–band than in any other
dobulges do not tend to follow the Kormendy relation. Fi-
region of the galaxy.
nally, if a galaxy hosts a pseudobulge, its center should be
mostly population I material (young stars, gas and dust, So far, only one galaxy able to launch a relativistic jet
Kormendy & Ho 2013). If we bear in mind that, in cases powerfulenoughtoaccelerateparticlesuptoγ−rayenergies,
of high recent starburst, supergiants contribute to K–band is known to host a pseudobulge; PKS 2004-447 (Kotilainen
MNRAS000,1–12(2015)
10 A. Olgu´ın–Iglesias et al.
radius[kpc] frequency (Lindblad 1974). The latter is located close to
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 corotation (Sellwood 2013), i.e. where the disc and the bar
4.4
corotate.
Observationsstatethatbarsendnearcorotation(Kent
4.2 1987; Sempere et al. 1995; Merrifield & Kuijken 1995;
Gerssen et al. 1999; Debattista & Williams 2001; Gerssen
g]4.0 2002; Corsini et al. 2003), and can drive structures such as
a
m inner rings approximately at the UHR (Kormendy & Ken-
[
Ks nicutt 2004). Therefore, the feature located at R = 3.20(cid:48)(cid:48),
−3.8 might be consistent with that of an inner ring.
J
Another scenario for the ring formation in FBQS
J164442.5+261913 is a minor merger event. Athanassoula
3.6
et al. (1997) show that the interaction of a small satel-
lite galaxy on a barred galaxy can produce a ring that en-
3.4 closes the bar. Also, (Mapelli et al. 2015) show that mi-
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
nor mergers with gas–rich satellites might explain the for-
radius[arcsec]
mation of rings in lenticular galaxies. This scenario is sup-
ported by the residuals in J–band (see Figure 4), where a
Figure 9.TheradialJ−Kscolourprofileofthehostgalaxyof
feature of surface brightness µ = 21.0±0.5 mag/arcsec2 is
FBQS J164442.5+261913. The AGN contribution has been sub-
shownabout∼5.15(cid:48)(cid:48)/13.10kpceastfromthecenterofFBQS
tractedfromthebestfitmodelofeachband.
J164442.5+261913(resemblingtheSeyfertgalaxyNGC1097
whoselightdistributionisstronglyaffectedbyasmallsatel-
etal.2016).Nevertheless,Leo´nTavaresetal.(2014)donot lite galaxy, Higdon & Wallin 2003). This feature seems to
discardthattheγ−NLSy11H0323+342isalsohostedbya interrupt the shape of the ring in the eastern part of the
pseudobulge. galaxy and even cause the color enhancement at 3.0(cid:48)(cid:48).
We now evaluate whether the parameters derived for Analternativeandmorelikelyscenariowasproposedby
the bar in FBQS J164442.5+261913 are in accordance with Marino et al. (2011) for their sample of lenticular galaxies.
those for active early–type galaxies. Using the maximum The formation of the ring might be a joint effect of secular
ellipticity of the ellipse fits to the bar region as bar length evolution driven by the bar and gas accreted from a small
(Marinova & Jogee 2007), we find that the length of the satellite galaxy (or many). Moreover, since S0 galaxies lack
bar in FBQS J164442.5+261913 is r = 8.13 kpc±0.25, of an own gas reservoir (unlike spirals), this scenario also
bar
if we normalized it to the disc scale length h , we obtain explainstheoriginofthegasneededtogrowamassivebulge
r
r /h =1.00±0.06. On the other hand, we can calculate (M =−22.42±0.40andM =−24.21±0.32)andactivate
bar r J Ks
the bar strength f (Abraham & Merrifield 2000, see also the black hole in FBQS J164442.5+261913, as well as the
bar
Whyte et al. 2002; Aguerri et al. 2009; Laurikainen et al. way this gas is channelled to the most central parts of the
2007; Hoyle et al. 2011) defined as: galaxy(i.e.throughangularmomentumtransportdrivenby
the bar, Shlosman et al. 1990; Ohta et al. 2007).
We finally observe that the parameters of the bar and
(cid:40) (cid:41)
f = 2 arctan(cid:104)(b/a)−0.5(cid:105)−arctan(cid:104)(b/a)0.5(cid:105) (3) the ring hosted by FBQS J164442.5+261913, are similar to
bar π thebarofPKS2004-447(Kotilainenetal.2016)andthering
in 1H 0323+342 (Leo´n Tavares et al. 2014). While the bars
where b/a is the minor to major axis ratio of the bar. We
of PKS 2004–447 and FBQS J164442.5+261913, are r ≈
bar
obtain a bar strength f = 0.17±0.03. According to e.g.
bar 7.80 kpcandr =8.13±0.25 kpc(takingthelengthofthe
bar
Aguerrietal.(2009)andLaurikainenetal.(2007),thebarin
bar as the maximum in the ellipticity profile), respectively,
FBQS J164442.5+261913 is long and weak, consistent with
withabsoluteK –bandmagnitudeofK =−23.44±0.38
s bar
S0 galaxies as found by (Laurikainen et al. 2002).
and K = −23.86±0.52, respectively; the rings of 1H
bar
The bar in FBQS J164442.5+261913 might be related 0323+342andFBQSJ164442.5+261913,are∼8.24 kpcand
to the ring through resonances (Athanassoula et al. 2010, ∼8.13 kpc,respectively.Moreover,PKS2004–447showsan
andreferencestherein),giventhatsecularevolutionislikely arm–like feature, whose origin might be related to a minor
themainevolutionaryprocessthatiscurrentlyinprogressin merger event (see Figure 19 of Athanassoula et al. 1997)
itshostgalaxy.Therefore,thering–likefeaturemightbethe andthat,atsomepoint,mightbecomearing,similartothe
resultofgasredistributionbyangularmomentumtransport feature shown in FBQS J164442.5+261913.
driven by the bar (i.e. a ring constructed by a rotating bar
According to the most accepted processes for jet for-
interacting with the disk gas). In this scenario, the gas is
mation, the Blandford–Znajek (BZ, Blandford & Znajek
movedbythebarintoorbitsneardynamicalresonances(for
1977; MacDonald & Thorne 1982; Penna et al. 2013) and
a review, see Athanassoula et al. 2013).
the Blandford–Payne (BP, Blandford & Payne 1982) mech-
ThemainresonancesaretheInnerLindbladResonance anisms,thejetlaunchingandcollimationrequiresverymas-
(ILR) Ω = Ω −κ/2, the Outer Lindblad Resonance sive black holes with high spins and strong magnetic fields.
ILR bar
(OLR) Ω = Ω +κ/2 (Buta & Combes 1996) and All of this require major mergers to occur, which fits well
OLR bar
theUltraHarmonicResonance(UHR)Ω =Ω −κ/4, withpreviousobservations(McLureetal.2004;Sikoraetal.
UHR bar
where Ω is the bar pattern speed and κ is the epicyclic 2007) and the jet formation paradigm (where powerful rel-
bar
MNRAS000,1–12(2015)