A Search for Blazar-Like Radio-Loud Narrow-Line Seyfert 1 Galaxies

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1 galaxies Review A Search for Blazar-Like Radio-Loud Narrow-Line Seyfert 1 Galaxies Hugh R. Miller 1, *, Jeremy D. Maune 1, Joseph R. Eggen 1, Clay S. Turner 1, Elizabeth C. Ferrara 1, Diana O. Gudkova 1 Amy M. Battles 2 1 Department of Physics Astronomy, Georgia State University, Atlanta, GA 30302, USA; maune@astro.gsu.edu (J.D.M.); eggen@astro.gsu.edu (J.R.E.); turner@astro.gsu.edu (C.S.T.); Elizabeth.C.Ferrara@nasa.gov (E.C.F.); diankald@gmail.com (D.O.G.) 2 Department of Physics, Georgia Gwinnett College, 1000 University Center Ln, Lawrenceville, GA 30043, USA; acambe2@ggc.edu * Correspondence: miller@chara.gsu.edu; Tel.: Academic Editors: Jose L. Gómez, Alan P. Marscher Svetlana G. Jorstad Received: 2 September 2016; Accepted: 23 February 2017; Published: 21 March 2017 Abstract: We report results of an observational program to investigate gamma-ray optical variability properties of vrl NLSY1 galaxies listed in Yuan et al. sample. We have identified 17 members of Yuan et al. sample possibly associated with gamma-ray sources based on a combination of ir optical polarization optical variability ir gamma-ray properties. Eight have previously been associated with gamma-ray sources. We find nine additional members that we predict are excellent cidates to be associated with gamma-ray sources in future. All 17 sources have many properties in common with flat spectrum radio quasars (FSRQs), suggesting that y may, in fact, constitute a new subclass of FSRQs. Keywords: blazar; narrow line seyfert 1 galaxy; gamma-ray source 1. Introduction During past decade, Fermi Gamma-Ray Space telescope has identified a small number of very radio-loud narrow-line Seyfert 1 galaxies (vrl NLSy1) associated with gamma-ray sources (e.g., PMN J , Abdo et al. [1]). These objects exhibit familiar double-peaked SED that is typical of that seen for blazars (Abdo et al. [2]). Their detection has, for first time, suggested that a number of vrl NLSy1s may have properties that are similar to those of FSRQs. Since Seyfert galaxies have long been known to have host galaxies with spiral morphologies, this would be first time that a blazar-like object (with a relativistic jet oriented close to line of sight to observer) has been found to reside in a spiral galaxy (Abdo et al. [1]). Yuan et al. [3] Komossa et al. [4] have identified a sample of vrl NLSy1 galaxies with R > 100, where R is defined as ratio of flux at 5 GHz regime to optical flux in B b. Indeed, it should also be noted that all gamma-ray detected vrl NLSy1s presently are included in this sample. This raises possibility that re may be additional vrl NLSy1s in this sample that may also be found to be future gamma-ray sources. If this is true, what might properties of se gamma-ray detected vrl NLSy1s be? How might y be different from presently known blazars? Do y, in fact, make up a new class of blazars? 2. Observational Program Motivated by gamma-ray detection of a few of se galaxies by questions posed above, we initiated an observational program jointly at gamma-ray optical wavelengths to fully investigate properties of galaxies listed in Yuan et al. sample. The goal of this Galaxies 2017, 5, 20; doi: /galaxies

2 Galaxies 2017, 5, 20 2 of 10 dual wavelength program is to identify additional members of this sample that exhibit blazar-like characteristics which would be prime cidates to monitor as future cidates to be associated with gamma-ray sources. As first step in initiating this program, we identified basic properties of vrl NLSy1 galaxies included in Yuan et al. sample. Kellerman et al. [5] has defined radio-loud as R > 10, as opposed to very radio-loud which corresponds to R > 100 in Yuan et al. sample. Osterbrock Pogge [6] identified following properties for NLSy1 galaxies: (a) contain a disk-like host galaxy (spiral?); (b) contain a low-mass central supermassive black hole (SMBH) that is near Eddington accretion rate; (c) exhibit a FWHM(H-beta) < 2000 km/s (Goodrich [7]); (d) exhibit a strong emission from FeII. Thus Yuan et al. sample is made up of objects that simultaneously satisfy both Osterbrock Pogge criteria as NLSy1 galaxies Yuan et al. definition of very radio-loud AGN. If some members of this sample are truly blazar-like objects, y should demonstrate some of classic characteristics of this class of AGN. Strittmatter et al. [8] were among first to list following observational properties for BL Lac objects: They (a) exhibit a featureless optical spectrum; (b) exhibit a non-rmal spectral energy distribution (SED); (c) are highly variable on all observed timescales wavelengths (including microvariability); (d) exhibit highly variable polarization; (e) are radio-loud ( many are detected at gamma-ray wavelengths). We have refore chosen to use unique blazar-identifying optical properties of large amplitude rapid optical flux variations (including microvariability), significant variable optical polarization, radio loudness (R > 100) as primary indicators for a blazar cidate in sample. We furr define microvariability as discrete events occurring on timescales of minutes to hours, or doubling times on similar timescales (Miller, Carini Goodrich [9]); however, we do not include simple linear trends spanning several hours. Utilizing 1.3 m SMARTS telescope located at CTIO 31 in NURO, 42 in Hall, 72 in Perkins telescopes at Lowell Observatory, we began, in 2010, a program to photometrically polarimetrically monitor each member of Yuan et al. sample for blazar-like properties of strong variable optical polarization optical microvariability. In addition, we have used Fermi Gamma-Ray Space Telescope (Fermi) to detect monitor members of this sample for gamma-ray emission. The presence of gamma-ray emission (in addition to property of very radio-loudness) is a key element indicating presence of a relativistic jet oriented near line of sight to observer. The gamma-ray data used in this work was collected with Large Area Telescope (LAT), which is primary instrument aboard Fermi (1) space telescope. The spacecraft has been operating in all-sky scanning mode almost continuously since its launch in 2008, which allows LAT to cover entire sky once every 3 h in an energy range of 20 MeV to several hundred GeV. Our data were reduced analyzed using ScienceTools v9r33p0, instrument response functions P7REP, stard background galactic model. The reader is referred to Eggen [10] for details of this analysis. Our data were downloaded from Fermi website on 20 February For each source, we analyzed a circular region in sky that was 15 degrees in radius, centered on target, covering an energy range of 100 MeV to 300 GeV. Please see Eggen, Miller, Maune [11] for details concerning event class selection pointing cuts. The gamma-ray light curves for each source were constructed from 66 bins, each of which was 30.5 days long. The first bin began on 4 August Normally, a positive gamma-ray detection of a Fermi source requires a test statistic TS > 25 (Mattox et al. [12]). Our results from this analysis are divided into two classes: those objects that are firmly detected at gamma-ray energies with a TS > 25 in Table 1, those in Table 2 that were detected with 9 < TS < 25. A more detailed summary of se procedures is found in Eggen [10]. To date, using radio optical criteria discussed above, we have confirmed previous gamma-ray detection of eight members of this sample with TS > 25 (See Table 1 as blazar-like NLSy1 galaxies. In addition, we have also identified nine additional members of this sample with 9 < TS < 25

3 Galaxies 2017, 5, 20 3 of 10 which we expect to be prime cidates for future gamma-ray detection. This second group of objects also exhibits variability polarization properties consistent with those commonly detected for blazars. The details of se results are discussed below. Table 1. Objects in sample that were detected at gamma-ray energies (Foschini et al. [13], references rein). (1) Object Name; (2) Right Ascension; (3) Declination; (4) Radio-Loudness; (5) Binning Number; (6) Gamma-ray Test Statistic; (7) Gamma-ray Flux. Object ID R.A. Dec. Log(R) Bin# TS Flux(err) 1H (2.73) J (2.20) J (2.32) J (2.34) J (0.06) PKS (2.71) J (1.04) PKS (0.52) Table 2. Objects with 25 > TS > 9 gamma-ray detections. (1) Object Name; (2) Right Ascension; (3) Declination; (4) Radio-Loudness; (5) Bin Number; (6) Gamma-ray Test Statistic; (7) Gamma-ray Flux. Object ID R.A. Dec. Log(R) Bin# TS Flux(err) J (0.56) (2.23) J (0.15) (0.36) J (0.15) J (0.81) J (1.66) J (0.60) J (0.23) IRAS (1.89) J (2.54) 3. Results In order to test our ability to identify additional blazar-like members of Yuan et al sample, we first analyzed optical microvariability polarization, gamma-ray observations for previously identified members of sample associated with gamma-ray sources. PMN J As shown earlier by Eggen et al [11], this object exhibits extraordinary optical variability on timescales of minutes to years (see Figure 1). It also rivals most extreme microvariability that is observed for blazars, as shown in Figure 2, where flux is observed to double on timescales of less than 4 h. Figure 3 shows long-term optical variability (R-mag), polarization (P), position angle (EVPA), gamma-ray flux, where all of se exhibit large-scale variations. Therefore, using our criteria defined above, we find conclusive evidence supporting classification of this member of sample as a blazar.

4 Galaxies 2017, 5, 20 4 of 10 Galaxies 2017, 5, 20 4 of 10 Galaxies 2017, 5, 20 4 of 10 Figure Figure Multi-year Multi-year light light curve curve of of J J Figure 1. Multi-year light curve of J (a) (a) (b) (b) Figure 2. (a) Intra-night light curve of J The light curve share a ~1.0 magnitude range. The Figure object is 2. in (a) an Intra-night excited state light showing curve of a flux J doubling The time light of 4.39 curve ± 0.19 share hours. a ~1.0 The magnitude arrows indicate range. The Figure 2. (a) Intra-night light curve of J The light curve share a ~1.0 magnitude range. object extreme is in range excited during state this showing observation. a flux All doubling data was time obtained of 4.39 in ± 0.19 optical hours. The R b; arrows (b) indicate Intra-night The object is in an excited state showing a flux doubling time of 4.39 ± 0.19 h. The arrows indicate extreme light curve range of J during this The observation. light curve All shows data was a ~0.8 obtained magnitude in range. optical The R object b; is (b) in Intra-night extreme range during this observation. All data was obtained in optical R b; (b) an Intra-night excited light state curve showing of J a flux doubling The light time curve of 3.60 shows ± 0.23 ~0.8 hours. magnitude The arrows range. indicate The object extremes. is in an excited light curve of J The light curve shows a ~0.8 magnitude range. The object is in an A excited low state amplitude showing ~0.10 a flux mag doubling event with time a duration of 3.60 ± of 0.23 a 1.4-hours hours. The is centered arrows indicate near ~ extremes. JD. All A data low state showing a flux doubling time of 3.60 ± 0.23 h. The arrows indicate extremes. A low amplitude amplitude was obtained ~0.10 in mag optical event R with b. a duration of a 1.4-hours is centered near ~ JD. All data ~0.10 mag event with a duration of a 1.4-h is centered near ~ JD. All data was obtained in was obtained in optical R b. optical R b.

5 Galaxies 2017, 5, 20 5 of 10 Galaxies 2017, 5, 20 5 of 10 Galaxies 2017, 5, 20 5 of 10 Figure 3. Quasi-simultaneous gamma-ray optical R-b data for J Figure 3. Quasi-simultaneous gamma-ray optical R-b data for J J Figure Maune 3. Quasi-simultaneous et al. [14] have gamma-ray demonstrated optical that R-b this object data for also J exhibits enormous J variability on Maune all timescales et al. [14] at both have optical demonstrated gamma-ray that this wavelengths object also (Figure exhibits 4) enormous it also exhibits variability on all a timescales high J degree at of both polarization Maune optical et al. (P [14] = 12%). gamma-ray have Figure demonstrated 5, wavelengths which displays that this (Figure object multiwavelength 4) also exhibits it also exhibits variability, enormous a high degree shows variability of polarization that on re all timescales appears (P = 12%). to at be both Figure a close optical 5, relationship which gamma-ray displays between wavelengths multiwavelength occurrence (Figure of 4) variability, gamma-ray it also exhibits shows that reoptical a appears high degree flares to be observed of a polarization closeduring relationship (P April = 12%) between Figure This event 5, which occurrence was displays followed of by multiwavelength a gamma-ray radio flare observed variability, optical a few flares months shows that later re which appears may be to related be a close to se relationship earlier optical between gamma-ray occurrence events. of gamma-ray observed during April This event was followed by a radio flare observed a few months later optical 1H flares observed The observational during April results This for 1H event was followed are similar by a to radio those flare found observed for above a few which may be related to se earlier optical gamma-ray events. two months objects later which are may summarized be related to in se Miller earlier et al. optical [15]. This gamma-ray includes events. rapid, low-amplitude 1H microvariations H shown The The observational observational in Figure 6. results results for for 1H 1H are similar are similar to those to found those for found above for abovetwo twoobjects objects are are summarized in in Miller Miller et al. et al. [15]. [15]. This This includes includes rapid, rapid, low-amplitude low-amplitude microvariations shown shown in Figure in Figure Figure 4. Rapid, large-amplitude gamma-ray optical variations for J Figure 4. Rapid, large-amplitude gamma-ray optical variations for J Figure 4. Rapid, large-amplitude gamma-ray optical variations for J

6 Galaxies 2017, 5, 20 6 of 10 Galaxies 2017, 5, 20 6 of 10 Galaxies 2017, 5, 20 6 of 10 Figure 5. Multiwavelength observations of J from year 2013, combining data from Figure 5. Multiwavelength observations of J from year 2013, combining data from Figure Owens 5. Valley Multiwavelength Radio Observatory, observations Lowell of J (optical R b), from Swift year (X-ray), 2013, combining Fermi data (gamma-ray) from Owens Valley Radio Observatory, Lowell (optical R b), Swift (X-ray), Fermi (gamma-ray) Owens telescopes. Valley The Radio dotted Observatory, lines indicate Lowell a period (optical in which R b), re Swift was a (X-ray), gradual 30% Fermi increase (gamma-ray) in IR flux, telescopes. reported The by Mexico s dotted lines National indicate Institute for period Astrophysics, in whichoptics, re was Electronics a gradual (Carrasco 30% increase et al. [16]). in IR flux, telescopes. The dotted lines indicate a period in which re was a gradual 30% increase in IR flux, reported reported by Mexico s by Mexico s National National Institute for forastrophysics, Optics, Optics, Electronics Electronics (Carrasco (Carrasco et al. [16]). et al. [16]). (a) (b) (a) (b) Figure 6. Intra-night light curves (LC) of 1H The LC taken using 72-in is shown as (a), Figure 6. LC Intra-night taken with light curves 31-in is (LC) shown of as 1H (b) Both light The curves LC taken are plotted using on a 72-in 0.5 magnitude is shown as scale. (a), Figure 6. Intra-night light curves (LC) of 1H The LC taken using 72-in is shown as (a), Microvariablity LC taken remains with detectable 31-in is shown for this as (b). object, Both albeit light on curves a much are smaller plotted on scale a 0.5 than magnitude for J scale. Microvariablity or J LC taken with Data remains was 31-in detectable obtained is shown in for as this optical (b). Both object, R b. light curves are plotted on a 0.5 magnitude scale. albeit on a much smaller scale than for J Microvariablity or J remains Data was detectable obtained for in thisoptical object, R albeit b. on a much smaller scale than for J or J Data was obtained in optical R b. The remaining members of Yuan et al. sample, included in Table 1, exhibit similar but less dramatic variability behavior compared to that shown for preceding objects. This demonstrates

7 Galaxies 2017, 5, 20 7 of 10 Galaxies The 2017, remaining 5, 20 members of Yuan et al. sample, included in Table 1, exhibit similar but 7 of less 10 dramatic variability behavior compared to that shown for preceding objects. This demonstrates that criteria outlined in Section 2 of this paper are good predictors of blazar-like characteristics for that members criteria outlined of this sample. in Section We 2also of this investigated paper are good microvariability predictors of blazar-like for remaining characteristics members for of members Yuan et of al. this sample sample. We failed alsoto investigated detect any cases microvariability of microvariations. for remaining members of Yuan Modifying et al. sample our newly failed defined to detect criteria anyfor cases prime of microvariations. cidates for future gamma-ray detection defined Modifying above, we our searched newly defined Yuan criteria et al. sample for prime for members cidates which forsatisfy futurethis gamma-ray (9 < TS < 25) detection criteria defined which above, also we have searched R > 25. We Yuan also et investigated al. sampleif for se members objects which also exhibit satisfy significant this (9 < TS optical < 25) polarization criteria which with both also have rapid R optical > 25. We variability also investigated microvariability. if se objectslisted also exhibit below significant in Table 2 optical is our polarization list of objects with that satisfy both rapid se optical criteria variability which we microvariability. predict will be Listed most below blazar-like in Table vrl 2NLSy1 is our galaxies list of objects in this that sample. satisfythese senine criteria objects are which excellent we predict cidates will be to be detected most blazar-like at gamma-rays vrl NLSy1 with a galaxies TS > 25 in in this sample. near future. These nine objects are excellent cidates to be detected at gamma-rays with a TS We > 25have in also near performed future. a statistical study of microvariability for 17 members of our sample Weof have blazar-like also performed vrl NLSy1s a statistical in an effort study to compare of microvariability m with or for radio-loud 17 members AGN. We ofhave our constructed sample of blazar-like a histogram vrl NLSy1s of number in an effort of microvariability to compare m events with or versus radio-loud amplitude AGN. Weof have observed constructed microvariations a histogram offor se number 17 of objects microvariability included in events our sample versus(figure amplitude 7). We n of compared observed this microvariations histogram to forsimilar se 17 histograms objects included constructed in our sample for radio-selected (Figure 7). We (RBL) n compared X-ray selected this histogram (XBL) blazars to similar (Miller histograms Noble constructed [17]). (Note for radio-selected that FSRQs are (RBL) included in X-ray selected RBLs.) In all three (XBL) histograms, blazars (Miller distributions Noble [17]). for small-amplitude (Note that FSRQsevents are included are quite insimilar. RBLs.) In However, all threeboth histograms, RBL distributions vrl NLSy1 histograms for small-amplitude show a significant events are number quite similar. of large-amplitude However, both events while RBLno large-amplitude vrl NLSy1 histograms events are found show ain significant XBL histogram. number ofmiller large-amplitude Noble events [17] performed while noa large-amplitude Kolmogorov-Smirnov events (K-S) are found test on in RBL XBL histogram. XBL histograms Miller Noble found [17] that performed re was only a Kolmogorov-Smirnov a 2.2% chance that y (K-S) were testdrawn on from RBL same XBL histograms parent distribution. found A K-S thattest re comparing was only a 2.2% RBL chance distribution that y to that were found drawn for from vrl NLSy1s same parent found distribution. that re Awas K-San test 89% comparing probability that RBLse distribution two distributions to that found were for drawn vrlfrom NLSy1s same foundparent that re distribution was an 89% (Maune probability [18]). that Therefore, se two distributions comparison were of drawn histograms from demonstrates same parent that distribution character (Maune of [18]). distribution Therefore, of comparison microvariations of histograms most similar demonstrates to that found that for character RBL blazars, of distribution strongly suggesting of microvariations that gamma-ray loud is most similarvrl to that NLSy1s foundare forclosely RBL related blazars, to strongly RBL blazars. suggesting that gamma-ray loud vrl NLSy1s are closely related to RBL blazars. Figure Figure Histograms Histograms showing showing number number of of microvariability microvariability events events vs. vs. amplitude. amplitude. The The top top figure figure is is reproduced reproduced from from Maune Maune [18] [18] uses uses a scale scale of of magnitude magnitude on on x-axis. x-axis. The The bottom bottom two two figures figures were were originally originally printed printed in in Miller Miller Noble Noble [17] [17] use use a one-magnitude one-magnitude scale. scale. Note Note that that XBL XBL sample sample was was generally generally brighter brighter than than or or two, two, allowing allowing for for a bias a bias in in detection detection of excess of excess lowamplitude low-amplitude events. events.

8 Galaxies 2017, 5, 20 8 of 10 We also have found extraordinary large-amplitude microvariations for two members contained in this sample (J J ), which rival most extreme behavior observed for any known blazar. In addition, we observed an optical orphan flare at optical wavelengths that had no detected gamma-ray counterpart. This also supports possibility that gamma-ray loud vrl NLSy1s are closely related to RBL blazars. In addition, duty cycle for gamma-ray detected vrl NLSy1s studied in present sample was found to be DC = 0.42 which is similar to DC ~0.45 found for RBL blazars (Carini, Miller Noble, [19]). Previously, duty cycle for a sample of radio-quiet NLSy1s was found to be DC ~0.02 (Ferrara, E.C. [20]). This clearly indicates that vrl NLSy1 galaxies exhibit quite different variability properties than those observed for normal NLSy1s. This also provides additional support for hyposis that vrl NLSy1s have many properties in common with RBL blazars. It should also be pointed out that no vrl NLSy1 has, to date, been detected at TeV energies, that duty cycles for XBL blazars are significantly different from those found for vrl NLSy1s. All se properties suggest that vrl NLSy1s seem to be closely related to RBL blazars. 4. Conclusions We have identified nine new gamma-ray loud members of Yuan et al. sample, all of which exhibit blazar-like properties. Our investigations have also shown that some (but not all) vrl NLSy1s in this sample exhibit blazar-like properties, including provisional gamma-ray detection, variability of optical polarization flux (including microvariability). It was also found that radio-loudness by itself is a poor indicator of wher a member exhibits blazar-like properties. It was furr determined that at least a gamma-ray detection with (9 < TS < 25) is likely required as a predictor of blazar-like properties for any object in this sample. We also found that microvariability, duty cycle optical polarization for those gamma-detected objects in this sample are consistently RBL-like when detected, suggesting, to date, that all vrl NLSy1 blazars are RBL-like. This suggests that this subclass of NLSy1s n is likely to have masses for central SMBH similar to those found for RBL blazars, leading to conclusion that y have significantly more massive SMBHs than normal, radio-quiet NLSy1s. This is consistent with recent results reported by Baldi et al. [21] utilizing spectropolarimetric observations of RL NLSy1 galaxies, earlier estimates of black hole masses for NLSy1 galaxies (Marconi et al. [22]). This was independently suggested by Calderone et al. [23] who found black hole mass estimates for a sample of RLNLSy1 galaxies of at least a factor of six to 10 times larger than earlier estimates based on single-epoch virial methods. This also means that Eddington ratios for se objects are correspondingly lower. Thus present results suggest that narrowness of lines detected in ir spectra may be explained as an orientation effect rar than an intrinsic property. Decarli et al. [24] have suggested that observed optical spectrum of vrl NLS1 galaxies is due to fact that se sources have a disk-like BLR we are observing BLR ~pole-on, with line of sight to observer near axis of relativistic jet. If this is case, n re is little or no component of velocity directed toward observer which can cause Doppler broadening in a cylindrical-like BLR. Therefore, mass of central SMBH for se objects could be closer to that of FSRQs (a sub-class of RBLs) than that of radio-quiet NLS1 galaxies. This study also raises a number of or questions. Do vrl NLSy1 galaxies in present sample exhibit giant-amplitude intraday X-ray variability commonly observed for NLSy1s (Boller et al. [25]), or do y exhibit smaller-amplitude intraday X-ray variations closer to that of FSRQs? Does morphology of host galaxy play a significant role in formation of relativistic jets? How do vrl NLSy1 galaxies differ from normal RBL blazars (or than morphology of host galaxy)? If vrl NLSy1 galaxies are part of population of RBL blazars, n are re XBL analogues to se objects, if so, why have y not been detected? Acknowledgments: The authors thank GSU for support through RPE program Lowell Observatory Cerro Tololo Interamerican Observatory for observation time. H.R.M. thanks NSF for partial support during

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