Browsing by Subject "quasars"
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Item Accretion Disk Temperatures Of QSOs: Constraints From The Emission Lines(2013-06) Bonning, E. W.; Shields, Gregory A.; Stevens, A. C.; Salviander, Sarah; Shields, Gregory A.; Stevens, A. C.; Salviander, SarahWe compare QSO emission-line spectra to predictions based on theoretical ionizing continua of accretion disks. The observed line intensities do not show the expected trend of higher ionization with theoretical accretion disk temperature as predicted from the black hole mass and accretion rate. Consistent with earlier studies, this suggests that the inner disk does not reach temperatures as high as expected from standard disk theory. Modified radial temperature profiles, taking account of winds or advection in the inner disk, achieve better agreement with observation. The emission lines of radio-detected and radio-undetected sources show different trends as a function of the theoretically predicted disk temperature.Item Accretion onto Intermediate-Mass Black Holes in Dense Protogalactic Clouds(2009-05) Milosavljevi?, Miloš; Couch, Sean M.; Bromm, Volker; Milosavljevi?, Miloš; Couch, Sean M.; Bromm, VolkerWe present the first results from two-dimensional simulations of radiatively efficient accretion of metal-free gas onto intermediate-mass black holes. We fix the shape of the spectral energy distribution of the radiation produced near the event horizon and study the structure of the irradiated low-angular-momentum accretion flow over 3 orders of magnitude in radius from the black hole, 10(14)-10(17) cm for a 100 M(circle dot) black hole. The luminosity of the central source is made to be proportional to the rate at which gas accretes across the inner boundary, which we set just inside the sonic radius. We find that photoionization heating and radiation pressure modify the structure of the flow. When the ambient gas density is 10(7) cm(-3), accretion is intermittent and on average reduced to 32% of the Eddington-limited rate, over 2 orders of magnitude below the "Bondi" rate evaluated ignoring radiation, in agreement with theoretical models. Even if the vicinity of the black hole is supplied with high-density gas, accretion is rendered inefficient through heating and radiation pressure.Item Adaptive Optics Imaging Of Quasi-Stellar Objects With Double-Peaked Narrow Lines: Are They Dual Active Galactic Nuclei?(2011-09) Rosario, D. J.; McGurk, R. C.; Max, C. E.; Shields, Gregory A.; Smith, K. L.; Ammons, S. M.; Shields, Gregory A.; Smith, K. L.Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)-dual active galactic nuclei (AGNs)-are predicted by many current and popular models of black-hole-galaxy co-evolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near-infrared laser guide star adaptive optics imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet quasi-stellar objects (QSOs) drawn from the Sloan Digital Sky Survey (SDSS), which show double-peaked narrow AGN emission lines. Of the 12 AGNs imaged, we find 6 with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec scales: similar to 0.3%-0.65%. We derive from this fraction the time spent in a QSO phase during a typical merger and find a value that is much lower than estimates that arise from QSO space densities and galaxy merger statistics. We discuss possible reasons for this difference. Finally, we compare the SMBH mass distributions of single and dual AGNs and find little difference between the two within the limited statistics of our program, hinting that most SMBH growth happens in the later stages of a merger process.Item Chandra Observations of A 1.9 Kpc Separation Double X-Ray Source in A Candidate Dual Active Galactic Nucleus Galaxy At Z=0.16(2011-08) Comerford, Julia M.; Pooley, David; Gerke, Brian F.; Madejski, Greg M.; Comerford, Julia M.; Pooley, DavidWe report Chandra observations of a double X-ray source in the z = 0.1569 galaxy SDSS J171544.05+600835.7. The galaxy was initially identified as a dual active galactic nucleus (AGN) candidate based on the double-peaked [O III] lambda 5007 emission lines, with a line-of-sight velocity separation of 350 km s(-1), in its Sloan Digital Sky Survey spectrum. We used the Kast Spectrograph at Lick Observatory to obtain two long-slit spectra of the galaxy at two different position angles, which reveal that the two Type 2 AGN emission components have not only a velocity offset, but also a projected spatial offset of 1.9 h(70)(-1) kpc on the sky. Chandra/ACIS observations of two X-ray sources with the same spatial offset and orientation as the optical emission suggest that the galaxy most likely contains Compton-thick dual AGNs, although the observations could also be explained by AGN jets. Deeper X-ray observations that reveal Fe K lines, if present, would distinguish between the two scenarios. The observations of a double X-ray source in SDSS J171544.05+600835.7 are a proof of concept for a new, systematic detection method that selects promising dual AGN candidates from ground-based spectroscopy that exhibits both velocity and spatial offsets in the AGN emission features.Item Color Variability Of HBC 722 In The Post-Outburst Phases(2015) Baek, Giseon; Pak, Soojong; Green, Joel D.; Meschiari, Stefano; Lee, Jeong-Eun; Jeon, Yiseul; Choi, Changsu; Im, Myungshin; Sung, Hyun-Il; Park, Won-Kee; Green, Joel D.; Meschiari, StefanoWe carried out photometric observations for HBC 722 in the Sloan Digital Sky Survey r, i, and z bands from 2011 April to 2013 May with the Camera for QUasars in EArly uNiverse attached to the 2.1 m Otto Struve telescope at McDonald Observatory. The post-outburst phenomena were classified into five phases according to not only brightness but also color variations, which might be caused by physical changes in the emitting regions of optical and near-infrared bands. A series of spectral energy distributions (SEDs) is presented to support color variations and track the time evolution of the SED in optical/near-infrared bands after the outburst. Given two years of data, possible periodicities of r, i, and z bands were checked. We found three families of signals around similar to 6, similar to 10, and similar to 1 days in three bands, which is broadly consistent with Green et al. We also examined short-term variability (intra-day and day scales) to search for evidences of flickering by using the micro-variability method. We found clear signs of day scale variability and weak indications of intra-day scale fluctuations, which implies that the flickering event occurs in HBC 722 after outburst.Item Dual Supermassive Black Hole Candidates In The AGN And Galaxy Evolution Survey(2013-11) Comerford, Julia M.; Schluns, Kyle; Greene, Jenny E.; Cool, Richard J.; Comerford, Julia M.Dual supermassive black holes (SMBHs) with kiloparsec-scale separations in merger-remnant galaxies are informative tracers of galaxy evolution, but the avenue for identifying them in large numbers for such studies is not yet clear. One promising approach is to target spectroscopic signatures of systems where both SMBHs are fueled as dual active galactic nuclei (AGNs), or where one SMBH is fueled as an offset AGN. Dual AGNs may produce double-peaked narrow AGN emission lines, while offset AGNs may produce single-peaked narrow AGN emission lines with line-of-sight velocity offsets relative to the host galaxy. We search for such dual and offset systems among 173 Type 2 AGNs at z < 0.37 in the AGN and Galaxy Evolution Survey (AGES), and we find two double-peaked AGNs and five offset AGN candidates. When we compare these results to a similar search of the DEEP2 Galaxy Redshift Survey and match the two samples in color, absolute magnitude, and minimum velocity offset, we find that the fraction of AGNs that are dual SMBH candidates increases from z = 0.25 to z = 0.7 by a factor of similar to 6 (from 2/70 to 16/91, or 2.9(-1.9)(+3.6)% to 18(-5)(+5)%). This may be associated with the rise in the galaxy merger fraction over the same cosmic time. As further evidence for a link with galaxy mergers, the AGES offset and dual AGN candidates are tentatively similar to 3 times more likely than the overall AGN population to reside in a host galaxy that has a companion galaxy (from 16/173 to 2/7, or 9(-2)(+3)% to 29(-19)(+26)%). Follow-up observations of the seven offset and dual AGN candidates in AGES will definitively distinguish velocity offsets produced by dual SMBHs from those produced by narrow-line region kinematics, and will help sharpen our observational approach to detecting dual SMBHs.Item The Gentle Growth of Galaxies at High Redshifts in Overdense Environments(2014-08) Romano-Diaz, Emilio; Shlosman, Issac; Choi, Jun-Hwan; Sadoun, Raphael; Shlosman, IssacWe have explored prevailing modes of galaxy growth for redshifts z similar to 6-14, comparing substantially overdense and normal regions of the universe, using high-resolution zoom-in cosmological simulations. Such rare overdense regions have been projected to host high-z quasars. We demonstrate that galaxies in such environments grow predominantly by a smooth accretion from cosmological filaments which dominates the mass input from major, intermediate, and minor mergers. We find that by z similar to 6, the accumulated galaxy mass fraction from mergers falls short by a factor of 10 of the cumulative accretion mass for galaxies in the overdense regions, and by a factor of 5 in the normal environments. Moreover, the rate of the stellar mass input from mergers also lies below that of an in situ star Formation (SF) rate. The fraction of stellar masses in galaxies contributed by mergers in overdense regions is similar to 12%, and similar to 33% in the normal regions, at these redshifts. Our median SF rates for similar to few x 10(9) M-circle dot galaxies agrees well with the recently estimated rates for z similar to 7 galaxies from Spitzer's SURF-UP survey. Finally, we find that the main difference between the normal and overdense regions lies in the amplified growth of massive galaxies in massive dark matter halos. This leads to the Formation of similar to 10(10) M-circle dot galaxies due to the similar to 100 fold increase in mass during the above time period. Such galaxies are basically absent in the normal regions at these redshifts.Item HST-COS Observations Of AGNs. II. Extended Survey Of Ultraviolet Composite Spectra From 159 Active Galactic Nuclei(2014-10) Stevans, Matthew L.; Shull, J. Michael; Danforth, Charles W.; Tilton, Evan M.; Stevans, Matthew L.The ionizing fluxes from quasars and other active galactic nuclei (AGNs) are critical for interpreting their emissionline spectra and for photoionizing and heating the intergalactic medium. Using far-ultraviolet (FUV) spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we directly measure the rest-frame ionizing continua and emission lines for 159 AGNs at redshifts 0.001 < Z(AGN) < 1.476 and construct a composite spectrum from 475 to 1875 A. We identify the underlying AGN continuum and strong extreme ultraviolet (EUV) emission lines from ions of oxygen, neon, and nitrogen after masking out absorption lines from the HI Ly alpha forest, 7 Lyman-limit systems (N-HI, 10(17.2) Cm-2) and 214 partial Lyman-limit systems (14.5 < log N-HI < 17.2). The 159 AGNs exhibit a wide range of FUV/EUV spectral shapes, F-V, proportional to v(proportional to v)(4, typically with -2 <= alpha(v), <= 0 and no discernible continuum edges at 912 angstrom (HI) or 504 angstrom (He I). The composite rest-frame continuum shows a gradual break at lambda(br) approximate to 1000 angstrom, with mean spectral index alpha(v) = -0.83 +/- 0.09 in the FUV (1200-2000 angstrom) steepening to alpha(v), = -1.41 +/- 0.15 in the EUV (500-1000 angstrom). We discuss the implications of the UV flux turnovers and lack of continuum edges for the structure of accretion disks, AGN mass inflow rates, and luminosities relative to Eddington values.Item In Search Of The Largest Velocity Dispersion Galaxies(2008-11) Salviander, Sarah; Shields, Gregory A.; Gebhardt, Karl; Bernardi, M.; Hyde, J. B.; Salviander, Sarah; Shields, Gregory A.; Gebhardt, KarlWe present Hobby-Eberly Telescope (HET) observations for galaxies at redshift z < 0:3 from the Sloan Digital Sky Survey (SDSS) showing large velocity dispersions while appearing to be single galaxies in HSTimages. The high signal-to-noise HET spectra provide more definitive velocity dispersions. The maximum velocity dispersion we find is sigma(*) = 444 km s(-1). Emission-line widths in QSOs indicate that black holes can exist with masses M-center dot exceeding 5 billion M-circle dot, implying sigma(*) > 500 km s(-1) by the local M-center dot sigma(*) relationship. This suggests either that QSO black hole masses are overestimated or that the black hole-bulge relationship changes at high black hole mass. The latter option is consistent with evidence that the increase in sigma(*) with luminosity levels off for the brightest elliptical galaxies.Item The Lick AGN Monitoring Project 2011: Dynamical Modeling Of The Broad-Line Region In Mrk 50(2012-07) Pancoast, Anna; Brewer, Brendon J.; Treu, Tommaso; Barth, Aaron J.; Bennert, Vardha N.; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor L.; Greene, Jenny E.; Li, Weidong; Malkan, Matthew A.; Sand, David J.; Stern, Daniel; Woo, Jong-Hak; Assef, Roberto J.; Bae, Hyun-Jin; Buehler, Tabitha; Cenko, S. Bradley; Clubb, Kelsey I.; Cooper, Michael C.; Diamond-Stanic, Aleksandar M.; Hiner, Kyle D.; Hoenig, Sebastian F.; Joner, Michael D.; Kandrashoff, Michael T.; Laney, C. David; Lazarova, Mariana S.; Nierenberg, A. M.; Park, Dawoo; Silverman, Jeffrey M.; Son, Donghoon; Sonnenfeld, Alessandro; Thorman, Shawn J.; Tollerud, Erik J.; Walsh, Jonelle L.; Walters, Richard; Walsh, Jonelle L.We present dynamical modeling of the broad- line region (BLR) in the Seyfert 1 galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN Monitoring Project (LAMP) 2011. We model the reverberation mapping data directly, constraining the geometry and kinematics of the BLR, as well as deriving a black hole mass estimate that does not depend on a normalizing factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is a nearly face-on thick disk, with a mean radius of 9.6(-0.9)(+1.2) light days, a width of the BLR of 6.9(-1.1)(+1.2) light days, and a disk opening angle of 25 +/- 10 deg above the plane. We also constrain the inclination angle to be 9(-5)(+7) deg, close to face-on. Finally, the black hole mass of Mrk 50 is inferred to be log(10)(M-BH/M-circle dot) = 7.57(-0.27)(+0.44). By comparison to the virial black hole mass estimate from traditional reverberation mapping analysis, we find the normalizing constant (virial coefficient) to be log(10) f = 0.78(-0.27)(+0.44), consistent with the commonly adopted mean value of 0.74 based on aligning the M-BH-sigma* relation for active galactic nuclei and quiescent galaxies. While our dynamical model includes the possibility of a net inflow or outflow in the BLR, we cannot distinguish between these two scenarios.Item The Lick AGN Monitoring Project 2011: Fe II Reverberation From The Outer Broad-Line Region(2013-06) Barth, Aaron J.; Pancoast, Anna; Bennert, Vardha N.; Brewer, Brendon J.; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor L.; Greene, Jenny E.; Li, Weidong; Malkan, Matthew A.; Sand, David J.; Stern, Daniel; Treu, Tommaso; Woo, Jong-Hak; Assef, Roberto J.; Bae, Hyun-Jin; Buehler, Tabitha; Cenko, S. Bradley; Clubb, Kelsey I.; Cooper, Michael C.; Diamond-Stanic, Aleksandar M.; Hoenig, Sebastian F.; Joner, Michael D.; Laney, C. David; Lazarova, Mariana S.; Nierenberg, A. M.; Silverman, Jeffrey M.; Tollerud, Erik J.; Walsh, Jonelle L.; Silverman, Jeffrey M.; Walsh, Jonelle L.The prominent broad Fe II emission blends in the spectra of active galactic nuclei have been shown to vary in response to continuum variations, but past attempts to measure the reverberation lag time of the optical Fe II lines have met with only limited success. Here we report the detection of Fe II reverberation in two Seyfert 1 galaxies, NGC 4593 and Mrk 1511, based on data from a program carried out at Lick Observatory in Spring 2011. Light curves for emission lines including H beta and Fe II were measured by applying a fitting routine to decompose the spectra into several continuum and emission-line components, and we use cross-correlation techniques to determine the reverberation lags of the emission lines relative to V-band light curves. In both cases, the measured lag (tau(cen)) of Fe II is longer than that of H beta, although the inferred lags are somewhat sensitive to the choice of Fe II template used in the fit. For spectral decompositions done using the Fe II template of Veron-Cetty et al., we find tau(cen)(Fe II)/tau(cen)(H beta) = 1.9 +/- 0.6 in NGC 4593 and 1.5 +/- 0.3 in Mrk 1511. The detection of highly correlated variations between Fe II and continuum emission demonstrates that the Fe II emission in these galaxies originates in photoionized gas, located predominantly in the outer portion of the broad-line region.Item The Mass of the Black Hole in Arp 151 from Bayesian Modeling of Reverberation Mapping Data(2011-06) Brewer, Brendon J.; Treu, Tommaso; Pancoast, Anna; Barth, Aaron J.; Bennert, Vardha N.; Bentz, Misty C.; Filippenko, Alexei V.; Greene, Jenny E.; Malkan, Matthew A.; Woo, Jong-Hak; Greene, Jenny E.Supermassive black holes are believed to be ubiquitous at the centers of galaxies. Measuring their masses is extremely challenging yet essential for understanding their role in the Formation and evolution of cosmic structure. We present a direct measurement of the mass of a black hole in an active galactic nucleus (Arp 151) based on the motion of the gas responsible for the broad emission lines. By analyzing and modeling spectroscopic and photometric time series, we find that the gas is well described by a disk or torus with an average radius of 3.99 +/- 1.25 light days and an opening angle of 68.9(-17.2)(+21.4) deg, viewed at an inclination angle of 67.8 +/- 7.8 deg (that is, closer to face-on than edge-on). The black hole mass is inferred to be 10(6.51 +/- 0.28) M-circle dot. The method is fully general and can be used to determine the masses of black holes at arbitrary distances, enabling studies of their evolution over cosmic time.Item Millimeter Observations Of A Sample Of High-Redshift Obscured Quasars(2009-11) Martinez-Sansigre, Alejo; Karim, Alexander; Schinnerer, Eva; Omont, Alain; Smith, Daniel J. B.; Wu, Jingwen; Hill, Gary J.; Klockner, Hans-rainer; Lacy, Mark; Rawlings, Steve; Willott, Chris J.; Hill, Gary J.We present observations at 1.2 mm with Max-Planck Millimetre Bolometer Array (MAMBO-II) of a sample of z greater than or similar to 2 radio-intermediate obscured quasars, as well as CO observations of two sources with the Plateau de Bure Interferometer. The typical rms noise achieved by the MAMBO observations is 0.55 mJy beam(-1) and five out of 21 sources (24%) are detected at a significance of >= 3 sigma. Stacking all sources leads to a statistical detection of < S(1.2 mm)> = 0.96 +/- 0.11 mJy and stacking only the non-detections also yields a statistical detection, with < S(1.2 mm)> = 0.51 +/- 0.13 mJy. At the typical redshift of the sample, z = 2, 1 mJy corresponds to a far-infrared luminosity L(FIR) similar to 4 x 10(12) L(circle dot). If the far-infrared luminosity is powered entirely by star formation, and not by active galactic nucleus heated dust, then the characteristic inferred star formation rate is similar to 700 M(circle dot) yr(-1). This far-infrared luminosity implies a dust mass of M(d) similar to 3 x 10(8) M(circle dot), which is expected to be distributed on similar to kpc scales. We estimate that such large dust masses on kpc scales can plausibly cause the obscuration of the quasars. Combining our observations at 1.2 mm with mid-and far-infrared data, and additional observations for two objects at 350 mu m using SHARC-II, we present dust spectral energy distributions (SEDs) for our sample and derive a mean SED for our sample. This mean SED is not well fitted by clumpy torus models, unless additional extinction and far-infrared re-emission due to cool dust are included. This additional extinction can be consistently achieved by the mass of cool dust responsible for the far-infrared emission, provided the bulk of the dust is within a radius similar to 2-3 kpc. Comparison of our sample to other samples of z similar to 2 quasars suggests that obscured quasars have, on average, higher far-infrared luminosities than unobscured quasars. There is a hint that the host galaxies of obscured quasars must have higher cool-dustmasses and are therefore often found at an earlier evolutionary phase than those of unobscured quasars. For one source at z = 2.767, we detect the CO(3-2) transition, with S(CO)Delta nu = 630 +/- 50 mJy km s(-1), corresponding to L(CO(3-2)) = 3.2 x 10(7) L(circle dot), or a brightness-temperature luminosity of L'(CO(3-2)) = 2.4 x 10(10) K km s(-1) pc(2). For another source at z = 4.17, the lack of detection of the CO(4-3) line suggests the line to have a brightness-temperature luminosity L'(CO(4-3)) < 1 x 10(10) K km s(-1) pc(2). Under the assumption that in these objects the high-J transitions are thermalized, we can estimate the molecular gas contents to be M(II2) = 1.9 x 10(10) M(circle dot) and < 8 x 10(9) M(circle dot), respectively. The estimated gas depletion timescales are tau(g) = 4 Myr and <16 Myr, and low gas-to-dust mass ratios of M(g)/M(d) = 19 and <20 are inferred. These values are at the low end but consistent with those of other high-redshift galaxies.Item Reverberation Mapping Of The Kepler Field AGN Ka1858+4850(2014-11) Pei, Liuyi; Barth, Aaron J.; Aldering, Greg S.; Briley, Michael M.; Carroll, Carla J.; Carson, Daniel J.; Cenko, S. Bradley; Clubb, Kelsey I.; Cohen, Daniel P.; Cucchiara, Antonino; Desjardins, Tyler D.; Edelson, Rick; Fang, Jerome J.; Fedrow, Joseph M.; Filippenko, Alexei V.; Fox, Ori D.; Furniss, Amy; Gates, Elinor L.; Gregg, Michael; Gustafson, Scott; Horst, J. Chuck; Joner, Michael D.; Kelly, Patrick L.; Lacy, Mark; Laney, C. David; Leonard, Douglas C.; Li, Weidong; Malkan, Matthew A.; Margon, Bruce; Neeleman, Marcel; Nguyen, My L.; Prochaska, J. Xavier; Ross, Nathaniel R.; Sand, David J.; Searcy, Kinchen J.; Shivvers, Isaac S.; Silverman, Jeffrey M.; Smith, Graeme H.; Suzuki, Nao; Smith, Krista Lynne; Tytler, David; Werk, Jessica K.; Worseck, Gabor; Silverman, Jeffrey M.KA1858+4850 is a narrow-line Seyfert 1 galaxy at redshift 0.078 and is among the brightest active galaxies monitored by the Kepler mission. We have carried out a reverberation mapping campaign designed to measure the broad-line region size and estimate the mass of the black hole in this galaxy. We obtained 74 epochs of spectroscopic data using the Kast Spectrograph at the Lick 3 m telescope from 2012 February to November, and obtained complementary V-band images from five other ground-based telescopes. We measured the H beta light curve lag with respect to the V-band continuum light curve using both cross-correlation techniques (CCF) and continuum light curve variability modeling with the JAVELIN method and found rest-frame lags of tau(CCF) = 13.53(+2.03)(-2.32) days and tau(JAVELIN) = 13.15(+1.08)(-1.00) days. The H beta rms line profile has a width of sigma line = 770 +/- 49 km s(-1). Combining these two results and assuming a virial scale factor of f = 5.13, we obtained a virial estimate of M-BH = 8.06(+1.59)(-1.72) x 10(6) M circle dot for the mass of the central black hole and an Eddington ratio of L/L-Edd approximate to 0.2. We also obtained consistent but slightly shorter emission-line lags with respect to the Kepler light curve. Thanks to the Kepler mission, the light curve of KA1858+4850 has among the highest cadences and signal-to-noise ratios ever measured for an active galactic nucleus; thus, our black hole mass measurement will serve as a reference point for relations between black hole mass and continuum variability characteristics in active galactic nuclei.Item Type 2 Active Galactic Nuclei With Double-Peaked O III Lines. II. Single AGNs With Complex Narrow-Line Region Kinematics Are More Common Than Binary AGNs(2011-07) Shen, Yue; Liu, Xin; Greene, Jenny E.; Strauss, Michael A.; Greene, Jenny E.Approximately 1% of low-redshift (z less than or similar to 0.3) optically selected type 2 active galactic nuclei (AGNs) show a doublepeaked [O III] narrow emission line profile in their spatially integrated spectra. Such features are usually interpreted as either due to kinematics, such as biconical outflows and/or disk rotation of the narrow line region (NLR) around single black holes, or due to the relative motion of two distinct NLRs in a merging pair of AGNs. Here, we report follow-up near-infrared (NIR) imaging and optical slit spectroscopy of 31 double-peaked [O III] type 2 AGNs drawn from the Sloan Digital Sky Survey (SDSS) parent sample presented in Liu et al. The NIR imaging traces the old stellar population in each galaxy, while the optical slit spectroscopy traces the NLR gas. These data reveal a mixture of origins for the double-peaked feature. Roughly 10% of our objects are best explained by binary AGNs at (projected) kpc-scale separations, where two stellar components with spatially coincident NLRs are seen. similar to 50% of our objects have [O III] emission offset by a few kpc, corresponding to the two velocity components seen in the SDSS spectra, but there are no spatially coincident double stellar components seen in the NIR imaging. For those objects with sufficiently high-quality slit spectra, we see velocity and/or velocity dispersion gradients in [O III] emission, suggestive of the kinematic signatures of a single NLR. The remaining similar to 40% of our objects are ambiguous and will need higher spatial resolution observations to distinguish between the two scenarios. Our observations therefore favor the kinematics scenario with a single AGN for the majority of these double-peaked [O III] type 2 AGNs. We emphasize the importance of combining imaging and slit spectroscopy in identifying kpc-scale binary AGNs, i.e., in no cases does one of these alone allow an unambiguous identification. We estimate that similar to 0.5%-2.5% of the z less than or similar to 0.3 type 2 AGNs are kpc-scale binary AGNs of comparable luminosities, with a relative orbital velocity greater than or similar to 150 km s(-1).