arXiv subjects

Jenny E. Greene

Publications and source records attributed to Jenny E. Greene.

At least 361 records · Page 20Linked to original sources

arXiv2013

The Effect of Spatial Gradients in Stellar Mass-to-Light Ratio on Black Hole Mass Measurements

We have tested the effect of spatial gradients in stellar mass-to-light ratio (Y) on measurements of black hole masses (MBH) derived from stellar orbit superposition models. Such models construct a static gravitational potential for a galaxy and its central black hole, but typically assume spatially uniform Y. We have modeled three giant elliptical galaxies with gradients alpha = d(log Y)/d(log r) from -0.2 to +0.1. Color and line strength gradients suggest mildly negative alpha in these galaxies. Introducing a negative (positive) gradient in Y increases (decreases) the enclosed stellar mass near the center of the galaxy and leads to systematically smaller (larger) MBH measurements. For models with alpha = -0.2, the best-fit values of MBH are 28%, 27%, and 17% lower than the constant-Y case, in NGC 3842, NGC 6086, and NGC 7768, respectively. For alpha = +0.1, MBH are 14%, 22%, and 17% higher than the constant-Y case for the three respective galaxies. For NGC 3842 and NGC 6086, this bias is comparable to the statistical errors from individual modeling trials. At larger radii, negative (positive) gradients in Y cause the total stellar mass to decrease (increase) and the dark matter fraction within one effective radius to increase (decrease).

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arXiv2013

The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei

We present an updated and revised analysis of the relationship between the Hbeta broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of 9 new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hbeta time lag, which is assumed to yield the average Hbeta BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of alpha = 0.533 (+0.035/-0.033), consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19(+/-0.02) dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the Universe to be probed by a separate population of objects, and over a larger range of redshifts.

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arXiv2013

Observations of Feedback from Radio-Quiet Quasars: I. Extents and Morphologies of Ionized Gas Nebulae

Black hole feedback -- the strong interaction between the energy output of supermassive black holes and their surrounding environments -- is routinely invoked to explain the absence of overly luminous galaxies, the black hole vs. bulge correlations and the similarity of black hole accretion and star formation histories. Yet direct probes of this process in action are scarce and limited to small samples of active nuclei. We present Gemini IFU observations of the distribution of ionized gas around luminous, obscured, radio-quiet (RQ) quasars at z~0.5. We detect extended ionized gas nebulae via [O III]5007 emission in every case, with a mean diameter of 28 kpc. These nebulae are nearly perfectly round. The regular morphologies of nebulae around RQ quasars are in striking contrast with lumpy or elongated nebulae seen around radio galaxies at low and high redshifts. We present the uniformly measured size-luminosity relationship of [O III] nebulae around Seyfert 2 galaxies and type 2 quasars spanning 6 orders of magnitude in luminosity and confirm the flat slope of the correlation (R ~ L^{0.25+/-0.02}). We find a universal behavior of the [O III]/H-beta ratio in our entire RQ quasar sample: it persists at a constant value (~10) in the central regions, until reaching a "break" isophotal radius ranging from 4 to 11 kpc where it starts to decrease. We propose a model of clumpy nebulae in which clouds that produce line emission transition from being ionization-bounded at small distances from the quasar to being matter-bounded in the outer parts of the nebula, which qualitatively explains the observed line ratio and surface brightness profiles. It is striking that we see such smooth and round large-scale gas nebulosities in this sample, which are inconsistent with illuminated merger debris and which we suggest may be the signature of accretion energy from the nucleus reaching gas at large scales.

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arXiv2012

Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected kiloparsec-Scale Binary Active Galactic Nuclei I. Nature of the Nuclear Ionizing Sources

Kiloparsec-scale binary active galactic nuclei (AGNs) signal active supermassive black hole (SMBH) pairs in merging galaxies. Despite their significance, unambiguously confirmed cases remain scarce and most have been discovered serendipitously. In a previous systematic search, we optically identified four kpc-scale binary AGNs from candidates selected with double-peaked narrow emission lines at redshifts of 0.1--0.2. Here we present Chandra and Hubble Space Telescope Wide Field Camera 3 (WFC3) imaging of these four systems. We critically examine and confirm the binary-AGN scenario for two of the four targets, by combining high angular resolution X-ray imaging spectroscopy with Chandra ACIS-S, better nuclear position constraints from WFC3 F105W imaging, and direct starburst estimates from WFC3 F336W imaging; for the other two targets, the existing data are still consistent with the binary-AGN scenario, but we cannot rule out the possibility of only one AGN ionizing gas in both merging galaxies. We find tentative evidence for a systematically smaller X-ray-to-[O III] luminosity ratio and/or higher Compton-thick fraction in optically selected kpc-scale binary AGNs than in single AGNs, possibly caused by a higher nuclear gas column due to mergers and/or a viewing angle bias related to the double-peak narrow line selection. While our result lends some further support to the general approach of optically identifying kpc-scale binary AGNs, it also highlights the challenge and ambiguity of X-ray confirmation.

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arXiv2012

Low-mass black holes as the remnants of primordial black hole formation

This article documents our ongoing search for the elusive "intermediate-mass" black holes. These would bridge the gap between the approximately ten solar mass "stellar-mass" black holes that are the end-product of the life of a massive star, and the "supermassive" black holes with masses of millions to billions of solar masses found at the centers of massive galaxies. The discovery of black holes with intermediate mass is the key to understanding whether supermassive black holes can grow from stellar-mass black holes, or whether a more exotic process accelerated their growth only hundreds of millions of years after the Big Bang. Here we focus on searches for black holes with masses of 10^4-10^6 solar masses that are found at galaxy centers. We will refer to black holes in this mass range as "low-mass" black holes, since they are at the low-mass end of supermassive black holes. We review the searches for low-mass black holes to date and show tentative evidence, from the number of low-mass black holes that are discovered today in small galaxies, that the progenitors of supermassive black holes were formed as ten thousand to one-hundred thousand solar mass black holes via the direct collapse of gas.

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arXiv2012

X-ray Properties of Intermediate-mass Black Holes in Active Galaxies. III. Spectral Energy Distribution and Possible Evidence for Intrinsically X-ray-weak AGNs

We present a systematic X-ray study, the third in a series, of 49 active galactic nuclei with intermediate-mass black holes (IMBH; ~10^5-10^6 M_sun) using Chandra observations. We detect 42 out of 49 targets with a 0.5-2 keV X-ray luminosity 10^41-10^43 erg/s. We perform spectral fitting for the 10 objects with enough counts (>200), and they are all well fit by a simple power-law model modified by Galactic absorption, with no sign of significant intrinsic absorption. While we cannot fit the X-ray spectral slope directly for the rest of the sample, we estimate it from the hardness ratio and find a range of photon indices consistent with those seen in more luminous and massive objects. The X-ray-to-optical spectral slope (alphaox) of our IMBH sample is systematically flatter than in active galaxies with more massive black holes, consistent with the well-known correlation between alphaox and UV luminosity. Thanks to the wide dynamic range of our sample, we find evidence that alphaox increases with decreasing M_BH as expected from accretion disk models, where the UV emission systematically decreases as M_BH decreases and the disk temperature increases. We also find a long tail toward low alphaox values. While some of these sources may be obscured, given the high L_bol/L_Eddington values in the sample, we argue that some may be intrinsically X-ray-weak, perhaps owing to a rare state that radiates very little coronal emission.

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arXiv2012

Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)

We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will have three channels covering wavelength ranges 3800 Å - 6700 Å, 6500 Å - 10000 Å, and 9700 Å - 13000 Å, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics.

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arXiv2012

Stellar Populations of UV-Selected Active Galactic Nuclei Host Galaxies at z ~ 2 - 3

We use stellar population synthesis modeling to analyze the host galaxy properties of a sample of 33 UV-selected, narrow-lined active galactic nuclei (AGNs) at z ~ 2 - 3. In order to quantify the contribution of AGN emission to host galaxy broadband spectral energy distributions (SEDs), we use the subsample of 11 AGNs with photometric coverage spanning from rest-frame UV through near-IR wavelengths. Modeling the SEDs of these objects with a linear combination of stellar population and AGN templates, we infer the effect of the AGN on derived stellar population parameters. We also estimate the typical bias in derived stellar populations for AGNs lacking rest-frame near-IR wavelength coverage, and develop a method for inferring the true host galaxy properties. We compare AGN host galaxy properties to those of a sample of UV-selected, star-forming non-AGNs in the same redshift range, including a subsample carefully matched in stellar mass. Although the AGNs have higher masses and SFRs than the full non-active sample, their stellar population properties are consistent with those of the mass-selected sample, suggesting that the presence of an AGN is not connected with the cessation of star-formation activity in star-forming galaxies at z ~ 2 - 3. We suggest that a correlation between M_BH and galaxy stellar mass is already in place at this epoch. Assuming a roughly constant Eddington ratio for AGNs at all stellar masses, we are unable to detect the AGNs in low-mass galaxies because they are simply too faint.

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arXiv2012

Physical Properties of the Narrow-Line Region of Low-Mass Active Galaxies

We present spectroscopic observations of 27 active galactic nuclei (AGN) with some of the lowest black hole (BH) masses known. We use the high spectral resolution and small aperture of our Keck data, taken with the Echellette Spectrograph and Imager, to isolate the narrow-line regions (NLRs) of these low-mass BHs. We investigate their emission-line properties and compare them with those of AGN with higher-mass black holes. While we are unable to determine absolute metallicities, some of our objects plausibly represent examples of the low-metallicity AGN described by Groves et al. (2006), based on their [N II]/H_alpha ratios and their consistency with the Kewley & Ellison (2008) mass-metallicity relation. We find tentative evidence for steeper far-UV spectral slopes in lower-mass systems. Overall, NLR emission lines in these low-mass AGN exhibit trends similar to those seen in AGN with higher-mass BHs, such as increasing blueshifts and broadening with increasing ionization potential. Additionally, we see evidence of an intermediate line region whose intensity correlates with L/L_Edd, as seen in higher-mass AGN. We highlight the interesting trend that, at least in these low-mass AGN, the [O III] equivalent width (EW) is highest in symmetric NLR lines with no blue wing. This trend of increasing [O III] EW with line symmetry could be explained by a high covering factor of lower ionization gas in the NLR. In general, low-mass AGN preserve many well-known trends in the structure of the NLR, while exhibiting steeper ionizing continuum slopes and somewhat lower gas-phase metallicities.

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arXiv2012

The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad Line Region in Mrk 50

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(+1.2,-0.9) light days, a width of the BLR of 6.9(+1.2,-1.1) light days, and a disk opening angle of 25\pm10 degrees above the plane. We also constrain the inclination angle to be 9(+7,-5) degrees, close to face-on. Finally, the black hole mass of Mrk 50 is inferred to be log10(M(BH)/Msun) = 7.57(+0.44,-0.27). By comparison to the virial black hole mass estimate from traditional reverberation mapping analysis, we find the normalizing constant (virial coefficient) to be log10(f) = 0.78(+0.44,-0.27), consistent with the commonly adopted mean value of 0.74 based on aligning the M(BH)-σ* relation for AGN 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.

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arXiv2012

Simultaneous Ultraviolet and Optical Emission-line Profiles of Quasars: Implications for Black Hole Mass Determination

The X-shooter instrument on the VLT was used to obtain spectra of seven moderate-redshift quasars simultaneously covering the spectral range 3000 Ang to 2.5 microns. At z ~ 1.5, most of the prominent broad emission lines in the ultraviolet to optical region are captured in their rest frame. We use this unique dataset, which mitigates complications from source variability, to intercompare the line profiles of C IV 1549, C III] 1909, Mg II 2800, and Halpha and evaluate their implications for black hole mass estimation. We confirm that Mg II and the Balmer lines share similar kinematics and that they deliver mutually consistent black hole mass estimates with minimal internal scatter (< 0.1 dex) using the latest virial mass estimators. Although no virial mass formalism has yet been calibrated for C III], this line does not appear promising for such an application because of the large spread of its velocity width compared to lines of both higher and lower ionization; part of the discrepancy may be due to the difficulty of deblending C III] from its neighboring lines. The situation for C IV is complex and, because of the limited statistics of our small sample, inconclusive. On the one hand, slightly more than half of our sample (4/7) have C IV line widths that correlate reasonably well with Halpha line widths, and their respective black hole mass estimates agree to within ~0.15 dex. The rest, on the other hand, exhibit exceptionally broad C IV profiles that overestimate virial masses by factors of 2-5 compared to Halpha. As C IV is widely used to study black hole demographics at high redshifts, we urgently need to revisit our analysis with a larger sample.

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arXiv2012

The Stellar Halos of Massive Elliptical Galaxies

We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107x107 sq arcsec), allowing us to achieve remarkably high signal-to-noise ratios of ~20-70 per pixel in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions sigma* > 150 km/s, we study the radial dependence in the equivalent widths (EWs) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by ~50%, and only a weak correlation between sigma* and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are approximately an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5R_e, while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high alpha-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.

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arXiv2011

A spectacular outflow in an obscured quasar

SDSS J1356+1026 is a pair of interacting galaxies at redshift z=0.123 that hosts a luminous obscured quasar in its northern nucleus. Here we present two long-slit Magellan LDSS-3 spectra that reveal a pair of symmetric ~10 kpc-size outflows emerging from this nucleus, with observed expansion velocities of ~250 km/s in projection. We present a kinematic model of these outflows and argue that the deprojected physical velocities of expansion are likely ~1000 km/s and that the kinetic energy of the expanding shells is likely 10^44-10^45 erg/s, with an absolute minimum of >10^42 erg/s. Although a radio counterpart is detected at 1.4GHz, it is faint enough that the quasar is considered to be radio-quiet by all standard criteria, and there is no evidence of extended emission due to radio lobes, whether aged or continuously powered by an ongoing jet. We argue that the likely level of star formation is probably insufficient to power the observed energetic outflow and that SDSS J1356+1026 makes a strong case for radio-quiet quasar feedback. In further support of this hypothesis, polarimetric observations show that the direction of quasar illumination is coincident with the direction of the outflow.

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arXiv2011

The Lick AGN Monitoring Project: Recalibrating Single-Epoch Virial Black Hole Mass Estimates

We investigate the calibration and uncertainties of black hole mass estimates based on the single-epoch (SE) method, using homogeneous and high-quality multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN) Monitoring Project for 9 local Seyfert 1 galaxies with black hole masses < 10^8 M_sun. By decomposing the spectra into their AGN and stellar components, we study the variability of the single-epoch Hbeta line width (full width at half-maximum intensity, FWHM_Hbeta; or dispersion, sigma_Hbeta) and of the AGN continuum luminosity at 5100A (L_5100). From the distribution of the "virial products" (~ FWHM_Hbeta^2 L_5100^0.5 or sigma_Hbeta^2 L_5100^0.5) measured from SE spectra, we estimate the uncertainty due to the combined variability as ~ 0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE mass estimates, which is dominated by uncertainties in the size-luminosity relation and virial coefficient, and is estimated to be ~ 0.46 dex (factor of ~ 3). By comparing the Hbeta line profile of the SE, mean, and root-mean-square (rms) spectra, we find that the Hbeta line is broader in the mean (and SE) spectra than in the rms spectra by ~ 0.1 dex (25%) for our sample with FWHM_Hbeta < 3000 km/s. This result is at variance with larger mass black holes where the difference is typically found to be much less than 0.1 dex. To correct for this systematic difference of the Hbeta line profile, we introduce a line-width dependent virial factor, resulting in a recalibration of SE black hole mass estimators for low-mass AGNs.

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arXiv2011

The Host Galaxies of Low-mass Black Holes

Using HST observations of 147 host galaxies of low-mass black holes (BHs), we systematically study the structures and scaling relations of these active galaxies. Our sample is selected to have central BHs with virial masses ~10^5-10^6 solar mass. The host galaxies have total I-band magnitudes of -23.2<M_I<-18.8 mag and bulge magnitudes of -22.9<M_I<-16.1 mag. Detailed bulge-disk-bar decompositions with GALFIT show that 93% of the galaxies have extended disks, 39% have bars and 5% have no bulges at all at the limits of our observations. Based on the Sersic index and bulge-to-total ratio, we conclude that the majority of the galaxies with disks are likely to contain pseudobulges and very few of these low-mass BHs live in classical bulges. The fundamental plane of our sample is offset from classical bulges and ellipticals in a way that is consistent with the scaling relations of pseudobulges. The sample has smaller velocity dispersion at fixed luminosity in the Faber-Jackson plane, compared with classical bulges and elliptical galaxies. The galaxies without disks are structurally more similar to spheroidals than to classical bulges according to their positions in the fundamental plane, especially the Faber-Jackson projection. Overall, we suggest that BHs with mass < 10^6 solar mass live in galaxies that have evolved secularly over the majority of their history. A classical bulge is not a prerequisite to host a black hole.

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arXiv2011

Black Hole Mass and Bulge Luminosity for Low-mass Black Holes

We study the scaling between bulge magnitude and central black hole (BH) mass in galaxies with virial BH masses < 10^6 solar mass. Based on careful image decomposition of a snapshot Hubble Space Telescope I-band survey, we found that these BHs are found predominantly in galaxies with pseudobulges. Here we show that the \mbulge\ relation for the pseudobulges at low mass is significantly different from classical bulges with BH masses >10^7 solar mass. Specfically, bulges span a much wider range of bulge luminosity, and on average the luminosity is larger, at fixed black hole mass. The trend holds both for the active galaxies from Bentz et al. and the inactive sample of Gultekin et al. and cannot be explained by differences in stellar populations, as it persists when we use dynamical bulge masses. Put another way, the ratio between bulge and BH mass is much larger than $\sim 1000$ for our sample. This is consistent with recent suggestions that black hole mass does not scale with the pseudobulge luminosity. The low-mass scaling relations appear to flatten, consistent with predictions from Volonteri & Natarajan for massive seed BHs.

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arXiv2011

Exploring the Low-Mass End of The M-Sigma Relation with Active Galaxies

We present new measurements of stellar velocity dispersions, using spectra obtained with the Keck Echellette Spectrograph and Imager (ESI) and the Magellan Echellette (MagE), for 76 Seyfert 1 galaxies from the recent catalogue of Greene & Ho. These objects were selected from the Sloan Digital Sky Survey (SDSS) to have estimated black hole (BH) masses below 2\times10^6 M\odot. Combining our results with previous ESI observations of similar objects, we obtain an expanded sample of 93 galaxies and examine the relation between BH mass and velocity dispersion (the M-Sigma relation) for active galaxies with low BH masses. The low-mass active galaxies tend to follow the extrapolation of the M-Sigma relation of inactive galaxies. Including results for active galaxies of higher BH mass from the literature, we find a zero pointα= 7.68\pm0.08 and slope of β= 3.32\pm0.22 for the M-Sigma relation [in the form log Mbh=α+βlog(σ*/200 km s-1)], with intrinsic scatter of 0.46\pm0.03 dex. This result is consistent, within the uncertainties, with the slope of the M-Sigma relation for reverberation-mapped active galaxies with BH masses from 10^6 to 10^9 M\odot. For the subset of our sample having morphological information from Hubble Space Telescope images, we examine the slope of the M-Sigma relation separately for subsamples of barred and unbarred host galaxies, and find no significant evidence for a difference in slope. We do find a mild offset between low-inclination and high-inclination disk galaxies, such that more highly inclined galaxies tend to have larger σ* at a given value of BH mass, presumably due to the contribution of disk rotation within the spectroscopic aperture. We also find that the velocity dispersion of the ionized gas trace the stellar velocity dispersion well for this large sample of low-mass Seyfert 1 galaxies.

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arXiv2011

Type 2 Active Galactic Nuclei with Double-Peaked [OIII] Lines. II. Single AGNs with Complex Narrow-Line Region Kinematics are More Common than Binary AGNs

(Abridged) Approximately 1% of low redshift (z<0.3) optically-selected type 2 AGNs show a double-peaked [OIII] narrow emission line profile in their spatially-integrated spectra. Such features are usually interpreted as due either to kinematics, such as biconical outflows and/or disk rotation of the narrow line region (NLR) around single black holes, or 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 [OIII] type 2 AGNs drawn from the SDSS parent sample presented in Liu et al (2010). 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. ~ 50% of our objects have [OIII] emission offset by a few kpc, corresponding to the two velocity components seen in the SDSS spectra, but there are no corresponding 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 [OIII] emission, suggestive of the kinematic signatures of a single NLR. The remaining ~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 [OIII] type 2 AGNs. We emphasize the importance of combining imaging and slit spectroscopy in identifying kpc binary AGNs, i.e., in no cases does one of these alone allow an unambiguous identification. We estimate that ~ 0.5-2.5% of the z<0.3 type 2 AGNs are kpc-scale binary AGNs of comparable luminosities, with a relative orbital velocity >~150 km/s.

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