GEMINI OBSERVATORY observing time request summary

Semester: 2013B Observing Mode: Queue Gemini Reference:

Instruments: NIFS

Time Awarded: NaN Thesis: Yes

Band 3 Acceptable: Yes Band 3 Time: 26.8 hr Band 3 Minimal Time: 26.8 hr

Title: A Stellar Dynamical Black Hole Mass for the Reverberation- Mapped Active NGC6814 Principal Investigator: Misty Bentz PI institution: Georgia State University, Department of Physics and Astronomy Atlanta GA 30303, USA PI status: PhD PI phone/e-mail: / [email protected] Co-Investigators: Emily Manne-Nicholas (thesis): Georgia State University, [email protected] Christopher Onken: Mt. Stromlo Observatory, [email protected] Monica Valluri: University of Michigan, [email protected]

Partner Submission Details (multiple entries for joint proposals) PI Request NTAC Recommendation Partner Lead Time Min Reference Time Min Rank Australia Onken 6.5 hr 6.5 hr G/2013B/004 NaN NaN USA Bentz 15.0 hr 15.0 hr US-2013B-017 NaN NaN Total Time 21.5 hr 21.5 hr 0.0 hr 0.0 hr

Abstract We propose to obtain spatially-resolved spectroscopy of the nucleus of the nearby (z=0.005) AGN NGC 6814 with Gemini NIFS+ to model the gravitational influence of the central on the stellar dynamics of the inner galaxy. A recent reverberation-based black hole mass of 2.0 x 10^7 M_sun for NGC 6814 places the black hole sphere of influence within the spatial resolution range of current ground-based AO systems. Because of the differing technical limitations of dynamical mass modeling and reverberation mapping, NGC 6814 is only the third galaxy where it is currently possible to directly compare a reverberation and a dynamical mass. Such a direct comparison provides an independent constraint on the geometric scaling factor that is currently the largest uncertainty in reverberation-based masses. All AGN black hole masses from spectroscopic surveys fundamentally rely on the reverberation sample, and thus our current understanding of the growth and evolution of black holes and across cosmic time relies on the accuracy of reverberation-based black hole masses. A stellar dynamical mass for NGC 6814 will increase by 50% the small sample of black holes that provide an independent check on the stability of the entire AGN black hole mass scale. We are also currently GEMINI OBSERVATORY observing time request summary targeting additional AGNs for reverberation-mapping campaigns with the intent of further increasing this sample in the future.

TAC Category / Keywords Extragalactic / Spiral galaxies, Nuclei, Active galaxies

Potential Problems The submitted proposal has 2 observations with a low probability of suitable guide .

Scheduling Constraints

TAC information (multiple entries for joint proposals) Partner Partner Partner Recommended Poor Weather NGO Support Email Ranking Ranking Time Decision Australia ( ) No Comments USA ( ) No Comments Gemini Observatory A Stellar Dynamical Black Hole Mass for the Section 1 Page 3 Reverberation-Mapped Active Galaxy NGC6814

Observation Details (Band 1/2)

Observation RA Dec Brightness Total Time (including overheads) NGC6814 19:42:40.576 -10:19:25.500 15.33 B Vega, 14.21 V 21.5 hr Vega, 8.66 J Vega, 7.95 H Vega, 7.66 K Vega Potential problems: Guiding is problematic (0%) Conditions: CC 50%/Clear, IQ 70%/Good, SB Any/Bright, WV Any Resources: NIFS NGS None K (1.99 - 2.40um)

Observation Details (Band 3)

Observation RA Dec Brightness Total Time (including overheads) NGC6814 19:42:40.576 -10:19:25.500 15.33 B Vega, 14.21 V 26.8 hr Vega, 8.66 J Vega, 7.95 H Vega, 7.66 K Vega Potential problems: Guiding is problematic (0%) Conditions: CC 70%/Cirrus, IQ 70%/Good, SB Any/Bright, WV Any Resources: NIFS NGS None K (1.99 - 2.40um)

Scientific Justification Be sure to include overall significance to astronomy. For standard proposals limit text to one page with figures, captions and references on no more than two additional pages. The proximity of the Galactic Center has allowed the existence of a black hole in the center of the Milky Way to be proven beyond a reasonable doubt (Ghez et al. 2008). The only other supermas- sive black hole whose existence is currently indisputable is revealed by water maser kinematics in NGC 4258 (Herrnstein et al. 2005). In these two cases, the black hole mass (MBH) is known to an unprecedented accuracy because of the precise measurements that are possible. For the other ∼ 100 galaxies with direct MBH measurements, systematic errors continue to hamper the MBH accuracy.

For quiescent galaxies, MBH is most often obtained through stellar or gas dynamics, where the spatially-resolved kinematics of stars or a nuclear gas disk are modeled to probe the gravitational influence of the central black hole. Both stellar and gas dynamics are thus limited by the spatial resolution of the observations and the distance to the galaxy. For active galactic nuclei (AGNs), reverberation mapping (Blandford & McKee 1982, Peterson 1993) measures the average size of the broad line region (BLR) through the time delay between variations in the continuum flux and the “echo” of those variations in the broad emission line flux. Combining the BLR size with the BLR gas velocity via the virial theorem results in a measure of MBH (Fig 1). Reverberation mapping relies on time resolution rather than spatial resolution, but it is the unknown geometry and kinematics of the BLR that are the limiting factors. To date, dynamical masses have been determined for the central black hole in ∼ 70 galaxies (McConnell & Ma 2013) and reverberation masses in ∼ 45 active galaxies (Peterson et al. 2004, Bentz et al. 2009), however, the number of supermassive black holes with masses determined through multiple independent techniques remains very small.

Stellar dynamical measurements of MBH are generally considered the most robust because the kinematics of stars near the black hole are not affected by the non-gravitational influences that can affect gas motions, but since the accuracy of the measurement depends on the spatial resolution, such measurements are only possible in relatively nearby galaxies. Broad-lined AGNs are generally rare, however, with distances that are too large to achieve high accuracy by dynamical means, but the ability to measure MBH at cosmological distances makes reverberation mapping especially promising. To date, the only broad-lined AGNs with both reverberation- and dynamical-based masses are the bright Seyfert galaxies NGC 4151 and NGC 3227 (Table 1). However, a recently- determined reverberation mass for NGC 6814 (Bentz et al. 2009) places it within the capabilities of current ground-based AO systems to spatially resolve the black hole’s sphere. We propose to obtain NIFS spatially-resolved spectroscopy of the center of NGC 6814 to model the gravitational effect of the black hole on the nuclear stellar dynamics and directly compare its stellar dynamical mass with its reverberation-based mass.

Hundreds of thousands of MBH estimates in AGN have been derived from spectroscopic surveys, but they all fundamentally rely on the small sample of reverberation-based masses for their calibra- tion. Dynamical measurements of MBH in reverberation-mapped AGNs are the only independent checks that we currently have available to investigate the reliability of the entire AGN MBH scale. Furthermore, reverberation mapping experiments are approaching the ability to map out the de- tailed physics of the BLR on size scales of ∼ 0.01 pc (e.g., Bentz et al. 2010) and may soon result in self-consistent MBH measurements (e.g., Brewer et al. 2011) that will also be able to provide an independent check on the reliability of masses from dynamical modeling. NGC 6814 is one of a small number of very nearby AGNs that we are able to target for both reverberation and dynami- cal MBH determinations, and we are currently undertaking reverberation campaigns with the goal of increasing this sample to ∼ 5 − 6 objects. Our understanding of the growth and evolution of supermassive black holes and their host galaxies across cosmic time fundamentally relies on the accuracy of the black hole masses that we determine for nearby galaxies like NGC 6814 (Fig 2). NOAO/GeminiProposal Section2.Page2 This box blank.

Table 1: Reverberation vs. Dynamical Masses for AGNs

Object σ⋆ MRM rh MSD rh MGD rh Ref

−1 7 ′′ 7 ′′ 7 ′′ (km s ) (10 M⊙) ( ) (10 M⊙) ( ) (10 M⊙) ( )

+0.57 +1.0 +0.8 NGC4151 116 ± 3 4.57−0.47 0.348 8.5−1.0 0.442 3.0−2.2 0.229 1,2,1,3 +0.16 +0.7 +1.0 NGC3227 139 ± 21 0.76−0.17 0.022 1.4−0.7 0.041 2.0−0.4 0.059 4,5,6,3 +0.35 NGC6814 95 ± 3 1.85−0.35 0.087 7,8

Note: MRM= reverberation-mapping mass (assuming hfi = 5.5), MSD= stellar dynamical mass, MGD=gas dynamical mass, rh = black hole sphere of influence References: 1. Onken et al. (2013), 2. Bentz et al. (2006), 3. Hicks & Malkan (2008), 4. Onken et al. (2004), 5. Denney et al. (2010), 6. Davies et al. (2006), 7. Woo et al. (2010), 8. Bentz et al. (2009).

Figure 1: Left: Broad-band B and V continuum light curves (top) and Hβ emission line light curve (bottom) for NGC 6814 from the LAMP monitoring campaign. The variations in the continuum flux, which arises from the or close to it, are clearly echoed in the emission-line light curve a few days later. The time delay between the two is just the light-crossing time from the accretion disk to the broad line region, or the average radius of the broad line region. Right: Auto-correlation functions for the continuum light curves (top) and cross-correlation functions for the Hβ light curve and continuum light curves (bottom). From Bentz et al. (2009). The BLR radius is measured to be 6.5 ± 1.0 lightdays which, when combined with the Hβ line width, gives 7 MBH = (1.85 ± 0.35) × 10 M⊙. NOAO/GeminiProposal Section2.Page3 This box blank.

Figure 2: HST WFC3 image of NGC 6814 at 547nm displayed with a logarithmic stretch. The bright AGN point source is apparent at the center of the galaxy and will serve as the guide “” for Altair. The nearby (z = 0.005) location of NGC 6814 will allow us to achieve the high spatial resolution in the core of the galaxy that is necessary to accurately model the gradient in the nuclear stellar kinematics and to detect the gravitational signature of the central supermassive black hole. The very face-on orientation of NGC 6814 negates the utility of a study of the nuclear gas dynamics if the nuclear gas was aligned with the disk of the galaxy. Stellar dynamics, however, could still be modeled via the Schwarzschild (1979) method.

References McConnell, N.J., & Ma, C.P. 2013, ApJ, Bentz, M. C., et al. 2006, ApJ, 651, 775 764, 184 Bentz, M. C., et al. 2009, ApJ, 705, 199 Onken, C. A., et al. 2004, ApJ, 615, 645 Blandford, R. D., & McKee, C. F. Onken, C. A., et al. 2007, ApJ, 670, 105 1982, ApJ, 255, 419 Peterson, B. M. 1993, PASP, 105, 247 Cretton, N., et al. 1999, ApJS, 124, 383 Peterson, B. M., et al. 2004, ApJ, 613, 682 Davies, R. I., et al. 2006, ApJ, 646, 754 Schwarzschild, M. 1979, ApJ, 232, 236 Denney, K. D., et al. 2010, ApJ, 721, 715 Storchi-Bergmann, T., et al. 2009, MNRAS, Gebhardt, K., et al. 2003, ApJ, 583, 92 394, 1148 Ghez, A. M., et al. 2008, ApJ, 689, 1044 Valluri, M., et al. 2004, ApJ, 602, 66 Herrnstein, J. R., et al. 2005, ApJ, 629, 719 van der Marel, R.P., et al. 1998, ApJ, 493, 613 Hicks, E. K. S., & Malkan, M. A. Winge, C., et al. 2009, ApJS, 185, 186 2008, ApJ, 174, 31 Woo, J.-H., et al. 2010, ApJ, 716, 269 NOAO/GeminiProposal Section2.Page4 This box blank.

Experimental Design Describe your overall observational program. How will these observations contribute toward the accomplishment of the goals outlined in the science justification? If you’ve requested long-term status, justify why this is necessary for successful completion of the science. (Limit text to one page) The proposed observations will allow us to construct a self-consistent, axisymmetric stellar dynam- ical model of the central region of NGC 6814, providing us with a direct measurement of the black hole mass. The orbit superposition method (Schwarzschild 1979, van der Marel et al. 1998, Cret- ton et al. 1999, Gebhardt et al. 2003, Valluri et al. 2004) has been successfully used to incorporate constraints from the higher order moments of the line-of-sight velocity profiles of stars obtained from high S/N integrated spectra. Employing velocity moments in the models significantly reduces the degeneracy between velocity anisotropy of the stellar distribution and the mass of the black hole, yielding accurate black hole masses. We are currently modeling NIFS nuclear spectra of NGC 4151 to constrain the black hole mass via stellar dynamics (Onken et al. 2013, in prep) and all the modeling codes will be directly applicable to the proposed observations. NGC 6814 will be the third black hole with mass measurements from both stellar dynamics and reverberation mapping. Accurate modeling of the detailed line-of-sight velocity distribution requires one to perform reliable fitting with stellar templates at a typical galaxy S/N ≈ 30 pixel−1. We estimate that we can reach this required S/N with 240 on-source exposures of 120-seconds each, or 8 hours of on-source time. With an observing efficiency of 40% and an estimate of the number of observing blocks (and therefore acquisitions) necessary to complete the program, this gives a total time of 21.5 hours. The AGN itself will be bright enough to serve as the guide “star” for Altair, so our observations will be appropriate for NGS mode. We will use the K−band stellar template libraries available from Gemini (Winge et al. 2009) to match the stellar population of NGC 6814. Our total request is for 21.5 hours of NIFS+Altair NGS time to measure the stellar dynamics in the center of NGC 6814 and increase by 50% the sample of black holes for which we can directly compare reverberation masses with dynamical masses. Both reverberation mapping and dynamical modeling are resource-intensive techniques, and as such, they can only be carried out on a limited number of objects at this time. Current technical limitations in spatial resolution and aperture size also set a hard limit for the applicability of dynamical modeling. We are currently targeting a small number of additional nearby AGNs for reverberation-mapping studies with the hope that their black hole spheres of influence will also be spatially resolvable with current technology. But the time- and resource-intensive nature of these studies means that we will only be able to increase this small sample where we can directly compare independent black hole mass measurement techniques one object at a time. This sample will never be particularly large because of the technological limitations we have already discussed, but these comparisons must be done to determine whether all black hole masses in the literature are on the same mass scale, from galaxies in the Local Group out to quasars at z = 6 − 7. We were previously awarded time to carry out this study with NIFS+Altair (GN-2012A-Q-118, PI Bentz), but unfortunately our observations were not executed. In the meantime, we have invested a large amount of resources on supporting observations that will allow us to carry out the comparison of black hole mass techniques in NGC 6814 at the highest level of accuracy currently possible (see below). Proprietary Period: 18 months NOAO/GeminiProposal Section2.Page5 This box blank.

Use of Other Facilities or Resources (1) Describe how the proposed observations complement data from non-Gemini facilities, including those available through NOAO. For each of these other facilities, indicate the nature of the observations (yours or those of others), and describe the importance of the observations proposed here in the context of the entire program. (2) Do you currently have a grant that would provide resources to support the data processing, analysis, and publication of the observations proposed here? The proposed observations complement the high-cadence spectrophotometric observations obtained over the course of 64 nights in Spring 2008 at Lick Observatory as part of the Lick AGN Monitoring Project (Bentz et al. 2009). Typical exposure times for NGC 6814 were 2 × 15 min, for a time investment of 32 hours (not including overheads or calibrations) for the reverberation campaign. Furthermore, we have been awarded 19 orbits of time during Cycle 20 to determine a Cepheid-based distance to NGC 6814 (GO-12961, PI Bentz). An accurate distance is a necessary component for the stellar dynamical modeling, as the dynamical mass scales linearly with the assumed distance. We expect our observations to trigger in August 2013 based on the visibility and necessary roll angle of the spacecraft. We were also awarded 6 nights on the ANU 2.3m telescope with WiFeS in July 2012 to obtain larger-scale spatially resolved stellar kinematics to constrain the dynamical models beyond the field-of-view of NIFS. These observations have been completed, and we are working through the data reduction.

Previous Use of NOAO Facilities List allocations of telescope time on facilities available through NOAO to the PI during the last 2 years for regular proposals, and at any time in the past for survey proposals (including participation of the PI as a Co-I on previous NOAO surveys), together with the current status of the data (cite publications where appropriate). Mark with an asterisk those allocations of time related to the current proposal. Please include original proposal semesters and ID numbers when available. NOAO Proposal ID Observatory ID Status ======⋆ 2012A-0163 GN-2012A-Q-118 observations were not executed 2011B-0120 WIYN-2011B-0120 observations obtained on 3 nights of 4, reductions completed, analysis currently underway NOAO/GeminiProposal Section2.Page6 This box blank.

Technical Description Describe the observations to be made during this observing run. Justify the specific telescope, the exposure times, and the constraints requested (seeing, cloud cover, sky brightness, and, if appropriate, water vapor and airmass limit). NIFS is the best instrument available through NOAO for undertaking this study. The area cov- ered by NIFS is nearly a factor of two greater than a GNIRS long-slit spectrum of comparable spatial and spectral resolution, and the NIFS spaxels are concentrated in the region of primary interest for measuring the stellar dynamics near the black hole. Based on prior experience with NIFS+Altair observations of NGC 4151 (Gemini program GN-2008A-Q-41, PI: Onken), we have designed our observations to yield sufficient S/N for measuring the stellar dynamics in the central region of NGC 6814 and determining the black hole mass. Analysis of HST imaging at 547 nm and 1.6 µm provides an estimate of the flux ratio (beyond the AGN point source) between NGC 6814 and NGC 4151 to be 1:4. Combining this flux ratio and the flux-calibrated NIFS observations of NGC 4151 presented by Storchi-Bergmann et al. (2009), we estimate a central stellar surface brightness of K = 11.5 mag arcsec−2, falling to 14.3 mag arcsec−2 at a radius of 0.7′′. To inform our selection of AO mode, we have analyzed HST+WFPC2 imaging of NGC 6814 at V (F547M) and I (F814W). We estimate the AGN point-source to have an R-band magnitude of 14.5 (note that this is in addition to the underlying stellar flux). The AGN dominates the light in the central few arcseconds, and so should be able to serve as the guide star for Altair in NGS mode. Estimates made from different epochs yield magnitudes consistent within 0.5 mag, giving us confidence that the AGN will work for Altair guiding even in the presence of AGN variability. Accurate modeling of the detailed line-of-sight velocity distribution requires one to perform reliable fitting with stellar templates at a typical galaxy S/N≈ 30 pixel−1. We use the NIFS ITC to estimate the required exposure time as follows: K = 14.3 mag arcsec−2, an elliptical galaxy spectrum (to simulate the bulge) at z = 0.005, the H-K filter with the K-grating centered at 2.25 µm, very low background detector readout, an Altair NGS guide star of R = 14.5 mag with no offset from the field-of-view and no Field Lens. The observing conditions are set to IQ70, CC50, SBany, WVany, with an assumed airmass of 1.5. To reach S/N≈ 30 pixel−1 for the CO(2-0) bandhead at 2.29 µm in a 0.2′′ × 0.2′′ region (i.e., binning 2 × 5 spaxels) at K = 14.3 mag arcsec−2, we require 240 on- source exposures of 120 s each; or 8 hours on-source. Assuming 40% observing efficiency, we request a program time of 20 hours. If we assume that the 20 hours are executed over the course of 8 observation blocks, an extra 1.5 hours of acquisition time would then be required. This brings our total time request to 21.5 hours. The requested integration time will provide a much higher S/N within the 0.7′′ radius used above because the surface brightness of the galaxy will continue to increase towards the center. This will be crucial in allowing us to probe as close to the black hole sphere of influence as possible. At the very center of the galaxy, we will need to separate the stellar light from the AGN light (the mixture of smooth continuum and emission lines acting as a source of noise in this case), and the higher S/N will facilitate this process. The K−band stellar template libraries available from Gemini (Winge et al. 2009) will be used to match the stellar population of NGC 6814, so no extra calibrations will be required for that aspect of the proposal. Our total request is for 21.5 hours of NIFS+Altair NGS time to measure the stellar dynamics in the center of NGC 6814 and increase by 50% the current sample of black holes for which we can directly compare reverberation masses with dynamical masses. NOAO/GeminiProposal Section2.Page7 This box blank.

Band 3 Plan If applying for queue time and it is acceptable for the proposal to be scheduled in Band 3, describe the changes to be made to allow it to be successful in Band 3 (limit text to half a page). Band 3 observations are used to fill the queue when no Band 1 or 2 programs are available. Successful Band 3 programs generally use poorer than median observing conditions, have targets away from the most popular regions of the sky, do not require strict timing or other constraints, and do not require special instrument configurations. This program is feasible under patchy cloud cover with 10 hours on-source time, 26.875 hours in total based on an expected observing efficiency of 40% and the acquisition time necessary assuming 10 observing blocks.

Classical Backup Program If applying for classically scheduled time, describe the program you will pursue should the weather be worse than the requested observing conditions (limit text to half a page). None.

Justify Target Duplications If your targets have been previously observed by Gemini using similar or identical setups to those proposed here, justify the duplication below. Duplicate observations can be identified through a search of the Gemini Science Archive. None.

A NOAO/Gemini observing proposal LTEX macros v1.02.