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 Galaxy 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+ALTAIR to model the gravitational influence of the central supermassive black hole 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 galaxies 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 stars. 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 accretion disk 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.