The Astrophysical Journal, 778:47 (21pp), 2013 November 20 doi:10.1088/0004-637X/778/1/47 C 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A. REFINING THE MBH–Vc SCALING RELATION WITH H i ROTATION CURVES OF WATER MEGAMASER GALAXIES Ai-Lei Sun1, Jenny E. Greene1,5, C. M. Violette Impellizzeri2,6, Cheng-Yu Kuo3, James A. Braatz2, and Sarah Tuttle4 1 Department of Astrophysics, Princeton University, Princeton, NJ 08540, USA 2 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA 3 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan 4 McDonald Observatory, The University of Texas, Austin, TX 78712, USA Received 2013 June 5; accepted 2013 September 12; published 2013 November 1 ABSTRACT Black-hole–galaxy scaling relations provide information about the coevolution of supermassive black holes and their host galaxies. We compare the black-hole mass–circular-velocity (MBH–Vc) relation with the black-hole- mass–bulge-stellar-velocity-dispersion (MBH–σ∗) relation to see whether the scaling relations can passively emerge from a large number of mergers or require a physical mechanism, such as feedback from an active nucleus. We present Very Large Array H i observations of five galaxies, including three water megamaser galaxies, to measure the circular velocity. Using 22 galaxies with dynamical MBH measurements and Vc measurements extending to large = −1 = +0.13 = +1.23 radius, our best-fit MBH–Vc relation, log MBH α + β log(Vc/200 km s ), yields α 7.43−0.13, β 3.68−1.20, = +0.11 and an intrinsic scatter int 0.51−0.09. The intrinsic scatter may well be higher than 0.51, as we take great care to ascribe conservatively large observational errors. We find comparable scatter in the MBH–σ∗ relations, = +0.10 int 0.48−0.08, while pure merging scenarios would likely result in a tighter scaling with the dark halo (as traced by Vc) properties rather than the baryonic (σ∗) properties. Instead, feedback from the active nucleus may act on bulge scales to tighten the MBH–σ∗ relation with respect to the MBH–Vc relation, as observed. Key word: quasars: supermassive black holes Online-only material: color figures 1. INTRODUCTION On the other hand, the pure merging scenario suggests that the correlation between linear quantities, for example, the BH mass The observed scaling relations between supermassive black MBH and the halo mass MDM, can emerge from a large number hole (BH) mass and properties of the host galaxy, intensively of mergers based on the central limit theorem, even without a studied over the past decade, suggest that BH growth is tied to the physical mechanism linking the two (Peng 2007; Hirschmann growth of the surrounding host galaxy. These galaxy properties et al. 2010; Jahnke & Maccio` 2011). include the bulge/spheroid stellar velocity dispersion σ∗ (e.g., Although both the feedback and merging phenomena may Ferrarese & Merritt 2000; Tremaine et al. 2002;Gultekin¨ et al. occur in galaxy evolution, it is unclear whether either of the 2009; Beifiori et al. 2012; McConnell & Ma 2013), the mass and mechanisms is essential for establishing the scaling relations. luminosity of galaxy bulges (e.g., Marconi & Hunt 2003;Haring¨ The most important physical scale for feedback is also a &Rix2004; McConnell & Ma 2013), and the circular velocity matter of debate (Booth & Schaye 2010; Debuhr et al. 2010). Vc (e.g., Ferrarese 2002; Kormendy & Bender 2011; Beifiori Furthermore, we do not know how the AGN output couples et al. 2012), which is the rotational velocity measured at large to the gas, whether via thermal energy (Silk & Rees 1998)or radius to probe the dark matter halos potential. It is intriguing momentum (Ostriker et al. 2010), nor do we know the average that these power-law relations, especially the MBH–σ∗ relation, efficiency of the feedback. hold over several orders of magnitude in BH mass with small Therefore, empirical evidence that distinguishes the relative scatter, even though the BH accounts for only a few thousandths importance of different physical processes in establishing the of the mass of the galaxy (e.g., Haring¨ & Rix 2004). scaling relations is key to constructing the coevolution history There are a wide array of theories attempting to explain the of BHs and galaxies. In this paper, we investigate the origin BH–galaxy scaling relations (e.g., Silk & Rees 1998; Ciotti & of BH–galaxy scaling relations by comparing the MBH–Vc Ostriker 2001; Murray et al. 2005; Hopkins et al. 2006; Peng relation with the MBH–σ∗ relation. Circular velocity Vc is a 2007). Two of the most popular models include variants of good indicator of dark matter halo mass and velocity dispersion feedback from active galactic nuclei (AGNs) and scenarios in σ∗ serves as its counterpart on bulge scales. While some AGN which merging alone can lead to BH–galaxy scaling laws. In feedback scenarios (e.g., Debuhr et al. 2010) suggest that BH AGN feedback models, the central BH accretes mass and grows mass will be most tightly linked to baryons (as opposed to dark until it is massive enough to expel gas from the galaxy potential matter), a pure merging scenario suggests that the MBH–MDM (or well and quench its own growth. BH growth in this picture is MBH–Vc) relation should be the cleanest and tightest relation, regulated by the depth of the galaxy potential well (Silk & Rees as it is free from the baryonic physics (e.g., star formation) 1998; Fabian 1999; Di Matteo et al. 2005; Robertson et al. 2006). that occurs during merging. Comparison of the two relations, especially their scatter, can help determine the mechanism that 5 Alfred P. Sloan Fellow. drives BH–galaxy coevolution (Ferrarese 2002; Novak et al. 6 Current address: Joint Alma Office, Alsonso de Cordova 3107, Vitacura, 2006; Kormendy & Bender 2011). Santiago, Chile. 1 The Astrophysical Journal, 778:47 (21pp), 2013 November 20 Sun et al. Table 1 VLA Observations Galaxy Date Flux Cal. Phase Cal. ΔθTtotal Tscan Antennas RFI (UTC) (deg) (minutes) (minutes) (1) (2) (3) (4) (5) (6) (7) (8) (9) NGC 1194 2010 Oct 8 3C48 J0323+0534 8.3 212 26.6 22 Yes NGC 2748 2010 Oct 10 3C147 J0841+7053 6.0 217 24.6 22 No NGC 2960 2010 Nov 19 3C286 J0943−0819 11.9 210 26.3 25 Yes NGC 7582 2010 Dec 4/5 3C48 J2326−4027 2.5 200 19.9 23 Yes UGC 3789 2010 Oct 7 3C147 J0614+6046 8.2 198 22.0 22 No Notes. Column 1: galaxy name. Column 2: observation date. Column 3: the flux and bandpass calibrator. Column 4: the phase calibrator. Column 5: the angular separation between the source (galaxy) and the phase calibrator. Column 6: total on-source observation time. Column 7: average length of each source scan, which is the separation between two phase calibrator scans. Column 8: number of antennas used in the observation. Some antennas were not used because the L-band receiver was not yet installed or because the antenna had unstable or noisy data quality. Column 9: whether or not radio frequency interference (RFI) was found in the data. The RFI was visually inspected and flagged. After the flagging, there was negligible or minor contamination from RFI in the data cube. The most severe case was NGC 1194, where some faint elongated stripes parallel to the galaxy can be seen. Ferrarese (2002) first proposed that BH mass may correlate 2. H i OBSERVATIONS with dark matter halo mass, based on the MBH–σ∗ relation and the correlation between σ∗ and Vc. Later, a number of papers We observed five spiral galaxies in H i with the VLA. The (Pizzella et al. 2005; Courteau et al. 2007;Ho2007) pointed observations were taken in the L-band and the C configuration − out that the σ∗–Vc relation depends on surface brightness, under project 10B 220 between 2010 October and December light concentration, and morphology and suggested that the (for details, see Table 1). The observations used dual circular ∗ polarizations and a single spectral window with 256 channels MBH–σ relation, not the MBH–Vc relation, is most fundamental. − Kormendy & Bender (2011) compiled a sample of 25 galaxies across the 4 MHz (852 km s 1) bandwidth, giving a channel −1 with both dynamical BH mass measurements and Vc from width of 3.3kms . Twenty-one edge channels on each side spatially resolved rotation curves. From this direct MBH–Vc were flagged due to a higher noise level. Removing these correlation, they concluded that the dark matter halo mass alone channels did not affect our results since none of the sources had emission in these parts of the band. The full width at half- cannot determine the BH mass, given that the BH mass can range 3 6 −1 power of the primary beam is 32 and the synthesized beam size from <10 –10 M at a circular velocity of 120 km s (for a different view, see Volonteri et al. 2011). Beifiori et al. (2012) ranges from 23 to 52 depending on the source declination and also found the scatter in the MBH–Vc relation to be about twice as number of antennas used (Table 2). large as that in the MBH–σ∗ relation using a large sample of MBH The duration of each observation was 5 hr and the on-source upper limits from Hubble Space Telescope spectra (Beifiori et al. time was ∼200 minutes per source. During a track, the gain 2009) and Vc from unresolved H i linewidth measurements.