Low-Mass Black Holes in Galaxy Centers
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POX 52 NGC 4395 Low-mass Black Holes in Galaxy Centers Jenny Greene (Princeton) Luis Ho (Carnegie), Aaron Barth (UC Irvine), Carol Thornton (UC Irvine), Jim Ulvestad (NSF), Joan Wrobel (NRAO), Ting Xiao (UC Irvine), Yanfei Jiang (Princeton), Cheng-Yu Kuo (UVa) BH Demographics Ho, Filippenko, & Sargent 1997 Rate (%) Detection • AGNs in 60% of galaxies earlier than Sbc: BHs are ubiquitous in early-type galaxies • Reverse is true for nuclear star clusters BH Demographics Ho, Filippenko, & Sargent 1997 NC detection fraction Rate (%) Detection • AGNs in 60% of galaxies earlier than Sbc: BHs are ubiquitous in early-type galaxies • Reverse is true for nuclear star clusters Ho, Filippenko, & Sargent 1997 Rate (%) Detection Optical spectroscopic searches plagued with incompleteness due to star formation, dust, and flux limits When do NCs and BHs coexist? Are they physically related? 1. A solid handle on BH demographics in late-type galaxies and at low BH mass 2. Do BH masses scale with galaxy (or NC?) properties at low mass? We do not (yet) know the space density or occupation fractions of low-mass BHs. Search Techniques 5 (10 M⦿ BHs) • Dynamical methods: inactive or active BHs, limited to a few Mpc • Optical spectroscopy: nuclear activity required, sensitive to dust and star formation • MIR spectroscopy: nuclear activity required • X-ray spectroscopy: nuclear activity required • tidal disruptions, gravitational radiation, high- resolution radio imaging, optical variability Dynamics (I) M33: Nuclear BH < 1500 M⦿ (Gebhardt et al. 2001) NGC 205: Nuclear BH < 20,000 M⦿ (Valluri et al. 2004) G1, Omega Cen, (other globular clusters?) (Gebhardt et al. 2002, 2005; Noyola et al.) 728 SETH ET AL. Vol. 714 5 Figure 16. Velocity field of the best-fitting H2 dynamical model (middle, top), with a BH mass of MBH 4.5 10 M and a2 disk inclination of 37◦, in comparisonBARTH ET AL. to the symmetrized data (top left). The velocity residual (data model) is shown in the right panel. The velocity= × curves in" the bottom panels are extracted along the line however, the black hole content of nuclear clusters in late- of nodes (overplotted to the velocity maps) and represent the peak velocity curves. The diamonds correspond to the model velocitytype spirals curve, is very while poorly constrained, the crosses and M33 correspond provides a TABLE 1 Dynamics (II)HUBBLE SPACE TELESCOPE ARCHIVAL DATA to the data. convincing demonstration that some nuclear clusters do not contain a black hole of dynamically significant mass. The Camera Filter Exposure Time (s) Observation Date best evidence that black holes can occur in at least some very (A color version of this figure is available in the online journal.) late-type disk galaxies comes from the detection of a small WFPC2/PC F606W 2× 80 1994-08-17 8 ACS/WFC1 F435W 3 × 360 2003-02-03 BARTH ET AL. number of active galactic nuclei (AGNs) in Scd and Sd-type F555W 3 × 360 2003-02-03 spirals. The best-studied case is the Sd galaxy NGC 4395, F814W 3 × 360 2003-02-03 which contains a Seyfert 1 nucleus (Filippenko & Sargent NICMOS/NIC3 F190N 6× 224 2007-03-31 nuclear star clusters and might be useful to apply to a wider 1989; Filippenko & Ho 2003); it remains the only clear exam- ple of a broad-lined AGN in a bulgeless galaxy. In addition, a sample (rather than just assuming a stellar-only model and few examples of Type 2 AGNs in very late-type spirals have using that as the upper limit). been detected recently in optical spectroscopic surveys, such as NGC 1042 (Seth et al. 2008a; Shields et al. 2008) and UGC 6192 (Barth et al. 2008). 6. SUMMARY AND CONCLUSIONS A recent Spitzer spectroscopic observation of the Sd galaxy NGC 3621 by Satyapal et al. (2007) led to the discovery of an AGN in this galaxy, based on the detection of [Ne V] emission lines at 14.3 µm and 24.3 µm. Since the ionization potential for ionization of Ne+3 to Ne+4 is 95 eV, ordinary H II regions Research by A.J.B. and M.C.B. is supported by NSF grant are not expected to be significant sources of [Ne V] emission, FIG. 1.— HST images of the nucleus of NGC 3621. Left panel: A portion but a hard AGN continuum can easily provide the necessary of the WFPC2/PC F606W image. The rectangle surrounding the nucleus AST-0548198. We thank Rachel Kuzio de Naray for helpful ionizing photons. As a result, the relative strengths of neon shows the position and size of the spectroscopic aperture used in the Keck observation. Right panel: A portion of the NICMOS/NIC3 F190N image. In conversations and suggestions. Data presented herein were infrared fine-structure lines from different ionization states of both panels, north is up and east is to the left. neon are useful as diagnostics of the ionization conditions obtained at the W.M. Keck Observatory, which is operated as within AGN narrow-line regions (e.g., Spinoglio & Malkan view. One ACS pointing placed the nucleus on the WFC1 1992; Voit 1992; Sturm et al. 2002; Groves et al. 2006). Abel CCD and the other pointing placed it on the WFC2. We se- a scientific partnership among Caltech, the University of Cal- & Satyapal (2008) used the results of new photoionization lected the WFC1 pointing since this image included a larger ifornia, and NASA. The Observatory was made possible by models to argue that the strength of the [Ne V] emission in region surrounding the nucleus. The NICMOS F190N ob- NGC 3621 could only be plausibly explained by the presence servation was taken as the continuum image for an F187N the generous financial support of the W.M. Keck Foundation. of an AGN,and not byan ordinaryburst of nuclearstarforma- (Paschen α) image; we do not use the F187N emission-line The authors wish to recognize and acknowledge the very sig- tion. The detection of an AGN in NGC 3621 is of significant image. interest since it is one of the latest-type spirals known to host The NICMOS and ACS images were retrieved from the nificant cultural role and reverence that the summit of Mauna an active nucleus, making it an important target for further HST data archives and we use the standard pipeline-processed observations to constrain its black hole mass and AGN ener- versions of these images. For the WFPC2 data, we use the Kea has always had within the indigenous Hawaiian commu- getics. Satyapal et al. (2007) note that there is no previously cosmic-ray cleaned and co-added image from the WFPC2 As- nity. This publication is based on observations made with the published optical spectrum of the nucleus of NGC 3621 suit- sociations archive. able for emission-line classification. Figure 1 displays the central regions of the WFPC2 and NASA/ESA Hubble Space Telescope, obtained from the Data In this paper, we use archival HST images to show that NICMOS images. The images show that the galaxy contains Archive at the Space Telescope Science Institute, which is op- Figure 18. Scaling relations for NSCsNGC and 3621 MBHs contains in a well-defined early-type and compact galaxies. nuclearFIG Data star. 8.— NGCa very compact 3621 and and thephotometricallyK-band black distinct hole nuclear mass- star cl bulgeus- luminosity re- cluster. A new optical spectrum of this star cluster is used to ter. Surrounding the cluster is a smooth and nearly featureless erated by the Association of Universities for Research in As- lation. Plotted points areBarth galaxies!! with et stellar-dynamica al. 2008 l and gas-dynamical for MBHs are from Haring¨ Seth & Rix et ( 2004al.examine 2010), while the classification for the of theNSCs active nucleus,these and are to from mea- region of radius ∼ 1. 5 (or ∼ 50 pc). At larger radii, dust lanes Figure 17. Constraining the mass of the central BH: the figure indicates the grid sure the stellar velocity dispersion of the cluster. Wemeasurements describe and of young black star clusters hole mass become as very compiled prominent in in the the optical “Group 1” sample of tronomy, Inc., under NASA contract NAS 5-26555. These Cotˆ e´ et al. (2006) with mass estimates from Seth et al. (2008a). The solidMarconi line & Huntimages, (2003). especially The in the solid ACS line F435W represents band. the best-fitting black hole- of models (in BH mass, MBH, and disk inclination) that was calculated, and the dynamical modeling of the nuclear cluster and the resulting observations are associated with programs 5446, 9492, and constraints on the masses of both the cluster and thebulge central relationship from Marconi & Hunt (2003). Arrows show the upper 2 shows the joint MBH/NSC fit from Ferrarese et al. (2006), while the dashed 2.1.1. GALFIT Modeling 11080. This publication makes use of data products from the contours show χ in the vicinity of the best-fit dynamical models for matching black hole. We also examine the structure of the galaxylimits us- to the bulge luminosity and black hole mass for NGC 3621. 2 5 line shows the fit to the MBH data froming near-infrared Haring¨ & images Rix from (2004 2MASS). in Just order to the determine bulge To determine the structure of the nuclear cluster, we use Two Micron All Sky Survey, which is a joint project of the the H2 kinematics. The minimum χ model is at MBH 4.5 10 M and a whether a bulge is present in this late-type disk galaxy. For the 2-dimensional modeling package GALFIT (Peng et al. disk inclination of 37 . The contours indicate the 1, 2, and∼ 3σ confidence× " levels, mass is plotted for NGC 404; the total galaxythe distance mass to NGC would 3621, we be adopt D30%=6.6 Mpc, larger.NIR based on relationships.2002).