The motions of gas and stars in the nuclei of nearby galaxies have demonstrated that massive black holes are common1 and that their masses correlate with the stellar velocity dispersion σ★ of the bulge2,3,4. This correlation suggests that massive black holes and galaxies influence each other’s growth5,6,7. Dynamical measurements are less reliable when the sphere of influence is unresolved; thus, it remains unknown whether this correlation exists in galaxies much smaller than the Milky Way. Light echoes from photoionized clouds around accreting black holes8,9, in combination with the velocity of these clouds, yield a direct mass measurement that circumvents this difficulty. Here we report an exceptionally low reverberation delay of 83 ± 14 min between variability in the accretion disk and Hα emission from the nucleus of the dwarf galaxy NGC 4395. Combined with the Hα velocity dispersion σline = 426 ± 1 km s−1, this lag determines a mass of about 10,000 M⊙ for the black hole (MBH). This mass is among the smallest central black hole masses reported, near the low end of expected masses for heavy ‘seeds’10,11,12, and the best direct mass measurement for a galaxy of this size. Despite the lack of a bulge, NGC 4395 is consistent with the MBH–σ★ relation, indicating that the relation need not originate from hierarchical galaxy assembly nor from black hole feedback.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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Kormendy, J. & Ho, L. C. Coevolution (or not) of supermassive black holes and host galaxies. Annu. Rev. Astron. Astrophys. 51, 511–653 (2013).
Ferrarese, L. & Merritt, D. A fundamental relation between supermassive black holes and their host galaxies. Astrophys. J. 539, L9–L12 (2000).
Gebhardt, K. et al. A relationship between nuclear black hole mass and galaxy velocity dispersion. Astrophys. J. 539, L13–L16 (2000).
Onken, C. A. et al. Supermassive black holes in active galactic nuclei. II. Calibration of the black hole mass–velocity dispersion relationship for active galactic nuclei. Astrophys. J. 615, 645–651 (2004).
Silk, J. & Rees, M. J. Quasars and galaxy formation. Astron. Astrophys. 331, L1–L4 (1998).
King, A. Black holes, galaxy formation, and the M BH–σ relation. Astrophys. J. 596, L27–L29 (2003).
Fabian, A. C. Observational evidence of active galactic nuclei feedback. Annu. Rev. Astron. Astrophys. 50, 455–489 (2012).
Blandford, R. D. & McKee, C. F. Reverberation mapping of the emission line regions of Seyfert galaxies and quasars. Astrophys. J. 255, 419–439 (1982).
Peterson, B. M. Reverberation mapping of active galactic nuclei. Publ. Astron. Soc. Pac. 105, 247 (1993).
Begelman, M. C., Volonteri, M. & Rees, M. J. Formation of supermassive blackholes by direct collapse in pre-galactic haloes. Mon. Not. R. Astron. Soc. 370, 289–298 (2006).
Dijkstra, M., Haiman, Z., Mesinger, A. & Wyithe, J. S. B. Fluctuations in the high-redshift Lyman–Werner background: close halo pairs as the origin of supermassive black holes. Mon. Not. R. Astron. Soc. 391, 1961–1972 (2008).
Agarwal, B. et al. Ubiquitous seeding of supermassive black holes by direct collapse. Mon. Not. R. Astron. Soc. 425, 2854–2871 (2012).
Filippenko, A. V. & Sargent, W. L. W. Discovery of an extremely low luminosity Seyfert 1 nucleus in the dwarf galaxy NGC 4395. Astrophys. J. 342, L11 (1989).
Filippenko, A. V. & Ho, L. C. A low-mass central black hole in the bulgeless Seyfert 1 galaxy NGC 4395. Astrophys. J. 588, L13–L16 (2003).
Edri, H., Rafter, S. E., Chelouche, D., Kaspi, S. & Behar, E. Broadband photometric reverberation mapping of NGC 4395. Astrophys. J. 756, 73 (2012).
La Franca, F. et al. Extending virial black hole mass estimates to low-luminosity or obscured AGN: the cases of NGC4395 and MCG-01-24-012. Mon. Not. R. Astron. Soc. 449, 1526–1535 (2015).
den Brok, M. et al. Measuring the mass of the central black hole in the bulgeless galaxy NGC 4395 from gas dynamical modeling. Astrophys. J. 809, 101 (2015).
Peterson, B. M. et al. Multiwavelength monitoring of the dwarf Seyfert 1 galaxy NGC 4395. I. A reverberation-based measurement of the black hole mass. Astrophys. J. 632, 799–808 (2005).
Desroches, L.-B. et al. Multiwavelength monitoring of the dwarf Seyfert 1 galaxy NGC 4395. III. Optical variability and X-ray/UV/optical correlations. Astrophys. J. 650, 88–101 (2006).
Woo, J.-H., Yoon, Y., Park, S., Park, D. & Kim, S. C. The black hole mass–stellar velocity dispersion relation of narrow-line Seyfert 1 galaxies. Astrophys. J. 801, 38 (2015).
Pancoast, A. K. A New Method for Measuring Black Hole Masses in Active Galaxies: Modeling the Broad Line Region Using Reverberation Mapping Data. PhD thesis, Univ. California, Santa Barbara (2015).
De Rosa, G. et al. Space telescope and optical reverberation mapping project. I. Ultraviolet observations of the Seyfert 1 galaxy NGC 5548 with the cosmic origins spectrograph on Hubble Space Telescope. Astrophys. J. 806, 128 (2015).
Jahnke, K. & Macciò, A. V. The non-causal origin of the black-hole-galaxy scaling relations. Astrophys. J. 734, 92 (2011).
Granato, G. L., De Zotti, G., Silva, L., Bressan, A. & Danese, L. A physical model for the coevolution of QSOs and their spheroidal hosts. Astrophys. J. 600, 580–594 (2004).
Croton, D. J. et al. The many lives of active galactic nuclei: cooling flows, black holes and the luminosities and colours of galaxies. Mon. Not. R. Astron. Soc. 365, 11–28 (2006).
Dubois, Y. et al. Black hole evolution—I. Supernova-regulated black hole growth. Mon. Not. R. Astron. Soc. 452, 1502–1518 (2015).
Anglés-Alcázar, D. et al. Black holes on FIRE: stellar feedback limits early feeding of galactic nuclei. Mon. Not. R. Astron. Soc. 472, L109–L114 (2017).
Greene, J. E. Low-mass black holes as the remnants of primordial black hole formation. Nat. Commun. 3, 1304 (2012).
White, R. J. & Peterson, B. M. Comments on cross-correlation methodology in variability studies of active galactic nuclei. Publ. Astron. Soc. Pac. 106, 879 (1994).
Peterson, B. M. et al. On uncertainties in cross-correlation lags and the reality of wavelength-dependent continuum lags in active galactic nuclei. Publ. Astron. Soc. Pac. 110, 660–670 (1998).
Kraemer, S. B., Ho, L. C., Crenshaw, D. M., Shields, J. C. & Filippenko, A. V. Physical conditions in the emission-line gas in the extremely low luminosity Seyfert nucleus of NGC 4395. Astrophys. J. 520, 564–573 (1999).
Denney, K. D. Are outflows biasing single-epoch C iv black hole mass estimates? Astrophys. J. 759, 44 (2012).
Komossa, S., Xu, D., Zhou, H., Storchi-Bergmann, T. & Binette, L. On the nature of Seyfert galaxies with high [O iii] λ5007 blueshifts. Astrophys. J. 680, 926–938 (2008).
This work has been supported by the Basic Science Research Program through the National Research Foundation of Korea government (2016R1A2B3011457), and by Samsung Science and Technology Foundation under Project Number SSTF-BA1501-05. This work was supported by K-GMT Science Program (PID: GN-2017A-Q-2) of Korea Astronomy and Space Science Institute. We thank the various contributions from the NGC 4395 Collaboration.
Supplementary Figs. 1 and 2.
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Nature Astronomy (2019)