Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

# Black-hole-triggered star formation in the dwarf galaxy Henize 2-10

## Abstract

Black-hole-driven outflows have been observed in some dwarf galaxies with active galactic nuclei1, and probably play a role in heating and expelling gas (thereby suppressing star formation), as they do in larger galaxies2. The extent to which black-hole outflows can trigger star formation in dwarf galaxies is unclear, because work in this area has previously focused on massive galaxies and the observational evidence is scarce3,4,5. Henize 2-10 is a dwarf starburst galaxy previously reported to have a central massive black hole6,7,8,9, although that interpretation has been disputed because some aspects of the observational evidence are also consistent with a supernova remnant10,11. At a distance of approximately 9 Mpc, it presents an opportunity to resolve the central region and to determine if there is evidence for a black-hole outflow influencing star formation. Here we report optical observations of Henize 2-10 with a linear resolution of a few parsecs. We find an approximately 150-pc-long ionized filament connecting the region of the black hole with a site of recent star formation. Spectroscopy reveals a sinusoid-like position–velocity structure that is well described by a simple precessing bipolar outflow. We conclude that this black-hole outflow triggered the star formation.

This is a preview of subscription content, access via your institution

## Access options

\$32.00

All prices are NET prices.

## Data availability

The spectroscopic data analysed in this study are available from the Mikulski Archive for Space Telescopes (MAST) at https://archive.stsci.edu/.

## References

1. Manzano-King, C. M., Canalizo, G. & Sales, L. V. AGN-driven outflows in dwarf galaxies. Astrophys. J. 884, 54 (2019).

2. Fabian, A. C. Observational evidence of active galactic nuclei feedback. Annu. Rev. Astron. Astrophys. 50, 455–489 (2012).

3. Gaibler, V. et al. Jet-induced star formation in gas-rich galaxies. Mon. Not. R. Astron. Soc. 425, 438–449 (2012).

4. Maiolino, R. et al. Star formation inside a galactic outflow. Nature 544, 202–206 (2017).

5. Gallagher, R. et al. Widespread star formation inside galactic outflows. Mon. Not. R. Astron. Soc. 485, 3409–3429 (2019).

6. Reines, A. E. et al. An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10. Nature 470, 66–68 (2011).

7. Reines, A. E. & Adam, T. D. Parsec-scale radio emission from the low-luminosity active galactic nucleus in the dwarf starburst galaxy Henize 2-10. Astrophys. J. Lett. 750, L24 (2012).

8. Reines, A. E. et al. Deep Chandra observations of the compact starburst galaxy Henize 2-10: X-rays from the massive black hole. Astrophys. J. Lett. 830, L35 (2016).

9. Riffel, R. A. Evidence for an accreting massive black hole in He 2-10 from adaptive optics integral field spectroscopy. Mon. Not. R. Astron. Soc. 494, 2004–2011 (2020).

10. Hebbar, P. R. et al. X-ray spectroscopy of the candidate AGNs in Henize 2-10 and NGC 4178: likely supernova remnants. Mon. Not. R. Astron. Soc. 485, 5604–5615 (2019).

11. Cresci, G. et al. The MUSE view of He 2-10: No AGN ionization but a sparkling starburst. Astron. Astrophys. 604, A101 (2017).

12. Kobulnicky, H. A. et al. Aperture synthesis observations of molecular and atomic gas in the Wolf-Rayet starburst galaxy. Astron. J. 110, 116 (1995).

13. Mathewson, D. S. et al. A new oxygen-rich supernova remnant in the Large Magellanic Cloud. Astrophys. J. 242, L73–L76 (1980).

14. Borkowski, K. J. et al. Asymmetric expansion of the youngest galactic supernova remnant G1. 9+ 0.3. Astrophys. J. Lett. 837, L7 (2017).

15. Gower, A. C. & Hutchings, J. B. A precessing relativistic jet model for 3C 449. Astrophys. J. 258, L63–L66 (1982).

16. Dunn, R. J. H., Fabian, A. C. & Sanders, J. S. Precession of the super-massive black hole in NGC 1275 (3C 84)? Mon. Not. R. Astron. Soc. 366, 758–766 (2006).

17. Pringle, J. E. Self-induced warping of accretion discs. Mon. Not. R. Astron. Soc. 281, 357–361 (1996).

18. Nixon, C. & King, A. Do jets precess… or even move at all? Astrophys. J. Lett. 765, L7 (2013).

19. Kharb, P. et al. Double-peaked emission lines due to a radio outflow in KISSR 1219. Astrophys. J. 846, 12 (2017).

20. Beck, S. C., Jean, L. T. & Michelle Consiglio, S. Dense molecular filaments feeding a starburst: ALMA maps of CO (3–2) in Henize 2-10. Astrophys. J. 867, 165 (2018).

21. Lee, M. G. et al. Optical spectroscopy of supernova remnants in M81 and M82. Astrophys. J. 804, 63 (2015).

22. Trump, J. R. et al. Accretion rate and the physical nature of unobscured active galaxies. Astrophys. J. 733, 60 (2011).

23. Reines, A. E. et al. A new sample of (wandering) massive black holes in dwarf galaxies from high-resolution radio observations. Astrophys. J. 888, 36 (2020).

24. Molina, M. et al. Outflows, shocks, and coronal line emission in a radio-selected AGN in a dwarf galaxy. Astrophys. J. 910, 5 (2021).

25. Allen, M. G. et al. The MAPPINGS III library of fast radiative shock models. Astrophys. J. Suppl. Ser. 178, 20 (2008).

26. Silk, J. & Norman, C. Global star formation revisited. Astrophys. J. 700, 262 (2009).

27. Silk, J. Unleashing positive feedback: linking the rates of star formation, supermassive black hole accretion, and outflows in distant galaxies. Astrophys. J. 772, 112 (2013).

28. Penny, S. J. et al. SDSS-IV MaNGA: evidence of the importance of AGN feedback in low-mass galaxies. Mon. Not. R. Astron. Soc. 476, 979–998 (2018).

29. Trump, J. R. et al. Spectropolarimetric evidence for radiatively inefficient accretion in an optically dull active galaxy. Astrophys. J. 732, 23 (2011).

30. Santoro, F. et al. AGN-driven outflows and the AGN feedback efficiency in young radio galaxies. Astron. Astrophys. 644, A54 (2020).

31. Constantin, A. et al. Probing the balance of AGN and star-forming activity in the local universe with ChaMP. Astrophys. J. 705, 1336 (2009).

32. Baganoff, F. K. et al. Chandra X-ray spectroscopic imaging of Sagittarius A* and the central parsec of the galaxy. Astrophys. J. 591, 891 (2003).

33. Nguyen, D. D. et al. Extended structure and fate of the nucleus in Henize 2-10. Astrophys. J. 794, 34 (2014).

34. Greene, J. E., Strader, J. & Ho, L. C. Intermediate-mass black holes. Annu. Rev. Astron. Astrophys. 58, 257–312 (2020).

35. Leitherer, C. et al. Starburst99: synthesis models for galaxies with active star formation. Astrophys. J. Suppl. Ser. 123, 3 (1999).

36. Newville, M., Stensitzki, T., Allen, D. B. & Ingargiola, A. LMFIT: non-linear least-square minimization and curve-fitting for Python version 0.8.0. Zenodo https://doi.org/10.5281/zenodo.11813 (2014).

37. Osterbrock, D. E., and Ferland, G. J. Astrophysics of Gas Nebulae and Active Galactic Nuclei (University Science Books, 2006).

38. Baldwin, J. A., Phillips, M. M. & Terlevich, R. Classification parameters for the emission-line spectra of extragalactic objects. Publ. Astron. Soc. Pac. 93, 5 (1981).

39. Veilleux, S. & Osterbrock, D. E. Spectral classification of emission-line galaxies. Astrophys. J. Suppl. Ser. 63, 295–310 (1987).

40. Kewley, L. J. et al. The host galaxies and classification of active galactic nuclei. Mon. Not. R. Astron. Soc. 372, 961–976 (2006).

41. Kauffmann, G. et al. The host galaxies of active galactic nuclei. Mon. Not. R. Astron. Soc. 346, 1055–1077 (2003).

42. Kewley, L. J. et al. Theoretical modeling of starburst galaxies. Astrophys. J. 556, 121 (2001).

43. Martín-Hernández, N. L. et al. High spatial resolution mid-infrared spectroscopy of the starburst galaxies NGC 3256, II Zw 40 and Henize 2-10. Astron. Astrophys. 455, 853–870 (2006).

44. Chandar, R. et al. The stellar content of Henize 2-10 from space telescope imaging spectrograph ultraviolet spectroscopy. Astrophys. J. 586, 939 (2003).

45. Nawaz, M. A. et al. Jet–intracluster medium interaction in Hydra A–II. The effect of jet precession. Mon. Not. R. Astron. Soc. 458, 802–815 (2016).

46. Cielo, S. et al. Feedback from reorienting AGN jets-I. Jet–ICM coupling, cavity properties and global energetics. Astron. Astrophys. 617, A58 (2018).

## Acknowledgements

We are grateful to M. Molina for useful discussions regarding shocks. We also thank M. Whittle and K. Johnson for their assistance with the HST/STIS proposal while A.E.R. was a graduate student at the University of Virginia, and for subsequent discussions. Support for Program number HST-GO-12584.006-A was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. A.E.R. also acknowledges support for this work provided by NASA through EPSCoR grant number 80NSSC20M0231. Z.S. acknowledges support for this project from the Montana Space Grant Consortium.

## Author information

Authors

### Contributions

Z.S. reduced and analysed the STIS data and compared the results with models. A.E.R. led the HST/STIS proposal and helped with the data reduction. Both authors worked on the interpretation of the results and the writing of the paper.

### Corresponding author

Correspondence to Zachary Schutte.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

## Extended data figures and tables

### Extended Data Fig. 1 Raw 2D spectra showing the [OI]6300 emission line at the location of the nucleus in the EW slit orientation.

The location of the nucleus is indicated by white circles and the two images correspond to the two dithered sub-exposures.

### Extended Data Fig. 2 Combined 2D spectra showing the [OI]6300 emission line at the location of the nucleus in the EW slit orientation.

Same as Extended Data Fig. 1 but showing the reduced 2D image with the dithered sub-exposures combined.

### Extended Data Fig. 3 The electron density, ne, along the EW slit orientation.

We measure the electron density along the EW slit from the ratio of [SII]6716/[SII]6731 and find the electron density ranges from $$\sim {10}^{2.5}-{10}^{4}$$ cm−3, which is within the range the [SII] ratio is sensitive to density. The high densities are consistent with those predicted by optical emission line diagnostics derived from the Allen et al.25 shock models.

### Extended Data Fig. 4 The spatial extraction regions taken along the EW slit orientation.

We place these regions on optical emission line diagnostic diagrams (Extended Data Figs. 57). Top panel: the extraction regions are shown on the narrow band H$$\alpha$$ + continuum image from HST to highlight the ionized gas features that several of the spatial extractions probe. Bottom panel: the extraction regions are shown on the archival 0.8 micron HST image, showing young star clusters that the EW slit orientation passes through.

### Extended Data Fig. 5 Narrow emission line diagnostic diagrams showing various extraction regions along the EW slit orientation (see Extended Data Fig. 4).

The nucleus (yellow point) falls in the Seyfert region of the [OI]/H$$\alpha$$ diagram. The young star-forming region ~70 pc to the east of the low-luminosity AGN is depicted with a blue triangle and star for the primary emission line component and the blue-shifted secondary component, respectively. [OI] is not detected in all of the regions.

### Extended Data Fig. 6 Optical emission line diagnostics from the shock and shock+precursor models with varying gas density.

We place the spatial extractions from the EW slit orientation shown in Extended Data Fig. 4 on a grid of shock excitation models (presented in Allen et al.25 with varying gas density (n = 0.01-1000 $${\mathrm{cm}}^{-3}$$) and shock velocity (v = 100-600 km/s). We fix the transverse magnetic field to be b = $$1{\rm{\mu }}$$G and the assume solar metallicity.

### Extended Data Fig. 7 Optical emission line diagnostics from the shock and shock+precursor models with varying magnetic field.

The models (presented in Allen et al.25) are shown as a grid with dashed blue lines indicating constant shock velocity and dashed black lines indicating constant transverse magnetic field. For these models, the density is fixed to n = 1000 $${\mathrm{cm}}^{-3}$$ and the transverse magnetic field parameter is allowed to vary from b = 0.01-32 $${\rm{\mu }}$$G.

### Extended Data Fig. 8 A diagram of the toy model of the bipolar outflow generated by the low-luminosity AGN in Henize 2-10.

Our simple model depends on the outflow velocity of the ionized gas ($${v}_{{outflow}}$$), the angle the outflow makes with its precession axis ($$\theta$$) and the angular frequency with which the outflow precesses ($$\omega$$). Similar models have been used to describe the bending seen in large radio jets15,16.

## Rights and permissions

Reprints and Permissions

Schutte, Z., Reines, A.E. Black-hole-triggered star formation in the dwarf galaxy Henize 2-10. Nature 601, 329–333 (2022). https://doi.org/10.1038/s41586-021-04215-6

• Accepted:

• Published:

• Issue Date:

• DOI: https://doi.org/10.1038/s41586-021-04215-6

• ### Hunting for massive black holes in dwarf galaxies

• Amy E. Reines

Nature Astronomy (2022)