Skip to main content

Thank you for visiting 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.

A tidally distorted dwarf galaxy near NGC 4449


NGC 4449 is a nearby Magellanic irregular starburst galaxy1 with a B-band absolute magnitude of −18 and a prominent, massive, intermediate-age nucleus2 at a distance from Earth of 3.8 megaparsecs (ref. 3). It is wreathed in an extraordinary neutral hydrogen (H i) complex, which includes rings, shells and a counter-rotating core, spanning 90 kiloparsecs (kpc; refs 1, 4). NGC 4449 is relatively isolated5, although an interaction with its nearest known companion—the galaxy DDO 125, some 40 kpc to the south—has been proposed as being responsible for the complexity of its H i structure6. Here we report the presence of a dwarf galaxy companion to NGC 4449, namely NGC 4449B. This companion has a V-band absolute magnitude of −13.4 and a half-light radius of 2.7 kpc, with a full extent of around 8 kpc. It is in a transient stage of tidal disruption, similar to that of the Sagittarius dwarf7 near the Milky Way. NGC 4449B exhibits a striking S-shaped morphology that has been predicted for disrupting galaxies7,8 but has hitherto been seen only in a dissolving globular cluster9. We also detect an additional arc or disk ripple embedded in a two-component stellar halo, including a component extending twice as far as previously known, to about 20 kpc from the galaxy’s centre.

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

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Figure 1: Image and halo-subtracted imagery of NGC 4449.
Figure 2: Surface photometry of NGC 4449 and NGC 4449B.


  1. Hunter, D. A., van Woerden, H. & Gallagher, J. S. Neutral hydrogen and star formation in the irregular galaxy NGC 4449. Astron. J. 118, 2184–2210 (1999)

    Article  ADS  CAS  Google Scholar 

  2. Böker, T. et al. A young stellar cluster in the nucleus of NGC 4449. Astron. J. 121, 1473–1481 (2001)

    Article  ADS  Google Scholar 

  3. Annibali, R. et al. Starbursts in the local Universe: New Hubble Space Telescope Advanced Camera for Surveys observations of the irregular galaxy NGC 4449. Astron. J. 135, 1900–1916 (2008)

    Article  ADS  CAS  Google Scholar 

  4. Hunter, D. et al. The nature of extended HI gas around NGC 449: the Dr. Jekyll/Mr. Hyde of irregular galaxies. Astrophys. J. 495, L47–L50 (1998)

    Article  ADS  CAS  Google Scholar 

  5. de Vaucouleurs, G. in Galaxies and the Universe (eds Sandage, A., Sandage, M. & Kristian, J. ) 557–597 (Univ. Chicago Press, 1975)

    Google Scholar 

  6. Theis, C. & Koble, S. Multi-method-modeling of interacting galaxies. I. A unique scenario for NGC 4449? Astron. Astrophys. 370, 365–383 (2001)

    Article  ADS  Google Scholar 

  7. Peñarrubia, J. et al. The signature of Galactic tides in Local Group dwarf spheroidals. Astrophys. J. 698, 222–232 (2009)

    Article  ADS  Google Scholar 

  8. Capuzzo Dolcetta, R., di Matteo, P. & Miocchi, P. Formation and evolution of clumpy tidal tails around globular clusters. Astron. J. 129, 1906–1921 (2005)

    Article  ADS  Google Scholar 

  9. Odenkirchen, M. et al. The extended tails of Palomar 5: a 10° arc of globular cluster tidal debris. Astron. J. 126, 2385–2407 (2003)

    Article  ADS  Google Scholar 

  10. Brosch, N. et al. The Centurion 18 telescope of the Wise Observatory. Astrophys. Space Sci. 314, 163–176 (2008)

    Article  ADS  Google Scholar 

  11. Schombert, J. & Wallin, J. F. Arp 227: a case for shells without mergers? Astron. J. 94, 300–305 (1987)

    Article  ADS  CAS  Google Scholar 

  12. Wallin, J. F. & Struck-Marcell, C. A collisional model for the formation of ripples in early-type disk galaxies. Astron. J. 96, 1850–1860 (1988)

    Article  ADS  Google Scholar 

  13. Purcell, C. W. et al. The Sagittarius impact as an architect of spirality and outer rings in the Milky Way. Nature 477, 301–303 (2011)

    Article  ADS  CAS  Google Scholar 

  14. Martin, D. C. et al. The Galaxy Evolution Explorer: a space ultraviolet survey mission. Astrophys. J. 619, L1–L6 (2005)

    Article  ADS  CAS  Google Scholar 

  15. Neff, S. G. et al. Ultraviolet emission from stellar populations within tidal tails: catching the youngest galaxies in formation? Astrophys. J. 619, L91–L94 (2005)

    Article  ADS  CAS  Google Scholar 

  16. Dale, D. A. et al. The Spitzer Local Volume Legacy: survey description and infrared photometry. Astrophys. J. 703, 517–556 (2009)

    Article  ADS  CAS  Google Scholar 

  17. Wang, J. L. et al. Luminous infrared galaxies in the local Universe. Astrophys. J. 649, 722–729 (2006)

    Article  ADS  CAS  Google Scholar 

  18. Majewski, S. R. et al. Discovery of Andromeda XIV: a dwarf spheroidal dynamical rogue in the Local Group? Astrophys. J. 670, L9–L12 (2007)

    Article  ADS  MathSciNet  CAS  Google Scholar 

Download references


R.M.R. acknowledges support from the National Science Foundation. The Saturn Lodge 0.7-m telescope was funded and implemented by R.M.R. and F.A.L. The authors acknowledge members of the Polaris Observatory Association, who maintain the observatory infrastructure and who assisted in the construction and implementation of the telescope and enclosure, and J. Riffle, who designed and built the Centurion 28-inch telescope. This research has made use of the NASA/IPAC Extragalactic Database (NED) and of the Sloan Digital Sky Survey.

Author information

Authors and Affiliations



R.M.R. conceived the project, obtained the data and coordinated the activity. M.L.M.C. fitted the surface photometry of NGC 4449 and NGC 4449B. C.M.B., F.M.L. and D.B.R. analysed and reduced various aspects of the dataset, including the surface photometry. F.A.L. and R.M.R. implemented the Saturn Lodge 0.7-m telescope and detector system. A.K. provided insight on dwarf galaxies and discussion, and A.B. provided a discussion of theoretical implications.

Corresponding author

Correspondence to R. M. Rich.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Rich, R., Collins, M., Black, C. et al. A tidally distorted dwarf galaxy near NGC 4449. Nature 482, 192–194 (2012).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing