On central black holes in ultra-compact dwarf galaxies

Mieske, S.; Frank, M. J.; Baumgardt, H.; Lützgendorf, N.; Neumayer, N.; Hilker, M.
November 2013
Astronomy & Astrophysics / Astronomie et Astrophysique;Nov2013, Vol. 558, p1
Academic Journal
Context. The dynamical mass-to-light (M/L) ratios of massive ultra-compact dwarf galaxies (UCDs) are about 50% higher than predicted by stellar population models. Aims. Here we investigate the possibility that these apparently elevated M/L ratios of UCDs are caused by a central black hole (BH) that heats up the internal motion of stars. We focus on a sample of ~50 extragalactic UCDs from the literature for which velocity dispersions and structural parameters have been measured. Methods. To be self-consistent in our BH mass estimates, we first redetermine the dynamical masses and M/L ratios of our sample UCDs, using up-to-date distance moduli and a consistent treatment of aperture and seeing effects. On average, the homogeneously redetermined dynamical mass and M/L ratios agree to within 5% with previous literature results. We calculate the ratio Ψ = (M/L)dyn/(M/L)pop between the dynamical and the stellar population M/L for an assumed age of 13 Gyr. Ψ > 1 indicates an elevated dynamical M/L ratio, suggesting dark mass on top of a canonical stellar population of old age. For all UCDs with Ψ > 1 we estimate the mass of a hypothetical central black hole needed to reproduce the observed integrated velocity dispersion Results. Massive UCDs (M > 107M☉) have an averageΨ = 1.7± 0.2, implying notable amounts of dark mass in them. We find that, on average, central BH masses of 10-15% of the UCD mass can explain these elevated dynamical M/L ratios. The implied BH masses in UCDs range from several 105 M☉ to several 107 M☉. In the MBH-luminosity plane, UCDs are offset by about two orders of magnitude in luminosity from the relation derived for galaxies. Our findings can be interpreted such that massive UCDs originate from progenitor galaxies with masses around ~109 M☉, and that those progenitors have SMBH occupation fractions of ~60-100%. The suggested UCD progenitor masses agree with predictions from the tidal stripping scenario. Also, the typical BH mass fractions of nuclear clusters in such ~109 M☉ galaxy bulges agree with the 10-15% BH fraction estimated for UCDs. Lower-mass UCDs (M < 107 M☉) exhibit a bimodal distribution in Ψ, suggestive of a coexistence of massive globular clusters and tidally stripped galaxies in this mass regime. Conclusions. Central BHs as relict tracers of tidally stripped progenitor galaxies are a plausible explanation for the elevated dynamical M/L ratios of UCDs. Direct observational tests of this scenario are suggested.


Related Articles

  • Tidal flares and rates from an archival cluster survey. Maksym, W. P. // EPJ Web of Conferences;2012, Issue 39, Special section p1 

    Tidal disruption flares (TDFs) are potent indicators of the co-evolution of galaxies and the massive black holes (MBHs) which they host in their nuclei, both in terms of the individual black holes revealed by tidal flares and in terms of the overall disruption rate. We examine key concerns...


    The article presents an answer from Amy Reines of the U.S. National Radio Astronomy Observatory to a question about what research into dwarf galaxies teaches about black holes.

  • IN BRIEF. YOUNG, MONICA // Sky & Telescope;Mar2015, Vol. 129 Issue 3, p18 

    The article discusses the possibility that a supermassive black hole might be the source of radiation detected near dwarf galaxy Markarian 177.

  • Dwarf Galaxies, MOND, and Relativistic Gravitation. Kosowsky, Arthur // Advances in Astronomy;2010, p1 

    MOND is a phenomenological modification of Newton's law of gravitation which reproduces the dynamics of galaxies, without the need for additional dark matter. This paper reviews the basics of MOND and its application to dwarf galaxies. MOND is generally successful at reproducing stellar velocity...

  • A class of compact dwarf galaxies from disruptive processes in galaxy clusters. Drinkwater, M. J.; Gregg, M. D.; Hilker, M.; Bekki, K.; Couch, W. J.; Ferguson, H. C.; Jones, J. B.; Phillipps, S. // Nature;5/29/2003, Vol. 423 Issue 6939, p519 

    Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and...

  • A flare to remember. Chiao, May // Nature Physics;Feb2014, Vol. 10 Issue 2, p86 

    The article discusses a research work from Davide Donato and Peter Maksym that was published in the 2014 issue of the periodical Astrophys, and was focused on the galaxy cluster star Abell 1795 that was cleaved apart by black hole creating explosion brighter than the Supernova.

  • Shorts From Down Under.  // Amateur Astronomy Magazine;Fall2008, Issue 59, p13 

    The article presents information on Omega Centauri, one of the best sights in the southern sky sights. It says that it is larger than the full moon and considered the largest and brightest globular cluster. The classification of Omega Centauri has been a contentious topic since it is regarded as...

  • A tidally distorted dwarf galaxy near NGC 4449. Rich, R. M.; Collins, M. L. M.; Black, C. M.; Longstaff, F. A.; Koch, A.; Benson, A.; Reitzel, D. B. // Nature;2/9/2012, Vol. 482 Issue 7384, p192 

    NGC 4449 is a nearby Magellanic irregular starburst galaxy with a B-band absolute magnitude of ?18 and a prominent, massive, intermediate-age nucleus 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,...

  • Small Galaxy Boasts Big Black Hole. CONOVER, EMILY // Sky & Telescope;Jan2015, Vol. 129 Issue 1, p14 

    The article reports on the identification of a supermassive black hole in the ultracompact dwarf galaxy M60-UCD1 by astronomers Anil Seth of University of Utah and colleagues.


Read the Article


Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics