4.7 Article

Structure and dynamics of galaxies with a low surface-brightness disc - II. Stellar populations of bulges

期刊

出版社

OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2012.20938.x

关键词

galaxies: abundances; galaxies: bulges; galaxies: evolution; galaxies: formation; galaxies: kinematics and dynamics; galaxies: stellar content

资金

  1. La Silla Paranal Observatory [76.B-0375, 80.B-00754]
  2. Padua University [CPDA089220/08, 60A02-5934/09, 60A02-1283/10, CPS0204, CPDR095001/09, CPDR115539/11]
  3. Italian Space Agency [ASI-INAF I/009/10/0]
  4. Spanish MICINN [CSD2006-00070, AYA2007-67965-C03-01, AYA2010-21887-C04-04]
  5. European Community [229517]

向作者/读者索取更多资源

We present the radial profiles of the H beta, Mg and Fe line-strength indices for a sample of eight spiral galaxies with a low-surface-brightness stellar disc and a bulge. The correlations between the central values of the line-strength indices and velocity dispersion are consistent with those known for early-type galaxies and bulges of high-surface-brightness galaxies. The age, metallicity and a/Fe enhancement of the stellar populations in the bulge-dominated region are obtained using stellar population models with variable element abundance ratios. Almost all the sample bulges are characterized by a young stellar population, ongoing star formation and a solar a/Fe enhancement. Their metallicity spans from high to subsolar values. No significant gradient in age and a/Fe enhancement is measured, whereas a negative metallicity gradient is found only in a few cases. These properties suggest that a pure dissipative collapse cannot explain the formation of all the sample bulges and that other phenomena, such as mergers or acquisition events, need to be invoked. Such a picture is also supported by the lack of a correlation between the central value and the gradient of the metallicity in bulges with very low metallicity. The stellar populations of the bulges hosted by low-surface-brightness discs share many properties with those of high-surface-brightness galaxies. Therefore, they are likely to have common formation scenarios and evolution histories. A strong interplay between bulges and discs is ruled out by the fact that, in spite of being hosted by discs with extremely different properties, the bulges of low- and high-surface-brightness discs are remarkably similar.

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