Hostname: page-component-7c8c6479df-7qhmt Total loading time: 0 Render date: 2024-03-29T13:14:32.625Z Has data issue: false hasContentIssue false

Rejuvenation of spiral bulges

Published online by Cambridge University Press:  01 July 2007

Daniel Thomas
Affiliation:
ICG, Mercantile House, University of Portsmouth, Portsmouth, PO1 2EG, UK email: daniel.thomas@port.ac.uk
Roger L. Davies
Affiliation:
Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK email: rld@astro.ox.ac.uk
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We seek to understand whether the stellar populations of galactic bulges show evidence of secular evolution triggered by the presence of the disc. To this end we re-analyse the sample of Proctor & Sansom (2002), deriving stellar population ages and element abundances from absorption line indices as functions of central velocity dispersion and Hubble type. In agreement with other studies in the literature, we find that bulges have relatively low luminosity weighted ages, the lowest age derived being 1.3 Gyr. Hence bulges are not generally old, but actually rejuvenated systems. We discuss evidence that this might be true also for the bulge of the Milky Way. The smallest bulges are the youngest with the lowest α/Fe ratios indicating the presence of significant star formation events involving 10 − 30 per cent of their total mass in the past 1 − 2 Gyr. No significant correlations of the stellar population parameters with Hubble Type are found. We show that the above relationships with σ coincide perfectly with those of early-type galaxies. At a given velocity dispersion, bulges and elliptical galaxies are indistinguishable as far as their stellar populations are concerned. These results favour an inside-out formation scenario and indicate that the discs in spiral galaxies of Hubble types Sbc and earlier cannot have a significant influence on the evolution of the stellar populations in the bulge component. The phenomenon of pseudobulge formation must be restricted to spirals of types later than Sbc.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2008

References

Balcells, M., Graham, A. W., & Peletier, R. F., 2007, ApJ, 665, 1104CrossRefGoogle Scholar
Bernardi, M., Nichol, R. C., Sheth, R. K., Miller, C. J., & Brinkmann, J., 2005, AJ, 131, 1288CrossRefGoogle Scholar
Cappellari, M., Bacon, R., Bureau, M., et al. , 2006, MNRAS, 366, 1126CrossRefGoogle Scholar
Courteau, S., de Jong, R. S., & Broeils, A. H., 1996, ApJ, 457, L73CrossRefGoogle Scholar
Davies, R. L., et al. , 2001, ApJ, 548, L33CrossRefGoogle Scholar
de Jong, R. S., 1996, A&A, 313, 377Google Scholar
Ferreras, I., Wyse, R. F. G., & Silk, J., 2003, MNRAS, 345, 1381CrossRefGoogle Scholar
Gadotti, D. A. & dos Anjos, S., 2001, AJ, 122, 1298CrossRefGoogle Scholar
Genzel, R., Baker, A. J., Tacconi, L. J., Lutz, D., Cox, P., Guilloteau, S., & Omont, A., 2003, ApJ, 584, 633CrossRefGoogle Scholar
Gorgas, J., Jablonka, P., & Goudfrooij, P., 2007, A&A, in press, astro-ph/0707.0407Google Scholar
Immeli, A., Samland, M., Gerhard, O., & Westera, P., 2004, A&A, 413, 547Google Scholar
Jablonka, P., Gorgas, J., & Goudfrooij, P., 2007, A&A, in press, astro-ph/0707.0561Google Scholar
Jablonka, P., Martin, P., & Arimoto, N., 1996, AJ, 112, 1415CrossRefGoogle Scholar
Kormendy, J., 1982, ApJ, 257, 75CrossRefGoogle Scholar
Kormendy, J. & Kennicutt, R. C., 2004, ARA&A, 42, 603Google Scholar
Mehlert, D., Thomas, D., Saglia, R. P., Bender, R., & Wegner, G., 2003, A&A, 407, 423Google Scholar
Moorthy, B.K. & Holtzman, J.A., 2006, MNRAS, 371, 583CrossRefGoogle Scholar
Nelan, J. E., et al. , 2005, ApJ, 632, 137CrossRefGoogle Scholar
Peletier, R. F., Balcells, M., Davies, R. L., Andredakis, Y., & Vazdekis, A., et al. , 1999, MNRAS, 310, 703CrossRefGoogle Scholar
Proctor, R. N. & Sansom, A. E., 2002, MNRAS, 333, 517CrossRefGoogle Scholar
Proctor, R. N., Forbes, D. A., & Beasley, M. A., 2004, MNRAS, 355, 1327CrossRefGoogle Scholar
Puzia, T., Saglia, R. P., Kissler-Patig, M., Maraston, C., Greggio, L., Renzini, A., & Ortolani, S., 2002, A&A, 395, 45Google Scholar
Thomas, D. & Davies, R. L., 2006, MNRAS, 366, 510CrossRefGoogle Scholar
Thomas, D., Maraston, C., & Bender, R., 2003, MNRAS, 339, 897CrossRefGoogle Scholar
Thomas, D., Maraston, C., Bender, R., & Mendes de Oliveira, C., 2005, ApJ, 621, 673CrossRefGoogle Scholar
Thomas, D., Maraston, C., & Korn, A., 2004, MNRAS, 351, L19CrossRefGoogle Scholar
Trager, S. C., Faber, S. M., Worthey, G., & González, J. J., 2000b, AJ, 120, 165CrossRefGoogle Scholar
van den Bosch, F. C., 1998, ApJ, 507, 601CrossRefGoogle Scholar
Wu, H., Shao, Z., Mo, H. J., Xia, X., & Deng, Z., 2005, ApJ, 622, 244CrossRefGoogle Scholar
Wyse, R. F. G., Gilmore, G., & Franx, M., 1997, ARA&A, 35, 637Google Scholar
Zoccali, M., et al. , 2003, A&A, 399, 931Google Scholar