Photochemical evolution of elliptical galaxies – I. The high-redshift formation scenario

By A. Pipino, F. Matteucci. 2003

141 citations recorded by the source corpus.

In this paper we compute new multizone photochemical evolution models for elliptical galaxies, taking into account detailed nucleosynthetic yields, feedback from supernovae and an initial infall episode. By comparing model predictions with observations, we derive a picture of galaxy formation in which the higher the mass of the galaxy, the shorter the infall and the star formation time-scales. Therefore, in this scenario, the most massive objects are older than the less massive ones, in the sense that larger galaxies stop forming stars at earlier times. Each galaxy is created outside-in, i.e. the outermost regions accrete gas, form stars and develop a galactic wind very quickly, compared with the central core in which the star formation can last up to ∼1.3 Gyr. In particular, we suggest that both the duration of the star formation and the infall time-scale decrease with galactic radius. In order to convert theoretical predictions into line-strength indices, different calibrations are adopted and discussed, focusing in particular on their dependence on the α enhancement. By means of our model, we are able to match the observed mass–metallicity and colour–magnitude relations for the centre of the galaxies as well as to reproduce the overabundance of Mg relative to Fe, observed in the nuclei of bright ellipticals, and its increase with galactic mass. Furthermore, we find that the observed Ca underabundance relative to Mg can be real, owing to the non-negligible contribution of type Ia SNe to the production of this element. We predict metallicity and colour gradients inside the galaxies that are in good agreement with the mean value of the observed ones. Finally, we conclude that models with a Salpeter initial mass function (IMF) are the best ones in reproducing the majority of the properties of ellipticals, although a slightly flatter IMF seems to be required in order to explain the colours of the most massive galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5bae7613bbda077d6525e7332534f889875a67d2

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In Astronomy and Astrophysics

1. R. Maiolino
2. C. Carilli
3. P. Hopkins
4. L. Hernquist
5. F. Bertoldi
6. P. Cox
7. F. Walter
8. A. Marconi

Citations in the corpus

• A Universal Stellar Initial Mass Function? A critical look at variations in extreme environments (2010, methodology): “Models of elliptical galaxies have been performed which can reproduce their photochemical properties (metallicity, gradients, etc) using a Salpeter IMF, which continues down to 0.1M⊙ (e.g. Pipino & Matteucci 2004; Calura, Pipino & Matteucci 2008).”
• Evidence for powerful AGN winds at high redshift: dynamics of galactic outflows in radio galaxies during the “Quasar Era” (2008, background): “In particular, the outflow time scales are short enough to explain the observed relative enhancement of α elements over iron as a function of velocity dispersion in early-type galaxies (e.g., Pipino & Matteucci 2004; Pipino et al. 2007).”
• First detection of [CII]158 μm at high redshift : vigorous star formation in the early universe (2005, background): “However, the chemical evolutionary models predict that theenrichment of carbon relative to theα elements is delayed (since carbon is mostly produced by intermediate/low mass stars), and in particular the C/O ratio should be about 1/6 in the young stages of massive elliptical galaxies, while the abso”
• The evolution of the broad-line region among SDSS quasars (2005, background): “In more realistic metallicity evolutionary scenarios abundances never scale linearly with the global metallicity (e.g., Pipino & Matteucci 2004).”
• Galaxy formation theory (2010, background): “…within the monolithic collapse scenario (Matteucci and Greggio 1986; Matteucci and Gibson 1995; Timmes et al. 1995; François et al. 2004; Pipino and Matteucci 2004, 2006; Romano et al. 2005), but have only received limited study within the physically motivated context of hierarchical…”