Chemical evolution of dwarf irregular and blue compact galaxies

Abstract

Aims. Dwarf irregular and blue compact galaxies are very interesting objects since they are relatively simple and unevolved. We aim at deriving the formation and chemical evolution history of late-type dwarf galaxies and at comparing it with DLA systems. Methods. We present new models for the chemical evolution of these galaxies by assuming different regimes of star formation (bursting and continuous) and different kinds of galactic winds (normal and metal-enhanced). The dark-to-baryonic mass ratio is assumed to be ten in these models. The chemical evolution model follows the evolution of He, C, N, O, S, Si, and Fe in detail. We have collected the most recent data on these galaxies and compared them with our model's results. We also collected data for damped-Lyman α-systems. Results. Our results show that in order to reproduce all the properties of these galaxies, including the spread in the chemical abundances, the star formation should have proceeded in bursts and the number of bursts should be not more than ten in each galaxy, and that metal-enhanced galactic winds are required. The presence of metal-enhanced galactic winds can by itself reproduce the observed mass-metallicity relation, although an increasing efficiency of star formation and/or number and/or duration of bursts can also reproduce such a relation equally well. Conclusions. Metal-enhanced winds, together with an increasing amount of star formation with galactic mass, are required to explain most of the properties of these galaxies. Normal galactic winds, where all the gas is lost at the same rate, do not reproduce the features of these galaxies. On the other hand, a global increase in the amount of star formation (increasing efficiency, number of bursts, or burst duration) with galactic mass is able by itself to reproduce the mass-metallicity relation even without winds, but without metalenhanced winds is not able to explain many other constraints. We suggest that these galaxies should have suffered a different number of bursts varying from two to ten and that the efficiency of metal-enhanced winds should not have been too high (λ mw ∼ 1). We predict for these galaxies present-time type Ia SN rates from 0.00084 and 0.0023 per century. Finally, by comparing the abundance patterns of damped Lyman-α objects with our models, we conclude that they are very likely the progenitors of the current dwarf irregulars.

VLT/UVES observations of peculiarαabundances in a sub-DLA atz≈ 1.8 towards the quasar B1101−26

“…Studies of DLAs are in line with the idea that these systems are the progenitors of present-day galaxies (e.g. Møller et al 2013;Rafelski et al 2012Rafelski et al , 2011Yin et al 2011;Zwaan et al 2005;Wolfe et al 2005;Boissier et al 2003;Fritze-v. Alvensleben et al 2001;Salucci & Persic 1999;Prochaska & Wolfe 1997). In contrast to DLAs, sub-DLAs have lower neutral gas column densities, but they are generally considered to be more metal rich than DLAs (Som et al 2013;Meiring et al 2009;Péroux et al 2007).…”

The nature of long-GRB host galaxies from chemical abundances

“…The nature of DLAs remains unclear, but many authors have suggested that their chemical properties and star-formation histories can be reproduced by models of irregular galaxies that slowly evolve due to a mild SFR (Bradamante et al 1998;Romano et al 2006;Yin et al 2010b). Typical elliptical galaxies are instead very unlikely to host the DLAs observed at high redshift primarily because ellipticals form rapidly (in less than 1.5 Gyr, see Pipino & Matteucci 2004;Pipino et al 2010) consuming and then losing any residual gas so quickly that additional star formation is inhibited.…”

“…ii) whether the LGRB-associated systems represent an evolutionary sequence, i.e., whether the same objects at low and high redshift are just seen at different phases of their evolution? To do this, we adopt updated chemical evolution models for galaxies of different morphological type that reproduce the properties of galaxies (Pipino et al (2010) for ellipticals, Yin et al (2010b) for irregulars and spirals), and compare our predicted chemical abundances with the observed ones.…”

The chemical evolution of IC 10

“…We have adopted a chemical evolution model for dwarf irregulars developed by Yin et al (2010). This model includes detailed metallicity-dependent stellar yields for both massive and low and intermediate mass stars.…”

“…The chemical evolution model adopted for IC 10 is the one of Yin et al (2010) which is an update of the Bradamante et al (1998) model for dwarf irregular galaxies. In this model, we can include different SFHs, either a sequence of short starbursts followed by quiescent periods or a continuous, but very mild, star formation.…”