The PDS versus Markarian starburst galaxies: comparing strong and weakIRASemitter at 12 and 25 μm in the nearby Universe

Abstract

The characteristics of the starburst galaxies from the Pico dos Dias survey (PDS) are compared with those of the nearby UV-bright Markarian starburst galaxies, having the same limit in redshift (vh < 7500 km s 1 ) and absolute B magnitude (MB < 18). An important difference is found: the Markarian galaxies are generally undetected at 12µm and 25µm in IRAS. This is consistent with the UV excess shown by these galaxies and suggests that the youngest star forming regions dominating these galaxies are relatively free of dust. The FIR selection criteria for the PDS is shown to introduce a strong bias towards massive (luminous) and large size late-type spiral galaxies. This is contrary to the Markarian galaxies, which are found to be remarkably rich in smaller size early-type galaxies. These results suggest that only late-type spirals with a large and massive disk are strong emitter at 12µm and 25µm in IRAS in the nearby universe. The Markarian and PDS starburst galaxies are shown to share the same environment. This rules out an explanation of the differences observed in terms of external parameters. These differences may be explained by assuming two different levels of evolution, the Markarian being less evolved than the PDS galaxies. This interpretation is fully consistent with the disk formation hypothesis proposed in Coziol et al. (2000) to explain the special properties of the Markarian SBNG.