Dust-to-gas Ratio and Metal Abundance in Dwarf Galaxies

U. Lisenfeld; A. Ferrara

doi:10.1086/305354

paper

Dust-to-gas Ratio and Metal Abundance in Dwarf Galaxies

arXiv:astro-ph/9705037 · doi:10.1086/305354

Abstract

We have compared the metallicity (represented by oxygen abundance), and the dust-to-gas ratio, in a sample of dwarf galaxies. For dwarf irregulars (dIrrs) we find a good correlation between the two quantities, with a power-law index $0.54 \pm 0.2$ . Blue Compact Dwarf (BCD) galaxies do not show such a good correlation; in addition both the dust-to-gas ratio and the metallicity tend to be higher than for dIrrs. We have then developed a simple but physical analytical model for the above relation. Comparing the model results with the data, we conclude that: (i) for low values of the dust-to-gas ratio, the relation between the dust-to-gas ratio and the metallicity is quasi-linear, whereas for higher values the curve strongly deviates from the linear behavior, implying that the commonly used power-law approximation is very poor; (ii) the deviation from the linear behavior depends critically on the parameter $χ$ , the ``differential'' mass outflow rate from the galaxy in units of the star formation rate (SFR); (iii) the shape of the curve representing the relation between the dust-to-gas ratio and the metallicity does not depend on the SFR, but only on $χ$ ; however, the specific location of a given galaxy on the curve does depend on $ψ$ ; (iv) the BCD metallicity segregation is due to a higher $ψ$ , together with a significant differential mass outflow. Thus, the lack of correlation can be produced by largely different star formation rates and values of $χ$ in these objects.

19 pages, aas-latex, 7 figures, to appear in ApJ in March 1998, final revised version

Dust-to-gas Ratio and Metal Abundance in Dwarf Galaxies

Abstract

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