Properties of the cluster population of NGC 1566 and their implications

Abstract

We present results of a photometric study into the cluster population of NGC 1566, a nearby grand design spiral galaxy, sampled out to a Galactocentric radius of ≈5.5 kpc. The shape of the mass-limited age distribution shows negligible variation with radial distance from the centre of the galaxy, and demonstrates three separate sections, with a steep beginning, flat middle and steep end. The luminosity function can be approximated by a power law at lower luminosities with evidence of a truncation at higher luminosity. The power-law section of the luminosity function of the galaxy is best fitted by an index ≈− 2, in agreement with other studies, and is found to agree with a model luminosity function, which uses an underlying Schechter mass function. The recovered power law slope of the mass distribution shows a slight steepening as a function of galactocentric distance, but this is within error estimates. It also displays a possible truncation at the high mass end. Additionally, the cluster formation efficiency (Γ) and the specific <it>U</it>-band luminosity of clusters (<it>T</it><inf><it>L</it></inf>(<it>U</it>)) are calculated for NGC 1566 and are consistent with values for similar galaxies. A difference in NGC 1566, however, is that the fairly high star formation rate is in contrast with a low Σ<inf>SFR</inf> and Γ, indicating that Γ can only be said to depend strongly on Σ<inf>SFR</inf>, not the star formation rate.