Infrared properties of Planetary Nebulae with PG1159 central stars

Abstract

We study the properties of 26 PNe with PG1159-type central stars known till date and compare them with the properties of PNe having [WR], $wels$ and hydrogen-rich central stars published earlier. We use archival photometric measurements of $2MASS$ for near-IR analysis and $WISE$ and $IRAS$ data for mid- and far-IR analysis and derive the IR properties of PG1159-PNe. We analyze the IR colour-colour diagrams of PG1159-PNe and compare them with the other three groups of PNe. Similar to the [WR]-PNe, many PG1159-PNe also show large amount of near-IR emission from the hot-dust component but their AGB dust is relatively cooler. We also report here the dust colour temperatures, dust masses, dust-to-gas mass ratios, IR luminosities and IR excess of PG1159-PNe and plot them against their surface H$\beta$ brightness (age) and compare them with the distribution of other groups of PNe. The IR luminosity and dust temperature show strong correlation with surface H$\beta$ brightness, however, the dust-to-gas mass ratio and IR excess do not show any trend. While the mean dust mass has a lower value for PG1159-PNe, in compared to other groups, the average dust-to-gas mass ratio is found to be marginally larger for PG1159-PNe. An analysis of the number distribution of different groups of PNe against surface H$\beta$ brightness shows that a) younger [WR]-, $wels$- and normal-PNe have a similar distribution indicating that they all have evolved from the AGB in a similar way, b) while there is an overlap of surface H$\beta$ brightness between [WR]- and PG1159-PNe, showing an evolutionary connection between them, there exists a significant gap between the values derived for $wels$- and PG1159-PNe.