Abundances in Galactic bulge planetary nebulae from optical, ultraviolet and infrared observations

Abstract

Iron suffers from high levels of depletion in the highly ionized environments of planetary nebulae, making the direct determination of undepleted elemental iron abundances difficult. Zinc, which does not suffer from the same depletion effects as iron, may be used as a surrogate element to measure iron abundances as there is an approximately constant zinc-to-iron ratio across a wide range of metallicities. In this paper, we report zinc abundances of six Galactic Bulge planetary nebulae determined from new observations taken with ISAAC on the Very Large Telescope, Chile, prior to the instrument's decommissioning as well as a further three based upon literature observations. UVES data of the sample planetary nebulae are presented and have been used to derive abundances, temperatures and densities of a variety of elements and ions. The abundances derived from the UVES data agree well with results from the literature. [Zn/H], determined from the ISAAC observations, is found to be generally sub-solar and [O/Zn] is found to be either consistent or enriched with respect to Solar.

Planetary Nebulae: Sources of Enlightenment

“…The median for both the disk and bulge samples was found to be Zn/H = 2.00 × 10 −8 , a bit less than the solar value of 3.63 × 10 −8 (Asplund et al 2009). They concluded that while Zn is generally subsolar in both the disk and bulge PNe, their ratios of O/Zn were above solar and indicated that O is enriched relative to Zn (Smith et al 2017…”

“…With a collision strength now available, they computed Zn abundances and concluded that Zn/H is subsolar in a majority of their sample objects. Three years later Smith et al (2017) observed six additional bulge PNe and updated their observations of the nine objects observed in Smith et al (2014). Values of Zn/H abundance ratios were determined for all 15 objects.…”

Gas and dust from solar metallicity AGB stars

“…However, the main advantages of PNe (with respect to AGB and post-AGB stars, see above) are that PNe can be easily observed at very large distances (because of their emission-line nature) and that known PNe samples are more complete (e.g., they cover the full range of initial masses, despite the masses estimated are more uncertain compared to post-AGB stars). Also, the abundances of key elements such as He, C, N, O, and Ne are accesible for all types of PNe; recent studies outlined the possibility of measuring the surface Zn (Smith et al 2017). On the other hand, the abundances of Na, Mg, and Al cannot be measured in PNe.…”

Planetary nebulae and how to find them: A concise review

“…The emission lines also allow the determination and analysis of chemical abundances and permit the estimation of shell expansion velocities (Gesicki and Zijlstra, 2000) and ages, so probing the physics and timescales of stellar mass loss (Iben, 1995). The measured radial velocities can trace the kinematic properties of observed PNe, enabling us to determine if they belong to a younger or older stellar population, in, say, the Galactic Bulge (Beaulieu et al, 2000;Smith et al, 2017). Their kinematic properties and visibility also make PNe useful kinematical probes for understanding the structure of galaxies, and to test whether a galaxy contains a substantial amount of dark matter (Romanowsky et al, 2003).…”