Temperature-­based oxygen abundances in H II regions and PNe: methods and uncertainties

Mónica Rodríguez ( INAOE, Mexico)

The oxygen abundances of H II regions and planetary nebulae (PNe) provide crucial clues for our understanding of galactic chemical evolution, especially when they are compared with each other and with the abundances derived for stars of different ages. However, the nebular oxygen abundances are critically uncertain, since the abundances we derive from oxygen recombination lines are larger than those derived from collisionally excited lines by factors around two or more. This abundance discrepancy could be due to the presence within the nebulae of metal-rich inclusions, composed of stellar ejecta, supernova ejecta, or planetary material. On the other hand, the discrepancy might arise from errors in the recombination coefficients or in the assumed temperature structure of the nebulae. I will discuss these possibilities in the context of a comparison of the resulting abundances with those derived using completely different techniques for stars and the diffuse interstellar medium.

Invited talk given at the meeting Mapping Oxygen in the Universe, Tenerife, Spain (14-18 May 2012)

Advertisements
This entry was posted in Atomic data applications and tagged , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s