SIMBAD references

1994A&A...288..921C - Astronomy and Astrophysics, volume 288, 921-928 (1994/8-3)

Planetary nebulae and the helium-to-metals enrichment ratio.


Abstract (from CDS):

A sample of planetary nebulae (PN), galactic and extragalactic H II regions and blue compact galaxies (BCG) was used in order to obtain the helium-to-metals enrichment ratio, dY/dZ. Adopting a simple linear variation for the helium abundance with metals, and taking into account the contamination of the observed helium abundance in PN by the fresh helium produced in their central stars, it is shown that dY/dZ>3, and that the linear model is limited to low metallicities. Finally, we conclude that the simple model of galactic chemical evolution is unable to explain the observed enrichment ratio unless infall of gaseous material on to the galactic disk is considered.

Abstract Copyright:

Journal keyword(s): planetary nebulae: general - Galaxy: evolution - Galaxy: abundances

CDS comments: table 1 : object 6822 not in SIMBAD

Simbad objects: 134

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