The True Luminosities of Planetary Nebulae in M31's Bulge: Massive Central Stars from an Old Stellar Population

Brian D. Davis, Robin Ciardullo, George H. Jacoby, John. J. Feldmeier, Briana L. Indahl
2018 Astrophysical Journal  
We measure the Balmer decrements of 23 of the brightest planetary nebulae (PNe) in the inner bulge (r ≲ 3 arcmin) of M31 and de-redden the bright end of the region's [O III] λ 5007 planetary nebula luminosity function. We show that the most luminous PNe produce ≳ 1,200 L_ of power in their [O III] λ 5007 line, implying central star luminosities of at least ∼ 11,000 L_. Even with the most recent accelerated-evolution post-AGB models, such luminosities require central star masses in excess of
more » ... M_, and main sequence progenitors of at least ∼ 2.5 M_. Since M31's bulge has very few intermediate-age stars, we conclude that conventional single-star evolution cannot be responsible for these extremely luminous objects. We also present the circumstellar extinctions for the region's bright PNe and demonstrate that the distribution is similar to that found for PNe in the Large Magellanic Cloud, with a median value of A_5007 = 0.71. Finally, we compare our results to extinction measurements made for PNe in the E6 elliptical NGC 4697 and the interacting lenticular NGC 5128. We show that such extinctions are not unusual, and that the existence of very high-mass PN central stars is a general feature of old stellar populations. Our results suggest that single-star population synthesis models significantly underestimate the maximum luminosities and total integrated light of AGB stars.
doi:10.3847/1538-4357/aad3c4 fatcat:67y6kj2hvbbxnfq5b3q7thxcq4