Abundances in a Sample of Halo/Thick Disk Planetary Nebulae in M31

Details Abundances in a Sample of Halo/Thick Disk Planetary Nebulae in M31 Abundances in a Sample of Halo/Thick Disk Planetary Nebulae in M31

Jan 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21725608k&link_type=abstract

American Astronomical Society, AAS Meeting #217, #256.08; Bulletin of the American Astronomical Society, Vol. 43, 2011

Astronomy and Astrophysics

Astronomy

Scientific paper

We present preliminary abundances for 16 planetary nebulae in M31 identified by Merrett et al. (MNRAS, 369, 120, 2006). Our objects are the brightest 16 in a λ5007 flux-ranked subsample (m5007 between 20.45 and 20.88) whose distances from the major axis of M31, measured parallel to the minor axis, are between 15 and 50 arcminutes. This group presumably includes non-thin-disk objects, i.e., members of the thick disk and halo of M31, but may also sample possible tidal streams. Spectroscopic data were obtained with the DIS instrument on the 3.5-m ARC telescope at Apache Point Observatory (3700-9600 Å) and with GMOS on the Gemini North 8.1-m telescope (3700-6400 Å). Abundances were derived using our ELSA package (Johnson et al., IAU Symp. #234, 439, 2006). The resulting preliminary average abundances based on observations to date are as follows: He/H=0.107(±0.010), O/H=4.29(±1.24)x10-4, N/O=0.703(±0.618), and Ne/O=0.212(±0.019). There remain six PNe for which we have only Gemini spectra; in the fall of 2010 we plan to complete our observations and obtain companion red spectra at APO, allowing an improved analysis. For now, we note that the average He/H ratio is similar to the average of Milky Way halo PNe (Henry, Kwitter & Balick, A.J., 127, 2284, 2004), and below that for a similar-sized sample of mostly bulge PNe in M31 reported by Jacoby & Ciardullo (Ap.J., 515, 169, 1999). Our O/H ratio is well above the Milky Way halo PN value, and slightly above that of the Jacoby & Ciardullo sample.
KBK, RBCH and BB are grateful to their respective institutions and to the NSF for support under grants #AST-0806490, AST-0806577, and AST-0880201, respectively. KBK and EML thank NOAO for their generous travel support.

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