Spectrophotometry of Planetary Nebulae. III. IIDS Observations of Compact Nebulae

Abstract

We give spectral line intensities, electron temperatures, electron densities, and chemical compositions for 25 compact planetary nebulae observed with the IIDS at Kitt Peak. Several (Ha 3-75, He 2-15, K 3-89, M 1-16, M 2-52, and M 3-28) are found to be especially rich in helium and/or nitrogen (He/H>0.15; N/0>1). The results minimally confirm the correlation between N/O and He/H, but also confirm the intrinsic scatter in the relation, as N-rich nebulae can be unenriched in He and vice versa.

The excitation mechanism of H2in bipolar planetary nebulae

“…The H2 3-2 S(3) line at λ2.2104 µm is not detected, implying large H2 1-0 S(1)/3-2 S(3) line ratios. These large line ratios are indicative of shock excitation as collisional de-excitation can be discarded because the electron densities of these sources are much lower than those required (>10 5 cm −3 ) for this mechanism to be efficient: 500 cm −3 for K 4-55 (Guerrero, Manchado, & Serra-Ricart 1996), 1100 cm −3 for M 1-75 (Guerrero, Stanghellini, & Manchado 1995), 2300 cm −3 for M 1-92 (Solf 1994), 100-1000 cm −3 for M 4-17 (Kaler et al 1996). On the other hand, the same line ratios implied by the data in Table 4 for the H2-weak PNe are much smaller, with H2 1-0 S(1)/2-1 S(1) in the range 0.8-2.1 for IC 4997 and Hb 12.…”

Spectroscopy of planetary nebulae in M 33

“…However, to identify bona fide PNe, more precise indicators should be used when, as in our case, a larger part of the spectrum is available. The empirical emission line diagrams (Sabbadin & D'Odorico 1976;García-Lario et al 1991;Riesgo-Tirado & López 2002) Kaler et al (1996), Cuisinier et al (2000) for Galactic PNe; de Freitas Pacheco et al (1993), Vassiliadis et al (1992) and Stanghellini et al (2002) for LMC and SMC; JC99 and Stasinska et al (1998) for M 31; Walsh et al (1997) for Fornax. Note that the new limits shift the upper border of the PNe band more into the H  region box.…”

Infrared helium-hydrogen line ratios as a measure of stellar effective temperature

“…The ratios tabulated are for 5007-A Ê [O iii]/Hb, 6678-A Ê He i/Hb and 4686-A Ê He ii/Hb. These are as follows: (a) Aller & Hyung (1995); (b) Baessgen, Hopfensitz & Zweigle (1997); (c) Kelly, Latter & Rieke (1992); (d) Kwitter & Henry (1998); (e) Aller & Czyzak (1979); (f) Sabbadin, Cappellaro & Turatto (1987); (g) Aller & Czyzak (1983); (h) Aller & Keyes(1987); (i) our own data; (j)Tamura & Shaw (1987); (k)Kingsburgh & Barlow (1994); (l)Cuisinier, Acker & Koppen (1996); (m)Aller (1984) as reported inKaler et al (1997); (n)Kaler (1985); (o)Acker et al (1992); (p)Kaler et al (1996); (q)Costa et al (1996); (r)Kaler et al (1993); (s)Keyes, Aller & Feibelman 1990; Shaw & Kaler (1989); (u)Dopita & Hua (1997).…”