Near-Infrared Spectroscopy of Planetary Nebulae

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Session 2 -- Planetary Nebula and Supernova Remnants
Display presentation, Monday, 9:20-6:30, Pauley Room

[2.05] Near-Infrared Spectroscopy of Planetary Nebulae

J.L.Hora (IfA, U. Hawaii)

Near-infrared spectra of several planetary nebulae (PN), including NGC 7026, IC 418, M 2-56, and AFGL 618 have been obtained using KSPEC, a new 1--2.5 $\mu$m spectrometer for the UH 2.2m telescope. The data have been used, along with broad-band near-IR imaging to understand the nature of the emission from these objects. The 1$\times$8 arcsec slit of KSPEC was used to obtain the spectrum of the PN at several positions, including the central star, the brightest part of the nebular ring or lobes, and the halo region if present.

In the PN NGC 7026 and IC 418, the nebular emission is dominated by the hydrogen Paschen, Brackett, and Pfund series recombination lines, with contributions from several He {\small I} lines. The H line ratios are close to those predicted by recombination theory. Also present in the NGC 7026 spectrum is the H$_2$ line at 2.122 $\mu$m and an unidentified line at 2.287 $\mu$m which has previously been detected in several other moderate- to high-excitation PN. No H$_2$ is detected in the spectra of IC 418, and a previously reported Mg {\small I} line was also not seen. A strong continuum component is present in the 2--2.5 $\mu$m region, presumably due to hot dust emission. The bipolar PN M 2-56 has an almost featureless continuum from 1.15--2.5 $\mu$m. The spectrum of the protoplanetary nebula AFGL 618 is dominated by H$_2$ lines, with Pa$\beta$ and Br$\gamma$ H recombination lines also detected.

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