SIMBAD references

We have observed 77 evolved planetary nebulae in the J, H, K, L', and M photometric bands. As a consequence, we note that most PN fall into a range -0.6 < (J-H)₀ < 0.2 mag , and 0.0 < (H-K)₀ < 1.2mag , whilst a few sources have also been detected in the range 1.0 < (K-L)₀ < 5.3 mag . Most indices (J-H)₀ are almost certainly depressed through the influence of HeI 2³ S 2³ P emission, whilst stellar continua appear to dominate ∼ 6 sources, and components of high temperature dust enhance (J-H)₀ in several others. Fully 60% of sources having (J-H)₀ ≥0.0 appear to be type I nebulae. Finally, we note that H₂S(1) and Q band quadrupole emission may be important in enhancing K band fluxes for several of the nebulae, and the mean value (H-K)₀ ≃ 0.88 mag for H₂S(1) emission sources is significantly in excess of the mean. As a consequence, the parameter (H-K)₀ may prove a useful tool in the prior selection of nebulae having shocked, neutral gas. By contrast, the various L' band detections are likely to derive from a mix of mechanisms, including emission from grains having a broad range of temperatures.