SIMBAD references

We present Two Micron All Sky Survey near-infrared (NIR) photometric mapping of the planetary nebulae A30, A78, NGC 7027, and BD +30 3639. It is shown that the NIR envelopes of both NGC 7027 and BD +30 3639 extend to much greater distances than has previously been supposed. It also appears that the dust in NGC 7027 has extinction properties similar to those of interstellar grains, and that the radii of the particles must be reasonably large. An analysis of emission in A78 and A30 shows the infrared indices to be reasonably large and implies grain temperatures T_grof order ~950 K. Similarly, the angular extensions of the continua (>18" and >22", respectively) suggest that they may arise from very small grains indeed. By contrast, while BD +30 3639 is also characterized by a high-temperature continuum, much of this emission appears to be confined to the core. This may imply that grain heating arises through direct stellar irradiation.