HST and UKIRT Observations of the Center of the Trifid Nebula: Evidence for the Photoevaporation of a Proplyd and a Protostellar Condensation

Astrophysics, abstract
astro-ph/0505155

From: Farhad Yusef-Zadeh [view email]

Date: Sun, 8 May 2005 17:04:32 GMT   (342kb)

The Trifid nebula (M20) is a well-known prominent optical HII region
trisected by bands of obscuring dust lanes and excited by an O7.5 star HD
164492A. Previous near-IR, mid-IR and radio continuum observations of the
cluster of stars at the center of the Trifid nebula indicated circumstellar
disks associated with hot stars with envelopes that are photoionized externally
by the UV radiation from the hot central star, HD 164492A. Using WFPC2 of the
HST, we present evidence of a resolved proplyd in H$\alpha$ and [SII] line
emission from a stellar source emitting cool dust emission. Using UKIRT, an
infrared observation of the stellar source with a proplyd indicates a late F —
mid G spectral type. We also note a remarkable complex of filamentary and
sheet-like structures which appear to arise from the edge of a protostellar
condensation. These observations are consistent with a picture in which the
bright massive star HD 164492A is responsible for the photoevaporation of
protoplanetary disks of other less-massive members of the cluster as well as
the closest protostellar condensation facing the central cluster. Using the
evidence for a proplyd, we argue that the massive and intermediate mass members
of the cluster, HD 164492C (B6 star) and HD 164492 (Herbig Be star) have disks
associated with them.

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