AAS 205th Meeting, 9-13 January 2005
Session 57 Atomic Abundances in Interstellar Gas
Poster, Tuesday, January 11, 2005, 9:20am-6:30pm, Exhibit Hall

## [57.05] Do Small, Neutral PAHs Survive in the ISM?

U. P. Vijh, A. N. Witt (U. Toledo), K. D. Gordon (U. Arizona)

Polycyclic aromatic hydrocarbon (PAH) molecules are ubiqutous in the universe. They reveal themselves primarily through emission features in the near- and mid-IR, commonly referred to as aromatic emission features (AEF) or the unidentified infrared (UIR) bands. We discovered the presence of small 3-4 ringed, neutral PAHs in the Red Rectangle (RR) through their blue fluorescence (Vijh et al. 2004; Vijh et al. 2005). The central star in the RR is in an active dust producing stage and these small PAHs are just being formed in the gas. Do these small PAHs survive under harsh interstellar conditions? Are the AEFs primarily due to larger PAHs? To answer these questions we have obtained long slit spectra of different reflection nebulae and star forming regions, where the temperatures of the illuminating stars cover a range from ~ 9000 - 25000 K. We will present results that establish the presence or absence of blue fluorescence from small, neutral PAHs as a function of the local radiation field density.

This research is funded by the NSF grant AST 0307307 to the University of Toledo.

\textbf{References}

Vijh, U.P., Witt, A. N., & Gordon, K. D. 2004, ApJ, 606, L68\\ Vijh, U.P., Witt, A. N., & Gordon, K. D. 2005, ApJ (in press)

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© 2004. The American Astronomical Society.