Mid-Infrared IRS Spectroscopy of NGC 7331: A First Look at the Spitzer Infrared Nearby Galaxies Survery (SINGS) Legacy

J.D.T. Smith, D.A. Dale, L. Armus, B.T. Draine, D.J. Hollenbach, H. Roussel, G. Helou, R.C. Kennicutt, Jr., A. Li, G.J. Bendo, D. Calzetti, C.W. Engelbracht, K.D. Gordon, T.H. Jarrett, L. Kewley, C. Leitherer, S. Malhotra, M.J. Meyer, E.J. Murphy, M.W. Regan, G.H. Rieke, M.J. Rieke, M.D. Thornley, F. Walter, M.G. Wolfire 2004, ApJS, 154, 199

The nearby spiral galaxy NGC 7331 was spectrally mapped from 5-38µm using all modules of Spitzer's IRS spectrograph. A strong new dust emission feature, presumed due to PAHs, was discovered at 17.1µm. The feature's intensity is nearly half that of the ubiquitous 11.3µm band. The 7-14µm spectral maps revealed significant variation in the 7.7 and 11.3µm PAH features between the stellar ring and nucleus. Weak [OIV] 25.9µm line emission was found to be centrally concentrated in the nucleus, with an observed strength over 10% of the combined neon line flux, indicating an AGN or unusually active massive star photo-ionization. Two [SIII] lines fix the characteristic electron density in the HII regions at n_e < 200 cm^-3. Three detected H₂ rotational lines, tracing warm molecular gas, together with the observed IR continuum, are difficult to match with standard PDR models. Either additional PDR heating or shocks are required to simultaneously match lines and continuum.

[XXX/astro-ph Preprint] [ADS Entry]

ADS Citation Query
# citations = 70
average # citations/year = 10.00 (# years = 7)
# citations vs. year [year=citations]
[2010=8] [2009=5] [2008=7] [2007=15] [2006=19] [2005=13] [2004=3]
[determined from ADS on 10 Sep 2010]