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Session 63 - First Results from the Infrared Space Observatory.
Display session, Wednesday, June 12
Great Hall,

[63.02] Far-Infrared Spectroscopy with ISO: The Physical Conditions of the ISM in the Normal Spiral Galaxy NGC 5713

S. Lord, S. Malhotra, G. Helou, C. A. Beichman, N. Lu (IPAC), T. Lim (ISO-SOC), D. J. Hollenbach, R. H. Rubin (NASA-ARC), H. Thronson (U. Wyoming), G. Stacey (Cornell), H. Dinerstein (U. Texas), M. W. Werner (JPL), D. A. Hunter (Lowell Obs.), K. Y. Lo (U. Illinois)

We report new ISO Long Wavelength Spectrometer (LWS) observations of the SAB(rs)bc galaxy NGC 5713. These are the first LWS results from our ``US Key Project'' on normal galaxies (Helou et al. 1996) which uses ISO LWS, CAM, and PHOT observations to study ISM properties in normal galaxies.

We have obtained strong detections of the fine-structure forbidden transitions of [CII] at 158 \mum and [OI] at 63 \mum; tentative detections of [NII] at 122 \mum and [OIII] at 88 \mum; and significant upper limits for [NIII] at 57 \mum and [OIII] at 52 \mum. We also clearly detect the continuum dust emission between 40 and 197 \mum. The aperture size of the instrument corresponds to roughly 12 kpc at the distance of NGC 5713.

The measurements of the continuum and of the [CII], [OI] and [OIII] line fluxes can be combined to derive the temperature of the warm atomic gas surrounding molecular clouds, the incident UV flux on the clouds and the gas pressure in different phases of the ISM. Combining the ISO measurements with CO observations from the literature, we can determine typical cloud sizes and filling factors.

Program listing for Wednesday