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Session 67 - ISM in Galaxies.
Display session, Wednesday, January 15
Metropolitan Ballroom,

[67.06] A Detection of Cold Dust in the Extended Disks of Nearby Field Galaxies

A. E. Nelson, D. Zaritsky (UCO/Lick Observatory), R. M. Cutri (IPAC-Caltech)

We present the detection of 100\mum emission at large radii (\sim 30 kpc) in two independent samples of nearby galaxies. Our aims are to test for the existence of dust at large radii in galaxies and to use the dust as a tracer of an extended baryonic component. From the IRAS 100\mum Sky Survey images, we construct two samples. First, we add the flux from 90 nearby (v < 6000 km/s) field galaxies, selected from the RC3 catalog to be of similar size (5 arcmin \leq D_25 \leq 10 arcmin), and luminosity (-22.5 \leq M_b \leq -18), and selected to be isolated in the 100\mum images to minimize contamination due to galactic cirrus or close companion galaxies. Using the data from the RC3, these galaxies are scaled by their D_25, rotated according to their major axis position angle, coadded, and rebinned into polar coordinates to produce maps of 100\mum emission as a function of radius and azimuthal angle. We apply the same procedure to a sample of 24 very nearby galaxies (v < 1500 km/s, D_25 \geq 10 arcmin). In both samples, we find 100\mum emission out to radii of \sim 30 kpc that is preferentially elongated along the major axis. We discuss some implications of this detection of extended 100\mum emission.

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