We present Earth-based imaging and photometry results of Deep Impact target comet 9P/Tempel 1 obtained at and in the nights surrounding the time of the spacecraft's impact. These observations establish the baseline behavior of Tempel 1 prior to impact, including a water vaporization rate of 6 ; 10 27 molecules s À1 , thereby enabling us to determine the effects directly caused by this explosive event. The instantaneous fireball was not detected, but a postimpact brightening from ejecta material was prominent and shows evidence of a slowly decreasing optical depth over more than an hour of time. We have successfully reproduced both the general morphology of the ejecta plume and many details of the shape and brightness distribution on successive nights following the impact using a modified Monte Carlo jet model, with an initial impulse event in the shape of an open, thick-walled cone. As seen from Earth, the center of the plume is derived to be at a position angle of about 255 and about 20 this side of the plane of the sky, i.e., near the limb of the nucleus. Most of the observed ejecta material had an initial outflow velocity of less than 0.23 km s À1and particle sizes of less than 2.5 m (assuming compact grains). This resulted in the rapid development of a dust tail from ejecta particles as they are pushed away from the Sun by radiation pressure. Each daughter gas species exhibited an increase in production, with peaks occurring 1-2 days after impact, followed by a gradual decay back to baseline values; the shapes of these light curves suggest that the postimpact excess is due to the vaporization of ices within the ejecta over the course of a few days. In nearly all respects, comet Tempel 1 returned to preimpact conditions only 6 days after the event.

We present results from new near-infrared (NIR) imaging from the Spitzer Space Telescope that trace the low surface brightness features of the outer disk and stellar stream in the nearby spiral galaxy, M83. Previous observations have shown that M83 hosts a faint stellar stream to the northwest and a star-forming disk that extends to ∼3 times the optical radius (R 25 ). By combining the NIR imaging with archival far-ultraviolet (FUV) and H i imaging, we study the star formation history of the system. The NIR surface brightness profile has a break at ∼5. 8 (equivalent to 8.1 kpc and 0.9 R 25 ) with a shallower slope beyond this radius, which may result from the recent accretion of gas onto the outer disk and subsequent star formation. Additionally, the ratio of FUV to NIR flux increases with increasing radius in several arms throughout the extended star forming disk, indicating an increase in the ratio of the present to past star formation rate with increasing radius. This sort of inside-out disk formation is consistent with observations of gas infall onto the outer disk of M83. Finally, the flux, size, and shape of the stellar stream are measured and the origin of the stream is explored. The stream has a total NIR flux of 11.6 mJy, which implies a stellar mass of 1 × 10 8 M in an area subtending ∼80 • . No FUV emission is detected in the stream at a level greater than the noise, confirming an intermediate-age or old stellar population in the stream.

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New deep optical and near-infrared imaging is combined with archival ultraviolet and infrared data for 15 nearby galaxies mapped in the Spitzer Extended Disk Galaxy Exploration Science survey. These images are particularly deep and thus excellent for studying the low surface brightness outskirts of these disk-dominated galaxies with stellar masses ranging between 108 and

We present results from multiwavelength observations of the galaxy NGC5005. We use new neutral hydrogen (HI) observations from the Very Large Array to examine the neutral gas morphology and kinematics. We find an HI disc with a well-behaved flat rotation curve in the radial range 20 ′′ -140 ′′ . Ionized gas observations from the SparsePak integral field unit on the WIYN 3.5m telescope provide kinematics for the central 70 ′′ . We use both the SparsePak and HI velocity fields to derive a rotation curve for NGC5005. Deep 3.6µm observations from the Spitzer Space Telescope probe the faint extended stellar population of NGC5005. The images reveal a large stellar disk with a high surface brightness component that transitions to a low surface brightness component at a radius nearly 1.6 times farther than the extent of the gas disk detected in HI. The 3.6µm image is also decomposed into bulge and disk components to account for the stellar light distribution. Optical broadband B and R and narrowband Hα from the WIYN 0.9m telescope complement the 3.6µm data by providing information about the dominant stellar population and current star formation activity. The neutral and ionized gas rotation curve is used along with the stellar bulge and disk light profiles to decompose the mass distributions in NGC5005 and determine a dark matter halo model. The maximum stellar disk contribution to the total rotation curve is only about 70%, suggesting that dark matter makes a significant contribution to the dynamics at all radii.