A long-slit spectral analysis of the nuclear region of M101

Using long-slit spectra centered in wavelength about H alpha, we have obtai ned a velocity map of a 20" x 140" east-west box centered on the nuclear re gion of M101. The velocity resolution is 2.5 km s(-1) and the spatial resol ution is approximately 1" east-west and variable (3"-4" on average) north-s outh. We have also obtained temperature, density, and shock maps of the sam e region using the [N II] lambda 6548, [N II] lambda 6583, H alpha, [S II] lambda 6717, and [S II] lambda 6731 lines. The temperatures range from 4100 to 14,100 K, with an intensity-averaged temperature of 6200 K. The densiti es range from 6.6 to 36,600 cm(-3), with an intensity-averaged density of 8 00 cm(-3). Regions northeast and southwest of the nucleus have [N II] lambd a 6583/H alpha ratios greater than or similar to 0.56 and [S II] lambda lam bda(6717 + 6731)/H alpha ratios greater than or equal to 0.4, which are ind icative of shock-heated or power-law photoionized gas. The gas in an S-shap ed region passing through the nucleus has [N II] lambda 6583/H alpha ratios less than or similar to 0.56 and [S II] lambda lambda(6717 + 6731)/H alpha ratios of approximate to 0.1, which is representative of gas in H II regio ns. The velocity data are consistent with gas infalling toward the nucleus as part of streaming motions traveling west to east on the north side of th e nucleus and east to west on the south side of the nucleus. However, there appears to be a local instability in which the motion southwest of the nuc leus is moving west to east, creating a collision of the two opposing gas m otions in a region of relatively high density and temperature. A blue are e manating from an unresolved source on or near the nucleus shows evidence of collision in this same high-density, high-temperature region. Our data sup port a previous conclusion that M101 may be considered an intermediate gala xy with respect to activity, possibly in transition between a normal nucleu s and a more active stage.