SIMBAD references

The inner regions (R∼1-2') of the nearby Sab type galaxy NGC 4736 (M 94) were observed using three different optical techniques: long-slit spectroscopy, CCD surface photometry and imaging spectroscopy, concentrating on the inner ring (R ≃50"), which was previously found to be kinematically and/or morphologically anomalous. A systemic velocity of 311±2km/s and a stellar central velocity dispersion of ca. 120±15km/s were found from the spectra. Curves of radial velocity (v_rad) versus radius for the stars on one hand and ionised gas on the other show a difference of 40km/s in amplitude. This is satisfactorily explained by a relatively simple model for the asymmetric drift of the stars, which assumes a constant ratio of vertical to radial velocity dispersion. In the v_rad(R) curves for the stars (absorption lines), a ca. 50km/s dip is observed to the East to Southeast of the nucleus. This feature is not seen in the emission line results. Comparison of the measured radial velocities with a model for galaxian rotation indicates a kinematic major axis position angle for the stars of 105 to 110deg, which is some 10deg lower than previously found. A B-R map shows spiral structure inside the inner ring, probably defined by dust, as corroborated by a B-K' map made with a K' image from a third party. Subtraction of the rotationally symmetric component of the inner 50" from the R frame clearly shows an elongated structure in the inner ca. 12" of radius, found earlier by others in a K image. The Hα distribution and velocity field presented here agree well with previous results. A residual velocity map indicates anomalous velocities in the gas of order 10-15km/s in the South-Eastern ring quadrant, as was also found before. Axisymmetric rotation model fits to the Hα velocity field yield a systemic velocity of 317±4km/s, kinematic major axis position angle within 3deg around 116deg and an essentially constant rotation velocity of 217km/s when fixing the inclination at 31deg for the inner ring (R in [35", 55"]). When left a free fit parameter, the kinematic inclination of the ionised gas in the inner ring is not well-determined by these fits. Major axis position angles, both morphologic and kinematic, of different galaxian constituents (stars, ionised gas, neutral gas) are compared in detail. Morphologic values are found to be larger than kinematic ones for any one constituent, by some 10deg for stars and for HII gas. Also, both the morphologic and kinematic values from the stellar continuum are lower than those found from Hα and HI, again by some 10deg.