Inward Flow - situations without coming close to the...

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Inward Flow A few objects show clear signs of inflow of material, always a good sign if we want to seriously discuss accretion power. There is a supposition that inflow and outflow may coexist in one object in different pieces of solid angle around the core source. Redshifted absorption lines of H I and OH have been seen toward the nuclei of Cen A (van der Hulst et al. 1983 ApJLett 264, L37; Seaquist and Bell 1990 ApJ 364, 94) and other radio galaxies (van Gorkom 1987 in Structure and Dynamics of Elliptical Galaxies , IAU Symp. 127, p. 421). They may have appreciable velocity width, as shown in Fig. 1 of Seaquist and Bell (courtesy of the AAS: These observations are crucial in clearly showing gas moving inward. It is not always clear how this relates to accretion - modest inflow velocities can be attained via orbital dynamics in some
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Unformatted text preview: situations without coming close to the nucleus. Also, the net inflow needed to fuel the nucleus may be very tiny at large radii and easily lost in the details of galaxy dynamics. One glaring example of this is in seeking bar-driven gas flows. Bars and oval distortions will populate orbits along the bar, and the observed velocities from such flows are very large compared to net inward streaming of gas as it loses angular momentum to collisions. Thus its kinematic signature will be swamped. Quillen et al. (1995 ApJ 441, 549) have used the 1/ r nature of the gravitational potential and K-band imaging to estimate the potential shape and infer the inflow rate from calculated torques on the gas-rich dust lanes in a few nearby bared spirals, pointing to one avenue that can (more or less) measure mass inflow on kpc scales....
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Inward Flow - situations without coming close to the...

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