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Date and Time of the Query: 2019-06-25 T21:13:55 PDT
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For refcode 1989A&A...225..317v:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
1989A&A...225..317v Distribution and motions of atomic hydrogen in lenticular galaxies IX. NGC 3941 and NGC 4694 W. van Driel and H. van Woerden Kapteyn Astronomical Institute, Groningen University, Postbus 800, NL-9700 AV Groningen, The Netherlands Observatoire de Paris, Section de Meudon, DAEC, UA 173, Laboratoire d'Astrophysique associe a l'Universite de Paris, VII. F-92195 Meudon Principal Cedex, France Astronomical Institute "Anton Pannekoek", University of Amsterdam. Roetersstraat 15, NL-1018 WB Amsterdam, The Netherlands Received August 3, 1988: accepted May 12, 1989 Summary. The gas-rich SB0 galaxy NGC 3941 was mapped at Westerbork in the 21 cm H I line with a spatial resolution of 40 km s^-1^. An SB0pec galaxy in the Virgo Cluster, NGC 4694, was mapped in the H I line with spatial resolutions of 13" x 67" and 24" x 127" and velocity resolutions of 10 and 40 km s^-1^, respectively. The H I gas in NGC 3941 is found to be distributed mainly in two ring-like structures. The outer ring has an average radius of 12 kpc (= 1.5 times the de Vaucouleurs' radius R_25_) and rotates in the plane of the stellar disk, if we assume it to be circular; the inner ring has a radius of ~ 5 kpc (= 0.6 R_25_) and seems to be inclined some 20^deg^ to the stellar disk. We fit a tilted rotating ring model to the velocity field and obtain an essentially flat rotation curve if we assume the inner H I to be warped. The total-mass-to-blue-light ratio is 9 M_sun_/L_sun_ within R = 17 kpc. The maximum azimuthally averaged H I surface density is quite low, 1.5 M_sun_ pc^-2^, and comparable to that found in other S0 galaxies. The H I distribution in and around NGC 4694 shows a central concentration in the galaxy itself with a maximum H I column density of ~ 3 10^20^ atoms cm^-2^), and a small velocity gradient along the minor axis of NGC 4694. However, most of the H I gas is found to form a tail, which peaks (N_H I_ ~ 7 10^20^ atoms cm^-2^) at the position of VCC 2062, a 19-th magnitude irregular dwarf galaxy, which lies at a projected distance of 3.8' (= 15 kpc) from NGC 4694. We compare various scenarios for the origin and evolution of the H I gas in both galaxies to the observations. The conclusions are not firm, but for NGC 3941 we prefer accretion for the inner ring and accretion or a burnt-out disk scenario for the outer gas. For NGC 4694 we suggest ram-pressure stripping by an intergalactic gas cloud; a merger with a substantial dwarf galaxy or protogalaxy is a reasonable alternative. Key words: clusters: of galaxies - galaxies: kinematics and dynamics of - galaxies: lenticular - galaxies: evolution of - galaxies: NGC 3941, NGC 4694
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