Deep Kinematics and Dynamics of Edge-on S0 Galaxies. I. NGC 3115

M. Capaccioli; E. Cappellaro; E. V. Held; M. Vietri

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Deep Kinematics and Dynamics of Edge-on S0 Galaxies. I. NGC 3115

M. Capaccioli·E. Cappellaro·E. V. Held·M. Vietri

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Abstract

As a first step of a program aimed to the detection of dark matter (or radial variations of M/L) in early-type galaxies, we report deep spectroscopic observations of the bulge-dominated edge-on S0 galaxy NGC 3115, made at ESO, La Silla, using EFOSC at the 3.6m telescope and EMMI at NTT. Such observations allow measurements of the rotational velocity out to 1.8 a_e (effective radii) from the galaxy center, where the surface brightness is μ_B ~ 24 mag arcsec**-2. The rotation curve quickly reaches an asymptotic value, v_f ~ 260 km/s, with only marginal indication of systematic decline within the range of our observations. The line-of-sight velocity dispersion has also been measured; it decreases steeply from a rather high central value and flattens out (<σ> ~ 100 km/s) within our observing range (a ~< 1.3 a_e). Models built on these data and simple dynamical arguments show that the M/L of NGC 3115 must thus be increasing from M/L = 6 (in solar units) in the inner regions (~ 1 a_e) to at least M/L >= 10 in the outermost regions (~ 2 a_e).

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M. Capaccioli, E. Cappellaro, E. V. Held, M. Vietri. 1993-04-05. Deep Kinematics and Dynamics of Edge-on S0 Galaxies. I. NGC 3115. https://arxiv.org/abs/astro-ph/9304004

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