Free Access
Volume 535, November 2011
Article Number A5
Number of page(s) 15
Section Galactic structure, stellar clusters and populations
Published online 24 October 2011

Online material

thumbnail Fig. 9

Histograms of the specific AM, l (in units of 100 kpc km s-1), and the radial (vr) and tangential (vt) velocities (in units of 100 km s-1) of stars between radii of 2–3 Rd in a number of minor merger remnants. The top three rows show direct minor mergers, with disk gas mass fractions increasing from 0 to 0.2. Indicated in each panel are the entire old stellar population (gray), new stars (blue) and old stars with |z|    ≤ 1 kpc (red). The vertical dashed lines show the average values of l, vr and vt for each of these three components. The three lowest rows are similar, but for retrograde mergers.

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thumbnail Fig. 10

Same as Fig. 9, but for two consecutive minor mergers.

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thumbnail Fig. 11

Same as Fig. 9, but for galaxies that were evolved in isolation for 3 Gyr: a gSa (upper panels) with a gas mass fraction fgas = 0.1 and a gSb (middle panels) with fgas = 0.2, as well as a galaxy with a much higher gas fraction of 0.5 which went through an unstable clumpy phase (bottom panels). In the latter case the parameters are also shown after 3 Gyr, when the clumps have dissolved through tidal effects or spiraled into the galaxy center through dynamical friction and interaction.

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thumbnail Fig. 12

Distribution of tangential velocities vt (in units of 100 km s-1) of old stars for six minor mergers. For each encounter a pair of panels is shown, with stars originally in the primary disk (left) and those accreted from the satellite (right). In each panel the histograms correspond to different heights above and below the galaxy midplane: |z|    ≤ 1 kpc (black), 1    <    |z|    ≤    3 kpc (blue), 3    <    |z|    ≤    5 kpc (green) and 5    <    |z|    ≤    10 kpc (orange). The average values of vt in the different regions is also indicated.

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thumbnail Fig. 13

Same as Fig. 12 but for an isolated, very gas-rich galaxy (fgas = 0.5), after an unstable, clumpy phase. Note that in this case the fourth and highest region is missing, due to a lack of stars above/below 5 kpc from the galaxy midplane.

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thumbnail Fig. 14

Specific AM, l, as a function of scaled radius for old stars in three direct merger remnants. For each encounter a pair of plots is shown, where stars are selected on their heights above (or below) the galaxy midplane: |z|    ≤ 1 kpc (upper panels) and |z|    > 1 kpc (lower panels). In each panel stars originally in the primary galaxy are shown as black points, stars originally in the satellite as blue points, and satellite stars with |z|    > 5 kpc as red points. The specific AM is in units of 100 kpc km s-1.

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thumbnail Fig. 15

Same as Fig. 14, but for three retrograde mergers.

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thumbnail Fig. 16

Fraction of counter-rotating stars (shown in blue) for four dissipationless retrograde mergers. Stars are divided into four regions, according to their height above (or below) the galaxy midplane: (1) at |z|    ≤    1 kpc; (2) at 1 kpc  ≤    |z|    ≤ 3 kpc; (3) at 3 kpc  ≤    |z|    ≤ 5 kpc; and (4) at 5 kpc ≤ |z|    ≤ 10 kpc. For each region the fraction of satellite stars to the total number of stars is also shown (gray).

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thumbnail Fig. 17

Same as Fig. 16, but for four dissipative retrograde mergers.

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thumbnail Fig. 18

Same as Fig. 16, but for a gS0 galaxy after a single retrograde merger (left panel) and after two consecutive retrograde mergers (right panel) with a dE0 satellite.

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© ESO, 2011

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