Astronomy & Astrophysics

All Figures

$\begin{figure} \par\subfigure[]{\includegraphics[width=8.8cm,clip]{4102fi1a.eps}... ...re[]{\includegraphics[width=8cm,clip]{4102fi1c.eps} }\hspace*{5cm}} \end{figure}$ Figure 1: a) Aitoff projection of the entire sky distribution of the HVCs in Galactic coordinates, based on measurements of the 21-cm emission line of HI (adapted from Bajaja et al. 1985; Hulsbosch & Wakker 1988; Morras et al. 2000). Plus (or darker regions) and minus signs mark respectively the positions of the HI lines with positive and negative high velocities in the LSR frame. b) Velocity of high-velocity HI lines with respect to the LSR plotted against Galactic longitude, from the collection of data used in Fig. 1a. The sinusoidal curve represents the $V_{\rm LSR}(\ell )$ pattern for $b=0^{\circ }$ corresponding to a hypothetical flow of HVCs, circulating in directions parallel to $\ell =90^{\circ }{-}270^{\circ }$ . c) Velocity of high-velocity HI lines with respect to the LSR plotted against Galactic latitude, from the collection of data used in Fig. 1a. The two half-cosine curves represent the $V_{\rm LSR}(b)$ pattern for $\ell =90^{\circ }$ and $270^{\circ }$ corresponding to a hypothetical flow of HVCs, circulating in directions parallel to $\ell =90^{\circ }{-}270^{\circ }$ .
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=8.8cm,clip]{4102fi2a.eps}... ...e[]{\includegraphics[width=8cm,clip]{4102fi2c.eps} }\hspace*{5cm}} \end{figure}$ Figure 2: a) Same as Fig. 1a, but with data adapted from Giovanelli (1981) and Putman (2002). The region centered at $\ell =120^{\circ }$ and $b=30^{\circ }$ is not covered by the observations of the two surveys used here, and is left empty. b) Same as Fig. 1b, but from the collection of data used in Fig. 2a. c) Same as Fig. 1c, but from the collection of data used in Fig. 2a.
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In the text

$\begin{figure} \par\includegraphics[width=8.05cm,clip]{4102fig3.eps} \end{figure}$ Figure 3: Locations of the LMC, the SMC and the Sun in Galactocentric coordinates (X,Y,Z). The past orbit of the LMC is represented by the solid curve. The position angles of the orbital plane are indicated.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=8cm,clip]{4102fi4a.eps} }... ...mm} \subfigure[]{\includegraphics[width=8cm,clip]{4102fi4b.eps} } \end{figure}$ Figure 4: a) Projection of the past orbits of the LMC and the SMC on the Galactocentric X-Y plane. The LMC and SMC positions are marked by crosses each 100 Myr. b) Projection of the past orbits of the LMC and the SMC on the Galactocentric X-Z plane. The LMC and SMC positions are marked by crosses each 100 Myr.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=7.6cm,clip]{4102fi5a.eps}... ...\includegraphics[width=6.8cm,clip]{4102fi5e.eps} }\hspace*{4.5cm}} \end{figure}$ Figure 5: a) Simulated celestial distribution of the HVCs: projection of the positions of the test particles at present moment on the sky plane. The plus and minus symbols have the same meanings as in Fig. 1a. The projections of the past orbit of the LMC (solid curve) and the present positions of the LMC and SMC (large and small projected circles) are shown. The cross at the end of the projected orbit curve is the projected position of the encounter between the LMC and the SMC. Compare this theoretical distribution with the observed ones (Figs. 1a and 2a). b) Simulated velocity-longitude relation for the HVCs: radial LSR velocities of the test particles at the present moment as a function of their respective Galactic longitudes. The solid curve has the same meaning as in Fig. 1b. Compare this theoretical relation with the observed ones (Figs. 1b and 2b). c) Simulated velocity-latitude relation for the HVCs: present radial LSR velocities of the test particles as a function of their respective Galactic latitudes. The solid curve has the same meaning as in Fig. 1c. Compare this theoretical relation with the observed ones (Figs. 1c and 2c). d) Simulated spatial distribution and velocity field in the Galactocentric rest frame for the HVCs: Present positions and velocities of the test particles. The test particles with initial velocities $\mid\! \vec{v}_{\rm p}\! \mid\ < 220~{\rm km~s^{-1}}$ have been omitted in the plot for clarity. The present positions of the LMC and the SMC (circles), the past orbit of the LMC (solid curve) and the point of encounter between the LMC and the SMC (circle) are represented. e) Same as Fig. 5d, but projected on the Galactocentric X-Z plane.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=7.7cm,clip]{4102fi6a.eps}... ...} \subfigure[]{\includegraphics[width=7.5cm,clip]{4102fi6b.eps} } \end{figure}$ Figure 6: a) Spatial distribution and velocity field of the test particles with an initial isotropic velocity distribution characterized by $\mid\! \!\vec{v}_{\rm p} \!\!\mid\ = 170~{\rm km~s^{-1}}$ . b) Spatial distribution and velocity field of the test particles with an initial isotropic velocity distribution characterized by $\mid\! \vec{v}_{\rm p} \!\mid\ = 270~{\rm km~s^{-1}}$ .
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=7.5cm,clip]{4102fi7a.eps}... ... \subfigure[]{\includegraphics[width=7.75cm,clip]{4102fi7b.eps} } \end{figure}$ Figure 7: a) Projection, on the Galactocentric X-Y plane, of the orbits of some of the test particles that interact with the Galactic disk. The filled circles indicate the positions of entry into the Galactic layer. The crosses mark the positions of the particle at intervals of 30 Myr. The times of entry of this subset of test particles lie between -220 and -120 Myr. The position of the Sun $(X_{\odot },Y_{\odot })$ is (0, 8.5) kpc. b) Projection of the orbits of the same test particles as those of Fig. 7a, but on the Galactocentric X-Z plane.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{4102fig8.eps} \end{figure}$ Figure 8: Same as Fig. 7a, but for the total set of test particles that interact with the Galactic layer. The filled and open circles indicate respectively the positions of entry into the Galactic gas layer, and the present positions of the impacted regions, resulting from the interaction of the test particles with a rotating disk. We have omitted the projection of their complete orbits for clarity. The numbers inside the circles refer to the ages of impacted regions in units of 10 Myr, defining age as the time elapsed from the entry of the particle into the Galactic layer up to the present. The solar circle is indicated.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=8cm,clip]{4102fi9a.eps} }... ...} \subfigure[]{\includegraphics[width=8.5cm,clip]{4102fi9b.eps} } \end{figure}$ Figure 9: a) Correlation between the times of entry of the test particles into the Galactic layer and the positions of the particles projected on the X-axis. The solid lines represent the position of the front edge (lower line) and the back edge of the accretion front as a function of time. Negative time means before the present. b) Angles (filled and open circles) and velocities (crosses) of entry of the test particles into the Galactic layer versus the respective positions projected on the X-axis. The open circles refer to angles of entry from above the Galactic plane.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=8.2cm,clip]{4102f10a.eps}... ...mm} \subfigure[]{\includegraphics[width=8cm,clip]{4102f10b.eps} } \end{figure}$ Figure 10: a) The time t₁ at which the head of the accretion front crosses a disk region, and the time t₂ at which the back of the accretion front leaves the region, as a function of the present azimuth for the regions at R= 22 kpc (dashed line) and R= 24 kpc (solid line). The duration of the transit of the accretion front, $t_{\rm a}=t_{2}-t_{1}$ , is also represented as a function of the present azimuth. b) Vertical Z-distances of the midplane of the Galactic layer from the plane b=0 at the Galactocentric distances R= 22 kpc (dashed line) and R= 24 kpc (solid line) as a function of the azimuth of the region, according to the simulation of the interaction between the accretion front due to the flow of HVCs and the Galactic gas layer.
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In the text

$\begin{figure} \par\subfigure[]{\includegraphics[width=8.8cm,clip]{4102fi2a.eps}... ...e[]{\includegraphics[width=8cm,clip]{4102fi2c.eps} }\hspace*{5cm}} \end{figure}$	Figure 2: a) Same as Fig. 1a, but with data adapted from Giovanelli (1981) and Putman (2002). The region centered at $\ell =120^{\circ }$ and $b=30^{\circ }$ is not covered by the observations of the two surveys used here, and is left empty. b) Same as Fig. 1b, but from the collection of data used in Fig. 2a. c) Same as Fig. 1c, but from the collection of data used in Fig. 2a.
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$\begin{figure} \par\includegraphics[width=8.05cm,clip]{4102fig3.eps} \end{figure}$	Figure 3: Locations of the LMC, the SMC and the Sun in Galactocentric coordinates (X,Y,Z). The past orbit of the LMC is represented by the solid curve. The position angles of the orbital plane are indicated.
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$\begin{figure} \par\subfigure[]{\includegraphics[width=8cm,clip]{4102fi4a.eps} }... ...mm} \subfigure[]{\includegraphics[width=8cm,clip]{4102fi4b.eps} } \end{figure}$	Figure 4: a) Projection of the past orbits of the LMC and the SMC on the Galactocentric X-Y plane. The LMC and SMC positions are marked by crosses each 100 Myr. b) Projection of the past orbits of the LMC and the SMC on the Galactocentric X-Z plane. The LMC and SMC positions are marked by crosses each 100 Myr.
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$\begin{figure} \par\subfigure[]{\includegraphics[width=7.7cm,clip]{4102fi6a.eps}... ...} \subfigure[]{\includegraphics[width=7.5cm,clip]{4102fi6b.eps} } \end{figure}$	Figure 6: a) Spatial distribution and velocity field of the test particles with an initial isotropic velocity distribution characterized by $\mid\! \!\vec{v}_{\rm p} \!\!\mid\ = 170~{\rm km~s^{-1}}$ . b) Spatial distribution and velocity field of the test particles with an initial isotropic velocity distribution characterized by $\mid\! \vec{v}_{\rm p} \!\mid\ = 270~{\rm km~s^{-1}}$ .
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