Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/people/Angel.Lopez-Sanchez/proceedings/sydney2003.pdf Äàòà èçìåíåíèÿ: Sun Feb 3 04:33:38 2008 Äàòà èíäåêñèðîâàíèÿ: Mon Apr 14 04:19:52 2008 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: south pole

Recycling intergalactic and interstel lar matter IAU Symposium Series, Vol. 217, 2004 Pierre-Alain Duc, Jonathan Braine and Elias Brinks, eds.

On the nature of dwarf galaxies in the interacting group HCG 31
´ Angel R. L´pez-S´nchez & C´sar Esteban o a e Instituto de Astrof´ ica de Canarias, E38200, Tenerife, Spain is M´nica Rodr´ uez o ig INAOE, Apdo. Postal 51 y 216, 72000 Puebla, Pue., M´xico e Abstract. We have analysed the morphology, kinematics, colors and chemical composition of the ionized gas of the different ob jects belonging to the interacting compact group HCG 31 in order to get a global view on the origin and evolution of the dwarf galaxies present in it.

1.

Discussion

Optical U, B and V images of HCG 31 were carried out at 2.56m NOT. We used the 1.55m CST to obtain J, H and Ks NIR images. Intermediate-resolution spectroscopy were carried out at 4.2m WHT. Three different slit positions were observed in order to study the kinematics and chemical composition of the ionized gas. We presented a preliminary analysis of the chemical abundances and the ages of the observed bursts in L´pez-S´nchez & Esteban (2003). o a An analysis of bright emission line profiles along each slit position was performed to study the kinematics of the ionized gas. We show the positionvelocity diagrams in Figure 1. We can conclude: 1. C shows a sinusoidal pattern in its center (Figure 1a ), indicating that a merging process is ongoing in the of A+C complex. 2. B shows a solid-body rotation pattern (Figure 1a ) that could be affected by a possible tidal streaming motion along the direction towards the A+C complex. G also shows solid-body rotation (Figure 1b ). 3. E shows a very different behavior between P.A. 133 (Figure 1b ) 128 (Figure 1c ). We consider that perhaps we are seeing two kinematical ob jects that coexists in apparent close proximity: E (P.A. 128 ) and a tidal tail extending from the south of A+C towards the faint member H (P.A. 133 ). and P.A. different member complex

4. F1 and F2 seem clearly to be kinematically different of that tidal tail. The mean velocities of F1 and F2 are similar to that of E and G, which coincides with the radial velocity of the H i cloud (Williams et al. 1991), suggesting that they are related to the arm-like H i structure that extends to the SE 1


2

A.R. L´pez-S´nchez, C. Esteban & M. Rodr´ uez o a ig

A

G

F2 F1

C

H2 H1 F2 F1 E

B E B

Figure 1.

Position-velocity diagrams obtained from long-slit spectroscopy.

of A+C complex. The velocity pattern and the morphology of the system are compatible with the presence of two spatially coincident kinematical structures: the arm-like H i structure that extends from A+C in direction to member G (from which ob jects E and F may be formed), and the optical tidal tail that emerges from the southwest of the A+C complex (which consist of a curved string of faint star-forming regions that ends at H). The H i extension has a rather constant radial velocity but the optical tidal tail shows a clear streaming motion. We propose that E, F1, and F2 are TDG candidates made by material from the southern arm-like H i extension, which was stripped from the parent galaxy (probably the A+C complex) due to a fly-by encounter between it and G. This hypothesis is both supported by their kinematic patterns and because their relatively high chemical abundances, very similar to those of the brightest galaxies. The apparent absence of old stellar population in E, F1 and F2 indicates that they are basically made of gaseous material. In fact, a local maximum in the distribution of H i emission coincides with the position of member F. 2. Conclusions

Our data suggest that is necessary a strong interaction between more than two galaxies in order to explain all the observed features in HCG 31. This behavior could be an interesting prototype of interaction between several galaxies, probably very common in high density systems and at high redshift. References
L´pez-S´nchez, A.R. & Esteban, C. 2003, in Satel lites and tidal streams, F. Prada and o a D. Mart´ inez-Delgado (eds), in prep. Williams, B.A., McMahon, P.M. & van Gorkom, J.H. 1991, AJ, 101, 1957