1. Tidal Dwarves in Wolf-Rayet galaxies Ángel R. López-Sánchez & César Esteban Instituto de Astrofísica de Canarias

2. 1.Wolf-Rayet galaxies Subset of emission-line and H II galaxies Broad emission feature at 4650 Å, attributed to Wolf-Rayet stars (WR Bump) –He II 4686 Å –CIII/CII 4650 Å –NIII 4640 Å Short-lived phase (< 6 Myr) Use of population synthesis models –STARBURST 99 (Leitherer et al, 1999) –Wolf-Rayet and O stars populations in young starburst (Schaerer & Vacca, 1998) NGC 3049 Vacca & Conti 1992

3. 2. Previous work What is the trigger mechanism in WR galaxies? Interactions between dwarf galaxies or dwarf companion objects? (Méndez & Esteban, 2000) 14 analysed galaxies, 7 interacting and 4 with probable interaction features Bridge between 2 galaxies (Zw 0855+06) Several candidates to tidal tails (Mrk 8, Tol 35 and Pox 4).

4. 3. Our sample ~ 15 galaxies (Schaerer & Vacca, 1998) 3.1 Mrk 1087 –Long-slit spectra (4.2m WHT – ISIS & 2.5m INT – IDS) –Deep V image (2.2m CAHA – CAFOS) –J, H and Ks nIR images (1.5m CST – CAIN) 3.2 HCG 31 –Long-slit spectra (4.2m WHT – ISIS) –Deep U, B and V images (2.6m NOT – ALFOSC) –J, H and Ks nIR images (1.5m CST – CAIN) MRK 1087 HCG 31 Colors: U, B, V

5. 3.1 Mrk 1087 S E 50 arcsec Méndez & Esteban (2000) –Faint objects with bridges and tails and interactioning Our new V image: –N companion in interaction –Shows nebular emission O/H ratios: –#1 y #3 tidal dwarves –#7 intense SF zone off-center –North companion is an independent nearby object  O/H ratios from empirical calibrations

6. 3.1 Mrk 1087 Ages using spectral synthesis models –North companion: ~ 5 Myr –Central body: ~ 7 Myr It is experiencing a strong star formation event due to the interaction with at least two external galaxies: –the relatively bright K72 103a at ~ 70 kpc and +53 km/s –the N companion at ~ 60 kpc and +117 km/s Is Mrk 1087 a compact group of galaxies? S E 50 arcsec

7. 3.2 HCG 31 UV studies of its centre (Conti, Leitherer & Vacca 1996) Johnson et al. (1999) obtained HST images and detected SSCs E, F and Mrk 1090 (G) included by Rubin et al (1990) H I map of the group: the galaxies are gas rich (Williams 1991) NGC 1741 is a very luminous WR galaxy (Conti, 1991) Johnson & Conti 2000, H  and continuum

8. 3.2 HCG 31 3 slit-positions for spectroscopy –Kinematics –Physical conditions: [OIII] 4363 Å  Te [OII] & [SII] doublets  Ne –Chemical Abundances WR features detected in C, F1 & F2 Deep V image From Schaerer & Vacca (1998) models

9. Ages obtained by –STARBURST 99 (using photometry) (Leitherer et al. 1999) –Stasinska & Leitherer (1996) and Schaerer & Vacca (1998) (using spectroscopy) O/H ratios –Direct determination of B, C, F1 –First direct determination of E, F2 and G –A and H calculated by empirical calibrations 3.2 HCG 31

10. 3.2 HCG 31: metallicity-luminosity relation O/H unusual taking into account the M-L relation of Richer & McCall (1995) –It is not appropriated for starburst galaxies –The photometric evolution could move their position toward lower luminosity (Leitherer et al. 1999)

11. Tidal features in HCG 31 Two kinematic systems in E –A tidal dwarf galaxy (E) –A tidal tail with streaming motion towards H F1 and F2: –Tidal dwarf galaxies B affected by a tidal streaming motion between it and AC G: fly-by encounter with the armlike H I estructure Hunsberger et al (1996): – A tidal tail located at the NE of AC – Other tail towards E Iglesias-Páramo & Vilchez (2001) – 7 candidates from E to F (H located in debris)

12. 4. Wolf-Rayet features and tidal tails in compact systems Increasing number of morphological interactions signs –Mendez de Oliveira & Hickson (1994) –Vílchez & Iglesias-Páramo (1998, 1999) –Iglesias-Páramo & Vílchez (2001) –Verdes-Montenegro et al. (1998, 2001, 2002) –Méndez & Esteban (2000) Finding WR features would let to study –Star formation (specially massive star formation), –Its triggering mechanism –Tidal tails and tidal dwarves evolution