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Nitrogen excess in starburst galaxies: chemical enrichment via winds of Wolf-Rayet stars?

The Local Volume HI Survey. Nitrogen excess in starburst galaxies: chemical enrichment via winds of Wolf-Rayet stars?. Ángel R. López-Sánchez César Esteban (IAC), Jorge García-Rojas (IA-UNAM), Adal Mesa Delgado (IAC) & Luis López-Martín (IAC).

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Nitrogen excess in starburst galaxies: chemical enrichment via winds of Wolf-Rayet stars?

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  1. The Local Volume HI Survey Nitrogen excess in starburst galaxies:chemical enrichment via winds of Wolf-Rayet stars? Ángel R. López-Sánchez César Esteban (IAC), Jorge García-Rojas (IA-UNAM), Adal Mesa Delgado (IAC) & Luis López-Martín (IAC) CSIRO /Australia Telescope National Facility (ATNF, Australia) The Cosmic Odyssey of the Elements – Aegina – Greece – 23 Jun 2008

  2. Chemical evolution of galaxies • a elements (S, Ne, Ar): const. with O/H • Primary production in massive stars (Izotov & Thuan 1999; Izotov et al. 2006) • N/O is not so evident! Dlog (N/O) ~ 0.5 • Constant for 12+log O/H < 7.6 Primary production • Dispersion for 7.6 < 12+log O/H < 8.3 Delay in N production & loss via galactic winds • Increases for 12+log O/H > 8.3 Secondary production Kobulnicky et al.1997; Izotov et al. 2006

  3. Starburst galaxies with high N/O HS 0837+4717: Dlog (N/O) = +0.8 • Dlog (N/O) ~ 0.5 for the typical O/H value • Pustilnik et al. 2004 • Common feature: Wolf-Rayet galaxies! • Winds of the WR stars may produce a N enrichment • However, the N enrichment should be very localized and a short episode • Observational problem: • [N II] ll6548,6583 are very close to Ha. • + broadening effects (kinematics) New data with enough spectral resolution and a systematic study is needed !! • ISIS @ 4.2m WHT : 0.36 A/pix • UVES @ 8.2m VLT: 0.024 A/pix Gaussian fit for Ha and [N II] in HS 0837+4717 using long-slit spectroscopic data from 6m BTA and a spectral resolution of 2.38 A/pix (Pustilnik et al. 2004).

  4. WN WC Emission lines of WR stars Wolf-Rayet galaxies A subset of emission-line and H II galaxies whose integrated spectra show broad emission features attributed to the presence of Wolf-Rayet stars. Blue WR Bump ~ 4650 Å WNL stars Blue WR Bump ~ 5800 Å WC stars • The number of WR stars with respect O stars is high, the burst shoud be short. • IMF extended to HIGH masses • Short-lived starburst(< 6 Myr) • Emission lines : • Recombination lines (RL) of H y He • Collisionally excitedlines (CEL) of O, N, S, Ne, Ar, Cl, Fe ... Last catalogue of WR galaxies140 objects(Schaerer et al. 1999),nowadays ~250 WR galaxies known

  5. III Zw 107 SBS 0948+532 • NGC 1741 • Mkn 1087 • Haro 15 • Mkn 1199 • Mkn 5 • POX 4 • UM 420 • III Zw 107 • IRAS 08339+6517 • IRAS 08208+2816 • NGC 1741 • Mkn 1087 • Haro 15 • Mkn 1199 • Mkn 5 • POX 4 • UM 420 • III Zw 107 • IRAS 08339+6517 • IRAS 08208+2816 • SBS 0926+606 • SBS 0948+532 • SBS 1054+365 • SBS 1211+540 • SBS 1319+579 • SBS 1415+437 • Tol 9 • Tol 1457-262 • Arp 252 • NGC 5253 • SBS 0926+606 • SBS 0948+532 • SBS 1054+365 • SBS 1211+540 • SBS 1319+579 • SBS 1415+437 • Tol 9 • Tol 1457-262 • Arp 252 • NGC 5253 SBS 1054+365 SBS 1415+437 UM 420 Mkn 5 Main aim: Study the massive star formation activity in WR galaxies and the role that interactions with dwarf objects have in the triggering mechanism of starbursts. SBS 1211+540 SBS 0926+606 IRAS 08339+6517 Á.R. López-Sánchez PhD Thesis (2006) supervised by C. Esteban (IAC): Massive star formation in WR galaxies We have performed a detailed analysis of a sample of 20 WR galaxies combining deep optical and NIR broad band and H imaging together with optical spectroscopy (long slit and echelle) data. The sample: See López-Sánchez & Esteban, 2008, paper I (in rev.) and II & III (in prep.)

  6. UM 420 • Located at 237 Mpc • At 16.5” from UGC 1809, located at 97 Mpc • It has very blue colors (U-B) = -0.8 • and a lot of Ha emission, with SFR = 3.7 Mo/yr UGC 1809 • Disturbed morphology and kinematics • New optical spectra (4.2m WHT) UM 420 López-Sánchez, 2006, PhD López-Sánchez & Esteban, 2008

  7. UM 420 • New optical spectra (4.2m WHT) • We detect both the WR bump and the He II l4686 emission line • Very good estimation of Te, Ne and C(Hb) • Excellent estimation of [N II] and Ha fluxes • 12 + log (O/H) = 7.95± 0.05 • log (N/O) = -1.11 ± 0.08 •  0.4 dex higher than expected!

  8. NGC 1741 (Mkn 1089) • NGC 1741 is the main member (A+C) in Hickson Compact Group 31 • A very luminous WR galaxy • A merger in progress!! • Optical spectrum (ISIS@WHT) • We detect the WR bump • Direct estimation of Te, Ne and C(Hb) • 12+log (O/H) = 8.22± 0.05 • log (N/O) = -1.12 ± 0.10 •  Typical values! López-Sánchez, Esteban & Rodríguez (2004a), ApJS

  9. 8.8’ The galaxy NGC 5253 • DHel= 4.0 Mpc (Karachentsev et al. 2004) • Scale: 19 pc / arcsec • Optical size: 5.0’  1.9’ • Classified as Im pec, H II starburst (NED), BCDG • One of the closest starbursts, observed at all wavelengths • It belongs to the M83 subgroup of the Centaurus Group • Deep analysis of its ionized gas using UVES@VLT López-Sánchez et al. 2007 NGC 5253 – B (blue) + V (green) + I (red) 2.5m du Pont telescope, Las Campanas Observatory, combined by Á.R. López-Sánchez NGC 5253 – V (blue) + I (green) + H (red) 2.5m du Pont telescope, LCO (V, I) + 1.5m CTIO (H) combined by Á.R. López-Sánchez

  10. A B C D NGC 5253: Deep VLT echelle spectroscopy • Four independent regions analized in detail: • Physical conditions: Ne, Te, reddening. • Chemical abundances: O, N, Ne, S, Cl, Ar, Fe, He, C • Kinematics of the ionized gas • 169 emission lines identified in region B 2 main results: • The confirmation of a localized chemical pollution, • The detection of O and C recombination lines. NGC 5253 – WFPC @ HST UV (blue) + H (green) + [S II] (red) Combined by Á.R. López-Sánchez H contours over the 2200 Å continuum image (Kobulnicky et al. 1997) and our VLT slit position. López-Sánchez, Esteban, García-Rojas, Peimbert & Rodríguez 2007, ApJ 656, 168 and López-Sánchez PhD Thesis

  11. 12+log O/H = 8.18 log N/O = – 0.91 12+log O/H = 8.28 log N/O = – 1.50 NGC 5253: Deep VLT echelle spectroscopy • Our deep VLT spectra CONFIRM the strong N overabundance in a particular zone and also suggest He enrinchement. • The comparison of our empirical stellar yields with • those obtained by stellar evolution models(Meynet & Maeder 2002) • empirical yields for ring nebulae associated to Galactic WR stars (Esteban et al. 1992) indicates that few WR stars CAN PRODUCE the observed N and He pollution • The amount of enrichment material needed is consistent with the mass lost by the number of WR stars estimated. López-Sánchez et al. 2007, ApJ 656, 168

  12. NGC 5253: Deep VLT echelle spectroscopy [O III] Ha [N II]

  13. NGC 5253: H I radio data New radio data of NGC 5253 from the LVHIS (Local Volume HI Survey) project using three different ATCA arrays Properties: • H I flux: 31.1  1.5 Jy km/s • H I mass: (8.0  0.4)  107 M • Dynamical mass: ~108 M López-Sánchez, Koribalski & Esteban 2007, NGC 5253 – H I map (blue) + R (green) + H (red)

  14. NGC 5253: H I radio data ESO 154-G023 ATCA H I velocity field H I velocity field: Rotating about the optical MAJOR axis? • Any kind of outflow? • Formation of a polar ring? • Interaction with M83 ~1 Gyr ago? • Disruption/accretion of a gas-rich companion López-Sánchez, Koribalski & Esteban 2007 and Kobulnicky & Skillman 2008 H I velocity field: Rotating about the optical MAJOR axis? • 

  15. Local starburst galaxy IC 10 • Starburst in the Local Group at ~660 kpc • 12+log (O/H) = 8.26(Garnett 1990) • A lot of WR stars! (26 studied byCrowther et al. 2003) • A good place to look for localized N enrichment!

  16. Local starburst galaxy IC 10 WR • Optical 3D spectra: PMAS@ 3.5m CAHA • 1”/pix, 0.8 A/pix • Detected WR signatures (WR-24 A, Crowther et al. 2003) • No detection of weak auroral lines (or affected by an ugly Hg emission line!) • But the maps do not show any evidence of localized N enrichment  López-Sánchez, López-Martín, Mesa-Delgado & Esteban, 2008, in prep.

  17. NGC 1512 NGC 1510 • NGC 1512: • SB(r)ab, • Z ~0.7 Zo • D = 9.5 Mpc • Many SF regions (Ha and UV-rich) • NGC 1510: • S0, BCD, WR • 5’ = 13.8 kpc from NGC 1512 12+log(O/H) ~ 7.95 log(N/O) ~ -1.2 Using data provided by Storch-Bergmann+ (1995) •  0.3 dex higher than expected! • ATCA H I mosaic(3.1 days integr. time) • Interaction features!! • Koribalski, López-Sánchez & McIntyre (2008, sub.)

  18. NGC 5253 A Mkn 1089 UM 420 X NGC 1510 NGC 5253 C Conclusions (I) Data of more galaxies with enough spectral and spatial resolution to get more definitive results (WORK IN PROGRESS)

  19. Conclusions (II) The multiwavelength analysis of a sample of Wolf-Rayet galaxies (López-Sánchez PhD, 2006; López-Sánchez & Esteban 2008) revealed that the majority of them (17 up to 20) show interaction features. New deep data are confirming this result in other WR galaxies. • Are interactions between dwarf objects the main triggering mechanism of starbursts, specially in BCDGs? • Is this fact related with the detection of N enrichment only in WR galaxies? (Very localized and short event consequence of the recent pollution of the WR winds?)

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