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Starbursts in Low Luminosity Active Galactic Nuclei Rosa M. González Delgado

Starbursts From 30 Dor to Lyman Break Galaxies Cambridge 2004. Starbursts in Low Luminosity Active Galactic Nuclei Rosa M. González Delgado Instituto de Astrofísica de Andalucía (CSIC, Granada, Spain) Roberto Cid Fernandes Universidade Federal de Santa Catarina (Florianópolis, Brasil).

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Starbursts in Low Luminosity Active Galactic Nuclei Rosa M. González Delgado

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  1. Starbursts From 30 Dor to Lyman Break Galaxies Cambridge 2004 • Starbursts in Low Luminosity • Active Galactic Nuclei • Rosa M. González Delgado • Instituto de Astrofísica de Andalucía (CSIC, Granada, Spain) • Roberto Cid Fernandes • Universidade Federal de Santa Catarina (Florianópolis, Brasil) • L. Colina (IEM-CSIC, Spain), T. Heckman (JHU, USA), C. Leitherer and L. Martins (STScI, USA), J.M. Mas-Hesse (CAB-CSIC, Spain), E. Pérez (IAA-CSIC, Spain), T. Storchi-Bergmann (UF Porto Alegre, Brasil), H. Schmitt (NRAO, USA), D. Schaerer (Geneva)

  2. Outline • Motivation: • Techniques to detect Starbursts in the nuclei of active galaxies • Starbursts in active galaxies: Seyferts, Radio Galaxies, QSOs • Low Luminosity Active Galactic Nuclei (LLAGN) • Sample and observations of LLAGNs • Stellar population in the nuclei(Cid Fernandes et al. 2004, ApJ, 605, 105 & González Delgado et al. 2004, ApJ, 605, 127) • Stellar population gradient(Cid Fernandes et al. 2004, MNRAS, submitted) • Central morphology(González Delgado et al. in preparation) • UV-optical SED(González Delgado et al. in preparation) • Connection LLAGN-Starbursts

  3. Techniques to detect starbursts • UV emission: Wind lines

  4. Techniques to detect starbursts Optical spectrum: Emission lines, WR features, HOBL (H8, H9,…) and HeI in absorption González Delgado, Leitherer & Heckman (1999) After the first 6 Myr, HOBL in absorption dominate over nebular emission

  5. Previous work: Nuclear Starburst in Seyfert 2 NGC 7130 IC3639 HST+FOC 210 pc +New HST ~ U-band snapshot survey by Schmitt et al 2004 (see POSTER#) González Delgado et al (1998) Heckman et al (1997)

  6. Previous work: Nuclear Starburst in Seyfert 2 • Nuclear Starburst of size a few 100 pc (similar size to NLR) • Starburst dominates the UV light • 1010< LBol< 1011 L: Similar to the estimated AGN luminosity

  7. Nuclear Starburst in Seyfert 2:HOBS in absorption All Sy2 with nuclear Starbursts detected at UV show HOBS in absorption: intermediate age population 40% of Seyfert 2 show compact (100 pc) and powerful (L>10 10 Lsol) nuclear starburst González Delgado et al (1998) González Delgado, Heckman, Leitherer (2001) Cid Fernandes et al (2001) HOBL

  8. Low-Luminosity AGN (LLAGNs) LLAGNs They are located in about 30% of the nearby and luminous galaxies (BT< 12.5) (Ho, Filippenko & Sargent 1995) • Liners/HII (Transitions Objects=TO) (weak Liners): weak [OI]/Ha • Classical Liners : strong [OI] 6300/Ha Previous work • Massive stars (Filippenko & Terlevich 1992) • Starburst in the Wolf-Rayet phase (Barth & Shields 2000) • Post-AGB (Binette et al 1994) and PN (Taniguchi et al 2000) • Do LINERs & Transition Objects also have nuclear starbursts? • Are they similar to those in Seyfert 2s? • Is there a link between st pops & ionization?

  9. Stellar Population in LLAGNs • Ground-based observations: • Telescope: NOT (ALFOSC) and 2.1m at KPNO • 3400 - 5500 Å • Nuclear spectra: 1x1 arcsec (100 pc) • 51 LLAGNs + 2 HII + 7 non-active galaxies • HST observations (from the archive): • STIS • G430L (2900 - 5700 Å) • Nuclear spectra: 0.2x0.3 arcsec and 0.2x1 arcsec • 28 LLAGNs • Strong-[OI]: [OI]/Ha > 0.25 -------- LINERs • Weak-[OI]: [OI]/Ha < 0.25 -------- TOs

  10. Strong-[OI] LLAGNs • Strong-[OI] LLAGNs: • All Liners (>90%) are dominated by old stellar population. • Very few Liners (< 10%) have intermediate age, 100 Myr to 1 Gyr, population

  11. Weak-[OI] LLAGNs • Many TOs (50%): • have HOBL in absorption, and relative weak metal lines • Many TOs (50%): • are dominated by intermediate age, 100 Myr to 1 Gyr, population

  12. Stellar Population in LLAGNsNon-detection of Woft-Rayet features

  13. [OI]/Ha-Stellar population connection90% objects with HOBL: (i) have weak metallic lines , (ii) are weak-[OI] LLAGNs • Strong-[OI]: LINERs [OI]/Ha > 0.25 • Weak-[OI]: TO [OI]/Ha < 0.25

  14. Summary of the tour through the data “Young” LINERs Old LINERs “Young” TOs Old TOs [OI] / Ha Stellar pop / age

  15. Stellar population SynthesisSED@ (code by M. Cerviño) High spectral resolution models (3000-7000 A)* Isochrones: Padova and Geneva groups*Stellar library: 2 solar, solar, half and 1/10 solar* Stellar atmospheres: TLUSTY, Kurucz, and Phoenix* Spectral sampling 0.3 A Spectral Evolution (Geneva and Padova track at solar metallicity) Models: González Delgado, Cerviño, Martins, Leitherer, Hauschildt , 2004, MNRAS Library: Martins, González Delgado, Leitherer, Cerviño, Hauschildt, 2004, MNRAS

  16. Stellar population Synthesis: ages Young-TO : 108—109 yrOld-Liners and TO: >10 GyrVery young (<10 Myr) stellar population contributes 10% of the 4000 A light in the young-TO EPS algorithm by Cid Fernandes et at (2001): inputs:Base of synthetic spectra covering from few Myr to 13 Gyr at different metallicitiesoutputs: x (%), Avcorrespond to a likelihood-weighted mean of combinations obtained from a Metropolis tour through the (x, Av) -space

  17. Summary of the nuclear spectra (100 pc) • High Order Balmer Absorption Lines are very common (~ 50% of TOs) • No WR bump • Intermediate age populations (108 – 109 yr) are very common (~ 50% of TOs) • Very young starbursts ( ≤ 107 yr), if present, are very weak

  18. Stellar population gradientSpatially resolved spectra (500 extractions in 47 objects)

  19. Stellar population gradientRadial profiles of Ew(CaIIK) Ew(CaIIK) < 15 A--- Intermediate age stellar populationYoung-TO have a diluted profilesThe dilution is produced by the intermediate age population

  20. Extinction profilesYoung-TO have larger central extinction than Old-LLAGN • The extinction profiles of young-TO are more complex that those of old LLAGN, which are often approximatelly flat. • Young-TO have centrally peaked extinction profiles • Young-TO have larger central extinction (Av= 0.5 mag) than Old-LLAGN

  21. Central morphology: HST+WFPC2 (optical filter)Young-TO have dustier central emission than Liners

  22. Central morphology: HST+WFPC2 (optical filter)Old-TO and Old-Liners

  23. Sizes of the intermediate age stellar population(< 100 pc) X(%) SB FWHM=size

  24. Comparison with Seyfert 2s & speculations... • “Young” TOs evolve to Old TOs or Old LINERs on ~ 1 Gyr • Only starburst+Seyfert 2 composites may evolve to “Young” TOs • Other Seyfert 2s will end up as Old LINERs or Old TOs

  25. Comparison with Radio Galaxies(FRII) Tadhunter, Robinson, González Delgado, et al 2004, MNRAS,submitted Are ULIRG the precursors of Radio Galaxies with (Post)-Starbursts?

  26. Summary of the optical results • Old-TO and Old-Liners have spatially uniform stellar population with very little amount of dust. • Young-TO have stronger stellar population gradients, intermediate age population, and moderate dust content. • This population is compact (< 100 pc) and has mass 107—108 Msol • These intermediate age populations were 10-100 times more luminous in their formation epoch, at which time massive stars (starbursts) dominated the bulge light.

  27. Is the star formation proceed at a residual level? UV emission in the core of some Young-TO: NGC 4303 STIS/MAMA (G140L) • E(B-V)= 0.1 • Age= 4 Myr • Mass= 2-3 X 105 Msol • Lbol= 2 x 108 Lsol STIS/MAMA (FUV) Size of the central knot (nucleus): 3 pc Colina, González Delgado, Mas-Hesse, Leithere, Jiménez Jailon, 2002,ApJ, 579, 545

  28. UV emission: evidence that the star formation proceeds at some level in Young-TO STIS (G140L)NGC 3507 and NGC 4303 NGC 4569WFPC2 (F220W)A compact but resolved source: Stellar cluster?

  29. Conclusions • Young-TO are clearly separated from the Old-TO and Liners in terms of the properties and spatial distribution of the stellar population. • Young-TO have stronger stellar population gradients, a luminous intermediate age stellar population which is concentrated in the nucleus (< central 100 pc) and larger amount of extinction than Old-TO and Liners. • These Young-TO could be classified as Starbursts 1 Gyr ago or as “composite” Seyfert 2 (Seyfert + nuclear starburst) • Young-TO will become old-LLAGN in a few Gyr.

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