Stellar Populations in the Central 10 pc of low-luminosity AGNs and Seyfert 2 Marc Sarzi (University of Hertfordshire, UK) In Collaboration with H.-W. Rix, J. Shields, A. Barth, L. Ho, A. Filippenko, W. Sargent, G. Rudnick, D. McIntosh, R. Pogge, P. Martini

OUTLINE The SU rvey of N earby N uclei with S TIS The SU rvey of N earby N uclei with S TIS Nuclear Stellar Populations of LLAGN Nuclear Stellar Populations of LLAGN A STIS survey of Seyfert 2s A STIS survey of Seyfert 2s New method New method Preliminary results… Preliminary results… ! Both studies are unique in that they probe the very central regions of galaxies, within ~ 10pc from the center ! Both studies are unique in that they probe the very central regions of galaxies, within ~ 10pc from the center

SUNNS: SUrvey of Nearby Nuclei with STIS G430L and G750M spectra for 24 S0-Sbc galaxies within 17 Mpc with EM-lines to study: G430L and G750M spectra for 24 S0-Sbc galaxies within 17 Mpc with EM-lines to study: Emission-Line Kinematics (Sarzi et al. 2001, 2002; Shields et al. 1999; Ho et al. 2000, 2002) Emission-Line Kinematics (Sarzi et al. 2001, 2002; Shields et al. 1999; Ho et al. 2000, 2002) Emission-Line Diagnostic (Shields et al. 2006) Emission-Line Diagnostic (Shields et al. 2006) Nuclear Stellar Populations (Sarzi et al. 2005) Nuclear Stellar Populations (Sarzi et al. 2005)  Relative Role in powering AGNs of Accretion onto SMBH and Star Formation

The Template Superposition Method 1.Select a 1 st guess template 2.Find optimal kinematical broadening with 1 st guess 3.Broaden all templates with the same LOSVD and get templates weights 4.With optimal templates run again through 2. & 3. to improve both LOSVD and templates weights Reddening by dust or a polynomial adjustment can be included in 3. Reddening by dust or a polynomial adjustment can be included in 3. From Bruzual & Charlot (2003) flux (arbitrary units)

Multiple Starburst Models  Mostly old and reddened objects.

NGC 4203 A Liner with very broad H   True AGN, Powered by a SMBH From Shields et al. (1999) See also Ho et al. (2000) for NGC 4450

Luminosity-Weighted Mean Ages  80% of our nuclei are very old (>3 Gyr). This holds when considering super-solar metallicities.

Very Young Stars: can they power EM-lines?  Seyferts: no hope. ● L1: not really ○ L2: maybe just 1 ∆ T: 2 yes, 2 no, 2 don’t know  H II : ok for the 2 with EM-lines  With such very conservative 3-  upper limits… This at 10 pc. At ~100 it would be worse.

Young Stars: Correlations?

SUNNS Conclusions 1) The Central 10 Parsec of Sb-S0 bulges are in ~80% of the cases dominated by very old (> 3Gyr) stars. 3) Reddening or Super-Solar metallicities do not change these results. 2) ~25% of them need some stars younger than 1Gyr, and their incidence depends on the nuclear classification. 4) Only 1 galaxy harbours a clearly young (3-Myr) Nuclear Cluster 5) Only 2 out of 5 H II nuclei have young stars or emission. Star formation in H II -nuclei may be mainly circumnuclear. 6) O-stars could contribute to ionization of some Liner2 and Transition objects. Gonzales-Delgado et al. (2004) reached independently similar conclusions Gonzales-Delgado et al. (2004) reached independently similar conclusions

Seyfert 2 Central Populations G430L and G750M spectra for 19 nearby Seyfert 2 galaxies to zoom in the central 10 pc to: G430L and G750M spectra for 19 nearby Seyfert 2 galaxies to zoom in the central 10 pc to: Reveal the presence of BLRs hidden in ground-based observations Reveal the presence of BLRs hidden in ground-based observations Understand whether ‘intrinsic’ Sy2 objects could exist Understand whether ‘intrinsic’ Sy2 objects could exist Investigate the star formation history on small scales Investigate the star formation history on small scales  Now, this will more difficult than in the case of the SUNNS survey

Seyfert 2 Central Populations Abundant nebular emission reduces the information about the stellar population content. Abundant nebular emission reduces the information about the stellar population content. Iterative procedures involving masking to narrow the regions contaminated by emission may not converge. Iterative procedures involving masking to narrow the regions contaminated by emission may not converge. A New Method  Solution: a simultaneous fit of emission and absorption lines, treating the emission-lines as Gaussian template in addition to treating the emission-lines as Gaussian template in addition to the stellar templates! the stellar templates! (see also Sarzi et al. 2006, for an application to the SAURON survey) (see also Sarzi et al. 2006, for an application to the SAURON survey)

Seyfert 2 Central Populations  Furthermore: with the STIS wavelength range we can constrain the: A) Diffuse reddening affecting gas + stars A) Diffuse reddening affecting gas + stars (continuum slope) (continuum slope) B) Internal reddening affecting gas B) Internal reddening affecting gas (Balmer decrement) (Balmer decrement) C) Contamination of Balmer emission in the age-sensitive C) Contamination of Balmer emission in the age-sensitive corresponding absorption feature corresponding absorption feature A New Method G430L G750M

Seyfert 2 Central Populations Preliminary Results Old Nuclei (10Gyr) - 9/21 including 3 Sy2 from SUNNS ) Old Nuclei (10Gyr) - 9/21 including 3 Sy2 from SUNNS )

Seyfert 2 Central Populations Preliminary Results Nuclei of Intermediate Age (1-2Gyr) - 2/21 Nuclei of Intermediate Age (1-2Gyr) - 2/21

Seyfert 2 Central Populations Preliminary Results Old Nuclei with O-stars - 10/21 (2 with BLR, all with strong emission) Old Nuclei with O-stars - 10/21 (2 with BLR, all with strong emission)

Seyfert 2 Central Populations Discussion The finding of a blue continuum could be consistent with star formation concomitant to intense AGN activity, which would subsequently fade. The finding of a blue continuum could be consistent with star formation concomitant to intense AGN activity, which would subsequently fade. Alternatively, we could be looking at the accretion source without a BLR. Alternatively, we could be looking at the accretion source without a BLR. We must keep in mind the relative shortage of intermediate stellar populations, which would be inconsistent with frequent and related star-formation and AGN episodes ! We must keep in mind the relative shortage of intermediate stellar populations, which would be inconsistent with frequent and related star-formation and AGN episodes ! Future work will include seeking evidence for a) absorption feature dilution, b) correlation between the luminosity of the blue continuum and the Eq. Width of emission, c) evidence for an impact of O-star in the emission-line ratios, and WR features Future work will include seeking evidence for a) absorption feature dilution, b) correlation between the luminosity of the blue continuum and the Eq. Width of emission, c) evidence for an impact of O-star in the emission-line ratios, and WR features