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)

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)

StarburstsFrom 30 Dor to Lyman Break Galaxies

Cambridge 2004

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

Techniques to detect starbursts

1. UV emission: Wind lines

Techniques to detect starbursts

40

60

80

100

4000 4500 5000wavelength (Å)

log

Flu

x (

10-1

6 e

rg s

-1 Å

-1)

NGC 604

NGC 7714

Optical spectrum: Emission lines, WR features, HOBL (H8, H9,…) and HeI in absorption

After the first 6 Myr, HOBL in absorption dominate over nebular emission

González Delgado, Leitherer & Heckman (1999)

Previous work: Nuclear Starburst in Seyfert 2

NGC 7130

González Delgado et al (1998)

Heckman et al (1997)

HST+FOC

++ New HST ~ U-band snapshot survey by Schmitt et al 2004 (see POSTER#)

IC3639

210 pc

10-15

10-14

1200 1300 1400 1500 1600

Flu

x (

erg

s-1 c

m-2

Å-1)

wavelength (Å)

NV

SiIV

CIV

SV

SiII

IC

III

SiII

I+P

III

SiII

SiII

+O

I

CII S

iII

L NGC 7130

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

Previous work: Nuclear Starburst in Seyfert 2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

3700 3900 4100 4300

Flu

x (r

ela

tive u

nits

)

wavelength (Å)

IC 3639

NGC 7130

NGC 5135

Mrk 1073

Mrk 1066

Mrk 273

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

3700 3900 4100 4300

Flu

x (r

ela

tive u

nits

)

wavelength (Å)

IC 3639

NGC 7130

NGC 5135

Mrk 1073

Mrk 1066

Mrk 273

All Sy2 with nuclear Starbursts detected at UV show HOBS in absorption: intermediate age population

Nuclear Starburst in Seyfert 2: HOBS in absorption

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

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]/H Classical Liners : strong [OI] 6300/H

• Do LINERs & Transition Objects also have nuclear starbursts?• Are they similar to those in Seyfert 2s?• Is there a link between st pops & ionization?

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)

Stellar Population in LLAGNs

HST observations (from the archive): STIS G430L (2900 - 5700 Å) Nuclear spectra: 0.2x0.3 arcsec and 0.2x1

arcsec 28 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

Strong-[OI]: [OI]/H > 0.25 -------- LINERs

Weak-[OI]: [OI]/H < 0.25 -------- TOs

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

Weak-[OI] LLAGNs

•Many TOs (50%): are dominated by intermediate age, 100 Myr to 1 Gyr, population

•Many TOs (50%): have HOBL in absorption, and relative weak metal lines

Stellar Population in LLAGNs Non-detection of Woft-Rayet features

[OI]/H-Stellar population connection90% objects with HOBL:

(i) have weak metallic lines , (ii) are weak-[OI] LLAGNs

Strong-[OI]: LINERs

[OI]/H > 0.25 Weak-[OI]: TO

[OI]/H < 0.25

Summary of the tour through the data

“Young” LINERs Old LINERs

“Young” TOs Old TOs

Stellar pop / age

[OI]

/ H

Stellar population SynthesisSED@ (code by M. Cerviño)

Spectral Evolution (Geneva and Padova track at solar metallicity)

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

Models: González Delgado, Cerviño, Martins,

Leitherer, Hauschildt , 2004, MNRAS

Library: Martins, González Delgado, Leitherer,

Cerviño, Hauschildt, 2004, MNRAS

Stellar population Synthesis: ages

Young-TO : 108—109 yrOld-Liners and TO: >10 Gyr

Very young (<10 Myr) stellar population contributes 10% of the 4000 A light in the young-TOEPS 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

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

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

Stellar population gradientRadial profiles of Ew(CaIIK)

Ew(CaIIK) < 15 A--- Intermediate age stellar populationYoung-TO have a diluted profiles

The dilution is produced by the intermediate age population

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

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

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

Sizes of the intermediate age stellar population

(< 100 pc)

)(

)0()(

)/(11)()(1)()(

2

W

WW

arWrfWrW

w

X(%

)S

B

FWHM=size

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

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

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.

Is the star formation proceed at a residual level?UV emission in the core of some Young-TO:NGC 4303

STIS/MAMA (FUV)

Size of the central knot (nucleus): 3 pc

STIS/MAMA (G140L)

• E(B-V)= 0.1•Age= 4 Myr• Mass= 2-3 X 105 Msol • Lbol= 2 x 108 Lsol

Colina, González Delgado, Mas-Hesse, Leithere, Jiménez Jailon, 2002,ApJ, 579, 545

UV emission: evidence that the star formation proceeds at some level in Young-TO

STIS (G140L) NGC 3507 and NGC

4303

NGC 4569 WFPC2 (F220W)A compact but

resolved source: Stellar cluster?

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.