Stellar Population in LIRGs and ULIRGs

Transkript

1 Spectroscopy in Cosmology and Galaxy Evolution Granada 2007 Stellar Population in LIRGs and ULIRGs Rosa M. González Delgado Instituto de Astrofísica de Andalucía (CSIC) Granada, Spain Roberto Cid Fernandes (UFSC, Brasil) Enrique Pérez (IAA, Spain) Javier Rodríguez (Univ. Sheffield, UK) Clive Tadhunter (Univ. Sheffield, UK) Montse Villar-Martín (IAA, Spain)

2 Starbursts at the FIR: ULIRGs and LIRGs Definition (Sanders & Mirabel 1996) IR Luminosity: µm LIRGs: log (LIR)=11-12 (Lsol) ULIRGs: log(lir)=12-13 (Lsol) Cool ULIRGs: f25/f60 < 0.3 Warm ULIRGs: f25/f60 > 0.3 (mostly QSO) Arp220 (ULIRG) (HST/ACS(F814W) (F435W) Properties Nuclear Activity: HII, LINER, Seyfert. Fraction of AGN increases with LIR, at LIR>10 12 L AGN fraction ~70% Nuclear gas concentrations of up to Msol within 0.5kpc! If LIRGs, ULIRGs powered by star formation: SFR of up to 1000 Msol/yr Morphology: Spirals, close pairs, mergers. # mergers increases with LIR NGC6240 (LIRG) HST/ACS (F814W)

3 LIRGs and ULIRGs: cosmological relevance Pérez-González et al. (2005) Spitzer results (MIPS at 24 µm emission) SFR at z=1 is dominated by LIRGs 1<z<2 50% LIRGs and 50% ULIRGs Z>3 HyLIRGs LIRGs dominate the SFR density at z=1 SBs LIRGs ULIRGs Le Floc h et al. (2005)

4 ULIRGs: evolutionary sequence Merger-driven evolutionary sequence Are ULIRGs elliptical galaxies in formation? ULIRGs--warm ULIRGs--Quasars (or Radio Galaxies) Cool ULIRGs--warm ULIRGs--Quasars (or Radio Galaxies)? Are LIRGs members of the evolutionary sequence? Genzel et al 2001 Fundamental Plane The end product of ULIRGs mergers are intermediate mass (L*) elliptical galaxies

5 ULIRGs: advance mergers LIRGs: Spirals, close pairs, mergers? Mergers increase with LIR NGC695 IRAS NGC6670 UGC4881 HST/ACS images of LIRGs NGC6090 NGC5236 UGC6436 NGC2623 NGC6240

6 LIRGs-ULIRGs: evolutionary sequence Are QSOs and Radio Galaxies part of a post-merger evolutionary sequence between LIRGs-ULIRGs and normal elliptical galaxies? At what stage during the merger sequence do the radio jets and QSO activity occur? LIRGs sample: nearby LIRGs from the IRAS Bright Galaxy catalog (Sanders et al 2003) ULIRGs sample: 2 Jy ULIRGs (Sanders & Kim) Radio Galaxies: 1 Jy Radio Galaxies sample (Tadhunter et al ) QSOs sample: Post-SB QSOs selected from the SDSS survey Age Dating : To use the starburst ages as a clock to set the possible evolution between LIRGs-ULIRGs, Radio galaxies, QSOs and elliptical galaxies. Evolutionary synthesis models for young stellar populations Stellar evolutionary tracks Stellar libraries

7 Evolutionary Synthesis Models: Granada library + SED (Cerviño) : Synthesis Stellar library TLUSTY+ Kurucz + PHOENIX Teff= to 3000 K Log g= -0.5 to 5.0 Z= 0.04, 0.02, 0.008, and Spectral range= 3000 to 7000 Å 0.3 Å sampling González Delgado et al, 2005,MNRAS, 357, 945 Martins, González Delgado et al 2005, MNRAS, 358, 49

8 Evolutionary Synthesis Models: Granada library + SED (Cerviño) : Stellar Population synthesis models (González Delgado et al 2005, MNRAS, 357, 945)

9 LMC Stellar Clusters: Starlight results NGC1818 From CMD: [Fe/H]= -0.9 Log (Age)= 7.54 Granada models: Z004 (1/5 Zsol) -0.7 Log (Age mean)= 7.30 NGC1831 From CMD: [Fe/H]= 0.01 Log (Age)= 8.57 Granada models: Z019 (Zsol), 0.0 Log (Age mean)= 8.59

10 Starlight code (Cid Fernandes) ( inputs: SSP from evolutionary synthesis models Ages: (4, 10, 25, 40, 100, 280, 500, 890) Myr and (1.25, 5, 14) Gyr Metallicity: z019, z008, z004 outputs: x (%): fraction of the continuum light provide by each component Av: extinction σ and vrad A likelihood-weighted mean of combinations obtained from a Metropolis tour through the (x(%), Av) -space.

11 Age Dating Technique: Star Formation History Emission lines are masked

12 LIRGs: NGC 6090 results HST/ACS F814W Models LIRGs+ULIRGs inputs: High extinction for the very young stellar componentes (<= 10 Myr) F814W F435W F210W HST/ACS(HRC): F220W

13 Age Dating Technique: Stellar Population synthesis results for LIRGs NGC6670

14 Age Dating Technique: Stellar Population synthesis results for LIRGs High extinction: Na and CaII lines Na

15 Age Dating Technique: Stellar Population synthesis results for LIRGs High extinction: Na and CaII lines NGC6240 Na

16 Age Dating Technique: Stellar Population synthesis Results for LIRGs < 10 Myr Myr <x (%)> <Av> Log age (yr)

17 Age Dating Technique: Stellar Population synthesis Results for Arp220 HST/ACS (F435W) Arp220pa160_C C A Myr Na <x (%)> < 10 Myr Rodríguez Zaurín, Tadhunter, González Delgado, 2007, MNRAS, submitted Log age (yr)

18 Stellar Population in Radio Galaxies Intermediate (1 Gyr) age populations contribute to the continuum Evolution: LIRGs-ULIRGs--Radio Galaxies--Ellipticals

19 Stellar Population in Radio Galaxies Young (< 100 Myr) +intermediate (200 Myr-1Gyr) age populations contribute to the continuum Evolution: LIRGs-ULIRGs--Radio Galaxies--Ellipticals

20 Stellar Population in QSOs: Post-Starburst QSOs SDSS spectra: HOBL in absorption and broad Hα emission Transitions objects (LIRGs, ULIRGs and QSOs)

21 Post-Starburst QSOs: HST/ACS images Transitions objects (LIRGs, ULIRGs and QSOs)

22 wide-field MOS & SIFU intermediate resolution spectroscopy PI. Paco Prada (IAA) Cosmology & Extragalactic Astronomy Galactic Astronomy & Stellar physics Solar System Observing modes: MOS & IFU 06/09/2007 wide-field MOS f.o.v. = 20 #objects (fibers) ~ 1000 GTC focus: Nasmyth IFU 1000 fibers f.o.v. ~ 0.5 x 0.5 Intermediate Resolution Optical + IR(<1.7µm) Optical rest-frame of galaxies at z=1: Optical (R, I) and NIR (Y, J and H) wavelenghts

23 Summary LIRG-ULIRGs: Stellar Populations are consistent with models that predict an epoch of enhanced star formation coinciding with the first pass of the merging nuclei (age < 100 Myr), with a further episode of SF occuring as the nuclei merge together (age= few 100 Myr- 1Gyr). Young stellar populations are more extinguished than the intermediate age SP. YSP detected at optical wavelengths can not account for all the FIR of these galaxies Radio Galaxies: (e.g. 3C459) Young (<100 Myr) + intermediate age (few 100 to 1 Gyr) stellar populations Radio activity is triggered at the peak of SF in a major-rich merger Optical and FIR consistent to be on ULIRGs (e.g. 3C213) Intermediate age SP (1 Gyr) Radio source is triggered after the SB phase