Stellar populations of quasar host galaxies

Transcription

1 Knud Jahnke AIP Galaxies division Hauskolloquium

2 Introduction/motivation Multicolour imaging On-nucleus spectroscopy What does this teach us? Outlook Overview

3 Introduction

4 Introduction HE z=0.068 Sb-Sc spiral

5 Introduction HE z=0.085 E0 elliptical

6 Introduction Nuclear model (Urry & Padovani 1995) nuclear black hole accretion disk relativistic jet dusty torus broad line region narrow line region

7 Introduction Knowledge quasars are rare: 10 (Wisotzki, Kuhlbrodt, Jahnke 2001) 4 compared to field galaxies of equal L massive black holes (BH) likely in all galaxies masses of BH connected to mass of surrounding galaxy (Magorrian et al. 1998) coupled evolution of BH and host galaxy! short duty cycle of quasars not an isolated phenomenon! quasar phase snapshot of galaxy evolution?

8 Introduction (McLure & Dunlop 2002)

9 Introduction morphology E to Sc/SBc, no Irr symmetric to disturbed for higher L: more E, less interaction and companions (e.g. Dunlop et al. 2001, Kuhlbrodt et al. 2003) luminosities correlation: bulge L to nuclear L (McLeod et al. 1999, McLure et al. 2001, 2002) luminosity function (LF) compatible to early type field galaxies (Wisotzki, Kuhlbrodt, Jahnke 2001) interaction trigger for activity?/! supporting hierarchical clustering

10 Introduction Spectral information: a new dimension compare morphology vs. stellar content vs. gas content search for spectroscopic signs of past tidal interaction spectral information very valuable

11 Introduction Colour and spectroscopic studies (multi-)colour studies expensive few studies contradictory results (normal vs. blue) spectroscopic studies expensive and difficult data treatment larger studies: Boroson et al , Nolan et al. 2001

12 Introduction Two spectroscopic approaches optical/nir multicolour broad band imaging long spectral baseline, coarse data on-nucleus spectroscopy high resolution, shorter baseline, expensive, difficult separation Problem in both cases: extraction of the host galaxy flux Solution in both cases: spatial modelling of host and nucleus

13 Multicolour imaging

14 Multicolour imaging

15 Multicolour imaging observe complete low-z quasar sample in B,V,R,I,J,H,K s remove nuclear light contribution investigate morphologies (light distribution, ellipticities, arms, asymmetries,...) colours (optical, optical NIR) stellar populations (evolution synthesis model fits) compare to inactive galaxies

16 MV (H050 km s 1 Mpc 1, q 00 5, Λ0) V objects, z 0 2, selected from HES, complete from 611 deg2, subsample of Köhler et al Sample selection Multicolour imaging

17 B 2 380/730 0 B NOT/ALFOSC / /pixel 0 39/pixel 0 29/pixel Band Instrument Objects t [s] ESO 3.6m/EFOSC2 12 B 300 Scale 61/pixel 34/pixel 39/pixel Mostly ESO telescopes: Observations Multicolour imaging

18 Multicolour imaging Two-dimensional spatial modelling nuclear shape and flux unknown Two-dimensional spatial modelling (PAMDAI, developed and tested by B. Kuhlbrodt (Kuhlbrodt, Wisotzki, Jahnke 2003)) properties of PAMDAI: all stars in the field used for point spread function (PSF) shape estimate modelling of spatial PSF variations precise estimate two-dimensional host galaxy model, one/two components two-dimensional convolution of host model with PSF adaptive subpixel grid for high efficiency best parameters via downhill-simplex χ 2 minimisation

19 " φ! fully elliptical: rr ε F 0 exp F r 7 67 r r (de Vaucouleurs & Capaccioli 1979) 1 4 de Vaucouleurs spheroidal: exponential disk: F r F 0 exp 68 1 r r (Freeman 1970) Host galaxy models Multicolour imaging

20 Multicolour imaging

21 Multicolour imaging Modelling and photometry homogeneous treatment of all bands identical fit areas identical masking identical final geometry identical photometry only in few cases variable scale lengths no bias in colours

22 Multicolour imaging Modelling results

23 # qb 1.5 kpc 10.4 kpc r1 2 a0 82 like luminous inactive ellipticals spheroidals high inclinations missing 3.5 kpc r kpc 2 unified model disks 9 disks, 9 spheroidals, 1 disk + bulge successful for all but 7 objects in B Results Multicolour imaging

24 Multicolour imaging Colours B V V R R I I J J H H K V K Ellipticals Inactive (0.12) QSO host sample (0.25) Disks (Sb) Inactive (0.36) QSO host sample (0.20) K -corrections: Fukugita et al (optical), Mannucci et al (NIR) inactive colours: Fukugita et al (optical), Fioc & Rocca-Volmerange 1999 (optical-nir, NIR-NIR)

25 Multicolour imaging

26 Multicolour imaging Stellar population models SSP model family by Bruzual & Charlot 1996 Scalo IMF solar metallicity but: general results not depending on choice of model! 0.1, 0.7, 2, 6, 14 Gyr + continuous star formation model (CSF) 1 SSP fit: age free 2 SSP fit: 0.1 Gyr fixed, second age free, relative mixing free χ 2 minimisation fitting to 6/7 data points

27 Multicolour imaging

28 Multicolour imaging Model fitting results objects with B missing not reliable 1 SSP: very similar for disks and ellipticals only 1 object each preferring 6 Gyr, none 14 Gyr 0.1 Gyr + 1 SSP: all consistent with 2 Gyr and CSF $2% of 0.1 Gyr required by only 2 disks intermediately young populations, also for E; evolved populations ruled out consistent with V K colours alone

29 &% as blue as late type disks SSP model fitting consistent with CSF or 2 Gyr population ellipticals: disks: largely normal, slightly bluer than inactive Sb M M correlation confirmed wide range of morphologies and asymmetries disks and ellipticals found Multicolour imaging: summary Multicolour imaging

30 On-nucleus spectroscopy

31 ' problem: very high contrast nucleus host solution: spatial modelling, similar to imaging wanted: on-nucleus spectroscopy control of nuclear residuals difficult sampling far outside nuclear region potentially boring drawbacks: off-nucleus spectroscopy, r nuclear residuals 3 avoiding nucleus plus removal of technique so far: On-nucleus spectroscopy On-nucleus spectroscopy

32 On-nucleus spectroscopy (RQQ) WHT (Hughes et al. 2000, Hutchings & Crampton 1990)

33 ' problem: very high contrast nucleus host solution: spatial modelling, similar to imaging wanted: on-nucleus spectroscopy control of nuclear residuals difficult sampling far outside nuclear region potentially boring drawbacks: off-nucleus spectroscopy, r nuclear residuals 3 avoiding nucleus plus removal of technique so far: On-nucleus spectroscopy

34 Multi-object-spectroscopy vs. long slit spectroscopy

35 λ r

36 very important: use all information available morphological parameter input from imaging slow wavelength dependence of parameters PSF: analytical model plus empirical correction host: exponential disk or de Vaucouleurs spheroidal reduction of parameters in successive steps final step: nuclear and host flux only free parameters 2d nuclear spectrum model 2d host galaxy spectrum

37 λ r

38 Quality of fit diagnostics resulting spectra should be positive no forbidden lines in absorption broad emission lines not in absorption shape of residual (=quasar nucleus host) broad band colours need to be reconstructable comparing different PSF stars comparing different images

39 The EFOSC sample 8 object subsample of multicolour sample ESO 3.6m with EFOSC: wavelength range: Å resolution: (250 /pixel integration time: s morphological parameters existing

40 The FORS sample 10 (total 20) objects from HES, z 0 33, MB 24 Collaboration with F. Courbin et al. (Liége) VLT Antu with FORS1, MOS: wavelength range: Å (3 grisms) resolution: ( /pixel integration time: s morphological parameter: B. Kuhlbrodt, L. Wisotzki

41 Modelling results EFOSC EFOSC: HE , extracted spectra: total, nucleus, host, residual

42 EFOSC: HE , extracted spectrum: host galaxy

43 Comparison to broad band colours and models HE : 100% 2 Gyr (disk)

44 HE : 100% 2 Gyr (elliptical)

45 Modelling results FORS FORS: HE , B grism: total, nucleus, host, residual

46 FORS: HE , B grism: host galaxy

47 FORS: HE , R grism: total, nucleus, host, residual

48 FORS: HE , R grism: host galaxy

49 FORS: HE , B grism: total, nucleus, host, residual

50 FORS: HE , B grism: host galaxy

51 FORS: HE , R grism: total, nucleus, host, residual

52 FORS: HE , R grism: host galaxy

53 Comparison to models HE : 100% CSF vs. 97.5% CSF + 2.5% 0.1 Gyr

54 HE : 53% 0.7 Gyr + 47% 1 Gyr (elliptical!)

55 Modelling results EFOSC successful: 3 successful (after modification): 4 S/N too low: 1 FORS successful: 2 successful (after modification): 5 S/N too low: 3

56 Rotation: emission lines C S G S C

57 Rotation EFOSC gas rotation for 2 disks, 1 elliptical clearly no gas rotation for 1 elliptical stellar rotation for 2 disks clearly no stellar rotation for 1 elliptical rotation velocities gas: km/s (observed) stars: km/s (observed)

58 Rotation FORS gas rotation for 7 of 8 (of these 3 ellipticals) clearly no gas rotation for 1 elliptical stellar rotation for 2 disks clearly no stellar rotation for 1 elliptical rotation velocities gas: km/s (observed) stars: km/s (observed) spatially resolved for 4 objects rotation curves

59

60 Line ratios determine ionisation source, hot stars vs. AGN (Veilleux & Osterbrock 1987): [O III] 5007/Hβ vs. [N II] 6583/Hα [O III] 5007/Hβ vs. [S II] ( )/Hα [O III] 5007/Hβ vs. [O I] 6300/Hα temperature: [O III] ( )/4363 electron densities: [S II] 6716/6731

61

62 On-nucleus spectroscopy: summary separation working, multicolour imaging fluxes reproduced spatial resolution achievable emission and absorption lines detectable quality depending on PSF quality, S/N, nucleus-to-host ratio

63 On-nucleus spectroscopy: summary disks: no signs of strong starbursts gas ionised by hot stars and/or nucleus in total very similar to inactive spirals ellipticals: young populations consistent with multicolour imaging no signs of old evolved populations excluded: only added starburst (massive) rotating gas disks in several objects ionised by nucleus

64 Discussion

65 Discussion Nolan et al. 2001: higher luminosity quasars only ellipticals with red, evolved population weak or absent gas emission no bias from off-nucleus position expected Boroson et al. 1985: luminous quasars: red spectra + weak gas lines or blue spectra + strong gas lines less luminous quasars: weak or strong gas lines contradictory results?

66 created in major merger of two disks merger induces nuclear activity dynamically transformed in merger elliptical morphology stellar populations as in progenitor galaxies colours, spectra (re-)creation of gas disk after merger? timescale problem? surface density of gas disk low no strong starburst passive evolution to red elliptical within 1 Gyr intermediately luminous (L 2L) ) elliptical host galaxies: Proposal: scenario supporting/supported by hierarchical merging Discussion

67 minor merger Discussion luminous elliptical host galaxies: activity created by more massive later in mass evolution disk host galaxies: activity created by minor merger events (slightly) enhanced SFR distortions, companions direct sign for hierarchical clustering? creation of luminous ellipticals caught in the act?

68 Discussion Open questions special initial conditions required for merger? gas disk creation what happens with other merger geometries? ULIRGs? radio galaxies? why is the gas/ionisation geometry so different in disks and ellipticals? obscuring material close to nucleus? the dust torus itself?

69 Outlook techniques: more detailed emission line modelling improved PSF determination extention to integral field spectroscopy data absorption line diagnostics ages/metallicities/dust velocity dispersions central masses more data: second half of FORS sample, integration times doubled multicolour-north, second sample from Palomar-Green 3d spectroscopy: PMAS, VIMOS luminosity dependence of spectral properties correlation broad-line shape and host properties with VIMOS host galaxy spectra available to z (0 5

70 Advertisement! More on quasar host galaxies: Tuesday, January 28, 16:00 Extragalactic Science Club Björn Kuhlbrodt (Hamburg) The luminosity function of QSO host galaxies