Induced Nuclear Activity in nearby isolated galaxy pairs of different morphologies

Transcription

1 Induced Nuclear Activity in nearby isolated galaxy pairs of different morphologies J. Jesús González (IA-UNAM, México) Deborah Dultzin, Francisco Hernández Ibarra, Yair Krongold Asención del Olmo & Jaime Perea (IAA, Spain) Interactive Galaxies & Binary Quasars: A Cosmic Rendezvous Trieste, Italy April

2 Objectives 1. STUDY NUCLEAR ACTIVITY FREQUENCIES IN WELL DEFINED SAMPLES OF LOCAL GALAXY PAIRS (SEP<100 KPC) & ISOLATED GALAXIES UNDER THE EFECT OF TIDAL FORCES. 2. TO DISTINGH AND TRACE LIKNS AMONG TYPES OF NUCLEAR ACTIVITY: AGN (SEYFERT TYPES 1, 2 OR LINER S) AND STARBURST. 3. TO FRAME DE OBSERVED SAMPLES IN TERMS OF UNIFIED SCENARIOS THAT INCLUDE POTENTIAL EVOLUTIONARY EFFECTS 4. TO EXPLORE TIDAL EFFECTS IN INTERACTIN PAIRS AS A FUNCTION OF SEPARATION AND MORPHOLOGY (B/D)

3 Our samples in this talk To study the secular effects of interactions in triggering BH accretion (AGN activity) we started exploring two well-defined samples of Bright galaxies in the local field: 1. The Catalog of Isolated Galaxy Pairs (CIPG, Karachentsev 1972) Similar mass pairs without a 3 rd comparable galaxy nearby. Further divided in 3 morphological classes: a) (E+E) isolated galaxy pairs (red-red or dry ) b) (S+S) isolated galaxy pairs (blue-blue or wet ) c) (E+S) isolated galaxy pairs (mixed encounters) 2. The Catalog of Isolated Galaxies (CIG, Karachentseva 1973) Northern high galactic latitude (b>20) from PSS (m zw! 17.5) Drawn with same Isolation and Morphology-Classification Criteria Share the same diameter, magnitude and Vr distributions.

4 Isolated Galaxies & Isolated Pair Catalogues Represent extremely consistent samples to study AGN frequencies in the low-density (field) local environment (Vr < 16,000 km/s) of galaxies that have not yet experience a major merger event We have revised them for an homogenous Morphology-Classification Vast majority of CIPG are physical pairs (spectroscopic confirmation) We have carried out two studies so far: 1. From all the available SDSS-DR7 spectra of both CIG & CIPG catalogues (Isolated Galaxies & Isolated Pairs). 2. Obtained Long-Slit spectra (SPM) of essentially all the Spirals in Mixed-Morphology (E+S) Isolated Pairs.

5 1 st Sample: CIG & CIPG galaxies in SDSS-DR7 900 galaxies (40% of CIG & CIPG) in SDSS-DR7 from which we could extract meaningful (host-subtracted) nuclear spectra for ~800 Measured the strongest emission lines (with S/N > 3 in EW): H!, [O III] "5007, [O I] "6300, H#, [N II] "6584 and [S II] ""6717,31 Classified the Nuclear Activity from BPT diagnostic diagrams (Baldwin, Phillips & Terlevich, 81; Kewley et al., 01-06; Kauffmann et al., 03) considering the four classical line-ratios: [O III]/H!, [N II]/H#, [S II]/H# & [O I]/H# 5

6 SDSS-DR7 Sub-sample of CIG & CIPG Combination of PCA and population synthesis were fitted to each observation to subtract the host-galaxy spectrum! before subtraction! after host subtraction In many cases this was essential even to detect (not to mention fit) and measure emission lines accurately

7 Isolated Galaxies (CIG) in SDSS-DR7

8 Isolated Galaxies (CIG) in SDSS-DR7

9 Members of Local Isolated Galaxy Pairs (CIPG) in SDSS-DR7 e.g. subsample of members of E+S pairs

10 Type 1s are extremely rare in both samples (not a single Sy 1.0) Activity Enhancement is not striking when looking at Isolated Pairs all together But... Enhancement is strong in some pair morphologies: Only LINER activity is (E+E) Isolated Pairs AGN are significantly more frequent in mixed morphology Pairs 10

11 AGN activity in Local Isolated (CIG) Nuclei (emission detected in SDSS-DR7 spectra) ISO Gal HII AGN Sy LINER E+S0 24 % 13/55 Sa 32 % 13/41 76 % 42/55 68 % 28/41 38 % 62 % 43 % 57 % Sb 51 % 66/130 Sc+Sm 72 % 106/147 Total 53 % 198/ % 64/ % 41/ % 175/ % 36.5 % 41.5 % 58.5 % 49% 51% Morphology is important to draw control samples of AGN galaxies SF steadily decrease with B/D ratio, AGN are more frequent in early types LINER dominates in Es Seyfert peak in Sb

12 AGNs in members of Isolated (E+S) pairs (CIPG) (emission detected in SDSS-DR7 spectra) Paired Gal HII AGN Sy LINER E+S0 22 % 8/36 Sa 31 % 4/13 78 % 28/36 69 % 9/13 44 % 56 % 42 % 58 % Sb 57 % 13/23 Sc+Sm 67 % 6/9 Total 38 % 31/81 43 % 10/23 33 % 3/9 62% 50/81 45 % 55 % 50 % 50 % 44% 56% At the early stages of interaction of mixed-morphology pairs: SFR nor AGN activity is enhanced in E-Sa members of isolated pairs AGN activity is enhanced only in the late Spiral members

13 2nd Sample: to study further mixed morpholgy (E+S) Isolated Galaxy Pairs. What for? Our general objective: Quantify the role of interactions in the secular evolution of galaxies dynamical, stellar and chemical evolution at global, circum-nuclear and nuclear unresolved- scales In these (E+S) pairs: 1. Reduced complexity & frequency of interactions in field isolated galaxy pairs 2. Provided a closer -more direct- comparison with isolated field galaxies 3. Mass ratios ~1 avoid complexity of hierarchical interactions 4. These are isolated physical pairs were members still maintain a clear morphology a. early stage of interaction (pre 1st passage) b. Have not experienced a large merger in the recent pass 5. Easier disentanglement of the origin and interaction response of the gas & stellar populations (blue-red, wet-dry, cold-hot)

14 Part of long-term campaigns: Optical multi-band imaging (V,B,R,I) Luminosities Color & SB profiles Morphology and interaction distortions (Franco-Balderas et al. 03; 04; 05) NIR imaging (J,H,K) H" Fabry-Perot 2-D maps Kinematical structures, time-scales and relative orbital constrains (M. Rosado et. al 07) Optical spectroscopy: S component: rotation curves (dynamical masses) E component: stellar population properties Nuclear and global SF and activity Completed full-wav long-slit spectra of spirals in (E+S)

15 Isolated (E+S) pairs: S-component spectroscopy 1. Nuclear: Kpg central Inner Disk: 1.5 > r > 0.4 R Main Disk: 2.5 > r > 0.8 R 25 " 2.1m SPM telescope, Low-R, Long-slit Spectrograph Range: A 4.5A resolution (FWHM) To derive H" rotation curves (Huerta et. al 2008) " 104 gals in 103 (E+S) pairs: 2 are actually (E+E) 1 we observed also the E ~95 pairs have >3# emission 1 - Nuclear: central Inner Disk: 1.5 > r > 0.4 R Main Disk: 2.5 > r > 0.8 R 25

16 Spirals in mixed morphology pairs: line intensities & widths Multi-component fit: a. Narrow emission (H", NII, SII) b. Broad H" (nucleus only) c. Stellar absorption H" & [NII]s Nucleus [SII]s d. Residual H" absorption e. Featureless continuum # Intensities, widths & velocities Disk After rotation-curve removal: 1. 3 main radial mashes (nucleus, inner disk, main disk) 2. Multi-component fit as before 3. Measured also [OI]6300 and HeI 5800 (fixed kinematics)

17 But we only covered the H" region Kpg019b Nucleus absorption+continuum fit HeI 5876 NaD [OI] Data - Fit Residual

18 Nuclear activity in (E+S) pairs (complete sample of S members) Only 1/38 + AGN Spirals is type-1 Indeed a very high fraction of S nuclei in (E+S) isolated pairs are AGN And activity is triggered/enhanced by interaction, even at early stages

19 Summary of Results Almost all Ellipticals have LINER activity (regardless of being in pairs or isolated) The incidence of Activity in S+S pairs is almost the same as for isolated Spirals (CIG) of similar morphology (even hgher compared to other local isolated galaxy samples, Varela 04) Relative to Isolated Spiral Galaxies, Activity is more enhased in the Spiral component of E+S isolated pairs The activity excess is more clear in late spirals, that is AGN activity in earlyier paired-gaalxies is as frequent as in thier isolated counterparts higher increase if compared with Varela s isolated sample. Activity enhancement is stronger at closer relative separations

20 Nuclear activity is more frequent in galaxies with early Hubble type (E/S0) --not new However, a very large fraction of E galaxies shows the presence of LINER activity. Relevance: How is the BH fed and prevented from starvation? as from the companion (in pairs) or from the IGM? Isolated Galaxy Pairs (present-day low-density environment) catch interaction at the very beginning, before a bright Seyfert can form => Tidal forces do not trigger strong BH at this early phase 20

21 These low-intensity AGN are accreting at low rates, feedback from the BH to the host galaxy is not yet important. Interesting point: Stone in the water interactions seem to have an earlier kick off. Would they keep been relevant at later phases? Given that the B/D vs. AGN fraction effect is present in both samples (isolated galaxies and pairs), morphology must play a relevant role in interactions (formation and secular processes) The absence of nuclear activity of type 1 (even! 1.5, i.e. strong Broad Lines) in our samples is an outstanding result. This cannot be explained by a simple UM version (Obscuration + Orientation only).

22 Unified Model for Seyfert galaxies AGN Unified Model Ty-1 and Ty-2 AGNs are intrinsically alike systems, but viewed at different orientations (Antonucci, 93; Urry & Padovani, 95) For Seyfert galaxies: Sy 1 and Sy 2 are intrinsically the same object (accreting central SMBH) but in Sy 2 the orientation of an obscuring torus prevents us to see the broad-line region Paradigm: all Sy2s must be obscured Sy1s

23 The UM is consistent with QSOs (post major mergers) and with several Seyfert observations as well.

24 But the Unified Scenario may not be the whole story for Seyfert galaxies (particularly low-accretion BHs) 1. Not all Sy 2 (and LINER 2) show broad lines in their polarized spectra (Barth, Filippenko & Moran, 99a,b; Tran, 2003)., and this is not just a sensitivity bias. 2. Not all optical Sy 2 show evidence of any X-ray obscuration in simultaneous observations (e.g. Biancci et al., 2007) 3. Relative to normal galaxies with same z, D & M distributions: bright Sy2 show a higher frequecny of close companioons, while bright Sy1 do not (Dultzin-Hacyan et al D; Krongold et al. 01, 02, Kolouridis et al. 06a,b 3D). 4. Just a torus orientation effect can not account for the absence of type 1 nuclei in local Isolated Galaxies and Pairs

25 Seyfert Evolutionary Scenario (similar-mass interactions) INTERACTION SB Type-2 AGN Type-1 AGN (Krongold et al. 02; Kouluoridis et al. 06, 11) A. Interaction aids cold gas to flow towards the central parts of the galaxy. B. Material falls even further to feed a central BH, giving birth to a unobservable AGN (due to obscuration and SB strength). C. As SB activity relaxes and obscuration decreases, a Sy2 nucleus is revealed. D. Remaining molecular gas settles into a central torus (as in Unification). E. Finally, as AGN strengthens and drives away most obscuring clouds, and the broad-line region AGN (Sy1) can be revealed. ~1-2 Gyr is the relevant timescale (fly-by, disruption or final merger in our pairs) Sy1 and Sy2 are the same objects indeed, but not necessarily at the same evolutionary phase Other luminosities: similar or related trends found in LINERs (Krongold et al. 03) QSOs (Serber et al. 06) and ULIRGs (Sanders et al. 99; Wang et al. 2006)

26 Conclusions Host morphology (B/D) plays a role on AGN frequencies and on the effects of interactions... in particular for field galaxies that have not experience a major merger since they formed UM alone does not explain the absence of Sy 1s in isolated galaxies or members of comparable mass galaxy pairs, in the local low-density environment Pair interactions trigger secular evolution of AGN activity, even at early stages. In similar mass pairs, the type and enhancement of the nuclear activity (BH feeding) depends on the morphology of the paired galaxies. Thanks!