Evidence for AGN impact on star formation in (unresolved) galaxy populations

Transcription

1 Evidence for AGN impact on star formation in (unresolved) galaxy populations (ESO, Germany) (see Harrison 2017)

2 Overview Evidence for AGN impact on star formation in (unresolved) galaxy populations 1. Motivation & Big Picture 2. Example Challenges 3. Approaches i. Evidence of impact on current SF levels ii. Evidence of impact on SF fuel iii. Evidence of impact in the past (-> Working Session 7)

3 Motivation Most models use AGN to prevent runaway stellar mass growth ``Quick fix solution proof of AGN impact Little constraints on how, when and where this occurs! Harrison 2017 Also: L X -T x relationship; cooling times in ICM; color-bimodality; M bulge -M BH relationship +

4 Motivation AGN STAR FORMATION BH Mass BH Mass Stellar Mass Mergers

5 Motivation Gas Reservoir Usable AGN fuel Usable star formation fuel FEEDING FEEDING AGN STAR FORMATION BH Mass BH Mass Stellar Mass Mergers

6 Motivation Gas Reservoir Usable AGN fuel Usable star formation fuel FEEDING FEEDBACK FEEDING FEEDBACK AGN STAR FORMATION BH Mass BH Mass Stellar Mass Mergers

7 Motivation Gas Reservoir Usable AGN fuel Usable star formation fuel FEEDING FEEDING FEEDBACK FEEDBACK AGN STAR FORMATION BH Mass BH Mass Stellar Mass Mergers

8 Challenges 1. Star formation <-> star formation AGN <-> AGN Star formation <-impact-> AGN How do we de-couple all these processes in (unresolved) galaxy populations? Harrison 2017 (arxiv version)

9 Challenges 2. AGN impact on the fuel that (may) forms stars they do not make/destroy stars directly! 1. ejective AGN on? 2. strangulation How does it happen? (e.g., ejective vs. preventative/strangulation) Is it rapid or slow? Peng+14 (adapted)

10 Challenges 2. AGN impact on the fuel that (may) forms stars they do not make/destroy stars directly! What are the time scales: 1. visible AGN activity? 2. energy injection? 3. observable impact? Harrison 17

11 Challenges 3. The result on star formation may be: positive, negative or zero! What is the contribution from each of these possibilities when looking at (unresolved) galaxy populations? Cresci+15

12 Challenges 4. Identifying and characterising black hole growth is difficult and complex Mechanically Dominated (Low Eddington Ratio 0.01 /ADAF/Low Excitation) Radio emission (+ lack of strong AGN signatures at other wavelengths) (Relatively) little BH growth End point of evolution? see e.g., Cattaneo+09; Goulding+14

13 Challenges 4. Identifying and characterising black hole growth is difficult and complex Radiatively Dominated (High Eddington Ratio/ Luminous /Quasar/High Excitation) UV-MIR continuum [colours] (Hard) X-rays Emission-line ratios Broad line regions (type 1) Radio continuum! Most BH growth occurs here Range of host galaxy properties see e.g., Cattaneo+09; Goulding+14 AURA/STScI/NASA/JPL (NASA photo # STScI-PRC96-35a)

14 Challenges 4. Identifying and characterising black hole growth is difficult and complex Biases against lowest luminosities and/or most obscured Challenging to de-couple BH and host galaxy emission e.g.,: Type 2 hard to get black hole properties Type 1 very hard to get most host galaxy properties

15 Approaches How should we find impact of AGN in galaxy populations? 1. Evidence of AGN impact on current SF levels? e.g., Galaxies that host AGN have reduced/enhanced star formation? 2. Evidence of AGN impact on SF fuel? e.g., Galaxies that host AGN have reduced ability to form stars 3. Evidence of AGN impact in the past? e.g., Past AGN activity changed galaxy properties - relic evidence? (stellar pops? masses? metalicity? +)

16 1. Evidence of AGN impact on current SF levels?

17 Evidence of AGN impact on current SF levels Redshift and mass dependencies on SFRs in galaxy population Main sequence of star-forming galaxies Compare AGN to all galaxies? Compare AGN to main sequence? We should always mass match? We should always redshift match? Wuyts+11 (also see e.g., Eales+17)

18 Evidence of AGN impact on current SF levels Your comparison can change your conclusions! Main sequence of star-forming galaxies The slope at high mass is very uncertain (affects most of our AGN samples)

19 Evidence of AGN impact on current SF levels X-ray AGN 2012: lots of disagreement on AGN impact on SF e.g., Silverman+09; Lutz+10; Hatziminaoglou+10; Shao+10; Mullaney+12; Mainieri+11; Rosario+12; Rovilos+12; Santini+12; Bongiorno+12; Page+12; Harrison+12

20 Evidence of AGN impact on current SF levels Current (almost) consensus for X-ray detected AGN (TBC) If you control for mass and redshift: - No dependence of (s)sfr on X-ray luminosity - AGN preferentially live in star-forming galaxies - But mode of distribution is moderately below the main sequence Stanley+15 Or maybe not (e.g., Barger+15).to be continued in working session e.g., Vito+14; Stanley+15; Azadi+15; Mullaney+15; Lanzuisi+17; Shimizu+17; Scholtz+17

21 Evidence of AGN impact on current SF levels Simultaneous AGN and SF quenching plus variability hides AGN impact EAGLE model predictions 100 Mpc 3 hydro simulation (Schaye+15) Huge (variable) range in luminosities AGN selection creams off the highest accretion rates Wide range of accretion rates (variable) Star formation quenching comes after AGN shuts itself off

22 Evidence of AGN impact on current SF levels Flat relationship between SF and L-AGN does not mean no feedback Samples 5 Harrison 17

23 Evidence of AGN impact on current SF levels AGN decrease mode and increase spread of ssfrs for ALL GALAXIES Scholtz+17

24 Evidence of AGN impact on current SF levels A mixture of messages for a mixture of AGN selection techniques Radio AGN samples: positive vs. negative vs no impact on SFRs e.g., Karouzos+14; Gürkan+15; Podigachoski+15; Magliocchetti+16; Kalfountzou+17; Stanley+17 But Low Excitation Radio Galaxies seem to have low (s)sfrs e.g., Hardcastle+13; Lanz+16; Ellison+16 Type 1 quasar samples: SFRs scale vs. do not scale with L AGN e.g., Rosario+13; Harris+16; Pitchford+16; Stanley+17; Duras+17; Wavelength selection: positive vs. negative vs. no difference on (s)sfrs e.g., Zinn+13; Cowley+16; Ellison+16; Azadi+17 to be continued in working session..

25 Evidence of AGN impact on current SF levels Can we see evidence of impact from AGN-driven outflows? Type 2 quasars; SDSS; z<1 Outflow from width of [O III] Negative correlation between ssfr and outflow but only for high SFRs (gas rich galaxies) (But not quenched compared to main sequence) Wyzlezalek+16 also see e.g., Farrah+12; Maddox+17

26 Evidence of AGN impact on current SF levels Can we see evidence of impact from AGN-driven outflows? Balmaverde+16 Type 1 quasars; SDSS; z<1 Outflow from width/vel of [O III] (s)sfrs do not depend on outflow velocities

27 Evidence of AGN impact on current SF levels Can we see evidence of impact from AGN-driven outflows? Strong outflows z<~0.3 SDSS Type 2 (s)sfrs show a positive correlation with outflow Medium outflows Weak/no outflows ssfr offset Woo+17 outflow strength to be continued in working session..

28 2. Evidence of AGN impact on star-formation fuel?

29 Evidence of AGN impact on SF fuel Low accretion rate AGN in massive local galaxies regulate growth Is this it for AGN impact? e.g., Fabian 94; Birzan+04; Best+06; Danielson+12; Simpson+13; Review: McNamara & Nulsen 2012 But these galaxies/bhs at end point of evolution.. Might not be enough (e.g., McCarthy+11) Danielson+12

30 Evidence of AGN impact on SF fuel Mass outflow rates can exceed star-formation rates Mass outflow rate / SFR Cicone+14 + many others (earlier this week) But we ve discussed the uncertainties/challenges Perhaps the outflow will stop and re-accrete

31 Evidence of AGN impact on SF fuel Investigating SF efficiencies and gas fractions ``Main sequence : -> gas mass (L CO ) vs. SFR (L FIR ). Used to infer star formation efficiency -> can also get expected gas fractions f mol = M mol /(M * + M mol ) Sargent+14

32 Evidence of AGN impact on SF fuel Molecular gas properties in AGN vs. non-agn 10 z~1.5 AGN L AGN = erg s -1 X-ray selected AGN SED -> FIR SFRs CO(2-1) Galaxy wide Kakkad+17 Efficiencies and gas fractions and are low in AGN host galaxies (matched z, M *, SFR) (also see e.g., Ho+2005; Brusa+; Carniani+17; Fiore+17)

33 Evidence of AGN impact on SF fuel Molecular gas properties in AGN vs. non-agn normal disks 20 Local AGN & 19 non-agn L AGN = erg s -1 X-ray selected AGN SED -> FIR SFRs CO(2-1) Inner 1-3 kpc Efficiencies and Gas fractions are unexceptional in AGN host galaxies (matched M *, SFR, morphology & inclination) Rosario+17

34 3. Evidence of AGN impact in the past?

35 Evidence of AGN impact in the past? Bulges masses and black hole masses tightly correlated Classical Bulges Models say implies AGN impact e.g., Silk & Rees 98; Murray+05 King & Pounds 2015 AGN Or not. -> common gas supply + regulated accretion: e.g., Anglés-Alcázar +17 STAR FORMATION -> Mergers are key: e.g., Peng 07; Hirschmann+10; Jahnke & Maccio 2011 Data from: Kormendy & Ho 2013

36 Evidence of AGN impact in the past? Other observational evidence for AGN impact? Compare observed galaxy populations with simple model predictions -> e.g., luminous AGN are the quenching population? [Bongiorno+16] Star-formation histories -> e.g., AGN have different quenching time Maybe AGN have more rapid quenching? [e.g., Smethurst+16] Bongiorno+16 to be continued in working session..

37 Evidence of AGN impact in the past? In simulations we can remove/change AGN prescriptions Beckmann+17 Segers+16 AGN AGN Scholtz+17 to be continued in working session..

38 Conclusions Evidence of AGN impact on current SF levels X-ray AGN don t look special on average[?] -> doesn t rule out AGN impact What is going on at AGN selected at other wavelengths? Evidence of AGN impact on SF fuel LERGs can regulate cooling in massive galaxies Mixed messages on SF efficiencies and gas fractions for quasars/luminous AGN Evidence of AGN impact in the past? How do we infer what impact AGN had in the past? Model predictions on the signature(s) with different AGN feedback prescriptions?

39 Cautionary notes We need to be careful of confirmation bias (either to prove right or wrong ) If star formation is enhanced we called it positive feedback If star formation is suppressed we called it negative feedback If star formation is consistent we attributed it to variability "Anything becomes interesting if you look at it long enough." Gustave Flaubert

40 BACK-UP SLIDES

41 Evidence of AGN impact on current SF levels At least some of the disagreement from random fluctuations Harrison+12,Harrison 14

42 Evidence of AGN impact on current SF levels Selection is critical for interpretation Galaxies in EAGLE McAlpine+17

43 Evidence of AGN impact on current SF levels Star-formation tracers for AGN UV-optical colors; stellar histories (SED fitting) PAH features H-alpha (and other optical/nir lines) Far infrared emission (sometimes with SED fitting)