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Raffaella Morganti (Astron, NL) C. Tadhunter (Sheffield, UK) T. Oosterloo (Astron, NL)

The interplay between radio-activity and the ISM in radio galaxies. Raffaella Morganti (Astron, NL) C. Tadhunter (Sheffield, UK) T. Oosterloo (Astron, NL) and many others. IAU 222- Gramado, March 2004. Topics of this talk. Merger origin for radio galaxies:

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Raffaella Morganti (Astron, NL) C. Tadhunter (Sheffield, UK) T. Oosterloo (Astron, NL)

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  1. The interplay between radio-activity and the ISM in radio galaxies Raffaella Morganti(Astron, NL) C. Tadhunter (Sheffield, UK) T. Oosterloo (Astron, NL) and many others IAU 222- Gramado, March 2004

  2. Topics of this talk Merger origin for radio galaxies: Recent results from studies of the stellar population. Compare this with the results from the study of gas (HI) on large scale to trace the assembly history of giant E galaxies ISM in Radio galaxies Rich ISM in their central regions Gas outflows Jet/cloud interaction in the first phase of evolution of a radio galaxy? Jet-induced star formation The case of Centaurus A

  3. Merger as a way to bring the gas to the central regions 3C 293 Morphological features: double nuclei, arcs, tails and bridges Molecular gas (CO) Radio cont. (5 GHz) also emission line kinematics consistent with accretion origin (Tadhunter et al. 1989; Baum et al. 1990) 4C 12.50 ~ 5 kpc (5’’) Nuclear concentration of molecular gas (Evans et al. 1999,2004) Heckman et al. 1986 HST image+ CO contours • presence of a starburst phase • rich ISM in the central regions (at least in the initial phase of the AGN)

  4. Characteristics of the merger Can we quantify better the characteristics of the merger? • Which type merger ? • When does the activity start? • Evolutionary status? Study of the stellar population

  5. Stellar population of radio galaxies 3C305 3C236 3C293 3C321 How common is the presence of a young stellar population (YSP)? What is it telling us? Results from UV imaging Allen et al. 2002 The presence of a young stellar population component known in some radio galaxies: Hydra A (Melnick et al.), 3C321 (Tadhunter et al. 1996) UV study of 3CR galaxies (Allen et al. 2003) Also noted in some radio galaxies with peculiar optical morphology (Heckman et al. 1986)

  6. Recent systematic studies Aretxaga et al. 2001 , Tadhunter et al., Wills et al. 2002, 2003 • young stellar populations (YSP) make a significant contribution to the optical/UV continua in 25 to 40% of radio galaxies • at low and intermediate redshifts and of different radio powers Consistent with the idea of (major?) mergers triggering the activity • these mergers are known to produce circum-nuclear starburst as the material is driven toward the central regions connection with UV excess and IR luminosity • tendency for the galaxies with YSP to be detected by IRAS  to be confirmed by the Spitzer telescope! 3C321 old stellar pop. young stellar pop. power law Tadhunter et al. 1996

  7. Evolution of the host galaxy from the YSP Results on 3C293, 3C305 and 4C12.50 (Tadhunter, Robinson, Gonzalez-Delgado et al. 2004) Assuming instantaneous burst model (BC96) ULIG • typical ages of the YSP between 0.5 and 2.5 Gyr • massive YSP: 109 <MYSP < 5x 1010 Msun (comparable to the mass of molecular gas) • that makes up a large proportion of the total • stellar mass (~ 1 to 50%) • link between radio galaxies and luminous- and • ultra luminous infrared galaxies LIG 3C305 LBOL 3C293 • consistent with AGN activity (in some radio galaxies) triggered by major merger • AGN appears late after the merger Age (Gyr)

  8. How about the radio galaxies with no YSP? Mass of the YSP is relatively minor  minor merger Sources observed long after the merger Reddened starburst (but none of the undetected are luminous in far-IR) Wills et al. 2002 • radio galaxies without YSP are • triggered by a small merger, or • are seen very late after the merger

  9. HI and early-type galaxies HI total intensity + optical (ATCA data) 200 kpc Sadler, Oosterloo & Morganti Other indication of merger origin for radio galaxies: HI emission, huge disks Normal early-type galaxies with huge amount of HI (about 5-10%) Large amount of HI MHI > 109 Msun Very extended structures (~ hundred kpc) Often, very regular kinematics  disks Long-lived gas structures Major mergers These are mainly radio quiet galaxies: any connection to radio loud galaxies?

  10. Do we see similar structures in radio galaxies? Southern radio galaxy PKS B1718-649 Very extended disk with more than 1010 Mof HI Total HI intensity 100 kpc <10pc VLBI continuum (Tingay et al. 1997) Veron-Cetty et al. 1995 Survey of radio galaxies in HI to look for similar extended structures (Emonts PhD thesis)

  11. Large HI disks in radio galaxies ~1kpc 125 kpc ~1kpc Both compact radio galaxies  young (107 yr) WSRT more than 1010 Mof HI! ~160 kpc HI total intensity Very extended H I disks remarkably regular distribution and kinematics

  12. Complex morphology of the ionized gas and neutral hydrogen (with similar kinematics) Tadhunter et al. 2000 30 kpc HI Morganti et al. 2002 Radio lobes expanding into gas disk Major merger is the possible scenario for some BUT……. so far large, HI-rich disks only in compact radio galaxies: no idea why! • selection effects? • the gas is ionized? (see Coma A) • different type of merger? • environment?

  13. AGN interaction with the ISM The neutral hydrogen considered so far is at very large distances from the center (tens of kpc) and is not directly connected to the activity as “fuel”  only a signature of the likely origin of the host galaxy. As result of the merger, we expect also a nuclear concentration of gas (at least in the first phase of the evolution of a radio galaxy) This gas is particularly important because: Evolution of the radio source and effect on the ISM AGN-induced outflows in radio galaxies? Jet induced star formation? Common at high z, important for evolution Study of the ionized gas and of the neutral hydrogen (observed in absorption against the strong radio continuum)

  14.  Ionized gas in radio galaxies with YSP: OUTFLOWS and EXTREME KINEMATICS • gas outflows observed in many of these galaxies • stratified gas outflows: different components originating from different regions (region of interaction with radio plasma vs quiescent cocoon) Ionized gas in the central regions Ionized gas in the central region of radio galaxies: can have regular kinematics, used also for determination of BH mass BUT Disturbed kinematics of the ionized gas known for a number of objects: young radio galaxies (compact steep spectrum) Gelderman & Whittle 1994

  15. Neutral hydrogen in the central regions NGC 4261 HI detections presence of HST dust disks absence of optical core. (van Langevelde et al. 2000) Similar situation for the HI: in some cases originating from regular circum-nuclear disks see also talk by Beswick

  16. HI and X-ray in the Compact Steep Spectrum 1946+708 Peck, Taylor & Conway 1999 Risaliti, Woltjer & Salvati 2003 Neutral hydrogen in the central regions High detection rate of HI absorption in young radio galaxies (compact steep spectrum), see talk by Vermeulen But the HI is not always associated with a circumnuclear disk/torus: extreme examples in the radio galaxies with YSP ALL the radio galaxies with YSP observed in HI have been detected!

  17. Compact and powerful radio galaxy (P5GHz = 1026 W Hz-1) Far-IR bright, LIR~2x1012 Lsun Large amount of CO, ~ 1010 Msun Outflows in 4C12.50 (PKS1345+12) HST [OIII] VLBI Very rich ISM Best example of link between radio galaxies and ULIRGs [OIII] Profiles WHT+ISIS -450 km/s -2000 km/s Holt et al. 2002

  18. [OII]-emitting cocoon HI clouds Shocked clouds Jet Bow shock [OIII] clouds Stratified outflow quiescent halo emitting narrow component narrow component intermediate component Far side ofgalaxy, completely obscured from view broad component Observer’s L.O.S. bi-polar radio jets bi-polar radio jets obscured quasar The broadest components are the most highly reddened & higher density (> 5000 cm-3)

  19. [OIII]4959,5007 fit with 3 components Ionized and neutral gas • Broad HI absorption: • full width of ~2000 km/s • mostly blueshifted "Deep" Absorption  only 1%, NH~2x1020cm-2for TSPIN=100K (already known from Mirabel 1989) Broad absorption  ~0.2% NH~1020 cm-2 forTSPIN=100K

  20. Broad HI absorption in 3C293 broad, shallow absorption by neutral gas WSRT Broad absorption ~0.15% NH~2 x 1020 cm-2 for TSPIN=100K Deep absorption: Haschick & Baan (1985) Beswick et al. (2002) see talk by Beswick Morganti et al. ApJL (2003)

  21. Same gas outflow in ionized gas HI OII Blueshifted wing at location of lobe, not core  jet-cloud interaction? Core 1’’ red: radio continuum (MERLIN, Beswick et al.) blue: CO (Evans et al.) Emonts et al. in prep

  22. Broad HI absorption in 3C236 ~1500 km/s Optical depthof the broad absorption  ~0.15% Schilizzi et al. 2001 O’Dea et al. 2001 More cases: poster Oosterloo et al.

  23. What produces the HI outflows Despite the highly energetic phenomena involved, gas remains (or becomes again) neutral Insight on the physical conditions of the medium around the AGN • Starburst wind • Adiabatically expanded broad emission line clouds (Elvis et al. 2002) • Radiation pressure+Dust (Dopita et al.)  see talk by Groves • Interaction between the radio jet and ISM need for high resolution data to localize the HI absorption

  24. Radio source evolution and ISM • For young radio sources the circum-nuclear medium (left-over from the merger?) is swept aside by AGN driven outflows. • “Feedback” mechanism: the effect of AGN activity regulates the correlation between BH mass and galaxy bulge Cavities are hollowed out: Cygnus A-like? Cygnus A, HST images Jackson et al, 1998

  25. “Fighting” its way out black=WSRT red = VLBI Integrated HI profile 2D simulations Bicknell et al. 2003 Results from the study of the ISM in the center of radio galaxies with YSP: rich ISM against which the jet has to fight against in order to expand out of the galaxy VLBI High column density (NH~1022cm-2) HI absorption 4C12.50 Core Mass of the HI cloud ~105-6 Msun Morganti, Oosterloo, Vermeulen et al. 2004

  26. What jet/cloud interaction can do for us? Mellema et al. 2002 Simulations show that cooled fragmented clouds do form as result of the interaction Mellema et al. 2002, Fragile et al. 2003 Evolution of clouds in radio galaxy cocoons: shock runs over a cloud compression phase (overpressured cocoon) fragmentation & cooling formation of dense, cool & fragmented structures looks promising also to explain the broad HI BUT can the fragmented clouds be accelerated to such high velocities?

  27. Jet induced star formation (observations) Considered to be very important for high-z radio galaxies, Nearby examples: Minkowsky object: van Breugel et al. (1985) (see talk by van Breugel) Even closer example: Centaurus A 15 kpc NGC541

  28. Jet/radio lobes extend 40 kpc from nucleus Emission line filaments (high ionization) extend ~20 kpc from nucleus Very turbulent (>200 km/s) over 1 arcsec, jet-cloud interaction? photo-ionized by nucleus? Jet and filaments interrelated Induced star formation ISM heating by shocks /bulk motions Radio CO HI Charmandaris et al. Schiminovich et al. 1994 Morganti et al. Cen-A Orientation: Jet and Filaments H Outer filaments Inner filaments

  29. Filaments contain young stars (10 Myr) H I cloud Graham 1998 outer filament H I ring at large radius, regular rotation One H I cloud near outer filament & jet Jet-induced star formation? Rejkuba et al. 2002

  30. Outer filament: FUV + H blue: FUV from GALEX (Neff et al. AAS 2004) red : H from WFI ESO-2.2m jet flow • UV emission from: • young blue stars • ionized gas in the filaments • Far-UV “leads” optical continuum and line emission –> shocks? FUV H I Ha jet flow shocks? ~1kpc young stars Jet hitting HI cloud near the outer filament?

  31. Kinematical signature of interaction in the HI? New ATCA data higher spatial (20’’) and velocity resolution (6 km/s) Kinematics of H I ring smooth except at the southern tip! velocity range of ionized gas jet ~1 kpc Kinematical signature of interaction?

  32. Conclusions • Young stellar populations (YSP) make a significant contribution to the optical/UV continua in 25 to 40% of radio galaxies: consistent with the merger hypothesis • For those well studied: • typical ages of the YSP between 0.5 and 2.5 Gyr • AGN (radio) activity triggered by major merger • radio activity appears late after the merger • However, not a single type of merger for all radio galaxies • Very extended, HI-rich disks observed around some radio galaxies: • another signature of major merger? • Outflows of ionized gas and neutral hydrogen observed in radio galaxies • with young stellar population • Evidence that the rich ISM (left over form the merger?) is swept aside by AGN driven outflows (in the first phase of evolution of the radio source) • Jet induced star formation seems to be happening: evidence for disturbed kinematics in the HI gas of the outer filament of Cen A

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