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

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

T. Oosterloo (Astron, NL)and many others

IAU 222- Gramado, March 2004

The interplay between radio-activity and the ISM

in radio galaxies

IAU 222 – Gramado, March 2004

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 galaxiesRich ISM in their central regions Gas outflowsJet/cloud interaction in the first phase of evolution of a radio galaxy?

Jet-induced star formationThe case of Centaurus A


Heckman et al. 1986

also emission line kinematics consistent with accretion origin(Tadhunter et al. 1989; Baum et al. 1990)

Morphological features: double nuclei, arcs, tails and bridges

Merger as a way to bring the gas to the central regions

~ 5 kpc (5’’)

3C 293 Molecular gas (CO)Radio cont. (5 GHz)

4C 12.50

HST image+ CO contours

Nuclear concentration of molecular gas (Evans et al. 1999,2004)

presence of a starburst phase

rich ISM in the central regions (at least in the initial phase of the AGN)


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


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)

How common is the presence of a young stellar population (YSP)?What is it telling us?

Stellar population of radio galaxies

Also noted in some radio galaxies with peculiar optical morphology (Heckman et al. 1986)

Results fromUV imaging

Allen et al. 2002

3C305

3C293 3C3213C236


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!

Aretxaga et al. 2001 , Tadhunter et al., Wills et al. 2002, 2003

Recent systematic studies

Tadhunter et al. 1996

3C321

old stellar pop.

young stellar pop. power law


Evolution of the host galaxy from the YSP

Results on 3C293, 3C305 and 4C12.50 (Tadhunter, Robinson, Gonzalez-Delgado et al. 2004)

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

consistent with AGN activity (in some radio galaxies) triggered by major merger AGN appears late after the merger

ULIG

LIG

3C293

3C305

Assuming instantaneous burst model (BC96)

Age (Gyr)L B

OL


How about the radio galaxies with no YSP?

Wills et al. 2002

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)

radio galaxies without YSP are • triggered by a small merger, or• are seen very late after the merger


These are mainly radio quiet galaxies: any connection to radio loud galaxies?

Large amount of HI MHI > 109 Msun Very extended structures

(~ hundred kpc) Often, very regular kinematics

disks Long-lived gas structures Major mergers

HI and early-type galaxies

Other indication of merger origin for radio galaxies: HI emission, huge disks

Normal early-type galaxies with huge amount of HI (about 5-10%)

20

0 k

pc

Sadler, Oosterloo & Morganti

(ATCA data) HI total intensity + optical


Veron-Cetty et al. 1995

100 kpc

Survey of radio galaxies in HI to look for similar extended structures

(Emonts PhD thesis)

Do we see similar structures in radio galaxies?

Southern radio galaxy PKS B1718-649Very extended disk with more than 1010 M of HI

Total HI intensity

VLBI continuum (Tingay et al. 1997)

<10pc


Large HI disks in radio galaxies

125 kpc

~160 kpc

~1kpc

Very extended H I disks

Both compact radio galaxies

young(107 yr)

HI total intensity

WSRT

more than 1010 M of HI!

~1kpc

remarkably regular distribution and kinematics


Major merger is the possible scenario for some BUT…….

Complex morphology of the ionized gas

and neutral hydrogen(with similar kinematics) 30 kpc

Morganti et al. 2002

HI

Tadhunter et al. 2000

Radio lobes expanding into gas disk

selection effects?

the gas is ionized?

(see Coma A)

different type of merger?

environment?

so far large, HI-rich disks only in compact radio galaxies: no idea why!


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)


Disturbed kinematics of the ionized gas known for a number of objects: young radio galaxies (compact steep spectrum) Gelderman & Whittle 1994

Ionized gas in the central region of radio galaxies: can have regular kinematics, used also for determination of BH mass

BUT

• 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 radio galaxies with YSP: OUTFLOWS and EXTREME KINEMATICS

Ionized gas in the central regions


HI detections

presence of HST dust disks absence of optical core.

Similar situation for the HI:in some cases originating from regular circum-nuclear disks

(van Langevelde et al. 2000)

NGC 4261

Neutral hydrogen in the central regions

see also talk by Beswick


Neutral hydrogen in the central regions

HI and X-ray in the Compact Steep Spectrum 1946+708

Peck, Taylor & Conway 1999Risaliti, Woltjer & Salvati 2003

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!


Outflows in 4C12.50 (PKS1345+12)

-450 km/s

-2000 km/s

[OIII] ProfilesWHT+ISIS

Holt et al. 2002

HST [OIII] VLBI

Compact and powerful radio galaxy (P5GHz = 1026 W Hz-1)

Far-IR bright, LIR~2x1012 Lsun

Large amount of CO, ~ 1010 Msun

Very rich ISM

Best example of link between radio galaxies and ULIRGs


Observer’s L.O.S.

quiescent halo emitting narrow component

narrow component

broad component

intermediate component

obscured quasar

bi-polar radio jets

bi-polar radio jets

The broadest components are the most highly reddened & higher density (> 5000 cm-3)

Stratified outflow

Bow shock

Jet

HI clouds

[OIII] clouds

Shocked clouds

[OII]-emitting cocoon

Far side of galaxy, completely obscured from view


[OIII]4959,5007fit with 3 components

"Deep" Absorption only 1%, NH~2x1020 cm-2 for TSPIN=100K

Broad absorption ~0.2% NH~1020 cm-2 forTSPIN=100K

Broad HI absorption: full width of ~2000 km/s mostly blueshifted

(already known from Mirabel 1989)

Ionized and neutral gas


WSRT

Deep absorption: Haschick & Baan (1985) Beswick et al. (2002)

broad, shallow absorption by neutral gas

Morganti et al. ApJL (2003)

Broad absorption ~0.15% NH~2 x 1020 cm-

2 for TSPIN=100K

Broad HI absorption in 3C293

see talk by Beswick


HI

OII

Emonts et al. in prep

Core

Blueshifted wing at location of lobe, not core jet-cloud interaction?

red: radio continuum (MERLIN, Beswick et al.)blue: CO (Evans et al.)

1’’

Same gas outflow in ionized gas


Schilizzi et al. 2001O’Dea et al. 2001

Optical depth of the broad absorption ~0.15%

~1500 km/s

Broad HI absorption in 3C236

More cases: poster Oosterloo et al.


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

Despite the highly energetic phenomena involved, gas remains (or becomes again) neutralInsight on the physical conditions of the medium around the AGN

need for high resolution data to localize the HI absorption

What produces the HI outflows


Radio source evolution and ISM

Cygnus A, HST imagesJackson et al, 1998

Cavities are hollowed out: Cygnus A-like?

“Feedback” mechanism: the effect of AGN activity regulates the correlation between BH mass and galaxy bulge

For young radio sources the circum-nuclear medium (left-over from the merger?) is swept aside by AGN driven outflows.


2D simulationsBicknell 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

“Fighting” its way out

4C12.50

Core

black=WSRTred = VLBI

Integrated HI profile

Mass of the HI cloud ~105-6 Msun

High column density (NH~1022 cm-2)

HI absorption

VLBI

Morganti, Oosterloo, Vermeulen et al. 2004


Mellema et al. 2002

looks promising also to explain the broad HI BUT can the fragmented clouds be accelerated to such high velocities?

Evolution of clouds in radio galaxy cocoons:

shock runs over a cloud compression phase (overpressured cocoon)

fragmentation & cooling

formation of dense, cool & fragmented structures

What jet/cloud interaction can do for us?

Simulations show that cooled fragmented cloudsdo form as result of the interaction Mellema et al. 2002, Fragile et al. 2003


Considered to be very important for high-z radio galaxies,

Nearby examples:

Minkowsky object: van Breugel et al. (1985)

Jet induced star formation (observations)

Even closer example: Centaurus A NGC 541

15 kpc

(see talk by van Breugel)


Cen-A Orientation: Jet and Filaments

• 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

H

Outer filaments

Innerfilaments

Schiminovich et al. 1994

HICO

Charmandaris et al.

Radio

Morganti et al.


outer filament

H I cloud

H I ring at large radius, regular rotationOne H I cloud near outer filament & jetJet-induced star formation? Rejkuba et al. 2002

Graham 1998

Filaments contain young stars (10 Myr)


jet flow

blue: FUV from GALEX (Neff et al. AAS 2004)red : H from WFI ESO-2.2m

Outer filament: FUV + H

FUVH I H

young stars

~1kpc

shocks?

jet flow

Jet hitting HI cloud near the outer filament?

• UV emission from:

– young blue stars

– ionized gas in the filaments

• Far-UV “leads” optical continuum and line emission –> shocks?


Kinematical signature of interaction?

jet

Kinematics of H I ring smoothexcept at the southern tip!

velocity range of ionized gas

New ATCA data higher spatial (20’’) and velocity resolution (6 km/s)

Kinematical signature of interaction in the HI?

~1 kpc


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

Documents

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