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
Jan 02, 2016
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
IAU 222 – Gramado, March 2004
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)
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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!
IAU 222 – Gramado, March 2004
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)
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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!
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
[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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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.
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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.
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 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
IAU 222 – Gramado, March 2004
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)
IAU 222 – Gramado, March 2004
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.
IAU 222 – Gramado, March 2004
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)
IAU 222 – Gramado, March 2004
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?
IAU 222 – Gramado, March 2004
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
IAU 222 – Gramado, March 2004
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