GalaxyGalaxy ClustersClusters inin radioradio
ÎÎ NonNon--thermalthermal phenomenaphenomena
Luigina Feretti
Istituto di Radioastronomia CNR Bologna, Italy
Tonanzintla, GH2005, 4-5 July 2005 Lecture 4 : Radio emission from cluster galaxies: Classical radio galaxies Radio – X-ray interaction Distorted structures: NAT and WAT Radio galaxies filling X-ray cavities Confinement : Trigger of radio emission: radio luminosity function Enhancement of star formation RadiogalaxiesRadiogalaxies
X-ray:X-ray: ThermalThermal ggasas
Radio:Radio: AA 119119 (z(z == 0.0441)0.0441) RadioRadio GalaxiesGalaxies PerseusPerseus
X-rayX-ray ROSAROSATT PSPCPSPC
HotHot gasgas
NGC 1265
RadioRadio WSRTWSRT 4949 cmcm
RadioRadio galaxiesgalaxies
NGC 1275 IC310 RadioRadio galaxiesgalaxies ooff highhigh andand lowlow ppowerower havehave quitequite differentdifferent morphologiesmorphologies onon thethe largelarge scalescale (Fanaroff(Fanaroff && RileyRiley 11974)974)
CygCyg AA FRFR IIII 24.24.55 -1-1 HighHigh popowewer:r: PP1.41.4 GHzGHz >> 1010 WW HzHz 3C3C 444499 24.524.5 -1-1 LowLow power:power: PP1.41.4 GHzGHz << 1010 WW HzHz FRFR II RADIORADIO GALAXIESGALAXIES ATAT INCREASINGINCREASING RADIORADIO POWERPOWER
1024 W Hz-1 at 1.4 GHz
3C 31
DA 240
4C 73.08
1026.5 W Hz-1
From Atlas of P.Leahy, powers computed With H0=75, q0=0.5 Owen and Ledlow 1994 TheThe radioradio emissionemission fromfrom INDIVIDUALINDIVIDUAL GALAXIESGALAXIES isis foufoundnd ttoo extendextend WELLWELL BEYONDBEYOND thethe physicalphysical sizesize ofof thethe hosthost opticaloptical galaxygalaxy (>(> oror >>>> 100100 kpc)kpc) ÎÎ interactioninteraction withwith thethe outerouter mmediumedium
3C3C 449449 InteractionInteraction betweenbetween thethe ICMICM andand thethe radioradio emittingemitting plasma:plasma: -- ddistortedistorted structuresstructures (NAT,(NAT, WAT)WAT) -- XX-ray-ray cavitiescavities -- cconfinementonfinement
EffectsEffects ofof thethe ICMICM onon radioradio galaxies:galaxies: -- ttriggerrigger ofof radioradio emissionemission -- eenhancementnhancement ofof starstar formationformation u51 NarrowNarrow AngleAngle TailedTailed (NAT)(NAT) RadioRadio GalaxiesGalaxies
ÎÎ FRFR II sourcessources bentbent atat extremeextreme aanglesngles
Identified with non-dominant cluster members
0053-0160053-016 (A119)(A119) NGCNGC 12651265 (Perseus)(Perseus) Slide 11 u51 R e' il raggio di curvatura
h e' la dimensione su cui la ram pressure e' trsmessa ai getti unibo, 3/15/2003 StandaStandardrd interpretainterpretation:tion: JetsJets curvedcurved byby ramram pressurepressure fromfrom highhigh velocityvelocity galaxygalaxy (Begelman(Begelman etet al.al. 1979)1979)
For a fluid in motion : the total force on a volume of fluid equals the pressure on the surface enclosing the volume (Euler equation)
For a unit volume: 2 2 ρ jv j ρevg = ρj = jet density R rj vj = jet velocity rj = jet radius* ρe = external density vg = galaxy velocity Centripetal force Ram pressure R = curvature radius
*scale height over which the ram pressure 2 R ∼ rj (ρj/ρe)(vj/vg) is transmitted to the jet
-1 Consistent with observations for vg ∼ 1000 km s •
• •
AA 119119 ••
AA 21632163
TAILEDTAILED R.G.R.G. WITHWITH SIMILARSIMILAR ORIENTAORIENTATTIONION OFOF THETHE TAILSTAILS • • BulkBulk larglarge-e-scalescale motionsmotions iinn AA 520520 mergingmerging cclusterslusters maymay bbee tthehe dominantdominant effecteffect inin thethe formationformation ooff thesethese NNAATT structuresstructures u82
VERY NARROW TAILED STRUCTURES :
A2256 (Miller et al 2003)
A2255 (Miller & Owen 2003) Slide 14 u82 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 WideWide AngleAngle TailedTailed (WAT)(WAT) RadioRadio GalaxiesGalaxies
ÎÎ generallygenerally associatedassociated withwith D/cDD/cD oror giangiantt eellipticalsllipticals atat thethe clustercluster ccentersenters
DominantDominant galaxiesgalaxies havehave generallygenerally aa tootoo sslowlow velocityvelocity (<(< 100100 kmkm ss-1-1)) toto bendbend thethe jetsjets byby ramram pressurepressure
u18
Other suggested possibilities: -electromagnetic force between the jet and B field -collisions with clouds (Eilek et al. 1984) 3C3C 465465 (A2634)(A2634) Slide 15 u18 meccanismi alternativi per piegare le WAT: - forza elettromagnetica tra il getto che porta una corrente e il campo magn. intergalattico - deflessione per collisione con nubi dense - galleggiamento (buoyancy) unibo, 3/15/2003 Interpretation is that ram pressure gradients arise from large scale gas motions during cluster mergers: typical velocities ∼ 1000 km s-1
u18
A562A562 (G(Gόόmezmez eett aal.l. 1997)1997) Slide 16 u18 meccanismi alternativi per piegare le WAT: - forza elettromagnetica tra il getto che porta una corrente e il campo magn. intergalattico - deflessione per collisione con nubi dense - galleggiamento (buoyancy) unibo, 3/15/2003 RadioRadio galaxiesgalaxies fillingfilling XX-ray-ray CavitiesCavities atat thethe centercenter ofof coolingcooling corescores 3C3C 8484 NGCNGC 12751275 (Perseus) (Perseus) CHANDRACHANDRA (Fabian(Fabian etet al.al. 2000,2000, 2001)2001)
19931993 -- RROSATOSAT ((BöhringerBöhringer eett aal.)l.) 350 kpc
LargeLarge ssccaalele radioradio emissioemissionn u25
RBSRBS 797797 zz =0.35=0.35 (Gitti(Gitti etet alal inin prepprep 2005)2005) Slide 18 u25 Jets of radio sources could provide the energy required to stop the copious amount of gas from cooling at low temperatures in the cooling cores of clusters
altri casi di cavita': A2052, A496, A2199 unibo, 3/26/2003 ConfinementConfinement
A119A119
ICMICM cconfinesonfines thethe radioradio llobesobes
ÎÎ TheThe radioradio emittingemitting regionsregions inin radioradio galaxiesgalaxies aarere inin pressurepressure equilibriumequilibrium withwith thethe externalexternal thermalthermal pplasmalasma inin clustercluster PressurePressure ooff thethe X-rayX-ray ggas:as: 2nkT2nkT ∼∼ 1010-10-10-10-10-13-13 dyndyn ccmm-3-3
PressurePressure withinwithin thethe radioradio lobes:lobes: ∼∼ 1010-12-12-10-10-14-14 dyndyn ccmm-3-3
ÎÎ derivedderived fromfrom equipartition:equipartition: EErelrel ∼∼ EEHH underunder assumptionsassumptions onon geometry,geometry,
spectrumspectrum νν11,,νν22 kk == EEproprott/E/Eelel == 11 ΦΦ == fillingfilling factorfactor == 11 AA 22552255 A2255 3C 449 Interpretations of apparent unbalance:
♦ equipartition holds but with different assumptions - projection effects - presence of low energy electrons - different energy in protons and electrons - filling factor ≠ 1
♦ thermal plasma mixed within the relativistic plasma
♦ conditions different from equipartition u24
ProbabilityProbability ofof radioradio emissionemission
Is the radio emission of a galaxy affected by the fact that the galaxy belongs to a cluster ? gal-gal interaction Î trigger r.e. more powerful or long lived r.e.
RadioRadio LuminosityLuminosity FunctionFunction (RLF):(RLF): ProbabilProbabilityity tthathat aa galaxygalaxy inin aa defineddefined samplesample emitsemits wwithith rradioadio powerpower inin thethe intervalinterval PP ±± dPdP
n( ∆Pi ) n = number of galaxies detected in the power f( P ) = interval ∆P N( ∆P ) i i N = total number of optical galaxies which could have been detected in the same bin
Integral function F(>P) can be obtained simply by summing the data of all bins up to P Slide 25 u24 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 u81
The local RLF of elliptical galaxies (cluster + field) can be described by two exponential laws with a break at a power P*: this corresponds to the transition between FRI and FRII radio galaxies 22 NOTE that radio galaxies with P1.4 > 10 W/Hz are AGN
It is found that the local P* RLF is the same for cluster and field galaxies Î all radio galaxies live in a cluster like environment
Auriemma et al 1977 Meier et al 1979 Best et al 2005 Fanti 1984 Ledlow & Owen 1994,1996
FractionalFractional locallocal ff(P)(P) forfor eellipticallliptical ggalaxiesalaxies ((z<0.1)z<0.1) Slide 26 u81 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 Comparison of the RLF in different magnitude ranges shows that the probability of a galaxy to develop a radio source is strongly dependent on the galaxy optical luminosity
Î Bivariate RLF f(P,M): probability that a galaxy with absolute magnitude in the range M ± dM is radioemitting in the radio power range P ± dP
Integral RLF : F(>P,M) u82
Integral bivariate RLF for ellipticals at z < 0.1
Îbrighter optical galaxies (more massive) have a higher probability of forming a radio source
P* depends on optical luminosity L following the law P*∝L2
No difference between RLF of cluster anf field galaxies
Note : plot obtained by Ledlow and Owen (1996) -1 -1 with H=50 km s Mpc q0=0.5 Slide 28 u82 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 u82
Relation to cluster mergers ?
Controversial results:
- The universality of RLF can be generalized also to merging clusters (Venturi et al. 2001, 2003, Giacintucci et al 2004)
- Excess of powerful Radio galaxies in A2255 (Miller & Owen 2003) Slide 29 u82 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 u82
A2255 (Miller & Owen 2003)
Excess of powerful Radiogalaxies
ÎDynamical state responsible for the large number of r.g. -more massiveg. -more turbulence
Importance of mergers would imply effect on clusters at high redshift, where clusters are being assembled Slide 30 u82 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 RLF evolution:
Stocke et al. (1999) report no evolution out to z = 0.8 (19 clusters)
Branchesi et al. (2005) analyzed 22 distant clusters of the Rosat North Ecliptic Pole Survey (z<0.8) (NEP, Gioia et al 2003):
Find a steeper slope and higher amplitude RLF with about a factor of 1.5-2 with respect to local consistent with reanalysis of Stocke
Î more distant clusters may host a higher number of radio galaxies Î to be confirmed Radio emission at low power levels:
22 -1 At low radio power (P1.4 GHz ~10 W Hz ) star formation becomes the dominant mechanism in the production of radio emission (rather than AGN).
Recent studies : (Morrison 1999, Morrison & Owen 2003, Owen et al. 2005)
30 very rich clusters with z ≤ 0.25 22 L1.4GHz ≥ 2 10 W/Hz MR ≤ -21
Data are sensitive to star formation rates M ≥ 5Msun/yr u82
A2125 (Owen et al. 1999): major cluster-cluster merger
Excess of low luminosity radiosources
A2255 (Miller & Owen 2003)
Excess of star forming galaxies Î merger
A3558 Cluster Complex (Giacintucciet al. 2003)
Sensitive to star formation rates 1.2 – 7.1 Msun/yr
Marginal evidence of enhanced star formation Slide 33 u82 La potenza di break corrisponde alla transizione tra le FRI e le FRII la potenza di break e' funzione della luminosita' ottica e va come L^2 cioe' la divisione tra FRI e FRII e' funzione della magnitudine L'universalita' della RLF si puo' generalizzare agli ammassi con merging
unibo, 3/20/2003 u28
MECHANISMS IN CLUSTERS - rate of galaxy mergers - change in the external pressure
- ISM stripping
INCREASE (Evrard 1991) or DECREASE (Fujita et al 1999) the SF or have DIFFERENT EFFECTS at differeent cluster locations (Fujita & Nagashima 1999)
NO firm conclusions that SF is enhanced in clusters
Growing evidence that STAR FORMATION is ENHANCED due to cluster merger Slide 34 u27 unibo, 3/21/2003 u28 A2125 e A2645 mappati fino a 10^23. hanno circa stesso redshift - 0.25- il primo ha merger il secondo no A2255 e A2256 mappati a livelli piu' deboli Shapley mappata a 10^22, forse bisogna andare piu' giu' unibo, 3/21/2003 Summary
♦ Interaction between radio galaxy and ICM (motions of galaxies and/or large scale gas motion) produces distorted radio structures Î TAILED RADIO GALAXIES
♦ Other examples of extreme RG – ICM interaction are GAS CAVITIES FILLED OF RADIO PLASMA
♦ The probability of radio emission is THE SAME for cluster and non-cluster galaxies. It depends on the local environment and optical magnitude. It can increase in mering clusters
♦ The cluster mergers affect the STAR FORMATION