Cosmological parameters with radio galaxies Oleg Verkhodanov Special astrophysical observator Nizhnij Arkhyz
Radio cosmology Dark ages
Radio galaxies - galaxies with radio power mostly due to nucleus activity Power of emission is up to 10^48 erg/s
What are the radio galaxies ?
Cygnus A E-galaxy m=16 z = 0.057, theta~2' (80 kpc), v = 0.02c, P= 3x10^44 erg/s
Centaurus A (NGC 5128) P = 10^42 erg/s, d = 12 kpc
Virgo A (NGC 4486, M87) cD-galaxy 20'' (1.5 kpc) optical jet
Radio galaxies identified with gE or cD galaxies and should be visible in optics and radio waves from very beginning (z<~6)
2 basic morphological types of RG Fanaroff – Riley I Fanaroff – Riley II
Unified model
Continuum radio galaxy spectra alpha S~nu Steep spectrum: alpha<-0.5
Radio galaxies as Universe reference point The most distant radio galaxy: z=5.19 (van Breugel et al., 1999)
Distribution of radio galaxies for Cambridge catalogs (Cruz et al., 2007)
Cosmology with radio galaxies a) “size – redshift” (standard rod) b) “luminosity – redshift” (standard candle) c) ''Log N – Log S'' (“source number – flux density”) d) Gravitational lensing e) Clustering and large stellar structure forming f) Age of stellar systems g) Black hole formation at high redshift h) Dark matter search in halos What is good ? (probably, we know) 1) Universe expands, accelerating; 2) There are CMB radiation and its angular fluctuations; 3) elements in Universe.
Radio galaxies and large scale structure
''Size – redshift'' diagram for radio sources and CMB (Jackson, Janneta, 2006)
Gravitational lenses Einstein ring (RC 1131+0456) B 1938+666
Source counts: Log N – Log S FR II: 1) FRII & QSR, alp<-0.5 2) QSR with flat Sp 3) RG, BL Lac, FR I: 6) BL Lac, 7) Starburst galaxies (Jackson, Wall, 1999)
“Big Trio” Program RATAN-600 VLA BTA
“Big Trio” program 1) Radio sources of the “Cold” survey ( >10 mJy at 7.6 cm) 2) Steep radio spectrum (synchrotron) selection 3) VLA (radio): morphology selection (FR II) 4) 6m telescope (optics): identification, BVRI-photometry, spectrosopy (redshift) 5) Age estimation
“Big Trio” program
Age of radio galaxies
Giant elliptical galaxies with old stellar population ==> photometrical study and existance at very high z ~4 (Pipino & Mantteucci, 2004). selection of distant gE (z>0.5) with radio galaxies ==> by radio astronomical methods (Pedani, 2003).
Estimation of stellar and galaxy age by thermal nuclear reactions - independent test for Universe expansion
Sample of 220 objects with 3 subsamples: (1) Famous radio galaxies FR II (1<z<4): initially 300 RGs (NED) ---> resulting 30 FRII (2) RGs of FR II from the “Cold” survey (“Big Trio”: Parijskij et al., 1990-2003), (3) Elliptical galaxies from clusters (Stanford, 2002) (0.1<z<1.3)
(Verkhodanov, Parijskij, Starobinsky, 2005) Approximation of t(z) with integral curve and detection of H_o и Omega_Lambda (Verkhodanov, Parijskij, Starobinsky, 2005) Sample binning dz=0.2 и dz=0.3 Take maximum in each bin
Two models of synthetic spectra
Age [Myr] Redshift z Age [Myr] Redshift z
Possible errors metalicity: error ~100 Myr (Jimenez, Loeb, 2002) initial mass function has low influence (Bolzonella et al., 2001), error in galaxy type detection, incomplete sample: robust detection Bootstrap method: mutiplication coefficient 100, variation of H_o ~ 10%
Model dz Om_mOm_L H_o epsilon SED [Myr] GISSEL 0.2 0.2 0.8 78 1695 GISSEL 0.3 0.2 0.8 72 1367 PEGASE 0.2 0.2 0.8 65 4101 PEGASE 0.3 0.2 0.8 53 2748 H_o = 72 +/- 10 Om_L = 0.8 +/- 0.1, not exelent, but satisfys the model
What is further ? 2) Combining different methods 1) Select ALL the distant RGs and typical close gEs 2) Combining different methods
z = 4.514 (Kopylov et al., 2006) The 2nd RG by z, the 1st RG by power among RGs, z>4
Thank you for hospitality !