USING LOW POWER RADIO GALAXIES AS BEACONS FOR CLUSTERS TO “FILL THE GAP” AT 1<z<2

1. USING LOW POWER RADIO GALAXIES AS BEACONS FOR CLUSTERS TO “FILL THE GAP” AT 1<z<2 Marco Chiaberge Space Telescope Science Institute A. Capetti INAF- OATO G. Tremblay RIT P. Tozzi INAF-OATS P. Rosati ESO D. MacchettoSTScI W.B. Sparks STScI 3C31 - ACS/HRC

2. MORPHOLOGICAL CLASSIFICATION OF RADIO GALAXIES FR I FR II Zirbel &Baum 1995 Jet decelerates to v<<c at ~1kpc Jet is relativistic on scales >100kpc LOW POWER HIGH POWER L178 ~< 2 x 1026 W Hz -1 L178 >~ 2 x 1026 W Hz -1 Fanaroff & Riley 1974

3. The radio-loud AGN unification model BL Lac FR II NLRG LEG? HEG FR I BLRG & SSRQ QSO HIGH POWER LOW POWER FSRQ L178 ~< 2 x 1026 W Hz -1 L178 >~ 2 x 1026 W Hz -1 Urry & Padovani 1995

4. THE UNIFICATION SCHEME IS NOT JUST A MERE GEOMETRIC EXERCISE It is a fundamental tool to investigate crucial aspects related to the physical properties of the innermost regions of active nuclei and galaxies in general • Accretion/ejection • The origin of radio loudness • The relationship between the AGN and the environment • (Induced/suppressed star formation, feedback…) Radio galaxies are particularly important since they are associated with the most massive elliptical galaxies

5. THE NUCLEI OF FRI RADIO GALAXIES HST is able to show faint nuclei superimposed to bright host galaxies 3C 338 - HST/ACS F814W 700s exp

6. THE RADIO-OPTICAL CORE CORRELATION OF 3CR FR I NUCLEI Optical emission from the base of the jet is observed in 80% of FRIs FRIs are unobscured Ldisk< 10-5Ledd No BLR (Nicastro 2000, Laor 2000) Similar correlations are found in near IR and X-rays Chiab, Capetti & Celotti 1999, Capetti et al. 2002, Verdoes-Kleijn et al. 2001, Whysong and Antonucci 2004; Balmaverde et al. 2006; Baldi , Chiab et al . in press  NON-THERMAL SYNCHROTRON EMISSION FROM THE BASE OF THE JET

7. The radio-loud AGN unification model BL Lac FR I

8. X-ray properties of FRIs Nuclei: LX ~ 1041 erg s-1 NH < 1022 cm-2 The nuclear emission is jet-dominated (e.g. Balmaverde, Capetti & Grandi 2006, Evans et al. 2006) Extended emission: synchrotron, from jets (e.g. Harris & Krawczynski 2006) LX < 1042 erg s-1 X-ray properties of FRIIs (and QSOs) Nuclei: more powerful and absorbed Extended emission (jets): IC (SSC or IC from CMB photons) (e.g. Celotti, Ghisellini and Chiab 2001) LX ~ 1044-45 erg s-1

9. FRIs at low redshifts “STARVED” QUASARS e.g. Chiab et al. 1999 ASSOCIATED WITH GIANT ELLIPTICAL GALAXIES HOSTING THE MOST MASSIVE BLACK HOLES (e.g. Donzelli, Chiab et al. 2007, Zirbel & Baum 1997) ENVIRONMENT: CLUSTERS (e.g Hill &Lilly 91,Zirbel 1997) MOST FRI ARE HOSTED BY cDGALAXIES FRIIs are typically not in clusters

10. WHY ARE WE LOOKING FOR FRIs AT 1 < z <2 ? Cosmological Evolution of FRIs is basically unknown Hints for strong evolution up to z~0.7 (Sadler et al. 2007)‏ FRI-QSOs are absent in the low-z universe: what is the fraction of FRI-QSO at high z? (e.g Blundell et al. 2002, Heywood et al. 2007)‏ The role of FRIs in the framework of the AGN unification scheme FRIs as probes for studying the formation and co-evolution of the most massive galaxies and most massive BH FRI as tracers of high-z clusters to bridge the gap 1 < z < 2 When does the red sequence form? Differently from FRIIs, in FRIs the AGN does not dominate the emission in crucial bands (IR, X-rays)‏

11. THE RED SEQUENCE IN HIGH-Z CLUSTERS z=0.8 At what redshift does the red sequence form? At what z do giant elliptical galaxies form? Red sequence selected clusters In the SpARCS survey Demarco et al 2010 z = 1.2

12. GIANT LyaEMITTERS AROUND POWERFUL HIGH-Z RADIO GALAXIES 4C 41.17 z = 3.8 Miley & De Breuck 2008

13. WHY ARE WE LOOKING FOR FRIs AT 1 < z <2 ? Cosmological Evolution of FRIs is basically unknown Hints for strong evolution up to z~0.7 (Sadler et al. 2007)‏ FRI-QSOs are absent in the low-z universe: what is the fraction of FRI-QSO at high z? (e.g Blundell et al. 2002, Heywood et al. 2007)‏ The role of FRIs in the framework of the AGN unification scheme FRIs as probes for studying the formation and co-evolution of the most massive galaxies and most massive BH FRI as tracers of high-z clusters to bridge the gap 1 < z < 2 When does the red sequence form? Differently from FRIIs, in FRIs the AGN does not dominate the emission in crucial bands (IR, X-rays)‏ Only less than 10 clusters are confirmed in the Xraysat z>1

14. X- ray observations of high-z clusters X-ray luminosity functions, mass, temperature, metallicity of the intracluster medium are compared with predictions from cosmological models CHANDRA RDCS1252.9-2927 z=1.24 kT= 6 keV Z= 0.36 Zsun M= 2x1014Msun Rosati et al. 2004

15. Extended emission around powerful high-z radio galaxies Studies of the hot gas environment are hampered by the AGN 3C 432 z=1.785 ICCMB radiation g ~1000 CMB scales with (1+z)4 Fabian et al. 2003, Erlund et al. 2006

16. A SEARCH FOR LOW LUMINOSITY RADIO GALAXIES IN THE DISTANT UNIVERSE FR I radio galaxies are known in the nearby universe only, as a result of the tight flux-redshift dependence in flux limited samples In the 3C catalog, FR Is are present only at z < 0.2 A few FR Is (~10) are included in the 6C and 7C samples up to z~0.8 The most distant FR I known is at z ~1 (Snellen & Best 2001) McLure et al (2004)

17. FLUX LIMITED SAMPLES CANNOT BE USED The search method must use of multiwavelength information COSMOS (Scoville et al 2007, Koekemoer et al. 2007) has all the data we need 2sq deg survey of an equatorial area of the sky Data were taken from the radio (VLA 1.4 GHz) to the X-rays Basic assumptions: the radio properties of high-z FRIs are similar to those of low z FRIs (no hot spots) The FRI/FRII break does not change with redshift The optical properties of high-z FRIs are similar to those of high-z FRIIs (they are hosted in red galaxies)

18. Selection Process

19. 36 HIGH-Z FRI CANDIDATES RADIO (VLA) AND OPTICAL (HST) IMAGES Schinnerer et al. 07 Koekemoer et al. 07 Chiab et al 2009

20. 3 cluster candidates at z~1.8 For each RG we count how many objects are at 1.6 < zphot < 2.3 within a 90” radius from the RG 90” ~ 0.8Mpc at z =1.8 COSMOS FRI 03 58 objects COSMOS FRI 05 51 objects COSMOS FRI 226 53 objects In 12 randomly selected control fields (that do not include any of our RGs): 32 ± 2 objects This is an overdensity factor ~2 at 4s Chiab et al 2010

21. COSMOS FRI 03 zphot =1.96 RED = Spitzer 3.6mm GREEN = r band BLUE = B band Mostly blue objects? A significant number of RED galaxies have no zphot estimate

22. PHOTO-z DISTRIBUTIONS COSMOS FRI 03 COSMOS FRI 05 COSMOS FRI 226 RED FRI fields BLACK control fields BINS: Dz = 0.2 The extremely red galaxies are missed (too faint in i band to be in the catalog) Chiab et al 2010

23. WHAT ABOUT FRIs at z~1 (and lower)? 5/8 FRI at 0.9 < zphot < 1.1 show clear over-densities VLA 1.4GHz Chiab et al. in prep. R = 3.6mm G = r band B = B band COSMOS FRI 01 zphot= 0.92 Chandra 0.5-2 kev

24. 1 orbit HST/ACS F814W COSMOS Koekemoer et al. 2007

25. LOW-z FRI in the COSMOS field VLA 1.4GHz FRI at zphot= 0.35

26. What about FRIIs? ~5 FRIIs in our sample between 1< zphot < 2 2 FRII at z~1 None of them show signs of over-densities FRII zphot= 1.17

27. CONCLUSIONS We discovered FRIs in the “unexplored” redshift range 1 < z < 2 The discovery of low luminosity radio galaxies at 1 < z < 2 opens a new way to find clusters of galaxies in that range of redshift It allows the study of the cosmological evolution of FRIs We have 3 cluster candidates dominated by “blue” galaxies at z~1.8 FRIs are better than FRIIs as “beacons” for clusters FUTURE WORK: The properties of high-z FRI: emission lines? X-rays? Radio? Host galaxies? Clusters: looking for X-ray emission (stacking) Detailed study of the z~1 cluster candidates Apply the same selection procedure to e.g. CDFs WE NEED OBSERVING TIME!! VLT spectra of candidate cluster galaxies using MOS HST high resolution imaging and high-precision photometry FRIIs: These are objects ~100 x less powerful than the FRIIs in the 3C sample, and still ~10x fainter than the FRIIs in the 6C and 7C