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. Macchetto STScI W.B. Sparks STScI 3C31 - ACS/HRC

MORPHOLOGICAL CLASSIFICATION OF RADIO GALAXIES FR IFR II LOW POWERHIGH POWER Fanaroff & Riley 1974 L 178 ~< 2 x W Hz -1 L 178 >~ 2 x W Hz -1 Jet decelerates to v<<c at ~1kpc Jet is relativistic on scales >100kpc Zirbel &Baum 1995

The radio-loud AGN unification model LOW POWER HIGH POWER FR I FR II BL Lac FSRQ NLRG LEG? HEG BLRG & SSRQ QSO Urry & Padovani 1995 L 178 ~< 2 x W Hz -1 L 178 >~ 2 x W Hz -1

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

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

 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 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 L disk < L edd No BLR (Nicastro 2000, Laor 2000) Similar correlations are found in near IR and X-rays

The radio-loud AGN unification model FR I BL Lac

X-ray properties of FRIs Nuclei: L X ~ erg s -1 N H < 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) L X < 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) L X ~ erg s -1

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 cD GALAXIES FRIIs are typically not in clusters FRIs at low redshifts “STARVED” QUASARS e.g. Chiab et al. 1999

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)‏

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

GIANT Ly  EMITTERS AROUND POWERFUL HIGH-Z RADIO GALAXIES 4C z = 3.8 Miley & De Breuck 2008

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 Xrays at z>1

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 RDCS z=1.24 kT= 6 keV Z= 0.36 Z sun M= 2x10 14 M sun Rosati et al. 2004

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

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)

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)

Selection Process

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

For each RG we count how many objects are at 1.6 < z phot < 2.3 within a 90” radius from the RG COSMOS FRI objects COSMOS FRI objects COSMOS FRI 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 4  90” ~ 0.8Mpc at z =1.8 3 cluster candidates at z~1.8 Chiab et al 2010

COSMOS FRI 03 z phot = 1.96 RED = Spitzer 3.6  m GREEN = r band BLUE = B band Mostly blue objects? A significant number of RED galaxies have no z phot estimate

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

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

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

FRI at z phot = 0.35 VLA 1.4GHz LOW-z FRI in the COSMOS field

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

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