FRI RADIO GALAXIES AT z > 1STUDYING THE BUILDING BLOCKS OF

TODAY'S MOST MASSIVE GALAXIES AND CLUSTERS

Marco ChiabergeSpace Telescope Science Institute

and INAF-IRA Bologna

G. Tremblay (STScI)A. Capetti (INAF-OATO)D. Macchetto (STScI)W.B. Sparks (STScI)P. Tozzi (INAF-OATS)

MORPHOLOGICAL CLASSIFICATION OF RADIO GALAXIES

FR I FR II

LOW POWER HIGH POWER

Fanaroff & Riley 1974

L178 ~< 2 x 1026 W Hz -1 L178 >~ 2 x 1026 W Hz -1

The radio-loud AGN unification model

FR I

BL Lac

Urry & Padovani 1995

THE HST VIEW of FR I radiogalaxies Complete sample:

33 objects, 32 with HST R-band observations

The HST/WFPC2 snapshot survey of 3CR radio sources (P.I. Sparks)Chiab, Capetti & Celotti 1999

FRI RADIO GALAXIES AT LOW Z

● ASSOCIATED TO GIANT ELLIPTICAL GALAXIES

HOSTING THE MOST MASSIVE BLACK HOLES (e.g. Donzelli et al. 2007, Zirbel & Baum 1997)

• ENVIRONMENT: CLUSTERS (e.g Zirbel 1997)

MOST FRI ARE HOSTED BY cD GALAXIES

• PROPERTIES OF THE AGN:

PROBABLY “RIAF” ACCRETION, RELATIVISTIC JET

NO THICK TORI, NO BLR, NO FRI-QSO, NO IR EXCESS (Chiaberge et al

1999)

DIFFERENT FROM ALL OTHER AGN

MORE SIMILAR TO “INACTIVE” GALAXIES

FR I radio galaxies are known in the nearby universe only

•A few FR Is (~10) are present in the 6C

and 7C samples up to z~0.8

•A few low-power radio galaxies are

found in the 2SLAQ survey (z < 0.7)

(Sadler et al. 2007)

•The most distant FR I known is at z ~1

(Snellen & Best 2001)

In the 3CR catalog FRIs are present only for z < 0.2

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-QSO are absent in the low-z universe: what is the fractionof FRI-QSO at high z? (e.g Blundell et al. 2002, Heywood et al. 2007)

The role of FRI in the framework of the AGN unification scheme

FRIs as probes for studying the formation and co-evolution of themost massive galaxies and most massive BH

FRI as tracers of high-z clusters

Differently from FRIIs, the AGN does not dominate the emissionin crucial bands (IR, X-rays)

FLUX LIMITED SAMPLES CANNOT BE USED

The search method must make use of multiwavelength information COSMOS (Scoville et al 2007) is perfectly suitable for this.

Radio selection (from FIRST): what is the flux of an FR I radio galaxy of a certain radio power in the redshift bin 1 < z < 2? (1mJy < F < 13mJy)

Morphology: FRIIs are excluded

Optical selection: optical counterparts are found using the COSMOScatalog (Mobasher et al 2007). Bright sources (detected in SDSS) are excluded (probably nearby starburst galaxies)

U-band dropouts are excluded (z > ~ 2.5)

Basic assumptions: the radio properties of high-z FRIs are similar to those of low z FRIs

the optical properties of high-z FRIs are similar to those of high-z FRIIs

182 radio sources in FIRST 133 match the flux requirements

28 FRI candidates 7 FRI-QSO candidates> 4 cluster candidates

RESULTS

COSMOS optical data are NOT deep enough to

detect a large fraction of cluster galaxies at z > 1

(Chiaberge et al.

in prep)

Using photometric

redshifts (Mobasher et al 2007)

and the K-z relation

for radio galaxies we

can check that our

selection criteria work

K-z relation for radio galaxies hosts

Projected linear size ~100kpc zphot

= 1.85

COSMOS-VLA COSMOS HST/ACS F814W 1 orbit

1”

Elliptical hosts (zphot

= 1.31)

zphot

= 2.09

zphot

= 2.04

zphot

= 0.72

zphot

= 1.23

10”

VLA ACS WFC F814W

Using FRIs to find high-z clusters

zphot

= 1.3

zphot

= 2.09

R = 3.m

G = V

B = B

2'

2'

SUMMARY

Future work:

• Spectroscopic redshifts (this week at Galileo, GEMINI?)

• Stacking Xray data to search for cluster/ICM emission

• Radio (low and high frequency, higher resolution data)

HST DEEP IMAGING TO STUDY HOST GALAXIES AND

CLUSTERS – ACS (OPTICAL) – WFC3 (IR)

• We discovered FRI radio galaxies at z >1

• FRIs can be used to study the formation and evolution

of the most massive galaxies and their relationship with

supermassive black holes

• FRIs can be used to find high z clusters