Radio Sources in High-Redshift Galaxy Clusters:

An Initial LookMegan Roscioli

University of Chicago

In collaboration withMike Gladders, U. Chicago

RCS-1,2 Collaboration

GLCW8, Columbus

Motivation

• We (finally) have large, well-characterized catalogs of clusters, so we should investigate the associated source populations at other wavelengths.

• What is the relation between AGN (and heating from AGN) and the formation/characteristics of BCGs and other cluster members?

• How significantly will radio point sources contaminate upcoming SZ surveys?

• How significantly do AGN contribute to the energy budget of clusters? Can heating from radio lobes of AGN provide enough energy into the ICM to counter cooling flows?

Outline:

• Cluster samples: RCS-1, RCS-2, details

• Radio source samples: FIRST, NVSS

• Radial distribution

• Radio luminosity dependence

• Cluster richness dependence

• Evolution with redshift

Data - optical

• RCS-1 two-band (RC and z’) optical survey at CFHT and

CTIO uses red sequence cluster finding methodswell-defined sub-sample of ~ 1,000 clusters (see

Gladders, et al. 2007) significance > 3.3 0.35 < z < 0.95 red galaxy richness > 300 richness errors < 50%

Near-complete to redshifts ~ 0.95

Reference: Gladders & Yee, 2005NOAO/AURA/NSF

Data - optical

• RCS-2 (www.rcs2.org)three-band (grz) optical survey at CFHT using

Megacam. Uses red sequence cluster finding methods

Survey ongoing: data acquisition completion planned end of 2007

Current cluster sample is ~30,000 clusters

…and more on the way!

Data - radio

• NVSSVLA compact D and DnC configurations, 1.4 GHz

resolution ~ 45” All-sky above -40 degrees declinationsensitivity limit ~ 2.5 mJy

• FIRSTVLA B-array, 1.4 GHz resolution ~ 5”10,000 square degrees sensitivity limit ~ 1.0 mJy

Reference: Condon, et al. 1998

References: Becker, White & Helfand 1995 White, et al. 1997

Image courtesy of NRAO/

Combined Overlap Areas

• RCS-2+NVSS

~414 square degrees

Pros: large area, many clusters, many radio sources

Cons: Cluster catalog not yet fully characterized

• RCS-1+FIRST

~40 square degrees

Pros: well characterized cluster sample with established cosmological context

Cons: much smaller sample

AGN profiles

Optical/Radio

X-ray

Ruderman & Ebeling, 2005

Radio Luminosity bins

Significance bins

Evolution with redshiftRCS1+FIRST: Number of FIRST sources/cluster:

for 0.3 < z < 0.650.067 +/- 0.010

for 0.65 < z < 0.95 0.094 +/- 0.014

discernible 40% increase in radio sources per cluster at high redshift

Where next?

• Scale radial distribution of radio sources to virial radius (R200)

• Consider radio morphology

• Calculate the radial distribution of radio sources around cluster BCGs

• Push to higher frequencies?

Summary of preliminary results

• We detect a significant association between NVSS and FIRST sources and RCS clusters over the entire RCS redshift range.

• Source numbers are sufficient to explore sample characteristics over a broad range of properties Radial distribution: radio sources most obviously found within the

central few hundred kpc. Radial distribution: some evidence for source excess at ~1-2

Mpc The highest luminosity radio sources avoid cluster centers

relative to lower luminosity sources More “massive” clusters contain more radio sources Discernible 40% increase at high redshifts in the number of radio

sources in clusters

And more to come!