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!