Strong Lensing in RCS-2 Strong Lensing in RCS-2 ClustersClusters

Matt BaylissMatt Bayliss

University of ChicagoUniversity of Chicago

Department of Astronomy & AstrophysicsDepartment of Astronomy & Astrophysics

Great Lakes Cosmology Workshop 8 – June 2, 2007Great Lakes Cosmology Workshop 8 – June 2, 2007

Collaborators: Collaborators: Michael Gladders - University of ChicagoMichael Gladders - University of ChicagoHoward Yee and David Gilbank – University of TorontoHoward Yee and David Gilbank – University of Torontoand the rest of the RCS-2 team.and the rest of the RCS-2 team.

Motivations: Why Strong Lensing? Motivations: Why Strong Lensing? Why Now?Why Now?

Large cluster Large cluster catalogs popping catalogs popping up –> good time up –> good time to start looking.to start looking.

Strong Lensing Strong Lensing relevant for relevant for cluster studies, cluster studies, cosmology and cosmology and study of study of background background universe.universe.

RCS Lensing Cluster at z = 0.77

So What Is It We Want to So What Is It We Want to Measure?Measure?

Directly Probe the Gravitational Potential. Directly Probe the Gravitational Potential. Mass Measurement + Mass ProfileMass Measurement + Mass Profile Unique window into small scale Dark Matter Unique window into small scale Dark Matter

DistributionDistribution Radial distribution of arcs from cluster coresRadial distribution of arcs from cluster cores Azimuthal angle covered by giant arcsAzimuthal angle covered by giant arcs

Large samples of giant arcs open the door Large samples of giant arcs open the door for statistical studies of lens and source for statistical studies of lens and source propertiesproperties Distributions of lens properties (with redshift)Distributions of lens properties (with redshift) Statistically characterize hundreds of high-z Statistically characterize hundreds of high-z

lensed sourceslensed sources

RCS-2 Lenses – A Quick Tour:RCS-2 Lenses – A Quick Tour:

RCS-2 Lensing Tour continuedRCS-2 Lensing Tour continued

RCS-2 Lenses – Mass-Redshift RCS-2 Lenses – Mass-Redshift DistributionDistribution

Mass calculated Mass calculated by assuming by assuming fitted circular fitted circular radii equal to radii equal to Einstein Radii for Einstein Radii for a SIS profile for a SIS profile for all cluster all cluster lenses, and lenses, and averaging over a averaging over a random random distribution of distribution of source redshifts.source redshifts.

RCS-2 Lenses – A Few StatisticsRCS-2 Lenses – A Few Statistics

Median azimuthal angle covered by giant arcs is Median azimuthal angle covered by giant arcs is 0.459 radians (or ~ 26 degrees, range is 10-60 0.459 radians (or ~ 26 degrees, range is 10-60 degrees)degrees) So our “giant arcs” are, in fact, reasonably giantSo our “giant arcs” are, in fact, reasonably giant

Median redshift = 0.549Median redshift = 0.549 Hennawi et al 2007 predict a median redshift of 0.49 for Hennawi et al 2007 predict a median redshift of 0.49 for

RCS-1 cluster lenses using simulations RCS-1 cluster lenses using simulations Hennawi prediction is biased high for RCS-2 comparison: Hennawi prediction is biased high for RCS-2 comparison:

σσ88, deeper SB limit and filter color, deeper SB limit and filter color

Hilbert et al: low-z, high mass population of Hilbert et al: low-z, high mass population of lenses predicted.lenses predicted.

Strong Lensing PredictionsStrong Lensing Predictions

Hennawi et al 2007, astro-ph/0506171

Hilbert et al 2007, astro-ph/0703803

RCS-2 Lenses – Mass-Redshift RCS-2 Lenses – Mass-Redshift DistributionDistribution

Things That Get You Space Telescope Things That Get You Space Telescope TimeTime

Extremely high mass Extremely high mass cluster at z = 0.700, cluster at z = 0.700, warranting a number warranting a number of followup of followup observations:observations:

XMM ~ 1 cnt/sXMM ~ 1 cnt/s Chandra (coming Chandra (coming

soon)soon) Magellan Magellan

Spectroscopy – Spectroscopy – early-type galaxy early-type galaxy σσ1D1D of 1400 +/- 70 km/sof 1400 +/- 70 km/s

SZA observation: SZA observation: strong source, strong source, analysis underwayanalysis underway

Weak lensing from Weak lensing from CFHT mass estimate CFHT mass estimate ~ 3e15 M~ 3e15 M๏๏

Multiple arcs Multiple arcs obvious – first obvious – first spectroscopic spectroscopic confirmation z=3.02, confirmation z=3.02, theta_E=49”theta_E=49”

HST+ACS+NICMOS HST+ACS+NICMOS imagingimaging

NICMOS F160WNICMOS F160W

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Object of Interest - Preliminary Object of Interest - Preliminary AnalysisAnalysis

F435F435 gg rr ii KK

ImageImage11

23.9823.98

23.8023.80 23.1823.18 22.9122.91 18.6418.64

ImageImage22

23.7823.78

23.4323.43 23.0823.08 22.8222.82 18.7618.76

ImageImage33

23.6723.67

23.6223.62 23.0323.03 22.8222.82 18.6818.68

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So What Is This Thing?So What Is This Thing?

R – K colors are R – K colors are ~ 4 - 4.2 for the ~ 4 - 4.2 for the three imagesthree images

Figure from Szokoly et al, 2004, ApJS..155..271S

Where Are We Going?Where Are We Going?

To Las Campanas!To Las Campanas!

Additional follow-up Additional follow-up observations.observations. Gemini + HSTGemini + HST

Rigorous definition Rigorous definition of RCS-2 Strong of RCS-2 Strong Lensing SampleLensing Sample Expect ~150 giant arc Expect ~150 giant arc

systems (complete) systems (complete) and similar numbers and similar numbers of galaxy-scale strong of galaxy-scale strong lenses (less complete)lenses (less complete)