WEAK GRAVITATIONAL LENSING OF X-RAYGROUPS

Alexie LeauthaudChamberlain Fellow

Lawrence Berkeley National Lab& Berkeley Center for Cosmological

Physics

Kevin Bundy, Matt George, Melody Wolk, Yen-Ting Lin, Stefania Giodini,Masayuki Tanaka

Jean-Paul Kneib, Alexis Finoguenov, Jeremy Tinker, Richard Massey, James Taylor, JasonRhodes, Peter Capak, Olivier Ilbert

& the COSMOS Collaboration

COSMOS surveyCHANDRA + XMM

A. Finoguenov et al. 2007

1.3 deg2

The cosmos X-ray group sampleThe cosmos X-ray group sample

Aim of this work: study the Dark Matterproperties of a sample of ~150 groups/clustersdetected via extended XMM emission in theCOSMOS survey

This is one of the largest samples of it’s kindand is comprised of groups with halo massesM200 ~ 1013 Msun to 1013 Msun .

Lensing constraints on halo centers andgroup members (Matt George)

Statistical nature of BCGs (Melody Wolk& Yen Ting Lin)

Assembly history of groups and BCGs(Kevin Bundy)

Baryon fraction (Stefania Giodini)

Alexie Leauthaud

The growth of the Dark Matter Mass Function overcosmic time - Heitmann et al. 2006

I. Constraints on cosmological parameterscan be improved by extendingmeasurements down to the low end ofthe mass function (on condition thatmasses can be measured correctly forgroups).

Motivations for pushing downMotivations for pushing down toto the low end of the mass functionthe low end of the mass function

Alexie Leauthaud

Most massive systems:- low numbers- mergers/ non relaxed- triaxiality

The growth of the Dark Matter Mass Function overcosmic time - Heitmann et al. 2006

I. Constraints on cosmological parameterscan be improved by extendingmeasurements down to the low end ofthe mass function (on condition thatmasses can be measured correctly forgroups).

II. Understanding the scaling relations ofgalaxy groups will lead to a better handleon the slope and amplitude of the scalingrelations of more massive systems.

Motivations for pushing downMotivations for pushing down toto the low end of the mass functionthe low end of the mass function

Alexie Leauthaud

The growth of the Dark Matter Mass Function overcosmic time - Heitmann et al. 2006

I. Constraints on cosmological parameterscan be improved by extendingmeasurements down to the low end ofthe mass function (on condition thatmasses can be measured correctly forgroups).

II. Understanding the scaling relations ofgalaxy groups will lead to a better handleon the slope and amplitude of the scalingrelations of more massive systems.

III. Galaxy groups may play in key role inprocesses of galaxy formation (lowvelocity dispersions ⇒ galaxies are morelikely to merge?). Groups are thebuilding blocks of clusters (in terms ofmass if not in terms of galaxynumbers).

Motivations for pushing downMotivations for pushing down toto the low end of the mass functionthe low end of the mass function

Alexie Leauthaud

The The cosmos group cosmos group samplesample

Alexie Leauthaud

In this project, we have looked into the calibration of the X-ray Luminosity (Lx) - Halomass (M200) relation. Nevertheless, the method outlined here can be applied to other massproxies such as Temperature, Richness, Velocity Dispersion, etc.

Lx - M200 T - M200 N200 - M200 σdyn - M200 MSZ - M200

A better understanding of each of these scaling relations is necessary for DE studies butwill also shed light on the the underlying physical processes within groups & clusters.

The X-ray luminosity of groups and clusters is considered a reasonable tracer of halomass with a logarithmic scatter of roughly 20% to 30% (Stanek et al. 2006, Maughan 2007,Pratt et al. 2008 Rozo et al. 2008, Rykoff et al. 2008, Vikhlinin et al. 2009).

Although more tightly correlated mass tracers have been found - such indicators requirethe measurement of an X-ray spectrum which is not possible for most surveys where countrates are low. Lx is a simple X-ray observable, accessible with survey quality data, and theonly one that can be easily measured at high-z.

The MThe M200200 - L - Lxx relation relation

!

M200" E(z)

M0

= A "LX" E(z)#1

L0

$

% &

'

( )

*Form of theM200 - LX relation:

Alexie Leauthaud

slope α

««  m-Lxm-Lx  » » is is not not the same the same as «as «  lx-Mlx-M  » !» !

For e.g seeappendix in

Leauthaud et al.2010

Also mentioned byGus Evrard.

P(M|Lx)

P(Lx|M)

Alexie Leauthaud

The Weak Lensing signals around The Weak Lensing signals around groupsgroups

Del

ta S

igm

a

[ h72

Msu

n p

c-2 ]

Radial mass profile of X-ray groups in nine Lx bins.

Physical transverse distance [ Mpc h72-1 ]

Alexie Leauthaud

Log10( Lx.E(z)-1 h72-2 ergs s-1)

Log 1

0( M

200.E

(z)-1

h72

-1 M

sun)

The MThe M200200 - L - Lxx relation relation

Form of the M200 - LXrelation:

We find a slope : α ~ 0.64in good agreement withStanek et al. 2007 and Rykoffet al. 2008.

Cluster data alone can bemisleading : Bardeau et al.2007 find α ~ 1.2!

Current relation is limitedby measurement of clustermasses.

!

M200" E(z)

M0

= A "LX" E(z)#1

L0

$

% &

'

( )

*

Leauthaud et al. 2010ApJ, 709, 97-114

Alexie Leauthaud

Combining Combining Groups Groups and and clustersclusters

COSMOS COSMOS + Hoekstra et al. 2007

Alexie Leauthaud

REDSHIFT EVOLUTION in Lx-M ?REDSHIFT EVOLUTION in Lx-M ?

!

M200" E(z)

M0

= A "LX" E(z)#1

L0

$

% &

'

( )

*E(z)

+

!

M200" E(z)

M0

= A "LX" E(z)#1

L0

$

% &

'

( )

*(1+ z)

+

γ = - 0.07 ± 0.9

δ = - 0.14 ± 0.8

COSMOS results are consistent with self-similar redshift evolution but thedata are not very constraining. Additional group and cluster data with weaklensing masses are required at 0.6<z<1.

Alexie Leauthaud

The slope The slope of of the the MM200200 - - LLxx relationrelation

Alexie Leauthaud

Lensing X-rays

Identify members using photoz probability distribution + measured field/group densities

dN/d

z (g

roup

), dN

/dz

(fiel

d), P

(zph

ot)

dN/d

z (g

roup

), dN

/dz

(fiel

d), P

(zph

ot)

z z

mF814W=22.9z=0.99Pmem=0.80

mF814W=23.9z=0.83Pmem=0.52

See Poster by Matt GeorgeAn algorithm to select group membersAn algorithm to select group members

Alexie Leauthaud

WHERE IS THE CENTER OF THE DARK MATTER?WHERE IS THE CENTER OF THE DARK MATTER?

X-ray centerSee Poster by Matt George

X-ray contours.

Alexie Leauthaud

The stacked weak lensing signal ismaximized when the chosen center isclosest to the center of the dark matter

halo.

Centroid of stellar mass

Centroid of light

Most massivegalaxy near centerof light

Most massive galaxynear centroid ofmass

‣ Define several “centers”‣ Calculate typical separations‣ Measure stacked WL signal‣ Study inner profile

# o

f gro

ups

ΔΣ (

h M

⊙ p

c-2)

ΔΣ [

M⊙ p

c-2]

Transverse separation [Mpc]

Preferred center Luminosity centroid

R [Mpc]

Preliminary weak Preliminary weak lensing lensing resultsresultsSee Poster by Matt George

R [Mpc] R [Mpc]

‣ Define several “centers”‣ Calculate typical separations‣ Measure stacked WL signal‣ Study inner profile

# o

f gro

ups

ΔΣ (

h M

⊙ p

c-2)

ΔΣ [

M⊙ p

c-2]

Transverse separation [Mpc]

Preferred center Luminosity centroid

R [Mpc]

Preliminary weak Preliminary weak lensing lensing resultsresultsSee Poster by Matt George

R [Mpc] R [Mpc]

Measuring the mass-concentration relation Accurate calibrations of mass-observable relations Understanding the profiles of dark matter halos

The colors and properties The colors and properties of « of « BCGBCG’’s s »»  (MMGG)(MMGG)

The (lack of a) cooling flow problem:

I. Lack of the detection of X-ray iron lines (e.g.Peterson et al. 2003)

II. Lack of blue massive galaxies in cluster centers

Nevertheless: moderate amounts of star formation can stillexist in the Central Galaxies of Clusters (alsomentioned by Eiichi Egami’s …):

Abell 1835 SFR ~ 100 solar masses yr-1

Abell 2204 SFR ~ 1 solar masses yr-1

Source of gas to fuel star formation:

I. Cooling from ICMII. Merger activity

Cavagnolo et al. 2008

Bildfell et al. 2008

Ko [Kev cm2]

L Hα [1

040 e

rgs s

-1]

Roff [kpc]M

btot

The colors and properties The colors and properties of « of « BCGBCG’’s s »»  (MMGG)(MMGG)

‘Wet’ merging ‘Dry’ merging ?? Cooling gas

Alexie Leauthaud

Pre

lim

ina

ry !

We observe a striking relation between Lx and halo mass over several decades inmass and luminosity. These are encouraging results in view of calibrating mass-observable relations for dark energy studies and to gain a better understanding ofcluster and galaxy physics.

The slope that we measure (α ~ 0.64 ) is inconsistent at the 3.7 sigma level withsimple models of self-similar evolution which predict α = 0.75.

Deeper X-ray data would enable calibration of T - M200

Extending halo mass measurements down to the group regime is necessary inorder to obtain an accurate determination of the slope of the Lx-M relation.

Galaxy formation as a function of halo mass: ⇒ Where is the center of the dark matter? (Matt George) ⇒ galaxy and AGN properties within groups as a function of halo mass ⇒ the assembly of the most massive galaxies, the central BCG’s (Kevin Bundy)

BOSS spectroscopic program to obtain ~ 3000 spectra for BCGs in Stripe 82 +170 deg2 of CFHT data for lensing.

conclusionsconclusions