WEAK GRAVITATIONAL LENSING OF X-RAY...
Transcript of WEAK GRAVITATIONAL LENSING OF X-RAY...
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