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Baryon content of galaxy groups
Baryon content of galaxy groups

Baryon content of galaxy groups - PowerPoint Presentation

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Baryon content of galaxy groups - Description

Ming Sun University of Virginia M Voit M Donahue MSU A Vikhlinin W Forman C Jones CfA N Sehgal KIPAC C Sarazin Virginia Groups Why ID: 541809 Download Presentation

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poor groups gas r500 groups poor r500 gas sun 2010 baryon mass metal fraction 2009 vikhlinin chandra iron rexcess pratt 2011 group

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Presentation on theme: "Baryon content of galaxy groups"— Presentation transcript

Slide1

Baryon content of galaxy groups

Ming Sun (University of Virginia)‏

M.

Voit, M. Donahue (MSU) A. Vikhlinin, W. Forman, C. Jones (CfA) N. Sehgal (KIPAC) C. Sarazin (Virginia)Slide2

Groups? Why do we care?

10

15 Mʘ

10

13

M

ʘ

group

cluster

Galaxy groups are the smallest halos where the bulk of baryons are accounted for .

Mass function

group

cluster

Detected baryons

(McGaugh

+ 2010)

‏Slide3

Groups are :1) Ideal systems to study baryonic physics (e.g., SN winds, cooling, AGN heating), which dominates the systematic uncertainties for cluster cosmology.The same baryonic physics is important to understand the formation and evolution of galaxies (most galaxies are in groups).

Stellar fraction(McGaugh + 2010)Slide4

Are groups gas / baryon poor

? Are groups metal poor ?Slide5

Sun + 2009 ; Vikhlinin +

2009, Chandra samples (r2500 ~ 1/3 rvir , r500 ~ 2/3 rvir)

Groups

are gas

poor

around the

center

cosmic baryon fraction

cosmic baryon fractionSlide6

LX - T Groups(Sun+09), Chandra +REXCESS(Pratt+09, +10), XMM(both samples also agree well on other scaling relations)Bolometric< r500Bolometric

(0.15 r500, r500)2.912.85Slide7

Are groups gas poor

at large radii ?

Vikhlinin +

09; REXCESS (Pratt + 09); Sun + 09 Slide8

Humphrey et al. 2011, Chandra

Deep observations are required for gas at large radii !LX, 2500 / LX, 500 ~ 4/5vs.Mgas, 2500 / Mgas, 500 ~ 1/410121013

1014

1015M2500 or M500 (Mʘ)Slide9

Pressure content in

groups

Sun, Sehgal

+

2011

The key to understand the SZ power spectrum (from SPT and ACT)

a

s ~

half of the SZ power at

l

= 3000 comes from low-mass systems !Low SZ power measured from SPT ( ~50% of expected for 8 = 0.8)Lueker + 2010 and Shirokoff + 2011 Slide10

What about baryon content in groups?1) fgas  at r > r500 (NFW, β=0.5, ~ 80% increase from r500 to r101 ) (but, slope change? mass bias? sample bias?

clumping?)

2) Intragroup light (IGL) ?

cosmic baryon fraction

cosmic baryon fraction

(Lin+03; Gonzalez+07; Giodini+09 Sun+09; Vikhlinin+09)

stars

g

as + starsSlide11

Are groups gas / baryon poor

? Are groups metal poor ?Slide12

Baumgartner et al. 2005

Are groups metal

(iron) poor

?

Emission-weighted (

ASCA

)

M

gas

-weighted

Sun

et al.

2011

(also

see Rasmussen &

Ponman,

2009; Bregman + 2010)Slide13

Why ? metal

loss at early time (e.g., SN winds, Quasars) late time (e.g., radio AGN)

Group gas is also iron poor around the center

If all metals produced were kept …

a

bundance of

clustersSlide14

Looking forward …1) Hydrostatic equilibrium mass to be calibrated2) Selection bias ? --- (try different samples)3) Extending to lower masses ! (low nH and back.)4) Go beyond r500 (e.g., stacking)5) More theory / simulation work

 Slide15

Conclusions:1) Groups are gas poor around the center (e.g., < 1/3

rvir) but not necessarily gas poor at large radii. The gas distribution has important implications on e.g., feedback and SZ power spectrum.2) Groups have a higher SF efficiency than clusters but the group stellar fraction (including IGL) needs to be better constrained.3) Groups are also metal (iron) poor around the center (e.g., < 1/3 rvir) .Slide16

The EndSlide17

Entropy scaling relations

(

Sun et al. 2009, 43 groups

; Vikhlinin et al. 2009, 14

clu.;

Pratt et al. 2010, 31

clu

.)

‏Slide18

Halo mass Stellar mass / Halo massHalo Stellar Fraction Slide19

Sehgal et al. 2010

Arnaud et al. 2010

(REXCESS)

Battaglia et al. 2010

Shaw et al. 2010

Trac et al. 2010

Sun, Sehgal et al. 2011Slide20

Why are groups metal poor?

Systematic issues:1) “iron bias” (Buote 2000) for group cool cores, but NOT the reason here2) “inverse iron bias” (Rasia et al. 2008) for 2 – 3 keV systems, up to 40%Physical reasons:1) re-accretion of pristine gas (e.g., Renzini 1997) ?2) metal loss at early times (SN winds)? related to pre-heating (see Rasmussen & Ponman 2009)3) late-stage metal loss (AGN? Kirkpatrick et al.; Simionescu, Werner et al.)Slide21

1) No pretty Chandra images

2) Hydrostatic equilibrium mass 3) Selection bias 4) Correlated errorsSlide22

Are groups gas poor

at large radii ?

Vikhlinin +

09; REXCESS (Pratt + 09); Sun + 09

@

r

500Slide23

LX - T Groups(Sun+09), Chandra +REXCESS(Pratt+09, +10), XMMBolometric< r5000.5-2 keV< r500

Bolometric(0.15 r500, r500)0.5-2 keV(0.15 r500, r500)2.912.852.60

2.55