the igm as a probe of galaxy evolution€¦ · snii model!central abundance excess arises almost...

The IGM as a probe of galaxy

evolution

Trevor Ponman

University of Birmingham

Plus: Jesper Rasmussen, Alastair Sanderson

Outline

! Introduction

! Abundance distributions in galaxy groups

• Iron, silicon and SNIa vs SNII

• Integrated metal mass and loss mechanisms

• Energetics and feedback

! Conclusions

Intergalactic gas in groups and

clusters

• Most baryons do not cool andform stars.

• Compression & shocks duringcollapse and virialisation shouldheat baryons in groups andclusters of galaxies to T>106 K.

• Virialised systems haveoverdensities !"/">100, allowing

emission from such hot baryonsto be detected.

# X-ray emission

XMM contours overlaid on an optical

image of the galaxy group N79-299A

Flow chart - evolution & feedbackCollapse &

hierarchical growth

IGM Galaxies

Stripping &

strangulation

Feedback (energy

& metals)

Feedback

Injection of energy intothe IGM can arise fromsupernova explosions

Deep Chandra observation of theAntennae - Fabbiano et al 2004

Feedback

NGC 4261

Radio contours overlaid on Chandra image

(Jetha)

Injection of energy intothe IGM can arise fromsupernova explosions,or from AGN.

Feedback


The former generatemetals, the latter donot.

Feedback


The former generatemetals, the latter donot.

For the study offeedback processes, itis advantageous tolook at galaxy groups.

Feedback in groups and clusters

Why look at groups?

If gas entropy profiles areextracted from X-rayimaging spectroscopy ofthe hot gas in clusters,and scaled according to T,then excess entropy isseen in cool systems,relative to hot ones.

This is believed to resultfrom the larger impact offeedback in low masssystems. Sanderson et al (in prep.)

Metal abundances in galaxy groups

Jesper Rasmussen Chandra study of 15 X-ray bright groups,chosen to be reasonably relaxed. All but one have cool cores.

! Annular spectra extracted and fitted with hot plasma models.

! Groups scaled to r500 and stacked.

Rasmussen & Ponman 2007

Z/Z!

r/r500

r/r500


Coadding the results for all 15 groups shows the average

distributions of metal abundances much more clearly.

Rasmussen & Ponman (in prep.)


!Central flat abundance peak at ~solar metallicity

!Outside this peak, iron abundance drops rapidly to~0.1 solar, by r~0.4r500

!Si drops less rapidly, and so Si/Fe rises, from ~solarratios in the core, to SNII-like ratio at large r.


!Decompose metals into SNIaand SNII contributions, assumingyields from Iwamoto et al (1999)WDD2 delayed detonation modelfor Ia, and Nomoto et al (2006)SNII model

!Central abundance excessarises almost entirely from SNIa(cf Finoguenov et al 2000)

!The Z peak constrains mixingand cooling out of metal-rich gas

!AGN-induced mixing mightaccount for the flat abundancewithin the central ~25 kpc


!Using the low z SNIa rates ofMannucci et al 2005) - hence anunderestimate at larger z - thecentral excess could arise fromthe central galaxy alone

!The flat distribution in SNIIproducts suggest they wereinjected before cluster formation,at z!2

Fe mass in the central peaknormalised to K band luminosity ofcentral galaxy

cf Metal abundances in clusters

• Metallicity in clusters oftenshows a centralenhancement, outside whichit drops to 0.2-0.3 solar.

• XMM results (e.g. Pratt &

Arnaud) confirm these

features.

• The central peak may beplausibly explained by ejectafrom the central galaxy -with predominantly SNIaorigin (lower O/Fe) - i.e.similarly to what we find ingroups.

Molendi 2004

Beppo-SAXabundances for CFand non-CF clusters

cf Metal abundances in clusters

• Metallicity in clusters oftenshows a centralenhancement, outside whichit drops to 0.2-0.3 solar.

• XMM results (e.g. Pratt &Arnaud) confirm thesefeatures.

Molendi 2004

Beppo-SAXabundances for CFand non-CFclusters

However, Fe abundance ingroups drops a factor ~2lower than in clustersoutside ~0.4r500


Integrating the iron mass within r500, we find a strong

trend with system mass in the iron-mass-to-light ratio.

Rasmussen & Ponman (in prep.)

cf Renzini

What happened to metals in groups?

Bulk gas loss from groups?

Vikhlinin et al (2006)

r500

Hot gas fractions do appear todrop in groups.


Bulk gas loss from groups?

Hot gas fractions do appear todrop in groups.

But if gas were ejected fromouter regions then meanabundance of remaining gasshould be raised, whereas ifanything it is lower in groups.

Rasmussen & Ponman (in prep.)Values within r500.


Less efficient starformation produces lessmetals in groups?

No - the fraction of thebaryons in stars is actuallyhigher in groups, whichshould lead to moreenrichment of the gas.

Rasmussen & Ponman (in prep.)Values within r500.


Metals cool out at thecentre?

Maybe - mass to light ratiosdo appear to be lower ingroups.

Cooling at low z shoulddeplete primarily SNIaproducts, and is limited bythe observation of the centralFe peak.

Cooling flows seem to besuppressed in groups, as inclusters. Parker et al (2005)


Preferential loss ofenriched gas?

Enriched by SNIa or SNII?

Which is missing?


Preferential loss ofenriched gas?

Enriched by SNIa or SNII?

Which is missing?

Split IMLR plot into Ia and IIproducts.

# Both are substantiallydeficient!

SNIa

SNII


!Bulk gas loss from groups? No

!Less efficient star formation produces less metalsin groups? No

!Metals cool out at the centre? Maybe

!Loss of SNII products - preheating prior to clustercollapse # SNII-enriched high entropy gas blownout of feeder filaments?

Preheating in filaments

Borgani et al 2005- baryons at z=2with low and highfeedback

Preheating at z~3 blows upthe baryons in filaments,increasing the entropy ofgas accreted by clusters,and accounting for the highexcess entropies seen tolarge radii in groups andclusters.

Could be due to SNIIand/or AGN.


!Bulk gas loss from groups? No

!Less efficient star formation produces less metalsin groups? No

!Metals cool out at the centre? Maybe

!Loss of SNII products - preheating prior to clustercollapse # SNII-enriched high entropy gas blownout of feeder filaments?

!Loss of SNIa products - cooling at halo centre&/or loss via AGN-heated bubbles?

Energetics

Energy input from SNIaand SNII can beinferred fromabundances, assuming1051 erg per SN, and noradiative losses.

Dominated by SNII.

Energetics

Energy input from SNIaand SNII can beinferred fromabundances, assuming1051 erg per SN, and noradiative losses.

Dominated by SNII.

Typical inferred SNenergy input is ~0.8keV per particle.

Energetics - comments

"Simulations (e.g. Borgani et al 2005) andobservations (e.g. Lloyd-Davies et al 2000) indicatethat energy input of ~1 keV per particle is requiredto account for similarity-breaking in the hot gas.

"The existence of X-ray bright galaxy groups withT~1 keV implies (Virial Theorem) that energy inputcannot greatly exceed 1 keV per particle.

"Hence, if SN energy is not radiated away, thenthere is limited scope for AGN feedback beyondwhat is required to counteract cooling in clustercores.

Conclusions! Galaxy groups, like cool core clusters, have central

abundance peaks dominated by SNIa products, which couldbe provided by the central galaxy.

! The presence of this peak limits cooling rates (naively ~10 M#

yr-1) and mixing in the IGM.

! Flat distribution of SNII metals # injection before group forms.

! Fe abundances in groups drop below those of clusters outsidethe core.

! Integrated Fe mass and IMLR are lower in groups by up to afactor ~10.

! This shortfall applies to both SNIa and SNII products.

! Requires preferential loss of metal-rich gas: two mechanisms?

! Inferred SN energy input is ~1 keV per particle - may leavelittle scope for AGN feedback barring large radiative losses.

Need to compare theseresults with cosmologicalsimulations (e.g. Kawata &Gibson, Romeo et al) whichincorporate metal tracking

- End -

the igm as a probe of galaxy evolution€¦ · snii model!central abundance excess arises almost...

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