The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Cool Cores in Galaxy Groups

Ewan O’SullivanHarvard-Smithsonian Center for Astrophysics

In Collaboration with

T. J. Ponman (University of Birmingham),

J. Vrtilek & L. P. David (CfA),

A. J. R. Sanderson (University of Illinois)

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Introduction The majority of galaxies in the universe are found in

galaxy groups (Tully 1987), and many elliptical- dominated groups have massive hot gas halos (Mulchaey 2003).

A general X-ray study of galaxy groups with Chandra and XMM-Newton (and ROSAT), focusing particularly on cooling and feedback processes

Questions It is now clear that AGN heating stops cooling flows

in clusters - is this also true in groups? How does group gas become enriched with metals?

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Groups Sample

• 23 groups from XMM archive, 18 from Chandra

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Analysis • 2-D multi-component surface brightness fits• Radial spectral profiles (circular or elliptical,

deprojected) Derive mass, entropy, cooling time, etc.

profiles, assuming hydrostatic equilibrium What about disturbed systems?• Adaptively binned spectral maps - each pixel

represents a separate spectral fit, but fits are not independent. Behaviour comparable to adaptive smoothing

Current focus on XMM data, work in progress!

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

NGC 5044From ROSAT (David et al 1994) Cooling flow (20 M/yr)

Cooling wake indicates ~100 km/s motion of galaxy

From Chandra / XMM:• No CF, no gas kT<0.6 keV

(Tamura et al 2003; Buote et al 2003)

Our XMM analysis:• No CF, but cooling time less

than 109 yrs• Minimal AGN activity, so

what prevents cooling?• Is cooling wake seen?

Deprojected temperature

Deprojected abundance

Gas cooling time

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Cooling wake

XMM X-ray image with optical contours

Temperature map

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

NGC 4636• Jones et al (2002) use

Chandra to find ‘spiral arms’ in core

Shocks from AGN outburst?• Ohto et al (2003) find high

kT, excess NH west of core

Cavity blown by AGN jets during previous outburst?

Chandra image with VLA-First contours

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

• Cavity to E clearly visible• SW ‘Spiral arm’ marks cavity boundary• Highest abundance gas outside galaxy core? Complex spectra…

Chandra image

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The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

NGC 4636 spectral maps

• Hot gas surrounds core on N and E sides• Highest abundances to SW

XMM Temperature XMM Abundance

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

NGC 4636 southwest region

• Plume of cool gas to SW with high abundance• AGN driving galaxy/group gas mixing?

XMM Temperature XMM Abundance

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

NGC 507• ROSAT shows strong

cooling in core (Kim & Fabbiano 1995)

• FR-I radio galaxy (Parma et al 1986)

• Paolillo et al (2003) find X-ray / radio structure correlated but no CF

• AGN power sufficient to stop cooling

• Kraft et al (2004) find abundance edge NE of core

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

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XMM gaussian smoothed

DSS optical

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Bright groups comparison

• Comparable Mtotal, Mgas profiles

• Large difference in kT, central density, Entropy

• NGC 507 AGN most active, NGC 4636 activity beginning

• AGN cycle governs core entropy?

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

AWM 4 & MKW 4: poor clusters

• ~2.5 keV systems chosen to be regular, undisturbed• Very large central dominant galaxies• NGC 4073 in MKW4 is radio quiet• NGC 6051 in AWM4 has 100 kpc radio jets

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

AWM 4

• kT and abundance clearly affected by AGN activity - cavity to E, shock and high abundance to NW

• Relaxed system, SB profile well described by two -models• Isothermal kT profile

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The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

MKW 4

• Maps show highest abundances in core and to SE, where SB profile shows steepest drop

• SB fits show cluster is asymmetrical

• Strong kT drop in core but no gas <0.5 keV

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The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

MKW 4 / AWM 4 comparison• Very similar

mass profiles• MKW4 has

cooler, denser, more gas-rich core

Rapid cooling• Gas fraction

step in AWM 4

Gas pushed out by AGN

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

AWM 4 / MKW 4 summary• Slight difference in core Mtotal caused by

difference in BCG mass (factor ~2)• Remaining differences caused by AGN cycle

- AWM 4 isothermal because of AGN heating - MKW 4 is cooling, soon to trigger AGN?

• Current radio power in AWM 4 ~1041 erg/s, but expect mechanical power to be up to 104 times greater

• Energy required to raise MKW 4 temperature to that of AWM 4: ~9x1058 erg or ~3x1043 erg/s for 100 Myr - reasonable for AGN

The Environments of Galaxies: from Kiloparsecs to Megaparsecs August 2004

Conclusions Cooling Flow / AGN connection holds across

wide range of mass scales (1 keV groups to massive clusters)

Enrichment of groups through AGN galaxy / group gas mixing likely (at least in central regions)

AGN outbursts probably a major source of energy feedback in groups as well as clusters