agn heating of the intergalactic medium in galaxy groups

Eric M. WilcotsEric M. Wilcots 11

AGN Heating of the AGN Heating of the Intergalactic Medium in Intergalactic Medium in

Galaxy GroupsGalaxy GroupsEric M. WilcotsEric M. Wilcots

University of Wisconsin-MadisonUniversity of Wisconsin-Madison

Kelley M. Hess (Wisconsin), Jana Grcevich (Michigan)


Why Galaxy Groups?Why Galaxy Groups?

~70% of nearby galaxies reside in groups~70% of nearby galaxies reside in groups What is the impact of the group environment What is the impact of the group environment

on galaxy evolution?on galaxy evolution? What is the impact of galaxy evolution on the What is the impact of galaxy evolution on the

group environment?group environment?

Groups define the large scale structureGroups define the large scale structure• What can the impact of AGN in groups tell us What can the impact of AGN in groups tell us about the about the

growth and evolution of large scale structuregrowth and evolution of large scale structure??


What are Galaxy Groups?What are Galaxy Groups?

3-10 members with M3-10 members with MVV < -19 within a < -19 within a radius of 0.5 Mpc (Zirbel 1997)radius of 0.5 Mpc (Zirbel 1997)

““poor cluster” (Bahcall 1980)poor cluster” (Bahcall 1980)• ~30 members with m such that m~30 members with m such that m33 < m < < m <

(m(m33+2)+2)

• mm3 3 is the magnitude of the 3is the magnitude of the 3rdrd brightest member brightest member

N > 4 with 200 km sN > 4 with 200 km s-1-1 < < σσ < 400 km s < 400 km s-1-1 (Carlberg 2001)(Carlberg 2001)

MMhalohalo ~ 10 ~ 101212-10-101414 M Moo (Eke 2004) (Eke 2004)


What are galaxy groups?What are galaxy groups?

GEMS Sample (Brough et al. 2006)GEMS Sample (Brough et al. 2006)• N ~ 3-20N ~ 3-20• σσ ~ 28 – 430 km s ~ 28 – 430 km s-1-1

• RR500500 ~ 0.22-0.56 Mpc ~ 0.22-0.56 Mpc Radius at which density = 500 x Radius at which density = 500 x ρρcritcrit

• log Llog LX X (erg s(erg s-1-1) ~ 40.7-42.11) ~ 40.7-42.11 2/16 with upper limits ~40.52/16 with upper limits ~40.5

Groups have long been defined by the luminosity and extent of their X-ray emission


Groups aren’t clusters….Groups aren’t clusters….

Variations in optical luminosity function, Variations in optical luminosity function, HI mass function…HI mass function…

Group velocity dispersion ~ internal Group velocity dispersion ~ internal velocity dispersion of individual velocity dispersion of individual galaxiesgalaxies• Ram pressure stripping & “harrassment” Ram pressure stripping & “harrassment”

less likelyless likely• Galaxies more likely to be falling into a Galaxies more likely to be falling into a

“dense” environment for the first time“dense” environment for the first time• Galaxy-galaxy mergers more likely in Galaxy-galaxy mergers more likely in

groups than clustersgroups than clusters


What do jets have to do with galaxy groups?


X-ray Emission from GroupsX-ray Emission from Groups

Mulchaey et al. 2003


X-ray propertiesX-ray propertiesMulchaey et al. 2003


Heating Problem in Galaxy GroupsHeating Problem in Galaxy Groups

Cosmology Cosmology pure gravitational infall pure gravitational infall should yield (purely thermal):should yield (purely thermal):

• TTXX ~ ~ σσ22 and L and LXX ~ T ~ TXX22

• Generally true for large clusters; not true Generally true for large clusters; not true for groupsfor groups

ROSAT/CXO/XMM observations of groupsROSAT/CXO/XMM observations of groups

• LLxx ~ T ~ TXXbb where b > 2 where b > 2 implies implies

additional heating by non-gravitational additional heating by non-gravitational meansmeans LLxx~T~Txx

2.72.7


Heating Problem = Excess EntropyHeating Problem = Excess Entropy

S = T/nS = T/nee2/32/3 (T = gas temperature) (T = gas temperature)

Excess EntropyExcess Entropy• Manifests as flatter density profile for Manifests as flatter density profile for

the X-ray emitting gasthe X-ray emitting gas• Makes groups less luminous than Makes groups less luminous than

expectedexpected• Drives deviations in LDrives deviations in Lxx-T relationship-T relationship

Conclusion Conclusion some non-gravitational some non-gravitational “preheating” of intragroup medium“preheating” of intragroup medium


Excess Entropy in Galaxy GroupsExcess Entropy in Galaxy Groups

Dashed line = pure gravitational, self-similar with clusters

Jeltema et al. 2006

Intermediate redshiftgroups


X-ray observations of galaxy groupsrequire non-gravitational heating

of the intragroup medium.


Gas Content of The Local GroupGas Content of The Local Group

Gas-rich spiralsGas-rich spirals Gas-rich irregularsGas-rich irregulars Tidal Debris/HVCsTidal Debris/HVCs

Total HI Mass of Local Group ~ 10.13 (log MHI)~ 10% Mstellar, ≤ 1% of Mdynamical


The Evolution of the Gas Content of Groups The Evolution of the Gas Content of Groups (Freeland et al 2007)(Freeland et al 2007)

Interaction rate much Interaction rate much higher in spiral-dominated higher in spiral-dominated groups.groups.

Spiral dominated/HI rich Spiral dominated/HI rich elliptical dominated/X-ray elliptical dominated/X-ray richrich

““Unattached” HI clouds Unattached” HI clouds (merger remnants) more (merger remnants) more common in elliptical common in elliptical dominated groupsdominated groups

Conversion of neutral gas Conversion of neutral gas into hot gas takes place into hot gas takes place with the intragroup with the intragroup medium and not in medium and not in individual galaxies individual galaxies


Helsdon, Ponman, Mulchaey 2006

Gas Properties of X-ray Luminous Galaxy Groups:

Mgas ~ 1-4 x 1011 M0 10 times MHI forgroups with similar dynamical mass


Evolution of the gas content of Evolution of the gas content of galaxy groupsgalaxy groups

Dynamically young systems Dynamically young systems most of the most of the gas mass remains undetected (WHIM??)gas mass remains undetected (WHIM??)

Dynamically evolved systems Dynamically evolved systems most of most of the gas mass exists as X-ray emitting the gas mass exists as X-ray emitting intragroup mediumintragroup medium

Some sort of heating mechanism is Some sort of heating mechanism is required to understand the evolution of required to understand the evolution of the gas content of galaxy groupsthe gas content of galaxy groups


What about AGN?


A statistical approach….A statistical approach….

2dF Galaxy Redshift Survey 2dF Galaxy Redshift Survey • 15000 square degrees15000 square degrees• 2.1 x 102.1 x 1066 galaxies galaxies

2dF Galaxy Group catalog (Eke et al 2004) 2dF Galaxy Group catalog (Eke et al 2004) • 2 x 102 x 1055 groups groups

2dFGRS/NVSS correlation (Sadler et al. 2dFGRS/NVSS correlation (Sadler et al. 2002)2002)• ~~4000 matched sources; 2200 AGN (50 mJy)4000 matched sources; 2200 AGN (50 mJy)


AGN in 2dFGRS GroupsAGN in 2dFGRS Groups(0.03 < z < 0.3)(0.03 < z < 0.3)

70% of AGN reside in 2dFGRS groups 70% of AGN reside in 2dFGRS groups 7.7% of groups with N > 4 have an 7.7% of groups with N > 4 have an

AGN (4.5% of all groups)AGN (4.5% of all groups) <<1% of groups have more than one <<1% of groups have more than one

AGNAGN

It is not obvious that, statistically, AGN have a tremendous impact on the overall

population of groups


A More Direct Statistical Approach..A More Direct Statistical Approach..(Croston et al. 2004)(Croston et al. 2004)


A Direct ApproachA Direct Approach

Is there evidence for past heating of the intragroup medium

in the form of low frequency radio relics?


A Direct ApproachA Direct Approach

Low frequency Low frequency (600/300 MHz) (600/300 MHz) mapping of x-ray mapping of x-ray luminous/radio loud luminous/radio loud galaxy groupsgalaxy groups

Dwarakananth & Dwarakananth & Nath (2007) found Nath (2007) found no extended 327 no extended 327 MHz emission in X-MHz emission in X-ray luminous/radio ray luminous/radio quiet groupsquiet groups 327 MHz GMRT Map (Hess & Wilcots)


ConclusionsConclusions

X-ray observations require extra non-X-ray observations require extra non-gravitational heatinggravitational heating

Comparison of HI and X-ray gas Comparison of HI and X-ray gas content of groups at different content of groups at different dynamical states requires some dynamical states requires some heating mechanism heating mechanism

Direct radio observations of X-ray Direct radio observations of X-ray luminous groups with radio galaxies luminous groups with radio galaxies are currently a mixed bag…are currently a mixed bag…

agn heating of the intergalactic medium in galaxy groups

Documents

wilcotswhy galaxy groups

galaxy groupseric

gasmakes groups

impact of galaxy evolution

spiraldominated groups

galaxy groupsdashed

timegalaxygalaxy mergers

individual galaxies