Spitzer Observations of Hickson Compact Groups of Galaxies

J. Hibbard ESO Workshop: Groups of Galaxies Dec 5-9 2005

J. E. Hibbard (NRAO), with:K. Johnson (P.I., UVa), A. Heiderman (NRAO REU), S. Gallagher (UCLA), A. Hornschemeier (GSFC) & J. Charlton (PSU)

Spitzer Observations of Hickson Compact Groups of Galaxies


Compact Groups: • Hickson 1982

– Richness: N>3 with m<m1+3mag– Isolation: Rneighbor>3Rgroup

– Compactness: G<26 mag/arcsec2

– (selected off of red plates, so bias towards early types)• May be stage in evolution to cluster core, field

early type, “fossil group”, or “dry merger remnants” (c.f. yesterdays talk by Emanuela Pompei)

• Stay tuned to meeting - 6 more CG talks on schedule!


Spitzer Survey of HCGs: • Kelsey Johnson (UVa) P.I.• IRAC and MIPS imaging of 12 close HCGs

spanning a range of evolutionary states• Use MIR to conduct a complete census of

activity (AGN; star formation) and dust content of HCGs

• This is VERY MUCH a work in progress! (some photometry completed yesterday). See Kelsey’s presentation & Amanda’s poster at January AAS (Washington D.C) for actual results!


Spitzer IRAC 3.6, 4.5, 5.8, 8 m bands+ MIPS 24m

Radio --->Brent Groves, 2005

Starburst SED ModelsDust

StarsSpitzer

3.6m 8m 24m


3.6 m

5.8 m 8 m

4.5 m

Spitzer IRAC & MIPS Mid-IR Imaging

24 m

Mostly Stars, some PAHs Just Stars

Some Stars, mostly PAHs PAHs

Hot dust


Nearby galaxies

Virgo

Virgo core

Huchtmeier 1997

So whats a nice radio astronomer like me involved for?

• Compact groups are deficient in HI with respect to field galaxies of the same type

Compact groups


Verdes-Montenegro et al. 2001

Compact groupsVirgo

Coma Coma I group


HI Deficiency:

HI properties of 324 isolated galaxies: Haynes & Giovanelli, 1984

DefHI = log[ M(HI:L)pred ] - log[ M(HI:L)obs ](positive for systems more deficient than isolated

galaxies of same type)

J. Hibbard ESO Workshop: Groups of Galaxies Dec 5-9 2005(L. Verdes-Montenegro, 2001)

• Evaluate evolution of HCGs, especially with respect to their cold gas content and proposed evolutionary scenario


Can this help us understand “quenching” of star formation in

massive galaxies??


In models, continued infall slows color evolution of remnants

(Somerville 2005)


SAMs can reproduce observed bimodality by truncating SF when bulge gets above some

critical value

(Somerville 2005)

Mcrit~2x1010 Mo


Spitzer IRAC 3.6m, 4.5m, 5.0m, 8.0m color images


• Phase 1: HI in individual galaxies. – HCG 02– HCG 61 – HCG 59– HCG 19*– HCG 22*– HCG 07**

*=at least one member HIdef

**=all members HIdef


HCG 61 (N=3)R-band Halpha

IRAC

Log Lx<41.6

24um

X

Not HI Def

Vilchez & Iglesias-Paramo 1998


HCG 19 (N=3+2)

IRAC

Optical+HI

No X-ray

24um

X

Optical

AC

B

DVLA Archive

Not HI Def

*


HCG 22 (N=3)Optical+HI

X X

OpticalA

C

B

DE

IRAC 24um

ATCA Archive, thanks to B. Koribalski

Mulchaey et al. 2003

ROSATA=dSy2

(Log Lx=40.6)

DefHI=0.59

*


R-band Halpha

IRAC

IRAC+HI

Log Lx<41.7

24um

HCG 07 (N=4)

VLA Archive


DefHI=0.64

**

**


• Phase 2: HI being tidal removed from galaxies. – HCG 31* – HCG 16*

*=at least one member HIdef

**=all members HIdef


HCG 16 (N=4+2)R-band Halpha

IRAC

Optical+HI

24um XMM

Verdes-Montenegro 2001Vilchez & Iglesias-Paramo 1998

A=LNRB=Sy2

C=SBNG

D=LNR

Log Lx=41.0

DefHI=0.41

***


HCG 31 (N=4+2)R-band Halpha

IRAC

Optical+HI

Log Lx<41.2

24um

Verdes-Montenegro 2001

DefHI=0.57

*



• Phase 4: X-ray medium. no HI in central galaxies; deficient galaxies in the outskirts– HCG 48?– HCG 90**– HCG 62?

?=no HI map**=all members

HIdef


Optical+HI


HCG 90 (N=4+1)

ROSAT

IRAC A

CB

D

A=Sy2

D=LNR Log Lx=40.8

DefHI=1.4

*

*


HCG 42 (N=4)

IRAC

24um

A

C

B

D


ROSAT

A=dLNR

Log Lx=41.8

E dominated


HCG 62 (N=4)

IRAC

A

CB

D

Chandra

Log Lx=42.9

E dominated


So what can we do with the MIR data?

• SEDs give dominant activity• Spatially separate SED


HCG7C: Def=0.55

HCG7D Def=0.55

HCG7BDef>1.3

HCG7ADef=0.85

Def vs. MIR SEDs

PAHs

PAHs + warm dust

Stars


Trends with MIR Colors

[4.5]-[8.0] (mag)

[3.6

]-[4.

5] (m

ag)

stars

AGN

PAHs

Blue=not HI DefRed=HI Def


Trends with MIR-FIR Colors

[4.5]-[8.0] (mag)

[8]-[

24] (

mag

)

stars

Blue=not HI DefRed=HI Def

hot dust

cool dust

no dust

stars + cool dust


MIR and FIR Colors vs. DEF

[4.5]-[8.0] (mag)

[8]-[

24] (

mag

)

[8]-[

24] (

mag

)

[4.5]-[8.0] (mag)

[3.6]-[4.5] (mag)

[3.6

]-[4.

5] (m

ag)


SFR[24um] vs. Def


Nuclear vs. Extranuclear MIR SEDs

• HCG 90

Mostly starlight

PAHs & Hot dust

HCG 90DDefHI>2.0


Conclusions:

• None yet. But track down Kelsey or Amanda Heiderman at January AAS Meeting



HCG 02 IRACOptical+HI


IRACOptical+HI HCG 07











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Project Goals• Optical images of the 12

Hickson Compact Groups (Hickson 1982) in the sample; they were chosen for this study based on distance (closest), angular extent (< 8 arcmin diameter), and membership (at least 3 galaxies with redshifts within 1000 km s-1 of the mean).

• Dotted blue lines enclose the groups with complete Spitzer data to date; the remainder will have a full suite of IRAC and MIPS (24 and 70 m) imaging by the end of Cycle 1.

Documents

Spitzer Observations of Hickson Compact Groups of Galaxies