1. Spitzer Observations of Hickson Compact Groups of Galaxies
J. E. Hibbard (NRAO), K. Johnson (P.I., UVa), A. Heiderman (NRAO REU), S. C. Gallagher, K. C. Peterson (UCLA), A. E. Hornschemeier (GSFC) & J. C. Charlton (PSU),
J. Hibbard ESO Workshop: Groups of Galaxies Dec

2. 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, or “fossil group”, or “dry merger remnants” (c.f. yesterdays talk by Emanuela Pompei)
Stay tuned to meeting - 6 more CG talks on schedule!
J. Hibbard ESO Workshop: Groups of Galaxies Dec

3. 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!
J. Hibbard ESO Workshop: Groups of Galaxies Dec

4. Spitzer IRAC 3.6, 4.5, 5.8, 8 m bands + MIPS 24m
Starburst SED Models
Spitzer
Dust
Stars
3.6m 8m 24m
Radio --->
Brent Groves, 2005
J. Hibbard ESO Workshop: Groups of Galaxies Dec

5. Spitzer IRAC & MIPS Mid-IR Imaging
Mostly Stars,
some PAHs
Just Stars
5.8 m
8 m
24 m
Some Stars,
mostly PAHs
PAHs
Hot dust
J. Hibbard ESO Workshop: Groups of Galaxies Dec

6. 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
Nearby galaxies
Virgo
Compact groups
Virgo core
Huchtmeier 1997
J. Hibbard ESO Workshop: Groups of Galaxies Dec

7. Verdes-Montenegro et al. 2001
Compact groups
Virgo
Coma
Coma I group
J. Hibbard ESO Workshop: Groups of Galaxies Dec

8. HI Deficiency: DefHI = log[ M(HI:L)pred ] - log[ M(HI:L)obs ]
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

9. Evaluate evolution of HCGs, especially with respect to their cold gas content and proposed evolutionary scenario
(L. Verdes-Montenegro, 2001)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

10. Can this help us understand “quenching” of star formation in massive galaxies??
J. Hibbard ESO Workshop: Groups of Galaxies Dec

11. In models, continued infall slows color evolution of remnants
(Somerville 2005)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

12. SAMs can reproduce observed bimodality by truncating SF when bulge gets above some critical value
Mcrit~2x1010 Mo
(Somerville 2005)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

13. Spitzer IRAC 3.6m, 4.5m, 5.0m, 8.0m color images
J. Hibbard ESO Workshop: Groups of Galaxies Dec

14. 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
(L. Verdes-Montenegro, 2001)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

15. Vilchez & Iglesias-Paramo 1998
HCG 61 (N=3)
Not HI Def
R-band
Halpha X
Vilchez & Iglesias-Paramo 1998
24um
IRAC
Log Lx<41.6
J. Hibbard ESO Workshop: Groups of Galaxies Dec

16. * HCG 19 (N=3+2) Not HI Def Optical+HI Optical X No X-ray IRAC 24um CB * X D
VLA Archive
No X-ray
IRAC
24um
J. Hibbard ESO Workshop: Groups of Galaxies Dec

17. * HCG 22 (N=3) DefHI=0.59 Optical Optical+HI X X ROSAT (Log Lx=40.6)B X X E
ATCA Archive,
thanks to B. Koribalski D
ROSAT
A=dSy2
(Log Lx=40.6)
IRAC
24um
J. Hibbard ESO Workshop: Groups of Galaxies Dec
Mulchaey et al. 2003

18. Vilchez & Iglesias-Paramo 1998
HCG 07 (N=4)
DefHI=0.64
R-band
Halpha
IRAC+HI * * * *
Vilchez & Iglesias-Paramo 1998
VLA Archive
24um
IRAC
Log Lx<41.7
J. Hibbard ESO Workshop: Groups of Galaxies Dec

19. Phase 2: HI being tidal removed from galaxies.
HCG 31**
HCG 16**
*=at least one member HIdef
**=all members HIdef
(L. Verdes-Montenegro, 2001)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

20. Vilchez & Iglesias-Paramo 1998
HCG 16 (N=4+2)
DefHI=0.41
Optical+HI
R-band
Halpha * * *
Vilchez & Iglesias-Paramo 1998
Verdes-Montenegro 2001
24um
XMM
IRAC
B=Sy2
A=LNR
C=SBNG
D=LNR
Log Lx=41.0
J. Hibbard ESO Workshop: Groups of Galaxies Dec

21. Vilchez & Iglesias-Paramo 1998
HCG 31 (N=4+2)
Optical+HI
R-band
Halpha *
Vilchez & Iglesias-Paramo 1998
Verdes-Montenegro 2001
DefHI=0.57
24um
IRAC
Log Lx<41.2
J. Hibbard ESO Workshop: Groups of Galaxies Dec

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

23. * * HCG 90 (N=4+1) DefHI=1.4 IRAC Optical+HI ROSAT Log Lx=40.8 A B
A=Sy2
IRAC A
Optical+HI * B C * D
ROSAT
Log Lx=40.8
D=LNR
Mulchaey et al. 2003
J. Hibbard ESO Workshop: Groups of Galaxies Dec

24. HCG 42 (N=4) E dominated IRAC ROSAT 24um Log Lx=41.8 C A B D
A=dLNR
Log Lx=41.8
Mulchaey et al. 2003
J. Hibbard ESO Workshop: Groups of Galaxies Dec

25. HCG 62 (N=4) E dominated Chandra IRAC Log Lx=42.9 B C A D
J. Hibbard ESO Workshop: Groups of Galaxies Dec

26. So what can we do with the MIR data?
SEDs give dominant activity
Spatially separate SED
J. Hibbard ESO Workshop: Groups of Galaxies Dec

27. Def vs. MIR SEDs Stars HCG7C: Def=0.55 PAHs HCG7D Def=0.55 HCG7B
Tidal interactions create or disrupt star formation (vm)
HCG7A
Def=0.85
PAHs + warm dust
J. Hibbard ESO Workshop: Groups of Galaxies Dec

28. Trends with MIR Colors Blue=not HI Def Red=HI Def [3.6]-[4.5] (mag)
AGN
[3.6]-[4.5] (mag)
PAHs
stars
[4.5]-[8.0] (mag)
J. Hibbard ESO Workshop: Groups of Galaxies Dec

29. Nuclear vs. Extranuclear MIR SEDs
HCG 90
PAHs &
Hot dust
Mostly starlight
HCG 90D
DefHI>2.0
J. Hibbard ESO Workshop: Groups of Galaxies Dec

30. Conclusions:
None yet. But track down Kelsey or Amanda Heiderman at January AAS Meeting
J. Hibbard ESO Workshop: Groups of Galaxies Dec