Molecular and ionized gas in the intergalactic medium of Stephan’ s Quintet Ute Lisenfeld (Universidad Granada) In collaboration with:
Pierre­Alain Duc (Saclay, France)
Jonathan Braine (Bordeaux, France)
Stephane Leon (IAA, Spain)
Vassilis Charmandaris (Cornell University, USA)
Elias Brinks (INAOE, Mexico)
Why is Stephan’ s Quintet interesting?
Compact Hickson group (HGC 91)
Rich interaction history (consequences, e.g. tidal tails)
Intergalactic starformation, including intergalactic starburst
The present and past of SQ
Interaction szenarios:
Moles et al. 1997, 1998
Sulentic et al. 2001
Velocities give information:
V 800 km/s: Foreground
(from Sulentic et al. 2001)
The present and past of SQ
Interaction szenarios:
Moles et al. 1997, 1998
Sulentic et al. 2001
4 galaxies with V 6600 km/s
(from Sulentic et al. 2001)
The present and past of SQ
Interaction szenarios:
Moles et al. 1997, 1998
Sulentic et al. 2001
1 galaxy: v 5800 km/s:
Colliding presently with group!!
(from Sulentic et al. 2001)
The present and past of SQ
Interaction szenarios:
(Moles et al. 1997, 1998
Sulentic et al. 2001)
1) Interaction ~ 1Gyr ago with NGC 7320c
Formation of new tidal tail
Interstellar medium out of parent galaxies
2) Now: Collision with NGC 7318b
Intergalactic starburst SQA
(from Sulentic et al. 2001)
Intergalactic star formation
SQ A
SQ B
Traced by dust emission (15µm)…
A
B
….and H emission (Xu et al. 1999) Intergalactic star clusters (Gallagher et al. 2001)
Atomic hydrogen outside the galaxies
Only little H2 in NGC 7319, and NGC 7318B (Yun et al. 1997, Smith & Struck 2001)
(from Williams et al. 2002)
Abundant intergalactic molecular gas
SQ B: MH2= 7x108 Mo MH2/MHI = 0.6
Lisenfeld et al. (2002)
SQ A: MH2= 3.1x109 Mo MH2/MHI = 1.1
Molecular gas observations at SQ B with IRAM Plateau de Bure Interferometer
(Lisenfeld et al. 2004, A&A, in press, astro­ph/0407473)
Goal:
Derive distribution of molecular gas at high resolution (3­4 arcsec). How closely is the molecular gas associated to SF traced by H
How closely is the molecular gas associated to SF traced by ?
Spectroscopy of ionized gas in SQ:
Goals:
Determine metallicty
indications about origin of the gas
Extinction in HII regions: important to correct and derive total SFR
Source of ionization: SF or shock
(done so far only around SQ A, Xu et al 2003)
Multiobject slit spectroscopy with MOSCA at Calar Alto
• Two concentrations of CO, coinciding with SF regions and dust lanes
Observations of SQ B with Plateau de Bure • Comparison with IRAM 30m observations: 50% of molecular Interferometer
gas in diffuse component
Lisenfeld et al. 2004
Overlay of CO with H and HI
CO exactly coincides with H !
Greyscale: H
Full contour: CO
Dashed contour: HI
Optical multi­slit spectroscopy at Calar Alto
1) 12+log(O/H)=8.7­8.9
Metallicity about solar in SQ B
2) Line ratios typical for star formation
3) High extinction: Av=3mag
Good agreement with extinction derived from gas surface density
Duc et al., in preperation
Conclusions from the observations
1) CO exactly coincides with H :
Shows that there is a physical connection between optical tidal arm and gas cloud:
SF visible in optical image (blue knots)
Coincides with H at two locations in tidal arm
H coincides with CO spatially and kinematically
CO and HI kinematics agree
Physical relation between all these components.
And: CO and HI most likely from NGC 7319 (where optical tidal arm stems from)
2) High metallicity of ionized gas: Origin in relatively inner regions in NGC 7319