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SCG 0018-4854: A YOUNG AND DYNAMIC GROUP. V. Presotto 1,2 , A. Iovino 1 , E. Pompei 3 , G. Temporin 4. 1 INAF-OABrera, Milano, I 2 Università dell’Insubria, Como, I 3 ESO-Chile 4 Institute fur Astrophysik, Innsbruck, A. OUTLINE. What are compact groups and why they are important? - PowerPoint PPT Presentation
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24-29 May 2009 Lucchin School -Bertinoro- 1
SCG 0018-4854:A YOUNG AND DYNAMIC
GROUP
1INAF-OABrera, Milano, I
2Università dell’Insubria, Como, I
3ESO-Chile
4Institute fur Astrophysik, Innsbruck, A
V. Presotto1,2, A. Iovino1 , E. Pompei 3, G. Temporin4
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OUTLINE
• What are compact groups and why they are important?
• SCG0018-4854
• Results
• Conclusions
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COMPACT GROUPS (CGs)
Selection criteria:• Richness: n≥4 with (m≤m1+3)• Isolation: RN≥3RG
• Compactness: G<26mag∙arcsec-2
SCGs sample:mmember<miso
=est-int>4
(Iovino 2002)
Properties:• Low dispersion: <>≈200km/s• High density: 300group108h2Mpc-2
• Lifetime ? cross≈0.016 1/H0
(Hickson 1982;1992)
Stephan’s quintet
Seyfert’s sextet
NEW
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INTERACTIONS IN CGs
• Tidal forces => morphological distorsion and disturbed kinematics• Gas infall => triggering of strong burst of star formation or feeding an AGN• Galaxies merger => new galaxy + TDGs
Compact groups are perfect laboratories to test galaxies’ interactions
Aim: reveal evidence of interaction in SCG 0018-4854 to investigate its evolution history
SCG 0018-4854
1 This work2 Pompei et al. 20073 Danks & Alcaino 19814 Temporin et al. 2005
• redshift: V≈3300 km/s (≈46Mpc)• richness: 4 gal in close proximity, R≈20 kpc• density2: 104.88 gal/Mpc-3
• velocity dispersion2: ≈120 km/s
Galaxy V1
(km/s)Class2 Activity2 Notes
A (NGC 92) 3384 Saap SBG Tidal tailDouble nuclei
3
B (NGC 89) 3284 SB0/a pec Sy2 Outflow 4
C (NGC 87) 3415 Irr SFG ---
D (NGC 88)
3432 SBab pec LINER ---
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From the SCGs cat (Iovino 2002)
Data from FORS2 @ VLT/ESO
Multi-slit spectroscopy: M & m axis (except M axis NGC 88)Grism: 1400V with 0 5200Å 20.8Å/mm (0.49 Å/px)Texp: 4X2699s
Photometry: all galFilters: 1. R-band 6550Å (FWHM 1650Å) 2. H 6615Å (FWHM 61Å)Texp: 3X119s (R-band)
3X100s (H)
R-band
SCG 0018-4854
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NGC 92
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NGC 92
H K
• Asymmetric gas radial velocity curve: AP=23% => recent
interaction:
• presence of a 8-shape1 along minor axis => Nuclear bar
misaligned with respect to PA major axis
0.2Gyr<coll<0.7Gyr
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NGC 89
Fig D
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NGC 89
• Asymmetric stellar/gas radial velocity curve: AP=33-24% =>
recent interaction: 0.2Gyr<coll<0.7Gyr
• NLR: presence of gas multiple components (3/4)
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NGC 89
H
Temporin et al. 2005
• SW direction: steep rise of gas velocity• Spectroscopical confirmation of the galactic-scale outflow• Not clear correlation between outflow & surrounding gas
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NGC 88
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NGC 88
• Low surface brightness tidal tail≈14x10kpc SW direction
R-band
Gas => regular pattern of rotation
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NGC 87
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NGC 87 (major & minor axis)
• Face-on irregular• Star forming regions H• Velocity gradients along M&m axis + peculiar motions
H
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CONCLUSIONS
• We found peculiar kinematics and morphological distortions probably due to
interactions among galaxies
• No double nucleus for NGC 92
• Recent interaction: 0.2Gyr<coll<0.7Gyr
• Spectroscopical confirmation of the galactic-scale outflow of NGC 89
Presotto et al. 2009 in preparation
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Thanks
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SCG 0018-4854 X-ray
KT ≈ 0.2 keV => coolest system detected so far
Trinchieri et al. 2008
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SCG 0018-4854 X-ray
• Phase 3b
• Hi bridge between NGC 92 and NGC 88
• NGC 89 completely stripped of HI
Pompei et al.2007
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SCG 0018-4854 gal properties
Galaxy V1
(km/s)
Class2 Activity2 Notes B mag1 M H(109 Mo)I
A (NGC 92)
3384 Saap SBG Tidal tailDouble nuclei 3
13.81 >3.29
B (NGC 89)
3284 SB0/a pec
Sy2 Outflow 4 14.18 <0.02
C (NGC 87)
3415 Irr SFG --- 14.67 0.81
D (NGC 88)
3432 SBab pec LINER --- 14.98 2.52