hi as a tracer of galaxy interactions · hi as a tracer of galaxy interactions bärbel s....
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ATNF Simulatons Workshop
What is HI ?
HI generally stands for the 21-cm line of atomic neutral hydrogen gas – results from the spin-flip of the single electron
orbiting the hydrogen nucleus– rest frequency: 1.420405751786 GHz
HI is an excellent tracer of galaxy dynamics (in gas-rich spiral and dwarf galaxies)
HI is the best tracer of galaxy interactions
ATNF Simulatons Workshop
The galaxy M 83
ATCA + Parkes HI data (Park, Staveley-Smith et al.)
1o
optical image (by Dave Malin, AAO)
ATNF Simulatons Workshop
Galaxy Pairs with one-sided HI tails
Arp 215M51
Arp 143
• D = 9.6 Mpc• HI tail: 90 kpc• MHI (tail) = 5 x 108
M¤ (Rots et al. 1990)
• D = 9.6 Mpc• HI tail: 90 kpc• MHI (tail) = 5 x 108
M¤
• D = 21.7 Mpc• HI tail: 70 kpc• MHI (tail) = 5 x 108 M¤
• D = 34 Mpc• HI tail: 54 kpc• MHI = 1.4 x 109
M¤
(Appleton et al. 1987)
Arp 270
(Clemens et al. 1999)
(Smith 1994, Jogee et al. 1998)
ATNF Simulatons Workshop
HI rings
Leo Ring
NGC 5291• D = 58 Mpc• HI extent: 170 kpc• MHI = 5 x 1010
M¤
• D = 10 Mpc• HI extent: 200 kpc• MHI = 109 M¤
(Malphrus et al. 1997)
(Schneider et al. 1989)
NGC 1533• D = 21 Mpc• HI extent: 70 kpc• MHI = 7 x 109
M¤
(Ryan-Weber et al. 2003)
ATNF Simulatons Workshop
Overview
the asymmetric spiral galaxy NGC 2442 + massive HI cloud“The Antennae” (NGC 4038/9)the giant spiral NGC 6872 + small companionthe one-armed spiral M99 in Virgointeracting spiral pair NGC 6221/15the peculiar NGC 3256 groupthe spiral IC 2554 + one-sided HI plume ….
ATNF Simulatons Workshop
Intergalactic HI gas near NGC 2442 (Ryder, Koribalski et al. 2001)
109 M¤ intergalactic HI gas250 kpc projected separation from the galaxy NGC 2442No optical counterpartresolved into numerous clumps with the ATCA
NGC 2442 UKS/DSS
HIPASS BGC
ATNF Simulatons Workshop
The galaxy pair NGC4038/9
“The Antennae’’nearby pair of merging galaxiesprominent tidal tails in the optical and HIstar formation in the nuclear disksone companionnew dwarf galaxy in formation
The spiral galaxy Messier 99
Reference: DSS2 B-band
M99 is a rather unusual one-armed spiral galaxy.
It’s in the Virgo cluster.
• D = 37.6 Mpc• HI cloud extent: ∼175 kpc x 100 kpc• MHI (cloud) = 109
M¤
NGC 3263
NGC 3256
NGC 3256C
ESO263-G044
NGC 3256B
The NGC 3256 galaxy group (English & Koribalski 2005)
10’ or 110 kpc
Zoom-In
To the east: the interacting galaxy NGC 3263 with
MHI = 2 x 1010 M¤
(v ∼ 2600 to 3300 km/s)
To the west: the giant diffuse HI cloud with MHI ∼ 109 M¤
(v ∼ 2760 to 2920 km/s)
NGC 3263
NGC 3262
ESO263-G044
WPV060
HI cloud
(Koribalski, Gordon & Jones 2003)
NGC 3136B
IC 2554one-sided HI tail/plume, attached to IC 2554• D = 16 Mpc
• tail extent: 30 kpc
• MHI = 2 x 109 M¤
• HI cloud to galaxy mass ratio = 1/3
• potential interaction partner: NGC 3136B, Δvsys ∼ 400 km/s
IC 2554