hi as a tracer of galaxy interactions · hi as a tracer of galaxy interactions bärbel s....

ATNF Simulatons Workshop

HI as a tracer of galaxy interactions

Bärbel S. Koribalski(ATNF, CSIRO)


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

Our Galaxy

(infrared image)

The Magellanic Clouds

SMC LMC

Neutral Hydrogen gas distribution in the Magellanic system

HIPASS: Putman et al. 2003

Prime Example: The

interacting galaxy group

M81-M82-NGC 3077

HI

(Yun et al. 1994)


The galaxy M 83

ATCA + Parkes HI data (Park, Staveley-Smith et al.)

1o

optical image (by Dave Malin, AAO)


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)


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)


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 ….


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


Bekki, Koribalski, Ryder & Couch 2005


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 galaxy pair NGC4038/9HI intensity distribution

HI velocity field (top)


simulations by Toomre & Toomre 1972

Recent simulation by Barnes & Hibbard

N

VLT ANTU + FORS1 BVR image(ESO PR 20b/99)

E

IC 4970

NGC 6872

ATCA HI data

here:

an HI peak flux density image


Snapshot 140 Myr after perigalacticon

Snapshot 140 Myr after periapse:

The spiral galaxy Messier 99

Reference: DSS2 B-band

M99 is a rather unusual one-armed spiral galaxy.

It’s in the Virgo cluster.

VLA HI observations of M99

by Phookun, Vogel & Mundy (1993)

Does M99 have a tidal stream ?

HI cloud

HI stream

for a paper by Bekki, Kilborn & Koribalski (2005)

N-body simulations by Kenji Bekki (UNSW)

Koribalski & Dickey (2004)

Interacting galaxy pair

NGC6221/15

NGC6221

NGC6215

• 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

hi as a tracer of galaxy interactions · hi as a tracer of galaxy interactions bärbel s....

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