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Extended ionized gas regions around the Coma cluster galaxies

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inter-galactic features in these data. Extended Ionized. Gas around the. Coma galaxies ... RB199: Splash-like filaments star-formation in the inter-galactic space ... – PowerPoint PPT presentation

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Title: Extended ionized gas regions around the Coma cluster galaxies


1
Extended ionized gas regions around the Coma
cluster galaxies
  • Michitoshi YOSHIDA
  • Okayama Astrophysical Observatory, NAOJ
  • with Masafumi Yagi, Sadanori Okamura, Yutaka
    Komiyama, Hisanori Furusawa, Nobunari Kashikawa,
    Yusei Koyama, Hitomi Yamanoi, Takashi Hattori

2
ABSTRACT
  • We discovered peculiar, large extended ionized
    gas regions around several galaxies in the Coma
    cluster.
  • They have a common structural feature one-sided
    flows from the galaxy disks
  • Detailed data-analysis was done for two of these
    objects ? I show them later
  • Possible formation mechanism
  • Ram pressure stripping by collision between
    galaxies infalling to the cluster with hot ICM ?
    plausible
  • Tidal stripping by galaxy-galaxy interaction /
    galaxy-cluster interaction cannot be totally
    excluded.
  • Excitation mechanism of the ionized gas
  • still unknown shock ? thermal conduction ? or
    else ?
  • We witness a phase of rapid gas removal from
    galaxies near the central region of a rich cluster

3
Introduction Environmental Effects on Galaxy
Evolution
  • Environment of galaxies affects galaxy evolution
    much.
  • Clusters of galaxies ? Ideal laboratories for
    investigating environmental effects on galaxy
    evolution
  • High number density of galaxies
  • Strong gravitational field (1014-15 M?)
  • High temperature intra-cluster gas (107-8 K)
  • Observational evidence on galaxy evolution in
    clusters
  • Morphological segregation (Morphology-Density
    relation), Butcher-Oemler effect, Rapid rise of
    faint-end LF, etc.
  • Various models have been proposed for
    environmental effects on cluster galaxy evolution
    ? Which is the dominant mechanism ? ? still
    unknown.

In order to study this subject
4
Observation Deep Ha Imaging of the Coma Cluster
of Galaxies
  • Primary Aim
  • Study star-formation activity and faint-end
    luminosity function in the core of rich cluster
    of galaxies
  • ? environmental effect on evolution of
    cluster galaxies
  • A part of an international multi-wavelength study
    of the Coma cluster
  • Object
  • Coma cluster (z0.0232?D95Mpc) Nearby rich,
    massive cluster
  • Observation 2006 - 2007
  • Subaru Telescope SuprimeCam 3427FOV
  • FiltersB?Rc?Ha

We found a number of peculiar inter-galactic
features in these data
5
Extended Ionized Gas around the Coma galaxies
6
Extended Ionized Gas around the Coma galaxies
D100
RB199
7
What are they?
8
Two examples
  1. The 60 kpc Optical Filament Associated with a
    Poststarburst Galaxy D100
  2. Strange Filamentary Structures (Fireballs'')
    around a Merger Galaxy RB199

9
1. The Remarkable 602 kpc Optical Filament
Associated with a Poststarburst Galaxy in the
Coma Cluster(Yagi, M. et al. 2007, ApJ, 660,
1209)
  • Unusual long, narrow, straight H-alpha filament
    extending from a post-starburst galaxy D100 in
    the Coma cluster
  • The filament has a length of 60 kpc and a width
    of 2 kpc.
  • Formation mechanism
  • Ram pressure stripping ?
  • Gas stripped off from a merged dwarf galaxy ?
  • Excitation mechanism of the filament is unknown.

10
60kpc
D100
11
Ha
H-alpha Surface Brightness 210-17
erg/s/cm2/arcsec2 Size 260kpc Mass 108
M? (if fv1)
12
Ram pressure stripping
Infalling galaxy
Stripped gas
?star
Hot ICM ?ICM
?gas
Infall velocity Vgal
Ram pressure
13
Stripping radius by ram pressure stripping
assuming an exponential disk
  • Rstrip 0.7 kpc

Almost all the disk gas of D100 can be stripped
by ram pressure stripping.
14
Velocity field
Velocity field of the H-alpha filament of D100
Ram pressure stripping !! How to collimate ? ? ??
15
2. Strange Filamentary Structures (Fireballs'')
around a Merger Galaxy in the Coma Cluster of
Galaxies (Yoshida, M. et al. 2008, ApJ, 688,
918.)
  • An unusual complex of narrow blue filaments,
    bright blue knots, and H-alpha emitting
    filaments, extending up to 80 kpc south from an
    EA galaxy RB199 in the Coma cluster.
  • We call it fireballs.
  • Strong Ha and UV emission appear in the bright
    knots.
  • ?Star formation recently ceased in the blue
    filaments and now continues in the bright knots.
  • The gas stripped by some mechanism from the disk
    of RB199 may be traveling in the inter- galactic
    space, forming stars left along its trajectory.

16
background galaxies
star
Member galaxy ?
background galaxy
Fireballs
17
2
4
3
1
5
18
Bright knots re 200 300 pc MR -13 mag ?
mass 107 M? (M/L1)
LHa 1038 erg/s
blue knot
Ha
blue filament
19
The filaments of the fireballs grow bluer with
distance from the host galaxy RB199.
20
The fireballs are detected in FUV(1650A)
and NUV(2500A). (GALEX archive data)
FUV on B
Star-formation rate at bright knots ? 10-210-3
M?/yr
NUV on B
21
Star formation
  • The gas stripped by some mechanism from the disk
    of RB199 may be traveling in the inter- galactic
    space, forming stars left along its trajectory.
  • knots ? SF sites blue filaments ? Trajectory of
    SF stream
  • Ha filaments ? Stripped gas Excitation
    mechanism ?

22
Formation mechanism of the fireballs
  • Tidal stripping by galaxy-galaxy interaction
  • Difficult to explain its peculiar morphology
  • One-sided, multiple, straight filaments
  • No stellar tidal tail
  • The blue filaments consist of newly formed stars
  • Tidal stripping by cluster gravitational
    potential
  • tidal force ltlt disk gravity
  • Ram pressure stripping by collision with ICM

23
Stripping radius by ram pressure stripping
  • Rstrip 1.2 kpc

Almost all the disk gas of RB199 can be stripped
by ram pressure stripping.
24
Similar structure (including star-formation) is
reproduced by numerical simulation
Numerical simulations by Kronberger et al. 2008
(AA, 481, 337)
25
Summary for two objects
  • D100 Strange long straight filament
  • RB199 Splash-like filaments star-formation in
    the inter-galactic space
  • ?
  • Ram pressure stripping is the most plausible
    formation-mechanism for both objects
  • These objects are in rapid gas removal phase

Other objects? ? also in violent gas removal
phase
26
Summary
  • We discovered peculiar, large extended ionized
    gas regions around several galaxies in the Coma
    cluster.
  • They have a common structural feature one-sided
    flows from the galaxy disks
  • Detailed data-analysis was done for two of these
    objects ? shown in this talk
  • Possible formation mechanism
  • Ram pressure stripping ? plausible
  • Tidal stripping by galaxy-galaxy interaction /
    galaxy-cluster interaction
  • Excitation mechanism of the ionized gas
  • still unknown shock ? thermal conduction ? or
    else ?
  • We witness a phase of rapid gas removal from
    galaxies near the central region of a rich cluster
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