Lowluminosity Extragalactic H2O Masers

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Low-luminosity Extragalactic H2O Masers
Yoshiaki Hagiwara ASTRON
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22 GHz Extragalactic H2O Masers
High-luminosity (LH2O gt 10 Lsun) ... ca.35
galaxies (Megamasers) NGC4258,
NGC3079, NGC4945, Circinus,......
Most of these have been found in
narrow-line AGNs Low-luminosity (LH2O lt
1 Lsun) ... ca.10 galaxies
NGC253, M82, IC342, M33, M51,.......
Found in nearby star-forming galaxies,
starbursts, and AGNs. NOTE Strongest
Galactic H2O maser (W49N) is as luminous as 1
Lsun. Some Low-L
masers arise in star-forming regions.
NGC 3079
These masers are associated with
AGN-activity.
Sherwood et al.
100 Lsun
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Why Study the Low-luminosity H2O masers?
VLBI/VLA actual images
Learn something about the extragalactic
star-formation. - The evolution and
kinematics. - Structures of exotic
star-formation in outer galaxies.
Learn something about the environment of
low-luminosity AGN. - The masers at shock
with molecular clouds.
Use the masers for Astrometry (IC10, M33, LMC,
SMC). - Parallaxes establish 3D-kinematics
for the Local group (Brunthaler et al.
2003, 2004). - Proper motions yield
galactic kinematics.
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Low-luminosity H2O Masers
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H2O maser in the starburst galaxy M82
Q

OH masers (blue-shifted) imply star-formation in
the expanding shell of SNR (Pedlar et al.
1999, Wills et al. 1999). Molecular super bubble
structures in CO (Matsushita et al. 2000, Weiss
et al. 2001) Weak (0.001-0.1 Lsun) H2O masers
(Claussen et al. 1984) VLA at 1" res could not
resolve the maser (Baudry Brouillet 1996).

H2O Maser Spectrum in M82 (Baudry, Henkel et
al. 1994)
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New VLA Observations
-Angular res 0.1 - 0.08 arcsec - A
Configuration -Velocity range V(LSR) 70 -155
km/s -Velocity res 1.3 km/s
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New1
New2
S1
Xray source
S2
S1
New2
New1
M82
S1 Compact HII Region S2 0.2 arcsec (3.5 pc)
away from Compact HII Region. -
Followed up by MERLIN. New1 2 Weak and
narrow lines No nearby
continuum
S2
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What is 'S2 ' and other 'new' masers?
No continuum counterparts for these H2O masers.
The masers are associated with
neither thermal HII regions nor
SNRs. The masers could trace the earlier phase
of SF, like bipolar outflows in YSOs.
Need for mapping at higher resolution lt
0.01 pc (Signatures of Galactic
SF structures lt 0.01 pc)
MERLIN, at res 30 mas 0.2 pc, barely resolved
the maser.
MERLIN 22 GHz
CO(2-1)
S2
S2
CO (2-1) Intensity map with PdBI the 30m (Weiss
et al. 2001) and positions of H2O masers.
H2O
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VLA Observations of NGC4051
-Type 1 Seyfert, D9.7 Mpc (VLA-A 0.1 arcsec
5pc) -Narrow-line Seyfert 1 (NLS1) (Osterbrock
Pogge 1985) -Weak H2O emission (2 Lsun)
(Hagiwara et al. 2004) -H2O maser in a type 1
nucleus is rather unique.
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Effelsberg and VLA Spectra
Quasi-symmetric velocity distribution w.r.t Vlsr
710 km/s. VLA-A could not resolve the
masers at 0.1 arcsec, or 5pc.
Vsys 730 km/s
Vsys
No high-velocity emission was seen at rms 5
mJy/ch within - 800 km/s w.r.t Vsys.
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What is the maser in NGC4051?
The radio continuum peak coincides with the
maser. -AGN-activity -But, why is the
low-luminosity ( 2 Lsun) ?
Because... -Narrow-line Seyfert 1
-Low inclination disc-like
configuration Lower column
density in the line-of-site Dense and warm
molecular gas environment (HCN, HCO).
-Star-forming activity ??
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The H2O maser in M51
-Nearby star-forming galaxy, hosting a
low-luminosity AGN -Weak (0.1-1 Lsun) H2O maser
(Ho et al. 1986) -Hagiwara, Henkel et al.
(2001) pinpointed the maser in the vicinity
(0.1", 5pc) of the radio continuum nucleus
with the VLA-A snap-shot. What is the origin
? AGN-activity or Star-forming-activity?
Vsys 470 km/s
Hard Xray point source
Terashima Wilson (2004)
Hagiwara, Henkel, et al. (2001)
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New VLA Observations of M51
0.08 arcsec resolution
A weak blue-shifted (V445 km/s) and red-shifted
(V538-585 km/s) components were detected.
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Where is the maser in M51 ?
Red-shifted maser 0.1" ( 5pc ) north the
radio (3.6-cm) nucleus
-Confirmed the results in Hagi, Henkel
et al. (2001) A blue-shifted maser 0.6"
(30pc) north-west the nucleus.
3.6-cm VLA map Bradley, Kaiser, Baan (2004)
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Origin of the maser in M51
The red-shifted masers are likely to be related
to AGN-activity. The blue-shifted maser might
be originated from the gas-rich environment in
star-forming region . VLBA resolved the maser !
The presence of a thin disc (Moran et al. 2003)?
Blue-shifted emission
VLA 3.6-cm
Red-shifted emission
VLA maps Bradley, Kaiser, Baan (2004)
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Jet Maser in NGC1068
Weak (10 Lsun) H2O maser at the radio knot (C),
located 30 pc north the nucleus.
- The maser intensity is variable.
- Proper motion over 2 epochs
(1983 and 1987)? The origin of the maser
(Gallimore et al. 2001) -
Molecular outflows in YSOs
- Amplifying the radio jet
- Shock in molecular clouds in star-forming site
C
Nakai et al. (1995)
Gallimore et al. (1996)
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MERLIN Observations of the Jet Maser
According to preliminary data analysis... The
jet maser was not detected in these observations
Because of ... -Intensity
variability -Maser is resolved at 30
mas, 3pc. -MERLIN sensitivity ( rms
4 mJy/beam/ch)
NGC1068
Knot C
Nucleus S1
1.3-cm Radio Continuum
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What do the Low-L H2O Masers tell us ?
Particular conditions required for H2O maser
-Density (108 - 1010 cm /cm3)
-Warm (200- 1000 K) What can be traced by
low-luminosity masers? Low-L H2O masers are
outside of the nucleus (e.g. Claussen Lo
1986).
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In AGN..... - Disc or torus of
low-luminosity AGN (e.g. M51) - Jet, or
non-nuclear region (NGC 1068) - Molecular
environments Outflows in YSOs.
In Star-forming and starburst galaxies .....
- Extragalactic star forming phenomena Shock,
disc around a central star,

and outflows in YSOs. (M82 ?)
Scales of Galactic star forming signatures are lt
0.001 -0.01 pc. - Even VLBI
cannot resolve ! - Thermal radio
continuum (M33, IC10, M82,) - Non-thermal
SNR - Expanding shell of SNRs.
- Startburst nucleus ? (NGC 253) -
Galaxy-galaxy merging or interaction ? (NGC
6240)
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21-cm VLA radio continuum - FIR (100 um 60 um)
Low-L H2O masers
FIR-excess galaxies OH megamasers
Radio-excess galaxies H2Omegamasers
21cmVLA data from Condon et al. (1990)
(Hagiwara, in prep)
21-cm compact radio continuum AGN or
SNR FIR
(100um) Dust emission
Two different populations of extragalactic H2O
masers (e.g. Ho et al. 1986)
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The future is ......
Water masers in general Diagnosing tools
in extragalactic objects -Tracers of
High density, warm regions Low-luminosity H2O
masers -Extragalactic star-forming
regions OH(H.Kloeckner and W.Baan), HCHO masers
and, of course, we need more H2O masers
CH3OH masers Massive star-forming regions in
outer galaxies ? (not yet detected)