MPIfR Colloquium, 23 April 2004

Yoshiaki Hagiwara ASTRON

Collaborators: P.J.Diamond, W.A. Sherwood, W. Baan, N.Nakai M.Miyoshi, C.Henkel, E.Rovilos, K.Hachisuka H. Imai. R,Kawabe

Extra-galactic Water Masers

Maser Transitions: H2O

616523 ,

22 G Hz

Several transitions were theoretically predicted at 22 – 321 G Hz , and detected around Galactic star-forming regions and late-type stars. (Neufeld & Melnick 1991; Menten & Melnick 1991)

(from Elitzur 1991)

Extra-galactic water masers – only at 22 G Hz The 1st discovery was toward M33 by Churchwell et al. (1977) using the MPIfR100-m telescope.

Some VLBI studies on OH Megamasers (Kloeckner et al. 2003) Mrk231, distant ULFIRG, D=170 Mpc

- 100 pc scale axis-symmetry torus (r ~ 65 pc) imaged by OH.

- OH masers shield (obscure) a radio source in the galaxy.

- dV/dx ~ 1 km/s/pc but no sign of Keplerian rotation.

Why study the water masers?

Learn about the circum-nuclear region of AGN. - R < 1 pc scales (1,000-10,000 Rs) (OH Megamasers: R ~ 10 – 100 pc scales) - Kinematics around accretion disks (e.g. Miyoshi et al. 1995)

Learn something about the extra-galactic star-formation - Kinematics and evolutions of star-formation in outer galaxies (e.g. Greenhill et al. 1990)

Tools for Astrometry - VLBI measurement at 10 micro arcsec level - The 3-D kinematics in Local group of galaxies ( e.g. Argon et al. 1994; Brunthaler PhD. Thesis, 2004)

What do the maser spectra look like?

12

8

4

01000800600400200

12

8

4

010008006004002000

0.40.30.20.10.0

1600140012001000800600

43210

500-500 -300 15001300

0.40.30.20.10.0

Flu

x D

en

sit

y (

Jy)

80007800760074007200

Heliocentric Velocity (km s-1

)

NGC4258

Circinus

NGC 4945

NGC 1068

IRAS22265-1826

(Greenhill 2003)

(Quasi-) symmetric distribution of Doppler-shifted lines w.r.t Vsys.

- High-velocity features

- Presence of a rotating disk, or a receding and approaching gas ?

Single broad-line (FWHM ~ 100 km/s) emission.

Properties of the masers

The masers are found towards ~ 40 objects.

1. The masers (< 10 Lsun) are exclusively found towards narrow- line AGNs (Type 2 Seyferts or LINERs).

2. High luminosity ~ 100 -1,000 Lsun (only ~ 1 Lsun for W49N )

3. Intensity is highly variable (> 50-100 %).

4. Host galaxies contain kpc-scale radio/optical–jet.

5. Highly Doppler-shifted components within < 1000 km/s wrt Vsys.

6. Intensity of red-shifted features > blue- features

Water masers and VLBI

VLBI imaging revealed that the masers trace the compact structures.

• - Very compact < ~ 1 mas

- High surface brightness 107 – 1015 K

- Kinematics Vlos, dV/dt, (x,y)

Credit: NRAO

Very Long Baseline Interferometry (VLBI) since 1993 inspire astronomers.

The Keplerian disk toward NGC 4258 (Nakai et al. 1993; Miyoshi et al. 1995; Herrnstein et al. 1997, 1998)

-R ~ 0.1 – 0.2 pc (~ 4,000 Rs)-Warped and thin

Central binding mass ~107 Msun

Vrot < 1,000 km/sdv/dt ~ 10 km/s/year for Vsys featureDistance to the galaxy ~7 %

Any other promising systems ? (Claussen et al. 1998; Greenhill et al. 2003)

Circinus - sub-Keplerian disk

Greenhill et al. 2003)

Mccallum 2004

'Outflow' components

NGC 1052 – Jet maser

- The masers are associated with radio continuum.

- NO hint of a disk or discernible structure.MPIfR 100-m spectra

Braatz, Wilson, Henkel (1994)

Seyfert 2 galaxy NGC 5793 (Hagiwara et al. 2001)

- Only blue-shifted components were detected with VLBI. ...... Where are the Vsys, red features? - The masers do not associate with any compact continuum like the case of NGC4258, Circinus. .....Obscuring a central engine?

- dV/d(RA) ~ 0.9 km/s/pc- Maser structure is unresolved.- Symmetric high-velocity features wrt Vsys – similar to NGC 4258.

IC 2560 - LINER (Ishihara et al. 2001)

NRO 45-m

NGC 6240 – Seyfert 2 (Hagiwara et al. 2002)

- Redshifted (~ 450 km/s) components

- The maser coincides with a nucleus.

- The maser traces a 'hotspot' in a more dominant nucleus.

VLA 1.3 cm

K-band continuum

What did we learn from these masers using VLBI?

Distribution: Resolved at < 1 pc

Classification: - Disk: NGC 4258, NGC 1068, Circinus - r ~ 0.1 – 0.9 pc - dV/dt ~ several km/s/yr - dV/d(Dec, RA) ~ 1 – 10 km/s/pc - Mbind – 106 ~ 107 Msun - Jet: NGC 1052, Mrk 348

- Outflow (large-scale): Circinus - Possible disk: NGC 3079, NGC 4945, NGC 5793, IC2560

(Greenhill et al. 1996, 1997, 2003; Hagiwara et al. 2001; Ishihara et al. 2001; Peck et al. 2003)

All these intense water masers (LH2O > 10 Lsun) are related to AGN-activity. --> Nuclear maser

No masers are found r < ~ 0.1 pc ( ~ 1,000 Rs).

- Water molecules are distroyed ?

Radio source

Radiation+ self (collision)- pumping

How do we model the rotating maser disk ?

Vrot

Longer gain pathfor self- amplification

Disk edge

Unseen

Radiation pumping

Vsys Vred = Vsys + Vrot Vbl = Vsys – Vrot

Thin disk or obscuring material

Radio source

Geometry and intensity of the maser

Strongest

Weak or unseen

Intensity of unsaturated maser I ~ hA21 N2L exp[-1]/ : optical depth L: path length N2: population density of excited level

Observable

Unseen

Maser Intensity variability

Single-dish or VLBI monitoringof the masers, for example, - Circinus (Maccllum et al. )

Long-term (~ an annual cycle) and rapid variation (maser flare ?)

Interstellar Scintillation (ISS) (Greenhill et al. 1997)

- NGC 3079 (Sherwood, Hagiwara , Baan) Search for a life-time of each feature

- to study origin of the maser disc, outflow, supernova ?

EffelsbergNGC 3079

Maser Intensity Variability

Short-term :

- Time scales on shorter than the light-crossing time for the maser

- Instabilities in radiative transfer equation on timescale ~ L/c This causes hrs and minutes.

- Observations with too wide a bandwidth (phase effects)

(Evance 1972; Watson 1992, 1994; Gray 2004)

Long-term:

- Gains modified by bulk-flows and turbulence

- May be connection to magnetic compensation (Cook 1966)

- Links to age and evolution of SFRs

- Observable with VLBI

Recent new results

(black et al. 1992)

VLA

(Tarchi et al. 2003; 2004)

3C403, the first distinct detection from a radio galaxy (FRII), a most distant water maser, LH2O ~ 1,000 Lsun

Mrk 1419, LINER

(Henkel et al. 2002)

Blue- and red-clusters are seen symmetrically offset by 475 km/s wrt Vsys.

There i s a hint of velocity driftonly for Vsys features.

The masers in 3C403, Mrk1419 are interesting systems but these new entries are very weak...... 50 mJy

It's not easy for VLBI imaging.

For imaging maser emission, ~100 mJy is limit using phase-referencing VLBI (plus the Eff 100-m).

Which masers are worth to pursue ?

Prototypes are NGC 4258, NGC 1068, Circinus, NGC 4945 (> 1 Jy).

IC 2560 is weaker but look promising.

NGC 3079 is just strong and look messy.

My current study is ...

High-luminosity (LH2O > ~10 Lsun) ... ca. 40 AGNs

NGC4258, NGC3079, NGC4945, Circinus,......

Low-luminosity (LH2O < ~1 Lsun) ... ca.10 nearby galaxies

NGC253, M82, IC342, M33, M51,.......

Found in nearby star-forming galaxies, starbursts, and also AGNs.

NOTE: Strongest Galactic H2O maser (W49N) is ~ 1 Lsun.

Low-luminosity water masers(Churchwell et al. 1977; Huchtmeier et al. 1988; Ho, Henkel et al. 1987; Greenhill 1993)

Learn something about the extragalactic star-formation.

- The evolution and kinematics. - Structures of exotic star-formation in outer galaxies.

Use the masers for extra-galactic Astrometry (IC10, M33).

- The masers are obseved in nearby galaxies.

- Parallaxes establish 3D-kinematics for the Local group. (Brunthaler PhD thesis 2004).

- Proper motions yield galactic kinematics.

Low-luminosity water masers

Why Low-L water masers ?

H2O Maser Spectrum in M82

(Baudry, Henkel et al. 1994)

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 -C at 1" res could not resolve the maser (Baudry & Brouillet 1996).

Star-burst galaxy in M 82 ? (Hagiwara, in prep.)

-Angular res: 0.1 - 0.08 arcsec - A Configuration-Velocity range: V(LSR) = 70 -155 km/s-Velocity res: 1.3 km/s

Any other promising systems ? (Claussen et al. 1998; Greenhill et al. 2003)

New VLA Observations

Xray source

S1

S2

S1

New2New1

New1New2

S2

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

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 ~ < 0.01 pc (Signatures of Galactic SF structures ~ < 0.01 pc) MERLIN, at res ~ 30 mas ~ 0.2 pc, barely resolved the maser.

S2S2

MERLIN 22 GHz

CO (2-1) Intensitymap with PdBI & the 30m(Weiss et al. 2001)and positions of H2O masers.

CO(2-1)

H2O

What is S2?

-Type 1 Seyfert, D=9.7 Mpc (VLA-A: 0.1 arcsec = ~ 5pc)

-Narrow-line Seyfert 1 (Osterbrock & Pogge 1985)

-Weak H2O emission (~2 Lsun) (Hagiwara et al. 2004)

-H2O maser in a type 1 nucleus is rather unique.

Water Maser in narrow-line Seyfert 1 (NLS1) galaxy in NGC 4051

Effelsberg and VLA SpectraEffelsberg and VLA Spectra

Quasi-symmetric velocity distributionw.r.t Vlsr = 710 km/s.

VLA-A could not resolve the masers at 0.1 arcsec, or 5pc.

Vsys

No high-velocity emission was seen at rms ~ 5 mJy/chwithin +- 800 km/s w.r.t Vsys.

What is the maser in NGC 4051?

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 ??

The HThe H22O maser in M51O maser in M51

Terashima & Wilson (2004)

+ : Hard Xray point source

Hagiwara, Henkel, et al. (2001)

Vsys ~ 470 km/s

-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?

Monitoring with the 100-m

(Hagiwara, Henkel, Menten et al. 2001)

Vsys

New VLA Observations of M51New VLA Observations of M51

A weak blue-shifted (V=445 km/s) and red-shifted (V=538-585 km/s) components were detected.

Higher resolution ~ 0.08 arcsec.

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.

Where is the maser in M51 ?

3.6-cm VLA map: Bradley, Kaiser, Baan

(2004)

Origin of the maser in M51Origin of the maser in M51

VLA maps: Bradley, Kaiser, Baan (2004)

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

Red-shifted emission

VLA 3.6-cm

Jet Maser in NGC1068Jet Maser in NGC1068

C

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

Nakai et al. (1995)Gallimore et al. (1996)

MERLIN Observations of the Jet MaserMERLIN 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)

Nucleus S1

Knot C

NGC1068

1.3-cm Radio Continuum

What do the Low-L HWhat do the Low-L H22O Masers tell O Masers tell us ?us ?

Particular conditions required for H2O masers -Density (108 - 1010 /cm3) -Warm (500 - 800 K)

What do low-luminosity masers trace?

Low-luminosity H2O masers are outside of the nucleus (e.g. Claussen & Lo 1986).

- Extra-galactic Young Stellar Object (YSO): disc, inflow/outflow (M82)

Scales of Galactic YSOs are < 0.001 -0.01 pc. - VLBI cannot resolve

- Thermal radio continuum, i.e. Compact HII region (M33, IC10, M 82, NGC2146)

- Non-thermal SNR (e.g. Expanding shells)

- Startburst nucleus (NGC 253 ?)

- Disc or torus around an active nucleus (M51 ?)

(Greenhill et al. 1993; Tarchi et al. 2002; Henkel et al. 2003; Moran et al. 2003)

Low-luminosity masers observed with VLA or VLBI

21-cm VLA radio continuum - FIR (100 um + 60 um)

21cmVLA data from Condon et al. (1990)

(Hagiwara, in prep)

Radio-excess galaxies = H2O Masers

FIR-excess galaxies = OH Masers

Arp200Arp220, Mrk231, Mrk273

NGC4258, NGC3079, NGC1068, NGC5506, NGC5793

M82, NGC253, M51

The future is ......The future is ......

Water masers in general are very useful for probing sub-pc scale kinematics

can also be used as iagnosing tools in extragalactic objects

-Tracers of High density, warm regions, i.e. Hotspots

Low-luminosity H2O masers

-Extragalactic star-forming regions

OH, H2CO masers

And, of course, we need more H2O masers