sma observations of 321 ghz water maser emission in cepheus a

N.A. Patel

IAU 242, March 20071

SMA Observations of 321 GHz water maser emission in Cepheus

ANimesh A. Patel

Harvard-Smithsonian Center for AstrophysicsSubmillimeter Array

Collaborators:

Salvador Curiel (UNAM)

Qizhou Zhang (CfA)

T. K. Sridharan (CfA)

Paul T. P. Ho (CfA, ASIAA)

Jose M. Torrelles (CSIC-IEEC)

Patel, Curiel, Zhang et al. (2007), ApJ 658,L55

N.A. Patel

IAU 242, March 20072Neufeld and Melnick (1991) ApJ 368,215

N.A. Patel

IAU 242, March 20073

N.A. Patel

IAU 242, March 20074

N.A. Patel

IAU 242, March 20075

Discovery of submillimeter H2O masers:

321 GHz: K. Menten, G. Melnick & G. Phillips, 1990, ApJ, 350, L41

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IAU 242, March 20076

Motivation:

To map the 321 GHz water maser emission with the SMA

To use the 22/321 GHz line ratio to probe the physical conditions in regions of massive star-formation with high spatial resolution.

To understand the physics of the excitation of submillimeter water maser transitions.

N.A. Patel

IAU 242, March 20077

Cepheus A massive star-forming regioncontours: VLA 1.3cm radio continuum, + 22 GHz masers @ 0.1”resolution Torrelles, Gomez, Garay et al. 1998, ApJ 509,262

725 AU

N.A. Patel

IAU 242, March 20078

Disk and jet in Cepheus A HW2

SMA (ext. array)0.8”

330 GHz continuum CH3CN

VLAradio continuum3.6 cm1.3 cm

Patel, Curiel, Sridharan et al., 2005, Nature, 427,109

Brogan et al. (2005 PPV)

Martin-Pintado et al. (2005, ApJ, 628,L61)

Comito et al. (2005 IAU#231)

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IAU 242, March 20079

Vlemmings, Diamond, van Langevelde & Torrelles, 2006, A&A, 448,597

See also:Posters on methanol masers VLBI observations by

K. Torstensson & H. J. van Langevelde(JIVE)

Sugiyama et al.(JVN)

200 AU

Gallimore et al.(2003) ApJ 586, 306MERLIN observations

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IAU 242, March 200710

Bipolar molecular outflow observed in HCO+

blueshifted

redshifted

0.07 pc

+

+HW2

Gomez, Sargent, Torrelles et al. 1999, ApJ, 514, 287CO outflow: Rodriguez, Ho & Moran, 1980, ApJ, 240, L149

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IAU 242, March 200711

Observations:

VLA

SMA 30 August 2004

12 October 2004

extended configuration, 0.8’’x0.7’’

A-array 0.09’’x0.07’’

rms noise ~350 mJy/beam

rms noise ~3 mJy/beam

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IAU 242, March 200712

Cepheus-A 321 GHz masers in HW2 and HW3c

-19-21

-11

-3.5 to +1km/s

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IAU 242, March 200713

N.A. Patel

IAU 242, March 200714

Neufeld & Melnick 1990

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IAU 242, March 200715

Modelling population inversion of submm. water maser transitions

Yates, Field & Gray (1997)MNRAS, 285, 303

ALIno LVG approximation

22 GHz line is invertedover a broad range ofparameters.200-2000Kn=10^8 - 10^9 cm^-3

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IAU 242, March 200716

time-variability of 22 GHz masers

Over time scales of months:

highly luminous sources less variable

brighter (>10 Jy) masers less variable

proper motion studies with VLBA

Cepheus A maser monitoring:

Lekht et al. 1983, Sov. Astron. 26, 170

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IAU 242, March 200717

Cepheus-A 321 GHz masers

Conclusions

321 GHz masers detected in HW2 and HW3c in the Cepheus-A high-mass star-forming region

3 out of 9 submillimeter masers are associated with 22 GHz masers

submillimeter masers trace the outflow jet, presumably arising in hot gas (1000~2000 K)

Multi-transition observations of H2O masers can be used to constrain theoretical models of excitation

Submillimeter masers, along with cm masers can be used to probe physical conditions such as temperature in star-forming regions

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IAU 242, March 200718

Future work

Other high-mass star-forming regions: W75N, W3(OH), NGC6334

Masers in 400 GHz band

Simultaneous observations with VLA

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IAU 242, March 200719

The SMA project is a collaboration between SAO and ASIAA, Taiwan.We thank the SMA staff for their help with observations.We thank Jim Moran, Gary Melnick, David Neufeld and Liz Humphreys for helpful discussions.