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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
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Discovery of submillimeter H2O masers:
321 GHz: K. Menten, G. Melnick & G. Phillips, 1990, ApJ, 350, L41
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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.
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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
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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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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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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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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
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Neufeld & Melnick 1990
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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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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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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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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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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.
