Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-23T15:16:14.106Z Has data issue: false hasContentIssue false

VLBA multi-epoch water maser observations towards Cepheus A

Published online by Cambridge University Press:  03 August 2017

José M. Torrelles
Affiliation:
Institut d'Estudis Espacials de Catalunya (IEEC/CSIC) and Instituto de Ciencias del Espacio (CSIC), Edifici Nexus, C/ Gran Capità, 2-4, E-08034 Barcelona, Spain
Nimesh A. Patel
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138
José F. Gómez
Affiliation:
Laboratorio de Astrofísica Espacial y Física Fundamental (INTA), Apdo. Correos 50727, E-28080 Madrid, Spain
Paul T. P. Ho
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138
Luiz F. Rodríguez
Affiliation:
Instituto de Astronomía (UNAM), Apdo. Postal 72-3, (Xangari), 58089 Morelia, Michoacán, México
Guillem Anglada
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 Instituto de Astrofísica de Andalucía (CSIC), Ap. Correos 3004, E-18080 Granada, Spain
Guido Garay
Affiliation:
Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago, Chile
Lincoln Greenhill
Affiliation:
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138
Salvador Curiel
Affiliation:
Instituto de Astronomía (UNAM), Apdo. Postal 70-264, DF 04510, Mexico
Jorge Cantó
Affiliation:
Instituto de Astronomía (UNAM), Apdo. Postal 70-264, DF 04510, Mexico

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

We have carried out and recently reported VLBA multi-epoch water maser observations toward Cepheus A with an angular and velocity resolution of 0.5 mas and 0.2 km s−1, respectively. Some of the masers detected previously with the VLA (observations made with angular and velocity resolutions of 80 mas and 1.3 km s−1, respectively) are resolved now into linear/arcuate coherent “microstructures”. These structures, while smaller than the VLA beam, are 6-200 times the size of the VLBA synthesized beam. The morphology and the observed proper motions found in these structures imply three different centers of star formation activity in a region of ⋍ 0.3 radius (⋍ 200 AU). The most remarkable result from these observations is the discovery of an arc of water masers which is perfectly fitted by a circle to one part in a thousand. This arc is expanding and suggests a spherical “puff” of ejected material ejected 33 years ago from a protostar located 600 mas south of the radio jet HW2. This spherical ejection represents a very strong challenge for theoretical studies of star formation.

Type
Part 1. Star Formation
Copyright
Copyright © Astronomical Society of the Pacific 2002 

References

Cohen, R. J., Rowland, P. R., & Blair, M. M. 1984, MNRAS, 210, 425 Google Scholar
Elitzur, M, Hollenbach, D. J., & McKee, C. F. 1992, ApJ, 394, 221 Google Scholar
Furuya, R. S., Kitamura, Y., Wootten, H. A., Claussen, M. J., Saito, M., Marvel, K. B., & Kawabe, R. 2000, ApJ, 542, L135 CrossRefGoogle Scholar
Hughes, V. A., & Wouterloot, J. G. A. 1984, ApJ, 276, 204 CrossRefGoogle Scholar
Hughes, V. A., Cohen, R. J., & Garrington, S. 1995, MNRAS, 272, 469 Google Scholar
Kaufmann, M. J., & Neufeld, D. A. 1996, ApJ, 456, 250 Google Scholar
Lada, C. J., Blitz, L., Reid, M. J., & Moran, J. M. 1981, ApJ, 243, 769 Google Scholar
Rodríguez, L. F., Garay, G., Curiel, S., Ramírez, S., Torrelles, J. M., Gómez, Y., & Velázquez, A. 1994, ApJ, 430, L65 Google Scholar
Torrelles, J. M., Gómez, J. F., Rodríguez, L. F., Curiel, S., Ho, P. T. P., & Garay, G. 1996, ApJ, 457, L107 CrossRefGoogle Scholar
Torrelles, J. M., Gómez, J. F., Garay, G., Rodríguez, L. F., Curiel, S., Cohen, R. J., & Ho, P. T. P. 1998, ApJ, 509, 262 CrossRefGoogle Scholar
Torrelles, J. M., Patel, N. A., Gómez, J. F., Ho, P. T. P., Rodríguez, L. F., Anglada, G., Garay, G., Greenhill, L., Curiel, S., & Cantó, J. 2001a, ApJ, submitted [Paper I] Google Scholar
Torrelles, J. M., Patel, N. A., Gómez, J. F., Ho, P. T. P., Rodríguez, L. F., Anglada, G., Garay, G., Greenhill, L., Curiel, S., & Cantó, J. 2001b, Nature, 411 [Paper II] Google Scholar