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7.3. Sgr A∗ in the mid-infrared reference frame: no evidence of an infrared counterpart, or interaction with nearby sources

Published online by Cambridge University Press:  25 May 2016

Dan Gezari*
Affiliation:
NASA/Goddard Space Flight Center, Code 685, Greenbelt, MD 20771

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We have determined the position of Sgr A∗ with respect to the mid-infrared (5-25 m) sources in the central parsec by direct correlation of our 12.4 m array image (Gezari et al. 1994) and the new 2-cm continuum VLA map (Yusef-Zadeh 1997; private communication), without a priori knowledge of any other position determinations. Menten et al. (1997) recently succeeded in registering the radio and near-infrared (2.2 m) reference frames with high precision (+0.03 arcsec) using VLA observations of Sgr A∗, SiO masers and H2O masers. Unfortunately, registering the mid-infrared and radio reference frames with comparable accuracy cannot be done by applying the 2.2 m calibration. Most near-infrared sources have no detectable mid-infrared counterparts, and it is not obvious which of those that do are coincident (if any), since near-infrared and mid-infrared emission generally does not arise from the same physical source component. Dramatic examples of shifts between the brightest near- and mid-infrared peaks can be seen in Orion BN/KL and the Ney-Allen Nebula (Gezari and Backman 1994; Gezari, Backman and Werner 1997) corresponding to 0.1 - 0.5 arcsec if they were located at 8.5 kpc. Further, several Sgr A West IRS sources are displaced significantly in the infrared and radio, suggesting they may actually be compact clusters of objects.

Type
Part II. Nuclear Interstellar Medium
Copyright
Copyright © Kluwer 1998 

References

Gezari, D. Y. and Backman, D. E. 1994, “Astrophysics with Infrared Arrays”, ed. McLean, I., Kluwer Acad. Pub. Co., 195.Google Scholar
Gezari, D. Y., Backman, D. E. and Werner, M. W. 1997, Ap. J. (in press).Google Scholar
Gezari, D. Y., Ozernoy, L., Varosi, F., McCreight, C. and Joyce, R. R. 1994, “Nuclei of Normal Galaxies,” ed. Genzel, R. and Harris, A., Kluwer Pub. Co., 445, 427.Google Scholar
Menten, K., Reid, M., Eckart, A. and Genzel, R. 1997, Ap. J. (Letters), 475, L119.CrossRefGoogle Scholar
Stolovy, S. R., Hayward, T. L. and Herter, T. 1996, Ap. J. (Letters), 470, L45.Google Scholar
Yusef-Zadeh, F. 1997, private communication.Google Scholar
Yusef-Zadeh, F. and Melia, 1992, Ap. J. (Letters), 385, L41.Google Scholar