Shared-optical-path VLBI frequency phase transfer from 86 to 258 GHz on an 8600km baseline: Demonstrated with the APEX and IRAM 30m telescopes
Journal article, 2025
Context. The receiver N3AR operating at a frequency range between 67 and 116 GHz was commissioned at the APEX telescope in October 2024. It adds a new low-frequency band for APEX, with the capability of simultaneous dual-frequency observations using a dichroic beamsplitter. The 3 mm receiver also allows APEX to join the existing 3 mm global very long baseline interferometry (VLBI) network. Aims. One of our commissioning goals was to perform simultaneous dual-band VLBI observations at 86 and 258 GHz using receivers with shared optical paths (SOPs) to correct the atmospheric phase fluctuations using the frequency phase transfer (FPT) technique. This was possible together with the IRAM 30 m telescope, which has already developed such a capability. We aimed to verify the expected phase coherence and sensitivity improvement at the higher frequency achievable by applying FPT. Methods. With the dual-band, single baseline data, we applied the FPT method, which uses the lower-frequency data to correct the simultaneously observed higher-frequency data. We evaluated the improvement compared to the conventional single-band observing mode by analyzing the coherence factor in the higher-frequency data. Results. Our results show that the phase fluctuations at the two bands correlate well. After applying FPT, the interferometric phases at the higher frequency vary much less, and the coherence factor is significantly improved. Conclusions. Our analysis confirms the feasibility of applying FPT to frequencies above 250 GHz with SOP receivers. Future observations in this mode could dramatically improve the sensitivity and imaging fidelity of high-frequency VLBI.
Galaxies: active
Techniques: interferometric
Techniques: high angular resolution
Methods: data analysis
Instrumentation: high angular resolution
Author
G. Y. Zhao
Max Planck Society
A. Roy
Max Planck Society
Jan Wagner
Max Planck Society
E. Donoso
University of Concepcion
Pablo Torne
Institut de Radioastronomie Millimétrique (IRAM)
Eduardo Ros
Max Planck Society
Michael Lindqvist
Chalmers, Space, Earth and Environment, Onsala Space Observatory
A. P. Lobanov
Max Planck Society
Venkatessh Ramakrishnan
Aalto University
University of Turku
T.P. Krichbaum
Max Planck Society
H. Rottmann
Max Planck Society
A.J. Zensus
Max Planck Society
J. P. Perez-Beaupuits
Pontificia Universidad Catolica de Chile
Max Planck Society
European Southern Observatory Santiago
Benjamin Klein
Max Planck Society
K. Menten
Max Planck Society
Oliver Ricken
Max Planck Society
N. Reyes
Max Planck Society
S. Sanchez
Institut de Radioastronomie Millimétrique (IRAM)
Ignacio Ruiz
Institut de Radioastronomie Millimétrique (IRAM)
C. Duran
Institut de Radioastronomie Millimétrique (IRAM)
D. John
Institut de Radioastronomie Millimétrique (IRAM)
J. L. Santaren
Institut de Radioastronomie Millimétrique (IRAM)
M. Sánchez Portal
Institut de Radioastronomie Millimétrique (IRAM)
M. Bremer
Institut de Radioastronomie Millimétrique (IRAM)
C. Kramer
Institut de Radioastronomie Millimétrique (IRAM)
K. Schuster
Institut de Radioastronomie Millimétrique (IRAM)
M. J. Rioja
Spanish National Observatory (OAN)
University of Western Australia
Richard Dodson
University of Western Australia
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 701 A132RadioNet 4
European Commission (EC) (EC/H2020/730562), 2017-01-01 -- 2020-12-31.
Subject Categories (SSIF 2025)
Atom and Molecular Physics and Optics
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202555346