Rashid, M and Roy, N and Pandian, JD and Dutta, P and Dokara, R and Vig, S and Menten, KM (2024) Reliability of In-band and Broadband Spectral Index Measurement: Systematic Study of the Effect of Signal-to-noise Ratio for uGMRT Data. In: Astrophysical Journal, 971 (1).
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Abstract
Low-radio-frequency spectral index measurements are a powerful tool for distinguishing between different emission mechanisms and, in turn, understanding the nature of the sources. Besides the standard method of estimating the �broadband� spectral index of sources from observations in two different frequency �bands,� if the observations were made with large instantaneous bandwidth, the �in-band� spectral index can be determined, either using images of emission at multiple frequency ranges within a band or using the novel Multi Term-Multi Frequency Synthesis (MT-MFS) imaging algorithm. Here, using simulated upgraded Giant Metrewave Radio Telescope (uGMRT) data, we have systematically studied the reliability of various methods of spectral index estimation for sources with a wide range of signal-to-noise ratios (S/Ns). It is found that for synthetic uGMRT point-source data, the MT-MFS imaging algorithm produces in-band spectral indices for S/N � 100 that have errors �0.2, making them unreliable. However, at a similar S/N, the sub-band splitting method produces errors �0.2, which are more accurate and unbiased than the in-band spectral indices. The broadband spectral indices produce errors �0.2 even for S/N � 15, and hence they are most reliable if there are no higher-order variations in the spectral index. These results may be used to improve the uGMRT observation and data analysis strategies, depending on the brightness of the target source. © 2024. The Author(s). Published by the American Astronomical Society.
| Item Type: | Journal Article |
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| Publication: | Astrophysical Journal |
| Publisher: | Institute of Physics |
| Additional Information: | The copyright for this article belongs to the authors. |
| Department/Centre: | Division of Physical & Mathematical Sciences > Joint Astronomy Programme Division of Physical & Mathematical Sciences > Physics |
| Date Deposited: | 28 Aug 2024 09:40 |
| Last Modified: | 28 Aug 2024 09:40 |
| URI: | http://eprints.iisc.ac.in/id/eprint/86010 |
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