On the estimation of intensity for low S/N ratio narrow emission lines.
Abstract
The aim of this paper is to investigate the errors involved by the intensity measure of low signal-to-noise ratio narrow emission lines. We also studied the errors associated with line intensity ratios. The spectral data acquisition was simulated by a Monte-Carlo program. These data were tested for the presence of a line and the lines detected were measured by a χ^2^ fitting program. This procedure generated a sample of intensities for a given signal-to-noise ratio. From these samples, we have established that the "measured" intensities are strongly biased towards overestimated values and their distribution is well represented by a log-normal distribution. If this phenomenon is not taken into account, erroneous astrophysical conclusions may be derived. In addition, we determined that a line ratio follows also a log-normal distribution. Finally we provide some charts able to give the error bars attached to a line intensity measurement and also to a line ratio. These charts are given in terms of signal-to-noise ratio, and can be easily converted into line intensities if the energy of the noise is known.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1994
- Bibcode:
- 1994A&A...287..676R
- Keywords:
-
- Emission Spectra;
- Errors;
- Intensity;
- Line Spectra;
- Signal To Noise Ratios;
- Spectroscopy;
- Data Acquisition;
- Data Processing;
- Monte Carlo Method;
- Simulation;
- Statistical Analysis;
- Astronomy;
- METHODS: DATA ANALYSIS;
- METHODS: NUMERICAL;
- METHODS: STATISTICAL;
- TECHNIQUES: SPECTROSCOPIC