Inferring contributions from unresolved point sources to diffuse emissions measured in UV sky surveys: general method and SOHO/SWAN case study
| Autor: | Marek Strumik, Maciej Bzowski, Marzena A. Kubiak, I. Kowalska-Leszczynska |
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| Rok vydání: | 2020 |
| Předmět: |
010504 meteorology & atmospheric sciences
Backscatter media_common.quotation_subject FOS: Physical sciences Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences 0103 physical sciences Calibration Astrophysics::Solar and Stellar Astrophysics 010303 astronomy & astrophysics Instrumentation and Methods for Astrophysics (astro-ph.IM) Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Background radiation media_common Physics Cosmic distance ladder Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies Interstellar medium Stars Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Sky Astrophysics of Galaxies (astro-ph.GA) Satellite Astrophysics - Instrumentation and Methods for Astrophysics |
| DOI: | 10.48550/arxiv.2006.12262 |
| Popis: | In observations of diffuse emissions like, e.g., the Lyman-$\alpha$ heliospheric glow, contributions to the observed signal from point sources (e.g., stars) are considered as a contamination. There are relatively few brightest point sources that are usually properly resolved and can be subtracted or masked. We present results of analysis of the distribution of point sources using UV sky-survey maps from the SOHO/SWAN instrument and spectrophotometry data from the IUE satellite. The estimated distribution suggests that the number of these sources increases with decreasing intensity. Below a certain threshold, these sources cannot be resolved against the diffuse signal from the backscatter glow, that results in a certain physical background from unresolved point sources. Detection, understanding and subtraction of the point-source background has implications for proper characterization of diffuse emissions and accurate comparison with models. Stars are also often used as standard candles for in-flight calibration of satellite UV observations, thus proper understanding of signal contributions from the point sources is important for the calibration process. We present a general approach to quantify the background radiation level from unresolved point sources in UV sky-survey maps. In the proposed method, a distribution of point sources as a function of their intensity is properly integrated to compute the background signal level. These general considerations are applied to estimate the unresolved-point-sources background in the SOHO/SWAN observations that on average amounts to $28.9$ R. We discuss also the background radiation anisotropies and general questions related to modeling the point-source contributions to diffuse UV-emission observations. Comment: To appear in Astrophysical Journal, 21 pages, 12 figures |
| Databáze: | OpenAIRE |
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