The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field
The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam−1 over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, t...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal article |
| Language: | English |
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EDP Sciences
2021
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| _version_ | 1826289541049221120 |
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| author | Sabater, J Best, PN Tasse, C Hardcastle, MJ Shimwell, TW Nisbet, D Jelic, V Callingham, JR Roettgering, HJA Bonato, M Bondi, M Ciardi, B Cochrane, RK Jarvis, MJ Kondapally, R Koopmans, LVE O'Sullivan, SP Prandoni, I Schwarz, DJ Smith, DJB Wang, L Williams, WL Zaroubi, S |
| author_facet | Sabater, J Best, PN Tasse, C Hardcastle, MJ Shimwell, TW Nisbet, D Jelic, V Callingham, JR Roettgering, HJA Bonato, M Bondi, M Ciardi, B Cochrane, RK Jarvis, MJ Kondapally, R Koopmans, LVE O'Sullivan, SP Prandoni, I Schwarz, DJ Smith, DJB Wang, L Williams, WL Zaroubi, S |
| author_sort | Sabater, J |
| collection | OXFORD |
| description | The LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam−1 over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 h, it reaches a root mean square noise level of ≲20 μJy beam−1 in the central region (and below 30 μJy beam−1 over 10 square degrees). The resolution is ~6 arcsecs and 84 862 radio sources were detected in the full area (68 square degrees) with 74 127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per square degree in the central region (~5 square degrees). We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115–177 MHz; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5 per cent. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10 per cent for ELAIS-N1.
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| first_indexed | 2024-03-07T02:30:26Z |
| format | Journal article |
| id | oxford-uuid:a70d258f-657e-42cf-a907-6f5fad999c8c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T02:30:26Z |
| publishDate | 2021 |
| publisher | EDP Sciences |
| record_format | dspace |
| spelling | oxford-uuid:a70d258f-657e-42cf-a907-6f5fad999c8c2022-03-27T02:51:56ZThe LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep fieldJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:a70d258f-657e-42cf-a907-6f5fad999c8cEnglishSymplectic ElementsEDP Sciences 2021Sabater, JBest, PNTasse, CHardcastle, MJShimwell, TWNisbet, DJelic, VCallingham, JRRoettgering, HJABonato, MBondi, MCiardi, BCochrane, RKJarvis, MJKondapally, RKoopmans, LVEO'Sullivan, SPPrandoni, ISchwarz, DJSmith, DJBWang, LWilliams, WLZaroubi, SThe LOFAR Two-metre Sky Survey (LoTSS) will cover the full northern sky and, additionally, aims to observe the LoTSS deep fields to a noise level of ≲10 μJy beam−1 over several tens of square degrees in areas that have the most extensive ancillary data. This paper presents the ELAIS-N1 deep field, the deepest of the LoTSS deep fields to date. With an effective observing time of 163.7 h, it reaches a root mean square noise level of ≲20 μJy beam−1 in the central region (and below 30 μJy beam−1 over 10 square degrees). The resolution is ~6 arcsecs and 84 862 radio sources were detected in the full area (68 square degrees) with 74 127 sources in the highest quality area at less than 3 degrees from the pointing centre. The observation reaches a sky density of more than 5000 sources per square degree in the central region (~5 square degrees). We present the calibration procedure, which addresses the special configuration of some observations and the extended bandwidth covered (115–177 MHz; central frequency 146.2 MHz) compared to standard LoTSS. We also describe the methods used to calibrate the flux density scale using cross-matching with sources detected by other radio surveys in the literature. We find the flux density uncertainty related to the flux density scale to be ~6.5 per cent. By studying the variations of the flux density measurements between different epochs, we show that relative flux density calibration is reliable out to about a 3 degree radius, but that additional flux density uncertainty is present for all sources at about the 3 per cent level; this is likely to be associated with residual calibration errors, and is shown to be more significant in datasets with poorer ionosphere conditions. We also provide intra-band spectral indices, which can be useful to detect sources with unusual spectral properties. The final uncertainty in the flux densities is estimated to be ~10 per cent for ELAIS-N1. |
| spellingShingle | Sabater, J Best, PN Tasse, C Hardcastle, MJ Shimwell, TW Nisbet, D Jelic, V Callingham, JR Roettgering, HJA Bonato, M Bondi, M Ciardi, B Cochrane, RK Jarvis, MJ Kondapally, R Koopmans, LVE O'Sullivan, SP Prandoni, I Schwarz, DJ Smith, DJB Wang, L Williams, WL Zaroubi, S The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title | The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title_full | The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title_fullStr | The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title_full_unstemmed | The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title_short | The LOFAR Two-meter Sky Survey: Deep fields data release 1: II. The ELAIS-N1 LOFAR deep field |
| title_sort | lofar two meter sky survey deep fields data release 1 ii the elais n1 lofar deep field |
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