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R P Norris - One of the best experts on this subject based on the ideXlab platform.
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blobcat software to catalogue flood filled blobs in radio images of total intensity and linear polarization
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: Christopher A Hales, Tara Murphy, James R Curran, E Middelberg, B M Gaensler, R P NorrisAbstract:We present BLOBCAT, new Source Extraction software that utilises the flood fill algorithm to detect and catalogue blobs, or islands of pixels representing Sources, in twodimensional astronomical images. The software is designed to process radio-wavelength images of both Stokes I intensity and linear polarization, the latter formed through the quadrature sum of Stokes Q and U intensities or as a byproduct of rotation measure synthesis. We discuss an objective, automated method by which estimates of positiondependent background root-mean-square noise may be obtained and incorporated into BLOBCAT’s analysis. We derive and implement within BLOBCAT corrections for two systematic biases to enable the flood fill algorithm to accurately measure flux densities for Gaussian Sources. We discuss the treatment of non-Gaussian Sources in light of these corrections. We perform simulations to validate the flux density and positional measurement performance of BLOBCAT, and we benchmark the results against those of a standard Gaussian fitting task. We demonstrate that BLOBCAT exhibits accurate measurement performance in total intensity and, in particular, linear polarization. BLOBCAT is particularly suited to the analysis of large survey data.
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blobcat software to catalogue flood filled blobs in radio images of total intensity and linear polarization
arXiv: Instrumentation and Methods for Astrophysics, 2012Co-Authors: Christopher A Hales, Tara Murphy, James R Curran, E Middelberg, B M Gaensler, R P NorrisAbstract:We present BLOBCAT, new Source Extraction software that utilises the flood fill algorithm to detect and catalogue blobs, or islands of pixels representing Sources, in two-dimensional astronomical images. The software is designed to process radio-wavelength images of both Stokes I intensity and linear polarization, the latter formed through the quadrature sum of Stokes Q and U intensities or as a byproduct of rotation measure synthesis. We discuss an objective, automated method by which estimates of position-dependent background root-mean-square noise may be obtained and incorporated into BLOBCAT's analysis. We derive and implement within BLOBCAT corrections for two systematic biases to enable the flood fill algorithm to accurately measure flux densities for Gaussian Sources. We discuss the treatment of non-Gaussian Sources in light of these corrections. We perform simulations to validate the flux density and positional measurement performance of BLOBCAT, and we benchmark the results against those of a standard Gaussian fitting task. We demonstrate that BLOBCAT exhibits accurate measurement performance in total intensity and, in particular, linear polarization. BLOBCAT is particularly suited to the analysis of large survey data. The BLOBCAT software, supplemented with test data to illustrate its use, is available at: this http URL .
Elisabetta Valiante - One of the best experts on this subject based on the ideXlab platform.
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spitzer mips 24 and 70 μm imaging near the south ecliptic pole maps and Source catalogs
Astrophysical Journal Supplement Series, 2010Co-Authors: K S Scott, Hans F Stabenau, F G Braglia, C Borys, Edward L Chapin, Mark J Devlin, Gaelen Marsden, D Scott, Matthew D P Truch, Elisabetta ValianteAbstract:We have imaged an 11.5?deg2 region of sky toward the South Ecliptic Pole (R.A. =04h43m, decl. =?53?40', J2000) at 24 and 70 ?m with MIPS, the Multiband Imaging Photometer for Spitzer. This region is coincident with a field mapped at longer wavelengths by AKARI and BLAST. We discuss our data reduction and Source Extraction procedures. The median 1? depths of the maps are 47??Jy?beam?1 at 24 ?m and 4.3?mJy?beam?1 at 70 ?m. At 24 ?m, we identify 93,098 point Sources with signal-to-noise ratio (S/N) ?5 and an additional 63 resolved galaxies; at 70 ?m? we identify 891 point Sources with S/N ?6. From simulations, we determine a false detection rate of 1.8% (1.1%) for the 24 ?m (70 ?m) catalog. The 24 and 70 ?m point-Source catalogs are 80% complete at 230??Jy and 11?mJy, respectively. These mosaic images and Source catalogs will be available to the public through the NASA/IPAC Infrared Science Archive.
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spitzer mips 24 and 70 micron imaging near the south ecliptic pole maps and Source catalogs
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: K S Scott, Hans F Stabenau, F G Braglia, C Borys, Edward L Chapin, Mark J Devlin, Gaelen Marsden, D Scott, Matthew D P Truch, Elisabetta ValianteAbstract:We have imaged an 11.5 sq. deg. region of sky towards the South Ecliptic Pole (RA = 04h43m, Dec = -53d40m, J2000) at 24 and 70 microns with MIPS, the Multiband Imaging Photometer for Spitzer. This region is coincident with a field mapped at longer wavelengths by AKARI and the Balloon-borne Large Aperture Submillimeter Telescope. We discuss our data reduction and Source Extraction procedures. The median depths of the maps are 47 microJy/beam at 24 micron and 4.3 mJy/beam at 70 micron. At 24 micron, we identify 93098 point Sources with signal-to-noise ratio (SNR) >5, and an additional 63 resolved galaxies; at 70 micron, we identify 891 point Sources with SNR >6. From simulations, we determine a false detection rate of 1.8% (1.1%) for the 24 micron (70 micron) catalog. The 24 and 70 micron point-Source catalogs are 80% complete at 230 microJy and 11 mJy, respectively. These mosaic images and Source catalogs will be available to the public through the NASA/IPAC Infrared Science Archive.
N Hurleywalker - One of the best experts on this subject based on the ideXlab platform.
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galactic and extragalactic all sky murchison widefield array gleam survey i a low frequency extragalactic catalogue
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: N Hurleywalker, Thomas M O Franzen, J R Callingham, P J Hancock, L Hindson, A D Kapinska, J MorganAbstract:Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey and present the resulting extragalactic catalogue, utilizing the first year of observations. The catalogue covers 24 831 square degrees, over declinations south of +30° and Galactic latitudes outside 10° of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307 455 radio Sources with 20 separate flux density measurements across 72–231 MHz, selected from a time- and frequency-integrated image centred at 200 MHz, with a resolution of ≈ 2 arcmin. Over the catalogued region, we estimate that the catalogue is 90 per cent complete at 170 mJy and 50 per cent complete at 55 mJy and large areas are complete at even lower flux density levels. Its reliability is 99.97 per cent above the detection threshold of 5σ, which itself is typically 50 mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date and calibrate the low-frequency flux density scale of the southern sky to better than 10 per cent. This paper presents details of the flagging, imaging, mosaicking and Source Extraction/characterization, as well as estimates of the completeness and reliability. All Source measurements and images are available online. 1 This is the first in a series of publications describing the GLEAM survey results.
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10c survey of radio Sources at 15 7 ghz i observing mapping and Source Extraction
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Thomas M O Franzen, Matthew L Davies, Elizabeth Waldram, Keith Grainge, Michael P Hobson, N Hurleywalker, Anthony Lasenby, Malak Olamaie, G G Pooley, Carmen RodriguezgonzalvezAbstract:We have observed an area of�27 deg 2 to an rms noise level of/ 0: 2 mJy at 15.7 GHz, using the Arcminute Microkelvin Imager Large Array. These observations constitute the most sensitive radio-Source survey of any extent (& 0: 2 deg 2 ) above 1.4 GHz. This paper presents the techniques employed for observing, mapping and Source Extraction. We have used a systematic procedure for extracting information and producing Source catalogues, from maps with varying noise and uv-coverage. We have performed simulations to test our mapping and Source-Extraction procedures, and developed methods for identifying extended, overlapping and spurious Sources in noisy images. In an accompanying paper, AMI Consortium: Davies et al. (2010), the first results from t he 10C survey, including the deep 15.7-GHz Source count, are presented.
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10c survey of radio Sources at 15 7 ghz i observing mapping and Source Extraction
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Thomas M O Franzen, Matthew L Davies, Elizabeth Waldram, Keith Grainge, Michael P Hobson, N Hurleywalker, Anthony Lasenby, Malak Olamaie, G G Pooley, Carmen RodriguezgonzalvezAbstract:We have observed an area of approximatley 27 deg^2 to an rms noise level of less than 0.2 mJy at 15.7 GHz, using the Arcminute Microkelvin Imager Large Array. These observations constitute the most sensitive radio-Source survey of any extent (greater than approximately 0.2 deg^2) above 1.4 GHz. This paper presents the techniques employed for observing, mapping and Source Extraction. We have used a systematic procedure for extracting information and producing Source catalogues, from maps with varying noise and uv-coverage. We have performed simulations to test our mapping and Source-Extraction procedures, and developed methods for identifying extended, overlapping and spurious Sources in noisy images. In an accompanying paper, AMI Consortium: Davies et al. 2010, the first results from the 10C survey, including the deep 15.7-GHz Source count, are presented.
M Malkan - One of the best experts on this subject based on the ideXlab platform.
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cfht megaprime megacam u band Source catalogue of the akari north ecliptic pole wide field
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Hideo Matsuhara, M Malkan, Ting Chi Huang, Tomotsugu Goto, Hyunjin Shim, Seong Jin Kim, Tetsuya Hashimoto, Ho Seong HwangAbstract:The $AKARI$ infrared (IR) space telescope conducted two surveys (Deep and Wide) in the North Ecliptic Pole (NEP) field to find more than 100,000 IR Sources using its Infrared Camera (IRC). IRC's 9 filters, which cover wavebands from 2 to 24 $\mu$m continuously, make $AKARI$ unique in comparison with other IR observatories such as $Spitzer$ or $WISE$. However, studies of the $AKARI$ NEP-Wide field Sources had been limited due to the lack of follow-up observations in the ultraviolet (UV) and optical. In this work, we present the Canada-France-Hawaii Telescope (CFHT) MegaPrime/MegaCam $u$-band Source catalogue of the $AKARI$ NEP-Wide field. The observations were taken in 7 nights in 2015 and 2016, resulting in 82 observed frames covering 3.6 deg$^2$. The data reduction, image processing and Source Extraction were performed in a standard procedure using the \textsc{Elixir} pipeline and the \textsc{AstrOmatic} software, and eventually 351,635 Sources have been extracted. The data quality is discussed in two regions (shallow and deep) separately, due to the difference in the total integration time (4,520 and 13,910 seconds). The 5$\sigma$ limiting magnitude, seeing FWHM, and the magnitude at 50 per cent completeness are 25.38 mag (25.79 mag in the deep region), 0.82 arcsec (0.94 arcsec) and 25.06 mag (25.45 mag), respectively. The u-band data provide us with critical improvements to photometric redshifts and UV estimates of the precious infrared Sources from the $AKARI$ space telescope.
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akari north ecliptic pole deep survey revision of the catalogue via a new image analysis
Astronomy and Astrophysics, 2013Co-Authors: Kazumi Murata, Hideo Matsuhara, Takehiko Wada, Ko Arimatsu, Toshinobu Takagi, Shinki Oyabu, Tomo Goto, Youichi Ohyama, M MalkanAbstract:Context. We present the revised near- to mid-infrared catalogue of the AKARI North Ecliptic Pole deep survey. The survey has the unique advantage of continuous filter coverage from 2 to 24 μm over nine photometric bands, but the initial version of the survey catalogue leaves room for improvement in the image analysis stage; the original images are strongly contaminated by the behaviour of the detector and the optical system. Aims. The purpose of this study is to devise new image analysis methods and to improve the detection limit and reliability of the Source Extraction. Methods. We removed the scattered light and stray light from the Earth limb, and corrected for artificial patterns in the images by creating appropriate templates. We also removed any artificial Sources due to bright Sources by using their properties or masked them out visually. In addition, for the mid-infrared Source Extraction, we created detection images by stacking all six bands. This reduced the sky noise and enabled us to detect fainter Sources more reliably. For the near-infrared Source catalogue, we considered only objects with counterparts from ground-based catalogues to avoid fake Sources. For our ground-based catalogues, we used catalogues based on
Thomas M O Franzen - One of the best experts on this subject based on the ideXlab platform.
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galactic and extragalactic all sky murchison widefield array gleam survey i a low frequency extragalactic catalogue
Monthly Notices of the Royal Astronomical Society, 2017Co-Authors: N Hurleywalker, Thomas M O Franzen, J R Callingham, P J Hancock, L Hindson, A D Kapinska, J MorganAbstract:Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey and present the resulting extragalactic catalogue, utilizing the first year of observations. The catalogue covers 24 831 square degrees, over declinations south of +30° and Galactic latitudes outside 10° of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307 455 radio Sources with 20 separate flux density measurements across 72–231 MHz, selected from a time- and frequency-integrated image centred at 200 MHz, with a resolution of ≈ 2 arcmin. Over the catalogued region, we estimate that the catalogue is 90 per cent complete at 170 mJy and 50 per cent complete at 55 mJy and large areas are complete at even lower flux density levels. Its reliability is 99.97 per cent above the detection threshold of 5σ, which itself is typically 50 mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date and calibrate the low-frequency flux density scale of the southern sky to better than 10 per cent. This paper presents details of the flagging, imaging, mosaicking and Source Extraction/characterization, as well as estimates of the completeness and reliability. All Source measurements and images are available online. 1 This is the first in a series of publications describing the GLEAM survey results.
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10c survey of radio Sources at 15 7 ghz i observing mapping and Source Extraction
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: Thomas M O Franzen, Matthew L Davies, Elizabeth Waldram, Keith Grainge, Michael P Hobson, N Hurleywalker, Anthony Lasenby, Malak Olamaie, G G Pooley, Carmen RodriguezgonzalvezAbstract:We have observed an area of�27 deg 2 to an rms noise level of/ 0: 2 mJy at 15.7 GHz, using the Arcminute Microkelvin Imager Large Array. These observations constitute the most sensitive radio-Source survey of any extent (& 0: 2 deg 2 ) above 1.4 GHz. This paper presents the techniques employed for observing, mapping and Source Extraction. We have used a systematic procedure for extracting information and producing Source catalogues, from maps with varying noise and uv-coverage. We have performed simulations to test our mapping and Source-Extraction procedures, and developed methods for identifying extended, overlapping and spurious Sources in noisy images. In an accompanying paper, AMI Consortium: Davies et al. (2010), the first results from t he 10C survey, including the deep 15.7-GHz Source count, are presented.
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10c survey of radio Sources at 15 7 ghz i observing mapping and Source Extraction
arXiv: Cosmology and Nongalactic Astrophysics, 2010Co-Authors: Thomas M O Franzen, Matthew L Davies, Elizabeth Waldram, Keith Grainge, Michael P Hobson, N Hurleywalker, Anthony Lasenby, Malak Olamaie, G G Pooley, Carmen RodriguezgonzalvezAbstract:We have observed an area of approximatley 27 deg^2 to an rms noise level of less than 0.2 mJy at 15.7 GHz, using the Arcminute Microkelvin Imager Large Array. These observations constitute the most sensitive radio-Source survey of any extent (greater than approximately 0.2 deg^2) above 1.4 GHz. This paper presents the techniques employed for observing, mapping and Source Extraction. We have used a systematic procedure for extracting information and producing Source catalogues, from maps with varying noise and uv-coverage. We have performed simulations to test our mapping and Source-Extraction procedures, and developed methods for identifying extended, overlapping and spurious Sources in noisy images. In an accompanying paper, AMI Consortium: Davies et al. 2010, the first results from the 10C survey, including the deep 15.7-GHz Source count, are presented.