PySE: Software for extracting sources from radio images

Carbone, D.; Garsden, Hugh; Spreeuw, H.; Swinbank, J.; Horst, A. J. van der; Rowlinson, A.; Broderick, J. W.; Rol, E.; Law, Casey J.; Molenaar, Gijs; Wijers, R. A. M. J.

doi:10.1016/j.ascom.2018.02.003

Cited by 27 publications

(18 citation statements)

References 31 publications

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“…Light curves are generated by extracting the source fluxes from each image with the Python Source Extractor (Carbone et al 2018), then the sources extracted from each image are associated with the extractions from previous images in a running catalogue database. This is performed using the LOFAR Transient Pipeline (TraP; Swinbank et al 2015, and references therein).…”

Section: Flux Density Scalementioning

confidence: 99%

AARTFAAC flux density calibration and Northern hemisphere catalogue at 60 MHz

Kuiack

Huizinga

Molenaar

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present a method for calibrating the flux density scale for images generated by the Amsterdam ASTRON Radio Transient Facility And Analysis Centre (AART-FAAC). AARTFAAC produces a stream of all-sky images at a rate of one second in order to survey the Northern Hemisphere for short duration, low frequency transients, such as the prompt EM counterpart to gravitational wave events, magnetar flares, blazars, and other as of yet unobserved phenomena. Therefore, an independent flux density scaling solution per image is calculated via bootstrapping, comparing the measured apparent brightness of sources in the field to a reference catalogue. However, the lack of accurate flux density measurements of bright sources below 74 MHz necessitated the creation of the AARTFAAC source catalogue, at 60 MHz, which contains 167 sources across the Northern Hemisphere. Using this as a reference results in a sufficiently high number of detected sources in each image to calculate a stable and accurate flux scale per one second snapshot, in real-time.

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Section: Flux Density Scalementioning

confidence: 99%

AARTFAAC flux density calibration and Northern hemisphere catalogue at 60 MHz

Kuiack

Huizinga

Molenaar

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…These analysis pointed out strong and weak features of the tested finders, triggering new developments in specific areas, such as source deblending and fitting [e.g. see Hancock et al (2018) and Carbone et al (2018) for recent works]. Existing works, however, concentrate on compact sources, and well-known source finders, such as Aegean (Hancock et al 2012), PyBDSF (Mohan et al 2015), and BLOBCAT (Hales et al 2012), have been shown not to perform well on extended sources, revealing the need for further developments in the characterisation of complex extended sources and for a systematic testing with simulations.…”

Section: Introductionmentioning

confidence: 99%

Caesar source finder: Recent developments and testing

Riggi

Vitello

Buemi

et al. 2019

Publ. Astron. Soc. Aust.

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A new era in radioastronomy will begin with the upcoming large-scale surveys planned at the Australian Square Kilometre Array Pathfinder (ASKAP). ASKAP started its Early Science program in October 2017 and several target fields were observed during the array commissioning phase. The SCORPIO field was the first observed in the Galactic Plane in Band 1 (792-1032 MHz) using 15 commissioned antennas. The achieved sensitivity and large field of view already allow to discover new sources and survey thousands of existing ones with improved precision with respect to previous surveys. Data analysis is currently ongoing to deliver the first source catalogue. Given the increased scale of the data, source extraction and characterization, even in this Early Science phase, have to be carried out in a mostly automated way. This process presents significant challenges due to the presence of extended objects and diffuse emission close to the Galactic Plane. In this context we have extended and optimized a novel source finding tool, named CAESAR, to allow extraction of both compact and extended sources from radio maps. A number of developments have been done driven by the analysis of the SCORPIO map and in view of the future ASKAP Galactic Plane survey. The main goals are the improvement of algorithm performances and scalability as well as of software maintainability and usability within the radio community. In this paper we present the current status of CAESAR and report a first systematic characterization of its performance for both compact and extended sources using simulated maps. Future prospects are discussed in light of the obtained results.

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“…not type 'S') in the TGSS catalogue. This likely has to do with subtleties in the source extraction step and we note that T P uses a different source extraction tool (P SE; Carbone et al 2018) than is used for TGSS (P BDSF; Mohan & Rafferty 2015). Therefore, B2.…”

Section: Catalogue Comparison and Transient Searchmentioning

confidence: 99%

Searching for low radio-frequency gravitational wave counterparts in wide-field LOFAR data

Gourdji,

Rowlinson,

Wijers

et al. 2021

Preprint

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The electromagnetic counterparts to gravitational wave (GW) merger events are highly sought after, but difficult to find owing to large localization regions. In this study, we present a strategy to search for compact object merger radio counterparts in wide-field data collected by the Low-Frequency Array (LOFAR). In particular, we use multi-epoch LOFAR observations centred at 144 MHz spanning roughly 300 deg 2 at optimum sensitivity of a since retracted neutron star-black hole merger candidate detected during O2, the second Advanced Ligo-Virgo GW observing run. The minimum sensitivity of the entire (overlapping) 1809 deg 2 field searched is 50 mJy and the false negative rate is 0.1 per cent above 200 mJy. We do not find any transients and thus place an upper limit at 95 per cent confidence of 0.02 transients per square degree above 20 mJy on one, two and three month timescales, which are the deepest limits available to date. Finally, we discuss the prospects of observing GW events with LOFAR in the upcoming GW observing run and show that a single multi-beam LOFAR observation can probe the full projected median localization area of binary neutron star mergers down to a median sensitivity of at least 10 mJy.

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PySE: Software for extracting sources from radio images

Cited by 27 publications

References 31 publications

AARTFAAC flux density calibration and Northern hemisphere catalogue at 60 MHz

AARTFAAC flux density calibration and Northern hemisphere catalogue at 60 MHz

Caesar source finder: Recent developments and testing

Searching for low radio-frequency gravitational wave counterparts in wide-field LOFAR data

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