AUTO-MULTITHRESH: A General Purpose Automasking Algorithm

Abstract

Producing images from interferometer data requires accurate modeling of the sources in the field of view, which is typically done using the CLEAN algorithm. Given the large number of degrees of freedom in interferometeric images, one constrains the possible model solutions for CLEAN by masking regions that contain emission. Traditionally this process has largely been done by hand. This approach is not possible with today's large data volumes which require automated imaging pipelines. This paper describes an automated masking algorithm that operates within CLEAN called AUTO-MULTITHRESH. This algorithm was developed and validated using a set of ~1000 ALMA images chosen to span a range of intrinsic morphology and data characteristics. It takes a top-down approach to producing masks: it uses the residual images to identify significant peaks and then expands the mask to include emission associated with these peaks down to lower signal-to-noise noise. The AUTO-MULTITHRESH algorithm has been implemented in CASA and has been used in production as part of the ALMA Imaging Pipeline starting with Cycle 5. It has been shown to be able to mask a wide range of emission ranging from simple point sources to complex extended emission with minimal tuning of the parameters based on the point spread function of the data. Although the algorithm was developed for ALMA, it is general enough to have been used successfully with data from other interferometers with appropriate parameter tuning. Integrating the algorithm more deeply within the minor cycle could lead to future performance improvements.

accepted to PASP

References in corpus (5)

• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• Bias-free Measurement of Giant Molecular Cloud Properties
• Cloud-Scale Molecular Gas Properties in 15 Nearby Galaxies
• ALMA Long Baseline Observations of the Strongly Lensed Submillimeter Galaxy HATLAS J090311.6+003906 at z=3.042
• The Southern HII Region Discovery Survey I: The Bright Catalog

Cited by in corpus (57)

• CASA, the Common Astronomy Software Applications for Radio Astronomy
• PHANGS-ALMA Data Processing and Pipeline
• Early Planet Formation in Embedded Disks (eDisk). I. Overview of the Program and First Results
• A kiloparsec view of a typical star-forming galaxy when the Universe was ~1 Gyr old. Part I. Outflow, halo, and interstellar medium properties
• The ALMA Interferometric Pipeline Heuristics
• ALMA reveals extended cool gas and hot ionized outflows in a typical star-forming galaxy at $z=7.13$
• CMZoom: Survey Overview and First Data Release
• Gravitational instability in a planet-forming disk
• FRagmentation and Evolution of dense cores Judged by ALMA (FREJA). I (Overview). Inner $\sim$1000 au structures of prestellar/protostellar cores in Taurus
• An ALMA Spectroscopic Survey of the Brightest Submillimeter Galaxies in the SCUBA-2-COSMOS field (AS2COSPEC): Survey Description and First Results
• Star formation in 'the Brick': ALMA reveals an active proto-cluster in the Galactic centre cloud G0.253+0.016
• ALMA-IRDC: Dense gas mass distribution from cloud to core scales
• ALMA CO Observations of the Mixed-Morphology Supernova Remnant W49B: Efficient Production of Recombining Plasma and Hadronic Gamma-rays via Shock-Cloud Interactions
• Data Combination: Interferometry and Single-dish Imaging in Radio Astronomy
• Embedded Young Massive Star Clusters in the Antennae Merger
• An Unbiased CO Survey Toward the Northern Region of the Small Magellanic Cloud with the Atacama Compact Array. I. Overview: CO Cloud Distributions
• ALMA Observations of Giant Molecular Clouds in M33 I: Resolving Star Formation Activities in the Giant Molecular Filaments Possibly Formed by a Spiral Shock
• ALMA Observation of a $z\gtrsim 10$ Galaxy Candidate Discovered with JWST
• Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): A Panchromatic View of DO Tau's Complex Kilo-au Environment
• Molecular Mapping of DR Tau's Protoplanetary Disk, Envelope, Outflow, and Large-Scale Spiral Arm
• Jet-ISM Interactions near the Microquasars GRS 1758-258 and 1E 1740.7-2942
• Kinematic analysis of the super-extended HI disk of the nearby spiral galaxy M83
• CO Excitation and its Connection to Star Formation at 200 pc in NGC 1365
• ALMA reveals a cloud-cloud collision that triggers star formation in N66N of the Small Magellanic Cloud
• A $\sim$15 kpc outflow cone piercing through the halo of the blue compact metal-poor galaxy SBS0335-052
• Discovery of a double radio relic in ZwCl1447.2+2619: A rare testbed for shock acceleration models with a peculiar surface brightness ratio
• Detection of nitrogen and oxygen in a galaxy at the end of reionization
• A large-scale kinematic study of molecular gas in high-z cluster galaxies: Evidence for high levels of kinematic asymmetry
• ALMA Observations of Giant Molecular Clouds in M33. II. Triggered High-mass Star Formation by Multiple Gas Colliding Events at the NGC 604 Complex
• A Chemical Map of the Outbursting V883 Ori system: Vertical and Radial Structures
• Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): Diverse outcomes of binary-disk interactions
• Mapping physical parameters in Orion KL at high spatial resolution
• Deviations from the Infrared-Radio Correlation in Massive, Ultra-compact Starburst Galaxies
• Charting Circumstellar Chemistry of Carbon-rich AGB Stars: I. ALMA 3 mm spectral surveys
• ACA CO($J=2-1$) Mapping of the Nearest Spiral Galaxy M33. I. Initial Results and Identification of Molecular Clouds
• On the Relationship between CH${}_3$OD Abundance and Temperature in the Orion KL Nebula
• On the thermal structure of the proto-Super Star Cluster 13 in NGC 253
• Sub-millimeter Detection of a Galactic Center Cool Star IRS 7 by ALMA
• Multi-frequency analysis of the ALMA and VLA high resolution continuum observations of the substructured disc around CI Tau. Preference for sub-mm-sized low-porosity amorphous carbon grains
• KK 242, a faint companion to the isolated Scd galaxy NGC 6503
• How to make CLEAN variants faster? Using clustered components informed by the autocorrelation function
• Molecules with ALMA at Planet-forming Scales (MAPS) XIX. Spiral Arms, a Tail, and Diffuse Structures Traced by CO around the GM Aur Disk
• ALMA 0.1 pc View of Molecular Clouds Associated with High-Mass Protostellar Systems in the Small Magellanic Cloud: Are Low-Metallicity Clouds Filamentary or Not?
• The Lyman Alpha Reference Sample. XVI. Global 21cm HI properties of Lyman-$\alpha$ emitting galaxies
• Molecules with ALMA at Planet-forming Scales (MAPS) III: Characteristics of Radial Chemical Substructures
• A PAH deficit in the starburst core of a distant spiral galaxy
• ALMA High-J CO Spectroscopy of High-Redshift Galaxies. II. 0.03" Resolution CO Kinematics Reveal Super-Eddington Accretion in a Dust-Obscured Galaxy at z=3.111
• The Arp 240 Galaxy Merger: A Detailed Look at the Molecular Kennicutt-Schmidt Star Formation Law on Sub-kpc Scales
• Metrewave Galactic Plane with the uGMRT (MeGaPluG) Survey: Lessons from the Pilot Study
• The Kinematic and Dynamic Properties of HBC 494's Wide-Angle Outflows
• Hunting for methanol in the water rich, planet forming disk around HL Tau
• CO Observations of the SMC-N66 Hii Region with ALMA: Properties of Clumps along Filamentary Molecular Clouds and Possible Expansion Motion
• The 107 GHz methanol transition is a dasar in G0.253+0.016
• Uncovering the absorbed atomic Universe with the [OI]63um line
• Resolving the large exoKuiper belt of the HD 126062 debris disc and extended gas emission in its vicinity
• Imaging Sources in the Third Realization of the International Celestial Reference Frame
• Molecules with ALMA at Planet-forming Scales (MAPS) II: CLEAN Strategies for Synthesizing Images of Molecular Line Emission in Protoplanetary Disks