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Published July 2021 | Published + Accepted Version
Journal Article Open

PHANGS-ALMA Data Processing and Pipeline

Abstract

We describe the processing of the PHANGS–ALMA survey and present the PHANGS–ALMA pipeline, a public software package that processes calibrated interferometric and total power data into science-ready data products. PHANGS–ALMA is a large, high-resolution survey of CO(2–1) emission from nearby galaxies. The observations combine ALMA's main 12 m array, the 7 m array, and total power observations, and use mosaics of dozens to hundreds of individual pointings. We describe the processing of the u − v data, imaging and deconvolution, linear mosaicking, combining interferometer and total power data, noise estimation, masking, data product creation, and quality assurance. Our pipeline has a general design and can also be applied to Very Large Array and ALMA observations of other spectral lines and continuum emission. We highlight our recipe for deconvolution of complex spectral line observations, which combines multiscale clean, single-scale clean, and automatic mask generation in a way that appears robust and effective. We also emphasize our two-track approach to masking and data product creation. We construct one set of "broadly masked" data products, which have high completeness but significant contamination by noise, and another set of "strictly masked" data products, which have high confidence but exclude faint, low signal-to-noise emission. Our quality assurance tests, supported by simulations, demonstrate that 12 m+7 m deconvolved data recover a total flux that is significantly closer to the total power flux than the 7 m deconvolved data alone. In the appendices, we measure the stability of the ALMA total power calibration in PHANGS–ALMA and test the performance of popular short-spacing correction algorithms.

Additional Information

© 2021. The American Astronomical Society. Received 2020 September 26; revised 2021 February 2; accepted 2021 February 14; published 2021 July 19. We gratefully acknowledge a prompt and constructive review by the anonymous referee during a difficult time. This work also benefited immensely from helpful discussions with Crystal Brogan, Jeffrey Mangum, and the North American ALMA Science Center and European Southern Observatory staff, including Dirk Petry. The computing and software infrastructure used to process PHANGS–ALMA and develop this pipeline at OSU was built and supported by David Will, who for years was the most supportive and welcoming person in a supportive and welcoming department. He will be sorely missed. This work was carried out as part of the PHANGS collaboration. The work of A.K.L., J.S., and D.U. is partially supported by the National Science Foundation (NSF) under grants No. 1615105, 1615109, and 1653300, as well as by the National Aeronautics and Space Administration (NASA) under ADAP grants NNX16AF48G and NNX17AF39G. E.R. acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC), funding reference number RGPIN-2017-03987, and computational support from Compute Canada. D.L., T.S., E.S., C.M.F., K.S., and T.G.W. acknowledge funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 694343). C.H., A.H., and J.P. acknowledge support by the Programme National "Physique et Chimie du Milieu Interstellaire" (PCMI) of CNRS/INSU with INC/INP co-funded by CEA and CNES. A.H. acknowledges support by the Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU with INP and IN2P3, co-funded by CEA and CNES. A.U. and A.G.-R. acknowledge support from the Spanish funding grants AYA2016-79006-P (MINECO/FEDER) and PID2019-108765GB-I00 (MICINN). A.U. acknowledges support from the Spanish funding grant PGC2018-094671-B-I00 (MCIU/AEI/FEDER). C.M.F. acknowledges support from the NSF under Award No. 1903946. M.C. and J.M.D.K. gratefully acknowledge funding from the German Research Foundation (DFG) through an Emmy Noether Research Group (grant No. KR4801/1-1). M.C., J.M.D.K., and J.J.K. gratefully acknowledge funding from the DFG Sachbeihilfe (grant No. KR4801/2-1). J.M.D.K. gratefully acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program via the ERC Starting Grant MUSTANG (grant agreement No. 714907). F.B., A.T.B., I.B., J.d.B., and J.P. acknowledge funding from the European Union's Horizon 2020 research and innovation program (grant agreement No. 726384/EMPIRE). R.S.K. and S.C.O.G. acknowledge financial support from the DFG via the collaborative research center (SFB 881, Project-ID 138713538) "The Milky Way System" (subprojects A1, B1, B2, and B8). They also acknowledge subsidies from the Heidelberg Cluster of Excellence STRUCTURES in the framework of Germany's Excellence Strategy (grant EXC-2181/1-390900948) and funding from the ERC via the ERC Synergy Grant ECOGAL (grant 855130). K.K. and F.S. gratefully acknowledge funding from the DFG in the form of an Emmy Noether Research Group (grant No. KR4598/2-1). E.W. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 138713538–SFB 881 ("The Milky Way System," subproject P2). C.E. acknowledges funding from the Deutsche Forschungsgemeinschaft (DFG) Sachbeihilfe, grant No. BI1546/3-1. A.S. is supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1903834. This paper makes use of the following ALMA data, which have been processed as part of the PHANGS–ALMA CO(2–1) survey: ADS/JAO.ALMA#2012.1.00650.S, ADS/JAO.ALMA#2013.1.00803.S, ADS/JAO.ALMA#2013.1.01161.S, ADS/JAO.ALMA#2015.1.00121.S, ADS/JAO.ALMA#2015.1.00782.S, ADS/JAO.ALMA#2015.1.00925.S, ADS/JAO.ALMA#2015.1.00956.S, ADS/JAO.ALMA#2016.1.00386.S, ADS/JAO.ALMA#2017.1.00392.S, ADS/JAO.ALMA#2017.1.00766.S, ADS/JAO.ALMA#2017.1.00886.L, ADS/JAO.ALMA#2018.1.01321.S, ADS/JAO.ALMA#2018.1.01651.S. ADS/JAO.ALMA#2018.A.00062.S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Software: ALMA Calibration Pipeline (L. Davis et al. 2021, in preparation), CASA (McMullin et al. 2007), numpy (Oliphant 2006), scipy (Virtanen et al. 2020), astropy (Astropy Collaboration et al. 2013, 2018) IDL Astronomy User's Library (Landsman et al. 1993), cprops (Rosolowsky & Leroy 2006), GILDAS Pety et al. (2005), R R Core Team (2015), PHANGS–ALMA Total Power Pipeline (Herrera et al. 2020), spectral-cube, radio-beam.

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Published - Leroy_2021_ApJS_255_19.pdf

Accepted Version - 2104.07665.pdf

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023