hips2fits Fast generation ofFITS cutoutsfrom HiPS datasets

Thomas Boch, P. Fernique, F. Bonnarel, Chaitra, C. Bot, F.-X. Pineau, M. Baumann, L. Michel IVOA Interop, Groningen, Apps 2

IVOA Groningen - Oct 2019 - hips2fits - Apps 2

HiPSdatasetscollections

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700+ image HiPS

60+ planetary HiPS

IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Firstimplementations

• AladinDesktopcodebehindTomcatserver—>bilinearresampling

• Othertestsusingstandard reprojectiontools

• Montage

• reproject

• SWarp3

IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Globalarchitecture

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IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Algorithm

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1.Foreach(x,y)pixel:computeα,δ (usingAstropyWCS)

2.RetrieveNlescoveredbythecutout—>quitefastasmostHiPSareavailableormirroredatCDS

3.Foreach(α,δ):retrieverespecNvecontribuNon from4nearestHEALPixcells(usingcdshealpix(Rust-based)Pythonlibrary)

4.ActualbilinearinterpolaNoncomputaNon,acceleratedbyNumbadecorators

5.ReturnFITSimagecutout

WCS, hips

FITS cutout

x, y α, δ

0.3 0.5

0.10.1

value = w1*val1 + w2*val2 + w3*val3 + w4*val4

IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Performances

6

500k pixels per second

IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Serviceupandrunning

• http://alasky.u-strasbg.fr/hips-image-services/hips2fits• testit

• useit

• sendyourfeedback

• Pythonnotebookexample

• generatecutoutsforMgalaxiesinNHiPSdatasets

• Examplesofgeneratedcutouts… …onthedome!

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IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Usageforoutreachneeds

• Generationofphotospheres

• All-skyCARtesianprojectionwithXMPmetadata

—>UsedbyGiuseppeGreco(VIRGO)forGravitationalWavesoutreach

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IVOA Groningen - Oct 2019 - hips2fits - Apps 2

Futureplans

• Accessfromastroquery.cds

• AchieveconvergencewithSODAinterface

• Extensiontocubecutouts

• Assessphotometryconservationquality

• AmessagetoHiPSproducers:

• «please,keepyourFITStiles,theyareprecious!»

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