astropy

Transcript

1. Adrian Price-Whelan Columbia University @astrodrian Monday, March 4, 13

2. Project Coordinators • Perry Greenfield, STScI • Thomas Robitaille, MPIA

   • Erik Tollerud, Yale Core package maintainers • Tom Aldcroft, CfA • Erik Bray, STScI • Matt Davis, STScI • Michael Droettboom, STScI Affiliated package maintainers • Tom Aldcroft, CfA (pyidlastro) • Rene Breton, University of Southampton (photutils) • Wolfgang Kerzendorf, ANU (specutils) • Taro Sato (kcorrect) Contributors • Demitri Muna, NYU • Adrian Price-Whelan, Columbia U • Steve Crawford, SALT • Adam Ginsburg, U Colorado • Frederic Grollier • Prasanth Nair • Neil Crighton, MPIA • Christoph Deil, MPIK • Kyle Barbary, LBNL Monday, March 4, 13

3. The Problem • astLib • astrolib • astropysics • pyephem

   • ephempy • pyast • pyastro • apwlib • chiantipy • pymidas • pandora • pyspec • pyraf • atpy • aplpy • pynovas • cosmopy • cosmolopy • kapteyn • cosmics.py • pyguide • astrogui • pyastronomy • pywcs • pyfits • sunpy • ...more? Monday, March 4, 13

4. astropy Documentation: docs.astropy.org Code: github.com/astropy/astropy (soon) Tutorials & Recipes: github.com/astropy/astropy-tutorials

   Mailing lists: Get help and discuss with users: astropy Discuss technicalities with developers: astropy-dev Report bugs (not installation problems!): issue tracker github.com/astropy/astropy/issues Monday, March 4, 13

5. bit.ly/APWAstropy bit.ly/APWAstropyData bit.ly/APWAstropyTalk Monday, March 4, 13

6. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

   .wcs .cosmology Monday, March 4, 13

7. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

   .wcs .cosmology Monday, March 4, 13

8. astropy.units A system for defining and converting between units, and

   performing arithmetic with physical quantities. >>> import astropy.units as u >>> q = (1.125*u.pc).to(u.km) >>> q <Quantity 3.47138727915e+13 km> >>> q.value 34713872791505.906 >>> q.unit Unit("km") Monday, March 4, 13

9. astropy.units Works really well in iPython Notebook. Monday, March 4,

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10. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

11. astropy.coordinates >>> import astropy.coordinates as coord >>> import astropy.units as

    u >>> coord.ICRSCoordinates('00h42m44.3s +41d16m9s') <ICRSCoordinates RA=10.68458 deg, Dec=41.26917 deg> >>> coord.ICRSCoordinates(10.68458, 41.26917, unit=(u.degree, u.degree)) <ICRSCoordinates RA=10.68458 deg, Dec=41.26917 deg> If units are unambiguous to humans, you don’t need to specify -> Otherwise, you have to tell the constructor degrees / hours / radians Monday, March 4, 13

12. astropy.coordinates >>> c = coord.ICRSCoordinates('00h42m44.3s +41d16m9s') >>> c.ra <RA 10.68458

    deg> >>> c.ra.hours 0.7123053333333333 >>> c.ra.format(u.hour, sep=”hms”) '0h42m44.30000s' >>> c.ra.format(u.degree, sep=”:”) '10:41:04.50000' Angle objects (e.g. RA, Dec) can be formatted into strings. Monday, March 4, 13

13. astropy.coordinates >>> c = coord.ICRSCoordinates('00h42m44.3s +41d16m9s') >>> c.galactic <GalacticCoordinates l=121.17431

    deg, b=-21.57280 deg> >>> c.transform_to(coord.GalacticCoordinates) <GalacticCoordinates l=121.17431 deg, b=-21.57280 deg> >>> c.galactic.l, c.galactic.b (<Angle 121.17431 deg>, <Angle -21.57280 deg>) Transformations are computed based on a registry of available conversions. Monday, March 4, 13

14. astropy.coordinates Monday, March 4, 13

15. astropy.coordinates Why do you care? If you define a new

    coordinate system, you only have to specify the transformation to and from one other, but can then transform to any system: SgrCoordinates `sgr` >>> c = coord.ICRSCoordinates('00h42m44.3s +41d16m9s') >>> c.transform_to(SgrCoordinates) <SgrCoordinates Lambda=113.81238 deg, Beta=-45.82266 deg> Monday, March 4, 13

16. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

17. astropy.time Functionality for manipulating times and dates. Supports UTC, TA,

    UT1. Adds JD, MJD, ISO 8601, etc. Monday, March 4, 13

18. astropy.time >>> from astropy.time import Time >>> t = Time(55672.5134,

    format=‘mjd’, scale=’utc’) >>> t.jd 2455673.0134 >>> t.iso '2011-04-21 12:19:17.760' >>> import datetime >>> t = Time(datetime.datetime.utcnow().isoformat(), scale='utc') >>> t.mjd Monday, March 4, 13

19. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

20. astropy.table - Store and manipulate heterogeneous tables of data -

    Modify rows, columns; swap columns; add new rows, columns - Create tables, write to many formats (ASCII, Latex, DAOPhot, etc.) Monday, March 4, 13

21. astropy.table Back to iPython... Monday, March 4, 13

22. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

23. astropy.io.fits pyfits --> astropy.io.fits Same syntax, just merged into Astropy

    Monday, March 4, 13

24. astropy.io.fits >>> from astropy.io import fits >>> hdulist = fits.open(“some_file.fits”)

    >>> hdulist.info() Filename: test1.fits No. Name Type Cards Dimensions Format 0 PRIMARY PrimaryHDU 220 () int16 1 SCI ImageHDU 61 (800, 800) float32 2 SCI ImageHDU 61 (800, 800) float32 3 SCI ImageHDU 61 (800, 800) float32 4 SCI ImageHDU 61 (800, 800) float32 >>> hdulist[0].data ... etc. Monday, March 4, 13

25. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

26. astropy.wcs pywcs --> astropy.wcs Same syntax, just merged into Astropy

    API overhaul coming in v0.3 Monday, March 4, 13

27. astropy.wcs >>> from astropy.io import fits >>> from astropy import

    wcs >>> hdulist = fits.open(“some_file.fits”) >>> wcs.WCS(hdulist[0].header) ... etc. Monday, March 4, 13

28. astropy .units / .constants .coordinates .time .table / .io.ascii .fits

    .wcs .cosmology Monday, March 4, 13

29. astropy.cosmology Classes for representing cosmologies Utility functions for calculating commonly

    used quantities that depend on a cosmological model Monday, March 4, 13

30. astropy.cosmology >>> from astropy.cosmology import LambdaCDM >>> cosmo = LambdaCDM(H0=85.,

    Om0=0.3, Ode0=0.5) >>> cosmo.lookback_time(0.612) 4.57737249034 >>> from astropy.cosmology import WMAP9 >>> WMAP9.lookback_time(0.612) 5.87117768853 >>> WMAP9.luminosity_distance(z=0.612) # (in Mpc) 3671.859892514587 Note: currently doesn’t use Units...coming very soon! Monday, March 4, 13

31. Questions so far? Monday, March 4, 13

32. worked example: - Read in and plot a list of

    SDSS coordinates - Color code points by u-r color Monday, March 4, 13