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celestial (R package)

R-CMD-check

Synopsis

Core package containing a collection of common astronomical conversion routines and functions. It provides tools for coordinate conversions (decimal degrees to/from HMS/DMS formats), cosmological calculations (distances, volumes, ages, structure growth), sky coordinate matching, WCS projections, halo profiles, and more.

Installation

Source installation from GitHub should be easy:

install.packages('remotes')
remotes::install_github("asgr/celestial")
library(celestial)

Package Dependencies

The above should also install the required packages. If you have trouble with this you can try installing the required packages manually first and then retry the installation for celestial:

install.packages(c('RANN', 'NISTunits', 'pracma')) # Required packages
install.packages(c('plotrix', 'igraph')) # Suggested packages
install.packages('remotes')
remotes::install_github("asgr/celestial")

Assuming you have installed all of the packages that you need/want, you should now be able to load celestial within R with the usual:

library(celestial)

Code Example

Coordinate Conversions

Convert decimal degrees to HMS (Hours, Minutes, Seconds) format, as commonly used for right ascension:

deg2hms(182.5, type='cat', sep=':')
# [1] "12:10:00.00"

deg2hms(182.5, type='cat', sep='hms')
# [1] "12h10m00.00s"

Convert decimal degrees to DMS (Degrees, Minutes, Seconds) format, as commonly used for declination:

deg2dms(-27.345, type='cat', sep=':')
# [1] "-27:20:42.00"

deg2dms(-27.345, type='cat', sep='dms')
# [1] "-27d20m42.00s"

Cosmological Distance Calculations

Compute cosmological distances and related quantities for a given redshift:

cosdist(z=1:10, H0=70, OmegaM=0.3)

This returns a data.frame with columns including comoving distance, luminosity distance, angular diameter distance, look-back time, and more.

For quick lookups you can use the convenient single-output wrapper functions:

cosdistLumDist(z=1, H0=70, OmegaM=0.3)   # Luminosity distance in Mpc
cosdistAngDist(z=1, H0=70, OmegaM=0.3)   # Angular diameter distance in Mpc
cosdistAngScale(z=1, H0=70, OmegaM=0.3)  # Angular scale in kpc/arcsec

You can also use built-in reference cosmologies:

cosdist(z=1, ref='Planck18')

Cosmological Volume Calculations

cosvol(zlo=0, zhi=0.1, H0=70, OmegaM=0.3)

Sky Coordinate Matching

Match two catalogues of sky coordinates:

# Create two sets of RA/Dec coordinates
coordref = cbind(RA=c(10.1, 10.5, 11.0), Dec=c(-20.1, -20.5, -21.0))
coordcompare = cbind(RA=c(10.11, 10.6, 12.0), Dec=c(-20.09, -20.4, -22.0))

# Match within 10 arcsec
match = coordmatch(coordref, coordcompare, rad=10, radunit = 'amin')

WCS Projections

Convert between RA/Dec (degrees) and x/y pixel coordinates:

radec2xy(RA=180.0, Dec=-30.0, CRVAL1=180.0, CRVAL2=-30.0, CRPIX1=512, CRPIX2=512,
         CD1_1=-2.78e-4, CD2_2=2.78e-4)

Motivation

celestial was developed to provide a self-contained collection of common astronomical utility functions in R, particularly for cosmological calculations and sky coordinate handling. It is used as a dependency by several other ProTools packages including ProFound and ProFit.

Contributors

Aaron Robotham

References

Driver S.P. & Robotham A.S.G., 2010, MNRAS, 407, 2131 (cosmic variance calculator)

Resources

https://github.com/asgr/celestial

Forums

Please sign up to http://profit.freeforums.net/ if you want to ask a question (or browse the questions asked).

License

GPL-3