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phosim_release / Instance Catalog

Instance Catalog

This is the main input file to PhoSim. There are two parts to the instance catalog: the observation parameters and the astrophysical inputs. Neither has any required inputs, so use the commands only to specify what is important to your simulation.

Observation Parameters

The observation parameters have no required inputs. The values will either be calculated self-consistently from other parameters or chosen from a distribution.

Common inputs

A common method is to choose to specify ra/dec or alt/az, but not both. However, you can specify inconsistent parameters for with the mjd/latitude/longitude if desired. Unspecified parameters that cannot be calculated self-consistently can be chosen from a distribution.

  • rightascension X (X= Unrefracted Right Ascension in decimal degrees)
  • declination X (X = Unrefracted Declination in decimal degrees)
  • azimuth X (X= Unrefracted Azimuth in decimal degrees)
  • altitude X (X = Unrefracted Altitude in decimal degrees)
  • mjd X (X= MJD of observation (e.g. 51544.5))
  • rottelpos X (X= Angle of sky relative to telescope in decimal degrees)
  • filter X (X= filter number starting at 0)
  • vistime X (X= total exposure time in seconds of observations (including read out times between exposures))
  • nsnap X (X= number of exposures in a sequence)

Advanced Inputs

The following sun/moon/time parameters or environmental parameters would most likely not be used because they can be self-consistently calculated by PhoSim. However, they can be specified and do not have to be consistent for certain studies. For example, moving the Moon below the horizon even if its not there for a given date/time or pretending you are an observer waiting for a particular good seeing value can be useful.

  • date X (X= Date of observation in format: 2000/1/1/0.5)
  • rotskypos X (X = Angle of sky relative to camera coordinates (from North over East) in decimal degrees)
  • moondec X (X = Declination of moon in decimal degrees)
  • moonra X (X = Right Ascension of moon in decimal degrees)
  • moonalt X (X= Altitude of moon in decimal degrees)
  • dist2moon X (X = distance to moon in degrees)
  • moonphase X (X = phase of moon from 0 to 100)
  • sunalt X (X= Altitude of the sun in decimal degrees)
  • seeing X (X= seeing at zenith at 500 nm (set to -1 for random))
  • temperature X (X= temperature in Celsius)
  • pressure X (X= mmHg)

The following bookkeeping and configuration parameters are also optional, but useful for simulation of calibration data (see the walkthrough), naming files, or setting the random number seed.

  • telconfig X (X=telescope configuration (0=dome open/dome light off ; 1=dome closed/dome light off; 2=dome closed/dome light on)
  • camconfig X (X=camera configuration (For LSST: bitmask where first bit is science sensors on; second bit is wavefront sensors on; third bit is guiders on))
  • domeint X (X= dome light intensity (mag per sq. arcseconds), if on)
  • domewav X (X = wavelength of dome light (nm), 0 to use flat SED)
  • overdepbias X (X = operating voltage of CCD)
  • ccdtemp X (X = CCD temperature (K))
  • obshistid X (X = observation identifier (names files))
  • seed X (X= random number seed)
  • minsource X (X=minimum number of source on chip to bother to simulate it)
  • isdithered X (X=0/1 (not used in phosim, except in header))
  • ditherra X (X=distance (degrees) (not used in phosim, except in header))
  • ditherdec X (X=distance (degrees) (not used in phosim, except in header))

Astrophysical inputs

The astrophysical inputs have no required inputs, but you will have to do at least one object or catalog command to produce any photons.

Simple Catalog Generation

  • stars X Y Z (X=lower magnitude limit, Y=upper magnitude limit, Z=diameter of catalog in degrees)
  • galaxies X Y Z (X=lower magnitude limit, Y=upper magnitude limit, Z=diameter of catalog in degrees)
  • stargrid X Y Z (X=spacing of sources in degrees, Y=size of catalog in degrees, Z= magnitude of sources)
  • includeobj X (X=external file that has the objects below. This is used only for massive catalogs.)

Individual Object Specification

For every object you wish to add, put the following line at the end of the instance catalog file. Note: an astrophysical object could be composed of more than one line (e.g. a bulge and disk of a galaxy). This enables complex wavelength-dependent morphologies.

object ID RA DEC MAG_NORM SED_NAME REDSHIFT GAMMA1 GAMMA2 KAPPA DELTA_RA DELTA_DEC SOURCE_TYPE source_pars DUST_REST_NAME dust_pars_1 DUST_LAB_NAME dust_pars_1

  • ID (A floating point number to keep track of the object, which is unused by PhoSim)
  • RA (The right ascension of the center of the object or image in decimal degrees.)
  • DEC (The declination of the center of the object in decimal degrees)
  • MAG_NORM (The normalization of the flux of the object. We use AB magnitudes at 500 nm (in the source's rest frame). This is roughly equivalent to V (AB) or g (AB).
  • SED_NAME (The name of the SED file relative to the data directory)
  • REDSHIFT (The redshift (or blueshift) of the object. The SED does not need to be redshifted if using this)
  • GAMMA1 (The value of the shear parameter gamma1 used in weak lensing.)
  • GAMMA2 (The value of the shear parameter gamma2 used in weak lensing.)
  • KAPPA (The value of the magnification parameter in weak lensing.)
  • DELTA_RA (The value of the declination offset in radians. This can be used either for weak lensing or objects that moved from another exposure if you do not want to change the source position in the first two columns.)
  • DELTA_DEC (The value of the declination offset in radians. This can be used either for weak lensing or objects that moved from another exposure if you do not want to change the source position in the first two columns.)
  • SOURCE_TYPE (The name of the spatial model to be used as defined below.)
  • spatial_pars (The associated parameters for each spatial model.There could be none or many. While the parser is reading the model it looks for more parameters based on the name of the model.)
  • DUST_REST_NAME (Dust model name in the object's rest frame. This is either the ccm for the CCM model, or calzetti for the calzetti model. If no dust model is desired, then put none for this field.)
  • dust_pars_1 (The parameters for both the calzetti and CCM are the A_v followed by the R_v value. If no dust model is used, do not use parameters)
  • DUST_LAB_NAME (Dust model name in the lab frame. This is either the ccm for the CCM model, or calzetti for the calzetti model. If no dust model is desired, then put none for this field.)
  • dust_pars_2 (The parameters for both the calzetti and CCM are the A_v followed by the R_v value. If no dust model is used, do not use parameters)

We have currently implemented the following spatial models:

  • point: This is a model primarily used for stars, but also unresolved objects. (This has no parameters.)
  • gauss: This is a model for a gaussian-shaped object. (1 parameter: sigma in arcseconds)
  • movingpoint: This is a point source that will move appreciably during the exposure (e.g. asteroid) (2 parameters: the derivative of the velocity arcseconds per second along the ra direction, the derivative of the velocity in arcseconds per second along the dec direction)
  • sersic2D: This is a 2-dimensional (projected on the sky) elliptical Sersic model for a simple galaxy shape. (4 parameters: half-light radius of semi-major axis in arcseconds, half-light radius of semi-minor axis in arcseconds, position angle in degrees, sersic index)
  • sersic: This is a 3-d dimensional ellipsoidal Sersic model. (6 parameters: size of axis 1 in arcseconds, size of axis 2 in arcseconds, size of axis 3 in arcseconds, polar angle in degrees, position angle in degrees, sersic index)
  • sersicDisk: This is a 2-d Sersic model with an exponential-scale height in the third dimension (6 parameters: half-light radius of semi-major axis in arcseconds, half-light radius of semi-minor axis in arcseconds, the exponential scale height, polar angle in degrees, position angle in degrees, sersic index)
  • sersicComplex: This a full 3-d galaxy model with both irregular knots and spiral structure. By choosing parameters, you can continuously represent elliptical, spiral, and irregular galaxies. (14 parameters: size of axis 1 in arcseconds, size of axis 2 in arcseconds, size of axis 3 in arcseconds, polar angle in degrees, position angle in degrees, sersic index, fraction of light in clumps, number of clumps, gaussian clump size in arcseconds, fraction of light in spiral, winding angle of spiral in degrees, spiral bar size in arcseconds, spiral gaussian width in arcseconds, position angle of spiral)
  • sersicDiskComplex: This is a full galaxy model disk model with irregular knots and spiral structure, but with an exponential disk scale height. (14 parameters: size of axis 1 in arcseconds, size of axis 2 in arcseconds, size of disk scale height in arcseconds, polar angle in degrees, position angle in degrees, sersic index, fraction of light in clumps, number of clumps, gaussian clump size in arcseconds, fraction of light in spiral, winding angle of spiral in degrees, spiral bar size in arcseconds, spiral gaussian width in arcseconds, position angle of spiral)
  • distortedSphere: This is a 3-d sphere distorted by spherical harmonics with an emission profile that follows a power law. (10 parameters: power law index, 9 spherical harmonic coefficients in arcseconds)
  • FITS files: If the SOURCE_TYPE contains the word fits or fit,it will look for that file in the image directory; (2 parameters: pixel size (in arcseconds) and rotation angle (in degrees). RA goes to the left and DEC goes up in physical coordinates Note that PhoSim will not use the header information, because you may want to use the same image in multiple field locations)

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