WFPC2 HST Gravitational Lens Image Creator

The main parameters that change the lens configuration are the (X,Y) offsets of Source and the Lens Mass axis ratio. The Critical radius governs the scale of the deflection. It is the Einstein ring radius for zero offsets and lens mass axis ratio equal to unity.

An ImageMap with the Caustic/Cut which can be clicked will be generated to change source location interactively.

To compare the simulation side by side with a HST WFPC2 image of a
lens candidate, create an image (.jpg or .gif) of a 6.4 arcsecond (64
WFC pixels) square region, and specify a URL to it.

The specified comparison image, the simulated image and the corresponding
caustic/cut image would be in the image stack on right and maybe blinked
in a javascript enabled browser.

The table below gives an array of links which model each of six
candidates in each of the six potentials models
used to compute gravitational lens configurations in

Knudson, A., Ratnatunga, K. U. & Griffiths, R. E.

*Investigation of Gravittional Lens Mass Models*

2001 **A. J.**
** 122 ** 103-112 .

Clicking on the **acronym** will simulate that maximum likelihood
model fitted to that lens.

HST | UMDS | Lens | Comment | Gravitational Lens Potential Model | ||||||

14176+5226 | u26x8 | 0009 | Quadruple - Confirmed | SIE | SIG | SML | NIE | SSS | NFW | |

12531-2914 | urz00 | 0035 | Quadruple | SIE | SIG | SML | NIE | SSS | NFW | |

01247+0352 | uci10 | 0034 | Double | SIE | SIG | SML | NIE | SSS | NFW | |

15433+5352 | uvd01 | 0014 | Arc+One - On Caustic | SIE | SIG | SML | NIE | SSS | NFW | |

16309+8230 | urg01 | 0010 | Arc - Mild Lens | SIE | SIG | SML | NIE | SSS | NFW | |

12368+6212 | uhdfk | 0056 | Distortion - Weak Lens | SIE | SIG | SML | NIE | SSS | NFW |

The potential model **acronyms** are described below.

SIE | Singular Isothermal Ellipsoid.
Korman, Schneider & Bartelmann 1994 A&A 284, 285. |

SIG | Same as SIE with the orientation of the lens mass is constrained to be the same as the light of lens galaxy by including an external shear term. |

SML | Same as SIE with the axis ratio and the orientation of the lens mass is constrained to be the same as the light of lens galaxy by including an external shear term. |

NIE | Isothermal Ellipsoid with a core radius.
Korman, Schneider & Bartelmann 1994 A&A 284, 285. |

SSS | Singular Spherical model with a softness parameter, with an
external shear term.
Witt, Mao & Schechter 1995 ApJ 443, 18 |

NFW | Spherical mass model from CDM simulations with an external
shear term.
Navarro, Frenk, & White 1995 MNRAS 275, 720 |

The table below gives similar links which will start with the maximum
likelihood model fitted using the simple SIE - singular isothermal
elliptical lens potential, to the other four gravitational lens
candidates published in

Ratnatunga, K. U., Griffiths, R. E. & Ostrander, E. J. 1999,

*The Top Ten List of Gravitational Lens Candidates from the
HST Medium Deep Survey*

**A. J.**
** 117 ** 2010-2013.
astro-ph/9802100.

HST | UMDS | Lens | Comment | Gravitational Lens Potential Model | |

14164+5215 | u26xi | 0017 | Double | SIE | |

01248+0351 | uci10 | 0050 | Double - edgeon Disk | SIE | |

16302+8230 | urg01 | 0042 | Almost Ring ? | SIE | |

18078+4600 | uqc00 | 0029 | Arc - galaxy group | SIE |

The deflection from gravitational lens used in the simulation is
defined by the *critical radius* which is the directly observed
quantity. It can be related to the potential of the lensing galaxy mass,
redshifts of the lens and source, and cosmological constants.
The true effective potential which depends also on the projection of
the mass distribution to the line-of-sight is at best only known
statistically.

Compute either the effective velocity dispersion corresponding to the input critical radius, or the critical radius coresponding to the input observed or estimated velocity dispersion.

Although it is OK to change, it is logical to keep without loss of generality
the parameters flagged with * at their default zero value.

The profile index for elliptical scale free models can only take values

0.25 (Bulge-like) or 1 (Disk-like) or 2 (Gaussian)

The simulated WFPC2 images are 64 pixel square with 0.1 arc second pixels.

They have been combined into a color jpg image using the same automated
f77 algorithm used for CMU/STScI/NASA Press Release
99-18
of 13 May 1999.

The transformation is non-linear and designed to highlight faint
components.

The temporary image files are named with the time of creation to avoid a cache copy being displayed. They are deleted by a cron task within 1 to 2 hours. The cgi driver has been written in f77 using the same subroutines used for the gravitational lens image analysis. Each computation takes under a second on the Athlon 700MHz Linux server.

Comments: E-mail Kavan Ratnatunga