Worthey model interpolation engine

This page was updated 2011 Feb to provide more output quantities. This page migrated to a new web server as of 2016 Feb. Do please let me know if there is a problem with service.

This form allows one to create arbitrary mixtures of single-burst populations. The models are those of Worthey 1994, ApJS, 95, 107. Keep ages between 1 and 18 Gyr, and [Fe/H] between -2 and +0.5. In addition, the [Fe/H]<-0.225, age<8 corner is not allowed. The relative (mass) weights you give will be normalized so that the total initial population mass comes out to a million solar masses. In the box, enter (Age in Gyr, [Fe/H], relative weight) trios separated by white space. E.g., typing 12 0 95 (return) 1 0 5 (return) will show you what an old, solar metallicity population looks like when "polluted" by 5% (by mass) of a younger population.

Output options:
Show colors, magnitudes, spectral indices, SBF magnitudes
Also add low-res integrated flux (1221 flux points)
Also add 0.5 A-resolution synthetic integrated flux, 3000-10000 A (14000 flux points)

Model flavor:
Default models: Salpeter (2.35) IMF between 0.1 and 100 Mo, Y=0.228 + 2.7Z, horizontal branch morphology shifting as a function of metallicity, low-resolution fluxes used to calculate colors.
IMF exponent up 0.5 (2.85)
IMF exponent up 1.0 (3.35)
IMF exponent down 0.5 (1.85)
IMF exponent down 1.0 (1.35)
Miller & Scalo (1979) piecewise IMF.
Shallow Y: Y = 0.228 + 6Z below Z=0.0077; Y = 0.274 above that value
Min Y: Y = 0.20 below [Fe/H] = -0.5; Y = 0.25 above [Fe/H] = -0.25
Max Y: Y = 0.30 below [Fe/H] = -0.5; Y = 0.35 above [Fe/H] = -0.25
No horizontal branch (clump) or later stages
Vanilla, but colors computed with a more recent, high-res set of synthetic fluxes.

Young ages available here without warranty: Dial-a-Padova-Model. (Output not updated for the Padova page yet. Also, check back soon for more isochrone options.)

Read the fine print for model limitations, tips, etc.

Go to:
Claus Leitherer's collection of population synthesis links plus models.
Guy Worthey page.
© 1996-2002. Guy Worthey.