Dr. Guy's Research

Stellar populations in external galaxies
Observational cosmology and galaxy formation
Theoretical models of stellar populations

The Dial-a-model page
allows the user to concoct their own population mix and view the results. Based on the Worthey 1994, ApJS, 95, 107 models.

The Lick/IDS system link
gives help (advice and data) for those wanting to measure Lick indices in their own spectra.

Coming soon: The Lick2 index system . . .

Recent papers:

The Observability of Abundance Ratio Effects in Dynamically Hot Stellar Systems, by J. Serven, Guy Worthey, and Michael M. Briley, ApJ, submitted.
Manuscript: serven.ps, serven.pdf.
Readable version of Tables 2 and 3: table23.ps, table23.pdf, and plain text version table23.txt.

Related to this paper are the data tables associated with Houdashelt et al. 2002, BAAS 201, 14.05, who computed the same synthetic Lick/IDS indices as Tripicco & Bell 1995, but with (1) the WO97 Balmer indices added, (2) TiO line lists added, and (3) a [C/M] enhancement of only 0.15 dex to avoid the nonlinear effects of having the C/O ratio approach unity. These tables have not been published in a journal, but they are valid, useful calculations that should be freely shared. Here they are, smoothed to the WO97 variable resolution, in ascii format.
Cool Dwarf
MS Turnoff Star

M31's Heavy Element Distribution and Outer Disk, by G. Worthey, A. Espana, Lauren A. MacArthur, and Stephane Courteau. Astrophysical Journal, submitted. Manuscript: m31.ps , m31.pdf

Balmer and Metal Feature Absorption Gradients in M32, by G. Worthey, 2004, Astronomical Journal, 128, 2826.
+ Preprint (one column, big figures, 23 pages): [ps], or [pdf].
+ Preprint (two columns, small figures, 16 pages): [ps], or [pdf].
Extra plots: H beta versus metals.eps, H delta A versus metals.eps, H gamma A versus metals.eps, H delta F versus metals.eps, H gamma F versus metals.eps, Table of all index measurements (text), Table of smoothed index measurements (text version of Table 1), Table of smoothed index measurements (text version of Table 2).

The Mg-sigma Relation and the Genesis of Early-Type Galaxies, by G. Worthey & M. Collobert. 2003 Astrophysical Journal vol. 586, p. 17. Resource Page: (manuscript, big figures, extra figures).

The Metal Abundances of NGC 188 and NGC 6791 from Low Resolution Spectra, by G. Worthey & Kelly J. Jowett, 2003 PASP, vol. 115, p. 96. Download the manuscript (paper.ps or paper.pdf) and the data in Table 1 (data.ps or data.pdf).

A project I am working on at the moment is measuring infrared brightnesses of stars in local group elliptical galaxy M32 using the Hubble Space Telescope's NICMOS camera. The stars pictured here are 2 million light years away!

How bright are these stars? How many of them are there? What is their elemental composition? These are the questions we can tackle with images like this one.

Less recent papers:
Abundance Ratio Trends and Nucleosynthesis in Elliptical Galaxies and Spheroids by G. Worthey, 1998, PASP, 110, 888. 431 KB of PostScript.
Color-color Relations for Red Giants in Star Clusters by von Braun et al., 1998, PASP, 110, 810. 575 KB of PostScript.
H delta and H gamma Absorption Features in Stars and Galaxies by G. Worthey and D. L. Ottaviani, 1997, ApJS 111, 377 (September). 572 KB of PostScript (but the journal version is significantly prettier). The tabular index data is available here.
Star Formation History of Elliptical Galaxies from Low-Redshift Evidence is an October 1996 10-page conference writeup. 300 Kilobytes of PostScript.
The G Dwarf Problem Exists in Other Galaxies is in the September 1996 AJ, v. 112, 948. 210 Kilobytes of PostScript.
Abundance ratio trends in elliptical galaxies is a conference review in "From Stars to Galaxies" ed. Leitherer, Fritze-von Alvensleben, & Huchra in the ASP conference series v. 98. 310 Kilobytes of Postscript.

Worthey, Faber, González, Burstein 1994, ApJS, 94, 687 here.
Worthey 1994, ApJS, 95, 107 here. (But also see the dial-a-model page!)
Worthey & Ottaviani 1997, ApJS, submitted here.

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