Kavli Affiliate: Wendy L. Freedman
| First 5 Authors: , , , ,
| Summary:
We present a comparative test of four widely used full spectral fitting
codes, with the aim of answering the question: how robust is the retrieval of
the stellar initial mass function (IMF) and other stellar properties of
galaxies? We used ALF, PyStaff, Starlight, and pPXF to fit a set of
optical+near-infrared spectroscopic data from the Magellan telescope of the two
brightest galaxies in the Fornax cluster, NGC1399 and NGC1404. By fitting the
same data set with the same models, we can compare the radial trends (out to ~
R_e) of IMF slope, age, metallicity and 19 elemental abundances when allowed
with the four codes. To further test the robustness of our analysis, we carried
out parallel simulations by creating inputs with different star formation
history (SFH) complexity. The results from simulations show that codes such as
ALF and PyStaff, which both assume a simple stellar population (SSP) return
greater precision and accuracy only when the underlying population is a pure
SSP; however, in cases where the SFH is more complex, these codes return
erroneous results. Although codes like Starlight and pPXF, which retrieve the
best-fit SFH without prior assumptions, tend to produce results with greater
scatter and bias, they are generally more reliable in identifying secondary
components. Our analysis on the two targets shows that ALF and PyStaff, that
assume an SSP, give results pointing to a single old age, a decreasing
metallicity with radius and a flat super-Salpeter IMF. In contrast, Starlight
and pPXF suggest the presence of a secondary component with different
metallicity and IMF characteristics.
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