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--- courses:ast403:population-synthesis [2026/02/12 07:29] – shuvo
+++ courses:ast403:population-synthesis [2026/02/17 21:22] (current) – shuvo
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-===== Population Synthesis =====
+====== Population Synthesis ======
 Population synthesis is a theoretical framework used to interpret the integrated spectra of galaxies as the sum of light emitted by their constituent stellar populations. Because the light of "normal" galaxies originates almost entirely from stars, and stellar evolution is relatively well-understood, astronomers can model a galaxy's spectral energy distribution (SED) by simulating its history of star formation and chemical enrichment.
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 [{{ :courses:ast403:color_evo.jpg?600 | Fig 2: (left) Evolution of colors between $0\le t \le 17 ×10^9$ yr
-for a stellar population with star-formation rate given by the experssion of $\psi(t)$, for five different values of the characteristic time-scale $\tau$ ($\tau=0$ is the limiting case for a constant star-formation rate) –Galactic center see solid curves. (right) The dependence of colors and $M/L$ on the metallicity
+for a stellar population with star-formation rate given by the experssion of $\psi(t)$, (right) The dependence of colors and $M/L$ on the metallicity
-of the population. The typical colors for four different morphological types of galaxies are plotted. For each $\tau$, the evolution begins at the lower left, i.e., as a blue population in both color indices. In the case of constant star-formation, the population never becomes redder than Irr’s; to achieve redder colors, $\tau$ has to be smaller. The dashed line connects points of $t =10^{10}$ yr on the different curves. }}]
+of the population. The typical colors for four different morphological types of galaxies are plotted. For each $\tau$, the evolution begins at the lower left, i.e., as a blue population in both color indices. In the case of constant star-formation, the population never becomes redder than Irr’s; to achieve redder colors, $\tau$ has to be smaller. }}]
-The dashed line connects points of $t = 10^{10}$ yr on the different curves. Here, a Salpeter IMF and Solar metallicity was assumed. The shift in color obtained by doubling the metallicity is indicated by an arrow, as well as that due to an extinction coefficient of E(B−V )= 0.1; both effects will make galaxies appear redder.
   * **Key Diagnostic Features:**
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 observations of galaxies at high redshift (and thus
 smaller age).
+  * **More**
+  * Astrobite article about SED fittings: [[https://astrobites.org/2026/01/30/sed-fitting/]]
+  * Various SED fitting softwares: [[http://www.sedfitting.org/Welcome.html]]