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Table 2
Model parameters considered in the proposed chemical evolution model distinguishing between “galaxy model”, “IRA”, “type Ia SNe & DTD” quantities.
| Model parameters | Description | ||
|---|---|---|---|
| Name | Dimension | ||
| N | 1 | Number of infall episodes | |
| τj | (Gyr) | Timescale of gas accretion for the jth infall episode | |
| tj | (Gyr) | Starting time of the jth infall episode | |
| Aj | (M⊙ pc−2 Gyr−1) | Normalisation coefficient of the jth infall episode | |
| Galaxy | σΑj | (M⊙ pc−2) | Total accreted surface mass density for the jth infall |
| model | ω | 1 | Wind-loading factor |
| vL | ([Gyr−1) | Star-formation efficiency | |
| σgas | (M⊙ pc−2) | Total Surface gas density | |
| σ* | (M⊙ pc−2) | Total Surface stellar mass density | |
| σX(0) | (M⊙ pc−2) | Initial surface mass density of the element X | |
| R | 1 | Recycling fraction | |
| IRA | 〈yX〉 | 1 | Yield per stellar generation for the element X |
| 〈mX,Ia〉 | (M⊙) | Average amount of X synthesized by each single Type Ia SN event. | |
| CIa |  |
Normalisation constant for the Type Ia SNe rate. | |
| AG | (Gyr−1) | Amplitude of the Gaussian term in the DTD. | |
| Type Ia SNe | AE | [Gyr−1] | Amplitude of the exponential term in the DTD. |
| and | AI | [Gyr−1] | Amplitude of the t−1 term in the DTD. |
| DTD model | σ′ | (Gyr) | Width of the Gaussian DTD. |
| τ′ | (Gyr) | Median of the Gaussian DTD. | |
| τD | (Gyr) | Timescale of the exponential DTD. | |
| τ0 | (Gyr) | Offset of the inverse DTD. It must satisfy τ0 < τI,1. | |
| τI | (Gyr) | Characteristic time of the inverse DTD (set to 1 Gyr). | |
| Δtj | (Gyr) | t − tj | |
| α | (Gyr−1) | vL(1 + ω − R) | |
| Solution | βj | (Gyr−1) | α − 1/τj |
| parameters | ηj | (Gyr) | τ′ + σ′2/τj |
| ηα | (Gyr) | τ′ + σ′2α | |
| σtot | (M⊙ pc−2) | σg + σ* | |
Notes. In the last rows, the parameters adopted in the solution reported in Appendix B are also indicated.
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