Chemical hints of Population III stars from silicon abundances in massive galaxies

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Table 2.

Individual abundance measurements for NGC 1277 and the massive ETG sample.

Galaxy	Method	Si index	Mg index	[Si/Fe]	[Mg/Fe]	[Si/Mg]
NGC 1277	1	SiI1.20	Mgb5177	0.77	0.27	0.49
	2	SiI1.20	Mgb5177	0.71	0.33	0.38
	1	SiI1.20	MgI1.18	0.85	0.45	0.40
	2	SiI1.20	MgI1.18	0.71	0.48	0.23
	1	SiI1.59	Mgb5177	1.70	0.21	1.49
	2	SiI1.59	Mgb5177	1.93	0.33	1.60
	1	SiI1.59	MgI1.18	1.55	0.44	1.11
	2	SiI1.59	MgI1.18	1.93	0.48	1.45

Posterior median ± 68% credible interval				$1 . 05_{- 0.27}^{+ 0.45}$ $Mathematical equation: $ 1.05^{+0.45}_{-0.27} $$	$0 . 36_{- 0.24}^{+ 0.27}$ $Mathematical equation: $ 0.36^{+0.27}_{-0.24} $$	$0 . 67_{- 0.27}^{+ 0.45}$ $Mathematical equation: $ 0.67^{+0.45}_{-0.27} $$

XSGs	1	SiI1.20	Mgb5177	0.22	0.24	−0.02
	2	SiI1.20	Mgb5177	0.10	0.26	−0.16
	1	SiI1.20	MgI1.18	0.25	0.30	−0.05
	2	SiI1.20	MgI1.18	0.10	0.31	−0.21
	1	SiI1.59	Mgb5177	0.48	0.22	0.26
	2	SiI1.59	Mgb5177	0.60	0.26	0.34
	1	SiI1.59	MgI1.18	0.47	0.30	0.17
	2	SiI1.59	MgI1.18	0.60	0.31	0.29

Posterior median ± 68% credible interval				$0 . 34_{- 0.25}^{+ 0.27}$ $Mathematical equation: $ 0.34^{+0.27}_{-0.25} $$	$0 . 27_{- 0.25}^{+ 0.26}$ $Mathematical equation: $ 0.27^{+0.26}_{-0.25} $$	$0 . 07_{- 0.25}^{+ 0.27}$ $Mathematical equation: $ 0.07^{+0.27}_{-0.25} $$

Notes. Individual abundance measurements are derived from eight combinations of Si and Mg spectral indices and abundance-estimation methods. The posterior rows report the median values and 68% credible intervals from the Bayesian hierarchical analysis, providing a statistical summary of the inferred abundance ratios for each galaxy.

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