GA-NIFS: Dissecting the multiple sub-structures and probing their complex interactions in the Lyα emitter galaxy CR7 at z = 6.6 with JWST/NIRSpec

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Volume 699 (July 2025)

A&A, 699 (2025) A154

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Table 2.

Summary of the parameters, prior probabilities, and posterior probabilities of the fiducial SED fitting prospector model (see also Fig. 9).

	Parameter	Free	Description	Prior	CR7	CR7-A	CR7-B	CR7-C
	(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
Free parameters	logM_★[M_⊙]	Y	Total stellar mass formed	$U (7, 13)$ ${\cal {{U}}}(7, 13)$	$9 . 29_{- 0.16}^{+ 0.17}$ $9.29^{+0.17}_{-0.16}$	$9 . 33_{- 0.07}^{+ 0.05}$ $9.33^{+0.05}_{-0.07}$	$8 . 52_{0.15}^{+ 0.16}$ $8.52^{+0.16}_{0.15}$	$8 . 29_{- 0.11}^{+ 0.31}$ $8.29^{+0.31}_{-0.11}$
	log Z[Z_⊙]	Y	Stellar metallicity	$U (- 2, 0.19)$ ${\cal {{U}}}(-2, 0.19)$	$- 1 . 03_{- 0.11}^{+ 0.11}$ $-1.03^{+0.11}_{-0.11}$	$- 1 . 37_{- 0.07}^{+ 0.08}$ $-1.37^{+0.08}_{-0.07}$	$- 1 . 22_{- 0.12}^{0.12}$ $-1.22^{0.12}_{-0.12}$	$- 0 . 42_{- 0.49}^{+ 0.26}$ $-0.42^{+0.26}_{-0.49}$
	logSFR ratios	Y	Ratio of the logSFR between adjacent SFH bins	$T (0, 0.3, 2)$ ${\cal {{T}}}(0, 0.3, 2)$	–	–	–	–
	τ_V	Y	Optical depth of the diffuse dust	$G (0.3, 1; 0, 2)$ ${\cal {{G}}}(0.3,1;0,2)$	$0 . 07_{- 0.01}^{+ 0.01}$ $0.07^{+0.0 1}_{-0.01}$	$0 . 18_{- 0.01}^{+ 0.01}$ $0.18^{+0.01}_{-0.01}$	$0 . 13_{- 0.03}^{+ 0.05}$ $0.13^{+0.05}_{-0.03}$	$0 . 07_{- 0.03}^{+ 0.04}$ $0.07^{+0.04}_{-0.03}$
	μ	Y	Ratio of the optical depth of the birth clouds to τ_V	$U (- 1.0, 0.4)$ ${\cal {{U}}}(-1.0,0.4)$	$1 . 12_{- 0.07}^{+ 0.07}$ $1.12^{+0.07}_{-0.07}$	$0 . 43_{- 0.12}^{+ 0.10}$ $0.43^{+0.10}_{-0.12}$	$0 . 72_{- 0.23}^{0.17}$ $0.72^{0.17}_{-0.23}$	$0 . 79_{- 0.19}^{4}$ $0.79^{4}_{-0.19}$
	σ_gas [km s⁻¹]	Y	Intrinsic velocity dispersion of the star-forming gas ^(‡)	$U (0, 300)$ ${\cal {{U}}}(0,300)$	$165_{- 50}^{+ 40}$ $165^{+40}_{-50}$	$124_{- 18}^{+ 50}$ $124^{+50}_{-18}$	$140_{- 30}^{+ 20}$ $140^{+20}_{-30}$	$108_{- 27}^{+ 50}$ $108^{+50}_{-27}$
	log Z_gas[Z_⊙]	Y	Metallicity of the star-forming gas	$U (- 2, 0.19)$ ${\cal {{U}}}(-2, 0.19)$	$- 0 . 59_{- 0.01}^{+ 0.01}$ $-0.59^{+0.01}_{-0.01}$	$- 0 . 59_{- 0.02}^{+ 0.01}$ $-0.59^{+0.01}_{-0.02}$	$- 0 . 64_{- 0.05}^{+ 0.05}$ $-0.64^{+0.05}_{-0.05}$	$- 0 . 40_{- 0.12}^{+ 0.06}$ $-0.40^{+0.06}_{-0.12}$
	log U	Y	Ionisation parameter of the star-forming gas	$U (- 4, - 1)$ ${\cal {{U}}}(-4, -1)$	$- 1 . 18_{- 0.07}^{+ 0.06}$ $-1.18^{+0.06}_{-0.07}$	$- 1 . 01_{- 0.02}^{+ 0.01}$ $-1.01^{+0.01}_{-0.02}$	$- 1 . 41_{- 0.11}^{+ 0.13}$ $-1.41^{+0.13}_{-0.11}$	$- 1 . 54_{- 0.18}^{+ 0.25}$ $-1.54^{+0.25}_{-0.18}$

Other	log SFR₁₀[M_⊙ yr⁻¹]	N	SFR averaged over the last 10 Myr	–	$1 . 74_{- 0.03}^{+ 0.02}$ $1.74^{+0.02}_{-0.03}$	$1 . 39_{- 0.02}^{+ 0.02}$ $1.39^{+0.02}_{-0.02}$	$0 . 73_{- 0.03}^{+ 0.04}$ $0.73^{+0.04}_{-0.03}$	$0 . 58_{- 0.09}^{+ 0.07}$ $0.58^{+0.07}_{-0.09}$
Other	log SFR₁₀₀[M_⊙ yr⁻¹]	N	SFR averaged over the last 100 Myr	–	$0 . 96_{- 0.08}^{+ 0.09}$ $0.96^{+0.09}_{-0.08}$	$0 . 58_{- 0.05}^{+ 0.05}$ $0.58^{+0.05}_{-0.05}$	$0 . 01_{- 0.06}^{+ 0.06}$ $0.01^{+0.06}_{-0.06}$	$0 . 06_{- 0.10}^{+ 0.16}$ $0.06^{+0.16}_{-0.10}$

Notes. (1) Parameter name and units (where applicable). (2) Only parameters marked with ‘Y’ have been optimised by prospector; parameters marked with ‘N’ are either tied to other parameters (see Column 4) or were calculated after the fit from the posterior distribution (in this case, Column 4 is empty). (3) Parameter description. (For the dust attenuation parameters n, τ_V, and μ see Tacchella et al. (2022, their Eqs. 4 and 5).) (4) Parameter prior probability distribution; $N (μ, σ)$ ${\cal {{N}}}(\mu , \sigma )$ is the normal distribution with mean μ and dispersion σ; $U (a, b)$ ${\cal {{U}}}(a, b)$ is the uniform distribution between a and b; $T (μ, σ, ν)$ ${\cal {{T}}}(\mu , \sigma , \nu )$ is the Student's t distribution with mean μ, dispersion σ, and ν degrees of freedom; $G (μ, σ, a, b)$ ${\cal {{G}}}(\mu , \sigma , a, b)$ is the normal distribution with mean μ and dispersion σ truncated between a and b. Columns (5), (6), (7), and (8) are the posterior median and 16^th–84^th percentile range of the marginalised posterior distribution for CR7-A, CR7-B, CR7-C, and total CR7, respectively. For some nuisance parameters, we do not present the posterior statistics (e.g. log SFR ratios).

^(‡)

The velocity dispersion of the emission lines is a nuisance parameter due to the low spectral resolution of the prism data (∼500 km s⁻¹ at the wavelength of [O III]λ5007); indeed, the posterior probability distributions for CR7 is consistent with 0 km s⁻¹.

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