Table 1.
High-redshift systems with a comparatively suppressed rate of star-formation, but show evidence of a developed stellar population indicative of an earlier starburst episode.
| Literature values |
Estimated quantities |
|||||||
|---|---|---|---|---|---|---|---|---|
| Galaxy ID | z(a) | ℛSF/M⊙ yr−1 | M*/109 M⊙ | τ*/Myr (b) | tSB/Myr (c) |
 (d) |
τdyn/Myr (e) | Refs. |
| A1689-zD1 | 7.60 |
 |
 |
 |
350 | 4.9 | 13 | (1, 2, 3, 4) |
| UDF-983-964 |
 |
 |
 |
 |
290 | 7.6 | 26 | (5, 6) |
| GNS-zD2 |
 |
 |
 |
 |
240 | 10 | 15 | (5) |
| MACS1149-JD1 (f) | 9.11 |
 |
 |
 |
100 | 11 | 23 | (7, 8) |
| CDFS-3225-4627 |
 |
 |
 |
 |
210 | 17 | 16 | (5, 9) |
| UDF-3244-4727 (g) |
 |
 |
 |
 |
80 | 35 | 24 | (5, 10) |
| HDFN-3654-1216 |
 |
 |
 |
 |
190 | 36 | 38 | (5) |
| GNS-zD3 |
 |
 |
 |
 |
110 | 38 | 22 | (5) |
| UDF-640-1417 |
 |
 |
 |
 |
140 | 47 | 26 | (5, 6) |
| GNS-zD4 |
 |
 |
 |
 |
120 | 57 | 19 | (5) |
| GNS-zD1 |
 |
 |
 |
 |
120 | 63 | 12 | (5) |
| GNS-zD5 |
 |
 |
 |
 |
110 | 110 | 14 | (5) |
Notes. The listed objects are among the most distant observed for which suitable information about the stellar population and star-formation rate is known.
Redshifts: in cases where the redshift was determined spectroscopically, the uncertainty was less than the precision to which these values are quoted, and so is not shown. Uncertainties are shown for the less precise photometric redshifts.
Stellar population ages: we quote the best-fit stellar ages only as constraints depend strongly on the assumed star-formation history.
Starburst timescale: this is estimated assuming a redshift of galaxy formation of zf = 15.4, the highest value suggested in the literature (see Ref. 7, and also Thomas et al. 2017, which suggests a similar but slightly lower redshift of formation of zf = 14.8), with the exception of A1689-zD1, for which there is evidence that a later epoch of formation is more appropriate, of z = 9 (see Ref. 4). In general, these values are intended to provide an over-estimate for the starburst time-scale to give a conservative star-formation rate, and so should be taken as an upper limit.
Star-formation rate during starburst phase: these are estimated from the stellar mass and the starburst timescale. As such, they should be considered a lower limit.
Dynamical timescales: these are estimates and should be treated as an upper limit. In general the stellar mass was used as a minimum mass to estimate the maximum plausible value of τdyn, as estimates of the galaxy mass were not stated or could not be estimated from the literature. The exceptions are MACS1149-JD1 and A1689-zD1 for which the full-width of half maximum of the O III (Ref. 7) and C III lines (Ref. 4) respectively were used to estimate the dynamical mass. Radial estimates were determined either by the half-light radius of the observed system, or the quoted galaxy radius where available, although we note that values for GNS-zD1, GNS-zD1, GNS-zD3, GNS-zD4, GNS-zD5, CDFS-3225-4627 and HDFN-3654-1216 were calculated based on half-light radii estimated by eye from the photometric images in ref (5), and so should be treated with caution.
Stellar population modelling suggests the presence of two distinct stellar populations in MACS1149-JD1 (see Ref. 7). Here, we quote the best-fit stellar population ages for the young component (top line) and the old component associated with the earlier starburst phase (second line).
References. (1) Bradley et al. (2008), (2) Watson et al. (2015), (3) Knudsen et al. (2017), (4) Mainali et al. (2018), (5) González et al. (2010), (6) Bouwens et al. (2004), (7) Hashimoto et al. (2018), (8) Owen et al. (2019), (9) Bouwens & Illingworth (2006), (10) Oesch et al. (2009).
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