J/A+A/708/A290 LEGA-C stellar population scaling relations. II (Gallazzi+, 2026)
LEGA-C stellar population scaling relations. II. Dissecting mass-complete
archaeological trends and their evolution since z∼0.7 with LEGA-C and SDSS.
Gallazzi A.R., Zibetti S., van der Wel A., Nersesian A., Kaushal Y.,
Bezanson R., Mattolini D., Bell E.F., Scholz-Diaz L., Leja J., D'Eugenio F.,
Wu P.-F., Pacifici C., Maseda M.
<Astron. Astrophys. 708, A290 (2026)>
=2026A&A...708A.290G 2026A&A...708A.290G
ADC_Keywords: Galaxies, spectra ; Stars, ages ; Abundances ; Galaxy catalogs ;
Optical
Keywords: galaxies: abundances - galaxies: evolution -
galaxies: fundamental parameters - galaxies: high-redshift -
galaxies: stellar content
Abstract:
We analysed a sample of 552 galaxies from the LEGA-C spectroscopic
survey (0.6<z<0.77), for which we estimated the stellar population
parameters by a Bayesian analysis of the stellar absorption features
and photometry. We investigated the effect of the current star
formation activity on light-weighted mean stellar ages and
metallicities and their median trends with stellar mass or velocity
dispersion. The bimodality in the global age-mass relation stems from
the different age distributions in the quiescent and star-forming
populations. No bimodality is observed in the stellar metallicity-mass
relation, although quiescent and star-forming galaxies have different
distributions in this parameter space. We identified a
high-metallicity sequence populated by quiescent and weakly
star-forming galaxies. At masses lower than 1010.8M☉, the
median stellar metallicity-mass relation of star-forming galaxies
steepens as a consequence of the increasing scatter towards lower
stellar metallicities for galaxies with an increasing specific star
formation rate at fixed mass. Relying on a consistent analysis of SDSS
DR7 spectra and accounting for aperture corrections, we quantified the
evolution of the volume-weighted stellar age and stellar metallicity
scaling relations between z=0.7 and the present. We found negligible
evolution in the stellar metallicity-mass relation of quiescent
galaxies and for M*>1011M☉ galaxies in general.
Lower-mass star-forming galaxies instead have typically lower
metallicities than their local counterparts, indicating significant
enrichment since z∼0.7 in the low-mass regime. Notably, the median of
the stellar ages of the general population and of quiescent galaxies
has changed by only 2Gyr between z=0.7 and z=0.1, which is less than
expected from cosmic ageing. Some quiescent galaxies must evolve
passively to reach the old boundary of the local population. In order
to explain the evolution of the median trends, however, both
individual evolution through rejuvenation and/or minor merging that
affects the outer galaxy regions and population evolution through
quenching of massive metal-rich star-forming galaxies are required.
Description:
We provide the median relations of light-weighted age and stellar
metallicity as a function of stellar mass and as a function of stellar
velocity dispersion as derived the paper, for galaxies in the silver
sample, weighted for volume and completeness, and for the subsample of
high-S/N galaxies (golden sample). Scaling relations are provided for
quiescent and star-forming galaxies, classified according to a cut in
specific star formation rate, for both the silver and the golden
sample. Stellar population physical parameters for LEGA-C galaxies are
derived with BaStA in Gallazzi et al., Paper I, 2026A&A...708A.289G 2026A&A...708A.289G,
Cat. J/A+A/708/A289.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
qparmg.dat 96 6 Median trends of light-weighted age and stellar
metallicity as a function of stellar mass for
quiescent galaxies in the golden sample
(Table B1)
qparms.dat 96 7 Median trends of light-weighted age and stellar
metallicity as a function of stellar mass for
quiescent galaxies in the silver sample
weighted for volume and completeness (Table B1)
qparsg.dat 95 5 Median trends of light-weighted age and stellar
metallicity as a function of stellar velocity
dispersion for quiescent galaxies in the
golden sample (Table B2)
qparss.dat 95 5 Median trends of light-weighted age and stellar
metallicity as a function of stellar velocity
dispersion for quiescent galaxies in the
silver sample weighted for volume and
completeness (Table B2)
sparmg.dat 96 8 Median trends of light-weighted age and stellar
metallicity as a function of stellar mass for
star-forming galaxies in the golden sample
(Table B1)
sparms.dat 96 8 Median trends of light-weighted age and stellar
metallicity as a function of stellar mass for
star-forming galaxies in the silver sample
weighted for volume and completeness (Table B1)
sparsg.dat 95 6 Median trends of light-weighted age and stellar
metallicity as a function of stellar velocity
dispersion for star-forming galaxies in the
silver sample weighted for volume and
completeness (Table B2)
sparss.dat 95 7 Median trends of light-weighted age and stellar
metallicity as a function of stellar velocity
dispersion for star-forming galaxies in the
golden sample (Table B2)
--------------------------------------------------------------------------------
See also:
J/ApJS/256/44 : LEGA-C DR3 catalog (van der Wel+, 2021)
J/A+A/703/A5 : Local galaxies scaling relations (Mattolini+, 2025)
J/A+A/708/A289 : LEGA-C stellar population scaling relation. I.
(Gallazzi+, 2026)
Byte-by-byte Description of file: [qs]parmg.dat [qs]parms.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 F5.2 [Msun] logMass Logarithm of the central value of
0.2dex-wide bin of stellar mass
9- 12 F4.2 [yr] logAgep50 Median of logarithm light-weighted mean
age of galaxies in the mass bin
16- 20 F5.2 [yr] E_logAgep50 Upper error on median logarithm
light-weighted age of galaxies in the
mass bin
24- 28 F5.2 [yr] e_logAgep50 [] Lower error on median logarithm
light-weighted age of galaxies in the
mass bin
32- 35 F4.2 [yr] logAgep16 16th percentile of logarithm
light-weighted age of galaxies in the
mass bin
39- 42 F4.2 [yr] logAgep84 84th percentile of logarithm
light-weighted age of galaxies in the
mass bin
46- 49 F4.2 [yr] medelogAge Mean of 84-16 percentile range of
individual logAge PDFs for galaxies in
stellar mass bin
53- 57 F5.2 [Sun] logZp50 Median of logarithm light-weighted mean
metallicity of galaxies in the mass bin
61- 65 F5.2 [Sun] E_logZp50 Upper error on median logarithm
light-weighted metallicity of galaxies
in the mass bin
69- 73 F5.2 [Sun] e_logZp50 [] Lower error on median logarithm
light-weighted metallicity of galaxies
in the mass bin
77- 81 F5.2 [Sun] logZp16 16th percentile of logarithm
light-weighted metallicity of galaxies
in the mass bin
85- 89 F5.2 [Sun] logZp84 84th percentile of logarithm
light-weighted metallicity of galaxies
in the mass bin
93- 96 F4.2 [Sun] medelogZ Mean of 84-16 percentile range of
individual logZ PDFs for galaxies in
stellar mass bin
--------------------------------------------------------------------------------
Byte-by-byte Description of file: [qs]parsg.dat [qs]parss.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 F4.2 [Msun] logSigma Logarithm of the central value of 0.1dex-wide
bin of stellar velocity dispersion
8- 11 F4.2 [yr] logAgep50 Median of logarithm light-weighted mean age
of galaxies in the velocity dispersion bin
15- 19 F5.2 [yr] E_logAgep50 Upper error on median logarithm
light-weighted age of galaxies in the
velocity dispersion bin
23- 27 F5.2 [yr] e_logAgep50 [] Lower error on median logarithm
light-weighted age of galaxies in the
velocity dispersion bin
31- 34 F4.2 [yr] logAgep16 16th percentile of logarithm light-weighted
age of galaxies in the velocity dispersion
bin
38- 41 F4.2 [yr] logAgep84 84th percentile of logarithm light-weighted
age of galaxies in the velocity dispersion
bin
45- 48 F4.2 [yr] medelogAge Mean of 84-16 percentile range of individual
logAge PDFs for galaxies in velocity
dispersion bin
52- 56 F5.2 [Sun] logZp50 Median of logarithm light-weighted mean
metallicity of galaxies in the velocity
dispersion bin
60- 64 F5.2 [Sun] E_logZp50 Upper error on median logarithm
light-weighted metallicity of galaxies in
the velocity dispersion bin
68- 72 F5.2 [Sun] e_logZp50 [] Lower error on median logarithm
light-weighted metallicity of galaxies in
the velocity dispersion bin
76- 80 F5.2 [Sun] logZp16 16th percentile of logarithm light-weighted
metallicity of galaxies in the velocity
dispersion bin
84- 88 F5.2 [Sun] logZp84 84th percentile of logarithm light-weighted
metallicity of galaxies in the velocity
dispersion bin
92- 95 F4.2 [Sun] medelogZ Mean of 84-16 percentile range of individual
logZ PDFs for galaxies in velocity
dispersion bin
--------------------------------------------------------------------------------
Acknowledgements:
Anna Gallazzi, anna.gallazzi(at)inaf.it
References:
Gallazzi et al., Paper I, 2026A&A...708A.289G 2026A&A...708A.289G, Cat. J/A+A/708/A289
License: CC-BY-4.0 [see https://spdx.org/licenses/]
(End) Anna Gallazzi [INAF, Italy], Patricia Vannier [CDS] 21-Mar-2026