J/MNRAS/528/2790 Age resolution in stellar population synthesis (Zibetti+ 2024)
On the maximum age resolution achievable through stellar population synthesis
models.
Zibetti S., Rossi E., Gallazzi A.R.
<Mon. Not. R. Astron. Soc. 528, 2790-2804 (2024)>
=2024MNRAS.528.2790Z 2024MNRAS.528.2790Z (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Galaxies, optical ; Populations, stellar ;
Stars, ages
Keywords: galaxies: evolution - galaxies: fundamental parameters -
galaxies: stellar content
Abstract:
As the reconstruction of the star-formation histories (SFH) of
galaxies from spectroscopic data becomes increasingly popular, we
explore the best age resolution achievable with stellar population
synthesis (SPS) models, relying on different constraints: broad-band
colours, absorption indices, a combination of the two, and the full
spectrum. We perform idealized experiments on SPS models and show that
the minimum resolvable relative duration of a star-formation episode
(time difference between 10% and 90% of the stellar mass formed
divided by the median age) is never better than 0.4, even when using
spectra with signal-to-noise ratio (SNR) larger than 100 per Å.
Typically, the best relative age resolution ranges between 0.4 and 0.7
over most of the age-metallicity plane, corresponding to minimum bin
sizes for SFH sampling between 0.15 and 0.25dex. This resolution makes
the spectroscopic exploration of distant galaxies mandatory in order
to reconstruct the early phases of galaxies' SFHs. We show that
spectroscopy with SNR≳20Å-1 is essential for good age
resolution. Remarkably, using the full spectrum does not prove
significantly more effective than relying on absorption indices,
especially at SNR≲20Å-1. We discuss the physical origins of the
age resolution trends as a function of age and metallicity, and
identify the presence of maxima in age resolution (i.e. minima in
measurable relative time duration) at the characteristic ages that
correspond to quick time variations in spectral absorption features.
We connect these maxima to bumps commonly observed in reconstructed
SFHs.
Description:
The minimum measurable relative duration of idealized star-formation
histories are reported for different constraints and different
signal-to-noise ratio regimes, as a function of the median age of the
stellar population (age50). The relative duration is expressed in
terms of {DELTA}age10-90/age50=dagen (dagen={DELTA}agen), where
{DELTA}age10-90 is the time span between the epoch at which 10% and
and 90% of the stellar mass have been already formed (see Sec. 2.1 in
the paper). All quantities represented in Figures 2, 3, 4, and A1 are
provided in log10.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig2.dat 111 83 Fig.2 min dagen(age50,Z), different constraints
fig3z002.dat 62 83 Fig.3.1 min dagen(age50), Z=0.02 Zsun for
different spectroscopic SNR (indices)
fig3z020.dat 62 83 Fig.3.2 min dagen(age50), Z=0.20 Zsun for
different spectroscopic SNR (indices)
fig3z040.dat 62 83 Fig.3.3 min dagen(age50), Z=0.40 Zsun for
different spectroscopic SNR (indices)
fig3z100.dat 62 83 Fig.3.4 min dagen(age50), Z=1.00 Zsun for
different spectroscopic SNR (indices)
fig3z250.dat 62 83 Fig.3.5 min dagen(age50), Z=2.50 Zsun for
different spectroscopic SNR (indices)
fig4.dat 146 83 Fig.4 min dagen(age50), Z=1.00 Zsun for
different spectroscopic constraints at
different SNR (different panels)
figa1.dat 146 83 Fig.A1 min dagen(age50), Z=0.20 Zsun for
different spectroscopic constraints at
different SNR (different panels)
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Byte-by-byte Description of file: fig2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.3 [yr] logage50 Median age of the stellar population
8- 13 F6.3 --- logdagen-col-Z002 ? Minimum dagen, colours only,
Z=0.02 Zsun
15- 20 F6.3 --- logdagen-col-Z020 ? Minimum dagen, colours only,
Z=0.20 Zsun
22- 27 F6.3 --- logdagen-col-Z040 ? Minimum dagen, colours only,
Z=0.40 Zsun
29- 34 F6.3 --- logdagen-col-Z100 ? Minimum dagen, colours only,
Z=1.00 Zsun
36- 41 F6.3 --- logdagen-col-Z250 ? Minimum dagen, colours only,
Z=2.50 Zsun
43- 48 F6.3 --- logdagen-idx-Z002 ? Minimum dagen, indices only,
Z=0.02 Zsun
50- 55 F6.3 --- logdagen-idx-Z020 ? Minimum dagen, indices only,
Z=0.20 Zsun
57- 62 F6.3 --- logdagen-idx-Z040 ? Minimum dagen, indices only,
Z=0.40 Zsun
64- 69 F6.3 --- logdagen-idx-Z100 ? Minimum dagen, indices only,
Z=1.00 Zsun
71- 76 F6.3 --- logdagen-idx-Z250 ? Minimum dagen, indices only,
Z=2.50 Zsun
78- 83 F6.3 --- logdagen-all-Z002 ? Minimum dagen, colours+indx,
Z=0.02 Zsun
85- 90 F6.3 --- logdagen-all-Z020 ? Minimum dagen, colours+indx,
Z=0.20 Zsun
92- 97 F6.3 --- logdagen-all-Z040 ? Minimum dagen, colours+indx,
Z=0.40 Zsun
99-104 F6.3 --- logdagen-all-Z100 ? Minimum dagen, colours+indx,
Z=1.00 Zsun
106-111 F6.3 --- logdagen-all-Z250 ? Minimum dagen, colours+indx,
Z=2.50 Zsun
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Byte-by-byte Description of file: fig3z???.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.3 [yr] logage50 Median age of the stellar population
8- 13 F6.3 --- logdagen-col ? Minimum dagen, colours only
15- 20 F6.3 --- logdagen-SNR5 ? Minimum dagen, colours+indices SNR=5
22- 27 F6.3 --- logdagen-SNR10 ? Minimum dagen, colours+indices SNR=10
29- 34 F6.3 --- logdagen-SNR20 ? Minimum dagen, colours+indices SNR=20
36- 41 F6.3 --- logdagen-SNR50 ? Minimum dagen, colours+indices SNR=50
43- 48 F6.3 --- logdagen-SNR100 ? Minimum dagen, colours+indices SNR=100
50- 55 F6.3 --- logdagen-SNR200 ? Minimum dagen, colours+indices SNR=200
57- 62 F6.3 --- logdagen-SNR500 ? Minimum dagen, colours+indices SNR=500
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Byte-by-byte Description of file: fig4.dat figa1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.3 [yr] logage50 Median age of the stellar population
8- 13 F6.3 --- logdagenIdxcol-5 ? Minimum dagen, SNR=5 colours+indices
(logdagen-idxcol-SNR5)
15- 20 F6.3 --- logdagen-FS-n-5 ? Minimum dagen, SNR=5 full spectrum
[3800-5600Å]
(logdagen-FS-narrow-SNR5)
22- 27 F6.3 --- logdagenFS-w-5 ? Minimum dagen, SNR=5 full spectrum
[3500-7000Å]
(logdagen-FS-wide-SNR5)
29- 34 F6.3 --- logdagenFS-r-n-5 ? Minimum dagen, SNR=5 full spectrum
rectified [3800-5600Å]
(logdagen-FS-rect-narrow-SNR5)
36- 41 F6.3 --- logdagenFS-r-w-5 ? Minimum dagen, SNR=5 full spectrum
rectified [3500-7000Å]
(logdagen-FS-rect-wide-SNR5)
43- 48 F6.3 --- logdagenIdxcol-10 ? Minimum dagen, SNR=10 colours+indices
(logdagen-idxcol-SNR10)
50- 55 F6.3 --- logdagenFS-n-10 ? Minimum dagen, SNR=10 full spectrum
[3800-5600Å]
(logdagen-FS-narrow-SNR10)
57- 62 F6.3 --- logdagenFS-w-10 ? Minimum dagen, SNR=10 full spectrum
[3500-7000Å]
(logdagen-FS-wide-SNR10)
64- 69 F6.3 --- logdagenFS-r-n-10 ? Minimum dagen, SNR=10 full spectrum
rectified [3800-5600Å]
(logdagen-FS-rect-narrow-SNR10)
71- 76 F6.3 --- logdagenFS-r-w-10 ? Minimum dagen, SNR=10 full spectrum
rectified [3500-7000Å]
(logdagen-FS-rect-wide-SNR10)
78- 83 F6.3 --- logdagenIdxcol-20 ? Minimum dagen, SNR=20 colours+indices
(logdagen-idxcol-SNR20)
85- 90 F6.3 --- logdagenFS-n-20 ? Minimum dagen, SNR=20 full spectrum
[3800-5600Å]
(logdagen-FS-narrow-SNR20)
92- 97 F6.3 --- logdagenFS-w-20 ? Minimum dagen, SNR=20 full spectrum
[3500-7000Å]
(logdagen-FS-wide-SNR20)
99-104 F6.3 --- logdagenFS-r-n-20 ? Minimum dagen, SNR=20 full spectrum
rectified [3800-5600Å]
(logdagen-FS-rect-narrow-SNR20)
106-111 F6.3 --- logdagenFS-r-w-20 ? Minimum dagen, SNR=20 full spectrum
rectified [3500-7000Å]
(logdagen-FS-rect-wide-SNR20)
113-118 F6.3 --- logdagenIdxcol-100 ? Minimum dagen, SNR=100
colours+indices
(logdagen-idxcol-SNR100)
120-125 F6.3 --- logdagenFS-n-100 ? Minimum dagen, SNR=100 full spectrum
[3800-5600Å]
(logdagen-FS-narrow-SNR100)
127-132 F6.3 --- logdagenFS-w-100 ? Minimum dagen, SNR=100 full spectrum
[3500-7000Å]
(logdagen-FS-wide-SNR100)
134-139 F6.3 --- logdagenFS-r-n-100 ? Minimum dagen, SNR=100 full spectrum
rectified [3800-5600Å]
(logdagen-FS-rect-narrow-SNR100)
141-146 F6.3 --- logdagenFS-r-w-100 ? Minimum dagen, SNR=100 full spectrum
rectified [3500-7000Å]
(logdagen-FS-rect-wide-SNR100)
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Acknowledgements:
Stefano Zibetti, stefano.zibetti(at)inaf.it
(End) Patricia Vannier [CDS] 06-Feb-2024