st ellar p opulation chal lenge - rijksuniversiteit groningensctrager/challenge/challenge.pdf ·...
TRANSCRIPT
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Stellar Population ChallengeS.C. Trager, organizer
(Kapteyn Astronomical Institute, University of Groningen)
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Purpose of challenge
• Reynier Peletier to Scott Trager, 9 January 2006:• It is not clear whether stellar population synthesis of
resolved galaxies gives the same results as population synthesis of unresolved galaxies. We could give people CM diagrams and integrated spectra of globular clusters or local group galaxies (possibly 47 Tuc, M32, M31, NGC 6822) and ask them to give solutions for metallicity and star formation history. To go a step further - we could also ask people to determine abundance ratios of various elements.
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Some background...
• In 1995, N. Arimoto conducted a similar experiment, asking several stellar population modelers to estimate ages and metallicities from the composite SEDs of two early-type galaxies
• Age-metallicity degeneracy clearly seen in the answers
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1996ASPC...98..287A
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• “They dig out the solution from their favorite domain on the age-metallicity plane”
• “None of [the] ... models are calibrated in the sense that they have never been tested whether they can reproduce the SEDs, not the CMDs, of globular clusters of different ages and metallicities.”
• Is this still true?
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• Spurred on by this challenge, Charlot, Worthey & Bressan (1996) compared the BC93, W94 & Padova SSP models and found
• discrepancy of 0.25 mag in V-K and 25% in M/LV due to different stellar evolution models
• Using colours, SSPs are accurate to
• 35% in age at fixed metallicity
• 25% in metallicity at fixed age, assuming scaled-solar abundances
• 35% in mass at fixed metallicity and IMF
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• In 2000-2001, an experiment in decoding the star formation histories of resolved galaxies was performed by a number of groups and presented as the “Coimbra Experiment” (Skillman & Gallart 2002)
• Uncovered differences between different SFH recovery methods and, to a lesser extent, stellar evolution models and the data
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(back to the story)
• ...so I (foolishly?) said yes.
• In late June 2006, at the workshop “Fine-tuning stellar population models,” a small group (Fritze, Martins, Rose, Salaris, Schiavon & Trager), inspired by the “Coimbra Experiment,” decided on the following purpose and course of action:
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• Purpose:
• Can modern, off-the-shelf stellar population model ingredients be combined to match BOTH the resolved stellar population data (colour-magnitude diagrams and luminosity functions) AND the integrated spectra?
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• Action:
• Test 1: Resolved populations
• test isochrones and colour-Teff relations through CMD matching
• test evolutionary lifetimes and bolometric corrections through LF matching
• Test 2: Unresolved populations
• test stellar libraries and fitting functions through spectral matching
• Test 3: (I’ll come back to this)
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Results!
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• First, two gold stars must be awarded to
• A. Vazdekis, A.J. Cenarro, A. de Lorenzo-Caceres & M. Beasley (IAC)
• Zhongmu Li et al. (Yunnan Observatory)
• ...as the only two groups who completed Tests 1 AND 2!
Results!
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Test 1• Three groups responded:
• Maurizio Salaris, using his version of the BaSTI isochrones
• Zhongmu Li, using the Yunnan model, which combines Hurley’s single- and binary-star evolutionary codes with BaSeL spectra
• Vazdekis et al., using Bertelli et al. (1994), Girardi et al. (2000), and Salasnich et al. (2000) isochrones combined with Alonso et al. and Lejeune et al. colour-Teff transformations
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Salaris
47 Tuc
10-11 Gyr
NGC 6528
8-10 Gyr
M67
3.5-4 GyrNGC1868
0.8-1 Gyr
NGC1805
30-50 Myr
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Li
NGC1805200-600 Myr
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Li
M673.2-3.6 Gyr
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Li
M673.2-3.6 Gyr
Note very strong model blue straggler population!
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Li47 Tuc
13.6 Gyr
Green: SSPRed: BSP
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Vazdekis et al.
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Test 2• 5 groups responded, and 2 more had answers
available elsewhere:• Li et al. (not 47 Tuc or NGC 6528)• Lilly & Fritze (M67 only)• Koleva (M67 only, from test 3)• Martins, Coelho & Fernandes• Ocvirk (47 Tuc and NGC 6528 only)• Schiavon (from Schiavon 2006; not NGC 1805
or NGC 1868)• Vazdekis et al. (not NGC 1868)
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Test 2• 5 groups responded, and 2 more had answers
available elsewhere:• Li et al. (not 47 Tuc or NGC 6528)• Lilly & Fritze (M67 only)• Koleva (M67 only, from test 3)• Martins, Coelho & Fernandes• Ocvirk (47 Tuc and NGC 6528 only)• Schiavon (from Schiavon 2006; not NGC 1805
or NGC 1868)• Vazdekis et al. (not NGC 1868)
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Details of the modelsGroup Model Isochrones
Spectral
library IMF
Fitting
technique
Li et al. SSP Hurley Lejeune (theory) Salpeter Spectral fitting
Lilly GALEV Padova94Lejeune (theory)
+ WortheySalpeter Index strengths
Koleva Pegase.HR Padova94 ELODIE Kroupa
Continuum-
corrected spectral
fitting
MILES Padova00 MILES Salpeter
Continuum-
corrected spectral
fitting
Martins et al. BC03 Padova00 STELIB Salpeter Spectral fitting
BC03 Padova94 STELIB Chabrier Spectral fitting
GALAXEV Padova00 Coelho Salpeter Spectral fitting
GALAXEV Padova00 Coelho Chabrier Spectral fitting
GALAXEV Padova94 Coelho Chabrier Spectral fitting
Starburst99 Padova94 Martins Salpeter Spectral fitting
Ocvirk Pegase.HR Padova94 ELODIE Kroupa
Continuum-
corrected spectral
fitting
BC03 Padova94 STELIB Chabrier
Continuum-
corrected spectral
fitting
MILES Padova00 MILES Salpeter
Continuum-
corrected spectral
fitting
Schiavon
(2006)
Schiavon
(2006)
Padova00 /
Salasnich00Jones Salpeter Index strengths
Vazdekis et
al.MILES Padova00 MILES Salpeter Index strengths
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Summary of tests 1 & 2
Black: isochrone fitsRed: spectral fits
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Summary of tests 1 & 2
Black: isochrone fitsRed: spectral fits
Salasnich α-enhanced
Salasnich scaled-solar
MILES Li SSP
Li SSPMILES
Li SSP
Padova2000
MILES
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Summary of tests 1 & 2
Black: isochrone fitsRed: spectral fits
Salasnich α-enhanced
Salasnich scaled-solar
MILES Li SSP
Li SSPMILES
Li SSP
Padova2000
MILES
Schiavon
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NGC 1805 NGC 1868 M67 NGC 6528 47 Tuc
δ<log t> 0.000±0.450 -0.041±0.193 0.078±0.209 -0.140±0.133 -0.258±0.220
w/o Li 0.259±0.032 -0.113±0.141 0.031±0.146
BC03 0.259±0.032 -0.184±0.083 0.077±0.163 -0.212±0.069 -0.402±0.101
MILES 0.097 -0.111±0.014 0.007±0.134 0.040±0.115
δ<[Z/H]> 0.170±0.147 -0.224±1.100 -0.163±0.186 -0.116±0.139 0.225±0.212
w/o Li 0.167±0.170 -0.250±0.792 -0.115±0.095
BC03 0.167±0.170 0.667±0.205 -0.100±0.115 -0.082±0.130 0.391±0.128
MILES >-1.3 -0.130±0.070 -0.268±0.133 -0.004±0.096
Parameters: Spectra - isochrones
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What have we learned?
• Most people don’t read directions!• including me, most of the time...
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Lessons learned, cntd.• It is possible to match isochrone-based ages
and [Fe/H] with spectra• and when it fails, it often - but not always - fails
along the age-metallicity degeneracy line• at least for pops with t>1 Gyr
• average discrepancy not the same for different clusters• BC03 typically too young, MILES typically too
old• Some fine tuning may be required (Schiavon et
al. 2002, Schiavon 2006)
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Lessons learned, cntd.
• Binary population synthesis (Li):
• Binary stellar population (BSP) models do not necessarily alter the stellar population parameters inferred from CMDs...
• ...but the strong excess of blue straggler stars (e.g., M67) suggests that BSP spectra will be much too blue with too-strong Balmer lines
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Test 3: “Extra credit”
• Purpose:
• To recover the star formation histories and chemical compositions of 7 spectra provided by organizer
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• This was the most popular test: 7 groups responded• Gomes & Fernandes (BC03 SSPs,
STARLIGHT/BC03)• Koleva (SSPs: Pegase.HR, MILES)• Magris et al. (GASPEX/BC03)• Mollá• Ocvirk (STECKMAP: BC03, MILES)• Panter (MOPED: BC03)
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• This was the most popular test: 7 groups responded• Gomes & Fernandes (BC03 SSPs,
STARLIGHT/BC03)• Koleva (SSPs: Pegase.HR, MILES)• Magris et al. (GASPEX/BC03)• Mollá• Ocvirk (STECKMAP: BC03, MILES)• Panter (MOPED: BC03)
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1. BC03 (Padova 1994 + Salpeter), 12.5 Gyr, [Z/H]=0, σ=251 km/s
2.BC03 (as above), “quenched” SFH: tstart=12.5 Gyr, SFR=1 M⊙☉/yr until tquench=7.5 Gyr, [Z/H]=0, σ=275 km/s
3. MILES (Padova 2000 + Salpeter), 88% by light in 12.6 Gyr, [Z/H]=0 + 12% by light in 2 Gyr, [Z/H]=+0.2; σ=251 km/s
Input spectra: “Reality”
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“Reality,” cntd.
4. Eisenstein et al. (2003) SDSS L* early-type composite spectrum
5. M676. BC03 (as above), 88% by light in 12.6 Gyr, [Z/
H]=0 + 12% by light in 2 Gyr, [Z/H]=+0.2; σ=251 km/s
7.MILES (as above), 12.6 Gyr, [Z/H]=0, σ=251 km/s
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Test 3 Spectrum 1 Spectrum 2 Spectrum 3 Spectrum 4 Spectrum 5 Spectrum 6 Spectrum 7
"Reality":BC03 Salpeter; 12.5 Gyr, [Z/H]=0; sigma=251.1 km/s
BC03 "quenched" spectrum: t_start=12.5 Gyr, 1 M_solar/yr until t_quench=7.5 Gyr, [Z/H]=0; sigma=275.3 km/s
MILES 88% by light in 12.6 Gyr, [Z/H]=0 + 12% by light in 2 Gyr, [Z/H]=+0.2; sigma-251.1 km/s
Eisenstein et al. (2002) SDSS L* early-type galaxy spectrum
M67
BC03 88% by light in 12.5 Gyr, [Z/H]=0 + 12% by light in 2 Gyr, [Z/H]=+0.4; sigma-251.1 km/s
MILES 12.6 Gyr, [Z/H]=0; sigma-251.1 km/s
Group Method
Gomes & Cid Fernandes
BC03 SSP
12.25 Gyr, [Z/H]=0; sigma=248.8 km/s; "perfectly represented by a single population"
8.25 Gyr, [Z/H]=-0.4; sigma=270.9 km/s; "perfectly represented by a single population"
1.61 Gyr, [Z/H]=0.4; sigma=230.7 km/s
3.00 Gyr, [Z/H]=0.; sigma=151.7 km/s; alpha-enhanced features
3.25 Gyr, [Z/H]=0.; sigma=0.; A_V=-0.232(!)
7.75 Gyr, [Z/H]=0.; sigma=245.8 km/s; "perfectly represented by a single population"
13.5 Gyr, [Z/H]=0; sigma=247.7; A_V=-0.115
STARLIGHT (BC03)
Exponentially decaying, solar Z burst at old times + very small metal-enriched burst at 1 Gyr; "absurdly good fit - must be drawn from BC03"; <log t>=10.06, <[Z/H]>=0.018
Slightly younger, growing then decaying, slightly subsolar ([Z/H]=-0.4) burst followed by small metal-enriched burst at 1 Gyr; "absurdly good fit - must be drawn from BC03"; <log t>=9.89, <[Z/H]>=-0.327
Old solar-metallicity burst at ~50% of flux (peak) + metal-rich burst at 1-2 Gyr at ~10% of flux (peak); <log t>=9.48, <[Z/H]>=0.273
Old, metal-enriched (mix of solar & super-solar) burst with young (500 Myr - 1 Gyr old) super-solar burst; <log t>=9.65, <[Z/H]>=0.089
Complex, bursty SFH (4 bursts from 12 to 1 Gyr) with anti-correlated age-metallicity relation; <log t>=9.55, <[Z/H]>=0.091
Old, wide, solar metallicity burst with significant burst (~20% flux) at 3 Gyr; "absurdly good fit - must be drawn from BC03"; <log t>=9.78, <[Z/H]>=0.170
Sharp old, solar metallicity burst with ~20% flux burst at 1-2 Gyr; <log t>=9.90, <[Z/H]>=0.149
Koleva Pegase.HR SSP 6.9 Gyr, [Fe/H]=+0.1 5.6 Gyr, [Fe/H]=-0.2 3.9 Gyr, [Fe/H]=0. 5.5 Gyr, [Fe/H]=-0.01 3.8 Gyr, [Fe/H]=-0.12 5.9 Gyr, [Fe/H]=+0.09 10.5 Gyr, [Fe/H]=+0.04
MILES SSP 10.2 Gyr, [Fe/H]=0. 7.0 Gyr, [Fe/H]=-0.3 4.4 Gyr, [Fe/h]=-0.05 5.8 Gyr, [Fe/H]=-0.04 3.2 Gyr, [Fe/H]=-0.06 5.2 Gyr, [Fe/H]=+0.10 12.6 Gyr, [Fe/H]=0.
commentsWavelength error around Mgb
[Mg/Fe]<0? (SCT sees wavelength error around Mgb)
[Mg/Fe]>0?[Mg/Fe]>0; older age if emission lines not masked
recognized as M67; age decreases with Pegase.HR if continuum-matching polynomial order is altered
Wavelength error around Mgb
"Inversion using [MILES] is perfect!"; sigma~250 km/s
Magris et al. GASPEX (BC03)
Very old (age > 8Gyr), solar metallicity stellar population; sigma=241 km/s
Old, mainly subsolar (84% of [Z/H]=-0.4) with traces of [Z/H]=-0.7, and possibly a 3% of solar stellar population
Old, 80% solar and 15% [Z/H]=-0.7, 2% of solar, younger (3-9 Gyr) population
Old, 60% solar 38% [Z/H]=-0.7
Intermediate age (>3 Gyr), solar and subsolar stellar population
82% of solar metallicity and 9% of [Z/H]=-0.4 mass with age > 9 Gyr, and 8% of younger (3-9) Gyr of solar metallicity
92% of old (> 9 Gyr), solar metallicity, 2% of [Z/H]=-0.4 and 5% of [Z/H]=-0.7
Mollá (own)
Sharp, exponentially-decaying burst at about 12 Gyr with rapid metallicity evolution resulting in [Fe/H]~+0.2
Ocvirk STECKMAPOld solar population. Single old burst or decreasing exponential SFR
Subsolar (log(Z/Zsun)=-0.4, 10 Gyr old burst, slightly younger than spectrum 1
My guess is a rather extended SFH , with a tentative second burst around 3 Gyr ago, just for the fun. The pop seems to be around solar metallicity.
Rather extended SFH.
Composite relatively old stuff: exponentially decreasing solar pop, about 10Gyr Luminosity-weighted age, with a supersolar burst around 3 Gyr
All I can see is an old solar pop. Possibly exponentially decreasing SFR
preferred model BC03 BC03MILES (problems with convolution?)
Real galaxy. BC03MILES (problems with convolution?)
Panter MOPED (BC03)
~10 Gyr old population with roughly solar metallicity. Possibly a small 1 Gyr pop, again solarish metallicity
Old component(s?), subsolar metallicity. Could be log(Z/Z_\odot)=[-0.5,-1.3] for two older populations, ~11 and 4 Gyr, older population dominant.
I think this has two components, one centred at ~10Gyr, the other at 1Gyr. Slightly higher than solar metallicity for older population, quite a lot higher for the younger one.
Longer period of early SF - hard to say anything much about the metallicity other than I suspect it could be two similarly aged populations with different metallicities of a similar age, which MOPED will fit (badly) by adjacent age bins with different metallicities. I'm suspicious of the two younger populations - one just less than a Gyr and one at about 0.06. I don't really trust this, but is does seem to be consistent through the different choices of bins.
Again, two populations - possibly both a bit broad. Older seems to be 7-10 Gyr old, with a spec of something younger at ~1Gyr (as ever...). Old component is sub solar metallicity, younger is I suspect, solar.
Old, solar metallicity component ~ 10 Gyr. Something there at 1-2 Gyr perhaps? Hard to say. log(Z/Z_\odot) ~ -0.5
Mainly about 10 Gyr, perhaps slightly above solar metallicity, second, younger population at about 1-Gyr. Sub solar metallicity.
![Page 36: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/36.jpg)
Spectrum 1: 12.5 Gyr, Z⊙☉ BC03 SSP
m22 = 0.005 Z! m32 = 0.02 Z! m42 = 0.2 Z!
m52 = 0.4 Z! m62 = 1.0 Z! m72 = 2.5 Z!
!2! !2
!! S/N"0 = 4020
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../spectrum1.pdb.txt
AMRavg!^2 =0.818399
!^21=0.00546987
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux
fra
ctio
ns
SAD
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
no
rma
lize
d S
FR
(M
sol/y
r)
SFR
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../spectrum2.pdb.txt
AMRavg!^2 =0.813795
!^21=0.00872665
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flux
fra
ctio
ns
SAD
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
no
rma
lize
d S
FR
(M
sol/y
r)
SFR
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../results061206/spectrum3.pdb.txt
AMRavg!^2 =0.849072
!^21=0.10031
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flu
x f
ractio
ns
SAD
../results061206/spectrum3.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
no
rma
lize
d S
FR
(M
so
l/yr)
SFR
../results061206/spectrum3.pdb.txt
G&F
Panter
Ocvirk Koleva (MILES)
![Page 37: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/37.jpg)
Spectrum 7: 12.5 Gyr, Z⊙☉ MILES SSP
G&F
Panter
Ocvirk Koleva (MILES)
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../results061206/spectrum4.pdb.txt
AMRavg!^2 =0.872893
!^21=0.347202
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flu
x f
ractio
ns
SAD
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
log(age[yr])
no
rma
lize
d S
FR
(M
so
l/yr)
SFR
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../spectrum6.pdb.txt
AMRavg!^2 =0.80718
!^21=0.00813411
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
log(age[yr])
flux
fra
ctio
ns
SAD
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
log(age[yr])
no
rma
lize
d S
FR
(M
sol/y
r)
SFR
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log
10
(Z/Z
su
n)
../results061206/spectrum7.pdb.txt
AMRavg!^2 =0.853467
!^21=0.119859
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flu
x f
ractio
ns
SAD
../results061206/spectrum7.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
no
rma
lize
d S
FR
(M
so
l/yr)
SFR
../results061206/spectrum7.pdb.txt
![Page 38: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/38.jpg)
Spectrum 5: M67
G&F
Panter
Koleva (MILES)
Magris et al.
![Page 39: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/39.jpg)
Spectrum 6: BC03, two bursts
G&F
Panter
Ocvirk Koleva (MILES)
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../results061206/spectrum4.pdb.txt
AMRavg!^2 =0.872893
!^21=0.347202
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../spectrum6.pdb.txt
AMRavg!^2 =0.80718
!^21=0.00813411
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
log(age[yr])
flux
fract
ions
SAD
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../results061206/spectrum7.pdb.txt
AMRavg!^2 =0.853467
!^21=0.119859
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum7.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum7.pdb.txt
![Page 40: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/40.jpg)
Spectrum 3: MILES, two bursts
G&F
Panter
Ocvirk Koleva (MILES)
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../spectrum1.pdb.txt
AMRavg!^2 =0.818399
!^21=0.00546987
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux
fract
ions
SAD
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../spectrum2.pdb.txt
AMRavg!^2 =0.813795
!^21=0.00872665
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flux
fract
ions
SAD
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../results061206/spectrum3.pdb.txt
AMRavg!^2 =0.849072
!^21=0.10031
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum3.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum3.pdb.txt
![Page 41: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/41.jpg)
Spectrum 2: BC03 “quenched” SFH
G&F
Panter
Ocvirk Magris et al.
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../spectrum1.pdb.txt
AMRavg!^2 =0.818399
!^21=0.00546987
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux
fract
ions
SAD
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum1.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../spectrum2.pdb.txt
AMRavg!^2 =0.813795
!^21=0.00872665
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flux
fract
ions
SAD
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum2.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsu
n)
../results061206/spectrum3.pdb.txt
AMRavg!^2 =0.849072
!^21=0.10031
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum3.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum3.pdb.txt
![Page 42: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/42.jpg)
Spectrum 4: SDSS L* composite
G&F
Panter
Ocvirk Magris et al.7.0 7.5 8.0 8.5 9.0 9.5 10.0
!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../results061206/spectrum4.pdb.txt
AMRavg!^2 =0.872893
!^21=0.347202
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum4.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../spectrum6.pdb.txt
AMRavg!^2 =0.80718
!^21=0.00813411
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
log(age[yr])
flux
fract
ions
SAD
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.1
0.2
0.3
0.4
0.5
0.6
log(age[yr])
norm
aliz
ed S
FR
(M
sol/y
r)
SFR
../spectrum6.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.0!2.0
!1.5
!1.0
!0.5
0.0
0.5
log(age[yr])
log10(Z
/Zsun)
../results061206/spectrum7.pdb.txt
AMRavg!^2 =0.853467
!^21=0.119859
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
1.0
log(age[yr])
flux fra
ctions
SAD
../results061206/spectrum7.pdb.txt
7.0 7.5 8.0 8.5 9.0 9.5 10.00.0
0.2
0.4
0.6
0.8
log(age[yr])
norm
aliz
ed S
FR
(M
sol/yr)
SFR
../results061206/spectrum7.pdb.txt
![Page 43: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/43.jpg)
What have we learned?
• Sharp features difficult to capture with codes that determine SFHs from spectra
• δ-function bursts become Gaussian
• sharp truncations of continuous SF become slowly declining SFHs
• Different codes find similar features in general
• cf. SDSS L* spectrum!
![Page 44: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/44.jpg)
Some detailed comments
• From Koleva’s analysis:
• MILES and PÉGASE-HR match nicely, although P-HR gives younger ages by 10-20% due mostly to 3% cooler giants
• STELIB-based BC03 models may have a wavelength offset (error?) around Mgb
![Page 45: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/45.jpg)
Conclusions?
• Arimoto (1996):
• “None of [the] ... models are calibrated in the sense that they have never been tested whether they can reproduce the SEDs, not the CMDs, of globular clusters of different ages and metallicities.”
• Is this still true? No. But it’s just beginning...
![Page 46: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/46.jpg)
Should the challenge continue?
• What’s next?
• Suggestions?
• A workshop next year devoted solely to this challenge?
![Page 47: St ellar P opulation Chal lenge - Rijksuniversiteit Groningensctrager/challenge/Challenge.pdf · Salpeter Index strengths Koleva Pegase.HR Padova94 ELODIE Kroupa Continuum-corrected](https://reader031.vdocuments.us/reader031/viewer/2022011904/5f1db8ce0303db5087631a5e/html5/thumbnails/47.jpg)
Additions and extensions
• UV and IR: extend wavelength range
• Provide “standard dataset” for testing stellar pop models
• Standardized interchange format for models
• Large sample of real galaxies
• Other “observational” problems:
• complex kinematics, errors, and extension
• [alpha/Fe]
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Thanks!
• Many thanks to Alexandre Vazdekis, Reynier Peletier, and the SOC of IAU Symp. 241; Maurizio Salaris, Ricardo Schiavon, Jim Rose, Lucimara Martins, Uta Frize, and the participants of the Fine-Tuning Stellar Population Models workshop; Richard de Grijs; Sofia Feltzing; and all of the participants in the challenge!