st ellar p opulation chal lenge - rijksuniversiteit groningensctrager/challenge/challenge.pdf ·...

Stellar Population ChallengeS.C. Trager, organizer

(Kapteyn Astronomical Institute, University of Groningen)

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.

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

1996ASPC...98..287A

• “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?

• 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

• 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

(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:

http://www.astro.rug.nl/~sctrager/challenge/




• 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?

• 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)

Results!

• 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!

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

Salaris

47 Tuc

10-11 Gyr

NGC 6528

8-10 Gyr

M67

3.5-4 GyrNGC1868

0.8-1 Gyr

NGC1805

30-50 Myr

Li

NGC1805200-600 Myr

Li

M673.2-3.6 Gyr

Li

M673.2-3.6 Gyr

Note very strong model blue straggler population!

Li47 Tuc

13.6 Gyr

Green: SSPRed: BSP

Vazdekis et al.

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)

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

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



Salasnich α-enhanced

Salasnich scaled-solar

MILES Li SSP

Li SSPMILES

Li SSP

Padova2000

MILES

Schiavon

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

What have we learned?

• Most people don’t read directions!• including me, most of the time...

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)

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

Test 3: “Extra credit”

• Purpose:

• To recover the star formation histories and chemical compositions of 7 spectra provided by organizer

• 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)

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”

“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

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.

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


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


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)


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


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


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


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


G&F

Panter

Ocvirk Koleva (MILES)

Spectrum 7: 12.5 Gyr, Z⊙☉ MILES SSP

G&F

Panter


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)


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


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


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)


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


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


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)


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


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


Spectrum 5: M67

G&F

Panter

Koleva (MILES)

Magris et al.

Spectrum 6: BC03, two bursts

G&F

Panter


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)


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


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


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)


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


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


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)


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


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


Spectrum 3: MILES, two bursts

G&F

Panter


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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)


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


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


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!

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

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...

Should the challenge continue?

• What’s next?

• Suggestions?

• A workshop next year devoted solely to this challenge?

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]

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!

st ellar p opulation chal lenge - rijksuniversiteit groningensctrager/challenge/challenge.pdf ·...

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