SN RATES 2008 – Arcetri, May 2008 Constraints on the DTD from SN Ia rates in Galaxies Laura Greggio INAF, Padova Astronomical Observatory.

SN RATES 2008 – Arcetri, May 2008

Constraints on the DTD from SN Ia rates in Galaxies

Laura Greggio

INAF, Padova Astronomical Observatory


OUTLINE

• Describe the DTD models in Greggio (2005)Analytic functions meant to describe the shape of the distribution expected on the basis

of general arguments in stellar evolution theory. The functions have a built in parametrization of relevant astrophysical quantities.

• Analyze the correlations between the SNIa rates and parent galaxy colors

to the end of exploring how these correlations constrain the DTD, and eventually the astrophysical parameters

• Conclusions


SINGLE DEGENERATES MODELSexplosion occurs when the secondary evolves off the MS

22 )()( dmmndn )(: 22 mm MS

22 )()( mmnf SDIa


DOUBLE DEGENERATES MODELS

),()( 2 AMm DDGWMS

DD CLOSE: CE evolution causes a sizable shrinkage, distribution of GW delay skewed at short values

DD WIDE: CE evolution leads to a wide distribution of DD separations


PARAMETERS OF SD MODELS

Sub-Chandra

Exponents of the distributions of primary mass and mass ratio

Mass limits for primary in successful systems

Efficiency of accretion, important at late delay times (low secondary mass)


PARAMETERS OF DD MODELS

Mass range of the secondary

Exponent for the distribution of The separations of DDs

Minumum GW delay


THE BOTTOM LINE IS:

DTDs for SDs and DDs are charaterized by an early steep rise,

a wide maximum,

a late epoch decline

Mass range of primary and secondary, their distributions, the distribution of

the separations and the shrinkage during the CE phases shape the DTDs

One can construct also MIXED models (SDs and DDs) in different proportions

We need solid observational evidence to constrain these parameters, and

derive astrophysical implications


Correlation of the specific SNIa ratewith the color of the parent galaxy

Stellar Evolution naturally predictsMore events at short delays

THE RATE PER UNIT MASS IN LATETYPE GALAXIES WILL BE LARGERTHAN IN EARLY TYPE GALAXIES(e.g. Greggio and Renzini 1983)

Bluer galaxies are ‘younger’,then they have larger specificSNIa rates


GALAXY MODELS

Families of models with someSF at current epoch, differentStarting epochs, different AGE distributions within theseepochs

Magnitudes from population synthesis based on Girardi et al.2007 isochrones


CORRELATION: RATE IN SNuM

IaIaSF

Ia fktM

tn)(

)(

DDC1: DD CLOSE with M2>3, β=-0.9DDW8: DD WIDE with M2>2, β=0MDP: Mannucci et al. (2006) DTDGAUSSIAN: centered at 3.4 G, σ=0.7

DATA: Mannucci et al. (2005) , kIa=0.003 /Mo (adjustable)

Difficult to reproduce the bluestgalaxy bin : metallicity effect?

The slope of the observed correlationdepends on the particular Galaxy mix (AGEs and Zs)






CORRELATION: RATE IN SNuMGALAXY MIX: young galaxies with low Zintermediate age and old galaxies with Zo

DDC5: DD CLOSE M2>2.5 β=0DDW4: DD WIDE M2>2.5 β=-0.9SD Ch: Chandra SD flat distribution of q ε(ACC)=1

The fit improves, but …. IS IT CONSISTENT?


Mass to Light ratio vs Color

959.0)(212.0log KBL

M

K

The rate in SNuM is derived by relyingon Bell and De Jong (2001) models to estimate the M/L(K) ratios for various galaxies

The CSP models used here have aSteeper dependence of M/L(K) onB-K for ‘young’ AGE DISTRIBUTIONS


CORRELATION: RATE IN SNuKGALAXY MIX

K

Ia

IaK

Ia

L

fk

tL

tn)(

)(

DDW8 (very flat) andGAUSSIAN are excluded

Other DTDs are consistent

END OF THE STORY?


CORRELATION: RATE IN SNuSAME GALAXY MIX AS PREVIOUS FIGURE

B

Ia

IaB

Ia

L

fk

tL

tn)(

)(

The rate in SNu rather indicatesflat DTDs

The sample of galaxies is theSame as before, but binning ofgalaxies is different: I’m allowed to try another galaxy mix


CORRELATION: RATE IN SNuANOTHER GALAXY MIX

Reddest bin: exp(-t/2)Ψ(t) = K t-0.5 and Z=Zo/5Ψ(t)=const and Z=Zo/5‘young’ CSPs all with Z=Zo/20

Still the rate in the bluest Galaxies is very smallwrt models


CONCLUSIONS

• THE FIT TO THE RELATION OF THE SPECIFIC RATE WITH PARENT GALAXY COLORS APPEARS DIFFERENT IN THE DIFFERENT BANDS

• NEED TO CHARACTERIZE IN DETAIL THE STELLAR POPULATIONS OF THE GALAXIES IN THE SAMPLE IN TERM

OF THEIR AGE (AND METALLICITY) DISTRIBUTION TO GET RELIABLE INFO ON THE DTD

• ALSO THE BINNING OF THE GALAXIES TO REPRESENT THEIR AVE PROPERTIES BEARS ON THE FIT

SN RATES 2008 – Arcetri, May 2008 Constraints on the DTD from SN Ia rates in Galaxies Laura Greggio INAF, Padova Astronomical Observatory.

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