SN RATES 2008 – Arcetri, May 2008 Constraints on the DTD from SN Ia rates in Galaxies Laura...
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Transcript of SN RATES 2008 – Arcetri, May 2008 Constraints on the DTD from SN Ia rates in Galaxies Laura...
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
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
SN RATES 2008 – Arcetri, May 2008
SINGLE DEGENERATES MODELSexplosion occurs when the secondary evolves off the MS
22 )()( dmmndn )(: 22 mm MS
22 )()( mmnf SDIa
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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)
SN RATES 2008 – Arcetri, May 2008
PARAMETERS OF DD MODELS
Mass range of the secondary
Exponent for the distribution of The separations of DDs
Minumum GW delay
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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)
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)
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)
SN RATES 2008 – Arcetri, May 2008
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?
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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?
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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
SN RATES 2008 – Arcetri, May 2008
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