Ringberg, July 8, 2005 COSMIC RATE OF SNIa Laura Greggio INAF, Padova Astronomical Observatory
Jan 11, 2016
Ringberg, July 8, 2005
COSMIC RATE OF SNIa
Laura Greggio
INAF, Padova Astronomical Observatory
Ringberg, July 8, 2005
Chemical evolution of galaxies Chemical evolution of the ICM and IGM Gas flows in Ellipticals The determination of cosmological parameters
SNIa are relevant to the study of:
To study # 1,2 and 3 we need the SNIa rate following a burst of SF
To address # 4 we need to understand the nature of the SNIa progenitor
The cosmic evolution of the SNIa rate helps constraining both
Ringberg, July 8, 2005
Dahlen et al. 2004: SNII trace the recent SF use the rate of type II to trace the cosmic SFR
SNIa come from longer lived progenitors:At a cosmic epoch t the SNIa rate is
t
IaIaIa
i
dftkAtn
)()()(
•τ is the delay time (interval between the birth of the stellar system and its explosion)•fIa is the distribution function of the delay
times •AIa is the realization probability of the SNIa event out of one stellar generation•kα is the number of stars per unit Mass of one stellar generation
Ringberg, July 8, 2005
Close Binary Evolution
(1984)
SD
DD
provides two main cathegories ofSNIa precursors:
Single Degenerate Systemsa CO WD accretes from a living companion
Double Degenerate Systemsthe companion is another WD
Explosion may occur when
• the WD mass reaches the Chandrasekhar limit (Ch-exploders)
•a Helium layer of ≈0.1 MO, accumulated on top of the WD, detonates (Sub-Ch exploders)
Ringberg, July 8, 2005
Pros and Cons
Single Degenerates:
Candidate precursors observed (SSXRS, Symbiotic, CV)
Fine tuning of accretion rate is needed to avoid nova and/or CE (small volume in the phase space)
Absence of H in the spectra
Double Degenerates:
Absence of H in the spectra
Theoretical likelyhood accounts for current rate in the MW
Theoretical explosion leads to neutron star
Observed DDs are not massive enough
CHANDRA exploders : uniform light curves and better spectra BUT few of them
SUB-CHANDRA : many of them BUT variety of Ni56 produced and high velocity of ejected Ni
Ringberg, July 8, 2005
Population Synthesis of Binaries
Yungelson and Livio 2000
Monte Carlo simulations of a population of binaries with n(m1), n(q), n(A0),following the evolution of each system through the RLOsand determining the outcome (CVs, RCBor, sdO,all varieties of DD.., sometimes SNIa)
Tutukov & Yungelson , Ruiz-Lapuente,Burket & Canal, Han et al., Nelemans et al.
The results are: (highly) model dependent ( CE, mass loss, criterion for mass transfer stability …)
hard to implement in other computations(for galaxy evolution, cosmic evolution…)
BUT the distribution function of the delay times can becharacterized on general grounds …
Ringberg, July 8, 2005
Single Degenerates:Clock is the nuclear timescale of the secondary
22 )()( dmmndn
22 )()( mmnf SDIa
21 m
+ limits on primary mass:
)(: 22 mm MS
Evolutionary clock andDistribution of the secondaries insystems which give rise to a SNIa
only Chandra
4.1,2 eWD mm
Ringberg, July 8, 2005
Double Degenerates
3
4
wd2wd1wd2wd1
4
gw 6.0)(
15.0
DDM
A
mmmm
A
Clock is the nuclear timescale of the secondary + the gravitational delay
Double CO WDs: m1, m22 then n≤ 1Gyr
The distribution function of the separations of the DD systems is crucial for the distribution of the gravitational delays
Shrinkage at RLO:• Start from: 100 R0 <A0 < 1000 R0
• Go through RLO:standard CE: (A/AO)≈few 10-3
heavier systems have smaller A/AO & shorter gw
Nelemans et al. : large range of (A/AO) no correlation between mass and gw
MDD=2 τgw ranges in 5Myr – 15 Gyr A ranges from 0.5 to 3.8 Ro
A small dispersion in DD masses and/or final separations yield a wide distributionof delay times
CLOSE DDs
WIDE DDs
Ringberg, July 8, 2005
The distribution function of the delay times for DDs
mainly controlled by:
maximum nuclear delay(minimum m2 of a successful system)
whether evolution leads to WIDE or CLOSE DD
distribution function of the separations of the DDwhether favouring larger or smaller A
Ringberg, July 8, 2005
The distribution function of the delay times
All models normalized at 12 Gyr : Main Parameters :
SD: minimum mass of the primary for a successful SNIa (distribution of mass ratios)
DD: 1) minimum mass of the secondary (fix maximum nuclear delay)
2) distribution function of the separations after II RLO 3) whether WIDE or CLOSE
Different models have:
• different
•different Fe production12
)12(
Ia
Ia
f
f
Ringberg, July 8, 2005
The Cosmic SNIa rate
t
IaIaIa
i
dftkAtn
)()()(
Ringberg, July 8, 2005
Results of the convolution:
The results of the convolutionare rather sensitive to theadopted cosmic SFR:
A steep increase from z=0 to 1favors a steep increase of thecosmic SNIa rate
A decrease from z=1 upwardCould explain the low SNIarate at z=1.6
Ringberg, July 8, 2005
SNIa rate in different galaxy typesAnother way to constrain the distribution function of the delay times
0
)()()( 00
t
IaIaIa
i
dftkAtn
•Younger stellar populations sample the peak of the distribution function of the delay times•Younger stellar populations are bluer Bluer galaxies have larger SPECIFIC SNIa rates
Data from Mannucci et al. 2005
Ringberg, July 8, 2005
CONCLUSIONS I illustrated how the SFR and the distribution function of the delay times
compose to determine the SNIa rate in galaxies
The current SNIa rate in Spirals mostly constrains the realization probability of the SNIa scenario; in Ellipticals it scales as the fIa functionThe ratio between the current SNIa rates in Spirals and Ellipticals constrains the shape of the function
I presented analytic expressions, describing the distribution function of the delay times for Single and Double Degenerate progenitors
These expressions are based on general stellar evolution arguments, which result into a fIa function controlled by a few main parameters Representing Es as instantaneous burst of SF, and using their current rate to
calibrate the fIa function, I showed that:
SD models greatly overproduce Fe in Galaxy Clusters and overpredict the current rate in Spiral galaxies
The data are met with either CLOSE DDs with flat n(A) or WIDE DDs with steep n(A)
Ringberg, July 8, 2005
NORMALIZATION
0
)()(t
Ia
IaIa
i
dft
nkA
0
)()()( 00
t
IaIaIa
i
dftkAtn
Horizontal levels derived from rate in galaxiesPoints derived from cosmic rate