Distribution Of Type Ia Supernovae Research Articles

The Spatial Distribution of Type Ia Supernovae within Host Galaxies

We study how type Ia supernovae (SNe Ia) are spatially distributed within their host galaxies, using data taken from the Sloan Digital Sky Survey (SDSS). This paper specifically tests the hypothesis that the SNe Ia rate traces the r-band light of the morphological component to which supernovae belong. A sample of supernovae is taken from the SDSS SN Survey, and host galaxies are identified. Each host galaxy is decomposed into a bulge and disk, and the distribution of supernovae is compared to the distribution of disk and bulge light. Our methodology is relatively unaffected by seeing. We find that, in galaxies dominated by disk light, SNe Ia trace light closely. The situation is less clear for bulges and ellipticals, because of resolution effects, but the available evidence is also consistent with the hypothesis that bulge/elliptical SNe Ia follow light.

Hints of FLRW breakdown from supernovae

A 10\% difference in the scale for the Hubble parameter constitutes a clear problem for cosmology. Here, considering angular distribution of Type Ia supernovae (SN) within the Pantheon compilation and working within flat $\Lambda$CDM cosmology, we observe a correlation between higher $H_0$ and the CMB dipole direction, confirming our previous results for strongly-lensed quasars \cite{Krishnan:2021dyb}. Concretely, we record a $\sim 1$ km/s/Mpc variation in $H_0$ at antipodal points on the sky within the Pantheon sample, which is evident in the Low $z$ subsample ($z \lesssim 0.075$) and gets enhanced by higher redshift SN. Our work raises the possibility that we may be at the precision required to probe anisotropic Hubble expansions, while providing a concrete prediction for future inferences of $H_0$.

Determining the 56Ni distribution of type Ia supernovae from observations within days of explosion

Recent studies have shown how the distribution of 56Ni within the ejected material of type Ia supernovae can have profound consequences on the observed light curves. Observations at early times can therefore provide important details on the explosion physics in thermonuclear supernovae, which are poorly constrained. To this end, we present a series of radiative transfer calculations that explore variations in the 56Ni distribution. Our models also show the importance of the density profile in shaping the light curve, which is often neglected in the literature. Using our model set, we investigate the observations that are necessary to determine the 56Ni distribution as robustly as possible within the current model set. We find that this includes observations beginning at least ∼14 days before B-band maximum, extending to approximately maximum light with a relatively high (≲3 day) cadence, and in at least one blue and one red band (such as B and R, or g and r) are required. We compare a number of well-observed type Ia supernovae that meet these criteria to our models and find that the light curves of ∼70–80% of objects in our sample are consistent with being produced solely by variations in the 56Ni distributions. The remaining supernovae show an excess of flux at early times, indicating missing physics that is not accounted for within our model set, such as an interaction or the presence of short-lived radioactive isotopes. Comparing our model light curves and spectra to observations and delayed detonation models demonstrates that while a somewhat extended 56Ni distribution is necessary to reproduce the observed light curve shape, this does not negatively affect the spectra at maximum light. Investigating current explosion models shows that observations typically require a shallower decrease in the 56Ni mass towards the outer ejecta than is produced for models of a given 56Ni mass. Future models that test differences in the explosion physics and detonation criteria should be explored to determine the conditions necessary to reproduce the 56Ni distributions found here.

The Delay Times of Type Ia Supernova

Abstract The delay time distribution of Type Ia supernovae (SNe Ia; the time-dependent rate of SNe resulting from a burst of star formation) has been measured using different techniques and in different environments. Here we study in detail the distribution for field galaxies, using the SDSS DR7 Stripe 82 SN sample. We improve a technique we introduced earlier, which is based on galaxy color and luminosity and is insensitive to details of the star formation history, to include the normalization. Assuming a power-law dependence of the SN rate with time, DTD(t) = A(t/1 Gyr) s , we find a power-law index and a normalization , corresponding to a number of SNe Ia integrated over a Hubble time of . We also implement a method used by Maoz and collaborators, which is based on star formation history reconstruction, and find that this gives a consistent result for the slope but a lower, marginally inconsistent normalization. With our normalization, the distribution for field galaxies is made consistent with that derived for cluster galaxies. Comparing the inferred distribution with predictions from different evolutionary scenarios for SNe Ia, we find that our results are intermediate between the various predictions and do not yet constrain the evolutionary path leading to SNe Ia.

Reconstructing the weak lensing magnification distribution of type Ia supernovae

Weak lensing of Type Ia supernovae (SNe Ia) is a systematic uncertainty in the use of SNe Ia as standard candles, as well as an independent cosmological probe, if the corresponding magnification distribution can be extracted from data. We study the peak brightness distribution of SNe Ia in the Pantheon sample, and find that the high $z$ sub-sample shows distinct weak lensing signatures compared to the low $z$ subsample: a long tail at the bright end due to high magnifications and a shift of the peak brightness toward the faint end, consistent with findings from earlier work. We have developed a technique to reconstruct the weak lensing magnification distribution of SNe Ia, $p(\mu)$, from the measured SN Ia flux distribution, and applied it to the Pantheon sample. We find that $p(\mu)$ can be reconstructed at a significance better than 2$\sigma$ for the subsample of SNe Ia at $z>0.7$ (124 SNe Ia), and at a lower significance for the SNe Ia at $z>0.9$ (49 SNe Ia), due to the small number of SNe Ia at high redshifts. The large number of $z>1$ SNe Ia from future surveys will enable the use of $p(\mu)$ reconstructed from SNe Ia as an independent cosmological probe.

Reconciling volumetric and individual galaxy type Ia supernova rates

Significant observational effort has been devoted to determining volumetric type Ia supernova rates at high redshifts, leading to clues about the nature of Ia supernova progenitors and constraints on the iron production in the universe. A complementary approach is to investigate type Ia supernova rates in individual, more nearby, galaxies. The popular A+B model for the specific supernova rate, while reliable for a wide range of galaxy properties, diverges for large specific star formation rates. Applying it outside its range of validity could lead to the prediction of excessive type Ia supernova rates. Moreover, the A+B model it is not directly derived from a delay time distribution. We here introduce a new model which is explicitly motivated by a simple delay time distribution composed of a prompt and a delayed component. The model is in remarkably good agreement with current observational constraints. It yields a prompt fraction of $f_{p}= 0.11^{+0.10}_{-0.06}$ in agreement with results based on volumetric rates of type Ia supernovae at high redshift (Rodney et al. 2014). The model is tested against realistic star formation rates from the Illustris-1 simulation and is found to be self consistent in the asymptotic limits. An analytic function that encapsulates the features of the new model is shown to be in excellent agreement with the data. In terms of goodness of fit, the new model is strongly preferred over the A+B model. At $\log{({\rm sSFR})} \gtrsim -9$ there are no constraints from observations. Observations in this regime will further constrain the delay time distribution of type Ia supernovae at short delay times.

Testing the cosmic anisotropy with supernovae data: Hemisphere comparison and dipole fitting

The cosmological principle is one of the cornerstones in modern cosmology. It assumes that the universe is homogeneous and isotropic on cosmic scales. Both the homogeneity and the isotropy of the universe should be tested carefully. In the present work, we are interested in probing the possible preferred direction in the distribution of type Ia supernovae (SNIa). To our best knowledge, two main methods have been used in almost all of the relevant works in the literature, namely the hemisphere comparison (HC) method and the dipole fitting (DF) method. However, the results from these two methods are not always approximately coincident with each other. In this work, we test the cosmic anisotropy by using these two methods with the Joint Light-Curve Analysis (JLA) and simulated SNIa datasets. In many cases, both methods work well, and their results are consistent with each other. However, in the cases with two (or even more) preferred directions, the DF method fails while the HC method still works well. This might shed new light on our understanding of these two methods.

Sample variance in the local measurements of the Hubble constant

The current $>3\sigma$ tension between the Hubble constant $H_0$ measured from local distance indicators and from cosmic microwave background is one of the most highly debated issues in cosmology, as it possibly indicates new physics or unknown systematics. In this work, we explore whether this tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the Hubble volume. We use a large-volume cosmological $N$-body simulation to model the local measurements and to quantify the variance due to local density fluctuations and sample selection. We explicitly take into account the inhomogeneous spatial distribution of type Ia supernovae. Despite the faithful modelling of the observations, our results confirm previous findings that sample variance in the local Hubble constant $(H_0^{\rm loc})$ measurements is small; we find $\sigma(H_0^{\rm loc})=0.31\,{\rm km\ s^{-1}Mpc^{-1}}$, a nearly negligible fraction of the $\sim6\,{\rm km\ s^{-1}Mpc^{-1}}$ necessary to explain the difference between the local and the global $H_0$ measurements. While the $H_0$ tension could in principle be explained by our local neighbourhood being a underdense region of radius $\sim 150 \,\rm Mpc$ , the extreme required underdensity of such a void $(\delta\simeq -0.8)$ makes it very unlikely in a $\Lambda$CDM universe, and it also violates existing observational constraints. Therefore, sample variance in a $\Lambda$CDM universe cannot appreciably alleviate the tension in $H_0$ measurements even after taking into account the inhomogeneous selection of type Ia supernovae.

The ejected mass distribution of Type Ia supernovae: a significant rate of non-Chandrasekhar-mass progenitors

The ejected mass distribution of type Ia supernovae directly probes progenitor evolutionary history and explosion mechanisms, with implications for their use as cosmological probes. Although the Chandrasekhar mass is a natural mass scale for the explosion of white dwarfs as type Ia supernovae, models allowing type Ia supernovae to explode at other masses have attracted much recent attention. Using an empirical relation between the ejected mass and the light curve width, we derive ejected masses $M_\mathrm{ej}$ and $^{56}$Ni masses $M_\mathrm{Ni}$ for a sample of 337 type Ia supernovae with redshifts $z < 0.7$ used in recent cosmological analyses. We use hierarchical Bayesian inference to reconstruct the joint $M_\mathrm{ej}$-$M_\mathrm{Ni}$ distribution, accounting for measurement errors. The inferred marginal distribution of $M_\mathrm{ej}$ has a long tail towards sub-Chandrasekhar masses, but cuts off sharply above 1.4 $M_\odot$. Our results imply that 25\%-50\% of normal type Ia supernovae are inconsistent with Chandrasekhar-mass explosions, with almost all of these being sub-Chandrasekhar-mass; super-Chandrasekhar-mass explosions make up no more than 1\% of all spectroscopically normal type Ia supernovae. We interpret the type Ia supernova width-luminosity relation as an underlying relation between $M_\mathrm{ej}$ and $M_\mathrm{Ni}$, and show that the inferred relation is not naturally explained by the predictions of any single known explosion mechanism.

On the brightness distribution of Type Ia supernovae from violent white dwarf mergers

We investigate the brightness distribution expected for thermonuclear explosions that might result from the ignition of a detonation during the violent merger of white dwarf (WD) binaries. Determining their brightness distribution is critical for evaluating whether such an explosion model could be responsible for a significant fraction of the observed population of SNe Ia. We argue that the brightness of an explosion realized via the violent merger model is determined by the mass of nickel 56 produced in the detonation of the primary WD. We use a set of sub-Chandrasekhar mass WD detonation models to derive a relationship between primary WD mass and expected peak bolometric brightness. We use this relationship to convert the masses of merging primary WDs from binary population models to a predicted distribution of explosion brightness. We find a striking similarity between the shape of our theoretical peak-magnitude distribution and that observed for SNe Ia: our model produces a brightness distribution that roughly covers the range and matches the shape of the one observed for SNe Ia. However, this agreement hinges on a particular phase of mass accretion during binary evolution: the primary WD gains ~0.15-0.35 Msun from a slightly-evolved helium star companion. We also find that with high probability, violent WD mergers involving the most massive primaries (which should produce bright SNe) have delay times <500 Myr (Abridged).

CHEMICAL EVOLUTION OF THE LARGE MAGELLANIC CLOUD

We adopt a new chemical evolution model for the Large Magellanic Cloud (LMC) and thereby investigate its past star formation and chemical enrichment histories. The delay time distribution of type Ia supernovae recently revealed by type Ia supernova surveys is incorporated self-consistently into the new model. The principle results are summarized as follows. The present gas mass fraction and stellar metallicity as well as the higher [Ba/Fe] in metal-poor stars at [Fe/H]<-1.5 can be more self-consistently explained by models with steeper initial mass functions. The observed higher [Mg/Fe] (> 0.3) at [Fe/H] ~ -0.6 and higher [Ba/Fe] (>0.5) at [Fe/H] ~ -0.3 can be due to significantly enhanced star formation about 2 Gyr ago. The observed overall [Ca/Fe]-[Fe/H] relation and remarkably low [Ca/Fe] (<-0.2) at [Fe/H]>-0.6 are consistent with models with short-delay supernova Ia and with the more efficient loss of Ca possibly caused by an explosion mechanism of type II supernovae. Although the metallicity distribution functions do not show double peaks in the models with a starburst about 2 Gyr ago, they show characteristic double peaks in the models with double starbursts at ~200 Myr and ~2 Gyr ago. The observed apparent dip of [Fe/H] around ~1.5 Gyr ago in the age--metallicity relation can be reproduced by models in which a large amount (~10^9 M_{sun}) of metal-poor ([Fe/H]<-1) gas can be accreted onto the LMC.

The delay-time distribution of Type Ia supernovae from Sloan II

We derive the delay-time distribution (DTD) of type-Ia supernovae (SNe Ia) using a sample of 132 SNe Ia, discovered by the Sloan Digital Sky Survey II (SDSS2) among 66,000 galaxies with spectral-based star-formation histories (SFHs). To recover the best-fit DTD, the SFH of every individual galaxy is compared, using Poisson statistics, to the number of SNe that it hosted (zero or one), based on the method introduced in Maoz et al. (2011). This SN sample differs from the SDSS2 SN Ia sample analyzed by Brandt et al. (2010), using a related, but different, DTD recovery method. Furthermore, we use a simulation-based SN detection-efficiency function, and we apply a number of important corrections to the galaxy SFHs and SN Ia visibility times. The DTD that we find has 4-sigma detections in all three of its time bins: prompt (t < 420 Myr), intermediate (0.4 < t < 2.4 Gyr), and delayed (t > 2.4 Gyr), indicating a continuous DTD, and it is among the most accurate and precise among recent DTD reconstructions. The best-fit power-law form to the recovered DTD is t^(-1.12+/-0.08), consistent with generic ~t^-1 predictions of SN Ia progenitor models based on the gravitational-wave induced mergers of binary white dwarfs. The time integrated number of SNe Ia per formed stellar mass is N_SN/M = 0.00130 +/- 0.00015 Msun^-1, or about 4% of the stars formed with initial masses in the 3-8 Msun range. This is lower than, but largely consistent with, several recent DTD estimates based on SN rates in galaxy clusters and in local-volume galaxies, and is higher than, but consistent with N_SN/M estimated by comparing volumetric SN Ia rates to cosmic SFH.

Supernovae in the Subaru Deep Field: the rate and delay-time distribution of Type Ia supernovae out to redshift 2

The Type Ia supernova (SN Ia) rate, when compared to the cosmic star formation history (SFH), can be used to derive the delay-time distribution (DTD; the hypothetical SN Ia rate versus time following a brief burst of star formation) of SNe Ia, which can distinguish among progenitor models. We present the results of a supernova (SN) survey in the Subaru Deep Field (SDF). Over a period of 3 years, we have observed the SDF on four independent epochs with Suprime-Cam on the Subaru 8.2-m telescope, with two nights of exposure per epoch, in the R, i′and z′ bands. We have discovered 150 SNe out to redshift z≈ 2. Using 11 photometric bands from the observer-frame far-ultraviolet to the near-infrared, we derive photometric redshifts for the SN host galaxies (for 24 we also have spectroscopic redshifts). This information is combined with the SN photometry to determine the type and redshift distribution of the SN sample. Our final sample includes 28 SNe Ia in the range 1.0 < z < 1.5 and 10 in the range 1.5 < z < 2.0. As our survey is largely insensitive to core-collapse SNe (CC SNe) at z > 1, most of the events found in this range are likely SNe Ia. Our SN Ia rate measurements are consistent with those derived from the Hubble Space Telescope (HST) Great Observatories Origins Deep Survey (GOODS) sample, but the overall uncertainty of our 1.5 < z < 2.0 measurement is a factor of 2 smaller, of 35–50 per cent. Based on this sample, we find that the SN Ia rate evolution levels off at 1.0 < z < 2.0, but shows no sign of declining. Combining our SN Ia rate measurements and those from the literature, and comparing to a wide range of possible SFHs, the best-fitting DTD (with a reduced χ2= 0.7) is a power law of the form Ψ(t) ∝tβ, with index β=−1.1 ± 0.1 (statistical) ±0.17 (systematic). This result is consistent with other recent DTD measurements at various redshifts and environments, and is in agreement with a generic prediction of the double-degenerate progenitor scenario for SNe Ia. Most single-degenerate models predict different DTDs. By combining the contribution from CC SNe, based on the wide range of SFHs, with that from SNe Ia, calculated with the best-fitting DTD, we predict that the mean present-day cosmic iron abundance is in the range ZFe= (0.09–0.37) ZFe, ⊙. We further predict that the high-z SN searches now beginning with HST will discover 2–11 SNe Ia at z > 2.

Comparative Analysis of Peculiar Type Ia 1991bg-like Supernovae Spectra

ABSTRACTSpectroscopic analyses of Type Ia supernovae have shown that there exist four spectroscopic groups—cool, broad line, shallow silicon, and core normal—defined by the widths of the Si II features λ5972 and λ6355. The 1991bg-like SNe Ia are classified as “cool.” Cool SNe Ia are dim, undergo a rapid decline in luminosity, and produce significantly less 56Ni than normal Type Ia supernovae. They also have an unusually deep and wide trough in their spectra at around 4200 Å and a relatively strong Si II absorption attributed to λ5972. We examine the spectra of supernova (SN) 1991bg and the cool SN 1997cn, SN 1999by, and SN 2005bl using the highly parameterized synthetic spectrum code SYNOW, and we find general agreement with similar spectroscopic studies. Our analysis reveals that this group of supernovae is fairly homogeneous, with many of the blue spectral features well fit by Fe II. The nature of the spectroscopic commonalities and the variations in the class are discussed. Finally, we examine intermediates such as SN 2004eo and discuss the spectroscopic subgroup distribution of Type Ia supernovae.

The delay-time distribution of Type Ia supernovae: a comparison between theory and observation

We investigate the contribution of different formation scenarios for type Ia supernovae in elliptical galaxies. The single degenerate scenario (a white dwarf accreting from a late main sequence or red giant companion) is tested against the double degenerate scenario (the spiral-in and merging of two white dwarfs through the emission of gravitational wave radiation). We use a population number synthesis code incorporating the latest physical results in binary evolution, and allowing to differentiate between certain physical scenarios (e.g. description of common envelope evolution) and evolutionary parameters (e.g. mass transfer efficiency during Roche lobe overflow). The obtained theoretical distributions of the delay times of type Ia supernovae are compared to those which are observed, both in morphological shape and absolute number of events. The critical dependency of these distributions on certain parameters is used to constrain the values of the latter. We find that the single degenerate scenario alone cannot explain the morphological shape of the observational delay time distribution, while the double degenerate scenario (or a combination of both) can. Most of these double degenerate type Ia supernovae are created through a normal quasi-conservative Roche lobe overflow followed by a common envelope phase, not through two successive common envelope phases. This may cast doubt on the use in other studies of analytical formalisms to determine delay times. In terms of absolute number, theoretical supernova Ia rates in old elliptical galaxies lie a factor of at least three below the observed ones. We propose a solution involving the effect of rotation on the evolution of intermediate mass binaries.

The delay time distribution of type Ia supernovae: theory and observation

AbstractUsing a population number synthesis code, the theoretical time distributions of type Ia supernovae in starburst galaxies are calculated, using competing models for the formation of such events: the single degenerate (a white dwarf accreting matter from a late main sequence or red giant companion) and double degenerate (the merger of two white dwarfs) scenario. The code includes the latest results in determining the progenitors for both models. Examples are the mass stripping effect in the case of the single degenerate scenario and the differentiation between the α- (based on the balance of energy) and γ- (based on the balance of angular momentum) description of energy conversion during common envelope evolution of binaries. The shape and extent of the obtained delay time distributions critically depends on which formation scenario is used. Comparing these results to the latest observed distributions allows to draw conclusions about the constraints put on the theoretical models by these observations. We also specifically investigate the influence of the degree of conservatism during Roche lobe overflow on the delay time distribution. We conclude that the single degenerate scenario alone cannot reproduce the observed delay time distributions, and that most double degenerate type Ia supernovae are formed through a quasi-conservative Roche lobe overflow phase followed by spiral-in, as opposed to a double common envelope evolution.

The radial distribution of Type Ia supernovae in early-type galaxies: implications for progenitor scenarios

Abstract We study the radial distribution of Type Ia supernovae (SNe Ia) in morphologically selected early-type host galaxies from the Sloan Digital Sky Survey (SDSS) and discuss its implications for the progenitor systems of SNe Ia. While new observations of early-type galaxies suggest that they contain small fractions of young stellar populations, they are also the most likely hosts for long time-delay SNe Ia. We find that there is no statistically significant difference between the radial distribution of SNe Ia and the light profile of their early-type host galaxies, which are dominated by old, metal-rich stellar populations. This confirms the commonly accepted idea that some SN Ia progenitors have time delays of the order of several Gyr.