Type Ia Supernova Rate Research Articles

Atypical Thermonuclear Supernovae from Tidally Crushed White Dwarfs

Suggestive evidence has accumulated that intermediate-mass black holes (IMBHs) exist in some globular clusters. As stars diffuse in the cluster, some will inevitable wander sufficiently close to the hole that they suffer tidal disruption. An attractive feature of the IMBH hypothesis is its potential to disrupt not only solar-type stars but also compact white dwarf stars. Attention is given to the fate of white dwarfs that approach the hole close enough to be disrupted and compressed to such an extent that explosive nuclear burning may be triggered. Precise modeling of the dynamics of the encounter, coupled with a nuclear network, allow for a realistic determination of the explosive energy release, and it is argued that ignition is a natural outcome for white dwarfs of all varieties passing well within the tidal radius. Although event rates are estimated to be significantly less than the rate of normal Type Ia supernovae, such encounters may be frequent enough in globular clusters harboring an IMBH to warrant a search for this new class of supernova.

The supernova rate in local galaxy clusters

We report a measurement of the supernova (SN) rates (Ia and core-collapse) in galaxy clusters based on the 136 SNe of the sample described in Cappellaro et al. (1999) and Mannucci et al. (2005). Early-type cluster galaxies show a type Ia SN rate (0.066 SNuM) similar to that obtained by Sharon et al. (2007) and more than 3 times larger than that in field early-type galaxies (0.019 SNuM). This difference has a 98% statistical confidence level. We examine many possible observational biases which could affect the rate determination, and conclude that none of them is likely to significantly alter the results. We investigate how the rate is related to several properties of the parent galaxies, and find that cluster membership, morphology and radio power all affect the SN rate, while galaxy mass has no measurable effect. The increased rate may be due to galaxy interactions in clusters, inducing either the formation of young stars or a different evolution of the progenitor binary systems. We present the first measurement of the core-collapse SN rate in cluster late-type galaxies, which turns out to be comparable to the rate in field galaxies. This suggests that no large systematic difference in the initial mass function exists between the two environments.

The Velocity Field of the Local Universe from Measurements of Type Ia Supernovae

We present a measurement of the velocity flow of the local universe relative to the CMB rest frame, based on the Jha, Riess & Kirshner (2007) sample of 133 low redshift type Ia supernovae. At a depth of 4500 km s{sup -1} we find a dipole amplitude of 279 {+-} 68 km s{sup -1} in the direction l = 285{sup o} {+-} 18{sup o}, b = -10{sup o} {+-} 15{sup o}, consistent with earlier measurements and with the assumption that the local velocity field is dominated by the Great Attractor region. At a larger depth of 5900 km s{sup -1} we find a shift in the dipole direction towards the Shapley concentration. We also present the first measurement of the quadrupole term in the local velocity flow at these depths. Finally, we have performed detailed studies based on N-body simulations of the expected precision with which the lowest multipoles in the velocity field can be measured out to redshifts of order 0.1. Our mock catalogues are in good agreement with current observations, and demonstrate that our results are robust with respect to assumptions about the influence of local environment on the type Ia supernova rate.

On the evolution of the Fe abundance and of the Type Ia supernova rate in clusters of galaxies

Abstract The study of the Fe abundance in the intracluster medium (ICM) provides strong constraints on the integrated star formation history and supernova rate of the cluster galaxies, as well as on the ICM enrichment mechanisms. In this Letter, using chemical evolution models for galaxies of different morphological types, we study the evolution of the Fe content of clusters of galaxies. We assume that the ICM Fe enrichment occurs by means of galactic winds arising from elliptical galaxies and from gas stripped from the progenitors of S0 galaxies via external mechanisms, due to the interaction of the interstellar medium with the ICM. The Fe-rich gas ejected by ellipticals accounts for the XFe,ICM values observed at z > 0.5, whereas the gas stripped from the progenitors of the S0 galaxies accounts for the increase of XFe,ICM observed at z < 0.5. We test two different scenarios for Type Ia supernova (SN) progenitors and we model the Type Ia SN rate observed in clusters, finding a good agreement between our predictions and the available observations.

Spectropolarimetric Diagnostics of Thermonuclear Supernova Explosions

Even at extragalactic distances, the shape of supernova ejecta can be effectively diagnosed by spectropolarimetry. We present results for 17 type Ia supernovae that allow a statistical study of the correlation among the geometric structures and other observable parameters of type Ia supernovae. These observations suggest that type Ia supernova ejecta typically consist of a smooth, central, iron-rich core and an outer layer with chemical asymmetries. The degree of this peripheral asphericity is correlated with the light-curve decline rate of type Ia supernovae. These results lend strong support to delayed-detonation models of type Ia supernovae.

Formation and evolution of compact binaries in globular clusters - I. Binaries with white dwarfs

In this paper, the first of a series, we study the stellar dynamical and evolutionary processes leading to the formation of compact binaries containing white dwarfs (WDs) in dense globular clusters (GCs). We examine the processes leading to the creation of X-ray binaries such as cataclysmic variables (CVs) and AM CVn systems. Using numerical simulations, we identify the dominant formation channels and we predict the expected numbers and characteristics of detectable systems, emphasizing how the cluster sources differ from the field population. We explore the dependence of formation rates on cluster properties and we explain in particular why the distribution of CVs has only a weak dependence on cluster density. We also discuss the frequency of dwarf nova outbursts in GCs and their connection with moderately strong WD magnetic fields. We examine the rates of Type Ia supernovae (SNe Ia) via both single and double degenerate channels in clusters and we argue that those rates may contribute to the total SN Ia rate in elliptical galaxies. Considering coalescing WD binaries, we discuss possible constraints on the common envelope evolution of their progenitors and we derive theoretical expectations for gravitational wave detection by Laser Interferometer Space Antenna (LISA).

The Hot Gas Content of Low‐Luminosity Early‐Type Galaxies and the Implications Regarding Supernova Heating and Active Galactic Nucleus Feedback

We have analyzed Chandra observations of 18 low-luminosity early-type galaxies with LB 3 × 1010 L☉B. Thermal emission from hot gas with temperatures between 0.2 and 0.8 keV comprises 5%-70% of the total 0.5-2.0 keV emission from these galaxies. We find that the total X-ray luminosity from LMXBs (resolved plus the power-law component of the unresolved emission) scales roughly linearly with the K-band luminosity of the galaxies with a normalization comparable to that found in more luminous early-type galaxies. All of the galaxies in our sample are gas-poor, with gas masses much less than that expected from the accumulation of stellar mass loss over the lifetime of the galaxies. The average ratio of gas mass to stellar mass in our sample is Mgas/M* = 0.001, compared to more luminous early-type galaxies that typically have Mgas/M* = 0.01. The time required to accumulate the observed gas mass from stellar mass loss in these galaxies is typically 3 × 108 yr. Since the cooling time of the gas is longer than the replenishment time, the gas cannot be condensing out of the hot phase and forming stars, implying that the gas is most likely being expelled from these galaxies in a wind. The one exception to this is NGC 4552, which is the most optically luminous galaxy in our sample and has the highest gas content. Using recent estimates of the Type Ia supernova rate and AGN heating rate in early-type galaxies, we find that, on average, heating by Type Ia supernovae should exceed AGN heating in galaxies with LB 3 × 1010 L☉B. We also find that heating by Type Ia supernovae is energetically sufficient to drive winds in these galaxies, even if the present Type Ia supernova rate is overestimated by a factor of 2 or the present stellar mass-loss rate is underestimated by a factor of 2.

Close Pairs as Probes of the Galaxy's Chemical Evolution

AbstractUnderstanding the galaxy in which we live is one of the great intellectual challenges facing modern science. With the advent of high quality observational data, the chemical evolution modeling of our galaxy has been the subject of numerous studies in the last years. However, all these studies have one missing element which is ‘the evolution of close binaries’. Reason: their evolution is very complex and single stars only perhaps can do the job. (Un)Fortunately at present we know that a significant fraction of the observed intermediate mass and massive stars are members of a binary or multiple system and that certain objects can only be formed through binary evolution. Therefore galactic studies that do not account for close binaries may be far from realistic. We implemented a detailed binary population in a galactic chemical evolutionary model. Notice that this is not something simple like replacing chemical yields. Here we discuss three topics: the effect of binaries on the evolution of 14N, the evolution of the type Ia supernova rate and the effects on the G-dwarf distribution, the link between the evolution of the r-process elements and double neutron star mergers (candidates of short gamma-ray burst objects).

The Type Ia Supernova Rate atz ≈ 0.5 from the Supernova Legacy Survey

We present a measurement of the distant Type Ia supernova (SN Ia) rate derived from the first 2 yr of the Canada-France-Hawaii Telescope Supernova Legacy Survey. We observed four 1° × 1° fields with a typical temporal frequency of (Δt) ~ 4 observer-frame days over time spans of 158-211 days per season for each field, with breaks during the full Moon. We used 8-10 m class telescopes for spectroscopic follow-up to confirm our candidates and determine their redshifts. Our starting sample consists of 73 spectroscopically verified SNe Ia in the redshift range 0.2 < z < 0.6. We derive a volumetric SN Ia rate of r_V((z) = 0:47) [0:42^(+0:13)-(-0:09)(syst:) ± 0:06(stat:)]x 10^-4 yr^-1 Mpc^3, assuming h = 0:7, Ω_m = 0:3, and a flat cosmology. Using recently published galaxy luminosity functions derived in our redshift range, we derive a SN Ia rate per unit luminosity of r_L((z) = 0:47) = 0:154^(+0:048)_(-0:033)(syst:)^(+0:039)_(-0:031)(stat:) SN units. Using our rate alone, we place an upper limit on the component of SN Ia production that tracks the cosmic star formation history of 1 SN Ia per 10^3 M_☉ of stars formed. Our rate and other rates from surveys using spectroscopic sample confirmation display only a modest evolution out to z = 0:55.

A new formulation of the Type Ia supernova rate and its consequences on galactic chemical evolution

In recent papers, Mannucci et al. and Mannucci, Della Valle & Panagia suggested, on the basis of observational arguments, that there is a bimodal distribution of delay times for the explosion of Type Ia supernovae (SNe). In particular, a percentage from 35 to 50 per cent of the total Type Ia SNe should be composed by systems with lifetimes as short as 10 8 yr, whereas the rest should arise from smaller mass progenitors with a much broader distribution of lifetimes. In this paper, we test this hypothesis in models of chemical evolution of galaxies of different morphological type: ellipticals, spirals and irregulars. We show that this proposed scenario is compatible also with the main chemical properties of galaxies. In this new formulation, we simply assume that Type Ia SNe are originating from C-O white dwarfs in binary systems without specifying if the progenitor model is the single-degenerate or the double-degenerate one or a mixture of both. In the framework of the single-degenerate model, such a bimodal distribution of the time delays could be explained if the binary systems with a unitary mass ratio are favoured in the mass range 5-8 M ⊙ , whereas for masses -2.0 dex, relative to the old models. For a typical elliptical of 10 11 M ⊙ of luminous mass, the new rate produces average [a/Fe] ratios in the dominant stellar population still in agreement with observations. The Type Ia SN rate also in this case shows an earlier peak and a subsequent faster decline relative to the previous results, but the differences are smaller than in the case of our Galaxy. We have also checked the effects of the new Type Ia SN rate on the evolution of the Fe content in the intracluster medium (ICM), as a consequence of its production from cluster ellipticals and we found that less Fe in the ICM is produced with the new rate, due to the higher fraction of Fe synthesized at early times and remaining locked into the stars in ellipticals. For dwarf irregular galaxies suffering few bursts of star formation, we obtain [O/Fe] ratios larger by 0.2 dex relative to the previous models.

Two populations of progenitors for Type Ia supernovae?

We use recent observations of the evolution of the Type Ia supernova (SN Ia) rate with redshift, the dependence of the SN Ia rate on the colours of the parent galaxies, and the enhancement of the SN Ia rate in radio-loud early-type galaxies to derive on robust empirical grounds, the delay time distribution (DTD) between the formation of the progenitor star and its explosion as an SN. Our analysis finds: (i) delay times as long as 3–4 Gyr, derived from observations of SNe Ia at high redshift, cannot reproduce the dependence of the SN Ia rate on the colours and on the radio-luminosity of the parent galaxies, as observed in the local Universe; (ii) the comparison between observed SN rates and a grid of theoretical ‘single-population’ DTDs shows that only a few of them are possibly consistent with observations. The most successful models are all predicting a peak of SN explosions soon after star formation and an extended tail in the DTD, and can reproduce the data but only at a modest statistical confidence level; (iii) present data are best matched by a bimodal DTD, in which about 50 per cent of SNe Ia (dubbed ‘prompt’ SNe Ia) explode soon after their stellar birth, in a time of the order of 108 yr, while the remaining 50 per cent (‘tardy’ SNe Ia) have a much wider distribution, well described by an exponential function with a decay time of about 3 Gyr. The presence in the DTD of both a strong peak at early times and a prolonged exponential tail, coupled with the well-established bimodal distribution of the decay rate (Δm15) and the systematic difference observed in the expansion velocities of the ejecta of SNe Ia in ellipticals and spirals, suggests the existence of two classes of progenitors. We discuss the cosmological implications of this result and make simple predictions, which are testable with future instrumentation.

Binaries Like to Be Twins: Implications for Doubly Degenerate Binaries, the Type Ia Supernova Rate, and Other Interacting Binaries

A recently published sample of 21 detached eclipsing binaries in the Small Magellanic Cloud provides a valuable test of the binary mass function for massive stars. We show that 50% of detached binaries have companions with very similar masses, q = M2/M1 > 0.87, where M1 and M2 denote the masses of the two binary components, M1 ≥ M2. A Salpeter relative mass function for the secondary is very strongly excluded, and the data are consistent with a flat mass function containing 55% of the systems and a population with q > 0.95 containing the remainder. We survey the existing literature on binary mass ratios and conclude that a significant twin population (of order 20%-25%) exists in binaries that are likely to interact across a broad range of stellar masses and metallicity. Interactions involving twins have distinctly different properties from those involving stars of unequal mass; the secondaries will tend to be evolved, and common-envelope evolution is qualitatively different. The implications of such a population for both binary interactions and star formation are substantial, and we present some examples. We argue that twin systems may provide a natural stellar population to explain the recently proposed prompt channel for Type Ia supernovae, and the presence of a twin population dramatically reduces the maximum inferred merger rate between neutron stars (NSs) and black holes relative to the NS-NS merger rate. Twins may also be important for understanding the tendency of white dwarf and NS binaries to be nearly equal in mass, and inclusion of twins in population studies will boost the blue straggler production rate.

The Rate of Type Ia Supernovae at High Redshift

We derive the rates of Type Ia supernovae (SNIa) over a wide range of redshifts using a complete sample from the IfA Deep Survey. This sample of more than 100 SNIa is the largest set ever collected from a single survey, and therefore uniquely powerful for a detailed supernova rate (SNR) calculation. Measurements of the SNR as a function of cosmological time offer a glimpse into the relationship between the star formation rate (SFR) and Type Ia SNR, and may provide evidence for the progenitor pathway. We observe a progressively increasing Type Ia SNR between redshifts z~0.3-0.8. The Type Ia SNR measurements are consistent with a short time delay (t~1 Gyr) with respect to the SFR, indicating a fairly prompt evolution of SNIa progenitor systems. We derive a best-fit value of SFR/SNR 580 h_70^(-2) M_solar/SNIa for the conversion factor between star formation and SNIa rates, as determined for a delay time of t~1 Gyr between the SFR and the Type Ia SNR. More complete measurements of the Type Ia SNR at z>1 are necessary to conclusively determine the SFR--SNR relationship and constrain SNIa evolutionary pathways.

The rates of type Ia supernovae

The aim of this paper is to provide a handy tool to compute the impact of type Ia SN (SNIa) events on the evolution of stellar systems. An effective formalism to couple the rate of SNIa explosions from a single burst of star formation and the star formation history is presented, which rests upon the definition of the realization probability of the SNIa event () and the distribution function of the delay times (()). It is shown that the current SNIa rate in late type galaxies constrains to be on the order of 10-3 (i.e. 1 SNIa every 1000 of gas turned into stars), while the comparison of the current rates in early and late type galaxies implies that ought to be more populated at short delays. The paper presents analytical formulations for the description of the function for the most popular models of SNIa progenitors, namely Single Degenerates (Chandrasekhar and Sub-Chandrasekhar exploders), and Double Degenerates. These formulations follow entirely from general considerations on the evolutionary behavior of stars in binary systems, modulo a schematization of the outcome of the phases of mass exchange, and compare well with the results of population synthesis codes, for the same choice of parameters. The derivation presented here offers an immediate astrophysical interpretation of the shape of the functions, and have a built in parametrization of the key properties of the alternative candidates. The important parameters appear to be the minimum and maximum masses of the components of the binary systems giving rise to a SNIa explosions, the distribution of the primary mass and of the mass ratios in these systems, the distribution of the separations of the DD systems at their birth. The various models for the progenitors correspond to markedly different impact on the large scales; correspondingly, the model for the progenitor can be constrained by examining the relevant observations. Among these, the paper concentrates on the trend of the current SNIa rate with parent galaxy type. The recent data by Mannucci et al. (2005, A&A, 433, 807) favor the DD channel over the SD one, which tends to predict a too steep distribution function of the delay times. The SD scenario can be reconciled with the observations only if the distribution of the mass ratios in the primordial binaries is flat and the accretion efficiency onto the WD is close to 100%. The various models are characterized by different timescales for the Fe release from a single burst stellar population. In particular the delay time within which half of the SNIa events from such a population have occurred, ranges between 0.3 and 3 Gyr, for a wide variety of hypothesis on the progenitors.

The Type Ia Supernova Rate

We explore the idea that the Type Ia supernovae (SNe Ia) rate consists of two components: a prompt piece that is proportional to the star formation rate (SFR) and an extended piece that is proportional to the total stellar mass. We fit the parameters of this model to the local observations of Mannucci and collaborators and then study its impact on three important problems. On cosmic scales, the model reproduces the observed SNe Ia rate density below z=1, and predicts that it will track the measured SFR density at higher redshift, reaching a value of 1-3.5 X 10^-4 per yr per Mpc^3 at z=2. In galaxy clusters, a large prompt contribution helps explain the iron content of the intracluster medium. Within the Galaxy, the model reproduces the observed stellar [O/Fe] abundance ratios if we allow a short (approximately 0.7 Gyr) delay in the prompt component. Ongoing medium-redshift SN surveys will yield more accurate parameters for our model

Brief history of metal accumulation in the intracluster medium

We use models of the rates of Type Ia supernovae (SNe Ia) and core-collapse supernovae, built in such a way that both are consistent with recent observational constraints at z 75 per cent of the Nickel mass observed locally are produced by SN Ia ejecta, (2) the SN Ia contribution to the metal budget decreases steeply with redshift and by z~1 is already less than half of the local amount and (3) a transition in the abundance ratios relative to the Iron is present between redshifts ~0.5 and 1.4, with core-collapse SN products becoming dominant at higher redshifts.

Supernovae from White Dwarfs Near Black Holes

We describe a new thermonuclear explosion model for Type I (or Type II) supernovae whereby relativistic terms enhance the self gravity of a carbon-oxygen white dwarf (or red-giant core) as it passes or orbits near a black hole. This relativistic compression can cause the central density to exceed the threshold for pycnonuclear or thermonuclear reactions so that an explosion ensues. We have considered three possible environments: 1) white dwarfs orbiting a low-mass (∼ 10 – 20 M ⊙ ) black hole; 2) white dwarfs encountering a massive (∼ 1 – 3 × 10 3 M ⊙ ) black hole in a dense globular cluster; and 3) white dwarfs passing a supermassive (∼ 10 6 – 10 9 M ⊙ ) black hole in a dense galactic core. We estimate the rate at which such events could occur to be significantly less than the rate of normal Type Ia supernovae for all three classes. Nevertheless, they should be frequent enough to warrant a search for this new class of supernova. We show results of three-dimensional thermonuclear burn calculations of white dwarfs or red-giant cores ignited near a supermassive black hole. Such an event might have produced the observed mixed-morphology Sgr A East supernova remnant (SNR) in the Galactic core.

Classical Novae as a Probe of the Cataclysmic Variable Population

Classical novae (CNe) are the brightest manifestation of mass transfer onto a white dwarf (WD) in a cataclysmic variable (CV). As such, they are probes of the mass transfer rate, , and WD mass, MWD, in these interacting binaries. Our calculations of the dependence of the CN ignition mass, Mign, on and MWD yields the recurrence times of these explosions. We show that the observed CNe orbital period distribution is consistent with the interrupted magnetic braking evolutionary scenario, in which at orbital periods Porb > 3 hr mass transfer is driven by angular momentum loss via a wind from the companion star, and at Porb < 3 hr by gravitational radiation. About 50% of CNe occur in binaries accreting at 10-9 M☉ yr-1 with Porb = 3 - 4 hr, with the remaining 50% split evenly between Porb longer (higher ) and shorter (lower ) than this. This resolution of the relative contribution to the CN rate from different CVs tells us that 3(9) × 105 CVs with WD mass 1.0(0.6) M☉ are needed to produce one CN per year. In addition, one CN per year requires a CV birthrate of 1(2) × 10-4 yr-1 and likely ejects mass into the interstellar medium at a rate of = 3(9) × 10-5 M☉ yr-1. Using the K-band-specific CN rate measured in external galaxies, we find a CV birthrate of 2(4) × 10-4 yr-1 per 1010 L☉,K, very similar to the luminosity specific Type Ia supernova rate in elliptical galaxies. Likewise, we predict that there should be 60-180 CVs for every 106 L☉,K in an old stellar population. The population of X-ray-identified CVs in the globular cluster 47 Tuc is similar to this number, showing no overabundance relative to the field. The observed CN Porb distribution also contains evidence for a CV population that has no period gap. These are likely systems with a strongly magnetic WD (polars) in which it has been suggested that the field interferes with the wind of the companion, limiting angular momentum losses to those of gravitational radiation and eliminating the period gap. With this reduced , polars evolve more slowly than systems that undergo magnetic braking. Using a two-component steady state model of CV evolution, we show that the fraction of CVs that are magnetic (22%) implies a birthrate of 8% relative to nonmagnetic CVs, similar to the fraction of strongly magnetic field WDs.

The Deepest Supernova Search is Realized in the Hubble Ultra Deep Field Survey

The Hubble Ultra Deep Field Survey has provided the deepest optical and near-infrared views of the universe yet, and has enabled a search for the most distant supernovae, to z ~ 2.2. We have found four supernovae by searching spans of integrations of the Ultra Deep Field and the Ultra Deep Field Parallels taken with the Hubble Space Telescope paired with the Advanced Camera for Surveys and with NICMOS. Interestingly, none of these events were Type Ia supernovae (SNe Ia) above a redshift of 1.4, despite the substantially increased sensitivity per unit area to such objects over other surveys, including the Great Observatories Origins Deep Survey. However, we find that the low frequency of SNe Ia observed at 1.4 < z < 2.4 is statistically consistent with current estimates of the Type Ia supernova rate per unit volume, including the global star formation history combined with the nontrivial assembly time of SN Ia progenitors.

The Rate and the Origin of Type Ia SNe in Radio Galaxies

SummaryAn analysis of type Ia supernova (SNIa) events in early type galaxies from the Cappellaro et al. [6] database provides strong evidence that the rate of type Ia supernovae (SNe) in radio-loud galaxies is about 4 times higher than the rate measured in radio-quiet galaxies, i.e. SNIa-rate(radio-loud) SNe per century and per 1010 (SNU) as compared to SNIa-rate(radio-quiet)= 0.11 ± 0.03 SNU. The exact value of the enhancement is still rather uncertain, but is likely to be in the range ~ 2 – 7. We discuss the possible causes of this result and we conclude that the enhancement of the SNIa explosion rate in radio-loud galaxies has the same common origin as their being strong radio sources, but that there is no causality link between the two phenomena. We argue that repeated episodes of interaction and/or mergers of early type galaxies with dwarf companions are responsible for inducing both strong radio activity in ~14% of early type galaxies, and the ~ 1 Gyr old stellar population needed to supply an adequate number SNIa progenitors.