SNe Type Research Articles

Genesis and evolution of dust in galaxies in the early Universe

We have developed a numerical galactic chemical evolution model. The model is constructed such that the effect of a wide range of parameters can be investigated. It takes into account results from stellar evolution models, a differentiation between diverse types of core collapse SNe and the contribution of AGB stars in the mass range 3-8 Msun. We consider the lifetime-dependent yield injection into the ISM by all sources as well as dust destruction due to SN shocks in the ISM. We ascertain the temporal progression of the dust mass, the dust-to-gas and dust-to-metal mass ratios as well as other physical properties of a galaxy and study their dependence on the mass of the galaxy, the IMF, dust production efficiencies and dust destruction in the ISM. The amount of dust and the physical properties of a galaxy strongly depend on the initial gas mass available. Overall, while the total amount of dust produced increases with galaxy mass, the detailed outcome depends on the SN dust production efficiency, the IMF and the strength of dust destruction in the ISM. Dust masses are higher for IMFs biased towards higher stellar masses, despite the fact that these IMFs are more strongly affected by dust destruction in the ISM. The sensitivity to the IMF increases as the mass of the galaxy decreases. SNe are primarily responsible for a significant enrichment with dust at early epochs (< 200 Myr). Dust production with a dominant contribution by AGB stars is found to be insufficient to account for dust masses in excess of 10^8 Msun within 400 Myr after starburst. We find that galaxies with initial gas masses between 1-5 x 10^11 Msun are sufficiently massive to enable production of dust masses >10^8 Msun. Our preferred scenario is dominated by SN dust production in combination with top-heavy IMFs and moderate dust destruction in the ISM.

EARLY SUPERNOVAE LIGHT CURVES FOLLOWING THE SHOCK BREAKOUT

The first light from a supernova (SN) emerges once the SN shock breaks out of the stellar surface. The first light, typically a UV or X-ray flash, is followed by a broken power-law decay of the luminosity generated by radiation that leaks out of the expanding gas sphere. Motivated by recent detection of emission from very early stages of several SNe, we revisit the theory of shock breakout and the following emission. We derive analytic light curves, paying special attention to the photon-gas coupling and deviations from thermal equilibrium. We then consider the breakout from several SNe progenitors. We find that for more compact progenitors, white dwarfs, Wolf-Rayet stars (WRs) and possibly more energetic blue-supergiant explosions, the observed radiation is out of thermal equilibrium at the breakout, during the planar phase (i.e., before the expanding gas doubles its radius), and during the early spherical phase. Therefore, during these phases we predict significantly higher temperatures than previous analysis that assumed equilibrium. When thermal equilibrium prevails, we find the location of the thermalization depth and its temporal evolution. Our results are useful for interpretation of early SN light curves. Some examples are: (i) Red supergiant SNe have an early bright peak in optical and UV flux, less than an hour after breakout. It is followed by a minimum at the end of the planar phase (about 10 hr), before it peaks again once the temperature drops to the observed frequency range. In contrast WRs show only the latter peak in optical and UV. (ii) Bright X-ray flares are expected from all core-collapse SNe types. (iii) The light curve and spectrum of the initial breakout pulse holds information on the explosion geometry and progenitor wind opacity. Its spectrum in compact progenitors shows a (non-thermal) power-law.

Confronting dark energy models using galaxy cluster number counts

The mass function of cluster-size halos and their redshift distribution are computed for 12 distinct accelerating cosmological scenarios and confronted to the predictions of the conventional flat $\Lambda$CDM model. The comparison with $\Lambda$CDM is performed by a two-step process. Firstly, we determine the free parameters of all models through a joint analysis involving the latest cosmological data, using SNe type Ia, the CMB shift parameter and BAO. Apart from a brane world inspired cosmology, it is found that the derived Hubble relation of theremaining models reproduce the $\Lambda$CDM results approximately with the same degree of statistical confidence. Secondly, in order to attempt distinguish the different dark energy models from the expectations of $\Lambda$CDM, we analyze the predicted cluster-size halo redshift distribution on the basis of two future cluster surveys: (i) an X-ray survey based on the {\tt eROSITA} satellite, and (ii) a Sunayev-Zeldovich survey based on the South Pole Telescope. As a result, we find that the predictions of 8 out of 12 dark energy models can be clearly distinguished from the $\Lambda$CDM cosmology, while the predictions of 4 models are statistically equivalent to those of the $\Lambda$CDM model, as far as the expected cluster mass function and redshift distribution are concerned. The present analysis suggest that such a technique appears to be very competitive to independent tests probing the late time evolution of the Universe and the associated dark energy effects.

TESTING THE DISTANCE–DUALITY RELATION WITH GALAXY CLUSTERS AND TYPE Ia SUPERNOVAE

In this letter we propose a new and model-independent cosmological test for the distance-duality (DD) relation, \eta=D_{L}(z)(1+z)^{-2}/D_{A}(z)=1, where D_{L} and D_{A} are, respectively, the luminosity and angular diameter distances. For $D_L$ we consider two sub-samples of SNe type Ia taken from Constitution data (2009) whereas $D_A$ distances are provided by two samples of galaxy clusters compiled by De Fillipis et al. (2005) and Bonamente et al. (2006) by combining Sunyaev-Zeldovich effect (SZE) and X-ray surface brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to coincide with the ones of the associated galaxy cluster sample (\Delta z<0.005) thereby allowing a direct test of DD relation. Since for very low redshifts, D_{A}(z) \approxeq D_{L}(z), we have tested the DD relation by assuming that $\eta$ is a function of the redshift parametrized by two different expressions: \eta(z) = 1 + \eta_{0}z and \eta(z) = 1 + \eta_{0}z/(1+z), where \eta_0 is a constant parameter quantifying a possible departure from the strict validity of the reciprocity relation (\eta_0=0). In the best scenario (linear parametrization) we obtain \eta_{0} = -0.28^{+ 0.44}_{- 0.44} (2\sigma$, statistical + systematic errors) for de Fillipis et al. sample (eliptical geometry), a result only marginally compatible with the DD relation. However, for Bonamente et al. sample (spherical geometry) the constraint is \eta_{0} = -0.42^{+ 0.34}_{- 0.34} (3\sigma$, statistical + systematic errors) which is clearly incompatible with the duality-distance relation.

Is there a mildly relativistic jet in SN2007gr?

AbstractSN2007gr was an ordinary type Ic supernova, with a hint of asymmetric explosion seen in the optical polarization spectrum. This type of SNe is occasionally associated with long duration gamma-ray bursts which generate ultra-relativistic jets; no relativistic outflows have yet been found by direct imaging in SNe Ib/c explosions. High resolution very long baseline interferometry (VLBI) data and simultaneous total radio flux density measurements indicated that SN2007gr has expanded mildly relativistically. We performed late time Westerbork Synthesis Radio Telescope (WSRT) observations to measure the level of the underlying extended emission. Comparison of the VLBI and the background-subtracted WSRT and independent VLA data indicate an at least partially resolved source with an average expansion velocity of ≥0.4c, although the VLBI data could be consistent with a fainter source with an expansion velocity of ~0.2c as well.

Hydrogen recombination with multilevel atoms

Hydrogen recombination is one of the most important atomic processes in many astrophysical objects such as Type II supernova (SN~II) atmospheres, the high redshift universe during the cosmological recombination era, and H II regions in the interstellar medium. Accurate predictions of the ionization fraction can be quite different from those given by a simple solution if one takes into account many angular momentum sub-states, non-resonant processes, and calculates the rates of all atomic processes from the solution of the radiative transfer equation instead of using a Planck function under the assumption of thermal equilibrium. We use the general purpose model atmosphere code PHOENIX 1D to compare how the fundamental probabilities such as the photo-ionization probability, the escape probability, and the collisional de-excitation probability are affected by the presence of other metals in the environment, multiple angular momentum sub-states, and non-resonant processes. Our comparisons are based on a model of SN 1999em, a SNe Type II, 20 days after its explosion.

The Ultraviolet View of Supernovae

The Ultraviolet View of Supernovae

EXTREMELY LUMINOUS SUPERNOVA 2006gy AT LATE PHASE: DETECTION OF OPTICAL EMISSION FROM SUPERNOVA

We performed optical spectroscopy and photometry of SN 2006gy at late time, ~400 days after the explosion, with the Subaru/FOCAS in a good seeing condition. We found that the SN faded by ~3 mag from ~200 to ~400 days after the explosion (i.e., by ~5 mag from peak to ~400 days) in R band. The overall light curve is marginally consistent with the 56Ni heating model, although the flattening around 200 days suggests the optical flux declined more steeply between ~200 and ~400 days. The late time spectrum was quite peculiar among all types of SNe. It showed many intermediate width (~2000 km/s FWHM) emission lines, e.g., [Fe II], [Ca II], and Ca II. The absence of the broad [O I] 6300, 6364 line and weakness of [Fe II] and [Ca II] lines compared with Ca II IR triplet would be explained by a moderately high electron density in the line emitting region. This high density assumption seems to be consistent with the large amount of ejecta and low expansion velocity of SN 2006gy. The H-alpha line luminosity was as small as ~1x10^39 erg/s, being comparable with those of normal Type II SNe at similar epochs. Our observation indicates that the strong CSM interaction had almost finished by ~400 days. If the late time optical flux is purely powered by radioactive decay, at least M_Ni ~ 3 M_sun should be produced at the SN explosion. In the late phase spectrum, there were several unusual emission lines at 7400--8800 AA and some of them might be due to Ti or Ni synthesized at the explosion. (abridged)

Simplified quartessence cosmology

We propose a new class of accelerating world models unifying the cosmological dark sector (dark matter and dark energy). All the models are described by a simplified version of the Chaplygin gas quartessence cosmology. It is found that even for Ω k ≠ 0 , this quartessence scenario depends only on a pair of parameters which can severely be constrained by the cosmological tests. As an example we perform a joint analysis involving the latest SNe type Ia data and the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations. In our analysis we have considered the SNe type Ia Union sample compiled by Kowalski et al. [M. Kowalski et al., Astrophys. J. 686 (2008) 749, arXiv:0804.4142]. At 95.4% (c.l.), we find for BAO + Union sample, α = 0.81 - 0.04 + 0.04 and Ω Q4 = 1.15 - 0.17 + 0.16 . The best-fit for this simplified quartessence scenario is a spatially closed Universe and its reduced χ 2 is exactly the same of the flat concordance model (ΛCDM).

NEAR-INFRARED PHOTOMETRY OF THE TYPE IIn SN 2005ip: THE CASE FOR DUST CONDENSATION

Near-infrared photometric observations of the Type IIn SN 2005ip in NGC 2906 reveal large fluxes (>1.3 mJy) in the K_s-band over more than 900 days. While warm dust can explain the late-time K_s-band emission of SN 2005ip, the nature of the dust heating source is ambiguous. Shock heating of pre-existing dust by post-shocked gas is unlikely because the forward shock is moving too slowly to have traversed the expected dust-free cavity by the time observations first reveal the K_s emission. While an infrared light echo model correctly predicts a near-infrared luminosity plateau, heating dust to the observed temperatures of ~1400-1600 K at a relatively large distance from the supernova (> 10^{18} cm) requires an extraordinarily high early supernova luminosity (~1 X 10^{11} L_solar). The evidence instead favors condensing dust in the cool, dense shell between the forward and reverse shocks. Both the initial dust temperature and the evolutionary trend towards lower temperatures are consistent with this scenario. We infer that radiation from the circumstellar interaction heats the dust. While this paper includes no spectroscopic confirmation, the photometry is comparable to other SNe that do show spectroscopic evidence for dust formation. Observations of dust formation in SNe are sparse, so these results provide a rare opportunity to consider SNe Type IIn as dust sources.

A simplified approach for Chaplygin-type cosmologies

A new class of accelerating cosmological models driven by a one-parameter version of the general Chaplygin-type equation of state is proposed. The simplified version is naturally obtained from causality considerations with basis on the adiabatic sound speed v S plus the observed accelerating stage of the universe. We show that very stringent constraints on the unique free parameter α describing the simplified Chaplygin model can be obtained from a joint analysis involving the latest SNe type Ia data and the recent Sloan Digital Sky Survey measurement of baryon acoustic oscillations (BAO). In our analysis we have considered separately the SNe type Ia gold sample measured by [A.G. Riess et al., Astrophys. J. 607 (2004) 665] and the supernova legacy survey (SNLS) from [P. Astier et al., Astron. Astrophys. 447 (2006) 31]. At 95.4% (c.l.), we find for BAO + gold sample, 0.91 ⩽ α ⩽ 1.0 and Ω M = 0.28 - 0.048 + 0.043 while BAO + SNLS analysis provides 0.94 ⩽ α ⩽ 1.0 and Ω M = 0.27 - 0.045 + 0.048 .

Constraining the dark energy and smoothness parameter with supernovae

The presence of inhomogeneities modifies the cosmic distances through the gravitational lensing effect, and, indirectly, must affect the main cosmological tests. Assuming that the dark energy is a smooth component, the simplest way to account for the influence of clustering is to suppose that the average evolution of the expanding Universe is governed by the total matter-energy density whereas the focusing of light is only affected by a fraction of the total matter density quantified by the $\ensuremath{\alpha}$ Dyer-Roeder parameter. By using two different samples of SNe type Ia data, the ${\ensuremath{\Omega}}_{m}$ and $\ensuremath{\alpha}$ parameters are constrained by applying the Zeldovich-Kantowski-Dyer-Roeder luminosity distance-redshift relation for a flat ($\ensuremath{\Lambda}\mathrm{CDM}$) model. A ${\ensuremath{\chi}}^{2}$-analysis using the 115 SNe Ia data of the Astier et al. sample (2006) constrains the density parameter to be ${\ensuremath{\Omega}}_{m}={0.26}_{\ensuremath{-}0.07}^{+0.17}$ ($2\ensuremath{\sigma}$) while the $\ensuremath{\alpha}$ parameter is weakly limited (all the values $\ensuremath{\in}[0,1]$ are allowed even at $1\ensuremath{\sigma}$). However, a similar analysis based the 182 SNe Ia data of Riess et al. (2007) constrains the pair of parameters to be ${\ensuremath{\Omega}}_{m}={0.33}_{\ensuremath{-}0.07}^{+0.09}$ and $\ensuremath{\alpha}\ensuremath{\ge}0.42$ ($2\ensuremath{\sigma}$). Basically, this occurs because the Riess et al. sample extends to appreciably higher redshifts. As a general result, even considering the existence of inhomogeneities as described by the smoothness $\ensuremath{\alpha}$ parameter, the Einstein-de Sitter model is ruled out by the two samples with a high degree of statistical confidence ($11.5\ensuremath{\sigma}$ and $9.9\ensuremath{\sigma}$, respectively). The inhomogeneous Hubble-Sandage diagram discussed here highlights the necessity of the dark energy, and a transition deceleration/accelerating phase at $z\ensuremath{\sim}0.5$ is also required.

Cosmological bounds on oscillating dark energy models

We study the cosmological constraints on the two purely phenomenological models of oscillating dark energy. In these oscillating models, the equation of state of dark energy varies periodically. The periodic equation of state may provide the natural way to unify the early acceleration (inflation) and the late time acceleration of the Universe. These models give the effective way to tackle the cosmic coincidence problem. We examine the observational constraints on the oscillatory models from the latest observational data including the gold sample of 182 SNe type Ia, the shift parameter, R, given by the WMAP and the BAO measurements from the SDSS.

The different faces of a phantom

The SNe type Ia data admit that the universe today may be dominated by some exotic matter with negative pressure violating all energy conditions. Such exotic matter is called phantom matter due to the anomalies connected with violation of the energy conditions. If a phantom matter dominates the matter content of the universe, it can develop a singularity in a finite future proper time. Here we show that, under certain conditions, the evolution of perturbations of this matter may lead to avoidance of this future singularity (the big rip). At the same time, we show that local concentrations of a phantom field may form, among other regular configurations, black holes with asymptotically flat static regions, separated by an event horizon from an expanding, singularity-free, asymptotically de Sitter universe.

NEW CONSTRAINTS ON THE VARIABLE EQUATION OF STATE PARAMETER FROM X-RAY GAS MASS FRACTIONS AND SNe Ia

Recent measurements are suggesting that we live in a flat Universe and that its present accelerating stage is driven by a dark energy component whose equation of state may evolve in time. Assuming two different parametrizations for the function ω(z), we constrain their free parameters from a joint analysis involving measurements from X-ray luminosity of galaxy clusters and SNe type Ia data.

Bayesian evidence as a tool for comparing datasets

We introduce a conservative test for quantifying the consistency of two or more datasets. The test is based on the Bayesian answer to the question, ''How much more probable is it that all my data were generated from the same model system than if each dataset were generated from an independent set of model parameters''. The behavior of the resulting odds ratio is demonstrated with a two-dimensional toy example. We make explicit the connection between evidence ratios and the differences in peak-chisquared values, the later of which is more widely used and more cheaply calculated. Calculating evidence ratios for three cosmological datasets (recent CMB data (WMAP, ACBAR, CBI, VSA), SDSS and the most recent SNe Type 1A data) we find that concordance is favored and the tightening of constraints on cosmological parameters is indeed justified.

Spectra of High-Redshift Type Ia Supernovae and a Comparison with Their Low-Redshift Counterparts

We present spectra for 14 high-redshift (0.17 < z < 0.83) supernovae, which were discovered by the Supernova Cosmology Project as part of a campaign to measure cosmological parameters. The spectra are used to determine the redshift and classify the supernova type, essential information if the supernovae are to be used for cosmological studies. Redshifts were derived either from the spectrum of the host galaxy or from the spectrum of the supernova itself. We present evidence that these supernovae are of Type Ia by matching to spectra of nearby supernovae. We find that the dates of the spectra relative to maximum light determined from this fitting process are consistent with the dates determined from the photometric light curves, and moreover the spectral time-sequence for SNe Type Ia at low and high redshift is indistinguishable. We also show that the expansion velocities measured from blueshifted CaHK are consistent with those measured for low-redshift Type Ia supernovae. From these first-level quantitative comparisons we find no evidence for evolution in SNIa properties between these low- and high-redshift samples. Thus even though our samples may not be complete, we conclude that there is a population of SNe Ia at high redshift whose spectral properties match those at low redshift.

Classifications of the Host Galaxies of Supernovae, Set III

ABSTRACTA homogeneous sample comprising host galaxies of 604 recent supernovae, including 212 objects discovered primarily in 2003 and 2004, has been classified on the David Dunlap Observatory system. Most SN 1991bg–like SNe Ia occur in E and E/Sa galaxies, whereas the majority of SN 1991T–like SNe Ia occur in intermediate‐type galaxies. This difference is significant at the 99.9% level. As expected, all types of SNe II are rare in early‐type galaxies, whereas normal SNe Ia occur in all Hubble types. This difference is significant at the 99.99% level. A small number of SNe II in E galaxies might be due to galaxy classification errors or to a small young‐population component in these mainly old objects. No significant difference is found between the distributions over the Hubble type of SNe Ibc and SNe II. This confirms that both of these types of objects have similar (massive) progenitors. The present data show that in order to understand the dependence of supernova type on host‐galaxy population, it is more important to obtain accurate morphological classifications than it is to increase the size of the data sample.

Roles of Supernova Ejecta in Nucleosynthesis of the Light Elements Li, Be, and B

Explosions of Type Ic supernovae (SNe Ic) are investigated using a relativistic hydrodynamic code to study the role of their outermost layers of the ejecta in light-element nucleosynthesis through spallation reactions as a possible mechanism of the ‘‘primary’’ process. We have confirmed that the energy distribution of the outermost layers with a mass fraction of only 0.001% follows the empirical formula proposed by previous work when the explosion is furious. In such explosions, a significant fraction of the ejecta (>0.1% in mass) have energy greater than the threshold energy for spallation reactions. On the other hand, we find that the outermost layers of ejecta become more energetic than the empirical formula would predict when the explosion energy per unit ejecta mass is smaller than � 1:3;10 51 ergs M � 1 � . As a consequence, it is necessary to numerically calculate explosions to estimate light-element yields from SNe Ic. The usage of the empirical formula would overestimate the yields by a factor of k3 for energetic explosions, such as SN 1998bw, and underestimate the yields by a similar factor for less energetic explosions, such as SN 1994I. The yields of the light elements Li, Be, and B (LiBeB) from SNe Ic are estimated by solving the transfer equation of cosmic rays originated from ejecta of SNe Ic and compared with observations. The abundance ratios Be/O and B/O produced by each of our SNe Ic models are consistent with those of metal-poor stars. The total amounts of these elements estimated from observations indicate that energetic SNe Ic, such as SN 1998bw, could be candidates for a production site of Be and B in the Galactic halo only when the fraction of this type out of all the SNe was more than a factor of 100 higher than the value estimated from current observational data. This primary mechanism would predict that there are stars significantly deficient in light elements that were formed from the interstellar medium not affected by SNe Ic. Since this has no support from current observations, other primary mechanisms, such as the light-element formation in superbubbles, are needed for other types of SNe. The observed abundance pattern of all elements including heavy elements in metal-poor stars suggests that these two mechanisms should have supplied similar amounts of Be and B. Our calculations show that SNe Ic can not produce an appreciable amount of Li. Subject heading gs: cosmic rays — nuclear reactions, nucleosynthesis, abundances — relativity — shock waves — supernovae: general

Identification of Type Ia Supernovae at Redshift 1.3 and Beyond with the Advanced Camera for Surveys on the Hubble Space Telescope

We present discoveries of SNe Ia at z > 1 and the photometric diagnostic used to discriminate them from other types of SNe detected during the GOODS Hubble Space Telescope Treasury program with the Advanced Camera for Surveys (ACS). Photometric redshift measurements of the hosts combined with deep f606w, f775w, and f850lp imaging discriminates hydrogen-rich SNe II from SNe I at z > 1 by exploiting the ultraviolet (UV) deficit in the energy distributions of SNe Ia. This sorting allows rapid follow-up of space-based discoveries. Subsequent spectroscopy of 11 GOODS SNe Ia obtained from the ground and with the grism on ACS confirmed the reliability of our photometric screening. We present the highest-redshift spectrum of any supernova published to date, SN Ia 2002fw at z = 1.3 observed near maximum brightness with the ACS grism. The lack of UV flux for true SNe Ia provides an effective tool for our ongoing efforts to build a sample of SNe Ia at 1.2 < z < 1.8 which will extend the useful range of the magnitude-redshift relation of SNe Ia.