Paired galaxies with different activity levels and their supernovae

We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The statistical study of SN hosts shows that there is no significant difference between morphologies of hosts in our sample and the larger general sample of SN hosts in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.     

Distributions of supernovae of different types along the radius and in <Emphasis Type="Italic">z</Emphasis> coordinate of galaxies

The distributions of supernovae of different types and subtypes along the radius and in z coordinate of galaxies have been studied. We show that among the type Ia supernovae (SNe Ia) in spiral galaxies, SNe Iax and Ia-norm have, respectively, the largest and smallest concentration to the center; the distributions of SNe Ia-91bg and Ia-91T are similar. A strong concentration of SNe Ib/c to the central regions has been confirmed. In spiral galaxies, the supernovae of all types strongly concentrate to the galactic plane; the slight differences in scale height correlate with the extent to which the classes of supernovae are associated with star formation.     

A comparative study of type I and type II supernovae

Revised photometric data are used to compare the light and colour curves of type I and type II supernovae (SNe I, SNe II); their statistical properties are also compared. No significant difference between SNe I and SNe II has been found in their radial distribution and frequency of outbursts in spiral galaxies. The comparison of light and colour curves reveals several features common to both types and the possibility of transition between types.     

The influence of host galaxy morphology on the properties of Type Ia supernovae from the JLA compilation

The observational cosmology with distant Type Ia supernovae (SNe) as standard candles claims that the Universe is in accelerated expansion, caused by a large fraction of dark energy. In this paper we investigate the SN Ia environment, studying the impact of the nature of their host galaxies on the Hubble diagram fitting. The supernovae (192 SNe) used in the analysis were extracted from Joint-Light-curves-Analysis (JLA) compilation of high-redshift and nearby supernovae which is the best one to date. The analysis is based on the empirical fact that SN Ia luminosities depend on their light curve shapes and colors. We confirm that the stretch parameter of Type Ia supernovae is correlated with the host galaxy type. The supernovae with lower stretch are hosted mainly in elliptical and lenticular galaxies. No significant correlation between SN Ia colour and host morphology was found. We also examine how the luminosities of SNe Ia change depending on host galaxy morphology after stretch and colour corrections. Our results show that in old stellar populations and low dust environments, the supernovae are slightly fainter. SNe Ia in elliptical and lenticular galaxies have a higher α (slope in luminosity-stretch) and β (slope in luminosity-colour) parameter than in spirals. However, the observed shift is at the 1-σ uncertainty level and, therefore, can not be considered as significant. We confirm that the supernova properties depend on their environment and that the incorporation of a host galaxy term into the Hubble diagram fit is expected to be crucial for future cosmological analyses.     

Supernovae with ''super-Hipparcos''

GAIA is the 'super- Hipparcos ' satellite scheduled for launch in 2010 by the European Space Agency. It is a scanning satellite that carries out multi-colour, multi-epoch photometry on all objects brighter than 20th mag. We conduct detailed simulations of supernovae (SNe) detection by GAIA . Supernovae of each type are chosen according to the observed distributions of absolute magnitudes, and located in nearby galaxies according to the local large-scale structure. Using an extinction model of the Galaxy and the scanning law of the GAIA satellite, we calculate how many SNe are detectable as a function of the phase of the light curve. Our study shows that GAIA will report data on ∼21 400 SNe during the five-year mission lifetime, of which ∼14 300 are SNe Ia, ∼1400 are SNe Ib/c and ∼5700 are SNe II. Using the simulations, we estimate that the numbers caught before maximum are ∼6300 SNe Ia, ∼500 SNe Ib/c and ∼1700 SNe II. During the mission lifetime, GAIA will issue about 5 SNe alerts a day.
The most distant SNe accessible to GAIA are at a redshift   z ∼ 0.14  and so GAIA will provide a huge sample of local SNe. There will be many examples of the rarer subluminous events, over-luminous events, SNe Ib/c and SNe II-L. SNe rates will be found as a function of galaxy type, as well as extinction and position in the host galaxy. Amongst other applications, there may be about 26 SNe each year for which detection of gravitational waves is possible and about 180 SNe each year for which detection of gamma-rays is possible. GAIA 's astrometry will provide the SN position to better than milliarcseconds, offering opportunities for the identification of progenitors in nearby galaxies and for studying the spatial distribution of SNe of different types in galaxies.     

The statistical investigation of type Ib/c and II supernovae and their host galaxies

This is a statistical study of the properties of type Ib/c and II supernovae and of the integral parameters of their spiral host galaxies. The methods of one-dimensional and multivariate statistics were applied to the data sample. It was found that the Ib/c supernovae are more concentrated radially toward the centers of the galaxies than those of type II. The distributions of the radial distances R_SN/R₂₅ for the type Ib/c and II supernovae in active galaxies are more concentrated toward the center than in normal galaxies. This effect is stronger for type Ib/c than for type II supernovae. __________ Translated from Astrofizika, Vol. 51, No. 1, pp. 89–98 (February 2008).     

Ia超新星的几个问题

首先利用Ａｓｉａｇｏ 超新星星表对Ｉａ 超新星作了统计分析。其次用具有精确测光的Ｉａ 超新星对其均匀性及多样性进行了研究。旋涡星系中Ｉａ 超新星的产生率比椭圆星系的要高。最亮的Ｉａ 超新星只出现于晚型旋涡星系中;而旋涡星系及早型的椭圆星系都是暗Ｉａ 超新星的寄主星系。离星系中心越近Ｉａ 超新星的光度弥散有增加的趋势,但这一趋势对蓝Ｉａ 超新星不明显。利用色指数可将Ｉａ 超新星划分为蓝超新星及红超新星。蓝Ｉａ 超新星构成了相对均匀的Ｉａ 超新星样本,是较好的距离指示器;而红Ｉａ 超新星的存在则表明了Ｉａ 超新星整体多样性的特点。最后,我们还探讨了Ｉａ 超新星中碳点火的非线性问题。     

Extinction curves expected in young galaxies

We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). We adopt Nozawa et al. (2003) for compositions and size distribution of grains formed in SNe II and PISNe. We find that the extinction curve is quite sensitive to internal metal mixing in supernovae (SNe). The extinction curves predicted from the mixed SNe are dominated by SiO₂ and are characterized by a steep rise from infrared to ultraviolet (UV). The dust from unmixed SNe shows a shallower extinction curve, because of the contribution from large-sized (∼0.1 μm) Si grains. However, the progenitor mass is important in unmixed SNe II: if the progenitor mass is smaller than  ∼20 M_⊙  , the extinction curve is flat in UV; otherwise, the extinction curve rises towards the short wavelength. The extinction curve observed in a high-redshift quasar  ( z = 6.2)  favours the dust production by unmixed SNe II. We also provide some useful observational quantities, so that our model might be compared with future high- z extinction curves.     

The local properties of supernova explosions and their host galaxies

We aim to understand the properties at the locations of supernova(SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph(IFS) of Mapping Nearby Galaxies at Apache Point Observatory(MaNGA) to generate 2 D maps of the parameter properties for 11 SN host galaxies. The sample galaxies are analyzed one by one in detail in terms of their properties of velocity field, star formation rate, oxygen abundance, stellar mass, etc.This sample of SN host galaxies has redshifts around z~0.03, which is higher than those of previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity(gas-phase oxygen abundance) estimated from integrated spectra can represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies(12+log(O/H) 8.5) except for NGC 6387, which means SNe may be more inclined to explode in metallicity-rich galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SNe Ia and SNe II. In our sample, both SNe Ia and SNe II can explode in normal galaxies, but SNe II can also explode in an interacting or a merging system, in which star formation is occurring in the galaxy.     

How old are SN Ia progenitor systems? New observational constraints on the distribution of time delays from GALEX

The time delay between the formation of the progenitor systems of Type Ia supernovae (SNe Ia) and their detonation is a vital discriminant between the various progenitor scenarios that have been proposed for them. We use Sloan Digital Sky Survey optical and Galaxy Evolution Explorer ( GALEX ) ultraviolet observations of the early-type host galaxies of 21 nearby SNe Ia and quantify the presence or absence of any young stellar population to constrain the minimum time delay for each supernova. We find that early-type host galaxies lack 'prompt' SNe Ia with time delays of ≲100 Myr and that ∼70 per cent SNe Ia have minimum time delays of 275 Myr–1.25 Gyr, with a median of 650 Myr, while at least 20 per cent SNe Ia have minimum time delays of at least 1 Gyr at 95 per cent confidence and two of these four SNe Ia are likely older than 2 Gyr. The distribution of minimum time delays observed matches most closely the expectation for the single-degenerate channel with a main sequence donor. Furthermore, we do not find any evidence that subluminous SNe Ia are associated with long time delays.     

Extinction curves flattened by reverse shocks in supernovae

We investigate the extinction curves of young galaxies in which dust is supplied from Type II supernovae (SNe II) and/or pair instability supernovae (PISNe). Since at high redshift ( z > 5), low-mass stars cannot be dominant sources for dust grains, SNe II and PISNe, whose progenitors are massive stars with short lifetimes, should govern the dust production. Here, we theoretically investigate the extinction curves of dust produced by SNe II and PISNe, taking into account reverse shock destruction induced by collision with ambient interstellar medium. We find that the extinction curve is sensitive to the ambient gas density around a SN, since the efficiency of reverse shock destruction strongly depends on it. The destruction is particularly efficient for small-sized grains, leading to a flat extinction curve in the optical and ultraviolet wavelengths. Such a large ambient density as   n _H≳ 1 cm⁻³  produces too flat an extinction curve to be consistent with the observed extinction curve for SDSS J1048+4637 at z = 6.2. Although the extinction curve is highly sensitive to the ambient density, the hypothesis that the dust is predominantly formed by SNe at z ∼ 6 is still allowed by the current observational constraints. For further quantification, the ambient density should be obtained by some other methods. Finally, we also discuss the importance of our results for observations of high- z galaxies, stressing a possibility of flat extinction curves.     

Supernovae in isolated galaxies, in pairs and in groups of galaxies

In order to investigate the influence of environment on supernova (SN) production, we have performed a statistical investigation of the SNe discovered in isolated galaxies, in pairs and in groups of galaxies. 22 SNe in 18 isolated galaxies, 48 SNe in 40 galaxy members of 37 pairs and 211 SNe in 170 galaxy members of 116 groups have been selected and studied.
We found that the radial distributions of core-collapse SNe in galaxies located in different environments are similar, and consistent with those reported by Bartunov, Makarova & Tsvetkov . SNe discovered in pairs do not favour a particular direction with respect to the companion galaxy. Also, the azimuthal distributions inside the host members of galaxy groups are consistent with being isotropics. The fact that SNe are more frequent in the brighter components of the pairs and groups is expected from the dependence of the SN rates on the galaxy luminosity.
There is an indication that the SN rate is higher in galaxy pairs compared with that in groups. This can be related to the enhanced star formation rate in strongly interacting systems.
It is concluded that, with the possible exception of strongly interacting systems, the parent galaxy environment has no direct influence on SN production.     

The chemical evolution of dwarf spheroidal galaxies: dissecting the inner regions and their stellar populations

Using three-dimensional hydrodynamical simulations of isolated dwarf spheroidal galaxies (dSphs), we undertake an analysis of the chemical properties of their inner regions, identifying the respective roles played by Type Ia supernovae (SNe Ia) and Type II supernovae (SNe II). The effect of inhomogeneous pollution from SNe Ia is shown to be prominent within two core radii, with the stars forming therein amounting to ∼20 per cent of the total. These stars are relatively iron-rich and α-element depleted compared to the stars forming in the rest of the galaxy. At odds with the projected stellar velocity dispersion radial profile, the actual three-dimensional one shows a depression in the central region, where the most metal-rich (i.e. [Fe/H]-rich) stars are partly segregated. This naturally results in two different stellar populations, with an anticorrelation between [Fe/H] and velocity dispersion, in the same sense as that observed in the Sculptor and Fornax dSphs. Because the most iron-rich stars in our model are also the most α depleted, a natural prediction and test of our model is that the same radial segregation effects should exist between [α/Fe] and velocity dispersion.     

Binary population synthesis study of the supersoft X-ray phase of single degenerate type Ia supernova progenitors

In the single degenerate(SD) scenario for type Ia supernovae(SNe Ia) ,a mass-accreting white dwarf is expected to experience a supersoft X-ray source(SSS) phase. However,some recent observations showed that the expected number of massaccreting WDs is much lower than that predicted from theory,regardless of whether they are in spiral or elliptical galaxies. In this paper,we performed a binary population synthesis study on the relative duration of the SSS phase to their whole massincreasing phase of WDs leadi...     

The evolution of barium and europium in local dwarf spheroidal galaxies

By means of a detailed chemical evolution model, we follow the evolution of barium (Ba) and europium (Eu) in four Local Group Dwarf Spheroidal (dSph) galaxies, in order to set constraints on the nucleosynthesis of these elements and on the evolution of this type of galaxies compared with the Milky Way. The model, which is able to reproduce several observed abundance ratios and the present-day total mass and gas mass content of these galaxies, adopts up-to-date nucleosynthesis and takes into account the role played by supernovae (SNe) of different types (II, Ia) allowing us to follow in detail the evolution of several chemical elements (H, D, He, C, N, O, Mg, Si, S, Ca, Fe, Ba and Eu). By assuming that Ba is a neutron-capture element produced in low-mass asymptotic giant branch stars by s-process but also in massive stars (in the mass range 10–30 M_⊙) by r-process, during the explosive event of SNe of Type II, and that Eu is a pure r-process element synthesized in massive stars also in the range of masses 10–30 M_⊙, we are able to reproduce the observed [Ba/Fe] and [Eu/Fe] as functions of [Fe/H] in all four galaxies studied. We confirm also the important role played by the very low star formation (SF) efficiencies (ν= 0.005–0.5 Gyr⁻¹) and by the intense galactic winds (6–13 times the star formation rate) in the evolution of these galaxies. These low SF efficiencies (compared to the one for the Milky Way disc) adopted for the dSph galaxies are the main reason for the differences between the trends of [Ba/Fe] and [Eu/Fe] predicted and observed in these galaxies and in the metal-poor stars of our Galaxy. Finally, we provide predictions for Sagittarius galaxy for which data of only two stars are available.     

Analysis of the spatial distribution of gamma-ray bursts in their host galaxies

We compare the radial distributions of known localized gamma-ray bursts (GRBs) relative to the centers of their host galaxies with the distributions of known objects in nearby galaxies (supernovae of various types, X-ray binaries), the hypothetical dark-matter profiles, and the distribution of luminous matter in galaxies in the model of an exponential disk. By comparing the moments of empirical distributions, we show that the radial distribution of GRBs in galaxies differs significantly from that of other sources. We suggest a new statistical method for comparing empirical samples that is based on estimating the number of objects within a given radius. The exponential disk profile was found to be in best agreement with the radial distribution of GRBs. The distribution of GRBs relative to the centers of their host galaxies also agrees with the dark matter profile at certain model parameters.     

The SAI catalog of supernovae and radial distributions of supernovae of various types in galaxies

We describe the Sternberg Astronomical Institute (SAI) catalog of supernovae. We show that the radial distributions of type-Ia, type-Ibc, and type-II supernovae differ in the central parts of spiral galaxies and are similar in their outer regions, while the radial distribution of type-Ia supernovae in elliptical galaxies differs from that in spiral and lenticular galaxies. We give a list of the supernovae that are farthest from the galactic centers, estimate their relative explosion rate, and discuss their possible origins.     

Chemical and dynamical evolution of spiral galaxies

We present the very first results of a new 3D numerical model for the formation and evolution of spiral galaxies along the Hubble sequence. We take into account the hydrodynamical properties of the gas with an SPH method while we use a tree code for the gravitational forces of the dark matter and stars. The chemical evolution is also fully included, with both SNe Ia and SNe II explosions being followed, and this will allows us to predict abundances of various chemical species, abundance ratios and their radial distributions. This revised version was published online in September 2006 with corrections to the Cover Date.     

Spectral and photometric monitoring of distant core-collapse supernovae in the SAO RAS

This paper describes the aims, objectives and first results of the observational program for the study of distant core-collapse supernovae (SNe) with redshifts z ≲ 0.3. This work is done within the framework of an international cooperation program on the SNe monitoring at the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, and other telescopes. We study both the early phases of events (SN type determination, redshift estimation, and a search for manifestations of a wind envelope), and the nebular phase (the effects of explosion asymmetry). The SNe, associated with cosmic gamma-ray bursts are of particular interest. An interpretation of our observational data along with the data obtained on other telescopes is used to test the existing theoretical models of both the SN explosion, and the surrounding circumstellar medium. In 2009 we observed 30 objects; the spectra were obtained for 12 of them. We determined the types, phases after maximum, and redshifts for five SNe (SN 2009db, SN 2009dy, SN 2009dw, SN 2009ew, SN 2009ji). Based on the obtained photometric data a discovery of two more SNe was confirmed (SN 2009bx and SN 2009cb). A study of two type II supernovae in the nebular phase (SN 2008gz and SN 2008in) is finalized, four more objects (SN 2008iy, SN 2009ay, SN 2009bw, SN 2009de) are currently monitored.     

The cooling time of white dwarfs produced from type Iasupernovae

Type Ia supernovae (SNe Ia) play a key role in measuring cosmological pa- rameters, in which the Phillips relation is adopted. However, the origin of the relation is still unclear. Several parameters are suggested, e.g. the relative content of carbon to oxygen (C/O) and the central density of the white dwarf (WD) at ignition. These parameters are mainly determined by the WD's initial mass and its cooling time, respectively. Using the progenitor model developed by Meng Yang, we present the distributions of the initial WD mass and the cooling time. We do not find any correlation between these parameters. However, we notice that as the range of the WD's mass decreases, its average value increases with the cooling time. These results could provide a constraint when simulating the SN Ia explosion, i.e. the WDs with a high C/O ratio usually have a lower central density at ignition, while those having the highest central density at ignition generally have a lower C/O ratio. The cooling time is mainly determined by the evolutionary age of secondaries, and the scatter of the cooling time decreases with the evolutionary age. Our results may indicate that WDs with a long cooling time have more uniform properties than those with a short cooling time, which may be helpful to explain why SNe Ia in elliptical galaxies have a more uniform maximum luminosity than those in spiral galaxies.