Type II Supernovae: Model Light Curves and Standard Candle Relationships

A survey of Type II supernovae explosion models has been carried out to determine how their light curves and spectra vary with their mass, metallicity, and explosion energy. The presupernova models are taken from a recent survey of massive stellar evolution at solar metallicity supplemented by new calculations at subsolar metallicity. Explosions are simulated by the motion of a piston near the edge of the iron core and the resulting light curves and spectra are calculated using full multi-wavelength radiation transport. Formulae are developed that describe approximately how the model observables (light curve luminosity and duration) scale with the progenitor mass, explosion energy, and radioactive nucleosynthesis. Comparison with observational data shows that the explosion energy of typical supernovae (as measured by kinetic energy at infinity) varies by nearly an order of magnitude -- from 0.5 to 4.0 x 10^51 ergs, with a typical value of ~0.9 x 10^51 ergs. Despite the large variation, the models exhibit a tight relationship between luminosity and expansion velocity, similar to that previously employed empirically to make SNe IIP standardized candles. This relation is explained by the simple behavior of hydrogen recombination in the supernova envelope, but we find a sensitivity to progenitor metallicity and mass that could lead to systematic errors. Additional correlations between light curve luminosity, duration, and color might enable the use of SNe IIP to obtain distances accurate to ~20% using only photometric data.Comment: 12 pages, ApJ in pres

Results from the High-Z Supernova Search Team

We review the use of Type Ia supernovae for cosmological distance determinations. Low-redshift SNe Ia ($z \lesssim 0.1$) demonstrate that (a) the Hubble expansion is linear, (b) $H_0 = 65 \pm 2$ (statistical) km s$^{-1}$ Mpc$^{-1}$, (c) the bulk motion of the Local Group is consistent with the COBE result, and (d) the properties of dust in other galaxies are similar to those of dust in the Milky Way. We find that the light curves of high-redshift SNe Ia are stretched in a manner consistent with the expansion of space; similarly, their spectra exhibit slower temporal evolution (by a factor of $1 + z$) than those of nearby SNe Ia. The luminosity distances of our 16 high-redshift SNe Ia are, on average, 10--15% farther than expected in a low mass-density ($\Omega_M=0.2$) universe without a cosmological constant. Our analysis strongly supports eternally expanding models with positive cosmological constant and a current acceleration of the expansion. We address many potential sources of systematic error; at present, none of them reconciles the data with $\Omega_\Lambda=0$ and $q_0 \geq 0$. The dynamical age of the Universe is estimated to be $14.2 \pm 1.7$ Gyr, consistent with the ages of globular star clusters.Comment: 17 pages, latex, plus 2 figures, to appear in the Proceedings of the 3rd International Symposium on Sources and Detection of Dark Matter in the Universe (DM98), Feb. 1998, ed. D. Clin

Do the photometric colors of Type II-P Supernovae allow accurate determination of host galaxy extinction?

We present infrared photometry of SN 1999em, plus optical photometry, infrared photometry, and optical spectroscopy of SN 2003hn. Both objects were Type II-P supernovae. The V-[RIJHK] color curves of these supernovae evolved in a very similar fashion until the end of plateau phase. This allows us to determine how much more extinction the light of SN 2003hn suffered compared to SN 1999em. Since we have an estimate of the total extinction suffered by SN 1999em from model fits of ground-based and space-based spectra as well as photometry of SN 1999em, we can estimate the total extinction and absolute magnitudes of SN 2003hn with reasonable accuracy. Since the host galaxy of SN 2003hn also produced the Type Ia SN 2001el, we can directly compare the absolute magnitudes of these two SNe of different types.Comment: 24 pages, 6 figure

La cultura digital en la formación de diseñadores

La sociedad de la información pone en jaque el modelo clásico, más aún en una profesión como el diseño, donde el papel de la técnica es muy grande. Si a esto sumamos la brecha generacional que esta revolución tecnológica ha producido, tendremos al menos dos componentes de tensión en el desarrollo del curriculum

Properties of SN-host galaxies

It is of prime importance to recognize evolution and extinction effects in supernovae results as a function of redshift, for SN Ia to be considered as distance indicators. This review surveys all observational data searching for an evolution and/or extinction, according to host morphology. For instance, it has been observed that high-z SNe Ia have bluer colours than the local ones: although this goes against extinction to explain why SN are dimmer with redshift until z ~ 1, supporting a decelerating universe, it also demonstrates intrinsic evolution effects. -- SNe Ia could evolve because the age and metallicity of their progenitors evolve. The main parameter is carbon abundance. Smaller C leads to a dimmer SN Ia and also less scatter on peak brightness, as it is the case in elliptical galaxy today. Age of the progenitor is an important factor: young populations lead to brighter SNe Ia, as in spiral galaxies, and a spread in ages lead to a larger scatter, explaining the observed lower scatter at high z. -- Selection biases also play a role, like the Malmquist bias; high-z SNe Ia are found at larger distance from their host center: there is more obscuration in the center, and also detection is easier with no contamination from the center. This might be one of the reason why less obscuration has been found for SNe Ia at high z. -- There is clearly a sample evolution with z: currently only the less bright SNe Ia are detected at high z, with less scatter. The brightest objects have a slowly declining light-curve, and at high z, no slow decline has been observed. This may be interpreted as an age effect, high-z SN having younger progenitors.Comment: 10 pages, 5 figures, review paper in "Supernovae and dust" (Paris, May 2003), to be published by New Astronomy Review