Cosmological Standard Candles Research Articles

Expected Changes of SNe with Redshift due to Evolution of Their Progenitors

SummaryWe have analyzed the influence of the stellar populations, from which SN progenitors come, on the observational outcome, including the metal free Pop. III. We use our models to study the evolution of the progenitor, the subsequent explosion and the light curves. For Type Ia, the variation of the main sequence mass of the progenitor of the exploding WD produces an offset in the maximum-decline relation of 0.2 mag. This effect is critical for the use of high redshift Type Ia SNe as cosmological standard candles. In contrast, the metallicity does not change the above relation (at maximum, ΔMV ≤0.06 mag). For Type II, we find a dependence of the light curve properties with both main sequence mass and metallicity of the progenitor, and we identify a rather homogeneous subclass, “Extreme II-P,” that may be used as a quasi-standard candle. Note that, although not as good as Type Ia for distance determinations, Type II are expected to have occurred since the first stars were formed.

Signature of Electron Capture in Iron‐rich Ejecta of SN 2003du

Late-time near-infrared and optical spectra of the normal-bright Type Ia supernova 2003du about 300 days after the explosion are presented. At this late epoch, the emission profiles of well-isolated [Fe II] lines (in particular that of the strong 1.644 μm feature) trace out the global kinematic distribution of radioactive material in the expanding supernova ejecta. In SN 2003du, the 1.644 μm [Fe II] line seems to show a flat-topped profile, indicative of a thick but hollow-centered expanding shell, rather than a strongly peaked profile that would be expected from a "center-filled" distribution. Based on detailed models for exploding Chandrasekhar-mass white dwarfs, we show that the feature is consistent with spherical explosion models. Our model predicts a central region of nonradioactive electron capture elements up to 2500-3000 km s-1 as a consequence of burning under high density and an extended region of radioactive 56Ni up to 9000-10,000 km s-1. Furthermore, our analysis indicates that the 1.644 μm [Fe II] line profile is not consistent with strong mixing between the regions of electron-capture isotopes and the 56Ni layers, as is predicted by detailed three-dimensional models for nuclear deflagration fronts. We discuss the possibility that the flat-topped profile could be produced as a result of an infrared catastrophe and conclude that such an explanation is unlikely. We discuss the limitations of our analysis and place our results into context by comparison with constraints on the distribution of radioactive 56Ni in other SNe Ia and briefly discuss the potential implications of our result for the use of SNe Ia as cosmological standard candles.

Cosmology with coalescing massive black holes

The gravitational waves generated in the coalescence of massive binary black holes will be measurable by LISA to enormous distances. Redshifts z ∼ 10 or larger (depending somewhat on the mass of the binary) can potentially be probed by such measurements, suggesting that binary coalescences can be made into cosmological tools. We discuss two particularly interesting types of probe. First, by combining gravitational-wave measurements with information about the cosmography of the universe, we can study the evolution of black-hole masses and merger rates as a function of redshift, providing information about the growth of structures at high redshift and possibly constraining hierarchical merger scenarios. Second, if it is possible to associate an ‘electromagnetic’ counterpart with a coalescence, it may be possible to measure both redshift and luminosity distance to an event with less than ∼1% error. Such a measurement would constitute an amazingly precise cosmological standard candle. Unfortunately, gravitational lensing uncertainties will reduce the quality of this candle significantly. Though not as amazing as might have been hoped, such a candle would nonetheless very usefully complement other distance-redshift probes, in particular providing a valuable check on systematic effects in such measurements.

The absolute magnitudes of Type IA supernovae

view Abstract Citations (1671) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Absolute Magnitudes of Type IA Supernovae Phillips, M. M. Abstract Absolute magnitudes in the B, V, and I bands are derived for nine well-observed Type Ia supernovae using host galaxy distances estimated via the surface brightness fluctuations or Tully-Fisher methods. These data indicate that there is a significant intrinsic dispersion in the absolute magnitudes at maximum light of Type Ia supernovae, amounting to +/- 0.8 mag in B, +/- 0.6 mag in V, and +/- 0.5 mag in I. Moreover, the absolute magnitudes appear to be tightly correlated with the initial rate of decline of the B light curve, with the slope of the correlation being steepest in B and becoming progressively flatter in the V and I bands. This implies that the intrinsic B - V colors of Type Ia supernovae at maximum light are not identical, with the fastest declining light curves corresponding to the intrinsically reddest events. Certain spectroscopic properties may also be correlated with the initial decline rate. These results are most simply interpreted as evidence for a range of progenitor masses, although variations in the explosion mechanism are also possible. Considerable care must be exercised in employing Type Ia supernovae as cosmological standard candles, particularly at large redshifts where Malmquist bias could be an important effect. Publication: The Astrophysical Journal Pub Date: August 1993 DOI: 10.1086/186970 Bibcode: 1993ApJ...413L.105P Keywords: Light Curve; Stellar Magnitude; Supernovae; White Dwarf Stars; Astronomical Photometry; Brightness Distribution; Stellar Luminosity; Astrophysics; COSMOLOGY: DISTANCE SCALE; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (18) NED (18)

SN 1984I---ANOTHER TYPE IB SUPERNOVA

ABSTRACT This object was discovered ~ 15 days before maximum light and was observed photometrically over a period of five weeks. A spectrum obtained near maximum shows that this supernova was a relatively distant Type-Ib event. Like other Type-Ib supernovae, 1984I was characterized by a red (B - V) color and low absolute magnitude at maximum. Comparison with preoutburst photographs shows that this supernova was located in an interarm region, approximately 1 kpc from the nearest bright H II region. It is important to be able to distinguish supernovae of this type from Ia events, considering the interest in using the latter objects as cosmological standard candles.

THE TYPE IA SUPERNOVA 1986G IN NGC 5128 : OPTICAL PHOTOMETRY AND SPECTRA.

ABSTRACT Optical light curves and spectra of the Type Ia supernova 1986G in NGC 5128 (Centaurus A) are presented. Although the spectral evolution closely resembled that of the more common "slower" photometric classes of Type Ia supernovae, subtle differences in the maximum-light spectra were detected. The expansion velocity of the photosphere of SN 1986G decreased rapidly at early phases. SN 1986G appears to have been heavily obscured by the dust lane of NGC 5128. This circumstances accounts for the strong interstellar-absorption lines of Ca II H and K and Na I D observed in the spectra as well as for features that the authors identify with the diffuse interstellar bands. SN 1986G provides graphic confirmation of the existence of intrinsic differences in the optical light curves and spectroscopic properties of Type Ia supernovae. Consequently, these objects must be used with considerable caution as cosmological standard candles. The authors derive a relative distance of DNGC 5128/DNGC 5055 = 0.39±0.04.