Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userRestframe I-band Hubble diagram for type Ia supernovae up to redshift z ~0.5
68
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We present a novel technique for fitting restframe I-band light curves on a data set of 42 Type Ia supernovae (SNe Ia). Using the result of the fit, we construct a Hubble diagram with 26 SNe from the subset at 0.01< z<0.1. Adding two SNe at z~0.5 yields results consistent with a flat Lambda-dominated``concordance universe ($Omega_M,Omega_Lambda$)=(0.25,0.75). For one of these, SN 2000fr, new near infrared data are presented. The high redshift supernova NIR data are also used to test for systematic effects in the use of SNe Ia as distance estimators. A flat, Lambda=0, universe where the faintness of supernovae at z~0.5 is due to grey dust homogeneously distributed in the intergalactic medium is disfavoured based on the high-z Hubble diagram using this small data-set. However, the uncertainties are large and no firm conclusion may be drawn. We explore the possibility of setting limits on intergalactic dust based on B-I and B-V colour measurements, and conclude that about 20 well measured SNe are needed to give statistically significant results. We also show that the high redshift restframe I-band data points are better fit by light curve templates that show a prominent second peak, suggesting that they are not intrinsically underluminous.
rate research
Read More
Aims: Spectroscopic observations of Type Ia supernovae obtained at the New Technology Telescope (NTT) and the Nordic Optical Telescope (NOT), in conjunction with the SDSS-II Supernova Survey, are analysed. We use spectral indicators measured up to a month after the lightcurve peak luminosity to characterise the supernova properties, and examine these for potential correlations with host galaxy type, lightcurve shape, colour excess, and redshift. Methods: Our analysis is based on 89 Type Ia supernovae at a redshift interval z = 0.05 - 0.3, for which multiband SDSS photometry is available. A lower-z spectroscopy reference sample was used for comparisons over cosmic time. We present measurements of time series of pseudo equivalent widths and line velocities of the main spectral features in Type Ia supernovae. Results: Supernovae with shallower features are found predominantly among the intrinsically brighter slow declining supernovae. We detect the strongest correlation between lightcurve stretch and the Si ii 4000 absorption feature, which also correlates with the estimated mass and star formation rate of the host galaxy. We also report a tentative correlation between colour excess and spectral properties. If confirmed, this would suggest that moderate reddening of Type Ia supernovae is dominated by effects in the explosion or its immediate environment, as opposed to extinction by interstellar dust.
The Carnegie Supernova Project-II (CSP-II) was an NSF-funded, four-year program to obtain optical and near-infrared observations of a Cosmology sample of $sim100$ Type Ia supernovae located in the smooth Hubble flow ($0.03 lesssim z lesssim 0.10$). Light curves were also obtained of a Physics sample composed of 90 nearby Type Ia supernovae at $z leq 0.04$ selected for near-infrared spectroscopic time-series observations. The primary emphasis of the CSP-II is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. In this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. In a companion paper, the near-infrared spectroscopy component of the project is presented.
We use the redshift-magnitude relation, as derived by Dc{a}browski (1995), for the two exact non-uniform pressure spherically symmetric Stephani universes with the observer positioned at the center of symmetry, to test the agreement of these models with recent observations of high redshift type Ia supernovae (SNIa), as reported in Perlmutter et al. (1997). By a particular choice of model parameters, we show that these models give an excellent fit to the observed redshifts and (corrected) B band apparent magnitudes of the SNIa data, but for an age of the Universe which is typically about two Gyr greater than in the corresponding Friedmann model. Based on a value of $H_0 sim 65$ and assuming $Lambda geq 0$, the P97 data implies a Friedmann age of at most 13 Gyr and in fact a best-fit (for $q_0 = 0.5$) age of only 10 Gyr. Our Stephani models, on the other hand, can give a good fit to the P97 data with an age of up to 15 Gyr and could, therefore, significantly alleviate the conflict between recent cosmological and astrophysical age predictions. The choice of model parameters is quite robust: one requires only that the non-uniform pressure parameter, $a$, in one of the models is negative and satisfies $|a| lte$ 3 km$^2$ s$^{-2}$ Mpc$^{-1}$. By allowing slightly larger, negative, values of $a$ one may `fine tune the model to give an even better fit to the P97 data.
We analyze 99 Type Ia supernovae (SNeIa) observed in $H$ band (1.6--1.8 $mu$m) and find that SNeIa are intrinsically brighter in $H$-band with increasing host galaxy stellar mass. We find that SNeIa in galaxies more massive than $10^{10.44} M_{odot}$ are brighter in $H$ than SNeIa in less massive galaxies by $0.18 pm 0.05$ mag. The same set of SNeIa observed at optical wavelengths, after width-color-luminosity corrections, exhibit a $0.17 pm 0.05$ mag offset in the Hubble residuals. Removing two significant outliers reduces the step in $H$ band to $0.10 pm 0.04$ mag but has no effect on the optical mass step size. An analysis based on information criteria supports a step function with a break at $10^{10.44}~M_{odot}$ over a constant model with and without outliers for NIR and optical residuals. Less massive galaxies preferentially host more higher-stretch SNeIa, which are intrinsically brighter and bluer. It is only after correction for width-luminosity and color-luminosity relationships that SNeIa have brighter optical Hubble residuals in more massive galaxies. Thus the finding that SNeIa are intrinsically brighter in $H$ in more massive galaxies is a significant and opposite correlation as the intrinsic optical brightness. If dust and the treatment of intrinsic color variation were the main driver of the host galaxy mass correlation, we would not expect a correlation of brighter $H$-band SNeIa in more massive galaxies. The correlation we find thus suggests that dust is not the main explanation of the observed correlation between Hubble residual and host galaxy stellar mass.
(Abridged) We present new results on the Hubble diagram of distant type Ia supernovae (SNe Ia) segregated according to the type of host galaxy. This makes it possible to check earlier evidence for a cosmological constant by explicitly comparing SNe residing in galaxies likely to contain negligible dust with the larger sample. The cosmological parameters derived from these SNe Ia hosted by presumed dust-free early-type galaxies supports earlier claims for a cosmological constant, which we demonstrate at 5 sigma significance, and the internal extinction implied is small even for late-type systems (A_B<0.2). Thus, our data demonstrate that host galaxy extinction is unlikely to systematically dim distant SNe Ia in a manner that would produce a spurious cosmological constant. We classify the host galaxies of 39 distant SNe discovered by the Supernova Cosmology Project (SCP) using the combination of HST STIS imaging, Keck ESI spectroscopy and ground-based broad-band photometry. We compare with a low-redshift sample of 25 SNe Ia. The scatter observed in the SNe Ia Hubble diagrams correlates closely with host galaxy morphology. We find the scatter in the SNe Ia Hubble diagram is smallest for SNe occurring in early-type hosts and largest for those occurring in late-type galaxies. Moreover, SNe residing in early-type hosts appear only ~0.14+/-0.09 mag brighter in their light-curve-width-corrected luminosity than those in late-type hosts, implying only a modest amount of dust extinction even in the late-type systems.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
