24 research outputs found
Perceptions towards Risks involved in Off-site Construction in the Integrated Design & Construction Project Delivery
The impact of thermal imaging on users' perception of energy consumption: The round hill project
The Role of Type Ia Supernovae in Chemical Evolution I: Lifetime of Type Ia Supernovae and Galactic Supernova Rates
We construct a new model of Type Ia Supernovae (SNe Ia), based on the single
degenerate scenario, taking account of the metallicity dependences of the white
dwarf (WD) wind and the mass-stripping effect on the binary companion star. Our
model naturally predicts that the SN Ia lifetime distribution spans a range of
0.1-20 Gyr with the double peaks at ~0.1 and 1 Gyr. While the present SN Ia
rate in elliptical galaxies can be reproduced with the old population of the
red-giants+WD systems, the large SN Ia rate in radio galaxies could be
explained with the young population of the main-sequence+WD systems. Because of
the metallicity effect, i.e., because of the lack of winds from WDs in the
binary systems, the SN Ia rate in the systems with [Fe/H]<-1, e.g., high-z
spiral galaxies, is supposed to be very small. Our SN Ia model can give better
reproduction of the [(alpha, Mn, Zn)/Fe]-[Fe/H] relations in the solar
neighborhood than other models such as the double-degenerate scenario. The
metallicity effect is more strongly required in the presence of the young
population of SNe Ia. We also succeed in reproducing the galactic supernova
rates with their dependence on the morphological type of galaxies, and the
cosmic SN Ia rate history with a peak at z~1. At z>1, the predicted SN Ia rate
decreases toward higher redshifts and SNe Ia will be observed only in the
systems that have evolved with a short timescale of chemical enrichment. This
suggests that the evolution effect in the supernova cosmology can be small.Comment: 56 pages, 20 figures, accepted to Ap
Supernova rates from the Southern inTermediate Redshift ESO Supernova Search (STRESS)
To measure the supernova (SN) rates at intermediate redshift we performed the
Southern inTermediate Redshift ESO Supernova Search (STRESS). Unlike most of
the current high redshift SN searches, this survey was specifically designed to
estimate the rate for both type Ia and core collapse (CC) SNe. We counted the
SNe discovered in a selected galaxy sample measuring SN rate per unit blue band
luminosity. Our analysis is based on a sample of ~43000 galaxies and on 25
spectroscopically confirmed SNe plus 64 selected SN candidates. Our approach is
aimed at obtaining a direct comparison of the high redshift and local rates and
at investigating the dependence of the rates on specific galaxy properties,
most notably their colour. The type Ia SN rate, at mean redshift z=0.3, amounts
to 0.22^{+0.10+0.16}_{-0.08 -0.14} h_{70}^2 SNu, while the CC SN rate, at
z=0.21, is 0.82^{+0.31 +0.30}_{-0.24 -0.26} h_{70}^2 SNu. The quoted errors are
the statistical and systematic uncertainties. With respect to local value, the
CC SN rate at z=0.2 is higher by a factor of ~2 already at redshift, whereas
the type Ia SN rate remains almost constant. This implies that a significant
fraction of SN Ia progenitors has a lifetime longer than 2-3 Gyr. We also
measured the SN rates in the red and blue galaxies and found that the SN Ia
rate seems to be constant in galaxies of different colour, whereas the CC SN
rate seems to peak in blue galaxies, as in the local Universe. SN rates per
unit volume were found to be consistent with other measurements showing a
steeper evolution with redshift for CC SNe with respect to SNe Ia. Finally we
have exploited the link between star formation (SF) and SN rates to predict the
evolutionary behaviour of the SN rates and compare it with the path indicated
by observations.Comment: Accepted for publication in A&A; 25 pages (including on line
material), 13 figure