7 research outputs found
Studying type II supernovae as cosmological standard candles using the Dark Energy Survey
Despite vast improvements in the measurement of the cosmological parameters,
the nature of dark energy and an accurate value of the Hubble constant (H)
in the Hubble-Lema\^itre law remain unknown. To break the current impasse, it
is necessary to develop as many independent techniques as possible, such as the
use of Type II supernovae (SNe II). The goal of this paper is to demonstrate
the utility of SNe II for deriving accurate extragalactic distances, which will
be an asset for the next generation of telescopes where more-distant SNe II
will be discovered. More specifically, we present a sample from the Dark Energy
Survey Supernova Program (DES-SN) consisting of 15 SNe II with photometric and
spectroscopic information spanning a redshift range up to 0.35. Combining our
DES SNe with publicly available samples, and using the standard candle method
(SCM), we construct the largest available Hubble diagram with SNe II in the
Hubble flow (70 SNe II) and find an observed dispersion of 0.27 mag. We
demonstrate that adding a colour term to the SN II standardisation does not
reduce the scatter in the Hubble diagram. Although SNe II are viable as
distance indicators, this work points out important issues for improving their
utility as independent extragalactic beacons: find new correlations, define a
more standard subclass of SNe II, construct new SN II templates, and dedicate
more observing time to high-redshift SNe II. Finally, for the first time, we
perform simulations to estimate the redshift-dependent distance-modulus bias
due to selection effects.Comment: 39 pages, 22 figures, 10 tables, Accepted for publication in MNRA
The SAMI Galaxy Survey : data release one with emission-line physics value-added products
SAMI DR1 data products available from http://datacentral.aao.gov.au/asvo/surveys/sami/We present the first major release of data from the SAMI Galaxy Survey. This data release focuses on the emission-line physics of galaxies. Data Release One includes data for 772 galaxies, about 20% of the full survey. Galaxies included have the redshift range 0.004 < z < 0.092, a large massrange (7.6 < log M∗/M⊙ < 11.6), and star-formation rates of ∼10−4 to ∼101 M⊙yr−1. For each galaxy, we include two spectral cubes and a set of spatially resolved 2D maps: single- and multi-component emission-line fits (with dust extinction corrections for strong lines), local dust extinction and star-formation rate. Calibration of the fibre throughputs, fluxes and differential-atmospheric-refraction has been improved over the Early Data Release. The data have average spatial resolution of 2.16 arcsec (FWHM) over the 15 arcsec diameter field of view and spectral (kinematic) resolution R= 4263 (σ= 30 km s−1) around Hα. The relative flux calibration is better than 5% and absolute flux calibration better than ±0.22 mag, with the latter estimate limited by galaxy photometry. The data are presented online through the Australian Astronomical Observatory’s Data Central.Publisher PDFPeer reviewe