3,391 research outputs found
Detection and classification of supernovae beyond z~2 redshift with the James Webb Space Telescope
Future time-domain surveys for transient events in the near- and mid-infrared
bands will significantly extend our understanding about the physics of the
early Universe. In this paper we study the implications of a deep (~27 mag),
long-term (~3 years), observationally inexpensive survey with the James Webb
Space Telescope (JWST) within its Continuous Viewing Zone, aimed at discovering
luminous supernovae beyond z~2 redshift. We explore the possibilities for
detecting Superluminous Supernovae (SLSNe) as well as Type Ia supernovae at
such high redshifts and estimate their expected numbers within a relatively
small (~0.1 deg^2) survey area. It is found that we can expect ~10 new SLSNe
and ~50 SNe Ia discovered in the 1 < z < 4 redshift range. We show that it is
possible to get relatively accurate (sigma_z < 0.25) photometric redshifts for
Type Ia SNe by fitting their Spectral Energy Distributions (SED), redshifted
into the observed near-IR bands, with SN templates. We propose that Type Ia SNe
occupy a relatively narrow range on the JWST F220W-F440W vs F150W-F356W
color-color diagram between +/- 7 rest-frame days around maximum light, which
could be a useful classification tool for such type of transients. We also
study the possibility of extending the Hubble-diagram of Type Ia SNe beyond
redshift 2 up to z~4. Such high-z SNe Ia may provide new observational
constraints for their progenitor scenario.Comment: accepted for publication in Ap
Gamma-ray probe of cosmic-ray pressure in galaxy clusters and cosmological implications
Cosmic rays produced in cluster accretion and merger shocks provide pressure
to the intracluster medium (ICM) and affect the mass estimates of galaxy
clusters. Although direct evidence for cosmic-ray ions in the ICM is still
lacking, they produce gamma-ray emission through the decay of neutral pions
produced in their collisions with ICM nucleons. We investigate the capability
of the Gamma-ray Large Area Space Telescope (GLAST) and imaging atmospheric
Cerenkov telescopes (IACTs) for constraining the cosmic-ray pressure
contribution to the ICM. We show that GLAST can be used to place stringent
upper limits, a few per cent for individual nearby rich clusters, on the ratio
of pressures of the cosmic rays and thermal gas. We further show that it is
possible to place tight (<~10%) constraints for distant (z <~ 0.25) clusters in
the case of hard spectrum, by stacking signals from samples of known clusters.
The GLAST limits could be made more precise with the constraint on the
cosmic-ray spectrum potentially provided by IACTs. Future gamma-ray
observations of clusters can constrain the evolution of cosmic-ray energy
density, which would have important implications for cosmological tests with
upcoming X-ray and Sunyaev-Zel'dovich effect cluster surveys.Comment: 12 pages, 5 figures; extended discussions; accepted by MNRA
HyperLEDA. III. The catalogue of extragalactic distances
We present the compilation catalogue of redshift-independent distances
included in the HyperLEDA database. It is actively maintained to be up-to-date,
and the current version counts 6640 distance measurements for 2335 galaxies
compiled from 430 published articles. Each individual series is recalibrated
onto a common distance scale based on a carefully selected set of high-quality
measurements. This information together with data on HI line-width, central
velocity dispersion, magnitudes, diameters, and redshift is used to derive a
homogeneous distance estimate and physical properties of galaxies, such as
their absolute magnitudes and intrinsic size.Comment: accepted to A&
Evolution of the solar irradiance during the Holocene
Aims. We present a physically consistent reconstruction of the total solar
irradiance for the Holocene. Methods. We extend the SATIRE models to estimate
the evolution of the total (and partly spectral) solar irradiance over the
Holocene. The basic assumption is that the variations of the solar irradiance
are due to the evolution of the dark and bright magnetic features on the solar
surface. The evolution of the decadally averaged magnetic flux is computed from
decadal values of cosmogenic isotope concentrations recorded in natural
archives employing a series of physics-based models connecting the processes
from the modulation of the cosmic ray flux in the heliosphere to their record
in natural archives. We then compute the total solar irradiance (TSI) as a
linear combination of the jth and jth + 1 decadal values of the open magnetic
flux. Results. Reconstructions of the TSI over the Holocene, each valid for a
di_erent paleomagnetic time series, are presented. Our analysis suggests that
major sources of uncertainty in the TSI in this model are the heritage of the
uncertainty of the TSI since 1610 reconstructed from sunspot data and the
uncertainty of the evolution of the Earth's magnetic dipole moment. The
analysis of the distribution functions of the reconstructed irradiance for the
last 3000 years indicates that the estimates based on the virtual axial dipole
moment are significantly lower at earlier times than the reconstructions based
on the virtual dipole moment. Conclusions. We present the first physics-based
reconstruction of the total solar irradiance over the Holocene, which will be
of interest for studies of climate change over the last 11500 years. The
reconstruction indicates that the decadally averaged total solar irradiance
ranges over approximately 1.5 W/m2 from grand maxima to grand minima
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