142 research outputs found
Supernova Siblings: Assessing the Consistency of Properties of Type Ia Supernovae that Share the Same Parent Galaxies
While many studies have shown a correlation between properties of the light curves of SNe Ia and properties of their host galaxies, it remains unclear what is driving these correlations. We introduce a new direct method to study these correlations by analyzing "parent" galaxies that host multiple SNe Ia "siblings." Here, we search the Dark Energy Survey SN sample, one of the largest samples of discovered SNe, and find eight galaxies that hosted two likely SNe Ia. Comparing the light-curve properties of these SNe and recovered distances from the light curves, we find no better agreement between properties of SNe in the same galaxy as any random pair of galaxies, with the exception of the SN light-curve stretch. We show at 2.8σ significance that at least one-half of the intrinsic scatter of SNe Ia distance modulus residuals is not from common host properties. We also discuss the robustness with which we could make this evaluation with LSST, which will find 100x more pairs of galaxies, and pave a new line of study on the consistency of SNe Ia in the same parent galaxies. Finally, we argue that it is unlikely that some of these SNe are actually single, lensed SN with multiple images.D.S. is supported by DOE grant DE-SC0010007, the David
and Lucile Packard Foundation. D.S. and R.K. are supported in
part by NASA under Contract No. NNG17PX03C issued
through the WFIRST Science Investigation Teams Programme.
D.B. and M.S. were supported by DOE grant DE-FOA0001358 and NSF grant AST-1517742. L.G. was funded by the
European Union’s Horizon 2020 research and innovation
programme under the Marie Skłodowska-Curie grant agreement No. 839090. This research used resources of the National
Energy Research Scientific Computing Center (NERSC), a
DOE Office of Science User Facility supported by the Office of
Science of the U.S. Department of Energy under Contract No.
DE-AC02-05CH11231. We are grateful for the support of the
University of Chicago Research Computing Center for
assistance with the calculations carried out in this work. R.F.
is supported in part by NSF grants AST-1518052 and AST1815935, the Gordon & Betty Moore Foundation, the HeisingSimons Foundation, and by fellowships from the David and
Lucile Packard Foundation, as well as the NASA contract
above. Funding for the DES Projects has been provided by the U.S.
Department of Energy, the U.S. National Science Foundation,
the Ministry of Science and Education of Spain, the Science
and Technology Facilities Council of the United Kingdom, the
Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of
Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for
Cosmology and Astro-Particle Physics at the Ohio State
University, the Mitchell Institute for Fundamental Physics
and Astronomy at Texas A&M University, Financiadora de
Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo
à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de
Desenvolvimento CientÃfico e Tecnológico and the Ministério
da Ciência, Tecnologia e Inovação, the Deutsche Forschungsgemeinschaft and the Collaborating Institutions in the Dark
Energy Survey. ...We acknowledge support from the Australian
Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020,
and the Brazilian Instituto Nacional de Ciência e Tecnologia
(INCT) e-Universe (CNPq grant 465376/2014-2). We
acknowledge support from EU/FP7-ERC grant No. 615929
Steve: A Hierarchical Bayesian Model for Supernova Cosmology
We present a new Bayesian hierarchical model (BHM) named Steve for performing Type Ia supernova (SN Ia) cosmology fits. This advances previous works by including an improved treatment of Malmquist bias, accounting for additional sources of systematic uncertainty, and increasing numerical efficiency. Given light-curve fit parameters, redshifts, and host-galaxy masses, we fit Steve simultaneously for parameters describing cosmology, SN Ia populations, and systematic uncertainties. Selection effects are characterized using Monte Carlo simulations. We demonstrate its implementation by fitting realizations of SN Ia data sets where the SN Ia model closely follows that used in Steve. Next, we validate on more realistic SNANA simulations of SN Ia samples from the Dark Energy Survey and low-redshift surveys (DES Collaboration et al. 2018). These simulated data sets contain more than 60,000 SNe Ia, which we use to evaluate biases in the recovery of cosmological parameters, specifically the equation of state of dark energy, w. This is the most rigorous test of a BHM method applied to SN Ia cosmology fitting and reveals small w biases that depend on the simulated SN Ia properties, in particular the intrinsic SN Ia scatter model. This w bias is less than 0.03 on average, less than half the statistical uncertainty on w. These simulation test results are a concern for BHM cosmology fitting applications on large upcoming surveys; therefore, future development will focus on minimizing the sensitivity of Steve to the SN Ia intrinsic scatter model.The DES data management system is supported by the
National Science Foundation under grant Nos. AST-1138766
and AST-1536171. The DES participants from Spanish
institutions are partially supported by MINECO under grants
AYA2015-71825, ESP2015-66861, FPA2015-68048, SEV2016-0588, SEV-2016-0597, and MDM-2015-0509, some of
which include ERDF funds from the European Union. IFAE is
partially funded by the CERCA program of the Generalitat de
Catalunya. Research leading to these results has received
funding from the European Research Council under the
European Union’s Seventh Framework Program (FP7/2007-
2013), including ERC grant agreements 240672, 291329, and
306478. We acknowledge support from the Australian
Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO) through project No. CE110001020 and
the Brazilian Instituto Nacional de Ciência e Tecnologia
(INCT) e-Universe (CNPq grant 465376/2014-2).
This manuscript has been authored by the Fermi Research
Alliance, LLC, under contract No. DE-AC02-07CH11359 with
the U.S. Department of Energy, Office of Science, Office of
High Energy Physics. The United States Government retains
and the publisher, by accepting the article for publication,
acknowledges that the United States Government retains a
nonexclusive, paid-up, irrevocable, worldwide license to
publish or reproduce the published form of this manuscript,
or allow others to do so, for United States Government
purpose
The 2-degree Field Lensing Survey: design and clustering measurements
We present the 2-degree Field Lensing Survey (2dFLenS), a new galaxy redshift survey performed at the Anglo-Australian Telescope. 2dFLenS is the first wide-area spectroscopic survey specifically targeting the area mapped by deep-imaging gravitational lensing fields, in this case the Kilo-Degree Survey. 2dFLenS obtained 70 079 redshifts in the range z < 0.9 over an area of 731 deg2, and is designed to extend the data sets available for testing gravitational physics and promote the development of relevant algorithms for joint imaging and spectroscopic analysis. The redshift sample consists first of 40 531 Luminous Red Galaxies (LRGs), which enable analyses of galaxy–galaxy lensing, redshift-space distortion, and the overlapping source redshift distribution by cross-correlation. An additional 28 269 redshifts form a magnitude-limited (r < 19.5) nearly complete subsample, allowing direct source classification and photometric-redshift calibration. In this paper, we describe the motivation, target selection, spectroscopic observations, and clustering analysis of 2dFLenS. We use power spectrum multipole measurements to fit the redshift-space distortion parameter of the LRG sample in two redshift ranges 0.15 < z < 0.43 and 0.43 < z < 0.7 as β = 0.49 ± 0.15 and β = 0.26 ± 0.09, respectively. These values are consistent with those obtained from LRGs in the Baryon Oscillation Spectroscopic Survey. 2dFLenS data products will be released via our website http://2dflens.swin.edu.au
Diverse Durham collection phages demonstrate complex BREX defence responses
Bacteriophages (phages) outnumber bacteria ten-to-one and cause infections at a rate of 1025 per second. The ability of phages to reduce bacterial populations makes them attractive alternative antibacterials for use in combating the rise in antimicrobial resistance. This effort may be hindered due to bacterial defenses such as Bacteriophage Exclusion (BREX) that have arisen from the constant evolutionary battle between bacteria and phages. For phages to be widely accepted as therapeutics in Western medicine, more must be understood about bacteria–phage interactions and the outcomes of bacterial phage defense. Here, we present the annotated genomes of 12 novel bacteriophage species isolated from water sources in Durham, UK, during undergraduate practical classes. The collection includes diverse species from across known phylogenetic groups. Comparative analyses of two novel phages from the collection suggest they may be founding members of a new genus. Using this Durham phage collection, we determined that particular BREX defense systems were likely to confer a varied degree of resistance against an invading phage. We concluded that the number of BREX target motifs encoded in the phage genome was not proportional to the degree of susceptibility
First cosmology results using Type IA supernovae from the dark energy survey: Effects of chromatic corrections to supernova photometry on measurements of cosmological parameters
Calibration uncertainties have been the leading systematic uncertainty in recent analyses
using Type Ia supernovae (SNe Ia) to measure cosmological parameters. To improve the
calibration, we present the application of spectral energy distribution-dependent ‘chromatic
corrections’ to the SN light-curve photometry from the Dark Energy Survey (DES). These
corrections depend on the combined atmospheric and instrumental transmission function for
each exposure, and they affect photometry at the 0.01 mag (1 per cent) level, comparable to
systematic uncertainties in calibration and photometry. Fitting our combined DES and lowz SN Ia sample with baryon acoustic oscillation (BAO) and cosmic microwave background
(CMB) priors for the cosmological parameters m (the fraction of the critical density of
the universe comprised of matter) and w (the dark energy equation of state parameter), we
compare those parameters before and after applying the corrections. We find the change in w
and m due to not including chromatic corrections is −0.002 and 0.000, respectively, for the
DES-SN3YR sample with BAO and CMB priors, consistent with a larger DES-SN3YR-like
simulation, which has a w-change of 0.0005 with an uncertainty of 0.008 and an m change of
0.000 with an uncertainty of 0.002. However, when considering samples on individual CCDs
we find large redshift-dependent biases (∼0.02 in distance modulus) for SN distances.Funding for the DES Projects has been provided by the U.S.
Department of Energy, the U.S. National Science Foundation,
the Ministry of Science and Education of Spain, the Science
and Technology Facilities Council of the United Kingdom, the
Higher Education Funding Council for England, the National Center
for Supercomputing Applications at the University of Illinois at
Urbana-Champaign, the Kavli Institute of Cosmological Physics
at the University of Chicago, the Center for Cosmology and
Astro-Particle Physics at the Ohio State University, the Mitchell
Institute for Fundamental Physics and Astronomy at Texas A&M
University, Financiadora de Estudos e Projetos, Fundac¸ao Carlos ˜
Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro, `
Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnologico ´
and the Ministerio da Ci ´ encia, Tecnologia e Inovac ˆ ¸ao, the Deutsche ˜
Forschungsgemeinschaft and the Collaborating Institutions in the
Dark Energy Survey...We acknowledge support from the
Australian Research Council Centre of Excellence for All-sky
Astrophysics (CAASTRO), through project number CE110001020,
and the Brazilian Instituto Nacional de Ciencia e Tecnologia (INCT) ˆ
e-Universe (CNPq grant 465376/2014-2)
First cosmological results using Type Ia supernovae from the Dark Energy Survey: measurement of the Hubble constant
We present an improved measurement of the Hubble constant (H0) using the ‘inverse distance
ladder’ method, which adds the information from 207 Type Ia supernovae (SNe Ia) from the
Dark Energy Survey (DES) at redshift 0.018 <z< 0.85 to existing distance measurements of
122 low-redshift (z < 0.07) SNe Ia (Low-z) and measurements of Baryon Acoustic Oscillations
(BAOs). Whereas traditional measurements of H0 with SNe Ia use a distance ladder of parallax
and Cepheid variable stars, the inverse distance ladder relies on absolute distance measurements
from the BAOs to calibrate the intrinsic magnitude of the SNe Ia. We find H0 = 67.8 ± 1.3 km
s−1 Mpc−1 (statistical and systematic uncertainties, 68 per cent confidence). Our measurement
makes minimal assumptions about the underlying cosmological model, and our analysis was
blinded to reduce confirmation bias. We examine possible systematic uncertainties and all are below the statistical uncertainties. Our H0 value is consistent with estimates derived from the
Cosmic Microwave Background assuming a CDM universeThe DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766
and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-
71825, ESP2015-66861, FPA2015-68048, SEV-2016-0588, SEV2016-0597, and MDM-2015-0509, some of which include ERDF
funds from the European Union. IFAE is partially funded by the
CERCA program of the Generalitat de Catalunya. Research leading
to these results has received funding from the European Research
Council under the European Union’s Seventh Framework Program
(FP7/2007-2013) including ERC grant agreements 240672, 291329,
and 306478. We acknowledge support from the Australian Research
Council Centre of Excellence for All-sky Astrophysics (CAASTRO), through project number CE110001020, and the Brazilian
Instituto Nacional de Ciencia e Tecnologia (INCT) e-Universe ˆ
(CNPq grant 465376/2014-2)
First cosmology results using type Ia supernovae from the Dark Energy Survey: the effect of host galaxy properties on supernova luminosity
We present improved photometric measurements for the host galaxies of 206 spectroscopically confirmed type Ia supernovae discovered by the Dark Energy Survey Supernova Program (DES-SN) and used in the first DES-SN cosmological analysis. For the DES-SN sample, when considering a 5D (z, x1, c, α, β) bias correction, we find evidence of a Hubble residual 'mass step', where SNe Ia in high-mass galaxies (>1010M⊙) are intrinsically more luminous (after correction) than their low-mass counterparts by γ=0.040 +- 0.019 mag. This value is larger by 0.031 mag than the value found in the first DES-SN cosmological analysis. This difference is due to a combination of updated photometric measurements and improved star formation histories and is not from host-galaxy misidentification. When using a 1D (redshift-only) bias correction the inferred mass step is larger, with γ=0.066 +- 0.020 mag. The 1D−5D γ difference for DES-SN is 0.026 +- 0.009 mag. We show that this difference is due to a strong correlation between host galaxy stellar mass and the x1 component of the 5D distance-bias correction. Including an intrinsic correlation between the observed properties of SNe Ia, stretch and colour, and stellar mass in simulated SN Ia samples, we show that a 5D fit recovers γ with −9 mmag bias compared to a +2 mmag bias for a 1D fit. This difference can explain part of the discrepancy seen in the data. Improvements in modelling correlations between galaxy properties and SN is necessary to ensure unbiased precision estimates of the dark energy equation of state as we enter the era of LSST.We acknowledge support from EU/FP7-ERC grant no. 615929. LG
was funded by the European Union’s Horizon 2020 research and
innovation programme under the Marie Skłodowska-Curie grant
agreement no. 839090.
The UCSC team is supported in part by NASA grant no.
NNG17PX03C, NSF grant nos AST-1518052 and AST-1815935,
the Gordon & Betty Moore Foundation, the Heising-Simons Foundation, and by fellowships from the Alfred P. Sloan Foundation and
the David and Lucile Packard Foundation to RJF.
This work was completed in part with resources provided by the
University of Chicago Research Computing Center. This research
used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science
User Facility operated under Contract No. DE-AC02-05CH11231.
Funding for the DES Projects has been provided by the U.S.
Department of Energy, the U.S. National Science Foundation,
the Ministry of Science and Education of Spain, the Science
and Technology Facilities Council of the United Kingdom, the
Higher Education Funding Council for England, the National Center
for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics
at the University of Chicago, the Center for Cosmology and
Astro-Particle Physics at the Ohio State University, the Mitchell
Institute for Fundamental Physics and Astronomy at Texas A&M
University, Financiadora de Estudos e Projetos, Fundac¸ao Carlos ˜
Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro, `
Conselho Nacional de Desenvolvimento Cient´ıfico e Tecnologico ´
and the Ministerio da Ci ´ encia, Tecnologia e Inovac ˆ ¸ao, the Deutsche ˜
Forschungsgemeinschaft and the Collaborating Institutions in the
Dark Energy Survey
Measuring the 2D baryon acoustic oscillation signal of galaxies in WiggleZ: Cosmological constraints
We present results from the 2D anisotropic baryon acoustic oscillation (BAO) signal present in the final data set from the WiggleZ Dark Energy Survey. We analyse the WiggleZ data in two ways: first using the full shape of the 2D correlation function and secondly focusing only on the position of the BAO peak in the reconstructed data set. When fitting for the full shape of the 2D correlation function we use a multipole expansion to compare with theory. When we use the reconstructed data we marginalize over the shape and just measure the position of the BAO peak, analysing the data in wedges separating the signal along the line of sight from that parallel to the line of sight. We verify our method with mock data and find the results to be free of bias or systematic offsets. We also redo the pre-reconstruction angle-averaged (1D) WiggleZ BAO analysis with an improved covariance and present an updated result. The final results are presented in the form of Ωc h2, H(z), and DA(z) for three redshift bins with effective redshifts z=0.44, 0.60, and 0.73.Within these bins and methodologies, we recover constraints between 5 and 22 per cent error. Our cosmological constraints are consistent with flat ΛCDM cosmology and agree with results from the Baryon Oscillation Spectroscopic Surve
The WiggleZ Dark Energy Survey: final data release and the metallicity of UV-luminous galaxies
The WiggleZ Dark Energy Survey measured the redshifts of over 200 000 ultraviolet (UV)- selected (NUV < 22.8 mag) galaxies on the Anglo-Australian Telescope. The survey detected the baryon acoustic oscillation signal in the large-scale distribution of galaxies over the redshift range 0.2 < z < 1.0, confirming the acceleration of the expansion of the Universe and measuring the rate of structure growth within it. Here, we present the final data release of the survey: a catalogue of 225 415 galaxies and individual files of the galaxy spectra. We analyse the emission-line properties of these UV-luminous Lyman-break galaxies by stacking the spectra in bins of luminosity, redshift, and stellar mass. The most luminous (-25 mag < MFUV < -22 mag) galaxies have very broad Hβ emission from active nuclei, as well as a broad second component to the [OIII] (495.9 nm, 500.7 nm) doublet lines that is blueshifted by 100 km s-1, indicating the presence of gas outflows in these galaxies. The composite spectra allow us to detect and measure the temperature-sensitive [O III] (436.3 nm) line and obtain metallicities using the direct method. The metallicities of intermediate stellar mass (8.8 < log (M*/M⊙) < 10)WiggleZ galaxies are consistent with normal emission-line galaxies at the samemasses. In contrast, the metallicities of high stellarmass (10 < log (M*/M⊙) < 12) WiggleZ galaxies are significantly lower than for normal emission-line galaxies at the same masses. This is not an effect of evolution as the metallicities do not vary with redshift; it is most likely a property specific to the extremely UV-luminous WiggleZ galaxies
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