86 research outputs found
Galaxy Clustering Evolution in the UH8K Weak Lensing Fields
We present measurements of the two-point galaxy angular correlation function
as a function of apparent magnitude, color, and morphology. We present new
galaxy number counts to limiting magnitudes of I=24.0 and V=25.0. We find
to be well described by a power-law of slope -0.8. We find the
amplitude of the correlation function to decrease monotonically with
increasingly faint apparent magnitude. We compare with predictions utilizing
redshift distributions based on deep spectroscopic observations. We conclude
that simple redshift-dependent models which characterize evolution by means of
the epsilon parameter inadequately describe the observations. We find a strong
clustering dependence on V-I color because galaxies of extreme color lie at
similar redshifts and the angular correlation functions for these samples are
minimally diluted by chance projections.
We then present the first attempt to investigate the redshift evolution of
clustering, utilizing a population of galaxies of the same morphological type
and absolute luminosity. We study the dependence of on
redshift for Lstar early-type galaxies in the redshift range 0.2<z<0.9.
Although uncertainties are large, we find the evolution in the clustering of
these galaxies to be consistent with stable clustering [epsilon=0]. We find
Lstar early-type galaxies to cluster slightly more strongly (rnought =
5.25\pm0.28 \hMpc assuming epsilon=0) than the local full field population.
This is in good agreement with the 2dFGRS value for Lstar early-type galaxies
in the local universe (abridged).Comment: 41 pages, including 12 figs, 10 tables, to appear in Ap
Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction
We present photospheric-phase observations of LSQ12gdj, a slowly-declining,
UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has
extinction-corrected absolute magnitude , and pre-maximum
spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN
2007if. We use ultraviolet photometry from Swift, ground-based optical
photometry, and corrections from a near-infrared photometric template to
construct the bolometric (1600-23800 \AA) light curve out to 45 days past
-band maximum light. We estimate that LSQ12gdj produced
of Ni, with an ejected mass near or slightly above the
Chandrasekhar mass. As much as 27% of the flux at the earliest observed phases,
and 17% at maximum light, is emitted bluewards of 3300 \AA. The absence of
excess luminosity at late times, the cutoff of the spectral energy distribution
bluewards of 3000 \AA, and the absence of narrow line emission and strong Na I
D absorption all argue against a significant contribution from ongoing shock
interaction. However, up to 10% of LSQ12gdj's luminosity near maximum light
could be produced by the release of trapped radiation, including kinetic energy
thermalized during a brief interaction with a compact, hydrogen-poor envelope
(radius cm) shortly after explosion; such an envelope arises
generically in double-degenerate merger scenarios.Comment: 18 pages, 10 figures, accepted to MNRAS; v2 accepted version. Spectra
available on WISEReP (http://www.weizmann.ac.il/astrophysics/wiserep/).
Natural-system photometry and bolometric light curve available as online
tables in MNRAS versio
Effects of losartan vs candesartan in reducing cardiovascular events in the primary treatment of hypertension
Although angiotensin receptor blockers have different receptor binding properties no comparative studies with cardiovascular disease (CVD) end points have been performed within this class of drugs. The aim of this study was to test the hypothesis that there are blood pressure independent CVD-risk differences between losartan and candesartan treatment in patients with hypertension without known CVD. Seventy-two primary care centres in Sweden were screened for patients who had been prescribed losartan or candesartan between the years 1999 and 2007. Among the 24â943 eligible patients, 14â100 patients were diagnosed with hypertension and prescribed losartan (n=6771) or candesartan (n=7329). Patients were linked to Swedish national hospitalizations and death cause register. There was no difference in blood pressure reduction when comparing the losartan and candesartan groups during follow-up. Compared with the losartan group, the candesartan group had a lower adjusted hazard ratio for total CVD (0.86, 95% confidence interval (CI) 0.77â0.96, P=0.0062), heart failure (0.64, 95% CI 0.50â0.82, P=0.0004), cardiac arrhythmias (0.80, 95% CI 0.65â0.92, P=0.0330), and peripheral artery disease (0.61, 95% CI 0.41â0.91, P=0.0140). No difference in blood pressure reduction was observed suggesting that other mechanisms related to different pharmacological properties of the drugs may explain the divergent clinical outcomes
OzDES Reverberation Mapping Programme: MgâII lags and RâL relation
The correlation between the broad line region radius and continuum luminosity (R-L relation) of active galactic nuclei (AGNs) is critical for single-epoch mass estimates of supermassive black holes (SMBHs). At z ⌠1-2, where AGN activity peaks, the R-L relation is constrained by the reverberation mapping (RM) lags of the Mg II line. We present 25 Mg II lags from the Australian Dark Energy Survey RM project based on 6 yr of monitoring. We define quantitative criteria to select good lag measurements and verify their reliability with simulations based on both the damped random walk stochastic model and the rescaled, resampled versions of the observed light curves of local, well-measured AGN. Our sample significantly increases the number of Mg II lags and extends the R-L relation to higher redshifts and luminosities. The relative iron line strength RFe has little impact on the R-L relation. The best-fitting Mg II R-L relation has a slope α = 0.39 ± 0.08 with an intrinsic scatter Ïrl = 0.15+â000203. The slope is consistent with previous measurements and shallower than the H ÎČ R-L relation. The intrinsic scatter of the new R-L relation is substantially smaller than previous studies and comparable to the intrinsic scatter of the H ÎČ R-L relation. Our new R-L relation will enable more precise single-epoch mass estimates and SMBH demographic studies at cosmic noon
New Constraints on , , and w from an Independent Set of Eleven High-Redshift Supernovae Observed with HST
We report measurements of , , and w from eleven
supernovae at z=0.36-0.86 with high-quality lightcurves measured using WFPC-2
on the HST. This is an independent set of high-redshift supernovae that
confirms previous supernova evidence for an accelerating Universe. Combined
with earlier Supernova Cosmology Project data, the new supernovae yield a
flat-universe measurement of the mass density
(statistical) (identified systematics), or equivalently, a
cosmological constant of (statistical)
(identified systematics). When the supernova results are combined
with independent flat-universe measurements of from CMB and galaxy
redshift distortion data, they provide a measurement of
(statistical) (identified systematic), if w
is assumed to be constant in time. The new data offer greatly improved color
measurements of the high-redshift supernovae, and hence improved host-galaxy
extinction estimates. These extinction measurements show no anomalous negative
E(B-V) at high redshift. The precision of the measurements is such that it is
possible to perform a host-galaxy extinction correction directly for individual
supernovae without any assumptions or priors on the parent E(B-V) distribution.
Our cosmological fits using full extinction corrections confirm that dark
energy is required with , a result consistent with
previous and current supernova analyses which rely upon the identification of a
low-extinction subset or prior assumptions concerning the intrinsic extinction
distribution.Comment: Accepted for publication in Astrophysical Journal; For data tables
and full-resolution figures, see http://supernova.lbl.go
Multiwavelength optical and NIR variability analysis of the Blazar PKS 0027-426
We present multiwavelength spectral and temporal variability analysis of PKS 0027-426 using optical griz observations from Dark Energy Survey between 2013 and 2018 and VEILS Optical Light curves of Extragalactic TransienT Events (VOILETTE) between 2018 and 2019 and near-infrared (NIR) JKs observations from Visible and Infrared Survey Telescope for Astronomy Extragalactic Infrared Legacy Survey (VEILS) between 2017 and 2019. Multiple methods of cross-correlation of each combination of light curve provides measurements of possible lags between opticalâoptical, opticalâNIR, and NIRâNIR emission, for each observation season and for the entire observational period. Inter-band time lag measurements consistently suggest either simultaneous emission or delays between emission regions on time-scales smaller than the cadences of observations. The colourâmagnitude relation between each combination of filters was also studied to determine the spectral behaviour of PKS 0027-426. Our results demonstrate complex colour behaviour that changes between bluer when brighter, stable when brighter, and redder when brighter trends over different time-scales and using different combinations of optical filters. Additional analysis of the optical spectra is performed to provide further understanding of this complex spectral behaviour
OzDES Reverberation Mapping Programme: Mg II lags and RâL relation
The correlation between the broad line region radius and continuum luminosity (R-L relation) of active galactic nuclei (AGNs) is critical for single-epoch mass estimates of supermassive black holes (SMBHs). At z ⌠1-2, where AGN activity peaks, the R-L relation is constrained by the reverberation mapping (RM) lags of the Mg II line. We present 25 Mg II lags from the Australian Dark Energy Survey RM project based on 6 yr of monitoring. We define quantitative criteria to select good lag measurements and verify their reliability with simulations based on both the damped random walk stochastic model and the rescaled, resampled versions of the observed light curves of local, well-measured AGN. Our sample significantly increases the number of Mg II lags and extends the R-L relation to higher redshifts and luminosities. The relative iron line strength RFe has little impact on the R-L relation. The best-fitting Mg II R-L relation has a slope α = 0.39 ± 0.08 with an intrinsic scatter Ïrl = 0.15+â000203. The slope is consistent with previous measurements and shallower than the H ÎČ R-L relation. The intrinsic scatter of the new R-L relation is substantially smaller than previous studies and comparable to the intrinsic scatter of the H ÎČ R-L relation. Our new R-L relation will enable more precise single-epoch mass estimates and SMBH demographic studies at cosmic noon
OzDES reverberation mapping program: Lag recovery reliability for 6-yr C iv analysis
We present the statistical methods that have been developed to analyse the OzDES reverberation mapping sample. To perform this statistical analysis we have created a suite of customizable simulations that mimic the characteristics of each source in the OzDES sample. These characteristics include: the variability in the photometric and spectroscopic light curves, the measurement uncertainties, and the observational cadence. By simulating the sources in the OzDES sample that contain the C iv emission line, we developed a set of criteria that rank the reliability of a recovered time-lag depending on the agreement between different recovery methods, the magnitude of the uncertainties, and the rate at which false positives were found in the simulations. These criteria were applied to simulated light curves and these results used to estimate the quality of the resulting Radius-Luminosity relation. We grade the results using three quality levels (gold, silver, and bronze). The input slope of the R-L relation was recovered within 1Ï for each of the three quality samples, with the gold standard having the lowest dispersion with a recovered a R-L relation slope of 0.454 ± 0.016 with an input slope of 0.47. Future work will apply these methods to the entire OzDES sample of 771 AGN
OzDES Reverberation Mapping Program: H beta lags from the 6-yr survey
Reverberation mapping measurements have been used to constrain the relationship between the size of the broad-line region and luminosity of active galactic nuclei (AGN). This RâL relation is used to estimate single-epoch virial black hole masses, and has been proposed to use to standardize AGN to determine cosmological distances. We present reverberation measurements made with HÎČ from the 6-yr Australian Dark Energy Survey (OzDES) Reverberation Mapping Program. We successfully recover reverberation lags for eight AGN at 0.12 &lt; z &lt; 0.71, probing higher redshifts than the bulk of HÎČ measurements made to date. Our fit to the RâL relation has a slope of α = 0.41 ± 0.03 and an intrinsic scatter of Ï = 0.23 ± 0.02âdex. The results from our multi-object spectroscopic survey are consistent with previous measurements made by dedicated source-by-source campaigns, and with the observed dependence on accretion rate. Future surveys, including LSST, TiDES, and SDSS-V, which will be revisiting some of our observed fields, will be able to build on the results of our first-generation multi-object reverberation mapping survey
Multiwavelength optical and NIR variability analysis of the Blazar PKSÂ 0027-426
Funding: EG and SFH acknowledge support from the Horizon 2020 ERC Starting Grant DUST-IN-THE-WIND (ERC-2015-StG-677117). EG acknowledges support from STFC for funding this PhD. Research leading to these results has received funding from the European Research Council under the European Union 7th Framework Programme (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Brazilian Instituto Nacional de CiĂȘncia Tecnologia (INCT) e-Universe (CNPq grant no. 465376/2014-2).We present multiwavelength spectral and temporal variability analysis of PKS 0027-426 using optical griz observations from Dark Energy Survey between 2013 and 2018 and VEILS Optical Light curves of Extragalactic TransienT Events (VOILETTE) between 2018 and 2019 and near-infrared (NIR) JKs observations from Visible and Infrared Survey Telescope for Astronomy Extragalactic Infrared Legacy Survey (VEILS) between 2017 and 2019. Multiple methods of cross-correlation of each combination of light curve provides measurements of possible lags between opticalâoptical, opticalâNIR, and NIRâNIR emission, for each observation season and for the entire observational period. Inter-band time lag measurements consistently suggest either simultaneous emission or delays between emission regions on time-scales smaller than the cadences of observations. The colourâmagnitude relation between each combination of filters was also studied to determine the spectral behaviour of PKS 0027-426. Our results demonstrate complex colour behaviour that changes between bluer when brighter, stable when brighter, and redder when brighter trends over different time-scales and using different combinations of optical filters. Additional analysis of the optical spectra is performed to provide further understanding of this complex spectral behaviour.Publisher PDFPeer reviewe
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