Tuning Gravitationally Lensed Standard Sirens

Gravitational waves emitted by chirping supermassive black hole binaries could in principle be used to obtain very accurate distance determinations. Provided they have an electromagnetic counterpart from which the redshift can be determined, these standard sirens could be used to build a high redshift Hubble diagram. Errors in the distance measurements will most likely be dominated by gravitational lensing. We show that the (de)magnification due to inhomogeneous foreground matter will increase the scatter in the measured distances by a factor ~10. We propose to use optical and IR data of the foreground galaxies to minimize the degradation from weak lensing. We find that the net effect of correcting the estimated distances for lensing is comparable to increasing the sample size by a factor of three when using the data to constrain cosmological parameters.Comment: 21 pages, 4 figures, accepted for publication in Ap

Correcting for lensing bias in the Hubble diagram

Gravitational lensing will cause a dispersion in the Hubble diagram for high redshift sources. This effect will introduce a bias in the cosmological parameter determination using the distance-redshift relation for Type Ia supernovae. In this note we show how one can diagnose and correct for this bias when doing precision cosmology with supernovae.Comment: 5 pages, 5 figures, accepted for publication in A&

The effect of inhomogeneities on dark energy constraints

Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred cosmological parameters. For precision constraints on the properties of dark energy, it is important to assess the potential systematic effects arising from these inhomogeneities. In this study, we use the Type Ia supernova magnitude-redshift relation to constrain the inhomogeneities as described by the Dyer-Roeder distance relation and the effect they have on the dark energy equation of state ($w$), together with priors derived from the most recent results of the measurements of the power spectrum of the Cosmic Microwave Background and Baryon Acoustic Oscillations. We find that the parameter describing the inhomogeneities ($\eta$) is correlated with $w$. The best fit values $w = -0.933 \pm 0.065$ and $\eta = 0.61 \pm 0.37$ are consistent with homogeneity at $< 2 \sigma$ level. Assuming homogeneity ($\eta =1$), we find $w = -0.961 \pm 0.055$, indicating only a small change in $w$. For a time-dependent dark energy equation of state, $w_0 = -0.951 \pm 0.112$ and $w_a = 0.059 \pm 0.418$, to be compared with $w_0 = -0.983 \pm 0.127$ and $w_a = 0.07 \pm 0.432$ in the homogeneous case, which is also a very small change. Current data are not sufficient to constrain the fraction of dark matter (DM) in compact objects, $f_p$ at the 95$\%$ C.L., however at 68$\%$ C.L. $f_p < 0.73$. Future supernova surveys will improve the constraints on $\eta$, and $f_p$, by a factor of $\sim$ 10.Comment: 16 pages, 4 figures, accepted by JCA

Rates and Properties of Strongly Gravitationally Lensed Supernovae and their Host Galaxies in Time-Domain Imaging Surveys

Supernovae that are strongly gravitationally lensed (gLSNe) by galaxies are powerful probes of astrophysics and cosmology that will be discovered systematically by next-generation wide-field, high-cadence imaging surveys such as the Zwicky Transient Facility (ZTF) and the Large Synoptic Survey Telescope (LSST). Here we use pixel-level simulations that include dust, observing strategy, and multiple supernova subtypes to forecast the rates and properties of gLSNe that ZTF and LSST will find. Applying the resolution-insensitive discovery strategy of Goldstein et al. (2018), we forecast that ZTF (LSST) can discover 0.02 (0.79) 91bg-like, 0.17 (5.92) 91T-like, 1.22 (47.84) Type Ia, 2.76 (88.51) Type IIP, 0.31 (12.78) Type IIL, and 0.36 (15.43) Type Ib/c gLSNe per year. We also forecast that the surveys can discover at least 3.75 (209.32) Type IIn gLSNe per year, for a total of at least 8.60 (380.60) gLSNe per year under fiducial observing strategies. ZTF gLSNe have a median $z_s=0.9$, $z_l=0.35$, $\mu_\mathrm{tot}=30$, $\Delta t_\mathrm{max}= 10$ days, $\min(\theta)= 0.25^{\prime\prime}$, and $N_\mathrm{img} = 4$. LSST gLSNe are less compact and less magnified, with a median $z_s=1.0$, $z_l=0.4$, $\mu_\mathrm{tot}\approx6$, $\Delta t_\mathrm{max} = 25$ days, $\min(\theta)=0.6^{\prime\prime}$, and $N_\mathrm{img} = 2$. As the properties of lensed host galaxy arcs provide critical information for lens mass modeling, we develop a model of the supernova--host galaxy connection and use it to simulate realistic images of the supernova--host--lens systems. We find that the vast majority of gLSN host galaxies will be multiply imaged, enabling detailed constraints on lens models with sufficiently deep high-resolution imaging taken after the supernova has faded. We release the results of our simulations to the public as catalogs at this URL: http://portal.nersc.gov/project/astro250/glsne/.Comment: 57 pages, 66 equations, 36 figures, 4 tables, Submitted to ApJS, comments welcome, v2 replaced some figures with rasterized versions to reduce load on PDF viewer

Probing for Dynamics of Dark-Energy in Mass Varying Neutrinos: Cosmic Microwave Background Radiation and Large Scale Structure

We present cosmological perturbation theory in neutrino probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for the cosmic acceleration today. We consider several types of scalar field potentials and put constraints on the coupling parameter between neutrinos and dark energy. Assuming the flatness of the universe, the constraint we can derive from the current observation is $\sum m_{\nu} < 0.87 eV$ at the 95 % confidence level for the sum over three species of neutrinos.Comment: 12 pages, 8 figures, Present in conferences COSPA-2006, NEPSE-2007 and Yong-Pyung APCTP-200

Herschel limits on far-infrared emission from circumstellar dust around nearby Type Ia supernovae

We report upper limits on dust emission at far-infrared (IR) wavelengths from three nearby Type Ia supernovae: SNe 2011by, 2011fe and 2012cg. Observations were carried out at 70 um and 160 um with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory. None of the supernovae were detected in the far-IR, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. Due to its proximity, SN 2011fe provides the tightest constraints, M_dust < 7 * 10^-3 M_sun at a 3 sigma-level for dust temperatures T_dust ~500 K assuming silicate or graphite dust grains of size a = 0.1 um. For SNe 2011by and 2012cg the corresponding upper limits are less stringent, with M_dust < 0.1 M_sun for the same assumptions.Comment: 6 pages, 3 figures, 1 table. Accepted for publication in MNRA

Lensing magnification of supernovae in the GOODS-fields

Gravitational lensing of high-redshift supernovae is potentially an important source of uncertainty when deriving cosmological parameters from the measured brightness of Type Ia supernovae, especially in deep surveys with scarce statistics. Photometric and spectroscopic measurements of foreground galaxies along the lines-of-sight of 33 supernovae discovered with the Hubble Space Telescope, both core-collapse and Type Ia, are used to model the magnification probability distributions of the sources. Modelling galaxy halos with SIS or NFW-profiles and using M/L scaling laws provided by the Faber-Jackson and Tully-Fisher relations, we find clear evidence for supernovae with lensing (de)magnification. However, the magnification distribution of the Type Ia supernovae used to determine cosmological distances matches very well the expectations for an unbiased sample, i.e.their mean magnification factor is consistent with unity. Our results show that the lensing distortions of the supernova brightness can be well understood for the GOODS sample and that correcting for this effect has a negligible impact on the derived cosmological parameters.Comment: 22 pages, 9 figures, accepted for publication by Ap