iPTF16geu Goobar, A.; Amanullah, R.; Kulkarni, S. R. ...
Science (American Association for the Advancement of Science),
04/2017, Volume:
356, Issue:
6335
Journal Article
Peer reviewed
Open access
We report the discovery of a multiply imaged, gravitationally lensed type Ia supernova, iPTF16geu (SN 2016geu), at redshift z = 0.409. This phenomenon was identified because the light from the ...stellar explosion was magnified more than 50 times by the curvature of space around matter in an intervening galaxy. We used high-spatial-resolution observations to resolve four images of the lensed supernova, approximately 0.3 arc seconds from the center of the foreground galaxy. The observations probe a physical scale of ~1 kiloparsec, smaller than is typical in other studies of extragalactic gravitational lensing. The large magnification and symmetric image configuration imply close alignment between the lines of sight to the supernova and to the lens. The relative magnifications of the four images provide evidence for substructures in the lensing galaxy.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
We study the very early light curve of supernova 2014J (SN 2014J) using the high-cadence broad-band imaging data obtained by the Kilodegree Extremely Little Telescope, which fortuitously observed M ...82 around the time of the explosion, starting more than 2 months prior to detection, with up to 20 observations per night. These observations are complemented by observations in two narrow-band filters used in an H alpha survey of nearby galaxies by the intermediate Palomar Transient Factory that also captured the first days of the brightening of the supernova. The evolution of the light curves is consistent with the expected signal from the cooling of shock heated material of large scale dimensions, > ~1R sub(middot in circle). This could be due to heated material of the progenitor, a companion star or pre-existing circumstellar environment, e.g., in the form of an accretion disk. Structure seen in the light curves during the first days after explosion could also originate from radioactive material in the outer parts of an exploding white dwarf, as suggested from the early detection of gamma-rays. The model degeneracy translates into a systematic uncertainty of + or -0.3 days on the estimate of the first light from SN 2014J.
We present the best 265 sampled R-band light curves of spectroscopically identified Type Ia supernovae (SNe) from the Palomar Transient Factory (PTF; 2009-2012) survey and the intermediate Palomar ...Transient Factory (iPTF; 2013-2017). A model-independent light-curve template is built from our data-set with the purpose to investigate average properties and diversity in our sample. We searched for multiple populations in the light-curve properties using machine learning tools. We also utilized the long history of our light curves, up to 4000 days, to exclude any significant pre- or post- supernova flares. From the shapes of light curves we found the average rise time in the R band to be 16.8&#x2212;0.6+0.5'>16.8 +0.5 −0.6 16.8−0.6+0.5 days. Although PTF/iPTF were single-band surveys, by modelling the residuals of the SNe in the Hubble–Lemaître diagram, we estimate the average colour excess of our sample to be 〈 E ( B − V )〉 ≈ 0.05(2) mag and thus the mean corrected peak brightness to be M R = −19.02 ± 0.02 +5log&#x2061;(H0kms&#x2212;1Mpc&#x2212;1/70)'>+5log(H 0 kms −1 Mpc −1 /70) +5log(H0kms−1Mpc−1/70) mag with only weak dependennce on light–curve shape. The intrinsic scatter is found to be σ R = 0.186 ± 0.033 mag for the redshift range 0.05 < z < 0.1, without colour corrections of individual SNe. Our analysis shows that Malmquist bias becomes very significant at z = 0.13. A similar limitation is expected for the ongoing Zwicky Transient Facility (ZTF) survey using the same telescope, but new camera expressly designed for ZTF.
ABSTRACT
In 2016, the first strongly lensed Type Ia supernova (SN Ia), iPTF16geu, at redshift z = 0.409 with four resolved images arranged symmetrically around the lens galaxy at z = 0.2163, was ...discovered. Here, refined observations of iPTF16geu, including the time delay between images, are used to decrease uncertainties in the lens model, including the the slope of the projected surface density of the lens galaxy, Σ ∝ r1 − η, and to constrain the universal expansion rate H0. Imaging with Hubble Space Telescope provides an upper limit on the slope η, in slight tension with the steeper density profiles indicated by imaging with Keck after iPTF16geu had faded, potentially due to dust extinction not corrected for in host galaxy imaging. Since smaller η implies larger magnifications, we take advantage of the standard candle nature of SNe Ia constraining the image magnifications, to obtain an independent constraint of the slope. We find that a smooth lens density fails to explain the iPTF16geu fluxes, regardless of the slope, and additional substructure lensing is needed. The total probability for the smooth halo model combined with star microlensing to explain the iPTF16geu image fluxes is maximized at 12 per cent for η ∼ 1.8, in excellent agreement with Keck high-spatial-resolution data, and flatter than an isothermal halo. It also agrees perfectly with independent constraints on the slope from lens velocity dispersion measurements. Combining with the observed time delays between the images, we infer a lower bound on the Hubble constant, $H_0 \gtrsim 40\, {\rm km \ s^{-1} Mpc^{-1}}$, at 68.3 per cent confidence level.
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 and 160 μm with the ...Photodetector Array Camera and Spectrometer onboard 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 at a 3σ level for dust temperatures T
dust ∼ 500 K assuming silicate or graphite dust grains of size a = 0.1 μm. For SNe 2011by and 2012cg the corresponding upper limits are less stringent, with M
dust 10−1 M for the same assumptions.
Aims. Strong lensing by massive galaxy clusters can provide magnification of the flux and even multiple images of the galaxies that lie behind them. This phenomenon facilitates observations of ...high-redshift supernovae (SNe) that would otherwise remain undetected. Type Ia supernovae (SNe Ia) detections are of particular interest because of their standard brightness, since they can be used to improve either cluster lensing models or cosmological parameter measurements. Methods. We present a ground-based, near-infrared search for lensed SNe behind the galaxy cluster Abell 370. Our survey was based on 15 epochs of J-band observations with the HAWK-I instrument on the Very Large Telescope (VLT). We use Hubble Space Telescope (HST) photometry to infer the global properties of the multiply-imaged galaxies. Using a recently published lensing model of Abell 370, we also present the predicted magnifications and time delays between the images. Results. In our survey, we did not discover any live SNe from the 13 lensed galaxies with 47 multiple images behind Abell 370. This is consistent with the expectation of 0.09 ± 0.02 SNe calculated based on the measured star formation rate. We compare the expectations of discovering strongly lensed SNe in our survey and that performed with HST during the Hubble Frontier Fields (HFF) programme. We also show the expectations of search campaigns that can be conducted with future facilities, such as the James Webb Space Telescope (JWST) or the Wide-Field Infrared Survey Telescope (WFIRST). We show that the NIRCam instrument aboard the JWST will be sensitive to most SN multiple images in the strongly lensed galaxies and thus will be able to measure their time delays if observations are scheduled accordingly.
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FMFMET, NUK, UL, UM, UPUK
We report lensing magnifications, extinction, and time-delay estimates for the first resolved, multiply imaged Type Ia supernova iPTF16geu, at z = 0.409, using Hubble Space Telescope (HST) ...observations in combination with supporting ground-based data. Multiband photometry of the resolved images provides unique information about the differential dimming due to dust in the lensing galaxy. Using HST and Keck AO reference images taken after the SN faded, we obtain a total lensing magnification for iPTF16geu of μ = 67.8(+2.6−2.9), accounting for extinction in the host and lensing galaxy. As expected from the symmetry of the system, we measure very short time-delays for the three fainter images with respect to the brightest one: −0.23 ± 0.99, −1.43 ± 0.74, and 1.36 ± 1.07 d. Interestingly, we find large differences between the magnifications of the four supernova images, even after accounting for uncertainties
in the extinction corrections: ∆m(1) = −3.88(+0.07−0.06), ∆m(2) = −2.99(+0.09−0.08), ∆m(3) = −2.19(+0.14−0.15),and ∆m(4) = −2.40(+0.14−0.12) mag, discrepant with model predictions suggesting similar image brightnesses. A possible explanation for the large differences is gravitational lensing by substructures, micro- or millilensing, in addition to the large-scale lens causing the image separations. We find that the inferred magnification is insensitive to the assumptions about the dust properties in the host and lens galaxy.
Abstract
We present a new technique to infer dust locations towards reddened Type Ia supernovae and to help discriminate between an interstellar and a circumstellar origin for the observed ...extinction. Using Monte Carlo simulations, we show that the time evolution of the light-curve shape and especially of the colour excess E(B − V) places strong constraints on the distance between dust and the supernova. We apply our approach to two highly reddened Type Ia supernovae for which dust distance estimates are available in the literature: SN 2006X and SN 2014J. For the former, we obtain a time-variable E(B − V) and from this derive a distance of $27.5^{+9.0}_{-4.9}$ or $22.1^{+6.0}_{-3.8}$ pc depending on whether dust properties typical of the Large Magellanic Cloud (LMC) or the Milky Way (MW) are used. For the latter, instead, we obtain a constant E(B − V) consistent with dust at distances larger than ∼50 and 38 pc for LMC- and MW-type dust, respectively. Values thus extracted are in excellent agreement with previous estimates for the two supernovae. Our findings suggest that dust responsible for the extinction towards these supernovae is likely to be located within interstellar clouds. We also discuss how other properties of reddened Type Ia supernovae – such as their peculiar extinction and polarization behaviour and the detection of variable, blue-shifted sodium features in some of these events – might be compatible with dust and gas at interstellar-scale distances.
The wavelength dependence of the extinction of Type Ia SN 2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical ...Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of an SN Ia is characterized over the full wavelength range of 0.2-2 mu m. A total-to-selective extinction, R sub(V) > or =, slanted 3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields R sub(V) = 1.4 + or - 0.1. The observed reddening of SN 2014J is also compatible with a power-law extinction, A sub(lambda)/A sub(V) = (lambda/lambda sub(V)) super(p) as expected from multiple scattering of light, with p = -2.1 + or - 0.1. After correcting for differences in reddening, SN 2014J appears to be very similar to SN 2011fe over the 14 broadband filter light curves used in our study.
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