Deja Vu All Over Again: The Reappearance of Supernova Refsdal (1512.04654v2)

Abstract: In Hubble Space Telescope (HST) imaging taken on 10 November 2014, four images of supernova (SN) "Refsdal" (redshift z=1.49) appeared in an Einstein-cross--like configuration (images S1-S4) around an early-type galaxy in the cluster MACS J1149.5+2223 (z=0.54). Almost all lens models of the cluster have predicted that the SN should reappear within a year in a second host-galaxy image created by the cluster's potential. In HST observations taken on 11 December 2015, we find a new source at the predicted position of the new image of SN Refsdal approximately 8" from the previous images S1-S4. This marks the first time the appearance of a SN at a particular time and location in the sky was successfully predicted in advance! We use these data and the light curve from the first four observed images of SN Refsdal to place constraints on the relative time delay and magnification of the new image (SX), compared to images S1-S4. This enables us, for the first time, to test "blind" lens model predictions of both magnifications and time delays for a lensed SN. We find that the timing and brightness of the new image are consistent with the blind predictions of a fraction of the models. The reappearance illustrates the discriminatory power of this blind test and its utility to uncover sources of systematic uncertainty. From planned HST photometry, we expect to reach a precision of 1-2% on the time delay between S1-S4 and SX.

• The paper reports the first successful prediction and observation of a gravitationally lensed supernova reappearing, validating gravitational lensing models.
• This event serves as a crucial empirical benchmark for testing and refining gravitational lens models, providing insights into cosmic parameters and dark matter distribution.
• Analysis confirms observed data matches predictions, providing an empirical test for lens models and highlighting the potential for future high-precision time delay measurements.

The Reappearance of Supernova Refsdal: A Detailed Analysis

The paper "The Reappearance of Supernova Refsdal" presents an intriguing astrophysical case paper pertaining to the observation and subsequent predictive analysis of a multiply-lensed supernova, denoted as SN Refsdal. Situated within the galaxy cluster MACS J1149.5+2223, the supernova offers a unique opportunity to paper gravitational lensing in detail, particularly its effects on distant astronomical phenomena.

Overview of Observations and Predictions

In the images captured by the Hubble Space Telescope (HST) on November 10, 2014, SN Refsdal was observed at a redshift of z = 1.49 in an Einstein cross pattern, around an elliptical galaxy within the cluster (z = 0.54). The presence of four distinct images, labeled S1 to S4, supported strong lens models suggesting the imminent reappearance of the supernova in a different host-galaxy image caused by the cluster's gravitational potential. Remarkably, in HST images from December 11, 2015, a new source was detected at the anticipated position, approximately 8 arcseconds from the original images. This event marks the first successful predictive modeling of a supernova's reappearance in a gravitational lensing context.

Implications and Significance

This successful prediction underscores several important aspects in cosmology and gravitational lensing studies:

1. Gravitational Lensing as a Predictive Tool: The ability to anticipate the appearance, timing, and brightness of a supernova image using lens models significantly bolsters our methodological tools for probing the cosmos. The precision of these models allows for detailed verification of theoretical predictions concerning gravitationally lensed objects.
2. Testing Lensing Model Predictions: SN Refsdal provides a rare chance to test "blind" predictions of magnifications and time delays, offering a direct measure of the models' accuracy and inherent systematic uncertainties. This case serves as an empirical benchmark to refine lens model frameworks and adjust for discrepancies.
3. Cosmic Parameters and Structure: The analysis reconfirms that time delays between images are crucial for extracting information about the cosmic expansion and the gravitational potential landscape. This provides insights into intervening mass distributions and dark matter constituents.

Observational and Computational Methodology

The WFC3 imaging data from HST was processed using 'DrizzlePac' tools, enabling precise photometric measurements. The data was compared against predictions from various lens modeling teams, which employed different sets of constraints and model parameterizations concerning the cluster potential. Key parameters derived include time delay and magnification ratios analyzed within established cosmologies.

Results and Interpretation

The paper found that the observed timing and brightness at the new predicted location (SX) were consistent with certain lens model predictions, indicating varying degrees of model accuracy and shedding light on possible systematic errors. Figure presentations in the paper exhibit the confidence intervals around theoretical predictions and illustrate the accurate matching of SX's position to predicted coordinates within reported rms scatter.

Future Directions

The continued investigation of SN Refsdal via planned HST photometry aims to achieve a precision of 1-2% on the time delay measurement between the original and newly observed supernova images. This enhancement in precision could further refine the accuracy of lensing models and possibly lead to improved constraints on cosmic distances and expansion rates.

This paper exemplifies the interplay between observational astronomy and theoretical modeling, providing compelling evidence of gravitational lensing's capacity to function as a predictive instrument in cosmic event analysis. The methodologies and outcomes of this paper set a precedent for future astrophysical investigations into the behavior of lensed supernovae and other cosmological events.