Webb Telescope Discovers Triply-Lensed Supernova 'H0pe' in Cosmic Lens G165
Sep 16, 2023 - Unlocking the Mysteries of the Universe: The JWST Discovery of Triply-imaged Type Ia Supernova 'H0pe' and the Fascinating Galaxy Cluster PLCK G165.7+67.0.
The universe never ceases to amaze us with its celestial wonders. In a groundbreaking discovery, the James Webb Space Telescope (JWST) has unveiled a remarkable event: a Type Ia supernova at a redshift of 1.78, situated within the galaxy cluster PLCK G165.7+67.0 (commonly known as G165), itself residing at a redshift of 0.35. This discovery not only showcases the remarkable capabilities of the JWST but also promises to yield profound insights into the nature of the cosmos.
The Cosmic Stage: PLCK G165.7+67.0 - PLCK G165.7+67.0, abbreviated as G165, is a galaxy cluster that initially attracted attention due to its gravitational lensing properties, notably its amplification of a bright background galaxy called "Arc 1." This galaxy, with its sub-mm flux density exceeding 700 mJy, made it detectable by missions like Planck and Herschel. However, G165 is not your typical galaxy cluster. G165 presents a double-cluster structure, with two prominent cluster cores. Its X-ray luminosity is lower than expected for its redshift, and its mass estimate is challenging due to a dusty, high-star-forming galaxy known as "Arc 1 b/c" that contributes significantly to the far-infrared flux density. These intriguing characteristics make G165 an ideal target for scientific exploration.
Strong Lensing Unveils the Universe's Secrets - G165's most striking feature is its capacity for strong gravitational lensing, which has allowed astronomers to observe objects in the background with unprecedented clarity. Strong lensing occurs when the gravitational field of a massive object, like G165, bends and magnifies light from background sources, creating multiple images of the same object. This effect is analogous to looking through a cosmic magnifying glass. In previous studies, the Hubble Space Telescope's Wide Field Camera 3 (HST WFC3) imaged G165, revealing multiple image systems and providing insights into the cluster's structure. The lensing effects allowed astronomers to confirm both the northeastern (NE) and southwestern (SW) cores of G165, emphasizing its high mass.
JWST: A New Frontier in Space Observation - Enter the James Webb Space Telescope, the successor to the Hubble Space Telescope. Equipped with advanced instruments like the Near Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec), the JWST embarked on a mission to explore G165 as part of the Prime Extragalactic Areas for Reionization and Lensing Science (PEARLS) program. The telescope's capabilities exceeded all expectations. The JWST's NIRCam imaging in the "Epoch 1" phase revealed three point sources previously unseen in HST images. These sources were initially believed to be a Type Ia supernova (SN) with a high degree of confidence. Subsequent observations during Epochs 2 and 3 provided additional data points for the SN light curve, enhancing the understanding of its behavior.
SN H0pe: A Potential Cosmic Yardstick - This supernova, affectionately named "SN H0pe" for its potential to measure cosmic distances, is situated at a redshift of 1.78 and is lensed into three distinct locations, labeled as SN 2a, 2b, and 2c. SN H0pe offers a unique opportunity to determine Hubble's constant (H0) by measuring the time delays between its multiple images. Such measurements can shed light on the expansion rate of the universe and its age.
Galaxy Overdensity at Arc 2 - NIRCam photometry not only unveiled SN H0pe but also exposed a galaxy overdensity at the redshift of Arc 2. NIRSpec spectroscopy confirmed the existence of six member galaxies, four of which surround Arc 2. Arc 2, with its massive stellar mass, dominates this compact galaxy group, displaying a factor of ten higher stellar mass than other group members.
High-Redshift Galaxy Groups - Another intriguing aspect of G165 is the presence of a galaxy group centered around the dusty star-forming galaxy Arc 1, which exists at a redshift of 2.24. The group's high star formation rate (SFR) suggests the potential for regular supernova observations in this cluster.
Exploring the Spectroscopic Universe - NIRSpec spectroscopy is the key to unraveling the mysteries of G165. The instrument has enabled the confirmation of galaxy redshifts, SN classifications, and the measurement of time delays. The collected spectra have provided a wealth of information about the physical properties of galaxies in this cosmic theater.
The JWST's discovery of SN H0pe in G165, along with the observation of galaxy overdensities and high-redshift galaxy groups, promises to unlock a treasure trove of knowledge about the universe's structure and evolution. The potential to measure Hubble's constant using SN H0pe's time delays highlights the instrumental role of this discovery in cosmology. As the JWST continues its mission, astronomers eagerly await more revelations from this exceptional observatory. The cosmos has once again shown that it has more secrets to share, and with the JWST at the helm, humanity is poised to embark on a thrilling journey of cosmic discovery. The story of SN H0pe and G165 is but one chapter in the ongoing saga of our quest to comprehend the profound mysteries of the universe.