February 18, 2025

Speaker: Brenda Frye (Steward Observatory)

Contact Information: 

Title:  The Tale of the Multiply-imaged Standard Candle Supernova "H0pe" That Yielded a Value for the Current Expansion Rate of the Universe 

Abstract:  

Abstract: We present results from the James Webb Space Telescope (JWST) Prime Extragalactic Areas and Reionization and Lensing Science (PEARLS) program in the direction of galaxy clusters, from the spectacle of "first light" observations to the scene of vast panoramas of gravitationally-lensed arcs. One point-source was discovered in the galaxy cluster field PLCK G165.7+67.0 (G165) that was bright and appeared in three locations as a result of strong gravitational lensing. Follow-up observations confirmed this source to be a normal Type Ia supernova (SN) at a redshift of 1.783 that we call "SN H0pe." The SN host galaxy is centrally-situated in a high star-forming galaxy group. A delay in the arrival times of the SN light into each image arises from their different geometric light paths, which together with a gravitational lensing model, returns a value for the Hubble-Lemaitre constant "H0."  Under double-blinded protocols, the two time delays were measured by a photometric approach and a rare spectroscopic approach, and seven lens models were constructed. The time delays were augmented by measurements of the absolute magnifications, summing up to a set of five observables. By a scaled fit of the lens model-predicted observables to the measured set, a best-fit value was inferred of H0 = 75.7(+8.1)(-5.5) km/s/Mpc. This is only the second time H0 has been measured by this method, and the first time using a standard candle. Regular monitoring of G165 and galaxy cluster fields with similar properties may be well-rewarded by the detection of additional strongly-lensed SNe.

Visitor's room: 129

Visit Schedule:

Note: Brenda will be at Peyton/IAS every day of the week, excluding Friday. Reach out to her at her guest office or at brendafrye@gmail.com if you'd like to schedule a one-on-one on a day besides Tuesday, Feb. 18th.

Tuesday

• 9:30 a.m.: 

• 10:00 a.m:  

• 10:30 a.m.:  Coffee

• 11:00 a.m.: Colloquium

• 11:30 a.m.: Colloquium 

• 12:00 p.m.: Bahcall lunch

• 12:30 p.m.: Bahcall lunch

• 1:00 p.m.: Bahcall lunch

• 1:30 p.m.:  Charlotte Ward

• 2:00 p.m.:  Neta Bahcall

• 2:30 p.m.: Jim Gunn

• 3:00 p.m.: Dongzi Li

• 3:30 p.m.: David Setton (Peyton 115)

• 4:00 p.m.:  Michael Strauss (Peyton 113)

• 4:30 p.m.:  Tea Time with Grad Students in Grand Central 

• 5:00 p.m.: Tea Time with Grad Students in Grand Central 

Dinner Sign-up - add your name here:

Day of week ( 18.02.2025)

1. Faculty Host: Michael Strauss

2. Postdoc Host: Jamie McCullough

3. James Sunseri

4. Christian Kragh Jespersen

5. Ronan Hix

6.  Camryn Phillips

7.  Jared Siegel

8.  Speaker

STUDENTS HAVE PRIORITY.

PLEASE NO MORE THAN 8 PEOPLE (it is more difficult to properly interact with the speaker in larger groups).