BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1

Diego, Jose M.; Li, Sung Kei; Meena, Ashish K.; Niemiec, Anna; Acebron, Ana; Jauzac, Mathilde; Struble, Mitchell F.; Amruth, Alfred; Broadhurst, Tom J.; Cerny, Catherine; Ebeling, Harald; Filippenko, Alexei V.; Jullo, Eric; Kelly, Patrick; Koekemoer, Anton M.; Lagattuta, David; Lim, Jeremy; Limousin, Marceau; Mahler, Guillaume; Patel, Nency; Remolina, Juan; Richard, Johan; Sharon, Keren; Steinhardt, Charles; Umetsu, Keiichi; Williams, Liliya; Zitrin, Adi; Palencia, Jose María; Dai, Liang; Ji, Lingyuan; Pascale, Massimo

Abstract

In this work, we present a constraint on the abundance of supergiant (SG) stars at redshift z ≈ 1, based on recent observations of a
strongly lensed arc at this redshift. First we derived a free-form model of MACS J0416.1-2403 using data from the Beyond Ultradeep Frontier Fields and Legacy Observations (BUFFALO) program. The new lens model is based on 72 multiply lensed galaxies that
produce 214 multiple images, making it the largest sample of spectroscopically confirmed lensed galaxies on this cluster. The larger
coverage in BUFFALO allowed us to measure the shear up to the outskirts of the cluster, and extend the range of lensing constraints
up to ∼1 Mpc from the central region, providing a mass estimate up to this radius. As an application, we make predictions for the
number of high-redshift multiply lensed galaxies detected in future observations with the James Webb Space Telescope (JWST).
Then we focus on a previously known lensed galaxy at z = 1.0054, nicknamed Spock, which contains four previously reported
transients. We interpret these transients as microcaustic crossings of SG stars and explain how we computed the probability of such
events. Based on simplifications regarding the stellar evolution, we find that microlensing (by stars in the intracluster medium) of
SG stars at z = 1.0054 can fully explain these events. The inferred abundance of SG stars is consistent with either (1) a number
density of stars with bolometric luminosities beyond the Humphreys-Davidson (HD) limit (Lmax ≈ 6 × 105 L for red stars), which
is below ∼400 stars kpc−2, or (2) the absence of stars beyond the HD limit but with a SG number density of ∼9000 kpc−2 for stars
with luminosities between 105 L and 6 × 105 L. This is equivalent to one SG star per 10 × 10 pc2. Finally, we make predictions for
future observations with JWST’s NIRcam. We find that in observations made with the F200W filter that reach 29 mag AB, if cool red SG stars exist at z ≈ 1 beyond the HD limit, they should be easily detected in this arc.

Citation

Diego, J. M., Li, S. K., Meena, A. K., Niemiec, A., Acebron, A., Jauzac, M., …Pascale, M. (2024). BUFFALO/Flashlights: Constraints on the abundance of lensed supergiant stars in the Spock galaxy at redshift 1. Astronomy & Astrophysics, 681, Article A124. https://doi.org/10.1051/0004-6361/202346761

• Journal Article Type: Article
• Acceptance Date: Nov 1, 2023
• Online Publication Date: Jan 24, 2024
• Publication Date: 2024-01
• Deposit Date: Mar 26, 2024
• Publicly Available Date: Mar 26, 2024
• Journal: Astronomy & Astrophysics
• Print ISSN: 0004-6361
• Electronic ISSN: 1432-0746
• Publisher: EDP Sciences
• Peer Reviewed: Peer Reviewed
• Volume: 681
• Article Number: A124
• DOI: https://doi.org/10.1051/0004-6361/202346761
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/2347711