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VENUS: A Strongly Lensed Clumpy Galaxy at $z\sim11-12$ behind the Galaxy Cluster MACS J0257.1-2325

Minami Nakane, Vasily Kokorev, Seiji Fujimoto, Masami Ouchi, Derek J. McLeod, Miriam Golubchik, Masamune Oguri, Adi Zitrin, Cecilia Bondestam, Callum T. Donnan, Gabriel Brammer, Steven L. Finkelstein, Chris Willott, Angela Adamo, Eros Vanzella, Marusa Bradač, Matteo Messa, Hiroto Yanagisawa, Fengwu Sun, Henry C. Ferguson, Ray A. Lucas, Dan Coe, Johan Richard, Abdurro'uf, Hollis B. Akins, Joseph F. V. Allingham, Ricardo O. Amorín, Yoshihisa Asada, Hakim Atek, Rachel Bezanson, Larry D. Bradley, John Chisholm, Christopher J. Conselice, Pratika Dayal, Miroslava Dessauges-Zavadsky, Jose M. Diego, Andreas L. Faisst, Qinyue Fei, Brenda L. Frye, Yoshinobu Fudamoto, Lukas J. Furtak, Yuichi Harikane, Tiger Yu-Yang Hsiao, Yolanda Jiménez-Teja, Jeyhan S. Kartaltepe, Tomokazu Kiyota, Anton M. Koekemoer, Claudia del P. Lagos, Georgios E. Magdis, Ashish Kumar Meena, Lamiya Mowla, Gaël Noirot, Pascal A. Oesch, Yoshiaki Ono, Rafael Ortiz, Richard Pan, Casey Papovich, Justin D. Pierel, Massimo Ricotti, Luke Robbins, Daniel Schaerer, Raffaella Schneider, Tommaso Treu, Francesco Valentino, Rogier A. Windhorst, Franz E. Bauer, Volker Bromm, Eiichi Egami, Mauro González-Otero, Kotaro Kohno, Ivo Labbe, Jorryt Matthee, Marcie Mun, Rohan P. Naidu, Roberta Tripodi

Abstract

We present the discovery of a strongly lensed galaxy at $z\sim11-12$, dubbed the ``Misty Moons'', identified in the JWST Treasury Survey, Vast Exploration for Nascent, Unexplored Sources (VENUS). The Misty Moons is gravitationally lensed by the galaxy cluster MACS J0257.1-2325 at $z=0.505$, and has five multiple images suggested by two independent lensing models. Two of the five images, ID1 and ID2 ($μ\sim 20-30$), are very bright (F200W$\sim26$ AB mag) and exhibit blue SEDs with prominent Ly$α$ breaks. In the source plane, the Misty Moons is a sub-$L^*$ galaxy ($M_{\rm UV}\sim-18.0$ mag) resolved into multiple stellar clumps, each of which has effective radius of $r_\mathrm{eff}\sim 10-70$ pc and stellar mass of $\sim10^7\ M_\odot$. These clumps dominate the stellar mass budget of the Misty Moons ($\gtrsim80\%$), similar to other high-$z$ clumps, which suggests a highly clustered mode of star formation in the early Universe, unlike seen in local dwarf galaxies. We convolve the source-plane image with the JWST/NIRCam point-spread function to produce a mock NIRCam image of the Misty Moons without lensing magnification, and find that the intrinsic galaxy has a radial surface-brightness profile comparable to those of $z\gtrsim10$ faint galaxies, such as JADES-GS-z13-0 and JADES-GS-z14-1, indicating that the Misty Moons represents a typical $z\gtrsim10$ faint galaxy. The Misty Moons, a lensed galaxy with resolved internal structures, provides an ideal laboratory for exploring the early stages of galaxy formation at $z\gtrsim10$.

VENUS: A Strongly Lensed Clumpy Galaxy at $z\sim11-12$ behind the Galaxy Cluster MACS J0257.1-2325

Abstract

We present the discovery of a strongly lensed galaxy at , dubbed the ``Misty Moons'', identified in the JWST Treasury Survey, Vast Exploration for Nascent, Unexplored Sources (VENUS). The Misty Moons is gravitationally lensed by the galaxy cluster MACS J0257.1-2325 at , and has five multiple images suggested by two independent lensing models. Two of the five images, ID1 and ID2 (), are very bright (F200W AB mag) and exhibit blue SEDs with prominent Ly breaks. In the source plane, the Misty Moons is a sub- galaxy ( mag) resolved into multiple stellar clumps, each of which has effective radius of pc and stellar mass of . These clumps dominate the stellar mass budget of the Misty Moons (), similar to other high- clumps, which suggests a highly clustered mode of star formation in the early Universe, unlike seen in local dwarf galaxies. We convolve the source-plane image with the JWST/NIRCam point-spread function to produce a mock NIRCam image of the Misty Moons without lensing magnification, and find that the intrinsic galaxy has a radial surface-brightness profile comparable to those of faint galaxies, such as JADES-GS-z13-0 and JADES-GS-z14-1, indicating that the Misty Moons represents a typical faint galaxy. The Misty Moons, a lensed galaxy with resolved internal structures, provides an ideal laboratory for exploring the early stages of galaxy formation at .

Paper Structure

This paper contains 14 sections, 8 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Observation and Photometry
  3. JWST and HST Observations
  4. Photometry
  5. Photometric Redshift
  6. Lens Models
  7. Zitrin-Analytic (dPIE-PIEMD) Model
  8. Glafic Model
  9. Clump Modeling
  10. Results and Discussion
  11. Physical Properties
  12. Clump Formation
  13. Summary
  14. Photometry

Figures (8)

  • Figure 1: NIRCam color image (R: F356W+F444W, G: F200W+F277W, B: F115W+F150W) of the MACS J0257.1-2325 cluster field. The white curve indicates the critical curve at $z=11-12$. The white squares show the positions of ID1-ID5 of the Misty Moons predicted by our independent lensing models while the colored circles denote the $z\sim1-8$ multiple images used to constrain the lensing models (see Section \ref{['sec:lensmodel']}). The $3"\times3"$ cutout images show the zoom in on ID1, ID2, and a candidate for ID3.
  • Figure 2: JWST + HST images and SED fitting results for the entire systems of ID1 (top) and ID2 (bottom) of the Misty Moons. The upper panels show the $1\hbox{$.\!\!^{\prime\prime}$}5\ \times\ 1\hbox{$.\!\!^{\prime\prime}$}5$ cutout images of $13$ filters (F435W, F555W, F814W, F090W, F115W, F150W, F200W, F210M, F277W, F300M, F356W, F410M, and F444W). The lower left and right panels present the results from EAZY and Prospector fitting, respectively. The black circles indicate observed fluxes with their $1\sigma$ errors and wavelength coverages. For filters with non-detections, the $2\sigma$ upper limits are presented. The red curves (squares) indicate best-fit spectra (photometry) with no Ly$\alpha$ emission. The blue curves and squares are the same as the red ones, but with Ly$\alpha$ emission. The inset panels show the posterior probability distributions for redshifts.
  • Figure 3: Absolute UV magnitude as a function of redshift. The red filled circles and squares indicate ID1 and ID2 of the Misty Moons ($z_\mathrm{phot}\sim11-12$), respectively. The magenta filled circles represent highly magnified galaxies of the Cosmic Gems arc ($z_\mathrm{spec}=9.63$; Adamo2024Bradley2024Messa2025b) and BulletArc-z11 ($z_\mathrm{spec}=11.10$; Bradac2025). The small filled symbols show the individual clumps of these galaxies. The magenta and black open circles denote the other spectroscopically confirmed $z>9$ galaxies in lensing fields Hsiao2023Hsiao2024Stiavelli2023Williams2023Bradac2024Fujimoto2024Marconcini2024McLeod2024Roberts-Borsani2024Napolitano2025Yanagisawa2025 and blank fields ArrabalHaro2023Bunker2023Curtis-Lake2023Carniani2024Castellano2024D'Eugenio2024Hainline2024Harikane2024Zavala2024Kokorev2025bNaidu2025Napolitano2025Schouws2025Tang2025Witstok2025, respectively.
  • Figure 4: Detection images (F200W + F277W + F356W + 444W) of ID1 and ID2 in the image plane (left) and source plane (right). The white lines indicate the isophotal regions where the entire systems and individual clumps are detected.
  • Figure 5: Clump modeling results for ID1 and ID2 of the Misty Moons system. From left to right, the $1\hbox{$.\!\!^{\prime\prime}$}5\times1\hbox{$.\!\!^{\prime\prime}$}5$ cutout images, best-fit model images, and residual images divided by the $1\sigma$ error maps are presented.
  • ...and 3 more figures