The "Cosmic Seagull": A Highly Magnified Disk-like Galaxy at z ≃ 2.8 behind the Bullet Cluster
Journal article, 2018

We present Atacama Large Millimeter/submillimeter Array measurements of the "Cosmic Seagull," a strongly magnified galaxy at z = 2.7779 behind the Bullet Cluster. We report CO(3-2) and continuum 344 μm (rest-frame) data at one of the highest differential magnifications ever recorded at submillimeter wavelengths (μ up to ∼50), facilitating a characterization of the kinematics of a rotational curve in great detail (at ∼620 pc resolution in the source plane). We find no evidence for a decreasing rotation curve, from which we derive a dynamical mass of (6.3 ± 0.7) × 1010Mowithin r = 2.6 ± 0.1 kpc. The discovery of a third, unpredicted, image provides key information for a future improvement of the lensing modeling of the Bullet Cluster and allows a measure of the stellar mass, , unaffected by strong differential magnification. The baryonic mass is expected to be dominated by the molecular gas content (fgas≤ 80 ± 20%) based on an mass estimated from the difference between dynamical and stellar masses. The star formation rate (SFR) is estimated via the spectral energy distribution (SFR = 190 ± 10 Moyr-1), implying a molecular gas depletion time of 0.25 ± 0.08 Gyr.

galaxies: ISM

galaxies: clusters: individual (1ES0657-558)

galaxies: evolution

gravitational lensing: strong

submillimeter: galaxies


V. Motta

University of Valparaíso

E. Ibar

University of Valparaíso

T. Verdugo

Universidad Nacional Autonoma de Mexico

J. Molina

Universidad de Chile

T. M. Hughes

Chinese Academy of Sciences

University of Science and Technology of China

University of Valparaíso

M. Birkinshaw

University of Bristol

O. López-Cruz

National Institute of Astrophysics, Optics and Electronics

John H Black

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

D. Gunawan

University of Valparaíso

Cathy Horellou

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

J. Magana

University of Valparaíso

Astrophysical Journal Letters

2041-8205 (ISSN) 2041-8213 (eISSN)

Vol. 863 2 L16

Subject Categories

Subatomic Physics

Astronomy, Astrophysics and Cosmology

Atom and Molecular Physics and Optics


Basic sciences



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