Skip to content

The "cosmic Seagull": A Highly Magnified Disk-like Galaxy at z ≃ 2.8 behind the Bullet Cluster

Research output: Contribution to journalArticle

  • V. Motta
  • E. Ibar
  • T. Verdugo
  • J. Molina
  • T. M. Hughes
  • M. Birkinshaw
  • O. López-Cruz
  • J. H. Black
  • D. Gunawan
  • C. Horellou
  • J. Magana
Original languageEnglish
Article numberL16
Number of pages5
JournalAstrophysical Journal Letters
Issue number2
Early online date13 Aug 2018
DateAccepted/In press - 28 Jul 2018
DateE-pub ahead of print - 13 Aug 2018
DatePublished (current) - 20 Aug 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) × 1010 M o within 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 (f gas ≤ 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 M o yr-1), implying a molecular gas depletion time of 0.25 ± 0.08 Gyr.

    Research areas

  • galaxies: clusters: individual (1ES0657-558), galaxies: evolution, galaxies: ISM, gravitational lensing: strong, submillimeter: galaxies

Download statistics

No data available



  • Full-text PDF (final published version)

    Rights statement: This is the final published version of the article (version of record). It first appeared online via IOP at Please refer to any applicable terms of use of the publisher.

    Final published version, 1.06 MB, PDF document


View research connections

Related faculties, schools or groups