Molecular gas and dust in the highly magnified z similar to 2.8 galaxy behind the Bullet Cluster
Journal article, 2012

Context. The gravitational magnification provided by massive galaxy clusters makes it possible to probe the physical conditions in distant galaxies that are of lower luminosity than those in blank fields and likely more representative of the bulk of the high-redshift galaxy population. Aims. We aim to constrain the basic properties of molecular gas in a strongly magnified submm galaxy located behind the massive Bullet Cluster (1E 0657-56). This galaxy (SMM J0658) is split into three images, with a total magnification factor of almost 100. Methods. We used the Australia Telescope Compact Array (ATCA) to search for (CO)-C-12(1-0) and (CO)-C-12(3-2) line emission from SMM J0658. We also used the SABOCA bolometer camera on the Atacama Pathfinder EXperiment (APEX) telescope to measure the continuum emission at 350 mu m. Results. CO(1-0) and CO(3-2) are detected at 6.8 sigma and 7.5 sigma significance when the spectra toward the two brightest images of the galaxy are combined. From the CO(1-0) luminosity we derive a mass of cold molecular gas of (1.8 +/- 0.3) x 10(9) M-circle dot, using the CO to H-2 conversion factor commonly used for luminous infrared galaxies. This is 45 +/- 25% of the stellar mass. From the width of the CO lines we derive a dynamical mass within the CO-emitting region L of (1.3 +/- 0.4) x 10(10)(L/1 kpc) M-circle dot. We refine the redshift determination of SMM J0658 to z = 2.7793 +/- 0.0003. The CO(3-2) to CO(1-0) brightness temperature ratio is 0.56(-0.15)(+0.21), which is similar to the values found in other star-forming galaxies. Continuum emission at 350 mu m from SMM J0658 was detected with SABOCA at a signal-to-noise ratio of 3.6. The flux density is consistent with previous measurements at the same wavelength by the Herschel satellite and BLAST balloon-borne telescope. We study the spectral energy distribution of SMM J0658 and derive a dust temperature of 33 +/- 5 K and a dust mass of 1.1(-0.3)(+0.8) x 10(7) M-circle dot. Conclusions. SMM J0658 is one of the least massive submm galaxies discovered so far. As a likely representative of the bulk of the submm galaxy population, it is a prime target for future observations.


cosmology: observations


submillimeter galaxies

disk galaxies



infrared: galaxies

lensing clusters

submillimeter: galaxies


luminous infrared galaxy

co observations

photometric redshifts


Daniel Johansson

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

Cathy Horellou

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

O. Lopez-Cruz

Sebastien Muller

Chalmers, Earth and Space Sciences, Onsala Space Observatory

M. Birkinshaw

John H Black

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

M. N. Bremer

W. F. Wall

F. Bertoldi

E. Castillo

H. J. Ibarra-Medel

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 543 Article Number: A62 (pp. 1-10)

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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