Lbt/lucifer observations of the z ∼ 2 lensed galaxy J0900+2234

Fuyan Bian, Xiaohui Fan, Jill Bechtold, Ian D. McGreer, Dennis W. Just, David J. Sand, Richard F. Green, David Thompson, Chien Y. Peng, Walter Seifert, Nancy Ageorges, Marcus Juette, Volker Knierim, Peter Buschkamp

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z = 2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared (NIR) instrument mounted on the Large Binocular Telescope. We fitted lens models to the rest-frame optical images and found that the galaxy has an intrinsic effective radius of 7.4 ± 0.8 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high signalto-noise ratio rest-frame spectra covered by the H+ K band, we detected Hβ, [O iii], Hα, [N ii], and [S ii] emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction toward the ionized H ii regions (Eg(B -V )) was computed from the flux ratio of Hα and Hβ and appears to be much higher than that toward the stellar continuum (Es (B -V )), derived from the optical and NIR broadband photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5 -1/3 solar abundance, which is much lower than for typical z ∼ 2 star-forming galaxies. From the flux ratio of [S ii]λ6717 and [S ii]λ6732, we found that the electron number density of the H ii regions in the high-z galaxy was ≃1000 cm-3, consistent with other z ∼ 2 galaxies butmuch higher than that in local H ii regions. The star formation rate was estimated via the Hα luminosity, after correction for the lens magnification, to be about 365±69M yr-1. Combining the FWHM of Hα emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 ± 0.9) × 1010M . The gas mass is (5.1 ± 1.1) × 10 10M from the Hα flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 ± 0.19 in J0900+2234.

Original languageEnglish (US)
Pages (from-to)1877-1885
Number of pages9
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 20 2010


  • Galaxies abundances
  • Galaxies:High-Redshift
  • Galaxies:ISM
  • Galaxies:evolution
  • Gravitational lensing:Strong

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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