LBT/LUCIFER OBSERVATIONS OF THE z {approx} 2 LENSED GALAXY J0900+2234
- Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States)
- Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, British Columbia, V9E 2E7 (Canada)
- Landessternwarte Koenigstuhl, Zentrum fuer Astronomie Heidelberg, Koenigstuhl 12, 69117 Heidelberg (Germany)
- Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching (Germany)
- Astronomisches Institut, Ruhr-Universitaet, Universitaetstrasse 150, D-44780 Bochum (Germany)
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 signal-to-noise ratio rest-frame spectra covered by the H + K band, we detected H{beta}, [O III], H{alpha}, [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 (E{sub g} (B - V)) was computed from the flux ratio of H{alpha} and H{beta} and appears to be much higher than that toward the stellar continuum (E{sub s} (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 {approx} 2 star-forming galaxies. From the flux ratio of [S II]{lambda}6717 and [S II]{lambda}6732, we found that the electron number density of the H II regions in the high-z galaxy was {approx_equal}1000 cm{sup -3}, consistent with other z {approx} 2 galaxies but much higher than that in local H II regions. The star formation rate was estimated via the H{alpha} luminosity, after correction for the lens magnification, to be about 365 {+-} 69 M{sub sun} yr{sup -1}. Combining the FWHM of H{alpha} emission lines and the half-light radius, we found that the dynamical mass of the lensed galaxy is (5.8 {+-} 0.9) x 10{sup 10} M{sub sun}. The gas mass is (5.1 {+-} 1.1) x 10{sup 10} M{sub sun} from the H{alpha} flux surface density using global Kennicutt-Schmidt law, indicating a very high gas fraction of 0.79 {+-} 0.19 in J0900+2234.
- OSTI ID:
- 21476675
- Journal Information:
- Astrophysical Journal, Vol. 725, Issue 2; Other Information: DOI: 10.1088/0004-637X/725/2/1877; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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