Issue |
A&A
Volume 522, November 2010
|
|
---|---|---|
Article Number | L4 | |
Number of page(s) | 4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361/201015673 | |
Published online | 29 October 2010 |
Letter to the Editor
Discovery of an extremely bright submillimeter galaxy at z = 3.93
1
Observatoire de Paris, LERMA, CNRS, 61 Av. de l’Observatoire, 75014
Paris,
France
e-mail: jean-francois.lestrade@obspm.fr
2
Institut d’Astrophysique de Paris, UMR 7095, CNRS, UPMC Univ. Paris 06,
98bis
Boulevard Arago, 75014, Paris, France
3
Argelander Institute for Astronomy, University of Bonn,
Auf dem Hügel 71,
53121
Bonn,
Germany
4
Laboratoire AIM Paris-Saclay, CEA/IRFU/SAp - CNRS, Université
Paris Diderot, 91191
Gif-sur-Yvette Cedex,
France
Received:
1
September
2010
Accepted:
13
October
2010
Serendipitously we have discovered a rare, bright submillimeter galaxy (SMG) with a flux density of 30 ± 2 mJy at λ = 1.2 mm, using MAMBO2 at the IRAM 30-m millimeter telescope. Although no optical counterpart is known for MM18423+5938, we were able to measure the redshift z = 3.92960 ± 0.00013 from the detection of CO lines using the IRAM Eight MIxer Receiver (EMIR). In addition, by collecting all available photometric data in the far-infrared and radio to constrain its spectral energy distribution, we derive the FIR luminosity 4.8 × 1014/mL⊙ and mass 6.0 × 109/m M⊙ for its dust, allowing for a magnification factor m caused by a probable gravitational lens. The corresponding star-formation rate is 8.3 × 104/mM⊙/yr. The detection of three lines of the CO rotational ladder, and a significant upper limit for a fourth CO line, allow us to estimate an H2 mass of between 1.9 × 1011/m M⊙ and 1.1 × 1012/m M⊙. The two lines C I and C I were clearly detected and yield a [C I]/[H2] number abundance of between 1.4 × 10-5 and 8.0 × 10-5. Upper limits are presented for emission lines of HCN, HCO+, HNC, H2O, and of other molecules. The moderate excitation of the CO lines is indicative of an extended starburst, and excludes the dominance of an AGN in heating this high-z SMG.
Key words: galaxies: evolution / galaxies: high-redshift / galaxies: ISM / infrared: galaxies / submillimeter: galaxies
© ESO, 2010
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