期刊
ASTRONOMY & ASTROPHYSICS
卷 496, 期 1, 页码 45-50出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361:200810876
关键词
galaxies: evolution; galaxies: high-redshift; galaxies: ISM; galaxies: starburst
资金
- INSU/CNRS (France)
- MPG (Germany)
- IGN (Spain)
- European Community's Sixth Framework Programme
- CNRS
- Deutsche Forschungsgemeinschaft (DFG) [SFB 494]
- DFG Priority Programme [1177]
Context. Submillimetre galaxies (SMGs) are distant, dusty galaxies undergoing star formation at prodigious rates. Recently there has been major progress in understanding the nature of the bright SMGs (i.e. S(850) mu m > 5 mJy). The samples for the fainter SMGs are small and are currently in a phase of being built up through identification studies. Aims. We study the molecular gas content in the two SMGs, SMMJ163555 and SMMJ163541, at redshifts z = 1.034 and z = 3.187 with unlensed submillimetre fluxes of 0.4 mJy and 6.0 mJy. Both SMGs are gravitationally lensed by the foreground cluster Abell 2218. Results. The CO(2-1) line was detected for SMMJ163555 at redshift 1.0313 with an integrated line intensity of 1.2 +/- 0.2 Jy kms(-1) and a line width of 410 +/- 120 km s(-1). From this a gas mass of 1.6 x 10(9) M(circle dot) is derived and a star formation efficiency of 440 L(circle dot)/M(circle dot) estimated. The CO(3-2) line was detected for SMMJ163541 at redshift 3.1824, possibly with a second component at redshift 3.1883, with an integrated line intensity of 1.0 +/- 0.1 Jy kms(-1) and a line width of 280 +/- 50 km s(-1). From this a gas mass of 2.2 x 10(10) M(circle dot) is derived and a star formation efficiency of 1000 L(circle dot)/M(circle dot) is estimated. For SMMJ163556, the CO(4-3) is undetected within the redshift range 4.035-4.082 down to a sensitivity of 0.15 Jy km s(-1) Conclusions. Our CO-line observations confirm the optical redshifts for SMMJ163555 and SMMJ163541. The CO-line luminosity L'(CO) for both galaxies is consistent with the L(FIR)-L'(CO) relation. SMMJ163555 has the lowest far-infrared luminosity of all SMGs with a known redshift and is one of the few high-redshift LIRGs whose properties can be estimated prior to ALMA.
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