Detection of molecular gas in a distant submillimetre galaxy at z=4.76 with ATCA
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Date
2010-04-22Author
Coppin, Kristen
Chapman, Scott
Smail, Ian
Swinbank, Mark
Walter, Fabian
Wardlow, Julie
Weiss, Axel
Alexander, David M.
Brandt, Niel
Dannerbauer, Helmut
De Breuck, Carlos
Dickinson, Mark
Dunlop, James
Edge, Alastair
Emonts, Bjorn
Greve, Thomas
Huynh, Minh
Ivison, Rob
Knudsen, Kirsten
Menten, Karl
Schinnerer, Eva
van der Werf, Paul
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We have detected the CO(2-1) transition from the submillimetre galaxy (SMG) LESSJ033229.4-275619 at z=4.755 using the new Compact Array Broadband Backend system on the Australian Telescope Compact Array. These data have identified a massive gas reservoir available for star formation for the first time in an SMG at z~5. We use the luminosity and velocity width (FWHM of 160 km/s) of the CO(2--1) line emission to constrain the gas and dynamical mass of Mgas~1.6x10^10 Msun and Mdyn(<2kpc)~5x10^10 (0.25/sin^2(i)) Msun, respectively, similar to that observed for SMGs at lower redshifts of z~2-4, although we note that our observed CO FWHM is a factor of ~3 narrower than typically seen in SMGs. Together with the stellar mass we estimate a total baryonic mass of Mbary~1x10^11 Msun, consistent with the dynamical mass for this young galaxy within the uncertainties. Dynamical and baryonic mass limits of high-redshift galaxies are useful tests of galaxy formation models: using the known z~4-5 SMGs as examples of massive baryonic systems, we find that their space density is consistent with that predicted by current galaxy formation models. In addition, these observations have helped to confirm that z~4-5 SMGs possess the baryonic masses and gas consumption timescales necessary to be the progenitors of the luminous old red galaxies seen at z~3. Our results provide a preview of the science that ALMA will enable on the formation and evolution of the earliest massive galaxies in the Universe.
Citation
Coppin, Kristen, Scott Chapman, Ian Smail, Mark Swinbank, et al. 2010. "Detection of molecular gas in a distant submillimetre galaxy at z=4.76 with ATCA." Monthly Notices of the Royal Astronomical Society 407:103