Herschel-ATLAS: A Binary HyLIRG Pinpointing a Cluster of Starbursting Protoellipticals

Ivison, R.; Swinbank, A.; Smail, I.; Harris, A.; Bussmann, R.; Cooray, A.; Cox, P.; Fu, H.; Kovács, A.; Krips, M.; Narayanan, D.; Negrello, M.; Neri, R.; Peñarrubia, J.; Richard, J.; Riechers, D.; Rowlands, K.; Staguhn, J.; Targett, T.; Amber, S.; Baker, A.; Bourne, N.; Bertoldi, F.; Bremer, M.; Calanog, J.; Clements, D.; Dannerbauer, H.; Dariush, A.; De Zotti, G.; Dunne, L.; Eales, S.; Farrah, D.; Fleuren, S.; Franceschini, A.; Geach, J.; George, R.; Helly, J.; Hopwood, R.; Ibar, E.; Jarvis, M.; Kneib, J.; Maddox, S.; Omont, A.; Scott, D.; Serjeant, S.; Smith, M.; Thompson, M.; Valiante, E.; Valtchanov, I.; Vieira, J.; Werf, P.P. van der

doi:doi:10.1088/0004-637X/772/2/137

Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies across an {ap}100 kpc region{mdash}a cluster of starbursting protoellipticals. Via subarcsecond interferometric imaging we have measured accurate gas and star formation surface densities. The two brightest galaxies span ~{}3 kpc FWHM in submillimeter/radio continuum and CO J = 4-3, and double that in CO J = 1-0. The broad CO line is due partly to the multitude of constituent galaxies and partly to large rotational velocities in two counter-rotating gas disks{mdash}a scenario predicted to lead to the most intense starbursts, which will therefore come in pairs. The disks have M $_{dyn}$ of several { imes} 10$^{11}$ M $_{⊙}$, and gas fractions of ~{}40%. Velocity dispersions are modest so the disks are unstable, potentially on scales commensurate with their radii:...Show more Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies across an {ap}100 kpc region{mdash}a cluster of starbursting protoellipticals. Via subarcsecond interferometric imaging we have measured accurate gas and star formation surface densities. The two brightest galaxies span ~{}3 kpc FWHM in submillimeter/radio continuum and CO J = 4-3, and double that in CO J = 1-0. The broad CO line is due partly to the multitude of constituent galaxies and partly to large rotational velocities in two counter-rotating gas disks{mdash}a scenario predicted to lead to the most intense starbursts, which will therefore come in pairs. The disks have M $_{dyn}$ of several { imes} 10$^{11}$ M $_{⊙}$, and gas fractions of ~{}40%. Velocity dispersions are modest so the disks are unstable, potentially on scales commensurate with their radii: these galaxies are undergoing extreme bursts of star formation, not confined to their nuclei, at close to the Eddington limit. Their specific star formation rates place them {gt}~{} 5 { imes} above the main sequence, which supposedly comprises large gas disks like these. Their high star formation efficiencies are difficult to reconcile with a simple volumetric star formation law. N-body and dark matter simulations suggest that this system is the progenitor of a B(inary)-type {ap}10$^{14.6}$-M $_{⊙}$ cluster.Show less

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Herschel-ATLAS: A Binary HyLIRG Pinpointing a Cluster of Starbursting Protoellipticals