Stellar archaeology1 shows that massive elliptical galaxies formed rapidly about ten billion years ago with star-formation rates of above several hundred solar masses per year. Their progenitors are probably the submillimetre bright galaxies2 at redshifts z greater than 2. Although the mean molecular gas mass3 (5 × 1010 solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies4 that already have stellar masses above 2 × 1011 solar masses at z ≈ 2. Here we report multi-wavelength high-resolution observations of a rare merger of two massive submillimetre bright galaxies at z = 2.3. The system is seen to be forming stars at a rate of 2,000 solar masses per year. The star-formation efficiency is an order of magnitude greater than that of normal galaxies, so the gas reservoir will be exhausted and star formation will be quenched in only around 200 million years. At a projected separation of 19 kiloparsecs, the two massive starbursts are about to merge and form a passive elliptical galaxy with a stellar mass of about 4 × 1011 solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z ≈ 1.5.
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McCarthy, P. J. et al. Evolved galaxies at z>1.5 from the Gemini Deep Deep Survey: the formation epoch of massive stellar systems. Astrophys. J. 614, L9–L12 (2004)
Barger, A. J. et al. Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift. Nature 394, 248–251 (1998)
Bothwell, M. S. et al. A survey of molecular gas in luminous sub-millimetre galaxies. Mon. Not. R. Astron. Soc. 429, 3047–3067 (2013)
Damjanov, I. et al. Red nuggets at z ∼ 1.5: compact passive galaxies and the formation of the Kormendy Relation. Astrophys. J. 695, 101–115 (2009)
Wardlow, J. L. et al. HerMES: candidate gravitationally lensed galaxies and lensing statistics at submillimeter wavelengths. Astrophys. J. 762, 59–86 (2013)
Oliver, S. J. et al. The Herschel Multi-tiered Extragalactic Survey: HerMES. Mon. Not. R. Astron. Soc. 424, 1614–1635 (2012)
Magnelli, B. et al. Dust temperature and CO→H2 conversion factor variations in the SFR-M* plane. Astron. Astrophys. 548, A22 (2012)
Kennicutt, J. & Robert, C. The global Schmidt law in star-forming galaxies. Astrophys. J. 498, 541–552 (1998)
da Cunha, E., Charlot, S. & Elbaz, D. A simple model to interpret the ultraviolet, optical and infrared emission from galaxies. Mon. Not. R. Astron. Soc. 388, 1595–1617 (2008)
Davé, R. et al. The nature of submillimetre galaxies in cosmological hydrodynamic simulations. Mon. Not. R. Astron. Soc. 404, 1355–1368 (2010)
Ivison, R. J. et al. Tracing the molecular gas in distant submillimetre galaxies via CO(1–0) imaging with the Expanded Very Large Array. Mon. Not. R. Astron. Soc. 412, 1913–1925 (2011)
Genzel, R. et al. A study of the gas-star formation relation over cosmic time. Mon. Not. R. Astron. Soc. 407, 2091–2108 (2010)
Murray, N., Quataert, E. & Thompson, T. A. The disruption of giant molecular clouds by radiation pressure and the efficiency of star formation in galaxies. Astrophys. J. 709, 191–209 (2010)
Di Matteo, T., Springel, V. & Hernquist, L. Energy input from quasars regulates the growth and activity of black holes and their host galaxies. Nature 433, 604–607 (2005)
Martin, D. C. et al. The UV-optical galaxy color-magnitude diagram. III. Constraints on evolution from the blue to the red sequence. Astrophys. J. 173 (Suppl.). 342–356 (2007)
van Dokkum, P. G. The recent and continuing assembly of field elliptical galaxies by red mergers. Astron. J. 130, 2647–2665 (2005)
Engel, H. et al. Most submillimeter galaxies are major mergers. Astrophys. J. 724, 233–243 (2010)
Chapman, S. C., Blain, A. W., Smail, I. & Ivison, R. J. A redshift survey of the submillimeter galaxy population. Astrophys. J. 622, 772–796 (2005)
Ilbert, O. et al. Galaxy stellar mass assembly between 0.2 < z < 2 from the S-COSMOS survey. Astrophys. J. 709, 644–663 (2010)
Strong, A. W. & Mattox, J. R. Gradient model analysis of EGRET diffuse galactic gamma-ray emission. Astron. Astrophys. 308, L21–L24 (1996)
Downes, D. & Solomon, P. M. Rotating nuclear rings and extreme starbursts in ultraluminous galaxies. Astrophys. J. 507, 615–654 (1998)
Narayanan, D., Krumholz, M. R., Ostriker, E. C. & Hernquist, L. A general model for the CO-H2 conversion factor in galaxies with applications to the star formation law. Mon. Not. R. Astron. Soc. 421, 3127–3146 (2012)
Magdis, G. E. et al. GOODS-Herschel: gas-to-dust mass ratios and CO-to-H2 conversion factors in normal and starbursting galaxies at high-z. Astrophys. J. 740, L15–L20 (2011)
Riechers, D. A., Hodge, J., Walter, F., Carilli, C. L. & Bertoldi, F. Extended cold molecular gas reservoirs in z≈3.4 submillimeter galaxies. Astrophys. J. 739, L31–L36 (2011)
Genzel, R. et al. The metallicity dependence of the CO → H2 conversion factor in z ≥ 1 star-forming galaxies. Astrophys. J. 746, 69–79 (2012)
Hainline, L. J. Multi-Wavelength Properties of Submillimeter-Selected Galaxies. PhD thesis, Cal. Inst. Technol. (2008)
Daddi, E. et al. Multiwavelength study of massive galaxies at z ∼ 2. I. Star formation and galaxy growth. Astrophys. J. 670, 156–172 (2007)
Elbaz, D. et al. GOODS-Herschel: an infrared main sequence for star-forming galaxies. Astron. Astrophys. 533, A119 (2011)
Narayanan, D., Bothwell, M. & Davé, R. Galaxy gas fractions at high redshift: the tension between observations and cosmological simulations. Mon. Not. R. Astron. Soc. 426, 1178–1184 (2012)
Behroozi, P. S., Conroy, C. & Wechsler, R. H. A comprehensive analysis of uncertainties affecting the stellar mass-halo mass relation for 0 < z < 4. Astrophys. J. 717, 379–403 (2010)
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. This research has made use of data from the HerMES project (http://hermes.sussex.ac.uk/). HerMES is a Herschel Key Programme using Guaranteed Time from the SPIRE instrument team, ESAC scientists and a mission scientist. SPIRE has been developed by a consortium of institutes led by Cardiff University (UK) and including the University of Lethbridge (Canada); NAOC (China); CEA, LAM (France); IFSI, the University of Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, the University of Sussex (UK); and Caltech/JPL, IPAC and the University of Colorado (USA). This development has been supported by the following national funding agencies: CSA (Canada); NAOC (China); CEA, CNES and CNRS (France); ASI (Italy); MCINN (Spain); SNSB (Sweden); STFC (UK); and NASA (USA). The data presented in this paper will be released through the HeDaM Database in Marseille at http://hedam.oamp.fr/HerMES.
The authors declare no competing financial interests.
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Fu, H., Cooray, A., Feruglio, C. et al. The rapid assembly of an elliptical galaxy of 400 billion solar masses at a redshift of 2.3. Nature 498, 338–341 (2013). https://doi.org/10.1038/nature12184