ALBERT

Description: Massive galaxies in the early Universe have been shown to be forming stars at surprisingly high rates. Prominent examples are dust-obscured galaxies which are luminous when observed at sub-millimetre wavelengths and which may be forming stars at a rate of 1,000 solar masses (M(middle dot in circle)) per year. These intense bursts of star formation are believed to be driven by mergers between gas-rich galaxies. Probing the properties of individual star-forming regions within these galaxies, however, is beyond the spatial resolution and sensitivity of even the largest telescopes at present. Here we report observations of the sub-millimetre galaxy SMMJ2135-0102 at redshift z = 2.3259, which has been gravitationally magnified by a factor of 32 by a massive foreground galaxy cluster lens. This magnification, when combined with high-resolution sub-millimetre imaging, resolves the star-forming regions at a linear scale of only 100 parsecs. We find that the luminosity densities of these star-forming regions are comparable to the dense cores of giant molecular clouds in the local Universe, but they are about a hundred times larger and 10(7) times more luminous. Although vigorously star-forming, the underlying physics of the star-formation processes at z approximately 2 appears to be similar to that seen in local galaxies, although the energetics are unlike anything found in the present-day Universe.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Swinbank, A M -- Smail, I -- Longmore, S -- Harris, A I -- Baker, A J -- De Breuck, C -- Richard, J -- Edge, A C -- Ivison, R J -- Blundell, R -- Coppin, K E K -- Cox, P -- Gurwell, M -- Hainline, L J -- Krips, M -- Lundgren, A -- Neri, R -- Siana, B -- Siringo, G -- Stark, D P -- Wilner, D -- Younger, J D -- England -- Nature. 2010 Apr 1;464(7289):733-6. doi: 10.1038/nature08880. Epub 2010 Mar 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE, UK. a.m.swinbank@dur.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20305639" target="_blank"〉PubMed〈/a〉

Description: The detection of circumstellar water vapour around the ageing carbon star IRC +10216 challenged the current understanding of chemistry in old stars, because water was predicted to be almost absent in carbon-rich stars. Several explanations for the water were postulated, including the vaporization of icy bodies (comets or dwarf planets) in orbit around the star, grain surface reactions, and photochemistry in the outer circumstellar envelope. With a single water line detected so far from this one carbon-rich evolved star, it is difficult to discriminate between the different mechanisms proposed. Here we report the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +10216 using the Herschel satellite. This includes some high-excitation lines with energies corresponding to approximately 1,000 K, which can be explained only if water is present in the warm inner sooty region of the envelope. A plausible explanation for the warm water appears to be the penetration of ultraviolet photons deep into a clumpy circumstellar envelope. This mechanism also triggers the formation of other molecules, such as ammonia, whose observed abundances are much higher than hitherto predicted.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Decin, L -- Agundez, M -- Barlow, M J -- Daniel, F -- Cernicharo, J -- Lombaert, R -- De Beck, E -- Royer, P -- Vandenbussche, B -- Wesson, R -- Polehampton, E T -- Blommaert, J A D L -- De Meester, W -- Exter, K -- Feuchtgruber, H -- Gear, W K -- Gomez, H L -- Groenewegen, M A T -- Guelin, M -- Hargrave, P C -- Huygen, R -- Imhof, P -- Ivison, R J -- Jean, C -- Kahane, C -- Kerschbaum, F -- Leeks, S J -- Lim, T -- Matsuura, M -- Olofsson, G -- Posch, T -- Regibo, S -- Savini, G -- Sibthorpe, B -- Swinyard, B M -- Yates, J A -- Waelkens, C -- England -- Nature. 2010 Sep 2;467(7311):64-7. doi: 10.1038/nature09344.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium. Leen.Decin@ster.kuleuven.be〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20811453" target="_blank"〉PubMed〈/a〉

Description: Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg(2-2x)Fe(2x)SiO(4)) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x approximately 0.29). In the cold outskirts of the beta Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of beta Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 +/- 0.001) and show that they make up 3.6 +/- 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though beta Pictoris is more massive and more luminous and has a different planetary system architecture.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉de Vries, B L -- Acke, B -- Blommaert, J A D L -- Waelkens, C -- Waters, L B F M -- Vandenbussche, B -- Min, M -- Olofsson, G -- Dominik, C -- Decin, L -- Barlow, M J -- Brandeker, A -- Di Francesco, J -- Glauser, A M -- Greaves, J -- Harvey, P M -- Holland, W S -- Ivison, R J -- Liseau, R -- Pantin, E E -- Pilbratt, G L -- Royer, P -- Sibthorpe, B -- England -- Nature. 2012 Oct 4;490(7418):74-6. doi: 10.1038/nature11469.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium. bldevries.science@gmail.com〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23038467" target="_blank"〉PubMed〈/a〉

Description: Massive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Bang.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Riechers, Dominik A -- Bradford, C M -- Clements, D L -- Dowell, C D -- Perez-Fournon, I -- Ivison, R J -- Bridge, C -- Conley, A -- Fu, Hai -- Vieira, J D -- Wardlow, J -- Calanog, J -- Cooray, A -- Hurley, P -- Neri, R -- Kamenetzky, J -- Aguirre, J E -- Altieri, B -- Arumugam, V -- Benford, D J -- Bethermin, M -- Bock, J -- Burgarella, D -- Cabrera-Lavers, A -- Chapman, S C -- Cox, P -- Dunlop, J S -- Earle, L -- Farrah, D -- Ferrero, P -- Franceschini, A -- Gavazzi, R -- Glenn, J -- Solares, E A Gonzalez -- Gurwell, M A -- Halpern, M -- Hatziminaoglou, E -- Hyde, A -- Ibar, E -- Kovacs, A -- Krips, M -- Lupu, R E -- Maloney, P R -- Martinez-Navajas, P -- Matsuhara, H -- Murphy, E J -- Naylor, B J -- Nguyen, H T -- Oliver, S J -- Omont, A -- Page, M J -- Petitpas, G -- Rangwala, N -- Roseboom, I G -- Scott, D -- Smith, A J -- Staguhn, J G -- Streblyanska, A -- Thomson, A P -- Valtchanov, I -- Viero, M -- Wang, L -- Zemcov, M -- Zmuidzinas, J -- England -- Nature. 2013 Apr 18;496(7445):329-33. doi: 10.1038/nature12050.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, California 91125, USA. dr@astro.cornell.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23598341" target="_blank"〉PubMed〈/a〉

Description: Stellar archaeology 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 galaxies at redshifts z greater than 2. Although the mean molecular gas mass (5 x 10(10) solar masses) of the submillimetre bright galaxies can explain the formation of typical elliptical galaxies, it is inadequate to form elliptical galaxies that already have stellar masses above 2 x 10(11) solar masses at z approximately 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 x 10(11) solar masses. We conclude that gas-rich major galaxy mergers with intense star formation can form the most massive elliptical galaxies by z approximately 1.5.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fu, Hai -- Cooray, Asantha -- Feruglio, C -- Ivison, R J -- Riechers, D A -- Gurwell, M -- Bussmann, R S -- Harris, A I -- Altieri, B -- Aussel, H -- Baker, A J -- Bock, J -- Boylan-Kolchin, M -- Bridge, C -- Calanog, J A -- Casey, C M -- Cava, A -- Chapman, S C -- Clements, D L -- Conley, A -- Cox, P -- Farrah, D -- Frayer, D -- Hopwood, R -- Jia, J -- Magdis, G -- Marsden, G -- Martinez-Navajas, P -- Negrello, M -- Neri, R -- Oliver, S J -- Omont, A -- Page, M J -- Perez-Fournon, I -- Schulz, B -- Scott, D -- Smith, A -- Vaccari, M -- Valtchanov, I -- Vieira, J D -- Viero, M -- Wang, L -- Wardlow, J L -- Zemcov, M -- England -- Nature. 2013 Jun 20;498(7454):338-41. doi: 10.1038/nature12184. Epub 2013 May 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University of California, Irvine, California 92697, USA. haif@uci.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23698363" target="_blank"〉PubMed〈/a〉

Description: The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report excess clustering over the linear prediction at arcminute angular scales in the power spectrum of brightness fluctuations at 250, 350 and 500 mum. From this excess, we find that submillimetre galaxies are located in dark matter haloes with a minimum mass, M(min), such that log(10)[M(min)/M(middle dot in circle)] = 11.5(+0.7)(-0.2) at 350 mum, where M(middle dot in circle) is the solar mass. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the Universe, and is lower than that predicted by semi-analytical models for galaxy formation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Amblard, Alexandre -- Cooray, Asantha -- Serra, Paolo -- Altieri, B -- Arumugam, V -- Aussel, H -- Blain, A -- Bock, J -- Boselli, A -- Buat, V -- Castro-Rodriguez, N -- Cava, A -- Chanial, P -- Chapin, E -- Clements, D L -- Conley, A -- Conversi, L -- Dowell, C D -- Dwek, E -- Eales, S -- Elbaz, D -- Farrah, D -- Franceschini, A -- Gear, W -- Glenn, J -- Griffin, M -- Halpern, M -- Hatziminaoglou, E -- Ibar, E -- Isaak, K -- Ivison, R J -- Khostovan, A A -- Lagache, G -- Levenson, L -- Lu, N -- Madden, S -- Maffei, B -- Mainetti, G -- Marchetti, L -- Marsden, G -- Mitchell-Wynne, K -- Nguyen, H T -- O'Halloran, B -- Oliver, S J -- Omont, A -- Page, M J -- Panuzzo, P -- Papageorgiou, A -- Pearson, C P -- Perez-Fournon, I -- Pohlen, M -- Rangwala, N -- Roseboom, I G -- Rowan-Robinson, M -- Portal, M Sanchez -- Schulz, B -- Scott, Douglas -- Seymour, N -- Shupe, D L -- Smith, A J -- Stevens, J A -- Symeonidis, M -- Trichas, M -- Tugwell, K -- Vaccari, M -- Valiante, E -- Valtchanov, I -- Vieira, J D -- Vigroux, L -- Wang, L -- Ward, R -- Wright, G -- Xu, C K -- Zemcov, M -- England -- Nature. 2011 Feb 24;470(7335):510-2. doi: 10.1038/nature09771. Epub 2011 Feb 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics & Astronomy, University of California, Irvine, California 92697, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21326201" target="_blank"〉PubMed〈/a〉

Description: The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Page, M J -- Symeonidis, M -- Vieira, J D -- Altieri, B -- Amblard, A -- Arumugam, V -- Aussel, H -- Babbedge, T -- Blain, A -- Bock, J -- Boselli, A -- Buat, V -- Castro-Rodriguez, N -- Cava, A -- Chanial, P -- Clements, D L -- Conley, A -- Conversi, L -- Cooray, A -- Dowell, C D -- Dubois, E N -- Dunlop, J S -- Dwek, E -- Dye, S -- Eales, S -- Elbaz, D -- Farrah, D -- Fox, M -- Franceschini, A -- Gear, W -- Glenn, J -- Griffin, M -- Halpern, M -- Hatziminaoglou, E -- Ibar, E -- Isaak, K -- Ivison, R J -- Lagache, G -- Levenson, L -- Lu, N -- Madden, S -- Maffei, B -- Mainetti, G -- Marchetti, L -- Nguyen, H T -- O'Halloran, B -- Oliver, S J -- Omont, A -- Panuzzo, P -- Papageorgiou, A -- Pearson, C P -- Perez-Fournon, I -- Pohlen, M -- Rawlings, J I -- Rigopoulou, D -- Riguccini, L -- Rizzo, D -- Rodighiero, G -- Roseboom, I G -- Rowan-Robinson, M -- Sanchez Portal, M -- Schulz, B -- Scott, D -- Seymour, N -- Shupe, D L -- Smith, A J -- Stevens, J A -- Trichas, M -- Tugwell, K E -- Vaccari, M -- Valtchanov, I -- Viero, M -- Vigroux, L -- Wang, L -- Ward, R -- Wright, G -- Xu, C K -- Zemcov, M -- England -- Nature. 2012 May 9;485(7397):213-6. doi: 10.1038/nature11096.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK. mjp@mssl.ucl.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22575961" target="_blank"〉PubMed〈/a〉

Description: Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Negrello, Mattia -- Hopwood, R -- De Zotti, G -- Cooray, A -- Verma, A -- Bock, J -- Frayer, D T -- Gurwell, M A -- Omont, A -- Neri, R -- Dannerbauer, H -- Leeuw, L L -- Barton, E -- Cooke, J -- Kim, S -- da Cunha, E -- Rodighiero, G -- Cox, P -- Bonfield, D G -- Jarvis, M J -- Serjeant, S -- Ivison, R J -- Dye, S -- Aretxaga, I -- Hughes, D H -- Ibar, E -- Bertoldi, F -- Valtchanov, I -- Eales, S -- Dunne, L -- Driver, S P -- Auld, R -- Buttiglione, S -- Cava, A -- Grady, C A -- Clements, D L -- Dariush, A -- Fritz, J -- Hill, D -- Hornbeck, J B -- Kelvin, L -- Lagache, G -- Lopez-Caniego, M -- Gonzalez-Nuevo, J -- Maddox, S -- Pascale, E -- Pohlen, M -- Rigby, E E -- Robotham, A -- Simpson, C -- Smith, D J B -- Temi, P -- Thompson, M A -- Woodgate, B E -- York, D G -- Aguirre, J E -- Beelen, A -- Blain, A -- Baker, A J -- Birkinshaw, M -- Blundell, R -- Bradford, C M -- Burgarella, D -- Danese, L -- Dunlop, J S -- Fleuren, S -- Glenn, J -- Harris, A I -- Kamenetzky, J -- Lupu, R E -- Maddalena, R J -- Madore, B F -- Maloney, P R -- Matsuhara, H -- Michaowski, M J -- Murphy, E J -- Naylor, B J -- Nguyen, H -- Popescu, C -- Rawlings, S -- Rigopoulou, D -- Scott, D -- Scott, K S -- Seibert, M -- Smail, I -- Tuffs, R J -- Vieira, J D -- van der Werf, P P -- Zmuidzinas, J -- New York, N.Y. -- Science. 2010 Nov 5;330(6005):800-4. doi: 10.1126/science.1193420.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK. m.negrello@open.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21051633" target="_blank"〉PubMed〈/a〉

Description: Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Barlow, M J -- Swinyard, B M -- Owen, P J -- Cernicharo, J -- Gomez, H L -- Ivison, R J -- Krause, O -- Lim, T L -- Matsuura, M -- Miller, S -- Olofsson, G -- Polehampton, E T -- New York, N.Y. -- Science. 2013 Dec 13;342(6164):1343-5. doi: 10.1126/science.1243582.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24337290" target="_blank"〉PubMed〈/a〉

Description: We present the results of the first, deep Atacama Large Millimeter Array (ALMA) imaging covering the full ~=4.5 arcmin 2 of the Hubble Ultra Deep Field (HUDF) imaged with Wide Field Camera 3/IR on HST . Using a 45-pointing mosaic, we have obtained a homogeneous 1.3-mm image reaching 1.3 ~= 35 μJy, at a resolution of ~=0.7 arcsec. From an initial list of ~=50 〉 3.5 peaks, a rigorous analysis confirms 16 sources with S 1.3 〉 120 μJy. All of these have secure galaxy counterparts with robust redshifts (〈 z 〉 = 2.15). Due to the unparalleled supporting data, the physical properties of the ALMA sources are well constrained, including their stellar masses ( M * ) and UV+FIR star formation rates (SFR). Our results show that stellar mass is the best predictor of SFR in the high-redshift Universe; indeed at z ≥ 2 our ALMA sample contains seven of the nine galaxies in the HUDF with M * ≥ 2 x 10 10 M , and we detect only one galaxy at z 〉 3.5, reflecting the rapid drop-off of high-mass galaxies with increasing redshift. The detections, coupled with stacking, allow us to probe the redshift/mass distribution of the 1.3-mm background down to S 1.3 ~= 10 μJy. We find strong evidence for a steep star-forming ‘main sequence’ at z ~= 2, with SFR M * and a mean specific SFR ~= 2.2 Gyr –1 . Moreover, we find that ~=85 per cent of total star formation at z ~= 2 is enshrouded in dust, with ~=65 per cent of all star formation at this epoch occurring in high-mass galaxies ( M * 〉 2 x 10 10 M ), for which the average obscured:unobscured SF ratio is ~=200. Finally, we revisit the cosmic evolution of SFR density; we find this peaks at z ~= 2.5, and that the star-forming Universe transits from primarily unobscured to primarily obscured at z ~= 4.