Volume 603, July 2017
|Number of page(s)||9|
|Published online||11 July 2017|
Dust and gas in star-forming galaxies at z ~ 3
Extending galaxy uniformity to 11.5 billion years⋆
1 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Mariesvej 30, 2100 Copenhagen, Denmark
2 Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, 15236 Athens, Greece
3 Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
4 Space Science & Technology Department, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
5 CEA, Laboratoire AIM, Irfu/SAp, 91191 Gif-sur-Yvette, France
6 Aix-Marseille Univ., CNRS, LAM, Laboratoire d’Astrophysique de Marseille, 13013 Marseille, France
7 INAF Observatory of Trieste, via G. B. Tiepolo 11, 34143 Trieste, Italy
8 Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Falmer, Brighton BN1 9QH, UK
9 Instituto de Astrofisica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
10 Universidad de La Laguna, Dpto. Astrofisica, 38206 La Laguna, Tenerife, Spain
11 NOAO, 950 N. Cherry Avenue, Tucson, AZ 85719, USA
12 National Astronomical Observatories of China, Chinese Academy of Sciences, 100012 Beijing, PR China
13 China-Chile Joint Center for Astronomy, Chinese Academy of Sciences, Camino El Observatorio, 1515 Las Condes, Santiago, Chile
14 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
Received: 25 April 2017
Accepted: 15 May 2017
We present millimetre dust emission measurements of two Lyman-break galaxies at z ~ 3 and construct for the first time fully sampled infrared spectral energy distributions (SEDs), from mid-IR to the Rayleigh-Jeans tail, of individually detected, unlensed, UV-selected, main sequence (MS) galaxies at z = 3. The SED modelling of the two sources confirms previous findings, based on stacked ensembles, of an increasing mean radiation field ⟨ U ⟩ with redshift, consistent with a rapidly decreasing gas metallicity in z> 2 galaxies. Complementing our study with CO[J = 3 → 2] emission line observations, we have measured the molecular gas mass reservoir (MH2) of the systems using three independent approaches: 1) CO line observations; 2) the dust to gas mass ratio vs. metallicity relation; and 3) a single band, dust emission flux on the Rayleigh-Jeans side of the SED. All techniques return consistent MH2 estimates within a factor of two or less, yielding gas depletion time-scales (τdep ≈ 0.35 Gyr) and gas-to-stellar mass ratios (MH2/M∗ ≈ 0.5−1) for our z ~ 3 massive MS galaxies. The overall properties of our galaxies are consistent with trends and relations established at lower redshifts, extending the apparent uniformity of star-forming galaxies over the last 11.5 billion years.
Key words: evolution / infrared: galaxies / galaxies: high-redshift / galaxies: evolution / galaxies: ISM
© ESO, 2017
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