Volume 641, September 2020
|Number of page(s)||16|
|Published online||22 September 2020|
A high redshift population of galaxies at the North Ecliptic Pole
Unveiling the main sequence of dusty galaxies⋆
European Space Astronomy Center, 28691 Villanueva de la Cañada, Spain
2 RAL Space, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX, UK
3 Oxford Astrophysics, University of Oxford, Keble Rd, Oxford OX1 3RH, UK
4 Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK
5 National Centre for Nuclear Research ul. Pasteura 7, 02-093 Warsaw, Poland
6 Aix Marseille Univ, CNRS, CNES, LAM Marseille, France
7 Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo Osservatorio, 3, 35122 Padova, Italy
8 Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, UK
9 Telespazio Vega UK for ESA, European Space Astronomy Centre, Operations Department, 28691 Villanueva de la Cañada, Spain
10 Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara, Kanagawa 252-5210, Japan
11 National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu, Taiwan 30013
12 Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
13 Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547, USA
14 National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo, Japan
15 Japan Space Forum, 3-2-1, Kandasurugadai, Chiyoda-ku, Tokyo 101-0062, Japan
16 Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
17 Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No.1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
18 Research Center for Space and Cosmic Evolution, Ehime University, 2-Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
19 Instituto de Astronomıia sede Ensenada Universidad Nacional Autonoma de Mexico Km 107, Carret. Tij.-Ens., Ensenada, 22060 BC, Mexico
Accepted: 3 July 2020
Context. Dusty high-z galaxies are extreme objects with high star formation rates (SFRs) and luminosities. Characterising the properties of this population and analysing their evolution over cosmic time is key to understanding galaxy evolution in the early Universe.
Aims. We select a sample of high-z dusty star-forming galaxies (DSFGs) and evaluate their position on the main sequence (MS) of star-forming galaxies, the well-known correlation between stellar mass and SFR. We aim to understand the causes of their high star formation and quantify the percentage of DSFGs that lie above the MS.
Methods. We adopted a multi-wavelength approach with data from optical to submillimetre wavelengths from surveys at the North Ecliptic Pole to study a submillimetre sample of high-redshift galaxies. Two submillimetre selection methods were used, including: sources selected at 850 μm with the Sub-millimetre Common-User Bolometer Array 2) SCUBA-2 instrument and Herschel-Spectral and Photometric Imaging Receiver (SPIRE) selected sources (colour-colour diagrams and 500 μm risers), finding that 185 have good multi-wavelength coverage. The resulting sample of 185 high-z candidates was further studied by spectral energy distribution fitting with the CIGALE fitting code. We derived photometric redshifts, stellar masses, SFRs, and additional physical parameters, such as the infrared luminosity and active galactic nuclei (AGN) contribution.
Results. We find that the Herschel-SPIRE selected DSFGs generally have higher redshifts (z = 2.57−0.09+0.08) than sources that are selected solely by the SCUBA-2 method (z = 1.45−0.06+0.21). We find moderate SFRs (797−50+108 M⊙ yr−1), which are typically lower than those found in other studies. We find that the different results in the literature are, only in part, due to selection effects, as even in the most extreme cases, SFRs are still lower than a few thousand solar masses per year. The difference in measured SFRs affects the position of DSFGs on the MS of galaxies; most of the DSFGs lie on the MS (60%). Finally, we find that the star formation efficiency (SFE) depends on the epoch and intensity of the star formation burst in the galaxy; the later the burst, the more intense the star formation. We discuss whether the higher SFEs in DSFGs could be due to mergers.
Key words: galaxies: evolution / galaxies: high-redshift / galaxies: starburst / submillimeter: galaxies
A table of the multi-wavelength photometry is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/641/A129
© ESO 2020
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