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The nature of sub-millimeter and highly star-forming galaxies in the EAGLE simulation

McAlpine, S, Smail, I, Bower, RG, Swinbank, MA, Trayford, JW, Theuns, T, Baes, M, Camps, P, Crain, RA and Schaye, J (2019) The nature of sub-millimeter and highly star-forming galaxies in the EAGLE simulation. Monthly Notices of the Royal Astronomical Society, 488 (2). pp. 2440-2454. ISSN 0035-8711

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Abstract

We exploit EAGLE, a cosmological hydrodynamical simulation, to reproduce the selection of the observed sub-millimeter (submm) galaxy population by selecting the model galaxies at $z \geq 1$ with mock submm fluxes $S_{850} \geq 1$ mJy. There is a reasonable agreement between the galaxies within this sample and the properties of the observed submm population, such as their star formation rates (SFRs) at $z<3$, redshift distribution and many integrated galaxy properties. We find that the bulk of the $S_{850} \geq 1$ mJy model population is at $z = 2.5$, and that they are massive galaxies ($M_* \sim 10^{11}$ Msol) with high dust masses ($M_{\mathrm{dust}} \sim 10^{8}$ Msol), gas fractions ($f_{\mathrm{gas}} \approx 50$%) and SFRs ($\dot M_* \approx 100$ Msol/yr). They have major and minor merger fractions similar to the general population, suggesting that mergers are not the primary driver of the model submm galaxies. Instead, the $S_{850} \geq 1$ mJy model galaxies yield high SFRs primarily because they maintain a significant gas reservoir as a result of hosting an undermassive black hole. In addition, we find that not all highly star-forming EAGLE galaxies have submm fluxes $S_{850} > 1$ mJy. Thus, we investigate the nature of $z \geq 1$ highly star-forming Submm-Faint galaxies (i.e., $\dot M_* \geq 80$ Msol/yr but $S_{850}< 1$ mJy). We find they are similar to the model submm galaxies; being gas rich and hosting undermassive black holes, however they are typically lower mass ($M_* \sim 10^{10}$ Msol) and are at higher redshifts ($z>4$). These typically higher-$z$ galaxies show stronger evidence for having been triggered by major mergers, and critically, they are likely missed by current submm surveys due to their higher dust temperatures. This suggests a potentially even larger contribution to the SFR density at $z > 3$ from dust-obscured systems than implied by current observations.

Item Type: Article
Additional Information: This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Stuart McAlpine, Ian Smail, Richard G Bower, A M Swinbank, James W Trayford, Tom Theuns, Maarten Baes, Peter Camps, Robert A Crain, Joop Schaye, The nature of submillimetre and highly star-forming galaxies in the EAGLE simulation, Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 2, September 2019, Pages 2440–2454 is available online at: https://doi.org/10.1093/mnras/stz1692
Uncontrolled Keywords: 0201 Astronomical and Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
Related URLs:
Date Deposited: 24 Jul 2019 13:18
Last Modified: 24 Jul 2019 13:30
DOI or Identification number: 10.1093/mnras/stz1692
URI: http://researchonline.ljmu.ac.uk/id/eprint/11105

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