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Optical colours and spectral indices of z = 0.1 eagle galaxies with the 3D dust radiative transfer code skirt

Trayford, JW and Camps, P and Theuns, T and Baes, M and Bower, RG and Crain, RA and Gunawardhana, MLP and Schaller, M and Schaye, J and Frenk, CS (2017) Optical colours and spectral indices of z = 0.1 eagle galaxies with the 3D dust radiative transfer code skirt. Monthly Notices of the Royal Astronomical Society, 470 (1). pp. 771-779. ISSN 0035-8711

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Abstract

We present mock optical images, broad-band and H α fluxes, and D4000 spectral indices for
30 145 galaxies from the EAGLE hydrodynamical simulation at redshift z = 0.1, modelling
dust with the SKIRT Monte Carlo radiative transfer code. The modelling includes a subgrid
prescription for dusty star-forming regions, with both the subgrid obscuration of these regions
and the fraction of metals in diffuse interstellar dust calibrated against far-infrared fluxes of
local galaxies. The predicted optical colours as a function of stellar mass agree well with
observation, with the SKIRT model showing marked improvement over a simple dust-screen
model. The orientation dependence of attenuation is weaker than observed because EAGLE
galaxies are generally puffier than real galaxies, due to the pressure floor imposed on the
interstellar medium (ISM). The mock H α luminosity function agrees reasonably well with
the data, and we quantify the extent to which dust obscuration affects observed H α fluxes.
The distribution of D4000 break values is bimodal, as observed. In the simulation, 20 per cent
of galaxies deemed ‘passive’ for the SKIRT model, i.e. exhibiting D4000 >1.8, are classified
‘active’ when ISM dust attenuation is not included. The fraction of galaxies with stellar mass
greater than 1010 M that are deemed passive is slightly smaller than observed, which is due
to low levels of residual star formation in these simulated galaxies. Colour images, fluxes and
spectra of EAGLE galaxies are to be made available through the public EAGLE data base.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Date Deposited: 20 Jul 2017 14:48
Last Modified: 20 Jul 2017 14:48
DOI or Identification number: /10.1093/mnras/stx1051
URI: http://researchonline.ljmu.ac.uk/id/eprint/6839

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