The main sequence of star forming galaxies beyond the Herschel confusion limit

Pearson, W J, Wang, L, Hurley, P D, Malek, K, Buat, V, Burgarella, D, Farrah, D, Oliver, S J, Smith, D J B and van der Tak, F F S (2018) The main sequence of star forming galaxies beyond the Herschel confusion limit. Astronomy and Astrophysics. ISSN 0250-6335 (Accepted)

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Context. Deep far-infrared (FIR) cosmological surveys are known to be affected by confusion, causing issues when examining the main sequence of star forming galaxies (MS). In the past this has typically been partially tackled by the use of stacking. However, stacking only provides the average properties of the objects in the stack. Aims. This work aims to trace the MS over 0.2 ≤ z < 6.0 using the latest de-blended Herschel photometry, which reaches ≈ 10 times deeper than the 5σ confusion limit in SPIRE. This provides more reliable star formation rates (SFRs), especially for the fainter galaxies, and hence a more reliable MS. Methods. We built a pipeline that uses the spectral energy distribution (SED) modelling and fitting tool CIGALE to generate flux density priors in the Herschel SPIRE bands. These priors where then fed into the de-blending tool XID+ to extract flux densities from the SPIRE maps. In the final step, multi-wavelength data were combined with the extracted SPIRE flux densities to constrain SEDs and provide stellar mass (M☉) and SFRs. These M☉ and SFRs were then used to populate the SFR-M☉ plane over 0.2 ≤ z < 6.0. Results. No significant evidence of a high-mass turn-over was found, resulting in the best fit being a simple two-parameter power law of the form log(SFR) = α(log(M☉) - 10:5] + β. The normalisation of the power law increased with redshift, rapidly at z ≲ 1.8, from 0.58 ± 0.09 at z ≈ 0:37 to 1.31 ± 0.08 at z ≈ 1.8. The slope was also found to increase with redshift, perhaps with an excess around 1.8 ≤ z < 2.9. Conclusions. The increasing slope indicates that galaxies become more self-similar as redshift increases. This implies that high-mass galaxies’ specific SFR increases with redshift, from 0.2 to 6.0, becoming closer to that of low-mass galaxies. The excess in the slope at 1.8 ≤ z < 2.9, if present, coincides with the peak of the cosmic star formation history.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Billy Wichaidit
Date Deposited: 04 Apr 2018 15:08
Last Modified: 04 Apr 2018 15:08

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