Browsing by Author "Jarvis, Matthew J."

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    MIGHTEE-Hi: The relation between the Hi gas in galaxies and the cosmic web
    (Oxford University Press, 2022) Tudorache, Madalina N.; Jarvis, Matthew J.; Heywood, Ian
    We study the 3D axis of rotation (3D spin) of 77 Hi galaxies from the MIGHTEE-Hi Early Science observations, and its relation to the filaments of the cosmic web. For this Hi-selected sample, the alignment between the spin axis and the closest filament (|cos 𝜓|) is higher for galaxies closer to the filaments, with h|cos 𝜓|i = 0.66 ± 0.04 for galaxies < 5 Mpc from their closest filament compared to h|cos 𝜓|i = 0.37±0.08 for galaxies at 5 < 𝑑 < 10 Mpc. We find that galaxies with a low Hi-to-stellar mass ratio (log10 (𝑀HI/𝑀★) < 0.11) are more aligned with their closest filaments, with h|cos 𝜓|i = 0.58 ± 0.04; whilst galaxies with (log10 (𝑀HI/𝑀★) > 0.11) tend to be mis-aligned, with h|cos 𝜓|i = 0.44 ± 0.04. We find tentative evidence that the spin axis of Hi-selected galaxies tend to be aligned with associated filaments (𝑑 < 10 Mpc), but this depends on the gas fractions. Galaxies that have accumulated more stellar mass compared to their gas mass tend towards stronger alignment.
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    The star formation rates of QSOs
    (Royal Astronomical Society, 2022) Symeonidis, Myrto; Maddox, Natasha; Jarvis, Matthew J.
    We examine the far-IR properties of a sample of 5391 optically selected QSOs in the 0.5 < z < 2.65 redshift range down to log [νLν,2500(erg/s)] > 44.7, using SPIRE data from Herschel-ATLAS. We split the sample in a grid of 74 luminosity-redshift bins and compute the average optical–infrared spectral energy distribution (SED) in each bin. By normalising an intrinsic AGN template to the AGN optical power (at 5100˚A) we decompose the total infrared emission (LIR; 8—1000µm) into an AGN (LIR,AGN) and star-forming component (LIR,SF). We find that the AGN contribution to LIR increases as a function of AGN power which manifests as a reduction of the ‘far-IR bump’ in the average QSO SEDs. We note that LIR,SF does not correlate with AGN power; the mean star formation rates (SFRs) of AGN host galaxies are a function of redshift only and they range from ∼6 M⊙/yr at z ∼ 0 to a plateau of . 200 M⊙/yr at z ∼ 2.6.