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Register a new userThe distribution and properties of DLAs at z $leq$ 2 in the EAGLE simulations
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Lilian Garratt-Smithson
Publication date
2020
fields
Physics
and research's language is
English
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Determining the spatial distribution and intrinsic physical properties of neutral hydrogen on cosmological scales is one of the key goals of next-generation radio surveys. We use the EAGLE galaxy formation simulations to assess the properties of damped Lyman-alpha absorbers (DLAs) that are associated with galaxies and their underlying dark matter haloes between 0 $leq$ z $leq$ 2. We find that the covering fraction of DLAs increases at higher redshift; a significant fraction of neutral atomic hydrogen (HI) resides in the outskirts of galaxies with stellar mass greater than or equal to 10$^{10}$ M$_odot$; and the covering fraction of DLAs in the circumgalactic medium (CGM) is enhanced relative to that of the interstellar medium (ISM) with increasing halo mass. Moreover, we find that the mean density of the HI in galaxies increases with increasing stellar mass, while the DLAs in high- and low-halo-mass systems have higher column densities than those in galaxies with intermediate halo masses (~ 10$^{12}$ M$_odot$ at z = 0). These high-impact CGM DLAs in high-stellar-mass systems tend to be metal-poor, likely tracing smooth accretion. Overall, our results point to the CGM playing an important role in DLA studies at high redshift (z $geq$ 1). However, their properties are impacted both by numerical resolution and the detailed feedback prescriptions employed in cosmological simulations, particularly that of AGN.
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We present an investigation of clumpy galaxies in the Hubble Ultra Deep Field at 0.5 $leq z leq$ 1.5 in the rest-frame far-ultraviolet (FUV) using HST WFC3 broadband imaging in F225W, F275W, and F336W. An analysis of 1,404 galaxies yields 209 galaxies that host 403 kpc-scale clumps. These host galaxies appear to be typical star-forming galaxies, with an average of 2 clumps per galaxy and reaching a maximum of 8 clumps. We measure the photometry of the clumps, and determine the mass, age, and star formation rates (SFR) utilizing the SED-fitting code FAST. We find that clumps make an average contribution of 19% to the total rest-frame FUV flux of their host galaxy. Individually, clumps contribute a median of 5% to the host galaxy SFR and an average of $sim$4% to the host galaxy mass, with total clump contributions to the host galaxy stellar mass ranging widely from less than 1% up to 93%. Clumps in the outskirts of galaxies are typically younger, with higher star formation rates, than clumps in the inner regions. The results are consistent with clump migration theories in which clumps form through violent gravitational instabilities in gas-rich turbulent disks, eventually migrate toward the center of the galaxies, and coalesce into the bulge.
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