| 1. |
- Binggeli, Christian, 1989-
(författare)
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Galaxies in the epoch of reionization : Investigating the high-redshift galaxy population through simulations and observations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The cosmic reionization is the last major gas phase transition in cosmic history, yet it remains poorly understood. Current constraints indicate that early star-forming galaxies drove the reionization process through producing and releasing large numbers of ionizing photons into the intergalactic medium. However, our understanding of the ionizing escape fraction (fesc) and the general properties of high-redshift galaxies is still limited.In this thesis, simulated galaxies and observations are used to investigate epoch-of-reionization galaxies and to explore methods that can aid future investigations of such objects. Using simulations, we have shown that it may be possible to constrain fesc in epoch-of-reionization galaxies using quite simple diagnostics that should be observable with the upcoming James Webb Space Telescope (JWST). We also show that variations in star formation activity larger than those predicted in our simulations may lead to a possible degeneracy with high fesc. However, auxiliary information obtained with the JWST may allow us to disentangle variations in the star formation activity from high fesc.We compare galaxies from several simulations to the recently spectroscopically confirmed z=9.1096 galaxy MACS1149-JD1. We find that none of the simulations are able to reproduce the large Balmer break observed in MACS1149-JD1, and argue that unless it represents an outlier in the high-redshift galaxy population, this may indicate that the simulations fail to capture some key physics. Finally, we present ALMA observations of the z=7.6637 galaxy z7_GSD_3811. This object remains undetected in several commonly detected FIR emission lines and FIR dust emission. Using SED-fitting and by comparing our observations to models and low-redshift observations, we show that our non-detections could indicate that the object is poor in metals and dust.Our findings could help future observers to further constrain the nature of high-redshift galaxies and their role in reionization.
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| 2. |
- Manolopoulou, M., et al.
(författare)
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Environmental dependence of X-ray and optical properties of galaxy clusters
- 2021
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 500:2, s. 1953-1963
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Tidskriftsartikel (refereegranskat)abstract
- Galaxy clusters are widely used to constrain cosmological parameters through their properties, such as masses, luminosity, and temperature distributions. One should take into account all kind of biases that could affect these analyses in order to obtain reliable constraints. In this work, we study the difference in the properties of clusters residing in different large-scale environments, defined by their position within or outside of voids, and the density of their surrounding space. We use both observational and simulation cluster and void catalogues, i.e. XMM Cluster Survey (XCS) and redMaPPer clusters, Baryon Oscillation Spectroscopic Survey (BOSS) voids, and Magneticum simulations. We devise two different environmental proxies for the clusters and study their redshift, richness, mass, X-ray luminosity, and temperature distributions, as well as some properties of their galaxy populations. We use the Kolmogorov-Smirnov two-sample test to discover that richer and more massive clusters are more prevalent in overdense regions and outside of voids. We also find that clusters of matched richness and mass in overdense regions and outside voids tend to have higher X-ray luminosities and temperatures. These differences could have important implications for precision cosmology with clusters of galaxies, since cluster mass calibrations can vary with environment.
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| 3. |
- Sahlén, Martin, Associate Professor (docent), 1979-, et al.
(författare)
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Galaxy population constraints on cosmology and star formation in the early Universe
- 2021
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Ingår i: The Astrophysical Journal.
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Tidskriftsartikel (refereegranskat)abstract
- We present the first post-cosmic-microwave-background early-Universe observational constraints on $\textbackslashsigma_8$, $\textbackslashOmega_\textbackslashrm m$, mean galaxy star-forming efficiency and galaxy UV magnitude scatter at redshifts $z = 4-10$. We perform a simultaneous 11-parameter cosmology and star-formation physics fit using the new code GalaxyMC, with redshift $z\textgreater4$ galaxy UV luminosity and correlation function data. Consistent with previous studies, we find evidence for redshift-independent star formation physics, regulated by halo assembly. For a flat $\textbackslashLambda$CDM universe with a low-redshift Hubble constant and a Type Ia supernovae $\textbackslashOmega_\textbackslashrm m$ prior, we constrain $\textbackslashsigma_8 = 0.81 \textbackslashpm 0.03$, and a mean star-forming efficiency peaking at $\textbackslashlog_10 \textbackslashrm SFE = -[(0.09 \textbackslashpm 0.20) + (0.58 \textbackslashpm 0.29) \textbackslashtimes \textbackslashlog_10 (1+z)]$ for halo mass $\textbackslashlog_10 M_\textbackslashrm p / h⌃-1 M_\textbackslashodot = 11.48 \textbackslashpm 0.09$. The suppression of star formation due to feedback is given by a double power law in halo mass with indices $\textbackslashalpha = 0.56 \textbackslashpm 0.08, \textbackslashbeta = -1.03 \textbackslashpm 0.07$. The scatter in galaxy UV magnitude for fixed halo mass is $\textbackslashsigma_M = 0.56 \textbackslashpm 0.08$. Without a prior on $\textbackslashOmega_\textbackslashrm m$ we obtain $\textbackslashsigma_8 = 0.78 \textbackslashpm 0.06$, $\textbackslashOmega_\textbackslashrm m = 0.33 \textbackslashpm 0.07$ and at most $1\textbackslashsigma$ differences in all other parameter values. Our best-fit galaxy luminosity functions yield a reionization optical depth $\textbackslashtau \textbackslashapprox 0.048$, consistent with the Planck 2018 value.
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