Theoretically modelling the 21-cm signals caused by Population III stars (Pop III stars) is the key to extracting fruitful information on Pop III stars from current and forthcoming 21-cm observations. In this work we develop a new module of Pop III stars in which the escape fractions of ionizing photons and Lyman-Werner (LW) photons, photo-heating by UV radiation, and LW feedback are consistently incorporated. By implementing the module into a public 21-cm semi-numerical simulation code, 21CMFAST, we demonstrate 21-cm signal calculations and investigate the importance of Pop III star modelling. What we find is that the contribution from Pop III stars to cosmic reionization significantly depends on the treatment of the escape fraction. With our escape fraction model, Pop III stars hardly contribute to reionization because less massive halos, whose escape fraction are high, cannot host Pop III stars due to LW feedback. On the other hand, Pop III stars well contribute to reionization with the conventional constant escape fraction. We also find that UV photo-heating has non-negligible impact on the 21-cm global signal and the 21-cm power spectrum if the ionization fraction of the Universe is higher than roughly 1 percent. In this case, the strength of the 21-cm global signal depends on the photo-heating efficiency and thus on the Pop III star mass. We conclude that detailed modelling of Pop III stars is imperative to predict 21-cm observables accurately for future observations.
The impact of source and survey modelling on the connection between [O III] emitters and Ly $α$ forest transmission at z ~ 6
The University of Nottingham（诺丁汉大学）；University of Edinburgh（爱丁堡大学）；Kavli Institute for Cosmology（卡弗里宇宙学研究所）；Tata Institute of Fundamental Research（塔塔基础研究所）；Leibniz-Institut für Astrophysik Potsdam（波茨坦阿斯特拉物理研究所）
A framework for modelling Population III stars in cosmological simulations
Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Indian Institute of Science Education and Research - Kolkata（印度科学教育与研究学院-加尔各答分院）；Universidad de Granada（格拉纳达大学）；York University（约克大学）
The dark matter halo shape of edge-on disk galaxies - III. Modelling the HI observations: results
这是一系列论文中的第三篇，我们试图对盘星系中暗晕的扁平化进行限制。为此，我们需要分析所观测到的侧边星系的XV图，以准确测量径向HI面密度、旋转曲线和HI速度色散。我们提出了8个HI丰富的，晚型，边缘星系的HI观测建模的结果。在所有这些中，我们发现了微分旋转。大多数系统显示HI速度色散为6.5至7.5 km s $^{-1}$，除一个外，所有系统均显示径向结构。有一个最大的旋转速度，至少高达120公里秒$^{-1}$的平均HI速度色散的增加。接下来，我们分析观测结果，得出HI层厚度的径向变化（耀斑）。我们发现，除了不对称的IC 5052，我们的样本中的所有星系都是三维质量建模测量暗晕形状的良好候选者。耀斑的轮廓是对称的，有一个共同的形状，线性增加的恒星盘内和指数外的引力势是由暗晕为主。在最好的例子中，UGC 7321，我们发现在内部区域的小偏离中平面和伴随的HI层的厚度增加，这可能是一个相对较强的酒吧的扰动的结果。
We performed a detailed photometric analysis and photoionisation modelling on three high excitation multiple shell planetary nebulae: NGC 3242, NGC 6826 and NGC 7662. Archival HST/WFPC2 narrow band filter images were used to investigate shocked regions by two independent methods: using low excitation ions (via H alpha/[N II] vs H alpha/[S II] extended diagnostic diagrams) and by means of high excitation species looking for regions of enhanced [O III]/H alpha line ratios. Shocked region analysis via low excitation ions shows that major deviations from the general inside to outside ionisation tr…
We present results of the first dynamical stream fits to the recently discovered Tucana III stream. These fits assume a fixed Milky Way potential and give proper motion predictions, which can be tested with the upcoming Gaia Data Release 2. These fits reveal that Tucana III is on an eccentric orbit around the Milky Way and, more interestingly, that Tucana III passed within 15 kpc of the Large Magellanic Cloud (LMC) approximately 75 Myr ago. Given this close passage, we fit the Tucana III stream in the combined presence of the Milky Way and the LMC. We find that the predicted proper motions dep…
We investigate the dust energy balance for the edge-on galaxy IC 2531, one of the seven galaxies in the HEROES sample. We perform a state-of-the-art radiative transfer modelling based, for the first time, on a set of optical and near-infrared galaxy images. We show that taking into account near-infrared imaging in the modelling significantly improves the constraints on the retrieved parameters of the dust content. We confirm the result from previous studies that including a young stellar population in the modelling is important for explaining the observed stellar energy distribution. However, …
We exploit stellar population models of absorption line indices in the ultraviolet (from 2000 - 3200 Angstrom) to study the spectra of massive galaxies. Our central aim is to investigate the occurrence at high-redshift of the UV upturn, i.e. the increased UV emission due to old stars observed in massive galaxies and spiral bulges in the local Universe. We use a large (~275,000) sample of z~0.6 massive (log M*/Msun > 11.5) galaxies using both individual spectra and stacks and employ a suite of models including a UV contribution from old populations, spanning various effective temperatures, fuel…
The increasing neutrality of the intergalactic medium at z>6 suppresses Ly-alpha emission, and spectroscopic confirmation of galaxy redshifts requires detecting alternative UV lines. The strong [C III] 1907 + C III] 1909 doublet frequently observed in low-metallicity, actively star-forming galaxies is a promising emission feature. We present CLOUDY photoionization model predictions for C III] equivalent widths (EWs) and line ratios as a function of starburst age, metallicity, and ionization parameter. Our models include a range of C/O abundances, dust content, and gas density. We also examine …
RABBITS - III. Modelling relativistic accretion discs around spinning black holes in galaxy formation simulations
The Institute of Cancer Research（癌症研究所）；Key Laboratory for Computational Astrophysics, National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台计算天体物理学重点实验室）；Cosmology, Gravity, and Astroparticle Physics Group, Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS)（基础科学研究院宇宙理论物理中心宇宙学、引力和高能粒子物理组）；Université Libre de Bruxelles（布鲁塞尔自由大学）；LUTH, Laboratoire Univers et Theories, Observatoire de Paris（巴黎天文台宇宙与理论实验室）；Department of Physics, University of Helsinki（赫尔辛基大学物理系）；Astronomy Centre, University of Sussex（萨塞克斯大学天文学中心）
To explain the properties of dust in the interstellar medium (ISM), the presence of a refractory organic mantle is necessary. The outflows of AGB stars are among the main contributors of stellar dust to the ISM. We present the first study of the refractory organic contribution of AGB stars to the ISM. Based on laboratory experiments, we included a new reaction in our extended chemical kinetics model: the photoprocessing of volatile complex ices into inert refractory organic material. The refractory organic feedback of AGB outflows to the ISM is estimated using observationally motivated parent …
The most metal-poor, high redshift damped Lyman-alpha systems (DLAs) provide a window to study some of the first few generations of stars. In this paper, we present a novel model to investigate the chemical enrichment of the near-pristine DLA population. This model accounts for the mass distribution of the enriching stellar population, the typical explosion energy of their supernovae, and the average number of stars that contribute to the enrichment of these DLAs. We conduct a maximum likelihood analysis of these model parameters using the observed relative element abundances ([C/O], [Si/O], a…
