Observations have revealed unexpectedly large amounts of dust in high-redshift galaxies and its origin is still much debated. Valiante et al. (2009, MNRAS, 397, 1661) suggested the net stellar dust production of the quasar host galaxy SDSS J1148+5251 may be sufficient to explain the large dust mass detected in this galaxy, albeit under some very special assumptions (e.g., 'closed box' evolution and a rather high gas mass). Here it is shown that since accretion of essentially pristine material may lower the efficiency of dust formation significantly, and the observationally derived dust-to-gas ratios for these high-redshift galaxies are remarkably high, stellar dust production is likely insufficient. A model including metallicity-dependent, non-stellar dust formation ('secondary dust') is presented. The required contribution from this non-stellar dust component appears too large, however. If all observational constraints are to be met, the resultant dust-to-metals ratio is close to unity, which means that almost all interstellar metals exist in the form dust. This is a very unlikely situation and suggests the large dust-to-gas ratios at high-redshifts may be due to observational uncertainties and/or or incorrect calibration of conversion factors for gas and dust tracers.
The Origin of Dust in the Early Universe: Probing the Star Formation History of Galaxies by their Dust Content
对于在高红移（z = 6.4）类星体J1148+5251中观测到的~ 4 \times 10^8 M \odot尘埃的起源，提出了两种不同的方案。第一个假设是这个星系比宇宙在那个时期的年龄年轻得多，所以只有超新星（SNe）才能产生这种尘埃。第二种情况假设银河系的年龄要大得多，因此尘埃可能是在质量较低的渐近巨星分支（AGB）恒星中形成的。提出了新的积分解决方案的化学演化的金属和尘埃在星系中，我们提供了一个关键的评估这两种情况下，和观测结果，可以区分两者。我们表明，AGB恒星可以产生推断质量的尘埃在这个对象中，然而，最终质量的幸存尘埃取决于星系的恒星形成历史（SFH）。一般来说，超新星不能产生观测到的尘埃量，除非平均SN事件在其喷出物中产生超过~ 1 M \odot的尘埃。然而，可以构建特殊的SFHS，其中SNe可以产生推断的尘埃质量，合理的平均尘埃产量约为0.15 M \odot。这两种情况提出了星系光谱能量分布的不同起源，不同的恒星形成效率和恒星质量，以及J1148+5251型超亮红外（IR）天体的不同共动数密度。诊断中红外精细结构线的检测，以及确定这些物体的共动数密度的更完整的调查可以区分这两种情况。
A cosmological model, in which the cosmic microwave background (CMB) is a thermal radiation of intergalactic dust instead of a relic radiation of the Big Bang, is revived and revisited. The model suggests that a virtually transparent local Universe becomes considerably opaque at redshifts $z > 2-3$. Such opacity is hardly to be detected in the Type Ia supernova data, but confirmed using quasar data. The opacity steeply increases with redshift because of a high proper density of intergalactic dust in the previous epochs. The temperature of intergalactic dust increases as $(1+z)$ and exactly com…
The first generation of stars were born a few hundred million years after the big bang. These stars synthesized elements heavier than H and He, that are later expelled into the interstellar medium, initiating the rise of metals. Within this enriched medium, the first dust grains formed. This event is cosmological crucial for molecule formation as dust plays a major role by cooling low-metallicity star-forming clouds which can fragment to create lower mass stars. Collecting information on these first dust grains is difficult because of the negative alliance of large distances and low dust masse…
In the last decade, it has become clear that the dust-enshrouded star formation contributes significantly to early galaxy evolution. Detection of dust is therefore essential in determining the properties of galaxies in the high-redshift universe. This requires observations at the (sub-)millimeter wavelengths. Unfortunately, sensitivity and background confusion of single dish observations on the one hand, and mapping efficiency of interferometers on the other hand, pose unique challenges to observers. One promising route to overcome these difficulties is intensity mapping of fluctuations which …
The presence of dust in the intracluster medium (ICM) has been a long-standing problem that is still awaiting elucidation. Direct observational diagnostics are rather challenging (though not impossible) either because of a sparse distribution of dust in the intracluster space that makes extinction measurements difficult or because of a low surface brightness of infrared emission from dust. Complex indirect approaches are currently available that can overcome uncertainties and provide a reasonable understanding of the basic regulations of the physical state of dust in the ICM. Contrary to the c…
We explore the effect of dust on the growth of seed black holes (BHs) in the early universe. Previous 1D radiation-hydrodynamic (RHD) simulations show that increased radiation pressure on dust further suppresses the accretion rate than the case for the chemically pristine gas. Using the Enzo+Moray code, we perform a suite of 3D RHD simulations of accreting BHs in a dusty interstellar medium (ISM). We use the modified Grackle cooling library to consider dust physics in its non-equilibrium chemistry. The BH goes through an early evolutionary phase, where ionizing BH radiation creates an oscillat…
Spectral Signatures of Spinning Dust from Grain Ensembles in Diverse Environments: A Combined Theoretical and Observational Study
University of Manchester（曼彻斯特大学）；Jodrell Bank Centre for Astrophysics, University of Manchester（曼彻斯特大学乔德雷尔银行天体物理学中心）；Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna (ULL)（拉帕鲁纳大学）
A number of codes for general-relativistic simulations of cosmological structure formation have been developed in recent years. Here we demonstrate that a sample of these codes produce consistent results beyond the Newtonian regime. We simulate solutions to Einstein's equations dominated by gravitomagnetism -- a vector-type gravitational field that doesn't exist in Newtonian gravity and produces frame-dragging, the leading-order post-Newtonian effect. We calculate the coordinate-invariant effect on intersecting null geodesics by performing ray tracing in each independent code. With this observ…
We propose a modified theory of gravitation constructed by the addition of the term $f(T_{μν}T^{μν})$ to the Einstein-Hilbert action, and elaborate a particular case $f(T_{μν}T^{μν})=α(T_{μν}T^{μν})^η$, where $α$ and $η$ are real constants, dubbed as energy-momentum powered gravity (EMPG). We search for viable cosmologies arising from EMPG especially in the context of the late-time accelerated expansion of the Universe. We investigate the ranges of the EMPG parameters $(α,η)$ on theoretical as well as observational grounds leading to the late-time acceleration of the Universe with pressureless…
