An HST/COS Survey of the Low-Redshift IGM. I. Survey, Methodology, & Overall Results
Charles W. Danforth, Brian A. Keeney, Evan M. Tilton, J. Michael Shull, Matthew Stevans, Matthew M. Pieri, John T. Stocke, Blair D. Savage, Kevin France, David … 展开作者
Charles W. Danforth, Brian A. Keeney, Evan M. Tilton, J. Michael Shull, Matthew Stevans, Matthew M. Pieri, John T. Stocke, Blair D. Savage, Kevin France, David Syphers, Britton D. Smith, James C. Green, Cynthia Froning, Steven V. Penton, Steven N. Osterman
备注：
This is the accepted version (v3) of the paper. Previous versions (July 2015 and Feb. 2014) should be replaced by this one. In particular, please note that the associated MAST high-level-science product has been updated to reflect the of the final state of the paper. It is available at: http://archive.stsci.edu/prepds/igm/
We use high-quality, medium-resolution {\it Hubble Space Telescope}/Cosmic Origins Spectrograph (\HST/COS) observations of 82 UV-bright AGN at redshifts $z_{AGN}<0.85$ to construct the largest survey of the low-redshift intergalactic medium (IGM) to date: 5343 individual extragalactic absorption lines in HI and 25 different metal-ion species grouped into 2610 distinct redshift systems at $z_{abs}<0.75$ covering total redshift pathlengths $Δz_{HI}=21.7$ and $Δz_{OVI}=14.5$. Our semi-automated line-finding and measurement technique renders the catalog as objectively-defined as possible. The cumulative column-density distribution of HI systems can be parametrized $dN(>N)/dz=C_{14}(N/10^{14} cm^{-2})^{-(β-1)}$, with $C_{14}=25\pm1$ and $β=1.65\pm0.02$. This distribution is seen to evolve both in amplitude, $C_{14}\sim(1+z)^{2.0\pm0.1}$, and slope $β(z)=1.73-0.26 z$ for $z<0.47$. We observe metal lines in 427 systems, and find that the fraction of IGM absorbers detected in metals is strongly dependent on N_{HI}. The distribution of OVI absorbers appear to evolve in the same sense as the Lya forest. We calculate contributions to $Ω_b$ from different components of the low-$z$ IGM and determine the Lya decrement as a function of redshift. IGM absorbers are analyzed via a two-point correlation function (TPCF) in velocity space. We find substantial clustering of \HI\ absorbers on scales of $Δv=50-300$ km/s with no significant clustering at $Δv>1000$ km/s. Splitting the sample into strong and weak absorbers, we see that most of the clustering occurs in strong, $N_{HI}>10^{13.5} cm^{-2}$, metal-bearing IGM systems. The full catalog of absorption lines and fully-reduced spectra is available via MAST as a high-level science product at http://archive.stsci.edu/prepds/igm/.
HST/COS Observations of Thirteen New He II Quasars
星系际氦的完全再电离是IGM历史上的一个重大事件，He II Gunn-Peterson槽的紫外观测使我们能够描述这一过程在z~3处的结束。由于中间的氢吸收，类星体允许这样的研究是罕见的，只有33个已知的文献中，其中大多数是最近发现的。我们扩展了我们以前的发现工作，并提出了13个新的He II类星体，其红移为2.82 < z < 3.77，这里选择的效率约为80%，其中包括几个比以前已知的绝大多数要亮得多的类星体。这是均匀观测到的He II类星体的最大样本，覆盖了如此宽的红移范围，它们显示出IGM不透明度随红移增加的证据，正如氦再电离时期所预期的那样。在单个或平均光谱中没有看到He II Lyα类星体发射的证据，这给宽线区域的标准模型带来了问题。目前的快速进展，在研究He II类星体已经大大促进了宇宙起源光谱仪的HST，我们讨论的仪器和其他微妙的，必须考虑到IGM He II观测。
HST Spectral Observations near the He II Ly-alpha Break: Implications for He II Reionization
能够研究IGM He II的类星体非常罕见，因为它们必须沿着没有大量氢吸收的视线处于高红移，但最近的工作显着扩大了已知的此类类星体的数量。我们分析了24个来自HST的高红移（z=3.1-3.9）低分辨率He II类星体的光谱，发现它们的He II Gunn-Peterson槽表明排除了非常早和非常晚的再电离模型，支持z~3的再电离红移。虽然数据的质量是不足以揭示细节，如预期的红移演变的氦不透明度，我们得到的第一个合奏措施的氦不透明度在高红移平均在许多视线：τ =4.90在z~3.3。我们还发现，从He II再电离开始观察IGM红翼吸收是非常困难的，但取决于再电离的红移和电离区的大小，用当前一代的紫外光谱仪在某些物体中可能这样做。
Giant Radio Sources as a probe of the cosmological evolution of the IGM, II. The observational constraint for the model of the radio-jets propagation through the X-ray halo--IGM interface
We present a new approach to measure the power-law temperature density relationship $T=T_0 (ρ/ \barρ)^{γ-1}$ and the UV background photoionization rate $Γ_{\rm HI}$ of the IGM based on the Voigt profile decomposition of the Ly$α$ forest into a set of discrete absorption lines with Doppler parameter $b$ and the neutral hydrogen column density $N_{\rm HI}$. Previous work demonstrated that the shape of the $b$-$N_{\rm HI}$ distribution is sensitive to the IGM thermal parameters $T_0$ and $γ$, whereas our new inference algorithm also takes into account the normalization of the distribution, i.e. t…
Dynamical Effect of the Turbulence of IGM on the Baryon Fraction Distribution
研究了星系际重子介质中湍流对重子分数分布的动力学影响。在充分发展的非线性区域，IGM将演变成湍流状态，包含强烈的和弯曲的激波，涡量和复杂的结构。湍流会导致IGM的密度和速度场与下面的无碰撞暗物质的密度和速度场不同。因此，重子分数f_b将偏离它的宇宙平均值。我们研究了这些现象与加权基本无振荡（WENO）的混合宇宙流体动力学/N体代码，这是有效的捕捉冲击和复杂的结构产生的模拟样本。我们发现，在几百kpc到几个Mpc的尺度上，重子分数的分布是高度不均匀的，f_b的变化范围从低到宇宙平均值的1%到几倍。我们进一步表明，IGM中的湍流压力是弱的尺度依赖性，并与质量约为10 ^11 h-1 M \odot的晕的引力能量密度相当。在质量等于或小于10 ^11 h^-1 M \odot的晕中，重子分数应该大大低于f_b^cosmic。数值计算结果表明，f_b从10^12 h^-1 M \odot附近晕质量尺度下的0.8 f_b^cosmic减小到10^11 h^-1 M \odot时的0.3 f_b ^cosmic，当晕质量小于10^11 h^-1 M \odot时，f_b进一步减小。f_b的强质量依赖性与观测结果相似。虽然模拟的f_b值比观测值高2倍，但IGM的湍流是导致质量为10 ^12 h^-1 M \leq的晕中重子物质明显缺失的重要动力学原因。
Because the same massive stars that reionized the intergalactic medium (IGM) inevitably exploded as supernovae that polluted the Universe with metals, the history of cosmic reionization and enrichment are intimately intertwined. While the overly sensitive Ly-alpha transition completely saturates in a neutral IGM, strong low-ionization metal lines like the MgII 2796,2804 doublet will give rise to a detectable `metal-line forest' if the metals produced during reionization (Z ~ 10^{-3}Z_sol) permeate the neutral IGM. We simulate the MgII forest for the first time by combining a large hydrodynamic…
The dispersion measure (DM)--redshift relation of fast radio bursts (FRBs) has been proposed as a potential new tool for probing intergalactic medium (IGM) and for studying cosmology. However, the poor knowledge of the baryon fraction in the IGM ($f_{\mathrm{IGM}}$) and its degeneracy with cosmological parameters impose restrictions on the cosmological applications of FRBs. Furthermore, DMs contributed by the IGM ($\mathrm{DM_{IGM}}$) and host galaxy ($\mathrm{DM_{host}}$), important cosmological quantities, cannot be exactly extracted from observations, which would bring uncontrolled systemat…
Fast radio bursts (FRBs) are millisecond-duration radio transients and can be used as a cosmological probe. However, the dispersion measure (DM) contributed by intergalactic medium (IGM) is hard to be distinguished from other components. In this paper, we use the IllustrisTNG simulation to realistically estimate the $DM_{\rm IGM}$ up to $z\sim 9$. We find $DM_{\rm IGM} = 892^{+721}_{-270}$ pc cm$^{-3}$ at $z=1$. The probability distribution of $DM_{\rm IGM}$ can be well fitted by a quasi-Gaussian function with a long tail. The tail is caused by the structures along the line of sight in IGM. Su…
The density and temperature properties of the intergalactic medium (IGM) reflect the heating and ionization history during cosmological structure formation, and are primarily probed by the Lyman-alpha forest of neutral hydrogen absorption features in the observed spectra of background sources (Gunn & Peterson 1965). We present the methodology and initial results from the Cholla IGM Photoheating Simulation (CHIPS) suite performed with the Graphics Process Unit-accelerated Cholla code to study the IGM at high, uniform spatial resolution maintained over large volumes. In this first paper, we exam…
Fast Radio Bursts (FRBs) are millisecond-duration radio transients with an observed dispersion measure ($DM$) greater than the expected Milky Way contribution, which suggests that such events are of extragalactic origin. Although some models have been proposed to explain the physics of the pulse, the mechanism behind the FRBs emission is still unknown. From FRBs data with known host galaxies, the redshift is directly measured and can be combined with estimates of the $DM$ to constrain the cosmological parameters, such as the baryon number density and the Hubble constant. However, the poor know…
The excessive dispersion measure (DM) of fast radio bursts (FRBs) has been proposed to be a powerful tool to study intergalactic medium (IGM) and to perform cosmography. One issue is that the fraction of baryons in the IGM, $f_{\rm IGM}$, is not properly constrained. Here we propose a method of estimating $f_{\rm IGM}$ using a putative sample of FRBs with the measurements of both DM and luminosity distance $d_{\rm L}$. The latter can be obtained if the FRB is associated with a distance indicator (e.g. a gamma-ray burst or a gravitational wave event), or the redshift $z$ of the FRB is measured …
Extragalactic dispersion measures (DMs) obtained from observations of fast radio bursts (FRBs) are an excellent tool for probing intergalactic medium (IGM) and for conducting cosmography. However, the DM contribution from the IGM (${\rm DM_{IGM}}$) depends on the fraction of baryon mass in the IGM, $f_{\rm IGM}$, which is not properly constrained. As $f_{\rm IGM}(z)$ is geometrically related to the Hubble parameter $H(z)$ and ${\rm DM_{IGM}}(z)$, here we propose that combining two independent measurements of FRBs and $H(z)$ in similar redshift ranges provides a novel and cosmology-free method …
Observations of high-redshift Type Ia supernovae (SNe~Ia) are used to study the cosmic transparency at optical wavelengths. Assuming a flat $Λ$CDM cosmological model based on BAO and CMB results, redshift dependent deviations of SN~Ia distances are used to constrain mechanisms that would dim light. The analysis is based on the most recent Pantheon SN compilation, for which there is a $0.03\pm0.01 {\textrm \,(\rm stat)}$ mag discrepancy in the distant supernova distance moduli relative to the $Λ$CDM model anchored by supernovae at $z<0.05$. While there are known systematic uncertainties that co…
We present semi-analytical models of galactic outflows in high redshift galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal pressure alone may not sustain a large scale outflow in low mass galaxies (i.e $M\sim 10^8$~M$_\odot$), in the presence of supernovae (SNe) feedback with large mass loading. We show that inclusion of cosmic ray pressure allows outflow solutions even in these galaxies. In massive galaxies for the same energy efficiency, cosmic ray driven winds can propagate to larger distances compared to pure thermally driven winds. On an average gas in the cosmic…
A Measurement of the Thermal and Ionization State of the IGM at $z < 0.5$
Aix Marseille Univ, CNRS, CNES, LAM（艾克斯-马赛大学）；University of California Santa Barbara（加州大学圣塔芭芭拉分校）；Indian Institute of Technology Tirupati（蒂鲁帕蒂印度理工学院）；Leiden University（莱顿大学）；University of Massachusetts, Amherst（马萨诸塞大学阿默斯特分校）；Universidad de Sevilla（塞维利亚大学）；Ludwig-Maximilians-Universität München（慕尼黑大学）；Excellence Cluster ORIGINS（ORIGINS卓越集群）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
Simba Simulation: The Effect of Feedback Physics on Matter Distribution in the Cosmic Web
Center for Data-Driven Discovery, Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学数据驱动发现中心，理化学研究所 Kavli 宇宙物理学与数学研究所（WPI），UTIAS）；Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo（东京大学 Kavli 宇宙物理学与数学研究所）；ENS Paris-Saclay, Paris-Saclay University（巴黎萨克雷高等师范学校，巴黎萨克雷大学）；Institute for Computational Cosmology, Department of Physics, Durham University（杜伦大学物理学院计算宇宙学研究所）；Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理研究所）；Department of Physics and Astronomy, University of the Western Cape（西开普大学物理与天文学系）
We present measurements of the large-scale (~40 comoving Mpc) effective optical depth of HeII Ly$α$ absorption, $τ_{\rm eff}$, at 2.54<z<3.86 toward 16 HeII-transparent quasars observed with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), to characterize the ionization state of helium in the intergalactic medium (IGM). We provide the first statistical sample of $τ_{\rm eff}$ measurements in six signal-to-noise ratio >3 HeII sightlines at z>3.5, and study the redshift evolution and sightline-to-sightline variance of $τ_{\rm eff}$ in 24 HeII sightlines. We confirm an i…
Fast radio bursts (FRBs) are a promising new probe for astronomy and cosmology. Thanks to their extragalactic and cosmological origin, FRBs could be used to study the intergalactic medium (IGM) and the cosmic expansion. It is expected that numerous FRBs with identified redshifts will be available in the near future through the identification of their host galaxies or counterparts. $\rm DM_{IGM}$, the contribution from IGM to the observed dispersion measure (DM) of FRB, carries the key information about IGM and the cosmic expansion history. We can thus study the evolution of the universe by usi…
We analyze the sources of free electrons that produce the large dispersion measures, DM $\approx 300-1600$ (in units cm$^{-3}$ pc), observed toward fast radio bursts (FRBs). Individual galaxies typically produce DM $\sim 25-60$ cm$^{-3}$ pc from ionized gas in their disk, disk-halo interface, and circumgalactic medium. Toward an FRB source at redshift $z$, a homogeneous IGM containing a fraction $f_{\rm IGM}$ of cosmological baryons will produce DM $= (935~{\rm cm}^{-3}~{\rm pc}) f_{\rm IGM} \, h_{70}^{-1} I(z)$, where $I(z) = (2/3 Ω_m)[ \{ Ω_m(1+z)^3 + Ω_Λ \}^{1/2} - 1 ]$. A structured IGM of…
Detecting neutral hydrogen structures in the intergalactic medium (IGM) during cosmic reionization via absorption (21 cm forest) against a background radiation is considered independent and complementary to the three-dimensional tomography and power spectrum techniques. The direct detection of this absorption requires very bright ($\gtrsim 10$-100 mJy) background sources at high redshifts ($z\gtrsim 8$), which are evidently rare; very long times of integration; or instruments of very high sensitivity. This motivates a statistical one-dimensional (1D) power spectrum approach along narrow sightl…
The distribution of the absorption line broadening observed in the Ly$α$ forest carries information about the temperature and widths of the filaments in the intergalactic medium (IGM). In this work, we present and test a new method for inferring the temperature of the IGM, the size of the absorbing filaments and the photo-ionization rate of hydrogen from the properties of absorption line broadening in the Ly$α$ forest. We apply our method to mock spectra from the reference model of the EAGLE cosmological simulation, and we demonstrate that we are able to reconstruct the IGM properties. Our met…
We investigate the spatial distribution of Lyman-$α$ (Ly $α$) absorbers within cosmic voids. We create a catalogue of cosmic voids in Sloan Digital Sky Survey Data Release 7 (SDSS DR7) with the VoidFinder algorithm of the Void Analysis Software Toolkit (VAST). Using the largest catalogue of low-redshift (z $\leq$ 0.75) IGM absorbers to date, we identify 392 Ly $α$ absorbers inside voids. The fraction of Ly $α$ absorbers inside voids (65 per cent) is comparable to the volume filling fraction of voids (68 per cent), and significantly greater than the fraction of galaxies inside voids (21 per cen…
Probing Large-scale Structure and the Multi-Phase IGM at the Cosmic Noon -- Insights from a Joint Survey with Euclid, CSST, JPCam, and JUST
Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）；Observatório Nacional（国家天文台）；University of Michigan（密歇根大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences(UCAS)（中国科学院大学天文与空间科学学院）；Department of Astronomy, Tsinghua University（清华大学天文系）；Department of Physics, University of Milano-Bicocca（米兰比可卡大学物理系）；Shanghai Jiao Tong University（上海交通大学）
HST/COS Observations of the Ly alpha Forest toward the BL Lac Object 1ES1553+113
本文介绍了BL Lac天体1 ES 1553 +113的宇宙起源摄谱仪（HST/COS）在1135-1795波长范围内的新的远紫外光谱。数据显示了一个平滑的连续谱，在ISM和IGM中产生了丰富的窄吸收特征。这些特征包括41个0<z<0.43的Lya吸收体，其中14个在多个莱曼线中检测到，6个在一个或多个金属线中检测到。我们分析了在z=0.188处的Lya吸收剂的富金属三重态，其中检测到OVI、NV和CIII吸收。硅离子（SiIII/IV）未被检测到相当强的上限，并且我们使用测量的SiIII/CIII上限来推导吸收剂络合物的最强组分的丰度极限[C/Si]>0.6。星系红移巡天显示，许多大质量星系的红移与这个吸收复合体大致相同，这表明它产生于大尺度的星系细丝中。1 ES 1553 +113是最亮的河外X射线源和γ射线源之一，是高能天体物理学界的重要研究对象。1 ES 1553 +113没有固有的发射或吸收特性，因此没有直接的红移测定。我们使用介入的Lya吸收体对红移进行直接限制：基于确认的Lya+OVI吸收体的z_em>0.395，基于Lya的单线检测的z_em>0.433。COS/FUV数据仅对z<0.47的Lya吸收体敏感，但我们提出了z_em 0.4的统计参数<0.58 based on the non-detection of any Lyb absorbers at z…
We present a new perturbative approach to "constrained Ly$α$ radiative transfer'" (RT) through the circum- and inter-galactic medium (CGM and IGM). We constrain the HI content and kinematics of the CGM and IGM in a physically motivated model, using the galaxy-Ly$α$ forest clustering data from spectroscopic galaxy surveys in QSO fields at $z\sim2-3$. This enables us to quantify the impact of the CGM/IGM on Ly$α$ emission in an observationally constrained, realistic cosmological environment. Our model predicts that the CGM and IGM at these redshifts transmit $\approx80~\%$ of Ly$α$ photons after…
We introduce LATIS, the Ly$α$ Tomography IMACS Survey, a spectroscopic survey at Magellan designed to map the z=2.2-2.8 intergalactic medium (IGM) in three dimensions by observing the Ly$α$ forest in the spectra of galaxies and QSOs. Within an area of 1.7 deg${}^2$, we will observe approximately half of $\gtrsim L^*$ galaxies at z=2.2-3.2 for typically 12 hours, providing a dense network of sightlines piercing the IGM with an average transverse separation of 2.5 $h^{-1}$ comoving Mpc (1 physical Mpc). At these scales, the opacity of the IGM is expected to be closely related to the dark matter …
Revealing the cosmic reionisation history is at the frontier of extragalactic astronomy. The power spectrum of the cosmic microwave background (CMB) polarisation can be used to constrain the reionisation history. Here we propose a CMB-independent method using fast radio bursts (FRBs) to directly measure the ionisation fraction of the intergalactic medium (IGM) as a function of redshift. FRBs are new astronomical transients with millisecond timescales. Their dispersion measure (DM$_{\rm IGM}$) is an indicator of the amount of ionised material in the IGM. Since the differential of DM$_{\rm IGM}$…
The recent observation of the 21-cm global absorption signal by EDGES suggests that the intergalactic medium (IGM) gas has been cooler than the cosmic microwave background during $15 \lesssim z \lesssim 20$. This result can provide a strong constraint on heating sources for the IGM gas at these redshifts. In this paper we study the constraint on the primordial magnetic fields (PMFs) by the EDGES result. The PMFs can heat the IGM gas through their energy dissipation due to the magnetohydrodynamic effects. By numerically solving the thermal evolution of the IGM gas with the PMFs, we find that th…
