scholarly journals Tracing the 107 K warm–hot intergalactic medium with UV absorption lines

2020 ◽  
Vol 499 (4) ◽  
pp. 5230-5240
Author(s):  
A Y Fresco ◽  
C Péroux ◽  
A Merloni ◽  
A Hamanowicz ◽  
R Szakacs
Keyword(s):  
Galaxy Formation ◽  
Spectral Resolution ◽  
Column Density ◽  
Intergalactic Medium ◽  
High Spectral Resolution ◽  
High Signal ◽  
Gas Temperature ◽  
X Ray ◽  
Quasar Spectra ◽  
Hydrodynamical Simulations

ABSTRACT Today, the majority of the cosmic baryons in the Universe are not observed directly, leading to an issue of ‘missing baryons’ at low redshift. Cosmological hydrodynamical simulations have indicated that a significant portion of them will be converted into the so-called warm–hot intergalactic medium (WHIM), with gas temperature ranging between 105 and 107 K. While the cooler phase of this gas has been observed using O vi and Ne viii absorbers at ultraviolet (UV) wavelengths, the hotter fraction detection relies mostly on observations of O vii and O viii at X-ray wavelengths. Here, we target the forbidden line of [Fe xxi] λ 1354 Å which traces 107 K gas at UV wavelengths, using more than 100 high-spectral resolution ($R\sim 49\, 000$) and high signal to noise VLT/UVES quasar spectra, corresponding to over 600 h of VLT time observations. A stack of these at the position of known Ly α absorbers lead to a 5σ limit of $\log [N\mathrm{([Fe\,{\small XXI}])]\lt }$17.4 (EWrest < 22 mÅ), three orders of magnitude higher than the expected column density of the WHIM $\log [N\mathrm{([Fe\,{\small XXI}])]\lt }$14.5. This work proposes an alternative to X-ray detected 107 K WHIM tracers, by targeting faint lines at UV wavelengths from the ground benefiting from higher instrumental throughput, enhanced spectral resolution, longer exposure times, and increased number of targets. The number of quasar spectra required to reach this theoretical column density with future facilities including 4MOST, ELT/HIRES, MSE, and the Spectroscopic Telescope appears challenging at present. Probing the missing baryons is essential to constrain the accretion and feedback processes that are fundamental to galaxy formation.

scholarly journals Probing the thermal state of the intergalactic medium at z > 5 with the transmission spikes in high-resolution  Ly α forest spectra

2020 ◽  
Vol 494 (4) ◽  
pp. 5091-5109 ◽  
Author(s):  
Prakash Gaikwad ◽  
Michael Rauch ◽  
Martin G Haehnelt ◽  
Ewald Puchwein ◽  
James S Bolton ◽  
...  
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
Intergalactic Medium ◽  
Thermal State ◽  
Neutral Hydrogen ◽  
High Spectral Resolution ◽  
Profile Fitting ◽  
Density Relation ◽  
Width Distribution ◽  
Hydrodynamical Simulations

ABSTRACT We compare a sample of five high-resolution, high S/N  Ly α forest spectra of bright 6 < z < ∼6.5 QSOs aimed at spectrally resolving the last remaining transmission spikes at z > 5 with those obtained from mock absorption spectra from the Sherwoodand Sherwood–Relics simulation suites of hydrodynamical simulations of the intergalactic medium (IGM). We use a profile-fitting procedure for the inverted transmitted flux, 1 − F, similar to the widely used Voigt profile fitting of the transmitted flux F at lower redshifts, to characterize the transmission spikes that probe predominately underdense regions of the IGM. We are able to reproduce the width and height distributions of the transmission spikes, both with optically thin simulations of the post-reionization Universe using a homogeneous UV background and full radiative transfer simulations of a late reionization model. We find that the width of the fitted components of the simulated transmission spikes is very sensitive to the instantaneous temperature of the reionized IGM. The internal structures of the spikes are more prominent in low temperature models of the IGM. The width distribution of the observed transmission spikes, which require high spectral resolution (≤ 8  km s−1) to be resolved, is reproduced for optically thin simulations with a temperature at mean density of T0 = (11 000 ± 1600, 10 500 ± 2100, 12 000 ± 2200) K at z = (5.4, 5.6, 5.8). This is weakly dependent on the slope of the temperature-density relation, which is favoured to be moderately steeper than isothermal. In the inhomogeneous, late reionization, full radiative transfer simulations where islands of neutral hydrogen persist to z ∼ 5.3, the width distribution of the observed transmission spikes is consistent with the range of T0 caused by spatial fluctuations in the temperature–density relation.

scholarly journals A High Spectral Resolution Observation of the Soft X‐Ray Diffuse Background with Thermal Detectors

2002 ◽  
Vol 576 (1) ◽  
pp. 188-203 ◽  
Author(s):  
D. McCammon ◽  
R. Almy ◽  
E. Apodaca ◽  
W. Bergmann Tiest ◽  
W. Cui ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
High Spectral Resolution ◽  
X Ray ◽  
Thermal Detectors ◽  
Resolution Observation ◽  
Diffuse Background

scholarly journals Galaxies and the intergalactic medium in groups

2000 ◽  
Vol 174 ◽  
pp. 187-196
Author(s):  
Trevor J. Ponman ◽  
Ed Lloyd-Davies ◽  
Stephen F. Helsdon
Keyword(s):  
Galaxy Formation ◽  
Intergalactic Medium ◽  
Preliminary Evidence ◽  
Early Type ◽  
Present Evidence ◽  
X Ray ◽  
Hot Gas ◽  
Isolated Galaxies ◽  
The Relationship

AbstractThe study of the relationship between the hot gas in groups and the galaxies they contain can help to constrain the evolution of both galaxies and groups. Here we present evidence that the intergalactic medium in groups has been strongly affected by preheating associated with galaxy formation which mostly preceded group collapse. The presence of this effect appears to be unrelated to the morphology of group galaxies, which supports models in which galaxy types are not primordial. We also present preliminary evidence that early-type galaxies in groups are not underluminous in the X-ray compared to isolated galaxies, suggesting that their dark halos may not have been substantially stripped.

scholarly journals Goals for the Application of High-Resolution X-ray Spectroscopy to the Diagnosis of Stellar Coronal Plasmas

1990 ◽  
Vol 115 ◽  
pp. 94-109 ◽  
Author(s):  
Jeffrey L. Linsky
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Transient Flow ◽  
Emission Measure ◽  
Active Regions ◽  
High Sensitivity ◽  
High Spectral Resolution ◽  
Spectral Features ◽  
Signal To Noise ◽  
X Ray

AbstractI provide examples of how high-resolution x-ray spectra may be used to determine the temperature and emission measure distributions, electron densities, steady and transient flow velocities, and location of active regions in stellar coronae. For each type of measurement I estimate the minimum spectral resolution required to resolve the most useful spectral features. In general, high sensitivity is required to obtain sufficient signal-to-noise to exploit the high spectral resolution. Although difficult, each measurement should be achievable with the instrumentation proposed for AXAF.

scholarly journals About diagnostics of Z-pinches hot points

2000 ◽  
Vol 18 (2) ◽  
pp. 291-296 ◽  
Author(s):  
V.Yu. POLITOV ◽  
A.V. POTAPOV ◽  
L.V. ANTONOVA
Keyword(s):  
Experimental Data ◽  
Theoretical Analysis ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
Electrical Discharges ◽  
Maximum Compression ◽  
X Ray ◽  
Average Temperature ◽  
Radiation Spectra ◽  
Spectral Intensities

We present the results of X-ray diagnostics of Z-pinch hot points, formed during fast electrical discharges through exploding Al wires. Experimental data include the pinhole images and X-ray time integrated radiation spectra. These spectra were obtained with high spectral resolution in the range 1.5–2.2 keV, contained the most intensive resonance lines of Al H- and He-like ions. Comparison of the recorded lines width and peak intensities with the corresponding modeled values, enables us to estimate the main hydrodynamical parameters of hot point, such as average temperature and density, being achieved at a moment of its maximum compression. Additionally, on the base of theoretical analysis of the spectral intensities distribution in well-resolved Lyα satellites, the gradient of compression velocities field is concluded. Some features of the investigated lines spectra forming are discussed.

scholarly journals Spatially resolving the thermally inhomogeneous outer atmosphere of the red giant Arcturus in the 2.3 μm CO lines

2018 ◽  
Vol 620 ◽  
pp. A23 ◽  
Author(s):  
K. Ohnaka ◽  
C. A. L. Morales Marín
Keyword(s):  
Spectral Resolution ◽  
Column Density ◽  
High Spectral Resolution ◽  
Molecular Gas ◽  
Very Large Telescope ◽  
Extended Component ◽  
Outer Atmosphere ◽  
Red Giant ◽  
The Individual ◽  
Photospheric Model

Aim. The outer atmosphere of K giants shows thermally inhomogeneous structures consisting of the hot chromospheric gas and the cool molecular gas. We present spectro-interferometric observations of the multicomponent outer atmosphere of the well-studied K1.5 giant Arcturus (α Boo) in the CO first overtone lines near 2.3 μm. Methods. We observed Arcturus with the AMBER instrument at the Very Large Telescope Interferometer (VLTI) at 2.28–2.31 μm with a spectral resolution of 12 000 and at projected baselines of 7.3, 14.6, and 21.8 m. Results. The high spectral resolution of the VLTI/AMBER instrument allowed us to spatially resolve Arcturus in the individual CO lines. Comparison of the observed interferometric data with the MARCS photospheric model shows that the star appears to be significantly larger than predicted by the model. It indicates the presence of an extended component that is not accounted for by the current photospheric models for this well-studied star. We found out that the observed AMBER data can be explained by a model with two additional CO layers above the photosphere. The inner CO layer is located just above the photosphere, at 1.04 ± 0.02 R⋆, with a temperature of 1600 ± 400 K and a CO column density of 1020 ± 0.3 cm−2. On the other hand, the outer CO layer is found to be as extended as to 2.6 ± 0.2 R⋆ with a temperature of 1800 ± 100 K and a CO column density of 1019 ± 0.15 cm−2. Conclusions. The properties of the inner CO layer are in broad agreement with those previously inferred from the spatially unresolved spectroscopic analyses. However, our AMBER observations have revealed that the quasi-static cool molecular component extends out to 2–3 R⋆, within which region the chromospheric wind steeply accelerates.

scholarly journals Global monitoring of terrestrial chlorophyll fluorescence from moderate spectral resolution near-infrared satellite measurements: methodology, simulations, and application to GOME-2

2013 ◽  
Vol 6 (2) ◽  
pp. 3883-3930 ◽  
Author(s):  
J. Joiner ◽  
L. Guanter ◽  
R. Lindstrot ◽  
M. Voigt ◽  
A. P. Vasilkov ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Spectral Resolution ◽  
Near Infrared ◽  
High Spectral Resolution ◽  
High Signal ◽  
Good Precision ◽  
Atmospheric Absorption ◽  
Red Fluorescence ◽  
Fluorescence Measurements ◽  
Global Mapping

Abstract. Globally mapped terrestrial chlorophyll fluorescence retrievals are of high interest because they can provide information on the functional status of vegetation including light-use efficiency and global primary productivity that can be used for global carbon cycle modeling and agricultural applications. In addition, fluorescence can contaminate photon path estimates from the O2 A-band that has become an integral part of missions to accurately measure greenhouse gas concentrations. Global mapping of far-red (~ 755–770 nm) terrestrial vegetation solar-induced fluorescence from space has been accomplished using the high spectral resolution (ν/Δ ν > 35 000) interferometer on the Japanese Greenhouse gases Observing SATellite (GOSAT). These satellite retrievals of fluorescence rely solely upon the filling-in of solar Fraunhofer lines that are not significantly affected by atmospheric absorption. Although these measurements provide near global coverage on a monthly basis, they suffer from relatively low precision and sparse spatial sampling. Here, we describe a new methodology to retrieve global far-red fluorescence information; we use hyperspectral data to disentangle the spectral signatures of three basic components in and surrounding the O2 A-band: atmospheric absorption, surface reflectance, and fluorescence radiance. Through detailed simulations, we demonstrate the feasibility of the approach and show that moderate spectral resolution measurements with a relatively high signal-to-noise ratio within and outside the O2 A-band can be used to retrieve far-red fluorescence information with good precision and accuracy. The method is then applied to data from the Global Ozone Monitoring Instrument 2 (GOME-2). The GOME-2 fluorescence retrievals display similar spatial structure as compared with GOSAT. GOME-2 enables global mapping of far-red fluorescence with higher precision over smaller spatial and temporal scales than is possible with GOSAT. It should be noted that both GOME-2 and GOSAT were designed to make atmospheric trace gas measurements and were not optimized for fluorescence measurements. Our approach can be applied to other existing and future space-based instruments that provide moderate spectral resolution observations in the near-infrared region.

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