First author: Paolo Da Vela
The presence of delayed GeV emission after a strong transient, such as a GRB (Gamma-Ray Burst), in the VHE (Very-High Energy, $E>100$ GeV) band can be the signature of a non-zero magnetic field in the intergalactic medium. We used a synchrotron self-Compton multiwavelength model to infer an analytical description of the intrinsic VHE spectrum (corrected for absorption by the Extragalactic Background Light, EBL) of GRB$,$190114C to predict the lightcurves and SEDs of the delayed emission with Monte Carlo simulations for different IGMF (Intergalactic Magnetic Field) configurations (strengths $B=8\times10^{-21}$ G, $10^{-20}$ G, $3\times 10^{-20}$G and correlation length $\lambda>1$ Mpc), and compared them with the Fermi-LAT (Fermi Large Area Telescope) limits computed for several exposure times.
First author: E. Gatuzz
The problem of missing baryons in the local universe remains an open question. One propose alternative is that at low redshift missing baryons are in the form of the Warm Hot Intergalactic Medium (WHIM). In order to test this idea, we present a detailed analysis of X-ray high-resolution spectra of six extragalactic sources, Mrk 421, 1ES 1028+511, 1ES 1553+113, H2356-309, PKS 0558-504 and PG 1116+215, obtained with the XMM-Newton Reflection Grating Spectrometer to search for signals of WHIM and/or circumgalactic medium (CGM) X-ray absorbing gas.
First author: Naim Göksel Karaçaylı
The abundance, temperature, and clustering of metals in the intergalactic medium are important parameters for understanding their cosmic evolution and quantifying their impact on cosmological analysis with the Ly $\alpha$ forest. The properties of these systems are typically measured from individual quasar spectra redward of the quasar’s Ly $\alpha$ emission line, yet that approach may provide biased results due to selection effects. We present an alternative approach to measure these properties in an unbiased manner with the two-point statistics commonly employed to quantify large-scale structure.
First author: Hamsa Padmanabhan
We use the measured scattering timescales of Fast Radio Bursts (FRBs) from the CHIME catalog to derive an upper limit on the magnetic field on sub-kpc scales in the intergalactic medium (IGM). A nonmagnetized, photoionized IGM is insufficient to explain the turbulent scattering at all redshifts, with a Warm-Hot component being marginally consistent with the data at $z \sim 1$. Accounting for the lower envelope of the temporal smearing distribution with a nonzero magnetic field leads to upper limits $B < 10$ nG on scales of 0.
First author: T. Tuominen
The current observational status of the hot (log T(K) > 5.5) warm-hot intergalactic medium (WHIM) remains incomplete. While recent observations from stacking large numbers of Cosmic Web filaments have yielded statistically significant detections, direct measurements of single objects remain scarce. The lack of such a sample currently prevents a robust analysis of the cosmic baryon content composed of the hot WHIM, which could help solve the cosmological missing baryons problem.
First author: Xiaohui Fan
Quasars at cosmic dawn provide powerful probes of the formation and growth of the earliest supermassive black holes (SMBHs) in the universe, their connections to galaxy and structure formation, and the evolution of the intergalactic medium (IGM) at the epoch of reionization (EoR). Hundreds of quasars have been discovered in the first billion years of cosmic history, with the quasar redshift frontier extended to z~7.6. Observations of quasars at cosmic dawn show that: (1) The number density of luminous quasars declines exponentially at z>5, suggesting that the earliest quasars emerge at z~10; the lack of strong evolution in their average spectral energy distribution indicates a rapid buildup of the AGN environment.
First author: Anna Uryson
In this paper intergalatic electromagnetic cascades are used as a probe of cosmic ray sources. This is achieved as follows. In extragalactic space cosmic rays initiate electromagnetic cascades in which gamma-ray and neutrino emission arises. We used the joint analysis of cosmic ray data, along with extragalactic gamma-ray and neutrino emission, to study particle acceleration in the vicinity of supermassive black holes. Particle injection spectra depend on processes of particle acceleration, and here we discuss models with various injection spectra.
First author: Amanda Butler Contreras
Known as the “Missing Baryon Problem”, about one-third of baryons in the local universe remain unaccounted for. The missing baryons are thought to reside in the warm-hot intergalactic medium (WHIM) of the cosmic web filaments, which are challenging to detect. Recent Chandra X-ray observations from Kov'acs et al. (2019) used a novel stacking analysis and detected an OVII absorption line toward the sightline of a luminous quasar, hinting that the missing baryons may reside in the WHIM.
First author: Xiangyu Jin
Cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (IGM). Current observations show that the IGM is significantly neutral at $z>7$, and largely ionized by $z\sim5.5$. However, most methods to measure the IGM neutral fraction are highly model-dependent, and are limited to when the volume-averaged neutral fraction of the IGM is either relatively low ($\bar{x}{\rm HI} \lesssim 10^{-3}$) or close to unity ($\bar{x}{\rm HI}\sim 1$).
First author: Tomáš Šoltinský
Enhanced ionizing radiation in close proximity to redshift $z\gtrsim 6$ quasars creates short windows of intergalactic Ly$\alpha$ transmission blueward of the quasar Ly$\alpha$ emission lines. The majority of these Ly$\alpha$ near-zones are consistent with quasars that have optically/UV bright lifetimes of $t_{\rm Q}\sim 10^{5}-10^{7}\rm,yr$. However, lifetimes as short as $t_{\rm Q}\lesssim 10^{4}\rm,yr$ appear to be required by the smallest Ly$\alpha$ near-zones. These short lifetimes present an apparent challenge for the growth of $\sim 10^{9}\rm,M_{\odot}$ black holes at $z\gtrsim 6$.
