Search

The thermal history and structure of the intergalactic medium (IGM) at |$z \ge 4$| is an important boundary condition for reionization, and a key input for studies using the Ly  |$\alpha$| forest to constrain the masses of alternative dark matter candidates. Most such inferences rely on simulations that lack the spatial resolution to fully resolve the hydrodynamic response of IGM filaments and minihaloes to H  i reionization heating. In this letter, we use high-resolution hydrodynamic + radiative transfer simulations to study how these affect the IGM thermal structure. We find that the adiabatic heating and cooling driven by the expansion of initially cold gas filaments and minihaloes sources significant small-scale temperature fluctuations. These likely persist in much of the IGM until |$z \le 4$|⁠. Capturing this effect requires resolving the clumping scale of cold, pre-ionized gas, demanding spatial resolutions of |${\le} 2$|   |$h^{-1}$| kpc. Pre-heating of the IGM by X-rays can slightly reduce the effect. Our preliminary estimate of the effect on the Ly  |$\alpha$| forest finds that, at |$\log (k /[{\rm km^{-1} s}]) = -1.0$|⁠ , the Ly  |$\alpha$| forest flux power (at fixed mean flux) can increase |${\approx} 10~{{\ \rm per\ cent}}$| going from 8 and 2  |$h^{-1}$| kpc resolution at |$z = 4{\!-\!}5$| for gas ionized at |$z \ \lt\ 7$|⁠. These findings motivate more careful analyses of how the effects studied here affect the Ly  |$\alpha$| forest. [ABSTRACT FROM AUTHOR]

Recent quasar absorption line observations suggest that reionization may end as late as |$z \approx 5.3$|⁠. As a means to search for large neutral hydrogen islands at |$z\ \lt\ 6$|⁠ , we revisit long dark gaps in the Ly  |$\beta$| forest in Very Large Telescope/X-Shooter and Keck/Echellette Spectrograph and Imager quasar spectra. We stack the Ly  |$\alpha$| forest corresponding to both edges of these Ly  |$\beta$| dark gaps and identify a damping wing-like extended absorption profile. The average redshift of the stacked forest is |$z=5.8$|⁠. By comparing these observations with reionization simulations, we infer that such a damping wing-like feature can be naturally explained if these gaps are at least partially created by neutral islands. Conversely, simulated dark gaps lacking neutral hydrogen struggle to replicate the observed damping wing features. Furthermore, this damping wing-like profile implies that the volume-averaged neutral hydrogen fraction must be |$\langle x_{\rm H\,{\small {I}}} \rangle \ge 6.1 \pm 3.9~{{\ \rm per\ cent}}$| at |$z = 5.8$|⁠. Our results offer robust evidence that reionization extends below |$z=6$|⁠. [ABSTRACT FROM AUTHOR]

Polycyclic Aromatic Hydrocarbons (PAHs) are organic molecules which comprise the smallest particles of dust in the interstellar medium (ISM). Due to their broad/complex emission profiles, obtaining kinematics is a challenge with traditional methods, especially before the advent of the JWST. In this work, we employ Principal Component Analysis (PCA) tomography to analyse JWST /NIRSpec IFU data of three nearby luminous infrared galaxies (LIRGs), namely, NGC 3256 N, NGC 3256 S, and NGC 7469. We detect the signature of rotation in the second principal component of the 3.3  |$\mu$| m PAH feature in all three targets. We construct velocity maps from the principal components for the 3.3  |$\mu$| m PAH feature, Br β (2.625  |$\mu$| m) and molecular hydrogen, H2 1–0 S(1) (2.12  |$\mu$| m). We find that in each target, the PAHs qualitatively follow the rotation of the galaxy, consistent with the rotational signature derived from Br β and H2. There are however some differences, with the PAH rotation in NGC 3256 N appearing at a different position angle, which suggest differences in the motion of the dust as compared to the gas. This kind of analysis opens a new window into this key component of the ISM. [ABSTRACT FROM AUTHOR]

We suggest that filaments in star-forming regions undergo frequent mergers. As stellar nurseries, filaments play a vital role in understanding star formation and mergers could pave the way for understanding the formation of more complex filamentary systems, such as networks and hubs. We compare the physical properties derived from hydrodynamic ramses simulations of merging filaments to those obtained from ALMA observations towards the LDN 1641-North region in Orion. We find similarities in the distributions of line-mass, column density, and velocity dispersion. Such common features support the hypothesis of filament mergers shaping the structure of the interstellar medium. [ABSTRACT FROM AUTHOR]

Ly α damping wings in the spectra of bright objects at high redshift are a useful probe of the ionization state of the intergalactic medium during the reionization epoch. It has recently been noted that, despite the inhomogeneous nature of reionization, these damping wings have a characteristic shape which is a strong function of the volume-weighted average neutral hydrogen fraction of the intergalactic medium. We present here a closer examination of this finding using a simulation of patchy reionization from the Sherwood–Relics simulation suite. We show that the characteristic shape and scatter of the damping wings are determined by the average neutral hydrogen density along the line of sight, weighted by its contribution to the optical depth producing the damping wing. We find that there is a redshift dependence in the characteristic shape due to the expansion of the Universe. Finally, we show that it is possible to differentiate between the shapes of damping wings in galaxies and young (or faint) quasars at different points in the reionization history at large velocity offsets from the point where the transmission first reaches zero. [ABSTRACT FROM AUTHOR]

Cosmic rays (CRs) may drive outflows and alter the phase structure of the circumgalactic medium, with potentially important implications on galaxy formation. However, these effects ultimately depend on the dominant mode of transport of CRs within and around galaxies, which remains highly uncertain. To explore potential observable constraints on CR transport, we investigate a set of cosmological fire -2 CR-magnetohydrodynamic simulations of L* galaxies which evolve CRs with transport models motivated by self-confinement (SC) and extrinsic turbulence (ET) paradigms. To first order, the synchrotron properties diverge between SC and ET models due to a CR physics-driven hysteresis. SC models show a higher tendency to undergo 'ejective' feedback events due to a runaway buildup of CR pressure in dense gas due to the behaviour of SC transport scalings at extremal CR energy densities. The corresponding CR wind-driven hysteresis results in brighter, smoother, and more extended synchrotron emission in SC runs relative to ET and constant diffusion runs. The differences in synchrotron arise from different morphology, interstellar medium gas, and B properties, potentially ruling out SC as the dominant mode of CR transport in typical star-forming L* galaxies, and indicating the prospect for non-thermal radio continuum observations to constrain CR transport physics. [ABSTRACT FROM AUTHOR]

We propose to employ emission line luminosities obtained via optical spectroscopy to estimate the content of neutral hydrogen (H  i) in galaxies. We use the optical spectroscopy data from the Mapping of Nearby Galaxies at APO (MaNGA) survey released in the frames of public DR17 of the Sloan Digital Sky Survey (SDSS). We compare the H  i mass estimated by us for a large sample of SDSS/MaNGA galaxies with direct H  i measurements from the Arecibo Legacy Fast ALFA survey and find a tight correlation between the masses with the correlation coefficient (CC) of 0.91 and the rms scatter of 0.15 dex for the logarithmic mass. The obtained relationship is verified via another sample of MaNGA galaxies with H  i masses measured with the Green Bank Telescope. Despite the coarser angular resolution of the radio data, the relation between the estimated and measured directly H  i mass is tight as well – in this case CC = 0.74 and the rms is 0.29 dex. The established relations allow us to estimate the total mass of neutral hydrogen as well as the spatial distribution of H  i surface density in galaxies from optical spectroscopic observations only in a simple and efficient way. [ABSTRACT FROM AUTHOR]

Spectroscopic analysis of Ly α damping wings of bright sources at z > 6 is a promising way to measure the reionization history of the universe. However, the theoretical interpretation of the damping wings is challenging due to the inhomogeneous nature of the reionization process and the proximity effect of bright sources. In this Letter, we analyse the damping wings arising from the neutral patches in the radiative transfer cosmological simulation suite cosmic reionization on computers. We find that the damping wing profile remains a tight function of volume-weighted neutral fraction < x H  i >v, especially when < x H  i >v > 0.5, despite the patchy nature of reionization and the proximity effect. This small scatter indicates that with a well-measured damping wing profile, we could constrain the volume-weighted neutral fraction as precise as Δ < x H  i >v ≲ 0.1 in the first half of reionization. Due to resonant Ly α absorption from the residual neutral hydrogen inside the ionized bubble, it may be challenging to find the starting point of the damping wing for faint sources like normal galaxies or gamma-ray bursts. However, for bright sources like quasars, it is hopeful to measure the entire damping wing and use them to measure the neutral fraction accurately. [ABSTRACT FROM AUTHOR]

In the standard quasar model, the accretion disc obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at z ≈ 1–3 and archival Atacama Large Millimetre/submillimetre Array submillimetre host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate star formation rates (SFR) and ISM column densities for the IR quasars and a control sample of submillimetre galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to |$\rm SFR\approx 300 \: {\rm M}_{\odot } \: yr^{-1}$|⁠ , and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at |$\rm SFR\gtrsim 300 \: {\rm M}_{\odot } \: yr^{-1}$|⁠ , the SMGs and IR quasars have similarly compact submillimetre sizes (⁠|$R_{\rm e}\approx 0.5{\!-\!}3\,\mathrm{ kpc}$|⁠) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick (⁠|$N_{\rm H}\gt 10^{24} \rm \: cm^{-2}$|⁠) levels in extreme cases. Based on our results, we infer that |${\approx} 10{\!-\!}30~{{ \rm per\ cent}}$| of the IR quasars with |$\rm SFR\gtrsim 300 \: {\rm M}_{\odot } \: yr^{-1}$| are obscured solely by the ISM. [ABSTRACT FROM AUTHOR]

The high-redshift galaxy UV luminosity function (UVLF) has become essential for understanding the formation and evolution of the first galaxies. Yet, UVLFs only measure galaxy abundances, giving rise to a degeneracy between the mean galaxy luminosity and its stochasticity. Here, we show that upcoming clustering measurements with the JWST , as well as with Roman, will be able to break this degeneracy, even at redshifts z ≳ 10. First, we demonstrate that current Subaru Hyper Suprime-Cam (HSC) measurements of the galaxy bias at z ∼ 4–6 point to a relatively tight halo-galaxy connection, with low stochasticity. Then, we show that the larger UVLFs observed by JWST at z ≳ 10 can be explained with either a boosted average UV emission or an enhanced stochasticity. These two models, however, predict different galaxy biases, which are potentially distinguishable in JWST and Roman surveys. Galaxy-clustering measurements, therefore, will provide crucial insights into the connection between the first galaxies and their dark-matter haloes, and identify the root cause of the enhanced abundance of z ≳ 10 galaxies revealed with JWST during its first year of operations. [ABSTRACT FROM AUTHOR]

The circumgalactic medium (CGM) is the most massive baryonic component of a spiral galaxy, shock heated to about 106 K for an |$\rm L^{\star }$| galaxy. The CGM of the Milky Way has been well-characterized through X-ray absorption line spectroscopy. However, the paucity of bright background sources makes it challenging to probe the CGM of external galaxies. Previously, using broad O  vi absorption as a signpost, we successfully detected the CGM of one galaxy in X-rays. Here we report on the detection of the O  vii K α absorption line at the redshift of a spiral galaxy at z ≈ 0.225, using 1.2 Ms of Chandra observations. This is a robust detection, clearly showing the presence of the hot gas. The mass in the hot phase is at least an order of magnitude larger than that in the cooler phases detected in the UV. The presence of hot gas 116 h−1 kpc from the centre of this galaxy provides credence to the existence of the extended CGM of the Milky Way. There has been a report of the detection of O  vii absorption from the warm-hot intergalactic medium in this sightline, using stacking analysis on older data set. We argue that the absorption line is from the CGM of the z ≈ 0.225 galaxy instead. [ABSTRACT FROM AUTHOR]

One of the most crucial yet poorly constrained parameters in modelling the ionizing emissivity is the escape fraction of photons from star-forming galaxies. Several theoretical and observational studies have been conducted over the past few years, but consensus regarding its redshift evolution has yet to be achieved. We present here the first non-parametric reconstruction of this parameter as a function of redshift from a data-driven reionization model using a Gaussian Process Regression method. Our finding suggests a mild redshift evolution of escape fraction with a mean value of |$4~{{\ \rm per\ cent}},7~{{\ \rm per\ cent}},\sim 10~{{\ \rm per\ cent}}$| at |$z$|  = 2, 6, 12. However, a constant escape fraction of |$6-10~{{\ \rm per\ cent}}$| at |$z$| ≳ 6 is still allowed by current data and also matches other reionization-related observations. With the detection of fainter high-redshift galaxies from upcoming observations of JWST, the approach presented here will be a robust tool to put the most stringent constraint on escape fraction as well as reionization histories. [ABSTRACT FROM AUTHOR]

Accurately reproducing the thin cold gas discs observed in nearby spiral galaxies has been a long standing issue in cosmological simulations. Here, we present measurements of the radially resolved H  i  scale height in 22 non-interacting Milky Way-mass galaxies from the FIREbox cosmological volume. We measure the H  i  scale heights using five different approaches commonly used in the literature: fitting the vertical volume density distribution with a Gaussian, the distance between maximum and half-maximum of the vertical volume density distribution, a semi-empirical description using the velocity dispersion and the galactic gravitational potential, the analytic assumption of hydrostatic equilibrium, and the distance from the midplane which encloses ≳60 per cent of the H  i  mass. We find median H  i  scale heights, measured using the vertical volume distribution, that range from ∼100 pc in the galactic centres to ∼800 pc in the outskirts and are in excellent agreement with recent observational results. We speculate that the presence of a realistic multiphase interstellar medium, including cold gas, and realistic stellar feedback are the drivers behind the realistic H  i  scale heights. [ABSTRACT FROM AUTHOR]

The discovery of faint Fanaroff–Riley type I (FR I) radio jets in the elliptical galaxy NGC 5322 is reported here using the 144-MHz image from Data Release 2 of the Low-Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS). The jets have an angular extent of ∼40 arcmin or a projected physical extent of ∼360 kpc. The faint jets remain well collimated and disappear in the intergalactic medium, without any detected hotspots or radio lobes. The relatively brighter jets, previously detected only up to the ∼21 kpc extent at higher frequencies, are within the optical extent of the galaxy. The jets become faint abruptly outside, where detection is made only in the LOFAR image. The total radio luminosity of the galaxy at 144 MHz is estimated to be (3.7 ± 0.4) × 1022 W Hz−1. The 144-MHz radio luminosity of the faint jets outside the optical extent is estimated to be (7.1 ± 2.0) × 1021 W Hz−1. The size of the jets is exceptionally large for the galaxy's low radio luminosity, when compared with other radio galaxies. It makes NGC 5322 a rare radio galaxy, previously not detected in other radio surveys. A combined effect of stellar core depletion and low-density environment around the jets, which results in a weak entrainment of the material surrounding the jets, could be responsible for its large size despite a low radio luminosity. [ABSTRACT FROM AUTHOR]

We report the detection of the ground state rotational emission of ammonia, ortho-NH3 (JK  = 10 → 00) in a gravitationally lensed intrinsically hyperluminous star-bursting galaxy at z  = 2.6. The integrated line profile is consistent with other molecular and atomic emission lines which have resolved kinematics well modelled by a 5 kpc-diameter rotating disc. This implies that the gas responsible for NH3 emission is broadly tracing the global molecular reservoir, but likely distributed in pockets of high density (n ≳ 5 × 104 cm−3). With a luminosity of 2.8 × 106 L⊙, the NH3 emission represents 2.5 × 10−7 of the total infrared luminosity of the galaxy, comparable to the ratio observed in the Kleinmann–Low nebula in Orion and consistent with sites of massive star formation in the Milky Way. If |$L_{\rm NH_3}/L_{\rm IR}$| serves as a proxy for the 'mode' of star formation, this hints that the nature of star formation in extreme starbursts in the early Universe is similar to that of Galactic star-forming regions, with a large fraction of the cold interstellar medium in this state, plausibly driven by a storm of violent disc instabilities in the gas-dominated disc. This supports the 'full of Orions' picture of star formation in the most extreme galaxies seen close to the peak epoch of stellar mass assembly. [ABSTRACT FROM AUTHOR]

Primordial black holes (PBHs) formed in the early Universe constitute an attractive candidate for dark matter. Within the gaseous environment of the interstellar medium, PBHs with accretion discs naturally launch outflows such as winds and jets. We discuss for the first time how PBHs with significant spin can sustain powerful relativistic jets and generate associated cocoons. Jets and winds can efficiently deposit their kinetic energies and heat the surrounding gas through shocks. Focusing on the Leo T dwarf galaxy, we demonstrate that these effects form novel tests and set new limits on PBHs over a significant ∼10−2 –106 M⊙ mass range, including the parameter space associated with gravitational wave observations by the LIGO and VIRGO Collaborations. Observing the morphology of emission will allow to distinguish between jet and wind contributions, and hence establishes a new method for identifying spinning PBHs. [ABSTRACT FROM AUTHOR]

The interstellar medium (ISM) is an inseparable part of the Milky Way ecosystem whose evolutionary history remains a challenging question. We trace the evolution of the molecular ISM using a sample of young stellar objects (YSO) association–molecular cloud complex (YSO–MC complex). We derive their three-dimensional (3D) velocities by combining the Gaia astrometric measurements of the YSO associations and the CO observations of the associated molecular clouds. Based on the 3D velocities, we simulate the motions of the YSO–MC complexes in the Galactic potential and forecast the ISM evolution by tracing the motions of the individual complexes, and reveal the roles of shear and stellar feedback in determining ISM evolution: Galactic shear stretches Galactic-scale molecular cloud complexes, such as the G120 Complex, into Galactic-scale filaments, and it also contributes to the destruction of the filaments; while stellar feedback creates interconnected superbubbles whose expansion injects peculiar velocities into the ISM. The Galactic-scale molecular gas clumps are often precursors of the filaments and the Galactic-scale filaments are transient structures under a constant stretch by shear. This evolutionary sequence sets a foundation to interpret other gas structures. [ABSTRACT FROM AUTHOR]

Odd Radio Circles or ORCs are recently discovered edge-brightened, low surface brightness circular radio sources. The progenitors and astrophysical processes responsible for their origins are presently debated. Some ORCs are host-less and some appear to be hosted in distant quiescent galaxies. Two plausible explanations consider ORCs as nearby supernova remnants with sizes a few hundred parsec in the intragroup medium of the Local Group of galaxies or alternatively shocked haloes of a few hundred kpc extent around distant galaxies. The input shock energy required to create ORCs of a few hundred kpc size is estimated in a range of 1055–1059 erg. It is shown here that the cumulative energy in unbound debris ejected from multiple (105–109) tidal disruption events over ∼100 Myr period around a central massive black hole can meet the required energies to generate ORCs around some galaxies, which have recently undergone a merger. The potential hosts for ORCs are identified here as abundant post-starburst galaxies at intermediate redshifts having massive black holes. A causal connection between ORC around quiescent galaxies and tidal disruption may find support in the observed dominance of tidal disruption events in post-starburst galaxies. [ABSTRACT FROM AUTHOR]

A significant fraction of massive stars move at speed through the interstellar medium of galaxies. After their death as core-collapse supernovae, a possible final evolutionary state is that of a fast-rotating magnetized neutron star, shaping its circumstellar medium into a pulsar wind nebula. Understanding the properties of pulsar wind nebulae requires knowledge of the evolutionary history of their massive progenitors. Using two-dimensional magnetohydrodynamical simulations, we demonstrate that, in the context of a runaway high-mass red-supergiant supernova progenitor, the morphology of its subsequent pulsar wind nebula is strongly affected by the wind of the defunct progenitor star pre-shaping the stellar surroundings throughout its entire past life. In particular, pulsar wind nebulae of obscured runaway massive stars harbour asymmetries as a function of the morphology of the progenitor's wind-blown cavity, inducing projected asymmetric up–down synchrotron emission. [ABSTRACT FROM AUTHOR]

A measurable fraction (∼8 per cent) of recently discovered arcmin-size circular diffuse radio sources termed as odd radio circles or ORCs can be supernovae remnants in the intragroup medium, within the Local Group and its immediate neighbour groups of galaxies. This estimate is based on the optical detection rate of the intragroup supernovae events in the nearby (z ∼ 0.1−0.2) galaxy groups. A rate of about 5400 intragroup supernovae per million year is expected within the local and its immediate neighbour groups of galaxies. For a radio detectability period of about 104 yr, on average 1.3 intragroup medium supernovae remnants per 1000 deg2 are expected to be detected in the radio surveys with a sensitivity that led to discovery of ORCs. The angular size, surface brightness, and radio flux of the supernova remnants up to a distance of ∼3 Mpc in the intragroup medium can be expected to be similar to the five known ORCs. The intragroup supernovae remnants are not residing in the dense and cold interstellar medium of the galaxies but evolving in low-density (10−4−10−5 cm−3) warm medium (105−106 K) in galactic haloes or beyond, and may find their progenitors in the diffuse stellar light associated with various tidal streamers surrounding the Milky Way and other nearby galaxies. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are a promising tool for studying the low-density universe as their dispersion measures (DM) are extremely sensitive probes of electron column density. Active galactic nuclei (AGN) inject energy into the intergalactic medium, affecting the DM and their scatter. To determine the effectiveness of FRBs as a probe of AGN feedback, we analysed three different AGN models from the EAGLE simulation series. We measured the mean DM–redshift relation, and the scatter around it, using 2.56 × 108 sightlines at 131 redshift (z) bins between 0 ≤ z ≤ 3. While the DM–redshift relation itself is highly robust against different AGN feedback models, significant differences are detected in the scatter around the mean: weaker feedback leads to more scatter. We find that ∼104 localized FRBs are needed to discriminate between the scatter in standard feedback and stronger, more intermittent feedback models. The number of FRBs required is dependent on the redshift distribution of the detected population. A lognormal redshift distribution at z  = 0.5 requires approximately 50 per cent fewer localized FRBs than a distribution centred at z  = 1. With the Square Kilometre Array expected to detect >103 FRBs per day, in the future, FRBs will be able to provide constraints on AGN feedback. [ABSTRACT FROM AUTHOR]

Fast radio burst (FRB) 191001 is localized at the spiral arm of a highly star-forming galaxy with an observed dispersion measure (DM) of 507 |$\mbox{pc cm$^{-3}$}$|⁠. Subtracting the contributions of the intergalactic medium and our Milky Way Galaxy from the total DM, one gets an excess of around 200 |$\mbox{pc cm$^{-3}$}$|⁠ , which may have been contributed by the host galaxy of the FRB. It is found in this work that the position of FRB 191001 is consistent with the distribution of supernovae (SNe) in the spiral arm of their parent galaxies. If this event is indeed due to an SN explosion, then, from the analysis of the SN contributions to the excess DM, a core-collapse (CC) channel is preferred over a thermonuclear runaway. For the CC explosion, depending on the density of the surrounding medium, the age of the central engine that powers the radio burst is within a couple of years to a few decades. However, the observed rotation measure of FRB 191001 does not confirm the fact that the radio burst has passed through the remnant of a young SN. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are extremely powerful sources of radio waves observed at cosmological distances. We use a sophisticated model of FRB observations – presented in detail in a companion paper – to fit FRB population parameters using large samples of FRBs detected by ASKAP and Parkes, including seven sources with confirmed host galaxies. Our fitted parameters demonstrate that the FRB population evolves with redshift in a manner consistent with, or faster than, the star formation rate (SFR), ruling out a non-evolving population at better than 98 per cent CL (depending on modelling uncertainties). Our estimated maximum FRB energy is |$\log _{10} E_{\rm max} [{\rm erg}] = 41.70_{-0.06}^{+0.53}$| (68 per cent CL) assuming a 1 GHz emission bandwidth, with slope of the cumulative luminosity distribution |$\gamma =-1.09_{-0.10}^{+0.14}$|⁠. We find a log-mean host DM contribution of |$129_{-48}^{+66}$|  pc cm−3 on top of a typical local (interstellar medium and halo) contribution of ∼80 pc cm−3, which is higher than most literature values. These results are insensitive to assumptions of the FRB spectral index, and are consistent with the model of FRBs arising as the high-energy limit of magnetar bursts, but allow for FRB progenitors that evolve faster than the SFR. [ABSTRACT FROM AUTHOR]

The ratio of the mass of interstellar dust to the total mass of metals (the dust-to-metals/DTM ratio) tends to increase with metallicity. This can be explained by the increasing efficiency of grain growth in the interstellar medium (ISM) at higher metallicities, with a corollary being that the low DTM ratios seen at low metallicities are due to inefficient stellar dust production. This interpretation assumes that the efficiency of dust destruction in the ISM is constant, whereas it might be expected to increase at low metallicity; the decreased cooling efficiency of low-metallicity gas should result in more post-shock dust destruction via thermal sputtering. We show that incorporating a sufficiently strong metallicity dependence into models of galaxy evolution removes the need for low stellar dust yields. The contribution of stellar sources to the overall dust budget may be significantly underestimated, and that of grain growth overestimated, by models assuming a constant destruction efficiency. [ABSTRACT FROM AUTHOR]

Galaxy clusters grow primarily through the continuous accretion of group-scale haloes. Group galaxies experience preprocessing during their journey into clusters. A star-bursting compact group, the Blue Infalling Group (BIG), is plunging into the nearby cluster A1367. Previous optical observations reveal rich tidal features in the BIG members, and a long H α trail behind. Here, we report the discovery of a projected ∼250 kpc X-ray tail behind the BIG using Chandra and XMM–Newton observations. The total hot gas mass in the tail is ∼7 × 1010 M⊙ with an X-ray bolometric luminosity of ∼3.8 × 1041 erg s−1. The temperature along the tail is ∼1 keV, but the apparent metallicity is very low, an indication of the multi- T nature of the gas. The X-ray and H α surface brightnesses in the front part of the BIG tail follow the tight correlation established from a sample of stripped tails in nearby clusters, which suggests the multiphase gas originates from the mixing of the stripped interstellar medium (ISM) with the hot intracluster medium (ICM). Because thermal conduction and hydrodynamic instabilities are significantly suppressed, the stripped ISM can be long lived and produce ICM clumps. The BIG provides us a rare laboratory to study galaxy transformation and preprocessing. [ABSTRACT FROM AUTHOR]

We report here the first detection in the interstellar medium of the cyanomidyl radical (HNCN). Using the Yebes 40m and the IRAM 30m telescopes, we have targeted the doublets of the N  = 2–1, 4–3, 5–4, 6–5, and 7–6 transitions of HNCN towards the molecular cloud G+0.693-0.027. We have detected three unblended lines of HNCN, these are the N  = 6–5 doublet and one line of the N  = 4–3 transition. Additionally, we present one line of the N  = 5–4 transition partially blended with emission from other species. The local thermodynamic equilibrium best fit to the data gives a molecular abundance of (0.91 ± 0.05) × 10−10 with respect to H2. The relatively low abundance of this species in G+0.693-0.027 and its high reactivity suggest that HNCN is possibly produced by gas-phase chemistry. Our work shows that this highly reactive molecule is present in interstellar space, and thus it represents a plausible precursor of larger prebiotic molecules with the nitrogen–carbon–nitrogen backbone such as cyanamide (NH2CN), carbodiimide (HNCNH), and formamidine (NH2CHNH). [ABSTRACT FROM AUTHOR]

In order to study the ram-pressure interaction between radio galaxies and the intracluster medium, we analyse a sample of 208 highly bent narrow-angle tail radio sources (NATs) in clusters, detected by the Low-Frequency Array Two-metre Sky Survey. For NATs within |$7R_{500}$| of the cluster centre, we find that their tails are distributed anisotropically with a strong tendency to be bent radially away from the cluster, which suggests that they are predominantly on radially inbound orbits. Within |$0.5R_{500}$|⁠ , we also observe an excess of NATs with their jets bent towards the cluster core, indicating that these outbound sources fade away soon after passing pericentre. For the subset of NATs with spectroscopic redshifts, we find the radial bias in the jet angles exists even out to |$10R_{500}$|⁠ , far beyond the virial radius. The presence of NATs at such large radii implies that significant deceleration of the accompanying inflowing intergalactic medium must be occurring there to create the ram pressure that bends the jets, and potentially even triggers the radio source. [ABSTRACT FROM AUTHOR]

In the outskirts of nearby spiral galaxies, star formation is observed in extremely low gas surface densities. Star formation in these regions, where the interstellar medium is dominated by diffuse atomic hydrogen, is difficult to explain with classic star formation theories. In this letter, we introduce runaway stars as an explanation for this observation. Runaway stars, produced by collisional dynamics in young stellar clusters, can travel kiloparsecs during their main-sequence lifetime. Using galactic-scale hydrodynamic simulations including a treatment of individual stars, we demonstrate that this mechanism enables the ejection of young massive stars into environments where the gas is not dense enough to trigger star formation. This results in the appearance of star formation in regions where it ought to be impossible. We conclude that runaway stars are a contributing, if not dominant, factor to the observations of star formation in the outskirts of spiral galaxies. [ABSTRACT FROM AUTHOR]

We present a detailed analysis of the gaseous component of the Si K edge using high-resolution Chandra spectra of low-mass X-ray binaries. We fit the spectra with a modified version of the ISMabs model, including new photoabsorption cross-sections computed for all Si ionic species. We estimate column densities for Si  i , Si  ii , Si  iii , Si  xii , and Si  xiii , which trace the warm, intermediate temperature, and hot phases of the Galactic interstellar medium. We find that the ionic fractions of the first two phases are similar. This may be due to the physical state of the plasma determined by the temperature or due to the presence of absorber material in the close vicinity of the sources. Our findings highlight the need for accurate modelling of the gaseous component before attempting to address the solid component. [ABSTRACT FROM AUTHOR]

Five fast radio bursts (FRBs), including three apparently non-repeating ones, FRB 180924, FRB 181112, and FRB 190523, and two repeaters, FRB 121102 and FRB 180916.J0158+65, have already been localized so far. We apply a method developed recently by us to these five localized FRBs to give a cosmology-insensitive estimate of the fraction of baryon mass in the intergalactic medium, f IGM. Using the measured dispersion measure (DM) and luminosity distance d L data (inferred from the FRB redshifts and d L of Type Ia supernovae at the same redshifts) of the five FRBs, we constrain the local |$f_{\rm IGM} = 0.84^{+0.16}_{-0.22}$| with no evidence of redshift dependence. This cosmology-insensitive estimate of f IGM from FRB observations is in excellent agreement with previous constraints using other probes. Moreover, using the three apparently non-repeating FRBs only we get a little looser but consistent result: |$f_{\rm IGM} = 0.74^{+0.24}_{-0.18}$|⁠. In these two cases, reasonable estimations for the host galaxy DM contribution (DMhost) can be achieved by modelling it as a function of star formation rate. The constraints on both f IGM and DMhost are expected to be significantly improved with the rapid progress in localizing FRBs. [ABSTRACT FROM AUTHOR]

Cosmic rays are a global source of ionization, and the ionization fraction represents a fundamental parameter in the interstellar medium. Ions couple to magnetic fields, and affect the chemistry and the dynamics of star-forming regions as well as planetary atmospheres. However, the cosmic ray ionization rate represents one of the bottlenecks for astrochemical models, and its determination is one of the most puzzling problems in astrophysics. While for diffuse clouds reasonable values have been provided from |${\mathrm{ H}_3}^+$| observations, for dense clouds, due to the lack of rotational transitions, this is not possible, and estimates are strongly biased by the employed model. We present here an analytical expression, obtained from first principles, to estimate the cosmic ray ionization rate from observational quantities. The theoretical predictions are validated with high-resolution 3D numerical simulations and applied to the well-known core L1544; we obtained an estimate of ζ2 ∼ 2–3 × 10−17 s−1. Our results and the analytical formulae provided represent the first model-independent robust tool to probe the cosmic ray ionization rate in the densest part of star-forming regions (on spatial scales of R ≤ 0.05 pc). An error analysis is presented to give statistical relevance to our study. [ABSTRACT FROM AUTHOR]

We present a novel method to simultaneously characterize the star formation law and the interstellar medium properties of galaxies in the epoch of reionization (EoR) through the combination of [C  ii ] 158  μ m (and its known relation with star formation rate) and C  iii ] λ1909 Å emission line data. The method, based on a Markov chain Monte Carlo algorithm, allows us to determine the target galaxy average density, n , gas metallicity, Z , and 'burstiness' parameter, κs, quantifying deviations from the Kennicutt–Schmidt relation. As an application, we consider COS-3018 (z  = 6.854), the only EoR Lyman Break Galaxy so far detected in both [C  ii ] and C  iii ]. We show that COS-3018 is a moderate starburst (κs ≈ 3), with |$Z \approx 0.4 \, \mathrm{Z}_{\odot }$|⁠ , and |$n \approx 500\, {\rm cm^{-3}}$|⁠. Our method will be optimally applied to joint ALMA and James Webb Space Telescope targets. [ABSTRACT FROM AUTHOR]

We present a semi-analytical description of the relative hydrogen deuteride (HD)/H2 abundance in the diffuse interstellar medium. We found three asymptotics of the relative HD/H2 abundance for different parts of the medium and their dependence on the physical parameters, namely, number density, intensity of the ultraviolet field, cosmic ray ionization rate, and metallicity. Our calculations are in a good agreement with the full network calculations using Meudon PDR code. We found that in the case of low metallicity and/or higher cosmic ray ionization rate, HD formation rate is significantly enhanced, HD/H2 ratio increases, and the D  i /HD transition occurs at lower penetration depth of ultraviolet radiation than the H  i /H2 transition. This can explain the observed difference in the HD/H2 abundance between the local and high-redshift measurements. [ABSTRACT FROM AUTHOR]

Dust particles play a major role in the formation, evolution and chemistry of interstellar clouds, stars, and planetary systems. Commonly identified forms include amorphous and crystalline carbon-rich particles and silicates. Also present in many astrophysical environments are polycyclic aromatic hydrocarbons (PAHs), detected through their infrared emission, and which are essentially small flakes of graphene. Astronomical observations over the past four decades have revealed a widespread unassigned 'extended red emission' (ERE) feature which is attributed to luminescence of dust grains. Numerous potential carriers for ERE have been proposed but none has gained general acceptance. In this Letter it is shown that there is a strong similarity between laboratory optical emission spectra of graphene oxide (GO) and ERE, leading to this proposal that emission from GO nanoparticles is the origin of ERE and that these are a significant component of interstellar dust. The proposal is supported by infrared emission features detected by the Infrared Space Observatory (ISO) and the Spitzer Space Telescope. [ABSTRACT FROM AUTHOR]

Radio, X-ray, and infrared observations of the inner few hundred parsecs of the Galactic Centre have highlighted two characteristics of the interstellar medium. The cosmic-ray ionization rate derived from molecular ions such as H |$^+_3$| is at least two to three orders of magnitude higher than in the Galactic disc. The other is bipolar X-ray and radio emission away from the Galactic plane. These features are consistent with a scenario in which high cosmic-ray pressure drives large-scale winds away from the Galactic plane. The interaction of such a wind with stellar wind bubbles may explain the energetic non-thermal radio filaments found throughout the Galactic Centre. Some of the implications of this scenario is the removal of gas driven by outflowing winds, acting as a feedback to reduce the star formation rate in the central molecular zone (CMZ), and the distortion of azimuthal magnetic field lines in the CMZ to vertical direction away from the plane. The combined effects of the wind and the vertical magnetic field can explain why most magnetized filaments run perpendicular to the galactic plane. This proposed picture suggests our Milky Way nucleus has recently experienced starburst or black hole activity, as recent radio and X-ray observations indicate. [ABSTRACT FROM AUTHOR]

The scatter in the relationship between the strength of [C  ıı] 158  μm emission and the star formation rate at high redshift has been the source of much recent interest. Although the relationship is well established locally, several intensely star-forming galaxies have been found whose [C  ıı] 158  μm emission is either weak, absent, or spatially offset from the young stars. Here we present new ALMA data for the two most distant gravitationally lensed and spectroscopically confirmed galaxies, A2744_YD4 at z  = 8.38 and MACS1149_JD1 at z  = 9.11, both of which reveal intense [O  ıı] 88 μm emission. In both cases we provide stringent upper limits on the presence of [C  ıı] 158  μm with respect to [O  ıı] 88  μm. We review possible explanations for this apparent redshift-dependent [C  ıı] deficit in the context of our recent hydrodynamical simulations. Our results highlight the importance of using several emission line diagnostics with ALMA to investigate the nature of the interstellar medium in early galaxies. [ABSTRACT FROM AUTHOR]

High-redshift quasi-stellar object (QSO) spectra show large spatial fluctuations in the Ly α opacity of the intergalactic medium on surprisingly large scales at |$z$| ≳ 5.5. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly α opacity distribution at 5 < |$z$| < 6. The simulation also reproduces the low Thomson scattering optical depth reported by the latest cosmic microwave background (CMB) measurement and is consistent with the observed short near-zones and strong red damping wings in the highest redshift QSOs. It also matches the rapid disappearance of observed Ly α emission by galaxies at |$z$| ≳ 6. Reionization is complete at |$z$|  = 5.3 in our model, and 50 per cent of the volume of the Universe is ionized at |$z$|  = 7. Agreement with the Ly α forest data in such a late reionization model requires a rapid evolution of the ionizing emissivity of galaxies that peaks at |$z$| ∼ 6.8. The late end of reionization results in a large scatter in the photoionization rate and the neutral hydrogen fraction at redshifts as low as |$z$| ≲ 5.5 with large residual neutral 'islands' that can produce very long Gunn–Peterson troughs resembling those seen in the data. [ABSTRACT FROM AUTHOR]

Theories of a pre-RNA world suggest that glycolonitrile (HOCH2CN) is a key species in the process of ribonucleotide assembly, which is considered as a molecular precursor of nucleic acids. In this Letter, we report the first detection of this pre-biotic molecule in the interstellar medium by using ALMA data obtained at frequencies between 86.5 GHz and 266.5 GHz toward the Solar-type protostar IRAS16293–2422 B. A total of 15 unblended transitions of HOCH2CN were identified. Our analysis indicates the presence of a cold (T |$\rm _{ex}$|  = 24 ± 8 K) and a warm (T |$\rm _{ex}$|  = 158 ± 38 K) component meaning that this molecule is present in both the inner hot corino and the outer cold envelope of IRAS16293 B. The relative abundance with respect to H2 is (6.5 ± 0.6) × 10−11 and ≥(6 ± 2) × 10−10 for the warm and cold components, respectively. Our chemical modelling seems to underproduce the observed abundance for both the warm and cold component under various values of the cosmic ray ionization rate (ζ). Key gas phase routes for the formation of this molecule might be missing in our chemical network. [ABSTRACT FROM AUTHOR]

The total amount of O  vi present in the interstellar medium (ISM) obtained via absorption measurements in UV and X-ray spectra is currently in disagreement, with the latter being significantly larger (by a factor of 10 or more) than the former. Previous works have proposed that the blend of the O  vi Kα line (22.032 Å) with the O  ii Kβ-L12 line (22.04 Å) could account for the stronger absorption observed in the X-ray spectra. Here, we present a detailed study of the oxygen absorption in the local ISM, implementing our new model IGMabs which includes photoabsorption cross-sections of highly ionized species of abundant elements as well as turbulence broadening. By analysing high-resolution Chandra spectra of 13 low-mass X-ray binaries (LMXBs) and 29 extragalactic sources, we have estimated the column densities of O  i – O  iii and from O  vi – O  viii along multiple line-of-sights. We find that in most cases the O  ii Kβ-L12 line accounts for <30 |${{\ \rm per\ cent}}$| of the total O  vi K α + O  ii K β. We conclude that the amount of O  ii predicted by our model is still insufficient to explain the discrepancy between X-ray and UV measurements of O  vi column densities. [ABSTRACT FROM AUTHOR]

We report the first detection in the interstellar medium (ISM) of the Z-isomer of cyanomethanimine (HNCHCN), an HCN dimer proposed as precursor of adenine. We identified six transitions of Z-cyanomethanimine, along with five transitions of E-cyanomethanimine, using IRAM 30m observations towards the Galactic Centre quiescent molecular cloud G + 0.693. The Z-isomer has a column density of (2.0 ± 0.6) × 1014 cm−2 and an abundance of 1.5 × 10−9. The relative abundance ratio between the isomers is [Z/E]∼6. This value cannot be explained by the two chemical formation routes previously proposed (gas phase and grain surface), which predicts abundances ratios between 0.9 and 1.5. The observed [Z/E] ratio is in good agreement with thermodynamic equilibrium at the gas kinetic temperature (130−210 K). Since isomerization is not possible in the ISM, the two species may be formed at high temperature. New chemical models, including surface chemistry on dust grains and gas-phase reactions, should be explored to explain our findings. Whatever the formation mechanism, the high abundance of Z-HNCHCN shows that precursors of adenine are efficiently formed in the ISM. [ABSTRACT FROM AUTHOR]

The nature and energetics of feedback from thermal winds in quasars can be constrained via observations of the Sunyaev–Zeldovich Effect (SZE) induced by the bubble of thermal plasma blown into the intergalactic medium by the quasar wind. In this letter, we present evidence that we have made the first detection of such a bubble, associated with the hyperluminous quasar HE 0515-4414. The SZE detection is corroborated by the presence of extended emission line gas at the same position angle as the wind. Our detection appears on only one side of the quasar, consistent with the SZE signal arising from a combination of thermal and kinetic contributions. Estimates of the energy in the wind allow us to constrain the wind luminosity to the lower end of theoretical predictions, ∼0.01 per cent of the bolometric luminosity of the quasar. However, the age we estimate for the bubble, ∼0.1 Gyr, and the long cooling time, ∼0.6 Gyr, means that such bubbles may be effective at providing feedback between bursts of quasar activity. [ABSTRACT FROM AUTHOR]

Here we investigate how LyC-opaque systems present in the intergalactic medium at |$z$| ≈ 3 can distort the spectral shape of a uniform UV background (UVB) through radiative transfer (RT) effects. With this aim in mind, we perform a multifrequency RT simulation through a cosmic volume of 10  h −1 cMpc scale polluted by metals, and self-consistently derive the ions of all the species. The UVB spatial fluctuations are traced by the ratio of He  |$\,\small {II}$| and H  |$\,\small {I}$| column density, η, and the ratio of C  |$\, \small {IV}$| and Si  |$\, \small {IV}$| optical depths, ζ. We find that: (i) η spatially fluctuates through overdense systems (Δ) with statistically significant deviations δη > 25 per cent in 18 per cent of the volume; (ii) same fluctuations in ζ are also present in 34 per cent of the enriched domain (only 8 per cent of the total volume) and derive from a combination of RT induced effects and in-homogeneous metal enrichment, both effective in systems with Δ > 1.5. [ABSTRACT FROM AUTHOR]

Interstellar CO2 is an important reservoir of carbon and oxygen, and one of the major constituents of the icy mantles of dust grains, but it is not observable directly in cold gas because it has no permanent dipole moment. Its protonated form, HOCO+, is believed to be a good proxy for gaseous CO2. However, it has been detected in only a few star-forming regions to date, so its interstellar chemistry is not well understood. We present new detections of HOCO+ lines in 11 high-mass star-forming clumps. Our observations more than treble the number of detections in star-forming regions to date. We derived beam-averaged abundances relative to H2 of between 0.3 and 3.8 × 10−11. We compared these values with the abundances of H13CO+, a possible gas-phase precursor of HOCO+, and of CH3OH, a product of surface chemistry. We found a positive correlation with H13CO+, but no correlation with CH3OH. We suggest that the gas-phase formation route starting from HCO+ plays an important role in the formation of HOCO+, perhaps more important than protonation of CO2 (upon evaporation of CO2 from icy dust mantles). [ABSTRACT FROM AUTHOR]

We modify the chemo-dynamical code gear to simulate the impact of self-interacting dark matter (SIDM) on the observable quantities of 19 low-mass dwarf galaxies with a variety star-forming properties. We employ a relatively high, velocity independent cross-section of |$\sigma /m=10\, \rm {cm^2\,g^{ -1}}$| and extract, in addition to integrated quantities, the total mass density profile, the luminosity profile, the line-of-sight velocities, the chemical abundance, and the star formation history. We find that despite the creation of large cores at the centre of the dark matter haloes, the impact of SIDM on the observable quantities of quenched galaxies is indiscernible, dominated mostly by the stochastic build up of the stellar matter. As such we conclude that it is impossible to make global statements on the density profile of dwarf galaxies from single or small samples. Although based mostly on quenched galaxies, this finding supports other recent work putting into question the reliability of inferred cored density profiles that are derived from observed line-of-sight velocities. [ABSTRACT FROM AUTHOR]

The 21 cm hyperfine transition of the atomic hydrogen (H  i) in ground state is a powerful probe of the neutral gas content of the Universe. This radio frequency transition has been used routinely for decades to observe, both in emission and absorption, H  i in the Galactic interstellar medium as well as in extragalactic sources. In general, however, it is not trivial to derive the physically relevant parameters like temperature, density, or column density from these observations. Here, we have considered the issue of column density estimation from the H  i 21 cm emission spectrum for sightlines with a non-negligible optical depth and a mix of gas at different temperatures. The complicated radiative transfer and a lack of knowledge about the relative position of gas clouds along the sightline often make it impossible to uniquely separate the components, and hinders reliable estimation of column densities in such cases. Based on the observed correlation between the 21 cm brightness temperature and optical depth, we propose a method to get an unbiased estimate of the H  i column density using only the 21 cm emission spectrum. This formalism is further used for a large sample to study the spin temperature of the neutral interstellar medium. [ABSTRACT FROM AUTHOR]

The tentative detection by the EDGES experiment of a global 21-cm absorption trough centred at redshift 17 opens up the opportunity to study the birth of the first luminous sources, the intensity of radiation backgrounds at cosmic dawn, the thermal and ionization history of the young intergalactic medium. Here, we focus on the astrophysical implications of the Ly α photon field needed to couple the spin temperature to the kinetic temperature of the gas at these early epochs. Under the basic assumption that the 21-cm signal is activated by extremely metal-poor stellar systems, we show that the EDGES results are consistent with an extrapolation of the declining galaxy UV luminosity density measured at |$4\lesssim z\lesssim 9$| by deep Hubble Space Telescope observations. A substantially enhanced star formation rate density or new exotic sources of UV photons are not required at the redshifts of the EDGES signal. The amount of ionizing radiation produced by the same stellar systems that induce Ly α coupling is significant, of order 0.5 LyC photons per H-atom per 100 Myr. To keep hydrogen largely neutral and delay the reionization process consistently with recent Planck cosmic microwave background results, mean escape fractions of |$f_{\rm esc}\lesssim 20$|  per cent are required at |$z$| > 15. [ABSTRACT FROM AUTHOR]

Detections of the cross-correlation signal between the 21 cm signal during reionization and high-redshift Lyman-α (Ly α) emitters (LAEs) are subject to observational uncertainties which mainly include systematics associated with radio interferometers and LAE selection. These uncertainties can be reduced by increasing the survey volume and/or the survey luminosity limit, i.e. the faintest detectable Ly α luminosity. We use our model of high-redshift LAEs and the underlying reionization state to compute the uncertainties of the 21-cm-LAE cross-correlation function at $$z$$  ≃ 6.6 for observations with SKA1-Low and LAE surveys with Δ $$z$$ = 0.1 for three different values of the average inter-galactic medium (IGM) ionization state (⟨χHi ⟩ ≃ 0.1, 0.25, 0.5). At $$z$$  ≃ 6.6, we find SILVERRUSH type surveys, with a field of view of 21 deg2 and survey luminosity limits of L α ≥ 7.9 × 1042 erg s−1, to be optimal to distinguish between an IGM that is 50 , 25 , and 10 per  cent neutral, while surveys with smaller fields of view and lower survey luminosity limits, such as the 5 and 10 deg2 surveys with WFIRST, can only discriminate between a 50  and 10 per  cent neutral IGM. [ABSTRACT FROM AUTHOR]

We now have mounting evidences that the circumgalactic medium (CGM) of galaxies is polluted with metals processed through stars. The fate of these metals is however still an open question and several findings indicate that they remain poorly mixed. A powerful tool to study the low-density gas of the CGM is offered by absorption lines in quasar spectra, although the information retrieved is limited to 1D along the sightline. We report the serendipitous discovery of two close-by bright z gal = 1.148 extended galaxies with a fortuitous intervening z abs = 1.067 foreground absorber. MUSE IFU observations spatially probes kpc-scales in absorption in the plane of the sky over a total area spanning ∼30 kpc−2. We identify two [O  ii ] emitters at z abs down to 21 kpc with SFR ∼ 2 M⊙ yr−1. We measure small fractional variations (<30 per cent) in the equivalent widths of Fe  ii and Mg  ii cold gas absorbers on coherence scales of 8 kpc but stronger variation on larger scales (25 kpc). We compute the corresponding cloud gas mass <2 × 109 M⊙. Our results indicate a good efficiency of the metal mixing on kpc-scales in the CGM of a typical z ∼ 1 galaxy. This study show-cases new prospects for mapping the distribution and sizes of metal clouds observed in absorption against extended background sources with 3D spectroscopy. [ABSTRACT FROM AUTHOR]