Intercluster Medium Research Articles

GASP XXXV: Characteristics of the Diffuse Ionised Gas in Gas-stripped Galaxies

Abstract Diffuse ionized gas (DIG) is an important component of the interstellar medium that can provide insights into the different physical processes affecting the gas in galaxies. We utilize optical IFU observations of 71 gas-stripped and control galaxies from the Gas Stripping Phenomena in galaxies (GASP) survey, to analyze the gas properties of dense ionized gas and DIG, such as metallicity, ionization parameter log(q), and the difference between the measured log[O i]/Hα and the value predicted by star-forming models given the measured log[Oiii]/Hβ (Δ log[O i]/Hα). We compare these properties at different spatial scales, among galaxies at different gas-stripping stages, and between disks and tails of the stripped galaxies. The metallicity is similar between the dense gas and DIG at a given galactocentric radius. The log(q) is lower for DIG compared to dense gas. The median values of log(q) correlate best with stellar mass and the most massive galaxies show an increase in log(q) toward their galactic centers. The DIG clearly shows higher Δ log[O i]/Hα values compared to the dense gas, with much of the spaxels having LIER/LINER-like emission. The DIG regions in the tails of highly stripped galaxies show the highest Δ log[O i]/Hα, exhibit high values of log(q), and extend to large projected distances from star-forming areas (up to 10 kpc). We conclude that the DIG in the tails is at least partly ionized by a process other than star formation, probably by mixing, shocks, and accretion of inter-cluster and interstellar medium gas.

Role of the Cluster Structure of Amorphous Fe67Cr18B15 Alloy in Magnetism and in the Changing of Electron Scattering Mechanisms under the Influence of Ion (Ar+) Irradiation

The contribution of clusters of different sizes to magnetism and the switching of electron scattering mechanisms in amorphous Fe67Cr18B15 alloy during ion Ar+ irradiation is studied. The cluster magnetism is found to be related to the presence of clusters of the following two types: large α-(Fe, Cr) clusters of size D = 150–250 A and small (D = 40–80 A) clusters in a random intercluster medium. The generation of small ferromagnetic and antiferromagnetic clusters during ion irradiation leads to the formation of cluster glass, which affects the electrical properties of the alloy and causes a magnetic frustration. The temperature dependence of the barrier height is shown to characterize the magnetic state of the alloy in low fields. On the whole, the temperature dependence of the order parameter is a universal characteristic of the system. The temperature dependence of resistivity of initial alloys in the temperature range 98–300 K (ρ(T) ∝ T2) is determined by electron scattering by quantum defects, and the transition into a ferromagnetic state is revealed when the derivative ∂ρ/∂T ∝ T is analyzed. The increase in resistivity and the relation ρ ∝ T1/2 in strongly inhomogeneous samples after irradiation at a dose Φ = 1.5 × 1018 ions/cm2 are caused by weak localization effects, and the transition to a ferromagnetic state becomes obvious when the derivative ∂ρ/∂T ∝ T–1/2 is considered. Irradiation by fluence Φ = 3 × 1018 ions/cm2 induces a giant (twofold) increase in the alloy density, restores the ferromagnetism of large clusters, decreases the resistivity by 37%, and restores the relation ρ(T) ∝ T2, which results from the overlapping of the irradiation-induced small clusters when their concentration increases and from an increase in the alloy density. The overlapping of clusters lowers the barrier height and decreases the sensitivity of the alloy to an applied field. The relation ρ(T) ∝ T2 is valid for the entire temperature range T = 2–300 K because of the partial screening of the magnetic moments of large clusters by a medium having the properties of cluster glass.

Condensates as components of dark matter and dark energy

We report on recent results according to which the vacuum condensate characterizing many physical systems can give contributions to dark energy and dark matter of the universe. In particular, it is shown that thermal states of the intercluster medium, the vacuum energy of fields in curved space-time and of mixed neutrinos contribute to the dark matter. The vacuum condensates generated by the mixing of axions and photons and the one produced by superpartners of neutrinos may represent a component of the dark energy.

ALMA finds dew drops in the dusty spider’s web

We present 0."5 resolution ALMA detections of the observed 246GHz continuum, [CI]^3P_2-^3P_1 fine structure line ([CI]2-1), CO(7-6) and H2O lines in the z=2.161 radio galaxy MRC1138-262, the 'Spiderweb Galaxy'. We detect strong [CI]2-1 emission both at the position of the radio core, and in a second component ~4kpc away from it. The 1100km/s broad [CI]2-1 line in this latter component, combined with its H2 mass of 1.6x10^10Msun implies this emission must come from a compact region <60pc, possibly containing a second AGN. The combined H2 mass derived for both objects using the [CI]2-1 emission is 3.3x10^10Msun. The total CO(7-6)/[CI]2-1 line flux ratio of 0.2 suggests a low excitation molecular gas reservoir and/or enhanced atomic carbon in cosmic-ray dominated regions. We detect spatially-resolved H2O 2_{11}-2_{02} emission - for the first time in a high-z un-lensed galaxy - near the outer radio lobe to the east, and near the bend of the radio jet to the west of the radio galaxy. No underlying 246GHz continuum emission is seen at either position. We suggest that the H2O emission is excited in the cooling region behind slow (10-40km/s) shocks in dense molecular gas (10^{3-5} cm^-3). The extended water emission is likely evidence of the radio jet's impact in cooling and forming molecules in the post-shocked gas in the halo and inter-cluster gas similar to what is seen in low-z clusters and other high-z radio galaxies. These observations imply that the passage of the radio jet in the interstellar and inter-cluster medium not only heats gas to high temperatures as is commonly assumed or found in simulations, but also induces cooling and dissipation which can lead to substantial amounts of cold dense molecular gas. The formation of molecules and strong dissipation in the halo gas of MRC1138-262 may explain both the extended diffuse molecular gas and young stars observed around MRC1138-262.

PREDICTED SIZES OF PRESSURE-SUPPORTED HI CLOUDS IN THE OUTSKIRTS OF THE VIRGO CLUSTER

ABSTRACT Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton, we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found for spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.

Multiscale structural changes of atomic order in severely deformed industrial aluminum

The regularities of multiscale structural changes in the atomic order of the aluminum alloy AD-1 after a severe cold plastic deformation by conventional rolling in smooth rolls or in rolls with relief recesses favorable for shear deformation have been investigated. It has been found that there are four types of structural fractions that differ in scale and perfection of atomic order: crystallographic planes with a long-range order; nanoscale fragments of the planes (D = 100–300 A) with an incipient long-range order; smaller groups of atoms (D = 20–30 A) of amorphized structure; and the least ordered structural fraction of intercluster medium, keeping only a short-range atomic order (2–3 interatomic distances, 10 A). The presence of diffuse halo bands in the region of intense Debye lines indicates phase transitions of the order → disorder type with the formation of one to three groups of amorphous clusters with the dominance, in the nanometer scale, of the atomic order characteristic of the family of planes (111), (220), and (311) of crystalline aluminum. We have found a dynamic phase transition with the changing crystallographic order of aluminum, with the matrix structure of a face-centered cubic (FCC) lattice, in the form of nanosized local groups of atoms, that is, the deformation clusters of aluminum with a simple cubic K6 lattice. In the case of conventional rolling, the development of large clusters 50–500 A in size is observed; however, in the use of rolls with relief recesses, the difference in the sizes of the clusters is one half as much: 50–250 A. Based on the analysis of the integrated intensity of incoherent X-ray scattering by the samples, we have elucidated the nature of the lowest measured density for the sample subjected to conventional rolling, which consists in the volume concentration of disorderly arranged atoms, the highest of the compared structures, which indicates the formation therein of the greatest amount of fluctuation “voids.”

Dark Matter and Dark Energy Induced by Condensates

It is shown that the vacuum condensate induced by many phenomena behaves as a perfect fluid which, under particular conditions, has zero or negative pressure. In particular, the condensates of thermal states of fields in curved space and of mixed particles have been analyzed. It is shown that the thermal states with the cosmic microwave radiation temperature and the Unruh and the Hawking radiations give negligible contributions to the critical energy density of the universe, while the thermal vacuum of the intercluster medium could contribute to the dark matter, together with the vacuum energy of fields in curved space-time and of mixed neutrinos. Moreover, a component of the dark energy can be represented by the vacuum of axion-like particles mixed with photons and superpartners of neutrinos. The formal analogy among the systems characterized by the condensates can open new scenarios in the possibility of detecting the dark components of the universe in table top experiments.

Changes in cluster magnetism and suppression of local superconductivity in amorphous FeCrB alloy irradiated by Ar+ ions

We show that сluster magnetism in ferromagnetic amorphous Fe67Cr18B15 alloy is related to the presence of large, D=150–250Å, α-(Fe Cr) clusters responsible for basic changes in cluster magnetism, small, D=30–100Å, α-(Fe, Cr) and Fe3B clusters and subcluster atomic α-(Fe, Cr, B) groupings, D=10–20Å, in disordered intercluster medium. For initial sample and irradiated one (Φ=1.5×1018ions/cm2) superconductivity exists in the cluster shells of metallic α-(Fe, Cr) phase where ferromagnetism of iron is counterbalanced by antiferromagnetism of chromium. At Φ=3×1018ions/cm2, the internal stresses intensify and the process of iron and chromium phase separation, favorable for mesoscopic superconductivity, changes for inverse one promoting more homogeneous distribution of iron and chromium in the clusters as well as gigantic (twice as much) increase in density of the samples. As a result, in the cluster shells ferromagnetism is restored leading to the increase in magnetization of the sample and suppression of local superconductivity. For initial samples, the temperature dependence of resistivity ρ(T)~T2 is determined by the electron scattering on quantum defects. In strongly inhomogeneous samples, after irradiation by fluence Φ=1.5×1018ions/cm2, the transition to a dependence ρ(T)~T1/2 is caused by the effects of weak localization. In more homogeneous samples, at Φ=3×1018ions/cm2, a return to the dependence ρ(T)~T2 is observed.

Characteristics of transonic spherical symmetric accretion flow in Schwarzschild-de Sitter and Schwarzschild anti-de Sitter backgrounds, in pseudo-general relativistic paradigm

In this paper, we present a complete work on steady state spherically symmetric Bondi type accretion flow in the presence of cosmological constant (Λ) in both Schwarzschild-de Sitter (SDS) and Schwarzschild anti-de Sitter (SADS) backgrounds considering an isolated supermassive black hole (SMBH), with the inclusion of a simple radiative transfer scheme, in the pseudo-general relativistic paradigm. We do an extensive analysis on the transonic behavior of the Bondi type accretion flow onto the cosmological BHs including a complete analysis of the global parameter space and the stability of flow, and do a complete study of the global family of solutions for a generic polytropic flow. Bondi type accretion flow in SADS background renders multiplicity in its transonic behavior with inner "saddle" type and outer "center" type sonic points, with the transonic solutions forming closed loops or contours. There is always a limiting value for ∣Λ∣ up to which we obtain valid stationary transonic solutions, which correspond to both SDS and SADS geometries; this limiting value moderately increases with the increasing radiative efficiency of the flow, especially correspond to Bondi type accretion flow in SADS background. Repulsive Λ suppresses the Bondi accretion rate by an order of magnitude for relativistic Bondi type accretion flow for a certain range in temperature, and with a marginal increase in the Bondi accretion rate if the corresponding accretion flow occurs in SADS background. However, for a strongly radiative Bondi type accretion flow with high mass accretion rate, the presence of cosmological constant do not much influence the corresponding Bondi accretion rate of the flow. Our analysis show that the relic cosmological constant has a substantial effect on Bondi type accretion flow onto isolated SMBHs and their transonic solutions beyond length-scale of kiloparsecs, especially if the Bondi type accretion occurs onto the host supergiant ellipticals or central dominant (CD) galaxies directly from ambient intercluster medium (ICM). However, for high mass accretion rate, the influence of cosmological constant on Bondi accretion dynamics, generically, diminishes. As active galactic nuclei (AGN)/ICM feedback can be advertently linked to Bondi type spherical accretion, any proper modeling of AGN feedback or megaparsecs-scale jet dynamics or accretion flow from ICM onto the central regions of host galaxies should take into account the relevant information of repulsive Λ, especially in context to supergiant elliptical galaxies or CD galaxies present in rich galaxy clusters. This could also explore the feasibility to limit the value of Λ, from the kinematics in local galactic-scales.

A new multi-scale structure finding algorithm to identify cosmological structure

We introduce a new structure finding algorithm that self-consistently parses large scale cosmological structure into clusters, filaments and voids. This structure finding algorithm probes the structure at multiple scales and classifies the appropriate regions with the most probable structure type and size. We show that it can identify the baryon fraction of intercluster medium and cosmological voids.

The thermal Sunyaev–Zeldovich effect of primordial recombination radiation

It is well known that recombination radiation of primordial hydrogen-helium plasma leads to the distortions of the planckian spectrum shape of the cosmic microwave background radiation (CMB). We discuss the thermal Sunyaev-Zeldovich (SZ) effect with taking into account primordial recombination radiation (PRR). Since in the thermal SZ effect the redistribution of the photons depends on the derivatives of the spectrum, the value of relative correction to SZ effect due to PRR significantly higher than relative corrections due to PRR in the initial spectrum. Calculations of corrections to the thermal SZ effect due to PRR show that depending on the cluster parameters: 1) in the range of frequencies $\nu$ = 0.3 - 700 GHz where the cosmic microwave background (CMB) dominates and spectrum is very close to the planckian one the relative corrections due to PRR have an order of $10^{-9} - 10^{-6}$ of "pure" SZ effect (i.e. SZ effect for pure planckian spectrum). The difference of intensities of PRR coming from different directions (through intracluster and near intercluster medium) reaches values up to 22 mJy/ster at $\nu\simeq 337$ GHz (maximum in considered range). 2) In the range of frequencies $\nu$ = 700 - 5000 GHz where cosmic infrared background (CIB) becomes significant or even dominates the relative corrections due to PRR can reach $10^{-8}$ - $10^{-5}$ of "pure" SZ effect. Corresponding intensity difference reaches values up to 25 mJy/ster (at $\nu\simeq 1700$ GHz). In addition we suggest a modification of the method of electron gas temperature determination using corrections of the SZ effect due to PRR. Such modification allows one to simplify the determination of the cluster electron gas temperature in comparison with known methods.

Spherical cluster ensembles with fractal structure in LaSrMnO: New form of self-organization in solids

The growth of La0.7Sr0.3MnO3 films in magnetron plasma, in special conditions, leads to the appearance of ensembles of micron-sized spherical crystalline clusters with fractal structure, which we consider to be a new form of self-organization in solids. Each ensemble contains 105–106 elementary clusters, 100–250 Å in diameter. Interaction of the clusters in the ensemble is realized through the interatomic chemical bonds, intrinsic to the manganites. Integration of peripheral areas of interacting clusters results in the formation of common intercluster medium in the ensemble. We argue that the ensembles with fractal structure built into paramagnetic disordered matrix have ferromagnetic properties. Absence of sharp borders between elementary clusters and the presence of common intercluster medium inside each ensemble permits to rearrange magnetic order and to change the volume of the ferromagnetic phase, providing automatically a high sensitivity of the material to the external field.

Planckintermediate results

About half of the baryons of the Universe are expected to be in the form of filaments of hot and low density intergalactic medium. Most of these baryons remain undetected even by the most advanced X-ray observatories which are limited in sensitivity to the diffuse low density medium. The Planck satellite has provided hundreds of detections of the hot gas in clusters of galaxies via the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for studying extended low density media through the tSZ effect. In this paper we use the Planck data to search for signatures of a fraction of these missing baryons between pairs of galaxy clusters. Cluster pairs are good candidates for searching for the hotter and denser phase of the intergalactic medium (which is more easily observed through the SZ effect). Using an X-ray catalogue of clusters and the Planck data, we select physical pairs of clusters as candidates. Using the Planck data we construct a local map of the tSZ effect centered on each pair of galaxy clusters. ROSAT data is used to construct X-ray maps of these pairs. After having modelled and subtracted the tSZ effect and X-ray emission for each cluster in the pair we study the residuals on both the SZ and X-ray maps. For the merging cluster pair A399-A401 we observe a significant tSZ effect signal in the intercluster region beyond the virial radii of the clusters. A joint X-ray SZ analysis allows us to constrain the temperature and density of this intercluster medium. We obtain a temperature of kT = 7.1 +- 0.9, keV (consistent with previous estimates) and a baryon density of (3.7 +- 0.2)x10^-4, cm^-3. The Planck satellite mission has provided the first SZ detection of the hot and diffuse intercluster gas.

Simulating Sunyaev-Zel'dovich intensity maps of giant active galactic nucleus cocoons

We perform relativistic hydrodynamic simulations of the formation and evolution of AGN cocoons produced by very light powerful jets. We calculate the intensity maps of the Sunyaev-Zel'dovich (SZ) effect at high frequencies for the simulated AGN cocoons using the relativistically correct Wright formalism. Our fully relativistic calculations demonstrate that the contribution from the high temperature gas (kb Te ~ 100 keV) to the SZ signal from AGN cocoons at high frequencies is stronger than that from the shocked ambient intercluster medium owing to the fact that the relativistic spectral functions peak at these temperature values. We present simulations of the SZ effect from AGN cocoons at various frequencies, and demonstrate that SZ observations at 217 GHz and at higher frequencies, such as 857 GHz, will provide us with knowledge about the dynamically-dominant component of AGN cocoons.

HIGH SPECTRAL RESOLUTION MEASUREMENT OF THE SUNYAEV–ZEL'DOVICH EFFECT NULL WITH Z-Spec

The Sunyaev-Zel'dovich (SZ) effect spectrum crosses through a null where dT_CMB = 0 near nu_0 = 217 GHz. In a cluster of galaxies, nu_0 can be shifted from the canonical thermal SZ effect value by corrections to the SZ effect scattering due to the properties of the inter-cluster medium. We have measured the SZ effect in the hot galaxy cluster RX J1347.5-1145 with Z-Spec, an R ~ 300 grating spectrometer sensitive between 185 and 305 GHz. These data comprise a high spectral resolution measurement around the null of the SZ effect and clearly exhibit the transition from negative to positive dT_CMB over the Z-Spec band. The SZ null position is measured to be nu_0 = 225.8 \pm 2.5 (stat.) \pm 1.2 (sys.) GHz, which differs from the canonical null frequency by 3.0 sigma and is evidence for modifications to the canonical thermal SZ effect shape. Assuming the measured shift in nu_0 is due only to relativistic corrections to the SZ spectrum, we place the limit T_e = 17.1 \pm 5.3 keV from the zero-point measurement alone. By simulating the response of the instrument to the sky, we are able to generate likelihood functions in {y_0, T_e, v_pec} space. For v_pec = 0 km/s, we measure the best fitting SZ model to be y_0 = 4.6 (+0.6, -0.9) x 10^-4, T_e,0 = 15.2 (+12,-7.4) keV. When v_pec is allowed to vary, a most probable value of v_pec = +450 \pm 810 km/s is found.

Polarization of X-ray lines from galaxy clusters and elliptical galaxies - a way to measure the tangential component of gas velocity

We study the impact of gas motions on the polarization of bright X-ray emission lines from the hot intercluster medium (ICM). The polarization naturally arises from resonant scattering of emission lines owing to a quadrupole component in the radiation field produced by a centrally peaked gas density distribution. If differential gas motions are present then a photon emitted in one region of the cluster will be scattered in another region only if their relative velocities are small enough and the Doppler shift of the photon energy does not exceed the line width. This affects both the degree and the direction of polarization. The changes in the polarization signal are in particular sensitive to the gas motions perpendicular to the line of sight. We calculate the expected degree of polarization for several patterns of gas motions, including a slow inflow expected in a simple cooling flow model and a fast outflow in an expanding spherical shock wave. In both cases, the effect of non-zero gas velocities is found to be minor. We also calculate the polarization signal for a set of clusters, taken from large-scale structure simulations and evaluate the impact of the gas bulk motions on the polarization signal. We argue that the expected degree of polarization is within reach of the next generation of space X-ray polarimeters.

Influence of electromagnetic radiation on the phase composition of clustered CN x films

The effect of white and UV radiation on the phase composition of amorphous CNx films are studied by X-ray diffraction analysis and visible-range spectroscopy. The films have variable-range atomic order and consist of amorphous graphite clusters (30 A) crystalline clusters (50–100 A) of graphite, diamond, and carbon nitride phases; and intercluster medium with long-range (1–2 A) atomic order. It is shown that irradiation of the films by white light facilitates the growth of fine graphite clusters. Irradiation by UV light suppresses the growth of the graphite and carbon nitride phases, favoring the growth of the diamond phase (1.5%). It is demonstrated that a change in the mesoscopic phase composition of the CNx films causes a change in the energy gap width in the visible range from Eg = 0.75 eV for the films irradiated by white light to Eg = 1.75 eV for those exposed to UV radiation.

Buoyancy Instabilities in Weakly Magnetized Low‐Collisionality Plasmas

I calculate the linear stability of a stratified low collisionality plasma in the presence of a weak magnetic field. Heat is assumed to flow only along magnetic field lines. In the absence of a heat flux in the background plasma, Balbus (2000) demonstrated that plasmas in which the temperature increases in the direction of gravity are buoyantly unstable to convective-like motions (the ``magnetothermal instability''). I show that in the presence of a background heat flux, an analogous instability is present when the temperature decreases in the direction of gravity. The instability is driven by the background heat flux and the fastest growing mode has a growth time of order the local dynamical time. Thus, independent of the sign of the temperature gradient, weakly magnetized low collisionality plasmas are unstable on a dynamical time to magnetically-mediated buoyancy instabilities. The instability described in this paper is predicted to be present in clusters of galaxies at radii from ~ 0.1-100 kpc, where the observed temperature increases outwards. Possible consequences for the origin of cluster magnetic fields, ``cooling flows,'' and the thermodynamics of the intercluster medium are briefly discussed.

The Sunyaev-Zel'dovich Effect from Quasar Feedback

The observed relationship between X-ray luminosity and temperature of the diffuse intercluster medium clearly shows the effect of nongravitational heating on the formation of galaxy clusters. Quasar feedback into the intergalactic medium can potentially be an important source of heating, and can have significant impact on structure formation. This feedback process is a source of thermal Sunyaev-Zel'dovich distortions of the cosmic microwave background. Using a simple one-dimensional Sedov-Taylor model of energy outflow, we calculate the angular power spectrum of the temperature distortion, which has an amplitude on the order of one micro-Kelvin. This signal will be at the noise limit of upcoming arcminute-scale microwave background experiments, including the Atacama Cosmology Telescope and the South Pole Telescope, but will be directly detectable with deep exposures by the Atacama Large Millimeter Array or by stacking many microwave images.

Cosmic ray scattering in compressible turbulence

We study the scattering of low-energy Cosmic Rays (CRs) in a turbulent, compressive MHD fluid. We show that compressible MHD modes -- fast or slow waves with wave lengths smaller than CR mean free paths induce cyclotron instability in CRs. The instability feeds the new small-scale Alfvenic wave component with wave vectors mostly along magnetic field, which is not a part of the MHD turbulence cascade. This new component gives feedback on the instability through decreasing the CR mean free path. We show that the ambient turbulence fully suppresses the instability at large scales, while wave steepening constrains the amplitude of the waves at small scales. We provide the energy spectrum of the plane-parallel Alfvenic component and calculate mean free paths of CRs as a function of their energy. We find that for the typical parameters of turbulence in the interstellar medium and in the intercluster medium the new Alfvenic component provides the scattering of the low energy CRs that exceeds the direct resonance scattering by MHD modes. This solves the problem of insufficient scattering of low-energy CRs in the turbulent interstellar or intracluster medium that was reported in the literature.