Constraining the thermal history of the Warm-Hot Intergalactic Medium

We have identified a large-scale structure traced by galaxies at z=0.8, within the Lockman Hole, by means of multi-object spectroscopic observations. By using deep XMM images we have investigated the soft X-ray emission from the Warm-Hot Intergalactic Medium (WHIM) expected to be associated with this large-scale structure and we set a tight upper limit to its flux in the very soft 0.2-0.4 keV band. The non-detection requires the WHIM at these redshifts to be cooler than 0.1 keV. Combined with the WHIM emission detections at lower redshift, our result indicates that the WHIM temperature is rapidly decreasing with redshift, as expected in popular cosmological models.Comment: 10 pages, 5 figures, 1 appendix. A&A accepte

A galaxy overdensity at z=0.401 associated with an X-ray emitting structure of Warm-Hot Intergalactic Medium

We present the results of spectroscopic observations of galaxies associated with the diffuse X-ray emitting structure discovered by Zappacosta et al. (2002). After measuring the redshifts of 161 galaxies, we confirm an overdensity of galaxies with projected dimensions of at least 2 Mpc, determine its spectroscopic redshift in z=0.401+/-0.002, and show that it is spatially coincident with the diffuse X-ray emission. This confirms the original claim that this X-ray emission has an extragalactic nature and is due to the Warm-Hot Intergalactic Medium (WHIM). We used this value of the redshift to compute the temperature of the emitting gas. The resulting value depends on the metallicity that is assumed for the IGM, and is constrained to be between 0.3 and 0.6 keV for metallicities between 0.05 and 0.3 solar, in good agreement with the expectations from the WHIM.Comment: 9 pages, A&A, in press, minor language change

An X-ray WHIM metal absorber from a Mpc-scale empty region of space

We report a detection of an absorption line at ~44.8 {\AA} in a > 500 ks Chandra HRC-S/LETG X-ray grating spectrum of the blazar H 2356-309. This line can be identified as intervening CV-K{\alpha} absorption, at z\approx0.112, produced by a warm (log T = 5.1 K) intergalactic absorber. The feature is significant at a 2.9{\sigma} level (accounting for the number of independent redshift trials). We estimate an equivalent hydrogen column density of log N_H=19.05 (Z/Zsun)^-1 cm^-2. Unlike other previously reported FUV/X-ray metal detections of warm-hot intergalactic medium (WHIM), this CV absorber lies in a region with locally low galaxy density, at ~2.2 Mpc from the closest galaxy at that redshift, and therefore is unlikely to be associated with an extended galactic halo. We instead tentatively identify this absorber with an intervening Warm-Hot Intergalactic Medium filament possibly permeating a large-scale, 30 Mpc extended, structure of galaxies whose redshift centroid, within a cylinder of 7.5 Mpc radius centered on the line of sight to H 2356-309, is marginally consistent (at a 1.8{\sigma} level) with the redshift of the absorber.Comment: ApJ accepted, 6 pages, 3 figure

Studying the WHIM Content of the Galaxy Large-Scale Structures along the Line of Sight to H 2356-309

We make use of a 500ks Chandra HRC-S/LETG spectrum of the blazar H2356-309, combined with a lower S/N spectrum of the same target, to search for the presence of warm-hot absorbing gas associated with two Large-Scale Structures (LSSs) crossed by this sightline at z=0.062 (the Pisces-Cetus Supercluster, PCS) and at z=0.128 ("Farther Sculptor Wall", FSW). No statistically significant (>=3sigma) individual absorption is detected from any of the strong He- or H-like transitions of C, O and Ne at the redshifts of the structures. However we are still able to constrain the physical and geometrical parameters of the associated putative absorbing gas, by performing joint spectral fit of marginal detections and upper limits of the strongest expected lines with our self-consistent hybrid ionization WHIM spectral model. At the redshift of the PCS we identify a warm phase with logT=5.35_-0.13^+0.07 K and log N_H =19.1+/-0.2 cm^-2 possibly coexisting with a hotter and less significant phase with logT=6.9^+0.1_-0.8 K and log N_H=20.1^+0.3_-1.7 cm^-2 (1sigma errors). For the FSW we estimate logT=6.6_-0.2^+0.1 K and log N_H=19.8_-0.8^+0.4 cm^-2. Our constraints allow us to estimate the cumulative number density per unit redshifts of OVII WHIM absorbers. We also estimate the cosmological mass density obtaining Omega_b(WHIM)=(0.021^+0.031_-0.018) (Z/Z_sun)^-1, consistent with the mass density of the intergalactic 'missing baryons' for high metallicities.Comment: 29 pages, 8 figures, 4 tables. Accepted for publication in Ap

A changing inner radius in the accretion disc of Q0056-363?

Q0056-363 is the most powerful X-ray quasar known to exhibit a broad, likely relativistic iron line (Porquet & Reeves 2003). It has been observed twice by XMM-$Newton$, three and half years apart (July 2000 and December 2003). In the second observation, the UV and soft X-ray fluxes were fainter, the hard X-ray power law flatter, and the iron line equivalent width (EW) smaller than in the 2000 observation. These variations can all be explained, at least qualitatively, if the disc is truncated in the second observation. We report also on the possible detection of a transient, redshifted iron absorption line during the 2003 observation.Comment: Accepted for publication in A&

The multi-phase winds of Markarian 231: from the hot, nuclear, ultra-fast wind to the galaxy-scale, molecular outflow

We present the best sensitivity and angular resolution maps of the molecular disk and outflow of Mrk 231, as traced by CO observations obtained with IRAM/PdBI, and we analyze archival Chandra and NuSTAR observations. We constrain the physical properties of both the molecular disk and outflow, the presence of a highly-ionized ultra-fast nuclear wind, and their connection. The molecular outflow has a size of ~1 kpc, and extends in all directions around the nucleus, being more prominent along the south-west to north-east direction, suggesting a wide-angle biconical geometry. The maximum projected velocity of the outflow is nearly constant out to ~1 kpc, thus implying that the density of the outflowing material decreases from the nucleus outwards as $r^{-2}$. This suggests that either a large part of the gas leaves the flow during its expansion or that the bulk of the outflow has not yet reached out to ~1 kpc, thus implying a limit on its age of ~1 Myr. We find $\dot M_{OF}=[ 500-1000]~ M_{\odot}~yr^{-1}$ and $\dot E_{kin,OF}=[7-10]\times 10^{43}$ erg s$^{-1}$. Remarkably, our analysis of the X-ray data reveals a nuclear ultra-fast outflow (UFO) with velocity -20000 km s$^{-1}$, $\dot M_{UFO}=[0.3- 2.1] ~M_\odot yr^{-1}$, and momentum load $\dot P_{UFO}/\dot P_{rad}=[0.2-1.6]$.We find $\dot E_{kin,UFO}\sim \dot E_{kin,OF}$ as predicted for outflows undergoing an energy conserving expansion. This suggests that most of the UFO kinetic energy is transferred to mechanical energy of the kpc-scale outflow, strongly supporting that the energy released during accretion of matter onto super-massive black holes is the ultimate driver of giant massive outflows. We estimate a momentum boost $\dot P_{OF}/\dot P_{UFO}\approx [30-60]$. The ratios $\dot E_{kin, UFO}/L_{bol,AGN} =[ 1-5]\%$ and $\dot E_{kin,OF}/L_{bol,AGN} = [1-3]\%$ agree with the requirements of the most popular models of AGN feedback.Comment: 16 pages, 17 figures. Accepted for publication in A&

THE INFLUENCE OF VISCO-ELASTIC INSOLES ON GROUND REACTION FORCES DISPLAYED BY ACHILLES TENDONITIS PATIENTS

INTRODUCTION: In our paper we describe the results obtained by quantifying the ground reaction forces with a Kistler force platform of 19 adults affected by achilles tendonitis, before during and after treatment with personalized viscoelastic insoles. Our goal was to quantify the functional deficit determined by that pathology, and quantify the recovery of normal function by treatment with personalized visco-elastic insoles. METHODS: We considered 19 adults athletes (runners) who got achilles tendonitis, to be put in causal relation with their sport activity; they were males and female, 19-63 aged (35 y.o in mean). They all made gait analysis, and the time evolution of the 3 components of ground reaction force was compared with 'normal' ones, so defined in the article by Chao and al. (1983) for healthy female and male adults, that matched with our patients for age, gender and gait velocity. From this comparison we found out some characteristics of the ground reaction of subjects affected by Achilles tendonitis, particularly for what is about the vertical and the antero-posterior components, that are related to the exercise of force on the ground in the first and the last moment of stance, and that for our patients resulted depressed than the normal data. After this first gait analysis the subjects were treated only with personalized visco-elastic insoles, for a mean period of 12 weeks (8 weeks - 6 months), to 'normalize' the foot-ground interaction during stance phase; the gait analysis was repeated at about the mean time of the treatment, and 18 months in mean (12 - 24 months) after his end. RESULTS: This treatment determined not only full remission of symptoms, but a recovery of good functionality of affected lower limbs, as we could verify by repeating gait analysis in the mean time of the treatment, and after 18 months in mean from his end, and performin a statistical elaboration of the data with the Student 't' test. We found that during the treatment functionality improves gradually, and after his end it remaines good, so that visco-elastic insoles resulted effective in avoiding relapses of pathology

The WISSH quasars Project: II. Giant star nurseries in hyper-luminous quasars

Studying the coupling between the energy output produced by the central quasar and the host galaxy is fundamental to fully understand galaxy evolution. Quasar feedback is indeed supposed to dramatically affect the galaxy properties by depositing large amounts of energy and momentum into the ISM. In order to gain further insights on this process, we study the SEDs of sources at the brightest end of the quasar luminosity function, for which the feedback mechanism is supposed to be at its maximum. We model the rest-frame UV-to-FIR SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 < z < 4.6 disentangling the different emission components and deriving physical parameters of both the nuclear component and the host galaxy. We also use a radiative transfer code to account for the contribution of the quasar-related emission to the FIR fluxes. Most SEDs are well described by a standard combination of accretion disk+torus and cold dust emission. However, about 30% of them require an additional emission component in the NIR, with temperatures peaking at 750K, which indicates the presence of a hotter dust component in these powerful quasars. We measure extreme values of both AGN bolometric luminosity (LBOL > 10^47 erg/s) and SFR (up to 2000 Msun/yr). A new relation between quasar and star-formation luminosity is derived (LSF propto LQSO^(0.73)) by combining several Herschel-detected quasar samples from z=0 to 4. Future observations will be crucial to measure the molecular gas content in these systems, probe the impact between quasar-driven outflows and on-going star-formation, and reveal the presence of merger signatures in their host galaxies.Comment: 19 pages, 12 figures; Accepted for publication in Astronomy & Astrophysics on June 13, 201

Mass assembly and AGN activity at z≳1.5z\gtrsim1.5 in the dense environment of XDCPJ0044.0-2033

XDCP0044.0-2033 is the most massive galaxy cluster known at z>1.5 and its core shows a high density of galaxies which are experiencing mergers and hosting nuclear activity. We present a multi-wavelength study of a region located 157 kpc from the center of this galaxy cluster, for which we have photometric and spectroscopic multi-wavelength observations (high resolution HST images in F105W, F140W and F160W bands, NIR KMOS data in H and YJ bands and Chandra ACIS-S X-ray data). Our main goal is to investigate the environmental effects acting on the galaxies inhabiting this high density region. We find that the analyzed region hosts at least nine different sources, six of them confirmed to be cluster members within a narrow redshift range 1.5728<z<1.5762. These sources form two different complexes at a projected distance of $\sim$13 kpc, which are undergoing merging on an estimated timescale off 10-30 Myr. One of the sources shows the presence of a broad H alpha emission line and is classified as Type 1 AGN. This AGN is associated to an X-ray point-like source, whose emission appears moderately obscured (with intrinsic absorption $N_{H} \sim 10^{22} cm^{-2}$) and hosts a relatively massive black hole with mass $M_{BH} \sim 10^{7} M_{\odot}$, which is accreting with an Eddington ratio of $\sim$0.2. We conclude that the analyzed region is consistent with being the formation site of a secondary BCG. These findings, together with an in-depth analysis the X-ray morphology of the cluster, suggest a merging scenario of the entire cluster, with two massive halos both harbouring two rapidly evolving BCGs on the verge of being assembled. Our results are also consistent with the scenario in which the AGN phase in member galaxies is triggered by gas-rich mergers, playing a relevant role in the formation of the red sequence of elliptical galaxies observed in the center of local galaxy clusters