We present results from a 577 ks XMM-Newton observation of SPT-CL J0459-4947, the most distant cluster detected in the South Pole Telescope 2500 square degree (SPT-SZ) survey, and currently the most ...distant cluster discovered through its Sunyaev-Zel'dovich effect. The data confirm the cluster's high redshift, \(z=1.71 \pm 0.02\), in agreement with earlier, less precise optical/IR photometric estimates. From the gas density profile, we estimate a characteristic mass of \(M_{500}=(1.8 \pm 0.2) \times 10^{14}M_{Sun}\); cluster emission is detected above the background to a radius of \(\sim 2.2 r_{500}\), or approximately the virial radius. The intracluster gas is characterized by an emission-weighted average temperature of \(7.2 \pm 0.3\) keV and metallicity with respect to Solar of \(0.37 \pm 0.08\). For the first time at such high redshift, this deep data set provides a measurement of metallicity outside the cluster center; at radii \(r > 0.3 r_{500}\), we find it to be \(0.33 \pm 0.17\), in good agreement with precise measurements at similar radii in the most nearby clusters, supporting an early enrichment scenario in which the bulk of the cluster gas is enriched to a universal metallicity prior to cluster formation, with little to no evolution thereafter. The leverage provided by the high redshift of this cluster tightens by a factor of 2 constraints on evolving metallicity models, when combined with previous measurements at lower redshifts.
Background
Abnormalities in blood lipid levels are causally linked with cardiovascular disease and pancreatitis. Data is limited regarding lipid abnormalities in Ireland.
Aims
As part of a ...cholesterol awareness campaign, we performed a pilot study of current lipid levels to preliminarily assess the extent and pattern of lipid abnormalities in Ireland.
Methods
Non-fasting, full lipid profiles and glucose measurements were performed in 259 people (32 on lipid-lowering medication and 225 untreated) using a validated Cholestech LDX machine. Untreated participants included 95 men and 130 women, aged 51 ± 16 years.
Results
The mean ± SD, total, low-density lipoprotein (LDL), high-density lipoprotein cholesterol (HDL) and median(IQR) non-HDL cholesterol and triglyceride levels in untreated individuals were 5.0 ± 1.1, 2.8 ± 1.0, 1.5 ± 0.5 and 3.4 (2.8–4.3), 1.6 (1.0–2.3) mmol/l respectively. Glucose was 5.3 (4.8–5.8) mmol/l. Glucose > 7.8 mmol/l occurred in 10 individuals (4%). Using defined criteria for non-fasting lipid levels, 60% of participants had some form of lipid abnormality with a frequency of 47% having a total cholesterol > 5, 35% with LDL > 3.0, 26% with HDL < 1.0/1.2, 33% with triglycerides > 2.0 and 32% with non-HDL cholesterol > 3.9 mmol/l. Three individuals had untreated LDL > 5 mmol/l (i.e. a ratio of 1:75 of those tested) and eight people had HDLc < 0.7 (1:28) and four had triglyceride above 7.3 mmol/l (1:56).
Conclusions
This pilot study reveals significant lipid abnormalities which require further larger more detailed lipid studies to assess the true burden of lipid abnormalities in Ireland. Cascade screening and genetic testing of relatives of those with severe lipid abnormalities should be considered.
Abell 2146 (\(z\) = 0.232) consists of two galaxy clusters undergoing a major merger. The system was discovered in previous work, where two large shock fronts were detected using the ...\(\textit{Chandra X-ray Observatory}\), consistent with a merger close to the plane of the sky, caught soon after first core passage. A weak gravitational lensing analysis of the total gravitating mass in the system, using the distorted shapes of distant galaxies seen with ACS-WFC on \(\textit{Hubble Space Telescope}\), is presented. The highest peak in the reconstruction of the projected mass is centred on the Brightest Cluster Galaxy (BCG) in Abell 2146-A. The mass associated with Abell 2146-B is more extended. Bootstrapped noise mass reconstructions show the mass peak in Abell 2146-A to be consistently centred on the BCG. Previous work showed that BCG-A appears to lag behind an X-ray cool core; although the peak of the mass reconstruction is centred on the BCG, it is also consistent with the X-ray peak given the resolution of the weak lensing mass map. The best-fit mass model with two components centred on the BCGs yields \(M_{200}\) = 1.1$^{+0.3}_{-0.4}$$\times\(10\)^{15}\(M\)_{\odot}\( and 3\)^{+1}_{-2}$$\times\(10\)^{14}\(M\)_{\odot}\( for Abell 2146-A and Abell 2146-B respectively, assuming a mass concentration parameter of \)c=3.5$ for each cluster. From the weak lensing analysis, Abell 2146-A is the primary halo component, and the origin of the apparent discrepancy with the X-ray analysis where Abell 2146-B is the primary halo is being assessed using simulations of the merger.
We present a Chandra study of surface brightness fluctuations in the diffuse intracluster medium of the Perseus Cluster. Our study utilizes deep, archival imaging of the cluster core as well as a new ...mosaic of 29 short 5 ks observations extending in 8 different directions out to radii of r_500 ~ 2.2r_2500. Under the assumption that the distribution of densities at a given radius is log-normally distributed, two important quantities can be derived from the width of the log-normal density distribution on a given spatial scale: the density bias, which is equal to the square root of the clumping factor C; and the one-component turbulent velocity, v_(k, 1D). We forward-model all contributions to the measured surface brightness, including astrophysical and particle background components, and account for the Poisson nature of the measured signal. Measuring the distribution of surface brightness fluctuations in 1 arcmin^2 regions, spanning the radial range 0.3-2.2 r_2500 (7.8-57.3 arcmin), we find a small to moderate average density bias of around 3% at radii below 1.6r_2500. We also infer an average turbulent velocity at these radii of v_1D <400 km s^-1. Direct confirmation of our results on turbulent velocities inferred from surface brightness fluctuations should be possible using the X-ray calorimeter spectrometers to be flown aboard the XRISM and Athena. observatories.
We extend our previous study of the cool gas responsible for the emission of OVII X-ray lines in the cores of clusters and groups of galaxies. This is the coolest X-ray emitting phase and connects ...the 10,000 K H {\alpha} emitting gas to the million degree phase, providing a useful tool to understand cooling in these objects. We study the location of the O VII gas and its connection to the intermediate Fe XVII and hotter O VIII phases. We use high-resolution X-ray grating spectra of elliptical galaxies with strong Fe XVII line emission and detect O VII in 11 of 24 objects. Comparing the O VII detection level and resonant scattering, which is sensitive to turbulence and temperature, suggests that OVII is preferably found in cooler objects, where the FeXVII resonant line is suppressed due to resonant scattering, indicating subsonic turbulence. Although a larger sample of sources and further observations is needed to distinguish between effects from temperature and turbulence, our results are consistent with cooling being suppressed at high turbulence as predicted by models of AGN feedback, gas sloshing and galactic mergers. In some objects the OVII resonant-to-forbidden line ratio is decreased by either resonant scattering or charge-exchange boosting the forbidden line, as we show for NGC 4636. Charge-exchange indicates interaction between neutral and ionized gas phases. The Perseus cluster also shows a high Fe XVII forbidden-to- resonance line ratio, which can be explained with resonant scattering by low-turbulence cool gas in the line-of-sight.
Abell 2146 consists of two galaxy clusters that have recently collided close to the plane of the sky, and it is unique in showing two large shocks on \(\textit{Chandra X-ray Observatory}\) images. ...With an early stage merger, shortly after first core passage, one would expect the cluster galaxies and the dark matter to be leading the X-ray emitting plasma. In this regard, the cluster Abell 2146-A is very unusual in that the X-ray cool core appears to lead, rather than lag, the Brightest Cluster Galaxy (BCG) in their trajectories. Here we present a strong lensing analysis of multiple image systems identified on \(\textit{Hubble Space Telescope}\) images. In particular, we focus on the distribution of mass in Abell 2146-A in order to determine the centroid of the dark matter halo. We use object colours and morphologies to identify multiple image systems; very conservatively, four of these systems are used as constraints on a lens mass model. We find that the centroid of the dark matter halo, constrained using the strongly lensed features, is coincident with the BCG, with an offset of \(\approx\) 2 kpc between the centres of the dark matter halo and the BCG. Thus from the strong lensing model, the X-ray cool core also leads the centroid of the dark matter in Abell 2146-A, with an offset of \(\approx\) 30 kpc.
Brightest cluster galaxies (BCGs) in the cores of galaxy clusters have distinctly different properties from other low redshift massive ellipticals. The majority of the BCGs in cool-core clusters show ...signs of active star formation. We present observations of NGC 4696, the BCG of the Centaurus galaxy cluster, at far-infrared (FIR) wavelengths with the Herschel space telescope. Using the PACS spectrometer, we detect the two strongest coolants of the interstellar medium, CII at 157.74 micron and OI at 63.18 micron, and in addition NII at 121.90 micron. The CII emission is extended over a region of 7 kpc with a similar spatial morphology and kinematics to the optical H-alpha emission. This has the profound implication that the optical hydrogen recombination line, H-alpha, the optical forbidden lines, NII 6583 Angstrom, the soft X-ray filaments and the far-infrared CII line all have the same energy source. We also detect dust emission using the PACS and SPIRE photometers at all six wavebands. We perform a detailed spectral energy distribution fitting using a two-component modified black-body function and find a cold 19 K dust component with mass 1.6x10^6 solar mass and a warm 46 K dust component with mass 4.0x10^3 solar mass. The total FIR luminosity between 8 micron and 1000 micron is 7.5x10^8 solar luminosity, which using Kennicutt relation yields a low star formation rate of 0.13 solar mass per yr. This value is consistent with values derived from other tracers, such as ultraviolet emission. Combining the spectroscopic and photometric results together with optical H-alpha, we model emitting clouds consisting of photodissociation regions (PDRs) adjacent to ionized regions. We show that in addition to old and young stellar populations, there is another source of energy, such as cosmic rays, shocks or reconnection diffusion, required to excite the H-alpha and CII filaments.
Extremely metal-poor galaxies (XMPGs) at relatively low redshift are
excellent laboratories for studying galaxy formation and evolution in the early
universe. Much effort has been spent on ...identifying them from large-scale
spectroscopic surveys or spectroscopic follow-up observations. Previous work
has identified a few hundred XMPGs. In this work, we obtain a large sample of
223 XMPGs at $z<1$ from the early data of the Dark Energy Spectroscopic
Instrument (DESI). The oxygen abundance is determined using the direct $T_{\rm
e}$ method based on the detection of the O III$\lambda$4363 line. The sample
includes 95 confirmed XMPGs based on the oxygen abundance uncertainty;
remaining 128 galaxies are regarded as XMPG candidates. These XMPGs are only
0.01% of the total DESI observed galaxies. Their coordinates and other
proprieties are provided in the paper. The most XMPG has an oxygen abundance of
$\sim 1/34 Z_{\odot}$, stellar mass of about $1.5\times10^7 M_{\odot}$ and star
formation rate of 0.22 $M_{\odot}$ yr$^{-1}$. The two most XMPGs present
distinct morphologies suggesting different formation mechanisms. The local
environmental investigation shows that XMPGs preferentially reside in
relatively low-density regions. Many of them fall below the stellar
mass-metallicity relations (MZRs) of normal star-forming galaxies. From a
comparison of the MZR with theoretical simulations, it appears that XMPGs are
good analogs to high-redshift star-forming galaxies. The nature of these XMPG
populations will be further investigated in detail with larger and more
complete samples from the on-going DESI survey.
We present findings of the detection of Magnesium II (Mg II, {\lambda} = 2796, 2803 Å) absorbers from the early data release of the Dark Energy Spectroscopic Instrument (DESI). DESI is projected to ...obtain spectroscopy of approximately 3 million quasars (QSOs), of which over 99% are anticipated to be at redshifts greater than z > 0.3, such that DESI would be able to observe an associated or intervening Mg II absorber illuminated by the background QSO. We have developed an autonomous supplementary spectral pipeline that detects these systems through an initial line-fitting process and then confirms the line properties using a Markov Chain Monte Carlo sampler. Based upon a visual inspection of the resulting systems, we estimate that this sample has a purity greater than 99%. We have also investigated the completeness of our sample in regard to both the signal-to-noise properties of the input spectra and the rest-frame equivalent width (W0) of the absorber systems. From a parent catalog containing 83,207 quasars, we detect a total of 23,921 Mg II absorption systems following a series of quality cuts. Extrapolating from this occurrence rate of 28.8% implies a catalog at the completion of the five-year DESI survey that will contain over eight hundred thousand Mg II absorbers. The cataloging of these systems will enable significant further research because they carry information regarding circumgalactic medium environments, the distribution of intervening galaxies, and the growth of metallicity across the redshift range 0.3 < z < 2.5.
