Abstract
Extending the earlier measurements reported in Hitomi collaboration (2016, Nature, 535, 117), we examine the atmospheric gas motions within the central 100 kpc of the Perseus cluster using ...observations obtained with the Hitomi satellite. After correcting for the point spread function of the telescope and using optically thin emission lines, we find that the line-of-sight velocity dispersion of the hot gas is remarkably low and mostly uniform. The velocity dispersion reaches a maxima of approximately 200 km s−1 toward the central active galactic nucleus (AGN) and toward the AGN inflated northwestern “ghost” bubble. Elsewhere within the observed region, the velocity dispersion appears constant around 100 km s−1. We also detect a velocity gradient with a 100 km s−1 amplitude across the cluster core, consistent with large-scale sloshing of the core gas. If the observed gas motions are isotropic, the kinetic pressure support is less than 10% of the thermal pressure support in the cluster core. The well-resolved, optically thin emission lines have Gaussian shapes, indicating that the turbulent driving scale is likely below 100 kpc, which is consistent with the size of the AGN jet inflated bubbles. We also report the first measurement of the ion temperature in the intracluster medium, which we find to be consistent with the electron temperature. In addition, we present a new measurement of the redshift of the brightest cluster galaxy NGC 1275.
Ultra-diffuse galaxies (UDGs) exhibit low surface brightness, but their optical extent is comparable to Milky Way-type galaxies. Due to their peculiar properties, it remains ambiguous whether UDGs ...are the descendants of massive galaxies or they are puffed-up dwarf galaxies. In this work, we explore a population of 404 UDGs in the Coma cluster to study their origin and AGN occupation fraction. To constrain the formation scenario of UDGs, we probe the X-ray emission originating from diffuse gas and from the population of unresolved low-mass X-ray binaries (LMXBs) residing in globular clusters (GCs). It is expected that both the luminosity of the hot gas and the number of globular clusters and hence the luminosity from GC-LMXBs are proportional to the total dark matter halo mass. We do not detect statistically significant emission from the hot gas or from GC-LMXBs. The upper limits on the X-ray luminosities suggest that the bulk of the UDGs reside in low-mass dark matter halos, implying that they are genuine dwarf galaxies. This conclusion agrees with our previous results obtained for isolated UDGs, arguing that UDGs are a homogenous population of galaxies. To probe the AGN occupation fraction of UDGs, we cross-correlate the position of detected X-ray sources in the Coma cluster with the position of UDGs. We identify two UDGs that have a luminous X-ray source at 3.0" and 3.2" from the center of the galaxies, which could be off-center AGN. However, Monte Carlo simulations suggest that one of these sources could be the result of spatial coincidence with a background AGN. Therefore, we place an upper limit of \(\lesssim0.5\%\) on the AGN occupation fraction of UDGs.
We present a simple, differentiable method for predicting emission line strengths from rest-frame optical continua using an empirically-determined mapping. Extensive work has been done to develop ...mock galaxy catalogues that include robust predictions for galaxy photometry, but reliably predicting the strengths of emission lines has remained challenging. Our new mapping is a simple neural network implemented using the JAX Python automatic differentiation library. It is trained on Dark Energy Spectroscopic Instrument Early Release data to predict the equivalent widths (EWs) of the eight brightest optical emission lines (including H\(\alpha\), H\(\beta\), O II, and O III) from a galaxy's rest-frame optical continuum. The predicted EW distributions are consistent with the observed ones when noise is accounted for, and we find Spearman's rank correlation coefficient \(\rho_s > 0.87\) between predictions and observations for most lines. Using a non-linear dimensionality reduction technique (UMAP), we show that this is true for galaxies across the full range of observed spectral energy distributions. In addition, we find that adding measurement uncertainties to the predicted line strengths is essential for reproducing the distribution of observed line-ratios in the BPT diagram. Our trained network can easily be incorporated into a differentiable stellar population synthesis pipeline without hindering differentiability or scalability with GPUs. A synthetic catalogue generated with such a pipeline can be used to characterise and account for biases in the spectroscopic training sets used for training and calibration of photo-\(z\)'s, improving the modelling of systematic incompleteness for the Rubin Observatory LSST and other surveys.
Recent advancements in the imaging of low-surface-brightness objects revealed numerous ultra-diffuse galaxies in the local Universe. These peculiar objects are unusually extended and faint: their ...effective radii are comparable to the Milky Way, but their surface brightnesses are lower than that of dwarf galaxies. Their ambiguous properties motivate two potential formation scenarios: the "failed" Milky Way and the dwarf galaxy scenario. In this paper, for the first time, we employ X-ray observations to test these formation scenarios on a sample of isolated, low-surface-brightness galaxies. Since hot gas X-ray luminosities correlate with the dark matter halo mass, "failed" Milky Way-type galaxies, which reside in massive dark matter halos, are expected to have significantly higher X-ray luminosities than dwarf galaxies, which reside in low-mass dark matter halos. We perform X-ray photometry on a subset of low-surface-brightness galaxies identified in the Hyper Suprime-Cam Subaru survey, utilizing the XMM-Newton XXL North survey. We find that none of the individual galaxies show significant X-ray emission. By co-adding the signal of individual galaxies, the stacked galaxies remain undetected and we set an X-ray luminosity upper limit of \({L_{\rm{0.3-1.2keV}}\leq6.2 \times 10^{37} (d/65 \rm{Mpc})^2 \ \rm{erg \ s^{-1}}}\) for an average isolated low-surface-brightness galaxy. This upper limit is about 40 times lower than that expected in a galaxy with a massive dark matter halo, implying that the majority of isolated low-surface-brightness galaxies reside in dwarf-size dark matter halos.
Many massive early-type galaxies host central radio sources and hot X-ray atmospheres indicating the presence of radio-mechanical active galactic nucleus (AGN) feedback. The duty cycle and detailed ...physics of the radio-mode AGN feedback is still a matter of debate. To address these questions, we present 1-2 GHz Karl G. Jansky Very Large Array (VLA) radio observations of a sample of the 42 nearest optically and X-ray brightest early-type galaxies. We detect radio emission in 41/42 galaxies. However, the galaxy without a radio source, NGC 499, has recently been detected at lower frequencies by the Low-Frequency Array (LOFAR). Furthermore, 27/42 galaxies in our sample host extended radio structures and 34/42 sources show environmental interactions in the form of X-ray cavities. We find a significant correlation between the radio flux density and the largest linear size of the radio emission and between the radio power and the luminosity of the central X-ray point-source. The central radio spectral indices of the galaxies span a wide range of values, with the majority of the systems having steep spectra and the rest flat spectra. These results are consistent with AGN activity, where the central radio sources are mostly switched on, thus the duty cycle is very high. 7/14 galaxies with point-like radio emission (Fanaroff-Riley Class 0; FR 0) also show X-ray cavities indicating that, despite the lack of extended radio structures at 1-2 GHz, these AGN do launch jets capable of inflating lobes and cavities.
We present the analysis of deep X-ray observations of 10 massive galaxy clusters at redshifts \(1.05 < z < 1.71\), with the primary goal of measuring the metallicity of the intracluster medium (ICM) ...at intermediate radii, to better constrain models of the metal enrichment of the intergalactic medium. The targets were selected from X-ray and Sunyaev-Zel'dovich (SZ) effect surveys, and observed with both the \textit{XMM-Newton} and \textit{Chandra} satellites. For each cluster, a precise gas mass profile was extracted, from which the value of \(r_{500}\) could be estimated. This allows us to define consistent radial ranges over which the metallicity measurements can be compared. In general, the data are of sufficient quality to extract meaningful metallicity measurements in two radial bins, \(r<0.3r_{500}\) and \(0.3<r/r_{500}<1.0\). For the outer bin, the combined measurement for all ten clusters, \(Z/Z_{\odot} = 0.21 \pm 0.09\), represents a substantial improvement in precision over previous results. This measurement is consistent with, but slightly lower than, the average metallicity of 0.315 Solar measured at intermediate-to-large radii in low-redshift clusters. Combining our new high-redshift data with the previous low-redshift results allows us to place the tightest constraints to date on models of the evolution of cluster metallicity at intermediate radii. Adopting a power law model of the form \(Z \propto \left(1+z\right)^\gamma\), we measure a slope \(\gamma = -0.5^{+0.4}_{-0.3}\), consistent with the majority of the enrichment of the ICM having occurred at very early times and before massive clusters formed, but leaving open the possibility that some additional enrichment in these regions may have occurred since a redshift of 2.
The PRObabilistic Value-Added Bright Galaxy Survey (PROVABGS) catalog will provide measurements of galaxy properties, such as stellar mass (\(M_*\)), star formation rate (\({\rm SFR}\)), stellar ...metallicity (\(Z_{\rm MW}\)), and stellar age (\(t_{\rm age, MW}\)), for >10 million galaxies of the DESI Bright Galaxy Survey. Full posterior distributions of the galaxy properties will be inferred using state-of-the-art Bayesian spectral energy distribution (SED) modeling of DESI spectroscopy and Legacy Surveys photometry. In this work, we present the SED model, Bayesian inference framework, and methodology of PROVABGS. Furthermore, we apply the PROVABGS SED modeling on realistic synthetic DESI spectra and photometry, constructed using the L-GALAXIES semi-analytic model. We compare the inferred galaxy properties to the true galaxy properties of the simulation using a hierarchical Bayesian framework to quantify accuracy and precision. Overall, we accurately infer the true \(M_*\), \({\rm SFR}\), \(Z_{\rm MW}\), and \(t_{\rm age, MW}\) of the simulated galaxies. However, the priors on galaxy properties induced by the SED model have a significant impact on the posteriors. They impose a \({\rm SFR}{>}10^{-1} M_\odot/{\rm yr}\) lower bound on \({\rm SFR}\), a \({\sim}0.3\) dex bias on \(\log Z_{\rm MW}\) for galaxies with low spectral signal-to-noise, and \(t_{\rm age, MW} < 8\,{\rm Gyr}\) upper bound on stellar age. This work also demonstrates that a joint analysis of spectra and photometry significantly improves the constraints on galaxy properties over photometry alone and is necessary to mitigate the impact of the priors. With the methodology presented and validated in this work, PROVABGS will maximize information extracted from DESI observations and provide a probabilistic value-added galaxy catalog that will extend current galaxy studies to new regimes and unlock cutting-edge probabilistic analyses.
We have observed the z=4.3 protocluster SPT2349-56 with ATCA with the aim of detecting radio-loud active galactic nuclei (AGN) amongst the ~30 submillimeter galaxies identified in the structure. We ...detect the central complex of SMGs at 2.2\,GHz with a luminosity of L_2.2=(4.42pm0.56)x10^{25} W/Hz. The ASKAP also detects the source at 888 MHz, constraining the radio spectral index to alpha=-1.6pm0.3, consistent with ATCA non-detections at 5.5 and 9GHz, and implying L_1.4(rest)=(2.4pm0.3)x10^{26}W/Hz. This radio luminosity is about 100 times higher than expected from star formation, assuming the usual FIR-radio correlation, which is a clear indication of an AGN driven by a forming brightest cluster galaxy (BCG). None of the SMGs in SPT2349-56 show signs of AGN in any other diagnostics available to us (notably 12CO out to J=16, OH163um, CII/IR, and optical spectra), highlighting the radio continuum as a powerful probe of obscured AGN in high-z protoclusters. No other significant radio detections are found amongst the cluster members, consistent with the FIR-radio correlation. We compare these results to field samples of radio sources and SMGs, along with the 22 SPT-SMG gravitational lenses also observed in the ATCA program, as well as powerful radio galaxies at high redshifts. Our results allow us to better understand the effects of this gas-rich, overdense environment on early supermassive black hole (SMBH) growth and cluster feedback. We estimate that (3.3pm0.7)x10^{38} W of power are injected into the growing ICM by the radio-loud AGN, whose energy over 100Myr is comparable to the binding energy of the gas mass of the central halo. The AGN power is also comparable to the instantaneous energy injection from supernova feedback from the 23 catalogued SMGs in the core region of 120kpc projected radius. The SPT2349-56 radio-loud AGN may be providing strong feedback on a nascent ICM.
We present updated cosmological constraints from measurements of the gas mass fractions (\(f_{gas}\)) of massive, dynamically relaxed galaxy clusters. Our new data set has greater leverage on models ...of dark energy, thanks to the addition of the Perseus Cluster at low redshifts, two new clusters at redshifts \(z>0.97\), and significantly longer observations of four clusters at \(0.6<z<0.9\). Our low-redshift (\(z<0.16\)) \(f_{gas}\) data, combined with the cosmic baryon fraction measured from the cosmic microwave background (CMB), imply a Hubble constant of \(h = 0.722 \pm 0.067\). Combining the full \(f_{gas}\) data set with priors on the cosmic baryon density and the Hubble constant, we constrain the dark energy density to be \(\Omega_\Lambda = 0.865 \pm 0.119\) in non-flat \(\Lambda\)CDM (cosmological constant) models, and its equation of state to be \(w = -1.13_{-0.20}^{+0.17}\) in flat, constant-w models, respectively 41 and 29 per cent tighter than our previous work, and comparable to the best constraints available from other probes. Combining \(f_{gas}\), CMB, supernova, and baryon acoustic oscillation data, we also constrain models with global curvature and evolving dark energy. For the massive, relaxed clusters employed here, we find the scaling of \(f_{gas}\) with mass to be consistent with a constant, with an intrinsic scatter that corresponds to just 3 per cent in distance.
Summary
Several epidemiological studies reported an inverse relationship between plasma high‐density lipoprotein (HDL) cholesterol levels and atherosclerotic cardiovascular disease (ASCVD). However, ...therapeutic interventions targeted at raising HDL‐cholesterol failed to improve cardiovascular outcomes, suggesting that HDL components distinct from cholesterol may account for the anti‐atherothrombotic effects attributed to this lipoprotein. Sphingosine‐1‐phosphate (S1P) and the acute phase protein serum amyloid A (SAA) have been identified as integral constituents of HDL particles. Evidence suggests that S1P and SAA levels within HDL particles may be affected by inflammation and oxidative stress, which are coexisting processes underlying ASCVD. Because SAA, an inflammation‐related marker, and S1P, an anti‐atherothrombotic marker, have relatively clear opposite characteristics among the HDL‐associated proteins, the approach of assessing the two markers simultaneously may provide new insights in clinical practice (S1P/SAA Index). This review focuses on evidence in support of the concept that the S1P/SAA Index may affect the HDL atheroprotective properties and may, therefore represent a potential target for therapeutic interventions.
PDF
