ABSTRACT
Scaling relations trace the formation and evolution of galaxy clusters. We exploited multi-wavelength surveys – the XXL survey at XMM-Newton in the X-ray band, and the Hyper Suprime-Cam ...Subaru Strategic Program for optical weak lensing – to study an X-ray selected, complete sample of clusters and groups. The scalings of gas mass, temperature, and soft-band X-ray luminosity with the weak lensing mass show imprints of radiative cooling and active galactic nucleus feedback in groups. From the multi-variate analysis, we found some evidence for steeper than self-similar slopes for gas mass ($\beta _{m_\text{g}|m}=1.73 \pm 0.80$) and luminosity (βl|m = 1.91 ± 0.94) and a nearly self-similar slope for the temperature (βt|m = 0.78 ± 0.43). Intrinsic scatters of X-ray properties appear to be positively correlated at a fixed mass (median correlation factor $\rho _{X_1X_2|m}\sim 0.34$) due to dynamical state and merger history of the haloes. Positive correlations with the weak lensing mass (median correlation factor $\rho _{m_\text{wl}X|m}\sim 0.35$) can be connected to triaxiality and orientation. Comparison of weak lensing and hydrostatic masses suggests a small role played by non-thermal pressure support ($9\pm 17{{\ \rm per\ cent}}$).
We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 yr, collective proper motion of 11.3 3.3 mas ...yr−1, or 0.68 0.20c, is detected for the fainter X-ray knots and other substructure present within the jet. The three brightest knots (AX1A, AX1C, and BX2) are found to be stationary to an upper limit of . Brightness variations up to 27% are detected for several X-ray knots in the jet. For the fading knots, BX2 and AX1C, the changes in spectral slope expected to accompany synchrotron cooling are not found, ruling it out and placing upper limits of 80 G for each of their magnetic field strengths. Adiabatic expansion can account for the observed decreases in brightness. Constraints on models for the origin of the knots are established. Jet plasma overrunning an obstacle is favored as the generator of stationary knots, while moving knots are likely produced either by internal differences in jet speed or the late stages of jet interaction with nebular or cloud material.
Abstract
We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art ...AGN radio-to-X-ray spectral energy distribution model fitting code (ARXSED). ARXSED combines multiple components to fit the spectral energy distributions (SEDs) of AGNs and their host galaxies. Emission components include radio structures such as lobes and jets, infrared emission from the AGN torus, visible-to-X-ray emission from the accretion disk, and radio-to-ultraviolet emission from the host galaxy. Applying ARXSED to the radio SEDs of 20 3CRR quasars at 1 <
z
< 2 verifies the need for more than a simple power law when compact radio structures are present. The nonthermal emission contributes 91%–57% of the observed-frame 1.25 mm to 850
μ
m flux, and this component must be accounted for when using these wavelengths to estimate star formation properties. We predict the presence of strong radio-linked X-ray emission in more than half the sample sources. ARXSED estimates median (and the associated first and third quartile ranges) BH mass of
2.9
1.7
6.0
×
10
9
M
☉
, logarithm of Eddington ratio of
−
1.0
−
1.2
−
0.6
, and spin of
0.98
0.94
0.99
for our sample. The inferred AGN torus and accretion disk parameters agree with those estimated from spectroscopic analyses of similar samples in the literature. We present the median intrinsic SED of the luminous radio-loud quasars at 1 <
z
≲ 2; this SED represents a significant improvement in the way each component is modeled.
ABSTRACT
We present results from simultaneous modelling of high angular resolution GBT/MUSTANG-2 90 GHz Sunyaev–Zel’dovich effect (SZE) measurements and XMM-XXL X-ray images of three rich galaxy ...clusters selected from the HSC-SSP Survey. The combination of high angular resolution SZE and X-ray imaging enables a spatially resolved multicomponent analysis, which is crucial to understand complex distributions of cluster gas properties. The targeted clusters have similar optical richnesses and redshifts, but exhibit different dynamical states in their member galaxy distributions: a single-peaked cluster, a double-peaked cluster, and a cluster belonging to a supercluster. A large-scale residual pattern in both regular Compton-parameter y and X-ray surface brightness distributions is found in the single-peaked cluster, indicating a sloshing mode. The double-peaked cluster shows an X-ray remnant cool core between two SZE peaks associated with galaxy concentrations. The temperatures of the two peaks reach ∼20–30 keV in contrast to the cool core component of ∼2 keV, indicating a violent merger. The main SZE signal for the supercluster is elongated along a direction perpendicular to the major axis of the X-ray core, suggesting a minor merger before core passage. The SX and y distributions are thus perturbed at some level, regardless of the optical properties. We find that the integrated Compton y parameter and the temperature for the major merger are boosted from those expected by the weak-lensing mass and those for the other two clusters show no significant deviations, which is consistent with predictions of numerical simulations.
Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under ...active debate, including synchrotron radiation, inverse-Comptonized cosmic microwave background (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high-resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136-135 obtained with the Hubble Space Telescope. We find that several knots are highly polarized in the optical, with fractional polarization productoperator > 30%. When combined with the broadband spectral shape observed in these regions, this is very difficult to explain via IC/CMB models, unless the scattering particles are at the lowest-energy tip of the electron energy distribution, with Lorentz factor gamma ~ 1, and the jet is also very highly beamed ( delta > or =, slanted 20) and viewed within a few degrees of the line of sight. We discuss both the IC/CMB and synchrotron interpretation of the X-ray emission in the light of this new evidence, presenting new models of the spectral energy distribution and also the matter content of this jet. The high polarizations do not completely rule out the possibility of IC/CMB optical-to-X-ray emission in this jet, but they do strongly disfavor the model. We discuss the implications of this finding, and also the prospects for future work.
ABSTRACT New images of the FR II radio galaxy Pictor A from the Hubble Space Telescope reveal a previously undiscovered tidal tail, as well as a number of jet knots coinciding with a known X-ray and ...radio jet. The tidal tail is approximately 5″ wide (3 kpc projected), starting 18″ (12 kpc) from the center of Pictor A, and extends more than 90″ (60 kpc). The knots are part of a jet observed to be about 4′ (160 kpc) long, extending to a bright hotspot. These images are the first optical detections of this jet, and by extracting knot flux densities through three filters, we set constraints on emission models. While the radio and optical flux densities are usually explained by synchrotron emission, there are several emission mechanisms that might be used to explain the X-ray flux densities. Our data rule out Doppler-boosted inverse Compton scattering as a source of the high-energy emission. Instead, we find that the observed emission can be well described by synchrotron emission from electrons with a low-energy index ( ) that dominates the radio band, while a high-energy index ( ) is needed for the X-ray band and the transition occurs in the optical/infrared band. This model is consistent with a continuous electron injection scenario.
The Sunyaev–Zel’dovich effect causes a change in the apparent brightness of the cosmic microwave background radiation towards a cluster of galaxies or any other reservoir of hot plasma. Measurements ...of the effect provide distinctly different information about cluster properties than X-ray imaging data, while combining X-ray and Sunyaev–Zel’dovich effect data leads to new insights into the structures of cluster atmospheres. The effect is redshift-independent, and so provides a unique probe of the structure of the Universe on the largest scales. The present review discusses the theory of the Sunyaev–Zel’dovich effect and collects published results for many clusters, presents the overall conclusions that may be drawn from the detections so far, and discusses the prospects for future research on the Sunyaev–Zel’dovich effects.
The XXL Survey Smolčić, Vernesa; Intema, Huib; Šlaus, Bruno ...
Astronomy and astrophysics (Berlin),
12/2018, Volume:
620
Journal Article
Peer reviewed
Open access
We present the 25 square-degree GMRT-XXL-N 610 MHz radio continuum survey, conducted at 50 cm wavelength with the Giant Metrewave Radio Telescope (GMRT) towards the XXL Northern field (XXL-N). We ...combined previously published observations of the XMM-Large Scale Structure (XMM-LSS) field, located in the central part of XXL-N, with newly conducted observations towards the remaining XXL-N area, and imaged the combined data-set using the Source Peeling and Atmospheric Modeling (SPAM) pipeline. The final mosaic encompasses a total area of 30.4 square degrees, with rms <150 μJy beam−1 over 60% of the area. The rms achieved in the inner 9.6 square degree area, enclosing the XMM-LSS field, is about 200 μJy beam−1, while that over the outer 12.66 square degree area (which excludes the noisy edges) is about 45 μJy beam−1. The resolution of the final mosaic is 6.5 arcsec. We present a catalogue of 5434 sources detected at ≥7 ×rms. We verify, and correct the reliability of, the catalog in terms of astrometry, flux, and false detection rate. Making use of the (to date) deepest radio continuum survey over a relatively large (2 square degree) field, complete at the flux levels probed by the GMRT-XXL-N survey, we also assess the survey’s incompleteness as a function of flux density. The radio continuum sensitivity reached over a large field with a wealth of multi-wavelength data available makes the GMRT-XXL-N 610 MHz survey an important asset for studying the physical properties, environments and cosmic evolution of radio sources, in particular radio-selected active galactic nuclei (AGN).
We present a multiwavelength analysis of a sample of four hot (TX > 8 keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru ...weak-lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius ~40'' (at z ~ 1.5), which when combined with our weak-lensing measurements implies a mass profile well fitted by a Navarro-Frenk-White model with a high concentration c vir ~ 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c vir ~ 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp northwest edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong-lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of f gas(<r 200) = 0.133 ± 0.027, for our sample with M vir = (1.2 ± 0.1) X 1015 M h -1. When compared to the cosmic baryon fraction fb = b / m constrained by the WMAP five-year data, this indicates f gas,200/fb = 0.78 ± 0.16, i.e., (22 ± 16)% of the baryons are missing from the hot phase of clusters.
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