- ID:
- ivo://CDS.VizieR/J/A+A/377/428
- Title:
- Abell 970 galaxies radial velocities
- Short Name:
- J/A+A/377/428
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a dynamical analysis of the galaxy cluster Abell 970 based on a new set of radial velocities measured at ESO, Pic du Midi and Haute-Provence observatories. Our analysis indicates that this cluster has a substructure and is out of dynamical equilibrium. This conclusion is also supported by differences in the positions of the peaks of the surface density distribution and X-ray emission, as well as by the evidence of a large-scale velocity gradient in the cluster. We also found a discrepancy between the masses inferred with the virial theorem and those inferred with the X-ray emission, which is expected if the galaxies and the gas inside the cluster are not in hydrostatic equilibrium. Abell 970 has a modest cooling flow, as is expected if it is out of equilibrium. We propose that cooling flows may have an intermittent behaviour, with phases of massive cooling flows being followed by phases without significant cooling flows after the accretion of a galaxy group massive enough to disrupt the dynamical equilibrium in the centre of the clusters. A massive cooling flow will be established again, after a new equilibrium is achieved.
« Previous |
1 - 10 of 178
|
Next »
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/618/A152
- Title:
- Abell 1795 GMRT and Chandra maps
- Short Name:
- J/A+A/618/A152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we analyze AGN activity signatures in the rich nearby galaxy cluster Abell 1795 aiming to confirm and characterize the long-term feedback history in the system. We combine radio observations at 610 and 235MHz from the Giant Metrewave Radio Telescope (GMRT) with 3.4Msec X-ray data from the Chandra Observatory. Extracting radial temperature profiles, as well as Xray and radio surface brightness profiles in three directions showing major morphological disturbances, we highlight the signatures of activity in the system. For the first time we observe radio emission corresponding to the NW X-ray depression, which provides evidence in favor of the classification of the depression as a cavity. We identify two other X-ray cavities situated NW and SW of the AGN. While the central radio emission corresponding to the inner cavities shows a flatter spectral index, the radio extensions associated with the farthest X-ray cavities consist of aged plasma. All observed signatures both in radio and X-ray are consistent with several consecutive episodes of AGN activity, which gave rise to the observed morphology NW and SW from the core. In the southern region, we confirm the cooling wake hypothesis for the origin of the long tail. The deep X-ray data also allows us to distinguish significant distortions in the tail's inner parts, which we attribute to the activity of the AGN.
- ID:
- ivo://CDS.VizieR/J/A+A/649/A37
- Title:
- Abell 1775 radio images
- Short Name:
- J/A+A/649/A37
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Thermal gas in the center of galaxy clusters can show substantial motions that generate surface brightness and temperature discontinuities known as cold fronts. The motions may be triggered by minor or o-axis mergers that preserve the cool-core of the system. The dynamics of the thermal gas can also generate radio emission from the intra-cluster medium (ICM) and impact the evolution of clusters radio sources. We study the central region of Abell 1775, a system in an ambiguous dynamical state at z=0.072 which is known to host an extended head-tail radio galaxy, with the aim of investigating the connection between thermal and non-thermal components in its center. We made use of a deep (100ks) Chandra observation accompanied by LOFAR 144MHz, GMRT 235MHz and 610MHz, and VLA 1.4GHz radio data. We find a spiral-like pattern in the X-ray surface brightness that is mirrored in the temperature and pseudo-entropy maps. Additionally, we characterize an arc-shaped cold front in the ICM. We interpret these features in the context of a slingshot gas tail scenario. The structure of the head-tail radio galaxy "breaks" at the position of the cold front, showing an extension that is detected only at low frequencies, likely due to its steep and curved spectrum. We speculate that particle re-acceleration is occurring in the outer region of this tail, that in total covers a projected size of 800kpc. We also report the discovery of revived fossil plasma with ultra-steep spectrum radio emission in the cluster core together with a central diffuse radio source that is bounded by the arc-shaped cold front. The results reported in this work demonstrate the interplay between thermal and non-thermal components in the cluster center and the presence of ongoing particle re-acceleration in the ICM on different scales.
- ID:
- ivo://CDS.VizieR/J/A+A/420/135
- Title:
- Abundances in intracluster medium with XMM
- Short Name:
- J/A+A/420/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- XMM-Newton observations of 19 galaxy clusters are used to measure the elemental abundances and their spatial distributions in the intracluster medium. The sample mainly consists of X-ray bright and relaxed clusters with a cD galaxy. Along with detailed Si, S and Fe radial abundance distributions within 300-700kpc in radius, the O abundances are accurately derived in the central region of the clusters. The Fe abundance maxima towards the cluster center, possibly due to the metals from the cD galaxy, are spatially resolved. The Si and S abundances also exhibit central increases in general, resulting in uniform Fe-Si-S ratios within the cluster. In contrast, the O abundances are in general uniform over the cluster. The mean O to Fe ratio within the cluster core is sub-solar, while that of the cluster scale is larger than the solar ratio. These measurements indicate that most of the Fe-Si-S and O in the intracluster medium have different origins, presumably in supernovae Ia and II, respectively. The obtained Fe and O mass are also used to discuss the past star formation history in clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A93
- Title:
- ACT-CL J0215.4+0030 NIKA2 image
- Short Name:
- J/A+A/644/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution mapping of the intracluster medium (ICM) up to high redshift and down to low masses is crucial to derive accurate mass estimates of the galaxy cluster and to understand the systematic effects affecting cosmological studies based on galaxy clusters. We present a spatially resolved Sunyaev-Zel'dovich (SZ) X-ray analysis of ACT-CL J0215.4+0030, a high-redshift (z=0.865) galaxy cluster of intermediate mass (M_500_~=3.5x10^14^M_{sun}_) observed as part of the ongoing NIKA2 SZ Large Program, which is a follow-up of a representative sample of objects at 0.5<=z<=0.9. In addition to the faintness and small angular size induced by its mass and redshift, the cluster is contaminated by point sources that significantly affect the SZ signal. This is therefore an interesting case study for the most challenging sources of the NIKA2 cluster sample. We present the NIKA2 observations of this cluster and the resulting data. We identified the point sources that affect the NIKA2 maps of the cluster as submillimeter galaxies (SMG) with counterparts in catalogs of sources constructed by the SPIRE instrument on board the Herschel observatory. We reconstructed the ICM pressure profile by performing a joint analysis of the SZ signal and of the point-source component in the NIKA2 150GHz map. This cluster is a very weak source that lies below the selection limit of the Planck catalog. Nonetheless, we obtained high-quality estimates of the ICM thermodynamical properties with NIKA2. We compared the pressure profile extracted from the NIKA2 map to the pressure profile obtained from X-ray data alone by deprojecting the public XMM-Newton observations of the cluster. We combined the NIKA2 pressure profile with the X-ray deprojected density to extract detailed information on the ICM. The radial distribution of its thermodynamic properties (the pressure, temperature and entropy) indicate that the cluster has a highly disturbed core. We also computed the hydrostatic mass of the cluster, which is compatible with estimations from SZ and X-ray scaling relations. We conclude that the NIKA2 SZ Large Program can deliver quality information on the thermodynamics of the ICM even for one of its faintest clusters after a careful treatment of the contamination by point sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/1467
- Title:
- AGN in supercluster A901/2
- Short Name:
- J/MNRAS/380/1467
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present XMM data for the supercluster A901/2, at z~0.17, which is combined with deep imaging and 17-band photometric redshifts (from the COMBO-17 survey), two degree field (2dF) spectra and Spitzer 24um data, to identify active galactic nuclei (AGN) in the supercluster. The 90ks XMM image contains 139 point sources, of which 11 are identified as supercluster AGN with LX(0.5-7.5keV)>1.7x10^41^erg/cm^2^/s. The host galaxies have M_R_<-20 and only two of eight sources with spectra could have been identified as AGN by the detected optical emission lines. Using a large sample of 795 supercluster galaxies, we define control samples of massive galaxies with no detected AGN. The local environments of the AGN and control samples differ at >~98 per cent significance. The AGN host galaxies lie predominantly in areas of moderate projected galaxy density and with more local blue galaxies than the control sample, with the exception of one very bright type I AGN very near the centre of a cluster. These environments are similar to, but not limited to, cluster outskirts and blue groups. Despite the large number of potential host galaxies, no AGN are found in regions with the highest galaxy density (excluding some cluster cores where emission from the intra-cluster medium obscures moderate luminosity AGN). AGN are also absent from the areas with lowest galaxy density. We conclude that the prevalence of cluster AGN is linked to their environment.
- ID:
- ivo://CDS.VizieR/J/ApJ/611/821
- Title:
- A2125 in X-ray
- Short Name:
- J/ApJ/611/821
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an 82ks Chandra ACIS-I observation of a large-scale hierarchical complex, which consists of various clusters/groups of galaxies and low surface brightness X-ray emission at z=0.247. This high-resolution Chandra observation allows us for the first time to separate unambiguously the X-ray contributions from discrete sources and large-scale diffuse hot gas. We detect 99 X-ray sources in a 17{arcmin}x17{arcmin} field.
- ID:
- ivo://CDS.VizieR/J/ApJ/714/25
- Title:
- AMUSE-Virgo survey. II.
- Short Name:
- J/ApJ/714/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We complete the census of nuclear X-ray activity in 100 early-type Virgo galaxies observed by the Chandra X-ray Telescope as part of the AMUSE-Virgo survey, down to a (3{sigma}) limiting luminosity of 3.7x10^38^erg/s over 0.5-7keV. The stellar mass distribution of the targeted sample, which is mostly composed of formally "inactive" galaxies, peaks below 10^10^M_{sun}_, a regime where the very existence of nuclear supermassive black holes (SMBHs) is debated. Out of 100 objects, 32 show a nuclear X-ray source, including 6 hybrid nuclei which also host a massive nuclear cluster as visible from archival Hubble Space Telescope images. After carefully accounting for contamination from nuclear low-mass X-ray binaries based on the shape and normalization of their X-ray luminosity function (XLF), we conclude that between 24% and 34% of the galaxies in our sample host an X-ray active SMBH (at the 95% confidence level). This sets a firm lower limit to the black hole (BH) occupation fraction in nearby bulges within a cluster environment.
- ID:
- ivo://CDS.VizieR/J/ApJ/511/595
- Title:
- An X-Ray Survey of Galaxies in Pairs
- Short Name:
- J/ApJ/511/595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results are reported from the first survey of X-ray emission from galaxies in pairs. The sample consists of 52 pairs of galaxies from the Catalog of Paired Galaxies (Cat. <VII/77>) whose coordinates overlap the ROSAT Position Sensitive Proportional Counter pointed observations. The mean observed log(L_x_) for early-type pairs is 41.35+/-0.21, while the mean log(L_x_) predicted using the (L_X_-L_b_) relationship for isolated early-type galaxies is 42.10+/-0.19. With 95% confidence, the galaxies in pairs are underluminous in the X-ray, compared with isolated galaxies, for the same L_b_. A significant fraction of the mixed pair sample also appears similarly underluminous. A spatial analysis shows that the X-ray emission from pairs of both types typically has an extent of 10 - 50 kpc, much smaller than the group intergalactic medium, and thus likely originates from the galaxies. CPG 564, the most X-ray luminous early-type pair, 4.7x10^42^ergs/s, is an exception. The extent of its X-ray emission, greater than 169 kpc, and HWHM, {~}80 kpc, is comparable to that expected from an intergalactic medium. The sample shows only a weak correlation, {~}81% confidence, between L_X_ and L_b_, presumably due to variations in gas content within the galaxies. No correlation between L_X_ and the pair velocity difference ({delta}v), separation ({delta}r), or far-infrared luminosity (L_fir_) is found, although the detection rate is low, 22%.
- ID:
- ivo://CDS.VizieR/J/AZh/87/760
- Title:
- Astrophysical catalog of clusters of galaxies
- Short Name:
- J/AZh/87/760
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog of rich clusters of galaxies contains information about the astrometric and physical characteristics of the 213 clusters of galaxies and data about evidences of the presence of cooling flows and filaments in selected clusters. The catalog lists also the references to the sources of the data.