scholarly journals Active galaxies and cluster gas

2005 ◽  
Vol 363 (1828) ◽  
pp. 725-738 ◽  
Author(s):  
A. C. Fabian
Keyword(s):  
Luminosity Function ◽  
Inner Core ◽  
Active Galaxies ◽  
X Rays ◽  
Temperature Relation ◽  
X Ray ◽  
Massive Galaxies ◽  
Cooling Flow ◽  
Hot Gas ◽  
Cluster Cores

Two lines of evidence indicate that active galaxies, principally radio galaxies, have heated the diffuse hot gas in clusters. The first is the general need for additional heating to explain the steepness of the X–ray luminosity–temperature relation in clusters, the second is to solve the cooling–flow problem in cluster cores. The inner core of many clusters is radiating energy as X–rays on a time–scale much shorter than its likely age. Although the temperature in this region drops by a factor of about three from that of the surrounding gas, little evidence is found for gas much cooler than that. Some form of heating appears to be taking place, probably by energy transported outward from the central accreting black hole or radio source. How that energy heats the gas depends on poorly understood transport properties (conductivity and viscosity) of the intracluster medium. Viscous heating is discussed as a possibility. Such heating processes have consequences for the truncation of the luminosity function of massive galaxies.

scholarly journals Hot Gas in Clusters of Galaxies

1980 ◽  
Vol 5 ◽  
pp. 387-396
Author(s):  
J. L. Culhane
Keyword(s):  
Surface Brightness ◽  
Luminosity Function ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
Will Emit ◽  
X Ray ◽  
Hot Gas ◽  
Sky Survey ◽  
To Come ◽  
Einstein Observatory

The discovery of extended X-ray sources associated with clusters of galaxies which resulted from the Uhuru X-ray sky survey was one of the most important observations to come from that programme. Following Uhuru, the Ariel V and HEAO-1 sky surveys have found many more cluster X-ray sources and the recently launched Einstein observatory has begun to increase further the number of identifications. However there is in any case evidence from the X-ray cluster luminosity function that all rich clusters of galaxies will emit X-rays at some level.Preliminary results from the Einstein observatory (Murray, 1979) suggest that the extended X-ray emission from centrally condensed (cD) clusters is itself centrally condensed and spherically symmetrical in appearance. However irregular clusters have non-uniform X-ray surface brightness distributions. In addition there are some galaxies in clusters of irregular morphology that have associated X-ray halos.

scholarly journals Multiwavelength morphological study of active galaxies

2019 ◽  
Vol 15 (S356) ◽  
pp. 295-298
Author(s):  
Betelehem Bilata-Woldeyes ◽  
Mirjana Pović ◽  
Zeleke Beyoro-Amado ◽  
Tilahun Getachew-Woreta ◽  
Shimeles Terefe
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Formation Rate ◽  
Stellar Mass ◽  
Active Galaxies ◽  
Morphological Properties ◽  
X Rays ◽  
Host Galaxies ◽  
X Ray ◽  
Public Data

AbstractStudying the morphology of a large sample of active galaxies at different wavelengths and comparing it with active galactic nuclei (AGN) properties, such as black hole mass (MBH) and Eddington ratio (λEdd), can help us in understanding better the connection between AGN and their host galaxies and the role of nuclear activity in galaxy formation and evolution. By using the BAT-SWIFT hard X-ray public data and by extracting those parameters measured for AGN and by using other public catalogues for parameters such as stellar mass (M*), star formation rate (SFR), bolometric luminosity (Lbol), etc., we studied the multiwavelength morphological properties of host galaxies of ultra-hard X-ray detected AGN and their correlation with other AGN properties. We found that ultra hard X-ray detected AGN can be hosted by all morphological types, but in larger fractions (42%) they seem to be hosted by spirals in optical, to be quiet in radio, and to have compact morphologies in X-rays. When comparing morphologies with other galaxy properties, we found that ultra hard X-ray detected AGN follow previously obtained relations. On the SFR vs. stellar mass diagram, we found that although the majority of sources are located below the main sequence (MS) of star formation (SF), still non-negligible number of sources, with diverse morphologies, is located on and/or above the MS, suggesting that AGN feedback might have more complex influence on the SF in galaxies than simply quenching it, as it was suggested in some of previous studies.

scholarly journals UHURU Results on Extragalactic X-Ray Sources

1973 ◽  
Vol 55 ◽  
pp. 171-183 ◽  
Author(s):  
Edwin M. Kellogg
Keyword(s):  
High Latitude ◽  
Luminosity Function ◽  
Optical Data ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
Total Contribution ◽  
X Ray ◽  
Normal Galaxies ◽  
X Ray Background ◽  
Individual Galaxies

Data from the UHURU satellite have provided a list of more than forty high latitude sources (|b| > 20°). X-rays have been detected from among the nearest normal galaxies, giant radio galaxies, Seyferts, QSOs and clusters of galaxies. The cluster sources appear to be extended by several hundred kiloparsecs as well as being very luminous. These cluster sources have systematic differences in their X-ray spectra from individual galaxies.About twenty sources are not reliably identified so far. A few of these are located near undistinguished 3C or MSH radio sources. The rest are either located near distant clusters or undistinguished bright galaxies, or are too far south, so that we have not sufficient optical data to allow a thorough search for possible association with clusters or unusual individual galaxies.The luminosity function for weak, high latitude X-ray sources is determined, and the contribution of sources just below the UHURU threshold of detectability to observed fluctuations in the diffuse X-ray background is evaluated. The total contribution of all observed types of extragalactic sources to the X-ray background is estimated.

scholarly journals Precessing AGN jets, bubbles and cooling flows

2010 ◽  
Vol 6 (S275) ◽  
Author(s):  
D. Falceta-Gonçalves ◽  
A. Caproni ◽  
Z. Abraham ◽  
E. M. de Gouveia Dal Pino ◽  
D. M. Teixeira
Keyword(s):  
Galaxy Clusters ◽  
Flow Problem ◽  
X Rays ◽  
Intracluster Medium ◽  
X Ray ◽  
Cooling Flows ◽  
Cooling Flow ◽  
Central Regions ◽  
Multiple Bubbles ◽  
Hydrodynamical Simulations

AbstractSeveral galaxy clusters are known to present multiple and misaligned pairs of cavities seen in X-rays, as well as twisted kiloparsec-scale jets at radio wavelengths. It suggests that the AGN precessing jets play a role in the formation of the misaligned bubbles. Also, X-ray spectra reveal that typically these systems are also able to supress cooling flows, predicted theoretically. The absence of cooling flows in galaxy clusters has been a mistery for many years since numerical simulations and analytical studies suggest that AGN jets are highly energetic, but are unable to redistribute it at all directions. We performed 3D hydrodynamical simulations of the interaction between a precessing AGN jet and the warm intracluster medium plasma, in which dynamics is coupled to a NFW dark matter gravitational potential. Radiative cooling has been taken into account and the cooling flow problem was studied. We found that precession is responsible for multiple pairs of bubbles, as observed. The misaligned bubbles rise up to scales of tens of kiloparsecs, where the thermal energy released by the jets are redistributed. After ~150 Myrs, the temperature of the gas within the cavities is kept of order of ~107 K, while the denser plasma of the intracluster medium at the central regions reaches T ~ 105 K. The existence of multiple bubbles, at diferent directions, results in an integrated temperature along the line of sight much larger than the simulations of non-precessing jets. This result is in agreement with the observations. The simulations reveal that the cooling flows cessed ~50–70 Myr after the AGN jets are started.

scholarly journals Development of New Analysis Method for Mapping Observations of Clusters of Galaxies

1998 ◽  
Vol 188 ◽  
pp. 312-313
Author(s):  
K. Kikuchi ◽  
T. Ohashi ◽  
H. Ezawa ◽  
M. Hirayama ◽  
H. Honda ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Stray Light ◽  
Physical Parameters ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
X Ray ◽  
Hot Gas ◽  
Cluster Data ◽  
Metal Abundance ◽  
Analysis System

Mapping observations of nearby large-extended clusters of galaxies (Coma, Perseus, Virgo, etc.) are being performed with ASCA. Such clusters allow us to map physical parameters of hot gas in the clusters, such as temperature, metal abundance, and X-ray surface brightness. To determine such parameters at each part of a cluster, one should take careful care of X-ray contamination from outside of a pointed field, which is mainly due to “stray-light” X-rays (Honda et al. 1997). For this reason, the only way to obtain the distribution of hot gas parameter is to process the whole cluster data in a self-consistent way. For this purpose, we are developing the new analysis system called TERRA.

scholarly journals The Nature of the Dusty Ionized Gas in NGC 5846: (And Other Elliptical Galaxies ?)

1999 ◽  
Vol 186 ◽  
pp. 199-199
Author(s):  
Paul Goudfrooij ◽  
Ginevra Trinchieri
Keyword(s):  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
Ionized Gas ◽  
Full Account ◽  
Optical Extinction ◽  
X Ray ◽  
Cooling Flow ◽  
Hot Gas ◽  
Optical Imagery ◽  
Astronomy And Astrophysics

We present new optical imagery and ROSAT HRI X-ray imagery of the elliptical galaxy NGC 5846. A filamentary dust lane is detected in its central region, with a morphology strikingly similar to that observed for the optical nebulosity and the X-ray emission (cf. Fig. 1). A physical connection between the different phases of the interstellar medium therefore seems likely. The energy deposited from the hot gas into heating of the dust grains is consistent with the temperature distribution of the X-ray-emitting gas, which is found to be lowest in the dusty regions. The optical extinction of the dust is consistent with the Galactic extinction curve. We argue that the dust as well as the optical nebulosity are products of an interaction with a small, gas-rich galaxy, not remnants of a cooling flow. A full account of this work is currently in press in Astronomy and Astrophysics, and a preprint is available through http://www.stsci.edu/science/preprints/prep1191/prep1191.html.

scholarly journals X-Rays from Galaxies and Clusters of Galaxies: Observations and Phenomenology

1987 ◽  
Vol 117 ◽  
pp. 165-181 ◽  
Author(s):  
C. R. Canizares
Keyword(s):  
Direct Evidence ◽  
Temperature Profiles ◽  
Clusters Of Galaxies ◽  
X Rays ◽  
Early Type ◽  
X Ray ◽  
Cluster Galaxies ◽  
Cooling Flows ◽  
Hot Gas ◽  
Relevant Work

X-Ray observations of galaxies and clusters can, in principle, trace the binding mass in these systems. I review some of the relevant work. The mass of hot gas in rich clusters is comparable to or exceeds the mass in visible stars. This proportion of gas to stellar material could be universal, although there is no direct evidence that it must be. Studies of the distribution of the gas indicate the presence of dark matter in the envelopes of some dominant cluster galaxies, most notably M87. The M/LB values increase with radius to values of ∼ 400–600 M⊙/L⊙. Uncertainties in the temperature distribution of the gas have hampered these analyses and have made it difficult to draw definitive conclusions about the binding mass in clusters. Recent work on Coma suggests that M/L is falling with radius and the total M/L for the cluster may be as low as ∼ 120. Studies of early type galaxies show that many contain hot gas with temperatures ∼107 K. There is evidence for the existence of cooling flows, and gravity rather than supernovae may be the dominant source of energy that heats the gas. The deduced binding masses for several bright galaxies are uncertain because of the unknown temperature profiles. Values of M/LB ≃ 20–30 within ∼ 30–40 kpc are indicated if one assumes isothermality, but values as low as 5 and as high as 100 are allowed. With better models one may be able to reduce these uncertainties.

scholarly journals The XXL Survey

2018 ◽  
Vol 620 ◽  
pp. A5 ◽  
Author(s):  
C. Adami ◽  
P. Giles ◽  
E. Koulouridis ◽  
F. Pacaud ◽  
C. A. Caretta ◽  
...  
Keyword(s):  
Present Article ◽  
Present State ◽  
Luminosity Function ◽  
Selection Function ◽  
Clusters Of Galaxies ◽  
Temperature Relation ◽  
X Ray ◽  
Cluster Sample ◽  
Medium Mass

Context. In the currently debated context of using clusters of galaxies as cosmological probes, the need for well-defined cluster samples is critical. Aims. The XXL Survey has been specifically designed to provide a well characterised sample of some 500 X-ray detected clusters suitable for cosmological studies. The main goal of present article is to make public and describe the properties of the cluster catalogue in its present state, as well as of associated catalogues of more specific objects such as super-clusters and fossil groups. Methods. Following from the publication of the hundred brightest XXL clusters, we now release a sample containing 365 clusters in total, down to a flux of a few 10−15 erg s−1 cm−2 in the [0.5–2] keV band and in a 1′ aperture. This release contains the complete subset of clusters for which the selection function is well determined plus all X-ray clusters which are, to date, spectroscopically confirmed. In this paper, we give the details of the follow-up observations and explain the procedure adopted to validate the cluster spectroscopic redshifts. Considering the whole XXL cluster sample, we have provided two types of selection, both complete in a particular sense: one based on flux-morphology criteria, and an alternative based on the [0.5–2] keV flux within 1 arcmin of the cluster centre. We have also provided X-ray temperature measurements for 80% of the clusters having a flux larger than 9 × 10−15 erg s−1 cm−2. Results. Our cluster sample extends from z ~ 0 to z ~ 1.2, with one cluster at z ~ 2. Clusters were identified through a mean number of six spectroscopically confirmed cluster members. The largest number of confirmed spectroscopic members in a cluster is 41. Our updated luminosity function and luminosity–temperature relation are compatible with our previous determinations based on the 100 brightest clusters, but show smaller uncertainties. We also present an enlarged list of super-clusters and a sample of 18 possible fossil groups. Conclusions. This intermediate publication is the last before the final release of the complete XXL cluster catalogue when the ongoing C2 cluster spectroscopic follow-up is complete. It provides a unique inventory of medium-mass clusters over a 50 deg2 area out to z ~ 1.

scholarly journals First constraints on the AGN X-ray luminosity function at z ~ 6 from an eROSITA-detected quasar

2021 ◽  
Vol 647 ◽  
pp. A5
Author(s):  
J. Wolf ◽  
K. Nandra ◽  
M. Salvato ◽  
T. Liu ◽  
J. Buchner ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Large Scale ◽  
High Redshift ◽  
Jet Physics ◽  
Selection Function ◽  
Source Population ◽  
X Rays ◽  
X Ray ◽  
Colour Parameter ◽  
Sky Survey

Context. High-redshift quasars signpost the early accretion history of the Universe. The penetrating nature of X-rays enables a less absorption-biased census of the population of these luminous and persistent sources compared to optical/near-infrared colour selection. The ongoing SRG/eROSITA X-ray all-sky survey offers a unique opportunity to uncover the bright end of the high-z quasar population and probe new regions of colour parameter space. Aims. We searched for high-z quasars within the X-ray source population detected in the contiguous ~140 deg2 field observed by eROSITA during the performance verification phase. With the purpose of demonstrating the unique survey science capabilities of eROSITA, this field was observed at the depth of the final all-sky survey. The blind X-ray selection of high-redshift sources in a large contiguous, near-uniform survey with a well-understood selection function can be directly translated into constraints on the X-ray luminosity function (XLF), which encodes the luminosity-dependent evolution of accretion through cosmic time. Methods. We collected the available spectroscopic information in the eFEDS field, including the sample of all currently known optically selected z > 5.5 quasars and cross-matched secure Legacy DR8 counterparts of eROSITA-detected X-ray point-like sources with this spectroscopic sample. Results. We report the X-ray detection of eFEDSU J083644.0+005459, an eROSITA source securely matched to the well-known quasar SDSS J083643.85+005453.3 (z = 5.81). The soft X-ray flux of the source derived from eROSITA is consistent with previous Chandra observations. The detection of SDSS J083643.85+005453.3 allows us to place the first constraints on the XLF at z > 5.5 based on a secure spectroscopic redshift. Compared to extrapolations from lower-redshift observations, this favours a relatively flat slope for the XLF at z ~ 6 beyond L*, the knee in the luminosity function. In addition, we report the detection of the quasar with LOFAR at 145 MHz and ASKAP at 888 MHz. The reported flux densities confirm a spectral flattening at lower frequencies in the emission of the radio core, indicating that SDSS J083643.85+005453.3 could be a (sub-) gigahertz peaked spectrum source. The inferred spectral shape and the parsec-scale radio morphology of SDSS J083643.85+005453.3 indicate that it is in an early stage of its evolution into a large-scale radio source or confined in a dense environment. We find no indications for a strong jet contribution to the X-ray emission of the quasar, which is therefore likely to be linked to accretion processes. Conclusions. Our results indicate that the population of X-ray luminous AGNs at high redshift may be larger than previously thought. From our XLF constraints, we make the conservative prediction that eROSITA will detect ~90 X-ray luminous AGNs at redshifts 5.7 < z < 6.4 in the full-sky survey (De+RU). While subject to different jet physics, both high-redshift quasars detected by eROSITA so far are radio-loud; a hint at the great potential of combined X-ray and radio surveys for the search of luminous high-redshift quasars.

scholarly journals Local Contributions to the 0.6 keV Diffuse X-Ray Background

1984 ◽  
Vol 81 ◽  
pp. 215-218 ◽  
Author(s):  
David N. Burrows
Keyword(s):  
Galactic Latitude ◽  
The Sun ◽  
X Rays ◽  
Diffuse Emission ◽  
General Direction ◽  
X Ray ◽  
Hot Gas ◽  
X Ray Background

The intensity of the X-ray background between 0.5 and 1.0 keV has surprisingly little dependence on galactic latitude. Possible mechanisms for the production of these X-rays include extragalactic emission and emission from dM stars, both of which should be strongly dependent on galactic latitude, and diffuse emission from hot gas (T ≃ 3 x 106 K) surrounding the Sun. These mechanisms can be distinguished by the presence or absence of absorption by gas within a few hundred parsecs of the Sun. We use X-ray data from the HEA0-1 LED detectors and HI data from the recent Crawford Hill 21 cm survey to place limits on the 0.6 keV intensity originating within 300 pc of the Sun in the general direction of (l,b) = (150°, -30°).

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