Disclosing the properties of low-redshift dual AGN through XMM-Newton and SDSS spectroscopy
A. De Rosa, C. Vignali, B. Husemann, S. Bianchi, T. Bogdanovic, M. Guainazzi, R. Herrero-Illana, S. Komossa, E. Kun, N. Loiseau, Z. Paragi, M. Perez-Torres, E. Piconcelli
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18 pages, 7 figures. Accepted for publication in MNRAS
We report on an optical (SDSS) and X-ray (XMM) study of an optically selected sample of four dual AGN systems at projected separations of 30--60~kpc. All sources are detected in the X-ray band (0.3-10 keV); seven objects are optically identified as Seyfert, while one source, optically classified as a LINER, is likely powered by accretion in virtue of its relatively high X-ray luminosity (1.2$\times10^{41}$ erg/s). Six of the eight objects are obscured in X-rays with N$_{\rm H} \geq$ 10$^{23}$ cm$^{-2}$; three of these, whose X-ray spectrum is dominated by a reflection component, are likely Compton-thick (N$_{\rm H} \geq$ 10$^{24}$ cm$^{-2}$). This finding is in agreement with the hypothesis that galaxy encounters are effective in driving gas inflow toward the nuclear region, thus increasing the obscuration. We compare the absorption properties in our dual AGN with those in larger samples observed in X-rays but selected in different ways (optical, IR and hard X-rays). We find that the obscured (N$_{\rm H} \geq$ 10$^{22}$ cm$^{-2}$) AGN fraction within the larger sample is 84$\pm$4 per cent (taking into account the 90 per cent error on the N$_{\rm H}$ measure) up to large pair separations ($\sim$100~kpc). This is statistically higher than the fraction of obscured AGN in isolated galaxies found in X-ray surveys.
We investigate the dichotomy in the radio loudness distribution of quasars by modelling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8,300 quasars drawn fro…
A brief Chandra observation of the ultraluminous quasar, SDSS J010013.02+280225.8 at redshift 6.326, showed it to be a relatively bright, soft X-ray source with a count rate of about 1 ct/ks. In this paper we present results for the quasar from a 65ks XMM-Newton observation, which well constrains its spectral shape. The quasar is clearly detected with a total of $\sim$ 460 net counts in the 0.2-10 keV band. The spectrum is characterised by a simple power-law model with photon index of $Γ= 2.30^{+0.10}_{-0.10}$, and the intrinsic 2-10 keV luminosity is $3.14\times10^{45}$ erg $\text{s}^{-1}$. T…
We report on XMM-Newton and optical results for 6 cataclysmic variables that were selected from Sloan Digital Sky Survey spectra because they showed strong HeII emission lines, indicative of being candidates for containing white dwarfs with strong magnetic fields. While high X-ray background rates prevented optimum results, we are able to confirm SDSSJ233325.92+152222.1 as an intermediate polar from its strong pulse signature at 21 min and its obscured hard X-ray spectrum. Ground-based circular polarization and photometric observations were also able to confirm SDSSJ142256.31-022108.1 as a pol…
A new serendipitous XMM survey in the area of the Sloan Digital Sky Survey is described (XMM/SDSS), which includes features such as the merging of overlapping fields to increase the sensitivity to faint sources, the use of a new parametrisation of the XMM point spread function for the source detection and photometry, the accurate estimation of the survey sensitivity. About 40,000 X-ray point sources are detected over a total area of 122deg2. A subsample of 209 sources detected in the 2-8keV spectral band with SDSS spectroscopic redshifts in the range 0.03<z<0.2, optical magnitudes r<17.77mag a…
The XMM-RM project was designed to provide X-ray coverage of the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) field. 41 XMM-Newton exposures, placed surrounding the Chandra AEGIS field, were taken, covering an area of 6.13 deg^2 and reaching a nominal exposure depth of ~15 ks. We present an X-ray catalog of 3553 sources detected in these data, using a PSF-fitting algorithm and a sample selection threshold that produces a ~5% fraction of spurious sources. In addition to the PSF-fitting likelihood, we calculate a second source reliability measure based on Poisson theory using source …
This work presents the catalogue of optical spectral properties for all X-ray selected SPIDERS active galactic nuclei (AGN) up to SDSS DR14. SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV programme that is currently conducting optical spectroscopy of the counterparts to the X-ray selected sources detected in the ROSAT all-sky survey and the XMM-Newton slew survey in the footprint of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). The SPIDERS DR14 sample is the largest sample of X-ray selected AGN with optical spectroscopic follow-up to date. The catalogue…
Recently we discovered an unprecedented supermassive black hole binary (SMBHB) candidate in the nearby Seyfert galaxy SDSS J1430+2303, which is predicted to merge within three years. X-ray spectroscopy may bring unique kinematic evidence for the last inspiraling stage, when the binary is too close to allow each of them to hold an individual broad line region. We try to confirm the unique SMBHB merger event and understand the associated high-energy processes from a comprehensive X-ray view. We observed SDSS J1430+2303 with XMM-Newton, NuSTAR, Chandra, and Swift spanning the first ~200 days sinc…
We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3<z<5.5 selected among the X-ray sources of the serendipitous XMM-Newton survey presented in the 3XMM-DR4 catalog (the median X-ray flux is 5x10^{-15} erg/s/cm^2 the 0.5-2 keV energy band) and located at high Galactic latitudes >20 deg in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg^2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error Delta z<0.2 and a color i-z<…
Optically quiescent quasars (OQQs) represent a recently systematised class of infrared-luminous active galactic nuclei (AGN) which have galaxy-like optical continua. They may represent an interesting, brief phase in the AGN life cycle, e.g. either cocooned within high-covering-factor media or indicative of recent triggering, though their nature remains unclear. Here, we present the first targeted simultaneous X-ray observations of an OQQ, our previously identified prototype, SDSS J075139.06+402811.2 at $z$=0.587. The source is significantly detected over 0.5-16 keV with XMM-Newton and NuSTAR, …
To understand the X-ray emission of active galactic nuclei (AGNs), we explored the optical-to-X-ray variation correlation of a radio-loud quasar (RLQ) SDSS J121426.52+140258.9 (hereafter J1214+1402) with multi-epoch observations of Swift and XMM-Newton telescopes. With the historical multi-band data, we found that the infrared to X-ray flux of RLQ J1214+1402 should not be dominated by the beamed jet emission. The Swift optical/UV and X-ray light curves showed that J1214+1402 has two optical states with low flux before 2014 April 08 and high flux after 2014 June 11, but has no significant X-ray…
SDSS J134244.4+053056 is a tidal disruption event candidate with strong temporal coronal line emitters and a long fading, mid-infrared dust echo. We present detailed analyses of X-ray emission from a Swift/XRT observation in 2009 and the most recent XMM-Newton/pn observation in 2020. The two spectra can be modeled with hard and soft components. While no significant variability is detected in the hard component above 2 keV between these two observations, the soft X-ray emission in 0.3-2 keV varies by a factor of $\sim5$. The luminosity of this soft component fades from $\sim1.8\times10^{41}$ to…
SPIDERS (SPectroscopic IDentification of eROSITA Sources) is an SDSS-IV survey running in parallel to the eBOSS cosmology project. SPIDERS will obtain optical spectroscopy for large numbers of X-ray-selected AGN and galaxy cluster members detected in wide area eROSITA, XMM-Newton and ROSAT surveys. We describe the methods used to choose spectroscopic targets for two sub-programmes of SPIDERS: X-ray selected AGN candidates detected in the ROSAT All Sky and the XMM-Newton Slew surveys. We have exploited a Bayesian cross-matching algorithm, guided by priors based on mid-IR colour-magnitude inform…
We present a multi-wavelength study of a newly discovered compact group (CG), SDSS J0959+1259, based data from XMM-Newton, SDSS and the Calar Alto optical imager BUSCA. With a maximum velocity offset of 500 km s$^{-1}$, a mean redshift of 0.035, and a mean spatial extension of 480 kpc, this CG is exceptional in having the highest concentration of nuclear activity in the local Universe, established with a sensitivity limit L$_{X}>4\times $10$^{40}$ erg s$^{-1}$ in 2--10 keV band and R-band magnitude $M_R < -19$. The group is composed of two type-2 Seyferts, one type-1 Seyfert, two LINERs and th…
We report on X-ray measurements constraining the spectral energy distribution (SED) of the high-redshift $z=5.18$ blazar SDSS J013127.34$-$032100.1 with new XMM-Newton and NuSTAR exposures. The blazar's X-ray spectrum is well fit by a power law with $Γ=1.9$ and $N_{\rm H}=1.1\times10^{21}\rm \ cm^{-2}$, or a broken power law with $Γ_l=0.5$, $Γ_h=1.8$, and a break energy $E_b=0.7$ keV for an expected absorbing column density of $N_{\rm H}=3.6\times 10^{20}\rm \ cm^{-2}$, supported by spectral fitting of a nearby bright source. No additional spectral break is found at higher X-ray energies (1-30…
Broad line region echo from highly accreting intermediate-mass black hole candidate SDSS J144850.08+160803.1. The first probe of intra-night variability and reverberation mapping
We aim to study the temporal and spectral behaviour of four polar CVs from the infrared to X-ray regimes, refine our knowledge of the physical parameters of these systems at different accretion rates, and to search for a possible excess of soft X-ray photons. We analysed four XMM X-ray observations of three of the sources, two of them discovered in SDSS, one in RASS. The X-ray data were complemented by optical photometry and spectroscopy and, for two sources, archival Swift observations. SDSSJ0328 was X-ray bright in two XMM and two Swift observations, and shows transitions from high and low a…
We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J211852.96-073227.5 (hereinafter J2118-0732). The galaxy, at a redshift of 0.26, is associated with a radio source of flat/inverted spectrum at high radio frequencies. The analysis of its optical spectrum obtained in the Sloan Digital Sky Survey (SDSS) revealed a small linewidth of the broad component of the Hβ line (full width at half-maximum = 1585 km s^{-1}), making it a radio-loud NLS1 galaxy -- an intriguing class of active galactic nuclei with exceptional multiwavelength properties. A new γ-…
We present a new method to identify luminous off-nuclear X-ray sources in the outskirts of galaxies from large public redshift surveys, distinguishing them from foreground and background interlopers. Using the 3XMM-DR5 catalog of X-ray sources and the SDSS DR12 spectroscopic sample of galaxies, with the help of this off-nuclear cross-matching technique, we selected 98 sources with inferred X-ray luminosities in the range $10^{41} < L_{\rm X} < 10^{44}\,{\rm erg\,s}^{-1}$, compatible with hyperluminous X-ray objects (HLX). To validate the method, we verify that it allowed us to recover known HL…
Using a suite of X-ray, mid-IR and optical active galactic nuclei (AGN) luminosity indicators, we search for Compton-thick (CT) AGNs with intrinsic L_X>10^42erg/s at z~0.03-0.2, a region of parameter space which is currently poorly constrained by deep narrow-field and high-energy (E>10keV) all-sky X-ray surveys. We have used the widest XMM-Newton survey (the serendipitous source catalogue) to select a representative sub-sample (14; ~10%) of the 147 X-ray undetected candidate CT AGNs in the Sloan Digital Sky Survey (SDSS) with f_X/f_[OIII]<1; the 147 sources account for ~50% of the overall Type…
We report the discovery of extreme X-ray variability in a type 1 quasar: SDSS J$075101.42+291419.1$. It has a black hole mass of $1.6\times 10^7~\rm M_\odot$ measured from reverberation mapping (RM), and the black hole is accreting with a super-Eddington accretion rate. Its XMM-Newton observation in 2015 May reveals a flux drop by a factor of $\sim 22$ with respect to the Swift observation in 2013 May when it showed a typical level of X-ray emission relative to its UV/optical emission. The lack of correlated UV variability results in a steep X-ray-to-optical power-law slope ($α_{\rm OX}$) of -…
We present the study on the X-ray emission for a sample of radio-detected quasars constructed from the cross-matches between SDSS, FIRST catalogs and XMM-Newton archives. A sample of radio-quiet SDSS quasars without FIRST radio detection is also assembled for comparison. We construct the optical and X-ray composite spectra normalized at rest frame $4215\,\rm Å$ (or $2200\,\rm Å$) for both radio-loud quasars (RLQs) and radio-quiet quasars (RQQs) at $z\le3.2$, with matched X-ray completeness of 19\%, redshift and optical luminosity. While the optical composite spectrum of RLQs is similar to that…
While theory and simulations indicate that galaxy mergers play an important role in the cosmological evolution of accreting black holes and their host galaxies, samples of Active Galactic Nuclei (AGN) in galaxies at close separations are still small. In order to increase the sample of AGN pairs, we undertook an archival project to investigate the X-ray properties of a SDSS-selected sample of 32 galaxy pairs with separations $\le$150 kpc containing one optically-identified AGN, that were serendipitously observed by XMM-Newton. We discovered only one X-ray counterpart among the optically classif…
We report on the discovery of an ultrasoft X-ray transient source, 3XMM J152130.7+074916. It was serendipitously detected in an XMM-Newton observation on 2000 August 23, and its location is consistent with the center of the galaxy SDSS J152130.72+074916.5 (z=0.17901 and d_L=866 Mpc). The high-quality X-ray spectrum can be fitted with a thermal disk with an apparent inner disk temperature of 0.17 keV and a rest-frame 0.24-11.8 keV unabsorbed luminosity of ~5e43 erg/s, subject to a fast-moving warm absorber. Short-term variability was also clearly observed, with the spectrum being softer at lowe…
In an XMM-Newton observation of the binary SDSS J121209.31+013627.7, consisting of a white dwarf and an L dwarf, we detect X-ray orbital modulation as proof of accretion from the substellar companion onto the magnetic white dwarf. We constrain the system geometry (inclination as well as magnetic and pole-cap angle) through modelling of the X-ray light curve, and we derive a mass accretion rate of 3.2 10^(-14) M_sun/yr from the X-ray luminosity (~ 3 10^(29) erg/s). From X-ray studies of L dwarfs, a possible wind driven from a hypothesized corona on the substellar donor is orders of magnitude to…
We present results on a multi-wavelength analysis of SDSS J025214.67-002813.7, a system which has been previously classified as a binary AGN candidate based on periodic signals detected in the optical light curves. We use available radio-X-ray observations of the system to investigate the true accretion nature. Analyzing new observations from XMM-Newton and NuSTAR, we characterize the X-ray emission and search for evidence of circumbinary accretion. Although the 0.5-10 keV spectrum shows evidence of an additional soft emission component, possibly due to extended emission from hot nuclear gas, …
X-ray variability of SDSS J000532.84+200717.4: from a normal state to an X-weak state
Shenzhen Technology University（深圳技术大学）；Guangzhou University（广州大学）；University of Science and Technology of China（中国科学技术大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；University of Chinese Academy of Sciences（中国科学院大学）
SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to Lx~3x10^44 ergs/s. It has the optical spectrum of a quiescent galaxy (z=0.146). Overall the X-ray flux has evolved consistently with the canonical t^-5/3 model, expected for returning stellar debris from a tidal disruption event, fading by a factor ~300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not t…
The X-ray luminosity function of distant (3<z<5.1) unabsorbed quasars has been measured. A sample of distant high-luminosity quasars ($10^{45} \leq L_{{\rm X},2-10} < 7.5 \times 10^{45}$ erg/s in the 2--10 keV energy band) from the catalog given in Khorunzhev et al. (2016) compiled from the data of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey and the Sloan Digital Sky Survey (SDSS) has been used. This sample consists of 101 sources. Most of them (90) have spectroscopic redshifts $z_{spec}\geqslant 3$. The remaining ones are quasar candidates with photometric redshift estimates $…
The majority of cataclysmic variables are predicted to be post-period minimum systems with degenerate donor stars, the period bouncers. Owing to their intrinsic faintness, however, only a handful of these systems have so far been securely identified. We want to study the X-ray properties of two eclipsing period bouncers, OV Bootis and SDSS J103533.02+055158.3, that were selected for this study due to their proximity to Earth. We have obtained XMM-Newton phase-resolved X-ray and ultraviolet observations of the two objects for spectral and timing analysis. Owing to a recent dwarf nova outburst O…
We aim to study the temporal and spectral behaviour of \vum from the optical to the X-ray regimes. We used archival \xmmn and \tes observations obtained in 2017 and 2019 to perform a spectral and timing analysis of the highly variable polar. The light curves of both satellites, TESS and XMM-Newton, reveal a double-humped pattern modulated with the periodicity of $91.058467 \pm 0.00001$ minutes. V496 UMa displays a two-pole accretion geometry in the high accretion state. X-ray spectra from both regions are composed of thermal plasma radiation and soft blackbody components with almost identical …
We present a catalog of 792 DR5 SDSS quasars with optical spectra that have been observed serendipitously in the X-rays with the \emph{XMM-Newton}. These quasars cover a redshift range of z = 0.11 - 5.41 and a magnitude range of i = 15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at >2sigma account for 87% of the sample (685 quasars), and 473 quasars are detected at >6sigma, sufficient to allow X-ray spectral fits. For detected sources, ~ 60% have X-ray fluxes between F(2-10 keV) = 1 - 10 x 10^-14 e…
We perform a spectral analysis of a sample of 11 medium redshift (1.5 < z < 2.2) quasars. Our sample all have optical spectra from the SDSS, infrared spectra from GNIRS and TSPEC, and X-ray spectra from XMM-Newton. We first analyse the Balmer broad emission line profiles which are shifted into the IR spectra to constrain black hole masses. Then we fit an energy-conserving, three component accretion model of the broadband spectral energy distribution (SED) to our multi-wavelength data. Five out of the 11 quasars show evidence of an SED peak, allowing us to constrain their bolometric luminosity …
The majority of active galactic nuclei (AGN) are obscured by large amounts of absorbing material that makes them invisible at many wavelengths. X-rays, given their penetrating power, provide the most secure way for finding these AGN. The XMM-Newton serendipitous source catalog is the largest catalog of X-ray sources ever produced; it contains about half a million detections. These sources are mostly AGN. We have derived X-ray spectral fits for very many 3XMM-DR4 sources ($\gtrsim$ 114 000 observations, corresponding to $\sim$ 77 000 unique sources), which contain more than 50 source photons pe…
Swift J2218.4+1925, a hard X-ray source detected by Swift BAT, has been proposed as a candidate magnetic cataclysmic variable of the polar type from optical spectroscopy. Using XMM-Newton we perform detailed timing and spectral analysis with simultaneous X-ray ($0.3-10$ keV) and optical B band data. We complement the spectral study with archival hard X-ray (14-70 keV) spectra collected by Swift BAT as well as with optical, near and mid-infrared photometry from $SDSS$, $2MASS$ and $WISE$ archive, respectively. A strong periodic X-ray signal at 2.16 h, consistent with the recently determined spe…
We explore the evolution with redshift of the rest-frame colours and space densities of AGN hosts (relative to normal galaxies) to shed light on the dominant mechanism that triggers accretion onto supermassive black holes as a function of cosmic time. Data from serendipitous wide-area XMM surveys of the SDSS footprint (XMM/SDSS, Needles in the Haystack survey) are combined with Chandra deep observations in the AEGIS, GOODS-North and GOODS-South to compile uniformly selected samples of moderate luminosity X-ray AGN [L_X(2-10keV) = 1e41-1e44erg/s] at redshifts 0.1, 0.3 and 0.8. It is found that …
We report the discovery of an off-nuclear ultrasoft hyper-luminous X-ray source candidate 3XMM J141711.1+522541 in the inactive S0 galaxy SDSS J141711.07+522540.8 (z=0.41827, d_L=2.3 Gpc) in the Extended Groth Strip. It is located at a projected offset of ~1.0 (5.2 kpc) from the nucleus of the galaxy and was serendipitously detected in five XMM-Newton observations in 2000 July. Two observations have enough counts and can be fitted with a standard thermal disk with an apparent inner disk temperature kT_MCD ~ 0.13 keV and a 0.28-14.2 keV unabsorbed luminosity L_X ~ 4X10^{43} erg/s in the source …
The emission-line dwarf galaxy NGC 3413 is known to host a bright X-ray source near its optical center. The 0.3-10 keV luminosity of this source is estimated to be approximately 10$^{39}$ erg$s^{-1}$ potentially qualifying it as an ultra-luminous X-ray (ULX) source. A recent XMM-Newton observation suggests that the source is not point-like, and instead, is more likely a composite of point-like sources with extended and/or diffuse emission. The spectral and temporal features of the bright region are similar to those associated with the so-called broadened disk state of ULXs. Based on a multi-co…
Owing to their thermal emission, tidal disruption events (TDEs) were regularly detected in the soft X-rays and sometimes in the optical. Only a few TDEs have been detected at hard X-rays: two are high redshift beamed events, one of which occurred at the core of a nearby galaxy, and the most recent one is of a different nature, involving a compact object in the Milky Way. The aims of this work are to obtain a first sample of hard X-ray-selected unbeamed TDEs, to determine their frequency and to probe whether TDEs usually or exceptionally emit at hard X-ray energies. We performed extensive searc…
Since its launch in 1999, the XMM-\textit{Newton} mission has compiled the largest catalogue of serendipitous X-ray sources, with the 3XMM being the third version of this catalogue. This is because of the combination of a large effective area (5000 $\rm cm^2$ at 1 keV) and a wide field of view (30 arcmin). The 3XMM-DR6 catalogue contains about 470,000 unique X-ray sources over an area of 982 $\rm deg^2$. A significant fraction of these (100,178 sources) have reliable optical, near/mid-IR counterparts in the SDSS, PANSTARRS, VIDEO, UKIDSS and WISE surveys. In a previous paper we have presented …
An all-sky comprehensive catalog of calculated radio and X-ray associations to optical objects is presented. Included are X-ray sources from XMM-Newton, Chandra and ROSAT catalogs, radio sources from NVSS, FIRST and SUMSS catalogs, and optical data, identifications and redshifts from the APM, USNO-A, SDSS-DR7 and the extant literature. This "Atlas of Radio/X-ray Associations" inherits many techniques from the predecessor Quasars.org (2004) catalog, but object selection is changed and processing tweaked. Optical objects presented are those which are calculated with >=40% confidence to be associ…
RE J2248-511 is one of only 14 non-blazar AGN detected in the far ultraviolet by the ROSAT Wide Field Camera implying a large ultrasoft X-ray flux. This soft X-ray excess is strongly variable on year timescales, a common property of Narrow Line Seyfert 1s, yet its optical linewidths classify this source as a broad-lined Seyfert 1. We use four nearly simultaneous optical--X-ray SEDs spanning 7 years to study the spectral shape and long term variability of RE J2248-511. Here we show that the continuum SED for the brightest epoch dataset is consistent with the mean SED of a standard quasar, and m…
We present modeling and interpretation of the continuum and emission lines for a sample of 51 unobscured Type 1 active galactic nuclei (AGN). All of these AGNs have high quality spectra from both XMM-Newton and Sloan Digital Sky Survey (SDSS). We extend the wavelength coverage where possible by adding simultaneous UV data from the OM onboard XMM-Newton. Our sample is selected based on low reddening in the optical and low gas columns implied by their X-ray spectra. They also lack clear signatures for the presence of a warm absorber. Therefore the observed characteristics of this sample are like…
In our study, we show a multiwavelength view of ACT-CL J0019.6+0336 (which hosts a radio halo), to investigate the cluster dynamics, morphology, and ICM. We use a combination of XMM-Newton images, Dark Energy Survey (DES) imaging and photometry, SDSS spectroscopic information, and 1.16 GHz MeerKAT data to study the cluster properties. Various X-ray and optical morphology parameters are calculated to investigate the level of disturbance. We find disturbances in two X-ray parameters and the optical density map shows elongated and axisymmetric structures with the main cluster component southeast …
We investigate claims according to which the X-ray selection of AGN is not as efficient compared to that based on [OIII] selection because of the effects of X-ray absorption.We construct the predicted X-ray luminosity function both for all Seyferts as well as separately for Seyfert-1 and Seyfert-2 type galaxies, by combining the optical AGN [OIII] luminosity functions derived in SDSS with the corresponding L_X-L_[OIII] relations. These relations are derived from XMM-Newton observations of all Seyfert galaxies in the Palomar spectroscopic sample of nearby galaxies after correction for X-ray abs…
The Swift Gamma-Ray Burst satellite has detected a largely unbiased towards absorption sample of local ($<z> \approx 0.03$) AGN, based solely on their 14--195 keV flux. In the first 9 months of the survey, 153 AGN sources were detected. The X-ray properties in the 0.3--10 keV band have been compiled and presented based on analyses with XMM-Newton, Chandra, Suzaku, and the Swift XRT (Winter et al. 2009). Additionally, we have compiled a sub-sample of sources with medium resolution optical ground-based spectra from the SDSS or our own observations at KPNO. In this sample of 60 sources, we have c…
