- ID:
- ivo://CDS.VizieR/J/A+A/474/473
- Title:
- XMM-LSS survey: AGN classifications
- Short Name:
- J/A+A/474/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our goal is to characterize AGN populations by comparing their X-ray and optical classifications within the framework of the standard orientation-based unified scheme. We present a sample of 99 spectroscopically identified (R<=22mag) X-ray selected point sources in the XMM-LSS survey which are significantly detected (>=3{sigma}) in the [2-10]keV band with fluxes between 8x10^-15^ and 8x10^-14^erg/s/cm^2^, and which have more than 80 counts. We have compared their X-ray and optical classifications. To this end, we performed an X-ray spectral analysis for all of these 99 X-ray sources in order to assess whether they are intrinsically absorbed or not. The X-ray classification is based on the measured intrinsic column density. The optical classification is based on the measured FWHM of the permitted emission lines, the absence of broad lines being due to obscuration within the framework of the standard AGN unified scheme.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/352/91
- Title:
- XMM-Newton/2dF survey. IV.
- Short Name:
- J/MNRAS/352/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the X-ray spectral properties of 61 hard X-ray (2-8keV) selected sources from the bright XMM-Newton/2dF (f(2-8keV)>10^-14^erg/cm^2^/s) survey. This comprises nine XMMNewton pointings in the North Galactic Pole region (~1.6deg^2^) and overlaps with the SDSS, 2QZ and 2dFGRS surveys. Our sources contribute about 50 per cent of the 2-10keV X-ray background down to the flux limit of 10^-14^erg/cm^2^/s. The hardness ratio distribution of the sample suggests a deficit of heavily absorbed sources. Spectroscopic identifications exist for 34 sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/371/147
- Title:
- XMM-Newton observation of NGC 2613
- Short Name:
- J/MNRAS/371/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an XMM-Newton observation of the massive edge-on Sb galaxy NGC 2613. We discover that this galaxy contains a deeply embedded active nucleus with a 0.3-10keV luminosity of 3.3x10^40^erg/s and a line-of-sight absorption column of 1.2x10^23^cm^-2^. Within the 25mag arcsec-2 optical B-band isophote of the galaxy, we detect an additional four sources with an accumulated luminosity of 4.3x10^39^erg/s. The bulk of the unresolved X-ray emission spatially follows the near-infrared (NIR) K-band surface brightness distribution; the luminosity ratio LX/LK~8x10^-4^ is consistent with that inferred from galactic discrete sources. This X-ray-NIR association and the compatibility of the X-ray spectral fit with the expected spectrum of a population of discrete sources suggest that low-mass X-ray binaries (LMXBs) are the most likely emitters of the unresolved emission in the disc region.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A99
- Title:
- XMM-Newton Slew Survey in 2-10keV
- Short Name:
- J/A+A/548/A99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The on-going XMM-Newton Slew Survey (XSS) provides coverage of a significant fraction of the sky in a broad X-ray bandpass. Although shallow by contemporary standards, in the "classical" 2-10keV band of X-ray astronomy, the XSS provides significantly better sensitivity than any currently available all-sky survey. We investigate the source content of the XSS, focussing on detections in the hard 2-10keV band down to a very low threshold (>=4counts net of background). At the faint end, the survey reaches a flux sensitivity of roughly 3x10^-12^erg/cm^2^/s (2-10keV). Our starting point was a sample of 487 sources detected in the XSS (up to and including release XMMSL1d2) at high galactic latitude in the hard band. Through cross-correlation with published source catalogues from surveys spanning the electromagnetic spectrum from radio through to gamma-rays, we find that 45% of the sources have likely identifications with normal/active galaxies. A further 18% are associated with other classes of X-ray object (nearby coronally active stars, accreting binaries, clusters of galaxies), leaving 37% of the XSS sources with no current identification. We go on to define an XSS extragalactic sample comprised of 219 galaxies and active galaxies selected in the XSS hard band. We investigate the properties of this extragalactic sample including its X-ray logN-logS distribution. We find that in the low-count limit, the XSS is, as expected, strongly affected by Eddington bias. There is also a very strong bias in the XSS against the detection of extended sources, most notably clusters of galaxies. A significant fraction of the detections at and around the low-count limit may be spurious. Nevertheless, it is possible to use the XSS to extract a reasonably robust sample of extragalactic sources, excluding galaxy clusters. The differential logN-logS relation of these extragalactic sources matches very well to the HEAO-1 A2 all-sky survey measurements at bright fluxes and to the 2XMM source counts at the faint end. The substantial sky coverage afforded by the XSS makes this survey a valuable resource for studying X-ray bright source samples, including those selected specifically in the hard 2-10keV band.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A74
- Title:
- XMM-Newton spectral-fit redshift catalogue
- Short Name:
- J/A+A/645/A74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since its launch in 1999, the XMM-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 (5000cm^2^ at 1keV) and a wide field of view (30 arcmin). The 3XMM-DR6 catalogue contains about 470000 unique X-ray sources over an area of 982deg^2^. A significant fraction of these (100178 sources) have reliable optical, near/mid-IR counterparts in the SDSS, PANSTARRS, VIDEO, UKIDSS and WISE surveys. In a previous paper we have presented photometric redshifts for these sources using the TPZ machine learning algorithm. About one fourth of these (22677) have adequate photon statistics so that a reliable X-ray spectrum can be extracted. Obviously, owing to both the X-ray counts selection and the optical counterpart constraint, the sample above is biased towards the bright sources. Here, we present XMMFITCAT-Z: a spectral fit catalogue for these sources using the Bayesian X-ray Analysis (BXA) technique. As a science demonstration of the potential of the present catalogue, we comment on the optical and mid-IR colours of the 765 X-ray absorbed sources with N_H_>10^22^cm^-2^. We show that a considerable fraction of X-ray selected AGN would not be classified as AGN following the mid-IR W1-W2 vs. W2 selection criterion. These are AGN with lower luminosities, where the contribution of the host galaxy to the MIR emission is non-negligible. Only one third of obscured AGN in X-rays present red colours or r-W2>6. Then it appears that the r-W2 criterion, often used in the literature for the selection of obscured AGN, produces very different X-ray absorbed AGN samples compared to the standard X-ray selection criteria.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/368
- Title:
- XMM-Newton survey in COSMOS field. IV.
- Short Name:
- J/ApJS/172/368
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed spectral analysis of pointlike X-ray sources in the XMM-Newton COSMOS field. Our sample of 135 sources only includes those that have more than 100 net counts in the 0.3-10keV energy band and have been identified through optical spectroscopy. The majority of the sources are well described by a simple power-law model with either no absorption (76%) or a significant intrinsic, absorbing column (20%). The remaining ~4% of the sources require a more complex modeling by incorporating additional components to the power law. For sources with more than 180 net counts (bright sample), we allowed both the photon spectral index Gamma and the equivalent hydrogen column NH to be free parameters. For fainter sources, we fix Gamma to the average value and allow NH to vary. The mean spectral index of the 82 sources in the bright sample is <Gamma>=2.06+/-0.08, with an intrinsic dispersion of ~0.24. Each of these sources has fractional errors on the value of Gamma below 20%. As expected, the distribution of intrinsic absorbing column densities is markedly different between AGNs with or without broad optical emission lines. We find within our sample four type 2 QSO candidates (L_X_>10^44^erg/s, NH>10^22^cm^-2^), with a spectral energy distribution well reproduced by a composite Seyfert 2 spectrum, that demonstrates the strength of the wide-field COSMOS XMM-Newton survey to detect these rare and underrepresented sources. In addition, we have identified a Compton-thick (NH>1.5x10^24^cm^-2^) AGN at z=0.1248. Its X-ray spectrum is well fitted by a pure reflection model and a significant Fe K{alpha} line at rest-frame energy of 6.4keV.
- ID:
- ivo://CDS.VizieR/J/ApJS/217/21
- Title:
- XMM-Newton survey of local OVII absorbers
- Short Name:
- J/ApJS/217/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Highly ionized, z=0 metal absorption lines detected in the X-ray spectra of background active galactic nuclei (AGNs) provide an effective method to probe the hot (T~10^6^K) gas and its metal content in and around the Milky Way. We present an all-sky survey of the K_{alpha}_ transition of the local OVII absorption lines obtained by Voigt-profile fitting archival XMM-Newton observations. A total of 43 AGNs were selected, among which 12 are BL Lac-type AGNs, and the rest are Seyfert 1 galaxies. At above the 3{sigma} level the local OVII absorption lines were detected in 21 AGNs, among which 7 were newly discovered in this work. The sky covering fraction, defined as the ratio between the number of detections and the sample size, increases from about 40% for all targets to 100% for the brightest targets, suggesting a uniform distribution of the OVII absorbers. We correlate the line equivalent width with the Galactic coordinates and do not find any strong correlations between these quantities. Some AGNs have warm absorbers that may complicate the analysis of the local X-ray absorber since the recession velocity can be compensated by the outflow velocity, especially for nearby targets. We discuss the potential impact of warm absorbers on our analysis.
- ID:
- ivo://CDS.VizieR/J/A+A/457/501
- Title:
- XMM-Newton survey of the ELAIS-S1 field
- Short Name:
- J/A+A/457/501
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The formation and evolution of cosmic structures can be probed by studying the evolution of the luminosity function of the Active Galactic Nuclei (AGNs), galaxies and clusters of galaxies and of the clustering of the X-ray active Universe, compared to the IR-UV active Universe. To this purpose, we have surveyed with XMM-Newton the central ~0.6{deg}^2^ region of the ELAIS-S1 field down to flux limits of ~5.5x10^-16^erg/cm^2^/s (0.5-2keV, soft band, S), ~2x10^-15^erg/cm^2^/s (2-10keV, hard band, H), and ~4x10^-15^erg/cm^2^/s (5-10keV, ultra hard band, HH). We present here the analysis of the XMM-Newton observations, the number counts in different energy bands and the clustering properties of the X-ray sources.
- ID:
- ivo://CDS.VizieR/J/A+A/488/417
- Title:
- XMM-Newton survey of the ELAIS-S1 field. II.
- Short Name:
- J/A+A/488/417
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical identifications and a multi-band catalogue of a sample of 478 X-ray sources detected in the XMM-Newton and Chandra surveys of the central 0.6deg^2^ of the ELAIS-S1 field. The most likely optical/infrared counterpart of each X-ray source was identified using the chance coincidence probability in the R and IRAC 3.6 micron bands.This method was complemented by the precise positions obtained through Chandra observations. We were able to associate a counterpart to each X-ray source in the catalogue. Approximately 94% of them are detected in the R band, while the remaining are blank fields in the optical down to R~24.5, but have a near-infrared counterpart detected by IRAC within 6 arcsec from the XMM-Newton centroid. The multi-band catalogue, produced using the positions of the identified optical counterparts, contains photometry in ten photometric bands, from B to the MIPS 24 micron band. The spectroscopic follow-up allowed us to determine the redshift and classification for 237 sources (~50% of the sample) brighter than R=24. The spectroscopic redshifts were complemented by reliable photometric redshifts for 68 sources. We classified 47% of the sources with spectroscopic redshift as broad-line active galactic nuclei (BL AGNs) with z=0.1-3.5, while sources without broad-lines (NOT BL AGNs) are about 46% of the spectroscopic sample and are found up to z=2.6. The remaining fraction is represented by extended X-ray sources and stars. We spectroscopically identified 11 type 2 QSOs among the sources with X/O>8, with redshift between 0.9 and 2.6, high 2-10keV luminosity (logLx>=43.8erg/s) and hard X-ray colors suggesting large absorbing columns at the rest frame (logN_H_ up to 23.6cm^-2^). BL AGNs show on average blue optical-to-near-infrared colors, softer X-ray colors and X-ray-to-optical colors typical of optically selected AGNs. Conversely, narrow-line sources show redder optical colors, harder X-ray flux ratio and span a wider range of X-ray-to-optical colors. On average the Spectral Energy Distributions (SEDs) of high-luminosity BL AGNs resemble the power-law typical of unobscured AGNs. The SEDs of NOT BLAGNs are dominated by the galaxy emission in the optical/near-infrared, and show a rise in the mid-infrared which suggests the presence of an obscured active nucleus. We study the infrared-to-optical colors and near-infrared SEDs to infer the properties of the AGN host galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/557/A123
- Title:
- XMM-Newton Wide Angle Survey (XWAS)
- Short Name:
- J/A+A/557/A123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the XMM-Newton Wide Angle Survey (XWAS), a new catalogue of almost a thousand X-ray sources spectroscopically identified through optical observations. Sources lie in high-galactic latitude (|b|>20deg) XMM-Newton fields mainly in the southern hemisphere. A sample of X-ray sources detected in 68 XMM-Newton pointed observations was selected for optical multi-fibre spectroscopy. Optical counterparts and corresponding photometry of the X-ray sources were obtained from the SuperCOSMOS Sky Survey. Candidates for spectroscopy were initially selected with magnitudes down to R~21, with preference for X-ray sources having a flux F_0.5-4.5keV_>=10^-14^erg/s/cm2. Optical spectroscopic observations were made using the Two Degree Field of the Anglo Australian Telescope, and the resulting spectra were classified based on optical emission lines. We have identified through optical spectroscopy 940 X-ray sources over {Omega}~11.8deg^2^ of the sky. Source populations in our sample can be summarised as 65% broad line active galactic nuclei (BLAGN), 16% narrow emission line galaxies (NELGs), 6% absorption line galaxies (ALGs) and 13% stars. An active nucleus is also likely to be present in the large majority of the X-ray sources spectroscopically classified as NELGs or ALGs.
