R. Della Ceca

The XMM-Newton serendipitous survey: V - The Second XMM-Newton serendipitous source catalogue

Aims. Pointed observations with XMM-Newton provide the basis for creating catalogues of X-ray sources detected serendipitously in each field. This paper describes the creation and characteristics of the 2XMM catalogue. Methods. The 2XMM catalogue has been compiled from a new processing of the XMM-Newton EPIC camera data. The main features of the processing pipeline are described in detail. Results. The catalogue, the largest ever made at X-ray wavelengths, contains 246 897 detections drawn from 3491 public XMM-Newton observations over a 7-year interval, which relate to 191 870 unique sources. The catalogue fields cover a sky area of more than 500 deg(2). The non-overlapping sky area is similar to 360 deg(2) (similar to 1% of the sky) as many regions of the sky are observed more than once by XMM-Newton. The catalogue probes a large sky area at the flux limit where the bulk of the objects that contribute to the X-ray background lie and provides a major resource for generating large, well-defined X-ray selected source samples, studying the X-ray source population and identifying rare object types. The main characteristics of the catalogue are presented, including its photometric and astrometric properties

Extremely compact massive galaxies at z ∼ 1.4

The optical rest-frame sizes of 10 of the most massive (∼5 × 10 11 h −2 M� ) galaxies found in the near-infrared MUNICS survey at 1.2 < z < 1.7 are analysed. Sizes are estimated in both the J and Kfilters. These massive galaxies are at least a factor of 4 +1.9 (±1σ ) smaller in the rest-frame V-band than local counterparts of the same stellar mass. Consequently, the stellar mass density of these objects is (at least) 60 times larger than that of massive ellipticals today. Although the stellar populations of these objects are passively fading, their structural properties are rapidly changing since that redshift. This observational fact disagrees with a scenario where the more massive and passive galaxies are fully assembled at z ∼ 1.4 (i.e. a monolithic scenario) and points towards a dry merger scenario as the responsible mechanism for the subsequent evolution of these galaxies.

The Kormendy relation of massive elliptical galaxies at z∼ 1.5: evidence for size evolution

We present the morphological analysis based on HST-NIC2 (0.075 arcsec pixel -1 ) images in the F160W filter of a sample of nine massive field (>10 11 M ⊙ ) galaxies spectroscopically classified as early-types at 1.2 < z < 1.7. Our analysis shows that all of them are bulge-dominated systems. In particular, six of them are well fitted by a de Vaucouleurs profile (n = 4) suggesting that they can be considered pure elliptical galaxies. The remaining three galaxies are better fitted by a Sersic profile with index 1.9 < n fit < 2.3 suggesting that a disc-like component could contribute up to 30 per cent to the total light of these galaxies. We derived the effective radius R e and the mean surface brightness (SB) (μ) e within R e of our galaxies and we compared them with those of early-types at lower redshifts. We find that the SB (μ) e of our galaxies should get fainter by 2.5 mag from z ∼ 1.5 to ∼0 to match the SB of the local ellipticals with comparable R e , that is, the local Kormendy relation. Luminosity evolution without morphological changes can only explain half of this effect, as the maximum dimming expected for an elliptical galaxy is ∼ 1.6 mag in this redshift range. Thus, other parameters, possibly structural, may undergo evolution and play an important role in reconciling models and observations. Hypothesizing an evolution of the effective radius of galaxies we find that R e should increase by a factor of 1.5 from z ∼ 1.5 to ∼0.

An XMM-Newton hard X-ray survey of ultraluminous infrared galaxies

XMM-Newton observations of 10 ULIRGs are reported. The aim is to investigate in hard X-rays a complete ULIRG sample selected from the bright IRAS 60

The XMM-Newton serendipitous survey - VII. The third XMM-Newton serendipitous source catalogue

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Arp 299: A Second Merging System with Two Active Nuclei?

m catalogue. All sources are detected in X-rays, 5 of which for the first time. These observations confirm that ULIRGs are intrinsically faint X-rays sources, their observed X-ray luminosities being typically L(2-10 keV) 1E45 erg/s. In all sources we find evidence for thermal emission from hot plasma with kT~0.7keV, dominating the X-ray spectra below 1keV, and likely associated with a nuclear or circumnuclear starburst. This thermal emission appears uncorrelated with the FIR luminosity, suggesting that,in addition to the ongoing rate of star formation, other parameters may also affect it. The soft X-ray emission appears to be extended on a scale of ~30kpc for Mkn231 and IRAS19254-7245, possible evidence of galactic superwinds. In these 2 sources, in IRAS20551-4250 and IRAS23128-5919 we find evidence for the presence of hidden AGNs, while a minor AGN contribution may be suspected also in IRAS20100-4156. In particular, we have detected a strong Fe line at 6.4keV in the spectrum of IRAS19254-7245 and a weaker one in Mkn231, suggestive of deeply buried AGNs. For the other sources, the X-ray luminosities and spectral shapes are consistent with hot thermal plasma and X-ray binary emissions of mainly starburst origin. We find that the 2-10keV luminosities in these sources, most likely due to high-mass X-ray binaries, are correlated with L_FIR: both luminosities are good indicators of the current global SFR in the galaxy. The composite nature of ULIRGs is then confirmed, with hints for a predominance of the starburst over the AGN phenomenon in these objects.

2-10 keV luminosity of high-mass binaries as a gauge of ongoing star-formation rate

© ESO, 2016.Context. Thanks to the large collecting area (3 × ∼1500 cm2 at 1.5 keV) and wide field of view (30′ across in full field mode) of the X-ray cameras on board the European Space Agency X-ray observatory XMM-Newton, each individual pointing can result in the detection of up to several hundred X-ray sources, most of which are newly discovered objects. Since XMM-Newton has now been in orbit for more than 15 yr, hundreds of thousands of sources have been detected. Aims. Recently, many improvements in the XMM-Newton data reduction algorithms have been made. These include enhanced source characterisation and reduced spurious source detections, refined astrometric precision of sources, greater net sensitivity for source detection, and the extraction of spectra and time series for fainter sources, both with better signal-to-noise. Thanks to these enhancements, the quality of the catalogue products has been much improved over earlier catalogues. Furthermore, almost 50% more observations are in the public domain compared to 2XMMi-DR3, allowing the XMM-Newton Survey Science Centre to produce a much larger and better quality X-ray source catalogue. Methods. The XMM-Newton Survey Science Centre has developed a pipeline to reduce the XMM-Newton data automatically. Using the latest version of this pipeline, along with better calibration, a new version of the catalogue has been produced, using XMM-Newton X-ray observations made public on or before 2013 December 31. Manual screening of all of the X-ray detections ensures the highest data quality. This catalogue is known as 3XMM. Results. In the latest release of the 3XMM catalogue, 3XMM-DR5, there are 565 962 X-ray detections comprising 396 910 unique X-ray sources. Spectra and lightcurves are provided for the 133 000 brightest sources. For all detections, the positions on the sky, a measure of the quality of the detection, and an evaluation of the X-ray variability is provided, along with the fluxes and count rates in 7 X-ray energy bands, the total 0.2-12 keV band counts, and four hardness ratios. With the aim of identifying the detections, a cross correlation with 228 catalogues of sources detected in all wavebands is also provided for each X-ray detection. Conclusions. 3XMM-DR5 is the largest X-ray source catalogue ever produced. Thanks to the large array of data products associated with each detection and each source, it is an excellent resource for finding new and extreme objects.

The XMM-Newton serendipitous survey - IV. Optical identification of the XMM-Newton medium sensitivity survey (XMS)

Recent BeppoSAX observations of Arp 299, a powerful far-IR merging starburst system composed of IC 694 and NGC 3690, clearly unveiled for the first time in this system the presence of a strongly absorbed active galactic nucleus (AGN). However, the system was not spatially resolved by BeppoSAX. Here we present the analysis of archival Chandra and (for the first time) XMM-Newton observations, which allow us to disentangle the X-ray emission of the two galaxies. The detection of a strong 6.4 keV line in NGC 3690 clearly demonstrates the existence of an AGN in this galaxy, while the presence of a strong 6.7 keV Fe-Kα line in the spectrum of IC 694 suggests that this nucleus might also harbor an AGN. This would be the second discovery of two AGNs in a merging system after NGC 6240.

XMM-Newton observations reveal AGN in apparently normal galaxies

Based on recent work on spectral decomposition of the emission of star-forming galaxies, we assess whether the inte- grated 2−10 keV emission from high-mass X-ray binaries (HMXBs), L HMXB−10 , can be used as a reliable estimator of ongoing star formation rate (SFR). Using a sample of 46 local (z < 0.1) star-forming galaxies, and spectral modeling of ASCA, BeppoSAX, and XMM-Newton data, we demonstrate the existence of a linear SFR -L HMXB−10 relation which holds over ∼5 decades in X-ray luminosity and SFR. The total 2−10 keV luminosity is not a precise SFR indicator because at low SFR (i.e., in normal and moderately-starbursting galaxies) it is substantially affected by the emission of low-mass X-ray binaries, which do not trace the current SFR due to their long evolution lifetimes, while at very high SFR (i.e., for very luminous FIR-selected galaxies) it is frequently affected by the presence of strongly obscured AGNs. The availability of purely SB-powered galaxies - whose 2−10 keV emission is mainly due to HMXBs - allows us to properly calibrate the SFR -L HMXB−10 relation. The SFR -L HMXB−10 relation holds also for distant (z ∼ 1) galaxies in the Hubble Deep Field North sample, for which we lack spectral information, but whose SFR can be estimated from deep radio data. If confirmed by more detailed observations, it may be possible to use the deduced relation to identify distant galaxies that are X-ray overluminous for their (independently estimated) SFR ,a nd are therefore likely to hide strongly absorbed AGNs.

The cosmological properties of AGN in the XMM-Newton Hard Bright Survey

Aims. X-ray sources at intermediate fluxes (a few x 10(-14) erg cm(-2) s(-1)) with a sky density of similar to 100 deg(-2) are responsible for a significant fraction of the cosmic X-ray background at various energies below 10 keV. The aim of this paper is to provide an unbiased and quantitative description of the X-ray source population at these fluxes and in various X-ray energy bands. Methods. We present the XMM-Newton Medium sensitivity Survey (XMS), including a total of 318 X-ray sources found among the serendipitous content of 25 XMM-Newton target fields. The XMS comprises four largely overlapping source samples selected at soft (0.5-2 keV), intermediate (0.5-4.5 keV), hard (2-10 keV) and ultra-hard (4.5-7.5 keV) bands, the first three of them being flux-limited. Results. We report on the optical identification of the XMS samples, complete to 85-95%. At the flux levels sampled by the XMS we find that the X-ray sky is largely dominated by Active Galactic Nuclei. The fraction of stars in soft X-ray selected samples is below 10%, and only a few per cent for hard selected samples. We find that the fraction of optically obscured objects in the AGN population stays constant at around 15-20% for soft and intermediate band selected X-ray sources, over 2 decades of flux. The fraction of obscured objects amongst the AGN population is larger (similar to 35-45%) in the hard or ultra-hard selected samples, and constant across a similarly wide flux range. The distribution in X-ray-to-optical flux ratio is a strong function of the selection band, with a larger fraction of sources with high values in hard selected samples. Sources with X-ray-to-optical flux ratios in excess of 10 are dominated by obscured AGN, but with a significant contribution from unobscured AGN.