We report a deep X-ray survey of the young (~140Myr), rich open cluster NGC 2516 obtained with the EPIC camera on board the XMM-Newton satellite. By combining data from six observations, a high sensitivity, greater than a factor of 5 with respect to recent Chandra observations, has been achieved. Kaplan-Meier estimators of the cumulative X-ray luminosity distribution are built, statistically corrected for non members contaminants and compared to those of the nearly coeval Pleiades. The EPIC spectra of the X-ray brightest stars are fitted using optically thin model plasma with one or two thermal components. We detected 431 X-ray sources and 234 of them have as optical counterparts cluster stars spanning the entire NGC 2516 Main Sequence.
We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on ~4/5 of our sight lines. The temperature is fairly uniform (median = 2.22x10^6^K, interquartile range = 0.63x10^6^K), while the emission measure and intrinsic 0.5-2.0keV surface brightness vary by over an order of magnitude (~(0.4-7)x10^-3^cm^-6^pc and ~(0.5-7)x10^-12^erg/cm2/s deg^-2^, respectively, with median detections of 1.9x10^-3^cm^-6^pc and 1.5x10^-12^erg/cm2/s deg^-2^, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.
We present an X-ray spectral analysis of 126 galaxies of the 12um galaxy sample (Rush et al. 1993, Cat. VII/157). By studying this sample at X-ray wavelengths, we aim to determine the intrinsic power, continuum shape and obscuration level in these sources. We improve upon previous works by the use of superior data in the form of higher signal-to-noise ratio spectra, finer spectral resolution and a broader bandpass from XMM-Newton. We pay particular attention to Compton thick active galactic nucleus (AGN) with the help of new spectral fitting models that we have produced, which are based on Monte Carlo simulations of X-ray radiative transfer, using both a spherical and torus geometry, and taking into account Compton scattering and iron fluorescence.
The XMM-OM Serendipitous Ultra-violet Source Survey (SUSS) is a
catalog of UV sources detected serendipitously by the Optical Monitor (OM)
on-board the European Space Agency's (ESA's) XMM-Newton observatory. It has
been created at the University College London's (UCL's) Mullard Space Science
Laboratory (MSSL) on behalf of ESA and is a partner resource to the 2XMM
serendipitous X-ray source catalogue.
The catalog contains source detections drawn from 2,417 XMM-OM observations in
up to three broad band UV filters made between 2000 February 24 and 2007 March
29. All datasets included were publicly available by 2007 May 01 but note
that, due to screening criteria, not all public observations are included
in this catalog. Taking account of substantial overlaps between observations,
the net sky area covered independently is 29 - 54 square degreees, depending
on UV filter. The primary content of the catalog is filter-dependent source
positions and magnitudes, and these are accompanied by profile diagnostics
and variability statistics.
The XMM-OM SUSS catalog contains 753,578 UV source detections above a
signal-to-noise threshold limit of 3-sigma which relate to 624,049 unique
objects. A significant fraction of sources (12% - UVW2, 11% - UVM2, 11.% -
UVW1) are visited more than once during XMM operation, and a large fraction
of sources (38% - UVW2, 23% - UVM2, 22% - UVW1) are observed more than once
per filter during an individual visit. UVW2, UVM2 and UVW1 refer to the filter
bandpasses defined in the Source Properties: Filter Set section of the MSSL
documentation for this catalog:
<a href="http://www.mssl.ucl.ac.uk/~mds/XMM-OM-SUSS/SourcePropertiesFilters.shtml">http://www.mssl.ucl.ac.uk/~mds/XMM-OM-SUSS/SourcePropertiesFilters.shtml</a>.
Consequently, the scope for science based on temporal source variability on
timescales of hours to years is broad.
The positional accuracy of the catalog detections is typically 1.0 arcsec
(1-sigma confidence radius) with a median positional error of 0.67 arcsec. The
median AB magnitude of the catalog detections in the three UV bands is 19.56
(UVW2), 20.23 (UVM2) and 20.69 (UVW1). 20% of sources have AB magnitudes
fainter than 20.28 (UVW2), 20.97 (UVM2) and 21.54 (UVW1).
As part of quality evaluation for the catalog, each field has been tested
for astrometric accuracy and visually screened for cosmetic problems,
compromising aspect anomalies, stray light, large extended sources and
telemetry dropouts. Observations affected by these issues (11.2%) have been
removed from the catalog sample. Furthermore, 2% of all observations were
selected at random where each source in this sample was tested for falsehood,
spuriousness and accuracy of quality flagging. The results of this detailed
screening are included in the full documentation.
The processing used to generate the catalog is based on the SAS8.0 pipeline
developed for the pipeline reduction of all XMM observations. This version
includes a number of significant improvements over the previous data
processing system (as used by the SSC in routine processing of XMM-Newton
data on behalf of ESA). These improvements include a more robust detection
scheme for sources close to the limit of sky background, refined quality
flagging and a higher success rate (90%) for refined aspect corrections.
Ultraluminous X-ray sources (ULXs) are some of the most enigmatic X-ray bright sources known to date. It is generally accepted that they cannot host black holes as large as those associated with active galaxies, but they appear to be significantly more luminous than their better understood Galactic X-ray binary (XRB) cousins, while displaying an intriguing combination of differences and similarities with them. Through studying large, representative samples of these sources we may hope to enhance our understanding of them. To this end, we derive a large catalogue of 650 X-ray detections of 470 ULX candidates, located in 238 nearby galaxies, by cross-correlating the 2XMM Serendipitous Survey with the Third Reference Catalogue of Bright Galaxies.
In this second paper of the series, we focus on the X-ray properties of the OB star population of NGC 6231. As a tool for our analysis, we performed a literature-based census of the OB stars in the field of view. More than one hundred objects are found, among which 30% can be associated with an X-ray source. All the O-type stars are detected in the X-ray domain as soft and reasonably strong emitters. [...] Among B-type stars, the detection rate is only about 25% in the sub-type range B0-B4 and remains mostly uniform throughout the different sub-populations while it drops significantly at later sub-types. The associated X-ray spectra are harder than those of O-type stars. Our analysis points towards the emission being rather associated with a physical (in a multiple system) PMS companion. However, we still observe a correlation between the bolometric luminosity of the B stars and the measured X-ray luminosity. [...]
We present the results of an X-ray campaign towards the young open cluster NGC 6231. The XMM-Newton observations, of a total duration of about 180 ks, reveals that NGC 6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources are detected in the present field of view, centered on the cluster core. The limiting sensitivity of our survey is approximately 610^-15^erg/s/cm^2^ but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogues, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 2.5 or 3-arcsec according to the optical/IR catalogue used. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin^2^ and a core radius close to 3.1-arcmin. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC 6231. Finally, beside a few bright but soft objects -- corresponding to the early-type stars of the cluster -- most of the sources are relatively faint (~5x10^-15^erg/s/cm^2^) with an energy distribution peaked around 1.0-2.0keV.
Cluster environments at z<0.5 were found to increase the gas metallicities of galaxies which enter inner regions of the clusters where the density of the intracluster medium is high enough to remove their hot halo gas by ram-pressure stripping effects and to stop the inflow of pristine gas. To extend these studies to z>1, the most massive clusters known at these redshifts are the sites where these environmental effects should be more pronounced and more easily observed with present day telescopes. We explore the massive cluster XMMXCSJ2215.9-1738 at z~1.5 with KMOS spectroscopy of Halpha and [NII] covering a region that corresponds to about one virial radius. Using published spectroscopic redshifts of 108 galaxies in and around the cluster we computed the location of galaxies in the projected velocity-versus-position phase-space to separate our cluster sample into a virialized region of objects accreted longer ago (roughly inside half R200) and a region of infalling galaxies. We measured oxygen abundances for ten cluster galaxies with detected [NII] lines in the individual galaxy spectra and compared the mass-metallicity relation of the galaxies inside half R200 with the infalling galaxies and a field sample at similar redshifts. We find that the oxygen abundances of individual z~1.5 star-forming cluster galaxies inside half R200 are comparable, at the respective stellar mass, to the higher local SDSS metallicity values. We compare our measurements with a field galaxy sample from the KMOS3D survey at similar redshifts. We find that the [NII]/H{alpha} line ratios inside half R200 are higher by 0.2dex and that the resultant metallicities of the galaxies in the inner part of the cluster are higher by about 0.1dex, at a given mass, than the metallicities of infalling galaxies and of field galaxies at z~1.5. The enhanced metallicities of cluster galaxies at z~1.5 inside 0.5 R200 indicate that the density of the intracluster medium in this massive cluster becomes high enough toward the cluster center such that the ram pressure exceeds the restoring pressure of the hot gas reservoir of cluster galaxies. This can remove the gas reservoir and initiate quenching; although the galaxies continue to form stars, albeit at slightly lower rates, using the available cold gas in the disk which is not stripped.
We report the scaling relations derived by fitting the X-ray parameters determined from analyzing the XMM-Newton observations of 120 galaxy clusters in the Planck Early Sunyaev-Zel'dovich (SZ) sample spanning the redshift range of 0.059<z<0.546. We find that the slopes of all the investigated scaling relations significantly deviate from the self-similar predictions, if self-similar redshift evolution is assumed. When the redshift evolution is left free to vary, the derived slopes are more in agreement with the self-similar predictions. Relaxed clusters have on average ~30% higher X-ray luminosity than disturbed clusters at a given mass, a difference that, depending on the relative fraction of relaxed and disturbed clusters in the samples (e.g., SZ vs. X-ray selected), has a strong impact on the normalization obtained in different studies. Using the core-excised cluster luminosities reduces the scatter and brings into better agreement the L-M_tot_ and L-T relations determined for different samples. M_tot_-T, M_tot_-YX, and M_tot_-M_gas_ relations show little dependence on the dynamical state of the clusters, but the normalizations of these relations may depend on the mass range investigated. Although most of the clusters investigated in this work reside at relatively low redshift, the fits prefer values of {gamma}, the parameter accounting for the redshift evolution, different from the self-similar predictions. This suggests an evolution (<2{sigma} level, with the exception of the M_tot_-T relation) of the scaling relations. For the first time, we find significant evolution (>3{sigma}) of the M_tot_-T relation, pointing to an increase of the kinetic-to-thermal energy ratio with redshift. This is consistent with a scenario in which higher-redshift clusters are on average more disturbed than their lower-redshift counterparts.
