- ID:
- ivo://CDS.VizieR/J/ApJ/814/11
- Title:
- Obscured AGNs from XMM-Newton and AKARI
- Short Name:
- J/ApJ/814/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a new sample of obscured active galactic nuclei (AGNs) selected from the XMM-Newton serendipitous source and AKARI point-source catalogs. We match X-ray sources with infrared (18 and 90{mu}m) sources located at |b|>10{deg} to create a sample consisting of 173 objects. Their optical classifications and absorption column densities measured by X-ray spectra are compiled and study efficient selection criteria to find obscured AGNs. We apply the criteria (1) X-ray hardness ratio defined by using the 2-4.5keV and 4.5-12keV bands >-0.1 and (2) EPIC-PN count rate (CR) in the 0.2-12keV to infrared flux ratio CR/F_90_<0.1 or CR/F_18_<1 where F_18_ and F_90_ are infrared fluxes at 18 and 90{mu}m in Jy, respectively, to search for obscured AGNs. X-ray spectra of 48 candidates, for which no X-ray results have been published, are analyzed and X-ray evidence for the presence of obscured AGNs such as a convex shape X-ray spectrum indicative of absorption of N_H_~10^22-24^/cm2, a very flat continuum, or a strong Fe-K emission line with an equivalent width of >700eV is found in 26 objects. Six of them are classified as Compton-thick AGNs, and four are represented by either Compton-thin or Compton-thick spectral models. The success rate of finding obscured AGNs combining our analysis and the literature is 92% if the 18{mu}m condition is used. Of the 26 objects, 4 are optically classified as an HII nucleus and are new "elusive AGNs" in which star formation activity likely overwhelms AGN emission in the optical and infrared bands.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/556/A114
- Title:
- Obscured AGNs in XMM deep survey in CDF-S
- Short Name:
- J/A+A/556/A114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accretion onto supermassive black holes is believed to occur mostly in obscured active galactic nuclei (AGN). Such objects are proving rather elusive in surveys of distant galaxies, including those at X-ray energies. Our main goal is to determine whether the revised IRAC criteria of Donley et al. (2012ApJ...748..142D; objects with an infrared (IR) power-law spectral shape), are effective at selecting X-ray type-2 AGN (i.e., absorbed N_H_>10^22^cm^-2^). We present the results from the X-ray spectral analysis of 147 AGN selected by cross-correlating the highest spectral quality ultra-deep XMM-Newton and the Spitzer/IRAC catalogues in the Chandra Deep Field South. Consequently it is biased towards sources with high S/N X-ray spectra. In order to measure the amount of intrinsic absorption in these sources, we adopt a simple X-ray spectral model that includes a power-law modified by intrinsic absorption at the redshift of each source and a possible soft X-ray component.
- ID:
- ivo://CDS.VizieR/J/ApJ/687/471
- Title:
- Observational comparison between ULXs and XRBs
- Short Name:
- J/ApJ/687/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To test the idea that ultraluminous X-ray sources (ULXs) in external galaxies represent a class of accreting intermediate-mass black holes (IMBHs), we have undertaken a program to identify ULXs and a lower luminosity X-ray comparison sample with the highest quality data in the Chandra archive. We establish as a general property of ULXs that the most X-ray-luminous objects possess the flattest X-ray spectra (in the Chandra bandpass). No prior sample studies have established the general hardening of ULX spectra with luminosity. This hardening occurs at the highest luminosities (absorbed luminosity >=5x10^39^erg/s) and is in line with recent models arguing that ULXs are actually stellar mass black holes. From spectral modeling, we show that the evidence originally taken to mean that ULXs are IMBHs - i.e., the "simple IMBH model" - is nowhere near as compelling when a large sample of ULXs is looked at properly. During the last couple of years, XMM-Newton spectroscopy of ULXs has to a large extent begun to negate the simple IMBH model based on fewer objects. We confirm and expand these results, which validates the XMM-Newton work in a broader sense with independent X-ray data.
- ID:
- ivo://CDS.VizieR/VI/117
- Title:
- Observation Log from ASCA
- Short Name:
- VI/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- ASCA (Advanced Satellite for Cosmology and Astrophysics) is the fourth Japanese X-ray astronomy satellite launched on February 20, 1993 (see Tanaka et al., 1994PASJ...46L..37T) The collaboration between Japanese and US scientists has been carried out in the developments of the X-ray telescopes, the X-ray CCD cameras, and software. ASCA observed more than 3000 targets before stopping scientific observations as a consequence of a huge solar flare occured in mid July, 2000. ISAS continued monitoring operation until the ASCA reentered the atmosphere on March 2, 2001. Scientific instrumentation of ASCA consists of four X-ray telescopes and corresponding focal plane detectors. Focal plane detectors are two X-ray CCD cameras (SIS: Solid-state Imaging Spectrometers) and two Gas Imaging Spectrometers (GIS). With these detectors, ASCA covers the energy range of 0.5-10 keV. This catalogue is a copy of the ASCA Observation log from the Data ARchive and Transmission System (DARTS), provided by the PLAIN center at ISAS/JAXA, Japan. All the ASCA data have been public. The data is archived in a target-oriented (strictly speaking, observation-oriented) structure, i.e., all the data produced from an observation is put into a directory --- although some exceptions exist for observations in very early epoch. Each dataset includes telemetry data, data products (event files, images, energy spectra, light curves, etc.), and calibration data. ISAS provides the telemetry and calibration data, and ASCA data processing center in ADF (Astrophysics Data Facility) at NASA/GSFC reproduces the data products.
- ID:
- ivo://CDS.VizieR/J/MNRAS/453/2682
- Title:
- Observation & modelling for radio-loud AGN
- Short Name:
- J/MNRAS/453/2682
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interactions between radio-loud AGN and their environments play an important role in galaxy and cluster evolution. Recent work has demonstrated fundamental differences between high- and low-excitation radio galaxies (HERGs and LERGs), and shown that they may have different relationships with their environments. In the Chandra Large Project ERA (Environments of Radio-loud AGN), we made the first systematic X-ray environmental study of the cluster environments of radio galaxies at a single epoch (z~0.5), and found tentative evidence for a correlation between radio luminosity and cluster X-ray luminosity. We also found that this relationship appeared to be driven by the LERG subpopulation. We have now repeated the analysis with a low-redshift sample (z~0.1), and found strong correlations between radio luminosity and environment richness and between radio luminosity and central density for the LERGs but not for the HERGs. These results are consistent with models in which the HERGs are fuelled from accretion discs maintained from local reservoirs of gas, while LERGs are fuelled more directly by gas ingested from the intracluster medium. Comparing the samples, we found that although the maximum environment richness of the HERG environments is similar in both samples, there are poorer HERG environments in the z~0.1 sample than in the z~0.5 sample. We have therefore tentative evidence of evolution of the HERG environments. We found no differences between the LERG subsamples for the two epochs, as would be expected if radio and cluster luminosities are related.
- ID:
- ivo://CDS.VizieR/J/A+A/458/245
- Title:
- Obs. of 2 Unidentified Gamma-ray Sources
- Short Name:
- J/A+A/458/245
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The systematic X-ray and optical coverage of low-latitude unidentified gamma-ray sources, aiming at sources with high X-ray/optical flux ratio, seems one of the most promising ways to spot INS candidate counterparts. We have focussed on two middle-latitude, probably galactic, EGRET sources: 3EG J0616-3310 and 3EG J1249-8330. Here we report on X-ray observations of the two gamma-ray error boxes performed with XMM-Newton and on their optical follow-up carried on with the Wide Field Imager at the ESO/MPG 2.2m telescope. Less than half of the ~300 sources detected by the X-ray coverage have no optical counterparts. Among those, we have selected few interesting sources with f_X_/f_opt_>100, which we consider promising INS candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/499/129
- Title:
- Old MS stars in young moving groups
- Short Name:
- J/A+A/499/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The associations and moving groups of young stars are excellent laboratories to investigate the stellar formation in the solar neighborhood. Past results confirmed that a non-negligible fraction of old main-sequence stars is present in the lists of members of the young stellar kinematic groups. A detailed study on the properties of these samples is needed to separate the young stars from old main-sequence stars with similar space motion, in order to identify the origin of these structures. Our intention is to characterize the sample of stars members of the young moving groups and determine their age distribution to quantify the contamination by old main-sequence stars, in particular, in the Local Association. For our study, we used the sample of stars possible members of the young (~10-650Myr) moving groups from the literature. In order to determine the age of the stars, we used several age indicators well suited for young main sequence stars: X-ray fluxes from the Rosat All-sky Survey database, photometric data from the Tycho-2, Hipparcos, and 2MASS database. We also used spectroscopic data, in particular the equivalent width of the lithium line LiI lambda6707.8{AA} and Halpha, to constrain the range of ages of the stars in the sample. The combination of photometric and spectroscopic data permitted to separate the young stars (10-650Myr) from the old (>1Gyr) field ones. In particular, the member list of the Local Association results contaminated by ~30% of old field stars. This value must be considered as the contamination of our particular sample, not to the entire Local Association. In other young moving groups it is more difficult to estimate the fraction of old stars in the samples of possible members. However, the X-ray emission level can help to separate, at least, two age populations: stars with 200Myr and stars older than this. The samples of candidates of the classical moving groups contain a non-negligible amount of old field stars that should be considered in studies on the stellar birthrate in the solar neighborhood. Our results agree with the scenario of the moving groups being composed by groups of young stars formed in a recent star formation episode and old field stars with similar space motion. Only combining both X-ray and optical spectroscopic data it is possible to distinguish between the two age populations.
- ID:
- ivo://CDS.VizieR/J/A+A/400/521
- Title:
- Omega Cen XMM observations
- Short Name:
- J/A+A/400/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the globular cluster Omega Cen (NGC 5139) with XMM-Newton on August 13th, 2001. The observation lasted 37ks and was performed with a medium filter. These tables list all the detected sources, and the spectral properties of selected sources within the field of view. For each source, we indicate its position, count rate, correlation with previous X-ray observation, and associated errors. For selected sources we also indicate its flux.
- ID:
- ivo://CDS.VizieR/J/AJ/126/119
- Title:
- Optical and radio data for rich Abell clusters
- Short Name:
- J/AJ/126/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical observations and radio continuum imaging data for a sample of rich, X-ray-bright Abell clusters at intermediate (z~0.2) redshifts. We find that the radio galaxy population varies substantially from cluster to cluster within this homogeneous sample. The spatial distribution of the high-luminosity radio galaxies (HLRGs; L1.4>10^23^W/Hz) is very different from the low-luminosity radio galaxies (LLRGs; L1.4<=10^22.75^W/Hz), with the LLRGs displaying a flat spatial distribution in contrast to the centrally peaked HLRGs. A color-morphology classification shows that the HLRGs are composed primarily of galaxies with old stellar populations, whereas the LLRGs have a much more diverse composition. We do not see a correlation between the cluster radio fraction and cluster blue fraction. However, there is a moderate anticorrelation with richness, suggesting that a rich cluster is less likely to have radio-bright galaxies, whether the radio emission is due to active galactic nuclei or star formation.
- ID:
- ivo://CDS.VizieR/J/A+A/565/A72
- Title:
- Optical and X-ray light curves of BAT6 sample
- Short Name:
- J/A+A/565/A72
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the rest-frame light curves in the optical and X-ray bands of an unbiased and complete sample of the Swift long gamma-ray bursts (GRBs), namely, the BAT6 sample. The unbiased BAT6 sample (consisting of 58 events) has the highest level of completeness in redshift (~95%), allowing us to compute the rest-frame X-ray and optical light curves for 55 and 47 objects, respectively. We compute the X-ray and optical luminosities, which accounte for any possible source of absorption (Galactic and intrinsic) that could affect the observed fluxes in these two bands.
