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17841. X-ray+Radio sources in XBootes
ID:
ivo://CDS.VizieR/J/MNRAS/396/2011
Title:
X-ray+Radio sources in XBootes
Short Name:
J/MNRAS/396/2011
Date:
21 Oct 2021
Publisher:
CDS
Description:
With the goal of investigating the nature and the environment of the faint radio sources (at mJy level), here are presented results of X-ray identifications of Faint Imaging Radio Survey at Twenty centimetres (FIRST) in the 9deg^2^ Bootes field of the National Optical Astronomy Observatory (NOAO) Deep Wide Field Survey (NDWFS), using data from the Chandra XBootes survey. A total of 92 (10 per cent) FIRST radio sources are identified above the X-ray flux limit f_X_)(0.5-7)keV=8x10^-15^erg/s/cm^2^, and 79 optical counterparts are common to both the radio and X-ray sources. Spectroscopic identifications [obtained from the Sloan Digital Sky Survey (SDSS) survey] were available for 22 sources (27 per cent).
17842. X-rays and protostars in Trifid nebula
ID:
ivo://CDS.VizieR/J/ApJ/562/446
Title:
X-rays and protostars in Trifid nebula
Short Name:
J/ApJ/562/446
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Trifid Nebula is a young HII region, recently rediscovered as a "pre-Orion" star-forming region, containing protostars undergoing violent mass ejections visible in optical jets as seen in images from the Infrared Space Observatory and the Hubble Space Telescope. We report the first X-ray observations of the Trifid Nebula using ROSAT and ASCA. The ROSAT image shows a dozen X-ray sources, with the brightest X-ray source being the O7 star, HD 164492, which provides most of the ionization in the nebula. We also identify 85 T Tauri star and young, massive star candidates from near-infrared colors using the JHKs color-color diagram from the Two-Micron All-Sky Survey (2MASS). Ten X-ray sources have counterpart near-infrared sources. The 2MASS stars and X-ray sources suggest there are potentially numerous protostars in the young HII region of the Trifid. ASCA moderate-resolution spectroscopy of the brightest source shows hard emission up to 10keV with a clearly detected FeK line.
17843. X-Ray Selected BL Lac Objects Catalog
ID:
ivo://nasa.heasarc/xrayselbll
Title:
X-Ray Selected BL Lac Objects Catalog
Short Name:
XRAYSELBLL
Date:
18 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains a catalog of 312 X-ray selected BL Lacertae objects (XBLs), optically identified through the end of 2011. It contains the names from different surveys, equatorial coordinates, redshifts, multi-frequency flux values, and luminosities for each source. In the reference, the different characteristics of these XBLs are statistically investigated (redshift, radio/optical/X-ray luminosities, central black hole (BH) mass, synchrotron peak frequency, broadband spectral indices, optical flux variability). Their values were collected through an extensive bibliographic and database search or calculated by the author. The redshifts range from 0.031 to 0.702 with a maximum of the distribution at z = 0.223. The 1.4-GHz luminosities of XBLs log (nu * L<sub>nu</sub>) ~ 39 - 42 (in units of erg s<sup>-1</sup>), while the optical V and X-ray (0.1-2.4 keV) bands show log (nu * L<sub>nu</sub>) ~ 43 - 46 (same units). The XBL hosts are elliptical galaxies with effective radii r<sub>eff</sub> = 3.26 - 25.40 kpc and ellipticities e = 0.04 - 0.52. Their R-band absolute magnitudes M<sub>R</sub> range from -21.11 mag to -24.86 mag with a mean value of -22.83 mag. The V - R indices of the hosts range from 0.61 to 1.52 and reveal a fourth-degree polynomial relationship with z that enabled the author to evaluate the redshifts of five sources whose V - R indices were determined from the observations, but whose redshifts values are either not found or not confirmed. The XBL nuclei show a wider range of 7.31 mag for M<sub>R</sub>, with the highest luminosity corresponding to M<sub>R</sub> = -27.24 mag. The masses of the central BHs are found in the interval log M<sub>BH</sub> = 7.39 - 9.30 (in units of solar masses), with the maximum of the distribution at log M<sub>BH</sub>/M<sub>sun</sub> = 8.30. The synchrotron peak frequencies are spread over the range log nu<sub>peak</sub> = 14.56 - 19.18 Hz, with a peak of the distribution at log nu<sub>peak</sub> = 16.60 Hz. The broad-band radio-to-optical (alpha<sub>ro</sub>), optical-to-X-ray (alpha<sub>ox</sub>), and radio-to-X-ray (alpha<sub>rx</sub>) spectral indices are distributed in the intervals (0.17, 0.59), (0.56, 1.48), and (0.41, 0.75), respectively. In the optical energy range, the overall flux variability increases, on average, towards shorter wavelengths: Delta(m) = 1.22, 1.50, and 1.82 through the R, V, B bands of the Johnson-Cousins system, respectively. XBLs seem be optically less variable at intranight timescales compared to radio-selected BL Lacs (RBLs). This table was created by the HEASARC in June 2013 based on an electronic version of Table 2 from the reference paper which was obtained form the AJ web site. This is a service provided by NASA HEASARC .
17844. X-ray-selected galaxy clusters BCG offsets
ID:
ivo://CDS.VizieR/J/MNRAS/478/5473
Title:
X-ray-selected galaxy clusters BCG offsets
Short Name:
J/MNRAS/478/5473
Date:
08 Feb 2022 11:49:23
Publisher:
CDS
Description:
We used optical imaging and spectroscopic data to derive substructure estimates for local Universe (z<0.11) galaxy clusters from two different samples. The first was selected through the Sunyaev-Zel'dovich (SZ) effect by the Planck satellite, and the second is an X-ray-selected sample. In agreement to X-ray substructure estimates, we found that the SZ systems have a larger fraction of substructure than the X-ray clusters. We have also found evidence that the higher mass regime of the SZ clusters, compared to the X-ray sample, explains the larger fraction of disturbed objects in the Planck data. Although we detect a redshift evolution in the substructure fraction, it is not sufficient to explain the different results between the higher-z SZ sample and the X-ray one. We have also verified a good agreement (~60 per cent) between the optical and X-ray substructure estimates. However, the best level of agreement is given by the substructure classification given by measures based on the brightest cluster galaxy (BCG), either the BCG-X-ray centroid offset, or the magnitude gap between the first and second BCGs. We advocate the use of those two parameters as the most reliable and cheap way to assess cluster dynamical state. We recommend an offset cut-off ~0.01xR_500_ to separate relaxed and disturbed clusters. Regarding the magnitude gap, the separation can be done at {Delta}m_12_=1.0. The central galaxy paradigm (CGP) may not be valid for ~20 per cent of relaxed massive clusters. This fraction increases to ~60 per cent for disturbed systems.
17845. X-Ray Selected High-z AGN Catalog
ID:
ivo://nasa.heasarc/xshzagncxo
Title:
X-Ray Selected High-z AGN Catalog
Short Name:
XSHZAGNCXO
Date:
18 Apr 2025
Publisher:
NASA/GSFC HEASARC
Description:
This table contains the results from an analysis of the largest high-redshift (z &gt; 3) X-ray-selected active galactic nucleus (AGN) sample to date, combining the Chandra Cosmological Evolution Survey and Chandra Multi-wavelength Project surveys and doubling the previous samples. The sample comprises 209 X-ray-detected AGNs, over a wide range of rest-frame 2-10 keV luminosities log L&lt;sub&gt;X&lt;/sub&gt; = 43.3 - 46.0 erg/s. X-ray hardness ratios show that ~39 per cent of the sources are highly obscured, N&lt;sub&gt;H&lt;/sub&gt; &gt; 10&lt;sup&gt;22&lt;/sup&gt; cm&lt;sup&gt;-2&lt;/sup&gt;, in agreement with the ~37 per cent of type-2 AGNs found in this sample based on their optical classification. For ~26 per cent of objects, there are mismatched optical and X-ray classifications. Utilizing the 1/V&lt;sub&gt;max&lt;/sub&gt; method, the authors confirm that the comoving space density of all luminosity ranges of AGNs decreases with redshift above z &gt; 3 and up to z ~ 7. With a significant sample of AGNs (N = 27) at z &gt; 4, it is found that both source number counts in the 0.5-2 keV band and comoving space density are consistent with the expectation of a luminosity-dependent density evolution (LDDE) model at all redshifts, while they exclude the luminosity and density evolution (LADE) model. The measured comoving space density of type-1 and type-2 AGNs shows a constant ratio between the two types at z &gt; 3. These results for both AGN types at these redshifts are consistent with the expectations of LDDE model. The high-redshift AGN sample used in this work has been selected from the C-COSMOS X-ray catalog, combining the spectroscopic and photometric information available from the identification catalogue of X-ray C-COSMOS sources (Civano et al. 2011, ApJ, 741, 91; 2012, ApJS, 201, 30) and the ChaMP (Chandra Multi-wavelength Project) X-ray catalog using only the 323 ChaMP ObsIDs overlapping with Sloan Digital Sky Survey (SDSS; Richards et al. 2006, AJ, 131, 2766) DR5 imaging. This table was created by the HEASARC in March 2016 based on the &lt;a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/445/1430"&gt;CDS catalog J/MNRAS/445/1430&lt;/a&gt; file tablea1.dat. This is a service provided by NASA HEASARC .
17846. X-ray-selected normal galaxies
ID:
ivo://CDS.VizieR/J/MNRAS/360/782
Title:
X-ray-selected normal galaxies
Short Name:
J/MNRAS/360/782
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we estimate the local (z<0.22) X-ray luminosity function of 'normal' galaxies derived from the XMM-Newton Needles in the Haystack Survey. This is an on-going project that aims to identify X-ray-selected normal galaxies (i.e. non-AGN dominated) in the local Universe. We are using a total of 70 XMM-Newton fields covering an area of 11deg^2^ which overlap with the Sloan Digital Sky Survey Data Release 2. Normal galaxies are selected on the basis of their resolved optical light profile, their low X-ray-to-optical flux ratio [log(fx/fo)<-2] and soft X-ray colours. We find a total of 28 candidate normal galaxies to the 0.58keV band flux limit of 2x10^-15^erg/cm2/s. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona fide normal galaxies with X-ray emission coming from diffuse hot gas emission and/or X-ray binaries rather than a supermassive black hole.
17847. X-ray selected ROSAT AGN spectra
ID:
ivo://CDS.VizieR/J/A+A/350/805
Title:
X-ray selected ROSAT AGN spectra
Short Name:
J/A+A/350/805
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the emission line properties of a sample of 76 bright soft X-ray selected ROSAT Active Galactic Nuclei. All optical counterparts are Seyfert 1 galaxies with rather narrow permitted lines, strong optical FeII line blends, and weak forbidden lines. By selection, they also have steep soft X-ray spectra when compared with typical Seyfert 1 galaxies. We discuss possible origins of these peculiar trends employing detailed correlation analyses, including a Principal Component Analysis. The optical spectra are presented in the Appendix.
17848. X-rays from HH 80/81 complex
ID:
ivo://CDS.VizieR/J/ApJ/605/259
Title:
X-rays from HH 80/81 complex
Short Name:
J/ApJ/605/259
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report detections of X-rays from HH 80 and HH 81 with the ACIS instrument on the Chandra X-Ray Observatory. These are among the most luminous Herbig-Haro (HH) sources in the optical, and they are now the most luminous known in X-rays. These X-rays arise from the strong shocks that occur when the southern extension of this bipolar outflow slams into the ambient material. We imaged the central region of the bipolar flow revealing a complex of X-ray sources, including one near but not coincident with the putative power source in the radio and infrared.
17849. X-rays from the star-forming complex W40
ID:
ivo://CDS.VizieR/J/ApJ/725/2485
Title:
X-rays from the star-forming complex W40
Short Name:
J/ApJ/725/2485
Date:
21 Oct 2021
Publisher:
CDS
Description:
The young stellar cluster illuminating the W40 HII region, one of the nearest massive star-forming regions, has been observed with the ACIS detector on board the Chandra X-ray Observatory. Due to its high obscuration, this is a poorly studied stellar cluster with only a handful of bright stars visible in the optical band, including three OB stars identified as primary excitation sources. We detect 225 X-ray sources, of which 85% are confidently identified as young stellar members of the region. Two potential distances of the cluster, 260pc and 600pc, are used in the paper.
17850. X-rays in the Orion nebula cluster
ID:
ivo://CDS.VizieR/J/ApJ/584/911
Title:
X-rays in the Orion nebula cluster
Short Name:
J/ApJ/584/911
Date:
21 Oct 2021
Publisher:
CDS
Description:
A recent observation of the Orion Nebula Cluster with the ACIS instrument on board the Chandra X-Ray Observatory detected 1075 sources, 525 of which are pre-main-sequence (PMS) stars with measured bulk properties such as bolometric luminosities, masses, ages, and disk indicators. Nearly half of these stars have photometrically measured rotational periods. This provides a uniquely large and well-defined sample to study the dependence of magnetic activity on bulk properties for stars descending the Hayashi tracks.

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