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- ID:
- ivo://CDS.VizieR/J/A+A/587/A81
- Title:
- T Tauri stars X-ray/accretion anti correlation
- Short Name:
- J/A+A/587/A81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Depending on whether a T Tauri star accretes material from its circumstellar disk or not, different X-ray emission properties can be found. The accretion shocks produce cool heating of the plasma, contributing to the soft X-ray emission from the star. Using X-ray data from the Chandra Orion Ultra-deep Project and accretion rates that were obtained with the Hubble Space Telescope/WFPC2 photometric measurements in the Orion Nebula Cluster, we studied the relation between the accretion processes and the X-ray emissions of a coherent sample of T Tauri sources in the region. We performed regression and correlation analyses of our sample of T Tauri stars between the X-ray parameters, stellar properties, and the accretion measurements. We find that a clear anti-correlation is present between the residual X-ray luminosity and the accretion rates in our samples in Orion that is consistent with that found on the XMM-Newton Extended Survey of the Taurus molecular cloud (XEST) study. A considerable number of classified non-accreting sources show accretion rates comparable to those of classical T Tauri Stars (CTTS). Our data do not allow us to confirm the classification between classical and weak-line T Tauri stars (WTTS), and the number of WTTS in this work is small compared to the complete samples. Thus, we have used the entire samples as accretors in our analysis. We provide a catalog with X-ray luminosities (corrected from distance) and accretion measurements of an Orion Nebula Cluster (ONC) T Tauri stars sample.
933. T Tau Stars
- ID:
- ivo://CDS.VizieR/J/A+A/326/211
- Title:
- T Tau Stars
- Short Name:
- J/A+A/326/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a study to investigate the spatial distribution of X-ray active young stellar objects near the Lupus star forming region (SFR). In this SFR, a recent study has led to the discovery of some 130 new weak-line T Tauri stars (WTTS) dispersed over a large area of some 230 square degrees. However, the true extent of the spatial distribution of these stars could not be determined in this study.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A32
- Title:
- Turin-SyCAT, Seyferts multifrequency catalog
- Short Name:
- J/A+A/659/A32
- Date:
- 02 Mar 2022 06:48:51
- Publisher:
- CDS
- Description:
- We present the first release of Turin-SyCAT, a multifrequency catalog of Seyfert galaxies. We selected Seyfert galaxies considering criteria based on radio, infrared, and optical properties and starting from sources belonging to hard X-ray catalogs and surveys. We visually inspected optical spectra available for all selected sources. We adopted homogeneous and stringent criteria in the source selection aiming at reducing the possible contamination from other source classes. Our final catalog includes 351 Seyfert galaxies distinguished in 233 type 1 and 118 type 2. Type 1 Seyfert galaxies appear to have mid-IR colors similar to blazars, but are distinguished from them by their radio-loudness. Additionally, Seyfert 2 galaxies have mid-IR colors more similar to quasars than BL Lac objects. As expected from their spectral properties, type 1 and 2 Seyfert galaxies show a clear distinction when using the u-r color. Finally, we found a tight correlation between the mid-IR fluxes at both 12 and 22 um (i.e., F12 and F22, respectively) and hard X-ray fluxes between 15 and 150 keV. Both Seyfert types appear to follow the same trend and share similar values of the ratios of F12 and F22 to FHX in agreement with expectations of the AGN unification scenario. As future perspectives, the Turin-SyCAT will then be used to search for heavily obscured Seyfert galaxies among unidentified hard X-ray sources, given the correlation between mid-IR and hard X-rays, and to investigate their large-scale environments.
- ID:
- ivo://CDS.VizieR/J/MNRAS/339/913
- Title:
- Two distant massive clusters of galaxies
- Short Name:
- J/MNRAS/339/913
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss the radio, optical, and X-ray properties of two newly discovered, very X-ray luminous, distant clusters of galaxies. Both systems were noted as cluster candidates in a cross-correlation of data from the WENSS (<VIII/162>) radio survey and the ROSAT All-Sky Survey (<IX/10>). Follow-up observations performed by us and the Massive Cluster Survey (MACS) team confirmed both sources as distant galaxy clusters. The first cluster, MACS J0717.5+3745 at a redshift of z=0.5548, contains a very extended, steep-spectrum radio source offset from the cluster core, making it the most distant radio relic known. The second cluster, MACS J1621.3+3810 at z=0.465, is a strong cooling flow with a relatively weak central radio source. We present results from ROSAT High-Resolution Imager (HRI, Cat. <IX/28>) observations of both clusters as well as from optical imaging and VLA radio interferometry observations. Our discoveries demonstrate that distant clusters can be efficiently identified in a relatively shallow X-ray survey, that radio/X-ray selection is efficient, and that both cooling flow and non-cooling flow clusters are selected.
- ID:
- ivo://CDS.VizieR/J/ApJ/761/162
- Title:
- Tycho-2 stars in Galactic Bulge Survey
- Short Name:
- J/ApJ/761/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 69 X-ray sources discovered by the Galactic Bulge Survey (GBS) that are coincident with or very close to bright stars in the Tycho-2 catalog. Additionally, two other GBS sources are resolved binary companions to Tycho-2 stars where both components are separately detected in X-rays. Most of these are likely to be real matches, but we identify nine objects with large and significant X-ray-to-optical offsets as either detections of resolved binary companions or chance alignments. We collate known spectral types for these objects, and also examine Two Micron All Sky Survey colors, variability information from the All-Sky Automated Survey, and X-ray hardness ratios for the brightest objects. Nearly a third of the stars are found to be optically variable, divided roughly evenly between irregular variations and periodic modulations. All fall among the softest objects identified by the GBS. The sample forms a very mixed selection, ranging in spectral class from O9 to M3. In some cases, the X-ray emission appears consistent with normal coronal emission from late-type stars, or wind emission from early-types, but the sample also includes one known Algol, one W UMa system, two Be stars, and several X-ray bright objects likely to be coronally active stars or binaries. Surprisingly, a substantial fraction of the spectroscopically classified, non-coincidental sample (12 out of 38 objects) have late B or A type counterparts. Many of these exhibit redder near-IR colors than expected for their spectral type and/or variability, and it is likely that the X-rays originate from a late-type companion star in most or all of these objects.
- ID:
- ivo://CDS.VizieR/J/A+A/534/A110
- Title:
- Type-2 AGN from XMM-COSMOS bolometric output
- Short Name:
- J/A+A/534/A110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Study of the multi-wavelength properties of a sample of 255 spectroscopically identified X-ray selected Type-2 AGN from the XMM-COSMOS survey. For each source, X-ray ID, spectroscopic redshift, logarithm of the 2-10keV luminosity, logarithm of the bolometric luminosity, bolometric correction, logarithm of the stellar mass, star formation rate, absolute magnitude M_U_, absolute magnitude M_V_, absolute magnitude M_J_ (Johnson-Kron-Cousin system), morphological class.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/102
- Title:
- Type 2 AGN host galaxies in Chandra-COSMOS
- Short Name:
- J/ApJ/841/102
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the star formation properties of a large sample of ~2300 X-ray-selected Type 2 Active Galactic Nuclei (AGNs) host galaxies out to z~3 in the Chandra COSMOS Legacy Survey in order to understand the connection between the star formation and nuclear activity. Making use of the existing multi-wavelength photometric data available in the COSMOS field, we perform a multi-component modeling from far-infrared to near-ultraviolet using a nuclear dust torus model, a stellar population model and a starburst model of the spectral energy distributions (SEDs). Through detailed analyses of SEDs, we derive the stellar masses and the star formation rates (SFRs) of Type 2 AGN host galaxies. The stellar mass of our sample is in the range of 9<logM_stellar_/M_{sun}_<12 with uncertainties of ~0.19dex. We find that Type 2 AGN host galaxies have, on average, similar SFRs compared to the normal star-forming galaxies with similar M_stellar_ and redshift ranges, suggesting no significant evidence for enhancement or quenching of star formation. This could be interpreted in a scenario, where the relative massive galaxies have already experienced substantial growth at higher redshift (z>3), and grow slowly through secular fueling processes hosting moderate-luminosity AGNs.
- ID:
- ivo://CDS.VizieR/J/A+A/535/A80
- Title:
- Type-2 QSOs in XMM-COSMOS
- Short Name:
- J/A+A/535/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the connection between black hole growth at the center of obscured quasars selected from the XMM-COSMOS survey and the physical properties of their host galaxies. We study a bolometric regime (<Lbol>=8x10^45^erg/s) where several theoretical models invoke major galaxy mergers as the main fueling channel for black hole accretion. To derive robust estimates of the host galaxy properties, we use an SED fitting technique to distinguish the AGN and host galaxy emission. We evaluate the effect on galaxy properties estimates of being unable to remove the nuclear emission from the SED. The superb multi-wavelength coverage of the COSMOS field allows us to obtain reliable estimates of the total stellar masses and star formation rates (SFRs) of the hosts. We supplement this information with a morphological analysis of the ACS/HST images, optical spectroscopy, and an X-ray spectral analysis.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/11
- Title:
- Type 1 vs 2 X-ray-selected COSMOS AGNs & environment
- Short Name:
- J/ApJ/878/11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The unified model of active galactic nuclei (AGNs) proposes that different AGN optical spectral types are caused by different viewing angles with respect to an obscuring "torus". Therefore, this model predicts that type 1 and type 2 AGNs should have similar host-galaxy properties. We investigate this prediction with 2463 X-ray-selected AGNs in the COSMOS field. We divide our sample into type 1 and type 2 AGNs based on their spectra, morphologies, and variability. We derive their host-galaxy stellar masses (M_*_) through spectral energy distribution (SED) fitting, and we find that the hosts M_*_ of type 1 AGNs tend to be slightly smaller than those of type 2 AGNs by {Delta}logM_*_~0.2dex (~4{sigma} significance). Besides deriving star formation rates (SFRs) from SED fitting, we also utilize far-infrared (FIR) photometry and a stacking method to obtain FIR-based SFRs. We find that the SFRs of type 1 and type 2 sources are similar once their redshifts and X-ray luminosities are controlled. We also investigate the cosmic environment, and we find that the surface number densities (sub-Mpc) and cosmic-web environments (~1-10Mpc) are similar for both populations. In summary, our analyses show that the host galaxies of type 1 and type 2 AGNs have similar SFRs and cosmic environments in general, but the former tend to have a lower M_*_ than the latter. The difference in M_*_ indicates that the AGN unification model is not strictly correct, and both host galaxy and torus may contribute to the optical obscuration of AGNs.
