- ID:
- ivo://CDS.VizieR/J/MNRAS/453/1136
- Title:
- XDF CHEF photometric catalogue
- Short Name:
- J/MNRAS/453/1136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric redshifts, which have become the cornerstone of several of the largest astronomical surveys like PanStarrs, DES, J-PAS and LSST, require precise measurements of galaxy photometry in different bands using a consistent physical aperture. This is not trivial, due to the variation in the shape and width of the point spread function (PSF) introduced by wavelength differences, instrument positions and atmospheric conditions. Current methods to correct for this effect rely on a detailed knowledge of PSF characteristics as a function of the survey coordinates, which can be difficult due to the relative paucity of stars tracking the PSF behaviour. Here we show that it is possible to measure accurate, consistent multicolour photometry without knowing the shape of the PSF. The Chebyshev-Fourier functions (CHEFs) can fit the observed profile of each object and produce high signal-to-noise integrated flux measurements unaffected by the PSF. These total fluxes, which encompass all the galaxy populations, are much more useful for galaxy evolution studies than aperture photometry. We compare the total magnitudes and colours obtained using our software to traditional photometry with SExtractor, using real data from the COSMOS survey and the Hubble Ultra-Deep Field (HUDF). We also apply the CHEF technique to the recently published eXtreme Deep Field (XDF) and compare the results to those from ColorPro on the HUDF. We produce a photometric catalogue with 35732 sources (10823 with signal-to-noise ratio >=5), reaching a photometric redshift precision of 2 per cent due to the extraordinary depth and wavelength coverage of the eXtreme Deep Field images.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJS/181/444
- Title:
- X-emitting stars identified from the RASS/SDSS
- Short Name:
- J/ApJS/181/444
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. Combining the RASS Bright and Faint Source Catalogs (Cat. <IX/10>, 1RXS and <IX/29>) yields an average of about three X-ray sources per square degree. However, while X-ray source counterparts are known to range from distant quasars to nearby M dwarfs, the RASS data alone are often insufficient to determine the nature of an X-ray source. As a result, large-scale follow-up programs are required to construct samples of known X-ray emitters. We use optical data produced by the Sloan Digital Sky Survey (SDSS) to identify 709 stellar X-ray emitters cataloged in the RASS and falling within the SDSS Data Release 1 footprint. Most of these are bright stars with coronal X-ray emission unsuitable for SDSS spectroscopy, which is designed for fainter objects (g>15[mag]). Instead, we use SDSS photometry, correlations with the Two Micron All Sky Survey and other catalogs, and spectroscopy from the Apache Point Observatory 3.5m telescope to identify these stellar X-ray counterparts. Our sample of 707 X-ray-emitting F, G, K, and M stars is one of the largest X-ray-selected samples of such stars. We identify 17 new X-ray-emitting DA (hydrogen) WDs, of which three are newly identified WDs. We report on follow-up observations of three candidate cool X-ray-emitting WDs (one DA and two DB (helium) WDs); we have not confirmed X-ray emission from these WDs.
- ID:
- ivo://CDS.VizieR/J/MNRAS/340/304
- Title:
- [X/Fe] of Galactic disc F and G dwarfs
- Short Name:
- J/MNRAS/340/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photospheric abundances are presented for 27 elements from carbon to europium in 181 F and G dwarfs from a differential local thermodynamic equilibrium (LTE) analysis of high-resolution and high signal-to-noise ratio spectra. Stellar effective temperatures (T_eff_) were adopted from an infrared flux method calibration of Stroemgren photometry. Stellar surface gravities (g) were calculated from Hipparcos parallaxes and stellar evolutionary tracks. Adopted T_eff_ and g values are in good agreement with spectroscopic estimates. Stellar ages were determined from evolutionary tracks. Stellar space motions (U, V, W) and a Galactic potential were used to estimate Galactic orbital parameters. These show that the vast majority of the stars belong to the Galactic thin disc.
17424. X1 Fornacis cluster DANCe
- ID:
- ivo://CDS.VizieR/J/A+A/654/A122
- Title:
- X1 Fornacis cluster DANCe
- Short Name:
- J/A+A/654/A122
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The {chi}^1^ Fornacis cluster (Alessi 13) is one of a few open clusters of its age and distance in the Solar neighbourhood that ought to benefit from more attention as it can serve as a cornerstone for numerous future studies related to star and planet formation. Aims: We take advantage of the early installment of the third data release of the Gaia space mission in combination with archival data and our own observations, to expand the census of cluster members and revisit some properties of the cluster. Methods: We applied a probabilistic method to infer membership probabilities over a field of more than 1000deg^2^ to select the most likely cluster members and derive the distances, spatial velocities, and physical properties of the stars in this sample. Results: We identify 164 high-probability cluster members (including 61 new members) covering the magnitude range from 5.1 to 19.6mag in the G-band. Our sample of cluster members is complete down to 0.04M_{sun}_. We derive the distance of 108.4+/-0.3pc from Bayesian inference and confirm that the cluster is comoving with the Tucana-Horologium, Columba, and Carina young stellar associations. We investigate the kinematics of the cluster from a subsample of stars with measured radial velocities and we do not detect any significant expansion or rotation effects in the cluster. Our results suggest that the cluster is somewhat younger (about 30Myr) than previously thought. Based on spectroscopic observations, we argue that the cluster is mass-segregated and that the distribution of spectral types shows little variation compared to other young stellar groups. Conclusions: In this study, we deliver the most complete census of cluster members that can be done with Gaia data alone and we use this new sample to provide an updated picture on the 6D structure of the cluster.
17425. xGASS catalog
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/875
- Title:
- xGASS catalog
- Short Name:
- J/MNRAS/476/875
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the extended GALEX Arecibo SDSS Survey (xGASS), a gas fraction-limited census of the atomic hydrogen (HI) gas content of 1179 galaxies selected only by stellar mass (M*=10^9^-10^11.5^M_{sun}_) and redshift (0.01<z<0.05). This includes new Arecibo observations of 208 galaxies, for which we release catalogues and HI spectra. In addition to extending the GASS HI scaling relations by one decade in stellar mass, we quantify total (atomic+molecular) cold gas fractions and molecular-to-atomic gas mass ratios, Rmol, for the subset of 477 galaxies observed with the IRAM 30m telescope. We find that atomic gas fractions keep increasing with decreasing stellar mass, with no sign of a plateau down to logM*/M_{sun}_=9. Total gas reservoirs remain HI-dominated across our full stellar mass range, hence total gas fraction scaling relations closely resemble atomic ones, but with a scatter that strongly correlates with Rmol, especially at fixed specific star formation rate. On average, Rmol weakly increases with stellar mass and stellar surface density {mu}*, but individual values vary by almost two orders of magnitude at fixed M* or {mu}*. We show that, for galaxies on the star-forming sequence, variations of Rmol are mostly driven by changes of the HI reservoirs, with a clear dependence on {mu}*. Establishing if galaxy mass or structure plays the most important role in regulating the cold gas content of galaxies requires an accurate separation of bulge and disc components for the study of gas scaling relations
- ID:
- ivo://CDS.VizieR/J/PAZh/38/763
- Title:
- XHIP-II: Clusters and associations
- Short Name:
- J/PAZh/38/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the absence of complete kinematic data it has not previously been possible to furnish accurate lists of member stars for all moving groups. There has been an unresolved dispute concerning the apparent inconsistency of the Hipparcos parallax distance to the Pleiades. To find improved candidate lists for clusters and associations represented among Hipparcos stars, to establish distances, and to cast light on the Pleiades distance anomaly. We use a six dimensional fitting procedure to identify candidates, and plot CMDs for 20 of the nearest groups. We calculate the mean parallax distance for all groups.
- ID:
- ivo://CDS.VizieR/J/ApJS/184/138
- Title:
- XID II: RASS/BSC-2MASS/PSC cross-association
- Short Name:
- J/ApJS/184/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 18806 ROSAT All Sky Survey Bright Source Catalog (RASS/BSC) X-ray sources are quantitatively cross-associated with near-infrared (NIR) sources from the Two Micron All Sky Survey Point Source Catalog (2MASS/PSC). An association catalog is presented, listing the most likely counterpart for each RASS/BSC source, the probability Pid that the NIR source and X-ray source are uniquely associated, and the probability Pno-id that none of the 2MASS/PSC sources are associated with the X-ray source. The catalog includes 3853 high quality (Pid>0.98) X-ray-NIR matches, 2280 medium quality (0.98>=Pid>0.9) matches, and 4153 low quality (0.9>=Pid>0.5) matches. Of the high quality matches, 1418 are associations that are not listed in the SIMBAD database, and for which no high quality match with a USNO-A2 optical source was presented for the RASS/BSC source in previous work. The present work offers a significant number of new associations with RASS/BSC objects that will require optical/NIR spectroscopy for classification. For example, of the 6133 Pid>0.9 2MASS/PSC counterparts presented in the association catalog, 2411 have no classification listed in the SIMBAD database. These 2MASS/PSC sources will likely include scientifically useful examples of known source classes of X-ray emitters (white dwarfs, coronally active stars, active galactic nuclei), but may also contain previously unknown source classes. It is determined that all coronally active stars in the RASS/BSC should have a counterpart in the 2MASS/PSC, and that the unique association of these RASS/BSC sources with their NIR counterparts thus is confusion limited.
- ID:
- ivo://CDS.VizieR/J/ApJ/887/15
- Title:
- Xinglong spectra of two changing-look SDSS AGNs
- Short Name:
- J/ApJ/887/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a spectroscopic identification of two new changing-look active galactic nuclei (CL-AGNs): SDSSJ104705.16+544405.8 and SDSSJ120447.91+170256.8, both with a "turn-off" type transition from type-1 to type-1.8/1.9. The identification is arrived at through a follow-up spectroscopic observation of the five CL-AGNs candidates that are extracted from the sample recently released in MacLeod+ (2019, J/ApJ/874/8). The candidates are extracted by the authors from the Sloan Digit Sky Survey Data Release 7, and are spectroscopically confirmed quasars with large amplitude variability. By compiling a sample of 26 previously identified CL-AGNs, we confirm the claim by MacLeod+ that CL-AGNs tend to be biased against a low Eddington ratio, and identify an overlap between the CL-AGNs at their dim state and the so-called intermediate-type AGNs. The overlap implies that there two populations of the intermediate-type AGNs with different origins. One is due to the torus orientation effect, and the other to the intrinsic change of the accretion rate of the central supermassive black holes.
17429. XMDS/VVDS 4{sigma} catalogue
- ID:
- ivo://CDS.VizieR/J/A+A/439/413
- Title:
- XMDS/VVDS 4{sigma} catalogue
- Short Name:
- J/A+A/439/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 286 X-ray sources with their optical identification taken from the XMDS survey (using the XMM-Newton EPIC instrument). This first version is limited to sources detected at 4{sigma} at least in one energy band, AND falling in the area covered by the optical VVDS survey.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A48
- Title:
- XMM AGN optical-UV luminosities
- Short Name:
- J/A+A/539/A48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Active galactic nuclei (AGN) emit radiation over a wide range of wavelengths, with a peak of emission in the far-UV region of the electromagnetic spectrum, a spectral region that is historically difficult to observe. Using optical, GALEX UV, and XMM-Newton data we derive the spectral energy distribution (SED) from the optical/UV to X-ray regime of a sizeable sample of AGN. The principal motivation is to investigate the relationship between the optical/UV emission and the X-ray emission and provide bolometric corrections to the hard X-ray (2-10keV) energy range, k_bol_, the latter being a fundamental parameter in current physical cosmology.
