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Artificial Star Test for Crowded Field CCD Photometry
摘要： A new method of performing an arti?cial star test (AST) for crowded ?eld stellar CCD photometry is proposed. This AST method is superior in the cases when it is necessary to account for varying photometric quality across the study ?eld, arising due to crowding variations. For this purpose, the color-magnitude diagrams (CMDs) of AST stars with statistically reliable error estimates, as well as completeness maps, can be generated at a required spatial resolution.
关键词： techniques: photometric,catalogs,galaxies: stellar content
更新于2025-09-23 15:21:01
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OmegaWINGS: OmegaCAM-VST observations of WINGS galaxy clusters
摘要： Context. Wide-field observations targeting galaxy clusters at low redshift are complementary to field surveys and provide the local benchmark for detailed studies of the most massive haloes in the local Universe. The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z = 0.04–0.07. The original 34' × 34' WINGS field of view has now been extended to cover a 1 deg2 field with both photometry and spectroscopy. Aims. We present the Johnson B- and V-band OmegaCAM at the VST observations of 46 WINGS clusters together with the data reduction, data quality, and Sextractor photometric catalogues. Methods. The data reduction was carried out with a modified version of the ESO-MVM (also known as ALAMBIC) reduction package, adding a cross-talk correction, the gain harmonisation, and a control procedure for problematic CCDs. The stray-light component was corrected for by employing our own observations of populated stellar fields. Results. With a median seeing of 1'' in both bands, our 25-min exposures in each band typically reach the 50% completeness level at V = 23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS and SDSS astrometry, and SDSS and previous WINGS imaging. Star-to-galaxy separation and sky-subtraction procedure were tested comparing them with previous WINGS data. Conclusions. The Sextractor photometric catalogues are publicly available at the CDS and will be included in the next release of the WINGS database on the Virtual Observatory together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega at the AAT and are being employed for a variety of studies.
关键词： galaxies: fundamental parameters,galaxies: clusters: general,galaxies: photometry,methods: observational,catalogs
更新于2025-09-19 17:15:36
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The Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) Quasar Survey: The Fourth and Fifth Data Releases
摘要： We present Data Releases 4 and 5 of the quasar catalog from the quasar survey by the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST), which includes quasars observed between 2015 September and 2017 June. There are a total of 19,253 quasars identi?ed by visual inspections of the spectra. Among them, 11,458 were independently discovered by LAMOST, in which 3296 were reported by the SDSS DR12 and DR14 quasar catalog after our survey began, while the remaining 8162 are new discoveries of LAMOST. We provide the emission line measurements for Hα, Hβ, Mg II, and/or C IV for 18,100 quasars. Since LAMOST does not have absolute ?ux calibration information, we obtain the monochromatic continuum luminosities by ?tting the SDSS photometric data using the quasar spectra, and then estimate the black hole masses. The catalog and spectra for these quasars are available online. This is the third installment in the series of LAMOST quasar surveys that has released spectra for ～43,000 quasars to date. There are 24,772 independently discovered quasars, 17,128 of which are newly discovered. In addition to this great supplement to the new quasar discoveries, LAMOST has also provided a large database (overlapped with SDSS) for investigating quasar spectral variability and discovering unusual quasars, including changing-look quasars, with ongoing and upcoming large surveys.
关键词： quasars: general,surveys,catalogs
更新于2025-09-19 17:15:36
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CARMENES input catalogue of M dwarfs
摘要： CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the CARMENES guaranteed time observations, in this paper we investigate the correlation of activity and rotation for approximately 2200 M dwarfs, ranging in spectral type from M0.0 V to M9.0 V. We present new high-resolution spectroscopic observations with FEROS, CAFE, and HRS of approximately 500 M dwarfs. For each new observation, we determined its radial velocity and measured its Hα activity index and its rotation velocity. Additionally, we have multiple observations of many stars to investigate if there are any radial velocity variations due to multiplicity. The results of our survey confirm that early-M dwarfs are Hα inactive with low rotational velocities and that late-M dwarfs are Hα active with very high rotational velocities. The results of this high-resolution analysis comprise the most extensive catalogue of rotation and activity in M dwarfs currently available.
关键词： stars: rotation,techniques: spectroscopic,stars: activity,catalogs
更新于2025-09-09 09:28:46
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Surface photometry of WINGS galaxies with GASPHOT
摘要： Aims. We present the B, V, and K band surface photometry catalogs obtained by running the automatic software GASPHOT on galaxies from the WINGS cluster survey with isophotal areas larger than 200 pixels. The catalogs can be downloaded at the Centre de Données Astronomiques de Strasbourg. Methods. The luminosity growth curves of stars and galaxies in a given catalog relative to a given cluster image were obtained simultaneously by slicing the image with a fixed surface brightness step in several SExtractor runs. Then, using a single Sersic law convolved with a space-varying point spread function (PSF), GASPHOT performed a simultaneous χ2 best-fit of the major- and minor-axis luminosity growth curves of galaxies. We outline the GASPHOT performances and compare our surface photometry with that obtained by SExtractor, GALFIT, and GIM2D. This analysis is aimed at providing statistical information about the accuracy that is generally achieved by the softwares for automatic surface photometry of galaxies. Results. The GASPHOT catalogs provide the parameters of the Sersic law that fit the luminosity profiles for each galaxy and for each photometric band. They are the sky coordinates of the galaxy center (RA, Dec), the total magnitude (m), the semi-major axis of the effective isophote (Re), the Sersic index (n), the axis ratio (b/a), and a flag parameter (QFLAG) that generally indicates the fit quality. The WINGS-GASPHOT database includes 41 463 galaxies in the B band, 42 275 in the V band, and 71 687 in the K band. The bright early-type galaxies have higher Sersic indices and larger effective radii, as well as redder colors in their center. In general, the effective radii increase systematically from the K to the V and B band. Conclusions. The GASPHOT photometry agrees well with the surface photometry obtained by GALFIT and GIM2D, and with the aperture photometry provided by SExtractor. In particular, the direct comparison of structural parameters derived by different softwares for common galaxies indicates that the systematic differences are small in general. The only significant deviations are most likely due to the peculiar (and very accurate) image processing adopted by WINGS for large galaxies. The main advantages of GASPHOT with respect to other tools are (i) the automatic finding of the local PSF; (ii) the short CPU execution time; and (iii) the remarkable stability against the choice of the initial-guess parameters. All these characteristics make GASPHOT an ideal tool for blind surface photometry of large galaxy samples in wide-field CCD mosaics.
关键词： surveys,catalogs,galaxies: clusters: general
更新于2025-09-04 15:30:14
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A Catalog of Photometric Redshift and the Distribution of Broad Galaxy Morphologies
摘要： We created a catalog of photometric redshift of ～3,000,000 SDSS galaxies annotated by their broad morphology. The photometric redshift was optimized by testing and comparing several pattern recognition algorithms and variable selection strategies, and was trained and tested on a subset of the galaxies in the catalog that had spectra. The galaxies in the catalog have i magnitude brighter than 18 and Petrosian radius greater than 5.5(cid:48)(cid:48). The majority of these objects are not included in previous SDSS photometric redshift catalogs such as the photoz table of SDSS DR12. Analysis of the catalog shows that the number of galaxies in the catalog that are visually spiral increases until redshift of ～0.085, where it peaks and starts to decrease. It also shows that the number of spiral galaxies compared to elliptical galaxies drops as the redshift increases.
关键词： galaxies: statistics,methods: data analysis,catalogs,galaxies: spiral
更新于2025-09-04 15:30:14
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Revised Exoplanet Radii and Habitability Using <i>Gaia</i> Data Release 2
摘要： Accurate stellar properties are crucial for determining exoplanet characteristics. Gaia DR2 presents revised distances, luminosities, and radii for 1.6 billion stars. Here, we report the calculation of revised radii and densities for 320 non-Kepler exoplanets using this data and present updated calculations of the incident ?ux received by 690 known exoplanets. This allows us to reassess the likelihood that those planets orbit in the habitable zone of their host stars. As a result of this analysis, three planets can be added to the catalog of potentially habitable worlds: HIP?67537?b, HD?148156?b, and HD?106720?b. In addition, the changed parameterization of BD?+49?898 means that its planet, BD?+49?898?b, now receives an incident ?ux that places it outside the optimistic habitable zone region, as de?ned by Kopparapu et al. We ?nd that use of the new Gaia data results in a mean increase in the calculated exoplanet radius of 3.76%. Previously, CoRoT-3 b had been reported as having the highest density of all known exoplanets. Here, we use updated information to revise the calculated density of CoRoT-3?b from 26.4 to 16.1?±?3.98 g cm?3. We also report in our data set, KELT-1?b, with a density of 22.1+5.62?9.16 g cm?3. Overall, our results highlight the importance of ensuring the parameterizations of known exoplanets are revisited whenever signi?cant improvements are made to the precision of the stellar parameters upon which they are based.
关键词： planets and satellites: fundamental parameters,astrobiology,planets and satellites: general,surveys,catalogs
更新于2025-09-04 15:30:14
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<i>Spitzer</i> mid-infrared point sources in the fields of nearby galaxies
摘要： Aims. To complement the study of transient phenomena and to assist subsequent observations in the mid-infrared, we extract point source photometry from archival mosaics of nearby galaxies with high star formation rates within 4 Mpc. Methods. Point spread function photometry was performed on sources detected in both Spitzer IRAC 3.6 μm and 4.5 μm bands at greater than 3σ above background. These data were then supplemented by aperture photometry in the IRAC 5.8 μm and 8.0 μm bands conducted at the positions of the shorter wavelength sources. For sources with no detected object in the longer wavelengths, we estimated magnitude limits based on the local sky background. Results. We present Spitzer IRAC mid-infrared point source catalogs for mosaics covering the ?elds of the nearby ((cid:46)4 Mpc) galaxies NGC 55, NGC 253, NGC 2366, NGC 4214, and NGC 5253. We detect a total of 20159 sources in these ?ve ?elds. The individual galaxy point source breakdown is the following: NGC 55, 8746 sources; NGC 253, 9001 sources; NGC 2366, 505 sources; NGC 4214, 1185 sources; NGC 5253, 722 sources. The completeness limits of the full catalog vary with bandpass and were found to be m3.6 = 18.0, m4.5 = 17.5, m5.8 = 17.0, and m8.0 = 16.5 mag. For all galaxies, this corresponds to detection of point sources brighter than M3.6 = ?10. These catalogs can be used as a reference for stellar population investigations, individual stellar object studies, and in planning future mid-infrared observations with the James Webb Space Telescope.
关键词： catalogs,stars: massive,galaxies: stellar content
更新于2025-09-04 15:30:14