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The VIMOS Ultra Deep Survey first data release: Spectra and spectroscopic redshifts of 698 objects up to <i>z</i> <sub/>spec</sub> ~ 6 in CANDELS
摘要： This paper describes the first data release (DR1) of the VIMOS Ultra Deep Survey (VUDS). The VUDS-DR1 is the release of all low-resolution spectroscopic data obtained in 276.9 arcmin2 of the CANDELS-COSMOS and CANDELS-ECDFS survey areas, including accurate spectroscopic redshifts zspec and individual spectra obtained with VIMOS on the ESO-VLT. A total of 698 objects have a measured redshift, with 677 galaxies, two type-I AGN, and a small number of 19 contaminating stars. The targets of the spectroscopic survey are selected primarily on the basis of their photometric redshifts to ensure a broad population coverage. About 500 galaxies have zspec > 2, 48 of which have zspec > 4; the highest reliable redshifts reach beyond zspec = 6. This data set approximately doubles the number of galaxies with spectroscopic redshifts at z > 3 in these fields. We discuss the general properties of the VUDS–DR1 sample in terms of the spectroscopic redshift distribution, the distribution of Lyman-α equivalent widths, and physical properties including stellar masses M* and star formation rates derived from spectral energy distribution fitting with the knowledge of zspec. We highlight the properties of the most massive star-forming galaxies, noting the wide range in spectral properties, with Lyman-α in emission or in absorption, and in imaging properties with compact, multi-component, or pair morphologies. We present the catalogue database and data products. All VUDS-DR1 data are publicly available and can be retrieved from a dedicated query-based database. Future VUDS data releases will follow this VUDS-DR1 to give access to the spectra and associated measurement of ～8000 objects in the full ～1 square degree of the VUDS survey.
关键词： surveys,cosmology: observations,galaxies: high-redshift,galaxies: distances and redshifts,catalogs
更新于2025-09-23 15:23:52
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The SAGE photometric survey: technical description
摘要： To investigate a huge sample of data related to the Stellar Abundance and Galactic Evolution (SAGE) survey in more detail, we are performing a northern sky photometric survey named SAGES with the SAGE photometric system. This system consists of eight filters: Str?mgren-u, SAGE-v, SDSS g, r, i, DDO-51, Hαwide and Hαnarrow, including three Sloan broadband filters, three intermediate-band filters, two narrow-band filters and one newly-designed narrow-band filter. SAGES covers ～12 000 square degrees of the northern sky with δ > ?5?, excluding the Galactic disk (|b| < 10?) and the sky area 12 h <RA <18 h. The photometric detection limit depth at signal-to-noise ratio 5σ can be as deep as V ～20 mag. SAGES will produce a photometric catalog with uniform depth for ～500 million stars with atmospheric parameters including effective temperature Teff, surface gravity log g and metallicity [Fe/H], as well as interstellar extinction to each individual target. In this work, we will briefly introduce the SAGE photometric system, the SAGE survey and a preliminary test field of the open cluster NGC 6791 and its surroundings.
关键词： surveys,astrometry,techniques: photometric,methods: observational,catalogs
更新于2025-09-23 15:23:52
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LOW-RESOLUTION NEAR-INFRARED STELLAR SPECTRA OBSERVED BY THE COSMIC INFRARED BACKGROUND EXPERIMENT (CIBER)
摘要： We present near-infrared (0.8–1.8 μm) spectra of 105 bright (mJ < 10) stars observed with the low-resolution spectrometer on the rocket-borne Cosmic Infrared Background Experiment. As our observations are performed above the Earth?s atmosphere, our spectra are free from telluric contamination, which makes them a unique resource for near-infrared spectral calibration. Two-Micron All-Sky Survey photometry information is used to identify cross-matched stars after reduction and extraction of the spectra. We identify the spectral types of the observed stars by comparing them with spectral templates from the Infrared Telescope Facility library. All the observed spectra are consistent with late F to M stellar spectral types, and we identify various infrared absorption lines.
关键词： stars: general,catalogs,infrared: stars,techniques: spectroscopic
更新于2025-09-23 15:22:29
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<i>Spitzer</i> Matching Survey of the UltraVISTA Ultra-deep Stripes (SMUVS): Full-mission IRAC Mosaics and Catalogs
摘要： This paper describes new deep 3.6 and 4.5 μm imaging of three UltraVISTA near-infrared survey stripes within the COSMOS field. The observations were carried out with Spitzer's Infrared Array Camera (IRAC) for the Spitzer Matching Survey of the UltraVISTA Deep Stripes (SMUVS). In this work we present our data reduction techniques, and document the resulting mosaics, coverage maps, and catalogs in both IRAC passbands for the three easternmost UltraVISTA survey stripes, covering a combined area of about 0.66 deg2, of which 0.45 deg2 have at least 20 hr of integration time. SMUVS reaches point-source sensitivities of about 25.0 AB mag (0.13 μJy) at both 3.6 and 4.5 μm, with a significance of 4σ, accounting for both survey sensitivity and source confusion. To this limit the SMUVS catalogs contain a total of ～350,000 sources, each of which is detected significantly in at least one IRAC band. Because of its uniform and high sensitivity, relatively large area coverage, and the wide array of ancillary data available in COSMOS, the SMUVS survey will be useful for a large number of cosmological investigations. We make all images and catalogs described herein publicly available via the Spitzer Science Center.
关键词： surveys,infrared: galaxies,catalogs
更新于2025-09-23 15:22:29
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Precision Light Curves from <i>TESS</i> Full-frame Images: A Different Imaging Approach
摘要： The Transiting Exoplanet Survey Satellite (TESS) will observe ～150 million stars brighter than T mag ? , with 16 photometric precision from 60 ppm to 3%, enabling an array of exoplanet and stellar astrophysics investigations. While light curves will be provided for ～400,000 targets observed at 2 minute cadence, observations of most stars will only be provided as full-frame images (FFIs) at 30 minute cadence. The TESS image scale of ～21″/pix is highly susceptible to crowding, blending, and source confusion, and the highly spatially variable point-spread function (PSF) will challenge traditional techniques, such as aperture and Gaussian-kernel PSF photometry. We use official “End-to-End 6” TESS simulated FFIs to demonstrate a difference image analysis pipeline, using a δ-function kernel, that achieves the mission specification noise floor of 60 ppm hr?1/2. We show that the pipeline performance does not depend on position across the field, and only ～2% of stars appear to exhibit residual systematics at the level of ～5 ppt. We also demonstrate recoverability of planet transits, eclipsing binaries, and other variables. We provide the pipeline as an open-source tool at https://github.com/ryanoelkers/DIA in both IDL and PYTHON. We intend to extract light curves for all point sources in the TESS FFIs as soon as they become publicly available, and will provide the light curves through the Filtergraph data visualization service. An example data portal based on the simulated FFIs is available for inspection at https://filtergraph.com/tess_ffi.
关键词： techniques: image processing,catalogs,methods: data analysis
更新于2025-09-23 15:22:29
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Photometric redshifts for the Kilo-Degree Survey
摘要： We present a machine-learning photometric redshift (ML photo-z) analysis of the Kilo-Degree Survey Data Release 3 (KiDS DR3), using two neural-network based techniques: ANNz2 and MLPQNA. Despite limited coverage of spectroscopic training sets, these ML codes provide photo-zs of quality comparable to, if not better than, those from the Bayesian Photometric Redshift (BPZ) code, at least up to zphot ? 0.9 and r ? 23.5. At the bright end of r ? 20, where very complete spectroscopic data overlapping with KiDS are available, the performance of the ML photo-zs clearly surpasses that of BPZ, currently the primary photo-z method for KiDS. Using the Galaxy And Mass Assembly (GAMA) spectroscopic survey as calibration, we furthermore study how photo-zs improve for bright sources when photometric parameters additional to magnitudes are included in the photo-z derivation, as well as when VIKING and WISE infrared (IR) bands are added. While the fiducial four-band ugri setup gives a photo-z bias ?δz/(1+z)? = ?2×10?? and scatter σδz/(1+z) < 0.022 at mean z ～ 0.23, combining magnitudes, colours, and galaxy sizes reduces the scatter by ～7% and the bias by an order of magnitude. Once the ugri and IR magnitudes are joined into 12-band photometry spanning up to 12 μm, the scatter decreases by more than 10% over the fiducial case. Finally, using the 12 bands together with optical colours and linear sizes gives ?δz/(1+z)? < 4×10?? and σδz/(1+z) < 0.019. This paper also serves as a reference for two public photo-z catalogues accompanying KiDS DR3, both obtained using the ANNz2 code. The first one, of general purpose, includes all the 39 million KiDS sources with four-band ugri measurements in DR3. The second dataset, optimised for low-redshift studies such as galaxy-galaxy lensing, is limited to r ? 20, and provides photo-zs of much better quality than in the full-depth case thanks to incorporating optical magnitudes, colours, and sizes in the GAMA-calibrated photo-z derivation.
关键词： methods: statistical,large-scale structure of Universe,galaxies: distances and redshifts,catalogs,methods: data analysis,methods: numerical
更新于2025-09-23 15:22:29
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Contrast sensitivities in the <i>Gaia</i> Data Release 2
摘要： The source detection sensitivity of Gaia is reduced near sources. To characterise this contrast sensitivity is important for understanding the completeness of the Gaia data products, in particular when evaluating source confusion in lower resolution surveys such as photometric monitoring for transits. Here, we statistically evaluate the catalogue source density to determine the Gaia Data Release 2 source detection sensitivity as a function of angular separation and brightness ratio from a bright source. The contrast sensitivity from ～0.4'' out to 12'' ranges in ?G = 0–14 mag. We find the derived contrast sensitivity to be robust with respect to target brightness, colour, source density, and Gaia scan coverage.
关键词： techniques: photometric,methods: data analysis,catalogs
更新于2025-09-23 15:22:29
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Deep <i>R</i> -band counts of <i>z</i> ≈ 3 Lyman-break galaxy candidates with the LBT
摘要： Aims. We present a deep multiwavelength imaging survey (UGR) in 3 different fields, Q0933, Q1623, and COSMOS, for a total area of ～1500 arcmin2. The data were obtained with the Large Binocular Camera on the Large Binocular Telescope. Methods. To select our Lyman-break galaxy (LBG) candidates, we adopted the well established and widely used color-selection criterion (U ? G vs. G ? R). One of the main advantages of our survey is that it has a wider dynamic color range for U-dropout selection than in previous studies. This allows us to fully exploit the depth of our R-band images, obtaining a robust sample with few interlopers. In addition, for 2 of our fields we have spectroscopic redshift information that is needed to better estimate the completeness of our sample and interloper fraction. Results. Our limiting magnitudes reach 27.0(AB) in the R band (5σ) and 28.6(AB) in the U band (1σ). This dataset was used to derive LBG candidates at z ≈ 3. We obtained a catalog with a total of 12 264 sources down to the 50% completeness magnitude limit in the R band for each field. We find a surface density of ～3 LBG candidates arcmin?2 down to R = 25.5, where completeness is ≥95% for all 3 fields. This number is higher than the original studies, but consistent with more recent samples.
关键词： surveys,ultraviolet: galaxies,galaxies: high-redshift,galaxies: photometry,catalogs
更新于2025-09-23 15:22:29
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Tidal Features at 0.05 < <i>z</i> < 0.45 in the Hyper Suprime-Cam Subaru Strategic Program: Properties and Formation Channels
摘要： We present 1201 galaxies at 0.05 < z < 0.45 that host tidal features in the first ～200 deg2 of imaging from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We select these galaxies from a sample of 21,208 galaxies with spectroscopic redshifts drawn from the Sloan Digital Sky Survey (SDSS) spectroscopic campaigns. Of these galaxies, we identify 214 shell systems and 987 stream systems. For 575 of these systems, we are additionally able to measure the (g?i) colors of the tidal features. We find evidence for star formation in a subset of the streams, with the exception of streams around massive ellipticals, and find that stream host galaxies span the full range of stellar masses in our sample. Galaxies that host shells are predominantly red and massive: we find that observable shells form more frequently around ellipticals than around disk galaxies of the same stellar mass. Although the majority of the shells in our sample are consistent with being formed by minor mergers, 15% ± 4.4% of shell host galaxies have (g?i) colors as red as their host galaxy, consistent with being formed by major mergers. These “red shell” galaxies are preferentially aligned with the major axis of the host galaxy, as previously predicted from simulations. We suggest that although the bulk of the observable shell population originates from fairly minor mergers, which preferentially form shells that are not aligned with the major axis of the galaxy, major mergers produce a significant number of observable shells.
关键词： techniques: image processing,galaxies: interactions,catalogs,galaxies: structure,galaxies: statistics
更新于2025-09-23 15:21:01
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DustPedia: Multiwavelength photometry and imagery of 875 nearby galaxies in 42 ultraviolet-microwave bands
摘要： Aims. The DustPedia project is capitalising on the legacy of the Herschel Space Observatory, using cutting-edge modelling techniques to study dust in the 875 DustPedia galaxies – representing the vast majority of extended galaxies within 3000 km s?1 that were observed by Herschel. This work requires a database of multiwavelength imagery and photometry that greatly exceeds the scope (in terms of wavelength coverage and number of galaxies) of any previous local-Universe survey. Methods. We constructed a database containing our own custom Herschel reductions, along with standardised archival observations from GALEX, SDSS, DSS, 2MASS, WISE, Spitzer, and Planck. Using these data, we performed consistent aperture-matched photometry, which we combined with external supplementary photometry from IRAS and Planck. Results. We present our multiwavelength imagery and photometry across 42 UV-microwave bands for the 875 DustPedia galaxies. Our aperture-matched photometry, combined with the external supplementary photometry, represents a total of 21 857 photometric measurements. A typical DustPedia galaxy has multiwavelength photometry spanning 25 bands. We also present the Comprehensive & Adaptable Aperture Photometry Routine (CAAPR), the pipeline we developed to carry out our aperture-matched photometry. CAAPR is designed to produce consistent photometry for the enormous range of galaxy and observation types in our data. In particular, CAAPR is able to determine robust cross-compatible uncertainties, thanks to a novel method for reliably extrapolating the aperture noise for observations that cover a very limited amount of background. Our rich database of imagery and photometry is being made available to the community.
关键词： surveys,dust,catalogs,extinction,galaxies: photometry,galaxies: general,techniques: photometric
更新于2025-09-23 15:21:01