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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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A multi-method approach to radial-velocity measurement for single-object spectra
摘要： Context. The derivation of radial velocities from large numbers of spectra that typically result from survey work, requires automation. However, except for the classical cases of slowly rotating late-type spectra, existing methods of measuring Doppler shifts require fine-tuning to avoid a loss of accuracy due to the idiosyncrasies of individual spectra. The radial velocity spectrometer (RVS) on the Gaia mission, which will start operating very soon, prompted a new attempt at creating a measurement pipeline to handle a wide variety of spectral types. Aims. The present paper describes the theoretical background on which this software is based. However, apart from the assumption that only synthetic templates are used, we do not rely on any of the characteristics of this instrument, so our results should be relevant for most telescope-detector combinations. Methods. We propose an approach based on the simultaneous use of several alternative measurement methods, each having its own merits and drawbacks, and conveying the spectral information in a different way, leading to different values for the measurement. A comparison or a combination of the various results either leads to a 'best estimate' or indicates to the user that the observed spectrum is problematic and should be analysed manually. Results. We selected three methods and analysed the relationships and differences between them from a unified point of view; with each method an appropriate estimator for the individual random error is chosen. We also develop a procedure for tackling the problem of template mismatch in a systematic way. Furthermore, we propose several tests for studying and comparing the performance of the various methods as a function of the atmospheric parameters of the observed objects. Finally, we describe a procedure for obtaining a knowledge-based combination of the various Doppler-shift measurements.
关键词： techniques: radial velocities,surveys,stars: kinematics and dynamics,methods: data analysis,techniques: spectroscopic
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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Bright lenses are easy to find: spectroscopic confirmation of lensed quasars in the Southern Sky
摘要： Gravitationally lensed quasars are valuable, but extremely rare, probes of observational cosmology and extragalactic astrophysics. Progress in these fields has been limited just by the paucity of systems with good ancillary data. Here we present a first spectroscopic confirmation of lenses discovered in the Southern Sky from the DES and KiDS-DR3 footprints. We have targeted seven high-graded candidates, selected with new techniques, with NTT-EFOSC2, and confirmed five of them. We provide source spectroscopic redshifts, image separations, gri photometry, and first lens model parameters. The success rate of ～70 per cent confirms our forecasts, based on the comparison between the number of candidate doubles and quadruplets in our searches over a ≈5000 deg2 footprint and theoretical predictions.
关键词： gravitational lensing: strong,Galaxies: formation,surveys
更新于2025-09-23 15:23:52
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Deep, multiband photometry of low-mass stars to reveal young clusters: A blind study of the NGC2264 region
摘要： Context. Thanks to their extensive and homogeneous sky coverage, deep, large-scale, multiwavelength surveys are uniquely suited to statistically identify and map young star clusters in our Galaxy. Such studies are crucial to address issues like the initial mass function, or the modes and dynamics of star cluster formation and evolution. Aims. We aim to test a purely photometric approach to statistically identify a young clustered population embedded in a large population of field stars, with no prior knowledge of the nature of stars in the field. We conducted our blind test study on the NGC 2264 region, which hosts a well-known, richly populated young cluster (～3 Myr-old) and several active star-forming sites. Methods. We selected a large (4 deg2) area around the NGC 2264 cluster, and assembled an extensive r, i, J catalog of the field from pre-existing large-scale surveys, notably Pan-STARRS1 and UKIDSS. We then mapped the stellar color locus on the (i ? J, r ? i) diagram to select M-type stars, which offer the following observational advantages with respect to more massive stars: (i) they comprise a significant fraction of the Galactic stellar population; (ii) their pre-main sequence phase lasts significantly longer than for higher mass stars; (iii) they exhibit the strongest luminosity evolution from the pre-main sequence to the main sequence; (iv) their observed r, i, J colors provide a direct and empirical estimate of AV . A comparative analysis of the photometric and spatial properties of M-type stars as a function of AV enabled us to probe the structure and stellar content of our field. Results. Using only r, i, J photometry, we could identify two distinct populations in our field: a diffuse field population and a clustered population in the center of the field. The presence of a concentration of occulting material, spatially associated with the clustered population, allowed us to derive an estimate of its distance (800–900 pc) and age (～0.5–5 Myr); these values are overall consistent with the literature parameters for the NGC 2264 star-forming region. The extracted clustered population exhibits a hierarchical structure, with two main clumps and peaks in number density of objects around the most reddened locations within the field. An excellent agreement is found between the observed substructures for the clustered population and a map of the NGC 2264 subregions reported in the literature. Our selection of clustered members is coherent with the literature census of the NGC 2264 cluster for about 95% of the objects located in the inner regions of the field, where the estimated contamination rate by field stars in our sample is only 2%. In addition, the availability of a uniform dataset for a large area around the NGC 2264 region enabled us to discover a population of about a hundred stars with indications of statistical membership to the cluster, therefore extending the low-mass population census of NGC 2264 to distances of 10–15 pc from the cluster cores. Conclusions. By making use solely of deep, multiband (r, i, J) photometry, without assuming any further knowledge of the stellar population of our field, we were able to statistically identify and reconstruct the structure of a very young cluster that has been a prime target for star formation studies over several decades. The method tested here can be readily applied to surveys such as Pan-STARRS and the future LSST to undertake a first complete census of low-mass, young stellar populations down to distances of several kiloparsecs across the Galactic plane.
关键词： techniques: photometric,stars: low-mass,methods: statistical,surveys,open clusters and associations: individual: NGC 2264,methods: observational
更新于2025-09-23 15:22:29
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The Herschel-PACS North Ecliptic Pole Survey
摘要： A detailed analysis of Herschel/Photoconductor Array Camera and Spectrometer (PACS) observations at the North Ecliptic Pole is presented. High-quality maps, covering an area of 0.44 deg2, are produced and then used to derive potential candidate source lists. A rigorous quality-control pipeline has been used to create ?nal legacy catalogues in the PACS Green 100 μm and Red 160 μm bands, containing 1384 and 630 sources respectively. These catalogues reach to more than twice the depth of the current archival Herschel/PACS Point Source Catalogue, detecting 400 and 270 more sources in the short- and long-wavelength bands, respectively. Galaxy source counts are constructed that extend down to ?ux densities of 6 mJy and 19 mJy (50% completeness) in the Green 100 μm and Red 160 μm bands, respectively. These source counts are consistent with previously published PACS number counts in other ?elds across the sky. The source counts are then compared with a galaxy evolution model which identi?es a population of luminous infrared galaxies as responsible for the bulk of the galaxy evolution over the ?ux range (5–100 mJy) spanned by the observed counts, contributing approximate fractions of 50% and 60% to the cosmic infrared background at 100 μm and 160 μm, respectively.
关键词： galaxies: evolution,surveys
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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The WIRCam Ultra Deep Survey (WUDS)
摘要： The aim of this paper is to introduce the WIRCam Ultra Deep Survey (WUDS), a near-IR photometric survey carried out at the CFH Telescope in the field of the CFHTLS-D3 field (Groth Strip). WUDS includes four near-IR bands (Y, J, H and Ks) over a field of view of ～400 arcmin2. The typical depth of WUDS data reaches between ～26.8 in Y and J, and ～26 in H and Ks (AB, 3σ in 1.3'' aperture), whereas the corresponding depth of the CFHTLS-D3 images in this region ranges between 28.6 and 29 in ugr, 28.2 in i and 27.1 in z (same S/N and aperture). The area and depth of this survey were specifically tailored to set strong constraints on the cosmic star formation rate and the luminosity function brighter or around L* in the z ～ 6?10 redshift domain, although these data are also useful for a variety of extragalactic projects. This first paper is intended to present the properties of the public WUDS survey in details: catalog building, completeness and depth, number counts, photometric redshifts, and global properties of the galaxy population. We have also concentrated on the selection and characterization of galaxy samples at z ～ [4.5?7] in this field. For these purposes, we include an adjacent shallower area of ～1260 arcmin2 in this region, extracted from the WIRCam Deep Survey (WIRDS), and observed in J, H and Ks bands. UV luminosity functions were derived at z ～ 5 and z ～ 6 taking advantage from the fact that WUDS covers a particularly interesting regime at intermediate luminosities, which allows a combined determination of M* and Φ* with increased accuracy. Our results on the luminosity function are consistent with a small evolution of both M* and Φ* between z = 5 and z = 6, irrespective of the method used to derive them, either photometric redshifts applied to blindly-selected dropout samples or the classical Lyman Break Galaxy color-preselected samples. Our results lend support to higher Φ* determinations at z = 6 than usually reported. The selection and combined analysis of different galaxy samples at z ≥ 7 will be presented in a forthcoming paper, as well as the evolution of the UV luminosity function between z ～ 4.5 and 9. WUDS is intended to provide a robust database in the near-IR for the selection of targets for detailed spectroscopic studies, in particular for the EMIR/GTC GOYA Survey.
关键词： surveys,first stars,reionization,galaxies: high-redshift,dark ages
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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KiDS-450: enhancing cosmic shear with clipping transformations
摘要： We present the first 'clipped' cosmic shear measurement using data from the Kilo-Degree Survey (KiDS-450). 'Clipping' transformations suppress the signal from the highest density, non-linear regions of cosmological fields. We demonstrate that these transformations improve constraints on S8 = σ8(Ωm/0.3)^0.5 when used in combination with conventional two-point statistics. For the KiDS-450 data, we find that the combined measurements improve the constraints on S8 by 17 per cent, compared to shear correlation functions alone. We determine the expectation value of the clipped shear correlation function using a suite of numerical simulations, and develop methodology to mitigate the impact of masking and shot noise. Future improvements in numerical simulations and mass reconstruction methodology will permit the precise calibration of clipped cosmic shear statistics such that clipping can become a standard tool in weak-lensing analyses.
关键词： gravitational lensing: weak,cosmological parameters,surveys,cosmology: observations
更新于2025-09-23 15:22:29