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801. Star-galaxy classification feature importance
ID:
ivo://CDS.VizieR/J/A+A/645/A87
Title:
Star-galaxy classification feature importance
Short Name:
J/A+A/645/A87
Date:
21 Oct 2021
Publisher:
CDS
Description:
Future astrophysical surveys such as J-PAS will produce very large datasets, the so-called "big data", which will require the deployment of accurate and efficient machine-learning (ML) methods. In this work, we analyze the miniJPAS survey, which observed about ~1deg^2^ of the AEGIS field with 56 narrow-band filters and 4 ugri broad-band filters. The miniJPAS primary catalog contains approximately 64 000 objects in the r detection band (mag_AB_<~24), with forced-photometry in all other filters. We discuss the classification of miniJPAS sources into extended (galaxies) and point-like (e.g., stars) objects, which is a step required for the subsequent scientific analyses. We aim at developing an ML classifier that is complementary to traditional tools that are based on explicit modeling. In particular, our goal is to release a value-added catalog with our best classification. In order to train and test our classifiers, we cross-matched the miniJPAS dataset with SDSS and HSC-SSP data, whose classification is trustworthy within the intervals 15<=r<=20 and 18.5<=r<=23.5, respectively. We trained and tested six different ML algorithms on the two cross-matched catalogs: K-nearest neighbors, decision trees, random forest (RF), artificial neural networks, extremely randomized trees (ERT), and an ensemble classifier. This last is a hybrid algorithm that combines artificial neural networks and RF with the J-PAS stellar and galactic loci classifier. As input for the ML algorithms we used the magnitudes from the 60 filters together with their errors, with and without the morphological parameters. We also used the mean point spread function in the r detection band for each pointing. We find that the RF and ERT algorithms perform best in all scenarios. When the full magnitude range of 15<=r<=23.5 is analyzed, we find an area under the curve AUC=0.957 with RF when photometric information alone is used, and AUC=0.986 with ERT when photometric and morphological information is used together. When morphological parameters are used, the full width at half maximum is the most important feature. When photometric information is used alone, we observe that broad bands are not necessarily more important than narrow bands, and errors (the width of the distribution) are as important as the measurements (central value of the distribution). In other words, it is apparently important to fully characterize the measurement. ML algorithms can compete with traditional star and galaxy classifiers; they outperform the latter at fainter magnitudes (r>~21). We use our best classifiers, with and without morphology, in order to produce a value-added catalog.
802. Statistial HATLAS Lensed Objects Selec.
ID:
ivo://CDS.VizieR/J/A+A/627/A31
Title:
Statistial HATLAS Lensed Objects Selec.
Short Name:
J/A+A/627/A31
Date:
21 Oct 2021
Publisher:
CDS
Description:
The statistical analysis of large sample of strong lensing events can be a powerful tool to extract astrophysical or cosmological valuable information. Their selection using submillimetre galaxies has been demonstrated to be very effective with more than ~200 proposed candidates in the case of Herschel-ATLAS data and several tens in the case of the South Pole Telescope. However, the number of confirmed events is still relatively low, i.e. a few tens, mostly because of the lengthy observational validation process on individual events. In this work we propose a new methodology with a statistical selection approach to increase by a factor of ~5 the number of such events within the Herschel-ATLAS data set. Although the methodology can be applied to address several selection problems, it has particular benefits in the case of the identification of strongly lensed galaxies: objectivity, minimal initial constrains in the main parameter space, and preservation of statistical properties. The proposed methodology is based on the Bhattacharyya distance as a measure of the similarity between probability distributions of properties of two different cross-matched galaxies. The particular implementation for the aim of this work is called SHALOS and it combines the information of four different properties of the pair of galaxies: angular separation, luminosity percentile, redshift, and the ratio of the optical to the submillimetre flux densities. The SHALOS method provides a ranked list of strongly lensed galaxies. The number of candidates within ~340{deg}^2^ of the Herschel-ATLAS surveyed area for the final associated probability, P_tot_>0.7, is 447 and they have an estimated mean amplification factor of 3.12 for a halo with a typical cluster mass. Additional statistical properties of the SHALOS candidates, as the correlation function or the source number counts, are in agreement with previous results indicating the statistical lensing nature of the selected sample.
803. Stellar Catalogue in the Chandra DFS
ID:
ivo://CDS.VizieR/J/A+A/392/741
Title:
Stellar Catalogue in the Chandra DFS
Short Name:
J/A+A/392/741
Date:
21 Oct 2021
Publisher:
CDS
Description:
Stellar catalogues in five passbands (UBVRI) over an area of approximately 0.3{deg}^2^, comprising about 1200 objects, and in seven passbands (UBVRIJK) over approximately 0.1{deg}^2^, comprising about 400 objects, in the direction of the Chandra Deep Field South are presented. The 90% completeness level of the number counts is reached at approximately U=23.8, B=24.0, V=23.5, R=23.0, I=21.0, J=20.5, K=19.0. These multi-band catalogues have been produced from publicly available, single passband catalogues. A scheme is presented to select point sources from these catalogues, by combining the SExtractor parameter CLASS_STAR from all available passbands. Probable QSOs and unresolved galaxies are identified by using the previously developed {chi}^2^-technique (Hatziminaoglou et al., 2002, Cat. <J/A+A/384/81>), that fits the overall spectral energy distributions to template spectra and determines the best fitting template. Approximately 15% of true galaxies are misclassified as stars by the {chi}^2^ method. The number of unresolved galaxies and QSOs identified by the {chi}^2^-technique, allows us to estimate that the remaining level of contamination by such objects is at the level of 2.4% of the number of stars. The fraction of missing stars being incorrectly removed as QSOs or unresolved galaxies is estimated to be similar. The resulting stellar catalogues and the objects identified as likely QSOs and unresolved galaxies with coordinates, observed magnitudes with errors and assigned spectral types by the {chi}^2^-technique are presented and are publicly available.
804. Stellar kinematics in CALIFA survey
ID:
ivo://CDS.VizieR/J/A+A/597/A48
Title:
Stellar kinematics in CALIFA survey
Short Name:
J/A+A/597/A48
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the stellar kinematic maps of a large sample of galaxies from the integral-field spectroscopic survey CALIFA. The sample comprises 300 galaxies displaying a wide range of morphologies across the Hubble sequence, from ellipticals to late-type spirals. This dataset allows us to homogeneously extract stellar kinematics up to several effective radii. In this paper, we describe the level of completeness of this subset of galaxies with respect to the full CALIFA sample, as well as the virtues and limitations of the kinematic extraction compared to other well-known integral-field surveys. In addition, we provide averaged integrated velocity dispersion radial profiles for different galaxy types, which are particularly useful to apply aperture corrections for single aperture measurements or poorly resolved stellar kinematics of high-redshift sources. The work presented in this paper sets the basis for the study of more general properties of galaxies that will be explored in subsequent papers of the survey.
805. Stellar masses of Lyman break galaxies at z~3
ID:
ivo://CDS.VizieR/J/MNRAS/401/1521
Title:
Stellar masses of Lyman break galaxies at z~3
Short Name:
J/MNRAS/401/1521
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results of a large survey of the mid-infrared (mid-IR) properties of 248 Lyman Break Galaxies (LBGs) with confirmed spectroscopic redshift using deep Spitzer/Infrared Array Camera (IRAC) observations in six cosmological fields. By combining the new mid-IR photometry with optical and near-infrared observations, we model the spectral energy distributions (SEDs) employing a revised version of the Bruzual and Charlot synthesis population code that incorporates a new treatment of the thermal-pulsating asymptotic giant branch phase (CB07). Our primary aim is to investigate the impact of the AGB phase in the stellar masses of the LBGs, and compare our new results with previous stellar mass estimates. We investigate the stellar mass of the LBG population as a whole and assess the benefits of adding longer wavelengths to estimates of stellar masses for high-redshift galaxies.
806. Stellar parameters of the EXPRESS sample
ID:
ivo://CDS.VizieR/J/A+A/647/A157
Title:
Stellar parameters of the EXPRESS sample
Short Name:
J/A+A/647/A157
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of the search for planets around evolved stars, we can understand planet populations around significantly higher-mass stars than the Sun on the main sequence. This population is difficult to study any other way, particularly with radial-velocities since these stars are too hot and rotate too fast to measure precise velocities. Here we estimate stellar parameters for all of the giant stars from the EXPRESS project, which aims to detect planets orbiting evolved stars, and study their occurrence rate as a function of stellar mass. We analyse high resolution echelle spectra of these stars, and compute the atmospheric parameters by measuring the equivalent widths for a set of iron lines, using an updated method implemented during this work. Physical parameters are computed by interpolating through a grid of stellar evolutionary models, following a procedure that carefully takes into account the post-MS evolutionary phases. Probabilities of the star being in the red giant branch (RBG) or the horizontal branch (HB) are estimated from the derived distributions. Results: We find that, out of 166 evolved stars, 101 of them are most likely in the RGB phase, while 65 of them are in the HB phase. The mean derived mass is 1.41 and 1.87M_{sun}_ for RGB and HB stars, respectively. To validate our method, we compared our results with interferometry and asteroseismology studies. We find a difference in the radius with interferometry of 1.7%. With asteroseismology, we find 2.4% difference in logg, 1.5% in radius, 6.2% in mass, and 11.9% in age. Compared with previous spectroscopic studies, and find a 0.5% difference in Teff, 1% in logg, and 2% in [Fe/H]. We also find a mean mass difference with respect to the EXPRESS original catalogue of 16%. We show that the method presented here can greatly improve the estimates of the stellar parameters for giant stars compared to what was presented previously.
807. Stellar Proper Motions in the Ogle II Galactic Bulge Fields
ID:
ivo://org.gavo.dc/gcpms/q/data
Title:
Stellar Proper Motions in the Ogle II Galactic Bulge Fields
Short Name:
gcpms.data
Date:
27 Dec 2024 08:31:03
Publisher:
The GAVO DC team
Description:
A proper-motion catalogue of 5080236 stars in 49 OGLE-II Galactic bulge (GB) fields, covering a range of -11°<l<11° and -6°<b<3°. Some columns have been left out from the original source.
808. Stellar velocity dispersions. II.
ID:
ivo://CDS.VizieR/J/ApJS/100/105
Title:
Stellar velocity dispersions. II.
Short Name:
J/ApJS/100/105
Date:
21 Oct 2021
Publisher:
CDS
Description:
A catalog of central velocity dispersion measurements is presented, current through 1993 September. The catalog includes 2474 measurements of 1563 (*) galaxies. A standard set of 86 galaxies is defined, consisting of galaxies with at least three reliable concordant measurements. It is suggested that future studies observe some of these standard galaxies so that different studies can be normalised to a consistent system. All measurements are reduced to a normalized system using these standards. (*) Actually 1562 galaxies.
809. Stripe 82X survey multiwavelength catalog
ID:
ivo://CDS.VizieR/J/ApJ/850/66
Title:
Stripe 82X survey multiwavelength catalog
Short Name:
J/ApJ/850/66
Date:
21 Oct 2021
Publisher:
CDS
Description:
Multiwavelength surveys covering large sky volumes are necessary to obtain an accurate census of rare objects such as high-luminosity and/or high-redshift active galactic nuclei (AGNs). Stripe 82X is a 31.3 X-ray survey with Chandra and XMM-Newton observations overlapping the legacy Sloan Digital Sky Survey Stripe 82 field, which has a rich investment of multiwavelength coverage from the ultraviolet to the radio. The wide-area nature of this survey presents new challenges for photometric redshifts for AGNs compared to previous work on narrow-deep fields because it probes different populations of objects that need to be identified and represented in the library of templates. Here we present an updated X-ray plus multiwavelength matched catalog, including Spitzer counterparts, and estimated photometric redshifts for 5961 (96% of a total of 6181) X-ray sources that have a normalized median absolute deviation, {sigma}_nmad_=0.06, and an outlier fraction, {eta}=13.7%. The populations found in this survey and the template libraries used for photometric redshifts provide important guiding principles for upcoming large-area surveys such as eROSITA and 3XMM (in X-ray) and the Large Synoptic Survey Telescope (optical).
810. Structural parameters of galaxies
ID:
ivo://CDS.VizieR/J/A+A/626/A61
Title:
Structural parameters of galaxies
Short Name:
J/A+A/626/A61
Date:
21 Oct 2021
Publisher:
CDS
Description:
High-resolution multi-wavelength photometry is crucial to explore the spatial distribution of star formation in galaxies and understand how these evolve. To this aim, in this paper we exploit the deep, multi-wavelength Hubble Space Telescope (HST) data available in the central parts of the GOODS fields and study the distribution of star formation activity and mass in galaxies located at different positions with respect to the Main Sequence (MS) of star-forming galaxies. Our sample consists of galaxies with stellar mass >=10^9.5^M_{sun}_ in the redshift range 0.2<=z<=1.2. Exploiting 10-band photometry from the UV to the near-infrared at HST resolution, we derive spatially resolved maps of galaxies properties, such as stellar mass and star formation rate and specific star formation rate, with a resolution of 0.16arcsec. We find that the star formation activity is centrally enhanced in galaxies above the MS and centrally suppressed below the MS, with quiescent galaxies (1dex below the MS) characterised by the highest suppression. The sSFR in the outer region does not show systematic trends of enhancement or suppression above or below the MS. The distribution of mass in MS galaxies indicates that bulges are growing when galaxies are still on the MS relation. Galaxies below the MS are more bulge-dominated with respect to MS counterparts at fixed stellar mass, while galaxies in the upper envelope are more extended and have Sersic indexes that are always smaller than or comparable to their MS counterparts. The suppression of star formation activity in the central region of galaxies below the MS hints at inside-out quenching, as star formation is still ongoing in the outer regions.

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