- ID:
- ivo://CDS.VizieR/J/PAZh/41/27
- Title:
- Classical Cepheids BVIc observations
- Short Name:
- J/PAZh/41/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In 2013-2014, we obtained 14959 CCD frames in the BVIc photometric system for 170 classical Cepheids from the General Catalogue of Variable Stars. We performed our observations with the 76-cm telescope of the South African Astronomical Observatory (SAAO, South Africa) using the SBIG ST-10XME CCD camera. The tables of observations, the plots of light curves, and the current light elements are presented.
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- ID:
- ivo://CDS.VizieR/J/ApJ/832/176
- Title:
- Classical Cepheids in MCs. I. LMC disk
- Short Name:
- J/ApJ/832/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed investigation of the Large Magellanic Cloud (LMC) disk using classical Cepheids. Our analysis is based on optical (I, V; OGLE-IV), near-infrared (NIR: J, H, K_S_) and mid-infrared (MIR: w1; WISE) mean magnitudes. By adopting new templates to estimate the NIR mean magnitudes from single-epoch measurements, we build the currently most accurate, largest, and homogeneous multi-band data set of LMC Cepheids. We determine Cepheid individual distances using optical and NIR Period-Wesenheit relations (PWRs), to measure the geometry of the LMC disk and its viewing angles. Cepheid distances based on optical PWRs are precise at 3%, but accurate to 7%, while the ones based on NIR PWRs are more accurate (to 3%), but less precise (2%-15%), given the higher photometric error on the observed magnitudes. We found an inclination of i=25.05+/-0.02(stat.)+/-0.55(syst.){deg}, and a position angle of the lines of nodes P.A.=150.76+/-0.02(stat.)+/-0.07(syst.){deg}. These values agree well with estimates based either on young (Red Supergiants) or on intermediate-age (Asymptotic Giant Branch, Red Clump) stellar tracers, but they significantly differ from evaluations based on old (RR Lyrae) stellar tracers. This indicates that young/intermediate and old stellar populations have different spatial distributions. Finally, by using the reddening-law fitting approach, we provide a reddening map of the LMC disk, which is 10 times more accurate and 2 times larger than similar maps in the literature. We also found an LMC true distance modulus of {mu}_0,LMC_=18.48+/-0.10(stat. and syst.)mag, in excellent agreement with the currently most accurate measurement.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A14
- Title:
- Classification-aided zph estimation
- Short Name:
- J/A+A/619/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broadband photometry offers a time and cost effective method to reconstruct the continuum emission of celestial objects. Thus, photometric redshift estimation has supported the scientific exploitation of extragalactic multiwavelength surveys for more than twenty years. Deep fields have been the backbone of galaxy evolution studies and have brought forward a collection of various approaches in determining photometric redshifts. In the era of precision cosmology, with the upcoming Euclid and LSST surveys, very tight constraints are put on the expected performance of photometric redshift estimation using broadband photometry, thus new methods have to be developed in order to reach the required performance. We present a novel automatic method of optimizing photometric redshift performance, the classification-aided photometric redshift estimation (CPz). The main feature of CPz is the unified treatment of all classes of objects detected in extragalactic surveys: galaxies of any type (passive, starforming and starbursts), active galactic nuclei (AGN), quasi-stellar objects (QSO), stars and also includes the identification of potential photometric redshift catastrophic outliers. The method operates in three stages. First, the photometric catalog is confronted with star, galaxy and QSO model templates by means of spectral energy distribution fitting. Second, three machine-learning classifiers are used to identify 1) the probability of each source to be a star, 2) the optimal photometric redshift model library set-up for each source and 3) the probability to be a photometric redshift catastrophic outlier. Lastly, the final sample is assembled by identifying the probability thresholds to be applied on the outcome of each of the three classifiers. Hence, with the final stage we can create a sample appropriate for a given science case, for example favoring purity over completeness. We apply our method to the near- infrared VISTA public surveys, matched with optical photometry from CFHTLS, KiDS and SDSS, mid-infrared WISE photometry and ultra-violet photometry from the Galaxy Evolution Explorer (GALEX). We show that CPz offers improved photometric redshift performance for both normal galaxies and AGN without the need for extra X-ray information.
- ID:
- ivo://CDS.VizieR/J/A+A/453/535
- Title:
- Classification of bright mid-IR sources
- Short Name:
- J/A+A/453/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context: The stellar populations in the central region of the Galaxy are poorly known because of the high visual extinction and very great source density in this direction. Aims: To use recent infrared surveys for studying the dusty stellar objects in this region. Methods: We analyse the content of a ~20x20arcmin^2 field centred at (l,b)=(-0.27,-0.06) observed at 7 and 15 microns as part of the ISOGAL survey. These ISO observations are more than an order of magnitude better in sensitivity and spatial resolution than the IRAS observations. The sources are cross-associated with other catalogues to identify various types of objects. We then derive criteria to distinguish young objects from post-main sequence stars. Results: We find that a sample of about 50 young stellar objects and ultra-compact HII regions emerges, out of a population of evolved AGB stars. We demonstrate that the sources colours and spatial extents, as they appear in the ISOGAL catalogue, possibly complemented with MSX photometry at 21 microns, can be used to determine whether the ISOGAL sources brighter than 300mJy at 15 microns (or [15]<4.5mag) are young objects or late-type evolved stars.
- ID:
- ivo://CDS.VizieR/J/A+AS/116/429
- Title:
- Classification of Coma early galaxies
- Short Name:
- J/A+AS/116/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an isophotal shape analysis of three samples of galaxies in the Coma cluster. Quantitative morphology, together with structural and photometric parameters, is given for each galaxy. Special emphasis has been placed on the detailed classification of early-type galaxies. The three samples are: i) a sample of 97 early-type galaxies brighter than m_B_=17.00 falling within one degree from the center of the Coma cluster; these galaxies were observed with CCD cameras, mostly in good to excellent resolution conditions; ii) a magnitude complete sample of 107 galaxies of all morphological types down to m_B_=17.00 falling in a circular region of 50arcmin diameter, slightly offcentered to the North-West of the cluster center; the images for this and the next sample come from digitized photographic plates; iii) a complete comparison sample of 26 galaxies of all morphological types down to m_R_=16.05 (or m_B_=~17.5), also in a region of 50arcmin diameter, but centered 2.6degrees West of the cluster center. The reliability of our morphological classifications and structural parameters of galaxies, down to the adopted magnitude limits, is assessed by comparing the results on those galaxies for which we had images taken with different instrumentation and/or seeing conditions, and by comparing our results with similar data from other observers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2917
- Title:
- Classification of Hipparcos variables
- Short Name:
- J/MNRAS/427/2917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hipparcos catalogue (ESA 1997, Cat. I/239) and the AAVSO Variable Star Index (Watson et al., 2011, Cat. B/vsx) are employed to complement the training set of periodic variables of Dubath et al. (2011, Cat. J/MNRAS/414/2602) with irregular and non-periodic representatives, leading to 3881 sources in total which described 24 variability types. The attributes employed to characterize light-curve features are selected according to their relevance for classification. Classifier models are produced with random forests and a multi-stage methodology based on Bayesian networks, achieving overall misclassification rates under 12%. Both classifiers are applied to predict variability types for 6051 Hipparcos variables associated with uncertain or missing types in the literature.
- ID:
- ivo://CDS.VizieR/J/MNRAS/474/1873
- Title:
- Classification of LAMOST DR4 galaxies
- Short Name:
- J/MNRAS/474/1873
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the classification and composite spectra of galaxies in the fourth data release (DR4) of the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST). We select 40182 spectra of galaxies from LAMOST DR4, which have photometric information but no spectroscopic observations in the Sloan Digital Sky Survey (SDSS). These newly observed spectra are recalibrated and classified into six classes - passive, H{alpha}-weak, star-forming, composite, LINER and Seyfert - using the line intensity (H{beta}, [OIII] 5007, H{alpha} and [NII] 6585). We also study the correlation between spectral class and morphological type through three parameters: concentration index, (u-r) colour and D4000n index. We calculate composite spectra of high signal-to-noise ratio (S/N) for six spectral classes and, using these composites, we pick out some features that can differentiate the classes effectively, including H{beta}, Fe5015, H{gamma}A, HK and the Mg2 band. In addition, we compare our composite spectra with the SDSS ones and analyse their differences. A galaxy catalogue of 40182 newly observed spectra (36601 targets) and the composite spectra of the six classes are available online (http://sciwiki.lamost.org/downloads/wll).
- ID:
- ivo://CDS.VizieR/J/AJ/140/34
- Title:
- Classification of nova light curves
- Short Name:
- J/AJ/140/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 93 very-well-observed nova light curves. The light curves were constructed from 229,796 individual measured magnitudes, with the median coverage extending to 8.0mag below peak and 26% of the light curves following the eruption all the way to quiescence. Our time-binned light curves are presented in figures and as complete tabulations. We also calculate and tabulate many properties about the light curves, including peak magnitudes and dates, times to decline by 2, 3, 6, and 9mag from maximum, the time until the brightness returns to quiescence, the quiescent magnitude, power-law indices of the decline rates throughout the eruption, the break times in this decline, plus many more properties specific to each nova class. We present a classification system for nova light curves based on the shape and the time to decline by 3mag from the peak (t3). The designations are "S" for smooth light curves (38% of the novae), "P" for plateaus (21%), "D" for dust dips (18%), "C" for cusp-shaped secondary maxima (1%), "O" for quasi-sinusoidal oscillations superposed on an otherwise smooth decline (4%), "F" for flat-topped light curves (2%), and "J" for jitters or flares superposed on the decline (16%). Our classification consists of this single letter followed by the t3 value in parentheses; so, for example, V1500 Cyg is S(4), GK Per is O(13), DQ Her is D(100), and U Sco is P(3).
- ID:
- ivo://CDS.VizieR/J/BaltA/5/1
- Title:
- Classification of Population II stars
- Short Name:
- J/BaltA/5/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The astrophysical parameters compiled from literature for 809 stars of different types, mainly Population II stars, are presented. The results of classification in the Vilnius photometric system for the same stars are given. For a description of the Vilnius photometric system, see e.g. <GCPD/21>
- ID:
- ivo://CDS.VizieR/J/ApJ/805/181
- Title:
- Classification of 1.5<=z<=3 HUDF galaxies
- Short Name:
- J/ApJ/805/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At z>~1, the distinction between merging and "normal" star-forming galaxies based on single band morphology is often hampered by the presence of large clumps which result in a disturbed, merger-like appearance even in rotationally supported disks. In this paper we discuss how a classification based on canonical, non-parametric structural indices measured on resolved stellar mass maps, rather than on single-band images, reduces the misclassification of clumpy but not merging galaxies. We calibrate the mass-based selection of mergers using the MIRAGE hydrodynamical numerical simulations of isolated and merging galaxies which span a stellar mass range of 10^9.8^-10^10.6^M_{sun}_ and merger ratios between 1:1-1:6.3. These simulations are processed to reproduce the typical depth and spatial resolution of observed Hubble Ultra Deep Field (HUDF) data. We test our approach on a sample of real z~=2 galaxies with kinematic classification into disks or mergers and on ~100 galaxies in the HUDF field with photometric/spectroscopic redshift between 1.5<=z<=3 and M>10^9.4^M_{sun}_. We find that a combination of the asymmetry A_MASS_ and M_20,MASS_ indices measured on the stellar mass maps can efficiently identify real (major) mergers with <~20% contamination from clumpy disks in the merger sample. This mass-based classification cannot be reproduced in star-forming galaxies by H-band measurements alone, which instead result in a contamination from clumpy galaxies which can be as high as 50%. Moreover, we find that the mass-based classification always results in a lower contamination from clumpy galaxies than an H-band classification, regardless of the depth of the imaging used (e.g., CANDELS versus HUDF).
