- ID:
- ivo://CDS.VizieR/J/MNRAS/274/1107
- Title:
- Morphological classifications of APM galaxies
- Short Name:
- J/MNRAS/274/1107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the consistency of visual morphological classifications of galaxies by comparing classifications for 831 galaxies from six independent observers. The galaxies were classified on laser print copy images or on computer screen using scans made with the Automated Plate Measuring (APM) machine. Classifications are compared using the Revised Hubble numerical type index T. We find that individual observers agree with one another with rms combined dispersions of between 1.3 and 2.3 type units, typically about 1.8 units. The dispersions tend to decrease slightly with increasing angular diameter and, in some cases, with increasing axial ratio (b/a). The agreement between independent observers is reasonably good but the scatter is non-negligible. In spite of the scatter, the Revised Hubble T system can be used to train an automated galaxy classifier, e.g. an artificial neural network, to handle the large number of galaxy images that are being compiled in the APM and other surveys.
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- ID:
- ivo://CDS.VizieR/J/AJ/134/579
- Title:
- Morphologically classified galaxies from SDSS DR3
- Short Name:
- J/AJ/134/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of morphologically classified bright galaxies in the north equatorial stripe (230deg^2^) derived from the Third Data Release of the Sloan Digital Sky Survey (SDSS). Morphological classification is performed by visual inspection of images in the g band. The catalog contains 2253 galaxies complete to a magnitude limit of r=16 after Galactic extinction correction, selected from 2658 objects that are judged to be extended in the photometric catalog in the same magnitude limit. A total of 1866 galaxies in our catalog have spectroscopic information. A brief statistical analysis is presented for the frequency of morphological types and mean colors in the catalog. A visual inspection of the images reveals that the rate of interacting galaxies in the local universe is approximately 1.5% in the r<=16 sample. A verification is made for the photometric catalog generated by the SDSS, especially as to its bright-end completeness.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/12
- Title:
- Morphological parameters of galaxies from Spitzer
- Short Name:
- J/ApJ/781/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The morphology of galaxies can be quantified to some degree using a set of scale-invariant parameters. Concentration (C), asymmetry (A), smoothness (S), the Gini index (G), the relative contribution of the brightest pixels to the second-order moment of the flux (M_20_), ellipticity (E), and the Gini index of the second-order moment (G_M_) have all been applied to morphologically classify galaxies at various wavelengths. Here, we present a catalog of these parameters for the Spitzer Survey of stellar structure in Galaxies, a volume-limited, near-infrared (NIR) imaging survey of nearby galaxies using the 3.6 and 4.5{mu}m channels of the Infrared Array Camera on board the Spitzer Space Telescope. Our goal is to provide a reference catalog of NIR quantified morphology for high-redshift studies and galaxy evolution models with enough detail to resolve stellar mass morphology. We explore where normal, non-interacting galaxies--those typically found on the Hubble tuning fork--lie in this parameter space and show that there is a tight relation between concentration (C_82_) and M_20_ for normal galaxies. M_20_ can be used to classify galaxies into earlier and later types (i.e., to separate spirals from irregulars). Several criteria using these parameters exist to select systems with a disturbed morphology, i.e., those that appear to be undergoing a tidal interaction. We examine the applicability of these criteria to Spitzer NIR imaging. We find that four relations, based on the parameters A and S, G and M_20_, G_M_, C, and M_20_, respectively, select outliers in morphological parameter space, but each selects different subsets of galaxies. Two criteria (G_M_>0.6,G>-0.115xM_20_+0.384) seem most appropriate to identify possible mergers and the merger fraction in NIR surveys. We find no strong relation between lopsidedness and most of these morphological parameters, except for a weak dependence of lopsidedness on concentration and M_20_.
- ID:
- ivo://CDS.VizieR/J/ApJ/864/123
- Title:
- Morphological parameters of galaxies with GALEX
- Short Name:
- J/ApJ/864/123
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Evolutionary studies that compare galaxy structure as a function of redshift are complicated by the fact that any particular galaxy's appearance depends in part on the rest-frame wavelength of the observation. This leads to the necessity for a "morphological k-correction" between different passbands, especially when comparing the rest-frame optical or infrared (IR) to the ultraviolet (UV). This is of particular concern for high-redshift studies that are conducted in the rest-frame UV. We investigate the effects of this "bandpass shifting" out of the UV by quantifying nearby galaxy structure via concentration, asymmetry, and clumpiness (CAS) parameters. For this study we combine panchromatic data from the UV through the near-IR with Galaxy Evolution Explorer (GALEX) data of 2073 nearby galaxies in the "near-UV" (NUV; ~230nm) and 1127 in the "far-UV" (FUV; ~150nm), providing the largest study of this kind in the mid- to far-UV. We find a relationship between the CAS parameters and observed rest-frame wavelength that make galaxies appear more late-type at shorter wavelengths, particularly in the UV. The effect is strongest for E/S0 galaxies in the far-UV, which have concentrations and asymmetries that more closely resemble those of spiral and peculiar/merging galaxies in the optical. This may be explained by extended disks containing recent star formation. Here, we also release the CAS values of the galaxies imaged in GALEX NUV and FUV for use in comparisons with deep Hubble Space Telescope imaging and the James Webb Space Telescope in the future.
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/2415
- Title:
- Morphological parameters of WHISP galaxies
- Short Name:
- J/MNRAS/416/2415
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lopsidedness of the gaseous disc of spiral galaxies is a common phenomenon in disc morphology, profile and kinematics. Simultaneously, the asymmetry of a galaxy's stellar disc, in combination with other morphological parameters, has seen extensive use as an indication of recent merger or interaction in galaxy samples. Quantified morphology of stellar spiral discs is one avenue to determine the merger rate over much of the age of the Universe. In this paper, we measure the quantitative morphology parameters for the HI column density maps from the Westerbork observations of neutral Hydrogen in Irregular and SPiral galaxies (WHISP). These are Concentration, Asymmetry, Smoothness, Gini, M20 and one addition of our own, the Gini parameter of the second-order moment (GM). Our aim is to determine if lopsided or interacting discs can be identified with these parameters. Our sample of 141 HI maps have all previous classifications on their lopsidedness and interaction.
- ID:
- ivo://CDS.VizieR/J/MNRAS/479/4136
- Title:
- Morphological properties of galaxies
- Short Name:
- J/MNRAS/479/4136
- Date:
- 31 Dec 2021 09:10:27
- Publisher:
- CDS
- Description:
- We consider an all-sky sample of 1029 Local Volume (LV) galaxies situated within a distance of 11 Mpc. Majority of them have precise distances and estimates of hydrogen mass fraction and star-formation rate derived from far-ultraviolet or H{alpha} fluxes. To describe an environment, we attribute two dimensionless values: the density contrast created by the most significant neighbour and the local density contrast produced by all neighbours within a separation of 1Mpc. The hydrogen mass fraction exhibits a weak effect of HI deficiency being the most pronounced for irregular dwarf galaxies. The specific star formation rate (sSFR) is more sensitive to the environment than the hydrogen mass fraction. Almost all (99 per cent) LV galaxies have their sSFRs below -9.4dex (yr^-1^). We notice that irregular dwarfs as well as late-type bulgeless galaxies are capable of reproducing their stellar mass with the observed sSFR over the cosmic time. Thus, the transformation of gas into stars in dIrs and spiral discs is rather sluggish unlike that in E, S0, dSph galaxies, whose star formation history has been stormy and short. The SFR(H{alpha})-to-SFR(FUV) scatter ratio increases from Sc, Sd, Sm galaxies towards BCD, Im, Ir types which favours the idea of bursty star formations in low-mass galaxies. However, this bursty activity is caused rather by internal processes than by an external tidal action. A fraction of quenched E, S0, dSph galaxies increases from ~5 per cent in the field up to ~50 per cent in the densest regions.
- ID:
- ivo://CDS.VizieR/J/MNRAS/410/166
- Title:
- Morphological types from Galaxy Zoo 1
- Short Name:
- J/MNRAS/410/166
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Morphology is a powerful indicator of a galaxy's dynamical and merger history. It is strongly correlated with many physical parameters, including mass, star formation history and the distribution of mass. The Galaxy Zoo project collected simple morphological classifications of nearly 900000 galaxies drawn from the Sloan Digital Sky Survey, contributed by hundreds of thousands of volunteers. This large number of classifications allows us to exclude classifier error, and measure the influence of subtle biases inherent in morphological classification. This paper presents the data collected by the project, alongside measures of classification accuracy and bias. The data are now publicly available and full catalogues can be downloaded in electronic format from http://data.galaxyzoo.org .
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/2835
- Title:
- Morphological types from Galaxy Zoo 2
- Short Name:
- J/MNRAS/435/2835
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the data release for Galaxy Zoo 2 (GZ2), a citizen science project with more than 16 million morphological classifications of 304122 galaxies drawn from the Sloan Digital Sky Survey (SDSS). Morphology is a powerful probe for quantifying a galaxy's dynamical history; however, automatic classifications of morphology (either by computer analysis of images or by using other physical parameters as proxies) still have drawbacks when compared to visual inspection. The large number of images available in current surveys makes visual inspection of each galaxy impractical for individual astronomers. GZ2 uses classifications from volunteer citizen scientists to measure morphologies for all galaxies in the DR7 Legacy survey with m_r_>17, in addition to deeper images from SDSS Stripe 82. While the original GZ2 project identified galaxies as early-types, late-types or mergers, GZ2 measures finer morphological features. These include bars, bulges and the shapes of edge-on discs, as well as quantifying the relative strengths of galactic bulges and spiral arms. This paper presents the full public data release for the project, including measures of accuracy and bias. The majority (>90 per cent) of GZ2 classifications agree with those made by professional astronomers, especially for morphological T-types, strong bars and arm curvature. Both the raw and reduced data products can be obtained in electronic format at http://data.galaxyzoo.org .
- ID:
- ivo://CDS.VizieR/J/ApJS/110/213
- Title:
- Morphological Types in 10 Distant Rich Clusters
- Short Name:
- J/ApJS/110/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present catalogs of objects detected in deep images of 11 fields in 10 distant clusters obtained using WFPC-2 on board the Hubble Space Telescope. The clusters span the redshift range z=0.37-0.56 and are the subject of a detailed ground- and space-based study to investigate the evolution of galaxies as a function of environment and epoch. The data presented here include positions, photometry and basic morphological information on ~9000 objects in the fields of the 10 clusters. For a brighter subset of 1857 objects in these areas, we provide more detailed morphological information.
- ID:
- ivo://CDS.VizieR/J/MNRAS/376/125
- Title:
- Morphologies and photometry in A2218
- Short Name:
- J/MNRAS/376/125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the stellar populations and morphologies of galaxies in the core of the galaxy cluster Abell 2218. Integral field spectroscopy (IFS) observations were performed using PMAS in the PPAK mode covering a field of view of ~74x64arcsec^2^ centred on the core of the cluster, in order to obtain spectroscopy of an unbiased flux-limited sample of cluster galaxies. 43 objects were detected in the IFS data, 31 of them with enough signal-to-noise ratio to derive the redshift, all of them brighter than I<21.5mag. 28 are at the redshift of the cluster (17 with previously unknown redshift). Individual spectra of the cluster members were extracted and compared with single stellar population models to derive the luminosity-weighted ages and metallicities. In addition, deep Hubble Space Telescope (HST)/ACS F475W-, F555W-, F625W- and F850LP-band images centred on the cluster core were obtained from the HST archive (zlim~28mag). A detailed morphological analysis of all the galaxies within the field of view of these images down to zlim<22.5mag was performed classifying them as late-type, intermediate and early-type, on the basis of their Sersic indices. The literature was scanned to look for spectroscopically confirmed cluster members located within the field of view of the ACS image. The final sample of 59 galaxies comprises our reported sample of 28 galaxies in the core, and 31 additional galaxies in the outer regions. In addition, multiband broad-band photometry was extracted from the literature for all objects.
