- ID:
- ivo://CDS.VizieR/J/AJ/108/1
- Title:
- Flatness of clusters of galaxies
- Short Name:
- J/AJ/108/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine relations between shape, richness, and velocity dispersion for a sample of 350 clusters of galaxies of all morphologies, including those with visible substructure. For our sample the apparent shape of clusters is correlated with velocity dispersion and Abell (1958ApJS....3..211A) richness in the sense that poor, low dispersion clusters are flatter in the mean than their richer, higher dispersion counterparts. These characteristics are also exhibited by the X-ray emitting gas. There are virtually no highly flattened clusters having high richness or high velocity dispersions in the sample. We find that the variation of richness and velocity dispersion with apparent shape is too steep to be assigned to projection effects, and conclude rich, high dispersion clusters are intrinsically more nearly spherical than poorer clusters and that two-body relaxation is probably not an effective anisotropy damping mechanism in Abell clusters.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/815/57
- Title:
- Follow-up spectroscopy of Ly{alpha} 3<z<7 emitters
- Short Name:
- J/ApJ/815/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We explore the relationship between the spectral shape of the Ly{alpha} emission and the UV morphology of the host galaxy using a sample of 304 Ly{alpha}-emitting BVi-dropouts at 3<z<7 in the Great Observatories Origins Deep Survey and Cosmic Evolution Survey fields. Using our extensive reservoir of high-quality Keck DEIMOS spectra combined with Hubble Space Telescope WFC3 data, we measure the Ly{alpha} line asymmetries for individual galaxies and compare them to axial ratios measured from observed J- and H-band (restframe UV) images. We find that the Ly{alpha} skewness exhibits a large scatter at small elongation (a/b<2), and this scatter decreases as the axial ratio increases. Comparison of this trend to radiative transfer models and various results from the literature suggests that these high-redshift Ly{alpha} emitters are not likely to be intrinsically round and symmetric disks, but they probably host galactic outflows traced by Ly{alpha} emitting clouds. The ionizing sources are centrally located, and the optical depth is a good indicator of the absorption and scattering events on the escape path of Ly{alpha} photons from the source. Our results find no evidence of evolution in Ly{alpha} asymmetry or axial ratio with look-back time.
- ID:
- ivo://CDS.VizieR/J/A+A/608/A142
- Title:
- Fornax Deep Survey with VST. III. LSB galaxies
- Short Name:
- J/A+A/608/A142
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of low surface brightness (LSB) galaxies in nearby clusters have revealed a sub-population of extremely diffuse galaxies with central surface brightness of {mu}_0,g'_>24mag/arcsec^2^, total luminosity M_g'_ fainter than -16mag and effective radius between 1.5kpc<R_e_<10kpc. The origin of these ultra diffuse galaxies (UDGs) is still unclear, although several theories have been suggested. As the UDGs overlap with the dwarf-sized galaxies in their luminosities, it is important to compare their properties in the same environment. If a continuum is found between the properties of UDGs and the rest of the LSB population, it would be consistent with the idea that they have a common origin. Our aim is to exploit the deep g', r' and i'-band images of the Fornax Deep Survey (FDS), in order to identify LSB galaxies in an area of 4deg^2^ in the center of the Fornax cluster. The identified galaxies are divided into UDGs and dwarf-sized LSB galaxies, and their properties are compared. We identified visually all extended structures having r'-band central surface brightness of {mu}_0,r'_>23mag/arcsec^2^. We classified the objects based on their appearance into galaxies and tidal structures, and perform 2D Sersic model fitting with GALFIT to measure the properties of those classified as galaxies. We analyzed their radial distribution and orientations with respect of the cluster center, and with respect to the other galaxies in our sample. We also studied their colors and compare the LSB galaxies in Fornax with those in other environments. Our final sample complete in the parameter space of the previously known UDGs, consists of 205 galaxies of which 196 are LSB dwarfs (with R_e_<1.5kpc) and nine are UDGs (R_e_>1.5kpc). We show that the UDGs have (1) g'-r' colors similar to those of LSB dwarfs of the same luminosity; (2) the largest UDGs (R_e_>3kpc) in our sample appear different from the other LSB galaxies, in that they are significantly more elongated and extended; whereas (3) the smaller UDGs differ from the LSB dwarfs only by having slightly larger effective radii; (4) we do not find clear differences between the structural parameters of the UDGs in our sample and those of UDGs in other galaxy environments; (5) we find that the dwarf LSB galaxies in our sample are less concentrated in the cluster center than the galaxies with higher surface brightness, and that their number density drops within 180 kpc from the cluster center. We also compare the LSB dwarfs in Fornax with the LSB dwarfs in the Centaurus group, where data of similar quality to ours is available. (6) We find the smallest LSB dwarfs to have similar colors, sizes and Sersic profiles regardless of their environment. However, in the Centaurus group the colors become bluer with increasing galaxy magnitudes, an effect which is probably due to smaller mass and hence weaker environmental influence of the Centaurus group. Our findings are consistent with the small UDGs forming the tail of a continuous distribution of less extended LSB galaxies. However, the elongated and distorted shapes of the large UDGs could imply that they are tidally disturbed galaxies. Due to limitations of the automatic detection methods and uncertainty in the classification the objects, it is yet unclear what is the total contribution of the tidally disrupted galaxies in the UDG population.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A165
- Title:
- Fornax Deep Survey with VST. IV. dwarf galaxies
- Short Name:
- J/A+A/620/A165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fornax Deep Survey (FDS), an imaging survey in the u', g', r', and i'-bands, has a supreme resolution and image depth compared to the previous spatially complete Fornax Cluster Catalog (FCC). Our new data allows us to study the galaxies down to r'- band magnitude mr~=21mag (Mr'~=-10.5mag), which opens a new parameter regime to investigate the evolution of dwarf galaxies in the cluster environment. After the Virgo cluster, Fornax is the second nearest galaxy cluster to us, and with its different mass and evolutionary state, it provides a valuable comparison that makes it possible to understand the various evolutionary effects on galaxies and galaxy clusters. These data provide an important legacy dataset to study the Fornax cluster. We aim to present the Fornax Deep Survey (FDS) dwarf galaxy catalog, focusing on explaining the data reduction and calibrations, assessing the quality of the data, and describing the methods used for defining the cluster memberships and first order morphological classifications for the catalog objects. We also describe the main scientific questions that will be addressed based on the catalog. This catalog will also be invaluable for future follow-up studies of the Fornax cluster dwarf galaxies. As a first step we used the SExtractor fine-tuned for dwarf galaxy detection, to find galaxies from the FDS data, covering a 26deg^2^ area of the main cluster up to its virial radius, and the area around the Fornax A substructure. We made 2D-decompositions of the identified galaxies using GALFIT, measure the aperture colors, and the basic morphological parameters like concentration and residual flux fraction. We used color-magnitude, luminosity-radius and luminosity-concentration relations to separate the cluster galaxies from the background galaxies. We then divided the cluster galaxies into early- and late-type galaxies according to their morphology and gave first order morphological classifications using a combination of visual and parametric classifications. Our final catalog includes 14,095 galaxies. We classify 590 galaxies as being likely Fornax cluster galaxies, of which 564 are dwarfs (Mr'>-18.5mag) consisting our Fornax dwarf catalog. Of the cluster dwarfs we classify 470 as early-types, and 94 as late-type galaxies. Our final catalog reaches its 50% completeness limit at magnitude Mr'=-10.5mag and surface brightness <{mu}_e,r'_=26mag/arcsec^2^, which is approximately three magnitudes deeper than the FCC. Based on previous works and comparison with a spectroscopically confirmed subsample, we estimate that our final Fornax dwarf galaxy catalog has <~10% contamination from the background objects.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A100
- Title:
- Fornax Deep Survey with VST. XI.
- Short Name:
- J/A+A/647/A100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies either live in a cluster, a group, or in a field environment. In the hierarchical framework, the group environment bridges the field to the cluster environment, as field galaxies form groups before aggregating into clusters. In principle, environmental mechanisms, such as galaxy-galaxy interactions, can be more efficient in groups than in clusters due to lower velocity dispersion, which lead to changes in the properties of galaxies. This change in properties for group galaxies before entering the cluster environment is known as preprocessing. Whilst cluster and field galaxies are well studied, the extent to which galaxies become preprocessed in the group environment is unclear. We investigate the structural properties of cluster and group galaxies by studying the Fornax main cluster and the infalling Fornax A group, exploring the effects of galaxy preprocessing in this showcase example. Additionally, we compare the structural complexity of Fornax galaxies to those in the Virgo cluster and in the field. Our sample consists of 582 galaxies from the Fornax main cluster and Fornax A group. We quantified the light distributions of each galaxy based on a combination of aperture photometry, Sersic+PSF (point spread function) and multi-component decompositions, and non-parametric measures of morphology. From these analyses, we derived the galaxy colours, structural parameters, non-parametric morphological indices (Concentration C; Asymmetry A, Clumpiness S; Gini G; second order moment of light M_20_), and structural complexity based on multi-component decompositions. These quantities were then compared between the Fornax main cluster and Fornax A group. The structural complexity of Fornax galaxies were also compared to those in Virgo and in the field. We find significant (Kolmogorov-Smirnov test p-value <alpha=0.05) differences in the distributions of quantities derived from Sersic profiles (g'-r', r'-i', Re, and {bar}{mu}_e,r'_), and non-parametric indices (A and S) between the Fornax main cluster and Fornax A group. Fornax A group galaxies are typically bluer, smaller, brighter, and more asymmetric and clumpy. Moreover, we find significant cluster-centric trends with r'-i', Re, and {bar}{mu}_e,r'_, as well as A, S, G, and M_20_ for galaxies in the Fornax main cluster. This implies that galaxies falling towards the centre of the Fornax main cluster become fainter, more extended, and generally smoother in their light distribution. Conversely, we do not find significant group-centric trends for Fornax A group galaxies. We find the structural complexity of galaxies (in terms of the number of components required to fit a galaxy) to increase as a function of the absolute r'-band magnitude (and stellar mass), with the largest change occurring between -14mag<~Mr'<~-19,mag (7.5<~log_10_(M*/M_{sun}_)~=9.7). This same trend was found in galaxy samples from the Virgo cluster and in the field, which suggests that the formation or maintenance of morphological structures (e.g. bulges, bar) are largely due to the stellar mass of the galaxies, rather than the environment they reside in.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/1756
- Title:
- Fourier-derived parameters of the CIG sample
- Short Name:
- J/MNRAS/397/1756
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here the results of a Fourier photometric decomposition of a representative sample of ~100 isolated CIG galaxies (Catalog of Isolated Galaxies) in the morphological range Sb-Sc. This study is an integral part of the AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) project. It complements the photometric analysis presented in our previous paper for the same sample of disc galaxies by allowing a description of the spiral structure morphology. We also estimate dynamical measures like torque strength for bar and spiral, and also the total non-axisymmetric torque by assuming a constant mass-to-light ratio, and explore the interplay between the spiral and bar components of galaxies. Both the length (l_bar_) and the contrast (e.g. A_2b_) of the Fourier bars decrease along the morphological sequence Sb-Sbc-Sc, with bars in earlier types being longer and showing higher contrast. The bars of Sb galaxies are ~ three times longer than the bars in Sc types, consistent with our previous study. We find that the longer bars are not necessarily stronger (as quantified by the torque Q_b_measure), but longer bars show a higher contrast A_2b_, in very good agreement with theoretical predictions. Our data suggest that bar and spiral components are rather independent in the sense that the torque strengths of the two components are not correlated. The total strength Q_g_ is a very reliable tracer of the bar strength measure Q_b_, the two quantities showing a very tight linear correlation. Comparison with a similar sample of disc galaxies (same morphological range) extracted from the OSUBGS (Ohio State University Bright Galaxy Survey) indicates that the isolated CIG/AMIGA galaxies host significantly longer Fourier bars and possibly show a different distribution of spiral torque Q_s_. The Fourier analysis also revealed a potential case of counterwinding spiral structure (KIG652/NGC5768), which deserves further kinematic study. We find that m=2 (i.e. dominating two-armed pattern) is the most common spiral arm multiplicity among the sample of Sb-Sc CIG/AMIGA galaxies (~40 per cent), m=2 and 3 and m=1 and 2 are found in ~28 and ~13 per cent of isolated galaxies, respectively.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1013
- Title:
- FR II radio galaxies in SDSS
- Short Name:
- J/MNRAS/415/1013
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Starting from the Cambridge Catalogues of radio sources, we have created a sample of 401 Fanaroff-Riley type II (FR II) radio sources that have counterparts in the main galaxy sample of the seventh Data release of the Sloan Digital Sky Survey (SDSS) and analyse their radio and optical properties.
- ID:
- ivo://CDS.VizieR/J/A+A/648/A102
- Title:
- FR-type radio sources at 3GHz VLA-COSMOS
- Short Name:
- J/A+A/648/A102
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Radio active galactic nuclei (AGN) are traditionally separated into two Fanaro-Riley (FR) type classes, edge-brightened FRII sources or edge-darkened FRI sources. With the discovery of a plethora of radio AGN of different radio shapes, this dichotomy is becoming too simplistic in linking the radio structure to the physical properties of radio AGN, their hosts, and their environment. We probe the physical properties and large-scale environment of radio AGN in the faintest FR population to date, and link them to their radio structure. We use the VLA-COSMOS Large Project at 3GHz (3GHz VLA-COSMOS), with a resolution and sensitivity of 0.75" and 2.3Jy/beam to explore the FR dichotomy down to Jy levels. We classified objects as FRIs, FRIIs, or hybrid FRI/FRII based on the surface-brightness distribution along their radio structure. Our control sample was the jet-less/compact radio AGN objects (COM AGN), which show excess radio emission at 3GHz VLA-COSMOS exceeding what is coming from star-formation alone; this sample excludes FRs. The largest angular projected sizes of FR objects were measured by a machine-learning algorithm and also by hand, following a parametric approach to the FR classification. Eddington ratios were calculated using scaling relations from the X-rays, and we included the jet power by using radio luminosity as a probe. Furthermore, we investigated their host properties (star-formation ratio, stellar mass, morphology), and we explore their incidence within X-ray galaxy groups in COSMOS, and in the density fields and cosmic-web probes in COSMOS. Our sample is composed of 59 FRIIs, 32 FRI/FRIIs, 39 FRIs, and 1818 COM AGN at 0.03<=z<=6. On average, FR objects have similar radio luminosities (L_3GHz_~10^23^W/Hz/sr), spanning a range of 10^21-26^W/Hz/sr, and they lie at a median redshift of z~1. The median linear projected size of FRIIs is 106.6^238.2^_36.9_kpc, larger than that of FRI/FRIIs and FRIs by a factor of 2-3. The COM AGN have sizes smaller than 30kpc, with a median value of 1.7^4.7^_1.5_kpc. The median Eddington ratio of FRIIs is 0.006^0.007^_0.005_, a factor of 2.5 less than in FRIs and a factor of 2 higher than in FRI/FRII. When the jet power is included, the median Eddington ratios of FRII and FRI/FRII increase by a factor of 12 and 15, respectively. FRs reside in their majority in massive quenched hosts (M*>10^10.5^M_{sun}_), with older episodes of star-formation linked to lower X-ray galaxy group temperatures, suggesting radio-mode AGN quenching. Regardless of their radio structure, FRs and COM AGN are found in all types and density environments (group or cluster, filaments, field). By relating the radio structure to radio luminosity, size, Eddington ratio, and large-scale environment, we find a broad distribution and overlap of FR and COM AGN populations. We discuss the need for a different classification scheme, that expands the classic FR classification by taking into consideration the physical properties of the objects rather than their projected radio structure which is frequency-, sensitivity- and resolution-dependent. This point is crucial in the advent of current and future all-sky radio surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/397/75
- Title:
- Fundamental Plane analysis in Shapley
- Short Name:
- J/MNRAS/397/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Fundamental Plane (FP) analysis of 141 early-type galaxies in the Shapley supercluster at z=0.049 based on spectroscopy from the AAOmega spectrograph at the Anglo-Australian Telescope and photometry from the WFI on the European Southern Observatory/MPI 2.2-m telescope.
- ID:
- ivo://CDS.VizieR/VIII/100
- Title:
- GaLactic and Extragalactic All-sky MWA survey
- Short Name:
- VIII/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Murchison Widefield Array (MWA), the low-frequency Square Kilometre Array (SKA1 LOW) precursor located in Western Australia, we have completed the GaLactic and Extragalactic All-sky MWA (GLEAM) survey, and present the resulting extragalactic catalogue, utilising the first year of observations. The catalogue covers 24,402 square degrees, over declinations south of +30{deg} and Galactic latitudes outside 10{deg} of the Galactic plane, excluding some areas such as the Magellanic Clouds. It contains 307,456 radio sources with 20 separate flux density measurements across 72-231MHz, selected from a time- and frequency- integrated image centred at 200MHz, with a resolution of ~=2'. Over the catalogued region, we estimate that the catalogue is 90% complete at 170mJy, and 50% complete at 55mJy, and large areas are complete at even lower flux density levels. Its reliability is 99.97% above the detection threshold of 5{sigma}, which itself is typically 50mJy. These observations constitute the widest fractional bandwidth and largest sky area survey at radio frequencies to date, and calibrate the low frequency flux density scale of the southern sky to better than 10%. This paper presents details of the flagging, imaging, mosaicking, and source extraction/characterisation, as well as estimates of the completeness and reliability. All source measurements and images are available online. This is the first in a series of publications describing the GLEAM survey results.
