- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2047
- Title:
- Formation of cD Galaxies and their Clusters
- Short Name:
- J/MNRAS/427/2047
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to study the mechanism of formation of cD galaxies we search for possible dependencies between the K-band luminosity of cDs and the parameters of their host clusters which we select to have a dominant cD galaxy, corresponding to a cluster morphology of Bautz-Morgan (BM) type I. As a comparison sample we use cD galaxies in clusters where they are not dominant, which we define here as non-BM I (NBMI) type clusters. We find that for 71 BM I clusters the absolute K-band luminosity of cDs depends on the cluster richness, but less strongly on the cluster velocity dispersion. Meanwhile, for 35 NBMI clusters the correlation between cD luminosity and cluster richness is weaker, and is absent between cD luminosity and velocity dispersion. In addition, we find that the luminosity of the cD galaxy hosted in BM I clusters tends to increase with the cD's peculiar velocity with respect to the cluster mean velocity. In contrast, for NBMI clusters the cD luminosity decreases with increasing peculiar velocity. Also, the X-ray luminosity of BM I clusters depends on the cluster velocity dispersion, while in NBMI clusters such a correlation is absent. These findings favour the cannibalism scenario for the formation of cD galaxies. We suggest that cDs in clusters of BM I type were formed and evolved preferentially in one and the same cluster. In contrast, cDs in NBMI type clusters were either originally formed in clusters that later merged with groups or clusters to form the current cluster, or are now in the process of merging.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/296/319
- Title:
- Fornax cluster early-type galaxies
- Short Name:
- J/A+A/296/319
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/other/PASA/38.20
- Title:
- Fornax cluster magnetic fields
- Short Name:
- J/other/PASA/38.
- Date:
- 17 Jan 2022 00:49:54
- Publisher:
- CDS
- Description:
- We present the first Faraday rotation measure (RM) grid study of an individual low-mass cluster - the Fornax cluster - which is presently undergoing a series of mergers. Exploiting commissioning data for the POlarisation Sky Survey of the Universe's Magnetism (POSSUM) covering a ~34 square degree sky area using the Australian Square Kilometre Array Pathfinder (ASKAP), we achieve an RM grid density of ~25 RMs per square degree from a 280MHz band centred at 887MHz, which is similar to expectations for forthcoming GHz-frequency 3-steradian sky surveys. These data allow us to probe the extended magnetoionic structure of the cluster and its surroundings in unprecedented detail. We find that the scatter in the Faraday RM of confirmed background sources is increased by 16.8+/-2.4rad/m^2^ within 1 degree (360kpc) projected distance to the cluster centre, which is 2-4 times larger than the spatial extent of the presently-detectable X-ray-emitting intracluster medium (ICM). The mass of the Faraday-active plasma is larger than that of the X-ray-emitting ICM, and exists in a density regime that broadly matches expectations for moderately-dense components of the Warm-Hot Intergalactic Medium. We argue that forthcoming RM grids from both targeted and survey observations may be a singular probe of cosmic plasma in this regime. The morphology of the global Faraday depth enhancement is not uniform and isotropic, but rather exhibits the classic morphology of an astrophysical bow shock on the southwest side of the main Fornax cluster, and an extended, swept-back wake on the northeastern side. Our favoured explanation for these phenomena is an ongoing merger between the main cluster and a sub-cluster to the southwest. The shock's Mach angle and stand-o distance lead to a self-consistent transonic merger speed with Mach 1.06. The region hosting the Faraday depth enhancement also appears to show a decrement in both total and polarised radio emission compared to the broader field. We evaluate cosmic variance and free-free absorption by a pervasive cold dense gas surrounding NGC 1399 as possible causes, but find both explanations unsatisfactory, warranting further observations. Generally, our study illustrates the scientific returns that can be expected from all-sky grids of discrete sources generated by forthcoming all-sky radio surveys.
- ID:
- ivo://CDS.VizieR/J/A+A/476/59
- Title:
- Fornax Cluster Spectroscopic Survey 2MASS galaxies
- Short Name:
- J/A+A/476/59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Fornax Cluster Spectroscopic Survey (FCSS) is an all-object survey of a region around the Fornax Cluster of galaxies undertaken using the 2dF multi-object spectrograph on the Anglo-Australian Telescope. Its aim was to obtain spectra for a complete sample of all objects with 16.5<b_j_<19.7 irrespective of their morphology (i.e. including `stars', `galaxies' and `merged' images). We explore the extent to which (nearby) cluster galaxies are present in 2MASS. We consider the reasons for the omission of 2MASS galaxies from the FCSS and vice versa. We consider the intersection (2.9 square degrees on the sky) of our data set with the infra-red 2 Micron All-Sky Survey (2MASS), using both the 2MASS Extended Source Catalogue (XSC) and the Point Source Catalogue (PSC). We match all the XSC objects to FCSS counterparts by position and also extract a sample of galaxies, selected by their FCSS redshifts, from the PSC. We confirm that all 114 XSC objects in the overlap sample are galaxies, on the basis of their FCSS velocities. A total of 23 Fornax Cluster galaxies appear in the matched data, while, as expected, the remainder of the sample lie at redshifts out to z=0.2 (the spectra show that 61% are early type galaxies, 18% are intermediate types and 21% are strongly star forming). The PSC sample turns out to contain twice as many galaxies as does the XSC. However, only one of these 225 galaxies is a (dwarf) cluster member. On the other hand, galaxies which are unresolved in the 2MASS data (though almost all are resolved in the optical) amount to 71% of the non-cluster galaxies with 2MASS detections and have redshifts out to z=0.32.
- 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/623/A1
- Title:
- Fornax Deep Survey with VST. V. Isophote fit
- Short Name:
- J/A+A/623/A1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is based on the multi-band (ugri) Fornax Deep Survey (FDS) with the VLT Survey Telescope (VST). We study bright early-type galaxies (m_B_<15mag) in the 9 square degrees around the core of the Fornax cluster, which covers the virial radius (R_vir~0.7Mpc). The main goal of the present work is to provide an analysis of the light distribution for all galaxies out to unprecedented limits (in radius and surface brightness) and to release the main products resulting from this analysis in all FDS bands. We give an initial comprehensive view of the galaxy structure and evolution as a function of the cluster environment. From the isophote fit, we derived the azimuthally averaged surface brightness profiles, the position angle, and ellipticity profiles as a function of the semi-major axis. In each band, we derived the total magnitudes, effective radii, integrated colours, and stellar mass-to-light ratios. The long integration times, the arcsec-level angular resolution of OmegaCam@VST, and the large covered area of FDS allow us to map the light and colour distributions out to large galactocentric distances (up to about 10^-15^Re) and surface brightness levels beyond mu_r_=27mag/arcsec^2^ (mu_B_>28mag/arcsec^2^). Therefore, the new FDS data allow us to explore in great detail the morphology and structure of cluster galaxies out to the region of the stellar halo. The analysis presented in this paper allows us to study how the structure of galaxies and the stellar population content vary with the distance from the cluster centre. In addition to the intra-cluster features detected in previous FDS works, we found a new faint filament between FCC 143 and FCC 147, suggesting an ongoing interaction. The observations suggest that the Fornax cluster is not completely relaxed inside the virial radius. The bulk of the gravitational interactions between galaxies happens in the W-NW core region of the cluster, where most of the bright early-type galaxies are located and where the intra-cluster baryons (diffuse light and globular clusters) are found. We suggest that the W-NW sub-clump of galaxies results from an infalling group onto the cluster, which has modified the structure of the galaxy outskirts (making asymmetric stellar halos) and has produced the intra-cluster baryons (ICL and GCs), concentrated in this region of the cluster.
- 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/504/3580
- Title:
- Fornax galaxy cluster NIR images & catalogs
- Short Name:
- J/MNRAS/504/3580
- Date:
- 06 Jan 2022 17:55:05
- Publisher:
- CDS
- Description:
- Ultra-compact dwarf galaxies (UCDs) were serendipitously discovered by spectroscopic surveys in the Fornax cluster 20 yr ago. Nowadays, it is commonly accepted that many bright UCDs are the nuclei of galaxies that have been stripped. However, this conclusion might be driven by biased samples of UCDs in high-density environments, on which most searches are based. With the deep optical images of the Fornax Deep Survey, combined with public near-infrared data, we revisit the UCD population of the Fornax cluster and search for UCD candidates, for the first time, systematically out to the virial radius of the galaxy cluster. Our search is complete down to magnitude m_g_=21mag or M_g_~-10.5mag at the distance of the Fornax cluster. The UCD candidates are identified and separated from foreground stars and background galaxies by their optical and near-infrared colours. This primarily utilizes the u-i/i-Ks diagram and a machine learning technique is employed to incorporate other colour combinations to reduce the number of contaminants. The newly identified candidates (44) in addition to the spectroscopically confirmed UCDs (61), increase the number of known Fornax UCD considerably (105). Almost all of the new UCD candidates are located outside the Fornax cluster core (360kpc), where all of the known UCDs were found. The distribution of UCDs within the Fornax cluster shows that a population of UCDs may form in low-density environments. This most likely challenges the current models of UCD formation.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A93
- Title:
- Fornax globular clusters
- Short Name:
- J/A+A/657/A93
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The Fornax cluster provides an unparalleled opportunity of investigating the formation and evolution of early-type galaxies in a dense environment in detail. We aim at kinematically characterising photometrically detected globular cluster (GC) candidates in the core of the cluster. We used VLT/VIMOS spectroscopic data from the FVSS survey in the Fornax cluster, covering one square degree around the central massive galaxy NGC 1399. We confirm a total of 777 GCs, almost doubling previously detected GCs, using the same dataset as was used before. Combined with previous literature radial velocity measurements of GCs in Fornax, we compile the most extensive spectroscopic GC sample of 2341 objects in this environment. We found that red GCs are mostly concentrated around major galaxies, while blue GCs are kinematically irregular and are widely spread throughout the core region of the cluster. The velocity dispersion profiles of blue and red GCs show a quite distinct behaviour. Blue GCs exhibit a sharp increase in the velocity dispersion profile from 250 to 400km/s within 5 arcminutes (~29kpc~1r_eff_ of NGC 1399) from the central galaxy. The velocity dispersion profile of red GCs follows a constant value between 200-300km/s until 8 arcminutes (~46kpc~1.6r_eff_, and then rises to 350km/s at 10 arcminutes (~58kpc~2r_eff_). Beyond 10 arcminutes and out to 40 arcminutes (~230kpc~8r_eff_), blue and red GCs show a constant velocity dispersion of 300+/-50km/s, indicating that both GC populations trace the cluster potential. We kinematically confirm and characterise the previously photometrically discovered overdensities of intra-cluster GCs. We found that these substructured intra-cluster regions in Fornax are dominated mostly by blue GCs.
